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Thermal Analysis in the Technological “Step” Test of H282 Nickel Alloy

Pirowski Z.

Archives of Foundry Engineering

2015

Vol. 15, iss. 1

87--92

Superalloys show a good combination of mechanical strength and resistance to surface degradation under the influence of chemically active environments at high temperature. They are characterized by very high heat and creep resistance. Their main application is in gas turbines, chemical industry, and in all those cases where resistance to creep and the aggressive corrosion environment is required. Modern jet engines could never come into use if not for progress in the development of superalloys. Superalloys are based on iron, nickel and cobalt. The most common and the most interesting group includes superalloys based on nickel. They carry loads at temperatures well in excess of the eighty percent of the melting point. This group includes the H282 alloy, whose nominal chemical composition is as follows (wt%): Ni - base, Fe - max. 1.5%, Al - 1.5% Ti - 2.1%, C - 0.06% Co - 10% Cr - 20% Mo - 8.5%. This study shows the results of thermal analysis of the H282 alloy performed on a cast step block with different wall thickness. Using the results of measurements, changes in the temperature of H282 alloy during its solidification were determined, and the relationship dT / dt = f (t) was derived. The results of the measurements taken at different points in the cast step block allowed identifying a number of thermal characteristics of the investigated alloy and linking the size of the dendrites formed in a metal matrix (DAS) with the thermal effect of solidification. It was found that the time of solidification prolonged from less than one minute at 10 mm wall thickness to over seven minutes at the wall thickness of 44 mm doubled the value of DAS.

Analysis of multibackground memory testing techniques

Mrozek I.

International Journal of Applied Mathematics and Computer Science

2010

Vol. 20, no 1

191-205

March tests are widely used in the process of RAM testing. This family of tests is very efficient in the case of simple faults such as stuck-at or transition faults. In the case of a complex fault model-such as pattern sensitive faults-their efficiency is not sufficient. Therefore we have to use other techniques to increase fault coverage for complex faults. Multibackground memory testing is one of such techniques. In this case a selected March test is run many times. Each time it is run with new initial conditions. One of the conditions which we can change is the initial memory background. In this paper we compare the efficiency of multibackground tests based on four different algorithms of background generation.