Tu Shan-dong, Ling Xiang, Gong Jian-ming, Shen Fu-zhong, Liu Min-shan. Research Progresses of Mechanics for Life Extensionof High Temperature Components[J]. Journal of Materials Engineering, 1998, 0(4): 3-5.
Some recent research progresses in mechanics for life extension of high temperature components has been summarized in this paper. Emphasis is laid on the structural mechanics principles for life extension.
Wang Zheng-dong, Qiao Yi, Cui Xian-feng, Wu Dong-di. A Finite Element Model of Local Damage Approach to Creep Fracture[J]. Journal of Materials Engineering, 1998, 0(4): 6-8.
A finite element model is given in the paper to simulate the local damage in creep fracture process. With a damage-coupled element introduced for the local degraded material at multiaxial stress,the initiation and evolution of creep damage has been described. A calculation has been made for creep deformation and damage on a double-V circumferentially notched round bar,and the results are coincided reasonably with the experimental results.
Yu Jin-xing, Dong Xian-ping, Zhou Can-dong, Zhang Yuan-hu, Yuan Fu-he, Zhou Long-jiang, Li Tie-fan, Sun Chuan-qi, Li Qi-juan, Wu Chang-xin, Liu Ze-yao. Tensile Fracture Behaviour of Single Crystal Alloy DD100 at Slow Strain Rate at High Temperature[J]. Journal of Materials Engineering, 1998, 0(4): 9-11.
An investigation has been made of tensile fracture behaviour of single crystal alloy DD100 slowly strained on [001],[221] or [111] orientation at high temperature.As compared with in vacuum,their properties and appearances of the fracture are different than that in air.Oxygen in air has little influence on the strength of DD100,but reduces the tensile elongation obviously.
Shen Fu-zhong, Ma Gong-xun, Yang Xu, Kee Bong-Yoon, Kyu In-Shin. Evaluation of Creep Crack Growth Rate of 1Cr0.5Mo Weld[J]. Journal of Materials Engineering, 1998, 0(4): 12-13.
The tests of creep crack growth rate of 1Cr0.5Mo weld at 538℃ temperature are done by CT specimens. The regularity,da/dt=0.014054[C*(t)]0.8849,is given in the weak region,near by fusion line on the parent material side. The SNS weld is made from old parent materials taken from the serviced main vapour pipe which have worked at the operation condition for 26 years. For the da/dt versus C*(t),the data of SNS weld are dropped into near by the scatter band of NNN weld which made from new materials. It is proven that the weld once seriously damaged will be repaired by reassembing and rewelding materials lain in the weld and near to it. The renewed weld can still service at the operation condition for considerable time.
Xu Zhi-chao, Xie Xi-shan. Relationship of Strengthening with Ductility and Crack Growth Rate in Superalloy Turbine Disks[J]. Journal of Materials Engineering, 1998, 0(4): 14-15.
Crack growth rate (CGR) of superalloy turbine disks is tested by means of direct current-voltage. The results show that the CGR of superalloy turbine disks is decided mainly by stress rupture ductility,not by strength of superalloy, and the valuation of CGR is also determined by slope of the curve and the range of stress strength factor.
Shi Rong, Hu Geng-xiang, Li He-jun, Kang Mo-kuang. Steady-state Creep Behavior of a 1D-C/C Prepared by CVI Process[J]. Journal of Materials Engineering, 1998, 0(4): 16-17,38.
Steady-state creep behavior of a 1D-C/C prepared by CVI process was investigated by using self-made testing device and automatic survey system of high temperature creep data. Some important parameters of heat activation to express the creep behavior were obtained. The detailed values of them are:apparent activation energy Q=428.96kJ/mol(σ=213.46MPa,T=2010~2160℃), stress index n=2.97(T=2010℃,σ=133.83~213.46MPa) and apparent activation volume V0=1.059nm3 respectively. Creep mechanism was also analyzed preliminarily.
Geng Ming-fa, Di Suo-zhu, Zhang Xing-an. The Effect of Cyclic Loading on Crack Growth and Rupture Life[J]. Journal of Materials Engineering, 1998, 0(4): 18-20.
