基于7075铝厚板铣削加工的初始残余应力释放与再分布模型

Model of Release and Redistribution of Initial Residual Stresses for the Milling Process of 7075 Aluminum Alloy Thick Plate

摘要:

在7075铝合金厚板的制造过程中,材料塑性变形和力学性能的非均匀性,势必导致毛坯内产生残余应力。而在后续的高速切削加工过程中,残余应力随着材料去除的释放与再分布,是引起飞机结构件加工变形的关键因素。因此,研究残余应力释放与再分布的解析方法能够更为清晰地了解加工变形的演变机理,是进行加工质量控制的核心环节,对于实现加工过程的高效化和精密化至关重要。通过材料的切削去除转化为残余应力的释放,利用静力平衡条件将作用于飞机结构件的残余应力等效为外力后,依据小变形理论创新性地建立加工变形的分析模型。通过全面地考虑拉压、弯曲、以及转角引起的飞机结构件的厚向位置变化,利用叠加原理建立了残余应力再分布的力学模型。本文建立的解析模型,不仅能够准确地计算飞机结构件的加工变形,还能够分析毛坯残余应力的再分布状态,通过与有限元仿真值、实验测量值进行比较,结果表明：无论是幅值还是变形曲线,解析值都与仿真值具有高度一致性,而与测量值相比,尽管在变形曲线上具有很好的吻合性,但由于残余应力的测量误差使得两者在幅值上亦存在一定误差。

关键词:7075铝合金厚板;残余应力释放;残余应力再分布;加工变形;材料去除

Abstract:

In the process of manufacturing 7075 aluminimun alloy thick plate, the non homogeneity of plastic deformations and mechanical properties of the material will generate residual stresses. During the following high speed machining process, the release and redistribution of residual stresses are key to deformations of aeronautical monolithic component with the removal of material. Therefore, the study of the analytical method on the residual stress release and redistribution can more clearly understand the evolution mechanism of machining deformation, which is the core link of controlling the machining quality. This is because it is very important for the realization of machining process with high efficiency and precise. Through equaling the removal of materials to the release of residual stresses, the residual stresses remained in the aeronautical monolithic component are converted into the external force according to the static equilibrium conditions, the analysis model is deduced for machining deformations based on the small deformation theory. Because the overall consideration on position variation is done by the tension/compression of neutral surface, bending of neutral surface, and rotation of end surface, the superposition principle can be used to formulize the mechanical model of residual stress redistribution. The proposed analytical model can be suitable for the accurate calculation of the machining deformations of aeronautical monolithic component, in addition to the analysis of the residual stress redistribution. The comparison among the model calculations, the simulated values and the experimental measurement data shows that, both the amplitude and deformation curve, the model calculations are good agreement with the simulated values. Moreover, the measurement error of residual stresses causes the little difference of the amplitude of the model calculations with the experimental measurement data, though the deformation curves of the two have a good agreement with each other.

Key words:7075 aluminum alloy thick plate; release of residual stresses; redistribution of residual stresses; machining deformation; removal of material