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... The distribution of this stress across the wall of the cylinder is non-linear, tending to reduce sharply toward the outer radius. Therefore, the traditional design of such a thick cylinder based on the maximum stresses at the inner radius resulted in unnecessary thickness and improper material utilization. 1 Figure 1 2 shows the large variation in tangential stress across the wall. In addition, in a thick cylinder, no matter how large the outside radius of the cylinder is to resist internal pressure, p i , the maximum tangential stress will not be smaller than p i , even if it goes to an infinite value. ...
... After the shrinkage process, when the compound cylinder is subjected to internal pressure Pi and external pressure equal to zero, the tangential and radial stresses due to the internal pressure can only be obtained by using Lame's equations, Eqs. (1) and (2), and considering the compound cylinder as a single thick cylinder. Then, the tangential and radial stresses due to Pi only at the inner radius of cylinder 1 are ...
... The analytical stress distribution across the wall of compound cylinder is obtained using LAME's theory, Eqs. (1) and (2), and the optimized parameters for working pressure of 187 MPa in Table II. Figures 13 and 14 show the tangential and radial stress distribution, where the solid curve represents the total stress, the dotted curve represents the residual stress and, finally, the dashed curve is the stress due to the internal pressure only. ...
The purpose of this work is to find the optimum design for two-layer compound cylinders of the same material with an open end condition by using the elimination method. The optimization method depends on reducing the number of design variables with a simultaneous yield hypothesis for all layers of the compound cylinder. A combination of von Mises and Tresca criteria is used as a yield criterion, and the superposition principle is used to evaluate the equivalent stresses for each cylinder. By considering the working pressure and the internal diameter of the inner cylinder as the design parameters (constants during optimization) and the total thickness of the compound cylinder as the objective function, the optimization algorithm has been programmed in C# with a user-friendly graphical interface. The optimization results (outer diameter, interference diameter, and shrinkage pressure) are obtained for different working pressures and compared with the optimum design, which is based only on the Tresca criterion. The total mass of the compound cylinder can be reduced by up to 50% by using the von Mises–Tresca combination criterion. The optimized results are validated numerically by using finite element analysis in the ANSYS Workbench. The theoretical result and the FEA result agree with each other with errors of about 2%. The behavior of the optimized parameters for different working pressures is also observed and presented.
... M z ≃ 545 Nm. The deflection of cantilever beam subjected to an end moment is given as [45]: ...
... Stresses are developed in the reflector material subjected to a temperature field by virtue of the thermal coefficient of expansion (κ). These stresses are given as [45]: where ∆T is the temperature difference. ...
... Note that the left hand side of Eqs.(45) has the dimension of a quaternion with the first scalar component being 0 and the vectorial part being the angular velocity (Eq. (45a)) and the angular acceleration (Eq. ...
... For static loads deflection of beams can be determined by various approaches, some of which are: the direct integration method, Clebsch method for calculating integration constants, moment-area approach (Mohr method), energy method, which includes Castigliano's theorems and unit load technique, stiffness and flexibility methods, principal superposition, three bending moments technique and singularity functions method, and Taylor's expansion series [1][2][3][4][5][6][7]. ...
... The deformed average fiber is considered to represent an infinite sum of sinusoidal functions, which are successively evaluated through sinusoidal trigonometric series (if this is considered to be a periodic function) or using the Fourier series if this is considered to be a non-periodic function. For static loads deflection of beams can be determined by various approaches, some of which are: the direct integration method, Clebsch method for calculating integration constants, moment-area approach (Mohr method), energy method, which includes Castigliano's theorems and unit load technique, stiffness and flexibility methods, principal superposition, three bending moments technique and singularity functions method, and Taylor's expansion series [1][2][3][4][5][6][7]. ...
... Thus, the displacement in the vertical plane of the center of gravity of the cross-section for a straight bar, simply supported, is studied for two loading cases: in the first case, a concentrated force acting in the vertical plane (in the direction of the y axis, according to Figure 1), positioned asymmetrically or symmetrically to the support points; in the second case of loading, a uniformly distributed load is considered over the entire length unit and which also acts in the direction of the y axis. The calculation relations of the displacement obtained with the help of the trigonometric series and the Fourier series are compared with those offered by the specialized literature (obtained by direct integration of the differential equation of the deformed average fiber) to check the convergence of the obtained results [1][2][3][4][5][6]. ...
The average deformed fiber is a continuous and smooth function of the fourth order. The deflection and rotation of beams can be determined by various methods available in the literature. Thus, in this paper, the expression of the average deformed fiber is defined in advance, then it is considered an infinite sum of sinusoidal functions that are successively evaluated using sinusoidal trigonometric series if it is considered a periodic function, or using Fourier series if it is considered a non-periodic function. The method is examined by solving several beam problems. The results indicate that the method can be used with confidence for solving any bending beam problem.
... Зависимостта между кривината и деформацията може да се изведе чрез следния израз [14]: ...
... фиг. 8а и израз (4)) се получава чрез решението на диференциалното уравнение [14]: ...
Steel structures subjected to extreme cyclic loading, characteristic of strong earthquakes, temperature with large range of deviation or various technological processes, realize significant plastic deformations before they failure. In such cases, the endurance of the structure depends on the cyclic behavior of the material. There is a plenty of information in the literature, both theoretical and experimental, on the behavior of steel under monotonic and cyclic loading at low levels of plastic strain (around and slightly beyond the yield strain). However, research on the performance of steel under extreme cyclic plastic deformation remains limited, with few experimental studies conducted worldwide. This paper presents an experimental program focusing on the study of the behavior of structural steel grade S235JR, subjected to cyclic loading of constant and variable amplitude, at large values of plastic strain.
... Torsional behavior of concrete made different coarse aggregate were next compared with the available torsional strength model. Five widely used models, i.e., elastic theory [45,46], plastic theory [46,47], ACI code method [48], Turkish standard TS500 [49], and Skew bending theory [50] were examined for this purpose. According to elastic theory, which is from St. Venant's principle, torsional capacity of plain concrete member is expressed as follows: ...
... Torsional behavior of concrete made different coarse aggregate were next compared with the available torsional strength model. Five widely used models, i.e., elastic theory [45,46], plastic theory [46,47], ACI code method [48], Turkish standard TS500 [49], and Skew bending theory [50] were examined for this purpose. According to elastic theory, which is from St. Venant's principle, torsional capacity of plain concrete member is expressed as follows: ...
