アルミニウム合金の熱疲労試験における二•三の現象

アルミニウム合金の熱疲労に関する研究(第1報)

抄録

Failures due to thermal fatigue often occur in aluminum alloy pistons and cylinder heads of engines, especially in those of Diesel-engines owing to their high operating temperatures.
This paper reports a method for investigating the resistance of aluminum alloys to thermal fatigue and the phenomena in thermal fatigue tests of Al-Si base alloy castings.
The results obtained were summarized as follows:
(1) It was found that a high rate thermal cycling could be achieved with a thermal fatigue testing apparatus of high frequency induction heating type (not the Coffin type.)
(2) The number of cycles to failure was decreased with the increase in temperature amplitude, thermal stress amplitude, and plastic strain amplitude.
(3) Specimens were tested at an average temperature of 300°C; they were radially expanded in the section heated to the maximum temperature and necking appeared in the both ends of the expanded section. The deformation of specimens was related with the distribution and variation of hardness in the specimens. The hardness was decreased in the section heated to above 300°C; and was minium in the necked parts, wehre the fracture took place.