基于ANSYS对某含有凹坑缺陷发酵罐的静力分析

对含有凹坑缺陷的发酵罐按照GB/T19624-2004《在用缺陷压力容器安全评定》进行安全性评定,在此基础上利用ANSYS对不同间距的轴向排列的多凹坑进行静力分析,得到轴向排列的多凹坑的最大应力值和应力集中系数与相邻凹坑间距和数量的关系。经过分析可知,当相邻凹坑间距增大到L/X≥3.0时,各凹坑之间的应力分布几乎无影响;应力集中系数随着两凹坑中心距的增加而减小,当间距L/X3时其变化幅度较大,当L/X≥3后趋于恒定;同时最大应力值和应力集中系数与凹坑缺陷数量成正比,而与相邻的凹坑间距成反比。     

含有不同间距凹坑缺陷的发酵罐应力分析与计算

对含有不同间距凹坑缺陷的发酵罐进行应力计算与分析,得到轴向排列的多凹坑区域应力值分布情况和应力集中系数与相邻凹坑间距L和凹坑数量的关系。经过分析可知,当相邻凹坑间距与X方向宽度比值L/X<3时,其应力值随着凹坑间距的增加而减小,当L/X≥3时,相邻凹坑之间间距对应力分布几乎无影响。应力集中系数随着两凹坑中心距离增加而减小,当L/X<3时,应力集中系数的变化幅度较大,当L/X≥3时其变化趋于恒定。最大应力值和应力集中系数与凹坑缺陷的数量成正比,而与相邻的凹坑间距成反比。     

压力容器多凹坑干涉效应分析

分析研究了多凹坑周围的应力分布以及应力集中的干涉效应。通过对单凹坑分析计算做出安全评价,建立了压力容器多凹坑模型。利用有限元软件ANSYS对该模型进行静力分析,得出沿环向排列的多凹坑最大主应力、应力集中系数和应变集中系数随凹坑数量变化的关系。通过对数据的分析和处理得到,在线弹性范围内薄壁圆筒形压力容器内沿环向排列的凹坑的最大主应力、应力集中系数和应变集中系数,随着凹坑个数的增加是线性递减的。     

容器表面不同角度双凹坑干涉效应及安全评定

凹坑缺陷的存在,导致应力集中,产生局部峰值应力,压力容器强度降低。针对这一现象展开分析计算,利用有限元 ANSYS 软件计算其最大应力,并分析不同角度凹坑缺陷间的应力集中干涉效应对压力容器的影响,并对其进行安全评定。     

含凹坑缺陷的薄壁圆筒形压力容器疲劳寿命数值模拟研究

利用有限元分析软件MSC.Patran和疲劳分析软件MSC.Fatigue对含凹坑缺陷的薄壁圆筒压力容器进行静力分析和疲劳寿命分析,得出满足G0>0.1的不同深度和长度的凹坑的最大主应力、应力集中系数和疲劳寿命的情况.通过对数据的分析和处理得到:随着凹坑深度的增加,最大主应力、应力集中系数是线性增加的,而疲劳寿命则是线性减小的.并且随着凹坑长度的增加,最大主应力和应力集中系数是不断减小的,而疲劳寿命也有上升趋势,但变化不明显,由此可知疲劳寿命的主要影响因素是凹坑的深度.     

开孔间距对压力容器应力影响的有限元分析

采用ANSYS Workbench软件进行开孔间距对压力容器应力影响的有限元分析。结果表明:应力集中程度受开孔间距的影响,随着K值增大,应力集中系数减小,当K1.3时,应力集中系数基本不变。开孔接管区的最小应力反应了两孔间干涉作用的强弱,随着K值增大,开孔接管区的最小应力逐渐减小,说明两孔间的干涉作用逐渐减弱。     

煤矿巷道连采连掘工艺应力分布仿真分析

为了确定多巷道采掘时应力的分布情况,针对两个巷道进行采掘时的应力分布进行仿真分析。结果表明,30m距离时的应力值减小较多,且应力集中和叠加的现象较小;应力集中系数随着轴向距离的增加,呈现逐渐变小的趋势,主要的应力集中系数变化产生在20m～30m的轴向距离上,结合支护的安全性来讲,确定在两条巷道进行连采连掘时轴向距离以30m为最佳的采掘距离。     

