No abstract

In this study, the damage regularity of saturated red clay under acidic conditions was investigated. The red clay was configured with different concentrations of acid solution (pH = 2, 3, 4, 5, and 7), and a consolidated undrained triaxial test (CU), scanning electron microscope (SEM) test, and mercury intrusion porosimetry (MIP) were conducted to derive the mechanical damage law of acid on red clay in combination with the Mohr-Coulomb damage criterion. The stress-strain relationship of red clay under different circumferential pressure and acid concentration was determined to be strain-hardening; the original cementing material eroded under strong acid, and the connections between particles were broken to form a "gully". The colloidal material in the red clay dissolved with the increase in acid concentration, destroying the original structure of the soil and producing a large number of pores, which increased the damage. The linkage strength between soil particles, therefore, gradually decreased, the soil particles became more dispersed, and the strength of the soil decreased, i.e., the damage to red clay increased.

In this paper, a new approach to damage tolerance determination, which is related to the critical rupture strain, is proposed for cylindrical shells subjected to inner transient high-pressure loading. The relation of damage variable and circumferential plastic strain is deduced on the basis of a damage evolution equation as well as a simplified dynamic viscoplastic constitutive equation. The value of damage variable can be obtained then if the strain is known by strain measurement, and the damage tolerance just corresponds to the rupture strain of the structure. Further, the damage tolerance has been applied as the strain-based rupture criterion in the FE simulation of the dynamic fracture process for transient-pressurized cylindrical shells. Especially for the notched shells, the strain concentration effect of notches on the rupture criterion is analyzed quantitatively.