Composite Wheel Research Articles

Pain's composite wheel of woe

Pain's composite wheel of woe

Precision Form Grinding of Slanted Circular Groove on Silicon High Voltage Thyristors

Summary To improve breakdown voltage for silicon high voltage thyristors, a slanted circular groove with precision form accuracy is required on a silicon element. Considering various forming processes, grinding has been selected as the best process to obtain a precision slanted groove. This paper presents a new grinding process concept. An original structure grinding machine, which is to assure an inclined infeed into the rotating work-piece, has been developed. Grinding wheels have been newly designed, composed of two wheels with different diameters and shapes forced together into a composite grinding wheel. By developing a grinding machine and the paired grinding wheels, all necessary precision slanted grooves have been ground with 60° inclined angle, 7.7 to 44.8 mm radius, 0.2 to 0.5 mm depth and 0.2 to 0.8 mm width. By establishing a high level form accuracy, efficiency and yield, this grinding process has been put to excellent use in a thyristor production line.

An Evaluation of Grinding Performance for Single and Polycrystal Grit Aluminum-Oxide Grinding Wheels

Dry surface grinding tests have shown a large difference in the number of passes to workpiece burn between structurally identical single and polycrystal Al2O3 vitrified grinding wheels. Special composite grinding wheels were designed and built to observe sequentially wear flat development in the scanning electron microscope. No difference in wear mechanisms was found for the two types of wheels. The difference in grinding performance is explained in terms of the number active cutting points per unit area and the dislodgment of dressing damage.

Burst Strengths and Deformations of Welded Composite Turbine Wheels as Related to Weld Quality and Plasticity Calculations

Experimental justification is presented for extending an existing rotating disk deformation theory-finite difference plastic flow calculation method to predicting the deformation and fracture of welded composite aircraft gas turbine wheels. Calculated deformations generally equaled but sometimes exceeded measured deformations. Fractures could be predicted for wheels containing no significant defects. Defects observed in fracture surfaces were incomplete penetration, incomplete fusion, porosity, and coarse columnar structure. Of these, incomplete penetration was significantly associated with losses in strength.

Closure to “Discussion of ‘Burst Strengths and Deformations of Welded Composite Turbine Wheels as Related to Weld Quality and Plasticity Calculations’” (1960, ASME J. Basic Eng., 82, p. 709)

Closure to “Discussion of ‘Burst Strengths and Deformations of Welded Composite Turbine Wheels as Related to Weld Quality and Plasticity Calculations’” (1960, ASME J. Basic Eng., 82, p. 709)

Discussion: “Burst Strengths and Deformations of Welded Composite Turbine Wheels as Related to Weld Quality and Plasticity Calculations” (Holms, A. G., and Repko, A. J., 1960, ASME J. Basic Eng., 82, pp. 695–708)

Discussion: “Burst Strengths and Deformations of Welded Composite Turbine Wheels as Related to Weld Quality and Plasticity Calculations” (Holms, A. G., and Repko, A. J., 1960, ASME J. Basic Eng., 82, pp. 695–708)