Abstract
The diameter of the threaded bottom hole determines whether the extrusion can proceed smoothly and the fullness of the tooth shape after extrusion. The tooth height rate is an important indicator of the strength of the threaded connection. In order to establish the relationship between the diameter of the bottom hole and the tooth height of the extruded internal thread, this paper takes the aluminum alloy M8×1.25 mm internal thread as an example, and uses a method of combining numerical simulation and process test. Obtained the changing law of internal thread profile and tooth height rate of extruded workpieces with different bottom hole diameters. Using MATLAB to fit the numerical simulation results, the relationship between the tooth height of the internal thread and the diameter of the prefabricated bottom hole of the workpiece was obtained. The reliability of the numerical simulation results and the feasibility of the fitting formula are verified through experiments. The results show that the diameter of the prefabricated bottom hole of the workpiece is controlled within 7.33~7.39 mm when the M8×1.25 mm internal thread is processed by the cold extrusion process. The high rate of the internal thread after extrusion meets the requirements of thread connection strength, and the internal thread has high forming quality and good surface quality.
Highlights
According to statistics, bolt connections account for more than 60% of the connection methods of modern manufacturing equipment and precision instruments
Liang Yuxuan et al [4,5] analyzed the change law of vibration signal during cold extrusion of internal threads with different bottom hole diameters based on vibration tapping technology, explain the influence of the size of the bottom hole diameter on the processing quality of the cold extrusion internal thread from the perspective of the vibration signal, that is, the larger the diameter of the bottom hole, the smaller the amplitude and vibration frequency, and the total energy of the vibration signal decreases; Peter Monka et al [6] studied the influence of the structural parameters of the tap on the service life of the tap from the perspective of tap failure, and developed a vibration diagnosis system to monitor the stability of the machining process
The tooth height rate of the internal thread is closely related to the connection strength, and the bottom hole diameter is a factor that can be controlled in advance during the machining process
Summary
Bolt connections account for more than 60% of the connection methods of modern manufacturing equipment and precision instruments. When using the cold extrusion process to process internal threads, the most important factor affecting the tooth height rate is the diameter of the prefabricated bottom hole of the workpiece. The above-mentioned documents have conducted different degrees of research on the effect of the bottom hole diameter in the cold extrusion forming process of the internal thread, but there is no targeted study on the relationship between the tooth height rate and the bottom hole diameter. This article takes aluminum alloy T6061-T6 and 40Cr as the research object, and reproduces the extrusion forming process of M8×1.25 mm internal thread, the internal thread profile of different prefabricated bottom hole diameters was obtained through numerical simulation, and the theoretical formula of bottom hole diameter and tooth height rate was obtained by the polynomial fitting method. Establishment of finite element model and analysis of numerical simulation results
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