里氏硬度计示值误差来源与分析

1 里氏硬度测试 装有碳化钨球或金刚石球的冲击体,在一定的冲击能量作用下,冲击试样表面,通过电磁感应原理测量出冲击体距试样表面1 mm位置处的冲击速度与反弹速度.里氏硬度值用冲击测头反弹速度vr与冲击速度va之比来表示,计算公式如下:     

Theoretical and Experimental Investigation of Laser Milling Assisted with Jet Electrochemical Machining

In laser milling assisted with jet electrochemical machining （LMAJECM）, the source of energy is a pulsed laser beam aligned coaxially with a jet of electrolyte, which focuses optical energy on the surface of work- piece. The impact of jet of electrolyte develops a state-of-art work to perform operations such as electrolytic etch- ing, effective cooling, and transportation of debris. Therefore, a special jet cell is designed to obtain stable jet as to be a kind of noneontact tool, i. e. , electrode. According to the theoretical model of on-off pulse time process, laser machining and electrolytic anodization are simulated by finite element analysis （FEA） method. Grooves on a 0.5 mm thick 321 stainless steel sheet produced by LMAJECM is performed with pulsed Nd：YAG laser at the second harmonic wavelength. Compared with laser milling under ambient atmosphere conditions, the recast layer and burrs are effectively diminished. And the accuracy of depth is dedicated to laser milling, whilst that of width is dominated by jet electrochemical machining. It is demonstrated that LMAJECM can be a highly potential approach for fabricating 3-D micro components.     

喷射液束电解-激光复合加工工艺试验研究

喷射液束电解 激光复合加工是一项新探索的加工技术,其特点是既发挥激光加工的高效率,又借助喷射电液束的冷却、冲刷、电解作用而实现在线去除再铸层。基于该加工原理的分析,在对激光电解液中衰减特性研究的基础上,研制了试验系统并对不锈钢片进行了打孔工艺试验。试验结果表明,应用液压1.5 MPa、浓度18%的NaNO₃电解液的喷射液束电解-激光复合加工可实现再铸层减少90%以上。通过对打孔形貌的对比以及加工工艺规律的初步分析,揭示了喷射液束电解-激光复合加工以激光加工为主,电解加工辅助去除再铸层的加工原理,证实了该复合加工工艺的可行性,可望在航空航天领域得到广泛工程应用。