New ceramic injection systems for hot chamber die casting of aluminium alloys

Abstract

The quality of hot chamber die cast aluminium alloys can vary, due to differences of casting conditions, in particular the casting pressure. This is caused by the plunger tip galling during the casting process. To solve this problem, a new injection system is proposed using a flexible movable plunger tip and an insert type shot sleeve. With this system, the plunger tip can be turned around and slid into the piston holder, which facilitates smooth insertion of the plunger into the shot sleeve. The proposed insert type sleeve can be made with a strong structure. Moreover, even if the sleeve is partially fractured, it can easily be replaced. With the proposed injection system, high quality hot chamber die cast components can be created. In addition, the maintenance cost of the injection system is dramatically reduced.     

Water analogue validation of numerical model for fluid flow during slow shot phase in die casting process

Abstract

Air that becomes entrapped in the molten metal during the die casting process has a major effect on the formation of porosity in horizontal cold chamber die castings. In this study, a three-dimensional computational fluid dynamics model was developed to study the flow patterns of liquid metal in the injection chamber, in which the moving boundary conditions of the plunger movement was considered in detail. According to the principle of die casting machines, a water analogue system was designed and built to investigate the slow shot process. A colour high speed camera was used to record the fluid flow patterns under different plunger movement profiles. The numerical simulation results agreed well with the water analogue experimental results, which validated the numerical model of shot processing in the cold chamber of the die casting process.     

SHOT──D_4设备介绍

ＳＨＯＴ—Ｄ４设备是一种专用光电混合端机，它用于程控交换机Ｓ１２４０母局与ＲＡＳＭ（远端模块）局之间的传输，能为两个用户架（即２０００门）提供传输通道。当通信容量超过２０００门时，可采用积木式迭加，组成容量更大的通信系统。采用该设备可以方便地将用户架作为远端模块搬出电信局，而交换设备的投资却不需要增加。     

基于SHOT特征描述子的自动提取球形标靶方法研究

针对复杂场景下的三维激光点云球形标靶精确自动化提取问题,提出了一种基于SHOT特征的自动精确提取球形标靶的方法。该方法设计了粗提取和精提取处理过程,粗提取过程首先采用SHOT特征描述子提取场景内全部的球形标靶点云;其次,利用欧氏聚类分割球形标靶点云,并采用最小二乘方法计算球形标靶的粗略参数。精提取过程依据迭代最小二乘方法和法向滤波剔除非球面点,得到球形标靶点云和精确的球形标靶参数。设计了含有4个球形标靶的实验场景,使用德国Z+FImage5016扫描仪进行场景数据采集,自动提取得到实验场景中的球形标靶点云和球形标靶参数。结果表明,在10m范围内,该方法自动提取的球形标靶半径中误差为0.25～0.33 mm,较人工提取球形标靶点云的半径中误差减小0.02～0.06 mm,较基于微分方法减少0.01～0.09mm;该方法能够得到较高的球形标靶定位精度和稳健地去除场景点云中的噪声,可在30s内完成百万级点云球形标靶的自动提取任务。     

解决译码器验证TB超限问题的方法

遥爆系统的同步一致性精度，直接影响着地震资料的质量。为了获得优质、高效地震数据资料，必须维修、维护好遥爆系统设备．把译码器验证TB超限的现象降到最低，提高设备的完好率和利用率。     

Microstructural alterations through heat treatment and its influence on wear response of a silicon containing zinc based alloy under different test conditions

Abstract

Observations pertaining to the influence of microstructural alterations brought about through heat treatment on the sliding wear behaviour of a zinc based alloy comprising of silicon have been analysed in this study. The effects of sliding conditions such as pressure and speed on the wear response of the alloy in as cast and heat treated conditions have also been investigated. The as cast alloy revealed dendritic structure consisting of primary α, eutectoid α + η, and ? phase. Silicon was present in the alloy microstructure as discrete particles. Heat treatment caused breaking of the dendritic structure and more homogeneous distribution of various microconstituents without affecting the morphology and mode of distribution of the silicon particles. The heat treated alloy attained superior wear response as compared with the as cast one especially under more severe wear conditions. Wear rate versus pressure plots revealed two slopes wherein the slope was low at low pressures and increased considerably beyond a critical pressure. The critical pressure decreased with speed while it was more for the heat treated alloy. The wear behaviour of the specimens deteriorated with pressure and speed. High wear rates were supplemented with severe surface/subsurface damage and coarse debris formation and vice versa. Changing microstructural features of the regions at different depths below the wear surface were attributed to the changing degree of deformation they experienced during wear. The wear behaviour of the specimens has been explained in terms of specific characteristics of various phases such as lubricating and load carrying capability, thermal stability and cracking tendency. Typical characteristics of worn surfaces/subsurface regions and debris further supplemented the specific wear behaviour of the alloy in different test/material conditions.     

SHOT PRO 爆炸系统的功能开发与应用

文章简要介绍了新一代遥爆系统SHOTPRO的基本操作原理及部分硬件连接。重点描述如何实现该爆炸系统井口信号的存储和计算机的实时监控，为野外现场质量控制和室内资料处理提供依据。     

SHOT PRO和BOOM BOX系统控制时序分析

本文主要对SHOTPRO和BOOMBOX两种遥爆系统的工作方式和控制时序进行分析。从遥爆系统的功能、起爆延迟时间（钟TB）的概念及其调整的意义着手，说明了这两种遥爆系统的普通工作方式和主一从（重复器）工作方式，并对它们的时序进行了详细的分析。     

Influence of process parameters on short fatigue crack growth on carburised case of DIN 20MnCr5 steel

Abstract

Carburising, quenching, tempering and shot peening treatments are widely used on mass production of automotive industry, such as pinion gears and master gears. Variations on these processes may influence the flexural fatigue life of described components. The aim of this work was to study the influence of variations in shot peening time and variations in tempering temperature, of short fatigue cracks growth of carburised case of DIN 20MnCr5 steel. Samples blasted about 30 min and 1 h and tempered at 160°C, showed the best results relative to crack growth and to fatigue life.