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Based on the influence of the ambient temperature, wind speed and other factors on the transformer monitoring system, the hot spot temperature model of the transformer outer wall is established by using thermoelectric analogy theory and lumped parameter model. Through the analysis of experimental data, mathematical model of influence of ambient temperature and wind speed on temperature of transformer is built, and the correction values on the temperature of the transformer are obtained under the different ambient temperature and wind speed. The correction values make the transformer hot-spot temperature more objective and more authentic, which has significant influence on the running of the transformer safely and efficiently.

This paper presents a comprehensive dynamic model that simulates infeed centerless grinding processes and predicts their instability-related characteristics. The new model has the unique ability of accurately predicting the coupled chatter and lobing process of a multi-degree of freedom and two-dimensional centerless grinding system by considering its critical issues. First, the model considers the complete two-dimensional kinematics, dynamics, surface profiles, and the geometrical interactions of the workpiece with the grinding wheel, regulating wheel, and supporting blade. Second, a two-dimensional distributed grinding force model along the contact length is adopted and modified for centerless grinding processes as a function of normalized uncut chip thickness. The forces of the work holding system are determined by balancing the grinding force and accordingly the work holding instability can be identified as well. Third, a two-dimensional contact deformation model under the condition of general surface profiles or pressure distributions is developed for the contacts of the workpiece with the grinding wheel, regulating wheel, and supporting blade. The new model is validated by comparing the predicted chatter and lobing occurrences with experimental results. Keywords: centerless grinding, chatter, dynamic simulation model, mechanistic model [DOI: 10.1115/1.2716729]

In this paper we present a comprehensive dynamic model that simulates surface grinding processes and predict their regenerative chatter characteristics. The model considers special aspects in surface grinding processes, such as interrupted grinding on a series of surfaces and step-like wheel wear along the axial direction due to crossfeed. A new theory for the wheel regenerative chatter mechanism, which describes the regenerative force as a function of not only the instantaneous chip thickness but also the distributed uneven grit wear/dullness, is introduced and applied in the model. Using the model, explanations are provided for those unrevealed wheel regenerative chatter phenomena observed from the experimental results in literature. The model is validated by comparing the simulated chatter frequencies and thresholds with the experimental results. [DOI: 10.1115/1.2137752]

This paper presents a time-domain dynamic model, which simulates cylindrical plunge grinding processes under general grinding conditions. The model focuses on the prediction of grinding chatter boundaries and growth rates. Critical issues are considered in the model including: the distributed nonlinear force along the contact length, the geometrical interaction between the wheel and workpiece based on their surface profiles, the structure dynamics with multiple degrees of freedom for both the wheel and workpiece, the response delay due to spindle nonlinearities and other effects, and the effect of the motion perpendicular to the normal direction. A simulation program has been developed using the model to predict regenerative forces, dynamic responses, surface profiles, stability regions, and chatter growth rates. The model is validated using existing numerical and experimental results. [DOI: 10.1115/1.2118748]

This paper presents a comprehensive time domain model that simulates end milling processes under general cutting conditions. Over an extensive range of axial depths of cut, the model can accurately predict regenerative forces and dynamic responses by considering varying dynamics along the cutting depth, three-dimensional forces, and cutting tool geometries. The prediction of stability limit is validated under cutting conditions of both large depths and very small radial immersions. In addition, three-dimensional surface profiles under both stable and chatter conditions are predicted and compared with measured ones. A new method to extract cutting pressure coefficients is also introduced and applied to the experimental validations. [DOI: 10.1115/1.2035694]

This paper presents a comprehensive integrated thermo-dynamic model for various high speed spindles. The entire model consists of fully coupled three sub-models: bearing, spindle dynamic and thermal models. Using a finite element approach, a new thermal model has been generated, which can describe complex structures of high-speed motorized spindles, and can predict more accurate temperature distributions. The spindle dynamic model is constructed using finite elements based on Timoshenko beam theory and has been improved by considering shear deformation, material and bearing damping, and the spindle/tool-holder interface. Using the new thermo-dynamic model, more general and detailed bearing configurations can be modeled through a systematic coupling procedure. The thermal expansions of the shaft, housing and bearings are calculated based on predicted temperature distributions and are used to update the bearing preloads depending on the operating conditions, which are again used to update the thermal model. Therefore, the model is fully integrated and can provide solutions in terms of all the design parameters and operating conditions. [DOI: 10.1115/1.1644545]

This paper presents a new solution procedure for an integrated thermo-dynamic spindle model and validation results. Based on the model presented in Part 1 of this paper, a computer program has been developed to generate comprehensive solutions for high speed spindle-bearing systems, such as bearing stiffness, contact load and temperature, spindle dynamic characteristics and response, temperature distributions, and thermal expansions. The model and the solution procedure are modular such that solutions for different spindle set-ups can be easily generated by combining a given spindle model with different toolholder models. Validation test results for thermal and dynamic predictions are presented for four different spindle systems, including the thermal and dynamic validation tests on a specially constructed spindle testbed. The validation results show the model has accurate predictive capabilities for a wide range of operating conditions and various spindle designs. [DOI: 10.1115/1.1644546]

Goll, Darrel E., Valery F. Thompson, Hongqi Li, Wei Wei, and Jinyang Cong. The Calpain System. Physiol Rev 83: 731-801, 2003; 10.1152/physrev.00029.2002.--The calpain system originally comprised three molecules: two [Ca.sup.2+]-dependent [...]