SUS304超薄板力学性能尺度效应及微盒形件拉深研究

发布时间：2018-07-18 13:29

【摘要】：随着微机电系统的发展,微型零件的需求量日益剧增。然而由于尺度的减小所带来的一系列的问题在微型零件制造过程中无法忽略,因此研究关于微成形尺度效应及其产生的机理进行十分重要。本文研究对象为SUS304超薄板,研究以微塑性理论分析和单拉实验所得材料力学性能尺度效应为基础,运用仿真模拟和实验相结合的方法对微盒形件拉深中所表现的塑性变形尺度效应进行了研究。首先,本文对尺度效应的物理机理进行了分析,介绍了尺寸效应的定义。给出了两类不同的尺度效应,并针对不同类别的尺度效应现象给出其理论解释。其次,本文选择多种不同试样尺寸和晶粒尺寸的SUS304超薄板,对其进行微拉伸实验。实验表明,板料试样尺寸(厚度)和晶粒尺寸对材料力学性能影响显著,结合表面钝化层强化原理和经典hall-petch公式,得出了针对不锈钢薄板屈服强度的算式。通过对试样延伸率、屈服强度尺寸效应的研究发现,试样的塑性能力随厚度下降而减弱,即“越小越脆”。利用ABA QUS软件对微盒形件拉深进行数值模拟研究。凸模圆角部位应力应变最大,厚度减薄严重。并研究了不同区域的厚度分布特点以及不同工艺参数影响下的微盒形件拉深变形特点,用以指导微拉深模具设计。研究了不同试样尺寸和不同热处理状态下不锈钢薄板微盒形件拉深尺度效应。通过对试样的镶嵌打磨获得其成形件截面,并对成形件的截面进行了厚度分布测量和微硬度检测。凸模圆角位置发生厚度最大减薄和最大加工硬化,板料厚度减小使其成形能力减弱且应变梯度的强化效应增强。相同厚度下,晶粒尺寸越大则应变梯度强化效应越明显。厚度方向上晶粒数量是决定成形尺度效应的关键因素,晶粒数量的减少使几何必须位错增多,应变梯度强化效应增强,且流动应力分布规律性开始消失,分散性增强。
[Abstract]:With the development of MEMS, the demand for micro-parts is increasing rapidly. However, a series of problems caused by the reduction of scale can not be ignored in the process of micro parts manufacturing, so it is very important to study the scale effect of micro forming and its mechanism. The research object of this paper is SUS304 ultra-thin plate. Based on the theoretical analysis of microplasticity and the scale effect of mechanical properties obtained from single tensile test, The scale effect of plastic deformation in the drawing of microbox-shaped parts is studied by using the method of simulation and experiment. Firstly, the physical mechanism of scale effect is analyzed, and the definition of size effect is introduced. Two different kinds of scale effects are given, and their theoretical explanations are given for different kinds of scale effects. Secondly, several kinds of SUS304 ultra-thin plates with different sample size and grain size were selected and microtensile tests were carried out. The experimental results show that the size (thickness) and grain size of sheet metal have a significant effect on the mechanical properties of the material. Combined with the strengthening principle of the surface passivation layer and the classical hall-petch formula, the formula for the yield strength of the stainless steel sheet is obtained. It is found that the ductility of the specimen decreases with the decrease of the thickness, that is, "the smaller the specimen is the more brittle it is" through the study of the elongation of the specimen and the size effect of the yield strength. The numerical simulation of microbox drawing was carried out by abscisic quus software. The stress and strain at the corner of the punch is the largest and the thickness is thinned seriously. The characteristics of thickness distribution in different regions and the characteristics of drawing deformation of microbox-shaped parts under the influence of different technological parameters are studied to guide the design of micro-drawing die. The deep drawing effect of stainless steel sheet microbox with different specimen sizes and different heat treatment conditions was studied. The cross section of the formed part was obtained by inlay grinding of the sample, and the thickness distribution and microhardness of the formed part were measured. The maximum thickness thinning and working hardening occur at the corner position of the punch. The forming ability is weakened and the strengthening effect of the strain gradient is enhanced when the sheet metal thickness decreases. At the same thickness, the larger the grain size, the more obvious the strain gradient strengthening effect. The number of grains in thickness direction is the key factor to determine the scale effect of forming. The decrease of grain number makes the geometry must dislocations increase, the strain gradient strengthening effect increases, and the regularity of flow stress distribution begins to disappear and the dispersity increases.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.71;TG386.32

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