The Effect of Infrequent Thermal Overloads on the Behavior of Plates Subjected to Cyclic Thermal Loading

1984 ◽  
Vol 106 (1) ◽  
pp. 86-92
Author(s):  
J. Phillips
Keyword(s):  
High Temperature ◽  
Thermal Cycle ◽  
Thermal Loading ◽  
Kinematic Hardening ◽  
Material Behavior ◽  
Thermal Loads ◽  
Plate Material ◽  
Hardening Material ◽  
Perfectly Plastic ◽  
Deformation Properties

Many components in high-temperature plant experience steady mechanical loads combined with cyclic thermal loads due to routine shutdowns. Less frequent but more severe thermal loads due to unplanned shutdowns may interrupt this routine loading pattern. This paper presents the results of computer calculations on the effect of such thermal overloads on the behavior of a “Bree plate.” Particular attention is given to the creep and plastic ratchetting deformation properties of the system. It is shown that the plate material properties are an important factor in the problem. With an elastic-perfectly plastic plate material, behavior can be predicted from an appropriate linear combination of the results for each type of thermal cycle, multiplied by an enhancement factor in certain cases. With a bilinear kinematic hardening, material behavior is generally determined by the properties of the overload thermal cycle. These results are relevant to many high-temperature design problems.

An Assessment of Kinematic Hardening Thermal Ratcheting

1974 ◽  
Vol 96 (3) ◽  
pp. 214-221 ◽  
Author(s):  
T. M. Mulcahy
Keyword(s):  
Thermal Loading ◽  
Kinematic Hardening ◽  
Isotropic Hardening ◽  
Strain Accumulation ◽  
Hardening Material ◽  
Perfectly Plastic ◽  
Thermal Ratcheting

Analytical comparisons are made between the thermal ratcheting response of a kinematic hardening material, a perfectly plastic, and an isotropic hardening material for a two-element assembly. Significant differences were found in the range of mechanical and thermal loading for which ratcheting occurred and the magnitude of the strain accumulation when ratcheting did occur. The kinematic hardening strain accumulation predicted was always smallest.

scholarly journals On the Plastic Strain Accumulation in Notched Bars During High-Temperature Creep Dwell

2020 ◽  
Vol 36 (2) ◽  
pp. 167-176 ◽  
Author(s):  
Daniele Barbera ◽  
Haofeng Chen
Keyword(s):  
High Temperature ◽  
Cyclic Loading ◽  
Plastic Strain ◽  
Kinematic Hardening ◽  
High Temperature Creep ◽  
Strain Accumulation ◽  
Material Models ◽  
Cyclic Loading Condition ◽  
Hardening Material ◽  
Temperature Creep

ABSTRACTStructural integrity plays an important role in any industrial activity, due to its capability of assessing complex systems against sudden and unpredicted failures. The work here presented investigates an unexpected new mechanism occurring in structures subjected to monotonic and cyclic loading at high temperature creep condition. An unexpected accumulation of plastic strain is observed to occur, within the high-temperature creep dwell. This phenomenon has been observed during several full inelastic finite element analyses. In order to understand which parameters make possible such behaviour, an extensive numerical study has been undertaken on two different notched bars. The notched bar has been selected due to its capability of representing a multiaxial stress state, which is a practical situation in real components. Two numerical examples consisting of an axisymmetric v-notch bar and a semi-circular notched bar are considered, in order to investigate different notches severity. Two material models have been considered for the plastic response, which is modelled by both Elastic-Perfectly Plastic and Armstrong-Frederick kinematic hardening material models. The high-temperature creep behaviour is introduced using the time hardening law. To study the problem several results are presented, as the effect of the material model on the plastic strain accumulation, the effect of the notch severity and the mesh element type and sensitivity. All the findings further confirm that the phenomenon observed is not an artefact but a real mechanism, which needs to be considered when assessing off-design condition. Moreover, it might be extremely dangerous if the cyclic loading condition occurs at such a high loading level.

