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Wang J.,Tsinghua University | Wang J.,Beijing Key Laboratory of Precision | Zhang C.,Beijing Institute of Electronic System Engineering | Feng P.,Tsinghua University | And 3 more authors.
International Journal of Advanced Manufacturing Technology

Subsurface damage (SSD) induced by the rotary ultrasonic face machining (RUFM) considerably influences the technological application of the optical components. However, currently, there is no method to detect the depth of SSD in real time. For the purpose of precise and nondestructive evaluation of the SSD depth generated in RUFM processes, a predictive model was developed by applying the indentation fracture mechanics of brittle material. This was the first time that the correlation between the measured cutting force and SSD depth had been established. It was found that the SSD depth was directly proportional to the exponent of the measured cutting force (namely dSSD=γFc χ). Using this model, the depth of SSD could be predicted rapidly and precisely in the RUFM of optical glass even in real time using the measuring cutting force. Subsequently, this method was verified by conducting RUFM tests on K9 glass specimens with Sauer Ultrasonic 50. Meanwhile, the cutting force and SSD depth were compared experimentally between RUFM and conventional grinding (CG) process, indicating that RUFM is a beneficial manufacturing method for optical glass with reduced cutting force and SSD depth. © Springer-Verlag London 2015. Source

Xu C.,Tsinghua University | Zhang J.,Tsinghua University | Zhang J.,Beijing Key Laboratory of Precision | Feng P.,Tsinghua University | And 5 more authors.
International Journal of Machine Tools and Manufacture

An understanding of the contact characteristics of a spindle-holder joint in machine tools calls for an in-depth analysis of its performance under machining conditions. This study specifically aims to model a spindle-holder taper joint to predict the stiffness and stress distribution under different clamping and centrifugal forces. A spindle-holder taper joint subjected to clamping and centrifugal forces was modeled using the finite element method. The stress distribution of the interface was revealed and it was found that the von-Mises stress had a non-linear distribution because of the clamping force of the holder. The centrifugal forces were included in the model to analyze the deformation of the joint. At high speed the centrifugal force caused a stress concentration at the large end of the holder. A typical 7/24 taper joint of a BT50 holder was investigated to identify the stiffness using a special experimental platform. The axial and radial stiffnesses, as well as the hysteresis cycles were obtained to predict the contact characteristics with different clamping forces. The experimental results showed that the model presented in this study was efficient in predicting the characteristics of the spindle-holder joint. The method presented is useful in identifying the dynamics of a spindle-holder and can thus be used to optimize the spindle system. © 2014 Elsevier Ltd. Source

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