Concrete was made with four different types of coarse aggregate, i.e., natural stone aggregate concrete (NSAC), crushed virgin clay brick aggregate concrete (VBAC), crushed recycled brick concrete aggregate concrete (RBAC), and crushed recycled stone concrete aggregate concrete (RSAC). Beam specimens prepared from these four types of concrete were subjected to pure torsional moment up to failure. From this experimental procedure, ultimate torque at failure along with twisting angle were observed. From the torque vs. twisting angle curves, torsional stiffness and torsional toughness were also evaluated for these four types of concrete. It was observed that ultimate torque of VBAC and RBAC was 95% and 90% of that of NSAC, respectively. The torsional toughness of VBAC was found to be 68%–72% of that of NSAC. In addition, experimental torques were compared with predictions of torsional strength as per five commonly used models. For VBAC, the ultimate torque prediction made by skew bending theory was found to be the closest to the experimental findings.
... A procedure to automate the design of two scissors lifts is used. The procedure was successfully used to design scrap metal balers [15] in a previous study. The study was improved and extended by including kinematic and kinetic analyses for the lift. ...
... f1 is the first natural frequency, Sx is the normal stress, and uy is the displacement in the -y direction. The formulation for the analytical results are well known and can be found in the literature [15,16]. It is observed that the analytical and SW simulation results are in good agreement. ...
In this study, the design of a two scissors greenhouse lift trolley is considered. The maximum height of the platform from the ground is 3500 mm. A program developed in Visual BASIC to automate the design is introduced. The lift is modeled in SolidWorks (SW) and the finite element (FE) modal and static analyses are performed as an initial design first by using graphical user interface (GUI). The lift contains revolute joints and slider joints. A simply supported beam which has two revolute joints and a slider joint is studied to verify how to model the joints. Pim connectors are defined for revolute joints in SW-FE analysis. Spring connectors with very large values are defined between sliding faces in the normal direction for translational joints. The results obtained with solid finite elements in SW are compared with analytical results for the natural frequency and static analyses and it was observed that the results are in good agreement for the simply supported beam. An Excel file where a main sheet contains the list of the bodies and all the geometric values is created after the initial design. The Excel file also contains sheets for each body. Body sheets have all the dimensions in the sketches and features. The dimension values in the cells of the body sheets are defined by formulas related to the geometric values given in the main sheet. Kinematic, kinetic, and revision of the SW model are performed by the design automation program. The FE analyses are done by GUI and the results are evaluated. If the results are not satisfactory, the geometric values are changed in Excel file and the analyses are repeated. The final design is obtained by the iteration easily. The automation program and the procedure developed in this work can be extended other scissors lifts.
... Based on the curvature-strain relationship in the section subjected to flexural moment (for small deformations: ε = * ∅ and large deformations: ε = * tan ∅, y: distance from the neutral fiber), assuming that for the inelastic deformations the relation ε = is established (for ST37 steel, ε = 167 means that the value of n at the moment of failure is 167 (Popov, 1990)), it can be concluded that at any curvature such as ∅ , the curvature equation can be written in (Equation (12)). If the strain hardening phenomenon in steel is ignored, = , i.e. the cross-section of the beam at a fixed moment = * will increase the curvature until it is finally collapsed at the curvature ∅ . ...
... Steel sections reach ∅ at the strain much less than ℎ (Figure 2) (this ratio is about 1.1 ~ 1.25 for I-shaped sections), i.e. ∅ = (1.1~1.25)∅ (Chen & Sohal, 2013) and for ST37 steel, ∅ ℎ = 10∅ (Popov, 1990). Therefore, in the interval ∅ to ∅ ℎ , although the strain at the section height will increase significantly, the stress along with the height of the cross-section is constant and equal to . ...
Among the methods for evaluating the nonlinear performance of structures, pushover analysis is an appropriate alternative instead of direct time history analysis. To accurately extract the capacity curve of a structure, according to the loading regulations/protocols such as FEMA-356 and ATC-40, lateral loads are incrementally applied to the structure in laboratory tests until the structural's failure occurs. Because of the cost and time-consuming nature of experimental tests, proposing mathematical/analytical methods could be the appropriate tools to predict the capacity curves of structures. The present study proposes a new method to find the capacity curves of cantilever steel beams based on mathematical formulations, structural analysis, and material properties. The reason to select a simple beam for this study is to discover all aspects of the system's nonlinear behavior. The strains, stresses, and other responses corresponding to large geometrical deformations have been extracted in two cases with and without strain hardening by considering changes in the behavior of materials. The proposed method has been verified using the finite element method with Abaqus software. The results indicate that the proposed model has acceptable accuracy and could be applied in the pushover analysis of steel structures.
... while a combined response is identified by: (33) and, the flexural response is identifiable by Eqs. (34) and (35): ...
... Hibbeler [32] and Popov [33] defined a shape coefficient, so the strain energy for a beam can be recalculated as: ...
The presence of openings in steel shear-walls is oftentimes necessary due to different design requirements. This paper investigates the behaviour of a panel in between two openings (mid-panel or MP) in shear-walls with dual openings under monotonic loading. The panel is analogised to link-beams in eccentrically-braced frames. To examine the structural response of these structures, two established conditions (elastic force and displacement) are addressed. Theoretical formulations are developed for a new condition (flexural stiffness of stiffeners to shear stiffness of a plate) in addition to the two conditions above. Furthermore, an equation was derived to calculate the shape factor of sections with box-shaped flanges, which is used to obtain the shear displacement (yield) of the mid-panel's plate. A comprehensive parametric study (44 models) is conducted using Finite Element Analysis (FEA) to examine the effect of six different geometric factors on the structural response of the mid-panel. The mid-panel's dominant structural responses (deformation and stress distribution) are classified as (i) flexural, (ii) shear, and (iii) combined (shear-flexure). The increase of the MP's width, the box-stiffeners' web height, flange's width and thickness causes a shear response, while the increase of the MP's height and the thickness leads to a flexural behaviour. Each structural response is carefully addressed theoretically and numerically leading to consistent results. The variables of the MP's plate bring about higher effects on the behaviour of the MP comparing to the parameters of the stiffeners. Overall, a shear response is structurally desirable, which enhances the MP's energy dissipation and post-buckling capacity.
... The mechanical properties of key interest for structural application are compressive strength, tensile strength, flexural strength and shrinkage (Popov, 1998 The findings by Lv et al. (2013) revealed that GO nanosheets played a role in facilitating the formation of hydrate crystals with a flower-like structure, leading to a significant improvement in the tensile, flexural, and compressive strengths of cement composites. Notably, when the GO content was 0.03%, the cement composites exhibited a remarkable increase in their tensile strength by 78.6%, flexural strength by 60.7%, and compressive strength by 38.9% when compared to composites without the inclusion of GO. ...
