Modeling of Bridge Collapse in Virtual Scene Based on Finite Element Simulation

Normally, FTire model parameters are determined by experimental tests. However, because of the high cost of experiment equipment and limitations in rig design and operating conditions, it is hard to obtain all the required data by experimental tests, especially for some large tires, such as the running wheel tires of straddle-type monorail vehicles. To solve this problem, a method based on finite element (FE) simulations is put forward. To achieve the goal, a three-dimensional FE model of a 345/85R16 radial tire is developed using ABAQUS software. In addition, a modified exponential decay friction model, derived from tire tread rubber friction tests, is put forward and applied in the following FE simulations using the ABAQUS user subroutine FRIC. To verify the accuracy of the present model, tire vertical stiffness test, lateral stiffness test, and tire contour geometry measurement are designed. Through the comparison of measurements and FE simulations, it turns out that the model is capable of predicting tire properties accurately. Tire static, steady-state, modal, and dynamic cleat tests are modeled. Finally, data such as vertical stiffness, cornering stiffness, and natural frequencies are derived from FE simulations. Based on the data derived from FE simulations, the FTire model parameters are identified and then validated by comparing the force responses of the FTire simulation in the ADAMS/Tire test rig and FE simulations. The results show that there is an acceptable agreement between them, reflecting that the method is feasible.

This paper deals with problems in the coining process for manufacturing surgical slit knife using two-dimensional (2D) and three-dimensional (3D) finite element (FE) simulations. The FE simulations are performed to investigate the material flow, and especially stress distribution on the coining dies. The main objective of this paper is to study the feasibility of a coining process for manufacturing a given geometry of surgical slit knife without forming defects and die failure. Very high stress distribution on the coining dies is found by 2D simulations of the coining process that exceeds the strength limit of the die material. The optimum preform and preforming die geometry are determined by FE simulations in order to reduce the die stress. 3D simulations of the preforming and coining processes are conducted with the optimal design to show that the geometry of the product can be achieved without defects by the coining process.

Current techniques for nondestructive quality evaluation of solder bumps in electronic packages are either incapable of detecting solder bump cracks, or unsuitable for in-line inspection due to high cost and throughput. As an alternative, a solder bump inspection system is being developed at Georgia Tech using laser ultrasound and interferometric techniques [1]. This system uses a pulsed Nd:YAG laser to induce ultrasound in electronic packages in the thermoelastic regime; it then measures the transient out-of-plane displacement responses on the surface of the chip or packages using laser interferometric technique. This paper presents a systematic study on thermo-mechanical reliability of flip chip solder bumps using laser ultrasound-interferometric inspection system and finite element (FE) simulation. The correlation between the failure parameter of solder bumps extracted from FE simulation and the quality degradation results of solder bumps from laser ultrasound testing has also been studied. Accelerated thermal cycling (ATC) tests were performed in two phases on flip chip package (FCP) test vehicles with 63Sn37Pb solder bumps. In phase I, four boards were thermal cycled up to 70 cycles. Every ten cycles, the boards were taken out and FCPs on each board were tested for presence of cracks using resistance and laser ultrasound testing methods. These measurements were repeated every 10 cycles and stopped after 70 cycles. Laser ultrasound testing results show that beginning from 10 cycles, testing values began to increase gradually until 50 cycles when there was a sharp jump (through crack verified at 50 cycles with cross-section). Cross-section was done only after 70 cycles, and the results show that solder bumps at the corners had through cracks, while solder bumps at the center had partial cracks. Phase II studies were refinements of phase I studies. In phase II studies, seven boards were thermal cycled starting from 27 cycles to 56 cycles at an increment of approximate five cycles. After every five cycles, only one board was pulled out and tested in order to track crack initialization and propagation in solder bumps. Smaller thermal cycle increments were used to help determine exactly when cracks initiated and propagated. It was shown that laser ultrasound technique could track solder bump crack propagation induced by thermal cycling. The elastic-plastic-creep and Anand's viscoplastic constitutive models have been used in FE simulation to describe the inelastic deformation behavior of solder bumps. A three-dimension FE model was implemented using ANSYSreg on the same FCP as used in the ATC testing. The stress-strain results were extracted from FE modeling and the inelastic strain energy density (SED) per cycle calculated at the critical solder bump position was used as a failure parameter. It was found that there was a good correlation between inelastic SED extracted from FE simulation and results from laser ultrasound testing.

