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A new failure criterion has been developed to improve modeling of orthotropic structural composites subjected to quasi-static and impact loadings. Rather than using an analytical expression that traditionally has been employed to predict failure, a point cloud failure surface is constructed in the stress/strain space using a combination of virtual and laboratory testing. These discrete points are obtained by building a micromechanical model that is subjected to uniaxial and multiaxial states of stress until the first failure of a finite element in the model is detected. The post-peak response behavior is then activated till the element meets the erosion criterion and is deleted from the model. One of the challenges in using the generated point cloud data is the ability to correctly predict when failure onset in a finite element takes place without being too conservative. Three predictive methods are compared in this paper – Approximate Nearest Neighbor (ANN), Simplified Approximate Nearest Neighbor (SANN), and Neural Network (NN). Point cloud data from a unidirectional composite, the T800-F3900, commonly used for aerospace applications, is used for comparative evaluation of these methods. The performances are first evaluated using a standalone program not connected with FE analysis. Finally, two of these methods (SANN and NN) are implemented in a commercial finite element program, LS-DYNA, and their performances are evaluated by simulating a laboratory impact test. Results indicate that the SANN and NN implementations are robust, efficient, and accurate. [ABSTRACT FROM AUTHOR]

A new failure criterion is developed to improve modeling of orthotropic structural composites subjected to quasi-static and impact loadings. Rather than using an analytical expression to predict failure that traditionally has been employed, a point cloud failure surface is constructed in the stress/strain space using a multi-scale modeling scheme based on a combination of virtual and laboratory testing. At the microscale, the constituent components of the composite are used in modeling a representative volume element (RVE) that is subjected to multi-axial state of stress until the first failure in the RVE is detected. A volumetric homogenization scheme is used to obtain the corresponding meso-scale properties for use at the meso or structural scales. During finite element analysis, the point cloud data is queried to check if the current state of stress in the finite element is inside or outside the failure surface using k -nearest neighbor (k -NN) classification concept. The failure criterion is implemented in an explicit finite element program as a part of the failure sub-model. A representative unidirectional composite is used to illustrate the developed procedure for two structural systems using thin shell finite elements – stacked-ply tests involving tensile and compressive loading at quasi-static, room temperature conditions, and a flat panel that is subjected to impact loading. Numerical results compare favorably with experimentally obtained results showing improved predictions compared to existing failure models. The developed multi-scale point cloud concept shows promise and potentially the developed framework can be extended to support a variety of composite architectures. [ABSTRACT FROM AUTHOR]

Submarine landslides pose a serious threat to the safety of underwater engineering facilities. To evaluate the safety of undersea structures, it is important to estimate and analyze the sliding processes of potential submarine landslides. In this study, a convenient model for simulating submarine landslide processes is established by using Abaqus Eulerian large deformation technology with an explicit finite element framework. The VUSDFLD Fortran subroutine is used to consider the strain-softening and rate-dependency characteristics of soil shear strength. The proposed method is validated by comparing its results with experimental data and those of mainstream numerical methods. Then, the results of a dynamic analysis of typical potential submarine landslides in the Shenhu sea area are analyzed using the proposed method. Case studies are carried out under different soil shear strength distributions, and the influence of initial stress is also analyzed. The shear strain-softening and rate-dependency effects are highly involved in the runout process. The simulated landslide's failure mode is consistent with the geophysical interpretation of existing landslide characteristics. [ABSTRACT FROM AUTHOR]

Despite its relevance for law enforcement applications, the design of soft armor has mainly been based on a trial-and-error approach. In this paper, a combined experimental, machine learning, and finite element analysis framework is used to build a predictive numerical model for the analysis and hence, design of soft armor. The material models for major components of the soft armor certification system--bullet, shoot pack, straps, and clay backing, are first constructed using laboratory tests and publicly available data. Next, three metrics, namely, back face signature (BFS), number of penetrated shoot-pack layers, and mushrooming of the bullet are established to gauge the model's accuracy with respect to the laboratory ballistic test data. A machine learning (ML) model is used as a surrogate to predict the BFS and the number of eroded elements. Finally, optimized material model parameters are obtained through ML-based surrogate model and Bayesian optimization algorithm. The final validation of the developed framework is carried out using laboratory ballistic test data involving multiple shots on the shoot pack. The results indicate that reliable predictive data can be obtained using the developed process, and likely, can be extended for use in modeling other impact simulations. [ABSTRACT FROM AUTHOR]

Submarine landslides pose a serious threat to the safety of underwater engineering facilities. To evaluate the safety of undersea structures, it is important to estimate and analyze the sliding processes of potential submarine landslides. In this study, a convenient model for simulating submarine landslide processes is established by using Abaqus Eulerian large deformation technology with an explicit finite element framework. The VUSDFLD Fortran subroutine is used to consider the strain-softening and rate-dependency characteristics of soil shear strength. The proposed method is validated by comparing its results with experimental data and those of mainstream numerical methods. Then, the results of a dynamic analysis of typical potential submarine landslides in the Shenhu sea area are analyzed using the proposed method. Case studies are carried out under different soil shear strength distributions, and the influence of initial stress is also analyzed. The shear strain-softening and rate-dependency effects are highly involved in the runout process. The simulated landslide’s failure mode is consistent with the geophysical interpretation of existing landslide characteristics.

