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Design of dimpled tubular structures for energy absorption

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... The experimentally validated FEM results showed that the collapse of axially crushed circular tubes could be guided by the pre-folded origami patterns, along with significantly enhanced energy absorption capacity. Later, Yang et al. [16] proposed another novel tube with predesigned ellipsoidal dimples on the tube surface. The results showed that with proper parameter designs the initial peak force and the fluctuation in the plateau region could be significantly reduced, without substantially sacrificing the mean crushing force. ...
... The full-diamond tube [15] was composed of Yoshimura-pattern, which had been found in axial crushing tests of circular tubes [17]. The dimpled tube [16] consisted of ellipsoidal dimples with staggered vertical and horizontal patterns concaving outward and inward. The new origami tubes studied in this paper were designed with the same dimensions as the dimpled ones with the height (H) of 100 mm and the diameter (D) of 47.75 mm. ...
... The finite element modelling was validated by uniaxial compression tests on 3D printed brass tubes following the previous work by the authors [16]. The tests were conducted on MTS machine (type 810) with the crushing speed setting at 10 -4 m/s to guarantee the quasi-static condition. ...
Conference Paper
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In this paper, the crushing performance of two novel types of tubular structures with predesigned Yoshimura-pattern and ellipsoidal dimples were studied by using finite element modelling and compared with conventional circular tubes. The influence of structural arrangement of representative structural units and material properties on the mechanical response of full-diamond tubes was identified. The results showed that properly designed origami tubes had substantially lower initial peak force, higher mean crushing force and remarkably less fluctuation of crushing force than the conventional circular and dimpled tubes. Moreover, the mean crushing force of origami tubes were highly sensitive to material constitutive relations.
... Using different patterns, Yang et al. [108] proposed a novel type of tubular structure, in which predesigned ellipsoidal dimples were introduced into conventional circular tubes. The proposed tubes were manufactured using a 3D printing technique. ...
... Therefore, Tian et al. [123] comprehensively investigated the crushing behaviour of thin-walled Table 6 Energy absorption characteristics of the folded tubes. [108] tubes with non-uniform groove depth under the oblique loading condition. They indicated that tubes in which the groove depth decreased from the loading end to the fixed end had the best performance, and vice versa. ...
... The final crushed displacement was set as 90 mm, i.e., 90% of the initial height of specimen. The material properties defined in the modelling used the true stress-strain curve obtained from uniaxial tensile tests on brass dog-bone specimens [27], and the mean values of the mechanical properties were: density, ρ = 8671 kg/m 3 ; Young's modulus, E = 49.51 GPa; and yield strength, σ y = 138.62 ...
... where, σ was the mean stress in the strain range 0 ≤ ε ≤ ε u ; and ε u was the ultimate strain for the material, which was calculated by the energy efficiency method [28] based on the engineering stress-strain curves obtained from uniaxial tensile tests on brass dog-bone specimens [27]. ...
Article
Three novel types of multi-cell tubular structures with pre-folded origami patterns were proposed in this paper, aimed at reducing the initial peak force and the crushing force fluctuation while maintaining or increasing the specific energy absorption during uniaxial crush. Experimentally validated finite element modelling was conducted to study the influence of geometric parameters on the mechanical properties. Optimal designs were obtained through multi-objective optimization. The results showed that predesigned origami patterns governed the buckling process of the tubes and quintuple-cell origami tubes could absorb the highest energy in crush with significantly reduced initial peak force and the crushing force fluctuation.
... Ren et al. [97] established two tubular structure models by random cut method [98] and vertical-horizontal (V-H) cut method. While previously mentioned auxetic tubular structures are either porous or comprise at least two phases, a nonporous auxetic tubular structure was proposed by Yang et al. [99,100], in which predesigned ellipsoidal dimples were introduced into conventional circular tubes. It's noted that the auxetic behaviour is induced by an ovel mechanism which exploits the out-of-plane deformation of the spherical dimples. ...
