Residual Stresses in a Ceramic-Metal Composite

The work of this study concerns the fine modelling of the thermomechanical and metallurgical behavior of interface ceramic-metal in order to determine the residual mechanical state of the structures during brazing process. For these cases, difficulties mainly arise in the modelling of the solid-solid phase transformations as well as in the modelling of the mechanical behavior of the multiphasic material. Within an original theoretical framework - generalized standard materials with internal constraints – we proposed models for the behavior of multiphasic material. The design of joints in engineering structures and the optimisation of the industrial brazing process require determining and analysing such a phenomenon. In this way, the present work aims at predicting the thermally induced stresses (localisation and level) through numerical simulations and then, at defining the main parameters which influence their development

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Morphologies of Nonadherent Al2O3 and Matching Substrate Surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009587x ◽

1972 ◽

Vol 30 ◽

pp. 524-525

Author(s):

C. S. Giggins ◽

J. K. Tien ◽

B. H. Kear ◽

F. S. Pettit

Keyword(s):

Electron Microscopy ◽

Oxide Scale ◽

Oxidation Resistance ◽

Substrate Surface ◽

Morphological Features ◽

Thermally Induced ◽

Oxide Spallation ◽

Oxidation Resistant ◽

Induced Stresses ◽

Substrate Surfaces

The performance of most oxidation resistant alloys and coatings is markedly improved if the oxide scale strongly adheres to the substrate surface. Consequently, in order to develop alloys and coatings with improved oxidation resistance, it has become necessary to determine the conditions that lead to spallation of oxides from the surfaces of alloys. In what follows, the morphological features of nonadherent Al2O3, and the substrate surfaces from which the Al2O3 has spalled, are presented and related to oxide spallation.The Al2O3, scales were developed by oxidizing Fe-25Cr-4Al (w/o) and Ni-rich Ni3 (Al,Ta) alloys in air at 1200°C. These scales spalled from their substrates upon cooling as a result of thermally induced stresses. The scales and the alloy substrate surfaces were then examined by scanning and replication electron microscopy.The Al2O3, scales from the Fe-Cr-Al contained filamentary protrusions at the oxide-gas interface, Fig. 1(a). In addition, nodules of oxide have been developed such that cavities were formed between the oxide and the substrate, Fig. 1(a).

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Heat Transfer and Thermal Stress Analysis of an Optoelectronic Package

Journal of Electronic Packaging ◽

10.1115/1.2905404 ◽

1991 ◽

Vol 113 (3) ◽

pp. 258-262 ◽

Cited By ~ 2

Author(s):

J. G. Stack ◽

M. S. Acarlar

Keyword(s):

Heat Transfer ◽

Thermal Management ◽

Power Dissipation ◽

Point Of View ◽

Optical Data ◽

Data Link ◽

Element Analysis ◽

Thermally Induced ◽

Temperature Changes ◽

Induced Stresses

The reliability and life of an Optical Data Link transmitter are inversely related to the temperature of the LED. It is therefore critical to have efficient packaging from the point of view of thermal management. For the ODL® 200H devices, it is also necessary to ensure that all package seals remain hermetic throughout the stringent military temperature range requirements of −65 to +150°C. For these devices, finite element analysis was used to study both the thermal paths due to LED power dissipation and the thermally induced stresses in the hermetic joints due to ambient temperature changes

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Residual Stress Measurements in Mo/CuCrZr Tiles Using Neutron Diffraction

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.59.299 ◽

2008 ◽

Vol 59 ◽

pp. 299-303

Author(s):

K. Mergia ◽

Marco Grattarola ◽

S. Messoloras ◽

Carlo Gualco ◽

Michael Hofmann

Keyword(s):

Residual Stress ◽

Finite Element ◽

Neutron Diffraction ◽

Residual Stresses ◽

Heat Sink ◽

High Yield ◽

Fusion Reactors ◽

Plasma Facing Components ◽

Induced Stresses ◽

Compliant Layer

In plasma facing components (PFC) for nuclear fusion reactors tungsten or carbon based tiles need to be cooled through a heat sink. The joint between the PFC and the heat sink can be realized using a brazing process through the employment of compliant layer of either a low yield material, like copper, or a high yield material, like molybdenum. Experimental verification of the induced stresses during the brazing process is of vital importance. Strains and residual stresses have been measured in Mo/CuCrZr brazed tiles using neutron diffraction. The strains and stresses were measured in Mo tile along the weld direction and at different distances from it. The experimental results are compared with Finite Element Simulations.

