Search Results for fatigue modeling

The purposes and methods of fatigue modeling and simulation in high-cycle fatigue (HCF) regime are to design either failsafe components or components with a finite life and to quantify remaining life of components with pre-existing cracks using fracture mechanics, with the intent of monitoring via an inspection scheme. This article begins with a discussion on the stages of the fatigue damage process. It describes hierarchical multistage fatigue modeling and several key points regarding the physics of crack nucleation and microstructurally small crack propagation in the HCF regime. The article provides a description of the microstructure-sensitive modeling to model fatigue of several classes of advanced engineering alloys. It describes the various modeling and design processes designed against fatigue crack initiation. The article concludes with a discussion on the challenges in microstructure-sensitive fatigue modeling.

The overarching goal of life-prediction research is to develop models for the various types of time dependencies in the crack-tip damage accumulation that occur in materials subjected to elevated temperatures. This article focuses on describing the models based on creep, oxidation kinetics, evolution of crack-tip stress fields due to creep, oxygen ingress, and change in the microstructure. It also provides a summary of creep-fatigue modeling approaches.

Understanding fatigue crack growth is critical for the safe operation of many structural components. This article reviews the standard fracture mechanics and methods to determine the crack growth rate for a material and loading condition experimentally. It also addresses the two most important aspects of crack-growth modeling: loading environment and crack geometry.

In the design of composite structures for durability and damage tolerance, the primary concerns are out-of-plane failures, such as delamination, material degradation associated with environment, stability under compression loading, large degree of scatter in fatigue life, and bearing failure of joints. This article presents an introductory discussion on the fatigue damage process, methodologies assessing fatigue behavior, and life prediction models. It describes the damage mechanisms introduced for a quasi-isotropic laminate under tension-compression fatigue loading. Delamination is a critical issue in fatigue and generally results from high interlaminar normal and shear stresses. The article schematically illustrates the structural elements in which high interlaminar stresses are common. It concludes with a discussion on the classification of fatigue models such as mechanistic or phenomenological, for composite materials under cyclic loading.

Corrosion modeling is an essential benchmarking element for the selection and life prediction associated with the introduction of new materials or processes. These models are most naturally expressed in terms of differential equations or in other nonexplicit forms of mathematics. This article discusses the principles and applications of various models developed for understanding the corrosion mechanism. These models include mechanistic models, including Pourbaix model, thermophysical module, electrochemical module, and ion association model; risk-based models; and knowledge models. The risk-based model and knowledge models are illustrated with examples for better understanding. The article also describes boundary-element modeling and pitting corrosion fatigue models.

Failure of structural polymeric materials under cyclic application of stress or strain is a subject of industrial importance. The understanding of fatigue mechanisms (damage) and the development of constitutive equations for damage evolution, leading to crack initiation and propagation as a function of loading or displacement history, represent a fundamental problem for scientists and engineers. This article describes the approaches to predict fatigue life and discusses the difference between thermal and mechanical fatigue failure of polymers.

Fretting is a special wear process that occurs at the contact area between two materials under load and subject to slight relative movement by vibration or some other force. During fretting fatigue, cracks can initiate at very low stresses, well below the fatigue limit of nonfretted specimens. This article describes the mechanisms of fretting and fretting fatigue; stress analysis, modeling, and prediction of fretting fatigue; fretting fatigue testing; and fretting prevention methods. Three general geometries and loading conditions for fretting fatigue, along with their remedies, are reviewed.

Integrated computational materials engineering refers to the use of computer simulations that integrate mathematical models of complex metallurgical processes with computer models used in component and process design. This article outlines an example of a computer-aided engineering tool, such as virtual aluminum castings (VAC), developed and implemented for quickly developing durable cast aluminum power train components. It describes the procedures for the model development of the VAC system. These procedures include linking the manufacturing process to microstructure, linking microstructures to mechanical properties, linking material properties to performance prediction, and model validation and integration into the engineering process. The article discusses the benefits of the VAC system in process selection, process optimization, and improving the component design criteria.

There are two parts to deal with uncertainty in fatigue design: determining the distributions of possible values for all uncertain inputs and calculating the probability of failure due to all the uncertain inputs. This article discusses the sources of uncertainty in a fatigue analysis, such as the material properties, distribution of applied stress levels within a given environment, environments or loading intensities, and modeling or prediction. It presents a probabilistic approach for analyzing the uncertainties and determining the level of reliability (probability of failure).