开孔处应力集中系数的简化计算

由于各种工业和结构的要求,不可避免地要在压力容器上开孔并安装接管,开孔必然会造成器壁强度的削弱,其削弱程度的大小可通过应力集中系数的大小来体现。通过对平板上开小圆孔边缘处的应力计算分析,得出开孔处应力集中系数的简便计算方法。运用该方法可以准确的计算出球壳以及圆柱壳等壳体上开圆孔的应力集中系数,确定危险位置及应力的大小,为确保压力容器的安全提供必要的条件。     

压力容器定期检验局部腐蚀凹坑的安全状况等级评定

大型石化检验过程,存在很多因为保温层使用不当造成的凹坑腐蚀,通过对定期检验过程发现的压力容器腐蚀凹坑进行计算分析,得出了不同深度凹坑的在用压力容器安全状况等级评定,为压力容器的定级提供依据。     

内压圆筒大开孔率接管弹塑性有限元分析

采用三维弹塑性有限元方法对内压圆筒大开孔率接管结构进行了应力分析,得到了不同尺寸参数影响下接管连接处的轴向与环向应力集中系数分布规律,并按JB4732-95《钢制压力容器———分析设计标准》进行了强度校核。确认在应力分析条件下,结构的强度满足安全要求。     

Packing Structure of Particles in a Green Compact and Its Influence on Sintering Deformation

The anisotropy of the structure in a die-pressed compact was studied directly through detailed analysis by confocal scanning laser fluorescent micrographs. The use of confocal optics and an immersion liquid produced micrographs that represented the structure of a cross section at a certain depth along two directions: parallel and normal to the pressing direction. The network formed by particles in contact was analyzed by measuring the components of particle contact parallel and normal to the pressing direction in the green compact. Different values were obtained in the total components of particle contact for the horizontal and normal directions for the cross section parallel to the direction of pressing: the ratio between these values was 1.15. This suggests that there should be 15% more shrinkage in the direction parallel to pressing, at least during the initial stages of sintering when the particle geometry is preserved.     

Bi4Si3O12晶列结构中的晶粒变化趋势和相关性分析

在常压下用烧结法制备了具有高有序晶列结构的Bi4Si3O12微晶.利用X射线衍射(X-ray diffraction,XRD)和环境扫描电镜(Environmental Scanning Electron Microscopy,ESEM)分析了生成晶体的物相和微观形貌.结果表明:生成的是纯的立方相Bi4Si3O12晶体.Bi4Si3O12晶粒总是成对分布,且排列成行,从而形成高有序的晶列结构.其晶粒尺寸变化趋势有两种,一种是逐渐增大或者减小,另一种是晶粒尺寸在某一区域值内基本保持不变.在大多数情况下,每个晶行两侧的晶粒变化趋势具有一致性,每行两侧的晶粒尺寸具有高度的正相关特性.如果某行两侧的晶粒尺寸变化趋势不一致,而且晶粒尺寸不相关,则该行两侧晶粒应该属于两种不同的变化趋势.     

压力容器分析设计中应力线性化原理及其计算

扼要介绍压力容器分析设计中应力线性化的基本原理,并详细阐述了非轴对称模型和轴对称模型下应力线性化的基本计算方法。目的在于为压力容器的分析设计提供参考,以准确地分析器壁的应力情况。     

Discrete particle simulations of solids compaction and conveying in a single‐screw extruder

This paper studies granular flow and compaction behavior of high‐density polyethylene by discrete particle modeling in order to gain greater understanding of the stress distribution within the solids‐conveying zone of a single‐screw extruder. The contact force–displacement model used in the simulations was first validated by simulating uniaxial compression in a batch compaction cell. Subsequently, the discrete particle approach was used to model in 3D the movement of particles within the solids‐inflow and solids‐conveying zone of a 32‐mm single‐screw extruder. Results of the simulations showed that axial pressure development did not increase in an exponential manner, as suggested by continuum models, largely due to the compressibility of the solids. The nature by which pressure developed was shown to be further complicated by the retarding frictional forces of the granular bed, indicating Archimedean transport phenomena close to the feed opening when the head pressure was low and inadequate stress transmission occurred along the screw. In the cross‐channel direction, the anisotropic stress field predicted found that the highest pressure in the screw channel was located at the screw root, while the lowest pressure corresponded to the retreating flight. The results were subsequently discussed in comparison to available continuum models. POLYM. ENG. SCI., 48:62–73, 2008. © 2007 Society of Plastics Engineers     

