The contraction of aluminium alloy sheets sandwiched in between iron plates under pressure during thermal cycles

The contraction of aluminium alloy sheets sandwiched in between iron plates under pressure was observed during thermal cycles, and was interpreted in terms of the thermal stress due to the difference of thermal expansion coefficients between iron and aluminium.The contraction of specimen (Al-0.5at.%Mg alloy) increases as the number of thermal cycles increases, and is dependent on the friction between the specimen and the iron plate and also dependent on the pressure putting upon the specimen. The thermal cycle is such that the specimen is heated up to 200°C and then cooled down. The fractional linear change of specimen during one thermal cycle amounted to 0.15%, being about 60 per cent of the maximum value of 0.24% deduced from the assumption that the dimensional change is caused by the difference of thermal expansion coefficients between iron and aluminium in the course of heating up to 200°C.It should be noted, however, that no appreciable change in dimensions was observed during thermal cycles provided that the specimen is inserted between aluminium plates. It is, therefore, expected that such dimensional change during thermal cycles could be observed in any case of sandwiched sheets having different thermal expansion coefficients.