IMPROVED METHODS OF STRESS-ANALYSIS TO AN ALYZE AND PREVENT FAILURES

The continuous rising demands on productivity and economy of modern pr ocesses, for example in the chemical or power generating industries, c ause a tendency for permanent rise of the process parameters pressure and temperature. But for the engineer of a project rising process para meters mean an unproportional increase of the number of mechanical/the rmal/chemical induced load collectives. During the basic design phase of a plant this aspect has to be taken into account with respect to th e materials choice and the analysis of all mechanical, thermal and che mical induced load cases. In this article modern computer based stress analysis methods for the complex simulation of combined mechanical/th ermal load cases are discussed using the example of pipe work. The emp hasis was focussed on ''pipe work'' with respect to the new German pre ssure vessel code of April, 21 st., 1989. Since then within the framew ork of this code the integrity of pipe work has to be verified. Due to this demand a general discussion was initiated to validate the approp riate analysis method. In this article different examples were chosen to demonstrate the influence of complex load situations on the total s tress level, for example the combination of external bending moments w ith stresses due to the mismatch of the physical properties of a selec ted material combination. Another goal of this paper is to show the de mand for further investigations to transfer brand new scientific resul ts to common engineering praxis. This aspect is discussed examining th e failure behaviour of heat resistant steels under complex mechanical/ thermal loading. It must be emphasized that the discussed analysis met hods are not a paragraph in the German pressure vessel code. But these methods are necessary to assist the code in effective analysis and pr evention of failures.