连续纤维复合材料环形试样蠕变行为研究

对连续玻璃纤维复合材料进行了拉伸蠕变试验研究，为了模拟复合材料在压力容器中的受力状态并减少夹具加持力对试样的影响，采用环形复合材料试样拉伸蠕变试验方法。对复合材料环形试样的拉伸强度及不同应力等级下的拉伸蠕变性能进行了研究，并基于时间?应力等效原理，通过双对数法拟合出压力容器50年使用寿命时复合材料的最大蠕变应力，为复合材料压力容器的设计提供支持。并基于时间?应力等效原理，通过双对数法拟合出压力容器50年使用寿命时复合材料的最大蠕变应力应低于其拉伸强度的44.4 %。     

长颈法兰偏转角的解析算法

螺栓法兰连接是石油、化工、核能、电力等部门压力容器和管道广泛采用的一种连接形式,其密封连接是否可靠直接关系到生产装置的安全运行和现场操作人员的安危。其失效极少是因强度不足引起的,泄漏是连接系统失效的主要原因。在真实螺栓法兰连接结构中,螺栓载荷和内压的作用使法兰发生偏转,法兰偏转引起垫片接触应力分布不均匀,垫片的局部接触应力对螺栓法兰连接结构密封性能的影响较垫片的平均压紧应力更大。文章在Warters法的基础上,考虑了操作压力的影响,对法兰变形进行理论分析,推导了法兰偏转角的计算公式,这为垫片接触应力分布的解析计算研究奠定基础。     

整体多层包扎式高压容器应力状态研究进展

介绍了国内外对整体多层包扎式高压容器在预紧状态下由包扎箍紧力和焊缝收缩引起的预应力的研究状况,以及对整体多层包扎式高压容器在内压作用及温度和压力共同作用下应力状态的研究进展,介绍了对层间存在间隙和在动载荷作用下的应力状态研究,并指出对考虑温度影响时的应力状态有必要进行系统而深入的综合研究。     

Studies on wire coating extrusion. II. The rheology of wire coating coextrusion

An experimental and theoretical study of wire coating coextrusion through a pressure-type die was carried out. For the experimental study, the wire coating apparatus employed was the same as that described in Part I of this series (14), except for the newly constructed coextrusion die. The die was provided with three melt pressure transducers along the axial direction, which permitted us to determine the pressure gradient in the die. It was found that a reduction in pressure gradient was realized when a lower viscosity polymer was coextruded with a high viscosity polymer. The materials used for the coextrusion were combinations of low-density polyethylene, high-density polyethylene, polystyrene, and two different commercially available thermoplastic rubbers (UniRoyal TPR-1900 and Shell Kraton G 2701). The use of a high shrinking (crystalline) polymer inside a low shrinking (amorphous) polymer was found to give rise to distorted coatings (non-circular cross section of the coated wire). The interface between the coextruded layers was examined under a magnifying lens, and it was found that under certain processing conditions, the interface was highly irregular. Experimental correlations were obtained to explain the onset of an unstable interface in terms of the rheological properties of the individual components being coextruded, and of the processing variables. It was found that interfacial instability occurs when the shear stress and the viscosity ratio (also elasticity ratio) of the two components at the interface exceed certain critical values. For the theoretical study, using a power-law model, the equations of motion were solved numerically to predict the volumetric flow rate as functions of the pressure gradient in the die and the rheological properties of the polymers being coextruded. Solution of the system of equations permitted us to predict the velocity profile and shear stress distributions of two molten polymers inside a pressure-type wire coating coextrusion die. Comparisons were made between the experimental and theoretically predicted volumetric flow rates. The comparison was found to be reasonably good with certain systems. The discrepancy between the experimentally obtained and the theoretically predicted volumetric flow rates was attributed to interface migration and interfacial instability.     

分相式多孔壁微通道流动冷凝传热强化与减阻

微通道换热器应用广泛,强化传热和减阻是新型换热器设计的重要目标。为了同时实现这两相目标,本文提出了一种分相式多孔壁微通道冷凝器,利用微针肋阵列组成的多孔壁在冷凝传热过程中实现了汽液两相分离。采用实验研究方法对比了分相式多孔壁微通道与普通实心壁微通道的流动和传热特性,结果证明分相式微通道在冷凝传热中同时具备强化传热和减阻的作用。深入研究了通道内两相流动摩擦耗散原理并提出了相分离减阻理论,指出汽液两相流内部摩擦耗散的减小是分相流减阻的关键。另一方面,分相过程使针肋换热面侧壁直接与高温蒸汽接触,极大消减了蒸汽与换热壁面之间的传热液膜厚度。沿流动方向不断扩展的液通道截面与不断减缩的汽通道截面积适应了流动冷凝过程延工质流动方向"水渐多,汽渐少"的规律,保证沿程传热效果不会恶化。