定电流短路引弧的逆变式空气等离子切割机

本文在分析试验的基础上，采用复合隔离型逆变电路和非高频起弧割炬，配以相应的内拖外特性控制方式和电路设计法，研制成功了低干扰高可靠性的逆变式空气等离子切割机。实验表明，该机具有可靠性高，切割质量好，操作简便等特点，为空气等离子切割工艺提供了一种新型的优良设备。     

多程序点焊控制器的研制

本文主要介绍了多程序点焊控制箱的程序过程以及主控制器及调制器的工作原理，并采用了一种新型的触发电路代替传统的脉冲变压器，具有触发可靠、大功率、高精度、电路简单等特点。     

宝钢热轧厂轧辊磨床的技术改造

介绍了宝山钢铁股份有限公司热轧厂对其轧辊磨床进行床身导轨、数控系统、测量系统、中心架、砂轮主轴及动平衡装置、集中控制、在线涡流探伤等方面的技术改造情况。改造后，磨床精度、效率和稳定性明显提高。     

钨合金的磨削加工去除机理

目的 解决钨合金磨削加工去除机理不明晰的问题。方法 基于单磨粒刻划有限元仿真、单磨粒刻划和磨削加工实验，探究钨合金的磨削加工去除机理。结果 在刻划过程中，划痕的不同位置材料的去除特性存在显著差异。在单颗粒刻划切入端，材料依次发生了塑性变形、隆起、微裂纹，再到钨相与黏结相的混杂交融。在划痕中段以材料去除为主，出现了材料微卷起和材料卷起现象，沿着刻划方向卷起现象越来越严重。在划痕切出端，划痕边缘和尾部均出现了“飞边”现象，且相较于切入端，切出端的形貌较差，实验与仿真吻合。此外，在不同相位处，材料的去除特性也存在一定不同。在钨相区域，同时存在脆性特征和塑性特征。在黏结相区域，刻划深度较浅时主要呈现塑性变形、塑性流动等特征，刻划中端深度较大时主要呈现与钨相的混杂和交融。在钨相与黏结相的相界处，相邻钨颗粒呈现不同的损伤或去除特征，且相界会阻断特征形貌的传递。最后，磨削后的钨合金表面存在单颗粒刻划痕上出现的所有去除特征，与单颗粒划痕的去除特征吻合。不同的是，磨削后划痕底部出现了区域性和放射状的裂纹。结论 钨合金的两相特性使得磨削表面的去除特征较复杂，存在塑性变形、微裂纹、微卷起、卷起、裂纹和两相交...     

Equivalent heat transfer coefficient at casting/Cu mould interface and temperature field simulation

1　INTRODUCTIONThesolidifiedmicrostructuresofalloysdependontheirsolidifyingprocesswhoseprimarycharacteristicsarethetemperaturedropofthesuperheatedmeltandthere leaseofthelatentheat.Sothestudyontheheattransferduringthesolidificationprocessistheessentialprobleminthesolidificationtheorystudy .Theresearchersworkingonthenumericalsimulationofthesolidificationprocessallknowthattheinterfacialheattransfercoefficientatthecasting/mouldisavariablechangingwithtime .Thusthedeterminationoftheinterfacialh…     

管内扭带传热与流动阻力的实验研究

为了研究管内强化换热技术,对3根不同结构参数的扭带插入光管的换热特性和流体动力学特性进行了实验研究.以空气为工质,Re在8 000～100 000之间,管外被水冷却.在大量实验数据的基础上,用多元线性回归法得到了具有较高精度的扭带管的传热系数和摩擦系数的统计关联式,分析了扭带管的传热与流阻性能,为换热器的设计及改造提供了理论依据.     

An analysis and optimisation of the geometrical inaccuracy due to wire lag phenomenon in WEDM

An extensive study of the wire lag phenomenon in Wire-cut Electrical Discharge Machining (WEDM) has been carried out and the trend of variation of the geometrical inaccuracy caused due to wire lag with various machine control parameters has been established in this paper. In an extremely complicated machining process like Wire-cut EDM, which is governed by as many as ten control factors, it is very difficult to select the best parametric combination for a particular situation arising out of customer requirements. In the present research study, all the machine control parameters are considered simultaneously for the machining operation which comprised a rough cut followed by a trim cut. The objective of the study has been to carry out an experimental investigation based on the Taguchi method involving thirteen control factors with three levels for an orthogonal array L₂₇ (3¹³). The main influencing factors are determined for given machining criteria, such as: average cutting speed, surface finish characteristic and geometrical inaccuracy caused due to wire lag. Also, the optimum parametric settings for different machining situations have been found out and reported in the paper.     

Effect of welding speed and electrode extension on the approximate entropy of welding current in short-circuiting GMAW

Based on the phase space reconstruction of welding current in short-circuiting transfer arc welding under carbon dioxide, the approximate entropy of welding current and its standard deviation have been calculated and analyzed at different welding speeds and different electrode extensions respectively. The experimental and calculated results show that at a certain arc voltage, wire feeding rate and gas flow rate, welding speed and electrode extension have significant effects not only on the approximate entropy of welding current, but also on the stability of welding process. Further analysis proves that when the welding speed and electrode extension are in an appropriate range respectively, the welding current approximate entropy attains maximum and its standard deviation minimum. Just under such circumstances, the welding process is in the most stable state.     

Mg-15Gd-0.6Zr合金的组织与力学性能

通过在Mg-Gd二元合金中添加少量的Zr后制备一种新型的Mg-15Gd-0．6Zr合金，并对合金的微观组织、时效特性和不同温度下的力学性能及拉伸断裂方式进行研究。合金在非平衡凝固过程中容易形成MgxGd（x=2，3，5）相，但用热处理的方法几乎不可能消除。在合金的Cast-T5、Cast-T6、Ext-T5和Ext—T6的4种时效状态中，Ext—T5态达到峰值硬度的时间最短，峰值硬度值最高；而Cast-T5态的则相反。合金具有较高的耐热强度和延伸率，其在不同温度下的抗拉强度与WE54的相当，而延伸率明显优于WE54及其它耐热镁合金的。合金在25℃时的断裂方式以准解理断裂为主，而250℃时的断裂方式以微孔聚集型断裂为主，300℃和350℃时的断裂方式以典型的微孔聚集型断裂为主。     

XK717数控铣床主轴系统的热特性分析

建立了主轴系统与普通水箱之间的冷却模型，并结合有限元方法，对XK717数控铣床主轴系统进行了热特性分析，得出了水箱设计参数和冷却泵的流量对铣床主轴系统热特性的影响规律，从而为数控铣床主轴冷却系统的设计提供了理论依据，具有一定的指导意义。