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To mitigate the consequences of bird strikes, compliance with bird ingestion requirements must be substantiated by corresponding physical tests relying on a jet engine. However, current simulation ...

In order to more accurately simulate the injury of riders and the motion characteristics of two-wheelers, the modeling method and the simulation model of two-wheeler traffic accidents are studied i...

The problem of large calculation models in bus–two-wheeled vehicle traffic accidents (TA) leads to the difficulty of balancing the calculation efficiency and accuracy, as well as difficulties in accident reconstruction. Herein, two typical accidents were reconstructed, based on the rigid–flexible coupled human model (HM) and the Facet vehicle model, and the vehicle damage conditions and the human head biomechanical injury were analyzed. The simulation results showed that the physical process of the human–vehicle collision was basically consistent with the accident video, the windshield fracture was consistent with the actual vehicle report, and the human biomechanical injury characteristics were also consistent with the autopsy report, which verified the feasibility of the simulation model, and provides a basis and reference for forensic identification and for traffic police to deal with accident disputes.

In the human-vehicle-road system of collisions, the human is the most important factor, and digital human models (DHMs) are developed with the aim of preventing or at least reducing human injury. Because most of the relevant literature is focused mainly on collisions in traffic accidents (TAs), only some of the literature reviewed in this paper involves research results on other aspects of collisions. In this review, based on the background of DHMs and the application of DHMs regarding human injury biomechanics in collisions field, research results regarding the development of DHMs are described, the methods for verifying such models are introduced, and the application of the research results is discussed based on the aspect of human injury biomechanics. From the research literature, the development and validation of DHMs and their application in human injury biomechanics are summarized, and future research trends are proposed and discussed.

To obtain a rider-vehicle-road coupling system that takes both efficiency and accuracy into account, so that the simulation model of two-wheeled vehicle traffic accident can reduce the calculation ...

In order to obtain the initial condition of the traffic accident and reconstruct the collision process of motorcycle and car in reverse, this paper proposes a multi-objective optimisation algorithm...

To reduce the computational time in the fields of dynamics, we introduce herein an efficient asynchronous step integration algorithm for a coupled finite-element–discrete-element method (FEM–DEM). Domain decomposition divides the whole model into an FEM subdomain and a DEM subdomain, where each subdomain selects the appropriate time step based on the element characteristics. The method of overlapping nodes and particles at the boundaries is adopted to handle the interface coupling problem, and the subcycling method is adopted to tackle the problem of transmission and matching of boundary data. Two numerical examples are presented to demonstrate the precision of the analysis and the overall efficiency. The algorithm provides the requisite calculation accuracy and significantly shortens the computer simulation. This approach further improves the efficiency of hybrid FEM–DEM modeling.

This paper presents a numerical investigation of bird attitude angles affecting the soft-impact damage of a full fan assembly. Firstly, considering the geometry of a mallard, a real bird model is established by the Smoothed Particle Hydrodynamics (SPH) method and calibrated with available test data. Then, complying with airworthiness requirements, simulations of a full-bladed fan assembly subjected to a real bird were conducted to determine the critical ingestion parameters (CIP). Furthermore, a real bird with different attitude angles aimed at a full fan assembly was simulated. Results show that attitude angles of the bird produce a significant impact on the effect of the bird strike on rotating blades and would increase the possibility of blade failures, especially for the yaw angle of -45° and the pitch angle of −60°. It is invaluable for commercial airlines and engine manufactures to provide safe flight and landing by adopting the real bird model with critical yaw and pitch angles in the design for resistance to bird ingestion.

Commercial finite-element and discrete-element software usually adopts a unified computational time step and limit the number of our computer cores. In the face of large-scale with refined scale computing models, this will undoubtedly increase the time cost. The multi time step method of integer step ratio is a method to deal with this kind of problem. A non-integer ratio multi-time step computing method based on domain decomposition and subcycling method is proposed and applied to the finite-element and discrete-element engineering problems. The whole model is divided into finite-element method (FEM) subdomains and discrete-element method (DEM) subdomains according to the load balance of CPU. A coupling region between adjacent domains consists of multiple boundary nodes and particles based on the non-integer step ratio. Boundary data in coupling region are transferred through MPI communication protocol. This method can make full use of the advantages of multi-core computer and improve the calculation efficiency of engineering software.

