scholarly journals Analysis of the Failure Process of Elements Subjected to Monotonic and Cyclic Loading Using the Wierzbicki–Bai Model

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6265
Author(s):  
Urszula Janus-Galkiewicz ◽  
Jaroslaw Galkiewicz
Keyword(s):  
Cyclic Loading ◽  
Failure Process ◽  
Stress Triaxiality ◽  
Stress Deviator ◽  
Short Life ◽  
Notched Specimens ◽  
Fatigue Loads ◽  
The Difference ◽  
Loading Methods ◽  
Super Alloy

This article presents the results of a simulation in which smooth cylindrical and ring-notched samples were subjected to monotonic and fatigue loads in an ultra-short-life range, made of Inconel 718 super alloy. The samples displayed different behaviors as a result of different geometries that introduced varying levels of stress triaxiality and loading methods. The simulations used the Wierzbicki–Bai model, which took into account the influence of stress tensors and stress-deviator invariants on the behavior of the material. The difference in the behaviors of the smoothed and notched specimens subjected to tensile and fatigue loads were identified and described. The numerical results were qualitatively supported by the results of the experiments presented in the literature.

Mismatch Effect on the Mixed Mode Type Creep Crack within Weldment

2016 ◽  
Vol 853 ◽  
pp. 281-285
Author(s):  
Jun Hui Zhang ◽  
Yan Wei Dai
Keyword(s):  
Mixed Mode ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Crack Tip Field ◽  
Creep Crack ◽  
Loading Mode ◽  
The Difference ◽  
Engineering Practices ◽  
Mismatch Effect ◽  
Transient And Steady State

Creep crack within weldments are very common in engineering practices, and the cracking location in these welding structures always appears at the HAZ location. The mismatch effect on the mixed mode creep crack is still not clear in these available literatures. The aim of this paper is to investigate the mismatch influence on the creep crack of mixed mode thoroughly. A mixed mode creep crack within HAZ is established in this paper. The leading factor that dominates the creep crack tip field under mixed loading mode is studied. The influences of mismatch effect on mode mixity, stress distribution and stress triaxiality are proposed. The difference of mixed mode creep crack and normal mode I or mode II creep crack are compared. The influence of mixity factor on the transient and steady state creep of crack tip are also analyzed.

Experimental Study of Bending Toughness on Hybrid Fiber Reinforced Concrete

2013 ◽  
Vol 327 ◽  
pp. 201-204
Author(s):  
Jin Song Shi ◽  
Bo Yuan ◽  
Da Zhang Wang ◽  
Zhe An Lu
Keyword(s):  
Experimental Study ◽  
Reinforced Concrete ◽  
Fiber Reinforced Concrete ◽  
Bending Test ◽  
Fiber Reinforced ◽  
Hybrid Fiber ◽  
Toughness Index ◽  
The Difference ◽  
Loading Methods ◽  
Index Value

In order to investigate the difference of current toughness index standards for fiber reinforced concrete, two main groups of specimens were made to take bending toughness test with the requirements of corresponded standards, loading methods and loading speeds, which are ASTM C1018 in America, ACI 544 and JSCE G552 in Japan. United with software Origin, the load-deflection curves gathered from bending test was calculated with relative standards. The results show that the calculated toughness index value with ASTM C1018-98 in America is more accurate with three grades but the requested deflection of testing is much longer than others while ACI 544 and JSCE G552 in Japan are quite the contrary.

Pressureless Co-Sintering of Al2O/ZrO2 Multilayers and Bilayers

1996 ◽  
Vol 434 ◽  
Author(s):  
Peter Z. Cai ◽  
David J. Green ◽  
Gary L. Messing
Keyword(s):  
Thermal Expansion ◽  
Cyclic Loading ◽  
Microscopic Observation ◽  
Surface Defects ◽  
Tape Casting ◽  
Thermal Expansion Mismatch ◽  
Heating Rates ◽  
The Difference ◽  
Extent Of Damage ◽  
Transverse Damage

AbstractVarious types of damage were observed in pressureless-sintered Al2O3/ZrO2 symmetric laminates (multilayers) and asymmetric laminates (bilayers) fabricated by tape casting and lamination. These defects included channel defects in ZrO2-containing layers, Al2O3 surface defects parallel to the layers, decohesion between the layers, and transverse damage within the Al2O3 layer in the bilayers. Detailed microscopic observation attributed the defects to a combined effect of mismatch in both sintering rate and thermal expansion coefficient between the layers. Crack-like defects were formed in the early stages of densification, and these defects acted as pre-existing flaws for thermal expansion mismatch cracks. Curling of the bilayers during sintering was monitored and the measured rate of curvature change, along with the layer viscosities obtained by cyclic loading dilatometry, was used to estimate the sintering mismatch stresses. The extent of damage could be reduced or even eliminated by decreasing the difference in layer sintering rate. This was accomplished by reducing the heating rates or by adding Al2O3 in the ZrO2 layers.

