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高温下混凝土动态力学特性试验 总被引:3,自引:0,他引:3
基于自行研制的适用于100 mm分离式霍普金森压杆(split Hopkinson pressure bar,SHPB)装置的高温试验设备,采用相应高温试验技术在100 mm SHPB装置上对混凝土分别在常温、200、400、600、800和1000℃下的动态力学特性进行了试验研究。结果表明:高温下混凝土的动态应力应变曲线体现出温度效应和应变率效应,随温度和应变率增大,曲线逐渐表现出塑性特性;高温下混凝土的动态抗压强度随温度升高或平均应变率增长先提高后降低;高温下混凝土的动态峰值应变随温度升高或平均应变率增大而不断提高,动态峰值应变与平均应变率之间存在近似线性增长关系;高温下的动态峰值应变大于常温下,相对增幅随温度升高或应变率增大而不断提高。 相似文献
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采用试验和数值模拟结合的方法对X80管线钢多道激光-MIG复合焊焊接过程的温度场和焊接残余应力场进行了研究,分析了激光功率对复合焊接头的显微组织、温度分布和残余应力分布的影响规律. 结果表明,激光功率增加,熔池最高温度明显上升,焊后冷却速度下降;粗晶热影响区组织中粒状贝氏体、针状铁素体增加,条状贝氏体减少. X80管线钢激光-MIG复合焊接头残余应力水平较高,纵向残余应力、横向残余应力和厚度方向残余应力的拉应力峰值均出现在焊缝区. 激光功率在2.0 ~ 3.5 kW范围时,等效残余应力、纵向残余应力、横向残余应力和厚度方向残余应力的峰值随着激光功率增加均出现下降趋势. 但激光功率从3.5 kW上升至4.0 kW时,各应力的峰值有所上升. 相似文献
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纯铁在高应变率下的流动应力特征及其动态塑性本构关系 总被引:2,自引:0,他引:2
利用MTS材料试验机和分离式Hopkinson压杆实验装置,对锻造后经930℃下退火2h的纯铁材料进行压缩实验,测定纯铁在准静态条件(10-3s-1~100s-1)和高应变率(650s-1~8500s-1)下的应力-应变曲线。实验结果表明,纯铁是应变率敏感材料,纯铁在高应变率条件下,具有应变率增强、增塑以及应变强化效应,高应变率下的塑性变形过程中产生的绝热升温对材料具有热软化作用。基于Johnson-Cook(J-C)本构模型,引入绝热温升软化项对模型进行修正,通过实验数据拟合得到了纯铁的动态塑性本构关系,模型计算结果和实验结果证明,该模型可以较好地预测纯铁在高应变率下的塑性流动应力。 相似文献
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Conclusions We measured the static bending strength, the hardness, and the impact strength of steels with low hardenability after induction heating followed by quenching and low-temperature tempering. We have recommended optimum quenching temperatures, tempering temperatures (in the case of induction heating), and the hardenability of steels for machine parts of different sizes. We have shown that the static bending strength and the impact strength of samples of quenched carbon steels are as high as those of case-hardened alloy steels.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 35–42, June, 1963 相似文献
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The oxidation properties of iron have been investigated at temperatures in the range 800–1000° C in oxygen over the pressure range 0.3–760 Torr. A duplex scale consisting of wustite and magnetite was formed during the earliest intervals examined. Hematite grew on the magnetite surface after an induction period which decreased with increasing oxygen pressure; this oxide developed as whiskers and platelets at temperatures less than 860° C and as small grains at higher temperatures. Iron transport occurs through the scale and involves short-circuit diffusion in the hematite layer. The oxidation kinetics obeyed a parabolic law independent of oxygen pressure since multilayer scale growth was directly dependent on the lattice diffusivity of iron and the iron gradient established in the wustite layer.This work was sponsored by the National Research Council of Canada. 相似文献
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Constitutive equation of annealed copper with high conductivity for deformation at high strain rates
After the discussion of a lot of constitutive equations, Zerilli-Armstrong constitutive equation (Z-A equation) was found to be a quasi-static equation. Based on this Z-A equation, a constitutive relations equation was constructed for dynamical calculation of fcc matels such as OFHC based on the thermal viscoplastic relations, where thermal dynamical parameters are related to the evolution of the microstructure of the deforming metals, and the variation of the density of the mobile dislocation was also considered. Data from the deformation of annealed copper were used to fit the parameters in the equation. The predicting results by using the constitutive equation are in good agreement with the experimental data. 相似文献
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B. G. Belov E. K. Zakharov L. V. Zubova A. V. Smirnova 《Metal Science and Heat Treatment》1976,18(3):238-240
1. | It was found that the spring alloy tested is suitable for elastic sensing elements. It is paramagnetic down to the temperature of liquid nitrogen. |
2. | The optimal heat treatment (quenching from 950° and aging at 700° for 4 h) ensures high ductility after quenching, and high strength and elasticity after aging. The alloy is resistant to relaxation in the temperature range from 250 to –196°. |
3. | The principal hardening phase is phase. The corrosion resistance of the alloy in 57% HNO3 at 20, 50, and 80° is no lower than that of alloy 36NKhTYu. |
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Peter Schaaf Sabine Günschmann Johannes Wilden Christian Borschel 《Surface & coatings technology》2010,205(5):1584-1588
Coated and nanostructured surfaces gain much importance for improving the efficiency of high temperature applications (e.g. in turbines). By embedding ceramic particles with a negative thermal expansion coefficient (NTEC) into a metallic matrix, a reversible thermal activation of a nanostructured surface can be established.At high temperatures a defined drag reducing surface microstructure (“shark-skin”) is formed in the coating surface, while at low temperatures a self-cleaning effect (in idle periods) is achieved by the reversal of the thermal deformation.A feedstock powder produced by high energy milling and consisting of nanocrystalline yttrium oxide and tungsten oxide particles embedded into a conventional MCrAlY alloy was used for the investigations. By using different thermal spray and cladding techniques the powder is deposited on steel- substrates. In the next step, the coating is implanted with yttrium or xenon in order to induce the formation of Y2W3O12. The latter is a ceramic with a strong negative thermal expansion coefficient and is stable up to temperatures above 1373 K. The effects during annealing and the morphology changes are analyzed in detail. Results of the phase transformation, the surface micro-morphology and the microstructured properties of these high-temperature coatings are presented. 相似文献
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High strain rate bulge test technique which is introduced in this paper adopts a rubber-pad as pressure carrying medium to bulge a sheet metal at high velocity using split Hopkinson pressure bar (SHPB) system. The experimental set-up is based on conventional hydraulic bulge test which is modified to mount on SHPB. The thickness thinning of the sheet metal during the test will be considered as a measure of true strain of the bulged sheet. The theoretical approach is developed in this study to attain pressure–strain curves of sheet metals during high strain rate bulge forming process. This approach is followed by a finite element simulation of the process in ABAQUS/Explicit software. To verify the developed method, analytical and finite element methods are compared with experiments. 相似文献