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51.
Legan Hou Tianzi Wang Ruizhi Wu Jinghuai Zhang Milin Zhang Anping Dong Baode Sun Sergey Betsofen Boris Krit 《材料科学技术学报》2018,34(2):317-323
Ultrafine-grain and high-strength Mg-5Li-1Al sheets were prepared by accumulative roll bonding (ARB) process. Evolution of microstructure and mechanical properties of ARB-processed Mg-5Li-1Al sheets was investigated.Results show that, during ARB process, the evolution of deformation mechanism of t Mg-5Li-1Al alloy is as follows: twinning deformation, shear deformation, forming macro shear zone, and finally dynamic recrystallization (DRX). The grain refining mechanism changes from twin DRX to rotation DRX. With the increase in ARB cycles, strength of the Mg-5Li-1Al sheets is enhanced, whilst elongation varies slightly. With the increase in rolling cycles, anisotropy of mechanical properties decreases. It is conclusive that strain hardening and grain refinement dominate the strengthening mechanism of Mg-5Li-1Al alloy. 相似文献
52.
通过力学性能测试得到发泡硅橡胶应力应变曲线,结合Ogden(Foam) 3阶超弹本构模型,建立发泡硅橡胶静密封系统的有限元仿真模型,得到大压缩量下发泡硅橡胶的von Mises应力及接触压力分布情况。仿真结果表明:大压缩量下发泡硅橡胶对称中心线位置的von Mises应力、接触压力值较大,在橡胶边缘和靠近限位环处接触应力数值有突增。开展140℃热空气老化试验,测定老化后发泡硅橡胶应力应变曲线,结合有限元仿真模型分析发泡硅橡胶老化后von Mises应力、接触压力的变化规律。结果表明:经过热空气老化后,在一定载荷下发泡硅橡胶等效应力和接触压力均呈增大的趋势。 相似文献
53.
空气源热泵热水器在寒冷地区运行时会出现排气温度过高、制热性能弱等弊端,准双级压缩循环技术可有效改善其在寒冷地区的运行特性。采用带中压补气的转子压缩机,研制了以R410A为循环工质的空气源热泵热水器,试验研究了系统在寒冷地区低温环境下的制热性能。结果表明:带中压补气的空气源热泵热水器系统排气温度较无补气有所降低,当室外温度从7.0下降到-25.0℃时,与无补气系统相比,补气系统制热量提升了6.2%~15.5%,压缩机功率提升了2.8%~9.5%,COP_h提升了3.3%~9.6%。 相似文献
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采用SEM、TEM、LF457型激光导热仪,DSC404型差示扫描量热仪和UMT-3型高温摩擦磨损试验机对高强钢板热冲压用新型模具钢的组织和热稳定性能、热物理性能及高温耐磨性能进行研究。试验结果表明:该模具钢具有良好的抗回火软化性能、热稳定性、高热导率和高温耐磨性,能更好地适应高强钢板热冲压工况。新型模具钢的碳化物以Mo2C和VC为主,使得该钢有更好的抗回火软化和热稳定性。新型钢具有高热导率,在室温下是H13钢的1.4倍。其低Si、Mn、Cr和高Mo的合金化特征是其高热导率的原因。该钢较H13钢有更好的高温耐磨性能,尤其是温度高于600 ℃后耐磨性要远远优于H13钢。新型模具钢良好的耐磨性能有益于减少模具修理频次,提高模具寿命。 相似文献
57.
对K439B合金进行了1165 ℃/150 MPa,4 h热等静压处理,采用光学显微镜和扫描电镜对比研究了铸态和热等静压态K439B合金的显微组织。结果表明:铸态K439B合金存在0.25%的显微疏松,热等静压后显微疏松基本消除(0.013%)。与铸态相比,经过热等静压处理后合金中的γ/γ′共晶组织体积分数和尺寸减小,各元素分布更加均匀,凝固偏析系数均更接近1。铸态K439B合金枝晶干处γ′相尺寸和体积分数分别是116.9 nm和17.8%,枝晶间部位γ′相尺寸和体积分数分别为244.4 nm和24.9%。热等静压后合金枝晶干部位的γ′相尺寸及体积分数分别为148.0 nm和17.5%,枝晶间部位γ′相尺寸和体积分数分别为159.1 nm和22.8%。热等静压处理使合金枝晶干、枝晶间部位的γ′相尺寸、体积分数和形貌接近,同时γ′相分布变得均匀。 相似文献
58.
Apoorva Karamchandani Hojae Yi Virendra M. Puri 《Particulate Science and Technology》2018,36(4):447-456
Mechanical and physical properties of ground corn stover, switchgrass, and willow were measured and compared in addition to the quality of pellets. Biomass was size-reduced with two different screen sizes (3.175 and 6.35?mm) and conditioned to obtain samples at two different moisture contents (17.5 and 20% on wet basis). Ground switchgrass had the smallest and willow had the highest D50 when size-reduced with the same screen size. Hydrostatic triaxial compression tests were performed using the cubical triaxial tester to determine the bulk modulus, compression index, and spring-back index at specific unloading pressures (20, 45, 70, and 95?kPa). The trends of pressure vs. volumetric strain and void ratio vs. natural log of pressure were similar for all three materials; however, the magnitudes were different. Willow, size-reduced with 3.175?mm screen size at 17.5% wet basis, had the highest bulk modulus among different conditions of all the three biomass. Pellet durability values for all the three materials were higher than 80%. Corn stover pellets formed with 3.175?mm screen size at 20% wet basis had the highest diametral tensile and axial compressive strengths among different conditions for all the three biomass, however the values were not significantly different (p?>?0.05). 相似文献
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Xuelin ZHANG Tong ZHANG Xiaodai XUE Yang SI Xuemin ZHANG Shengwei MEI 《Frontiers in Energy》2020,14(4):889
Hot dry rock is a new type of geothermal resource which has a promising application prospect in China. This paper conducted a comparative research on performance evaluation of two eligible bottoming cycles for a hot dry rock power plant in the Gonghe Basin. Based on the given heat production conditions, a Kalina cycle and three organic Rankine cycles were tested respectively with different ammonia-water mixtures of seven ammonia mass fractions and nine eco-friendly working fluids. The results show that the optimal ammonia mass fraction is 82% for the proposed bottoming Kalina cycle in view of maximum net power output. Thermodynamic analysis suggests that wet fluids should be supercritical while dry fluids should be saturated at the inlet of turbine, respectively. The maximum net power output of the organic Rankine cycle with dry fluids expanding from saturated state is higher than that of the other organic Rankine cycle combinations, and is far higher than the maximum net power output in all tested Kalina cycle cases. Under the given heat production conditions of hot dry rock resource in the Gonghe Basin, the saturated organic Rankine cycle with the dry fluid butane as working fluid generates the largest amount of net power. 相似文献