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通过对40CrNiMo光滑与三种不同缺口状态的试样进行试验发现,氢对材料强度的影响与外加应变速率的大小有关。在空气中试验,缺口状态对材料断裂强度几乎无影响;而在氢气中试验,则发现缺口根部半径R的变化对材料断裂强度影响极大;当缺口根部半径一定,仅改变外径D或缺口处最小直径d所得两种缺口状态对缺口强度的影响不大。 相似文献
204.
Austenitic Mn-Al alloys (20–32 W/O Mn, 7–10 Al, 2–3 Si, 1C) were found to have satisfactory oxidation resistance up to 950°C under isothermal conditions in air. Surface enrichment of aluminum is a necessary condition for obtaining an almost pure alumina scale for uses at higher temperatures. Four different Mn-steels were Al-coated by the Capuano electroplating process. In all the steels there was an increase in the hot-oxidation resistance. The best results were obtained with steels containing both Al and Si, and this for temperatures up to 1100°C. No spalling was noticed during rapid cooling of the test pieces. Silicon was found to act as a diffusion barrier to outward iron diffusion. It appears that there is formation of a pure, thin film of alumina from the matrix which interacts with the aluminum diffusing from the superimposed, coating for the formation of good bonds. 相似文献
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207.
改性脲醛树脂胶粘剂的研究 总被引:8,自引:1,他引:8
主要利用混合改性剂,改进生产工艺以及施胶时加入填料等方法研究脲醛树脂胶粘剂的游离甲醛含量,剪切强度、耐水性等问题,得到低毒,综合性能良好的胶粘剂。 相似文献
208.
改性BMI微孔轴承保持器材料研究 总被引:1,自引:0,他引:1
采用改性双马来酰亚胺树脂制备微孔轴承保持器材料,探讨了制备工艺和最佳工艺参数,得到性能优良的改性双马来酰亚胺微孔轴在保持器材料。 相似文献
209.
This study investigates the effects of cement type, curing temperature, and age on the relationships between dynamic and static elastic moduli or compressive strength. Based on the investigation, new relationship equations are proposed. The impact-echo method is used to measure the resonant frequency of specimens from which the dynamic elastic modulus is calculated. Types I and V cement concrete specimens with water-cement ratios of 0.40 and 0.50 are cured isothermally at 10, 23, and 50 °C and tested at 1, 3, 7, and 28 days.Cement type and age do not have a significant influence on the relationship between dynamic and static elastic moduli, but the ratio of static to dynamic elastic modulus approaches 1 as temperature increases. The initial chord elastic modulus, which is measured at low strain level, is similar to the dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic moduli for various cement types, temperatures, and ages. 相似文献
210.
Number of blends were prepared by intergrinding clinker, gypsum, fly ash, calcined clay, microsilica and limestone in laboratory ball mill in varying percentages, and their physical properties such as fineness, consistency, setting time and compressive strength have been determined. The durability tests on selected compositions were also conducted by exposing the mortar cubes separately in 5% Na2SO4 and 5% NaCl solutions till the age of 90 and 180 days. The performance was observed by compressive strength development criteria after various length of exposure. Results have been discussed and found that the durability of blended cement is higher than the ordinary Portland cement. 相似文献