Multi-core clusters have become primary tools for high performance computing due to their great computing power and cost-to-performance effectiveness in nowadays. However, it introduces new challenges for the design of efficient parallel algorithms because of the different storage mechanisms and non-uniform communication latencies on these machines. The traditional domain decomposition methods use the direct partition method to achieve load balancing, which directly divides the structure into a number of subdomains with equal according to the number of processing cores involved in parallel computing. As the number of processing cores in a single node of multi-core clusters increases exponentially, the number of subdomains will increase dramatically as well. A substantial increase in the number of subdomains leads to the rapid expansion of the size and the condition number of interface equations, thereby reducing the numerical convergence of the system. In addition, it leads to a considerable increase in the number of processes involved in parallel computing, thereby increasing contention for the limited network ports and bandwidth. The decrease of the numerical convergence and the increase of network communication overheads seriously affect the solution efficiency of interface equations, and greatly reduce the overall parallel efficiency of the domain decomposition method. In order to make full use of the computing power of multi-core clusters to improve the parallel efficiency of large-scale finite element structural analysis, a hierarchical load balancing approach is proposed in the paper. The proposed approach is based on the full mining of computational tasks. In order to adapt to the hardware topology architecture of multi-core clusters, the computational tasks of finite element structural analysis are divided into three layers: inter-node parallelism, inter-chip parallelism and inter-core parallelism. The coarse grain parallel computing method is utilized in inter-node parallelism and inter-chip parallelism, and the fine grain parallel computing method is used in inter-core parallelism. Through mapping computing tasks to different hardware layers of multi-core clusters, the proposed method not only efficiently achieves the load balancing at different layers, but also greatly reduces the communication overheads of the system. Furthermore, it considerably reduces the number of subdomains and significantly improves the numerical convergence of the interface equations. In order to verify the effectiveness of the algorithms, two numerical experiments about finite element structural linear static analysis for large-scale parallel computing were conducted on “Tianhe 2” supercomputer. For each model, both the traditional domain decomposition method and the proposed hierarchical load balancing approach were employed for numerical simulation utilizing 50, 100, 150, and 200 nodes, respectively. Test results show that the proposed method could obtain higher speedup and parallel efficiency compared with the conventional domain decomposition method. The proposed approach can be widely used for solving many kinds of structural analysis problems including linear static analysis, nonlinear static analysis and nonlinear dynamic analysis and so on. In this paper, the authors’ current research only focuses on the linear static analysis. For the nonlinear static or dynamic analysis and other kinds of structural analysis, the proposed method can be used as a sub-procedure because the calculations are still dominated by solutions of the same sort of equations.

Transparent ceramics are promising materials in the fields of high pressure and high temperature. Based on a lattice-spring simulation method, a novel polycrystalline model for shock-wave compression is established to explore the dynamic response and damage evolution of yttrium aluminum garnet (YAG) under shock loading. The macro-response and micro-fracture process under impact loading can be obtained simultaneously, and a correlation between the macroscopic response and mesoscale damage is shown. The process of crack propagation along a grain boundary and through grain-boundary deflection is observed in the simulation. A change in deformation behavior from intergranular fracture to transgranular fracture in the vicinity of grain boundaries, associated with the transition from an elastic response to a plastic response, is observed, as the shock stress increases from below to above the Hugoniot elastic limit. Computational results demonstrate a clear, exponential attenuation of the elastic precursor wave with the propagation of shock waves. The reasons for the elastic precursor decay and the transition from an elastic response to a plastic response are the stress relaxation and energy dissipation caused by internal transgranular fracture. The polycrystalline model will aid in microstructure design and provide a reference for the development of polycrystalline transparent ceramics in the fields of engineering and scientific research.