The structural performance of perforated steel columns (PSCs) is significantly more complex than the one of solid web I-shaped elements under the diversity of blast loading scenarios. The damage criterion of PSCs is not only related to initial deformation response during the blast but also the residual axial load capacity and it can be considered as a reliable index after the blast effects. Therefore, the PSCs damages will be studied in two stages; direct and post blast effects. In the present study, the dynamic response of PSCs was numerically evaluated under different levels of blast threats using LS-DYNA software. Extensive explicit finite element (FE) analyses are carried out to investigate the effect of various parameters, such as web opening shapes, boundary conditions and strengthening details on the damage index and toughness of the PSCs compared to the parent steel sections. The results of the comparative study show that the damage and toughness decrease when the support condition changes from pinned to fixed ends through the two stages of loadings. PSCs give high toughness compared to its parent sections during blast shock stage while, a remarkable decrease in toughness is observed during the application of axial gravity after blast shock. Furthermore, the web opening shapes have slight effects on the global dynamic behavior of PSCs, particularly in terms of residual capacity. On the contrary, the retrofitting strategy using both closed holes at end and vertical stiffeners have an effective enhancement to get higher toughness in case of the extreme blasts.

Computational modelling of complex timber-metal connections undergoing large deformations is crucial for the design of safe and robust multi-storey timber structures. Accurate simulation through large deformations requires constitutive models that suitably capture the full post-elastic behaviour of materials. Post-elastic behaviour of timber is particularly challenging to model due to strong anisotropy and material non-linearity in the post-elastic regime. Efficient simulation of complex connections requires advanced numerical modelling techniques to expedite explicit solution in the finite element domain. In this study, a suitable constitutive model for ductile metal components through large deformations, including consideration of stress localisation and triaxiality post-necking, is described. Some existing constitutive models for timber are discussed, and new constitutive models capturing both ductile and brittle failure modes are presented. A new formulation of the Hoffmann yield criterion with isotropic hardening for explicit solution is presented, and new VUMAT user subroutines for explicit solution in ABAQUS for Hoffmann, Sandhaas, Gharib, Hill-Gharib and Hoffmann-Gharib models are developed and made available for the benefit of other researchers. A benchmarked numerical model incorporating advanced modelling techniques to improve computational efficiency without compromising accuracy is presented for a complex timber, aluminium and steel dowelled beam-column connection tested shear and moment dominated testing. The simulation results compare favourably with experimental results in the literature, demonstrating that the proposed constitutive models and numerical modelling techniques provide realistic predictions of behaviour, including failure mode, and thus have the potential to support the design of complex timber-metal connections through large deformations under quasi-static and dynamic loading. • Behavior of complex timber-metal connections under large deformations is modelled using explicit FEA. • Composite Hill-Gharib and Hoffmann-Gharib constitutive models for timber are proposed. • Subroutines for explicit FEA are developed for Hoffman, Sandhaas, Gharib, Hill-Gharib and Hoffmann-Gharib timber models. • The VUMAT user subroutines developed in this study are made available for the benefit of other researchers. • Load-rate and mass-scaling techniques allow computationally efficient explicit FEA under quasi-static test conditions. • A composite Hill-Gharib constitutive model is shown to best simulate behavior in a benchmarked FEA example. [ABSTRACT FROM AUTHOR]

Tractor and earth-moving machine rollover has become one of the leading causes of occupational death in the agricultural/constructional industry. Therefore, these machines need proper protective structures to protect operators. In this study, explicit finite element (FE) analysis is adapted to predict the performance of rollover protective structure (ROPS) of a hydraulic excavator in the early design stage based on ISO 12117-2. The virtual test includes three sequential quasi-static loads applied in side, longitudinal and vertical directions, one at a time. Well-organized load sequence enables the simulation model to take the cumulative deformations caused by the three sequential loads into account and reduce the computational cost. A ROPS prototype is fabricated and tested to validate the FE model. The simulation-based results have a close agreement with the experimental test results. This FE-based safety prediction could be used to assess the new design in the early design stage to save design time and money. [ABSTRACT FROM AUTHOR]

Spacecraft are exposed to severe mechanical loads, i.e., shock loads, during their journey to orbit. Such loads usually develop due to a separation event through the activation of pyrotechnic devices. They might be transmitted throughout the entire structure and strongly influence the service performance of electronic components. Therefore, it is crucial to study whether the instruments can resist such a harsh environment. However, due to the vulnerability and high cost of the equipment, experimental setups are required to be designed and calibrated with dummy equipment, which takes considerable time and effort as well. In this context, the current study aims to investigate the potential of explicit FE solution techniques to mimic the calibration tests. In order to realize this, various experiments are conducted in a metal-to-metal impact pyroshock test bench and the obtained Shock Response Spectrum (SRS) responses are fitted to the explicit finite element simulations, which shows good agreement after a sensitivity analysis. Then, the simulations are repeated with the dummy device using the fitted parameters, and the potential of the numerical approach to predict a realistic response is discussed. [ABSTRACT FROM AUTHOR]

