Failure analysis of threaded connections in large-scale steel tie rods

Steel tie rods are very important load-carrying components in applications where high levels of pre-stresses are required. The bearing capacity of a steel tie rod is determined not only by the strength of the rod body, but also by the strength of the threaded connection that resists force. Analysis of the strength of the threaded connection and determining the optimal number of turns of thread engagement is critical to ensure structural safety. This paper reports the results of full-scale tensile rupture experiments on two categories of large-scale steel tie rods provided by China JULI Corporation: (i) LG75-00 steel tie rods with triangle threaded connection, and (ii) LG100-00 steel tie rods with trapezoidal threaded connection. The full-scale tensile rupture experiments were carried out to test the maximum allowable axial working load under different numbers of turns of engaged threads. The results of these experiments suggest strong guidelines on the minimum number of turns of thread engagement for preventing the failure of thread teeth of steel tie rods in practical shear and bending applications.     

地质钻探高强度铝合金钻杆研制及其应用

铝合金钻杆的设计制造技术属高新技术范畴,世界上只有俄罗斯、美国等少数发达国家能够批量生产。简要介绍了我国地质钻探用铝合金管材研制、铝合金钻杆制造关键技术及野外试验情况,并对今后铝合金钻杆的研发和应用方向提出了建议。项目工作成果对今后我国开发特深孔铝合金绳索取心钻杆和超深孔铝合金钻杆具有重要价值。安徽彭桥煤矿区的铝合金钻杆钻探试验最大孔深超过1000 m,应用效果良好,开辟了我国地质钻探铝合金钻杆在中深孔应用的先河。     

火电厂管道螺纹吊杆最大使用荷载计算研究

火电厂管道螺纹吊杆最大使用荷载是设计和选择螺纹吊杆的重要依据,然而现有的相关规定给出的结果并不相同,造成在相同设计条件下选择的螺纹吊杆规格并不相同,影响了螺纹吊杆的准确设计和选择。为规范螺纹吊杆的设计和选择,确保火电厂的安全和经济运行,对螺纹吊杆最大使用荷载的相关问题进行了分析和探讨。分析和探讨了与螺纹吊杆最大使用荷载有关的螺纹根部截面积计算方法、许用应力确定以及材质选择等问题,并给出了相应的措施和建议。分析和研究了螺纹吊杆最大使用荷载计算方法,基于许用应力法给出了螺纹吊杆最大使用荷载计算结果。     

石墨炉原子吸收法测定橡胶奶嘴铅含量

采用石墨炉原子吸收光谱法(GFAAS)检测橡胶奶嘴浸出液中微量铅的含量.考察了基体改进剂、灰化温度、原子化温度等因素对测定的影响,建立了石墨炉原子吸收光谱法测定橡胶奶嘴中微量铅的方法.结果表明,在选定的最佳仪器条件下检出限为0.18μg/L,回收率为94.2%～107.5%,相对标准偏差为3.86%(n=5).方法简便...     

切分生产螺纹钢弯曲度超标的设备改进

针对切分后钢在冷床摔直板、齿条、对齐辊道槽型上每齿槽内存放2～3根倍尺棒材钢,摔直板变形、冷床齿条槽型不适合、对齐辊道对不齐等造成螺纹钢弯曲度超差的问题进行了分析,提出了相应的改进措施.通过重新设计冷床摔直板散热孔,提高散热能力,改进齿条槽型形式和对齐辊槽型等冷床设备,解决了螺纹钢切分生产时的弯曲度超差问题,冷床弯钢现象得到了有效的控制,提高了产品质量,降低了备件消耗.     

浅谈慢走丝线切割在模具制造中的应用

主要阐述慢走丝线切割的特点及加工技术     

Failure analysis of cylinder clamping rods in diesel engines

This article discusses the failure of cylinder clamping rods in single cylinder diesel engines. The AISI 4140 hardened and tempered steel clamping rods were failing after 200–250 h of operation. The fatigue failures initiated at the root of the last thread on the clamping rod that was engaged in a blind hole in the cylinder block. The failures were caused by loose tolerances on the threads that resulted in a non-uniform distribution of load. The load was concentrated on the last threads to engage, thus causing fatigue crack nucleation at the thread root and propagation until the rod broke by overload. Changing the tolerance on the threads virtually eliminated the fatigue problem.     

JVS多功能复合材料堵漏防水技术

本文通过用JVS多功能复合材料治理地下工程渗漏防水的几个实例 ,介绍JVS多功能复合材料的性能及螺管嘴阀压力灌浆堵漏法 ,螺管 -堵头堵漏法的工艺流程。体现此材料性能独特 ,此法施工工艺行之有效 ,经验证施工质量可靠 ,兼有堵漏防水与修补加固的双重功能 ,且综合经济效益显著。     

缺牙油管接头接触特性及应力应变分析

开发了存在螺牙损伤的油管螺纹接头参数化有限元自动建模程序,应用ANSYS软件对缺牙油管螺纹接头进行了弹塑性接触特性及应力应变分析.并以27/8TBG油管螺纹接头为例,给出了油管在预紧及拉伸载荷工况下接头的应力应变云图及螺牙面的接触应力曲线,分析了螺牙损伤位置及数目变化时接头应力应变的变化规律.本文研究结果对旧油管判废具有工程应用价值.     

近临界压力下R410A在水平螺纹管内的冷凝换热研究

为研究近临界压力下R410A在水平螺纹管内的冷凝换热特性,在质量流率为200 ～ 800 kg/(m2·s)、干度为0.1～0.9、冷凝压力比为0.8和0.9时,对3种不同管径的内螺纹铜管(5、7和9.52 mm)进行单管冷凝换热实验.结果 表明:冷凝换热系数随着质量流率和干度的增加而增加,冷凝压力越接近临界压力,换热...