Archives of Civil and Mechanical Engineering

Published by Elsevier
Online ISSN: 1644-9665
Publications
Article
Cotton waste results from the mechanical processing of raw cotton in yarn mills. Recycle Paper Mills constitute 30% of total pulp and paper mill segment in India. With 85% average efficiency of Recycle Paper Mills, 15% waste is produced annually. Recycle Paper Mills waste and cotton waste has been utilized to make Waste Crete Bricks. It helps in solid waste management, generate additional revenue and help in earning carbon credits. Waste Crete Bricks with varying content of cotton waste (1–5 wt.%), Recycle Paper Mills waste (89–85 wt.%) and fixed content of Portland cement (10 wt.%) have been prepared and tested as per IS 3495 (Part 1–3): 1992 standards. The characteristics of raw materials, which is the base material for Waste Crete Bricks, have been determined using XRF, TG–DTA, and SEM. TG–DTA indicate that bricks is thermally stable up to a temperature of 280 °C while SEM monographs show its porous and fibrous nature. The bricks meet of IS 3495 (Part 1–3): 1992.
 
Chronology of structural steels development.
-Mechanical properties of Weldox 1300 steel and filler metal.
-Chemical composition of Weldox 1300 steel and filler metal X96.
-Welding conditions for Tekken test.
-Results of Tekken tests.
Article
The cold cracking process in MAG welding, microstructure and mechanical properties of ultra-high strength steel Weldox 1300 were investigated. It has been shown that the microstructure of the Weldox 1300 steel is composed of tempered martensite and inside the lathes the minor precipitations mainly V(CN) and molybdenum carbide Mo2C were observed. A Tekken cold cracking test was used to assess the weldability of steel at two different net heat input and different preheating temperatures in the range of 20–200 °C. The experimental results showed that the heat input and preheating temperature decided of tendency to cold cracking and the optimal preheating temperature was 100 °C. Additionally the results revealed that the analytical formulas of calculating the preheating temperature are not useful for this kind of steel.
 
Article
The influence of the solution treatment on microstructures and mechanical properties of 2099 Al–Li alloy was investigated by means of optical microscopy, scanning electron microscopy, transmission electron microscopy and tensile properties measurement. With increasing solution temperature, the quantity of primary particles in the alloy decreased, and the degree of recrystallization gradually increased, leading to softening of solution treated alloy. Dissolution of primary particles in the solution treatment process promoted δ′ and T1 phases to precipitate during sequent aging treatment resulting in increase of strength. The number of T1 phases increased to peak value when the alloy was solution treated at 540 °C because almost no further dissolution of Cu-containing particles occurred at higher temperature. However, exorbitant solution temperature caused the drastic increase in the size and quantity of recrystallized grains that softened the alloy. Thus, mechanical properties of aged alloy were determined by two mechanisms: precipitation strengthening and solution softening. Compared with solution temperature, solution time had less effect on microstructures and mechanical properties of alloy. The suitable solution treatment for 2099 Al–Li alloy was 540 °C for 1 h, treated by which the yield strength of the aged alloy was 604 MPa with the elongation of 7.9%.
 
Article
Hot-forging process of dual-phase titanium alloy was analysed. The aim of the work concerned selected technological problems of impression-die forging. Calculation included two variants of forging with variable temperature of billet. Estimation was made based on maps of distribution of temperature, effective strain and mean stress in a part and in the tools. A verification of the results with physical modelling was also carried out. Computer simulation was made with a use of commercial program QForm2D/3D.
 
Article
The object of analysis is a plane structure reinforced by a system of thin parallel-distributed ribs. It will be assumed that the number of the ribs is very large. The thickness of neighbouring ribs can smoothly change. The aim of contribution is to derive 2D-macroscopic mathematical models describing elastodynamic behaviour of the plate structure in plane-stress state. The consideration will be based on the tolerance averaging technique 0045 and 0050. The general results of the contribution will be illustrated by the analysis of the free vibrations of a structure under consideration.
 
Article
The ineffectiveness of conventional coolants and their adverse impact on the environment have led to the use of cryogenic LN2 (liquid nitrogen) as an alternative coolant, which is effective in reducing the grinding zone temperature, and providing better lubrication, in addition to being a clean technology. The sol–gel (SG) alumina grinding wheel, with a self-sharpening characteristic, is used for the experiment. The grinding experiments were conducted on AISI 316 stainless steel under the three environments of dry, wet and cryogenic cooling. The Cryogenic coolant delivers a reduction of about 32% in the grinding forces, 30–49% improvement in the surface roughness, and 45–49% lesser temperature even at higher material removal rates. Cryogenic cooling produces fewer surface defects compared to dry and wet cooling. The effects of the LN2 delivery pressure on the machining zone, in terms of the grinding forces, surface roughness, and grinding zone temperature, were also studied.
 