Sustainability in construction has been an everlasting global goal to reduce the emission of greenhouse gases that have had detrimental effects on the environment and negatively impacted human life in general. Graphene, a two-dimensional material exhibiting exceptionally desirable properties, has shown great potential to impact the building and construction sectors significantly. Graphene and its derivatives can easily be used as an additive in concrete-based composites (CBC) to improve their mechanical and durability properties and their safety, with prospects of fostering sustainability. This paper uses a scoping and compressive thorough mixed review approach, and this research aims to assess the endeavors in utilizing Graphene and Its derivatives in cementitious composites and to chart the perspectives found in the existing literature. The paper selected 64 articles from a pool of 576 publications based on their relevance. The comprehensive review concludes that the benefit of using Graphene and its derivatives as a reinforcement in cement composites lies in its superior ability to improve mechanical properties, including tensile strength and compressive strength, and improves durability by restricting crack initiation and expansion at the nanoscale, and enhances resistance to chloride and sulphate attacks as well as improving the safety of concrete based composites, setting it apart from traditional reinforcement methods.
... The results provided in Figure 10b are based on the well-known calculation of the bending stresses, σ (see, [8] as an example): (1) Where M is the bending moment, E is the Young modulus of the lumber and I is the moment of inertia of the beam's cross section. ...
... While we acknowledge the existence of an undergraduate textbook like Popov [31] that briefly elaborates on probabilistic assessments, we observe a general trend where the majority do not delve deeply into the comparative analysis of failure theories from a probabilistic viewpoint. The scarcity of in-depth treatment of probabilistic tools in undergraduate educational resources underscores a missed opportunity to foster a comprehensive understanding of design principles among structural engineers. ...
This tutorial examines the failure theories of Tresca and von Mises, both of which are crucial for designing metallic structures. Conventionally, Tresca is regarded as more conservative than von Mises from a deterministic perspective. This tutorial, however, introduces a different viewpoint, presenting a scenario where von Mises theory may appear more conservative when variability in the mechanical system parameters is considered. This often overlooked aspect is not extensively addressed in standard textbooks on solid mechanics and the strength of materials. The tutorial aims to shed light on the non-negligible probability where von Mises criterion yields a smaller equivalent stress than Tresca, thus being more conservative. It underscores the importance of integrating probabilistic considerations into stress analyses of solids, offering valuable insights for the education of structural mechanics.
... In region II (red), the cycle period is longer than the limb's natural period, and actuator torque is almost entirely in phase with the limb angle, as indicated by the positive-slope work loops shown in Fig. 2C and D. The phase shift (ϕ) in this region is 0°. We call this region "quasi-static" because the static forces of gravity and elasticity dominate (28), and most actuator work is converted into potential energy (shaded red). Finally, in region III (orange), cycle period is short relative to the resonant frequency of the limb, but the limb has very little mass, so most actuator energy is dissipated due to viscous forces within the joint (orange shading in Fig. 2E). ...
During behavior, the work done by actuators on the body can be resisted by the body's inertia, elastic forces, gravity, or viscosity. The dominant forces that resist actuation have major consequences on the control of that behavior. In the literature, features and actuation of locomotion, for example, have been successfully predicted by nondimensional numbers (e.g. Froude number and Reynolds number) that generally express the ratio between two of these forces (gravitational, inertial, elastic, and viscous). However, animals of different sizes or motions at different speeds may not share the same dominant forces within a behavior, making ratios of just two of these forces less useful. Thus, for a broad comparison of behavior across many orders of magnitude of limb length and cycle period, a dimensionless number that includes gravitational, inertial, elastic, and viscous forces is needed. This study proposes a nondimensional number that relates these four forces: the phase shift (ϕ) between the displacement of the limb and the actuator force that moves it. Using allometric scaling laws, ϕ for terrestrial walking is expressed as a function of the limb length and the cycle period at which the limb steps. Scale-dependent values of ϕ are used to explain and predict the electromyographic (EMG) patterns employed by different animals as they walk.
... Lateral resistance of masonry walls against seismic forces applied parallel to their plane has been predicted analytically as per the procedure given in ASCE-41 (American Society of Civil Engineers, 2017) and model presented by "Popov" (Paul, 1999). According to Popov and Balan (1998), the shear force corresponding to the flexural tensile cracking in bed joints of the pier is V fl,cr , and is computed by Eq. (2). ...
The purpose of this study is to experimentally investigate the performance of brick masonry specimens, strengthened with fiber-reinforced Engineered Cementitious Composites (ECCs). Testing of constituent materials and masonry prisms were
included in the experimental program of the study. Material testing included compression and fexure strength of brick samples, compression test of ordinary mortar, and ECC cubes. Moreover, a total of 6 brick masonry prisms of 508 mm×406 mm (20″×18″) were tested for compressive strength. Three samples consisted of ordinary plaster, while in the remaining three samples, the ordinary plaster was replaced with 10-mm-thick ECC plaster. Similar plaster strategy was used for six masonry walls tested for diagonal tension having dimension of 1219 mm×1219 mm (48″×48″). This study has found that the ECC plaster can efectively enhance the shear strength and principal tensile strength by 33.7%, compressive strength by 48.2%, and energy absorption capacity of brick masonry by 125.4%, while the estimated lateral load capacity against seismic forces has been improved by 34%.
... Structural engineering problems are solved using both classical analytical approach (Mechanics of solids) and numerical solutions approach. In Mechanics of Solids approach, the principle of superposition of forces method is used when forces are applied at different locations [2]. This approach becomes complicated when forces act on the entire surface. ...
Prediction of deflections in structures is imperative for safety and stability. Classical approach and numerical solutions are currently being employed to predict the deflections of beams. However, the results from these approaches varies when compared to tests. But testing is time consuming and expensive. During the initial design stages, designers would like to quickly perform various design iterations. In order to get a quick and accurate prediction, Machine Learning models are used. In this study, regression algorithms like linear, Lasso and Ridge are used to predict the deflections in three different beams: cantilever, clamped-clamped and overhang. The database for training the algorithm is generated using the principle of superposition of forces. Around 100 datasets were generated for each type of beams in excel. Python Scikit Learn library is used to train and test the regression algorithm. The root mean square error (RMSE) for the three types of beams is nearly zero. Hence, the linear regression model resulted in high accuracy predictions. This study proposed an effective model that is cheap, accurate and efficient, to help designers predict deflections at an early stage of the design.
... Extension of the fabric in the axial direction causes contraction in the lateral direction perpendicular to the direction of tensile load. This phenomenon is called the Poisson's effect, and the ratio of the lateral contraction to the extension strain is defined as Poisson's ratio [3]. This property depends on the direction in which the force is applied, as the mechanical properties of nonwoven fabrics vary in different directions. ...
