SUS304超薄板力學(xué)性能尺度效應(yīng)及微盒形件拉深研究
發(fā)布時(shí)間：2018-07-18 13:29
【摘要】：隨著微機(jī)電系統(tǒng)的發(fā)展,微型零件的需求量日益劇增。然而由于尺度的減小所帶來的一系列的問題在微型零件制造過程中無法忽略,因此研究關(guān)于微成形尺度效應(yīng)及其產(chǎn)生的機(jī)理進(jìn)行十分重要。本文研究對象為SUS304超薄板,研究以微塑性理論分析和單拉實(shí)驗(yàn)所得材料力學(xué)性能尺度效應(yīng)為基礎(chǔ),運(yùn)用仿真模擬和實(shí)驗(yàn)相結(jié)合的方法對微盒形件拉深中所表現(xiàn)的塑性變形尺度效應(yīng)進(jìn)行了研究。首先,本文對尺度效應(yīng)的物理機(jī)理進(jìn)行了分析,介紹了尺寸效應(yīng)的定義。給出了兩類不同的尺度效應(yīng),并針對不同類別的尺度效應(yīng)現(xiàn)象給出其理論解釋。其次,本文選擇多種不同試樣尺寸和晶粒尺寸的SUS304超薄板,對其進(jìn)行微拉伸實(shí)驗(yàn)。實(shí)驗(yàn)表明,板料試樣尺寸(厚度)和晶粒尺寸對材料力學(xué)性能影響顯著,結(jié)合表面鈍化層強(qiáng)化原理和經(jīng)典hall-petch公式,得出了針對不銹鋼薄板屈服強(qiáng)度的算式。通過對試樣延伸率、屈服強(qiáng)度尺寸效應(yīng)的研究發(fā)現(xiàn),試樣的塑性能力隨厚度下降而減弱,即“越小越脆”。利用ABA QUS軟件對微盒形件拉深進(jìn)行數(shù)值模擬研究。凸模圓角部位應(yīng)力應(yīng)變最大,厚度減薄嚴(yán)重。并研究了不同區(qū)域的厚度分布特點(diǎn)以及不同工藝參數(shù)影響下的微盒形件拉深變形特點(diǎn),用以指導(dǎo)微拉深模具設(shè)計(jì)。研究了不同試樣尺寸和不同熱處理狀態(tài)下不銹鋼薄板微盒形件拉深尺度效應(yīng)。通過對試樣的鑲嵌打磨獲得其成形件截面,并對成形件的截面進(jìn)行了厚度分布測量和微硬度檢測。凸模圓角位置發(fā)生厚度最大減薄和最大加工硬化,板料厚度減小使其成形能力減弱且應(yīng)變梯度的強(qiáng)化效應(yīng)增強(qiáng)。相同厚度下,晶粒尺寸越大則應(yīng)變梯度強(qiáng)化效應(yīng)越明顯。厚度方向上晶粒數(shù)量是決定成形尺度效應(yīng)的關(guān)鍵因素,晶粒數(shù)量的減少使幾何必須位錯(cuò)增多,應(yīng)變梯度強(qiáng)化效應(yīng)增強(qiáng),且流動應(yīng)力分布規(guī)律性開始消失,分散性增強(qiáng)。
[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.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG142.71;TG386.32
[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.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG142.71;TG386.32
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