This paper presents the large deformation, and failure response of a thin flat scored metallic disc (FSMD) subjected to a pressure impulse as experienced in a break-away disc or an explosion vent. The response of this thin FSMD is numerically simulated for a loading rate and validated with an experiment, where a good agreement is found on plastic strains, burst pressure, and deformation pattern. The loading rate and several geometric parameters of FSMD significantly influence its response. Therefore, the influence of loading rate (P), score depth and width-todisc thickness ratio (t1/t and b/t), diameter-to-disc thickness ratio (D/t), score length-to-disc radius ratio (l/R), score pattern, and score geometry on the deformation and failure response of the thin FSMD is thoroughly investigated. The studies demonstrate that 1) the failure initiation point shifts from disc centre to between 1/5th and 1/3rd radius for loading rates = 25 MPa/s; 2) the responses such as burst pressure, burst time, central deflection, and equivalent strain are i) sensitive to the loading rates up to 100 MPa/s, ii) sensitive to score's depth, only up to 0.6t and insensitive to score's width, iii) significantly unaffected for the number of scores N > 8, iv) stabilised for l/R > 0.5 and D/t > 250, v) almost the same for semi-circular, rectangular and triangular score geometries, and vi) very minimal for the number of scores N = 3; and 3) the failure do not initiate and propagate along all scores for N > 4 in the disc. [ABSTRACT FROM AUTHOR]

The structural performance of perforated steel columns (PSCs) is significantly more complex than the one of solid web I-shaped elements under the diversity of blast loading scenarios. The damage criterion of PSCs is not only related to initial deformation response during the blast but also the residual axial load capacity and it can be considered as a reliable index after the blast effects. Therefore, the PSCs damages will be studied in two stages; direct and post blast effects. In the present study, the dynamic response of PSCs was numerically evaluated under different levels of blast threats using LS-DYNA software. Extensive explicit finite element (FE) analyses are carried out to investigate the effect of various parameters, such as web opening shapes, boundary conditions and strengthening details on the damage index and toughness of the PSCs compared to the parent steel sections. The results of the comparative study show that the damage and toughness decrease when the support condition changes from pinned to fixed ends through the two stages of loadings. PSCs give high toughness compared to its parent sections during blast shock stage while, a remarkable decrease in toughness is observed during the application of axial gravity after blast shock. Furthermore, the web opening shapes have slight effects on the global dynamic behavior of PSCs, particularly in terms of residual capacity. On the contrary, the retrofitting strategy using both closed holes at end and vertical stiffeners have an effective enhancement to get higher toughness in case of the extreme blasts. [ABSTRACT FROM AUTHOR]

The increasing miniaturization of functional devices drives the microelectronic industry to pursuit large-span-ratio and high-density wire bonding packaging technology as it can facilely interconnect various chips at a low cost. The design method of wire bonder head trace is urgently needed in the Post Moore Era. Herein, a rational design strategy of wire bonder head trace was proposed. By solving the geometric mapping equations derived from the geometrical evolution of the wire loop, the wire bonder head trace can be easily designed to fit the desired loop profile. The explicit finite element model was also developed to verify the designed wire bonder head trace and disclose the dynamic evolution of strain/stress on wire loops simultaneously. Furthermore, by using orthogonal experimental design, the trace height was found to be the most critical geometric factor influencing loop profiles. The proposed strategy was illustrated to design wire bonder head traces with which large span-ratio loops (>5) with the finest reported gold wire (sub-10 μm) were successfully formed. The mechanical strength tests showed the wire loops were superior to loops with other larger wire. The proposed strategy significantly improves the efficiency of design reliable wire bonder head trace for high-density packaging and will have broad application prospects in microelectronic industry.

This study explores the effect of impact loading in structural bar and tube welded and threaded joints. Specifically, this work concentrates on stress wave propagation and mechanical impedance to show the effect of geometric parameters on stress distribution and history inside these joined members. In this experimental work, welded and threaded bar-and-tube networks are compared with equivalent length single bars to provide a measure of joint quality. Application to dynamic experimental equipment, known as Hopkinson Bars, is considered herein due to the stringent need for wave uniformity within these systems. Explicit finite element analysis on the experimental setup was performed to provide internal stress history information to provide more insight into the causes of stress risers and spurious load reflections. A key finding in this study shows that joint impact performance reduces when joint size is either too small or too large. This optimized joint size is found to depend on the joint'seffective mechanical impedance. This study serves as a new look at potential joining considerations under impact loading.

Spacecraft are exposed to severe mechanical loads, i.e., shock loads, during their journey to orbit. Such loads usually develop due to a separation event through the activation of pyrotechnic devices. They might be transmitted throughout the entire structure and strongly influence the service performance of electronic components. Therefore, it is crucial to study whether the instruments can resist such a harsh environment. However, due to the vulnerability and high cost of the equipment, experimental setups are required to be designed and calibrated with dummy equipment, which takes considerable time and effort as well. In this context, the current study aims to investigate the potential of explicit FE solution techniques to mimic the calibration tests. In order to realize this, various experiments are conducted in a metal-to-metal impact pyroshock test bench and the obtained Shock Response Spectrum (SRS) responses are fitted to the explicit finite element simulations, which shows good agreement after a sensitivity analysis. Then, the simulations are repeated with the dummy device using the fitted parameters, and the potential of the numerical approach to predict a realistic response is discussed.