The Poisson’s ratio is one of the mechanical properties of fabrics, which is a measure of the deformation during the load exertion. In this research, five groups of spunbonded nonwovens with different areal weights were investigated. These fabrics were subjected to uniaxial extension in the machine direction, bias, and the cross-machine direction. The Poisson’s ratio of spunbonded fabrics has been analyzed considering the effects of two aspects of the areal weight and the loading direction. The results of this study show that at the first stages of extension, the value of the Poisson’s ratio is relatively low, but after the rise of elongation, it increases until reaching a constant value, followed by a decreasing trend, due to the occurrence of the structural jamming. Furthermore, it was observed that the effects of the areal weight and the loading direction on the Poisson’s ratio of nonwoven fabrics were significant at the confidence level of 95%. The value of Poisson’s ratio in the machine direction is greater than the two other directions and with increasing the areal weight, the Poisson’s ratio decreases. Changes in the Poisson’s ratio versus extension and the tensile load follow a Gaussian function with a good approximation.
... The Mohr-Coulomb equations in Eqs. (1)-(3) are used for predicting the shear strength and estimating the friction and cohesion coefficients [66]: ...
... In that case, the applied load was a fixed load, and the structure's response was assumed not to change with time. Types of loading applied in the static analysis included external forces, inertial forces, non-zero displacements, and temperature for thermal strains [12]. Modal analysis was used to determine natural frequencies and mode shapes, which was the shape of the structural mode that tended to vibrate according to its frequency [13]. ...
... So, the curvature distribution would stand between the boundaries during the test from the cracking stage until the MOR stage for a specified mid-span curvature (Figures 22 & 23). Via the classical beam theory of differential equations, the curvature of a point on a curve could be simplified, as represented in equation (4), in the Cartesian coordinate with approximately 1% error from the exact solution, if the deflections of a simple span are on the order of one-twentieth of its length, as most of the inspected specimens in this research, it would be remarkably accurate [39]. According to the structural mechanics, equation (5) was obtained by Qian and Li in the UM indirect method by considering the described initial boundary to relate the load-point deflection (u) to the mid-span curvature (φ) in an FPBT with a span length of L for some SHCCs beam with the height of h. ...
... This is somewhat surprising given the simplicity of BTA and relative complexity of FEA. However, the constraints and loads we applied in our FEA simulations closely matched those of the assumptions made in BTA [8,23,85]. We essentially modelled canines as a cantilever beam in our FEA simulations, with their constrained dorsal surface and application of lateral loads. ...
Canine teeth are vital to carnivore feeding ecology, facilitating behaviours related to prey capture and consumption. Forms vary with specific feeding ecologies; however, the biomechanics that drive these relationships have not been comprehensively investigated. Using a combination of beam theory analysis (BTA) and finite-element analysis (FEA) we assessed how aspects of canine shape impact tooth stress, relating this to feeding ecology. The degree of tooth lateral compression influenced tolerance of multidirectional loads, whereby canines with more circular cross-sections experienced similar maximum stresses under pulling and shaking loads, while more ellipsoid canines experienced higher stresses under shaking loads. Robusticity impacted a tooth's ability to tolerate stress and appears to be related to prey materials. Robust canines experience lower stresses and are found in carnivores regularly encountering hard foods. Slender canines experience higher stresses and are associated with carnivores biting into muscle and flesh. Curvature did not correlate with tooth stress; however, it did impact bending during biting. Our simulations help identify scenarios where canine forms are likely to break and pinpoint areas where this breakage may occur. These patterns demonstrate how canine shape relates to tolerating the stresses experienced when killing and feeding, revealing some of the form–function relationships that underpin mammalian carnivore ecologies.
... The rotation due to slip at the column end, θ slip , is calculated by dividing δ slip by the depth of the neutral axis, c. [69]. Finally, the shear deformation was calculated by dividing the moment by the effective shear area and by the effective shear modulus [70]: ...
Externally bonded (EB) and near-surface-mounted (NSM) systems have been investigated in the literature to be
used in flexural strengthening of reinforced concrete (RC) columns. Research has shown that NSM-FRP systems
are preferred in most cases over the use of EB-FRP systems especially in flexural strengthening RC columns
against lateral loads. However, limited studies have been conducted to accurately compare the behavior of
columns strengthened with EB-FRP or NSM-FRP systems. In this study, six specimens were fabricated and tested.
To add to the novelty of this investigation, CFRP ropes were used for the first time in flexural strengthening of RC
columns against cyclic lateral loads. Two of the columns were strengthened with NSM-CFRP ropes, one with
NSM-CFRP rods, one with EB-CFRP sheet, and one with CFRP lateral confinement only. The results showed that
both EB-CFRP and NSM-CFRP techniques can improve the flexural resistance of RC columns. The percentage of
enhancement in lateral resistance ranged from 35% to 60%. Limited slippage of NSM-CFRP rods was an
advantage and led to a more ductile response. Finally, theoretical analyses were performed to predict the lateral
response of strengthened RC columns. The predicted load–displacement relationships had good agreement with
the experimental results.
... Finally, the shear deformation was calculated by dividing the moment by the effective shear area and by the effective shear modulus [70]: (22) In this study, the value of the shear area ( is equal to 5 ⁄ 6 of the cross-sectional area, and the value of the shear modulus ( ) is one half of concrete modulus of elasticity [71]. The parameters definitions are available in Table 1. ...
Externally bonded (EB) and near-surface-mounted (NSM) systems have been investigated in the literature to be used in flexural strengthening of reinforced concrete (RC) columns. Research has shown that NSM-FRP systems are preferred in most cases over the use of EB-FRP systems especially in flexural strengthening RC columns against lateral loads. However, limited studies have been conducted to accurately compare the behavior of columns strengthened with EB-FRP or NSM-FRP systems. In this study, six specimens were fabricated and tested. To add to the novelty of this investigation, CFRP ropes were used for the first time in flexural strengthening of RC columns against cyclic lateral loads. Two of the columns were strengthened with NSM-CFRP ropes, one with NSM-CFRP rods, one with EB-CFRP sheet, and one with CFRP lateral confinement only. The results showed that both EB-CFRP and NSM-CFRP techniques can improve the flexural resistance of RC columns. The percentage of enhancement in lateral resistance ranged from 35% to 60%. Limited slippage of NSM-CFRP rods was an advantage and led to a more ductile response. Finally, theoretical analyses were performed to predict the lateral response of strengthened RC columns. The predicted load-displacement relationships had good agreement with the experimental results.
... The elastic flexure formula for composite beams was employed to calculate the stress amplitudes during the fatigue testing of the coated samples [41]. The thickness of the sample was increased only by 4.5% after depositing a 140-μm AA7075 layer on the substrate. ...