– Schematic of SLM device [12]. 
SLM process parameters.
XCT porosity measurements.
Microscopic porosity measurements.
Article
Industrial tomography (XCT) is a nondestructive test method that provides information about spatial distribution of X-ray absorption in the analyzed structures. The aim of this paper was to examine the possibility and accuracy of application of XCT method for discontinuity and porosity detection in parts made of 316L stainless steel powder produced by Selective Laser Melting technology. Analysis conducted on three produced test samples showed that the application of XCT as a method of quality control of specimens produced with an additive manufacturing technology offers a wide range of possibilities to detect porosity within materials. Parameters such as the amount of porosity, pore size and pore shape are presented. Accuracy of XCT method strongly depends on the size of the samples analyzed, but the possibility of obtaining information in 3D nondestructively shows considerable advantages of XCT method over traditional metallographic cross-sectional analysis.
 
Article
The paper presents a computational approach to the process of creation of complex three-dimensional composite structures making use of STL files. The process of numerical treatment of measuring points' coordinates is shown. The construction of the model of human thigh bone head is demonstrated. Finally, the geometrical model of the object, which can be used by PATRAN system, is obtained.
 
Article
Appropriate methods and parameters best describing the surface roughness are searched for. Concrete is a heterogeneous material and various types of damage and surface cleaning cause an increase of the roughness. Surface roughness depends i.a. on the quality and method of cleaning used. Mapping the shape of the profile is usually performed using profilografs. Description of surface roughness is usually expressed via standards parameters or fractografic parameters that must be determined using the cycloid grid imposed on selected images of surface profiles. This method is approximate. Described in this article is a new method for measuring shapes which can be applied for any area (not just concrete), and most importantly, gives information about the roughness of the entire surface in an accurate manner. The calculations are made directly from geometric measurements of the whole surface, and not based on averaging the results of the selected profiles. The method uses a 3D scanner and CAD capabilities available in research centers or freeware programs.
 
Article
The article presents the experimental and numerical results of rectangular cup drawing of DC03 cold-rolled steel sheet. The aim of the experimental study was to analyse material behaviour under deformation. The received numerical results were further verified by experimental results. A 3D parametric finite element model was built using the commercial package ABAQUS. If the material and friction anisotropy are taken into account in the numerical model, this approach undoubtedly gives the most approximate numerical results to real processes.
 
Article
The article describes a possible solution of the boundary problem for the long rope and underwater hydroacoustic antenna system with density insignificantly greater than the density of the water and small rigidity. There is only known a point of rope connection to the ship and depth on which the end of the towed object is placed. The paper presents the analysis of the towed antenna system with rope and calculation form of the system, forces of weights, buoyancy force and lift with changeable longitudinal rope's tension. The results of calculations give us information about the depth of dip of the antenna end point in function of ship speed and lengths of ropes towing. Other results of antenna bending in horizontal plane allow us to define an error in measurements of antennas. Taking into account this error if will give us better accuracy of the executed measurement by the underwater hydroacoustic antenna towed by a maneuvering ship.
 
Article
In the paper, a new method (Hori and Hayashi) for the design of tooth addendum in a Mechanical Paradox 3K transmission gear was presented. A meshing scheme obtained in agreement with this method and actual meshing schemes after inclusion of generation and engagement limitations were presented. The results of calculations using a different approach proposed by the author to the problem of access/recess contact ratio equalisation were also included.
 
Article
The aim of this paper was to carry out an analysis of screw propeller 4119 using the RANS method. A computer program for creating spatial propeller geometry was developed for this purpose. Two-equation turbulence models: k-ɛ and k-ω were adopted for calculations. The calculations were performed for an isolated propeller. The results were used to determine the propeller's hydrodynamic characteristics. The calculation results were compared with experimental results.
 
Article
The paper deals with an investigation of the influence of tool shape and weld configuration on the microstructure and mechanical properties of Al 6082 alloy FSW joints. Three types of tool with different probe shapes and shoulder surfaces and two weld configurations (one-sided and two-sided) were used in experiments. It was shown that all tool types produce high quality butt joints free from defects or imperfections. The best tensile performance was obtained for FSW joints produced by a conventional and Triflute tool. The results obtained for joints produced by a simple unthreaded probe without grooves and with a flat shoulder are significantly lower. The joint configuration influenced mechanical properties – the two-sided welds exhibited lower mechanical properties due to greater heat transference into the material during the second pass. The changes in mechanical properties reflected changes in weld microstructure, in particular, the softening of the weld nugget was associated with intense dynamic recovery producing grains that were nearly free of dislocations. A hypothesis explaining the well-known differences in microstructure between the advancing and retreating sides is also advanced. The differences were predicted based on a recently elaborated coupled thermal/flow model developed for FSW joints.
 
