ZrO2-Ni功能梯度材料的热冲击与热疲劳行为

通过抗热震参数分析和热循环试验研究了ZrO2-Ni功能梯度材料（FGM）的热冲击与热疲劳行为及其影响因素。结果表明,ZrO2-Ni FGM热热震参数呈梯度分布,ZrO2侧抗热冲击断裂能力强而富Ni区热疲劳抗力高。其热震破坏符合热疲劳损伤机理,裂纹的准静态扩展为其控制因素。热疲劳裂纹在梯度层内以微孔聚集、连接方式萌生和扩展,而在梯度层间无横向贯穿裂纹,克服了传统陶瓷／金属结合体的界面热应力剥离问题。     

金属热疲劳a-N曲线测定方法的研究

提出了在金属的热疲劳试验中,用测试样表面裂纹代替测断口裂纹,用“单组试样法”代替“多组试样法”来测定a-N曲线;通过同一循环次数时试样在不同表面粗糙度条件下的实际观测和所测裂纹长度的比较,确定出测量表面裂纹长度所必须达到的粗糙度指标;给出了用“单组试样法”测定a-N曲线的具体操作方法;分析了金属热疲劳裂纹扩展的一般规律并提出了拟合a-N曲线的方法。     

金属非对称循环下的匀变速加载问题

由损伤力学理论可知,疲劳是由材料内部的损伤演化导致的,但其损伤演化的机理并不清楚。为此,我们将高分子物理中断裂的分子理论推广应用于金属的疲劳损伤,认为金属的断裂是一个松驰过程,宏观断裂是微观原子键断裂热活化的结果。以Q235钢为例,在CMT5105万能电子试验机上进行拉压非对称循环疲劳试验。从原子键离解的视角出发并结合试验数据,讨论并推算诸多因素影响下匀、变速加载时非对称循环疲劳损伤演化律的具体形式。再将速率作为重点考虑因素提出了新的疲劳损伤演化律,分别讨论了匀、变速情况下损伤演化律的基本形式,并对速率相关参数因子进行了修正。结果表明,新的疲劳损伤演化律形式简单、参数少、应用广泛且与试验结果贴合较好。     

国内外金属材料热机械疲劳试验方法标准比较

对GJB 6213-2008,ASTM E2368-2010和ISO CD 12111-2002三个金属材料热机械疲劳试验方法标准分别从试验设备要求、试样要求、试验程序控制和试验结果评定等方面进行了对比分析,归纳总结了以上标准的异同点,建议今后在制定或修订热机械疲劳试验方法国家标准时增加对试样温度梯度、感应线圈温度场分布、应变速率变化和热应变补偿精度检验等参数要求。     

金属热疲劳α-N曲线测定方法的研究

提出了在金属的热疲劳试验中,用测试样表面裂纹代替测断口裂纹,用"单组试样法"代替"多组试样法"来测定α-N曲线;通过同一循环次数时试样在不同表面粗糙度条件下的实际观测和所测裂纹长度的比较,确定出测量表面裂纹长度所必须达到的粗糙度指标;给出了用"单组试样法"测定α-N曲线的具体操作方法;分析了金属热疲劳裂纹扩展的一般规律并提出了拟合α-N曲线的方法.     

4Cr5MoSiV1，8407钢的热疲劳性能

采用自约束热疲劳试验方法,对比研究了相同热处理条件的4Cr5MoSiV1,8407钢的热疲劳特性,观察分析了疲劳裂纹形貌和深度,采用热疲劳损伤因子定量研究了二种钢的热疲劳过程。结果表明：两种钢的热疲劳裂纹萌生发生在100－200次之间。8407钢热疲劳裂纹的萌生较4Cr5MoSiV1钢均匀,细小;在1600次冷热循环前,二者的热疲劳损伤程度无明显差别,在1600次热循环后,前者的热疲劳损伤程度低于后者;在较低的回火温度条件下,8407钢的热疲劳抗力稍优于4Cr5MoSiV1;而在高温回火时,8407钢的热疲劳抗力属于4Cr5MoSiV1钢。分析了这二种钢的热疲劳机制,指出决定材料热疲劳裂纹抗力的是钢的热稳定性和钢的强度或硬度。     

一种新型耐高温表面复合层的研制

为提高耐高温合金工作层性能,本文采用材料逆向设计准则及表面复合技术,在耐高温合金表面堆焊熔敷层金属,并对堆焊金属的高温磨损性能及热疲劳行为进行了研究。结果表明,在转速一定时,随着试验温度的升高,堆焊层的磨损失重量先增加后减少;在试验温度一定时,随着转速的增加,材料的磨损失重量也是先增加后减少;堆焊层在上限温度为400℃和600℃时,具有良好的热疲劳性能。该材料可作为高速列车制动盘、石油钻机盘式刹车制动盘等高能制动盘工作层材料。     

