基本拧紧技术-阿特拉斯力矩加转角技术分析及工具介绍.pptVIP

基本拧紧技术 基本拧紧技术 为什么使用螺栓连接 50-40-10 规则 再假如完全没有摩擦力会怎样？会不会有扭矩产生？ 扭矩能保持吗？ 夹紧力与摩擦力的关系 弹性松弛会影响夹紧力 软连接、硬连接 软、硬连接 Torque Control /Angle Monitor 扭矩控制／角度监控 Angle Control / Torque Monitor 角度控制／扭矩监控 Torque and Angle Control 扭矩和角度控制 Fastener Yield Control 屈服点控制 ……… Quality /质量 The Torque It is well known that a torque can be achieved by applying a force F on a lever (with a length L). Force has the unit N (Newton) or lb (pound) or even kgf (kilogram foce) Length is m (meter) or ft (foot). The length of the lever arm is obviously as important as the “strength” of the operator. Wrenches or spanners are generally more of size to match the palm of a hand than to enable you achieve a correct torque on a given size of screws. The ones with a small width across flats will normally give too high a torque where as the wider ones normally will not enable you to fully tighten a big size screw. Try a few examples. Also look at what happens to different sizes of square drives. What torque could you apply to a 3/8” square drive? (1/4”, ?” etc) The clamp force which is created by the screw acts in two places: -under the head and -in the thread. The pitch of the thread is small in order to prevent the screw joint from falling apart by itself. The friction could for instance decrease by hugh frquency vibrations spinning the screw loose. For a static force the statement is correct then it is safe to have a clamp load which is just larger than the external load. A dynamic load should be much smaller than this. Depending of how the external forces act and of which nature they are the joint should be designed in such a way the it the aditional load on the screw from a pulling force is small. Elastic and permanent deformation – yield. Tightening too much will stretch the screw until it breaks. This means that when using torque controlled tightening the final torque allways has to be set in such a way that you never reach the yield point. Examples of hard joints would be: Seat b