Article
The article presents the modelling of a bus superstructure and its strength analysis and evaluates the requirements of Regulation No. 66 using the finite element method, with consideration of nonlinearity of materials and geometry. The analysis includes a strength test simulation in the form of a rollover test, which was performed in accordance with the requirements specified in Regulation No. 66 of UN/ECE and annex no. 3 of Regulation 66 of UN/ECE. The article presents the results of the dynamic analysis which uses the finite element method.
 
Article
The titanium–aluminium–niobium alloy is used in bone, dental and articular prosthetics, where high final surface quality is required. Bone scaffolds for tissue engineering require optimized cellular structures to provide pore diameters allowing the growth of osteoblasts. The aim of the presented paper is to estimate the quality of surface treatment of components with complex spatial structure, made of Ti–6Al–7Nb alloy by powder-bed selective laser melting (SLM), which is one of the additive manufacturing technologies for metal materials. Test pieces were subjected to chemical polishing to improve surface quality and remove loose powder particles trapped in the porous structure. It was found that resulting surface roughness and reduction of the number of non-melted powder particles on the scaffold surface are influenced mostly by chemical composition and concentration of the bath, as well as the method of medium delivery and exchange during the process. Further investigations were aimed at optimizing the process and increasing the number of workpieces processed in a single lot.
 
Article
In this work a microporous oxide layer was formed on two phase (α+β) Ti–6Al–7Nb titanium alloy by the micro-arc oxidation process in an electrolyte containing (CH3COO)2CaH2O and Na3PO4. The thickness of the surface layer was in the range of 2.7 μm–3.6 μm. Microstructure of the surface layer and the substrate alloy was characterized with use of scanning- and transmission electron microscopy as well as by X-ray diffractometry. The microstructure of the surface layer consisted of TiO2 rutile and anatase nanocrystals as well as of amorphous regions containing mainly Ti, Ca and O atoms and a minority of P, Al and Nb ones. The surface layer was highly porous. The open pores, with diameter up to 6 µm, were homogenously distributed in the specimen surface. Electron tomography was used to investigate the pores morphology and spatial distribution. It was found that open pores exhibited a complex geometry. The closed pores had nearly spherical shape. Adhesion of the surface layer to the titanium alloy substrate was investigated by means of the scratch-test. The value of critical load LC2=14 N indicates a good layer adhesion to the underlying substrate.
 
Article
In this work, a combined forming and fracture limit diagram, fractured void coalescence and texture analysis have been experimentally evaluated for the commercially available aluminum alloy Al 8011 sheet annealed at different temperatures viz. 200 °C, 250 °C, 300 °C and 350 °C. The sheets were examined at different annealing temperatures on microstructure, tensile properties, formability and void coalescence. The fractured surfaces of the formed samples were examined using scanning electron microscope (SEM) and these images were correlated with fracture behavior and formability of sheet metals. Formability of Al 8011 was studied and examined at various annealing temperatures using their bulk X-ray crystallographic textures and ODF plots. Forming limit diagrams, void coalescence parameters and crystallographic textures were correlated with normal anisotropy of the sheet metals annealed at different temperatures.
 
Article
Demand for better surface finish has been increasing recently for super alloys. Carbon nano tube (CNT) is mixed with dielectric fluid in EDM process because of high thermal conductivity. The analysis of surface characteristics like surface roughness, micro cracks of Inconel-825 is carried out and an excellent machined nano finish can be obtained by setting the machining parameters at optimum level. The Taguchi design of experimental technique is used to optimize the machining parameters and an L9 orthogonal array is selected. The predicted surface roughness was estimated using S/N ratio and compared with actual values. ANOVA analysis is used for finding the significant factors affecting the machining process in order to improve the surface characteristics of Inconel-825 material. Taguchi design of experiments were used to identify the best experiment which optimize the surface roughness to nano level and meet the demand of high surface finish and accuracy to great extent. AFM analysis using CNT improves the surface characteristics like surface morphology, surface roughness and micro cracks from micro level to nano level. The regression analysis are used to predict the error between actual and regression values of surface roughness using carbon nano tube as dielectric fluid in EDM process.
 
