2592 N. Eswara Prasad et al. Engineering Fracture Mechanics 71(2004)2589-2605 All the fracture toughness tests were conducted on a computer controlled, servohydraulic Instron 8801 est system using a self-articulating 3-point bend fixtures of MTS 880 test system. The tests were conducted at ambient temperature(23C)and in laboratory air atmosphere. The notched specimens were loaded in ramp control at a constant ramp rate of 0.5 mm/min. The load-displacement curves thus obtained were analysed to obtain various measures of fracture resistance, and the results are presented and discussed in the following sections 3. Results and discussion 3. 1. Load-displacement data and crack path observations The load-displacement data obtained for crack divider and crack arrester orientations are shown in Figs 2 and 3, respectively. Crack lengths are given as normalised values(crack length'a, normalised with the specimen width, ' W). Though six tests with different a/w values were conducted in the crack arrester direction, for the sake of clarity, only three load-displacement plots are included in Fig 3. On the other hand, all the four load-displacement plots obtained are included in Fig. 2 for the crack divider direct CRACK DIVIDER DIRECTION 0.32a 0.44 DISPLACEMENT (6) Fig. 2. Load-displacement data obtained during the evaluation of fracture resistance using specimens with varied crack length(given in terms of the normalised crack length with specimen width) in case of the material in the"crack divider"orientationAll the fracture toughness tests were conducted on a computer controlled, servohydraulic Instron 8801 test system using a self-articulating 3-point bend fixtures of MTS 880 test system.The tests were conducted at ambient temperature (
23 C) and in laboratory air atmosphere.The notched specimens were loaded in ramp control at a constant ramp rate of 0.5 mm/min. The load–displacement curves thus obtained were analysed to obtain various measures of fracture resistance, and the results are presented and discussed in the following sections. 3. Results and discussion 3.1. Load–displacement data and crack path observations The load–displacement data obtained for crack divider and crack arrester orientations are shown in Figs.2 and 3, respectively.Crack lengths are given as normalised values (crack length ‘a’, normalised with the specimen width, ‘W ’).Though six tests with different a=W values were conducted in the crack arrester direction, for the sake of clarity, only three load–displacement plots are included in Fig.3.On the other hand, all the four load–displacement plots obtained are included in Fig.2 for the crack divider direction. Fig.2.Load–displacement data obtained during the evaluation of fracture resistance using specimens with varied crack length (given in terms of the normalised crack length with specimen width) in case of the material in the ‘‘crack divider’’ orientation. 2592 N. Eswara Prasad et al. / Engineering Fracture Mechanics 71 (2004) 2589–2605