Multi-damage life assessment under continuous damage mechanics

2016 ◽  
Author(s):  
Chaojie Qi ◽  
Yufeng Sun
Keyword(s):  
Damage Mechanics ◽  
Life Assessment

Elevated-Temperature Life Assessment

2021 ◽  
pp. 146-166
Author(s):  
Arun Sreeranganathan ◽  
Douglas L. Marriott
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Stress Relaxation ◽  
Damage Mechanics ◽  
Elevated Temperatures ◽  
Constitutive Models ◽  
Life Assessment ◽  
Remaining Life ◽  
High Temperature Components ◽  
Remaining Life Assessment

Abstract This article provides some new developments in elevated-temperature and life assessments. It is aimed at providing an overview of the damage mechanisms of concern, with a focus on creep, and the methodologies for design and in-service assessment of components operating at elevated temperatures. The article describes the stages of the creep curve, discusses processes involved in the extrapolation of creep data, and summarizes notable creep constitutive models and continuum damage mechanics models. It demonstrates the effects of stress relaxation and redistribution on the remaining life and discusses the Monkman-Grant relationship and multiaxiality. The article further provides information on high-temperature metallurgical changes and high-temperature hydrogen attack and the steps involved in the remaining-life prediction of high-temperature components. It presents case studies on heater tube creep testing and remaining-life assessment, and pressure vessel time-dependent stress analysis showing the effect of stress relaxation at hot spots.

Modeling the Effects of Damage and Microstructural Evolution on the Creep Behavior of Engineering Alloys

2000 ◽  
Vol 122 (3) ◽  
pp. 273-278 ◽  
Author(s):  
M. McLean ◽  
B. F. Dyson
Keyword(s):  
Creep Behavior ◽  
Damage Mechanics ◽  
Complex Loading ◽  
Phase Changes ◽  
Life Assessment ◽  
Engineering Alloys ◽  
Improved Design ◽  
Remaining Life Assessment ◽  
Aging Phenomena ◽  
Evolution Of Microstructure

A quantitative representation of the creep behavior of materials is required to determine the operating lives of high temperature plant. Although the creep performance of such materials is normally governed by the development of microstructural features that can either be associated with the normal aging phenomena or by the development of damage in the material, most previous analyses of creep data have been empirical. It has been implicitly assumed that similar forms of creep curves can be adequately represented by a single generic equation. However, it is clear that different materials are subject to different combinations of structural change during their creep lives (e.g., cavitation/cracking, particle coarsening, phase changes, dislocation accumulation) all of which can influence the creep performance. An empirical representation can always be made to fit an available database, but effective extrapolation to longer lives and more complex loading conditions requires that the differing mechanisms be integrated in the creep equations. This paper will explore the implications of the evolution of microstructure and damage on the creep performance of a range of materials and will consider the potential of a microstructure-based state-variable (or damage-mechanics) approach for improved design life prediction of new plant and remaining life assessment of geriatric plant. [S0094-4289(00)00603-4]

scholarly journals Microscopic Multiple Fatigue Crack Simulation and Macroscopic Damage Evolution of Concrete Beam

2019 ◽  
Vol 9 (21) ◽  
pp. 4664 ◽  
Author(s):  
Baijian Wu ◽  
Zhaoxia Li ◽  
Keke Tang ◽  
Kang Wang
Keyword(s):  
Fatigue Crack ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Concrete Beam ◽  
Crack Formation ◽  
Concrete Beams ◽  
Life Assessment ◽  
Engineering Practice ◽  
Stiffness Reduction ◽  
Fatigue Rupture

Microcracks in concrete can coalesce into larger cracks that further propagate under repetitive load cycles. Complex process of crack formation and growth are essentially involved in the failure mechanism of concrete. Understanding the crack formation and propagation is one of the core issues in fatigue damage evaluation of concrete materials and components. In this regard, a numerical model was formulated to simulate the thorough failure process, ranging from microcracks growth, crack coalescence, macrocrack formation and propagation, to the final rupture. This model is applied to simulate the fatigue rupture of three-point bending concrete beams at different stress levels. Numerical results are qualitatively consistent with the experimental observations published in literature. Furthermore, in the framework of damage mechanics, one damage variable is defined to reflect stiffness reduction caused by fatigue loading. S-N curve is subsequently computed and the macroscopic damage evolution of concrete beams are achieved. By employing the combined approaches of fracture mechanics and damage mechanics, made possible is the damage evolution of concrete beam as well as the microscopic multiple fatigue crack simulation. The proposed approach has the potential to be applied to the fatigue life assessment of materials and components at various scales in engineering practice.

A Deformation and Life Prediction of a Circumferentially Reinforced SiC/Ti 15-3 Ring

1993 ◽  
Author(s):  
S. M. Arnold ◽  
T. E. Wilt
Keyword(s):  
Finite Element ◽  
Stress Analysis ◽  
Damage Mechanics ◽  
Damage Model ◽  
Three Dimensional ◽  
Life Assessment ◽  
Burst Pressure ◽  
Internal Damage ◽  
Current Application ◽  
The Matrix

Abstract A computational methodology has been developed to predict the fatigue life of typical aerospace components, here the specific example is a circumferentially reinforced SiC/Ti-15-3 compressor ring designed for applications at 800° F. The analysis encompasses both a static burst pressure prediction and a life assessment of the cladded ring. A three dimensional stress analysis was performed using MARC, a nonlinear finite element code, wherein both the matrix cladding and the composite core were assumed to behave elastic-plastic. The composite core behaviour was represented using Hill’s anisotropic continuum based plasticity model with bilinear hardening. Similarity, the matrix cladding was represented by an isotropic perfectly plastic model. The load-displacement (i.e., internal pressure versus radial deflection) response of the ring was used to determine the static burst pressure. The life assessment was conducted using the stress analysis results, in conjunction with a recently developed multiaxial, isothermal, continuum damage mechanics model for the fatigue of unidirectional metal matrix composites. This model is phenomenological, stress based, and assumes a single scalar internal damage variable, the evolution of which is anisotropic. The accumulation of damage is included in the stress analysis by employing the concept of effective stress. In the current application, however, the damage model is computationally-decoupled from the finite element solution. The specific methodology for this computationally-decoupled fatigue damage simulation is outlined and results are given in terms of the evolution of damage and design life curves.

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