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Characterization of Hot Deformation Behavior and Processing Map of As‑Cast H13 Hot Work Die Steel
Yahui Han,Changsheng Li,Jinyi Ren,Chunlin Qiu,En LI,Shuaishuai Chen 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9
The hot-working behavior of as-cast H13 hot work die steel was investigated in the method of isothermal compression testinvolving the wide deformation temperatures of 900–1150 °C and strain rates of 0.01–10 s−1, with the true strain to 0.8, onthe MMS-200 thermo-mechanical simulator. Two characteristic parameters involving the critical strain for DRX initiation(c ) and the strain for peak stress (p ) were identified. The ratio of critical strain to peak strain ranged from 0.26 to 0.6, whichdecreased with the increase in temperature and decrease in strain rate. Processing maps were established using dynamicmaterial model at strains of 0.2, 0.4, 0.6, 0.8. The power dissipation maps were not significantly affected by the strain, whilethe instability maps were sensitivity with the strain when it was over 0.4. The area of instability domain at strain of 0.8 wasthe largest. The instable characteristics contained the mixed grain structure, adiabatic shear band, intense deformation inserious deformation area and brittle elemental segregation area. The chief effect on the power dissipation was the strain rate,the optimum hot working parameters at strain of 0.8 (910–985 °C, 1010–1150 °C and 0.01–0.05 s−1) were determined. Inthis filed, the original coarse as-cast grains were gradually refined by dynamic recrystallization mechanism and the DRXgrain numbers had a significant increase with the increase of power dissipation efficiency.
Shi Yao,Lu Jiewen,Gao Shan,Pan Guang,Ren Jinyi 대한조선학회 2023 International Journal of Naval Architecture and Oc Vol.15 No.-
In this paper, an experimental system was independently designed to investigate the cavitation flow mechanism and motion characteristic of the vehicle launched underwater. Conducted experiments based on high-speed photography, and the influence of cavity morphological evolution and kinematic characteristics with the different launch and transverse velocities were analyzed. The results show that cavity shedding phenomenon occurs on different scales. Subsequently, a wide range of pressure impulse on the surface of the vehicle is caused by the collapse of large-scale cavity groups, resulting in an obvious sputtering phenomenon on its surface during the water-exit stage. The more the launch speed increases, the longer the initial cavity length is. Moreover, the moment of completely shedding the cavity delays during the water exit process; Furthermore, with the increase of transverse speed, the attitude angle generally shows an increasing trend, but its growth rate slowed down during the large-scale shedding stage of the cavity.