Article
Friction welded similar material (work hardened and thermally treated) alloy Incoloy MA 956 joints and Incoloy MA 956 alloy/austenitic steel X10CrNiTi 189 joints were tested. The microstructures, microhardness and tensile strength of the joints were determined. Optimum friction welding process parameters were matched. Friction welding has been found to be useful for joining Incoloy MA 956 alloys together and for joining the latter with austenitic steel X10CrNiTi 189.
 
Article
Friction stir processing (FSP) has evolved as a novel solid state technique to fabricate aluminium matrix composites (AMCs) in the recent years. FSP technique was applied to synthesis AA6082/TiC AMCs in order to analyze the effect of TiC particles, its volume fraction on the microstructure, mechanical and the sliding wear behaviour. A single pass FSP was carried out using a tool with 1200 rpm rotational speed, whose travel speed of 60 mm/min and an axial force of 10 kN to produce the composite. AMCs with five different volume fractions (0, 6, 12, 18 and 24 vol.%) were synthesized. The microstructure of the AA6082/TiC AMCs was studied using optical and scanning electron microscopy. The microhardness and ultimate tensile strength (UTS) were measured and the sliding wear behaviour was evaluated using a pin-on-disc apparatus. Thus the results revealed that the TiC particles significantly influenced the area of the composite, dispersion, grain size of matrix, microhardness, UTS and sliding wear behaviour of the AA6082/TiC AMCs. With this the effect of TiC particles on fracture surface and worn surface is also reported in this paper.
 
Article
Aluminum alloy AA7075 reinforced TiB2 particulate composites were prepared by the in situ reaction of K2TiF6 and KBF4 to molten aluminum. The prepared aluminum matrix composites (AMCs) were characterized using X-ray diffraction and scanning electron microscopy (SEM). The sliding wear behavior of the AMCs was evaluated using a pin-on-disc wear apparatus. The effect of TiB2 particulate content (0, 3, 6 and 9 wt%) and temperature (30, 60, 90, 120, 150, 180, 210 and 240 °C) on wear rate and worn surface of the AMCs were studied. The results indicated that TiB2 particles were effective to enhance the wear resistance of the AMCs at all test temperatures studied in this work. The wear rate of the AMCs increased when the applied temperature was increased. The in situ formed TiB2 particles pushed the transition wear temperature by another 30 °C. The wear mode was observed to be abrasive at room temperature and metal flow at high temperature.
 
Article
The thermovision method was applied for determination of the temperature of grinding wheel during abrasive cutting. Abrasive cutting of steel workpieces by using grinding wheels purchased from 3 different manufacturers was conducted under different conditions. Temperature distribution along the grinding wheel circumference and along its radial cross-section was determined. The relative efficiency of grinding wheel was estimated.
 
Article
The present work discuss criteria of the cutting process optimization using the original BorJet method that allows the suspension abrasive-water jet and the suspension hybrid water jet to be formed. Results of optimization investigations carried out on the base of criteria for minimizing the costs of abradant consumption and the total costs of machining are presented too.
 
Article
The article presents an experimental study of slide bearings operating in lubricant contaminated by Al2O3 abrasive particles. The aim of this work was the comparison of wear resistance of slide bearings with different surface geometry on the journal. It was found that helical groove on the journal significantly reduced wear of sliding pairs. The results of experiments showed that groove cross section area and helical groove lead affected abrasive wear. Valuable results concerning the sleeve wear reduction were obtained with respect to bearings with textured journals.
 
Article
The paper presents properties and operational conditions for a high-pressure hydro-abrasive jet used for surface treatment. Methods of the assessment of abrasive grain distribution in such a high-pressure jet are discussed in. Basing on experiments and analytical consideration, dependences occurring between grain's traces distribution after hitting the surface and grains distribution inside such a jet were evaluated. Formulas derived on that let to calculate grains number and their distribution in a jet basing on their traces left inside the surface after single jet spray passage upon treated material. The present findings illustrate conditions necessary to form the hydro-abrasive jet with the most favourable distribution of abrasive grains conditioning the efficiency of surface treatment.
 
Article
The paper presents some problems connected with the topography of coated abrasives. Various classes of coating are discussed, ranging from conventional single-layer ones to modern engineered coatings of the TRIZACT type. Actual parameters of the active face for various makes are given. Principal in-service properties of abrasive belts are discussed: instantaneous grinding efficiency and variation in surface roughness of the machined workpiece. A grinding process model is outlined which, after completion, will be capable of controlling precisely automated grinding operations using coated abrasives.
 
