The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
D. Vangi - One of the best experts on this subject based on the ideXlab platform.
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energy loss in vehicle to vehicle Oblique Impact
International Journal of Impact Engineering, 2009Co-Authors: D. VangiAbstract:Since the seventies, many methodologies have been developed for estimating from energy loss the delta V produced in a vehicle to vehicle Impact. Normal energy loss, is calculated by a discrete number of residual crush measurements in the direction parallel to the vehicle's axis, using the stiffness coefficients. In the case of Oblique Impact, a correction factor is applied to the normal energy loss to determine energy loss in the impulse direction. In this paper the concept of principal direction of deformation is introduced, presenting a new method for estimating energy loss in vehicle to vehicle collision, starting from a discrete number of crush measurements, which are, however, performed considering the effective displacement of the points during the crush. This novel approach, in addition to providing a more rigorous model of the physical phenomena, leads to improvement in the results: with the new approach, the mean error committed in estimating energy loss is about 10%, as compared to the 20% of the previous methodology.
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Energy loss in vehicle to vehicle Oblique Impact
International Journal of Impact Engineering, 2009Co-Authors: D. VangiAbstract:Since the seventies, many methodologies have been developed for estimating from energy loss the delta V produced in a vehicle to vehicle Impact. Normal energy loss, is calculated by a discrete number of residual crush measurements in the direction parallel to the vehicle's axis, using the stiffness coefficients. In the case of Oblique Impact, a correction factor is applied to the normal energy loss to determine energy loss in the impulse direction. In this paper the concept of principal direction of deformation is introduced, presenting a new method for estimating energy loss in vehicle to vehicle collision, starting from a discrete number of crush measurements, which are, however, performed considering the effective displacement of the points during the crush. This novel approach, in addition to providing a more rigorous model of the physical phenomena, leads to improvement in the results: with the new approach, the mean error committed in estimating energy loss is about 10%, as compared to the 20% of the previous methodology. ?? 2008 Elsevier Ltd. All rights reserved.
David Thambiratnam - One of the best experts on this subject based on the ideXlab platform.
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dynamic energy absorption characteristics of foam filled conical tubes under Oblique Impact loading
International Journal of Impact Engineering, 2010Co-Authors: Zaini Ahmad, David ThambiratnamAbstract:This paper treats the crush behaviour and energy absorption response of foam-filled conical tubes subjected to Oblique Impact loading. Dynamic computer simulation techniques validated by experimental testing are used to carry out a parametric study of such devices. The study aims at quantifying the energy absorption of empty and foam-filled conical tubes under Oblique Impact loading, for variations in the load angle and geometry parameters of the tube. It is evident that foam-filled conical tubes are preferable as Impact energy absorbers due to their ability to withstand Oblique Impact loads as effectively as axial Impact loads. Furthermore, it is found that the energy absorption capacity of filled tubes is better maintained compared to that of empty tubes as the load orientation increases. The primary outcome of this study is design information for the use of foam-filled conical tubes as energy absorbers where Oblique Impact loading is expected.
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dynamic simulation and energy absorption of tapered thin walled tubes under Oblique Impact loading
International Journal of Impact Engineering, 2006Co-Authors: Gregory Nagel, David ThambiratnamAbstract:In real-world Impact loading situations the structure could be subjected to both axial and off-axis loads. Tapered thin-walled rectangular tubes have been considered desirable Impact energy absorbers due to their ability to withstand Oblique Impact loads as effectively as axial loads. Despite this, relatively few studies have been reported on the response of such structures under Oblique loading. The aim of this paper is to compare the energy absorption response of straight and tapered thin-walled rectangular tubes under Oblique Impact loading, for variations in the load angle, Impact velocity and tube dimensions. It is found that the mean load and energy absorption decrease significantly as the angle of applied load increases. Nevertheless, tapering a rectangular tube enhances its energy absorption capacity under Oblique loading. The outcome of the study is design information for the use of straight and tapered thin-walled rectangular tubes as energy absorbers in applications where Oblique Impact loading is expected.
Chang Qi - One of the best experts on this subject based on the ideXlab platform.