Shakedown Limit Load Determination for a Kinematically Hardening 90-Degree Pipe Bend Subjected to Constant Internal Pressure and Cyclic Bending

2007 ◽  
Author(s):  
Hany F. Abdalla ◽  
Mohammad M. Megahed ◽  
Maher Y. A. Younan
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Plastic Material ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Material Behavior ◽  
Pipe Bend ◽  
Cyclic Bending ◽  
Perfectly Plastic ◽  
Shakedown Limit

A simplified technique for determining the shakedown limit load of a structure employing an elastic-perfectly-plastic material behavior was previously developed and successfully applied to a long radius 90-degree pipe bend. The pipe bend is subjected to constant internal pressure and cyclic bending. The cyclic bending includes three different loading patterns namely; in-plane closing, in-plane opening, and out-of-plane bending moment loadings. The simplified technique utilizes the finite element method and employs small displacement formulation to determine the shakedown limit load without performing lengthy time consuming full cyclic loading finite element simulations or conventional iterative elastic techniques. In the present paper, the simplified technique is further modified to handle structures employing elastic-plastic material behavior following the kinematic hardening rule. The shakedown limit load is determined through the calculation of residual stresses developed within the pipe bend structure accounting for the back stresses, determined from the kinematic hardening shift tensor, responsible for the translation of the yield surface. The outcomes of the simplified technique showed very good correlation with the results of full elastic-plastic cyclic loading finite element simulations. The shakedown limit moments output by the simplified technique are used to generate shakedown diagrams of the pipe bend for a spectrum of constant internal pressure magnitudes. The generated shakedown diagrams are compared with the ones previously generated employing an elastic-perfectly-plastic material behavior. These indicated conservative shakedown limit moments compared to the ones employing the kinematic hardening rule.

Modelling Material Behavior of Austenitic Stainless Steel under Monotonic and Cyclic Loadings

2012 ◽  
Vol 151 ◽  
pp. 721-725
Author(s):  
R. Suresh Kumar ◽  
P. Chellapandi ◽  
C. Lakshmana Rao
Keyword(s):  
Stainless Steel ◽  
Cyclic Loading ◽  
Austenitic Stainless Steel ◽  
Mechanical Behavior ◽  
Room Temperature ◽  
Material Parameter ◽  
Kinematic Hardening ◽  
Cyclic Hardening ◽  
Material Behavior ◽  
Hardening Material

Mechanical behavior of the austenitic stainless steel under monotonic and cyclic loading at room temperature has been mathematically predicted. Materials like SS 316 LN exhibit cyclic hardening behavior under cyclic loading. Based on the characteristics of yield surface, cyclic hardening can be classified into isotropic and kinematic hardening. Armstrong-Frederic model is used for predicting the kinematic hardening of this material. It is basically a five parameter, nonlinear kinematic hardening model. Cyclic tests for various ranges were carried out to derive the isotropic material parameter required for modeling. Kinematic hardening material parameter required for modeling were computed based on both monotonic tension and torsion tests. By using these parameters the developed program is able to model the mechanical behavior of austenitic stainless steel under monotonic and cyclic loading conditions at room temperature. Comparison of the predicted results with the experimental results shows that the kinematic hardening material parameters derived from the monotonic torsion tests were in good agreement than that of the monotonic tension tests. Also it is recommended to use more material parameter constitutive models to improve the accuracy of the mathematical predictions for the material behavior under cyclic loading.

Plastic Strain Concentration in a Cylindrical Shell Subjected to an Axial or a Radial Temperature Gradient

1987 ◽  
Vol 109 (2) ◽  
pp. 184-187 ◽  
Author(s):  
H. Hu¨bel
Keyword(s):  
Cylindrical Shell ◽  
Temperature Gradient ◽  
Plastic Strain ◽  
Thermal Loading ◽  
Kinematic Hardening ◽  
Hardening Material ◽  
Radial Temperature ◽  
Strain Concentration ◽  
Asme Code ◽  
Concentration Factors

Plastic strain concentration factors for use in elastic fatigue analyses (like Ke in ASME Code) are usually overly conservative, but may be unsafe in certain cases. Especially for unnotched structures under thermal loading, many elastic-plastic analyses demonstrated that these plastic strain concentration factors are too restrictive. Thus, the present work derives appropriate factors for the idealized case of a cylindrical shell made of a linear kinematic hardening material and subjected to a radial or an axial temperature gradient. The results obtained are considered to be applicable to many practical problems.