-Properties of the polyurethane foams. 
Article
In this article, some theoretical relations are derived to predict instantaneous crushing force and absorbed energy during initial fold formation in polyurethane foam-filled quadrangle tubes under the axial crushing load. Theoretical analysis is performed based on the energy method. In the theoretical analysis, crushing wavelength is considered as a constant parameter through the process and as a function of column geometrical dimensions. In the analytical calculations, interaction effects between the polyurethane foam and inner wall of quadrangle tubes are considered and a formula is presented to predict absorbed energy by the interaction effects. In the experiment part, some foam-filled specimens were prepared and axially crushed to obtain experimental diagram of crushing force versus axial displacement. Comparison of the theoretical predictions of crushing force and absorbed energy with corresponding experimental results showed a good agreement. Also, it was found that theoretical predictions by considering the interaction effects have a better correlation respect to the experiments.
 
Article
On-line condition monitoring system for railway hydraulic shock absorbers is presented. The shock absorbers are used for controlling the yaw movement of the bogie, highspeed ICE II trains. Uncontrolled yaw (hunting) movement can cause the instability of the bogie, which may lead to the derailment of the train. The hydraulic shock absorbers are the devices widely used in automotive and railway applications. They are the subject of regular servicing. The railway shock absorbers are tested in the special testing rigs after dis-asseblying from the train. The testing procedure is very expensive and time consuming and generates high idle cost. Application of the condition monitoring system of the anti-yaw shock absorbers can increase the safety and reduce the maintenance costs of the train. The train operator will be informed about the condition of shock absorbers, thus the shock absorbers will be replaced if needed, not according to the mileage schedule. The thesis deals with the condition monitoring system for the choice of the measured variables, which describe the properties of shock absorbers. The choice is based on numerical and laboratory experiments. The testing has been performed on the dampers with simulated failures. The performance of shock absorbers can be described using the graphs on the phase plane, combining the force acting on the piston rod and the velocity of the movement between piston and cylinder. The artificial neural networks (ANN) have been successfully applied in the inference engine. The thesis presents the results of the learning of the neural networks and the results of validation testing.
 
Stress-strain dependence for foams with different densities [13] a) d)
Parameters describing capacity to absorb energy by tested tailored blanks
Article
This paper presents the key aspects of the use of thin-walled sections for collision energy absorbing components. The process of deformation of thin-walled structures and the parameters expressing their energy absorption are described in detail. The research on improving the energy absorption of thin-walled sections, through the use of, e.g., tailored blanks, polyurethane foams and mechanical joining methods, conducted for many years in the Institute of Production Engineering and Automation at Wrocław University of Technology is reported.
 
Article
The problem discussed in this paper runs on propagation of disturbances in the segmental rod of slowly varying cross-section area. The rod is made of three homogeneous and isotropic hyperelastic materials. This paper employs an approximate form of analysis based on the assumption of one-dimensional stress to find the transport equation for the intensity of the incident, reflected and refracted acceleration wave. Moreover, the numerical analysis of the problem of propagation of the acceleration wave in the thin segmental elastic rod of slowly varying cross-section was made. Results are illustrated for Murnaghan's nonlinear elastic materials.
 
Article
The paper presents the methodology of analyses and estimation of the accident situation in the building industry. The indices, elaborated by the author, which enable to analyse the accident situation in the building industry as a static, homogeneous phenomenon, as a static non-homogeneous phenomenon and as a dynamic phenomenon, are the base for the above methodology. The analysis and estimation of the accident situation in the building industry were done on the grounds of the statistical database, published by the GUS (The Central Statistical Office). The indices values of the accident situation, suggested for the estimation of the accident situation, were calculated and next the mathematical model of the development tendency of the accident situation was elaborated. The model consists of two parts: i.e. the model of the development tendency (which is m-degree polynomial) and the model of the general downward or upward tendency of the analysed phenomena described by the linear function.
 
Article
A thorough analysis of the accidents in the Polish building industry in years 1992–2004 is presented. The accident situation, if assumed to be a homogeneous phenomenon, is estimated based on the accident rate of minor, serious and fatal accidents and all the accidents jointly as well as based on the accident seriousness index. However, the accident situation is not a homogeneous phenomenon. The frequency of the particular kinds of accidents and their structure change over the years. The standardised accident rate (which takes into account all the kinds of accidents and their structure at the same time) is proposed for the estimation of the accident situation treated as a nonhomogeneous phenomenon. It is constructed the model of development tendency for a phenomenon according to the information on the accident situation expressed by the accident rate and the accident seriousness index in the years 1992–2004.
 
