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Effect of U-Notch Depth on Impact Resistance under Simple Beam Loading
This study was made in an attempt to establish impact values for Mesnager and DVM notched specimens which would correspond to the 15 ft-lb American Charpy-U acceptance value. Two in. thick plate materials, carbon steel (A 201) and 3.5 per cent nickel steel (A 203 grade D) were investigated. All impact specimens were taken parallel to the rolling direction. Although the transverse direction was not studied, it is presumed that a correlation similar to that reported herein exists. During breaking of impact specimens, a volume of material under the notch is plastically deformed. The major portion of the energy required to fracture the specimen is absorbed by this plastic deformation. Therefore, for impact specimens of constant width and varying notch depth, the impact strength should vary as the square of any similar cross-sectional dimension of plastically deformed metal. This theory has been substantiated by the present study. Using notches 2, 3, and 5 mm deep (Mesnager, DVM, and American Charpy-U specimens, respectively), the height of metal under the notch was chosen as the cross-sectional dimension of plastically deformed metal to investigate. The impact strength was found to vary almost exactly as (8) : (7) : (5). Therefore, for Mesnager and DVM specimens to have impact strength equivalent to 15 ft-lb Charpy-U they should exhibit strengths of approximately 38 and 29 ft-lb, respectively.
Reymond, Donald C.
Metallurgical Engineer, Esso Research and Engineering Co., Florham Park, N. J.