活塞热疲劳试验控制系统

本文介绍了一个用可编程控制器ＰＬＣ与ＰＣ机构成的活塞热疲劳模拟试验控制系统。文中就控制系统在不同设计方案进行了对比，阐述了选用ＰＬＣ＋ＰＣ机方案的优越性，并对该方案的硬件和软件设计思想作了说明。     

WC/铁基表面复合材料的热疲劳裂纹形成过程

为了对高热疲劳性能的表面复合材料的设计提供理论依据 , 采用热震试验方法对通过真空实型铸渗(V2 EPC) 方法制备的 WC/铁基表面复合材料的热疲劳性能进行了研究 , 重点讨论了热疲劳裂纹的形成机制。研究结果表明 , 随着 WC颗粒体积分数的增加 , 表面复合材料的热疲劳性能有所改善 , 当 WC体积分数达到 52 %时 , 复合层表面在经过 10次热循环后能保持完好。热疲劳裂纹扩展机制研究表明 , 陶瓷 WC颗粒增强铁基表面复合材料的热疲劳裂纹的产生和扩展是由 WC和基体本身的热应力和二者界面交变循环应力共同交互作用的结果 , 可以通过选用高热导率的陶瓷颗粒作为增强体、 改善陶瓷颗粒本身的微观质量和采用与陶瓷颗粒热膨胀系数相接近的基体等方法提高复合材料的热疲劳性能。      

TiN气相沉积层对3Cr2W8V钢热疲劳性能的影响

采用自约束热劳试验方法研究了ＴｉＮ等离子气相沉积怪对３Ｃｒ２Ｗ８Ｖ钢热疲劳性能的影响。结果表明：ＴｉＮ沉积层可以有效地提高钢的疲劳抗力，随沉积层厚度减薄，热疲劳抗力增加；随热循环上限温度和蔼同，ＴｉＮ沉积层的热疲劳抗力降低；ＴｉＮ沉积层具有很的热循环稳定及抗氧化性。     

Uddeholm热疲劳图谱的分析与定量评定

通过建立热疲劳裂纹图像采集和计算机分析系统，对Uddeholm热疲劳评定标准图谱进行了分析，结果表明，Uddeholm标准图谱评定热疲劳程度是不够精确的，即无法用肉眼精确地评定热疲劳裂纹的级别，针对Uddeholm标准图谱的不足，提出损伤因子概念，并制作出一套相应的计算软件；用它定量地分析了进口8407S钢和国产4Cr5MoSiV1钢的热疲劳性能，揭示了两种钢的热疲劳性能的变化规律，实现了热疲劳裂纹的计算机辅助评定。     

Effect of heating temperature and magnesium content on the thermal cyclic failure behaviour of ductile irons

Abstract

This study elucidates the effect of residual magnesium content and heating temperature on the thermal cyclic failure behaviour of ductile irons by applying repeated heating and cooling cycles. Five irons with different residual magnesium contents ranging from 0.038 to 0.066 wt-% were obtained by controlling the amount of nodulariser additions. The thermal fatigue cracking behaviour was investigated during thermal cycling from 25°C to 650, 700, 750, and 800°C, respectively. Experimental results indicate that the thermal fatigue cracking resistance of ductile iron decreases with increasing residual magnesium content. The maximum heating temperatures of 700°C and 750°C led to the most severe thermal fatigue cracking in the specimens containing 0.054 wt-% and 0.060 wt-% residual magnesium content. Recrystallisation of ferrite grain occurred when the thermal cycles exceeded a certain number after testing at 800°C, which deferred the initiation of thermal fatigue cracking.     

热模拟试验在金属热变形研究中的应用

利用Gleeble-2000热模拟试验机对钢进行受热及加工过程的模拟,通过测定钢的奥氏体再结晶图,变形抗力,CCT曲线和热塑性图等。配合必要的物理和化学检验方法,探索生产工艺与显微组织,相变,力学性能的关系,促进热加工工艺的研制及改善。     

THE FREQUENCY RESPONSE MODEL OF THERMAL STRIPING FOR CYLINDRICAL GEOMETRIES

Abstract— The random temperature fluctuation produced by the incomplete mixing of hot and cold fluid streams passing over the surface of a component or structure is known as thermal striping. This phenomenon may cause thermal fatigue to occur. It is of particular concern in various types of nuclear reactors, for rapid shut-downs of hot plant and in thermal stratification. A computer code, "TBL", is a design tool which has been developed to assess thermal striping damage in plates. This model is further developed in this paper to assess such damage in cylindrical components. A recent, universal weight function method is examined and incorporated into TBL. Good comparisons are found between TBL and finite element results for a sinusoidally varying temperature-time-striping history. Potential thermal striping damage is assessed for a cylindrical component of material typically found in the above-core region of a fast reactor under a random temperature-time-striping history.     

