Issue 37

M. S. Raviraj et alii, Frattura ed Integrità Strutturale, 37 (2016) 360-368; DOI: 10.3221/IGF-ESIS.37.47 362 initiates and propagates by 2.5mm the fatigue loading would stop by the control options as given in the software to operate the testing machine. All fracture toughness tests were conducted using BiSS servo-hydraulic testing machine at room temperature. The machine capacity is of 100kN and is equipped with a load cell, Crack Mouth Opening Displacement (CMOD) gauge and a Linear Variable Differential Transformer (LVDT). All mentioned equipments associated with the test are calibrated. The CMOD gauge attached to a specimen was mounted in the loading system by the use of special grips as shown in Fig. 3. The fatigue pre-cracked CT specimens were tested under monotonically increasing tensile load using the commercial programme for determination of stress intensity factor. For the practical analyses, 5 identical CT specimens were considered for various Al6061-TiC composites and B / W ratios of a / W =0.5. Totally 90 specimens are considered for the practical analysis to estimate the fracture toughness of Al6061-TiC composite. All the test control was by stroke mode with a rate of 0.01667mm/sec. All the specimens were examined optically and by using Scanning Electron Microscope (SEM) to study the nature of the cracks and other details of bonding between matrix and particulates. The topography of fractured specimens and the microstructures were examined in detail using scanning electron microscope of ZEISS EVO18 make and an optical microscope (OM). This is done to characterize the fracture mechanisms of the composites. The particle and matrix interface details and the profile of crack propagation through the matrix and near the particles can (b) (a) Figure 2 : (a) Machined CT specimens of various thicknesses. (b) Fatigue pre-crack. Figure 3 : Test set up showing the mounted specimen in grips with COD gauge.