Assessment of the Cyclic Behavior of Structural Components Using Novel Approaches

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
K. D. Panagiotou ◽  
K. V. Spiliopoulos
Keyword(s):  
Residual Stress ◽  
Decomposition Method ◽  
Plastic Material ◽  
Low Cycle Fatigue ◽  
Direct Methods ◽  
Cyclic Behavior ◽  
Loading History ◽  
Perfectly Plastic ◽  
Stress Decomposition ◽  
Safety Margins

To extend the life of a structure, or a component, which is subjected to cyclic thermomechanical loading history, one has to provide safety margins against excessive inelastic deformations that may lead either to low-cycle fatigue or to ratcheting. Direct methods constitute a convenient tool toward this direction. Two direct methods that have been named residual stress decomposition method (RSDM) and residual stress decomposition method for shakedown (RSDM-S) have recently appeared in the literature. The first method may predict any cyclic elastoplastic state for a given cyclic loading history. The second method RSDM-S that is based upon RSDM is suggested for the shakedown analysis of structures. Both methods may be directly implemented in any finite-element (FE) code. An elastic perfectly plastic material with a von Mises yield surface has been assumed. In this work, through their application to structures that are used as benchmarks in the literature, both methods, applied together, prove their efficiency and capacity to determine shakedown boundaries and reveal unsafe conditions.

scholarly journals A Simplified Approach for the Hydro-Forming Process of Bi-Metallic Composite Pipe

2017 ◽  
Vol 62 (2) ◽  
pp. 879-883 ◽  
Author(s):  
M. Zheng ◽  
H. Gao ◽  
H. Teng ◽  
J. Hu ◽  
Z. Tian ◽  
...  
Keyword(s):  
Residual Stress ◽  
Plastic Material ◽  
Material Model ◽  
Forming Process ◽  
Simplified Approach ◽  
Metallic Composite ◽  
Perfectly Plastic ◽  
Proposed Model ◽  
Composite Pipe ◽  
Elastic Perfectly Plastic

AbstractIn this article, it aims to propose effective approaches for hydro-forming process of bi-metallic composite pipe by assuming plane strain and elastic-perfectly plastic material model. It derives expressions for predicting hydro-forming pressure and residual stress of the forming process of bi-metallic composite pipe. Test data from available experiments is employed to check the model and formulas. It shows the reliability of the proposed model and formulas impersonally.

scholarly journals RSDM: A Powerful Direct Method to Predict the Asymptotic Cyclic Behavior of Elastoplastic Structures

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Konstantinos V. Spiliopoulos ◽  
Ioannis A. Kapogiannis
Keyword(s):  
Low Cycle Fatigue ◽  
Direct Method ◽  
Time History ◽  
Direct Methods ◽  
General Purpose ◽  
Cyclic Behavior ◽  
Asymptotic State ◽  
Engineering Structures ◽  
History Of ◽  
Elastic Shakedown

AbstractMechanical engineering structures and structural components are often subjected to cyclic thermomechanical loading which stresses their material beyond its elastic limits well inside the inelastic regime. Depending on the level of loading inelastic strains may lead either to failure, due to low cycle fatigue or ratcheting, or to safety, through elastic shakedown. Thus, it is important to estimate the asymptotic stress state of such structures. This state may be determined by cumbersome incremental time-stepping calculations. Direct methods, alternatively, have big computational advantages as they focus on the characteristics of these states and try to establish them, in a direct way, right from the beginning of the calculations. Among the very few such general-purpose direct methods, a powerful direct method which has been called RSDM has appeared in the literature. The method may directly predict any asymptotic state when the exact time history of the loading is known. The advantage of the method is due to the fact that it addresses the physics of the asymptotic cycle and exploits the cyclic nature of its expected residual stress distribution. Based on RSDM a method for the shakedown analysis of structures, called RSDM-S has also been developed. Despite most direct methods for shakedown, RSDM-S does not need an optimization algorithm for its implementation. Both RSDM and RSDM-S may be implemented in any Finite Element Code. A thorough review of both these methods, together with examples of implementation are presented herein.

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.

Experiment and FEM Simulation on Residual Stress of Cold Expansion Hole

2007 ◽  
Vol 561-565 ◽  
pp. 1783-1786 ◽  
Author(s):  
Xiao Jun Shao ◽  
Jun Liu ◽  
Yong Shou Liu ◽  
Zhu Feng Yue
Keyword(s):  
Residual Stress ◽  
Plastic Material ◽  
Fem Simulation ◽  
Stress Fields ◽  
Material Models ◽  
Hardening Material ◽  
Cold Expansion ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Cold Expansion Hole

A 2D cylindrical plate model has been established to study the distribution of residual stress of cold expansion hole under different interference values. In addition, the effects of material models on residual stress fields are considered also. Experiments are carried out to measure the residual stress of cold expansion hole and verify simulation results. FEM results show, with interference values increasing, the higher residual radial and circumferential stresses are obtained. At same interference value, the residual stress of Hardening Material( HM ) model is much larger than that of Elastic Perfectly Plastic Material( EPPM ) model.