... To overcome these shortcomings, many methods have been proposed to improve the design. Yang et al. [100] systematically investigated the influence of different design parameters on the energy absorption of dimpled tubes via numerical simulations and experiments. It is found that properly designed dimpled tubes had substantially lower initial peak force and remarkably less fluctuation in the crushing force than circular tubes, without significantly sacrificing the mean crushing force. ...
Article
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Auxetic materials and structures have attracted increasing attention because of their extraordinary mechanical properties. Various types of auxetic tubular structures have been designed and studied in diverse fields, including mechanical and medical engineering. In this paper, design methods and advanced manufacturing technologies of auxetic tubular structures are extensively reviewed, including various types of cellular auxetic tubes, nonporous and porous auxetic tubes, macro and micro auxetic tubes. Furthermore, auxetic behaviour, mechanical properties and potential applications of auxetic tubular structures are elaborated. Finally, the challenges and opportunities on the auxetic tubes are discussed to inspire future research work.
... The fundamental principle of origami is to transform a flat sheet square (2-D) of paper into a finished sculpture (3-D) through folding and sculpting techniques along pre-defined creases. Because of its unique properties, origami has been imitated and developed to design foldable mechanisms ( Hanna et al., 2014), self-deployable structures (Delimont et al., 2015), robots (Jayaram and Full, 2016), self-folding structures ( Na et al., 2015), metamaterials ( Overbelde et al., 2017), energy absorbing structures ( Yang et al., 2016Yang et al., , 2017 and to solve plant structure folding (Couturier et al., 2013), soft matter folding ( Lin et al., 2016) and even protein folding problems (Gethin and Sambrook, 1992). From an engineering viewpoint, mechanical properties of the crease for designing origami structures are of significant importance, which should be fully understood and characterised. ...
Article
In this study the mechanical behaviour of a creased thin strip under opposite-sense bending was investigated. It was found that a simple crease, which led to the increase of the second moment of area, could significantly alter the overall mechanical behaviour of a thin strip, for example the peak moment could be increased by 100 times. The crease was treated as a cylindrical segment of a small radius. Parametric studies demonstrated that the geometry of the strip could strongly influence its flexural behaviour. We showed that the uniform thickness and the radius of the creased segment had the greatest and the least influence on the mechanical behaviour, respectively. We further revealed that material properties could dramatically affect the overall mechanical behaviour of the creased strip by gradually changing the material from being linear elastic to elasticperfect plastic. After the formation of the fold, the moment of the two ends of the strip differed considerably when the elasto-plastic materials were used, especially for materials with smaller tangent modulus in the plastic range. The deformation patterns of the thin strips from the finite element simulations were verified by physical models made of thin metal strips. The findings from this study provide useful information for designing origami structures for engineering applications using creased thin strips.
... They found that the patterned tubes exhibited a lower IPCF and more uniform crushing load compared with the conventional tubes. Yang et al. [18] introduced the pre-designed ellipsoidal dimples into the conventional circular tubes. They demonstrated that the dimpled tubes had substantially lower IPCF and remarkably less fluctuation in the crushing force than the conventional circular tubes. ...
Article
In this study, a new tubular corrugated configuration mimicking the coconut tree profile, here named “conical corrugation tube” (CCT), was proposed, in an attempt to enhance the energy absorption, minimize the initial peak crushing force, and stabilize the crushing process. The effects of geometrical features, especially tapered angle and wavelength of CCTs on the deformation mode and energy absorption characteristics, were investigated through a series of numerical simulations. The results showed that the deformation modes of CCTs could be mainly classified into four modes, which were clearly influenced by the tapered angle and the wavelength of the CCTs. Moreover, the initial peak force of the CCTs was reduced significantly compared with that of the circular straight tube and the tapered tube. In addition, the undulation of the load-carrying capacity parameter, which is used to evaluate the stability of the crushing force, is minimized, and the CCTs produced smoother force-displacement curves compared with the circular straight tube and the tapered tube. Finally, a theoretical model was proposed to predict the mean crushing force of CCTs under dynamic impact loading. The theoretical results showed a good agreement with the numerical results.
