Characteristics Of Deformation Bands Research Articles

Deformation Bands and Associated FIP Characteristics From High-Porous Triassic Reservoirs in the Tarim Basin, NW China: A Multiscale Analysis

Deformation bands are widely formed and distributed in Triassic high-porous rocks as a result of multistage tectonic movement. In this research, core observation, the rock thin section (fluorescence and casting thin section), FIB-SEM, X-ray diffraction, Raman laser, and thermometry of fluid inclusions were employed to describe the macro- and micro characteristics of deformation bands and their associated relationship with microfractures. Results indicate that the main types of deformation bands formed in the Lunnan Triassic high-porosity sandstone during the Yanshanian and Himalayan periods under different temperature and pressure conditions are compaction shear bands, and their quantity increases evidently with the distance of thrust faults. The density of deformation bands near the fault is about 15/m; porosity and permeability decrease sharply compared with those of the host rock. Microscopically, two obtained fluid-inclusion planes (FIPs) can be distinguished as 51 samples collected from 12 wells by the cutting relationship and mechanical characteristics. The homogenization temperature of associated aqueous inclusion is generally characterized by two peaks, mainly 70–80°C and 110–120°C, which were formed in the Late Yanshanian and Late Himalayan periods. The formation period of deformation bands induced by the intragranular microfractures improved the reservoir seepage capacity. In the later stage, as the interlayer and barrier with low porosity and low permeability affects the distribution of oil and gas, which is an important factor in this study of the local fluid dynamic field and high-quality reservoir evolution distribution.

Effects of strain rate on the characteristics of PLC deformation bands for AA5083-H116 aluminium alloy

An experimental, theoretical and numerical investigation of the Portevin-Le Chatelier (PLC) effect in the aluminium alloy AA5083-H116 is described. Five different tests at different overall strain rates were carried out on smooth flat specimens in order to determine the effects of strain rate on the characteristics of the deformation bands and their propagation. Both digital image correlation and digital infrared thermography were used to capture and characterize the spatio-temporal features of the PLC behavior. Inhomogeneous deformation with various localization bands caused by the PLC effect was observed in all the tests and the formation, evolution and propagation of these deformation bands were visualized, allowing their characteristics to be measured. An elasto-viscoplastic constitutive model, developed for metals exhibiting dynamic strain ageing, is used to represent the material behavior. Linear stability analysis with the adopted constitutive model is shown to give the orientations of the bands, but fails to predict the critical strain at which serrated yielding occurs. Finally, the model is used in three-dimensional numerical simulations of the physical tests using explicit finite element analysis. The numerical results are compared with the experimental observations and the main deviations between tests and simulations are discussed.

Portevin-Le Chatelier plastic instabilities: characteristics of deformation bands

Two aluminium-magnesium alloys (5182 and 5754) were investigated at room temperature. Tests were conducted on a soft tensile machine in the stress rates range where Portevin-Le Chatelier (PLC) phenomena occur. Experimental measurements on deformation bands associated with the PLC effect have shown that the band strain ε b decreases with increasing stress rate σ ˙ at low values of σ ˙ . At high stress rates, however, ε b increases with σ ˙ . The band propagation velocity V b decreases with the applied stress rate. The critical strain ε c for the occurrence of the PLC effect increases with increasing σ ˙ at high stress rates. At low stress rates an inverse behaviour of the critical strain is observed. All the experimental results obtained show that there is a similarity of behaviour between the critical strain ε c and the band strain ε b .