Article
Theoretical and numerical research into the stability and free vibrations of a slender system in the form of a hydraulic cylinder subjected to Euler's load was carried out in this paper. The rigidities in the constructional nods realising the load of the considered system were taken into account in the system. Both rotational and translational springs were applied to the loading nods. Regions of the flexural rigidity asymmetry factor for the piston rod and cylinder, where the system is subject to damage as a result of stability loss, were determined in the frame of numerical research into the hydraulic cylinder. In this paper critical load and characteristic curves were also determined in the plane: load–natural frequency. These two quantities were determined for different parameters of the system: the flexural rigidity asymmetry factor for the piston rod and cylinder, the degree of coverage of cylinder, the rigidities of the rotational and translational springs, and the total rigidity factor of the system.
 
Article
One of the basic exploitation decision is to choose successful maintenance strategy. A lot of maintenance models accept an assumption that unlimited resources are necessary to make all maintenance actions in the system. This assumption, however, is not accepted by all authors, because usually resources are used according to needs and replenished again. The thesis concentrates on the problem of spare elements provision in the technical systems, when elements are critical from the up-time point of view. Based on the research we can conclude that if one chooses the best inventory order level and order quantity, one should take into consideration reliability characteristics of provisioned system. When the possible severe consequences of system down-time are taken into account, the best parameters of system procurement policy change in comparison with reference models.
 
Article
Development of the rheological model of copper based alloys, accounting for the state of the solid solution prior to deformation, is the objective of the paper. Two alloys are considered, Cu-1%Cr and Cu-0.7%Cr-1%Si-2%Ni. Plastometric tests were performed at various temperatures and various strain rates. Different preheating conditions before the tests were applied aimed at investigation of the effect of the initial microstructure on the flow stress. Three different rheological models for the investigated alloys were developed using inverse analysis of the tests results. Accuracy of the inverse analysis for various models was compared and the best model was selected. This model allowed comparison of the flow stress for various preheating schedules at different temperatures and strain rates, including also those which were not applied in the plastometric tests. Developed models were implemented into the finite element code FORGE based on the Norton-Hoff visco-plastic flow rule and simulations of forging of the alloys were performed.
 
Article
An energy criterion of fatigue crack propagation in the isotropic body has been formulated. It is based on the first principle of thermodynamics as a balance between energy variation rates (work of external forces, energy of body deformation, fracture energy, heat energy of the body) and the surface change due to fatigue crack under a cyclic loading. Finally, a kinetic equation of fatigue fracture as an analytical relation between the rate of fatigue crack surface propagation and the dissipation energy of plastic deformation in the precracked zone has been obtained. The method of an approximate solution of such an equation and determination of the period of precritical crack growth has been suggested. This method is based on the assumption that kinetics of the surface variation of the crack studied is close to the variation of a round crack with the same surface, but the solution for a round crack is given in a closed form. The validity of this method has been confirmed in the case of an elliptical crack. A new method of constructing kinetic fatigue fracture diagrams (KFFD) has been presented on the basis of measurement results of hysteresis loop area for the isotropic body with an internal flat crack under cyclic loading. For the experimental verification, the results of fatigue crack propagation studies for 18G2A and 40H steels have been utilized. In contradistinction to the force factor Kmax, the energetic parameter ΔH describes synonymously the propagation rate of the fatigue crack independently of a cycle asymmetry R. The linear dependence of crack propagation rate da/dN on energy dissipation of plastic deformation before the crack tip for one loading cycle has been discussed with taking into consideration the consequences for fitting models in double logarithmic axes.
 
Article
Energy methods in acoustic were introduced more than 40 years ago but new techniques of data analyses can give new possibility for hydraulic system health assessment. Possibilities of applying energetistic techniques to the measurement of complex vibroacoustic processes are presented using as an example a hydraulic feeder. These research methods open up new prospects for the reduction of noise emission in hydraulic machinery and equipment. The described vector techniques of locating sound sources by means of an acoustic probe and a measuring plane antenna deserve special attention. As a result of the measurement a distribution of the intensity of emissions originating from different parts of the source is obtained in the form of emission maps. The techniques can be applied to any object (e.g. a pump, a motor) to determine the main sources of noise emission and then this information can be used to improve the object's design. This paper is based on research in the fields of the design and operation of hydraulic systems, conducted for many years in the Institute of Machine Design and Operation at Wrocław University of Technology.
 
Article
Application of the acoustic emission method (IADP), to the analysis of crack initiation and growth in concrete and reinforced concrete beams is presented in the paper. This method is based on the idea that every active destructive process becomes a source of acoustic emission. Comparing AE signals, generated within structures under service load, with previously created database, one can identify the processes of active deterioration occurring in an element. They can be located on the basis of the difference in the time, that AE signal reaches the sensors with known wave velocity. Because the cracking process (micro-cracking) occurs in concrete already at the maturing stage, experiments were performed on unloaded concrete members just after concreting (when shrinkage occur) as well as on concrete beams (in technical scale) subjected to continuous loading. It was found that using the IADP method, it was possible to detect and locate creation of micro-cracks (not visible on the member surface) and initiation and growth of cracks, which are visible on the element surface.
 