... For a lower bound design, two equations were extracted from the results in order to generalise the response of such structures. Yang et al. (2017) designed and tested a dimpled body for tubes to obtain their energy absorption and they concluded that dimpled structures had a significantly reduced initial peak load compared with intact tubes. ...
Article
This study was conducted using finite element analyses on CHS steel tubes with geometric variables. The ultimate capacity and buckling modes were evaluated and discussed in this paper. The effect of dent-shaped damages was assessed for different models with a varying slenderness, and the buckling behaviour was compared for such models. In general, the dent imperfection appeared to have a moderately reducing effect on the capacity. Yet, a reduction of 25% for the largest dents was found in slender models, which is significant when design and/or rehabilitation of these elements are taken into consideration. Very good agreement was seen comparing experiments and the present models demonstrating that the present FE approach was capable of being employed to examine the buckling response of dented cylindrical shells.
... Thin-walled structures are wildly used as energy absorption devices to protect the passengers and reduce the financial loss in the case of vehicle collisions [1]. Recently, considerable researches were conducted on the design of the thin-walled structures with complex geometry to achieve a higher energy absorption capacity, such as multi-cell tubes [2][3][4], dimpled tubular structures [5], functionally graded structures [6][7][8] and architected polymeric sandwich panels [9]. Complex manufacture process, such as wire cutting, and additive manufacturing technology, were employed to manufacture those structures, which significantly limits their real world application. ...
Article
Cruciforms are frequently used as energy absorption components in engineering structures. The kirigami cru-ciforms (KCs) are designed by kirigami approach to simplify the manufacture process and reduce the initial peak force. However, the mean crushing force of KC is less than half of that of conventional cruciform (CC), which is negative for energy absorption purpose. The weak interaction between two component plates (plates A and B) in KC (no material connection) is a crucial factor for the decrease of mean crushing force. Therefore, laser welding technology is employed to enhance the connection between plates A and B by applying welding lines on the intersection line between components. Detailed analyses concerning the welding lines and boundary constraints are conducted to investigate the effect of connection between plates A and B. The results show that the mean crushing force of KC is close to that of CC if these conditions are met: the location of welding line is at the center of intersection line, and the length of welding line is no less than 30% and 43% of the length of cruciforms without and with symmetric boundary constraints on outside flanges, respectively. The conclusions indicate that the energy absorption capacity of thin-walled structure can be tuned by adjusting the connection strength between components in an energy absorption system.
... Generally, the shape of the slit of the auxetic tubular structure is predesigned. Recently, inspired by origami art and perforation techniques, many researchers create a variety of auxetic tubular structures with new perforation pattern design (Yang et al., 2016(Yang et al., , 2017. These perforated shapes are generally arranged in order. ...
Article
Purpose This paper aims to study the tensile performance, deformation characteristics, auxeticity and stability of different auxetic tubular structures generated by cutting method and pattern scale factor (PSF) method using validated finite element analysis. Design/methodology/approach Two types of auxetic tubular structures were designed by a coordinate transformation method and the PSF adjustment method, respectively. ABAQUS/explicit solver was used for the large deformation analysis and the displacement of key nodes was extracted to calculate Poisson’s ratio value and evaluate the deformation of tubular structures. Findings The random cut method was not suitable for designing auxetic tubular structures. Vertical and horizontal cut approach was suitable, but the change of the tubular diameter was lower than the tubular structures generated by the PSF adjustment method. Research limitations/implications Simple ways to generate auxetic tubular structure, which can be made into intelligent and foldable equipment, such as annuloplasty rings, angioplasty stents and oesophageal stents. By combined with shape memory polymer, various smart tubular materials and structures with various functions can be designed, especially in medical scaffold and other medical equipment fields. Originality/value The auxetic characteristic of tubular structure designed by using random cut method has been investigated for the first time. The outcome of this study would be very useful design tubular structures with better mechanical properties.
