The Fatigue Threshold Computation of Steel in Hydrogen Environment by Shakedown Analysis

2017 ◽  
Author(s):  
Song Huang ◽  
Zhiping Chen ◽  
Wenqiang Su
Keyword(s):  
Residual Stress ◽  
Lower Bound ◽  
Plastic Strain ◽  
Yield Stress ◽  
Plastic Flow ◽  
Fatigue Threshold ◽  
Shakedown Analysis ◽  
Hydrogen Environment ◽  
Hydrogen Trap ◽  
Perfectly Plastic

In this paper, the fatigue threshold of steel servicing in hydrogen environment is studied by means of shakedown analysis. First of all, the application of shakedown analysis on the fatigue threshold prediction is reviewed briefly. Secondly, the classical static shakedown theorem for elasto-perfectly plastic structure is modified to take hydrogen’s effect into consideration. In the proposed method, the effect of hydrogen is described by a yield stress associated with hydrogen concentration and hydrogen content in metal is assumed to be composed of the hydrogen in lattice sites and in reversible trap sites. The effect of plastic flow on hydrogen trap density is involved in by considering the plastic strain as the function of residual stress, which is expected to result in a lower bound of the shakedown load. Finally, the fatigue threshold of a steel is computed as example. The performance of the proposed method is discussed and compared with the results from references. The results indicate that the proposed method is of validity.

Thermal Stress in a Viscoelastic-Plastic Plate With Temperature-Dependent Yield Stress

1960 ◽  
Vol 27 (2) ◽  
pp. 297-302 ◽  
Author(s):  
H. G. Landau ◽  
J. H. Weiner ◽  
E. E. Zwicky
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Yield Stress ◽  
Plastic Material ◽  
Numerical Procedure ◽  
Yield Condition ◽  
Residual Stress Distribution ◽  
Transient Temperature ◽  
Temperature Dependent ◽  
Perfectly Plastic

Equations are given for the determination of transient and residual stresses in plates subject to transient temperature distributions, based on the assumption of a viscoelastic, perfectly plastic material obeying a von Mises temperature-dependent yield condition. A numerical procedure for integrating the equations is developed and applied to the case of a symmetrically cooled plate. It is found that, for steel, viscoelasticity has little effect on the residual stress distribution, but the temperature dependence of yield stress is important. The types of residual stress distribution after cooling are similar to those for an elastic-plastic material with constant yield stress, and for this case the residual stress is given approximately by formulas developed earlier for a slowly varying heat input.

Lower Bound Methods in Elastic-Plastic Shakedown Analysis

2010 ◽  
Author(s):  
Wolf Reinhardt ◽  
Reza Adibi-Asl
Keyword(s):  
Lower Bound ◽  
Plastic Material ◽  
Shakedown Analysis ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Efficient Calculation ◽  
Asme Code ◽  
Elastic Shakedown ◽  
Plastic Shakedown

Several methods were proposed in recent years that allow the efficient calculation of elastic and elastic-plastic shakedown limits. This paper establishes a uniform framework for such methods that are based on perfectly-plastic material behavour, and demonstrates the connection to Melan’s theorem of elastic shakedown. The paper discusses implications for simplified methods of establishing shakedown, such as those used in the ASME Code. The framework allows a clearer assessment of the limitations of such simplified approaches. Application examples are given.

Models of elastic–perfectly plastic materials

1990 ◽  
Vol 1 (2) ◽  
pp. 131-150 ◽  
Author(s):  
J. M. Greenberg
Keyword(s):  
Yield Stress ◽  
Plastic Flow ◽  
New Model ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Impact Problems ◽  
Elastic Perfectly Plastic

This note deals with a new model of elastic–perfectly plastic materials in which the yield stress is regarded as a threshold above which plastic flow occurs rather than a constraint which cannot be violated. This modelling change allows us to treat a number of signalling and impact problems not solvable within the classic framework of elastic–perfectly plastic materials.

