稀土电解槽石墨内衬氧化腐蚀-应力损伤耦合本构模型

利用Weibull分布函数表征石墨内衬微元强度分布,对石墨内衬氧化腐蚀劣化的力学性质进行研究,建立石墨内衬单轴压缩下力学损伤本构关系。考虑石墨内衬氧化腐蚀作用下孔隙率变化,引入石墨内衬化学损伤变量,得到氧化腐蚀损伤本构关系。根据推广的lemaitre应变等效原理,综合考虑氧化腐蚀-应力损伤耦合作用影响,建立石墨内衬氧化腐蚀-应力损伤耦合本构模型。利用CT显微技术获取受到氧化腐蚀的试样孔隙结构演化图像,通过石墨内衬在不同氧化腐蚀时间下的单轴压缩实验得到应力-应变曲线,检验氧化腐蚀-应力损伤耦合本构模型的合理性。结果表明:模型预测曲线和实验结果基本吻合,能较客观地反映石墨内衬氧化腐蚀下损伤演化特性。     

复合材料天然气气瓶预紧压力的研究

本文针对铝内衬全缠绕复合材料天然气气瓶,应用ALGOR FEAS有限元分析系统进行了气瓶材料的弹塑性历程分析,设计了气瓶的预紧压力。采用轴对称的应力－应变关系对气瓶金属内衬、复合材料进行了应力分析,确定了气瓶的应力分布状态。研究表明,通过预紧压力设计,降低了铝内衬工作状态下的最大拉应力,实现了提高复合材料气瓶疲劳寿命的目的。     

整体浇注钢包烘烤过程中内衬温度场和应力场分析

采用数值分析方法研究整体浇注钢包烘烤过程中内衬温度随时间变化情况,得出内衬各点温度随时间变化特征及不同点处温度分布,并通过现场测试验证模型结果正确性.采用有限元方法对烘包某一时间点内衬应力分析,探讨烘烤过程中整体浇注钢包应力分布集中情况及原因,为提高整体浇注钢包使用寿命提供一定的指导作用.     

碳纤维缠绕铝内衬储氢容器力学分析及优化控制

基于经典复合板理论与网格理论简化了纤维缠绕金属内衬压力容器模型,提出正交各向异性假设并认为材料处于线弹性,应力由纤维承受,忽略压力容器复合增强层的拉应力与切应力耦合作用,分别得到内外压作用时的应力计算公式。提出纤维预紧力控制方法,优化纤维缠绕金属内衬压力容器最终应力分布,通过实例模型验证了理论推导及方法的合理性。     

受内压复合材料压力容器最佳预紧力有限元分析

本文利用大型通用有限元分析软件ANSYS对受内压作用的碳纤维缠绕压力容器进行应力数值分析。结果表明,对压力容器施加预紧压力后,会使复合压力容器的内衬在工作压力下的应力显著降低,且应力分布趋于均匀,碳纤维材料的利用率得到提高,有效提高了复合材料压力容器的疲劳寿命。     

磷酸反应槽拱门内衬碳砖温度应力的分析

运用有限元分析软件ANSYS对磷酸反应槽拱门墙体内衬碳砖在温度载荷下的应力进行模拟分析,结果表明:拱门碳砖局部较大的拉应力成为拱门碳砖墙体产生破坏的主要因素.选择膨胀量比混凝土大的碳砖内衬拱门,虽然碳砖层仍受拉应力的影响,但应力值大幅下降,可以解决拱门墙体内衬碳砖在工作温度下产生破坏的问题.     

两种不同铝内衬碳纤维缠绕复合材料气瓶受力状况的对比分析

基于复合材料层合板弹塑性分析理论,参考DOT CFFC《铝内胆碳纤维全缠绕复合气瓶的基本要求》标准,利用网格理论设计了容积70L的铝内衬碳纤维缠绕复合气瓶。在相同的预紧力和工作压力下,研究对比分析了两种不同型号铝合金6061和7075作为内衬的气瓶的受力状况。结果表明,铝合金6061作为内衬时,其内衬应力水平分布比较均匀,可以更好地发挥外缠碳纤维的高强度特性,且价格经济实惠,较7075更适合作为复合材料气瓶的内衬材料。     

高压储氢容器氢环境疲劳试验系统研制

通过对70 MPa氢环境疲劳试验系统的设计和制造,研制了80 MPa扁平钢带缠绕式高压储氢容器,利用钢带预应力的调节实现了容器壁内衬低应力、绕带层等应力的合理应力分布。设计了疲劳试验系统的控制系统,实现手动和自动控制两种控制模式,以满足不同的试验需要。该系统是目前国内惟一的一套可用于真实氢环境疲劳试验的系统,已投入应用。     

