scanning electron micrographs of the micro-sized specimens. The crack will propagate perpendicular to the deposition direction in the in-plane type specimen, while the crack will propagate parallel to the deposition direction in the out-of-plane type specimen. The breadth of the specimen, B, was 10µm, the distance from the loading point to the notch position, L, was 30µm, and the width of the specimen, W, was 10µm. Notches with a depth of 2.5 µm were introduced into the specimens as shown in Fig. 1 by focused ion beam machining. The width of the notch was 0.5 µm, and the notch radius was thus deduced to be 0.25 µm. The notch position was 10 µm from the fixed end of the specimen. In our previous studies [2, 3], we have demonstrated that the introduction of a fatigue pre-crack is required to evaluate fracture toughness even for micro-sized specimens. A fatigue pre-crack was then introduced ahead of the notch in air at room temperature under constant load amplitude using a mechanical testing machine for micro-sized specimens, which was developed in our previous investigation [4, 5]. The length of the fatigue pre-crack was adjusted to be approximately 2.5 µm. The total crack length over specimen width (a/W) was then approximately 0.5 for all the specimens. Fracture tests were also carried out in air at room temperature using the same mechanical testing machine which was used for introducing fatigue pre-cracks. RESULTS AND DISCUSSION Fracture Behavior Figure 3 shows load-displacement curves during fracture tests for the in-plane and the out-of-plane type specimens. The fracture behavior is different between these two types of specimens. The maximum load of the out-of-plane type specimen is higher than that of in-plane type specimen in spite of the size of specimen and the length of fatigue pre-crack being approximately the same. This suggests that the electroless plated Ni-P amorphous thin film exhibits anisotropic fracture behavior. As crack opening displacement was not able to be measured for these specimen, the crack initiation load was not able to be determined. The maximum load was then assumed to be the crack initiation load and this load was used to calculate fracture toughness value. Stress intensity factor, K, is calculated from the equation for a single edge notched cantilever beam specimen [6]. The total pre-crack length was measured from scanning electron micrographs of the fracture surfaces. The calculated provisional fracture toughness values (KQ) for the out-of-plane and in-plane specimens are 7.3 and 4.2 MPam1/2, Figure 3: Load-displacement curves for in-plane and out-of-plane type micro-sized specimens. 0 2 4 6 8 10 0 5 10 15 20 25 In-plane type Out-of-plane type Load / mN Displacement / µm
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