Traffic accident reconstruction is a reverse dynamic problem, which requires hundreds of iterations to reconstruct the whole process of accident. However, in current pedestrian-vehicle accident reconstructions, it is difficult to quickly establish a pedestrian model based on specific cases, and it is hard to solve the contradiction between calculation accuracy and calculation time. In this paper, a personalized pedestrian customization method is proposed. First, the pedestrian structure is divided into independent modules according to obvious bony markers. For each independent module, multi-body (MB) model and finite element (FE) model are established, respectively. Then the appropriate modules are selected to form the whole hybrid pedestrian model. This method can customize the structure of pedestrian model according to the injury characteristics of pedestrians in specific accidents, and customize the parameters of pedestrian model according to the height and weight of pedestrians. The impact simulation tests are carried out on hybrid pedestrian models to verify the reliability of the models. The proposed method can effectively improve the modeling efficiency of pedestrian models and the reconstruction quality of pedestrian traffic accidents.

Smoothed Particle Hydrodynamics (SPH) is widely adopted to predict bird strike events. To improve the parallel computing efficiency of the SPH approach, parallel computing was performed on the process of a bird striking the fan assembly. Since the cube-shaped domains aligned along the coordinate axes that are inherent in the decomposition algorithm may result in low computational efficiency, the effect of customized data partitioning on the efficiency is investigated. The results show that customized decompositions can minimize communication between processors and ensure the load balance during the simulation process. Besides, distributed computing with domain decompositions can present reasonable predictions at soft-impact damage, achieving consistent results within a range of less than 7% of the reference data derived from shared memory computing.

This paper investigates the dynamic response of a train-bridge system subjected to earthquakes, and the running safety indices of the train on the bridge under earthquake are studied. Taking a long span cable-stayed bridge across the Huangpu River as an example, a full three-dimensional finite element model of the train-bridge system was established, in which the soil-bridge and rail-train interactions were considered. Parallel computing based on contact balance was utilized to deal with this large-scale numerical simulation problem. The dynamic nonlinear analysis was performed on a Hummingbird supercomputer using the finite element code LS-DYNA 971. The results show that the acceleration responses of the train subjected to an earthquake are much greater than the ones without earthquake input, and the running safety of a moving train is affected by both the earthquake intensity and the running speed of the train. The running safety of the moving train can be evaluated by the threshold curve between earthquake intensity and train speed. The proposed modeling strategies and the simulated results can give a reference prediction of the dynamic behaviour of the train-bridge subjected to an earthquake.

In order to improve the parallel efficiency of large-scale structural dynamic analysis, a hierarchical approach adapted to the hardware topology of multi-core clusters is proposed. The hierarchical approach is constructed based on the strategies of two-level partitioning and two-level condensation. The data for parallel computing is first prepared through two-level partitioning to guarantee the load balancing within and across nodes. Then during the analysis of each time step, the convergence rate of interface problem is significantly improved by further reducing its size with two-level condensation. Furthermore, the communication overheads are considerably reduced by separating the intra-node and inter-node communications and minimizing the inter-node communication. Numerical experiments conducted on Dawning-5000A supercomputer indicate that the hierarchical approach was superior in performance compared with the conventional Newmark algorithm based on the domain decomposition method.

Rubble-mound breakwaters are generally subjected to strong seismic waves propagating even when seated on weak soil deposits, and they interact with seawater in most cases. The purpose of this article is to understand the dynamic response of a rubble-mound breakwater with seawater–breakwater-foundation interaction after a real earthquake shock. In this study, employing the arbitrary Lagrangian–Eulerian approach and dynamic finite element method, in which the seawater and the foundation of rubble-mound breakwater are considered, the dynamic responses of rubble-mound breakwater during earthquakes are simulated using the LS-DYNA finite element program. It is found that the seawater–breakwater-foundation interaction does have a considerable effect on residual displacements of the rubble-mound breakwater. The influence on horizontal residual displacement caused by the effect of seawater-breakwater interaction is greater than that on the vertical residual displacement, and the seawater–breakwater-foundation interaction does not necessarily reduce the horizontal and vertical displacements but also increases them. The vertical component of earthquake has a considerable effect on hydrodynamic pressure on the breakwater face. This investigation considers the seismic behavior of rubble-mound breakwaters by taking into account the coupling between the hydrodynamic loading and the shaking of the structure. According to the results, presented in this study, it is significant to consider the effect of interaction for rubble-mound breakwaters seismic safety evaluation.