38升铝内衬玻璃钢气瓶充灌一氧化碳气体会议在上海市召开

上海市轻工业局于1977年在上海第五皮鞋厂召开了38升铝内衬玻璃钢气瓶充灌一氧化碳气体会议。会议就该厂生产的38立升铝内衬玻璃钢气瓶充灌CO以来的情况作了介绍,并对充灌CO的气瓶作了现场爆破试验(表1)和实物解剖分析,中国科学院上海冶金研究所的同志介绍了内衬铝的应力腐蚀试验情况。会议认为: 1.根据应力腐蚀测试和实物解剖分析,铝内衬玻璃钢气瓶可以充灌CO(充灌CO的成     

金属内衬纤维缠绕高压容器的设计

本文根据网格理论,提出了具有金属内衬的纤维缠绕高压容器的设计方法。通过控制纤维予应力,进而控制了内衬的应力,使容器具有良好的耐疲劳性能,解决了容器的早期渗漏问题。最后简要介绍了这种方法的应用结果。     

垂直水冷壁异形鳍片区域温度与热应力分布

超/超超临界锅炉垂直水冷壁中间集箱附近的水冷壁异形鳍片区域向火侧易出现横向裂纹,可能导致水冷壁泄漏或爆管。以某660 MW超超临界锅炉为对象,介绍了水冷壁异形鳍片区域温度和热应力的数值计算模型。针对横向裂纹问题,基于计算数据分析了该区域的温度和热应力分布特征,以及锅炉负荷变化和水冷壁尺寸的影响。结果表明,异形鳍片旁的管壁向火侧顶点的轴向拉应力和等效应力大,锅炉变负荷运行易产生交变热应力,导致横向裂纹;异形鳍片中心为整个模型温度最高处,轴向应力和等效应力值也较大,需要重点关注;异形鳍片与管壁交接处等效应力大,材料失效时容易产生裂纹,可能向旁边的异形鳍片区域管壁向火侧延伸。     

Modeling birefringence in SiO2 glass fiber using surface stress relaxation

The retardance of silica glass fibers was evaluated using photoelastic techniques. Here, surface birefringence in glass fibers is shown to be a consequence of surface stress relaxation for as-received fibers drawn from Suprasil II. The surface features of the birefringent fibers were compared to a model of the residual axial stress profile resulting from a diffusion-controlled surface stress relaxation. Additionally, a uniform birefringence in the fiber equivalent to a constant tensile stress was recognized and attributed to structural anisotropy produced during fiber drawing. The contribution of structural anisotropy to the observed birefringence remained constant as the surface features were successively etched away. Surface compressive stress generation was also observed, as retardance corresponding to a surface compressive stress was found to increase with applied tensile stress during short heat treatments. Significant features of the retardance profile in as-received silica glass fibers, with a thin surface compressive stress layer and compensating interior tensile stress, agreed with the residual stress profiles predicted by the surface stress relaxation model after correcting for this observed structural anisotropy.     

Development of a simplified relationship between uniaxial creep,stress relaxation,and constant strain-rate results for viscoelastic polymeric materials

This publication introduces a new mathematical model to describe a definitive relationship between constant strain-rate, creep, and stress-relaxation analysis for viscoelastic polymeric compounds. This new concept is especially significant since it adequately describes all the important characteristics of both creep and stress relaxation in the same model. In particular, all three phases of creep (i.e., primary, secondary, and tertiary) can be described adequately using this model. This new model for polymeric materials also indicates that yielding for constant strain-rate measurements and the inception of tertiary creep appear to be directly related and may, in fact, be manifestations of the same phenomena. The initial buildup of stress followed by the drop off in stress as a function of time for stress relaxation is also adequately described. This new formulation approach also offers a reasonably simple process in which to shift from a constant strain-rate configuration to a creep calculation or stress-relaxation configuration without changing formulation considerations. Most importantly, this model can be used to make a transition from one of these stress-configuration modes to another without stress or strain discontinuities. It is hoped that this analysis approach will open new doors for the design of plastic products for both short-term and long-term applications. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 527–540, 2001     

2-D Hydro-Viscoelastic Model for Convective Drying of Highly Deformable Saturated Product

The aim of this work was to simulate in two-dimensions the spatio-temporal evolution of the moisture content, the temperature, and the mechanical stress within a highly deformable and water saturated product during convective drying. The material under study was an elongated potato sample with a square section placed in hot air flow. A comprehensive hydro-thermal model had been merged with a mechanical model, assuming a viscoelastic material, a plane deformation, and an isotropic linear hydric-shrinkage of the sample. This model was validated on the basis of the average water content and core temperature curves for drying trials under different operating conditions. The material viscoelastic properties were measured by means of stress relaxation tests at different water contents. The viscoelastic behavior was described by a generalized Maxwell model whose parameters were correlated to water content. The simulations of the spatio-temporal distributions of mechanical stress were performed and interpreted in terms of product potential damage. The sample shape was also predicted all aver the drying process with reasonable accuracy.     