The sheet hydroforming with punch (SHF‐P) process offers great potential for low and medium volume production, especially for forming: (1) lightweight sheet materials such as aluminum (Al) and magnesium (Mg) alloys and (2) thin gage high strength steels (HSS). Mg and Al alloys are being increasingly considered for automotive applications, primarily due to their lightweight and high strength‐to‐weight ratios. However, there is limited experience‐based knowledge of process parameter selection and tool design for SHF‐P of these materials. Thus, there is a need for a fundamental understanding of the influence of process parameters on part quality. This paper summarizes analyses of the SHF‐P process of AA5754‐O sheet using finite element (FE) simulations. FE simulations and preliminary experiments of SHF‐P were conducted to determine the process parameters (blank holder force versus punch stroke and pot pressure versus stroke) to form a challenging shape (a cylindrical cup with a reverse bulge) successfully at room and elevated temperature (∼150 °C). The material properties of the sheet material were obtained from tensile tests at room temperature up to 260 °C as presented by [1]. The FE model was established using PAMSTAMP 2G, Version 2009. SHF‐P experiments were conducted in order to (i) evaluate the formability of the part at room and elevated temperatures and (ii) validate FE simulation results. This study shows that the SHF‐P at elevated temperature can form a cup with larger cup height and better reverse bulge profile than SHF‐P at room temperature. Moreover, the FE predictions of part profiles and thinning distributions matched reasonably well with the experimental results.

There has been a growing interest in recent years in the assessment of suitable vial/stopper combinations for storage and shipment of frozen drug products. Considering that the glass transition temperature (Tg) of butyl rubber stoppers used in container closure systems (CCSs) is between -55 °C to -65 °C, a storage or shipment temperature of a frozen product below the Tg of the rubber stopper may require special attention because below the Tg the rubber becomes more plastic like and loses its elastic (sealing) characteristics. Thus, they risk not maintaining container closure integrity (CCI). Given that the rubber regains its elastic properties and reseals after rewarming to ambient temperature, leaks during frozen temperature storage and transportation are transient and the CCI methods used at room temperature conditions are unable to confirm CCI in the frozen state. Hence, several experimental methods have been developed in recent years in order to evaluate CCI at low temperatures. Finite element (FE) simulations were applied in order to investigate the sealing behaviour of rubber stoppers for the drug product CCS under frozen storage conditions. FE analysis can help in reducing the experimental design space and thus the number of measurements needed, as they can be used as an add-on to experimental testing. Several scenarios have been simulated including the effect of thermal history, rubber type, storage time, worst-case CCS geometric tolerances, and capping pressure. The results of these calculations have been validated with experimental data derived from laboratory experiments (CCI at low temperatures), and a concept for tightness has been developed. It has been concluded that FE simulations have the potential to become a powerful predictive tool toward a better understanding of the influence of cold storage on the rubber sealing properties (and hence on CCI) when dealing with frozen drug products.LAY ABSTRACT: The growing interest in the assessment of suitable vial/stopper combinations for storage and shipment of frozen drug products has led to the development of a number of experimental methods to evaluate container closure integrity at low temperatures. The application of finite element simulations could aid in the investigation of the sealing behaviour of rubber stoppers for drug product container closure systems under frozen storage conditions by simplifying the experimental design space and the number of experimental measurements needed. In this work several scenarios have been simulated including the effect of thermal history, rubber type, storage time, worst-case container closure system geometric tolerances, and capping pressure. The results have been further validated with experimental data derived from laboratory experiments and a concept for tightness was developed. In conclusion, finite element simulations have shown the potential to become a powerful predictive tool toward a better understanding of the influence of cold storage on the rubber sealing properties (and hence on container closure integrity) when dealing with frozen drug products.