The effect of cold spray coating parameters on the fatigue life and cracking mechanism of AZ31B-H24 coated with AA7075 powder is investigated. Two sets of coated samples are fabricated based on the selection of different coating parameters. An in-situ control of heat transfer is performed to obtain different residual stress states and microstructure at the aluminum/magnesium interface. Subsequently, the samples are tested under load-controlled fatigue tests at different load amplitudes. Fatigue lives are obtained and the cracking behavior of the two samples is studied and compared with that of uncoated baseline samples. It is revealed that the samples with compressive residual stress at the coating/substrate interface have significantly longer lives (approximately 85 % improvement at the same stress) compared with that of the baseline samples. In contrast, samples with tensile residual stress at the interface have similar or slightly improved lives (approximately 24 %) compared with that of the baseline samples. The cracking mechanisms of these two samples are considerably different. In the case of compressive samples, cracks initiate at the coating surface and propagate through the splat boundaries of the cold spray coating to the substrate. Conversely, in the case of tensile samples, delamination and cracking initiate at the interface and subsequently propagate to the substrate and through the splats in the coating. The different lives and cracking mechanisms obtained are attributed to the differences in the initial state of stress, details of the microstructure of the nano-size interface layer, and the morphology of the substrate grains adjacent to the interface.
... Following large scale yielding, J increases abruptly and leads to an infinite slope in the J -P curve, due to the plastification of the whole uncracked ligament. Since the CB specimens subjected to fracture under the mode I configuration experience bending, the following dimensionless normalized parameters, which are based on the Euler-Bernoulli beam theory [41] , are used in order to bring the responses of microand bulk-CB specimens on to a common ground: load P = P/ P y , J -integral J = J/ ( σ t y × l ) , and load point displacement δ = δ/l. P y = ( t × b 2 × σ t y ) / ( 6 × l ) . ...
Fracture tests using notched micro-cantilever (MC) specimens are increasingly being used to measure the fracture toughness of materials at the micro-scale. Detailed finite element analyses (FEAs) of loading of self-similar micro- and bulk cantilever beam fracture specimens using isotropic, elastoplastic constitutive models, are conducted to critically examine the validity of the toughness data obtained using MC specimens. From the simulated normalized load versus load point displacement and the corresponding normalized energy release rate versus load curves, the transition of the failure regimes from crack propagation to plastic collapse of the uncracked notch ligament are identified. While the crack propagation regime allows for the estimation of valid fracture toughness of the probed material, the plastic collapse regime does not. The effects of specimen aspect ratios, material hardening, and yield criteria on the master curves and transition point are examined. A method to interpret the failure regimes, assess the validity and size effects in micro-cantilever fracture tests is proposed. An expression is derived for the minimum size requirements of MC fracture specimens in order to get a valid fracture test. The data reported in the literature from fracture tests on bulk metallic glasses, nano-crystalline materials and ultra-fine grained materials are assessed using the proposed methodology. The present work has important implications for specimen design, interpretation of failure regimes, and potential size effects in MC fracture tests.
... The 40 displacement associated with rebar slip was determined using an equation proposed by Sezen and Moehle [60], which depends on the stress and strain developed in the steel rebar, the diameter of the rebar, and the bond strength between steel rebars and concrete. Finally, the shear deformation was calculated by dividing the moment by the effective shear area and by the effective shear modulus [61]. ...
... This pressure is applied through the solid part to the melted material. On the other hand, the critical buckling load for elastic columns is given by [83]: ...
One of the major drawbacks of material extrusion additive manufacturing (AM) is hot-end clogging. This study aims to answer the question, “How clogging happens and what thermal conditions lead to clogging during filament-based material extrusion?” Answering this question requires a clear understanding of temperature distribution inside the liquefier. However, this could not be achieved only through experimental measurements. Therefore, numerical simulations were also carried out by developing a 3D finite volume model of the hot-end. The results obtained from numerical simulations show good agreement with experimental measurements. They also give us a detailed picture of the temperature gradient near the nozzle. A series of experiments were performed to determine at what thermal conditions clogging occurs, and some criteria for avoiding clogging were presented. The temperature distribution of those thermal conditions that leads to clogging is then investigated numerically to analyze the clogging mechanism. As the results show, overheating the heat barrier increases the length of the filament, whose temperature is above the glass transition temperature. As this length exceeds a critical value, the filament buckles under the extruder motor force, and consequently clogging occurs.
Graphical abstract
... Experimental horizontal strain and shear strain, i.e. the strain functions, can be obtained from a rectangular rosette array by applying the following equations from Popov (1990): ...
En las economías emergentes, la implementación de la Gestión de Infraestructura del Transporte es una necesidad imperante. Con el propósito de utilizar de la forma más eficiente posible los limitados recursos disponibles, la tecnología surge como un aliado estratégico en dicho objetivo. Con el fin de preservar los pavimentos y puentes, diferentes metodologías han sido desarrolladas para la detección de vehículos con sobrepeso. En el presente artículo se presenta la implementación y validación del pesaje de vehículos en movimiento mediante la instrumentación de un puente en servicio ubicado en Costa Rica, con una cantidad reducida de sensores. Se utilizó el enfoque basado en áreas de influencia de ondas de respuesta de deformaciones unitarias. Dada la distribución de los sensores, minimizando los requisitos de instrumentación, se utilizaron dos tipos de deformación unitaria: horizontal y cortante. Dos camiones de calibración fueron utilizados como referencia y luego se procedió a estimar el peso del tráfico aleatorio, para confrontar dichos resultados con los datos de la estación de pesaje estática más cercana.
... By using a simple approximation of elastic energy, it can be assumed that 2 ≅ 2 / . Hence, both parameters will be inversely proportional to 2 / , which is related to the stored elastic strain energy (Popov 1998). Indeed, this energy is the primary source of force for initiating and propagating cracks within the material. ...