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crashworthiness and lightweight optimisation of thin walled conical tubes subjectedto an Oblique Impact
International Journal of Crashworthiness, 2014Co-Authors: Chang Qi, Shu YangAbstract:Two major requirements for a vehicular system's crash components are being lightweight and having good crashworthiness. Thin-walled round and conical tubes, which are either empty or foam filled and that can potentially be used as the front rails of a passenger car subjected to Oblique Impact, are numerically analysed using the finite element method. The conical tube was found to have the best performance in terms of both specific energy absorption and peak crushing force. A maximum of 106.6% increase in the specific energy absorption was observed for the empty conical tube than the foam-filled round tube in the load angle range of 0°–30°. Using the Kriging metamodels with a maximum relative error less than 4%, multi-objective design optimisation of the conical tube was performed with a weight constraint of 0.2 kg. Lightweight and improved crashworthiness were obtained simultaneously for the conical tube through optimisation. It was also found that the optimal tube configurations differ for different impa...
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front rail crashworthiness design for front Oblique Impact using a magic cube approach
SAE International journal of transportation safety, 2013Co-Authors: Sibo Hu, Chang Qi, Yi DingAbstract:The front rail, as one main energy absorption component of vehicle front structures, should present steady progressive collapse along its axis and avoid bending collapse during the front Oblique Impact, but when the angle of loading direction is larger than some critical angle, it will appear bending collapse causing reduced capability of crash energy absorption. This paper is concerned with crashworthiness design of the front rail on a vehicle chassis frame structure considering uncertain crash directions. The objective is to improve the crash direction adaptability of the front rail, without deteriorating the vehicle's crashworthiness performance. Magic Cube (MQ) approach, a systematic design approach, is conducted to analyze the design problem. By applying Space Decomposition of MQ, an equivalent model of the vehicle chassis frame is generated, which simplifies the design problem. Based on this model, a two-layered front rail is proposed using a multi-step multi-domain topology optimization method and a response surface method. Numerical simulations are carried out with Altair/Hypermesh and LS-DYNA to compare the crashworthiness performances of the original front rail and the proposed two-layered design. The result shows that the two-layered front rail, with a reduced weight by 17%, can absorb 46% more energy in the 30 degree front Impact than the original design, meanwhile, the proposed design eliminates the bending collapse on its rear end when the angle of loading direction reaches the critical angle. The energy absorption capability and the direction uncertainty adaptability of the front rail are significantly improved. Language: en
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multiobjective optimization for empty and foam filled square columns under Oblique Impact loading
International Journal of Impact Engineering, 2013Co-Authors: Shu Yang, Chang QiAbstract:Abstract This paper aims at optimizing the crashworthiness of empty and foam-filled thin-walled square columns under Oblique Impact loading, for variations in the load angle, geometry and material parameters of the column. Another focus is to reveal the relative merits of the optimized configurations for both types of columns under such loads. Dynamic finite element analysis (FEA) techniques validated by theoretical solutions and experimental data in the literature are used to simulate the crash responses of such devices subjected to different Impact angles. Based on the FEA results, the Kriging metamodels are constructed for the two columns to predict the crashworthiness criteria of specific energy absorption (SEA) and peak crushing force (PCF) under Oblique Impact loading, which are set as design objectives in the following multiobjective optimization design (MOD) process. The Pareto fronts are identified for the MOD problems of the two types of columns under both single angle Impact and the cases involving multiple Impact angles, using the multiobjective particle swarm optimization (MOPSO) algorithm. It is found that the optimal designs are generally different under different load angles for either empty or foam-filled column. Results also indicate that more robust designs against Oblique Impact could be achieved by including multiple load angles in the MOD process. Compared to the empty column, the optimal foam-filled column may have better crashworthiness under pure axial loading, but the optimal empty column has more room to enhance the crashworthiness under Oblique Impact.
