A Unified Approach to Metal Fatigue Based on the Theory of Damage Mechanics

2009 ◽  
pp. 165-165-21 ◽  
Author(s):  
CL Chow ◽  
LG Yu
Keyword(s):  
Damage Mechanics ◽  
Metal Fatigue ◽  
Unified Approach ◽  
Theory Of Damage

Viscoplastic Constitutive Modeling of Anisotropic Damage Under Nonproportional Loading

2000 ◽  
Vol 123 (4) ◽  
pp. 403-408 ◽  
Author(s):  
C. L. Chow ◽  
X. J. Yang ◽  
Edmund Chu
Keyword(s):  
Constitutive Modeling ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Evolution Equations ◽  
Forming Limit ◽  
Anisotropic Damage ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Localized Necking ◽  
Theory Of Damage

Based on the theory of damage mechanics, a viscoplastic constitutive modeling of anisotropic damage for the prediction of forming limit curve (FLC) is developed. The model takes into account the effect of rotation of principal damage coordinates on the deformation and damage behaviors. With the aid of the damage viscoplastic potential, the damage evolution equations are established. Based on a proposed damage criterion for localized necking, the model is employed to predict the FLC of aluminum 6111-T4 sheet alloy. The predicted results agree well with those determined experimentally.

scholarly journals Study on the Damage Evolution Process and Fractal of Quartz-Filled Shale under Thermal-Mechanical Coupling

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zhonghu Wu ◽  
Huailei Song ◽  
Liping Li ◽  
Zongqing Zhou ◽  
Yujun Zuo ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Critical Temperature ◽  
Failure Mode ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Thermal Damage ◽  
Failure Modes ◽  
Factors Affecting ◽  
Mechanical Coupling ◽  
Theory Of Damage

Filling of brittle minerals such as quartz is one of the main factors affecting the initiation and propagation of reservoir fractures in shale fracturing, in order to explore the failure mode and thermal damage characteristics of quartz-filled shale under thermal-mechanical coupling. Combining the theory of damage mechanics and thermoelasticity, RFPA2D-Thermal is used to establish a numerical model that can reflect the damage evolution of shale under thermal-solid coupling, and the compression test under thermal-mechanical coupling is performed. The test results show that during the temperature loading process, there is a temperature critical value between 60°C and 75°C. When the temperature is less than the critical temperature, the test piece unit does not appear obvious damage. When the temperature is greater than the critical temperature, the specimen unit will experience obvious thermal damage, and the higher the temperature, the more serious the cracking. Under the thermal-mechanical coupling of shale, the tensile strength and elastic modulus of shale show a decreasing trend with the increase of temperature. The failure modes of shale under thermal-solid coupling can be roughly divided into three categories: “V”-shaped failure (30°C, 45°C, and 75°C), “M”-shaped failure (60°C), and inverted “λ”-shaped failure (90°C). The larger the fractal dimension, the more complex the failure mode of the specimen. The maximum fractal dimension is 1.262 when the temperature is 60°C, and the corresponding failure mode is the most complex “M” shape. The fractal dimension is between 1.071 and 1.189, and the corresponding failure mode is “V” shape. The fractal dimension is 1.231, and the corresponding failure mode is inverted “λ” shape.

A New Method to Calculate Damage Variable with Unload/Load Response Ratio

2014 ◽  
Vol 1065-1069 ◽  
pp. 2040-2043
Author(s):  
Juan Zhang ◽  
Yuan Zhang ◽  
Ke Qiang He ◽  
Wei Gong Chen
Keyword(s):  
Large Scale ◽  
Damage Mechanics ◽  
Health Assessment ◽  
Damage Variable ◽  
Response Ratio ◽  
Load Response ◽  
Set Up ◽  
The University ◽  
Theory Of Damage ◽  
The Relationship

As an exploration and extension of load/unload response ratio theory, unload/ load response ratio theory (ULRR for short) is introduced firstly, and the relationship between ULRR (Y′) and elastic modulus (E for short) is obtained. Based on the basic theory of damage mechanics,the relationship between ULRR and damage variable (D for short) is set up and analyzed with the relationship between E and D. The unloading and loading experiments on a two-story structure carried out in the University of Naples in Italy are introduced;and calculated damage variable is compared with that calculated by Zhang Langping who put forward Weibull distribution as random distribution function. The results show that damage variable of the structure keep highly consistent with calculations of these two methods. Therefore, the relationship between Y′and D provides a new approach to a health assessment to catastrophic failure of large-scale structures and prediction of engineering.