... In fact, besides the above methods, there are many other ways to induce the tubes to deform in stable and progressive mode. Such as adding holes [26], grooves [27], tendons [28], corrugations [29][30][31][32] and origami features [33][34][35][36] on the wall, or diaphragms [37] and ribs [13,38] inside the tube. However, while these methods cause progressive deformation, they reduce the energy absorption efficiency. ...
... The whole bottom half of the defective empty tube are dominated by the X-shaped dentinduced plastic hinge ( Table 1). The collapse of the plastic hinge leads to a lower and much flatter stress plateau (0.10 < ε < 0.45, red curve in Fig. 2c), which is consistent with previously reported results [38,39]. When the curved and extended dent is in contact with the bottom cap at ε around 0.45 (Table 1), the tube stiffness increases. ...
... Recently, Song et al. [21] and Yang et al. [33] investigated square and circular tubes with origami patterns. All of the results showed that these tubes performed better in terms of energy absorption with lower F max and higher F m compared to conventional tubes. ...
Article
Full-text available
An origami crash box (OCB) has a desirable crashworthiness performance because it is inclined to deform in the diamond mode (DM) with a low initial peak force Fmax and high mean crushing force Fm. Theoretically, if an OCB whose shape approaches that of a conventional tube deforms in DM, the energy absorption will be the highest. Whereas, an OCB can deform in an undesirable incomplete diamond mode when its shape approaches that of a conventional tube. Additionally, the manufacture of OCBs is still complicated because it involves welding process. Therefore, a novel origami-ending tube (OET) is proposed in this paper. This OET was designed by introducing some small triangular origami patterns into the ends of the tube module, which greatly simplified the manufacturing process because it did not require welding. The validation experiments showed that the OET could deform in DM with a 46% reduction of Fmax and a 99% increase of Fm, compared to the conventional tube, even though the geometry of the OET was very close to that of a conventional tube. Combined with the results drawn from the validation experiments, parameters and comparison studies, it could be concluded that the OET performed better than the OCB.
... Auxetic tubular structures exhibit multifunctional and unusual performance, such as impact resistance performance [42,43], bending performance [44] and synclastic behaviour [45]. Based on this, widely studies have been implemented on auxetic tubular structures towards exploring their applications as adjustable medical and energy-absorbing devices. ...
Article
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Concrete-filled stainless steel tube (CFSST) members take advantage of the high strength and the outstanding corrosion resistance to act as an important role in civil engineering structures. However, the steel tube could not provide the perfect confinement effect for the core concrete during the initial elastic compression stage because Poisson’s ratio of the concrete is smaller than that of the stainless steel tube (SST). In this paper, a novel concrete-filled auxetic stainless steel tube (CFASST) composite structure was designed and manufactured to actively restrain the concrete, making the best use of the desirable deformation characteristics of auxetic tubular structures. The axial compressive performance of these CFASST members and their control factors were investigated experimentally and numerically. Test results were discussed in detail which included failure modes, load versus displacement curves and strain analysis. Finally, parametric analyses were conducted to further study the effects of different parameters (Poisson’s ratio, thickness of the stainless tube) on the CFSST composite structure under axial compression. It was found that CFASST composite structures possess an unusual deformation mode and an improved confinement effect.
... The whole bottom half of the defective empty tube are dominated by the X-shaped dentinduced plastic hinge ( Table 1). The collapse of the plastic hinge leads to a lower and much flatter stress plateau (0.10 < ε < 0.45, red curve in Fig. 2c), which is consistent with previously reported results [38,39]. When the curved and extended dent is in contact with the bottom cap at ε around 0.45 (Table 1), the tube stiffness increases. ...
