Procedure of Determining Creep and Creep-Rupture Strength Parameters for Isotropic Materials under Nonisothermal Loading

A procedure has been developed for determining the parameters of creep and creep-rupture strength that appear in constitutive equations of thermoviscoplasticity for describing nonisothermal processes of deformation and damage accumulation in isotropic materials due to creep. The procedure is tried out using a high-temperature chromium-nickel alloy ÉI437.     

Aspen 软件在低温精馏分离稳定同位素13C中的应用

本工作对低温精馏分离¹³C同位素的稳态模拟与动态模拟进行了研究。使用商用流程模拟软件Aspen Plus建立低温精馏过程的稳态模型,通过对比模拟数据与实验数据,验证物性参数和模型的可靠性。使用Aspen Dynamics建立低温精馏过程的动态模型,动态模拟结果与实验数据吻合良好。结果表明,可以使用Aspen Dynamics对碳同位素分离过程进行动态特性研究,并对精馏过程进行开车时间预测、控制方案分析、操作性分析和安全性分析等。     

循环加载处理对聚氯乙烯涂层膜材料蠕变性能的影响

为深入研究膜材料在受力过程中的蠕变作用机制,以聚氯乙烯涂层膜材料为研究对象,对其历经循环加载过程后的蠕变性能进行测试,分析了循环加载次数、循环峰值应力与循环加载速率对蠕变性能及初始变形保持能力的影响规律.研究结果表明:经不同循环加载过程后的涂层膜材料蠕变机制基本一致,蠕变性能及对初始变形的保持能力不仅受循环加载次数、循...     

火电站用T23/TP316H异种金属焊接接头服役损伤分析

通过试验研究分析了服役后的高温蒸汽管道中T23/TP316H异种金属焊接接头的微观组织、成分和氧化情况.结果表明,在540℃/17 MPa条件下服役10万h后,TP316H钢侧虽会被氧化,但未发现明显的会导致接头早期失效的潜在危险因素;T23钢侧会出现沿焊缝/热影响区界面的氧化,并出现了沿界面的开裂.T23钢与镍基焊缝...     

Experimental study on creep of high-performance concretes

In order to investigate the compression creep of two kinds of high-performance concrete mixtures used for prestressed members in a bridge,an experimental test under laboratory conditions was carried out.Based on the experimental results,a power exponent function was used to model the creep degree of these high-performance concretes(HPCs) for structural numerical analysis,and two series parameters of this function for the HPCs were given with the optimum method of evolution program.The experimental data were compared with CEB-FIP 90 and ACI 92 models.Results show that the two code models both overestimate the creep degree of two HPCs,so it is recommended that the power exponent function should be used for the creep analysis of bridge structure.     

节理岩体本构模型数值模拟及其验证

为了深入研究节理裂隙岩体的破坏机理,基于Mohr-Coulomb准则,利用(PFC)离散元程序,引入颗粒接触连接本构关系,建立了含孔洞岩样Burgers蠕变模型,以数值模拟的应力-应变曲线与试验曲线吻合作为PFC细观力学参数选取的准则,并利用获得的力学参数对含孔洞节理岩体破坏过程进行数值再现,模拟了不同颗粒单元参数试样...     

A structural experimental technique to characterize the viscoelastic behavior of concrete under restrained deformations

An innovative variable restraint frame is proposed to characterize the viscoelastic behavior of concrete under tensile stresses induced by restraints to shrinkage deformations (mainly due to drying). Two concrete specimens with the same cross section are used, subjected to equal thermal and moisture conditions: one is made of plain concrete, to assess the “free” deformations due to shrinkage and temperature; the other is reinforced with two steel threaded rods, which induce a manually controlled axial restraint to shrinkage. The restrained specimen is installed on a reaction frame, being stretched in force control mode. The concrete and the rods are instrumented with strain gauges and temperature sensors, which allow separation of the different components of concrete strains with the aid of equations based on equilibrium and compatibility conditions. This permits identifying the elastic and tensile creep concrete strains, as well as the concrete tensile stresses induced by the restrained shrinkage. The device also allows assessing the concrete modulus of elasticity during the test and remains operational even upon concrete cracking, features of great interest for the intended material characterization.     

中压蒸汽管道设计的探讨

结合工程实例,讨论了中压蒸汽管道材质的选取、蠕变监测的设置、球型补偿器和隔热管托的应用及管道绝热设计。