Optimal Cooling Paths for a Class of Thermorheologically Complex Viscoelastic Materials

1985 ◽  
Vol 52 (3) ◽  
pp. 634-638 ◽  
Author(s):  
B. D. Harper
Keyword(s):  
Residual Stress ◽  
Thermal Stresses ◽  
Optimal Path ◽  
Shift Factor ◽  
Plate Material ◽  
Viscoelastic Materials ◽  
Vertical Shift ◽  
Jump Discontinuities ◽  
Cooling Path ◽  
Thermorheological Behavior

This paper concerns the optimal cooling of thin viscoelastic plates so as to minimize the residual thermal stresses upon completion of the cool-down process. The thermorheological behavior of the plate material is assumed complex in the sense that both horizontal and vertical shift factors are employed. The optimal path is shown to possess initial and final jump discontinuities and to depend on only one of the two components of the vertical shift factor. It is further demonstrated that significant reductions in the level of residual stress may be attained by following the optimal cooling path.

scholarly journals Thermal Stresses in Chemically Hardening Elastic Media With Application to the Molding Process

1974 ◽  
Vol 41 (3) ◽  
pp. 647-651 ◽  
Author(s):  
Myron Levitsky ◽  
Bernard W. Shaffer
Keyword(s):  
Residual Stress ◽  
Chemical Reaction ◽  
Thermal Stresses ◽  
Stress Component ◽  
Elastic Solid ◽  
Molding Process ◽  
Hardening Process ◽  
Exothermic Chemical Reaction ◽  
Component Parallel

A method has been formulated for the determination of thermal stresses in materials which harden in the presence of an exothermic chemical reaction. Hardening is described by the transformation of the material from an inviscid liquid-like state into an elastic solid, where intermediate states consist of a mixture of the two, in a ratio which is determined by the degree of chemical reaction. The method is illustrated in terms of an infinite slab cast between two rigid mold surfaces. It is found that the stress component normal to the slab surfaces vanishes in the residual state, so that removal of the slab from the mold leaves the remaining residual stress unchanged. On the other hand, the residual stress component parallel to the slab surfaces does not vanish. Its distribution is described as a function of the parameters of the hardening process.

Analysis of Thermal Stresses and Residual Stress Changes in Railroad Wheels Caused by Severe Drag Braking

1977 ◽  
Vol 99 (1) ◽  
pp. 18-23 ◽  
Author(s):  
M. R. Johnson ◽  
R. E. Welch ◽  
K. S. Yeung
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Yield Point ◽  
Thermal Stresses ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Residual Stress Field ◽  
Thermal Stress Field ◽  
Stress Changes ◽  
Railroad Wheels

A finite-element computer program, which takes into consideration nonlinear material behavior after the yield point has been exceeded, has been used to analyze the thermal stresses in railroad freight car wheels subjected to severe drag brake heating. The analysis has been used with typical wheel material properties and wheel configurations to determine the thermal stress field and the extent of regions in the wheel where the yield point is exceeded. The resulting changes in the residual stress field after the wheel has cooled to ambient temperature have also been calculated. It is shown that severe drag braking can lead to the development of residual circumferential tensile stresses in the rim and radial compressive stresses in the plate near both the hub and rim fillets.

Optimal Cool-Down in Linear Viscoelasticity

1980 ◽  
Vol 47 (1) ◽  
pp. 35-39 ◽  
Author(s):  
Y. Weitsman
Keyword(s):  
Residual Stress ◽  
Optimal Path ◽  
Viscoelastic Plate ◽  
Geometric Constraints ◽  
Optimal Temperature ◽  
Cooling Process ◽  
Linear Viscoelastic ◽  
Stress Free State ◽  
Temperature Path ◽  
Optimal Cool

An optimal temperature path is derived for a thin viscoelastic plate which is cooled from a stress-free state against geometric constraints. The optimal path, which minimizes the final residual stress due to cool down, is shown to possess discontinuities at the initial and final times and to be smooth and continuous during all intermediate times. An iterative convergent scheme is provided for a wide class of linear viscoelastic responses and typical paths are determined for two specific cases. In addition, a time-temperature path which maintains constant stress values during cool-down is derived. The problem is motivated by the cooling process of composite materials.

NUMERICAL INVESTIGATION OF THERMOMECHANICAL PROCESSES UNDER SHORT-PULSED LASER IRRADIATION OF A HALF-SPACE

2021 ◽  
Vol 6 ◽  
pp. 55-65
Author(s):  
Kamila Storchak ◽  
◽  
Nina Yakovenko ◽  
Olga Polonevych ◽  
Irina Sribna ◽  
...  
Keyword(s):  
Residual Stress ◽  
Laser Irradiation ◽  
Half Space ◽  
Strain State ◽  
Thermal Stresses ◽  
Equations Of Motion ◽  
Thermomechanical Loading ◽  
Stress Strain ◽  
Stress Strain State ◽  
Residual Strains

The laser irradiation of metallic surfaces by intense heat sources is used for the generation of short probing pulses, which propagate into thin specimens and enable one to estimate their structure and mechanical properties within the framework of the classical acoustic approach. High thermal stresses and residual strains occur during the short-term irradiation of the surface of a construction by an energy source of high density. In the present work, we solve the axially symmetric problem of a half-space under thermomechanical loading. We take into account the influence of volume and inelastic characteristics of separate phases on the residual stress-strain state of the half-space. The statement of the problem includes: Cauchy relations, equations of motion, heat conduction equation, initial conditions, thermal and mechanical boundary conditions. The thermomechanical behavior of an isotropic material is described by the Bodner-Partom unified model of flow. The problem is solved with using the finite element technique. The numerical realization of our problem is performed with the help of step-by-step time integration. The equations of motion are integrated by the Newmark method. The residual stress-strain state is described using the method of numerical solution of the axisymmetric dynamic problem for a half-space under thermomechanical loading and the flow model. We established that microstructural transformations, which are taken into account due to the thermophase volume strain and dependence of inelastic characteristics of the material on the phase composition, significantly reduce residual inelastic strain and promote the appearance of compressive stresses. The three-zone region of residual stresses field formation is obtained.

