Q4 (a) A chemical reaction chamber, similar to the one shown below, is made of type 304 stainless steel. The cover bolts of the chamber, which are made of the same steel, are pre-tensioned at room temperature to a stress of 69 MPa. The service temperature of this chamber is 595C. It may be assumed that the deflection of the flanges during tightening is negligible compared to the extension of the bolts. This implies that the total strain remains constant throughout the life of the chamber. How long can the chamber be used at this temperature before the stress in the bolts drops below 40 MPa at the operating temperature? [25] (Pressure vessel) You may assume a constitutive law for creep for 304 stainless steel of the form: (s ) Aam exp where m= 7, A= 6.3 x 10 MPa's, Q = 3.28 x 105 J/mol, R = 8.314 J/mol.K Note: The elastic modulus varies linearly with temperature: Eroom temp = 200 GPa, E595 c=154 GPa