Papers by Keyword: R-Curves

Abstract: This article is focused on optimization of fundamental utility properties and technological process of advanced low alloy steel 15NiCuMoNb5 used for power engineering mainly for production of large capacity steam boilers. Consequently problem critical locality in weld after post weld heat treatment is studied. Optimization of welding technology is proposed. Fracture behaviour of welded joint made from boiler plates 80 mm in thickness of 15NiCuMoNb5 type steel after N + T PWHT regime after welding procedure were studied. Stable crack growth measurement and evaluation of fracture toughness of base material as well as weld metal in temperature region from 0 up 350°C were carried out. Unstable cleavage fracture and fracture toughness KJc of both parts of welded joint at test temperatures cover the transition region were evaluated. The reference temperature T0 approach was used for evaluation of temperature dependence of fracture toughness in transition range.

Abstract: The paper reports on an experimental study of the Mode I interlaminar fracture of unidirectional carbon fibers/epoxy resin composites. Mode I delamination strain energy release rate GIC was determined in double cantilever beam (DCB) test, before and after gamma irradiation at various doses. Glass transition temperature, Tg of epoxy matrix was determined from dynamic mechanical measurements. The delamination surfaces of tested coupons were observed by scanning electron microscopy. The variations in GIC values were correlated with irradiation doses, Tg values and the features of delamination microfractographs, as well as with the variation under irradiation of matrix or fibre/matrix dominated mechanical properties.

Abstract: The R-curve (KR versus crack length c) behavior has been examined in alumina-10 wt% zirconia ceramics with 3 mol% yttria stabilized zirconia, alumina-10 wt% zirconia ceramics with 12 mol% nano ceria stabilized zirconia and Al2O3-30 wt% Ti(C,N) ceramics. An observation of in situ microscopic long-through thickness crack growth during three point bending (3PB) of a single edge notched beam (SENB) enabled measurement of the R-curve. It was found that both aluminazirconia ceramics with yttria or ceria stabilized zirconia exhibit a rising R-curve while for Al2O3-30 wt% Ti(C,N) ceramics such relationship was not observed. Moreover the slow crack growth parameters (n, logA) were determined by means of load-relaxation technique for tested alumina matrix ceramics.