Coupled Mass Diffusion with Stress in a Pressure Vessel

Pressure vessels which contain hydrogen in different temperature and pressure may be exposed to crack growth and then fast fracture will be happened. Two important parameters can have distinct influence on them like stress and concentration because of pressure and mass diffusion which would like to fail PV. Mass diffusion may be controlled either by stress or strain. It is assumed that stress plays main role and controls the mass diffusion as driving force. According to extended fick’s law, two terms of stress and concentration have been considered to describe coupled mass diffusion with stress phenomena which finally causes fast fracture and crack propagation. So, it shall be shown that what’s happed during mass diffusion in pressure vessels. For this purpose, one model of a pressure vessel is introduced that it has definite this event. In fact, finite element is employed to solve the sequentially coupled mass diffusion with stress near a crack front in a pressure vessel. Modeling of simulated hydrogen is investigated. According to the simulation, distribution of hydrogen and stress are indicating that their maximum amounts occur near the crack front. This phenomenon is happened exactly the region between elastic and plastic field. Therefore, hydrogen is highly mobile and can diffuse through crystal lattice so that this zone is potential to trap high volume of hydrogen. At the end, the paper’s results compare with experimental work which has been in good agreement.

Keywords:

Embrittlement , Hydrogen , Crack , Pressure Vessel