Cette thèse s'inscrit dans le cadre du projet Européen ATHOR (Advanced THermomechanical Multiscale Modelling of Refractory Linings). Les matériaux réfractaires sont des céramiques hétérogènes, résistantes à des températures élevées pour lesquelles, dans de nombreux cas, des microfissures préexistantes au sein de la microstructure jouent un rôle clé dans la résistance aux chocs thermiques. La Méthode des Eléments Discrets (MED) est aujourd’hui considérée comme un outil numérique majeur qui peut contribuer, à l'avenir, à concevoir des microstructures plus performantes. Ainsi, cette thèse est dédiée à la simulation numérique de matériaux réfractaires intégrant leur microstructure, leurs hétérogénéités, ainsi que la présence de fissures, et leur influence sur le comportement mécanique macroscopique. Ces travaux ont par ailleurs été réalisés dans le cadre d'un partenariat avec la société "ITASCA consultants". Au sein de l’outil Particle Flow Code (PFC), utilisé comme plateforme numérique MED, le model de contact Flat Joint Model (FJM) a été choisi car celui-ci permet de modéliser des microstructures de grains imbriqués, analogues à celles des matériaux réfractaires. Afin de développer des modèles numériques permettant de décrire les relations entre la microstructure et le comportement thermomécanique macroscopique, il est essentiel de mettre en oeuvre une approche multi-échelles, micro à macro, précise pour chacune des propriétés physiques clés intervenant dans la tenue aux chocs thermiques, en commençant par les propriétés d’élasticité. Dans cet objectif, la MED n'étant pas, à ce stade, aussi robuste que la Méthode des Eléments Finis (MEF), une approche d'homogénéisation périodique est proposée pour des milieux continus. Cette approche a ici été validée en comparant les résultats obtenus à des matériaux modèles, des modèles analytiques et MEF. A l’échelle méso-scopique, un modèle MED utilisant une approche statistique pour imiter l'influence mécanique des microfissures préexistantes est mis en oeuvre. Cette approche a également été validée par des données mécaniques expérimentales. Par la suite, afin de vérifier l'applicabilité du modèle MED proposé, des simulations de Wedge Splitting Test (WST) sont proposées pour étudier le processus de fissuration et le comparer qualitativement aux résultats expérimentaux obtenus en DIC. Finalement, un modèle hybride discret/continu (MED/MVF) est proposé pour optimiser ces simulations de WST et réduire les temps de calculs. Ces résultats clés ouvrent de nouvelles voies très intéressantes d'utilisation de la MED pour prédire le comportement thermomécanique de matériaux hétérogènes contenant de nombreuses microfissures pouvant se propager simultanément.
... Brazilian Journal of Development, Curitiba, v.7, n.9, p. 88727-88736 sep. 2021 Desta forma, um valor constante de E não seria apropriado para representar esta propriedade mecânica do material do tendão de Aquiles.De maneira alternativa, o módulo tangente pode ser definindo como a derivada local da tensão em função da deformação[8].Para o cálculo do módulo tangente, Oliveira et al. [3] apresentaram valores de BM e AST variando em função do ângulo do tornozelo durante a mobilização passiva. A AST variável foi obtida pelo coeficiente de Poisson aplicado na AST de repouso e a variação do BM por equações de regressão propostas por Menegaldo et al. [6]. ...
O Módulo Tangente parece ser a forma mais adequada para analisar as propriedades mecânicas do tendão calcanear, cuja a metodologia foi recentemente publicada (Oliveira et al., 2016). O objetivo do trabalho é investigar a confiabilidade das medidas utilizadas no cálculo do módulo tangente pela metodologia proposta: ângulo de repouso do tornozelo, braço de momento do tendão, comprimento da perna, comprimento do tendão calcanear , área de secção transversa do tendão, ângulo máximo de dorsiflexão e pico de torque passivo. As medidas foram realizadas em duas visitas ao laboratório em dez indivíduos saudáveis. A confiabilidade dos parâmetros analisados variou de razoável (com CCI de 0,523) a excelente (com CCI de 0,952) e a consistência interna encontrada foi de “moderada” a “muito alta” (alfa de Cronbach variando de 0,687 a 0,975). Os resultados indicam a possibilidade de reproduzir a metodologia e garantir resultados confiáveis na estimativa do módulo tangente.
... In this study, it is considered that the transverse shear stress is the main component that causes delamination in short-beams [18]. The samples in the current study have a circular cross-section, and, calculating the polar moment of inertia and applying it to the transverse shear stress equation [19], Eq. (1) is obtained: ...
Short-beam shear test has been used to evaluate the fatigue strength of round curved pultruded carbon fiber – epoxy matrix composite specimens in three point bending test of a convex-beam. The specimens were cyclically loaded at peak stresses from 50 to 80% of the quasi-static short-beam strength, and load ratios of 0.1 to 0.5, and damage evolution was monitored using the apparent stiffness method. Basquins’ law was used to fit the experimental S-N data. The results showed that the fatigue strength of curved pultruded composites is lower than for conventional thin flat unidirectional laminates, and less sensitive to load-ratio effects. Residual strength of pre-fatigued specimens was determined by quasi-static short-beam tests, and it sometimes exceeded the pristine material performance due to fatigue-induced strengthening phenomenon. Stress redistribution and residual manufacturing-induced stress relief due to the previous cyclic loading were found the main responsible for mitigating damage growth under quasi-static loading. Fractographic survey indicated that stress redistribution and stress relief governed the strengthening process under high-cycle and low-cycle fatigue regime, respectively.
... The ACLD treated beam is modelled by finite element (FE) method in two-dimensional (2-D) IOP Publishing doi:10.1088/1757-899X/1166/1/012001 3 xz -plane by considering the plane stress assumption [22] in y -axis (figure 1). So the state of strain/stress in terms of shear/bending counterparts (subscript s / b ) within xz -plane can be expressed as, ...
In the present work, the ascendancy of actively constrained zig-zag 1-3 viscoelastic composite (VEC) layer on hybrid damping is studied. For this analysis, structural beam is taken that consists of substrate layer/beam, constrained zig-zag 1-3 VEC layer and constraining extension actuated piezoelectric layer. The zig-zag 1-3 VEC is configured by incorporating graphite wafers in zig-zag pattern within conventional viscoelastic material (VEM). In order to investigate the hybrid damping characteristics, the finite element (FE) model for structural beam is evolved. In order to study the ascendancy of incorporating graphite wafers in zig-zag pattern within VEM layer, initially, bending and shear strain distributions are evaluated. Moreover, optimal geometrical configuration of present zig-zag 1-3 VEC layer is obtained based on maximal hybrid damping using exhaustive search optimization technique. The results reveal that the augmentation in energy dissipation or hybrid damping for the beam with zig-zag 1-3 VEC layer occurs due to rise in both bending and shear strain in VEM by incorporating graphite wafers in zig-zag pattern while for conventional VEM layer it occurs due to shear strain only. And this augmented energy dissipation ameliorates extension and shear counterparts as well as overall modal loss factor of beam with actively constrained zig-zag 1-3 VEC layer compared to conventional VEM layer.
The IoT Enabled Grass Cutter Robo-Car project represents a transformative leap in the realm of lawn maintenance, merging cutting-edge robotics with the expansive capabilities of the Internet of Things (IoT). At its core, this project introduces a state-of-the-art Robo-Car, meticulously engineered to be remotely controlled through an Android application. The crux of the communication infrastructure is a web server, with the ESP8266 serving as the linchpin by receiving signals from the server. These signals orchestrate the nuanced operations of a L298N motor driver, steering the precise movement of 100 RPM motors, and a relay module that commands the activation of the grass cutter motor. With a vision to redefine the landscape of lawn care, this project stands as an exemplar of efficiency, convenience, and remote accessibility in the realm of smart agriculture.