Analytical Model to Predict Thermomechanical Relaxation of Shot Peening Induced Residual Stresses

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Min Huang ◽  
Yogesh K. Potdar ◽  
Srikanth Akkaram
Keyword(s):  
Residual Stress ◽  
High Temperature ◽  
Residual Stresses ◽  
Mechanical Loading ◽  
Shot Peening ◽  
Kinematic Hardening ◽  
Closed Form Solution ◽  
Thermal Relaxation ◽  
Hardening Material ◽  
Recovery Strain

Shot peening is widely used to improve the fatigue life of engine blades and rotors by inducing compressive residual stress on component surfaces. However, the residual stresses can relax due to exposure at high service temperature and mechanical loading. A physics-motivated analytical solution is developed to predict the residual stress relaxation at high temperature and under mechanical loading. In this thermomechanical relaxation model, the plastic strains in the shot peening layer and the substrate are obtained analytically by using linear kinematic hardening material law, and the plastic strain evolution at high temperature is modeled by using a recovery strain term. The final residual stress as a function of time, temperature, and mechanical loading is obtained analytically by combining this recovery strain with equilibrium and compatibility conditions. The whole method can be implemented into Microsoft Excel, and is easy to use and validate. As a special case, an analytical closed-form solution to predict the pure thermal relaxation of a shot peening residual stress is developed. The model predictions agree satisfactorily with published experimental measurements.

Analytical Correction of Nonlinear Thermal Stresses Under Thermomechanical Cyclic Loadings

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Sarendra Gehlot ◽  
Pradeep Mahadevan ◽  
Ragupathy Kannusamy
Keyword(s):  
Finite Element ◽  
Thermal Stresses ◽  
Kinematic Hardening ◽  
Nonlinear Finite Element ◽  
Material Behavior ◽  
Hardening Material ◽  
Elastic Stresses ◽  
Duty Cycles ◽  
Nonlinear Stress ◽  
Analytical Approaches

Automotive turbocharger components frequently experience complex thermomechanical fatigue (TMF) loadings which require estimation of nonlinear plastic stresses for fatigue life calculations. These field duty cycles often contain rapid fluctuations in temperatures and consequently transient effects become important. Although current finite element (FE) software are capable of performing these nonlinear finite element analyses, the turnaround time to compute nonlinear stresses for complex field duty cycles is still quite significant and detailed design optimizations for different duty cycles become very cumbersome. In recent years, a large number of studies have been made to develop analytical methods for estimating nonlinear stress from linear stresses. However, a majority of these consider isothermal cases which cannot be directly applied for thermomechanical loading. In this paper a detailed study is conducted with two different existing analytical approaches (Neuber’s rule and Hoffman-Seeger) to estimate the multiaxial nonlinear stresses from linear elastic stresses. For the Neuber’s approach, the multiaxial version proposed by Chu was used to correct elastic stresses from linear FE analyses. In the second approach, Hoffman and Seeger’s method is used to estimate the multiaxial stress state from plastic equivalent stress estimated using Neuber’s method for uniaxial stress. The novelty in the present work is the estimation of nonlinear stress for bilinear kinematic hardening material model under varying temperature conditions. The material properties including the modulus of elasticity, tangent modulus and the yield stress are assumed to vary with temperature. The application of two analytical approaches were examined for proportional and nonproportional TMF loadings and suggestions have been proposed to incorporate temperature dependent material behavior while correcting the plasticity effect into linear stress. This approach can be effectively used for complex geometries to calculate nonlinear stresses without carrying out a detailed nonlinear finite element analysis.

