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。     

汽爆罐快开齿啮法兰结构的有限元分析

通过面-面接触单元模拟汽爆罐快开齿啮法兰的啮合齿接触过程,运用整体有限元应力分析的方法对汽爆罐快开齿啮法兰结构进行计算与分析,对危险截面进行了强度评定和疲劳分析.     

基于ANSYS换热器法兰有限元分析及应力评定

为了换热器在运行过程中,法兰结构安全。利用ANSYS有限元分析软件,对换热器壳体法兰在机械载荷和温度载荷共同作用下的应力强度进行了分析,并对其危险截面做了应力评定和强度校核。对壳体法兰不同危险部位进行分析与评定并且合格,这样才能保证其安全可靠地运行。     

基于有限元的除砂器非标法兰的应力分析

对一除砂器的非标法兰进行了局部的装配体应力校核,该除砂器设计压力高达69 MPa,其上下两端分别采用了管帽螺纹密封与螺栓法兰密封,为典型的高压非标设备,故采用分析设计的方法对其进行校核是十分必要的。利用有限元软件通过简化模型、划分网格、设置接触、施加载荷与约束,求解出各部件的应力,并按相关标准分别校核了筒体、法兰盖、螺栓的强度。     

无垫片密封焊反向法兰强度计算

针对无垫片密封焊反向法兰的结构形式和受力特点,分析了普通反向法兰和无垫片焊接密封法兰的强度计算,总结了无垫片密封焊接反向法兰的强度计算方法。     

烧结炉卡箍快开结构强度分析

应用ANSYS软件对烧结炉的主要部分卡箍快开结构进行模型建立和网格划分,并且在卡箍齿与上下法兰啮合处做了接触分析,根据设计条件进行了热-力耦合分析。依据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。     

基于有限元的齿啮式快开容器上法兰结构优化

采用ANSYS软件对某齿啮式快开容器的罐盖法兰进行了有限元模拟,并进行了应力强度评定,结果表明齿的上表面齿根处及封头与法兰连接处为高应力区域。分析了啮合齿宽、啮合齿厚、法兰径向宽度、法兰轴向高度、封头厚度及封头与法兰连接处过渡圆半径等结构参数对罐盖法兰的应力特性影响,并依据影响结果对罐盖法兰结构尺寸进行了优化,优化后罐盖法兰应力满足应力强度要求,为罐盖法兰的设计提供了参考和依据。     

高压容器端盖法兰上螺栓孔对强度的削弱分析

对高压容器端盖法兰的受力情况和螺栓孔对法兰强度的削弱影响进行了分析,认为华特斯法确定法兰强度的计算方法适用于常用直径的低中压法兰,但对高压容器的端盖法兰并不适用。经分析,当容器直径很大、设计压力很高时,应该将螺栓孔中心圆的环向承载截面也作为危险截面进行强度校核。     

法兰对开孔接管局部应力影响的研究

以三种典型的压力容器开孔结构为例,采用有限元方法,研究了法兰对开孔接管局部结构应力强度的影响。结果发现,法兰对开孔接管局部应力的影响甚微。法兰自身的受力情况仅影响其自身的应力分布,对接管与壳体连接处的应力强度几乎没有影响。     

换热器异形法兰应力分析

以某型号换热器的异形法兰为研究对象,应用有限元软件ANSYS分析了稳态条件下异形法兰的温度场,并计算了该异形法兰在温度载荷与压力载荷作用下的应力分布。根据ASME规范对异形法兰的危险受力部位进行了强度评定,结果表明,换热器异形法兰的强度满足安全要求。     

容器特殊法兰的计算

通过使用CONTACT单元对快开特殊法兰进行分析,从而得到了这种特殊形式法兰的受力特点和力学分布规律,然后对这种特殊法兰进行了应力评定以及疲劳寿命计算。工程表明,此方法设计的特殊法兰满足应力和寿命要求。     

Fatigue testing of taper press fits bonded with anaerobic adhesives

This article compares the static strength and the fatigue strength (under repeated stress) of axially loaded taper press fits, either dry or bonded with an anaerobic adhesive. A general increase of both static and fatigue strength with the contact pressure is observed, the strength buildup being greater for the dry joints than for the bonded ones. No significant difference between the static and the fatigue strength is measured for the dry joints. For the bonded joints, the fatigue strength decay is nearly independent (in absolute terms) of the assembly contact pressure.     

FATIGUE TESTING OF TAPER PRESS FITS BONDED WITH ANAEROBIC ADHESIVES

This article compares the static strength and the fatigue strength (under repeated stress) of axially loaded taper press fits, either dry or bonded with an anaerobic adhesive. A general increase of both static and fatigue strength with the contact pressure is observed, the strength buildup being greater for the dry joints than for the bonded ones. No significant difference between the static and the fatigue strength is measured for the dry joints. For the bonded joints, the fatigue strength decay is nearly independent (in absolute terms) of the assembly contact pressure.     

Dynamic Fatigue Analysis of Indentation Flaws Using an Exponential-Law Crack Velocity Function

The effect of residual contact stresses on the dynamic fatigue behavior of indentation flaws was analyzed using an exponential-law crack velocity function based on stress corrosion theory. Analysis of strength data from Vickers-indented soda-lime glass specimens in water showed that the contact residual stress can be properly accounted for and that the exponential-law fatigue parameters can be straightforwardly obtained.     