An algorithm for extracting the equivalent stress versus equivalent plastic strain curve of a necking material in tensile test is proposed (the curve is called here the equivalent-plastic (EP) stress–strain (SS) curve). The presented algorithm traces the force–elongation curve via iterative finite element (FE) simulations without assuming a constitutive model and is suitable for a general-purpose FE solver available to a general audience. In the FE simulation and experiment, a slightly tapered geometry was employed around the specimen center to stably initiate necking there. The proposed algorithm and mentioned necking initiation method have been applied to extracting the EP SS curve of a high-strength steel material using an axisymmetric specimen. Because necking was initiated stably in simulation at the specimen center for a range of mesh sizes, the convergence of the extracted EP SS curve with the mesh size could be successfully verified. The EP SS curve of the tested material was extracted up to an EP strain of 0.85 with average strain intervals of approximately 2.5 mili-strain. The error values were less than 0.2 and 0.1% after four and seven FE simulations, respectively. The presented algorithm and necking initiation method in simulation can also be used for simultaneously quantifying the fracture EP strain of a necking material in the tensile test.

Self-piercing riveting (SPR) has been widely used in automobile industry, and the strength prediction of SPR joints always attracts the attention of researchers. In this work, a prediction method of the cross-tension strength of SPR joints was proposed on the basis of finite element (FE) simulation and extreme gradient boosting decision tree (XGBoost) algorithm. An FE model of SPR process was established to simulate the plastic deformations of rivet and substrate materials and verified in terms of cross-sectional dimensions of SPR joints. The residual mechanical field from SPR process simulation was imported into a 2D FE model for the cross-tension testing simulation of SPR joints, and cross-tension strengths from FE simulation show a good consistence with the experiment result. Based on the verified FE model, the mechanical properties and thickness of substrate materials were varied and then used for FE simulation to obtain cross-tension strengths of a number of SPR joints, which were used to train the regression model based on the XGBoost algorithm in order to achieve prediction for cross-tension strength of SPR joints. Results show that the cross-tension strengths of SPR steel/aluminum joints could be successfully predicted by the XGBoost regression model with a respective error less than 7.6% compared to experimental values.

Additive manufacturing (AM) allows fabrication of complex geometric parts that are difficult to fabricate using a traditional subtractive manufacturing process. Stereolithography (SLA) printing is an AM technique that prints the 3D part from liquid resin based on the principle of photopolymerization. Part deformation and failure during the separation process are the key bottlenecks in printing high-quality parts using bottom-up SLA printing. Cohesive zone models have been successfully used to model the separation process in the bottom-up SLA printing process. However, the finite element (FE) simulation of the separation process is prohibitively computationally expensive and thus cannot be used for online monitoring of the SLA printing process. This paper outlines a deep learning (DL)–based framework to predict the stress distribution on the cured layer of the bottom-up SLA process–based printed part in real time. The framework consists of (1) a new 3D model database that captures a variety of geometric features that can be found in real 3D parts and (2) FE simulation on the 3D models present in the database that is used to create inputs and corresponding labels (outputs) to train the DL network. Two different types of DL networks were trained to predict the stress on the test dataset. Results further show that this framework drastically reduces computational time in comparison with FE simulations.