With the advancement of new processor and memory architectures, supercomputers of multicore and multinode architectures have become general tools for large-scale engineering and scientific simulations. However, the nonuniform latencies between intranode and internode communications on these machines introduce new challenges that need to be addressed in order to achieve optimal performance. In this paper, a novel hybrid solver that is especially designed for supercomputers of multicore and multinode architectures is proposed. The new hybrid solver is characterized by its two-level parallel computing approach on the basis of the strategies of two-level partitioning and two-level condensation. It distinguishes intranode and internode communications to minimize the communication overheads. Moreover, it further reduces the size of interface equation system to improve its convergence rate. Three numerical experiments of structural linear static analysis were conducted on DAWNING-5000A supercomputer to demonstrate the validity and efficiency of the proposed method. Test results show that the proposed approach was superior in performance compared with the conventional Schur complement method. Copyright © 2014 John Wiley & Sons, Ltd.

Purpose– The great magnitude differences between the integral tunnel and its structure details make it impossible to numerically model and analyze the global and local seismic behavior of large-scale shield tunnels using a unified spatial scale, even with the help of supercomputers. The paper aims to present a combined equivalent & multi-scale simulation method, by which the tunnel's major mechanical properties under seismic loads can be represented by the equivalent model, and the seismic responses of the interested details can be studied efficiently by the coupled multi-scale model.Design/methodology/approach– The nominal orthotropic material constants of the equivalent tunnel model are inversely determined by fitting the modal characteristics of the equivalent model with the corresponding segmental lining model. The critical sections are selected by comprehensive analyzing of the integral compression/extension and bending loads in the equivalent lining under the seismic shaking and the coupled multi-scale model containing the details of interest is solved by the mixed time explicit integration algorithm.Findings– The combined equivalent & multi-scale simulation method is an effective and efficient way for seismic analyses of large-scale tunnels. The response of each flexible joint is related to its polar location on the lining ring, and the mixed time integration method can speed-up the calculation process for hybrid FE model with great differences in element sizes.Originality/value– The orthotropic equivalent assumption is, to the best of the authors’ knowledge, for the first time, used in the 3D simulation of the shield tunnel lining, representing the rigidity discrepancies caused by the structural property.

This paper investigates the ship–bridge collision process and its influences on the running safety of the moving light rail train. Taking a long span cable-stayed bridge across the Huangpu River as example, the 3-D dynamic model of train-bridge coupled system subjected to ship impact was studied with the aid of the finite element analysis (FEA) code LS-DYNA 971. The bridge model and the coupled rigid–flexible multi-body train model were coupled through non-linear wheel–rail interface, and the coupled dynamic model was solved using mixed time explicit integration approach. By studying the effects of train speed and the momentum of impacting ship on the running safety of the rail train, the relationship between the maximum safety speed of the train and the momentum of the impacting ship is predicted, that is, the maximum allowable train speed decreases with the increase of the momentum of the impacting ship. The mixed time integration method could speed up the calculation process for crashworthiness analysi...

Due to the requirement of stability, the time step in explicit dynamics must be small enough. This inevitably leads to a waste of computing time to adopt a unified time step for dynamics models with partial refined mesh. Multi-time step or subcycling method especially the integer step ratio is a classical method to deal with these problems. An explicit non-integer ratio multi-time step computing method is proposed in this paper. The finite element model is divided into different subdomains by node partition and the coupling region is formed by multiple overlapping boundary nodes according to the step ratio between adjacent subdomains. Each subdomain chooses explicit integration time step according to mesh characteristics. Non-integer step ratio is used among adjacent subdomains. The method provides a new implement for explicit finite element analysis.

