【摘要】 本文提出了根据已知的路面谱输入计算汽车的传递函数与车架动应力的方法.首先,将一辆汽车分为若干个子结构,对每个子结构进行模态分析,略去高阶模态并应用模态综合的方法,即得一多自由度的动力学模型.从而可建立整车的运动微分方程,并确定模态坐标的传递函数.并由此计算车架的变形及动应力.更多还原

【Abstract】 This paper proposed a simplified model of a whole vehicle and a calculating method of the dynamic stress for a vehicle frame at given spectral imputs of road surface.First the whole vehicle was divided into two elastic substructures-frame and platform and four rigid bodies-cab, engine, front and rear axles. By Finite Element Method the models of the frame and platform under free-free condition were calculated with the aid of digital computer. Secondly only the first several modes of elastic substructures were considered. And all rigid models which have been already known are connected to the frame through elastic elements and damping elements and a simplefied global model with 28 degrees of freedom for the vehicle were developed. Thus the defferential equation of motion for the model has been derived, and the transfer functions of mode coordinates are determind.To calculate the dynamic stress of the frame under random loads, the stress response of the frame was determined. The road surface for the front and rear wheel are assumed the same. For the sake of simplification the road surface for the lcft and right wheel are also assumed the same. What we concern of most is the normal stress of the main beam. It is composed of two parts: one is the bending normal stress and the other is the normal stress due to cross sectional warping in twisting. The maximum normal stress can be obtained through multiplying the column matrix of elastic mode coordinate by corresponding transformation matrix.To check the result, the stress of certain points of the frame was measured when vehicle was running under corresponding road surface. The computed values and the tested values are roughly the same. Thus the proposed method can be used to prodict the rms of the dynamic stress of the vehicle.更多还原