A Damage Model for Low Cycle Fatigue Analysis of Stiffened Plates

2014 ◽  
Vol 496-500 ◽  
pp. 561-566
Author(s):  
Qin Dong ◽  
Ping Yang ◽  
Jun Lin Deng ◽  
Hong Wang
Keyword(s):  
Cyclic Loading ◽  
Plastic Strain ◽  
Fatigue Damage ◽  
Damage Mechanics ◽  
Integral Transformation ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Stiffened Plates ◽  
Cycle Fatigue ◽  
Cyclic Loading Condition

A low-cycle fatigue damage model for stiffened plates has been derived based on the theory of damage mechanics. The fatigue damage variable equation of the stiffened plate under cyclic loading was introduced into the accumulative plastic strain equation. Then by means of integral transformation, the evolution equation of axial plastic strain was derived under low cyclic loading condition. The analysis results by the presented model compare well with those by the finite element method.

Effect of Low Cycle Fatigue Damage on Ultimate Strength of Aged Ship Structures

2011 ◽  
Author(s):  
Yu Tian ◽  
Zhuo-shang Ji
Keyword(s):  
Ultimate Strength ◽  
Fatigue Damage ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Simple Procedure ◽  
Damage Model ◽  
Continuum Damage Mechanics ◽  
Strength Reduction ◽  
Cycle Fatigue ◽  
Theoretical Results

The main objective of this paper is to study the effects of general low cycle fatigue (LCF) damage on ultimate strength of unstiffened ship plates under uniaxial compression. A nonlinear LCF damage model has been derived on basis of continuum damage mechanics (CDM) coupled with plastic mechanics in order to define the deterioration of materials. The theoretical results show that the damage variable D can be measured by a simple procedure and it can be related to the mechanical property of material directly. Formulae predicting ultimate strength reduction have been proposed based on amended Faulkner’s simple and useful expression. Nonlinear finite element analyses (FEA) of panels with various material damages have been carried out. The results indicate that the deterioration of materials is important factors determining the amount of strength reduction. It was also found that the proposed formulae can accurately predict the residual ultimate strength of unstiffened plate with general fatigue damage.

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.

Damage in Adhesive Joints During Low Cycle Fatigue

2010 ◽  
Author(s):  
Iva´n C. Ca´bulo-Pe´rez ◽  
Juan P. Casas-Rodri´guez
Keyword(s):  
Plastic Strain ◽  
Low Cycle Fatigue ◽  
Stress Test ◽  
Damage Model ◽  
Fatigue Tests ◽  
Constant Stress ◽  
Cycle Fatigue ◽  
Damage Behavior ◽  
Non Linear ◽  
Compressive Loads

The objective of this research is to study the damage behavior of bulk adhesive and single lap joint (SLJ) specimens during low cycle fatigue (LCF). Fatigue tests under constant stress amplitude were done and strain response was measured through cycles to failure using the bulk adhesive and SLJ data. A non linear damage model was used to fit experimental results. Identification of the damage parameters for bulk adhesive was obtained from the damage against accumulated plastic strain plot. It is shown that the plastic strain can be obtained from the constant stress test if the instantaneous elastic modulus, i.e. modulus affected by damage, is evaluated for each cycle. On the other hand, damage in SLJ was seen mainly in the adhesive for itself — no substrate failure — this fact is used to propose that fatigue response in the joint is due to continuum damage accumulation in the adhesive as the number of cycles increases. Damage behavior under compressive loads was not taken into account but good correlation of numerical and experimental data was obtained. It was found that damage evolution behaves in a non linear manner as the plastic deformation grows for each cycle: on fatigue onset an accelerated damage grow is observed, then a proportional evolution, and finally a rapid failure occurs; this characteristics were seen in both the SLJ and bulk adhesive specimen. So far, this research takes the damage model found in a standard adhesive specimen and assumes it is accurate enough to represent the damage behavior of the SLJ configuration.

scholarly journals Extremely-Low-Cycle Fatigue Damage for Beam-to-Column Welded Joints Using Structural Details

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1768
Author(s):  
Lizhen Huang ◽  
Weilian Qu ◽  
Ernian Zhao
Keyword(s):  
Fatigue Damage ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Multiaxial Fatigue ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Butt Weld ◽  
Damage Models ◽  
Structural Details

The multiaxial fatigue critical plane method can be used to evaluate the extremely-low-cycle fatigue (ELCF) damage of beam-to-column welded joints in steel frameworks subjected to strong seismic activity. In this paper, fatigue damage models using structural detail parameters are studied. Firstly, the fatigue properties obtained from experiments are adopted to assess ELCF life for steel frameworks. In these experiments, two types of welded specimens, namely, plate butt weld (PB) and cruciform load-carrying groove weld (CLG), are designed according to the structural details of steel beam and box column joints, in which both structural details and welded factors are taken into account. Secondly, experiments are performed on three full-scale steel welded beam-to-column joints to determine the contribution of stress and/or strain to damage parameters. Finally, we introduce a modification of the most popular fatigue damage model of Fatemi and Socie (FS), modified by us in a previous study, for damage evaluation, and compare this with Shang and Wang (SW) in order to examine the applicability of the fatigue properties of PB and CLG. This study shows that the modified FS model using the fatigue properties of CLG can predict the crack initiation life and evaluate the damage of beam-to-column welded joints, and can be subsequently used for further investigation of the damage evolution law.

