Papers by Keyword: Fracture Energy

Abstract: The fracture toughness tests and a new miniature specimen technology named hydraulic bulge test (HBT) of 3Cr1Mo1/4V at four service time were carried out. Four J-R resistance curves by single-specimen method with one inch CT specimens were obtained to compute the J_IC. Different definitions of equivalent fracture strain according to the section morphologies of HBT testing specimens were compared, and fracture energy of miniature specimens with three different thicknesses (0.4mm, 0.5mm and 0.6mm) were also calculated. Results showed that the typical HBT load-deflection curve can be divided into four sections like SPT curve. Equivalent fracture strain and fracture energy E_HB can be chosen as two fracture parameters for the HBT specimen. Ductile fracture toughness J_IC can be related approximately linearly to both the equivalent fracture strain and fracture energy E_HB.

Abstract: The use of foam concrete as an alternative material in the construction industry has become popular in structure industries due to the low density range, good strength, high serviceability, and lightness of this material. Several studies have been conducted to determine the mechanical properties and strength of foam concrete. However, research on fracture energy is still ongoing. Therefore, these studies aim to experimentally investigate the effect of span-to-depth (S/W) ratio on the fracture energy of foam concrete using beam specimens with V-notches through a three-point bending test. Beam specimens were encased and prepared at a density of 1600 kg/m³. Moreover, three different S/W ratios (4, 5, and 6) with a notch height of 20 mm were adopted. Fracture energy was determined using the Hillerborg, Bazant, and Comite Euro-International du Beton models. From the experiment, results showed that S/W ratio affected fracture energy.

Abstract: Natural fibers are potentially used as composite reinforcement in polymeric materials, but lacking of research exploration such as kenaf fibers has limited implementation in Malaysia. The advantages of natural fibers are renewable, less hazardous during fabrication and handling process and relatively cheaper as compared to synthetic fibers. The objectives of current project are to determine the fracture energy of woven fabric kenaf composite (KFRP) plates with various fiber orientations. The experiment framework includes a variation of fiber orientations as designated in testing series by using single-edge notch (SEN) testing technique. The experimental results demonstrated that testing coupons with woven fabric with 90^o fiber orientation has largest fracture toughness G_c value compared to other fiber orientations understudied. Good correlations and findings were found in other parametric studied.

Abstract: The paper presents an analysis aiming at capturing the phenomenon of quasi-brittle fracture based on the record of the fracture tests on notched specimens. A method of separation of the energy amounts released for the crack advance and that dissipated within the volume of the sizeable nonlinear zone at the crack tip – the fracture process zone– is introduced. The approach is tested on selected data of published experimental campaigns accompanied with own conducted numerical simulations.

Abstract: The scenario of a severe accident in the containment building of a nuclear plant results in an increase in pressure, temperature and relative humidity that can reach respectively 5 bars, 140 °C and the saturation of water vapour. As well as the regulatory calculations, accurate knowledge of the thermal and mechanical behaviour of materials and more specifically of concrete is required to carry out more precise numerical simulations. Our study aims to investigate the mechanical behaviour of concrete under homogeneous conditions of moisture and temperature. An experimental apparatus was designed in order to assess the evolutions of the fracture energy of concrete. Different temperature levels up to a maximum of 110 °C and at different values of the controlled moisture content were investigated. The equipment was used to perform DCT (Disk-shape Compact Tension) tests at 30, 90 and 110 °C. Five levels of degree of liquid water saturation (S_w) were investigated for each temperature level.

Abstract: The influence of three mineral admixtures, Silica Fume (SF), Fly Ash (FA), and Rice Husk Ash (RHA) on the fracture energy of Refractory Cement (RC) over a wide range of temperature from 300K to 1173K is studied. The optimum percentage replacement of RC by these admixtures is found to be around 0.5 for all the temperatures considered but for FA. Fracture energy of control (0% admixture) and blended RC (with 0.5% admixture) are determined by three point bending of notched beam specimens. Fracture energy of RC blended with the three mineral admixtures is lower than that of control RC for temperature range of 300K to 873K. But at elevated temperature of 1173K, blending plays its role as an admixture. Experimental results are corroborating with XRD. It is observed that phenomenon of pseudo dryness of Gismondine in the blended RC causes higher fracture energy which is double that of RC only at 1173K.

Abstract: The paper presents results of numerical investigation of fracture behaviour of initially notched beams made of foamed concrete. Extended Finite Element Method (XFEM) was used to simulate the damage and fracture process of the beams subjected to three-point bending. Subsequently, the numerical models were validated by a series of static loading tests. Numerical models simulate correctly the fracture behaviour of beams observed during testing. XFEM method and computer simulation technologies allow for reliable approximation of load–bearing capacity and damage mechanisms of beams made of foamed concrete, which provides some foundations for realistic structural applications.

Abstract: The evolution of crack models based on fracture mechanics is reviewed. The brittle cracking model in Abaqucs is used to simulate the machining process of Al₂O₃. The result shows that it’s appropriate to simulate the machining process of ceramics with fracture energy cracking criterion and post-failure constitutive relation in a smeared cracking representation. Although more works are needed in the future to resolve the mesh sensitivity. The material removal mechanism of ceramics is confirmed to be the brittle fracture regime.

Abstract: Nowadays, lightweight foamed concrete (LFC) is increasingly being used for structural purposes. Physical and mechanical properties of LFC are unlike the properties of traditional concrete thus constitutive models for concrete may not be used directly to describe its the fracture behavior. The paper presents an attempt to adapt the elastoplastic model with degradation known as Barcelona model for this purpose. The constitutive model is traditionally used for non-linear analyses of concrete and masonry structures. However, when it is used to describe behavior of non-traditional material such as foamed concrete, its parameters must be calibrated. Moreover, the results from Barcelona model are compared with XFEM method of modeling discontinuities in materials. The results of numerical simulations of three-point bending foamed beam with an initial notch are presented.

Abstract: The paper presents an analysis with an attempt to capture the phenomenon of quasi-brittle fracture based on the record of the fracture test on a notched specimen via separation the energy amounts released for the crack advance and dissipated within the volume of the sizeable nonlinear zone at the crack tip – the fracture process zone (FPZ). The described approach is tested on selected data of published experimental campaigns accompanied with own conducted numerical simulations.