Quantitative Non-Destructive Detection of Residual Stresses of the 2 nd and 3 rd Order by Using Micro Magnetic Methods
Micro residual stresses (MRS) of the 2 and 3 order play an important role in the lifetime analysis of thermally-cycled materials. The coherent residual stresses (MRS of 3 order) appear when the lattice parameter of the second phase particles (coherently embedded in the matrix) and the lattice parameter of the matrix are different from each other. Such differences in case of the Fe-Cu alloys between the lattice parameters of coherent Cu precipitates and the lattice parameters of the αFe matrix lead to distortion of the lattice around the Cu particles causing coherent tensile MRS of 3 order. Thermally induced MRS of the 2 order appear when individual material phases exhibit different thermal expansion coefficients. Such differences in temperature-related expansion coefficients of copper precipitates and the α-Fe matrix promote the development of thermally induced compressive MRS of the 2 order. The main objective of the presented research project is to develop an integral, economical and fast micro-magnetic non-destructive method for quantitative characterisation of MRS of the 2 and 3 order in Fe-Cu and Fe-Cu-Ni alloys. For this purpose Fe-Cu and Fe-Cu-Ni alloy samples with different Cu and Ni contents were prepared.
A comparison of the effect of electron irradiation and of thermal aging on the hardness of FeCu binary alloys
The hardening of binary FeCu alloys under 2.5 MeV electron irradiation between 175°C and 360°C was investigated. We show that an extra-hardening component which cannot be ascribed to copper precipitation is induced during irradiation with electrons. We discuss the possible nature of the objects responsible for this extra-hardening component. They have to be very small since they are not visible by transmission electron microscopy. We come to the conclusion that they most likely are very small interstitial clusters nucleated by random encounter of interstitials. An important issue from the technological point of view raised by this work is to know whether it is reasonable to totally ignore any hardening component of the pressure vessel steels attributed to the clustering of freely migrating point defect escaping from the core of the displacement cascades or created between them.
Ignition and burning rates of segregated waste combustion in packed beds.
Recent developments in national recycling and re-use programmes for municipal waste have led to segregation of an increasing proportion of waste to enhance material recovery. Several of the segregated streams contain materials that can not viably be re-used or recycled but can be used for energy recovery. In this study, the combustion of cardboard and waste wood was investigated in a small-scale packed bed reactor in order to provide fundamental data for the design/operation of moving bed furnaces. Key parameters of combustion including the ignition and burning rates were evaluated for various air flowrates and compared to the modelling results. Two successive stages of combustion were identified for both samples: the propagation of ignition front into the bed and combustion of the fuel above the ignition front. The burning rate of cardboard reached a peak of about 300 kg/m(2)h at the air flowrate of 936 kg/m(2)h and decreased at higher air flowrates. For waste wood, both the ignition and burning rates increased in the tested range of the air flowrate up to 702 kg/m(2)h, of which the values were very close to those for the cardboard. The model prediction was in good agreement with the test results for waste wood. However, the burning rate for cardboard was under-predicted due to strongly irregular shapes of the fuel.