The effect of short-range ordering (SRO) on the low-cycle fatigue (LCF) behavior of low solid-solution hardening Ni-Cr alloys with high stacking fault energies (SFEs) was systematically studied under cycling at consta...The effect of short-range ordering (SRO) on the low-cycle fatigue (LCF) behavior of low solid-solution hardening Ni-Cr alloys with high stacking fault energies (SFEs) was systematically studied under cycling at constant total strain amplitude (Δε t /2) in the range of 0.1%–0.7%. The results show that an inducement of SRO structures can notably improve the fatigue life of the alloy regardless of Δε t /2, and several unique fatigue characteristics have been detected, including the transition of fatigue cracking mode from intergranular cracking to slip band cracking, the non-negligible evolution from non-Masing behavior in pure Ni to Masing behavior in the Ni-40Cr alloy, and the secondary cyclic hardening behavior in the Ni-10Cr and Ni-20Cr alloys. All these experimental phenomena are tightly associated with the transformation in cyclic deformation mechanisms that is induced by SRO based on the “glide plane softening” effect. Furthermore, a comprehensive fatigue life prediction model based on total hysteresis energy has been reasonably proposed, focusing on the analyses of the macroscopic model parameters (namely the fatigue cracking resistance exponent β and the crack propagation resistance parameter W 0 ) and microscopic damage mechanisms. In brief, on the premise that the effects of SFE and friction stress can be nearly ignored, as in the case of the present low solid-solution hardening Ni-Cr alloys with high SFEs, an enhancement of SRO in face-centered cubic metals has been convincingly confirmed to be an effective strategy to improve their LCF performance.展开更多
This paper investigates the ordering decision problem for a short-life-cycle product under Bayesian updating. For a product characterized by a single manufacturing cycle and two selling periods, we depict a Two-Stage ...This paper investigates the ordering decision problem for a short-life-cycle product under Bayesian updating. For a product characterized by a single manufacturing cycle and two selling periods, we depict a Two-Stage （TS） ordering strategy with a stochastic dynamic programming model in the view of the whole system, and prove that the expected profit function of the whole system is concave on the first ordering quantity and the remedial ordering quantity, respectively. Then, the optimal ordering decision is developed. Finally, characteristics of the optimal ordering quantities are analyzed with several examples. Our results show that the suggested TS decision model is better than a Quick Response （QR） decision model.展开更多
基金financially supported by the National Natural Science Foundation of China(NSFC)under Grant Nos.51571058 and 52171108。
文摘The effect of short-range ordering (SRO) on the low-cycle fatigue (LCF) behavior of low solid-solution hardening Ni-Cr alloys with high stacking fault energies (SFEs) was systematically studied under cycling at constant total strain amplitude (Δε t /2) in the range of 0.1%–0.7%. The results show that an inducement of SRO structures can notably improve the fatigue life of the alloy regardless of Δε t /2, and several unique fatigue characteristics have been detected, including the transition of fatigue cracking mode from intergranular cracking to slip band cracking, the non-negligible evolution from non-Masing behavior in pure Ni to Masing behavior in the Ni-40Cr alloy, and the secondary cyclic hardening behavior in the Ni-10Cr and Ni-20Cr alloys. All these experimental phenomena are tightly associated with the transformation in cyclic deformation mechanisms that is induced by SRO based on the “glide plane softening” effect. Furthermore, a comprehensive fatigue life prediction model based on total hysteresis energy has been reasonably proposed, focusing on the analyses of the macroscopic model parameters (namely the fatigue cracking resistance exponent β and the crack propagation resistance parameter W 0 ) and microscopic damage mechanisms. In brief, on the premise that the effects of SFE and friction stress can be nearly ignored, as in the case of the present low solid-solution hardening Ni-Cr alloys with high SFEs, an enhancement of SRO in face-centered cubic metals has been convincingly confirmed to be an effective strategy to improve their LCF performance.
基金This work was supported in part by Natioanl Natural Science Foundation of China under Grant No.70321001 Nature Science Foundation of Henan Province Education Committee under Grant No.2006120004 Natural Science Foundation for PhD of Henan Agricultural University under Grant No.30700300
文摘This paper investigates the ordering decision problem for a short-life-cycle product under Bayesian updating. For a product characterized by a single manufacturing cycle and two selling periods, we depict a Two-Stage （TS） ordering strategy with a stochastic dynamic programming model in the view of the whole system, and prove that the expected profit function of the whole system is concave on the first ordering quantity and the remedial ordering quantity, respectively. Then, the optimal ordering decision is developed. Finally, characteristics of the optimal ordering quantities are analyzed with several examples. Our results show that the suggested TS decision model is better than a Quick Response （QR） decision model.
