服役环境下材料蠕变对挤压筒过盈量的影响

在传统Lamé公式的基础上引入直接位移求解法（DDM）,推导了考虑蠕变效应的挤压筒应力/应变分布解析模型,分析了各层筒应力随时间的变化情况。针对挤压筒用热作模具钢H13进行了高温蠕变试验,获取了500 ℃下热作模具钢H13的蠕变行为和Norton表达式,探讨了材料蠕变对挤压筒各层之间过盈量的影响规律。研究结果表明,交界面处各层筒的蠕变应变有差别,造成径向变形不一,从而使得过盈量减小。     

蠕变现象的小冲杆试验研究--蠕变应力分析

主要阐述根据小冲杆试样实测中心挠度求蠕变应力的问题。包括：借助“表征”概念，将试样中心点视为整片试样的表征点；利用压力容器薄膜理论之力平衡关系确定特定时间状态下试样中心区域的应力状态，推导小冲杆试样中心点的蠕变应力估算公式；按该估算公式处理12CrlMoV钢在特定试验条件下获得的小冲杆变试验数据，并对比由此求得的蠕变应力－时间关系与有限元计算的同类结果，根据两者的一致程度判定应力计算模型和工程估算公式的可信度。最后，文章还对具体如何确定特定小冲杆试验之表征蠕变应力值给出了建议。     

核级SA-508 Gr.3 Cl.1材料拉伸与压缩蠕变行为的比较研究

堆芯熔融物堆内滞留(In-vessel retention,IVR)是压水堆的严重事故缓解措施。IVR过程中,反应堆压力容器底封头(Reactor pressure vessels,RPV)沿壁厚方向同时存在拉伸和压缩应力。为保证IVR过程中RPV的结构完整性,有必要研究SA-508 Gr.3 Cl.1材料的拉伸和压缩蠕变行为及其差异。基于此,开展了SA-508 Gr.3 Cl.1材料的拉伸蠕变和压缩蠕变试验测试,分析了材料的拉伸和压缩蠕变行为以及变形机制的不同。结果表明：拉伸和压缩蠕变的第一、二阶段基本吻合,但压缩蠕变没有出现明显的蠕变第三阶段;拉伸蠕变在试验应力范围内的变形机制为单一的位错攀移,而随着应力的降低,压缩蠕变变形机制由位错攀移转变为晶界滑移/空位扩散;拉伸蠕变对亚晶组织演化程度的影响大于压缩蠕变,这可能与蠕变变形机制的转变相关。     

一种多晶石墨材料的高温压缩蠕变行为

在氩气介质中测定一种多晶石墨材料在１９００～２３５０℃范围内的压缩蠕变行为。试验中用红外仪测量温度，温度波动控制在±３℃以内，用最小读数为１μｍ的ＬＶＤＴ测量蠕变变形，实验数据满足式ε＝Ａσｎｘｐ（－Ｑ／ＲＴ），其中ｎ＝１．９８，Ｑ＝１８５ｋＪ／ｍｏｌ。经计算蠕变激活体积为２１．４６ｎｍ３，相当于几分之一个石墨晶粒尺寸范围被激活。在２０５０，２１５０，２２００℃的蠕变摩擦应力分别为４．６２，４．５９，４．４１ＭＰａ。     

光纤传感技术的研究现状与展望

介绍了光纤传感器的基本原理，总结了光纤传感器对传统的仪器仪表工业的促进作用，指出了光纤传感器研究中存在的问题及发展趋势。     

多核微结构光纤传感器

提出了一种新型n通道马赫-泽德干涉传感器(MZI),它依赖于多核微结构光纤(MC-MOF)连接标准单模光纤的两个部分。对MC-MOF的模态特性进行实验分析,验证其敏感度与温度和拉伸应变之间的关系。结果表明这种干涉仪对温度不敏感,对拉伸量较敏感,可以克服拉伸应变与温度之间的交叉敏感问题。     

Analysis of the impression creep test method using a rectangular indenter for determining the creep properties in welds

The results of a theoretical and finite element investigation of an impression creep test method using a long rectangular indenter under plane strain conditions, rather than the conventional cylindrical indenter, are presented. The application of the technique for determining the creep properties of the various zones within welds is considered. The finite element method is used to obtain accurate (creep) or approximate (elasto-plastic limit load) reference stress solutions for the rectangular indenters placed at several positions in the base material, heat affected zone and weld metal. The effect of varying the geometric test parameters is reported. The possible advantages of the technique for determining some of the important creep properties in welded structures are identified.     

