scholarly journals Strain based approach in fatigue damage modeling of brittle material-application to concrete

2019 ◽  
Vol 2 (1) ◽  
pp. 49-60
Author(s):  
Indra Narayan Yadav
Keyword(s):  
Fatigue Damage ◽  
Brittle Material ◽  
Inelastic Deformation ◽  
Damage Mechanics ◽  
Fatigue Loading ◽  
Biaxial Stress ◽  
Stiffness Degradation ◽  
Experimental Result ◽  
Variable Theory ◽  
Strain Space

Due to very good compressive strength of concrete, it is used widely in all over the world during three decades. The Formulation of Concrete is through combination of Cement, stone aggregate, sand and water according to their design mix based on the ultimate strength required for the structural component. The Mixing of concrete is as mortar, the layer of cement, sand and water is wrapped around the aggregate. When the load is applied to the concrete, the weaker zone i.e. mortar of cement, sand is weaker than stone aggregate, damage by formulation of crack before crack in aggregate. The Damage behavior of Concrete is thus to be analyzed according to their fatigue behavior. Strain Based approach in Fatigue Damage Modelling of Brittle Material in Concrete is presented to describe the behavior and failure of con-crete by utilizing Damage Mechanics approach. Stiffness degradation and inelastic deformation are the essential features of concrete that develop due tothe formation of multitude of microcracks in the fatigue environment. Microcracking, which is anisotropic in nature, destroys the bond between material grains, and affects the elastic properties resulting in the reduction of material stiffness in elastic as well as plastic stage. This paper presents an anisotropic fatigue damage model for plain concrete subjected to cyclic tension. The model is developed, in strain space, using the general framework of internal variable theory of continuum thermodynamics and Damage Mechanics. It is argued that within the damage surface of given strain states the unloadingreloading cycles (fatigue loading) stimulate the nucleation and growth microcracks in concrete, which will result in stiffness degradation and inelastic deformation, and hence material is termed as damaged. Damage is reflected through the fourthorder stiffness tensor involving a damage parameter whose increment is governed by the consistency equation associated with a cycle dependent damage surface in strain space. The model is capable of predicting stiffness degradation, inelastic deformation and strength reduction under fatigue loading and compared against experimental result. By increasing the number of loading cycles, the strength of concrete gradually decreases and the limit surface is allowed to contract and form new curves representing residual strengths. The magnitude of loading, load range, and the load path are known to influence the fatigue life and hence are addressed in this formulation. In this paper, a strength softening function is proposed in order to address the re-duction in the strength of concrete due to fatigue. Separate softening functions are also proposed to account for the deformation characteristics in concrete under cyclic loading. Numerical simula-tions predicted by the model in both uniaxial and biaxial stress paths show a good correlation with the experimental data available in the literature.

scholarly journals Analysis of Fatigue Strain, Fatigue Modulus and Fatigue Damage for the Model formulation of Concrete based on Strain Life Approach

2019 ◽  
Author(s):  
Indra Yadav ◽  
Kamal Bahadur Thapa
Keyword(s):  
Fatigue Damage ◽  
Residual Strain ◽  
Inelastic Deformation ◽  
Evaluation Model ◽  
Strain Curve ◽  
Fatigue Loading ◽  
Vital Role ◽  
Evolution Model ◽  
Stiffness Degradation ◽  
The Impact

Analysis of Fatigue Strain, Fatigue Modulus and Fatigue Damage for the modeling of concrete plays a vital role in the evolution material behaviour which is heterogeneous and anisotropic in nature. In this paper, the Level-S nonlinear fatigue strain curve, fatigue modulus curve, residual strain curve of concrete in compression, tension, flexure and torsional fatigue loading were proposed using strain life approach. The parameters such as physical meaning, the ranges, and the impact on the shape of the curve were discussed. Then, the evolution model of fatigue modulus was established based on the fatigue strain evolution model, fatigue modulus evaluation model, residual strain evaluation model, secondary strain evaluation model. The hypothesis of fatigue modulus is inversely related with the fatigue strain amplitude. The fatigue evolution of concrete damages the bond between material grains, changed the orientation of structure of molecules and affects the elastic properties resulting in the reduction of material stiffness and modulus by utilizing strain life analysis, regarding stiffness degradation and inelastic deformation by formation of microcracking, macro cracking, cracking which is heterogeneous and anisotropic in nature . This paper presents the Fatigue Strain Life Model and analyses of fatigue strain, fatigue modulus and damage parameters of concrete which is capable of predicting stiffness degradation, inelastic deformation, strength reduction under fatigue loading. Hence, the obtainable results were compared with experimental results for the validation of the proposed model.