Effects of local plastic instabilities in the form of yield point phenomena (YPP) were investigated on local and global deformation and failure behavior of resistance spot-welded tension–shear (TS) samples made from M1700 advanced high-strength steel (AHSS) by means of finite element (FE) simulations. Material models with and without YPP were used in FE simulations, and sensitivity of results to YPP material model characteristics and failure criteria was investigated. Results from FE simulations revealed several stages of load oscillations in predicted global load–displacement curves with different amplitudes depending on material model with YPP. Results also showed the existence of heterogeneous distribution of equivalent stress in heat-affected zone (HAZ) of TS samples with strong sensitivity to the upper and the lower yield stress values in YPP material model. A stress-based failure criterion was added to the damage model to account for this stress heterogeneity, and results from this model showed that the loading and failure behavior of TS sample can significantly change from ductile to premature semi-brittle failure with significant reduction in strength of TS sample. Results from FE simulations were also compared with those from TS experiments and indicated the need for development of proper material and damage models suitable for materials with YPP.

To prevent traumas to abdominal organs, the selection of efficient safety devices should be based on a detailed knowledge of injury mechanisms and related injury criteria. In this sense, finite element (FE) simulation coupled with experiment could be a valuable tool to provide a better understanding of the behaviour of internal organs under crash conditions. This work proposes a methodology based on inverse analysis which combines exploration process optimisation and robustness study to obtain mechanical behaviour of the complex structure of the liver through FE simulation. The liver characterisation was based on Mooney–Rivlin hyperelastic behaviour law considering whole liver structure under uniform quasi-static compression. With the global method used, the model fits experimental data. The variability induced by modelling parameters is quantified within a reasonable time.

Study on ring compression test using physical modelling and FE simulation

Bio-inspired engineering design has drawn increased attention in recent years for the excellent structural and mechanical properties of the biological systems. In this study, the horsetail-bionic thin-walled structures (HBTSs) were investigated for their crashworthiness under axial dynamic loading. Six HBTSs with different cross section configurations (i.e., number of cells) were evaluated using nonlinear finite element (FE) simulations. To obtain the optimal design of the HBTSs, an ensemble metamodel-based multi-objective optimization method was employed to maximize the specific energy absorption while minimizing maximum impact force of the HBTSs. Using the ensemble metamodeling, FE simulations and the NSGA-II algorithm, the Pareto optimum designs of all six HBTSs were obtained and the HBTS with 16 cells were found to have the best crashworthiness. An optimum design of the HBTS with 16 cells was verified using FE simulation and found to have good agreement with simulation results.

Molecular dynamics (MD) and finite-element (FE) simulations of a nano-crystalline diamond (NCD) grain system subjected to indentation were undertaken to understand how contact behavior pertaining to the surface roughness of NCD crystals can be spanned from the molecular to the continuum scale. It is shown that if the same surface roughness morphology, grain orientations, and elastic properties are used for both MD and FE simulations, there is agreement between contact pressures for relatively low indentation loads and shallow substrates. It should be emphasized that the strong correlation between MD and FE methods can also be due to the lack of defect nucleation associated with the elastic deformation of the NCD system. These predictions can be used for a hierarchical computational framework to harness the advantages of both computational approaches. Inherent to this approach is representation of surface roughness and crystal orientation that is physically consistent for both computational approaches. Using the techniques presented herein, MD simulations of fluids and fluid solid interactions may be able to be accurately performed using computational fluid dynamics (CFD) and FE simulations if an appropriate set of translation rules can be found for converting MD models to CFD models. An initial analysis of the requirements to convert MD models to CFD is undertaken and a subset of the necessary rules is postulated.

Due to the material deformation process in drilling are quite complicated, research using finite element simulation on drilling is limited and not widely reported. To investigate drilling process, a coupled thermo-mechanical finite element model of drilling is developed. Several key technologies, such as material constitutive model, material failure law, contact and friction law, have been implemented to improve the accuracy of finite element simulation. Using this finite element model, drilling process of Ti6Al4V alloy is predicted. Comparing the predicted cutting forces with the measured forces shows the finite element model is reasonable. Analyses show that the distributions of Misses stress and temperature during drilling process all increase at first, and get maximal value when drilling is in steady state, then decrease gradually till the hole is drilled through. These results confirm the capability of finite element simulation in predicting drilling process and selecting optimal tool and cutting parameters.

Finite element simulation and theoretical analysis of fiber-optical switches