Invsetigation about Residual Stresses of Plasma-Spraying Sm2Zr2O7/YSZ Thermal Barrier Coatings of Different Substrate Conditions

2011 ◽  
Vol 308-310 ◽  
pp. 1177-1181 ◽  
Author(s):  
Hong Song Zhang ◽  
Gang Yi Cai ◽  
Shu Sen Yang
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Plasma Spraying ◽  
Thermal Stresses ◽  
Thermal Barrier ◽  
Shear Stresses ◽  
Substrate Thickness ◽  
Optimum Thickness ◽  
Slight Effect ◽  
Axial Residual Stress

Effect of substrate conditions, including material type, thickness and radius of substrate, on residual thermal stresses of plasma spraying Sm2Zr2O7/YSZ TBCs was analyzed through finite element method in this paper. The radial and shear stresses of the coating decrease with increasing of distance from the center to edge, and they decrease abruptly at the edge of the specimen, while the axial residal stress increase abruptly at the edge of substrate. All residual stresses increase with increasing of thermal expansion coefficient of substrate. The thickness of substrate has slight effect on the radial residual stress, axial residual stress and shear stress are almost uneffected by substrate thickness. The optimum thickness of substrate is 10mm. Radius of substrate have no effect on radial stress when it is greater than 28mm.

Development of Residual Stress Improvement for Nuclear Pressure Vessel Instrumentation Nozzle Weld Joint (P-43+P-8) by Means of Induction Heating

2006 ◽  
Author(s):  
Takuro Terajima ◽  
Takashi Hirano
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Residual Stresses ◽  
Induction Heating ◽  
Weld Joint ◽  
Thermal Stresses ◽  
Pressure Vessels ◽  
Weld Joints

As a counter measurement of intergranular stress corrosion cracking (IGSCC) in boiling water reactors, the induction heating stress improvement (IHSI) has been developed as a method to improve the stress factor, especially residual stresses in affected areas of pipe joint welds. In this method, a pipe is heated from the outside by an induction coil and cooled from the inside with water simultaneously. By thermal stresses to produce a temperature differential between the inner and outer pipe surfaces, the residual stress inside the pipe is improved compression. IHSI had been applied to weld joints of austenitic stainless steel pipes (P-8+P-8). However IHSI had not been applied to weld joints of nickel-chromium-iron alloy (P-43) and austenitic stainless steel (P-8). This weld joint (P-43+P-8) is used for instrumentation nozzles in nuclear power plants’ reactor pressure vessels. Therefore for the purpose of applying IHSI to this one, we studied the following. i) Investigation of IHSI conditions (Essential Variables); ii) Residual stresses after IHSI; iii) Mechanical properties after IHSI. This paper explains that IHSI is sufficiently effective in improvement of the residual stresses for this weld joint (P-43+P-8), and that IHSI does not cause negative effects by results of mechanical properties, and IHSI is verified concerning applying it to this kind of weld joint.

Residual Stress Evaluation in TiN Coatings Used for Erosion Protection of Aerospace Components

2006 ◽  
Vol 524-525 ◽  
pp. 867-872 ◽  
Author(s):  
Mariusz Bielawski
Keyword(s):  
Residual Stress ◽  
Stress Relaxation ◽  
Thermal Stresses ◽  
Stress Evaluation ◽  
Tin Coatings ◽  
Steel Substrates ◽  
Temperature Correlations ◽  
Stress Accumulation ◽  
Deposition Conditions

A laser beam profilometry technique was used to investigate residual stress accumulation during TiN deposition and stress relaxation during post-deposition heat treatment. The test coatings were reactively sputtered on silicon and steel substrates using a UMS technique. TiN coatings, deposited at different bias and pressure levels, were evaluated for residual stress and microhardness. It was found that both the residual stress and the hardness were strongly affected by the coating deposition conditions. In addition, stress-temperature correlations were obtained by subjecting the coatings to temperature cycles up to 450°C. Stress-temperature plots revealed that the level of residual stress relaxation depended on deposition conditions and only coatings deposited at low ion bombardment could be fully annealed. The role of intrinsic and thermal stresses in the total residual stress in the coating/substrate system was also discussed.

Residual Stress Analysis of Microwave Plasma CVD Diamond Films

2005 ◽  
Vol 495-497 ◽  
pp. 1359-1364 ◽  
Author(s):  
Leng Chen ◽  
Wei Min Mao ◽  
Fan Xiu Lu ◽  
Ping Yang
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Microwave Plasma ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Orientation Distribution ◽  
X Ray ◽  
Plasma Chemical Vapor Deposition ◽  
Microwave Plasma Cvd

The residual stress and crystallographic texture of diamond films were investigated in the present work. The diamond films were synthesized on (100) silicon wafer by Microwave Plasma Chemical Vapor deposition (MPCVD). Then the residual stresses of the films were measured by X-ray diffractometer equipped with the two-dimensional detector. The residual stresses can be classified into two categories, i.e., the intrinsic stresses and the thermal stresses. It was shown that the thermal stresses were compressive in the temperature range studied and the intrinsic stresses were tensile. The crystallographic textures of the films were measured by X-ray diffractometer with the method of pole figure and orientation distribution function (ODF). The experimental results suggest that the crystallographic textures of the films depend upon the deposition temperature and methane flow rates, and the components and intensity of crystallographic textures have effect on the residual stresses in diamond films to a certain extent.

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