NUMERICAL PREDICTION OF STIFFNESS DEGRADATION OF THIN-PLY CFRP LAMINATES UNDER FATIGUE LOADING

2021 ◽  
Author(s):  
RYOMA AOKI ◽  
RYO HIGUCHI ◽  
TOMOHIRO YOKOZEKI
Keyword(s):  
Composite Laminates ◽  
Damage Mechanics ◽  
Crack Density ◽  
Continuum Damage Mechanics ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Cfrp Laminates ◽  
Mechanics Model ◽  
Element Simulation ◽  
Proposed Model

This study aims to conduct a fatigue simulation for predicting the stiffness degradation of thin-ply composite laminates with several ply thicknesses. For the simulation, a fatigue evolution model of intra-laminar damage in thin-ply composite laminates considering the effect of ply thickness was proposed. The intra-laminar damage evolution was modeled using the continuum damage mechanics model and the static and fatigue evolution law were formulated by relating the transverse crack density to the damage variable. The finite element simulation using the proposed model was conducted to predict the stiffness degradation of the laminates as a function of the number of loading cycles. The simulation results show that the experimental data can be reproduced by using the proposed fatigue model.

scholarly journals Progressive failure mechanism of laminated composites under fatigue loading

2020 ◽  
Vol 55 (1) ◽  
pp. 137-144
Author(s):  
Ghalib R Ibrahim ◽  
A Albarbar ◽  
Khaldoon F Brethee
Keyword(s):  
Experimental Data ◽  
Fatigue Damage ◽  
Damage Mechanics ◽  
Cohesive Zone Model ◽  
Laminated Composites ◽  
Progressive Failure ◽  
Damage Model ◽  
Fatigue Loading ◽  
Zone Model ◽  
Lap Joint

A cohesive zone model for delamination propagation in laminated composites under static and fatigue loading has been derived and validated with experimental data under different mode conditions. This study presents a new approach to quantify fatigue delamination degradation based on damage mechanics to evaluate the rate of fatigue damage ([Formula: see text]). The static damage evaluation and fatigue damage degradation are derived from damage surface concept. Both static and fatigue damage linked each other to establish fatigue crack growth formula in the laminated composites. A user-defined subroutine, UMAT, has been employed to develop and implement a damage model in ABAQUS. Two different specimens; a double cantilever beam and a single lap joint were used to investigate the effectiveness of the new method. The simulation results revealed that the developed model had good agreement with experimental data available in literature.

scholarly journals Low-Cycle Fatigue Crack Initiation Simulation and Life Prediction of Powder Superalloy Considering Inclusion-Matrix Interface Debonding

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4018
Author(s):  
Shuming Zhang ◽  
Yuanming Xu ◽  
Hao Fu ◽  
Yaowei Wen ◽  
Yibing Wang ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Fatigue Loading ◽  
Interface Debonding ◽  
Damage Evolution Equation ◽  
Finite Element Software

From the perspective of damage mechanics, the damage parameters were introduced as the characterizing quantity of the decrease in the mechanical properties of powder superalloy material FGH96 under fatigue loading. By deriving a damage evolution equation, a fatigue life prediction model of powder superalloy containing inclusions was constructed based on damage mechanics. The specimens containing elliptical subsurface inclusions and semielliptical surface inclusions were considered. The CONTA172 and TARGE169 elements of finite element software (ANSYS) were used to simulate the interfacial debonding between the inclusions and matrix, and the interface crack initiation life was calculated. Through finite element modeling, the stress field evolution during the interface debonding was traced by simulation. Finally, the effect of the position and shape size of inclusions on interface debonding was explored.

Study on the stiffness degradation in concrete continuous beam with externally prestressed CFRP tendons under fatigue loading

2021 ◽  
pp. 136943322199249
Author(s):  
Xing Li ◽  
Jiwen Zhang ◽  
Jun Cheng
Keyword(s):  
Fatigue Life ◽  
Fatigue Loading ◽  
Load Level ◽  
Fiber Reinforced Polymer ◽  
Stiffness Degradation ◽  
Test Results ◽  
Reinforced Polymer ◽  
Continuous Beams ◽  
Practical Engineering ◽  
Good Agreement

This paper presents fatigue behaviors and the stiffness degradation law of concrete continuous beams with external prestressed carbon fiber-reinforced polymer (CFRP) tendons. Three specimens were tested under fatigue loading, and the influence of different load levels on the stiffness degradation and fatigue life were studied, and it was found that the stiffness degradation of three test specimens exhibited a three-stage change rule, namely rapid decrease, stable degradation, and sharp decline, but there are obvious differences in the rate and amplitude of stiffness degradation. The load level has a significant influence on the fatigue life of the test specimens. An analytical model with load level considered was proposed to calculate the residual stiffness and predict the stiffness degradation, which is in good agreement with the test results. The model of stiffness degradation presents a possible solution for practical engineering applications of concrete continuous beams with externally prestressed CFRP tendons subjected to different fatigue loadings.

