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压痕法测定热压MoSi2基复合材料K1C值的研究 总被引:8,自引:1,他引:8
用不同的压痕方程计算了纳米ZrO2粒子韧化MoSi2基复合材料的室温断裂韧性K1c值,同时研究了压痕载荷对K1c值的影响。结果表明,试验材料在试验条件下的断裂韧性不遵从半月状裂纹系统方程,而遵从巴氏裂纹系统方程,其室温压痕断裂韧性保持与压痕载荷的独立性。 相似文献
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介绍了对某直升机加强侧垂直安定面复合材料结构件的加载及无损检测跟踪试验全过程,通过分析试验结果确定无损检测方法和预加载值的大小。 相似文献
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本文着重研究了2024锻造铝合金经过T4及T6热处理后其单轴及多轴疲劳性能。采用了两种不同热处理方式制备出具有不同微结构的2024锻造铝合金,研究其在不同加载状态下的变形行为、疲劳机制及疲劳寿命。主要内容包括:对2024锻造铝合金进行单向拉伸、应力控制的单轴拉压疲劳及两种多轴拉扭疲劳试验,研究了加载状态与疲劳寿命的关系。结果表明,2024锻造铝合金材料的疲劳寿命对热处理和加载状态的敏感性很大,表现为在相同加载状态下2024-T4和2024-T6试样的寿命差别较大,以及同一热处理试样在不同应力幅值和不同加载路径下疲劳寿命差异大。 相似文献
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铸造生产中热物性参数的变化 总被引:1,自引:0,他引:1
介绍了热扩散率α、比热容C、热导率K等热物性参数(热三数)在金属中(纯金属与加入其他材料的合金)、球铁、蠕铁和灰铁等三种不同石墨形状影响下的变化。结果表明,纯金属(铜)的α值比掺入Al合金及加碳纤维的铜合金大。而比热容C则与α相反,纯铜最小,加入Al的合金次之,加碳纤维的最大。而K值则与α值成正比,纯铜的K值远大于另两种合金的K值。铸件中球状石墨的α数值远远小于片状石墨的α值。蠕虫状石墨介于二者之间。片状石墨的K值大于球状石墨的K值(差值大于2倍),C值差异不明显。片状石墨的α曲线随温度上升呈下降趋势。材料(3Cr13)密度大则α和K值均较密度小的大。一般情况下,造型材料的K值都随温度的提高而增大。 相似文献
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本文对次级调节扭矩伺服加载系统的工作原理进行了详尽的分析,给出了系统的传递函数方框图,设计了用于加载系统的带加权因子的模糊控制器,对加载系统的两个主要组成部分转速和扭矩控制系统在不同输入信号下分别进行了试验研究,同时还对二者之间的相互干扰进行了试验研究。 相似文献
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二元合金非平衡凝固溶质分配的统计模型 总被引:4,自引:0,他引:4
本文用非平衡统计理论研究二元合金凝固时界面的溶质分配,得到了一般情况下溶质分配系数K与时间t的函数关系。当t→∞,K就成为平衡溶质分配系数K0,在t大于热平衡弛豫时间ζ,小于结构平衡弛豫时间ζ0的时间区间内,K对K-的偏离随过热度ΔT的增大而增大,与实验结果一致。 相似文献
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采用激光脉冲试验法研究不同淬火和回火工艺对高速列车制动盘用Cr-Mo-V钢在50~800℃时的比热容、热扩散系数和导热系数。结果表明,当试验温度低于700℃时,随着试验温度的提高,试验料热扩散系数和导热系数逐渐降低,比热容逐渐提高;当试验温度超过700℃时,试验料热扩散系数和导热系数又随之提高,比热容随之下降。当试验温度低于700℃时,随着回火温度或淬火温度的提高,试验料在不同试验温度条件下热扩散系数和导热系数均稍有提高,比热容稍有降低;当试验温度为800℃时,几组试验料的比热容、热扩散系数和导热系数基本相当。 相似文献
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The evaluation of reliability for zirconium diboride composite with additives of graphite 总被引:1,自引:0,他引:1
Guoqian Liu Songhe Meng Jing An Shilong Sun Xiaoheng Ding 《International Journal of Refractory Metals and Hard Materials》2009,27(5):868-871
Statistical distribution of strength was investigated with different load speeds for ultra high temperature ceramic. It shows that the strengths under different load speeds follow Weibull probability well. Inertial stress was obtained for the ceramic under different load speeds.Finally, an application was implemented for the ceramic suffering quenching test. Dynamic thermal stress was obtained during quenching test, which was much higher than quasi-static one. The effect of heat transfer coefficients on failure probability range was evaluated for the ceramic during quenching test. 相似文献
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磁性材料的应用对低温制冷机的发展有着重要的意义。目前磁性材料在液氮以下温区热物性参数的缺乏严重限制了制冷机回热器的设计与优化。研制了颗粒状磁性材料低温表观热导率测量装置,对Er3Ni在4-40 K及不同氦气压力下的表观热导率进行了测量并计算了Er3Ni热导率系数。在不同温区的测试结果表明,真空状态下,Er3Ni颗粒表观热导率为0.11-0.22 W/m·K,对应的热导率系数为0.31-0.53;当氦气压力增大至1.4-2.2 MPa后,表观热导率趋于稳定,稳定后的平均值为3 W/m·K,对应的热导率系数为7。进一步研究了Er3Ni型回热器不同工况下的漏热特性,提出了丝网与颗粒混合填充的方案以降低冷热两端的轴向漏热。结果表明,在Er3Ni回热器中混合填充尼龙网和316 L不锈钢丝网后制冷性能显著提高,在1.6 MPa压力下漏热降低幅度分别高达12%和8%。 相似文献
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推导了恒定激光脉冲激励作用下的焊点瞬态热平衡方程,及基于极限温差反问题识别的缺陷尺寸及热阻解析求解方法;通过建立空洞缺陷焊点数字化模型,对恒定激光脉冲激励过程进行了热分析仿真,得到了焊点温差、热阻及缺陷尺寸之间的演化规律;通过制备虚焊缺陷焊点试验样本,实施了不同温度参数组合下的热试验,并对热试验后的焊点缺陷演化情况进行红外测温分析.试验结果表明,热试验过程中的焊点缺陷演化机理具有与金属材料蠕变曲线相似的变化规律,缺陷尺寸呈现先增大、后减小及再增大的变化行为,有助于完善和补充焊点的热试验理论. 相似文献
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采用自主研制的带补偿加热的接触热导测试装置,测试了航空发动机用高温结构材料GH4169/K417间不同温度(160~280℃)和粗糙度下的接触热导,研究温度对其接触热导的影响行为,对比分析有无补偿加热条件下接触热导的测试结果。结果表明,带有补偿加热的接触热导测试装置能有效降低横向热流损失,且随着温度的升高效果逐渐明显。不同粗糙度的GH4169/K417材料组合,温度对其接触热导的影响不同,主要与其界面处材料的变形、氧化有关。 相似文献
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《Intermetallics》1999,7(9):1049-1057
