On the Analysis of Residual Stresses Introduced in Sheet Metals by Thermal Shock Treatment

1976 ◽  
Vol 43 (1) ◽  
pp. 117-123 ◽  
Author(s):  
T. R. Hsu ◽  
S. R. Trasi
Keyword(s):  
Residual Stresses ◽  
Thermal Shock ◽  
Theoretical Study ◽  
Numerical Technique ◽  
Iteration Scheme ◽  
Plasticity Theory ◽  
Shock Treatment ◽  
Axially Symmetric ◽  
Specific Distribution ◽  
Thin Metal Sheet

This paper presents a theoretical study of the residual stresses in a thin metal sheet with a circular hole subjected to an axially symmetric thermal shock over a concentric annular area. Quasi-static, uncoupled, thermoelastoplasticity theory incorporating the postulates of incremental plasticity theory is employed. The solution is sought through a numerical technique incorporating an iteration scheme and numerical integration. Several numerical examples are considered for a specific distribution and duration of the thermal shock and some optimization considerations are discussed.

Effects of Powder Morphology, Microstructure, and Residual Stresses on Thermal Barrier Coating Thermal Shock Performance

1996 ◽  
Author(s):  
J. Wigren ◽  
J.-F. de Vries ◽  
D. Greving
Keyword(s):  
Residual Stresses ◽  
Thermal Shock ◽  
Thermal Barrier Coating ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Spray Parameters ◽  
Powder Morphology ◽  
Barrier Coatings ◽  
Barrier Coating

Abstract Thermal barrier coatings are used in the aerospace industry for thermal insulation in hot sections of gas turbines. Improved coating reliability is a common goal among jet engine designers. In-service failures, such as coating cracking and spallation, result in decreased engine performance and costly maintenance time. A research program was conducted to evaluate residual stresses, microstructure, and thermal shock life of thermal barrier coatings produced from different powder types and spray parameters. Sixteen coatings were ranked according to their performance relative to the other coatings in each evaluation category. Comparisons of residual stresses, powder morphology, and microstructure to thermal shock life indicate a strong correlation to thermal barrier coating performance. Results from these evaluations will aid in the selection of an optimum thermal barrier coating system for turbine engine applications.

scholarly journals A Semianalytical Model for the Determination of Bistability and Curvature of Metallic Cylindrical Shells

2019 ◽  
Vol 3 (1) ◽  
pp. 22
Author(s):  
Pavlo Pavliuchenko ◽  
Marco Teller ◽  
Markus Grüber ◽  
Gerhard Hirt
Keyword(s):  
Residual Stresses ◽  
Shell Thickness ◽  
Cylindrical Shells ◽  
Model Verification ◽  
Experimental Results ◽  
Steel Shell ◽  
Diffraction Measurement ◽  
Stable States ◽  
Forming Process ◽  
Specific Distribution

Bistable metal shells with a fully closed unfolded geometry are of great interest as lightweight construction parts which could be transported without housing and unfolded at the construction place. In order to achieve the effect of bistability in metallic shells, residual stresses with a specific distribution along the shell thickness are necessary. These residual stresses can be introduced in bending processes. The tools with specific bending radii are used to influence the curvature of the shell in the different stable states and thus determine whether a completely closed profile can be achieved. In addition to the forming process, the shell thickness and the shell material have an effect on the achievable geometries and stability. In order to manufacture bistable metallic cylindrical shells from different materials and shell thicknesses, it is necessary to be able to determine a promising process sequence and corresponding bending radii in advance. For this reason, this article presents a semianalytical model for the calculation of bistability and final curvatures. This model is applied to an incremental die-bending process using two bending operations with bending radii of 6 to 12 mm and a 0.2 mm thick steel shell of grade 1.1274 (AISI 1095). The calculation results show that bistability cannot be reached for all combinations of the two bending radii. Moreover, the model indicates that a bistable and fully closed shell is only achieved for a bending radii combination of R1 = 6 mm and R2 = 6 mm. With the aim of model verification, experiments with a closed-die incremental bending tool were performed. Calculated and experimental results show good correlation regarding bistability and curvature. In addition, X-ray diffraction measurement of the residual stresses shows a good qualitative agreement regarding the calculated and experimental results.