Article
The work aims to experimentally validate the identification and location of destructive processes in reinforced concrete structures using the method based on the measurements of acoustic emissions generated by those processes. The system that employs the method was presented in works Gołaski et al. (2010) [3], Gołaski et al. (2006) [4] and Świt (2008) [11]. As it is very difficult to document the results obtained with the acoustic emission (AE) method, the validation of the process was conducted. The tests involved reinforced concrete beams loaded until failure. The measurements of acoustics emission were taken continuously, at the same time the strains in the beam lateral surface were recoded using 3D optical scanner (Aramis). The comparison of the results demonstrated that the recorded acoustic emission signals really correspond to the process of crack initiation and development. It was shown that the AE method not only identifies the process of formation of cracks, but also makes it possible to locate them.
 
Article
This paper presents the results of an investigation of the grinding wheel wear in a peripheral surface grinding process. During this investigation varying geometrical parameters of an active grinding wheel surface have been measured and the components of the grinding force and acoustic emission signal have been recorded. On the basis of these output quantities an analysis has been conducted of an acoustic emission descriptor's practicability, i.e. a root-mean-square (RMS) value, to characterize the cutting abilities of a grinding wheel in the time progress of its work. This article also presents a new energy coefficient, which determines the rate of grinding wheel wear in the form of a RMS value of acoustic emission signal falling on a contact surface of a grinding wheel. Moreover, the article presents some examples of a correlation between the root-mean-square value of acoustic emission signal and the surface roughness of a workpiece, which shows that the parameters of acoustic emission signal can be a useful tool to monitor the surface roughness during the grinding process.
 
Article
The paper focuses on the propagation of 1-D acoustic waves in an elastic isotropic material with the elastic potential proposed by Blatz and Ko [1]. Two special models of materials are described by this potential: foamed polyurethane elastomers and solid polyurethane rubbers. The problem of reflection and transmission of 1-D acoustic waves at the interface of two different media and the problem of multiple reflections in an elastic layer of finite length bounded by two elastic half spaces are discussed. The standard procedure for the linearisation of equations of motion was used. This approach is based on the assumption that small, time-dependent motions are superimposed on large static deformations.
 
Article
The present study deals with crush tests of concrete cylinders confined by shape memory alloy (SMA) wires. Two cases were considered. First, an active confinement was achieved by wrapping a wire previously prestrained in martensitic state and then subjected to the memory effect. Second, a passive confinement was obtained by using the same SMA, but in austenite state. For comparison purpose, an unconfined cylinder was also tested. The influence of the unwrapped zones of the confined cylinders was also investigated, leading to the use of a specially designed device to avoid premature failure in these zones. The comparison between active and passive confinements was investigated. The test results show that stiffness, strength and ductility are significantly improved in the case of the active confinement.
 
Article
Deterioration in structures starts from meso-scale defects on vulnerable joints where damage evolution becomes main reason of fatigue accumulation. Therefore analyses on structural failure induced by fatigue accumulation must be carried out in multi-scale. This paper is aimed to provide a multi-scale computational approach for structural failure analyses. Scale coupling method based on numerical integrated constraint equations is developed. This scale coupling method can guarantee sufficient computing precision when material at the trans-scale boundary keep elastic. However in structural deterioration process, material nonlinearities can evolve to the trans-scale boundary, thus make this scale coupling method invalid. A methodological strategy considering adaptive trans-scale boundary is proposed to deal with the extension of local nonlinear response during analyses. With application of the multi-scale modeling and computation strategy developed in this paper, failure processes of a beam component with defect and a longitudinal stiffening truss are analyzed. Results show that, damage evolution has acceleration effect on macroscopic deterioration of structure property, and localization phenomenon of damage evolution is obvious. Comparison of failure route of upper and bottom joints of the truss shows different deterioration process.
 
Article
The paper presents the process of selection the foundation instalment alternative, which have to be the most appropriate and safe for building which stands on the aquiferous soil. The selection is based on a set of criteria: costs of instalment, instalment duration, the complexity of decisions, advantages and disadvantages of decisions, transferability and maintainability of installed foundation system, past experience implementing the approved decisions, etc. The criteria for evaluation and their importance are selected by taking into consideration the interests and goals of the client as well as factors that influence the efficiency of construction process and safety of future building. The solution of problem was made by applying Additive Ratio ASsessment (ARAS) method. The proposed technique could further be applied to substantiate the selection of effective alternative of structures, technologies, investments and etc.
 
