Effect of loading point position on fracture mode of rock

Anti symmetric four point bending specimen with different loading point positions was used to study effect of loading point position on fracture mode of rock in order to explore a feasible method for achieving Mode Ⅱ fracture and determining Mode Ⅱ fracture toughness of rock, K ⅡC . Numerical and experimental results show that the distance between the inner and outer loading points, L 1+ L 2, has a great influence on stresses at notch tip and fracture mode. When L 1+ L 2>0.5 L or 0.1 L < L 1+ L 2<0.5 L , maximum principal stress σ 1 exceeds the tensile strength σ t. The ratio of τ max / σ 1 is relatively low or high and thus Mode Ⅰ or mixed mode fracture occurs. When L 1+ L 2< 0.1 L , σ 1 is smaller than σ t and the ratio of τ max / σ 1 is much higher, which facilitates the occurrence of Mode Ⅱ fracture.

一种用于焊接生产线大型工件上下料的智能天车

大型工件焊接生产线采用人工上下料方式,劳动强度大,且存在安全隐患。随着时代的发展、当前市场需求和技术水平的变革,传统制造业面临越来越多的困难,亟需智能化转型升级。因此,介绍了焊接生产线大型工件采用智能天车上下料的解决方案。该方案能满足现场的使用需求,取得了较好的效果。

Characteristics of gravity signal and loading effect in China

The complex geographical environment in China makes its gravity signals miscellaneous.This work gives a comprehensive representation and explanation in secular trend of gravity change in different regions,the key features of which include positive trend in inner Tibet Plateau and South China and negative trend in North China plain and high mountain Asia（HMA）.We also present the patterns of amplitudes and phases of annual and semiannual change.The mechanism underlying the semiannual period is explicitly discussed.The displacement in three directions expressed in terms of geo-potential spherical coefficients and load Love numbers are given.A case study applied with these equations is presented.The results show that Global Positioning System（GPS） observations can be used to compare with Gravity Recovery and Climate Experiment（GRACE） derived displacement and the vertical direction has a signal-noise-ratio of about one order of magnitude larger than the horizontal directions.

焊接变位机关键参数的校核及设计

以理论计算为基础,结合实际工厂中使用的经验数据,并借助现代的设计工具,分析校核了焊接变位机设计中的几个关键参数,详细论述了焊接变位机的设计方法。以焊接行业常用的典型非标变位机为例,概述其设计流程,分析计算其几个关键的设计参数诸如负载率相关的扭矩、转动惯量、惯性扭矩等以及强度相关的应力、应变等,并基于实际使用经验总结出一套科学实用的焊接变位机设计方法和理念。

变位机用转盘轴承的载荷分析与仿真

针对变位机的实际要求,选择4点接触球转盘轴承作为其主要承力部件,简要介绍了转盘轴承的构造、特点及变位机的工作要求,采用载荷叠加法在Matlab中编程计算,得到全载荷状态下当量负荷的分布情况,从而得出转盘轴承工作过程中当量负荷的最大值及其受力最差的位置,通过静力弹性接触理论公式得到此时受载最大的滚动体对滚道的接触应力。在ANSYS中对4点接触球转盘轴承进行有限元分析,得到静力下的应力和变形云图及受载最大的滚动体对外滚道的接触应力。与理论计算结果相比较,验证了有限元分析结果的正确性与可信性。

机器人焊接系统中三轴变位机的标准化设计

为了更加快速优质的设备提供给客户,根据公司常用变位机的机型和结构进行标准化设计,形成公司标准设备,使公司整个项目的生产时间大大缩短,提高工作效率,更快的将焊接工作站提供给客户。本文概述了三轴垂直翻转变位机在机器人焊接工作站中典型的应用实例、标准变位机的主要技术参数、三轴垂直翻转变位机的工作原理、结构设计、驱动选型。将模块化的思路贯彻到整个变位机设计的过程,三轴垂直翻转变位机的结构拆分成:驱动单元、从动单元、旋转机架、底座、首箱、尾箱等模块。每个模块有统一的安装尺寸,但是每个模块有不同的结构尺寸,这样经过组合,设计出多种类型,满足多种焊接夹具的需要,适应更广泛的机器人焊接工作站。

The evolution characteristics of positive and negative earthquakes before strong quakes in Kanto area and the Hyugo earthquake in Japan

This paper studies the evolution charateristics of positive and negative quakes before Hyugo earthquake of M =7.2 and several strong quakes in Kanto area in Japan.The results show that the earthquakes over a certain megnitude are mainly positive ones a certain time before the main shock in or near the focal regions of most strong quakes,and form a concentratingintervals of positive quakes,The main quakes generally locate in or near the areas of positive quake distribution.Negative quakes often occur several months before the main shocks (not excluding positive ones), with the decrease of LURR (Loading/Unloading Response Ratio) values.It possibly shows that earthquake generating process has come to a short term stage.These characteristics may help to predict the time and location of the future earthquakes,and have been applied to the preliminary prediction of the time and the location of the earthquake of M =6.6 on Sep.11,1996 in Kanto area.

浅析自动装车系统中二段式球阀的应用原理及改进方案

基于装车系统自动化程度要求越来越高,二段式球阀应用更为广泛。本文重点阐述二段式球阀工作原理和存在的问题,最后提出改进方案。