Due to the limitation of memory and time, the traditional serial grid generation algorithms are usually the bottleneck to make the distributed computing be widely used in engineering science. To solve this problem and make the true large-scale parallel simulation in engineering science practical, a fast parallel grid generation algorithm has been proposed and the corresponding grid generator has been developed. Firstly, the initial coarse volume mesh is generated by using advancing front method. Then, two-level domain decomposition is applied and each subdomain is distributed to its corresponding process. By doing so, the intra-node and inter-node communication are distinguished and the communication overheads are reduced. Lastly, the mesh refinement algorithm is performed to generate large-scale grids without communication. Applications of the proposed algorithm and the developed generator for large-scale grid generation on supercomputer (TIANHE-2) are carried out. The reasonably good parallel scalability is obtained and the effectiveness and correctness of the developed generator are verified.

Parallel analyses about the dynamic responses of a large-scale water conveyance tunnel under seismic excitation are presented in this paper. A full three-dimensional numerical model considering the water-tunnel-soil coupling is established and adopted to investigate the tunnel’s dynamic responses. The movement and sloshing of the internal water are simulated using the multi-material Arbitrary Lagrangian Eulerian (ALE) method. Nonlinear fluid–structure interaction (FSI) between tunnel and inner water is treated by using the penalty method. Nonlinear soil-structure interaction (SSI) between soil and tunnel is dealt with by using the surface to surface contact algorithm. To overcome computing power limitations and to deal with such a large-scale calculation, a parallel algorithm based on the modified recursive coordinate bisection (MRCB) considering the balance of SSI and FSI loads is proposed and used. The whole simulation is accomplished on Dawning 5000 A using the proposed MRCB based parallel algorithm optimized to run on supercomputers. The simulation model and the proposed approaches are validated by comparison with the added mass method. Dynamic responses of the tunnel are analyzed and the parallelism is discussed. Besides, factors affecting the dynamic responses are investigated. Better speedup and parallel efficiency show the scalability of the parallel method and the analysis results can be used to aid in the design of water conveyance tunnels.

In order to study the dynamic problem due to the high-speed EMS maglev vehicle travelling through a tunnel, this paper presents a large-scale 3D model of the maglev vehicle-guideway-tunnel-soil coupling system. The 3D finite element is used for modeling the guideway-tunnel-soil system, and the heterogeneous soil conditions, detailed geometry features of guideway and tunnel, and soil-tunnel interaction are all considered. The high-speed EMS maglev vehicle is modeled as rigid bodies and coupled to the guideway through the equivalent spring/damping magnetic force model. The initial stress of the guideway-tunnel-soil is also considered in the model by the stress reduction method. The computing is accomplished on a Dawning 5000A supercomputer using the finite-element code LS-DYNA 971 MPP. The dynamic factor of the guideway is estimated in comparison with the German design guideline. The result provides a comprehensive insight into the tunnel and guideway, as well as the ground vibration.

Structure analysis of the long tunnel is difficult due to the lack of available computing power. Water hammer simulation in the water conveyance tunnel is also complicated because of strong fluid structure interactions (FSIs). In this paper, the multi-scale modeling method is used to simulate water hammer impacts in the long tunnel. The method can not only yield water hammer simulations along the full tunnel length, but also the detailed structural responses of the segment linings. In the proposed partitioned approach, the structural field is solved with the finite-element program LS-DYNA. The fluid field is solved with the CFD software package FLUENT. The interaction between two physical fields is realized using ALE description. A practical case study is presented and the results are discussed in detail. The results provide us with a better understanding of water hammers and their effects on tunnel linings.