Models of elastic–perfectly plastic materials

1990 ◽  
Vol 1 (3) ◽  
pp. 225-244 ◽  
Author(s):  
J. M. Greenberg
Keyword(s):  
Yield Stress ◽  
Plastic Flow ◽  
New Model ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Impact Problems ◽  
Elastic Perfectly Plastic

This note deals with a new model of elastic–perfectly plastic materials in which the yield stress is regarded as a threshold above which plastic flow occurs rather than a constraint which cannot be violated. This modelling change allows us to treat a number of signalling and impact problems not solvable within the classic framework of elastic–perfectly plastic materials.

scholarly journals Lower and Upper Bound Shakedown Analysis of Structures With Temperature-Dependent Yield Stress

2009 ◽  
Author(s):  
Haofeng Chen
Keyword(s):  
Lower Bound ◽  
Yield Stress ◽  
Upper Bound ◽  
Yield Condition ◽  
Static Field ◽  
Upper And Lower Bounds ◽  
Residual Stress Field ◽  
Temperature Dependent ◽  
Shakedown Analysis ◽  
Shakedown Limit

Based upon the kinematic theorem of Koiter, the Linear Matching Method (LMM) procedure has been proved to produce very accurate upper bound shakedown limits. This paper presents a recently developed LMM lower bound procedure for shakedown analysis of structures with temperature-dependent yield stress, which is implemented into ABAQUS using the same procedure as for upper bounds. According to the Melan’s theorem, a direct algorithm has been carried out to determine the lower bound of shakedown limit using the best residual stress field calculated during the LMM upper bound procedure with displacement-based finite elements. By checking the yield condition at every integration point, the lower bound is calculated by the obtained static field at each iteration, with the upper bound given by the obtained kinematic field. A number of numerical examples confirm the applicability of this procedure and ensure that the upper and lower bounds are expected to converge to the theoretical solution after a number of iterations.

scholarly journals Lower and Upper Bound Shakedown Analysis of Structures With Temperature-Dependent Yield Stress

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Haofeng Chen
Keyword(s):  
Lower Bound ◽  
Yield Stress ◽  
Upper Bound ◽  
Solid Mechanics ◽  
Yield Condition ◽  
Static Field ◽  
Upper And Lower Bounds ◽  
Residual Stress Field ◽  
Temperature Dependent ◽  
Shakedown Analysis

Based upon the kinematic theorem of Koiter (1960, “General Theorems for Elastic Plastic Solids,” in Progress in Solid Mechanics 1, J. N. Sneddon and R. Hill, eds., North-Holland, Amsterdam, pp. 167–221) the linear matching method (LMM) procedure has been proved to produce very accurate upper bound shakedown limits. This paper presents a recently developed LMM lower bound procedure for shakedown analysis of structures with temperature-dependent yield stress, which is implemented into ABAQUS using the same procedure as for upper bounds. According to the Melan’s theorem (1936, “Theorie statisch unbestimmter Systeme aus ideal-plastichem Baustoff,” Sitzungsber. Akad. Wiss. Wien, Math.-Naturwiss. Kl., Abt. 2A, 145, pp. 195–210), a direct algorithm has been carried out to determine the lower bound of shakedown limit using the best residual stress field calculated during the LMM upper bound procedure with displacement-based finite elements. By checking the yield condition at every integration point, the lower bound is calculated by the obtained static field at each iteration, with the upper bound given by the obtained kinematic field. A number of numerical examples confirm the applicability of this procedure and ensure that the upper and lower bounds are expected to converge to the theoretical solution after a number of iterations.

Lower Bound Methods in Elastic-Plastic Shakedown Analysis

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Wolf Reinhardt ◽  
Reza Adibi-Asl
Keyword(s):  
Lower Bound ◽  
Plastic Material ◽  
Material Behavior ◽  
Shakedown Analysis ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Efficient Calculation ◽  
Asme Code ◽  
Elastic Shakedown ◽  
Plastic Shakedown

Several methods were proposed in recent years that allow the efficient calculation of elastic and elastic-plastic shakedown limits. This paper establishes a uniform framework for such methods that are based on perfectly-plastic material behavior, and demonstrates the connection to Melan's theorem of elastic shakedown. The paper discusses implications for simplified methods of establishing shakedown, such as those used in the ASME Code. The framework allows a clearer assessment of the limitations of such simplified approaches. Application examples are given.