Blow-up of solutions of a nonlinear parabolic equation in damage mechanics

1997 ◽  
Vol 8 (1) ◽  
pp. 89-123 ◽  
Author(s):  
MICHIEL BERTSCH ◽  
PAOLO BISEGNA
Keyword(s):  
Parabolic Equation ◽  
Damage Mechanics ◽  
Blow Up ◽  
Quasilinear Equation ◽  
Nonlinear Parabolic ◽  
Nonzero Measure ◽  
Degenerate Parabolic ◽  
Theory Of Damage ◽  
Well Posed ◽  
Nonlinear Degenerate

A fully nonlinear, degenerate parabolic equation arising in the theory of damage mechanics is shown to be well-posed. Its solutions blow up in finite time and, under suitable conditions on the initial configuration, the blow-up set, corresponding to the portion of the material which breaks at the blow-up time, is an interval of nonzero measure. In a special but physically relevant case the problem reduces to the study of the blow-up set of solutions of the quasilinear equation

Prediction of Forming Limit Diagram Based on Damage Coupled Kinematic-Isotropic Hardening Model Under Nonproportional Loading

2002 ◽  
Vol 124 (2) ◽  
pp. 259-265 ◽  
Author(s):  
C. L. Chow ◽  
X. J. Yang ◽  
E. Chu
Keyword(s):  
Damage Mechanics ◽  
Kinematic Hardening ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Isotropic Hardening ◽  
Strain History ◽  
Sheet Metals ◽  
Nonproportional Loading ◽  
Localized Necking ◽  
Theory Of Damage

Based on the theory of damage mechanics, an anisotropic damage coupled mixed isotropic-kinematic hardening plastic model for the prediction of forming limit diagram (FLD) is developed. The model includes the formulation of nonlinear anisotropic kinematic hardening. For the prediction of limit strains under nonproportional loading, a damage criterion for localized necking of sheet metals subjected to complex strain history is proposed. The model is employed to predict the FLDs of AL6111-T4 alloy. The predicted results agree well with those determined experimentally.

scholarly journals Advances in Cyclic Behavior and Lifetime Modeling of Tempered Martensitic Steels Based on Microstructural Considerations

2008 ◽  
Vol 378-379 ◽  
pp. 81-100 ◽  
Author(s):  
Vincent Velay ◽  
Denis Delagnes ◽  
Gérard Bernhart
Keyword(s):  
Damage Mechanics ◽  
Constitutive Models ◽  
Complex Loading ◽  
Continuum Damage Mechanics ◽  
Cyclic Behavior ◽  
Irreversible Processes ◽  
Martensitic Steels ◽  
Unified Approach ◽  
Strain Stress ◽  
Strain Mechanisms

Cyclic behavior and life prediction of two tempered martensitic steels (AISI H11 and L6) are investigated under thermo-mechanical loading conditions. Two non isothermal constitutive models developed in the same framework of the thermodynamics of irreversible processes are introduced. The first one, in relation with the tempering state, considers the fatigue-ageing phenomena whereas the second one is intended to take into account more complex loading paths. This last non unified approach allows to define different strain mechanisms which can be related to microstructural considerations. The strain-stress parameters provided by both approaches can be introduced into a lifetime model which is based on continuum damage mechanics.

A Study of Microdeformation and Creep-Fatigue Damage using Acoustic Emission Technique

1988 ◽  
Vol 142 ◽  
Author(s):  
Yunxu Liu ◽  
Xingren Li
Keyword(s):  
Plastic Deformation ◽  
Fatigue Damage ◽  
High Performance ◽  
Damage Mechanics ◽  
High Strength Steels ◽  
High Strength ◽  
Optical Microscope ◽  
Plastic Deformation Behavior ◽  
Creep Fatigue ◽  
Theory Of Damage

AbstractThis paper deals with the relationship between the plastic deformation damage and microstructure by means of Acoustic Emmission. The plastic deformation behavior of AISI 4340 steel of various microstructures was investigated in both the tensile and creep-fatigue testings with a view to providing new insights into properties of high performance steel. Based on Theory of Damage Mechanics, a creep-fatigue law was derived and formulated. The reason of early failure and the service life prophecy of high strength steels was studied.The damage micromechanism of four stages was studied by the optical microscope, scanning electron microscope, and microhardness tester. It seems that the nucleation and the growth of the voids at the martensiteferrite interface is the dominant mechanism of damage. The monitoring of Acoustic Emmission indicated that the plastic deformation did not appear in the circulating hardening stage. But in the circulating softening stage, the accumulation of the plastic deformation and the creep-fatigue damage become more and more severe. The total energy of Acoustic Emmission was successfully applied to measure the degree of the damage caused by the plastic deformation.

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