Chapter
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Thin-walled structures have been widely used in automotive and aerospace industries to improve the system crashworthiness and impact protection. However, during manufacturing, transporting and handling processes, initial geometric imperfections are inevitably introduced to the thin-walled structures, which imposes negative impacts to the mechanical performance and service life of the thin-walled structures. In this study, we have introduced structural imperfection with controlled geometry and dimension to thin-walled steel tubes and characterized the mechanical response of these empty tubes and LN-filled tubes by quasi-static compression tests. Results show, the structural imperfection reduces the energy absorption capacity of empty tubes by about 20%. As the tube is filled with LN, the structural imperfection does not affect the energy absorption capacity of LN filled tube. The enhanced imperfection resistance is attributed to the suppression of imperfection growth caused by the strong liquid-solid interaction between the LN and tube wall. These findings suggest that the LN filling material can effectively reduce the adverse impact of structural imperfection and shed light on future design of thin-walled energy absorption devices.
... An ideal energy absorber has a long, flat plateau that is just below the peak stress that will damage the object being protected -and it must absorb all the energy needed from it prior to reaching densification. Hollow tubes [140][141][142][143][144], honeycombs [145][146][147][148][149], and metal foams [150][151][152] have been used for these applications since their behaviour approaches that of an ideal energy absorber. Once the force-displacement curve shown in Figure 13a is converted into an effective stress-strain curve, several metrics may be defined to enable comparison across different energy absorber designs and materials. ...
Article
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Additive manufacturing (AM) refers to a collection of manufacturing methods involving the incremental addition of material to build a part directly in its final or near-final geometry, usually in a layer-by-layer process. Metal AM in particular has seen great industrial adoption and maturation. This technology enables increased freedom of design in engineered materials with complex geometries, of which architected cellular or lattice structures are particularly promising in a wide range of applications. These materials are similar to stochastic foams which have found many industrial applications over the last few decades, but regular cellular structures possess a higher degree of control over the manufactured architectures made possible by additive manufacturing. These architected porous materials have properties that can be fine-tuned for a particular application (for mechanical performance, permeability, thermal properties, etc.). The control over the design and manufacturing of such architected structures in comparison to stochastic structures opens new application possibilities and enables a range of new products and features. This potential is only starting to be realized as metal AM techniques are maturing and are increasingly being adopted in various industries, and as design-for-AM capabilities improve. This review paper summarizes the unique properties of AM lattice structures and how these have been successfully employed for specific applications so far, and highlights various application areas of potential interest for the near future. The focus in this review paper is therefore on unique achievable properties and the associated applications for metal additively manufactured lattice structures.
... Lunhaizhi et al. (2018) has performed wind tunnel test and field measurements of wind loading on a super tall structure and found a fine agreement between the two results. Yang et al. (2017) has introduced the concept of predesigned ellipsoidal dimples into circular tubes and evaluated the impact of different design input parameters on it. ...
Article
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For the design of tubular structures, various researches have been inducted in past but still, there is no regulation made for providing the column spacing in the tube frame. This paper presents the comparison of four different types of a tubular structural frame with different spacing of columns in their periphery. The main objective of the research is to find an optimum spacing of columns in a tube frame without compromising the structural response. The columns are assigned at 7.5ft, 10ft, 15ft, and 30ft respectively in four tubular structures with the building height of 600 ft. Here the flat plate system has been used and its effect on the cost of the structure is observed. A simple linear static analysis is carried out and seismic loading has been applied in each model and their base shear and drifts were optimized by changing the column cross-section to get minimum steel ratio. Based on their total cost consumption and drift control, the most optimum and economical framing system has been concluded and a tube frame with 10 ft column spacing is recommended as the most suitable option for a symmetrical high-rise structure. Furthermore, these tubes were also get compared with a conventional moment resisting frame system, and all the analyzed tube frames are found to be more economical than a moment-resisting frame.
... Introducing auxeticity into the tubular structure could further widen their application prospects [23]. Auxetic tubular structure exhibits improved impact energy absorption performance [24][25][26], thus could be used in the energy-absorbing device [27][28][29]. It also possesses superior bending performance [30,31] and interesting extension twist deformation response [32,33]. ...
