LS-DYNA MAT54 modeling of the axial crushing of a composite tape sinusoidal specimen

The suitability of a progressive failure material model to simulate the quasi-static crushing of a composite specimen is evaluated. The commercially available material model MAT54 “Enhanced Composite Damage” in LS-DYNA is often utilized to simulate damage progression in dynamic failure simulations because it requires a reduced number of experimental input parameters compared to damage mechanics-based material models. The composite specimen used for the experiments is a semi-circular sinusoid, and is comprised of carbon fiber/epoxy unidirectional prepreg tape. Results show that MAT54 can successfully reproduce experimental results, however the simulation is highly sensitive to changes in model parameters, which are either non-physical (i.e. are purely mathematical expedients), or cannot be measured experimentally. These include element size, contact definition, load–penetration curve, and crush front softening parameter, among others. Therefore, achieving successful simulation results requires extensive calibration of these parameters by trial and error, and a deep understanding of the strengths and challenges of the selected modeling strategy.     

Multiobjective optimization for tapered circular tubes

As more and more new functional requirements are placed, some novel development of sectional configurations of the structural members has been increasingly introduced. This paper presents the optimal design for tapered tubes of three different configurations, namely hollow single, foam-filled single and collinear double tubes. To represent complex crashworthiness objective functions, a surrogate model method, more specifically, response surface method (RSM), was adopted in this study. The design of experiments (DoEs) of the factorial design and Latin Hypercube Sampling techniques is employed to construct the response surface models of specific energy absorption (SEA) and the maximum impact load (MaxL), respectively. In this paper, the linearly weighted average, geometrical average and particle swarm optimization methods are utilized in the multiobjective optimization for these three different tapered tube cases, respectively. A comparison is made among the different tapered profiles with the different optimization algorithms, and the crashworthiness merits of foam-filled tapered tubes are identified.     

乘用车两车侧面碰撞事故统计研究

在NASS／CDS数据库统计数据基础上，对乘用车两车侧面碰撞交通事故进行了统计研究，并对比分析了FARS数据库统计结果。研究结果表明，在CAR对LTV的侧面碰撞事故中，CAR乘员的损伤机率是LTV的数倍。     

Collision performance of square tubes with diaphragms

The energy absorption responses of conventional tubes and tubes with diaphragms are analysed here by means of finite element simulation. Numerical results show that tubes with diaphragms exhibit a relatively stable crushing process. The effect of imperfect energy absorption responses is also analysed, including the top shape of tubes and oblique loading. The strain rate affects the dynamic response of tubes with diaphragms. Four prototypes of these tubes were constructed and tested; however, sizeable differences were obtained between experimental results and the results of numerical simulation of the ideal structure in terms of process errors.     

Crashworthiness design of functionally graded foam-filled multi-cell thin-walled structures

Foam-filled thin-walled structure has recently gained attention due to its excellent crashworthiness. Based on the previous study, a new kind of foam-filled thin-walled structure called as functionally graded foam-filled thin-walled structure has more excellent crashworthiness than the traditional uniform foam-filled thin-walled structure. Moreover, as far as we know multi-cell thin-walled structure has more excellent crashworthiness than the traditional single-cell thin-walled structure. As an integrator of the above two kinds of excellent thin-walled structures, functionally graded foam-filled multi-cell thin-walled structure (FGFMTS) may has extremely excellent crashworthiness. Based on our study, the crashworthiness of the FGFMTSs is significantly affected by the design parameter of the graded functional parameter m. Thus, in order to obtain the optimal design parameters, the FGFMTSs with different cross sections and different wall materials are optimized using the multiobjective particle swarm optimization (MOPSO) algorithm to achieve maximum specific energy absorption (SEA) capacity and minimum peak crushing force (PCF). At the same time, the corresponding uniform foam-filled multi-cell thin-walled structures (UFMTS) which have the same weight as these FGFMTSs are also optimized in our study. In the multiobjective design optimization (MDO) process, polynomial functional metamodels of SEA and PCF of FGFMTSs are used to reduce the computational cost of crash simulations by finite element method. The MDO results show that the FGFMTS with PCF in the initial period of its crash not only has better crashworthiness than the traditional UFMTS with the same weight but also performs superior balance of crashing stability. Thus, the optimal design of the FGFMTS with PCF occurring in the initial crash is an extremely excellent energy absorber and can be used in the practical engineering.     

