安全破裂板の一定および変動繰返し圧力下における疲労強度

抄録

Fatigue tests on a Cu safety rupture disc were carried out under constant and two-step variable pressure amplitudes. Fatigue strength and change of burst pressure caused by repeated pressure were studied. In addition, deformation behaviour, tensile properties and crack growth in fatigue process were observed.
Under the application of constant pressure amplitude P_C, burst pressure P_CS decreased with increasing cycle ratio R. Variation of P_CS is expressed by a following empirical equation
(P_CS-P_C)/(P_S-P_C)=(1-R)^m
where P_S is rated burst pressure and m is a material constant which is dependent on P_C. The decrease of P_CS could be attributed to reduction of tensile strength and growth of fatigue cracks. Allowable number of cycles N_L (critical number of cycles in which P_CS falls below 95% of the rated burst pressure P_S) may be estimated by use of above equation.
Experimental cycle ratio sums with respect to N_L as well as fatigue life N_f were greater than unity for variable amplitude tests in which the lower cyclic pressure was followed by higher pressure. These values tend to become larger with increasing the difference between primary and secondary pressure level. Estimation of N_f and N_L based on above equation results in conservative prediction.