Pressure vessel

Pagina 1

Gussoni Enrico 804089 Olivari Laura 876599 PRESSURE VESSEL OBJECTIVES 1. Perform a static strength (LEFM) of the vessel. Use a pressure equal to P=2Pw 2. Adopting the classic elastic approach (crack presence is neglected), calculate the fatigue life applying a pulsing pressure from zero. The standard requires to use a maximum pressure equals to P=1.5Pw and it also require s a minimum lifespan of N=12000 cycles. For the assessment, use the Sines criterion. 3. Adopting the Paris law, determine the number of cycles so tat the crack depth reaches 95% of the shell thickness. Moreover, evaluate if the vessel fails due to the leak before break or by unstable crack propagation (burst). Use a pressure P = 1.5Pw. 4. Static assessment (LEFM) considering a completely through-thickness crack. Use a pressure P=2Pw. Note we don’t have to provide further safety factor, they are already taken into account POINT 1 - Static assessment (LEFM) GEOMETRICAL DATA, LOAD AND MATERIAL PROPERTIES D=230 mm t=5.8 mm Pw=200 bar UTS=1000 MPa KIC=200 MPaѴm m=3; C=2.5e-13 with R=0 a0 = 0.05*t and c0 = 5* a0 We have first to evaluate the stress intensity factor (SIF). To do it we can consider the shell as a specimen having a rectangular section and a constant remote stress (no stress change are considered in thickness). The analytical solution to estimate K has been computed by Newman and Raju. We get the value evaluating geometry and load data. The Newman and Raju approach considers the presence of both axial and bending loads . In our case the bending is not present and we can evaluate the axial stress due to hoop stress using Mariotte. KA= 24.8028 MPaѴm KC= 12.2110 MPaѴm Static assessment: K <= KIC The static assessment is verified, thus we don’t have brittle fracture. POINT 2 – Fatigue assessment…