不同复合材料蒙皮机身段的适坠性研究

基于典型客机机身结构建立了三框两跨机身段有限元模型,模拟了金属蒙皮机身段和复合材料蒙皮机身段的坠撞过程,分析了机身结构变形、加速度响应、能量变化趋势和各结构吸能特征,研究了蒙皮对机身段适坠性的影响。结果表明,抗剪切能力较差的复合材料蒙皮会导致结构破坏不够充分引发较大的坠撞加速度进而对乘员安全造成威胁。复合材料蒙皮刚度较大会导致"三角区域"产生加速度过载。蒙皮作为飞机坠撞时的重要吸能结构之一,不仅会影响自身的吸能特性,还会显著影响各个结构的吸能特性和整个机身段的适坠性。     

Effect of fiber orientation on energy absorption characteristics of glass cloth/epoxy composite tubes under axial quasi-static and impact crushing condition

The collapse characteristics and energy absorption capability of composite tubes made of 759/5224 woven glass cloth/epoxy with different fiber orientations were studied in the present article under axial quasi-static and impact crushing condition. The effects of fiber orientation and loading condition on the crushing modes and energy absorption capability were discussed in detail. The fiber orientation could be found to have significant influences on energy absorption performance. Based on results, the energy absorption capability could be improved by selecting proper fiber orientation. The energy absorption capability in impact crushing tests could be found to be slightly lower than that in quasi-static crushing tests.     

Experimental investigation of bitubal circular energy absorbers under quasi-static axial load

In this article, bitubal circular energy absorbers consist of two AL-6063-O tubes with unequal diameters placed coaxially and compressed under quasi-static axial load are studied experimentally. The effects of diameter and wall-thickness of each tube and the interaction between two tubes on the crashworthiness parameters are investigated in detail. In order to reduce the high value of peak load induced in the bitubal absorbers, two worthwhile solutions are proposed. The first one is to use two tubes with different lengths and the other one is to cut groove at the end portion of one of the tubes.     

Analysis of factors that increase motorcycle rider risk compared to car driver risk

As in other parts of the Western world, there is concern in New Zealand about increasing popularity of motorcycles because of potential increases in road trauma. This study sought to identify important factors associated with increased risk for motorcyclists to inform potential policy approaches to reduce motorcyclist injury, such as changes to motorcyclist licensing, training and education. Using data extracted from a register of all New Zealand licensed motor vehicles that were matched to crash data, statistical models were fitted to examine patterns of motorcycle risk in comparison with small cars. These showed generally elevated risks for motorcyclists compared to cars, but particularly elevated risks for motorcycle owners aged in their 20s or who lived in more urbanised settings. In crashes, motorcyclists have little protection from injury, putting the motorcyclist at high risk of injury. When comparing new motorcycles with new cars, the odds of fatal or serious injury to a motorcycle rider involved in an injury crash were almost eight times the odds for a car driver.     

A material and gauge thickness sensitivity analysis on the NVH and crashworthiness of automotive instrument panel support

This paper provides a finite element analysis of the effects of using alternative materials and gauge thickness on the weight and structural performance of the VN127 instrument panel support. Two types of analyses were performed, NVH and crashworthiness. The NVH analysis was used to determine the structure’s natural frequencies, whereas the crashworthiness analysis was used to examine the structure’s crash behavior under two different impact conditions. The materials used in this study included mild steel, aluminum and magnesium alloys. The thickness of the structure was varied from 0% to 40%, in increments of 10%. The results of different models were compared with the baseline model, i.e., the mild steel model with nominal thickness. It was found that by replacing mild steel with aluminum alloys, and increasing the gauge thickness of the structure by 40%, the NVH and crashworthiness performance of the structure was equivalent to the baseline model.     

基于TRB结构的汽车前纵梁轻量化设计

以某汽车的前纵梁为例,参照我国C-NCAP中车辆正面碰撞测试要求,建立汽车前纵梁碰撞简化模型作为有限元仿真模型,并通过正交试验采样和多项式回归法构建响应面近似模型,将连续变截面板技术应用于前纵梁轻量化设计。结果表明:基于连续变截面板结构的汽车前纵梁相对于等厚板前纵梁具有更好的耐撞性,并且具有明显的减重效果,前纵梁质量减少了3.85kg,减重17.7%。     

Theoretical prediction and crashworthiness optimization of multi-cell triangular tubes

The triangular tubes with multi-cell were first studied on the aspects of theoretical prediction and crashworthiness optimization design under the impact loading. The tubes׳ profiles were divided into 2-, 3-, T-shapes, 4-, and 6-panel angle elements. The Simplified Super Folding Element theory was utilized to estimate the energy dissipation of angle elements. Based on the estimation, theoretical expressions of the mean crushing force were developed for three types of tubes under dynamic loading. When taking the inertia effects into account, the dynamic enhancement coefficient was also considered. In the process of multiobjective crashworthiness optimization, Deb and Gupta method was utilized to find out the knee points from the Pareto solutions space. Finally, the theoretical prediction showed an excellent coincidence with the numerical optimal results, and also validated the efficiency of the crashworthiness optimization design method based on surrogate models.     

Progress in braided composite tube crush simulation

The high Specific Energy Absorption (SEA) of composite tubular structures makes them attractive candidates in energy absorbing structural applications such as front rails in vehicles. To incorporate primary composite components in vehicle structures requires numerical simulation tools that can predict the structural performance of the vehicle under various loading conditions including crashworthiness. In previous studies, axial crush simulations of braided composite tubes tended to generate global buckling, which are inconsistent with the steady crush behavior observed in experiments. It was found that the constitutive models based on the continuum damage mechanics (CDM) framework are inadequate to represent the unloading response of damaged composites. In axial crush experiments, braided composite tubes form multiple continuous crush fronds. Local unloading occurs when material moving out of the crush front becomes part of the crush frond. Improper representation of the material unloading response affects the computed total energy absorption of the structure. To address this issue, an analog model was developed to describe the unloading path of compressively damaged composites. This approach was implemented in CODAM, as a user defined composite CDM model for the explicit finite element code LS-DYNA^®. The improved CODAM model results in a significantly improved prediction of the tube crush.     

Investigating the quasi-static axial crushing behavior of polymeric foam-filled composite pultrusion square tubes

The capability of structures to absorb large amounts of energy is a crucial factor, particularly for structural components of vehicles, in reducing injury in case of collision. In this study, an experimental investigation was conducted to study the crashworthiness of polymeric foam-filled structures to the pultruded square cross-section E-Glass fiber-reinforced polyester composite tube profiles. Quasi-static compression was applied axially to composite tubes to determine the response of the quasi-static load displacement curve during progressive damage. Three pultruded composite tube wall thicknesses at different sizes were examined, and the effects of crushing behavior and failure modes were analyzed and discussed. Experimental results indicated that the foam-filled profile is superior to the non-filled foam composite tube profile in terms of the capacity to absorb specific energy.     

飞机机身结构非正常着陆耐撞性仿真分析

飞机结构在非正常着陆情况下,必须保证飞机内乘员的安全,这是飞机适航条例CCAR-23中明确规定的。文中首次以某小型飞机机身结构为研究对象,建立飞机结构非正常着陆的仿真模型,针对各种非正常着陆状态下的地板加速度、撞击载荷和结构吸收能量占总动能比例等进行分析,给出这些分析结果与飞机撞击速度之间的关系。研究指出,水平撞击速度对飞机撞击过程影响很大,并且可以降低飞机的撞击载荷。研究结果显示,该小型民用飞机的地板下结构可以进行改进设计,以获得更佳的耐撞性能。