Performance analysis of fibre metal laminated thin conical frusta under axial compression

The crushing behaviour and energy absorption capacity of frustrated conical shells made-up of bare aluminium (AC) and E-glass fibre/epoxy resin composite overwrapped aluminium (CWAC) was studied under quasi-static axial compression condition. Using spinning process, the hollow frustrated conical specimens were fabricated with the help of wooden conical shaped mandrill with semi apical angles of 16° and 21°. Thin commercial aluminium sheets of average thickness 0.87 mm were obtained for making aluminium conical specimen. CWAC frusta were fabricated by wrapping glass fibre/epoxy resin over aluminium conical shell to form hybrid composite with required thickness by hand layup process. Quasi-static axial compression load was applied over top end of the specimen with cross head speed as 2 mm/min using Universal Testing Machine (UTM). From the experiment results, the load–deformation characteristics of different AC and CWAC frusta were investigated. Energy absorption capacities or crashworthiness and mode of collapse of all models of AC and CWAC are determined from load–deformation curve and the same was validated with finite element analysis package ABAQUS®.     

Bending behavior of empty and foam-filled beams: Structural optimization

Bending crash tests on empty and foam-filled square aluminum beams have been performed. Furthermore, in order to find more details about crash processes, finite element simulations have been done. In terms of improving crash behavior of the aluminum beams, the crashworthiness optimization procedure has been applied to maximize specific energy absorption of the square beams with the target energy absorption. A comprehensive study about the strengthening effect of foam in the filled beam has been performed and finally the optimization technique has been implemented to find the optimum foam-filled beam that absorbs the same energy as optimum empty tubes with lower weight.     

Safety impacts due to the incompatibility of SUVs, minivans, and pickup trucks in two-vehicle collisions

This research sets out to estimate the effects of vehicle incompatibility on the risk of death or major injury to drivers involved in two-vehicle collisions.Based on data for 2,999,395 drivers, logistic regression was used to model the risk of driver death or major injury (defined has being hospitalized). Our analyses show that pickup trucks, minivans and sport utility vehicles (SUVs) are more aggressive than cars for the driver of the other vehicle and more protective for their own drivers. The effect of the pickups is more pronounced in terms of aggressivity. The point estimates are comparable to those in the Toy and Hammitt study [Toy, E.L., Hammitt, J.K., 2003. Safety impacts of SUVs, minivans, and pickup trucks in two-vehicle crashes. Risk Analysis 23, 641–650], but, in contrast to that study, we are now able to establish that a greater number of these effects are statistically significant with a larger sample size.Like vehicle mass and type, other characteristics of drivers and the circumstances of the collision influence the driver’s condition after impact. Male drivers, older drivers, drivers who are not wearing safety belts, collisions occurring in a higher speed zone and head-on collisions significantly increase the risk of death. Except for the driver’s sex, all of these categories are also associated with an increased risk of death or of being hospitalized after being involved in a two-vehicle collision. For this risk, a significant increase is associated with female drivers.     

Automotive side glazing failure due to simulated human interaction

Failure mechanisms due to simulated occupant interaction with tempered and laminated automobile side glazing were tested and the results discussed. Both OEM and modified glazing systems were tested under dynamic and quasi-static loading conditions. The testing showed that the extent to which the automobile glazing was able to withstand occupant interaction was dependent upon the glazing material used and the hardware design of the door system used to retain it. An overview of current glazing systems is included for comparison.     

Observations on the design and modelling of some joined thin-walled structural sections

In a recent experimental and analytical study for the axial progressive collapse of some thin-walled structural sections, no consistent reliability could be obtained for the prediction of crush parameters for different geometries and materials with an analytical approach that relied on a yield hinge model. Square and spot-welded top-hat sections were compared. This situation occurs because the assumed equivalence between the top-hat and square sections according to the yield hinge model of the folding structures, does not appear valid for the actual structures. Some of the dependences between the actual structure and the model are discussed, particularly for the top-hat geometry. Observations on a beneficial positioning of the spot-welds in a top-hat section are reported, and common recommendations for an optimum weld pitch are critically examined. Modes 1 and 2 deformations are identified for the well-known quasi-inextensional, regular (asymmetric) progressive folding of thin-walled sections having a rectangular (core) cross-section, such as square and top-hat sections. The deformation modes are characterized by different proportions of inward and outward movements of the material during folding. Possible implications for the stability of collapse and for the analytical formulae are indicated.