Modeling of Plasticity in Spectral Methods for Fatigue Damage Estimation of Narrowband Random Vibrations

2011 ◽  
Author(s):  
Herve Rognon ◽  
Tony Da Silva Botelho ◽  
Imad Tawfiq ◽  
Andre Galtier ◽  
Mohamed Bennebach
Keyword(s):  
Experimental Data ◽  
Fatigue Damage ◽  
Spectral Methods ◽  
High Cycle Fatigue ◽  
Damage Evaluation ◽  
Cycle Fatigue ◽  
Damage Estimation ◽  
Random Vibrations ◽  
Plastic Behaviour ◽  
Non Linear

In this paper, we present techniques for fatigue damage evaluation using spectral methods and a model taking into account elasto-plastic behaviour. The model is associated with a non linear fatigue law, covering the whole endurance domain (low cycle and high cycle fatigue). It uses Neuber’s method and is valid for limited plasticity. To validate this modeling, we perform a correlation between spectral methods, modified spectral methods and experimental data. We present here, the results obtained in the case of narrowband random vibrations.

High Cycle Fatigue Damage Evaluation of Steel Pipelines Based on Microhardness Changes During Cyclic Loads: Part II

2018 ◽  
Author(s):  
Geovana Drumond ◽  
Bianca Pinheiro ◽  
Ilson Pasqualino ◽  
Francine Roudet ◽  
Didier Chicot
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Steel Structures ◽  
New Method ◽  
Microplastic Deformation ◽  
Surface Phenomenon ◽  
Cyclic Loads ◽  
Cycle Fatigue ◽  
Indentation Tests

The hardness of a material shows its ability to resist to microplastic deformation caused by indentation or penetration and is closely related to the plastic slip capacity of the material. Therefore, it could be significant to study the resistance to microplastic deformations based on microhardness changes on the surface, and the associated accumulation of fatigue damage. The present work is part of a research study being carried out with the aim of proposing a new method based on microstructural changes, represented by a fatigue damage indicator, to predict fatigue life of steel structures submitted to cyclic loads, before macroscopic cracking. Here, Berkovich indentation tests were carried out in the samples previously submitted to high cycle fatigue (HCF) tests. It was observed that the major changes in the microhardness values occurred at the surface of the material below 3 μm of indentation depth, and around 20% of the fatigue life of the material, proving that microcracking is a surface phenomenon. So, the results obtained for the surface of the specimen and at the beginning of the fatigue life of the material will be considered in the proposal of a new method to estimate the fatigue life of metal structures.

Random Loads Fatigue: The Use of Spectral Methods Within Multibody Simulation

2005 ◽  
Author(s):  
Claudio Braccesi ◽  
Filippo Cianetti ◽  
Luca Landi
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Dynamic Simulation ◽  
Fatigue Damage ◽  
Spectral Methods ◽  
Mechanical Systems ◽  
Frequency Domain Method ◽  
Stress And Strain ◽  
Damage Evaluation ◽  
Multibody Dynamic

The evaluation of the fatigue damage performed by using the Power Spectral Density function (PSD) of stress and strain state is proving to be extremely accurate for a family of random processes characterized by the property of being stationary. The present work’s original contribution is the definition of a methodology which extracts stress and strain PSD matrices from components modelled using a modal approach (starting from a finite element modelling and analysis) within mechanical systems modelled using multibody dynamic simulation and subject to a generic random load (i.e. multiple-input, with partially correlated inputs). This capability extends the actual stress evaluation scenario (principally characterised by the use of finite element analysis approach) to the multibody dynamic simulation environment, more powerful and useful to simulate complex mechanical systems (i.e. railway, automotive, aircraft and aerospace systems). As regards the fatigue damage evaluation, a synthesis approach to evaluate an equivalent stress state expressed in terms of the PSD function of Preumont’s “equivalent von Mises stress (EVMS)”, starting from the complete stress state representation expressed in terms of PSD stress matrix and easily usable in the consolidated spectral methods, is proposed. This approach allows and has allowed the use of the above methods such as the Dirlik formula as a damage evaluation method. An additional result is the conception and implementation of a frequency domain method for the component’s most probable state of stress, allowing quickly identification of the most stressed and damageble locations. The described methodologies were developed and embedded into commercial simulation codes and verified by using as a test case a simple reference multibody model with a simple flexible component.