“Strength of Materials” provides engineering and architecture students with a clear overview of the fundamentals of this discipline and the keys for their practical application.
The understanding of the different topics is favored by the inclusion of numerous examples worked step by step.
In this research work a reliable numerical approach is developed to determine the axial and the radial forces, the strains, the stresses and the induced vibrations in vertical submersible pumps. The use of this approach in the manufacture of these pumps allows to further improve their performances in terms of head, shaft power and efficiency while increasing the reliability and the service life of the pump shaft bearings and/or bushings. Sizing starts from the design point characterized by a flow rate of 141 m3/h, a head of 92 m and a rotating speed of 3600 rpm. After determining the various geometrical parameters of the impellers, the diffusers and the shaft, a 3D model of the pump is obtained in the solid and fluid domains. Numerical simulations are carried out and the results achieved are validated comparing them with the experimental results from the Technosub company. Thus, the axial and the radial forces and the torques resulting from the analysis of the liquid flow in the impeller and the diffuser induce the loads on the pump shaft and make it possible to determine the stresses and the strains including the vibration amplitudes on this shaft. Moreover, the impacts of the outer diameter of the impellers, the number of submersible pump stages and the rotating speed on the pump performances are carried out in order to improve the design of the vertical submersible pumps.
ABSTRACT
This work describes an Alternative Algorithm for solve SPE problems.
The problem's context is represented by an economic system where
a given commodity has potential to
ow between all system's agents,
in which act in perfect competition mode. The problem's model accepts
the classical SPE's constraints in conjunction with the general
formulation of agent's non-linear price functions, in which must have
positivity, twice-di�erentiable continuity and monotonicity properties.
The Alternative Algorithm is based on Graph's theory and Matricial
representation to handle data structures to represent bipartite maximal
connected subgraphs as operands of sucessive insertion processes of
chosen arcs called \free arcs". Each augmented subgraph is considered
as a new SPE subproblem that is submitted to a series of linearization
processes. A dual matricial representation for that subproblem is
builded aiming to extract a self-dual operator that mapps a unique approximated
solution into a dual �nite-dimensional inner product linear
space, in which is spanneable by a set of maximal orthonormal basis.
The primal and dual approximations are in one-to-one correspondence.
An additional task is performed aiming to identify which arcs must be
retired from the augmented subgraph when the positivity's restriction
for their
ows are in violating phase. The linear convergence is accomplished.
The �nal solution is obtained when no more arcs are to be
inserted to any subproblems. The non-linear convergence is measured
by comparing the di�erence between linear and non-linear solutions
with a preseted error. A case study is provided after Alternative Algorithm
presentation.
Keywords: Spatial price equilibrium model, Non-linear Optimization
Problems, Mathematical Programming , Maximal connected subgraphs.
Among the methods for evaluating the nonlinear performance of structures, pushover analysis is an appropriate alternative instead of direct time history analysis. To accurately extract the capacity curve of a structure, according to the loading regulations/protocols such as FEMA-356 and ATC-40, lateral loads are incrementally applied to the structure in experimental tests until the structural failure occurs. Because of the cost and time-consuming nature of experimental tests, proposing mathematical/analytical methods could be the appropriate tools to predict the capacity curves of a system. The present study proposes a new method to find the capacity curves of cantilever steel beams based on mathematical formulations, structural analysis, and material properties. The reason to select a simple beam in this study is to shed more light on the unknown aspects of the system’s behavior. Therefore, in this research, the effect of axial load is ignored to clarify the nonlinear behavior of complicated systems such as frames. The strains, stresses, and other responses corresponding to large geometric deformations have been extracted in two cases with and without strain hardening by considering changes in the behavior of materials. The proposed method has been verified using the finite-element method with Abaqus software. The results indicate that the proposed method has acceptable accuracy and could be applied in the pushover analysis of steel structures.
This chapter explores different basic transducer designs and examines how the previously discussed elements can be combined to produce an effective underwater sonar design. It constructs equivalent circuits for transducers by combining the equivalent circuits of transducer elements. Spherical projector transducers are widely used in both commercial and military transducer applications. The chapter details spherical projectors that are filled with highly compliant air and investigates fluid‐filled spherical projectors. It then considers the impact of internal losses on the equivalent circuit and performance of an air‐backed spherical projector. Radially polarized cylindrical projectors are widely used in both commercial and military transducer applications. These types of projectors generally produce a toroidal beam pattern or, in the case of a free‐flooded cylinder with a backing plate, a hemispherical beam pattern. The tonpilz transducer device is one of the most reliable tone generators or transducers available today.
Engineering components that can be modeled as a rotating disc include the rotor of a turbine engine, saw blades, grinding wheels, and computer magnetic recording disks etc. The rotating disc is subjected to centrifugal force which tends to pull the disc in radial direction, introduces large stresses and displacements on the disc. Further the disc is mounted on a shaft by interference fit. The stresses and displacements of the rotating disc are estimated for potential boundary conditions by building a finite element model using ANSYS. The disc is meshed using SOLID45 elements by taking the rotating disc to be 3D cyclic symmetric model. The contact simulation is done for shaft and disc using surface to surface contacts in ANSYS. The linear isotropic material model is used. The model creation for the given dimension with the required material properties is done by APDL (Ansys Parametric Design Language) macro. The user inputs the dimensions of the disc in the macro, which takes care of the model preparation, mesh generation, applying boundary conditions, solution and post processing for the load case. This gives flexibility to change the parameters and material properties according to user specification and saves time for finite element model preparation.
Abstrak Kata kunci Mesin pencetak pakan, pelet, ikan lele Ikan lele merupakan salah satu jenis ikan air tawar yang jamak dibudidayakan secara komersial oleh sebagian masyarakat Indonesia. Salah satu permasalahan yang dihadapi oleh peternak ikan lele adalah tingginya harga pakan pelet ikan dan hal itu mempengaruhi penghasilan. Oleh karena itu membuat pelet sendiri adalah salah satu solusi untuk meningkatkan margin keuntungan. Metode pelaksanaan dilakukan dengan rekasaya alat pencetak pelet. Sesuai kebutuhan, tim merancang dan membangun mesin pencetak pelet berkapasitas 200 kg/jam yang berukuran panjang 90 cm, lebar 50 cm, dan tinggi 80 cm.. Pakan pelet yang dihasilkan berdiameter 4 mm dan dapat terapung di permukaan air. Hasil lain yang sangat penting adalah mitra bisa menghemat biaya pengadaan pelet ikan sebesar 35% setara dengan Rp 5.500.000,-tiap periode panen. Abstract Keywords Feed Machine, pellet, catfish Catfish is one type of freshwater fish that is widely cultivated commercially by some Indonesian people. One of the problems faced by catfish farmers is the high price of fish pellet feed and it affects their income. Therefore, making your own pellets is one solution to increase profit margins. The implementation method is carried out by engineering a pellet press. According to the needs, the team designed and built a pellet press with a capacity of 200 kg/hour which is 90 cm long, 50 cm wide, and 80 cm high.. The resulting pellet feed is 4 mm in diameter and can float on the surface of the water. Another very important result is that partners can save on the cost of procuring fish pellets by 35%, equivalent to Rp. 5,500,000 per harvest period.
