18 KB798 KB17 KB200020262006Capelle, JanineDmytrakh, I.Gilgert, JosephJodin, PhilippePluvinage, Guyletnik:405 straništevilka:6str. 233-238ISSN:1580-2949COBISSID:578730URN:URN:NBN:SI:doc-XB5VIK7JenInštitut za kovinske materiale in tehnologijeMateriali in tehnologijecevimehanika lomarazpokaA comparison of experimental results and computations for cracked tubes subjected to internal pressure|A cylindrical pipe that is used for gas transportation is mainly submitted to stresses originating from internal pressure. Other stresses are due to weight and the unexpected movements of supports and/or the ground. The first give rise to circumferential stresses, the second to longitudinal bending stresses. Here, we study the case of pipes that are joined by welding. This weld is an eventual source of defects, where cracks can originate. But there are other kinds of defects that can come from corrosion pits or accidental notches caused by diving machines, or in the case of work on the pipe. In this last case, the notch corresponds to a reduction of the section, which is enhanced by the stress-concentration factor. The objective of this work is to compare the prediction of finite-element computations with fracture experiments on such notched pipes. The results are given in terms of stress-concentration factors and show some discrepancy with the experimental results. As the mechanical properties have been measured on standard plane specimens, a transfer problem to curved structures is suspected to be at the origin of the difference, because with the dimensions of the pipe it is not possible to have standard and curved specimens in the same direction of rolling, and the mechanical properties of this pipe are different in the circumferential and transverse directionsV valjasti cevi za pretok plina so napetosti zaradi notranjega pritiska. Druge napetosti nastanejo zaradi gravitacije in nepričakovanih premikov podpor ali zemljišča. Prve napetosti so obodne, druge pa podolžne in upogibne. V tem delu obravnavamo primer cevi, ki so povezane z varjenjem. Zvar je eventualni vir napak, na katerih nastanejo razpoke. Druge vrste napak lahko nastanejo zaradi korozijskih zajed ali odrgnin, ki jih povzročijo gradbeni stroji ali nastanejo že pri izdelavi cevi. V tem primeru zareza ustreza zmanjšanju prereza, napetost pa je povečana zaradi zarezne koncentracije napetosti. Cilj tega dela je primerjava napovedi na podlagi izračuna z metodo končnih elementov s preizkusi preloma cevi z napako. Rezultati izračunov, ki so predstavljeni v obliki faktorja intenzitete napetosti, se ne ujemajo popolnoma z rezultati preizkusov. Ker se mehanske lastnosti določijo pri standardnih ravninskih preizkušancih, predpostavljamo, da je vzrok za razliko prenos na ukrivljeno strukturo. Zaradi izmer cevi ni mogoče izdelati standardnih in ukrivljenih preizkušancev v enaki smeri valjanja in so mehanske lastnosti cevi drugačne v obodni kot v prečni smeriTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije