DP 鋼板における疲労き裂進展速度について

概要

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Characteristics of fatigue crack growth in DP (with dual-phase, ferritic-martensitic microstructure) steel sheets have been investigated. SPHC (hot-rolled mild steel) sheets also have been examined for the purpose of comparison. For the both materials, the variation in fatigue crack growth rate (da/dN) with stress intensity factor range (ΔK) was measured by using CCT specimens, as well as the threshold values of ΔK by using CT specimens. From the results of these measurements, m in the formula of Paris, da/dN=C(ΔK)^m, was determined as 3.5 for DP steel as well as for SPHC steel. The threshold values (ΔK_<th>) at R=0.1 were shown as 6.5 MPa・m^<1/2> and 5.7 MPa・m^<1/2> for DP and SPHC steels, respectively. It is concluded that the characteristics of fatigue crack growth in DP steel sheet with a microstructure where a continuous ferrite matrix encapsulates islands of martensite are little different from those in conventional mild steel sheets.
社団法人日本材料学会の論文
1986-02-15