Residual stress – strain relations inversely derived from experimental moment – curvature response of RC beams with fibres compared to the recommendations of design codes

Mechanical dents often occur in transmission pipelines, and are recognized as one of major threats to pipeline integrity because of the potential fatigue failure due to cyclic pressures. With matured in-line-inspection (ILI) technology, mechanical dents can be identified from the ILI runs. Based on ILI measured dent profiles, finite element analysis (FEA) is commonly used to simulate stresses and strains in a dent, and to predict fatigue life of the dented pipeline. However, the dent profile defined by ILI data is a purely geometric shape without residual stresses nor plastic deformation history, and is different from its actual dent that contains residual stresses/strains due to dent creation and re-rounding. As a result, the FEA results of an ILI dent may not represent those of the actual dent, and may lead to inaccurate or incorrect results. To investigate the effect of residual stress or plastic deformation history on mechanics responses and fatigue life of an actual dent, three dent models are considered in this paper: (a) a true dent with residual stresses and dent formation history, (b) a purely geometric dent having the true dent profile with all stress/strain history removed from it, and (c) a purely geometric dent having an ILI defined dent profile with all stress/strain history removed from it. Using a three-dimensional FEA model, those three dents are simulated in the elastic-plastic conditions. The FEA results showed that the two geometric dents determine significantly different stresses and strains in comparison to those in the true dent, and overpredict the fatigue life or burst pressure of the true dent. On this basis, suggestions are made on how to use the ILI data to predict the dent fatigue life.

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Analyses of sintering residual stress and microscopic stress/strain under uniaxial tension in WC-Co hardmetal.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ◽

10.1299/kikaia.53.1969 ◽

1987 ◽

Vol 53 (495) ◽

pp. 1969-1976 ◽

Cited By ~ 1

Author(s):

Akio OTSUKA ◽

Keiichiro TOHGO ◽

Tetsuya TAGAWA

Keyword(s):

Residual Stress ◽

Uniaxial Tension ◽

Stress Strain

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NUMERICAL INVESTIGATION OF THERMOMECHANICAL PROCESSES UNDER SHORT-PULSED LASER IRRADIATION OF A HALF-SPACE

Journal of Automation and Information sciences ◽

10.34229/1028-0979-2021-6-6 ◽

2021 ◽

Vol 6 ◽

pp. 55-65

Author(s):

Kamila Storchak ◽

◽

Nina Yakovenko ◽

Olga Polonevych ◽

Irina Sribna ◽

...

Keyword(s):

Residual Stress ◽

Laser Irradiation ◽

Half Space ◽

Strain State ◽

Thermal Stresses ◽

Equations Of Motion ◽

Thermomechanical Loading ◽

Stress Strain ◽

Stress Strain State ◽

Residual Strains

The laser irradiation of metallic surfaces by intense heat sources is used for the generation of short probing pulses, which propagate into thin specimens and enable one to estimate their structure and mechanical properties within the framework of the classical acoustic approach. High thermal stresses and residual strains occur during the short-term irradiation of the surface of a construction by an energy source of high density. In the present work, we solve the axially symmetric problem of a half-space under thermomechanical loading. We take into account the influence of volume and inelastic characteristics of separate phases on the residual stress-strain state of the half-space. The statement of the problem includes: Cauchy relations, equations of motion, heat conduction equation, initial conditions, thermal and mechanical boundary conditions. The thermomechanical behavior of an isotropic material is described by the Bodner-Partom unified model of flow. The problem is solved with using the finite element technique. The numerical realization of our problem is performed with the help of step-by-step time integration. The equations of motion are integrated by the Newmark method. The residual stress-strain state is described using the method of numerical solution of the axisymmetric dynamic problem for a half-space under thermomechanical loading and the flow model. We established that microstructural transformations, which are taken into account due to the thermophase volume strain and dependence of inelastic characteristics of the material on the phase composition, significantly reduce residual inelastic strain and promote the appearance of compressive stresses. The three-zone region of residual stresses field formation is obtained.

