Properties, in-service

Heat treatment. Solid-solution-strengthened high-temperature alloys are normally supplied in the solution-heat-treated condition unless otherwise specified. In this condition, microstructures generally consist of primary carbides dispersed in a single-phase matrix, with essentially clean grain boundaries. This is usually the optimum condition for the best elevated temperature properties in service and the... 

A comparative test is carried out on the chemicophysical nature of accelerator NS made in China and an imported one, and their in-mbber physical properties and curing characteristics. The results show that the chemicophysical nature and the properties in service of accelerator NS made in China are similar to those of the import and it is suitable to replace the latter. It is concluded that the accelerator NS made in China needs to be improved by the following measures to lower the ash content and to increase the purity to develop the granular product and to decrease the cost and to increase the stability of product quality. CHINA... 

The JME Editor is a Java program which allows one to draw, edit, and display molecules and reactions directly within a web page and may also be used as an application in a stand-alone mode. The editor was originally developed for use in an in-house web-based chemoinformatics system but because of many requests it was released to the public. The JME currently is probably the most popular molecule entry system written in Java. Internet sites that use the JME applet include several structure databases, property prediction services, various chemoinformatics tools (such as for generation of 3D structures or molecular orbital visualization), and interactive sites focused on chemistry education [209]. 

The magnitude and nature of the load are considered in formulating the design. The load may be essentially quasistatic, cycHc, or impact. Many stmctural failures, for example, have been caused by supposedly innocuous stmctural details welded in place without any consideration given to their effect on fatigue properties. The service temperatures are also important, since they affect the fracture resistance of a material. 

The ideal high level heat-transfer medium would have excellent heat-transfer capabiUty over a wide temperature range, be low in cost, noncorrosive to common materials of constmction, nondammable, ecologically safe, and thermally stable. It also would remain Hquid at winter ambient temperatures and afford high rates of heat transfer. In practice, the value of a heat-transfer medium depends on several factors its physical properties in relation to system efficiency its thermal stabiUty at the service temperature its adaptabiUty to various systems and certain of its physical properties. 

Eor steel and other ferromagnetic materials, property deterrnination is more difficult. Other tests are made to measure the continuity of protective metallic coatings. Residual stresses induced in welded stmctures and in components in service owing to chemical attack may contribute to early failure. 

Selection of Proper Antidegradant. Because the various antioxidants function by different mechanisms, an antioxidant under one condition may become an oxidation promoter in a different condition. Therefore, an antioxidant should be carefully selected depending on service requirements. Most antioxidants are either amines, phenols, or phosphates. The following are some important properties in the selection of proper antidegradant that should be considered. 

Durability. The term "durable" has several meanings, but in the present context it is used to describe an asphalt that possesses the necessary chemical and physical properties required for the specified pavement performance, being resistant to change during the in-service conditions that are prevalent during the life of the pavement. 

Stress Relaxation. Copper alloys are used extensively in appHcations where they are subjected to moderately elevated temperatures while under load. An important example is the spring member for contacts in electrical and electronic coimectors. Critical to rehable performance is the maintenance of adequate contact force, or stabiUty, while in service. Excessive decrease in this force to below a minimum threshold value because of losses in spring property can lead to premature open-circuit failure (see Electrical connectors). 

Fatigue properties in bending are most appropriate for copper aHoys as these are often used as spring contact components in beUows and electrical switches and coimectors. These articles are usuaHy designed for acceptable service Hves at a moderate to high number of stress cycles. 

Virtually all design parameters such as tolerances, material properties and service loads exhibit some statistical variability and uncertainty that influence the adequacy of the design. A key requirement in the probabilistic approach is detailed knowledge... 

It is probably most useful to consider toughness as a property of a plastics part under some specified conditions of service. Whilst it is possible to devise impact tests and to rank a series of plastics materials according to the results obtained in such tests it remains almost impossible to use such tests to try to predict whether or not an article made from a specific material will or will not be satisfactory in service. 

The properties of a unidirectional fibre will not be nearly so good in the transverse direction compared with the longitudinal direction. As a material in service is likely to be subjected to stresses and strains in all directions it is important to be aware of the properties in all directions. The transverse direction will, of course, be the weakest direction and so it is necessary to pay particular attention to this. 

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