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RISS 인기검색어
- 검색키워드
- 저자 : Peishi Yu (검색결과 3 건)
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Peishi Yu,Jin Zhang,Chaofeng Zhang,Junhua Zhao 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.10
The low-yielding-strength (LYS) steel is promising for energy-absorbing devices due to its outstanding plasticity. Although the mechanical properties of LYS steel for quasi-static and ultra-high-rate were studied, the link between them has not been established yet. Here we report both experiments and numerical simulations on the dynamic behavior of a LYS steel (quasi-static yielding stress > 225 MPa, LYS225) under moderate dynamic loadings, which covers the typical range of strain rate in engineering applications. Our results quantify the rate effect of LYS225 under moderate loading speed, and the strain-rate dependent constitutive and damage models are proposed. Moreover, the stress and strain concentration for elliptic-holed LYS225 plate is numerically analyzed based on the proposed constitutive model, which shows significant difference compared to the static solutions. This work could bridge the gap between their quasi-static and ultra-high-rate properties, thereby improve the designing precision of LYS steel-based energy-absorbing structures.
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Yu, Yan,Qiu, Jingyun,Cao, Jincheng,Guo, Yingying,Bai, Hui,Wei, Shengjuan,Yan, Peishi Asian Australasian Association of Animal Productio 2021 Animal Bioscience Vol.34 No.9
Objective: This study was conducted to investigate the potential effects of prolonged photoperiod on the serum lipids, carcass traits, and meat quality of Jinjiang cattle during winter. Methods: Thirty-four Jinjiang bulls aged between 14 and 16 months were randomly assigned to two groups that were alternatively subjected to either natural daylight +4 h supplemental light (long photoperiod, LP) or natural daylight (natural photoperiod, NP) for 96 days. The potential effects on the levels of serum lipids, carcass traits, meat quality, and genes regulating lipid metabolism in the intramuscular fat (IMF) of the cattle were evaluated. Results: Jinjiang cattle kept under LP showed significant increase in both dry matter intake and backfat thickness. the serum glucose and the plasma leptin levels were significantly reduced, while that of melatonin and insulin were observed to be increased. The crude fat contents of biceps femoris muscle and longissimus dorsi muscle were higher in LP than in NP group. In longissimus dorsi muscle, the proportions of C17:0 and C18:0 were significantly higher but that of the C16:1 was found to be significantly lower in LP group. The relative mRNA expressions in IMF of longissimus dorsi muscle, the lipid synthesis genes (proliferator-activated receptor gamma, fatty acid-binding protein) and the fatty acid synthesis genes (acetyl-coa carboxylase, fatty acid synthetase, 1-acylglycerol-3-phosphate acyltransferase) were significantly up-regulated in LP group (p<0.05); whereas the hormone-sensitive lipase and stearoyl-CoA desaturase 1 were significantly down-regulated in LP than in NP group. Conclusion: Prolonged photoperiod significantly altered the growth performance, hormonal levels, gene expression and fat deposition in Jinjiang cattle. It suggested that the LP improved the fat deposition by regulating the levels of different hormones and genes related to lipid metabolism, thereby improving the fattening of Jinjiang cattle during winter.
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Yanqiu Chen,Jin Zhang,Peishi Yu,Jian Wu,Weibo Wang,Junhua Zhao 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.4
The stress and strain concentration in some component has been a signifi cant topic for structural safety assessment. However, the evaluation of the stress and strain concentration based on the widely existing solutions for linear elastic material under static loading would lead to remarkable errors when the material undergoes the dynamic loading, since the coupling eff ect induced by the nonlinearity of the stress–strain relationship and the strain-rate strengthening could be of signifi cant infl uence. Here we analyzed the strain-rate dependent concentration of stress and strain for a visco-plastic plate with an elliptic hole subjected to dynamic loading. The three-dimensional stress and strain are calculated by fi nite element analyses based on a rate-dependent Johnson–Cook model in which the material constants are set according to a typical visco-plastic standard 45 carbon steel. Our results show that both the plastic stress and strain concentration factors signifi cantly depend on not only the strain but also the strain rate. With the increment of the remote strain rate, the stress concentration monotonically increases, while the strain concentration shows decreasing tendency.
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