Large strain surface deformation in machining and sliding processes

Yang Guo, Purdue University

Abstract

The sliding of a wedge indenter (tool) against a metal surface provides a model system in which deformation and flow phenomena underlying surface generation processes such as machining, burnishing, surface attrition, polishing and sliding wear can be explored in situ. Particle Image Velocimetry are used in conjunction with high-speed imaging of the sliding region to analyze characteristics of the plastic flow such as strain, strain rate, rotation and kinematics. The evolution of large plastic strains on the metal surfaces is characterized in terms of process parameters, e.g., wedge incidence angle, velocity and material initial condition. It is shown that the surface strain and subsurface strain distributions can be controlled within limits. Methods for creation of very large plastic strains (>10) on surfaces are demonstrated. The sliding wedge system also provides capability to impose controlled strain rates in conjunction with the large strains. Since the microstructure and mechanical properties of the generated (or conditioned) surface are a consequence of the interactive combinations of strain, strain rate and temperature imposed in the deformation zone, the results provide guidance for engineering surfaces with graded microstructures and properties. When the angle of incidence between the wedge and the surface is varied from small to large values, various transitions in the metal flow are observed including plastic instabilities, surface fold formation and fluid-like flow features, and segmented chip/wear particle formation. The in-situ observations have enabled an understanding of the origins of these flow transitions, including a new mechanism of delamination wear. Various methods for in-situ flow visualization in metal deformation constitute another important outcome.

Degree

Ph.D.

Advisors

Chandrasekar, Purdue University.

Subject Area

Industrial engineering|Mechanical engineering

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