Research On Internal Thread Formed By Cold Extrusion Based On Low Frequency Vibration

With the rapid development of modern industry, the thread connection parts have been widelyused in mechanical, instrumentation, marine and aerospace industries. At the same time, they are moreand more used in high-speed, high load and dynamic load cases. Therefore, more stringentrequirements have been proposed for thread connection parts, such as higher strength, hardness,precision and surface quality. Internal thread formed by cold extrusion is based on metal plasticdeformation theory, which can ensure the continuity of the metal fibrous tissue of the internal thread,therefore meet the higher requirements of the internal thread. But the internal thread formed by coldextrusion still have some deficiencies, such as higher extrusion temperature and extrusion torque,coolant not easy to squeeze into the extrusion zoon and the extrusion tap easily wear and break. In thispaper, vibration processing techniques is introduced to solve these problems. The main works are asfollows:(1) The theory of internal thread formed by cold extrusion based on low frequency vibration isestablished by both cold extrusion theory and vibration processing theory, which can explain why thefriction between the material of workpiece and extrusion tap can be reduced. Because the traditionalinternal thread formed by cold extrusion can produce high extrusion force. So the coolant is largelyexhausted out of the extrusion zoon. Therefore dry friction is formed between the material ofworkpiece and extrusion tap, which can greatly increase the wear of the extrusion tap and cause highextrusion temperature and extrusion torque. The internal thread formed by cold extrusion based onlow frequency vibration can make the extrusion tap vibration regularly, which can make extrusion tapintermittent contact with the material of workpiece, so the coolant can go back to the extrusion zoonand form boundary friction. Therefore it can greatly reduce the wear of the extrusion tap and improveits life.(2)The vibration processing method and vibration frequency range are determined by the theoryof internal thread formed by cold extrusion based on low frequency vibration and the processingmethod of the traditional internal thread formed by cold extrusion. A set of vibration processingequipment is devised for internal thread formed by cold extrusion based on low frequency vibration.The vibration processing equipment can smoothly transfer the vibration from vibration source toextrusion and realize vibration cold extrusion.(3)Model analysis is done for the vibration processing equipment and according the analysisresult to improve the vibration processing equipment. The first12natural frequencies and vibration models shows that the base and vibration plate can deform more easily. So the stiffness of thevibration processing equipment can be improved by installing the ribs and increasing the thickness ofthe two side of the base.(4)Dynamics simulation analysis is done for the vibration processing equipment. The variation ofthe vibration plate and vibration pole by different vibration parameters can be obtained. It can guidethe test of the internal thread formed by cold extrusion based on low frequency vibration.(5)Fully use of the advantage of LabVIEW and MATLAB to design a set of signal analysissoftware, which can easily complete the signal analysis.(6)The impact of three kinds of vibration parameters to internal thread formed by cold extrusioncan be obtained: with the exciting frequency increasing, the friction and extrusion torque is alsoincreasing; with exciting force increasing, the extrusion torque first decreasing then increasing; withthe exciting arm increasing, the extrusion torque is also increasing; when the other parameters are thesame, internal thread formed by cold extrusion based on low frequency vibration can obtain betterhigh rate of internal thread tooth. And at the same time, it also can further improve the micro hardnessof the internal thread surface and surface morphology.