A Historical Overview of Design Analyses and Experimental Observations of Ratcheting Phenomenon

2020 ◽  
Author(s):  
Jean Macedo ◽  
Stéphane Chapuliot ◽  
Jean-Michel Bergheau ◽  
Eric Feulvarch ◽  
Olivier Ancelet ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
State Of The Art ◽  
Constitutive Models ◽  
Experimental Tests ◽  
Design Codes ◽  
Historical Overview ◽  
Design Rules ◽  
Current Article ◽  
The Difference ◽  
Design Analyses

Abstract In order to investigate the ratcheting behavior and to determine new design rules, some experimental tests were conducted in many countries in the last decades. In France, some tests were carried out under mechanical or thermal cyclic loading to examine this risk. The first section of the current article is addressed to the state of the art concerning the ratcheting effects. The difference between Local and Global Ratcheting is clarified. The second section is dedicated to the experimental observations of ratcheting. The following section describes the constitutive models which are able to simulate material/structural ratcheting responses. The models presented are Linear Kinematic, Armstrong-Frederick, Chaboche, Ohno-Wang and Chen-Jiao-Kim. Finally, the ratcheting rules in design codes are exposed. Both simple and complex rules are presented.

scholarly journals Resistivity and AE Response Characteristics in the Failure Process of CGB under Uniaxial Loading

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Tingye Qi ◽  
Guorui Feng
Keyword(s):  
Failure Process ◽  
Peak Stress ◽  
Uniaxial Loading ◽  
Energy Curve ◽  
Cumulative Energy ◽  
Response Characteristics ◽  
Before And After ◽  
The Difference ◽  
Linear Slope ◽  
The Stability

To understand the characteristics of the acoustic emission (AE) and electrical resistivity of cemented coal gangue backfill (CGB) under uniaxial compression, the variations in these characteristics at 1 day, 3 days, and 7 days are analyzed by means of a stress-strain-resistivity-AE test, and the microperformances are investigated. The research results indicate that the AE can reflect the initiation and propagation of cracks and later explain the variation of the resistivity of the specimens under the uniaxial loading. The cumulative energy curve of AE is approximately two straight lines corresponding to the peak stress, and the difference in the linear slope gradually decreased with the increasing curing time due to the lower pore solution content and the compact pore structure. The relationships between the stress and resistivity and the loading condition before and after the peak stress at different curing times were established. Therefore, it is of great significance to predict the stability of the filling body by monitoring the AE and resistivity variations of the filling body. In addition, it is possible to calculate the roof stress using the relation equation between the resistivity and stress.

MULTIFRACTAL OF ELECTROMAGNETIC WAVEFORM AND SPECTRUM ABOUT COAL ROCK SAMPLES SUBJECTED TO UNIAXIAL COMPRESSION

Fractals ◽  
2020 ◽  
Vol 28 (04) ◽  
pp. 2050061 ◽  
Author(s):  
LIMING QIU ◽  
DAZHAO SONG ◽  
XUEQIU HE ◽  
ENYUAN WANG ◽  
ZHENLEI LI ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Failure Process ◽  
Dominant Frequency ◽  
Rock Failure ◽  
Electromagnetic Signal ◽  
Failure Behavior ◽  
Electromagnetic Spectrum ◽  
Dimension Formula ◽  
Coal Rock ◽  
The Difference

During coal and rock loading, a significantly large number of electromagnetic signals are generated as a result of fracture appearance and crack expansion. The generation of electromagnetic signal is the comprehensive embodiment of the coal rock failure behavior. Therefore, the generated signals contain complex and rich messages that can reflect the damage process and degree of coal and rock. In this work, the multifractal theory is applied to analyze the nonlinear characteristics of the electromagnetic wave and its spectrum induced during coal rock, which present good correlation with failure process. The failure process of coal rock is non-uniform, non-continuous and nonlinear, during which, there is a good synchronization and correlation between the electromagnetic pulses and the stress drop, rather than the stress. Both waveform and its spectrum of electromagnetic signal have multifractal characteristics, the larger the fracture scale is, the more significant the multifractal characteristic of electromagnetic signal is, and the multifractal characteristic of electromagnetic signal from coal is higher than that from sandstone. The difference of fracture energy and size can be represented by the maximum of the multifractal dimension [Formula: see text] of the electromagnetic wave and its spectrum during coal rock failure. In the electromagnetic spectrum, small signals are always dominant, and the dominant frequency is only a few isolated points. What is more, with the increase of fracture size, the difference between the dominant frequency and the non-dominant frequency is gradually enhanced.

scholarly journals Low Cycle Fatigue Life Evaluation of Notched Specimens Considering Strain Gradient

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 1001
Author(s):  
Shenghuan Qin ◽  
Zaiyin Xiong ◽  
Yingsong Ma ◽  
Keshi Zhang
Keyword(s):  
Cyclic Loading ◽  
Constitutive Model ◽  
Strain Gradient ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Plastic Behavior ◽  
Cycle Fatigue ◽  
New Model ◽  
Hysteresis Behavior ◽  
Notched Specimens

An improved model based on the Chaboche constitutive model is proposed for cyclic plastic behavior of metal and low cycle fatigue of notched specimens under cyclic loading, considering the effect of strain gradient on nonlinear kinematic hardening and hysteresis behavior. The new model is imported into the user material subroutine (UMAT) of the finite element computing software ABAQUS, and the strain gradient parameters required for model calculation are obtained by calling the user element subroutine (UEL). The effectiveness of the new model is tested by the torsion test of thin copper wire. Furthermore, the calibration method of strain gradient influence parameters of constitutive model is discussed by taking the notch specimen of Q235 steel as an example. The hysteresis behavior, strain distribution and fatigue failure of notched specimens under cyclic loading were simulated and analyzed with the new model. The results prove the rationality of the new model.

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