15CrMo钢的蠕变-疲劳试验及蠕变回复行为

试验测试了500℃时峰值保持时间分别为0,2,5,10和20 min条件下15CrMo钢的蠕变疲劳性能,重点分析了材料在蠕变疲劳载荷下的变形行为和蠕变回复行为。结果表明,随着峰值保持时间的延长,材料的蠕变-棘轮总变形显著增加;当疲劳-蠕变存在峰值保持时间时,前一个循环中峰值保持结束时的应变值大于再次加载达到峰值时的应变值,存在一定的蠕变回复行为;峰值保持时间越长,15CrMo钢蠕变应变回复量越大,且相同保持时间下的蠕变应变回复量总体上保持恒定。     

Systematic variation of polymer jacketed fibres and the effects on tip etching dynamics

Using a chemically etched fibre probe through a plastic jacket provides a simple way to smooth a tip's surface. Convection flow in the plastic tube and lateral diffusion with fixed meniscus height has been proposed to explain such improvement. Fibres with additive thin polymer layers and bare fibres with thick untapered/tapered plastic layers have been prepared to verify the dominant mechanism. The additive layers greatly change the tip's geometry and bare‐fibres with untapered plastics cannot form tips. This confirmed that lateral diffusion dominates the etching process. Based on our investigation, we propose a new non‐meniscus end‐etching method by using tapered plastics. Unlike etching methods with meniscus, the end‐etching method can regularly form very smooth tips. It is insensitive to vibrations and temperature drifts and also suitable for most fibres.     

Transmitted light microscopy of a fibre reinforced metal

A method is presented for studying fibre damage in continuous fibre reinforced composites. It is based on contrasting the transmission of light through intact translucent fibres with the light through fractured or dead‐ended fibres. The method is applied in order to detect processing‐induced fibre fractures in aluminium reinforced with continuous alumina fibres.     

10CrMo910钢的蠕变损伤分析

从连续损伤力学方法着手研究了蠕变损伤的力学过程，基于连续损伤变量D，建立了单向应力状态下的蠕变损伤模型。通过10CrMo910钢在550℃温度下的蠕变断裂试验，借助Origin5．0数值分析的功能，快速确定了有关材料常数，从而得到了10CrMo910钢在给定温度下的蠕变损伤本构和演变方程，与蠕变试验结果进行了比较，得到了与实验相一致的结论。     

Impression creep: Effects of slip, stick and cavity depth

The impression creep of a power-law material by pushing a rigid cylindrical punch into an existing cavity of the same diameter as the punch located in the surface of a half-space was studied by using finite element method. For both the slip and stick conditions at the interface of the punch and the half-space, there is a well-defined steady punch penetration velocity after a transient stage. The steady penetration velocity is a power function of the applied load, which has the same stress exponent as by conventional creep tests. It increases with the stress exponent but decreases with increasing cavity depth, and is the largest for all slip condition and the smallest for both stick condition on the circular interface between the punch and the cavity and all stick condition.     

连续纤维增强玻璃钢球阀研究

介绍了由材料性能试验获取的连续玻璃纤维增强复合材料的力学性能,包括沿各个不同方向的拉伸、压缩、剪切、弯曲等性能参数,并依据这些性能参数,研究连续纤维增强玻璃钢球阀的设计要点,导出其详细设计公式。通过对材料组成及制备工艺进行改进,使得设计出的玻璃钢球阀较国内普通的玻璃钢球阀力学性能更为优秀。     

机床液压系统爬行原因分析及消除

全面阐述了机床液压系统出现爬行的机理、危害，分析了产生爬行的原因，指出了消除爬行的措施，为改善机床液压系统稳定性和提高机床加工精度提供了重要的参考。     

压缩非石棉密封板材蠕变松弛性能的理论和试验研究

从压缩非石棉密封板材恒应力蠕变出发，分析了实际法兰连接系统中垫片的蠕变松弛行为，并导出了该材料以一般粘弹性模型为基础的蠕变松弛计算公式，试验结果表明两者具有较好的一致性。     