The Influence of Microstructure Heterogeneities on the Very High Cycle Fatigue Behavior of Duplex Stainless Steel

2016 ◽  
Vol 258 ◽  
pp. 255-258
Author(s):  
Ulrich Krupp ◽  
Marcus Söker ◽  
Tina Waurischk ◽  
Alexander Giertler ◽  
Benjamin Dönges ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Ion Beam ◽  
Cyclic Plasticity ◽  
Cycle Fatigue ◽  
Heterogeneous Distribution ◽  
Very High Cycle Fatigue ◽  
Structural Applications ◽  
Very High

As being used for structural applications, where a high corrosion resistance is required, the fatigue behavior of duplex stainless steels (DSS) is governed by the partition of cyclic plasticity to the two phases, ferrite and austenite, respectively. Under very high cycle fatigue (VHCF) loading conditions, the heterogeneous distribution of crystallographic misorientations between neighboring grains and phases yields to a pronounced scatter in fatigue life, ranging from 1 million to 1 billion cycles for nearly the same stress amplitude. In addition, the relevant damage mechanisms depend strongly on the atmosphere. Stress corrosion cracking in NaCl-containing atmosphere causes a pronounced decrease in the VHCF life. By means of ultrasonic fatigue testing at 20kHz in combination with high resolution scanning electron microscopy, electron back-scattered diffraction (EBSD), focused ion beam milling (FIB) and synchrotron tomography, the microstructure heterogeneities were quantified and correlated with local fatigue damage. It has been shown that the fatigue process is rather complex, involving redistribution of residual stresses and three-dimensional barrier effects of the various interfaces. The application of a 2D/3D finite element model allows a qualitative prediction of the fatigue-damage process in DSS that is controlled by stochastic local microstructure arrangements.

scholarly journals Topology optimization for transversely isotropic materials with high-cycle fatigue as a constraint

2020 ◽  
Vol 63 (1) ◽  
pp. 161-172
Author(s):  
Shyam Suresh ◽  
Stefan B. Lindström ◽  
Carl-Johan Thore ◽  
Anders Klarbring
Keyword(s):  
Topology Optimization ◽  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Transverse Isotropy ◽  
Transversely Isotropic ◽  
Back Stress ◽  
Optimization Method ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Time Model

AbstractWe propose a topology optimization method for design of transversely isotropic elastic continua subject to high-cycle fatigue. The method is applicable to design of additive manufactured components, where transverse isotropy is often manifested in the form of a lower Young’s modulus but a higher fatigue strength in the build direction. The fatigue constraint is based on a continuous-time model in the form of ordinary differential equations governing the time evolution of fatigue damage at each point in the design domain. Such evolution occurs when the stress state lies outside a so-called endurance surface that moves in stress space depending on the current stress and a back-stress tensor. Pointwise bounds on the fatigue damage are approximated using a smooth aggregation function, and the fatigue sensitivities are determined by the adjoint method. Several problems where the objective is to minimize mass are solved numerically. The problems involve non-periodic proportional and non-proportional load histories. Two alloy steels, AISI-SAE 4340 and 34CrMo6, are treated and the respective as well as the combined impact of transversely isotropic elastic and fatigue properties on the design are compared.

Generalization of Spectral Methods for High-Cycle Fatigue Analysis to Accommodate Non-Stationary Random Processes

2019 ◽  
Author(s):  
Mohamed Khalil ◽  
Roland Wüchner ◽  
Kai-Uwe Bletzinger
Keyword(s):  
Sensitivity Analysis ◽  
Fatigue Life ◽  
Spectral Methods ◽  
High Cycle Fatigue ◽  
Random Processes ◽  
Stationary Processes ◽  
Cycle Fatigue ◽  
Material Fatigue ◽  
Frequency Domains ◽  
Stationary Random Processes

Abstract Estimation of material fatigue life is an essential task in many engineering fields. When non-proportional loads are applied, the methodology to estimate fatigue life grows in complexity. Many methods have been proposed to solve this problem both in time and frequency domains. The former tends to give more accurate results, while the latter seems to be more computationally favorable. Until now, the focus of frequency-based methods has been limited to signals assumed to follow a stationary statistic process. This work proposes a generalization to the existing methods to accommodate non-stationary processes as well. A sensitivity analysis is conducted on the influence of the formulation’s hyper-parameters, followed by a numerical investigation on different signals and various materials to assert the robustness of the method.

A Perspective on Fatigue Damage by Decoupling LCF and HCF Loads in a Type 316LN Stainless Steel

2015 ◽  
Vol 34 (5) ◽  
Author(s):  
Aritra Sarkar ◽  
A. Nagesha ◽  
R. Sandhya ◽  
M.D. Mathew
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Fatigue Damage ◽  
Strain Amplitude ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Applied Strain ◽  
Cycle Fatigue ◽  
316Ln Stainless Steel ◽  
Type 316Ln Stainless Steel

AbstractPrior low cycle fatigue (LCF) deformation in a 316LN austenitic stainless steel reduced the remnant high cycle fatigue (HCF) life as a function of the amount of LCF exposure and the applied strain amplitude. A critical LCF pre-damage was found necessary for an effective LCF-HCF interaction to take place.

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