Article
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Auxetic materials exhibit interesting deformation characteristics and excellent mechanical properties. A novel combined tubular structure with tunable stiffness is proposed in this work, aiming to improve the bearing capacity and stability by length design of the central column. Specimens were fabricated via 3D printing technique. Experimental test was performed to study their mechanical property and deformation characteristics under uniaxial compression. The validity of the finite element model was proved by comparing the experimental result with simulation prediction. The compression process and stress-strain curve of the tubular structure with tunable stiffness exhibited four distinct stages (elastic, stiffness change, densification and buckling). Subsequently, a parametrical analysis was conducted to investigate the influences of the central connecting column on the stressstrain response, Poisson’s ratio and stability of the structure. By properly choosing the length of the central connecting column, the tubular structure could possess tunable stiffness, higher stability and compressive capacity. Furthermore, this design concept could be of benefit to the development of adaptive structures, smart devices and applications for civil engineering and protective engineering.
... In the case of consuming all stroke, i.e., when the tube "bottoms out", high peak loads emerge [5]. The high peak loads and violent fluctuations in loads increase the risk of whiplash [6]. To prevent this undesirable consequence and increase energy absorption capacity, auxetic materials have been considered [7]. ...
Article
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Our research investigated the energy absorption characteristics of chiral auxetic lattices filled cylindrical composite tubes subjected to a uniaxial and lateral quasi-static load. The lattice structures were manufactured using a 3D printing technique. Carbon fiber composite tubes without filler material were initially subjected to uniaxial and lateral quasi-static crushing load. The same types of experiment were then performed on chiral lattices and chiral lattices filled composite tubes. For the different cases, the load–displacements curves were analyzed and the specific energy absorption (SEA) values were compared. The SEA capability for the axial quasi-static crushing of the chiral lattices filled composite tubes decreased in comparison with the hollow composite design. However, the most significant result was that the average SEA value in the case of lateral loading increased dramatically in comparison with the hollow composite configuration.
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The bumper systems (beams and face bars) are parts of the car body structure, one of the most important components of an auto vehicle because of its role in absorbing the energy of an impact by deformation. The main objective of this paper is to study, optimize the built shape of the frontal members beams used in the endurance structure of motor vehicles in terms of their ability to absorb internal energy resulting from a frontal impact under the principles of sustainability. The study combines the classical technology used in the construction of vehicles with, the Origami Engineering” technique, which is generally used by NASA, but also by engineers in other fields: aeronautics, nanotechnology or medical technique. Simulation analyses were performed using the finite element on different types of thin-walled metal tubes, but also an origami structure.
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Thin-walled tubes subjected to axial crushing have been extensively employed as energy absorption devices in transport vehicles. Conventionally, they have a square or rectangular section, either straight or tapered. Dents are sometimes added to the surface in order to reduce the initial buckling force. This paper presents a novel thin-walled energy absorption device known as the origami crash box that is made from a thin-walled tube of square cross section whose surface is prefolded according to a developable origami pattern. The prefolded surface serves both as a type of geometric imperfection to lower the initial buckling force and as a mode inducer to trigger a collapse mode that is more efficient in terms of energy absorption. It has been found out from quasi-static numerical simulation that a new collapse mode referred to as the completed diamond mode, which features doubled traveling plastic hinge lines compared with those in conventional square tubes, can be triggered, leading to higher energy absorption and lower peak force than those of conventional ones of identical weight. A parametric study indicates that for a wide range of geometric parameters the origami crash box exhibits predictable and stable collapse behavior, with an energy absorption increase of 92.1% being achieved in the optimum case. The origami crash box can be stamped out of a thin sheet of material like conventional energy absorption devices without incurring in-plane stretching due to the developable surface of the origami pattern. The manufacturing cost is comparable to that of existing thin-walled crash boxes, but it absorbs a great deal more energy during a collision.