Article
The paper contains results of studies on the formation of oxide layers on X10CrMoVNb9-1 (P91) steel long-term operated at an elevated temperature. X10CrMoVNb9-1 steel operated at the temperature of 595 °C for 54,144 h was the studied material. X-ray structural examinations (XRD) were carried out, microscope observations using an optical and scanning microscope were performed. The native material chemical composition was analysed by means of emission spark spectroscopy, while that of oxide layers on a scanning microscope (EDS). Mechanical properties of the oxide layer – steel (substrate) were characterised on the basis of scratch test. The adhesion of oxide layers, friction force, friction coefficient, scratching depth was determined as well as the force at which the layer was delaminated. It has been found that the oxide layer formed under the influence of applied pressure is more degradeted in the areas where are porous and cracks.
 
Article
The main aim of the present work is to predict the formability of adhesive bonded sheets and validate the same with experimental results at different adhesive properties. The tensile and in-plane plane-strain formability tests are carried out to predict the formability of adhesive bonded sheets. The forming limit strains are predicted using thickness gradient necking criterion (TGNC) and effective strain rate criterion (ESRC), and validated with the experimental limit strains. A simulation methodology has been analyzed thoroughly in the present work, and the prediction accuracies are compared and discussed. The results show that the adhesive bonded blanks show improved elongation and forming limit strains as compared to un-bonded base materials with increase in hardener/resin ratio of adhesive. The true stress–strain predictions are accurate as compared to experimental data. There is a moderate difference in adhesive bonded sheets limit strains between predictions and experiments. This may be due to the absence of interface bonding between adhesive and base materials during predictions. The necking criterion, TGNC, shows better prediction as compared to ESRC.
 
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This paper presents the analysis of the effect of surface topography on shear strength of lap adhesive joints from steel S235JR. Steel surfaces were prepared to bond with various methods of mechanical treatment. It was found after using the linear correlation method that strengthening properties of tested joints are strongly correlated with hybrid surface topography parameters. Shear strength of milled adherends can be increased as a result of subsequent grit blasting.
 
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A discernible increase in importance of the methods used to evaluate and to control industrial processes has been observed over recent years. More and more frequently, companies utilize advanced methods of non-destructive testing to be competitive on the market and to provide high quality products. Thus, constant qualities of each single product are guaranteed and company's reputation is strengthened. This paper supplements various investigations and potential applications of ultrasonic testing to analyze imperfections in adhesive joints in practice. The findings should extend a relatively scarce knowledge on potential use of ultrasounds to determine the types and sizes of defects in adhesive joints.
 
Article
Belt conveyors are commonly used in-factory transportation devices built of sections of belt (e.g., a fabric-rubber belt) bonded into a continuous loop. Conveyor belt joints are exposed to substantial dynamic loads during the long time of their operation. Taking into account the fact that ensuring a high durability of conveyor belt joints is tantamount to guaranteeing their reliable operation and that the results of research conducted so far fail to provide unambiguous solutions to a number of problems that emerge in this case, it is advisable that advanced studies using computer techniques should be conducted within this area. Of particular help in the search for new structures and optimum methods for joining conveyor belt sections is finite element analysis, which, however, entails a number of problems. This paper describes the circumstances of occurrence of these problems and potential solutions to them. One important problem in FEM modeling is appropriate definition of the models of the analyzed materials. In the case of conveyor belt adhesive-bonded joints composed of rubber and a gum rubber adhesive, the analyses found in the literature, as a general rule, assume the hyperelastic material model based on the Mooney-Rivlin law, which, however, is a fairly arbitrary choice made without verification against actual strength test data. Rubber is a unique material, capable of very large deformations, by virtue of which it is counted among hyperelastic materials. Such materials require appropriate constitutive models and a reliable choice thereof in each particular case. Adequately precise modeling of the behavior of rubber materials still remains an open question. However, access to strength test data makes it possible to check experimentally which of the available theoretical models best reproduce the behavior of the modeled material. For that purpose, the available hyperelastic material models were tested separately for each constituent rubber material of the analyzed conveyor belt adhesive joint. The models were assessed with regard to the degree of their conformity with experimental data by analyzing the behavior of the hyperelastic material in a given case based on the constructed reaction curves using selected strain energy potentials for the available test data.
 
Top-cited authors
Edmundas Kazimieras Zavadskas
  • Vilnius Gediminas Technical University
R. Kawalla
  • Technische Universität Bergakademie Freiberg
Zenonas Turskis
  • Vilnius Gediminas Technical University
Roman Kuziak
  • Instytut Metalurgii Żelaza
Edward Chlebus
  • Wroclaw University of Science and Technology