Biocementation is a biochemical reaction that occurs in soil structures in which insoluble calcium carbonate forms in the soil pores and ultimately improves the soil stiffness and strength. The present study investigates this process by injecting and mixing Bacillus pasteurii into clay soils from the Meighan Desert of Iran, which contain specific salt and mineralogical compounds. Unconfined compressive strength tests were performed to evaluate the strength of the soils after being treated to a range of bacteria injection and mixing conditions. The plastic properties, pH, and electrical conductivity of the samples were measured to examine the soil changes after treatment. To address the specific regional and standard culture medium characteristics, two new culture media were prepared and tested according to the salt composition in the regional soil. Wind tunnel and flexural strength tests were also conducted to examine the sample changes after bacterial treatment. Scanning electron microscopy and X-ray diffraction analyses were applied to evaluate the microstructural changes in the samples. The method of mixing clay with bacteria was found to increase the clay sample strength by 78.5% after 28 days compared with the untreated sample. This environmentally friendly method can be used to increase soil strength and reduce wind erosion in geotechnical engineering projects.
Mathematics is part of our day-to-day life. Many field works employ extensive use of mathematics knowingly or unknowingly. Engineering field cannot be imagined without involvement of mathematics, and it forms the backbone of mother branch ‘civil engineering.’ For many peoples, applying mathematics to engineering problems found a little difficult. The reason behind this, in most of cases, civil engineering problems are not discussed with respect to their compatibility with basic mathematics which makes difficult for people to understand interlinking. The aim of this paper is to exhibit some applications of mathematics to various fields of civil engineering. Some simple and basic examples are discussed to build a bridge between civil engineering and engineering mathematics. This paper is divided into three case studies. Each case study represents application mathematics with examples in particular field of civil engineering.KeywordsEngineeringMathematicsCivilApplications
Biocomposites or green composites are mainly defined as mixture of two or more components in which any building raw materials possess large quantity as matrix and natural fibers possess in smaller quantity as reinforcement. Due to the increase in greenhouse gas emissions and the global energy crisis, the demand for composites with natural fibers and biodegradable resins is increasing due to its low cost, renewable nature, and biodegradability. This paper presents the most comprehensive review on recent studies and development of natural fibers which includes animal-based fibers and various types of plant-based fibers and their potential applications in building materials and construction.KeywordsBiocompositesMatrixNatural fibersReinforcementBiodegradable resins
Assessing potential mechanical homeostasis requires appropriate solutions to the initial-boundary value problems that define the biophysical situation of interest and appropriate definitions of what is meant by homeostasis, including its range.
Sub-micrometer-thick lithium niobate on an insulator is a promising integrated photonic platform that provides optical field confinement and optical nonlinearity useful for state-of-the-art electro-optic modulators and wavelength converters. The fabrication of lithium niobate on insulator on a silicon substrate through ion slicing is advantageous for electronic-photonic integration but is challenging because of debonding and cracking due to the thermal expansion coefficient mismatch between silicon and lithium niobate. In this work, the fabrication of thin film lithium niobate on insulator on a silicon handle wafer is achieved, informed by structural modeling, and facilitated by accommodating for dissimilar wafer bows using a bonding apparatus. Structural finite element analysis of strain energy and stress, due to thermal expansion coefficient mismatch at elevated temperatures, is conducted. High strain energies and stresses that result in debonding and cracking, respectively, are studied through modeling and reduced by selecting optimized substrate thicknesses followed by an experimental technique to bond substrates with dissimilar bows. A lithium niobate thin film with a thickness of 800 nm is successfully transferred to an oxidized silicon wafer with a root mean square surface roughness of 5.6 nm.
Current structural models used for the flexural design of prestressed concrete sleepers assume that ballast bearing support is static and located within a fixed region. This assumption implies a linear relationship between wheel load and bending moment. However, field data gathered from instrumented sleepers shows that this trend is non-linear, and the difference in flexural behavior between model predictions and field-measured demand is significant. Using back-calculation techniques and the development of a sleeper support analysis tool, this paper investigates the load-dependency of sleeper support condition. It is hypothesized that a given support condition redistributes ballast reaction forces due to the mechanical interaction of ballast particles with the sleeper’s deflected shape. It was found that redistribution of support conditions can reduce the expected flexural bending moment up to 45% when compared with moments calculated using traditional design guidelines. This effect (non-linearity) is greater as wheel loads increase. Results from revenue service field experimentation provided insight into the interaction between sleeper and ballast and serve as a foundation for the development of more complex analytical models. This will facilitate revisions to the future flexural design procedures for concrete sleepers, to ensure they are optimized for their expected service loading conditions.
The present work deals with the influence of cryogenic coolants LN2 delivered through holes made on flank surface and rake surface of tungsten carbide cutting tool inserts in turning of super duplex stainless steel (SDSS) using in-house developed cryogenic setup. Experiments were conducted with the cryogenically treated tool, cryogenically treated tool with tempering and cryogenic coolant directly passed through a modified cutting tool insert. Results are compared with dry cutting conditions. The cutting conditions are low feed rate/high depth of cut, medium feed rate/medium depth of cut, and high feed rate/low depth of cut. The material removal rate and cutting speed is kept constant under all three cutting conditions. Microstructural study of the tool as received and cryogenically treated is examined using SEM. The population of harder tungsten carbide phase (gamma phase) is found to be more in the cryogenically treated tool. Due to tempering, the hardness of insert is improved by 8% which in turn increased tool life. By direct supply of LN2 through modified cutting tool increased tool life by 23%, more than the cryogenically tempered tool. There are no appreciable changes in the temperature of the cutting tool under dry cutting and cryogenically treated inserts. However, there is a large difference observed in temperature of cutting tool when LN2 is supplied through a modified insert directly, which in turn yielded high tool life.
The first chapter introduces to major idea and the continuum mechanical background to model structural members. It is explained that physical problems are described based on differential equations. In the context of structural mechanics, these differential equations are obtained by combining the three basic equations of continuum mechanics, i.e., the kinematics relationship, the constitutive law, and the equilibrium equation. Furthermore, some explanations on the choice of the coordinate system for bending problems are provided.
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