激励对往复式骨架油封密封性能的影响

为改善往复式骨架油封的泄漏问题,建立油封唇口密封区流体润滑的数值计算模型,模型考虑密封面粗糙形貌以及油封唇口的径向变形,通过求解雷诺方程分析密封区的流体力学特性,获得密封区的油膜厚度和压力分布,并分析激振频率和振幅对密封性能的影响规律。结果表明:随着激振频率的增加,内外行程中密封区的最小膜厚呈先增加后减小的变化趋势,激振频率越大,往复式骨架油封的密封性越差;内外行程中密封区的的最小膜厚随激振振幅的增加呈非线性增加,激振振幅越大,往复式骨架油封的密封性越好。综合考虑,为提高密封效果,往复式骨架油封适用于小频高幅的工作场合。     

Study on formation mechanisms of serrated chip based on valence electron structure

Abstract

High-speed machining experiment of pure copper and aluminum bronze (QAl9-4) is carried out at the same cutting condition to obtain the different chips. The valence electron structure (VES) parameters that affect adiabatic shearing sensitivity were studied in this paper. The results show the bond energy and lattice electron number are related to adiabatic shearing sensitivity. Adiabatic shearing sensitivity increases with the increase of bond energy, and the decrease of lattice electron number. For pure copper, the bond energy is smaller and the lattice electron number is higher, so its adiabatic shearing sensitivity is low. The shape of chip is approximate ribbon. For aluminum bronze (QAl9-4), the bond energy is increased and the lattice electron number is decreased due to aluminum (Al) addition, so its adiabatic shearing sensitivity is higher than that of pure copper. The serrated chip divided uniformly by Adiabatic Shear Band (ASB) was formed. The basis can be provided for optimizing process parameters, improving and selecting materials with different cutting performance by studying the specific alloy elements on the influence of adiabatic shearing sensitivity to predict the chip morphology to some extent in VES level.     

Thermal modeling of drilling process in titanium alloy (Ti-6Al-4V)

Abstract

In drilling in titanium alloys, heat trapped in a hole adversely affects tool life, hole surface quality and integrity. Therefore, modeling temperature distribution in drilling is vital for effective heat dissipation and improving quality of drilled surfaces. The existing numerical and finite element models consider only frictional heat, whereas the effect of shear heat generation and tertiary heat generation is neglected. In the present work, a comprehensive thermal model of the drilling process is developed by considering all heat generated in shear, friction and tertiary zones. The drill cutting edges are divided into a series of independent elementary cutting tools (ECT). The calculated heat flux loads are applied on an individual ECT in the finite element model to determine the temperature distribution and the maximum temperature around the cutting edge. The temperature in the drill was also measured experimentally with the help of an Infrared (IR) camera. The results of numerical simulations lie within the error of ～8.75% when compared to the prior studies, and ～5.41% when compared to our experimental work. The thermal model gives the temperature distribution, and the maximum temperature observed at the corner of cutting edge was 604.2°C at a cutting speed of 35?m/min.     

前刀面槽型结构对D型刀片车削球墨铸铁性能的影响

通过切削力、磨损和冲击切削试验,研究了前刀面槽型结构对D型刀片车削球墨铸铁切削性能的影响。试验结果显示,刀具的第一前角对切削力的影响最大;在10°~15°范围内,刀具前角越大,切削力越低;棱带宽度大的刀片具有更加优异的耐磨损性能;具有正刃倾角的刀片显示出更优异的耐冲击性能。     

面向流屑角突变建模的切削状态参数经验公式的获得及应用

从提高流屑角突变模型的预测精度出发,建立了切削状态参数与3个切削控制参数之间关系的新经验公式。提出了一种通过迭代法准确设定有限元仿真软件刀-屑摩擦因数的方法,并通过直角切削Al6061-T6工件的有限元仿真试验,获得了一组不同切削控制参数组合条件下的切削状态参数数据。根据该数据拟合出剪切角φ、刀-屑摩擦角β、剪切应力τs关于刀具前角γ0、进给量f和切削速度v的经验公式,并通过一组直角切削试验,验证了所得经验公式的有效性。将新建经验公式应用于流屑角突变建模过程后,所得模型关于突变临界切削宽度的平均预测误差减小了27.2%。     

硬孔攻丝用高性能先端丝锥的设计及应用

热后硬孔攻丝螺纹变形量小、尺寸稳定、强度高。该工艺方法对刀具强度要求较高,使用普通高速钢丝锥和螺纹铣刀加工时,普通高速钢丝锥无法承受热后硬孔攻丝所产生的大扭矩而频繁折断,报废率较高,同时螺纹铣刀成本高,不适合大批量生产。针对热后硬孔攻丝工艺复杂、成本高的问题,专门设计了硬孔攻丝用高性能先端丝锥,解决硬孔攻丝难题,并与其他种类丝锥进行了切削力对比。     

一个塔箍的等壁厚塔器自振周期的计算

本文从理论上到工程应用上,对带有一个塔箍的等壁厚塔器自振周期的计算方法进行了探讨,可供工程技术人员参考。     

确定绝热材料和经济厚度的新方法

通过对单层和双层保温层总费用的研究,对现有的单层保温层经济厚度的公式进行了修正,导出了双层保温层经济厚度的计算公式,扩大了绝热材料的使用范围,附有计算实例说明其应用。     

高温下碳在α-γ型异种钢焊接接头中的扩散

对高温下碳在α－ γ型异种钢焊接接头中的扩散行为进行了研究。通过非线性回归分析,建立了增脱碳层厚度（ Ｈ） 与加热温度（ Ｔ） 和保温时间（ｔ） 之间关系的数学模型。研究结果表明：增脱碳层的最大厚度是温度的函数,数值上等于数学模型的前半部分;模型的后半部分受扩散系数的影响,是温度和时间的函数。此数学模型与试验结果具有良好的一致性,可用来估算不同条件下增碳层和脱碳层的厚度。     

利用“计算机网络”建立大规模金属材料下料中心是降低金属结构产品成本的关键

通过在钢铁企业建立大现模金属材料下料中心,利用“计算机网络”将钢铁厂、金属材料下料中心及众多用户联系起来,使得钢厂的排产、金属材料下料中心的套料加工及用户产品的下料有序结合.钢铁厂由提供原始板材改为按用户要求直接提供切割加工的成形坯料或部件,金属材料下料中心可全部使用数控切割机下料.提高了金属材料下料的精度和质量.由于采用计算机编排套料系统集中下料,钢材的利用率可由目前的60%左右提高到80%以上.在钢材利用率、运输量、储料周期、资金占用周期、金属材料下料设备的投人、料场土地的利用率、人工工时、金属材料下料质量、表面处理等诸多方面都降低了金属结构的生产制造成本,同时也有利于环境保护.