共查询到19条相似文献,搜索用时 62 毫秒
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采用盲孔法对烧结、机加成形的SR40超半球和Φ60圆柱的LiH材料测试件进行残余应力测量。结果表明:SR40超半球测试件球面45°处残余应力值最大,径向σr达到-9.5670 MPa,周向σt达到2.2352 MPa;球面各点径向σr残余应力均为压应力,而周向σt残余应力均为拉应力,且径向σr大于周向σt,测试件呈压应力状态。Φ60圆柱测试件端面中心残余应力值最小,从端面中心到端面边缘,径向σr和周向σt残余应力是先增大后减小。 相似文献
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硬质合金螺旋孔棒材是一类尺寸精度要求高、成型难度大而具有高附加值的产品,属于粉末冶金行业重点研究的对象。本文从螺旋孔棒的螺距、同心度、孔径、孔间距等关键指标出发,探讨了螺旋孔棒的尺寸及公差标准,分析了螺旋孔棒尺寸精度的影响因素,进行了提高螺旋孔棒尺寸精度的工艺研究。研究结果说明:模具固化工艺制备的螺旋孔棒比电动调节工艺的内外螺距一致性更好;挤压速度对螺距的影响比挤压压力更大;内孔位置度以同心度表征比孔偏离更科学;孔间距的稳定性与力学平衡相关;通过对芯杆座的改进,三螺旋孔棒的孔夹角精度达到120°±4°。 相似文献
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钻孔法测量残余应力的范围是应力不超过材料屈服极限的一半。但是在许多情况下,钻孔法是用于测量焊接残余应力,而该应力峰值往往接近材料的屈服极限。本文探讨了盲孔法测量高残余应力的可靠性与精确度。为了模拟工程应用中测量残余应力的实际过程,本文采用标定的方法,即在试验机保持一定载荷不变的条件下进行贴片与钻孔操作,测得释放应变值。试验结果表明,用测得释放应变值计算出的应力值与标定应力值吻合较好,最大绝对误差仅为21 MPa。 相似文献
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《Journal of Materials Processing Technology》2014,214(3):556-564
Electrochemical drilling (ECD) is a promising and low-cost process for yielding multiple holes simultaneously in difficult-to-machine materials. In this process, the hole exit accuracy is very sensitive to the electrode feeding depth. In practice, excessive electrode feeding is necessary to ensure that all holes are drilled through simultaneously when there is an error in thickness of the workpiece plate. This results in stray removal at the hole exit and an etched and pitted surface. In the modification of ECD described here, a potential difference is introduced via an insoluble platinum auxiliary electrode that is attached beneath a dielectric perforated plate and arranged opposite to the hole exits to diminish the damage from the stray current and thereby improve the tolerance of the exit accuracy to excessive electrode feeding. Simulation results indicate that an appropriate value of the potential difference concentrates the current at the tool tip and may reverse the current direction on the workpiece surface. Experiments verify that this approach is effective in obtaining holes with good exit accuracy in the case of excessive electrode feeding. Furthermore, it is confirmed that this method is capable of drilling multiple holes with remarkably enhanced exit accuracy and uniformity. 相似文献
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随着机械制造业的不断发展,对机械压力机的吨位和精度都提出了更高的要求,本文从诸多方面论述了大型闭式压力机上横梁孔系的加工方法,并结合工程力学和计算机有限元分析技术,对各种加工方法进行了分析论证。 相似文献
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Toshihiko Kuwabara Kazuma Hashimoto Eiji Iizuka 《Journal of Materials Processing Technology》2011,211(3):475-481
The deformation behavior of 780 MPa grade dual-phase steel sheet subjected to hole expansion is investigated both experimentally and analytically to clarify the effect of the material model (anisotropic yield function) on the predictive accuracy of finite element analysis of hole expansion. Biaxial tensile tests of the material were conducted; contours of plastic work and the directions of plastic strain rates are precisely measured and are in good agreement with those predicted from the Yld2000-2d yield function with an exponent of 4 (
[Barlat et al., 2003] and [Yoon et al., 2004]). Finite element and experimental analyses on the hole expansion of the material were conducted. The Yld2000-2d yield function with an exponent of 4 provides closer agreement with the experimental results than other yield functions. Consequently, the anisotropic yield functions significantly affect the predictive accuracy of the deformation behavior of the steel sheet subjected to hole expansion, and the biaxial tensile test is effective for identification of the appropriate anisotropic yield function to be used for hole expansion simulation. 相似文献
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多点拉形是将整体拉形模具离散成多点模具,可以在一套多点拉形模具上实现不同形状零件的拉形,省去了模具的设计、制造等大量的生产成本,实现了蒙皮件的柔性成形。多点拉形主要适于成形小曲率、大变形的蒙皮件,材料和目标曲面形状都是影响多点拉形成形结果的重要因素。通过对3种材料成形不同曲率半径球形件的多点拉形过程进行数值分析,研究材料和成形件目标形状对多点拉形的影响。结果表明,在成形件中心区域的形状误差小于边缘区的形状误差,拉伸方向的形状误差大于垂直拉伸方向的误差,成形件的曲率半径越小,成形件的形状误差越大。 相似文献