Understanding the effects of microstructure variability on fatigue resistance is a key to selection and design of materials for fatigue applications. The traditional empirical approach rooted in experiments is being increasingly combined with systematic computational modeling. This work is concerned with demonstrating the feasibility of linking effects of microstructure variability on cyclic plasticity at the scale of intrinsic microstructure of a single crystal nickel-base superalloy. The precipitate and the matrix phases of the alloy are modeled explicitly using a physically based crystal viscoplasticity constitutive framework with appropriate scale and spacing effects to reflect dislocationprecipitate interactions. The model is implemented as a user material subroutine within a finite element code. Various realizations of different microstructures are generated using a constrained Poisson point process. Statistical volume elements (SVEs) with random-periodic boundary conditions are simulated under fully reversed cyclic loading at 650 • C. Primary cooling γ precipitate size and volume fraction are considered in terms of their effects on the macroscopic stress-strain response and on distributed cyclic microplasticity within the SVE. To compare various microstructures in terms of probability of fatigue crack formation, an appropriate nonlocal measure of cyclic plastic shear strain range is proposed based on percolation of cyclic microplasticity at the scale of the SVE.
K9 optical glass drilling experiments were carried out. Bright nickel electroplated diamond tools with small slots and under heat treatment in different temperature were fabricated. Scan electro microscope was applied to analyze the wear of electroplated diamond tool. The material removal rate and grinding ratio were calculated. Machining quality was observed. Bond coating hardness was measured. The experimental results show that coolant is needed for the drilling processes of optical glasses. Heat treatment temperature of diamond tool has influence on wearability of diamond tool and grinding ratio. There were two wear types of electroplated diamond tool, diamond grit wear and bond wear. With the machining processes, wear of diamond grits included fracture, blunt and pull-out, and electroplated bond was gradually worn out. High material removal rates could be obtained by using diamond tool with suitable slot numbers. Bright nickel coating bond presents smallest grains and has better mechanical properties. Bright nickel electroplated diamond tool with slot structure and heat treatment under 200°C was suitable for optical glass drilling.
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