固定管板釜式再沸器壳程斜锥应力分析

以某固定管板釜式再沸器为例,忽略局部结构,建立整体应力分析模型,利用ANSYS软件对各工况下的应力进行了计算;同时,仅取设备壳程筒体建立局部应力分析模型,对比分析了斜锥最大倾角路径上的轴向应力和薄膜应力.结果显示：前者的最大应力强度位于斜锥大端内壁处,而后者的最大应力强度位于斜锥小端外壁处;对比同时表明采用整体模型分析所得斜锥各项应力强度水平均远低于局部模型分析结果,以此为基础进行设计可大大降低斜锥壁厚.     

Interfacial property determination for immiscible polymer blends: A model system of polycarbonate/poly(ethylene terephthalate)

A model system, a tri-layer of polycarbonate/poly(ethylene terephthalate)/polycarbonate, was used in this study to investigate the interfacial properties of an immiscible polymer blend system. The model system was compression molded and quenched in three different media: ice, water, and hot water. The interfacial properties of interest were the through-thickness residual stress profiles and the interfacial strength. A method of estimating the interfacial strength of an immiscible polymer blend was also proposed, enabling the prediction of failure. The method was based on a single-notch 4-point bending test. The load at which failure occurred was then analyzed using finite element stress analysis to resolve the interfacial stress, i.e., the strength of the interface.     

New approach to evaluate the influence of compressive stress on the oxidation of non-oxide ceramics

The oxidation process of non-oxide ceramics (NOCs) is accompanied with the formation of the compressive stress generated within the oxide film, which in turn affects the oxidation behavior. To shed light on the influence of the compressive stress, a modified model combining the stress equilibrium equation and RPP model has been herein proposed. This modified model can not only quantify the effect of stress evolution on the oxidation process but also accurately describe the relationship between oxidation fraction and other factors including time and temperature, etc. The comparison between experimental data and theoretical calculations for the oxidation of different NOCs verifies the validity of the modified model. It is predictable that this modified model can be applied to treat the oxidation behavior of different NOCs with the consideration of compressive stress.     

基于有限单元法的法兰连接中的接触分析

应用ANSYS软件对法兰接头结构进行建模和网格划分,并且对法兰与螺栓接触处做了非线性接触分析,得到了在设计压力下螺栓结构的应力分布和变形。之后分别对整体模型和螺栓模型做出了应力强度分析。按照JB4732—1995《钢制压力容器-分析设计标准》对危险截面进行应力强度评定。分析结果表明,强度满足要求。     

Evaluate the nonlinear viscoelasticity of polyolefin melts using the Larson model

Nonlinear rheological properties of polyolefins have long been studied and predicted by using the Larson model with the damping function generally obtained from the stress relaxation measurements. In this study, we investigate the nonlinear rheological properties of high density polyethylene (HDPE) and polypropylene (PP) using the Larson model with damping functions obtained from either the dynamic frequency sweep or the stress relaxation test. Experimental measurements and their corresponding model predictions for the rheological parameters were then compared to evaluate the applicability of the Larson model to the nonlinear rheology, and the following conclusions could be achieved. The steady shear viscosity could be satisfactorily described by the Larson model with the damping functions obtained from the two different methods, except at shear rates higher than 10³ s^?1. The predicted first normal stresses also account for the measured data, except for those using the stress relaxation data showing a little deviation for the PP sample. In addition, the predictions for elongation viscosity are also in good agreement with the experimental results within the short range of elongation rate achieved in this work. POLYM. ENG. SCI., 54:2354–2361, 2014. © 2013 Society of Plastics Engineers     

狭缝对透气砖热应力影响的模拟研究

对透气砖吹氩时热应力模拟计算,探索狭缝对透气砖热应力影响,寻求合理的狭缝布置提高透气砖使用寿命.首先,在保持固定的狭缝尺寸与位置的前提下建立径向与切向两种狭缝布置形式钢包透气砖物理模型,然后设置合适的边界条件,计算在吹氩时两种模型整体应力及轴向不同位置路径热应力分布.研究发现:两种狭缝形式的透气砖在工作面附近都有明显应力梯度;狭缝径向布置与切向布置时轴中心区域在相同路径上应力最大值比较,前者是后者的3到6倍;切向狭缝截面中心呈现较低应力,狭缝至截面边缘的区域应力较高,而狭缝径向布置时截面上狭缝之间的位置呈现出一个应力较高的环形区域.