不锈钢超薄板微成形摩擦尺度效应试验研究

发布时间：2018-04-09 01:17

本文选题：摩擦　切入点：SUS304不锈钢薄板　出处：《江苏大学》2017年硕士论文

【摘要】：随着高新技术和产业的兴起,微系统技术和微机电系统备受青睐,促使微成形零部件等产品的需求量迅猛增长。虽然薄板微塑性成形技术优点突出,然而,因为零部件尺寸微小化,材料的力学性能、成形机理呈现出明显的尺度效应。因此,传统的板料塑性成形技术不能直接按比例缩小应用于微成形中,而摩擦作为薄板塑性微成形研究热门方向,各方面还有待进一步完善。本文将SUS304不锈钢超薄板作为试验对象,研究了材料力学性能尺度效应以及各工艺参数对超薄板摩擦的影响规律,揭示了摩擦尺度效应产生机理,探讨了实际微拉深成形工艺的摩擦尺度效应现象,主要研究内容有以下几个方面:1)分别对不同规格超薄板开展单拉试验,结果显示,当超薄板厚度或者晶粒尺寸逐渐减小时,其流动应力均随之不断上升,即“越小越强”力学性能尺度效应现象显著;基于表面钝化膜强化作用、应变梯度强化效应、以及多晶体材料的细晶强化理论,阐述了力学性能尺度效应机理,并分析了单拉断口形貌。2)分别对不同厚度及不同晶粒尺寸的超薄板进行了线性往复式球-盘摩擦试验,结果表明,力学性能尺度效应并未在很大程度上使摩擦系数发生变化。研究了工艺参数对不同尺寸超薄板摩擦系数的影响规律,通过磨痕形貌观察及磨痕截面尺寸测量,其结果表明,在干摩擦条件下,超薄板的摩擦系数随钢球表面粗糙度增大而明显上升,随线性往复摩擦速度增大而缓慢下降,随试样表面粗糙度或摩擦载荷增加而缓慢上涨;工艺参数保持不变时,厚度减薄没有影响到钢球和超薄板表面间的机械啮合或分子吸引作用,即没有表现出摩擦尺度效应。3)采用圆柱销-条形试样接触方式,对不同规格的条形超薄板进行了线性往复式销-盘摩擦试验,结果表明,在液体润滑状态下,条形超薄板的摩擦系数随着宽度尺寸减小而明显上升,摩擦尺度效应现象显著;基于摩擦形貌观察和模型分析,揭示了摩擦尺度效应机理。采用多尺度精密微矩形拉深模具,对条形超薄板开展了微拉深成形,结果显示,在液体润滑状态下,当试样尺寸或模具尺度逐渐减小时,摩擦力所占拉深成形力的比例增加,摩擦系数随之增大,即摩擦尺度效应对成形力的影响较为显著。
[Abstract]:With the rise of high and new technology and industry, micro-system technology and micro-electromechanical system are favored, which makes the demand of micro-forming parts and other products grow rapidly.Although the advantages of sheet metal microplastic forming technology are outstanding, due to the miniaturization of the parts size, the mechanical properties of the material and the forming mechanism show obvious scale effect.Therefore, the traditional sheet metal plastic forming technology can not be directly reduced in proportion to the application in micro-forming, but friction as a hot research direction of thin plate plastic micro-forming, all aspects need to be further improved.In this paper, the scale effect of mechanical properties of SUS304 stainless steel sheet and the influence of various process parameters on friction of ultra-thin plate are studied, and the mechanism of friction scale effect is revealed.In this paper, the friction scale effect of the actual micro-drawing forming process is discussed. The main research contents are as follows: (1) A single tensile test is carried out on the ultra-thin sheet with different specifications. The results show that when the thickness or grain size of the ultra-thin plate decreases gradually,The flow stress increases continuously, that is, the "smaller and stronger" mechanical properties scale effect phenomenon is obvious, based on the surface passivation film strengthening effect, strain gradient strengthening effect, and the fine crystal strengthening theory of polycrystalline materials,The mechanism of the scale effect of mechanical properties is described, and the morphology of single tensile fracture. 2) the linear reciprocating ball disk friction tests of ultra-thin plates with different thickness and different grain size are carried out respectively. The results show that: 1.The scale effect of mechanical properties does not change the friction coefficient to a great extent.The influence of process parameters on friction coefficient of ultra-thin plates with different sizes is studied. The results show that under dry friction conditions, the friction coefficient of ultra-thin plates with different sizes is measured by observing the morphology of wear marks and measuring the cross section of wear marks.The friction coefficient of the ultra-thin plate increases obviously with the increase of the surface roughness of the steel ball, decreases slowly with the increase of the linear reciprocating friction velocity, and increases slowly with the increase of the surface roughness or friction load of the specimen.Thickness thinning does not affect the mechanical meshing or molecular attraction between the steel ball and the surface of the ultra-thin plate, that is, it does not show a friction scale effect .3) the cylindrical pin-strip specimen contact mode is adopted.The linear reciprocating pin-disk friction test was carried out on the strip ultra-thin plates with different specifications. The results show that the friction coefficient of the strip ultra-thin plates increases obviously with the decrease of the width and the friction scale effect is obvious under liquid lubrication.Based on the observation of friction morphology and model analysis, the mechanism of friction scale effect is revealed.The microdrawing forming of strip ultra-thin plate was carried out by using multi-scale precision micro-rectangular drawing die. The results showed that under liquid lubrication condition, when the sample size or die size gradually decreased, the proportion of friction force in drawing forming force increased.The friction coefficient increases, that is, the friction scale effect has a significant effect on the forming force.
【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;TG301

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