Analysis on ability of HCA to imitate cyclic principal stress rotation under constant confining pressure

Nowadays most hollow cylinder apparatus(HCA)in the world could only apply two dynamical loads,namely,axial load and torque during cyclic principal stress rotation.The limitation of this loading mode was presented through rigorous deduction,and based on such limitation the possible and applicable loading modes were put forward:① by setting the axial load W equal to 3πrori(pi-po),the stress path of shear stress q regularly varied with rotation angle α under constant b(the effect of intermediate stress)and the mean principal stress p could be achieved by changing torque MT;② setting a constant b(not equal to 0.5)the linear relationship between p and q could be realized under regular change of α.In this case W and MT should satisfy a certain equation and meanwhile the peak value of q should be restricted within p-q critical state line;③ without the effect of intermediate principal stress the monotonous variation of stress path of(σ1+σ3)/2 with α could be achieved under constant q.Then W and MT must satisfy some simple trigonometric functions.