平面板材表面辊压成形微沟槽数值模拟研究

发布时间：2018-08-19 07:28

【摘要】：随着表面微沟槽的功能特性被科学研究所证实，其应用前景和潜在的使用价值引起世界广泛地关注，因此微沟槽加工技术也不断发展起来。目前微沟槽加工技术还难以同时满足工业生产上的大批量、低成本、高质量的要求，因此本文提出一种平面板材表面微沟槽辊压成形技术。它是利用带有一定功能特性微沟槽的刚性辊对板材件进行辊压成形，使得板材表面发生塑性变形，从而在板材表面得到一定尺寸的微细沟槽的加工方法。与其它微细加工技术相比，该技术不仅能够实现带有微沟槽板材件的连续成形，提高生产效率，而且可以获得较好的成形质量，有利于后续的二次加工。本文建立了板材表面微沟槽辊压成形有限元模型，并对不同工艺参数进行了数值模拟分析。通过对比分析成形过程中成形件的应力、应变分布和微沟槽尺寸，以得到最佳的辊压成形参数；并利用辊压成形实验装置，在铝合金板材表面加工出带有一定尺寸的微沟槽，验证了该成形方式的可行性。本文得出主要结论如下： 1.根据成形过程中成形力的变化规律，将成形过程分为挤压阶段、稳定成形阶段、结束阶段。在挤压阶段，随着辊子压入深度的增大，成形力随之增大到最大值；当进入稳定成形阶段，成形力在最大值附近稳态波动；在辊压结束阶段，随着辊子与板材接触面积减小，成形力逐渐减小，直至板材脱离辊缝。根据板材变形后等效应变分布可知，板沟槽底部的应变值相对于沟槽侧壁处较大。沿板材辊压纵向对比板材入口端、中间端、出口端的金属流入辊子凹槽的高度(微沟槽填充高度)，结果表明：在板材出口端和入口端处，表面沟槽成形高度小于板材中间部分。 2.研究分析45°底角的等腰梯形、60°底角的等腰梯形、正弦波纹、等边三角形四种结构微沟槽在不同压下量下的成形结果。结果表明：45°底角的等腰梯形沟槽、60°底角的等腰梯形沟槽和正弦曲线沟槽在材料填满时，所需的压下量分别为0.7mm、0.75mm、0.83mm；而等边三角形沟槽在压下量为0.9mm时，沟槽仅基本接近目标形状，在三角形顶边处仍未填满。 3.分析了板材宽展和板材厚度对成形结果的影响。当约束板材宽展时，板材的纵向延展大，，并且具有一致性；当板材自由宽展时，板材表面沟槽成形高度相对较小，且成形均匀性较差。随着厚度的减薄，表面沟槽填充高度相对增大。 4.论文对比分析了压下量、摩擦系数、辊子转速三种参数对表面微沟槽成形结果的影响。结果表明：随着压下量增大，板材表面微沟槽成形高度呈线性增长。当摩擦系数较大时，辊压微沟槽的成形力较大，微沟槽成形高度减小。当上、下两辊转速相同时，随着辊子转速的增大，板材表面微沟槽成形高度减小；当上、下两辊具有一定的转速差时，随着差值的增大，沟槽成形高度增大。
[Abstract]:As the functional characteristics of surface microgrooves have been confirmed by scientific research, their application prospects and potential use value have attracted worldwide attention, so micro-grooves processing technology has been continuously developed. At present, it is difficult to meet the requirements of large quantity, low cost and high quality in industrial production. It is a kind of machining method that the rigid roll with certain function characteristic micro-grooves is used to roll forming the sheet metal, which makes the sheet surface plastic deformation, and then obtains a certain size micro-groove on the plate surface. Compared with other micro-machining techniques, this technology can not only realize continuous forming with micro-grooves, improve production efficiency, but also obtain better forming quality, which is conducive to subsequent secondary processing. In this paper, the finite element model of sheet metal surface micro-groove roll forming is established, and the different process parameters are numerically simulated and analyzed. By comparing and analyzing the stress, strain distribution and microgroove size of the forming parts, the optimum roll forming parameters are obtained, and the micro-grooves with certain size are machined on the surface of aluminum alloy sheet by using the roller forming experimental device. The feasibility of the forming method is verified. The main conclusions are as follows: 1. According to the changing law of forming force in forming process, the forming process is divided into extrusion stage, stable forming stage and end stage. In the extrusion stage, the forming force increases to the maximum with the increase of the roller indentation depth; when it enters the stable forming stage, the forming force fluctuates in the vicinity of the maximum value; at the end of the roll pressing, the contact area between the roller and the sheet metal decreases, The forming force gradually decreases until the sheet is separated from the roll gap. According to the equivalent strain distribution of the plate after deformation, the strain value at the bottom of the plate groove is larger than that at the side wall of the groove. The height of the metal flowing into the roller groove (the filling height of the micro-groove) at the inlet end, the middle end, and the outlet end of the plate is compared along the plate roll press. The results show that: at the exit end and the inlet end of the sheet metal, Surface groove forming height less than the middle part of sheet. 2. The forming results of four microgrooves with isosceles trapezoids, sinusoidal ripples and equilateral triangles with isosceles trapezoids of 45 掳and 60 掳bottom angles of 60 掳are studied. The results show that the isosceles trapezoidal grooves at the bottom angle of 45 掳and the isosceles trapezoidal grooves and sinusoidal grooves at 60 掳bottom angles require a reduction of 0.7 mm / 0.75 mm / 0.83 mm respectively when the material is filled, while the equilateral triangular grooves are reduced by 0.9mm. The grooves are only close to the target shape and are still unfilled at the top of the triangle. The influence of sheet width and sheet thickness on forming results is analyzed. The longitudinal extension of the plate is large and consistent when the plate is restrained, and the forming height of the surface grooves is relatively small and the forming uniformity is poor when the sheet is freely expanded. As the thickness decreases, the surface groove filling height increases relatively. 4. 4. The effects of three parameters, such as reduction, friction coefficient and roll speed, on the forming results of surface grooves are compared and analyzed in this paper. The results show that the forming height of the micro-grooves on the surface increases linearly with the increase of the reduction. When the friction coefficient is high, the forming force and height of the micro-grooves are larger and the forming height of the micro-grooves decreases. When the rotation speed of the next two rollers is the same, the forming height of the micro-grooves on the surface of the plate decreases with the increase of the rotational speed of the roller, and the forming height of the grooves increases with the increase of the difference between the two rollers when the next two rollers have a certain rotational speed difference.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG306

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