Abstract In this study, the contact interface friction, its reduction and the frictionless stress in ultrasonic vibration assisted forming process are investigated by a combination of experimental, analytical and numerical methods. Conventional and ultrasonic vibration assisted compression tests of pure titanium without lubrication are implemented. The flow stress is significantly lessened by applying the oscillation and decreasing the diameter-to-height ratio due to the friction reduction. The friction coefficient and the real/frictionless stress can be predicted by the relation among the experimental/apparent stress, strain and friction coefficient established from theoretical analysis. Iterative finite element simulation including the estimated coefficient is also performed to correct the compressive stress. By comparing the stress obtained in lubricated compression test, the analytical friction coefficient and the numerical true stress are verified and recommended. Accurate evaluation of the friction and the material behavior using the proposed analytical and numerical methods is of importance for metal forming behavior with or without the ultrasonic vibration.

中文翻译：

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超声波振动成形过程减摩与无摩擦应力的评价

摘要 本研究采用实验、解析和数值方法相结合的方法研究了超声振动辅助成形过程中的接触界面摩擦及其减小和无摩擦应力。对无润滑纯钛进行常规和超声振动辅助压缩试验。由于摩擦减少，通过施加振荡和降低直径与高度的比率，流动应力显着降低。摩擦系数和真实/无摩擦应力可以通过理论分析建立的实验/表观应力、应变和摩擦系数之间的关系来预测。还执行包括估计系数的迭代有限元模拟以校正压缩应力。通过比较润滑压缩试验中获得的应力，验证并推荐了解析摩擦系数和数值真实应力。使用所提出的分析和数值方法准确评估摩擦和材料行为对于有或没有超声波振动的金属成形行为非常重要。