Instability following reverse shoulder arthroplasty is influenced by various factors such as component design, component positioning, and soft tissue tensioning. Patients may achieve glenohumeral motion beyond initial scapular impingement during activities of daily living which could further compound instability. However, instability/subluxation risk postscapular impingement is not well documented. Conventional range of motion analysis tools cannot account for the restraining effect of soft tissues or subluxation risk after impingement. Using a previously validated finite element analysis approach, the purpose of this study was to investigate the effects of glenoid component lateralization and humeral component angle of inclination (AOI), with or without simulated subscapularis repair, on postimpingement subluxation. We hypothesized that lack of subscapularis repair, a valgus humeral component AOI, and glenoid medialization would all result in greater postimpingement instability. A FE model of the shoulder including the subscapularis tendon and middle deltoid was created, incorporating a general representation of a commercial reverse shoulder arthroplasty implant placed under the direction of a fellowship-trained shoulder surgeon. The deltoid and subscapularis were tensioned and wrapped around the reconstructed glenohumeral joint prior to simulating motion. Humeral rotations were then prescribed to simulate external rotation (neutral to 50°), extension (neutral to 50°), adduction (neutral to 30°), and abduction (neutral to 90°). The effects of three glenosphere lateralization offsets (2, 4, and 10 mm) and 2 humeral liner angles of inclination (varus-150° and valgus-155°) on subluxation propensities were investigated with and without the subscapularis tendon present. Simulated subscapularis repair resulted in 21%-34% less postimpingement subluxation. Presence of the subscapularis provided stability over a greater range of abduction. Impingement-free range of motion was similar regardless of the presence or absence of the subscapularis. The valgus AOI resulted in 23% less subluxation during abduction. During other motions however, the valgus AOI resulted in 67%-110% greater postimpingement subluxation (subscapularis present), which further worsened without the subscapularis. Implant design modifications to improve stability may not be beneficial for all motions, highlighting the importance of directionality when investigating instability. Liner-bone impingement appears to compound instability/subluxation and the subscapularis appears to restrain postimpingement instability. Basic Science Study; Computer Modeling [ABSTRACT FROM AUTHOR]

The importance of simulation has grown significantly in recent years and, in addition to its application in product and process planning, it is increasingly used in all planning and implementation phases as well as in the optimization of existing systems. The solderless wrapping process is a highly reliable electrical connection technology. A wrapped connection is a gas-tight, mechanically, and electrically durable pressure connection and often exhibits a lower probability of failure under vibration load compared to soldered connections. Appropriate material selection and correct execution of the wrapping process are prerequisites. In order to achieve these, an exact knowledge of the wire behavior and the design of the process parameters is necessary. In this paper, the wrapping process is simulated using a finite element simulation. In the first step, the relevant parameters are identified by a cause-effect analysis and then integrated into the modeling. The validation of the model is carried out by comparing geometric parameters of the connection and the resulting mechanical stresses of simulation and experiment. The model can be used to simulate a wrapped connection with an accuracy of approximately 95 %. The model is suitable for varying process parameters and investigating their influence on the quality of the connection. [ABSTRACT FROM AUTHOR]

This paper addresses the impact penetration and perforation behaviour of sandwich panels having a low density core expanded polystyrene foam (EPS) bonded to two aluminum (6061-T6) face-sheets. The effects of foam and plate thicknesses on the impact energy absorption of sandwich panels were also investigated. The dynamic response of panels was analyzed using the explicit finite element method. The foam core material was modeled as a crushable foam material with ductile damage, and the metal face-sheets as Johnson-Cook (JC) material. The cohesive response of the adhesive interface was considered using cohesive zone model. The analyses showed that the impact energy, face-sheet and foam core thickness affected significantly failure modes, contact force levels and histories. The low-speed impact tests of the sandwich panels with different face-sheet and foam core thicknesses showed similar contact force histories, energy absorption ability and deformation modes to those of finite element analyses. [ABSTRACT FROM AUTHOR]

Boşluklu beton, agrega tanelerinin birbirine ince bir çimento hamuru tabakası ile bağlanması sonucu oluşan, yüksek oranda mezo-boyutta boşluk içeren özel bir tip betondur. Güvenlik uygulamalarında kullanılmak üzere dayanımı arttırılmış boşluklu betonlar geliştirilmesi amacıyla gerçekleştirilen bir projede, boşluklu betonların dinamik davranışları sonlu eleman yöntemiyle analiz edilmiştir. Analizlerde, ABAQUS/Explicit programında tanımlı bulunan açık direct entegrasyon metodu kullanılarak dairesel agregalı boşluklu betonlar incelenmiştir. Boşluklu betonlar ve bir yalın betonda basınç gerilmesi kontürlerinin gelişiminden yola çıkarak dalga ilerlemesi hızı tahmin edilmiştir. Hesaplanan değerlerin literatürdeki değerlere ve deneysel ultrases dalga hızı sonuçlarına çok yakın olduğu belirlenmiştir. Bunun yanında iki farklı boyutta agrega içeren boşluklu betonun dayanımlarının birbirine neredeyse eşit olduğu tespit edilmiştir. Boşluklu betonlarda oluşan hasar dağılımı ve gerilme konsantrasyonları incelendiğinde, deneylerde de tespit edildiği gibi dinamik yükleme altında çoklu çatlaklar ve yaklaşık olarak agrega boyutunda fragmanlar oluştuğu görülmektedir. Bu nedenle, fragman boyutunun agrega boyutu tarafından belirlendiği tespit edilmiştir.

