Key Engineering Materials Vols. 417-418

Abstract: Several masonry panels are studied by means of destructive tests such as compressive, diagonal compression and shear-compression tests. The experimental research allows to characterize the mechanical properties of masonry walls in order to assess the masonry performance. Moreover, a brief recall of the most important experimental progress is presented in order to understand the state of the art of the research in the field of destructive tests.

Abstract: The fatigue crack growth behavior in integrally stiffened, welded panels is influenced by residual stresses caused by the welding process. The paper presents a semi-numerical method for the determination of stress intensity factors, taking into account the residual stresses in such a way that the relaxation of the residual stresses during the crack propagation phase is covered. This approach is different from the one presented in [1].

Abstract: The paper deals with the determination of the characteristic strength and as well as the Weibull moduli and of the Si3N4+SiC micro/nanocomposite determined by the four-point bending test and the contact test using opposite spheres both applied to specimens of different size, respectively. Material failure in the bending and contact modes is caused by the presence of processing defects as fracture origins, and by the formation of cone cracks, respectively, where a stable growth of the cone cracks initiated during contact loading is assumed to be a reason of , . A microstructural analysis of the processing flaws, and a mathematical analysis of the propagation of the cone cracks regarding different dimensions of a specimen are also presented.

Abstract: This study is focused on examining the effect of cracks on chloride penetration into concrete. In order to get reliable results, short-term and long term experiments were set up and chloride penetration behaviour through cracks was examined. It was noticed that chloride penetration through cracks tends to decrease with time. One of the explanations is crack-healing. Especially, this trend was obvious in concrete samples with larger crack width. However, measuring the border between chloride contaminated zone and healthy zone was clear in concrete of short-term experiment, while it was ambiguous in long term experiment.

Abstract: The paper is devoted to numerical modelling of R-curve behaviour in laminates with strong interfaces, in particular multilayers made of alumina (A) and zirconia (Z). Contrary to previous studies based upon the application of approximate weight function method originally developed for homogeneous specimens, a full field analysis by FE of a three-point bending test of a sandwich beam is attempted and compared with the results obtained by approximate weight function method. Also the crack penetration across the layer interfaces is discussed, particularly in the case of a weak singularity.

Abstract: Due to the stress concentration effect around the hole, cracks are likely to initiate at the hole under the action of fatigue loading. This paper is specifically concerned with cracks emanating from a surface semi-spherical cavity in a finite body by using the boundary element software FRANC3D developed by a fracture mechanics investigation group of Cor-nell University. The numerical results can reveal the effect of the geometry of the surface cavity on the stress intensity factors.

Abstract: On 12 May 2008, a magnitude 8.0 earthquake happened in Wenchuan, China .It was the most serious earthquake in china since 1949, causing very huge casualties and engineering damages. The complex building of the Xuankou secondary school in Yingxiu town was designed by the Code for Seismic Design of Buildings of China (GB50011-2001), the seismic fortification intensity of the buildings was 7 degree. In the earthquake, it was destroyed most seriously, and the engineering damage was characteristic. In the paper, the property of material nonlinearity was considered ,the nonlinear analysis model of infilled frame structure was established, the time history analysis and nonlinear static analysis were used during inelastic stage, the main cause of structural destruction was obtained, the influence of the infill wall on the structure was discussed.Therefore ,the results can provide valuable reference for the seismic design of infilled frame structure.

Abstract: High-resolution elastoplastic simulations of a plane-strain tensile crack under cyclic loading visualised the Laird-Smith mechanism of fatigue crack growth, which manifested the effects of K and overload, but no signs of crack closure. Simulations discarded the supposed mechanism of plasticity-induced crack closure (PICC) via out-of-plane stretching of material elements filling-in the crack and coming in contact at unloading. Specimen compliance curves turned out to be nonlinear merely by virtue of plasticity with no contribution of crack closure. Thus the results manifested the ambiguity of main justifications about the phenomenon of PICC.

Abstract: This study is focused on modification of a conventional bumper damper to increase its energy absorbability. This bumper damper device is currently used on passenger vehicles for reducing structural damage, as well as part of the pedestrian protection system. A hollow aluminium cylinder with 2mm in thickness was subjected to a range of experiments. The energy absorption takes place as a ram displaces along the cylinder’s bore, where the outer diameter of the ram is slightly wider than the inner diameter of this cylinder.

Abstract: Thermoplastic elastomers are a relatively new group of engineering materials and are increasingly used in various technical applications (i.e., seals, gaskets, damping elements, and membranes) where the fatigue resistance plays an important role. The fracture behavior of elastomers is often characterized using the tearing energy concept, T. However, hardly any data are available for these types of materials. Hence, an unfilled and a filled thermoplastic polyurethane (TPU) type were investigated under cyclic loading conditions. The pure shear specimen configuration was used in the experimental part of this study. Crack growth kinetics curves were determined and the cycle number and the tests frequency dependence of these curves investigated. While a stable crack growth process was observed at 2 Hz the crack growth became unstable above specific test amplitude at 10 Hz.