FATIGUE BEHAVIOR OF A PLASMA-SPRAYED 8%Y2O3-ZrO2 THERMAL BARRIER COATING

Abstract— Thick thermal barrier coatings with thicknesses on the order of a few millimeters are being developed for use in diesel engines with operating temperatures of about 800°C. In this environment, a coating will experience thermomechanical cycling due to differences in elastic and thermal expansion properties between the coating and the substrate. The inelastic constitutive behavior of the coating material results in both compressive and tensile stresses. To observe the effects of such stresses, specimens of plasma-sprayed 8%Y₂O₃-ZrO₂ were fabricated to allow testing of the coating material independent of the substrate. Cyclic compression fatigue tests were conducted at room and high temperature (800°C) to simulate the loading environment to which the coating materials will be exposed during service. At high temperature, the compressive fatigue strength of the coating material increased by nearly 100%. Fatigue tests in tension and combined tension/compression were conducted at room temperature to evaluate the effect of mean stress. It was observed that a varying mean stress had no significant impact on the fatigue lives of the coating material and the fatigue life was controlled by the maximum tensile stress of the cycle. Results from fatigue tests and SEM observations indicated that the damage accumulated during the tensile and the compressive portions of the fatigue cycle were independent of each other.     

硅酸铝短纤维增强ZL109复合材料的热疲劳性能

研究了用Ａｌ２Ｏ３溶胶或硅溶胶作粘结剂制备硅酸铝短纤维增强ＺＬ１０９复合材料的热疲劳性能，结果表明，仅用Ａｌ２Ｏ３溶胶粘结剂能制备的复合材料的热疲劳性能最好，仅用硅酸作粘剂制备复合材料的热疲劳性能最差，热疲劳裂纹不是沿纤维与基体之间的界面扩展，就是穿过纤维扩展，且与裂纹扩展方向和纤维的取向有关，随着热循环次数的增加，上述复合材料的硬度逐渐下降。     

Fatigue behavior of thin Au and Al films on polycarbonate and polymethylmethacrylate for micro-optical components

The thermal and mechanical fatigue behavior of thin metal films on polymer substrates has been investigated and compared for different combinations of materials, which are typical for micro-optical components: gold or aluminum film deposited on PolyCarbonate (PC) or PolyMethylMethAcrylate (PMMA) substrate. Mechanical fatigue testing has been carried out using an experimental setup, which allows for testing in an equi-biaxial loading condition, mimicking the strain state of the film during thermal cycling. Using scanning electron microscopy, fatigue damage morphologies for the different film/substrate combinations have been found to be quite different for both thermal and mechanical cycling. Furthermore, our results indicate a somewhat lower resistance of the films deposited onto PMMA as compared to PC to both thermal and mechanical fatigue. Under mechanical loading, Au/PC specimens show a longer time to failure as compared to the Al/PC specimens.     

铝硅合金热疲劳过程的应力应变分析

对铝硅合金进行了热疲劳模拟实验和应力、应变分析。铝硅合金的导热系数高,高温弹性模量低,温度涨落过程产生的宏观热应力低于同一温度下合金的屈服应力和疲劳极限;而铝、硅热膨胀系数的差异将在铝硅相界等局部区域产生远大于宏观热应力的微观热应力,并因此萌生热疲劳裂纹。通过变质工艺改变硅相形态,可改善合金的抗热疲劳性能。     

Modeling of residual stresses variation with thermal cycling in thermal barrier coatings

Thermal barrier coatings (TBCs) are commonly used as protective coatings for engine metal components to improve performance. Many investigations have shown that residual stresses in TBCs applications play an important role, but the residual stresses are mainly obtained by simulation method. As we know, there are a few analytical solutions of residual stress in TBCs system. In this paper, a new two-dimensional analytical solution has been obtained under the condition of non-linear coupled effects of temperature gradient, thermal fatigue, deposited residual stress, thermally grown oxide (TGO) thickening, elasto-plasticity deformation and creep deformation of TBC. Moreover, the influences of bending moment and curvature on stress variation in TBCs are considered during thermal cycling. The calculated results are in agreement with the prior experimental results.     

水和油脂对硝酸铵热稳定性的影响

为了研究水和油脂对硝酸铵热稳定性的影响规律,采用FCY 1型发火点测定仪测定爆发点的方法对含有不同杂质的硝酸铵的热稳定性进行了研究。实验结果表明,纯硝酸铵中加水至硝酸铵质量分数为95%时,爆发点由333.65℃降至311.69℃,热稳定性降低,继续加水至硝酸铵质量分数为85%时,爆发点略微升高至317.79℃,热稳定性略微增强。在95%硝酸铵中加入油脂至油脂质量分数为3.85%时,爆发点降至295.66℃,热稳定性降低。