This article introduces a platform for computer-aided engineering-based optimiza-tion using a Grid-based environment. Established upon China National Grid (CNGrid) environ-ment, the platform is designed to maximize the efficiency of optimization process while takingadvantage of Grid computing. This research provides the grid users with easier access to simula-tion-based optimization problem, so that they will not be distracted by lower level details and canconcentrate on the problem itself. The architecture and the techniques used are thoroughlyexplained in this article. Practicality of the platform is further validated through application onan optimization project in automotive industry for lightweight design of a body in white.Keywords: optimization, Grid environment, CAE, BIW1 INTRODUCTIONGrid computing, a close relative to distributed andparallel computing, has been generally accepted asan effective way to implement scientific and engi-neering projects, especially those that require large-scale simulation and huge database. Inspired by theprospects it was to bring, many Grid computing infra-structures were developed and deployed by govern-ments around the world [1–6]. These developmentsbenefit many scientific and industrial institutionswho cannot afford or do not have access to a largelocal computing centre. Although the advantages ofGrid computing has been proved through worldwideapplication, the number of users in general remainssmall compared to the forecasts publicly announcedin project descriptions and visionary publications [7].This leads to the question of what measures can betaken to make Grid computing more accessible andapplicable to researchers and engineers.In almost every field of applied science and engi-neering, the need to solve optimization problemexists in one way or the other. To tackle optimizationproblem properly, one needs to have a comprehen-sive understanding of the whole process, fromabstraction of the specific problem, through designand realization of optimization algorithm, to alloca-tion of computing resources. In this article, an opti-mization platform established upon China NationalGrid (CNGrid) environment that can maximize theefficiency of optimization process while takingadvantage of Grid computing is presented. Thetarget of this research is to provide the grid userswith easier access to simulation-based optimizationproblem, so that they will not be distracted by lowerlevel details and can concentrate on the problemitself.This article is organized as follows: Section 2 dis-cusses the background for the development of anoptimization platform using a Grid-based environ-ment; Section 3 presents the general framework, thearchitecture of the platform, and its functionality

SUMMARY Shanghai Center Tower, which is 632 m in height with 126 stories, will be the tallest building in China at the end of 2014. The extreme height of the building combined with the exterior shrink-constructed and torsion-constructed curtain wall imposes a great challenge on the seismic design of the curtain wall. This paper establishes a finite element (FE) model of the real-scale building by considering the combination of the curtain wall and the main structure. The lower order modes of the building's vibration have been predicted, and good agreement has been observed between the numerical and experimental data, which validates the FE model of the building. Seismic response of the curtain wall was then investigated under three earthquake levels, including frequent, moderate and severe earthquakes. The acceleration magnification factors, the inter-story drift ratios and the interior forces of the curtain wall met the requirements of the Chinese Design Code, which indicates that the structure is a good solution to withstand earthquakes. The present study provides an important database for the seismic design of curtain wall structure in Shanghai Center Tower, and it can be used as a seismic design reference for similar projects. Copyright © 2011 John Wiley & Sons, Ltd.

This article presents an application of data mining method on finite element data and crashworthiness result data of an occupant restraint system. According to the characteristics of the CAE (Computer-Aided Engineering) data, a framework for data preparation is developed based on object-oriented programming concepts. Training sets are built from data recorded in 98 crash simulations that adhere to FMVSS208, the America occupant crash protection testing standard. Relationship between design parameters and system effectiveness is implied in these data sets. Decision tree using C4.5 algorithm and attribute selection method based on attribute's estimated importance are introduced to perform data mining on the building of training sets. The result yielded by data mining endows us with a deeper insight into the interrelations between the key design parameters and the performance of the occupant restraint system in crash simulations. Finally, the learned rules are tested on the real crash simulation data sets. The result of the testing shows that these rules are proper, and can been used as a guidance for the design of the occupant restraint system.

