Search Results for variable-amplitude load

This article summarizes fatigue phenomena in metallic materials. It discusses fatigue under variable-amplitude (VA) loading, with emphasis on crack growth. The article presents the prediction models of crack initiation and crack growth under VA loading. It concludes with a discussion on the conditions associated with engineering applications of VA loading.

Damage tolerance analysis consists of three parts such as the calculation of the residual strength diagram to obtain the permissible crack size, calculation of the crack growth curve, and calculation of the inspection interval. This article discusses the aspects of obtaining material property data and geometry factors to analyze any fracture or crack growth problem. It describes the integration of crack growth rates in terms of constant-amplitude loading and cycle-by-cycle counting with variable-amplitude loading. The article concludes with information on the classification of sources of error in damage tolerance analysis.

This article discusses two major approaches in estimating fatigue life from the viewpoint of their use as engineering methods. These include the stress-based (S-N curve) approach and strain-based approach. The stress-based and strain-based approaches are compared, with some comments on their manner of use and limitations. The use of the Palmgren-Miner rule for life prediction for variable amplitude loading is also discussed.

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. This article focuses on measures to avoid or minimize crack initiation and fretting fatigue. It lists the factors that are known to influence the severity of fretting and discusses the variables that contribute to shear stresses. These variables include normal load, relative displacement (slip amplitude), and coefficient of friction. The article describes the general geometries and loading conditions for fretting fatigue. It presents the types of fretting fatigue tests and the effect of variables on fretting fatigue from different research test programs. The article also lists the general principles and practical methods for the abatement or elimination of fretting fatigue.

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).

Fatigue properties are an integral part of materials comparison activities and offer information for structural life estimation in many engineering applications. This article presents three general approaches to fatigue design, with a discussion on their respective attributes. These include infinite-life criterion, finite-life criterion, and damage tolerant criterion. The article describes the individual property requirements of these approaches. It also presents selected examples of properties that reflect some detail of these approaches.

This article reviews the general characteristics of fretting wear in mechanical components with an emphasis on steel. It focuses on the effects of physical variables and the environment on fretting wear. The variables include the amplitude of slip, normal load, frequency of vibration, type of contact and vibration, impact fretting, surface finish, and residual stresses. The form, composition, and role of the debris are briefly discussed. The article also describes the measurement, mechanism, and prevention of fretting wear. It concludes with several examples of failures related to fretting wear.

Fatigue crack growth rate testing and data analysis are performed to characterize the crack propagation resistance of material environment combinations in order to predict crack growth life under anticipated stress histories. This article presents analyses performed on the numerical output of crack growth rate tests, including the analysis framework for modeling fatigue crack growth rate data. It describes the numerical methods for calculating da/dN as a function of stress intensity factor. The article discusses the principles in fatigue crack growth damage analysis.

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.

This article describes the effects of cyclic fatigue properties on aluminum alloys. It provides a discussion on strain-control fatigue and the effects of two microstructural features on the strain life of aluminum alloys: shearable precipitates and precipitate-free zones. The article discusses various models of fatigue crack growth (FCG) and the effects of alloy microstructure and composition on FCG.

This article summarizes the general fatigue and fracture properties of cast steels, namely, toughness, fatigue, and component design factors such as section size and discontinuities. It describes the various factors that influence fatigue of cast steels. These factors include section size, defect size, stress modes, and waveform types. The article discusses various fracture mechanics in cast steels: cyclic stress-strain behavior and low- and high-cycle fatigue life behavior; plane-stress fracture toughness; plane-strain fracture toughness; constant-amplitude fatigue crack initiation and growth; and variable-amplitude fatigue crack initiation and growth.