Anisotropy Characteristics of Stress Relaxation in Coal: An Improved Fractional Derivative Constitutive Model

2018 ◽  
Vol 52 (2) ◽  
pp. 335-349
Author(s):  
Tingting Cai ◽  
Zengchao Feng ◽  
Yulong Jiang ◽  
Dong Zhao ◽  
Xiaoqiang Zhang
Keyword(s):  
Stress Relaxation ◽  
Constitutive Model ◽  
Fractional Derivative

Prediction of Stress Relaxation in Power Plant Components Based on a Constitutive Model

2017 ◽  
Author(s):  
Y. Kostenko ◽  
K. Naumenko
Keyword(s):  
Power Plant ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Evolution Equations ◽  
Material Behavior ◽  
Assessment Procedure ◽  
Reliable Prediction ◽  
Inelastic Material ◽  
Plant Components

Many power plant components and joint connections are subjected to complex thermo-mechanical loading paths under severe temperature environments over a long period. An important part in the lifetime assessment is the reliable prediction of stress relaxation using improved creep modeling to avoid possible integrity or functionality issues and malfunction in such components. The aim of this work is to analyze the proposed constitutive model for advanced high chromium steels with the goal of predicting stress relaxation over the long term. The evolution equations of the constitutive model for inelastic material behavior are introduced to account for hardening and softening phenomena. The material properties were identified for 9–12%CrMoV steels in the creep range. The model is applied to the stress relaxation analysis of power plant components. The results for long-term assessment, which are encouragingly close to reality, will be presented and discussed. An outlook on further developments of the model and assessment procedure is also provided.

A novel constitutive model for multi-step stress relaxation ageing of a pre-strained 7xxx series alloy

2018 ◽  
Vol 106 ◽  
pp. 31-47 ◽  
Author(s):  
Jing-Hua Zheng ◽  
Jianguo Lin ◽  
Junyi Lee ◽  
Ran Pan ◽  
Chen Li ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Constitutive Model ◽  
Series Alloy

A novel constitutive model for stress relaxation of Ti-6Al-4V alloy sheet

2019 ◽  
Vol 161-162 ◽  
pp. 105034 ◽  
Author(s):  
Xuexi Cui ◽  
Xiangdong Wu ◽  
Min Wan ◽  
Bolin Ma ◽  
Yanling Zhang
Keyword(s):  
Stress Relaxation ◽  
Constitutive Model ◽  
Alloy Sheet

Experimental In Situ Characterization and Creep Modeling of Tin-Based Solder Joints on Commercial Area Array Packages at −40 °C , 23 °C , and 125 °C

2004 ◽  
Vol 127 (4) ◽  
pp. 430-439 ◽  
Author(s):  
Ahmad Abu Obaid ◽  
Jay G. Sloan ◽  
Mark A. Lamontia ◽  
Antonio Paesano ◽  
Subhotosh Khan ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Constitutive Model ◽  
Solder Ball ◽  
Solder Joints ◽  
Shear Loading ◽  
Area Array ◽  
Commercial Area ◽  
Wide Range ◽  
Solder Balls

The objective of this work was to experimentally determine the in situ creep behavior and constitutive model equations for a commercial area array package and printed wiring board assembly at −40, 23, and 125 °C through shear loading. The chip is connected to the printed circuit board by means of solder joints made of 62%Sn–36%Pb–2%Ag alloy. It was shown that the creep rate of solder ball arrays could be investigated using a stress relaxation method. Under the shear relaxation mode, the creep strain increases with temperature and can be described by a power law model with coefficients determined by finite element modeling (FEM). An analytical model was developed to describe the stress relaxation of an array with an arbitrary number of solder balls by defining an equivalent solder ball shear area as a fitting parameter. The resulting constitutive model is in excellent agreement with both FEM and experimental results at all test temperatures. A parametric study is conducted to investigate the creep response as a function of temperature for arrays consisting of a wide range of solder balls.

scholarly journals Constitutive Modeling of Time-Dependent Response of Human Plantar Aponeurosis

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
P. G. Pavan ◽  
P. Pachera ◽  
C. Stecco ◽  
A. N. Natali
Keyword(s):  
Experimental Data ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Transverse Isotropy ◽  
Model Fitting ◽  
Viscoelastic Behavior ◽  
Time Dependent ◽  
Plantar Aponeurosis ◽  
Structural Conformation ◽  
Dependent Behavior

The attention is focused on the viscoelastic behavior of human plantar aponeurosis tissue. At this purpose, stress relaxation tests were developed on samples taken from the plantar aponeurosis of frozen adult donors with age ranging from 67 to 78 years, imposing three levels of strain in the physiological range (4%, 6%, and 8%) and observing stress decay for 240 s. A viscohyperelastic fiber-reinforced constitutive model with transverse isotropy was assumed to describe the time-dependent behavior of the aponeurotic tissue. This model is consistent with the structural conformation of the tissue where collagen fibers are mainly aligned with the proximal-distal direction. Constitutive model fitting to experimental data was made by implementing a stochastic-deterministic procedure. The stress relaxation was found close to 40%, independently of the level of strain applied. The agreement between experimental data and numerical results confirms the suitability of the constitutive model to describe the viscoelastic behaviour of the plantar aponeurosis.

Stress Relaxation Effects in TiNi SMA During Superelastic Deformation: Experiment and Constitutive Model

2017 ◽  
Vol 3 (4) ◽  
pp. 392-402 ◽  
Author(s):  
Elżbieta A. Pieczyska ◽  
Zbigniew L. Kowalewski ◽  
Vladimir Lj. Dunić
Keyword(s):  
Stress Relaxation ◽  
Constitutive Model ◽  
Relaxation Effects ◽  
Superelastic Deformation
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