The rupture lives and the fracture features of iron base surperalloy GH2132 under creep and cyclic creep conditions have been studied in present paper.It is shown that effect of cyclic loading on crack growth in earlier stage (σ<σ0.2) is reversed to that in later stage (σ>σ0.2), and that final effect of cyclic loading on rupture life will depend on the sum of different roles before and after the point σ=σ0.2.
Chen Hong-jun. Interaction between Creep and Fatigue for a Nickel Base Superalloy IN738LC at Elevated Temperature[J]. Journal of Materials Engineering, 1998, 0(4): 21-22,27.
The creep-fatigue property of nickel base superalloy IN738LC was investigated at elevated temperature. It was observed that the cyclic life (number of cycle to failure) decreases with the increase of creep deformation. The microscopical examination didn′t show the typical creep damage in form of porosity formed at grain boundaries. Instead, carbide oxidation and grain boundary oxidation on the specimen surface were frequently observed. All cracks were formed on the specimen surface and propagated along the grain boundaries. Therefore, the oxidation of grain boundaries under creep load is a possible creep damage. In this work a damage mechanism was discussed with the Danzer-Relation. It can explain the decrease of cyclic life in creep-fatigue tests well.
Zhou Hao, Wang Xiang, Zhu Hui-wen, Tian Mao-sheng, Kong Qing-ping, Gao Wei-jia, Zhou Nai-biao. Cyclic Creep in a GH132 Alloy[J]. Journal of Materials Engineering, 1998, 0(4): 23-24,8.
The cyclic creep behaviour of the GH132 alloy (Fe-25Ni-15Cr based) under two testing conditions: (1) 773K and peak stress 862MPa, and (2) 923K and peak stress 510MPa has been investigated. The experiments show that, under the both experimental conditions with the decrease of the cyclic period, the fracture life increases and the envelope minimum creep rate decreases. After the normalization of the fracture data, it is found that the data obey the linear cumulative law. The origin for the behaviour of cyclic creep is analyzed in the light of scanning and transmission electron microscopy observations.
Peng Liang-ming, Zhu Shi-jie, Chen Hao-ran, Wang Fu-gang. Compression Creep Behavior of Al-8.5Fe-1.3V-1.7Si Alloy[J]. Journal of Materials Engineering, 1998, 0(4): 25-27.
The compression creep behavior of a heat-resisting monolithic Al-8.5Fe-1.3V-1.7Si (wt%) alloy produced by powder metallurgy has been investigated in the temperature range of 300~450℃. The alloy exhibits a high apparent stress exponent and a high apparent activation energy than those of pure Al or traditional aluminum alloys for creep Such abnormal creep behavior can be interpreted by the Rosler-Arzt model for attractive dislocation/particle interaction and final detachment from the dispersoids,and the relaxation parameter is temperature-dependent with an average value of 0.93,which demonstrates the dislocation/particle interaction is of moderate strength. The predictions based on the new creep equation are in good agreement with the experimental results.
Lu Yong, Chai Guo-zhong, Wang Zheng-dong, Wu Dong-di. An Approach of Line-spring Model and BEM to the 3-Dimensional Creep Crack[J]. Journal of Materials Engineering, 1998, 0(4): 28-29,31.
In this paper,a computational model for 3-dimensional creep crack growth was proposed with integrating line-spring model and some other numerical method,which enables the investigators to avoid the direct analysis of 3-dimensional creep crack tip stress strain field and obtain satisfactorily precise results. The computation and prediction of 3-dimensional embedded creep crack growth of a certain material was performed on the basis of the new method.
Bai Shi-hong, Qiao Sheng-ru, Zhou Shao-rong, Tian Chao-xu. Influence of Temperatures on the Flexural Properties of Structural Ceramics[J]. Journal of Materials Engineering, 1998, 0(4): 30-31.