A non-local macroscopic constitutive model is presented to simulate the progression of intra-laminar damage in laminated composite structures. A novel feature of the model is an orthotropic, non-local averaging scheme that is specially designed to capture the preferred path of damage / fracture propagation in laminated structures consisting of strongly orthotropic layers. In addition to maintaining the objectivity of the numerical results, through rendering them mesh size and mesh orientation invariant, the orthotropic nonlocal regularization results in a more realistic prediction of damage pattern and damage growth trajectory in orthotropic laminates. The new model, CODAM2, has been implemented in the open source finite element (FE) code, OOFEM, as well as the commercial explicit FE code, LS-DYNA. Numerical examples are presented to demonstrate the capabilities of CODAM2 in predicting the overall response and extent of damage in quasi-statically loaded, notched laminated specimens with various root notch radii ranging from sharp to blunt geometries. The developed methodology serves as a useful tool for robust and efficient inelastic analysis of large-scale composite structures leading to their damage tolerant design. [ABSTRACT FROM AUTHOR]

Development and application of the numerical model for the simulation of human heart mitral valve (MV) transapical repair is presented. Transapical repair with neochordae implantation is a novel surgical technique allowing beating-heart correction of mitral regurgitation caused by chordae tendineae rupture through a minimally-invasive approach. In the present study, the structural finite element model of the MV decoupled from the blood flow is considered. It comprises two leaflets and chordae tendineae described by nonlinear material model. Geometry of the model and kinematic boundary conditions for fixed points of MV annulus, papillary muscles, and left ventricle apex are defined by patient-specific data. Decoupled behavior of blood is specified by the time-dependent physiologic transvalvular pressure. Personalized computational modelling strategy is applied to perform virtual transapical MV repair by positioning neochordae following the real-life surgery procedure executed by surgeons. A transient analysis in time frame between end-diastole and peak systole is conducted to evaluate post-repair MV function. Computational MV simulation and modelling results provide quantitative information about the neochordae contribution to the MV function improvement and present practical value for the surgical planning of transapical MV repair.

This paper presents a three-dimensional thermo-mechanical finite element (FE) model on the micro-scale for the orthogonal cutting simulation of unidirectional carbon fiber reinforced polymer (UD-CFRP) materials. Fiber, matrix and the fiber-matrix interface are modeled separately to simulate failure mechanisms associated with fiber breakage, matrix cracking and fiber-matrix debonding. Experiments on orthogonal cutting of UD-CFRP workpieces with various fiber orientations have been conducted and compared to the micro-scale FE simulations. The good correlation between the experimental and numerical results with respect to cutting forces, chip formation and surface quality enables for an in-depth FE energy analysis to quantify dominating failure mechanisms in different fiber orientations. In addition, the contribution of each fiber failure mode during orthogonal cutting is evaluated. It is found that dissipated energies associated with various failure modes and friction vary with the fiber orientations and that the simulation provides insight into the characteristic fiber orientation-dependent quantities observed in the experiments such as chip formation and surface morphology. Finally, a sensitivity analysis is carried out to assess the variation of the simulated cutting response with respect to input parameters with high uncertainty including friction coefficients or fiber strength values. [ABSTRACT FROM AUTHOR]

• Drop-weight impact tests were performed on steel or GFRP bars RC slabs. • Effects of bar type, reinforcement ratio and arrangement were investigated. • Effects of concrete strength and slab thickness were also investigated. • Singly RC slab with higher tensile bars than doubly RC slab perform better. • The results obtained from experiment and numerical simulation are in good agreement. Reinforced concrete slabs are common structural elements that could be exposed to impact loading. Although use of reinforced concrete slabs and utilization of Fiber Reinforced Polymer (FRP) as alternative to traditional steel reinforcement slabs are growing, but the influence of various parameters on their response under impact loads is not properly evaluated. This study investigated the effect of rebar's material, amount and arrangement of reinforcements, concrete strength and slab thickness on dynamic behavior of reinforced concrete slabs using both laboratory experiments and numerical simulations. Performance of fifteen 1000 × 1000 mm concrete slabs, including two 75 mm thick plain slabs, five 75 mm thick steel reinforced concrete slabs, six 75 mm thick reinforced concrete slabs with Glass Fiber Reinforced Polymer (GFRP) bars and two 100 mm thick steel reinforced concrete slabs under drop weight impact loads was experimentally investigated. Failure mode, crack development, displacement-time, strain-time, and acceleration-time responses were studied and compared between various slabs. Finite element analyses and simulation of specimens were conducted using LS-DYNA explicit software. The results obtained from experiments and numerical models are in good agreement, and they indicate that increasing the reinforcement ratio or the slab thickness enhance the behavior of RC slabs under impact loads. By adjusting the amount and arrangement of GFRP, better performance in GFRP slabs than steel reinforced slabs can be achieved, which considering the corrosion resistance of this material, can make it an appropriate selection of reinforcement material. [ABSTRACT FROM AUTHOR]

