Finite element analysis and optimization of multi-layer combined ultrahigh pressure cylinder
The finite element model was established by the finite element method of Workbench. The prestressed state and the working state of the multi-layer composite cylinder was used to calculate by the finite element method. The general distribution law of the stress of the multi-layer cylinder is obtained, and the equivalent stress distribution is not uniform. At the same time theoretically based on the elastic limit of multilayer composite cylinder unified solution, and the optimization condition is determined. The design of multi-layer ultrahigh pressure cylinder is optimized. The results show that the nonuniformity of the stress distribution of the cylinder can be improved greatly. The study can provide technical support for the structural design and optimization of the multi-layer ultrahigh pressure cylinder.
Fracture strain of gun steel for ultra-high-pressure vessels considering triaxiality effect
To better understand the local failure of ultra-high-pressure vessels, the ductile fracture behavior of a gun steel, PCrNi3MoVA used for ultra-high-pressure vessel in China, was studied through experimental and numerical investigations. Tests on smooth and notched specimens of different notch radius values were performed, and the stress–strain states of specimens in the loading history were obtained through finite element analysis. Fracture was identified by means of comparing the engineering stress versus the strain obtained from tests with the finite element analysis results. The effect of triaxiality on the ductile fracture behavior of PCrNi3MoVA was discussed. Finally, a new plastic design-by-analysis method considering triaxiality effect was proposed to protect against local failure of ultra-high-pressure vessels.
Optical rotatory dispersion and absolute configuration—III
Abstract Optical rotatory dispersion measurements on pyrrolidine, piperidine, and tetrahydro-isoquinoline alkaloids indicate that the absolute configuration of the α-asymmetric center may be assigned directly from the dispersion curve, provided either that the nitrogen atom is not protonated, or that the compound contains a chromophore absorbing above 200 mμ.