A Multi-Level Low Cycle Fatigue Damage Model for Forging Die Material

2006 ◽  
Vol 514-516 ◽  
pp. 804-809
Author(s):  
S. Gao ◽  
Ewald Werner
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Fatigue Loading ◽  
Cycle Fatigue ◽  
Die Material ◽  
Multi Level ◽  
Loading Sequence ◽  
Forging Die

The forging die material, a high strength steel designated W513 is considered in this paper. A fatigue damage model, based on thermodynamics and continuum damage mechanics, is constructed in which both the previous damage and the loading sequence are considered. The unknown material parameters in the model are identified from low cycle fatigue tests. Damage evolution under multi-level fatigue loading is investigated. The results show that the fatigue life is closely related to the loading sequence. The fatigue life of the materials with low fatigue loading first followed by high fatigue loading is longer than that for the reversed loading sequence.

Learnings From Strain Measurements on an In-Field Conductor and Wellhead System

2018 ◽  
Author(s):  
Rohit Shankaran ◽  
Alexander Rimmer ◽  
Alan Haig
Keyword(s):  
Fatigue Damage ◽  
Strain Gauge ◽  
Transfer Functions ◽  
Fatigue Loading ◽  
Accurate Method ◽  
Environmental Data ◽  
Analytical Methodology ◽  
Data Set ◽  
Soil Model ◽  
Drilling Operations

In recent years due to use of drilling risers with larger and heavier BOP/LMRP stacks, fatigue loading on subsea wellheads has increased, which poses potential restrictions on the duration of drilling operations. In order to track wellhead and conductor fatigue capacity consumption to support safe drilling operations a range of methods have been applied: • Analytical riser model and measured environmental data; • BOP motion measurement and transfer functions; • Strain gauge data. Strain gauge monitoring is considered the most accurate method for measuring fatigue capacity consumption. To compare the three approaches and establish recommendations for an optimal approach and method to establish fatigue accumulation of the wellhead, a monitoring data set is obtained on a well offshore West of Shetland. This paper presents an analysis of measured strain, motions and analytical predictions with the objective of better understanding the accuracy, limitations, or conservatism in each of the three methods defined above. Of the various parameters that affect the accuracy of the fatigue damage estimates, the paper identifies that the selection of analytical conductor-soil model is critical to narrowing the gap between fatigue life predictions from the different approaches. The work presented here presents the influence of alternative approaches to model conductor-soil interaction than the traditionally used API soil model. Overall, the paper presents the monitoring equipment and analytical methodology to advance the accuracy of wellhead fatigue damage measurements.

A Nonlinear Damage Model of Hardening-Softening Materials

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
M. Ganjiani
Keyword(s):  
Damage Mechanics ◽  
Damage Model ◽  
Continuum Damage Mechanics ◽  
Tensile Tests ◽  
Internal Variable ◽  
Integration Algorithm ◽  
Finite Element Program ◽  
Variable Theory ◽  
Numerical Predictions ◽  
Type Variable

In this paper, an elastoplastic-damage constitutive model is presented. The formulation is cast within the framework of continuum damage mechanics (CDM) by means of the internal variable theory of thermodynamics. The damage is assumed as a tensor type variable and its evolution is developed based on the energy equivalence hypothesis. In order to discriminate the plastic and damage deformation, two surfaces named as plastic and damage are introduced. The damage surface has been developed so that it can model the nonlinear variation of damage. The details of the model besides its implicit integration algorithm are presented. The model is implemented as a user-defined subroutine user-defined material (UMAT) in the abaqus/standard finite element program for numerical simulation purposes. In the regard of investigating the capability of model, the shear and tensile tests are experimentally conducted, and corresponding results are compared with those predicted numerically. These comparisons are also accomplished for several experiments available in the literature. Satisfactory agreement between experiments and numerical predictions provided by the model implies the capability of the model to predict the plastic deformation as well as damage evolution in the materials.

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