INFLUENCE OF CONVECTIVE COOLING ON THE TEMPERATURE AND THERMAL STRESSES IN A FRICTIONALLY HEATED SEMISPACE

Thermoelastic stresses arising from a moving band source of heat on the surface of a semi-infinite solid have been calculated using well-known temperature solutions and a finite element stress analysis. Results are presented in nondimensional form for a wide range of conditions for both quasi-steady state and transient regimes. The effect of convective cooling at the surface has also been investigated. Peak stresses, which occur at the surface, have been related to a modified source Peclet number for instances in which surface cooling is not employed. Reduction in stress levels due to convective cooling at the surface has also been determined. For all cases considered, the greatest stress levels were found to occur at the surface of the constrained direction. Using results obtained in this study, thermoelastic stresses in sliding and machining processes may be calculated in order to predict the onset of yielding which can result in residual tensile stresses and cracking.

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Thermal Stress Analysis for Rapid Thermal Process With Convective Cooling

Journal of Manufacturing Science and Engineering ◽

10.1115/1.1949618 ◽

2004 ◽

Vol 127 (3) ◽

pp. 564-571 ◽

Cited By ~ 1

Author(s):

Shih-Yu Hung ◽

Ching-Kong Chao

Keyword(s):

Thermal Stress ◽

Flow Field ◽

Thermal Stresses ◽

Transient Flow ◽

Cooling Time ◽

Radiative Energy ◽

Guard Ring ◽

Convective Cooling ◽

Significant Temperature ◽

Wafer Edge

A fast temperature ramp of rapid thermal processing (RTP) with convective cooling used to shorten the cooling time for the wafer is presented in this paper. Based on thermal and stress analyses, the behavior of the highly coupled physics in RTP, such as radiative heat transfer, transient flow, and thermal stress is studied in detail. From simulation results of the flow field, a large recirculation cell between the wafer edge and the chamber wall is predicted and the effect of buoyancy on the behavior of the flow field is examined. Since the buoyancy-induced recirculation aggregates thermal nonuniformity due to edge effect, a guard ring is then suggested to be placed at the edge of the wafer to reduce the heat loss from the wafer edge and reflect the radiative energy back into the wafer during the cooling process. Furthermore, a large inlet gas mass flow rate is found to suppress the recirculation and shorten the cooling time. However, a fast convective cooling rate would result in a significant temperature difference between center and edge of the wafer, thus causing material failure due to an increase of thermal stresses.

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Deformation at interfaces of Ti-6Al-4V/SiC fiber composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121193 ◽

1992 ◽

Vol 50 (1) ◽

pp. 158-159

Author(s):

Warren J. Moberly ◽

Daniel B. Miracle ◽

S. Krishnamurthy

Keyword(s):

Thermal Stresses ◽

Load Transfer ◽

Coefficient Of Thermal Expansion ◽

Hot Isostatic Pressing ◽

Matrix Composites ◽

Ongoing Research ◽

Aerospace Applications ◽

Sic Fiber ◽

The Matrix ◽

Intermetallic Matrix Composites

Titanium-aluminum alloy metal matrix composites (MMC) and Ti-Al intermetallic matrix composites (IMC), reinforced with continuous SCS6 SiC fibers are leading candidates for high temperature aerospace applications such as the National Aerospace Plane (NASP). The nature of deformation at fiber / matrix interfaces is characterized in this ongoing research. One major concern is the mismatch in coefficient of thermal expansion (CTE) between the Ti-based matrix and the SiC fiber. This can lead to thermal stresses upon cooling down from the temperature incurred during hot isostatic pressing (HIP), which are sufficient to cause yielding in the matrix, and/or lead to fatigue from the thermal cycling that will be incurred during application, A second concern is the load transfer, from fiber to matrix, that is required if/when fiber fracture occurs. In both cases the stresses in the matrix are most severe at the interlace.

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