Material properties fatigue

Table 27.5 Properties of body-panel materials toughness, fatigue and creep...

Throne has reported that the relationship between foam modulus and density can be generalised to other properties such as tensile strength, fatigue strength, creep properties as well as shear and compression modulus. Thus if X is the general material property then... 

Material Properties. Materials possess various mechanical and chemical properties, and, therefore, it is possible to select materials appropriate for severe corrosion conditions. For example, if the equipment is under cyclic loading, a material with high fatigue strength is desired. Similarly, it is desirable to have corrosion-resistant materials for the corrosive environments. There are several sources for obtaining information on materials properties. Some are listed in Table 4-173. 

Thompson, R. B., Fiedler, C. J., and Buck, O. (1984). Inference of fatigue crack closure stresses from ultrasonic transmission measurements. In Nondestructive methods for materials property determination (ed. C. O. Ruud and R. B. Thompson), pp. 161-70. Plenum Press, New York. [278]... 

The essential material property of rubbers is their low elastic modulus, which ensures that the contact deformation remains elastic over a very wide range of contact conditions. The abrasive wear of rubbers is due to either fatigue of the material or tearing by a cutting force from impacts with sharp-edged particles. 

Damping is responsible for heat dissipation under fatigue conditions the temperature increase may cause drastic changes in the material properties. 

Mechanical Characterization of Sulfur-Asphalt. The serviceable life of a pavement comes to an end when the distress it suffers from traffic and climatic stresses reduces significantly either the structural capacity or riding quality of the pavement below an acceptable minimum. Consequently, the material properties of most interest to pavement designers are those which permit the prediction of the various forms of distress—resilient modulus, fatigue, creep, time-temperature shift, rutting parameters, and thermal coefficient of expansion. These material properties are determined from resilient modulus tests, flexure fatigue tests, creep tests, permanent deformation tests, and thermal expansion tests. 

Fig. 22 a Three-way stop cock as a component for medical infusion system, b FCP plots of PC with Mw = 30000 an improvement in material properties leads to better fatigue resistance of PC2 in lipid fat emulsion compared to PCI... 

A number of processing techniques are currently under development which enhance material properties by generating thin polymer layers within components, either via the formation of microcellular foams or microlayered structures. Microcellular foamed polymers contain high concentrations (> 10 bubbles cm ) of gas bubbles of the order of 1-10 pm in diameter.Such materials can provide a reduction in density of 20 to 40% in combination with increased fatigue and impact resistance without significantly compromising modulus and yield strength and will be processed by either extrusion or... 

Since no satisfactory theory has been developed to describe the fatigue behaviour of composite materials as a function of (micro) mechanical material properties, and as the engineering practice calls for less complex and more easily applied design rules, means of modifying lifetime prediction formulations to improve the predictions have been investigated. 

Dr. Hamish Fraser at Ohio State University directs a project intended to develop modeling tools that will predict material properties for a set of components critical to the operation of aircraft gas turbine engines. The properties of interest are low cycle fatigue and fatigue crack growth. Expected outcomes of this research not only will effect an acceleration of the materials optimization and insertion process but also will play a major role in the reduction of costs associated with extension of component life. 

We have shown that strength and stability can be obtained under selected conditions in nanostructured and dispersion reinforced systems. However, for structural applications, a balance of properties is critical - fracture and fatigue behavior of these systems are not well-established. Processing scale-up is another big challenge in these systems most of the properties have been demonstrated on laboratory-scale materials. Process scale-up is required to produce useful quantities of materials for sub-scale component demonstration as well as design property evaluation. The retention of useful microstructures, microstructural homogeneity as well as critical material properties has to be demonstrated in scaled-up materials. While our focus has been on structural applications, there may be other non-structural or functional applications for these systems. Future investigations will be focused on such opportunities. 

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