Evaluation of the bond strength of hard coatings by the contact fatigue test

The conventional contact fatigue test was applied to evaluate the bond strength between hard coatings and substrates. It was designated as an interfacial fatigue test for coated samples and was conducted with either cylindrical or spherical rolling. A shear stress range at the interface was derived based on the mechanics of elasticity and used as a measure of the interfacial fatigue strength between the coating and the substrate. It was found that the coating exfoliated after the coated specimen was subjected to a number of cycles under cyclic contact loading, but it would be intact when the cyclic load was decreased to a critical value. The shear stress range corresponding to this critical load was defined as the bond strength which would reflect the change in the physical and/or chemical state in the interfacial region. In the calculation of the shear stress range, the effects of the thickness and Young's modulus of the coatings were taken into account.     

Flaw Characteristics in Dynamic Fatigue: The Influence of Residual Contact Stresses

The effect of residual contact stresses on the dynamic fatigue response of surfaces containing indentation-induced flaws is studied. Indentation fracture mechanics is used to analyze the growth of well-defined "median/radial" cracks in combined residual (elastic/plastic) contact and applied (uniform) tensile fields, and thence to determine strength characteristics. In this way a general formulation is obtained for the fatigue strength at constant stress rate. Experimental confirmation of the essential predictions of the theory is obtained from strength tests on Vickers-indented soda-lime glass disks in water environment. It is thereby implied that residual stresses can have a significant deleterious influence on the fatigue behavior of any brittle solid whose controlling flaws have a contact history. Such effects need to be considered in the design of structural ceramics, most notably where fracture-mechanics calibrations of crack-velocity parameters are used for lifetime predictions.     

Mixed-Mode Fracture in Soda-Lime Glass Using Indentation Flaws

Mixed-mode failure of soda-lime glass under inert and fatigue test conditions was studied using Knoop indentation flaws. For annealed cracks (residual stress-free) crack extension (catastrophic or subcritical) is by an abrupt transition from the initial crack plane to a noncoplanar crack plane followed by a reorientation of the crack normal to the applied stress. Although fatigue strength of these inclined flaws increased linearly with respect to orientation of the flaws to the applied stress up to an angle of 60°, this increase was considerably less than what was predicted by existing theories. It is believed that subcritical crack growth causes the crack to be realigned perpendicular to the applied stress before failure for all orientations; hence, fatigue strength does not show the dramatic increase at orientation angles as predicted by theory. For as-indented cracks the contact residual stress causes the crack extension to be less inclined to the initial crack plane than for annealed cracks, but in this case also, the crack realigns itself perpendicular to the applied stress. Again, fatigue strength is relatively insensitive to the orientation angle as predicted by theory and subcritical crack growth is believed to play a primary role in determining this strength dependency.     

压力容器角焊缝应力分析方法研究

以立式压力容器为例,研究了支座垫板与承压壳体间角焊缝的应力分析和疲劳评定的计算方法。建立了一体模型和接触对连接模型,发现最大应力发生在角焊缝与封头外表面连接点上,断裂位于非承压部件上并沿着焊缝宽度方向扩展。在疲劳评定时,将两种建模方法的计算结果与JB 4732中规定的角焊缝疲劳减弱系数法的计算结果进行对比,发现这两种计算结果几乎一致,而JB 4732规定的方法更偏于保守。故可以采用较简便的一体模型方法。     

Improvement of impact fatigue strength of adhesive joint by CTBN modification

Impact fatigue behaviors of the steel/CTBN-modified adhesive/steel butt joint were investigated. The adhesive butt joint specimens used in the present work were bonded with epoxy–polyamide and CTBN-modified epoxy–polyamide adhesives. Fatigue tests were also conducted under nonimpact stress conditions to compare with the results from the impact fatigue test. The experiments showed that for the joint specimen from the adhesive modified with the CTBN the fatigue strength becomes higher under both of the stress conditions. In particular, the fatigue strength was improved remarkably under impact stress condition, that is, the distinct stress cycles dependence of impact strength was decreased by modifying the adhesive with CTBN. Furthermore, the effect of adhesive thickness on the fatigue strength was also discussed for the adhesive joint modified with CTBN. Under impact stress conditions, the relation between the fatigue strength and the adhesive layer thickness is different from that under the nonimpact one.     

Model for Cyclic Fatigue of Quasi-Plastic Ceramics in Contact with Spheres

A model of contact damage accumulation from cyclic loading with spheres and ensuing strength degradation in relatively tough, heterogeneous ceramics is developed. The damage takes the form of a quasi-plastic zone beneath the contact, consisting of an array of closed frictional shear faults with attendant "wing" microcracks at their ends. Contact fatigue takes place by attrition of the frictional resistance at the sliding fault interfaces, in accordance with an empirical degradation law, allowing the microcracks to extend. At large numbers of cycles or loads the microcracks coalesce, ultimately into radial cracks. Fracture mechanics relations for the strength degradation as a function of number of cycles and contact load are derived. Indentation–strength data from two well-studied coarse-grain quasi-plastic ceramics, a micaceous glass-ceramic and a silicon nitride, are used to evaluate the model. Comparative tests in static and cyclic contact loading confirm a dominant mechanical component in the fatigue. At the same time, the presence of water is shown to enhance the fatigue. The model accounts for the broader trends in the strength degradation data, and paves the way for consideration of key variables in microstructural design for optimum fatigue resistance.