Isogeometric B-Rep Analysis (IBRA) was the first approach that enabled a full integration of Computer Aided Design (CAD) and Computer Aided Engineering (CAE) based on trimmed NURBS B-Rep models ubiquitous in industrial CAD. However, the applicability of IBRA to explicit dynamic problems such as vehicle crash simulations and especially the effect of trimming and penalty coupling on the critical time step were not systematically investigated in the literature. To fill this gap, we developed Explicit IBRA, a combination of the patch coupling capabilities of IBRA with the explicit dynamic features of the FE solver LS-DYNA. For Explicit IBRA, we particularly (i) developed a new penalty-based B-Rep element formulation for the application to a Reissner–Mindlin shell with six degrees of freedom, (ii) formally extended the IBRA theory to explicit time integration schemes, (iii) showed that the common stability criterion and the maximum eigenvalue-based time step estimation from FE still hold, and (iv) used the IBRA exchange format to implement a closed design workflow between the CAD program Rhinoceros and the solver LS-DYNA. We solved selected benchmark problems, from quasi-static linear elastic to highly dynamic elasto-plastic with large deformations, and obtained accurate results with penalty factors that cause no or only a minor decrease in stable time step size. That is, we found that penalty coupling does not have a severe impact on the critical time step in explicit analysis, making Explicit IBRA practically applicable. Finally, we studied an industrial BMW engine bonnet model under dynamic loading and observed good agreement with reference finite element simulations. • We extend Isogeometric B-Rep Analysis (IBRA) to explicit dynamics: Explicit IBRA. • We present a new B-Rep element to couple rotation-based Reissner–Mindlin shells. • Explicit IBRA enables crash-type simulations on trimmed multi-patch NURBS models. • Accurate solutions & feasible time step size in trimmed, penalty-coupled benchmarks. • Explicit dynamic analysis on a trimmed multi-patch BMW engine bonnet model. [ABSTRACT FROM AUTHOR]

Concrete-filled Rectangular Hollow Sections have been tested under large-scale, far-field, air-blast loading for the first time. The concrete-filled, cold-formed steel tubes performed well under the blast loads, with a significant reduction in the global and local displacements compared to unfilled RHS members. The heavily instrumented tests provided a large quantity of response data that was used for the validation of numerical models. Numerical models of the concrete-filled steel tubes were first developed using explicit finite element methodologies. A parametric study was conducted with the validated finite element model to further characterize the response of the concrete-filled steel tubes under air-blast loading. The influence of several key variables on the response of the tubular members was determined and preliminary design guidance is provided. Finally, the test and finite element results were used to develop an idealized single-degree-of-freedom numerical model that is well-suited to future use in design problems. [ABSTRACT FROM AUTHOR]

The transient dynamic characteristic of a tire, which has a significant effect on vehicle handling stability and ride comfort, is difficult to study in detail because of its highly non-linear behavior. In this study, the transient dynamic characteristics of a non-pneumatic wheel, called the mechanical elastic wheel (MEW), which was rolling over a ditch were investigated by the explicit dynamic finite element (FE) method. A three-dimensional FE model of MEW considering geometric nonlinearity, material nonlinearity and large contact deformation between the wheel and the road, was established. For the validation of the accuracy and reliability of the FE model of MEW, the simulation and the experimental results of the radial stiffness and footprint of MEW were compared and analyzed. A dynamic simulation of the validated FE model of MEW rolling over a ditch was conducted using the ABAQUS/Explicit program. The equivalent stress and the contact stress generated during the process of the rolling MEW impacting the ditch were studied in detail. The effect of the rolling speed on the transient dynamic characteristics was also analyzed based on the simulation results. The simulation results could provide guidance for the optimization of the MEW structure and vehicle dynamics. [ABSTRACT FROM AUTHOR]

Modeling progressive failure of bolted composite joints under high bearing strains is challenging due to the highly nonlinear geometric and material behavior and multiple contact surfaces. In this study, the progressive failure of bolted single-lap joints of woven composites is investigated numerically and experimentally. The finite element (FE) model employs continuum shell elements for each ply and cohesive elements for the material interfaces. Explicit FE analysis is employed due to its capability in treating contact with complex geometries. Material nonlinearities due to fiber rupture in the tows and matrix micro-cracking are accounted for by appropriate material degradation modelling. A set of experiments was conducted and digital image correlation (DIC) was used to measure displacements around the bolted area. The bearing failure characteristics of the bolted joint, including the crushing of the composite material due to the rotation of the bolt head as predicted by FE analysis agree with experimental observations. Element deletion as a practical numerical strategy to overcome convergence issues is proposed for large local element distortions and extensive local material crushing. It is shown that the errors could be acceptable if very fine mesh is employed around the bolted area and only relatively few elements are deleted. [ABSTRACT FROM AUTHOR]