Globalization and increasing market competition are forcing the automotive industry to develop technology that will enable more efficient collaboration between carmakers and their suppliers. One of the options that can meet this demand is to adopt grid technology in the collaboration process. For the system to be successfully applied, the trust relationship among Virtual Organization (VO) members becomes a very important factor. Systems lacking in secure mechanisms require all the collaborating members to fully trust each other, and thus make their application quite limited. Based on grid technology, this paper proposes a collaborative simulation system for vehicle crash safety design, and discusses the trust relationship among VO members. The grid middleware VEGA and web services working for the collaboration also contribute to the simulation system. Also, a test bed is set up on the basis of the Local Area Network (LAN). At the end of this paper, a real case involving a carmaker and a door supplier is presented to demonstrate how the grid-based collaborative simulation system works.

Car manufacturers and their suppliers are usually geographically dispersed, heterogeneous characters of various resources. To solve the resource sharing and data security problems in vehicle collaborative design environment, grid technology and Computer Supported Collaborative Work (CSCW) technology are integrated. This paper proposes a collaborative design system for vehicle crash safety design based on grid technology that is conformed to the OGSA framework, and explains how the grid middleware VEGA contributes to make collaboration more efficiently. Web services about the functions in this collaborative system are realized based on VEGA. Design principles and methods based on the FE analysis tool LS-DYNA are also presented. Finally, a test bed is built based on LAN and a case of a carmaker collaborating with a seat supplier is presented.

PurposeThis paper aims to provide a 3D finite element (FE) model for dynamic simulation of cutterhead and soil interaction in slurry shield tunneling.Design/methodology/approachDynamic numerical simulation of excavation process is realized by combined use of submodeling method and arbitrary Lagrangian Eulerian (ALE) approach. The model size reduction, soil mesh refinement and stress state initialization are fulfilled by submodeling. The large soil deformations, failures and flows are handled by ALE approach. Computation time is reduced by parallel domain decomposition with recursive coordinate bisection method. Validation of the proposed approach is achieved by comparing the numerical results with monitored data from the model test for Yangtze River tunneling project.FindingsThe proposed approach proves to be an effective technique to simulate the cutterhead and soil interaction dynamically in tunnel excavation. Comparative study on the effect of mesh density indicates the requirement of relative mesh refinement. Exploration of the parallel computing performance points out the best decomposed domain for the simulation. Parametric study on the effect of rotary speed and investigation on soil properties presents the significant factors for torque.Practical implicationsThe proposed numerical model can help in the development process of reduced‐scale model test, as well as design and selection of slurry shield machines.Originality/valueThe originality comes from the need to evaluate the excavation performance of slurry shield machine in tunneling project. This contribution provides a 3D numerical approach, which takes into account the stress state in soil and dynamic contact effects between soil and cutterhead. In this work, large deformation in soil is handled. Besides, soil failures and flows are captured.

This paper studies the feasibility of investigating a traffic accident and offering initial data for traffic accident reconstruction (TAR) using a photogrammetric technique. Compared with the conventional roller tape applied by the traffic police of Shanghai Municipal Bureau of Public Security in 142 traffic cases, photogrammetry is proven to be a time saving and cost effective method for accident investigation. The 2D photogrammetry method and the trajectory analysis accident reconstruction technique are applied to actual traffic accidents. With the assistance of a Portable-Control System as the reference system, the 3D photogrammetry method can be used in a vehicle deformation survey. The measurement results obtained in accordance with the CRASH survey criteria for vehicle deformation can be adopted as initial information for the damage analysis reconstruction technique. It appears that photogrammetry has greater potential for application to traffic accident investigation and reconstruction.

The simulation mechanism of seismic ground motion is presented in this paper, and the parallel numerical algorithm is applied as the attempt for the simulation of spatial seismic ground motion time histories on parallel computers, which is consistent with arbitrary response spectra from a specified target. The basic methods of simulation, which involve calculations of auto power spectra, phase difference spectra, cross power spectra, Fourier spectra, and response spectra, etc., are also within the discussions in this paper. According to these analyses, this paper presents a set of integrated methods for nonstationary seismic ground motion simulation with greater capacity of processing multiple spatial points. In additional, Parallel Seismic Ground Motion Simulator, the parallel program for artificial generation of seismic ground motion, has been developed, which is based on Message-Passing Interface and written in Fortran90, and also provides a user-friendly visualized interface based on a commer...