Nonlinear Analysis of Axisymmetrically Wrinkled Pipes Under Axial Loads and Internal Pressures

2015 ◽  
Author(s):  
Ashutosh Sutra Dhar ◽  
Abu Hena Muntakim
Keyword(s):  
Residual Stress ◽  
Strain Hardening ◽  
Plastic Material ◽  
Stress History ◽  
Element Analysis ◽  
Hardening Material ◽  
Perfectly Plastic ◽  
History Effects ◽  
Conservative Estimation ◽  
Surrounding Soil

Nonlinear finite element analysis of axi-symmetrically dented/wrinkled pipe has been presented in this paper. The pipe including surrounding soil was modelled using three different approaches to indicate the effects of modelling approaches on the simulation of pipe behavior. In the first approach, pipe was modelled with the geometry of the dented/wrinkled pipe without consideration of any residual stress and stress history. In the second approach, residual stress was applied at the nodal points of the pipe geometry modelled as in the first approach. In the third approach, a dent/wrinkle was created on the pipe wall through applying nodal displacements to include residual stress as well as the stress history effects. The analysis revealed that the first approach provides an un-conservative estimation of the pipe capacity. The second approach provides a reasonable estimation of the pipe capacity for elastic perfectly plastic material. However, the second approach provides a conservative estimation for strain hardening material, since pipe stress history is not considered. For strain hardening materials, both residual stress and the stress history should be considered for the simulation of the pipe behavior. The surrounding soil appears not to contribute to the capacity of the pipes under the loading conditions investigated.

Stress concentration factors and elastic-plastic stress and strain predictions for axisymmetric internal projections on hollow tubes subjected to axial loading

1989 ◽  
Vol 24 (1) ◽  
pp. 45-54 ◽  
Author(s):  
S J Hardy ◽  
A R Gowhari-Anaraki
Keyword(s):  
Stress Concentration ◽  
Plastic Material ◽  
Low Cycle Fatigue ◽  
Axial Loading ◽  
Material Model ◽  
Published Data ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Stress Concentration Factors ◽  
Elastic Perfectly Plastic

The finite element method has been used to obtain stress concentration factor data for hollow tubes with axisym-metric internal projections subjected to axial loading. A range of geometries has been considered in the investigation, and the results are complementary to previously published data. Preliminary results from an elastic-plastic analysis of a component with an internal projection are presented. Strain predictions with an elastic-perfectly-plastic material model are found to be between those estimated using linear and Neuber rules for low cycle fatigue life predictions.

Random impact FEM simulation of irregularly-shaped media for parametric study of vibratory surface enhancement

2021 ◽  
pp. 095440542199012
Author(s):  
Jing Zhang ◽  
Joselito Yam Alcaraz ◽  
Swee-Hock Yeo ◽  
Arun Prasanth Nagalingam ◽  
Abhay Gopinath
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Parametric Study ◽  
Thermal Loading ◽  
Low Cycle Fatigue ◽  
Fem Simulation ◽  
Surface Finishing ◽  
Aerospace Materials ◽  
Surface Enhancement ◽  
Steel Balls

Aerospace materials experience high levels of mechanical and thermal loading, high/low cycle fatigue, and damage from foreign objects during service, which can lead to premature retirement. Mechanical surface treatments of metallic components, for example, fan blades and blisks, are proven to improve fatigue life, improve wear resistance and avoid stress corrosion by introducing work hardening, compressive residual stresses of sub-surface, and surface finishing. Vibropeening can enhance aerospace materials’ fatigue life involving the kinetic agitation of hardened steel media in a vibratory finishing machine that induces compressive stresses into the component sub-layers while keeping a finished surface. Spherical steel balls are the most widely used shape among steel-based media and have been explored for decades. However, they are not always versatile, which cannot access deep grooves, sharp corners, and intricate profiles. Steel ballcones or satellites, when mixed with round steel balls and other steel media (diagonals, pins, eclipses, cones), works very well in such areas that ball-shaped media are unable to reach. However, a methodology of study the effect of irregularly-shaped media in surface enhancement processes has not been established. This paper proposes a finite element-based model to present a methodology for the parametric study of vibratory surface enhancement with irregularly-shaped media and investigates residual stress profiles within a treated area of an Inconel component. The methodology is discussed in detail, which involves a stochastic simulation of orientation, impact force, and impact location. The contrasting effects of a high aspect ratio, or an edge contact, as opposed to rounded and oblique contacts are demonstrated, with further analysis on the superposition of these effects. Finally, the simulation results are compared with actual residual stress measurements and was found to have a max percent difference of 34% up to 20 [Formula: see text]m below the media surface.

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