High Strength Steel Wire Mesh and High Performance Mortar (HSSWM-HPM) are widely used for structural reinforcement and retrofit. Recent research suggests that HSSWM-HPM can be applied to enhance seismic loading-resistance of structures. In this study, the mechanical performance of reinforced concrete (RC) beams covered with the HSSWM-HPM under impact loading were evaluated using both laboratory experiments, and numerical simulations. In the laboratory experiments, the performance of eight full-size beams, including five retrofitted RC beams and three un-retrofitted RC beams, subjected to the drop-weight impact loading and static loading were evaluated. During the drop-weight impact tests, the contributions of the following critical parameters, including the impact loads, strains, accelerations, velocities, and deflections of the beams, and residual damage, were studied and compared among different specimens. Another comparative study on the failure pattern and the impact resistance of beams with and without reinforcement were performed in the commercial finite element software LS-DYNA. A general prediction of response time histories and maximum mid-span deflections of the beams were obtained from LS-DYNA. The results obtained from both laboratory experiments and finite element analyses indicated that the impact resistance and ductility of the RC beams were significantly improved after retrofitted with HSSWM-HPM. [ABSTRACT FROM AUTHOR]

In this article, the ballistic impact response of square clamped fiber–metal laminates and monolithic plates consisting of different aluminum alloys is investigated using the ANSYS LS-DYNA explicit nonlinear analysis software. The panels are subjected to central normal high velocity ballistic impact by a cylindrical projectile. The implemented finite element models have been validated by comparison with published experimental data concerning GLARE 5 and monolithic 2024-T3 aluminum plates. Using the validated models, the influence of the mechanical properties of the constituent aluminum alloy on the ballistic resistance of the fiber–metal laminates and the monolithic plates is studied. Apart from 2024-T3, the aluminum alloys 2024-T351, 2024-O, 6061-T6, 7039 and 7075-T6 are considered. It is found that the ballistic limits of the panels can be substantially affected by the constituent aluminum alloy. The 7075-T6 aluminum alloy offers the highest ballistic resistance whereas 2024-O aluminum alloy offers the lowest ballistic resistance. [ABSTRACT FROM AUTHOR]

In the design of AFVs, study of structures subjected to land mine blast is important. Generally, blast related experimental studies are very time consuming and costly. A simple first cut alternative is finite element modelling and analysis. Here, modelling of mine and simulating the blast effect involves large number of mesh elements, which makes the model computationally intensive and time consuming. Hence, instead of using full scale model for analysis, a suitable scaled down model would reduce analysis time and leads to a faster DOE studies. A proper scaling mechanism is to be evolved in order to get accurate results. Discusses about the scaling of plate subjected to mine blast using dimensional analysis approach. The out-of-plane surface deformation, including velocity fields during the blast loading are compared between the scaled and unscaled plate. [ABSTRACT FROM AUTHOR]

This paper presents a simple novel crash energy absorbing system made of plain aluminium thin-walled tubes and honeycomb. The proposed tube/honeycomb system is characterized by slightly shorter tubes inserted into the cells of the honeycomb with close fit. The individual tube and honeycomb structures are numerically modelled under low-speed vertical impact loading and compared with experiments conducted in this study. Next, three representative triangular sections, which involve the symmetric boundary conditions of each cell group, are employed to model the tube/honeycomb system. Load-displacement curves and deformation patterns are compared with the experiments. The proposed honeycomb/tube system is found to produce higher energy absorption capacities for both per unit mass and volume, compared to an ordinary superposition of the constituents. Almost a perfect crushing load plateau is achieved without a peak force. These enhancements are associated with the spontaneous pre-deformation of the tubes pushed by the collapsed honeycomb walls. This interaction also enables synchronised deformation throughout the crash. Finally, a parametric study is performed, based on the height difference between the tubes and honeycomb, which is found to be the determiner of the performance for the proposed system. [ABSTRACT FROM AUTHOR]

This work presents a finite element approach for modeling longitudinal wave propagation in thick cylindrical rods with circular cross-section. The formulation is based on simple time domain response of the structure to a properly chosen excitation, and is calculated with an explicit finite element solver. The proposed post-treatment procedure identifies the wavenumber for each mode of wave propagation at the desired frequency. The procedure is implemented and integrated in an efficient way in the explicit finite element code Europlexus. The numerical results are compared to the analytical ones obtained from the solution of the Pochhammer — Chree equation, which provides the dispersion curves for wavetrains in solid cylinders of infinite length.

This paper presents the results of an experimental and numerical study on aluminium honeycomb sandwich structures under low-velocity impact loadings. In order to investigate the impact behavior of honeycomb sandwich structures, which is consisted of two identical aluminium facesheets and an aluminium honeycomb core, an experimental study was carried out by using a drop-weight impact test system. Using this system, the contact forces and absorbed energies were measured to determine the influence of impact energy for one configuration of the sandwich structure. According to these results, a numerical model by finite element method of sandwich structures was developed, which is in good agreement with experimental results in terms of contact forces and deformations. Later, the effect of the cell size and the height variation of aluminum honeycomb core on the impact response of sandwich structures were investigated using the improved numerical model. The obtained numerical and experimental results were interpreted in detail. [ABSTRACT FROM AUTHOR]

