曲げ角度を有する軟鋼線材の引張疲労強度

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A composite material, ferrocement, is a thin cement mortar with multiple layers of reinforcing mesh. The strength of composite materials is dependent upon the strength of reinforcing materials. The purpose of this paper is to investigate the fatigue strength of reinforcing meshes used for ferrocement. Specimens with weave angle are extracted from square woven wire cloths, and tested under pulsating load. The woven wires used for these specimens are about I mm diameter-cold drawn and galvanized low carbon steel wires. The sizes of mesh openings are 6,8 and l0mm. For the comparison, 2%- and 5%- prestrained woven wires and a straight wire are also tested. The summary of concluding remarks is as follows. The knuckle points of the specimens are subjected to bending moment as well as axial load. Therefore the S-N curve between the nominal stress S and the number of cycles to failure N does not have linearity. On the high stress level close to the yield point where the weave angle is diminished, the fatigue strength is improved by work hardening, though the shortest fatigue life appears on the middle stress level. Therefore this S-N curve may be difficult to be applied to design purposes. On the middle stress level of S-N curves, the fatigue life shows minimum cycles when the extreme fiber stress of a knuckle point calculated by elastic analysis has maximum value. The maximum strains, or peak strains, calculated by elastic stress analysis at a knuckle point are used to convert a S-N curve into a ε-N curve. The obtained ε-N curve is given by ε-N^<0.148>=0.0206. The equation provides a significant coverage for all the experimental data of the specimens with different weave angles. The fatigue strength at N=2×l0^6 cycles becomes ε=0.0024. This value is close to the proof stress (2% strain), the fatigue strength (2×l0^6 cycles) of the straight wire and the 5%-prestrained woven wire. This ε-N curve can be applied easily to design.
社団法人日本船舶海洋工学会の論文

曲げ角度を有する軟鋼線材の引張疲労強度

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