A Modified Peric Model for Al-Mg Alloy Sheet with Rate-Independent Initial Yield Stress at Warm Temperatures

2019 ◽  
Vol 287 ◽  
pp. 3-7
Author(s):  
Yong Zhang ◽  
Qing Zhang ◽  
Yuan Tao Sun ◽  
Xian Rong Qin
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Strain Rate ◽  
Yield Stress ◽  
Constitutive Models ◽  
Mg Alloy ◽  
Initial Yield Stress ◽  
Initial Yield ◽  
Rate Dependent ◽  
Dependent Flow

The constitutive modeling of aluminum alloy under warm forming conditions generally considers the influence of temperature and strain rate. It has been shown by published flow stress curves of Al-Mg alloy that there is nearly no effect of strain rate on initial yield stress at various temperatures. However, most constitutive models ignored this phenomenon and may lead to inaccurate description. In order to capture the rate-independent initial yield stress, Peric model is modified via introducing plastic strain to multiply the strain rate, for eliminating the effect of strain rate when the plastic strain is zero. Other constitutive models including the Wagoner, modified Hockett–Sherby and Peric are also considered and compared. The results show that the modified Peric model could not only describe the temperature-and rate-dependent flow stress, but also capture the rate-independent initial yield stress, while the Wagoner, modified Hockett–Sherby and Peric model can only describe the temperature-and rate-dependent flow stress. Moreover, the modified Peric model could obtain proper static yield stress more naturally, and this property may have potential applications in rate-dependent simulations.

Recent Advances in Lower Bound Shakedown Analysis

2009 ◽  
Author(s):  
Dieter Weichert ◽  
Abdelkader Hachemi
Keyword(s):  
Finite Element ◽  
Lower Bound ◽  
Process Engineering ◽  
Operating Conditions ◽  
Structural Elements ◽  
Shakedown Analysis ◽  
Material Models ◽  
Practical Engineering ◽  
Safe Operating ◽  
New Algorithms

The special interest in lower bound shakedown analysis is that it provides, at least in principle, safe operating conditions for sensitive structures or structural elements under fluctuating thermo-mechanical loading as to be found in power- and process engineering. In this paper achievements obtained over the last years to introduce more sophisticated material models into the framework of shakedown analysis are developed. Also new algorithms will be presented that allow using the addressed numerical methods as post-processor for commercial finite element codes. Examples from practical engineering will illustrate the potential of the methodology.

scholarly journals Elasto-plastic analysis of the contact region between a rigid ellipsoid and a semi-flat surface

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879739 ◽  
Author(s):  
Pengyang Li ◽  
Lingxia Zhou ◽  
Fangyuan Cui ◽  
Quandai Wang ◽  
Meiling Guo ◽  
...  
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Plastic Strain ◽  
Contact Pressure ◽  
Contact Region ◽  
Three Dimensional ◽  
Von Mises Stress ◽  
Effective Plastic Strain ◽  
Normal Forces ◽  
Von Mises

When the load acting on a mechanical structure is greater than the yield strength of the material, the contact surface will undergo plastic deformation. Cumulative plastic deformation has an important influence on the lifespan of mechanical parts. This article presents a three-dimensional semi-analytical model based on the conjugate gradient method and fast Fourier transform algorithm, with the aim of studying the characteristic parameters of the contact region between a rigid ellipsoid and elasto-plastic half-space. Moreover, normal forces and tangential traction were considered, as well as the contact pressure resulting from various sliding speeds and friction coefficients. The contact pressure, effective plastic strain, von Mises stress, and residual stress were measured and shown to increase with increasing sliding velocity. Finally, when the friction coefficient, contact pressure, and effective plastic strain are increased, the von Mises stress is also shown to increase, whereas the residual stress decreases.

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