In order to address various noise generation mechanisms and noise propagation phenomena of a tyre, it is necessary to study the tyre dynamic behaviour in terms of modal parameters. This paper enumerates a novel method of finding the modal parameters of a rolling tyre using an Explicit Finite Element Analysis and Operational Modal Analysis (OMA). ABAQUS Explicit, a commercial Finite Element (FE) software code has been used to simulate the experiment, a tyre rolling over a semi-circular straight and inclined cleat. The acceleration responses obtained from these simulations are used as input to the OMA. LMS test lab has been used for carrying out the Operational Modal Analysis. The modal results are compared with the published results of Kindt [22] and validated. Also, the modal results obtained from OMA are compared with FE modal results of stationary unloaded tyre, stationary loaded tyre and Steady State Transport rolling tyre. [ABSTRACT FROM AUTHOR]

Box-shaped bumper beams mounted on vehicles serve as shock absorbers in a potential crash. In this study, their optimal shape design is investigated. The objective is to maximize the crashworthiness of the beam. The crash phenomenon in standard tests is simulated in which the vehicle hits a deformable barrier with 40% offset by 64 km/h speed. The bumper beam and the brackets supporting the beam are modeled as deformable bodies in full detail. For the rest of the car, a lumped parameter model is developed. The crash event is simulated using explicit finite element method. The design variables are the parameters defining the cross-sectional shape of the beam. The beam is optimized using a hybrid search algorithm combining Genetic and Nelder & Mead algorithms. The results indicate significant improvement in the crashworthiness of the bumper beam currently in-use. Resistance to low-velocity impact is also improved. [ABSTRACT FROM AUTHOR]

In order to obtain the ultimate bearing characteristics, failure behavior and safety manners, the explicit finite element analysis calculation and the physical experiment were introduced to implement on the car seat elevation. On the finite element modeling, especially the material stress exceeding the yield limit, the real stress and real strain were used to descript the plasticity of material constitutive model. The structural displacement, velocity and acceleration response curves were obtained and the saw tooth effect was distinctive gradually with loading history. The phase transition was tracked through the response behavior and the phase point was extracted from the response curve. The ultimate torque of bearing seat elevation was about 96 N ½ m calculated through the phase point and loading history curve, which is in good agreement with the experiment. The seat elevation was lost failure and found that the structural damage location, accounting for the simulation and the physics experiment disassembled was very close. The results indicate that the method is validity to give an efficient guidance design and to assure the reliability of the seat elevation, which can give some evidence to estimate the maximum bearing moment and the failure behavior owning to the key components. [ABSTRACT FROM AUTHOR]

We report on modeling mechanical response of cylindrical lithium-ion battery cells that are commonly used in automotive applications when subjected to impact testing. The developed homogenized model that accurately captures mechanical response of a cell to lateral crash is reported. The proposed model was validated using static and dynamic experimental testing. Highly nonlinear mechanical deformations of the cells were captured experimentally using a high-speed camera and later characterized through computer tomography. Numerically, we have investigated the feasibility of using explicit finite element code for accurate modeling of impact on one cell, so it can be used for an entire battery pack that consists of hundreds or thousands of cells. In this study, we have developed and compared two homogenization methods for the jellyroll in a cylindrical lithium-ion battery cell. Homogenization was conducted in a lateral/radial direction. Based on the results of the homogenization, the material model utilizing crushable foam constitutive behavior was then developed for simulations. Experimental results showed a very good agreement with simulations, thus validating the proposed approach and giving us confidence to move forward with the crush simulations of an entire battery pack. Zones of potential electric shortages were determined based on the experiments and simulations. [ABSTRACT FROM AUTHOR]

Pull-through failure of bolted joints in composites is due to the relatively low through-thickness properties of laminated materials. Recently it has been identified that pull-through failure also plays an important role in the ultimate bearing load and total energy absorption of bolted joints, especially under dynamic conditions. It has been previously found that bolted joints loaded in bearing exhibit rate sensitivity whereas bolts loaded in pull-through experience very little sensitivity, for nearly identical joint configurations. The primary focus of this paper was to use explicit finite element simulation of pull-through failure to shed light on discrepancies between experimentally observed rate sensitivity for seemingly similar tests. The paper uses the stacked-shell modelling approach to efficiently model the interaction of delamination and ply failure under the complex dynamic load state. The results of the simulation indicated that the properties of the interface susceptible to loading rate sensitivity, Mode I and II strain energy release rates (SERRs), did not have a great effect on the overall joint response; despite the prevalence of delamination during the failure process. A weak relationship between Mode II SERR and joint response was discovered which was consistent with experimental observations. [ABSTRACT FROM AUTHOR]

In this study, the objective is to maximize the crashworthiness of thin-walled tubes under axial impact loads by shape optimization. As design variables, parameters defining the cross-sectional profile of the tube as well as parameters defining the longitudinal profile like the depths and lengths of the circumferential ribs and the taper angle are used. The methodology is applied to the design optimization of a crash-box supporting the bumper beam of a vehicle for the loading conditions in standard EuroNCAP crash tests. The crash event is simulated using explicit finite element method. While the crash-box is fully modeled, the structural response of the remaining parts during the tests is taken into account by developing a lumped-parameter model. A hybrid search algorithm combining Genetic and Nelder & Mead algorithms is developed. The results indicate significant improvement in the crashworthiness over the benchmarks designs. [ABSTRACT FROM AUTHOR]