Uと2SALとの関連変形について

抄録

The authors have investigated two fundamental experiments on the deformation behaviours of the aluminium sheath which might be restricted by the uranium fuel core, for exsample, as the combination of the uranium rod and the aluminium sheath used for the fuel element of JRR-3 type reactor.
The first experiment was studied for the stress behaviours and the micro structure changes etc. of extruded 2S aluminium which was subjected to the same length changes as that of β-quenched uranium under the thermal cycling between 110° and 550°C. In this case, the experiment was done under the condition separated the uranium rod and the aluminium sheath from each other.
The second one was studied to clarify the systematic deformation behaviour of the aluminium caused by the thermal growth of the uranium for reference to the first results, and then the experiments carried out for the repeated strain cyclic tests with the growth of constant rate of five kinds in the tensile direction only, that is, 0, 0.020, 0.037, 0.053 and 0.074 per cent per cycle, respectively.
In these experiments, the strain cyclic amplitude, the test temperature of 2S aluminium and time per cycle was about 0.59 per cent strain, 75°C and 27.5min., respectively.
The testing machine used was“the universal thermal fatigue testing machine”which was designed by the authors.
The outline of the experimental results was as follows:
The effect of the growth was clarified to accelerate the local deformation of 2S aluminium from these results, and consequently the fatigue life decreases with increase of the growth rate per cycle, and the relation between the growth rate per cycle and the logarithm of cycles to failure was approximately presented by a straight line.
The degree of softening and hardening to be caused by strain cycles with the growth and the time for softening and hardening depended upon large or small of the growth rate per cycle.
Furthermore, it was defined from the point of view of the microstructure behaviour that the changes of microstructure due to progress of the deformation follow the same process in spite of large or small of the growth rate per cycle, but the progress rate of the microstructre change becomes late with decrease of the growth rate per cycle. That is, it dependens apparently upon the number of various deformation bands and their forms.
The experiments showed that the growth and the strain cycle have the reversal effect on the changes in strength each other, and this opposite phenomenon was explained from the point of view of the microstructure changes between the repeated strain cycle and the simple tension.