Advanced Models for Fatigue Life Estimation of Combustor Components for Gas Turbine Application

2019 ◽  
Author(s):  
Dileep Sivarama Iyer ◽  
Nikhil Chandran Pillai
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Multiaxial Fatigue ◽  
Universal Method ◽  
Cycle Fatigue ◽  
Operating Cycle ◽  
Experimental Values

Abstract Modern day combustors operate at very high temperatures which are close to combustor material softening temperatures. At the same time, to meet stringent emission legislations there is a strong drive to improve upon the rich burn combustor technology or shift to advanced lean burn combustor technologies. One of the key driver to improve emission is to save the cooling air budget and use the saved air for primary combustion but this approach would require more advanced and efficient cooling techniques. Fan shaped effusion cooling technology is a very promising technique as it offers high film cooling effectiveness. However, complex cooling features associated with this technology can lead to higher stress concertation and localized triaxial stress state. This stressstrain field in combination with a typical gas turbine engine operating cycle makes such effusion holes highly vulnerable to the thermo-mechanical fatigue failure. Hence to ensure the safety and reliability of combustor liners with such innovative features, it is essential to have thorough understanding of the stress-strain field in the vicinity and accurate prediction of life to first crack. The biggest challenge the designers and engineers face while predicting the initiation life of a structure is selecting the appropriate fatigue damage model for an application. This is due to following reasons: (a) The scatter in fatigue life predicted using different models and experimental values are very huge (b) There is no general universal method which can predict the multiaxial fatigue life accurately for all the materials and loading conditions (c) No general consensus exits among the researchers on which model have to be used for a particular application, material, loading and geometry (d) Application level studies are seldom available on this subject, most of the studies are restricted to laboratory level specimens with very limited implications to industry. Ideally, the fatigue damage model which has to be used for a particular application has to be validated through experiments. To meet this objective, several test specimens featuring novel fan shaped hole geometries were mass-produced using state of the art laser drilling technology. All these specimens were subjected to strain controlled isothermal low cycle fatigue test and the cycles to crack initiation was monitored using potential drop method. Six different multiaxial fatigue damage models (which can be used in low cycle fatigue regime) viz. Walker model, Smith Watson and Topper model (SWT), Fatemi Socie model (FS), Wang and Brown model (WB), Shang model (SW) and Xu model were selected and the life estimated by these models were compared with the experimental values. From the study it is observed that Xu model in which the damage parameter is built using the concept of shear strain energy looks most promising for this application.

Identification and Validation of a Low Cycle Fatigue Damage Model for Al 7075-T6 Alloy

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Saeed Masih ◽  
Mohammad Mashayekhi ◽  
Noushin Torabian
Keyword(s):  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Fatigue Crack Initiation ◽  
Life Time ◽  
Continuum Damage Mechanics ◽  
Material Behavior ◽  
Cycle Fatigue ◽  
Explicit Finite Element ◽  
Al 7075

In this paper, the behavior of 7075-T6 aluminum alloy under low cycle fatigue (LCF) loading is experimentally and numerically investigated using continuum damage mechanics (CDM). An experimental procedure is established to identify the damage parameters for Al 7075-T6. A damage-coupled explicit finite element code is developed using the experimentally extracted damage parameters to study the material behavior under LCF loading. Moreover, fractographic examinations are conducted to identify the fatigue crack initiation locations and propagation mechanisms. The model is employed for life-time assessment of stringer-skin connection of a fuselage and the results are compared with the data available in the literature.

Crack Initiation Life Model of Stiffened Plates Based on Damage Mechanics

2014 ◽  
Vol 904 ◽  
pp. 508-512
Author(s):  
Hong Wang ◽  
Ping Yang ◽  
Jun Lin Deng ◽  
Qin Dong
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Plastic Strain ◽  
Fatigue Damage ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Stiffened Plate ◽  
Crack Initiation Life

Based on the continuum damage mechanics theory, according to the development of the fatigue damage evolution equation, and combining the interaction coefficient of stiffener and plate, with plastic strain as the control quantity of damage evolution, the stiffened plate low cycle fatigue damage mechanics model is established, and the calculation method of the fatigue crack initiation life is obtained. This method for the initiation life of fatigue crack is divided into the life before the damage and the life of the damage evolution. The model results are compared with those of the finite element results. Conclusions show that the model can reflect the regularity of axial plastic strain evolution of stiffened plate, and can be directly used for fatigue loads analysis under the mechanism of initiation life.

Low Cycle Fatigue Study for GH901 Material Based on Damage Mechanics Theory

2014 ◽  
Vol 711 ◽  
pp. 40-43 ◽  
Author(s):  
Yong Qi Wang ◽  
Hai Bing Zhang
Keyword(s):  
Fatigue Damage ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Continuum Damage Mechanics ◽  
Practical Method ◽  
Test Results ◽  
Cycle Fatigue ◽  
Mechanics Model

The low cycle fatigue damage of turbine disc which is made of GH901 material is systematic analyzed and studied in the article that is based on the theory of continuum damage mechanics and fatigue testing, we improved the common Lemaitre’s low cycle fatigue damage mechanics model, the damage evolution law that the model describes is in good agreement with the test results throughout the course of the fatigue damage. The simplified analysis method for low cycle fatigue damage evolution and life prediction is proposed based on the GH901 low cycle damage features, the practical method of getting damaged material’s constants by existing data is proposed as well.

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