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A series of over 120 axial crushing tests were conducted on circular and square steel tubes loaded either statically or dynamically. Approximate theoretical predictions for static and dynamic progressive buckling are developed. Fair agreement with the experimental results is achieved provided the effective crushing distance is taken into account and the infuence of material strain rate sensitivity is retained for dynamic loads.
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Thin-walled structures are widely used as energy absorbing devices for their proven advantages on lightweight and crashworthiness. However, conventional thin-walled structures often exhibit unstable collapse modes and excessive initial peak crushing force (IPCF) followed by undesirable fluctuation in force-displacement curves under impact loading. This paper introduces a novel tubal configuration, namely sinusoidal corrugation tube (SCT), to control the collapse mode, and minimize the IPCF and fluctuations. Through validating the finite element (FE) models established, the effects of wavelength, amplitude, thickness and diameter of SCTs on collapse mode and energy absorption were investigated. The results showed that SCTs can make the deformation mode more controllable and predictable, which can be transformed from a mixed mode to a ring mode by simply changing the wavelength and amplitude. Compared with the traditional straight circular tube, the IPCF is reduced appreciably. Furthermore, SCTs have lower fluctuation in the force-displacement curves than traditional straight circular tubes. Finally, a multiobjective optimization is conducted to obtain the optimized SCT configuration for maximizing specific energy absorption (SEA), minimizing IPCF under the constraint of fluctuation criterion. The optimal SCTs are of even more superior crashworthiness and great potential as an energy absorber.
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Thin-walled tubes are widely used as energy absorption components. In this study, two different origami patterns were introduced to circular tubes. The influence of the origami patterns on the energy absorption capacity and the deformation mechanism of tubes under uniaxial loading were investigated both numerically and experimentally. The results showed that the initial peak force of origami tubes would be significantly reduced, while the energy absorption capacity could be improved or maintained. Brass tubes with and without origami patterns were fabricated using 3D printing and were tested to validate the finite element models.
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This paper presents a novel thin-walled tube design with a pre-folded kite-shape rigid origami pattern as an energy absorption device. Numerical simulation of the quasi-static axial crushing of the new device shows that a smooth and high reaction force curve can be achieved in comparison with those of conventional square tubes, with an increase of 29.2% in specific energy absorption and a reduction of 56.5% in initial peak force being obtained in the optimum case. A theoretical study of the energy absorption of the new device has also been conducted, which matches reasonably well with the numerical results.
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This important study focuses on the way in which structures and materials can be best designed to absorb kinetic energy in a controllable and predictable manner. Understanding of energy absorption of structures and materials is important in calculating the damage to structures caused by accidental collision, assessing the residual strength of structures after initial damage and in designing packaging to protect its contents in the event of impact. Whilst a great deal of recent research has taken place into the energy absorption behaviour of structures and materials and significant progress has been made, this knowledge is diffuse and widely scattered. This book offers a synthesis of the most recent developments and forms a detailed and comprehensive view of the area. It is an essential reference for all engineers concerned with materials engineering in relation to the theory of plasticity, structural mechanics and impact dynamics. © 2003 Woodhead Publishing Limited Published by Elsevier Ltd All rights reserved.
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Inextensional collapse modes are presented for the axial compression of thin-walled tubes. Shortening is achieved by folding about fixed hinge lines to form a number of flat triangular planes. A new mechanism is propounded by which collapse proceeds progressively from one end of the tube, following the passage of a travelling hinge. Simple expressions are developed for mean collapse load and the energy absorbed during collapse of rigid-perfectly plastic tubes. Comparison of collapse modes and predicted loads with those obtained from experiments on rigid P.V.C. tubes of various thickness, diameter and length give encouraging agreement.
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A series of axial crushing tests on steel circular cylindrical shells loaded either statically or dynamically is reported and compared with various theoretical predictions and empirical relations. A modified version of Alexander's theoretical analysis for axisymmetric, or concertina, deformations gives good agreement with the experimental results when the effective crushing distance is considered and provided that the influence of material strain rate sensitivity is retained in the dynamic crushing case.
