基于n阶剪切变形理论的表面梯度脱碳汽车前轴弯曲分析

Analysis of Surface Gradient Decarburization in Automotive Front Axle Bending Based on n-Order Shear Deformation Theory

汽车前轴在热锻和热处理过程中,材料的表面会发生一定深度的脱碳,脱碳层的力学性能随脱碳深度呈梯度变化,影响了前轴在载荷下的弯曲性能。利用分段函数构建两侧表面功能梯度变化、内部性能均匀的简支夹芯梁,根据n阶剪切变形理论研究梁在两点载荷作用下的弯曲行为。利用虚功原理推导出位移场控制方程,采用Navier解析方法得到简支边界条件下梁的弯曲行为,并与相关文献中的实例进行比较。结果表明:n阶剪切变形理论具有良好的精度与可靠性;梁的挠度与转角随脱碳指数k的增大而增大,并于k≈10处达到准稳态;脱碳深度大于5 mm时,脱碳层厚度对梁弯曲时产生应力的影响比梁的高度变化带来的影响更大;两侧脱碳深度不对称时,物理中性面发生迁移;梁的弯曲挠度与转角随梁的厚度、宽度的增大而减小,但梁的厚度变化的影响更大。

During the hot forging and heat treatment processes of the automotive front axle,decarburization occured on the surfaces of the material,leading to change in the mechanics properties of the decarburized layer with varying depths.This phenomenon significantly impacted the bending performance of the front axle under load.A segmented function was used to create a graded variation in surface functionality on both sides of the axle,resulting in a simply supported sandwich beam with uniform internal properties.The bending behavior of the beam under two-point loading was investigated using the n-order shear deformation theory.The displacement field control equation was derived using the principle of virtual work,The Navier analytical method was used to obtain the bending behavior of a beam under simply supported boundary conditions,and compared with examples in the literature.The results indicate that the n-order shear deformation theory has good accuracy and reliability.The deflection and rotation of the beam increase with the increase of the decarburization index k,and reach quasi-steady state at k≈10.When the depth of decarburization is greater than 5 mm,the stress caused by the bending of the beam is more strongly influenced by the thickness of the decarburized layer than by the height change.When the depth of decarburization on both sides is asymmetric,the physical neutral surface migrates.The bending deflection and rotation of the beam decrease with the increase of thickness and width,but the change in beam thickness has a greater impact.