Issue 47

A. Chouiter et alii, Frattura ed Integrità Strutturale, 47 (2019) 30-38; DOI: 10.3221/IGF-ESIS.47.03 36 Mechanical & thermal properties of material Material - SA 516 GR. 70 Allowable stress - 38000 psi Mean metal temperature for the shell - 129o F Mean metal temperature for tube- 187o F Elasticity Modulus E - 27400000 psi Shell stress for case-2 = 1129.5 psi Poisson ratio υ - 0.3 Dimensions of material O.D of outer cylinder=19.6875 inch, I.D of outer cylinder= 19.3125 inch, G=32.125 inch, Length of outer cylinder, lo=2 inch, Length of inner cylinder, li=13.4962 inch, Thickness of bellows, t = 0.375 inch, Thickness of shell, ts = 0.4375 inch Radius of inner and outer knuckle ra=rb=1.125 inch. Table 1 : Mechanical, thermal properties and Dimensions of material. O PERATING CONDITIONS he internal pressure of thick wall bellows is acting on shell side shell. The smaller diameter end is unrestrained in axial direction and restrained in radial direction and the large diameter end are restrained in the axial direction and unrestrained in radial direction (see Fig. 3 above). The loading in the axial direction is entered as displacement which is calculated as δ = (Ss x As) / KFES where Ss= shell stress, As=shell cross-sectional area and KFSE=spring rate of main shell. In general, δapplied = δ (1/2NFSE) where δ=amount of applied displacement and NFSE is total number of bellow. The calculated applied displacement from shell stress is given in Tab. 2. Operating condition Shell side pressure (psi) Shell stress (psi) Applied displacement (δ) inch Shell side pr + Differential expansion 250 1129.58 0.02043 Table 2 : Operating conditions. The result of life cycles to failure plots obtained from our proposed method and ASME VIII Div 1 are as shown in Fig. 7. A NALYSIS AND INTERPRETATION OF RESULTS rom the results obtained, we can conclude that our results are quite close to the results obtained by ASME approach. . We can still optimize our results by decreasing the mesh so that we can get a fine mesh and results much more accurate. We calculated the results for a service condition, considering only the differential expansion and the internal pressure on the shell side, neglecting the tube-side pressure. Taking into account the tube-side pressure, our results will be even closer to reality. The results obtained using our model are lower than those of the ASME code, which will allow a safer and more secure design, hence the design is safe. T F