【作者】 李兵；

【导师】 庄蔚敏；

【作者基本信息】 吉林大学 ， 机械工程， 2015， 硕士

【摘要】 汽车行业的快速发展,导致了近些年能源以及环境方面的问题日益严重。汽车轻量化作为缓解这些问题的一个重要的技术手段越来越受到人们的重视。而先进高强钢以及铝合金作为优越的轻量化材料正在越来越多的应用于汽车生产上,那么如何更好的解决他们之间的连接问题成为一个重要的研究热点。现在汽车生产上使用的先进高强钢抗拉极限普遍在1500Mpa以上,传统无铆钉铆接技术无法实现如此高强度的钢板和铝合金之间的连接。因此,研究针对先进高强钢的无铆钉铆接连接技术具有重要意义。本文研究了适用于22MnB5先进高强钢的粘弹塑性材料模型,同时由于不考虑温度的影响,研究了适用于7075铝合金分段线性塑性材料模型,在此两种材料模型的基础上建立针对22MnB5先进高强钢和7075铝合金的无铆钉铆接连接过程有限元仿真模型。针对此仿真模型分析了铆接接头在凸模冲裁力作用下的应力应变变化过程,得到铆接接头形状尺寸中的重要参数包括颈厚值Tn,自锁值Tu以及底部厚度值X。同时观察了板件的布置形式对接头的成形影响,先进高强钢板件在铆接过程中的温度变化情况以及不同初始温度下的凸模冲裁力的变化情况。分析Akerstrom的关于硼钢冷却奥氏体分解相变数学模型用于研究淬冷速度对先进高强钢力学性能的影响。使用试验研究的方法对先进高强钢原质钢进行热处理试验,对比空冷、风冷、水冷、油冷四种冷却方式下先进高强钢的力学性能,从而得到不同冷却形式下铆接接头处先进高强钢的力学性能。同时应用有限元分析的方法得到不同冷却速度下先进高强钢的马氏体含量分布,和试验结果对比之后得出符合预期的结论。在对无铆钉铆接连接以及后续的淬冷过程进行分析之后,通过建立单向拉伸以及十字剪切力学有限元模型确定以抵抗轴向载荷的能力作为判断接头力学性能的标准。同时研究不同模具尺寸参数包括冲头半径、凹槽半径以及凹模深度对铆接接头尺寸参数的影响,设计正交试验完成模具尺寸参数优化,得到针对2mm板件厚度的先进高强钢以及铝合金之间的最优模具尺寸参数。确定模具尺寸参数后研究工艺参数包括摩擦系数、冲头行程、板件初始温度、压边力对铆接接头尺寸参数的影响,同样设计正交试验确定最优工艺参数。最后依据仿真得到的最优模具尺寸参数进行模具设计,在现有的试验条件的基础上依据优化后的工艺参数搭建试验平台完成对先进高强钢和铝合金之间的无铆钉铆接试验。更多还原

【Abstract】 The rapid development of automobile industry in recent years has led to the problem of energy and the environmental issues has becoming increasingly serious. As an important technical means to alleviate these problems. Automotive lightweight getting more and more people’s attention. Advanced high-strength steel and aluminum as superior lightweight materials are increasingly used in automobile production, so how better to resolve connectivity issues between them has become an important research focus. Now the ultimate tensile AHSS used on automobile production are prevalent more than 1500Mpa, but connections between such high intensity steel and aluminum can’t be achieved by the traditional clinch technology. Therefore, the study is significant for the clinch technology of AHSS.This paper studies the sticky elastic-plastic material model that applicable for 22MnB5 AHSS, and because they do not consider the effect of temperature on the mechanical properties of aluminum alloy 7075, so I studied the piecewise linear plastic material model, established for 22MnB5 advanced on the basis of high-strength steel and 7075 aluminum rivet-free connection FEM simulation model. Based on this model,the clinch joints were analyzed at the stress and strain changes in the process under the punch punching force, get in the important parameters of the shape and size of clinch joints include the neck thicker value Tn, self-locking value Tu and bottom thickness value X. Also I observed the impact of forming to the joint at different arrangement of the plate member, the temperature changes in advanced high strength steel member during the clinch process and the changes of punch punching force at different initial temperatures.I research on the Akerstrom’s mathematical model that the decomposition of austenite phase because of boron steel cooling. Then use the experimental research methods for advanced high strength precursor steel to do heat treatment test, compared to the mechanical properties of advanced high strength steel under air cooling, air-cooled, water-cooled, oil-cooled four cooling way, resulting in mechanical properties of advanced high-strength steel clinch joints under different cooling way; at the same time using the finite element analysis method to obtained AHSS martensite content distribution under different cooling rates, and test results come as expected conclusions after contrast.After analysis of the clinch and subsequent quenching process, through the establishment of the one-way stretch and the cross shear mechanical finite element model, the resist axial load capability was determined as a standard to the mechanical properties of the joint. At the same time research the impact of the size of different mold parameters including punch radius, groove radius and die depth on clinch joints size parameters, design orthogonal experiment to complete die size parameter optimization and obtained optimal parameters of die size for the thickness of 2mm plate between advanced high strength steel and aluminum alloy. After determining in the size of the mold parameters, research the impact of process parameters include the coefficient of friction, punch stroke, the initial temperature of the plate, blank holding force to the size parameters of clinch joints, the same orthogonal test was designed to determine the optimal process parameters.Finally, according to the optimal mold dimensions parameters obtained by simulation design mold, build the test platform based on the optimized process parameters to complete clinch test between advanced high strength steel and aluminum on the basis of existing test conditions.更多还原