In this paper, the flexural properties of ceramic materials (Al2O3 and Si3N4) at high temperatures were studied by the fourpoint bending method. The auther investigated the relation between the flexural properties and temperatures for ceramic materials. The experimental results show that the flexural strength is unchanged when temperature is less than 1000℃, but it sharply decreased with temperature rising above 1000℃. Si3N4 has the bigger deformation ability at high temperatures.
Zhang Xing-an, Xia Hui-qin, Wu Zhong-tang, Hu Geng-xiang. Study of Expressive Method of Creep Plastic[J]. Journal of Materials Engineering, 1998, 0(4): 32-33.
Several expressive methods of creep plastic were compared.A new method was proposed by third stage of creep curve with requirement. It was verifed by creep curve for DD3 single crystal superalloy.
Liu Min-shan, Dong Qi-wu. Thermal Stress Analysis of Tubesheet with Higher and Lower Temperature Parts in a New Type Waster Heat Boiler[J]. Journal of Materials Engineering, 1998, 0(4): 34-35.
In this paper,the temperature field and thermal stress are analyzed for an 16MnR tubesheet with higher and lower temperature parts. A three-dimensional finite element code is programmed. Experimental measurement of stresses versus strain gauges is performed on a tubesheet model. The test results agree fairly well with the analysis. This work provides some basis for life extension and safe operation of the waste heat boilers.
Chen Jia-nan, Gong Jian-ming, Song Ying-jian, Zhou Zhao-qi. Aspects of Material Selection on the Design of Ethylene Furnace Tubes[J]. Journal of Materials Engineering, 1998, 0(4): 36-38.
Material selection criteria for the design of ethylene furnace tubes are discussed. The strengths and weaknesses of tube materials has been compared. A fast qualification procedure is recommended for the evaluation of long-term strength of the materials. Design considerations for life extension is given.
Yang Xu, Shen Fu-zhong, Ning Zhi-wei, Ling Xiang, Gu Li. A Study of Residual Life for the High Temperature Tube by Constitutive Relationship and Finite Element Method[J]. Journal of Materials Engineering, 1998, 0(4): 39-40,11.
For the tube operated at elevated temperature,the variations of critical damage with service time are obtained in light of the constitutive relationshops taken from the creep and rupture test data,as well as analysis model of the finite element mothod.The radiant heating furnace PG2032 centrifugally casting alloy tube taken for an example is discussed in this paper.The acquired result of damage development can be compared with the result of non-destructive inspection,therefore,predicting residual life of the tube can be more accurate.
Zhao Cong-bao, Wang Yu-jiang, Chen Guang, Pan Hao, Weng Yu-qing. The Effects of Temperature on Creep Behavior in 18Ni(350) Maraging Steel[J]. Journal of Materials Engineering, 1998, 0(4): 41-42.
Creep behavior of an 18Ni(350) maraging steel was studid in a temperature range of 90~150℃. The results show that secondary creep rate increases with increase of temperature for a given stress, secondary creep rate can be expressed by εs=4.3×10-3exp (-26.6kJ/RT).
Wang Zhe, Zheng Han-ping, Jin Xin, Tan Ju-fen, Xing Wei-dong. Study on Hot Plasticity of GH742 Alloy[J]. Journal of Materials Engineering, 1998, 0(4): 43-44,15.
Hot plasticily rule of GH742 alloy has been found through hot tensile test of cast sample taken from double-vac melting φ250mm selfconsumption electrode and plotting working and solution recrystalllzation diagrams,GH742 disks of φ180mm×105mm have been produced.
Zhou Feng-yun, Xiong Wei-hao, Ming Wen-long, Xiao Jian-zhong. The Thermal Fatigue Behavior of Ti(C,N) Based Cermets without Cobalt[J]. Journal of Materials Engineering, 1998, 0(4): 45-48.
The thermal fatigue behavior of Ti(C,N) based cermets and 3Cr2W8V steel has been qualitatively studied and compared by simulant means of cracking net for alike cyclic number.The results show that thermal fatigue cracks of Ti(C,N) based cermet without cobalt originate from the edges of a specimen surface Those cracks are straight and fast expanding.The thermal fatigue cracks of 3Cr2W8V steel are thin cracking net that is slow expand.
