深小锥孔零件无芯棒开式冷挤压刚塑性边界分析

运用场论及流体动力学的理论,分析了深小锥孔零件无芯棒开式冷挤压的变形特点,给出了该变形过程非稳态速度场的瞬时流函数方程,并由流函数方程建立了运动学许可速度场。分析了影响速度场变化的主要因素,从位置和形式2方面确定了刚塑性变形区边界和速度间断线方程。     

中碳钢(45~#)开式冷挤压极限变形程度的实验研究

首次通过试验给出了中碳钢 ( 4 5 #)在不同参数组合下的极限变形程度 ,并与低碳钢材料 ( 2 0 #钢、2 0 Cr钢 )的极限变形程度进行了比较 ;分析了厚径比及模具锥角对极限变形程度的影响 ;并给出了可供实际应用的数据     

开式冷挤压成形功率及挤压力的研究

给出了开式冷挤压动可容连续速度场及上限挤压力计算公式,讨论了主要参数对挤压力的影响,理论分析结果得到了实验验证。     

三孔小净距隧道群极限状态下围岩破坏特征研究

平行三孔大断面小净距隧道开挖时,围岩应力场经过多次扰动叠加发生重分布,不再是单个隧道的简单叠加.利用强度储备法求得极限状态下的隧道围岩各点的安全系数,绘出开挖断面附近围岩的点安全系数分布图,并对不同净距与埋深对围岩极限状态的破坏特点进行研究.结果表明:随着净距的增大,洞周达到强度极限的围岩范围增大,围岩自身稳定性不断提高;埋深较小时,边洞的拱项变形小于中洞,而当埋深大于25 m时,三洞的沉降大致相等.     

厚壁管件无芯棒开式冷挤压尺寸预测的实验研究

对于无芯棒开式冷挤压厚壁管件的相对伸长量的研究与预测是设计开式冷挤压管类零件及其专用设备的依据.本文通过对厚壁管件无芯棒开式冷挤压尺寸预测的实验研究,分析了影响相对伸长量的主要参数,找出了它们与相对伸长量之间的变化规律曲线,为指导实际生产提供了依据.     

开式冷挤压成形可行模角及最佳模角的理论与实验研究

给出了开式冷挤压动可容速度场及上限挤压力计算公式,讨论了主要参数对最佳模角的影响,理论分析结果得到实验验证。由理论及实验给出了可行模角及最佳模角。     

Effects of the deep rolling process on the surface roughness and properties of an Al-3vol%SiC nanoparticle nanocomposite fabricated by mechanical milling and hot extrusion

Deep rolling is one of the most widely used surface mechanical treatments among several methods used to generate compressive residual stress. This process is usually used for axisymmetric components and can lead to improvements of the surface quality, dimensional accuracy, and mechanical properties. In this study, we deduced the appropriate deep rolling parameters for Al-3vol%SiC nanocomposite samples using roughness and microhardness measurements. The nanocomposite samples were fabricated using a combination of mechanical milling, cold pressing, and hot extrusion techniques. Density measurements indicated acceptable densification of the samples, with no porosity. The results of tensile tests showed that the samples are sufficiently strong for the deep rolling process and also indicated near 50% improvement of tensile strength after incorporating SiC nanoparticle reinforcements. The effects of some important rolling parameters, including the penetration depth, rotation speed, feed rate, and the number of passes, on the surface quality and microhardness were also investigated. The results demonstrated that decreasing the feed rate and increasing the number of passes can lead to greater surface hardness and lower surface roughness.