含不确定性参数的复合材料薄壁结构吸能特性评估方法研究

Evaluation method for energy-absorbing composite structures with uncertain parameters

由于复合材料性能分散度大、加工精度较低,为复合材料薄壁吸能结构引入了不可忽略的不确定性因素,为此,提出了一种含不确定参数的复合材料薄壁结构吸能特性的评估方法并进行了算例研究。复合材料薄壁圆管是一种典型的吸能元件,圆管的壁厚和内径是对其吸能特性有显著影响的特征几何尺寸,考虑了这两个参数的不确定性,在准静态压溃的条件下评估了薄壁圆管的引发比应力和比吸能这两个关键吸能指标。首先,利用区间分布来描述壁厚和内径的不确定性,其次应用有限元方法建立区间内不确定参数和结构吸能特性指标间的二阶响应面函数,最后对响应面函数进行区间摄动从而确定吸能特性指标的分布区间。算例研究结果显示,与比吸能相比,引发比应力受壁厚和内径不确定性的影响更大。此外,相比于内径,壁厚的不确定性对吸能特性影响更显著,因此为获得稳定的结构吸能特性应尽量提高复合材料圆管壁厚的加工精度。

Due to the large dispersion of material properties and inherent machining tolerance,uncertain factors should be considered in designing and analyzing composite structures.An evaluation method for energy-absorbing characteristics of thin-walled composite structures with uncertain parameters was proposed and developed herein.Thin-walled composite tubes extensively applied in automobile and aircraft engineering are typical crushable elements for absorbing collision energy.The uncertainties due to machining tolerance of thickness and inner diameter of a tube were considered in the present paper and represented by an interval model.Triggering Specific Stress （TSS）and Specific Energy Absorption （SEA） were concerned and calculated by finite element method for indicating energy-absorbing characteristics of the specimen under quasi-static axial crushing.Response surface method was then used to build a second-order function between uncertain parameters and the two indicators of energy-absorbing characteristics.Interval perturbation of the response surface function was at last performed to establish the intervals of TSS and SEA respectively. The results show that,compared to SEA,TSS is more affected by the uncertainty of wall thickness and inner diameter.In addition,the effect of uncertainty of wall thickness on energy-absorbing characteristics is more significant than that of inner diameter.The investigation reveals that the machining tolerance of composite tube should be limited as low as possible to keep designed energy-absorbing characteristics.