内燃机铝合金活塞疲劳寿命预测研究

以内燃机铝合金活塞弹塑性有限元计算为基础，研究了高温蠕变影响下铝合金活塞寿命的预测方法，给出了寿命宏观预测公式。针对一具体的高强化柴油机铝合金活塞，计算预测了其寿命，并将计算结果与活塞台架试验及发动机整机可靠性试验数据进行了比较，证明了预测公式及预测方法的可靠性。     

Microstructure and creep characteristics of experimental SiCf–YMAS composites

A unidirectional SiC_f –YMAS glass–ceramic composite has been developed by Céramiques-Composites (Bazet) and ONERA (Establishment of Palaiseau) in France. The matrix is totally crystalline and consists essentially of two main phases, cordierite and yttrium disilicate, with some minor phases, mullite, spinel, zirconium and titanium oxides. Image analysis methods have been used to characterize the homogeneity of the composite plates and to obtain granulometric information on the different matrix phases. Different interphase layers formed during the process by reaction between the matrix and the Nicalon NLM 202 fibres have been studied by using HREM and EDX. Their chemical composition has been determined by stepping the probe (8 nm) across the fibre–matrix interface. Two distinct nanoscale sublayers have been imaged. The sublayer on the matrix side has a light contrast in the TEM. The microstructure of this layer (≈ 80 nm) is typical of a turbostratic carbon. The carbon layer also contains Al, O, Mg and Si. The silicon content is low in the carbon layer. The sublayer on the fibre side (≈ 100 nm thick) has a dark contrast in the TEM. Profiles have been taken across this sublayer also. Tensile creep tests in air have been performed to investigate the tensile creep behaviour at 1223 K. They have been conducted in the 50–200 MPa stress range. Tensile creep results indicate that creep rates are of the same order of magnitude as for other glass–ceramic composites. Optical micrographs and SEM observations have revealed the damage in the composite. Changes occurring in the interface region have been studied at a finer scale by TEM and HREM at the surface of the sample and in the core. These observations enable us to explain the mechanical behaviour of the composite observed on a macroscopic scale.     

Preparation of ceramic fibre TEM cross-sections using ultramicrotomy and ion beam thinning methods

The preparation of specimens for detailed TEM microanalysis of micrometre-diameter, ceramic fibre cross-sections is described. The starter material is ceramic fibre in powder form and both ultramicrotomy-based and ion beam thinning-based methods are described. Requirements for specimens of uniform and adequate thinness, for easy selection of representative fibre cross-sections within the same specimen and for a reliable and time-efficient preparation method, resulted in choice of the ultramicrotomy-based method and the associated development of a novel extrusion and sedimentation technique of embedding the fibres to provide necessary pre-alignment and packing.     

金属石墨缠绕垫片蠕变对法兰接头密封性能的影响

法兰接头在高温环境中工作时,接头各个部件的蠕变松弛会加剧,然而在法兰接头的研究中,大多没有考虑垫片的蠕变松弛。以金属石墨缠绕垫片为例,在不同温度及不同初始密封比压情况下进行蠕变松弛性能试验;将试验结果进行拟合得到垫片蠕变松弛性能计算公式,将其代入法兰接头变形协调方程中,计算得到接头蠕变2年的螺栓力随时间的变化情况。使用ANSYS软件建立法兰接头有限元模型,并计算不同部件蠕变2年所造成的螺栓力的松弛情况。理论计算结果与有限元计算结果相近,表明建立的理论模型可用于接头螺栓力松弛的评估。研究结果表明：初始密封比压相同时,温度越大则垫片的蠕变量越大,温度相同时,初始密封比压越大则垫片的蠕变量越大;垫片蠕变对法兰接头有显著影响,在一些情况下仅垫片蠕变就能使螺栓力下降40%,因此垫片蠕变对法兰接头的影响不能忽略。     

Excel软件在蠕变等温线法中的应用

利用Excel软件,对蠕变试验数据进行分析,通过数据采集、曲线绘制、公式运算、添加趋势线等处理,结合等温线法,可以外推出持久温度极限和蠕变温度极限[1];对比通过手工描绘的曲线图,利用Excel处理过的曲线更清晰准确地为金属材料在高温条件下的力学性能提供参考。