Research On Anti-fatigen Processing Technology Of High-strength Steel Internal Thread Based On Cold Extrusion Technology

As external thread processing develops to high Performance, low cost and lower energy consumption, the cold-extruding shaping technology of internal thread is an important part of anti-fatigue machining technology. It has great potential for aeronautics, astronautics and rapid trains. Aiming at the problems in cold-extruding high-strength steel internal thread, the key technique of cold-extruding high-strength steel internal thread was systematically investigated through combining theoretical analysis and testing technique. And surface properties of cold-extruding internal thread, online monitoring of the extrusion process and finite element analysis were studied deeply. The work can provide a basis for the application and dissemination of this cold-extruding internal thread. The main work is as follows:1. Establishing mechanical model of contact stress and extrusion force in the process of cold-extruding internal thread. The mechanical model of contact stress and extrusion force in the process of cold-extruding internal thread was established. The technological parameters in the extrusion processes of internal thread were determined through reasonable propositions. And the contact stress along the normal direction of the tap-teeth and the extrusion force were calculated. It is provide the theory basis for the optimization of technological parameters, machining stability, controlling quality, predicting the failure mechanism of extrusion tap, and so on.2. Analysis on cold-extruding technology characteristics of high-strength steel internal thread. The cold-extruding technology characteristics of Q460 high-strength steel internal thread were studied experimentally by using self-made extrusion tap and corresponding special torque holding device. And the effect of the technology parameters on the quality of internal thread was analyzed. The ideal internal thread was obtained through selecting processing parameters, and the cold-extruding technology of the large diameter internal thread was investigated. It provides a basis for the application and dissemination of this cold-extruding internal thread.3. Analysis on the surface properties of cold-extruding internal thread. In microscopic condition, the surface properties of cold-extruding internal thread of Q460 high-strength steel was studied from the part state such as surface residual stress, roughness, microstructure, micro-hardness and hardened-layer and from running conditions such as corrosion environment.4. Designed by online monitoring system of the extrusion process of internal thread. Based on multi-sensor data fusion technique, the torque signal, temperature signal, vibration signal and acoustic emission signal were studied on signal analysis, feature parameters extraction and selection and pattern recognition by using self-designed monitoring system. And it predicted the emergence of a range of issues in processed Q460 high-strength steel internal thread. It increased the reliability of cold-extruding internal thread.5. Simulation on the cold-extruding process of internal thread. The deformation cloud of temperature field, stress field and strain field was obtained by using DEFORM to simulate the cold-extruding process of Q460 high-strength steel internal thread. The effects of the hole-diameter of the work, extrusion speed, friction factor and extrusion times on the extrusion temperature and the extrusion torque were analyzed. And the validity of the model was verified by experiment. It provides the data support for practical application of decision-making support system of cold-extruding internal thread technology.6. Development on the decision-making support system of cold-extruding internal thread technology. The model libraries, knowledge base, application example libraries and experiment libraries were established and the decision-making support system was developed. The relevant information of the extrusion technology was centralized and unified management. It maintained real-time consistency of the data and increased information share.