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Mathematical Model Establishment and Analysis on the Pipe Deformation under External Pressure with the Ovality

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.760-762.2263 ◽

2013 ◽

Vol 760-762 ◽

pp. 2263-2266

Author(s):

Kang Yong ◽

Wei Chen

Keyword(s):

Mathematical Model ◽

Theoretical Analysis ◽

Yield Strength ◽

Residual Stresses ◽

Numerical Simulations ◽

Significant Influence ◽

External Pressure ◽

Pipe Diameter ◽

Axial Loads ◽

The Stability

Beside the residual stresses and axial loads, other factors of pipe like ovality, moment could also bring a significant influence on pipe deformation under external pressure. The Standard of API-5C3 has discussed the influences of deformation caused by yield strength of pipe, pipe diameter and pipe thickness, but the factor of ovality degree is not included. Experiments and numerical simulations show that with the increasing of pipe ovality degree, the anti-deformation capability under external pressure will become lower, and ovality affecting the stability of pipe shape under external pressure is significant. So it could be a path to find out the mechanics relationship between ovality and pipe deformation under external pressure by the methods of numerical simulations and theoretical analysis.

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Thermally Induced Stresses and Deformations in Angle-Ply Composite Tubes

Journal of Composite Materials ◽

10.1177/002199838702100504 ◽

1987 ◽

Vol 21 (5) ◽

pp. 454-480 ◽

Cited By ~ 35

Author(s):

M.W. Hyer ◽

Carl Q. Rousseau

Keyword(s):

Composite Tubes ◽

Thermally Induced ◽

Induced Stresses

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Evaluation of residual thermally induced stresses in the cooling of polymer melt via transfinite element computations

Polymer Engineering & Science ◽

10.1002/pen.760290204 ◽

1989 ◽

Vol 29 (2) ◽

pp. 100-106 ◽

Cited By ~ 4

Author(s):

K. K. Tamma ◽

S. B. Railkar

Keyword(s):

Polymer Melt ◽

Thermally Induced ◽

Induced Stresses ◽

Transfinite Element

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Limitation of Distortion in Friction Stir Welded (FSW) Panels Using Needle Peening

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.1203 ◽

2010 ◽

Vol 638-642 ◽

pp. 1203-1208 ◽

Cited By ~ 2

Author(s):

Simon Larose ◽

Laurent Dubourg ◽

C. Perron ◽

Mohammad Jahazi ◽

Priti Wanjara

Keyword(s):

Residual Stresses ◽

Shot Peening ◽

Sheet Material ◽

Travel Speed ◽

Needle Size ◽

Friction Stir ◽

Average Value ◽

Aa 2024 ◽

Induced Stresses ◽

Needle Diameter

Friction stir welding (FSWing) induces residual stresses and distortions in welded structures. Such residual stresses reduce the fatigue life of welded components, while the induced distortions prevent the welding of large or thin components. In the present study, needle peening was used to induce additional residual stresses in 2.3-mm thick (FSWed) aluminum alloy (AA) 2024-T3 sheets. This was done with the objective to counterbalance the welding-induced stresses and thus reduce the overall stresses and distortions. The needle peening process, which stems from shot peening, consists of hammering a surface using cylindrical spherical ended shots sliding back and forth in a treatment head. An instrumented needle peening machine was used to carry out peening on as-received (or bare) and bead-on-plate FSWed AA2024-T3 material. In both cases, the width of the peening area corresponded to that of a typical weld. The influence of the peening process parameters such as needle size, applied power and travel speed on the surface quality and magnitude of the induced distortions were evaluated. The results indicate that, by increasing the needle diameter from 1.2 mm to 2.0 mm, the peening-induced deflection on bare sheet material increased by an average value of 27% while the roughness average, Ra, decreased by an average value of 47%. It was also found that a surface finish qualitatively similar to that of conventional shot peening could be obtained by using appropriate needle peening trajectories. Finally, needle peening with an applied power of 10% was sufficient for eliminating 37% of the welding-induced transverse curvature and 82% of the welding-induced longitudinal curvature.

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