This paper presents a method of structural dynamic analysis with finite element method to identify the cause failure of solder joint caused by the vibration of ultrasonic welding. In this method, explicit FE method and its contact algorithm are used to simulate the energy transmission from vibrational energy to internal energy under some assumptions. Therefore, firstly, its feasibility is verified by 2D coupled thermal–mechanical analysis. Then, based on a certain type of cell phone battery, a 3D FE model is established for analyzing the vibration of the solder joints during ultrasonic welding. According to the simulation, we analyze the cause of the failure from three aspects: the location of the chip, the shape of the PCB and the structure of the housing. Correspondingly, the improvements are presented and applied to trial manufacture. The result from mass production shows that the improvements can decrease the reject ratio by 90% compared with the original design.

The objective of vehicle crash accident reconstruction is to investigate the pre-impact velocity. Elastic-plastic deformation of the vehicle and the collision objects are the important information produced during vehicle crash accidents, and the information can be fully utilized based on the finite element method (FEM), which has been widely used as simulation tools for crashworthiness analyses and structural optimization design. However, the FEM is not becoming popular in accident reconstruction because it needs lots of crash simulation cycles and the FE models are getting bigger, which increases the simulation time and cost. The use of neural networks as global approximation tool in accident reconstruction is here investigated. Neural networks are used to map the relation between the initial crash parameter and deformation, which can reduce the simulation cycles apparently. The inputs and outputs of the artificial neural networks (ANN) for the training process are obtained by explicit finite element analyses performed by LS-DYNA. The procedure is applied to a typical traffic accident as a validation. The deformation of the key points on the frontal longitudinal beam and the mudguard could be measured according to the simulation results. These results could be used to train the neural networks adapted back-propagation learning rule. The pre-impact velocity could be got by the trained neural networks, which can provide a scientific foundation for accident judgments and can be used for vehicle accidents without tire marks.

This study evaluates the effect of front shape on pedestrian safety by simulation test on the basis of a flat-front car. In this simulation, the multi-body models of full-scale dummy and vehicle are used. The contact stiffness is derived from the finite-element simulations of the European Experimental Vehicles Committee sub-system tests, which is validated by the application to a real-world accident reconstruction. The results show that the acceptance levels in the existing regulation are not suitable for a flat-front car. Particularly, the test conditions for the upper legform to bumper test need to be improved to be more severe. The simulations also show that the frontal additional structure, like the bumper bar, will enhance the tendency of the pedestrian rotation and increase the risk of the severe injuries to head and thorax.

Precise integration methods to solve structural dynamic responses and the corresponding time integration formula are composed of two parts: the multiplication of an exponential matrix with a vector and the integration term. The second term can be solved by the series solution. Two hybrid granularity parallel algorithms are designed, that is, the exponential matrix and the first term are computed by the fine-grained parallel algorithm and the second term is computed by the coarse-grained parallel algorithm. Numerical examples show that these two hybrid granularity parallel algorithms obtain higher speedup and parallel efficiency than two existing parallel algorithms.

In a traffic accident, a commercial vehicle in the developing stage crashed against a wall due to the faulty operation of the driver. According to the result of the analysis, the speed of the vehicle was 50 km/h at the moment of contact, and the angle between the tire mark and the wall was 17°. In the accident, it was found that the hinge of the engine hood went fractured. The limitation of the design was also shown in the simulation result and the real crash tests of the standard test that forced the vehicle to crash against the rigid wall at the speed of 50 km/h. To solve the problem, the design of the outer and the inner panel was modified on the one hand, and the high strength steel was applied on fourteen energy-absorbing parts on the otherhand. The simulation result showed that the new design could greatly improve the crashworthiness of the vehicle, and provided a solution to the hinge problem as well.