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Fatigue Strength Assessment of a Butt-Welded Joint in Ship Structures Based on Time-Domain Strain Approach

Journal of Ship Research ◽

10.5957/josr.04180019 ◽

2020 ◽

pp. 1-16

Author(s):

Yan Dong ◽

Yordan Garbatov ◽

Carlos Guedes Soares

Keyword(s):

Residual Stress ◽

Fatigue Strength ◽

Time Domain ◽

Welded Joint ◽

Stress Strain ◽

Ship Structures ◽

Strength Assessment ◽

Variable Amplitude ◽

Notch Stress ◽

Fatigue Strength Assessment

Fatigue strength assessment of a butt-welded joint in ship structures based on a time-domain strain approach is performed in this study. The service life load histories applied to the butt-welded joint located on the deck of a bulk carrier are generated, accounting for the still-water and wave-induced loads. The rainflow counting method is applied to analyze the load histories, and the long-term distributions of the load range are compared with those based on the conventional spectral fatigue analysis. An approach of converting the load history to a series of closed notch stress-strain hysteresis loops and several open notch stress-strain hysteresis curves is proposed and demonstrated under variable amplitude loading. The approach is based on analytical notch stress-strain estimations and consists of several steps to consider the material memory effect, overcoming some limitations of the existing methods. To determine the fatigue damage for the variable amplitude loading, a design fatigue curve is derived considering the uncertainty in the fatigue lives and load sequence effects. The intrinsic fatigue limit concept is used to filter the small amplitude cycles that do not have a damaging effect. The fatigue strength of the butt-welded joint is analyzed, taking the weld-induced residual stress and misalignment effects into account explicitly. The notch mean stresses or strain amplitudes of the cycles are significantly enhanced because of the presence of a high level of weld-induced tensile residual stress or misalignment, resulting in highly severe fatigue damage. 1. Introduction Complex ship structures containing geometrical and material discontinuities are prone to fatigue because of cyclic loads. Therefore, fatigue strength assessment has been an important criterion in the ship structural design (Guedes Soares & Moan 1991). Various fatigue design concepts for the assessment of welded joints, where fatigue failures mostly originate, are applied (Xu 1997; Radaj et al. 2006), and they can be classified into two types. The first one is based on S-N curves in combination with the Palmgren-Miner rule, and the second one is based on the crack propagation models and failure criteria.

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Residual stress, strain and faults in nanocrystalline palladium and copper

Materials Science and Engineering A ◽

10.1016/0921-5093(95)09928-x ◽

1995 ◽

Vol 204 (1-2) ◽

pp. 7-11 ◽

Cited By ~ 66

Author(s):

P.G. Sanders ◽

A.B. Witney ◽

J.R. Weertman ◽

R.Z. Valiev ◽

R.W. Siegel

Keyword(s):

Residual Stress ◽

Stress Strain

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Residual Stress/Strain Effect on the Bending Properties of the Cu/Al/Cu Clad Plate

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.737.214 ◽

2017 ◽

Vol 737 ◽

pp. 214-219

Author(s):

Yong Keun Kim ◽

Sun Ig Hong

Keyword(s):

Heat Treatment ◽

Residual Stress ◽

Fracture Strain ◽

Interface Debonding ◽

Strain Effect ◽

Convex Side ◽

Interface Bonding ◽

Bending Properties ◽

Stress Strain ◽

Lower Strength

One of the important issue in the production of the industrial scale Cu/Al/Cu clad plate is the evolution of residual stress/strain during rolling the stack of thick slabs into thin wide and long plates. In this study, the effect of residual stress/strain and annealing on the bend forming behaviors of Cu/Al/Cu clad composite were studied. Tensile strength of separated convex side Cu layer from the bent Cu/Al/Cu clad plate was observed 350MPa, smaller than that of concave side Cu-layer (380MPa). The lower strength and higher fracture strain in the convex side Cu layer is attributed to the presence of the compressive residual strain in the convex side. After heat-treatment at 380°C no pronounced interface debonding and separation between Cu and Al layers were noted, supporting a reliable interface bonding between Cu and Al. The ductility of Cu/Al/Cu clad plate was observed to be greater than that of Al, which can be explained by the co-deformation induced the interaction and constraint between bonded Al and Cu layers. The bend forming behavior of the bent Cu-Al-Cu clad composite was not greatly influenced by the residual stress/strain developed during rolling because of the thick Al layers with negligible residual stress between Cu.

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