Key Engineering Materials Vol. 627

Abstract: The fracture analysis for two-dimensional nonlocal elasticity is presented by the numerical approaches i.e. the Local Integral Equation Method (LIEM). Based on the Eringen’s model, the nonlocal stresses at the crack tip are regular. Numerical simulation by LIEM is proposed for the nonlocal elasticity fracture problems. A rectangular cracked plate subjected to tensile load is observed numerically to demonstrate the convergence and accuracy of LIEM.

Abstract: In this paper, an in-situ measurement of crack size as a function of applied indentation load during indentation test was conducted. To perform the in-situ measurement, an instrumented indentation test machine with the in-situ observation system was developed and used. The joints of transparent ceramics by diffusion bonding were prepared as the specimen used in this study. The indentations were performed at the interface of the joints, and in the monolithic transparent ceramics by means of the instrumented indenter with the in-situ observation system. The relationship between crack shape and indentation load, as well as, the effect of the indenter shape on it were discussed.

Abstract: The oversaturated solutes in the alloy matrix, which are caused by nonequilibrium phase transformation during casting or T4 treatment, can precipitate in the subsequent annealing treatments or during service at high temperatures. Under deformation the precipitation could be enhanced in comparison to conventional isothermal ageing. The present work investigates the dynamic precipitation of oversaturated Mg-Sn alloys during creep. The influence of this dynamic precipitation on creep properties is discussed. It is found that the distribution of deformation-induced precipitates is inhomogeneous. These precipitates are first formed at grain boundaries and then at deformation bands which are kinetically and thermodynamically favourable. The dynamic precipitation accompanies the volume change of phases, which influences the subsequent formation and growth of voids. Consequently, the creep behaviour also changes due to different precipitation under deformation.

Abstract: The purpose of this study was to analyze the mechanical properties of concrete produced with wastepaper for obtaining the optimum mix design of that. The concrete produced with wastepaper was made up of the cement, water, sand, and cut wastepaper. For this purpose, the concrete which had variety mixing ratio of materials was mixed and cured to find out the mechanical properties of that. And, it was performed the compressive and tensile test and the measurement of hardened concrete. The test result of this study was showed that the partial replacement ratio of wastepaper was the decisive influence variable and the correlation between the mechanical properties

Abstract: In the paper the polymer pipes loaded by internal pressure with additional point load on the external surface are studied using numerical methods. It is shown that the additional external loading can significantly influence residual lifetime of the pressured pipe. In this study the effect of the pipe geometry is considered. The shape of the propagating crack is estimated based on a special algorithm and the stress intensity factor is evaluated by direct method. The relation between crack size and a geometric function YasYas for specific material and geometrical properties is found. The results of this paper should contribute to better understanding of the real pipe behavior and to prevent unexpected failure of the pressured pipe system due to non-homogenous distribution of the soil load.

Abstract: In this paper, a technique for the detection and the sizing of cracks on isotropic plate structures is presented. The generation and the reception of the detection signals – Lamb waves – are made possible by piezoelectric transducers. The presence and the length of cracks are found by the method of triangulation using signals scattered by crack tips. The practicability of the technique is then assessed by a numerical experiment.

Abstract: The paper deals with a new second-order computational homogenization procedure for modeling of heterogeneous materials at small strains, where C¹ continuity is preserved at the microlevel. The multiscale model is based on the Aifantis theory of gradient elasticity. The C¹ two dimensional triangular finite element used for the discretization of macro-and microlevel is described. Contrary to the C¹ - C⁰ transition, here besides the displacements, the displacement gradients are included into the boundary conditions on the representative volume element (RVE). According to the second order continuum at microlevel, the relevant homogenization relations are derived. Finally, the performance of the algorithms derived is investigated. Dependency of homogenized stresses on mesh density and microstructural parameter l are examined in simple loading cases.

Abstract: Fly ash and blast furnace slag dumped not only pollutes environment, but also consumes landfills. With the aim of sustainable development, the isolated contribution of fly ash and blast furnace slag in concrete to the mechanical properties of frame concrete is investigated. An experimental study is conducted to investigate mechanical properties of high performance concrete. Test variables are the replacement levels for FA series (10%, 20% and 30%) and for BS series (10%, 30%, 50% and 70%) in place of part of cement. Compressive, splitting tensile strength, modulus of elasticity and flexural strength tests were carried out to evaluate the mechanical properties for up to 7days and 28 days. The mechanical properties of high performance concrete compared with predicted values by ACI 318-02 Code, EC 2-02, JSCE Code, KCI Code and proposed Eq.

Abstract: This study performed compressive, tensile and restrained shrinkage tests to find out the optimized mixture including shrinkage reducing admixture (SRA) and expansive admixture (EA) enabling to reduce the shrinkage of Ultra High Performance Fiber Reinforced Concrete (UHPFRC). The test results showed that the mixture using 1% of SRA and 7.5% of EA satisfied the design strength criterion despite of slight loss in the compressive and tensile strengths. In addition, this mixture exhibited the lowest restrained shrinkage strain by offsetting the quick setting and delaying the development of the restrained shrinkage stress.

Abstract: This study investigates the effects of the compressive strength and area ratio of coarse aggregate of concrete for offshore construction on the erosion depth. To evaluate the erosion resistance of concrete, test was performed according to ASTM C 1138 using a plain mix with design strength of 30 MPa using only Portland cement and five other mixes including different quantities of fly ash and blast furnace slag. The test results showed that the erosion depth is influenced not only by the compressive strength but also by the area ratio of coarse aggregate.