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crushing analysis and multiobjective crashworthiness optimization of tapered square tubes under Oblique Impact loading
Thin-walled Structures, 2012Co-Authors: Chang Qi, Shu Yang, Fangliang DongAbstract:In this paper, a class of axisymmetric thin-walled square (ATS) tubes with two types of geometries (straight and tapered) and two kinds of cross-sections (single-cell and multi-cell) are considered as energy absorbing components under Oblique Impact loading. The crash behavior of the four types of ATS tubes, namely single-cell straight (SCS), single-cell tapered (SCT), multi-cell straight (MCS) and multi-cell tapered (MCT), are first investigated by nonlinear finite element analysis through LS-DYNA. It is found that the MCT tube has the best crashworthiness performance under Oblique Impact regarding both specific energy absorption (SEA) and peak crushing force (PCF). Sampling designs of the MCT tube are created based on a four-level full factorial design of experiments (DoE) method. Parametric studies are performed using the DoE results to investigate the influences of the geometric parameters on the crash performance of such MCT tubes under Oblique Impact loading. In addition, multiobjective optimization design (MOD) of the MCT tube is performed by adopting multiobjective particle swarm optimization (MOPSO) algorithm to achieve maximum SEA capacity and minimum PCF with and without considering load angle uncertainty effect. During the MOD process, accurate surrogate models, more specifically, response surface (RS) models of SEA and PCF of the MCT tubes are established to reduce the computational cost of crash simulations by finite element method. It is found that the optimal designs of the MCT tubes are different under different load angles. It is also found that the weighting factors for different load angles are critical in the MOD of the MCT tubes with load angle uncertainty.
Yinsheng Li - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of local damage to reinforced concrete panels subjected to Oblique Impact by soft missile
Nuclear Engineering and Design, 2019Co-Authors: Akemi Nishida, Haruji Tsubota, Zuoyi Kang, Minoru Nagai, Yinsheng LiAbstract:Abstract Many empirical formulas have been proposed for evaluating local damage to reinforced concrete (RC) structures due to Impact by rigid missiles. Most of these formulas have been derived based on the results of tests involving perpendicular Impacts on target structures. Thus far, few tests have been conducted considering Oblique Impact on target structures. As the final goal of this research, we aim to propose a new formula for evaluating local damage due to Oblique Impact based on previous experimental and simulation results. Herein, we perform simulation analyses for evaluating local damage to RC panels due to Oblique Impacts at various angles by soft missiles under various Impact velocities by using a simulation method that was validated using the results of previous Impact experiments. Based on the results of these simulation analyses, we investigate quantitatively the reduction in local damage due to the difference in Impact angle and Impact velocity. The results of the investigation results and the knowledge obtained from the results are then presented.
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A Study for Evaluating Local Damage to Reinforced Concrete Panels Subjected to Oblique Impact: Part 3 — Simulation Analysis for Evaluating Perforation Phenomena Caused by Oblique Impact of Deformable Projectiles
Volume 2: Plant Systems Structures Components and Materials, 2017Co-Authors: Haruji Tsubota, Yoshimi Ohta, Akemi Nishida, Yinsheng LiAbstract:The purpose of this study is to propose a new formula for evaluating the local damage to reinforced concrete structures caused by Oblique Impact based on past experimental results and simulation results. In this paper, we present the results of simulation analyses for evaluating the perforation of concrete panels due to Oblique Impact by deformable projectiles. Various response characteristics and perforation mechanisms such as detailed perforation behavior, damage to reinforced concrete panels, rupture states of the deformable projectiles, reduction in projectile velocity, and residual velocity of the projectile after perforation, and energy transfer processes are clarified. Especially, it is found that the sliding energy consumed by friction occurring at the contact surface between a projectile and a reinforced concrete panel due to Oblique Impact is remarkably larger than that due to normal Impact.
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A Study for Evaluating Local Damage to RC Panels Subjected to Oblique Impact: Part 1 — A Study for Evaluating Local Damage Caused by Oblique Impact of Rigid Projectiles
Volume 2: Plant Systems Structures Components and Materials, 2017Co-Authors: Yoshimi Ohta, Haruji Tsubota, Akemi Nishida, Yinsheng LiAbstract:Many empirical formulae have been proposed to evaluate the local damage to reinforced concrete structures caused by the Impact of rigid projectiles. Most of these formulae have been derived based on Impact tests perpendicular to the target structures. To date, few Impact tests Oblique to the target structures have been conducted. The purpose of this study is to propose a new formula for evaluating the local damage caused by Oblique Impacts based on experiments and simulations. The new formula is derived by modifying an empirical formulation for normal Impact and the agreement with results of past Oblique Impact tests is discussed.
W J Stronge - One of the best experts on this subject based on the ideXlab platform.