Characterization of residual stresses generated during inhomogeneous plastic deformation

1998 ◽  
Vol 33 (3) ◽  
pp. 243-252 ◽  
Author(s):  
T Lorentzen ◽  
T Faurholdt ◽  
B Clausen ◽  
J Danckert
Keyword(s):  
Plastic Deformation ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Numerical Technique ◽  
Numerical Approach ◽  
Explicit Finite Element ◽  
Numerical Predictions ◽  
Deformation Processes ◽  
Elastic Strains

Residual stresses generated by macroscopic inhomogeneous plastic deformation are predicted by an explicit finite element (FE) technique. The numerical predictions are evaluated by characterizing the residual elastic strains by neutron diffraction using two different ( hkl) reflections. Intergranular residual elastic strains between subsets of grains are predicted numerically and verified by neutron diffraction. Subsequently, the measured residual strain profiles in the test samples are modified by the intergranular strains and compared to the engineering predictions of the FE technique. Results compare well and verify the capability of the numerical technique as well as the possibilities of experimental validation using neutron diffraction. The presented experimental and numerical approach will subsequently be utilized for the evaluation of more complicated plastic deformation processes resembling forming operations.

Integral numerical technique for the study of axially symmetric resonant devices

1989 ◽  
Vol 37 (11) ◽  
pp. 1814-1816
Author(s):  
J. Ruiz ◽  
M.J. Nunez ◽  
A. Navarro ◽  
E. Martin
Keyword(s):  
Numerical Technique ◽  
Axially Symmetric

Computing Flatness Defects in Sheet Rolling by Arlequin and Asymptotic Numerical Methods

2014 ◽  
Vol 611-612 ◽  
pp. 186-193 ◽  
Author(s):  
Kekeli Kpogan ◽  
Yendoubouam Tampango ◽  
Hamid Zahrouni ◽  
Michel Potier-Ferry ◽  
Hachmi Ben Dhia
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Numerical Technique ◽  
Three Dimensional ◽  
Nonlinear Problems ◽  
Rolling Process ◽  
Three Dimensional Model ◽  
Sheet Rolling ◽  
Arlequin Method ◽  
Roll Bite

Rolling of thin sheets generally induces flatness defects due to thermo-elastic deformation of rolls. This leads to heterogeneous plastic deformations throughout the strip width and then to out of plane displacements to relax residual stresses. In this work we present a new numerical technique to model the buckling phenomena under residual stresses induced by rolling process. This technique consists in coupling two finite element models: the first one consists in a three dimensional model based on 8-node tri-linear hexahedron which is used to model the three dimensional behaviour of the sheet in the roll bite; we introduce in this model, residual stresses from a full simulation of rolling (a plane-strain elastoplastic finite element model) or from an analytical profile. The second model is based on a shell formulation well adapted to large displacements and rotations; it will be used to compute buckling of the strip out of the roll bite. We propose to couple these two models by using Arlequin method. The originality of the proposed algorithm is that in the context of Arlequin method, the coupling area varies during the rolling process. Furthermore we use the asymptotic numerical method (ANM) to perform the buckling computations taking into account geometrical nonlinearities in the shell model. This technique allows one to solve nonlinear problems using high order algorithms well adapted to problems in the presence of instabilities. The proposed algorithm is applied to some rolling cases where “edges-waves” and “center-waves” defects of the sheet are observed.

Thermal Shock Behavior of an Al2O3/ZrO2 Multilayered Ceramic with Residual Stresses due to Phase Transformations

2005 ◽  
Vol 290 ◽  
pp. 191-198 ◽  
Author(s):  
Raúl Bermejo ◽  
Luis Llanes ◽  
Marc Anglada ◽  
Peter Supancic ◽  
Tanja Lube
Keyword(s):  
Residual Stresses ◽  
Thermal Shock ◽  
Thermal Strain ◽  
Experimental Tests ◽  
Element Model ◽  
The Body ◽  
Stress Profile ◽  
Distribution Profile ◽  
Shock Testing ◽  
Thermal Shock Behavior

In this work, the thermal shock behavior of an Al2O3-5%tZrO2/Al2O3-30%mZrO2 multilayer ceramic is studied. On these materials, a tetragonal to monoclinic phase transformation within the Al2O3-30%mZrO2 layers takes place when cooling down from sintering. The latter induces an increase in volume and therefore compressive residual stresses arise in these layers. The residual stress distribution profile in the laminate influences the thermal shock response of the material. A finite element model has been developed to estimate both the thermal strain effects during the sintering process as well as the temperature distribution and stress profile within the laminate during thermal shock testing. Experimental tests on the monoliths and laminates were carried out and compared to the model. It is observed that the presence of the compressive layers within the laminate inhibits the penetration of thermal shock cracks into the body at even more severe conditions than in the monolithic material.

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