Diffraction-Based Investigation Methods in Analysing Plastic Strain Zone Underneath Fracture Surface

We used samples of the ВТ41 two-phase titanium alloy to estimate the relationship between testing temperature, KCV fracture toughness values, width of the plastic strain zone and its formation specifics. We developed an efficient method of estimating the plastic strain zone width, based on a special X-ray imaging geometry enabling a high degree of locality for measuring variations in the X-ray line broadening when moving away from the fracture surface. We studied material texture close to the fracture zone and at a distance from it, which allowed us to detect the specifics of grain reorientation, in particular, texture diffusion and an increase in the concentration of basal and prismatic planes parallel to the fracture surface as a result of plastic strain and dislocation saturation. We hypothesise that pole density in the [0001] region grows due to the [1012]-oriented grain slip, while in the region around [1010] pole density grows due to slip of the grains whose orientation is close to [1120]. We verified our X-ray texture analysis data by texture analysis via electron backscatter diffraction (EBSD).

Residual Stress Study of Autofrettaged Barrel under Impulsive Loading

An analysis model of barrel was established for rapid-firing gun by using the thermal structure direct coupling analysis method. As a solving tactics, finite element method was employed to analyze the influence of degree of autofrettage on the residual stress of the tube under impact load caused by high temperature and high pressure powder gases during continuous shots process. The results indicated that there is a significant effect of degree of autofrettage on the residual stress distribution of barrel. As the autofrettage level increases, the radius of the compressive tangential plastic strain zone on the inner wall and the maximal residual stress of the base near chromium-steel interface become larger. This is the cause that the tensile tangential plastic strain in the self-reinforced barrel easily occurred in the process of continuous shots after cooling. This goes against stability of the stress condition of the gun tube.

Numerical Simulation of Pipeline Deformation Caused by Rockfall Impact

Rockfall impact is one of the fatal hazards in pipeline transportation of oil and gas. The deformation of oil and gas pipeline caused by rockfall impact was investigated using the finite element method in this paper. Pipeline deformations under radial impact, longitudinal inclined impact, transverse inclined impact, and lateral eccentric impact of spherical and cube rockfalls were discussed, respectively. The effects of impact angle and eccentricity on the plastic strain of pipeline were analyzed. The results show that the crater depth on pipeline caused by spherical rockfall impact is deeper than by cube rockfall impact with the same volume. In the inclined impact condition, the maximum plastic strain of crater caused by spherical rockfall impact appears when incidence angleαis45°. The pipeline is prone to rupture under the cube rockfall impact whenαis small. The plastic strain distribution of impact crater is more uneven with the increasing of impact angle. In the eccentric impact condition, plastic strain zone of pipeline decreases with the increasing of eccentricityk.