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An approximate theory for the process is derived, leading to a solution of the type P = Ct1.5√D, where P is the collapse load, t the shell thickness, D the shell diameter, and C a constant for any given material. Good agreement is exhibited between this relationship and experimental results.
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Similar to the concertina mode, the wall of axially crushed tubes deforming in multi-lobe or diamond mode, will be laid down partly to the inside and partly to the outside of the tube generator with the latter part being smaller than the former. Such proportion of the folding length is known as the eccentricity factor, in both the concertina and multi-lobe modes. The present work examines the collapse of tubes in the multi-lobe in an attempt to evaluate the crushing load using this unique factor. The analysis produced a distinctive value for the eccentricity factor that simplifies the expression for the mean collapse load, which is a function of tube geometry and number of lobes. The analytical outcome for the mean crushing load, the total deflection is in a reasonable agreement with those obtained from experiment. Furthermore, the measured values of the eccentricity factor and the critical folding angles obtained for tubes of different materials and geometric ratios are also in good agreement with those produced by the analysis which postulates that the distinctive value of m is independent of the tube’s material and geometric ratios.
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This paper examines the effective crushing distance of thin-walled box columns. In contrast to previous work on this subject where a perfectly plastic material was assumed, the hardening property of a material is now taken into account. A simplified theoretical model of a compressed rigid-linearly strain hardening metal strip is studied and a closed-form solution is derived for the crushing distance of unstiffened as well as transversly stiffened box columns. The theoretical predictions are in excellent agreement with experimental data.
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This paper presents further experimental investigations into axial compression of thin-walled circular tubes, a classical problem studied for several decades. A total of 70 quasi-static tests were conducted on circular 6060 aluminium tubes in the T5, as-received condition. The range of D/t considered was expanded over previous studies to D/t=10–450. Collapse modes were observed for L/D⩽10 and a mode classification chart developed. The average crush force, FAV, was non-dimensionalised and an empirical formula established as FAV/MP=72.3(D/t)0.32. It was found that test results for both axi-symmetric and non-symmetric modes lie on a single curve. Comprehensive comparisons have been made between existing theories and our test results for FAV. This has revealed some shortcomings, suggesting that further theoretical work may be required. It was found that the ratio of FMAX/FAV increased substantially with an increase in the D/t ratio. The effect of filling aluminium tubes with different density polyurethane foam was also briefly examined.
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The results of an experimental investigation of the axial crushing modes and energy absorption properties of quasi-statically compressed aluminium alloy tubes are presented. In particular, the influence of tube length on these properties is discussed and quantified and a classification chart presented. This chart together with other experimental data, enables a designer to predict the energy absorbing properties of a given tube as well as its mode of crushing.
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The energy absorption characteristics of corrugated tubes are experimentally studied. The corrugations are introduced in the tube to force the plastic deformation to occur at predetermined intervals along the tube generator. The aims are to improve the uniformity of the load—displacement behaviour of axially crushed tubes, predict and control the mode of collapse in each corrugation in order to optimize the energy absorption capacity of the tube. Effect of heat treatment and foam filling of these tubes are also considered. Metal tubes are mostly used throughout this study, however, PVC tubes are also considered for comparison purposes. The experimental results of crushing of the corrugated tubes make these tubes a good candidate for a controllable energy absorption element.
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An extensive experimental database has been established for the structural behaviour of aluminium foam and aluminium foam-based components (foam-filled extrusions). The database is divided into three levels, these are: (1) foam material calibration tests, (2) foam material validation tests and finally (3) structural interaction tests where the foam interacts with aluminium extrusions. This division makes it possible to validate constitutive models applicable to aluminium foam for a wide spectrum of loading configurations. Several existing material models for aluminium foam from the literature are discussed and compared. To illustrate the use of the database, four existing material models for foams in the explicit, non-linear finite element code LS-DYNA have been calibrated and evaluated against configurations in the database.
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