The two kinds of spark sintered titanium aluminides, series 1 (70% TiAl, 30% TiAl/Ti3Al lamella) and series 2 (10% TiAl, 90% TiAl/Ti3Al lamella) specimens, having different volume fraction of the TiAl and TiAl/Ti3Al lamellar grains at or near the notch tip, are prepared for Charpy impact testing. These tests are conducted in air at various temperatures between 293 and 1373 K. Charpy impact value increases monotonously as temperature rises and its value is 2.0 to 8.1 kJ/m2, regardless of microstructural differences in the vicinity of the notch tip. However, the value (0.25×10−3m) of the deflection to failure is very low, even in the result obtained from the highest temperature (1373 K). On the other hand, the fracture load or maximum fracture load tends to increase as the test temperature is raised to 793 and 873 K in the series 2 and 1 specimens, respectively, and thereafter it decreases significantly. The maximum fracture load of the series 1 specimen is higher than that of the series 2 specimen throughout the test temperatures. The predominant mode of failure changes from transgranular fracture to intergranular fracture as the temperature is increased, which corresponds with the behaviour of the maximum fracture load. 相似文献
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In a fusion reactor, plasma-facing components(PFCs) will suffer severe thermal shock; behavior and performance of PFCs under high heat flux(HHF) loads are of major importance for the long-term stable operation of the reactor. This work investigates the thermo-mechanical behaviors of tungsten armor under high heat loads by the method of finite element modeling and simulating. The temperature distribution and corresponding thermal stress changing rule under different HHF are analyzed and deduced. The Manson–Coffin equation is employed to evaluate the fatigue lifetime(cyclic times of HHF loading) of W-armored first wall under cyclic HHF load. The results are useful for the formulation design and structural optimization of tungsten-armored PFCs for the future demonstration fusion reactor and China fusion experimental thermal reactor. 相似文献
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Thermal conductivity and elastic modulus evolution of thermal barrier coatings under high heat flux conditions 总被引:2,自引:1,他引:1
Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings
(TBCs) under near-realistic temperature and thermal gradients that may be encountered in advanced engine systems. Thermal
conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures.
A significant thermal conductivity increase was observed during the laser-simulated engine heat flux tests. For a 0.25 mm
thick ZrO2-8% Y2O3 coating system, the overall thermal conductivity increased from the initial value of 1.0 W/m K to 1.15, 1.19, and 1.5 W/m
K after 30 h of testing at surface temperatures of 990, 1100, and 1320 °C, respectively, Hardness and elastic modulus gradients
across a 1.5 mm thick TBC system were also determined as a function of laser testing time using the laser sintering/creep
and microindentation techniques. The coating Knoop hardness values increased from the initial hardness value of 4 GPa to 5
GPa near the ceramic/bond coat interface and to 7.5 GPa at the ceramic coating surface after 120 h of testing. The ceramic
surface modulus increased from an initial value of about 70 GPa to a final value of 125 GPa. The increase in thermal conductivity
and the evolution of significant hardness and modulus gradients in the TBC systems are attributed to sintering-induced microporosity
gradients under the laser-imposed high thermal gradient conditions. The test techniques provide a viable means for obtaining
coating data for use in design, development, stress modeling, and life prediction for various TBC applications. 相似文献
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CaB6作为一种新型的热电材料,原料丰富且环保。以硼粉和氢化钙粉为原料,通过放电等离子烧结原位反应合成成功制备出了CaB6块体材料。第一性原理计算结果表明,CaB6呈现金属输运特性。试验结果表明,CaB6呈现n型金属输运特性。在373~773 K测试温度范围内,功率因子随着温度的升高呈上升趋势,从2.86×10-3 W·m-1 K-2增加到3.6×10-3 W·m-1 K-2,热导率随着温度的升高呈下降趋势,从11.63 W·m-1 K-1减小到9.06 W·m-1 K-1,其中晶格热导率占主导,且晶格热导率随温度的变化趋势与理论计算结果一致。在1 673 K制得的CaB6样品在773 K取得最大ZT值,达到0.34。 相似文献