An Experimental Study on the Fracture Toughness of Middle Carbon Steel

중탄소강(中炭素鋼)의 파속인성치(破續靭性値)에 관(關)한 실험적(實驗的) 연구(硏究)

The fracture of a hot rolled SM 45C steel plate was investigated for various crack ratio, thickness and loading point using the method of J-integral. It was found that the stable crack growth increased as the thickness and crack ratio of the specimen. The results are summerized as follows. 1. The more crack ratio increase, the less fracture toughness tend to. 2. Considering fracture toughness, a thin specimen is stronger a thick one. 3. Considering only the bending of specimen without thickings of the axial direction, we can get $J_{1c}$ value decreased about 10 percentage within the scope of experimental crack ratio.