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painleve paradox during Oblique Impact with friction
European Journal of Mechanics A-solids, 2011Co-Authors: Yunian Shen, W J StrongeAbstract:Abstract In analyses using non-smooth dynamics, Oblique Impact of rough bodies in an unsymmetrical configuration can result in self-locking or “jam” at the sliding contact if the coefficient of friction is sufficiently large; this has been termed, Painleve’s paradox. In the range of configurations and coefficients of friction where Painleve’s paradox occurs, analyses based on rigid body dynamics give results indicating that either there are multiple solutions or the solution is nonexistent. This conundrum has been resolved by considering that the contact has small normal and tangential compliance which is representative of deformability in a local region around the contact point. An analysis using a hybrid model which includes local compliance of the contact region has calculated the time-dependent changes in relative motion of colliding bodies for a range of incident angles of obliquity, tan −1 [− V 1 (0)/ V 3 (0)] where V 1 (0)and V 3 (0) are the incident tangential and normal relative velocities at the contact point, respectively. The paradox is shown to result from a negative relative acceleration of the contact points during an initial period of sliding – a negative acceleration that is inconsistent with the assumption of rigid-body contact.
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ballistic limit for Oblique Impact of thin sandwich panels and spaced plates
International Journal of Impact Engineering, 2008Co-Authors: D W Zhou, W J StrongeAbstract:Abstract Ballistic perforations of monolithic steel sheets, two-layered sheets and lightweight sandwich panels were investigated both experimentally and numerically. The experiments were performed using a short cylindrical projectile with either a flat or hemispherical nose that struck the target plate at an angle of obliquity. A total of 170 tests were performed at angles of obliquity 0–45°. The results suggest that during perforation by a flat-nosed projectile, layered plates cause more energy loss than monolithic plates of the same material and total thickness. There was no significant difference in the measured ballistic limit speed between monolithic plates and layered plates during Oblique Impact perforation by a hemispherical-nosed projectile. To develop understanding of the process of fracture development and perforation of a thin stainless-steel sheet resulting from Oblique Impact by a hard, flat-nosed projectile, numerical simulations by ABAQUS/Explicit finite element code were compared against the experimental fracture patterns, residual velocities and ballistic limits of perforated plates. Effects of projectile length-to-diameter ratio and spacing between layered plates struck by flat-nosed projectiles were investigated. For projectiles of equal mass, a longer projectile (larger ratio of length to diameter, L / D >2) results in a drastic decrease in the ballistic limit speed for a double-layered plate. For thin, layered plates, the ballistic limit speed is affected significantly by the spacing between layers.
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Oblique Impact of inflated balls at large deflections
International Journal of Impact Engineering, 2007Co-Authors: W J Stronge, A D C AshcroftAbstract:A planar theory for Oblique Impact of thin-walled spherical balls against a rough rigid surface has been developed on the basis of an assumed deformation field—an initially spherical ball is assumed to flatten against the constraint surface while the remainder of the ball remains undeformed. For inflated thin-walled balls, which are represented by these assumptions (basketballs, soccer balls, volleyballs, etc) the normal reaction force acting on the flattened contact patch is predominately due to the internal gas pressure—the reaction due to shell bending is insignificant in comparison with this gas force. During Impact of a thin-walled ball there also is a non-conservative momentum flux reaction that is caused by the flow of momentum into and out-of the flattened contact patch. If the ball is translating as well as rotating about an axis perpendicular to the plane of motion, the distribution of the normal component of velocity for material entering and exiting the flattened contact patch results in a distribution of momentum flux force intensity around the periphery of the contact patch and consequently, a momentum flux torque acting on the flattened sphere. The effect of these reaction forces and torque on Oblique Impact of thin-walled spherical balls is calculated as a function of the ball deflection (or normal component of Impact velocity). In comparison with rigid body calculations for Oblique Impact of a spinning ball against a rough surface at angleso451 from normal, the effect of maximum deflections as large as half the initial radius is to slightly accentuate the effect of friction on angle of rebound and moderately decrease the angular velocity of the ball. However, for angles 4451 from normal, the final angular velocity can be as small as 40% of that predicted by rigid body theory. The most significant changes in rebound angle are for cases with initial backspin—a technique commonly used in many ball sports.
