Material Problems at Elevated Temperatures
This has been stated already that more materials lose their strength on higher temperatures. Such can be conceived being because of greater mobility of atoms on high temperatures. The elastic constants also decrease at high temperature for the similar reason and thus greater deformation results at estimated temperature. The estimated temperatures further deteriorate material behaviour via causing oxidation.
Now day technology could boast range of materials such are able of working at extremely high temperatures. It has become possible for constant insist of higher technology involving applications in gas turbines, power generation steam and nuclear engineering and high pressure boilers, transportation and oil technology engineering. The modest temperature of 500oC in steam turbines has raised to 800oC in gas turbines and need of highly powerful engines for jet planes has drive this limit to 1000oC. The rocket engines, ballistic-missile nose cones and re-entry vehicle face now higher temperatures. All such factors have been greatly causes to accelerate the researches upon high temperature resistant ceramic and alloys material that are being employed presently.
Whilst static properties of materials are not much affected by time-required for testing at room temperatures, the strain rate affects high temperature properties significantly. It is uniqueness of high temperature properties such time element as to be essential for them. It is of particular interest since a static load much below yield load of material could conclude into gradual deformation at approximated temperature.