基于SDT的浮动圆柱域公差数学模型研究

以浮动圆柱公差域的形位公差数学模型为研究对象,结合小位移旋量(SDT)理论建立了浮动圆柱公差域在MMR和LMR条件下的公差数学模型,分析了公差边界与位姿旋量的数学关系和约束条件,通过具体实例对相关数学模型进行验证。     

Deforming mechanism of non-mandrel drawing process of circular aluminium tube by simulation

The aluminium tubes with high strength and smooth outer-surface can be produced by non-mandrel drawing process. It is an effective method to study forming mechanism of drawing process by simulation, based on which the relevant dies with reasonable dimensions can be designed to ensure tube precision. The dynamic model and elasto-plastic finite element model of the forming process were established based on FEM software Deform-3D, then the simulation was performed. The expressions about drawing load were deduced, and the influence of friction coefficient on drawing load was computed by the expressions and software respectively. Based on simulation results the deformation mechanism of drawing process without plug was expounded. According to flowing speed vector graph the law of material flowing was summarized, by which the deformation regions were partitioned. Furthermore, some potential problems of drawing process such as diameter shrinking, thickness varying were forecast and analyzed quantificationally.     

基于临界损伤因子的40Cr伞齿轮锻造温度优化

为获得40Cr材料韧性断裂的临界损伤因子，采用了模拟与试验拟合的方法．分别完成了动态压缩试验和一组高度方案下的模拟分析，获得了材料断裂时的高度压缩率，对所得一组损伤值求平均值确定了40Cr材料临界损伤因子为0．402。设计一组不同始锻温度的温成形方案，仿真分析获得齿轮锻件最大损伤值随始锻温度变化的规律曲线，与40Cr临界损伤因子做比较，发现了一个温度范围730～770℃。适合于温成形而不会出现开裂。仿真分析在室温下锻造的过程，发现最大损伤值高达1．19，可能有开裂，从而确定该规格伞齿轮冷精锻工艺是不可行的。     

水韧处理对ZGMn18Cr2铸件组织与性能影响

采用两种不同水韧处理工艺对未达到使用寿命即发生破裂的ZGMn18Cr2超高锰钢衬套试样进行处理,并对比分析了水韧处理前后试样的组织与力学性能。结果表明,加热至1 120℃,保温15 h后快速水冷的水韧处理的硬度值降低,钢中未溶碳化物和析出碳化物几乎消失,碳化物级别显著提高;钢的抗拉强度、伸长率、断面收缩率、冲击吸收能量等力学性能指标得到大幅度提高,显著改善了钢的综合力学性能,提高了衬套的使用寿命。     

渗碳对17CrNiMo6钢大截面齿轮轴锻件的硬度影响研究

17CrNiMo6钢大截面齿轮轴锻件渗碳后齿面硬度偏低,易产生疲劳裂纹。通过采用在渗碳淬火后,对其表面敷干冰做深冷处理,以及提高回火温度,增加回火次数的方法,减少了残余奥氏体,提高了齿轮轴的硬度。