Theoretical Analysis of Hydraulically Expanded Tube-to-Tubesheet Joints With Linear Strain Hardening Material Behavior

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Nor Eddine Laghzale ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Strain Hardening ◽  
Material Behavior ◽  
Plastic Behavior ◽  
Element Analysis ◽  
Hardening Material ◽  
Perfectly Plastic ◽  
Expansion Pressure ◽  
Proper Material ◽  
Elastic Perfectly Plastic ◽  
Design Calculations

The mechanism of failure of tube-to-tubesheet joints is related to the level of stresses produced in the tube expansion and transition zones during the expansion process. Maintaining a lower bound limit of the initial residual contact pressure over the lifetime of the expanded joint is a key solution to a leak free joint. An accurate model that estimates these stresses can be a useful tool to the design engineer to select the proper material geometry combination in conjunction with the required expansion pressure. Most existing design calculations are based on an elastic perfectly plastic behavior of the expansion joint materials. The proposed model is based on a strain hardening with a bilinear material behavior of the tube and the tubesheet. The interaction of these two components is simulated during the whole process of the application of the expansion pressure. The effects of the gap and the material strain hardening are to be emphasized. The model results are validated and confronted against the more accurate numerical finite element analysis models. Additional comparisons have been made to existing methods.

An Analytical Solution of Hydraulically Expanded Tube-to-Tubesheet Joints With Linear Strain Hardening Material Behaviour

2008 ◽  
Author(s):  
Nor Eddine Laghzale ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Strain Hardening ◽  
Material Behavior ◽  
Plastic Behavior ◽  
Hardening Material ◽  
Whole Process ◽  
Perfectly Plastic ◽  
Expansion Pressure ◽  
Proper Material ◽  
Elastic Perfectly Plastic ◽  
Design Calculations

The mechanism of failure of tube-to-tubesheet joints is related to the level of stresses produced in the tube expansion and transition zones during the expansion process. Maintaining a lower bound limit of the initial residual contact pressure over the lifetime of the expanded joint is a key solution to a leak free joint. An accurate model that estimates these stresses can be a useful tool to the design engineer to select the proper material geometry combination in conjunction with the required expansion pressure. Most existing design calculations are based on an elastic perfectly plastic behavior of the expansion joint materials. The proposed model is based on a strain hardening with a bilinear material behavior of the tube and the tubesheet. The interaction of these two components is simulated during the whole process of the application of the expansion pressure. The effects of the gap and the material strain hardening will be emphasized. The model results are validated and confronted against the more accurate numerical FEA models. Additional comparisons have been made to existing methods.

Analytical Correction of Nonlinear Thermal Stresses Under Thermo-Mechanical Cyclic Loadings

2012 ◽  
Author(s):  
Sarendra Gehlot ◽  
Pradeep Mahadevan ◽  
Ragupathy Kannusamy
Keyword(s):  
Finite Element ◽  
Thermal Stresses ◽  
Kinematic Hardening ◽  
Nonlinear Finite Element ◽  
Material Behavior ◽  
Hardening Material ◽  
Elastic Stresses ◽  
Duty Cycles ◽  
Nonlinear Stress ◽  
Analytical Approaches

Automotive turbocharger components frequently experience complex Thermo-Mechanical Fatigue (TMF) loadings which require estimation of nonlinear plastic stresses for fatigue life calculations. These field duty cycles often contain rapid fluctuations in temperatures and consequently transient effects become important. Although current FE software are capable of performing these nonlinear finite element analyses, the turnaround time to compute nonlinear stresses for complex field duty cycles is still quite significant and detailed design optimizations for different duty cycles become very cumbersome. In recent years, a large number of studies have been made to develop analytical methods for estimating nonlinear stress from linear stresses. However, a majority of these consider isothermal cases which cannot be directly applied for thermo-mechanical loading. In this paper a detailed study is conducted with two different existing analytical approaches (Neuber’s rule and Hoffman-Seeger) to estimate the multi-axial nonlinear stresses from linear elastic stresses. For the Neuber’s approach, the multi-axial version proposed by Chu was used to correct elastic stresses from linear FE analyses. In the second approach, Hoffman and Seeger’s method is used to estimate the multiaxial stress state from plastic equivalent stress estimated using Neuber’s method for uniaxial stress. The novelty in the present work is the estimation of nonlinear stress for bilinear kinematic hardening material model under varying temperature conditions. The material properties including the modulus of elasticity, tangent modulus and the yield stress are assumed to vary with temperature. The application of two analytical approaches were examined for proportional and non-proportional TMF loadings and suggestions have been proposed to incorporate temperature dependent material behavior while correcting the plasticity effect into linear stress. This approach can be effectively used for complex geometries to calculate nonlinear stresses without carrying out a detailed nonlinear finite element analysis.

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