基于ANSYS的卧式容器鞍座截面开孔可行性研究

针对某鞍座截面带有大开孔的特定卧式容器,利用有限元分析软件ANSYS进行了整体强度分析,通过对比各开孔处的应力大小,得出在满足GB150开孔限制条件下,简体上开孔位置的选择不影响开孔的补强效果。然后阐述了卧式容器鞍座处的扁塌效应和GB150关于开孔补强的相关理论。最后得出结论,卧式容器鞍座截面的扁塌效应不影响该区域的开孔补强,鞍座截面的开孔不会诱导区域产生扁塌效应。     

基于有限元的压力容器开孔接管区的应力分析及优化设计

采用有限元法研究开孔接管区域的应力分布规律,对危险区域进行应力强度评定。结果表明:开孔接管区域应力分布复杂,梯度变化明显;最大应力发生在筒体与接管连接区域的内侧且对称分布,是筒体失效的最危险区域。在保证压力容器安全运行的工况下,对容器的结构进行优化设计,分析计算得到容器的最优解,保证容器高效安全运行的同时降低制造成本。     

压力容器球壳不连续区域应力分析和强度评定

球壳开孔接管区的应力较高且分布状况较复杂。借助ANSYS Workbench软件,通过建立球壳开孔接管模型,实现压力容器开孔接管区不连续应力的模拟分析,探讨了开孔率、厚度比以及不同受载情况对球壳开孔接管区最大应力的影响,并进行了正交试验和应力评定。结果表明:随着开孔率和内压载荷的增大,最大应力呈增大的趋势;随着厚度比的增大,最大应力呈减小的趋势;厚度比对球壳最大应力的影响程度最大,开孔率对球壳最大应力的影响程度最小;应力评定能满足强度要求,试验结果可为球壳的设计提供借鉴。     

某压缩空气罐接管区的力学分析

通过Ansys方法对某压缩空气罐开孔区域进行了有限元计算应力分析。根据该压缩空气罐接管区域的应力云图与受力情况,按照压力容器应力分析标准进行了应力强度评定。     

基于数值计算方法的换热器管板等效方法研究

换热器管板等效方法影响到管板受力变形计算的准确性。以管壳式换热器为例,分别建立了开孔管板结构、共用节点的实心管板结构和主从节点绑定的实心管板结构有限元模型。采用数值计算方法,对管板的应力和变形进行了分析。有限元计算结果表明:采用主从节点绑定的实心管板结构与开孔管板结构变形最大相对误差为8.4%、孔边应力相对误差超过60%,说明主从节点绑定的实心管板结构仅可准确描述管板的变形。通过对比分析主从节点绑定的实心管板结构与开孔管板结构开孔区域应力分布,得到开孔边缘的应力集中系数为约3,开孔中部的应力集中系数约为2。     

椭圆形管孔管板应力强度的有限元分析

为比较管板在不同形式管孔下的应力强度,分别在UG中建立了八分之一模型,即圆形开孔和椭圆形开孔的管板结构。在ANSYS中进行温度场和应力场的的分析。对计算结果进行分析,结果表明在本文计算工况下,圆形开孔的管板应力值与椭圆形开孔的管板应力值相比,其值很大且分布很不均匀,在管板中心布管区域的应力比较大,出现应力集中。而椭圆形开孔的管板,应力值普遍较低,应力的分布比较均匀。目前,所有的标准均是针对圆管的,这样的结果为工程实际应用提供了依据。     

球形封头开孔接管的峰值应力

前言高压容器封头一般采用半球形,当顶点开孔接管时,接口处外表面层出现较大的应力集中,故必须做成圆角,如图1所示,这种圆角的曲率半径r如果太小,则应力太大,容易引起疲劳破坏,一般规定为壁厚h的一半,为了确定容器的疲劳寿命,必须精确地计算出接口处的最大应力,或称峰值     

喷嘴洗涤器弯头开孔结构有限元分析及强度评定

由于弯头开孔结构无法按常规设计方法进行开孔补强计算,故对弯头接管开孔区域建立了三维有限元力学分析模型。利用三维实体模型,真实地模拟了特殊结构的形状、载荷分布、边界条件,计算出最接近真实状况的应力分布情况;根据有限元分析结果,按JB4732-1995《钢制压力容器——分析设计标准》进行了应力强度评定,为详细工程设计提供了弯头开孔补强计算方法。     

基于子模型技术的压力容器切向接管应力分析

压力容器上切向接管的存在,必然会破坏原有的应力分布,并在接管与壳体相贯区产生复杂的高应力,严重削弱压力容器的承载能力。基于ANSYS的子模型分析技术,分别探讨了相对厚度和开孔系数两个无因次参数对相贯区最大应力及其分布位置的影响规律并作出一定的理论分析:随相对厚度的增大,最大应力分布呈现出应力衰减、平稳及增加三个明显的变化区域;随开孔系数的增大,最大应力呈逐渐增大的趋势;最大应力分布位置则会随相对厚度与开孔系数的不同出现在相贯区不同位置的内外表面;最后,基于应力分析对切向接管结构设计提出了若干优化原则,以期为工程设计提供一定的理论指导。     

圆平盖中心大开孔的极限载荷和结构的分析研究

利用有限元法对大开孔平盖进行了极限载荷分析,比较了平盖与筒体连接处采用的锥形段过渡与圆角过渡两种形式。结果表明,二者均能有效地降低平盖与筒体连接处的边缘应力。设计过渡段时,δ2/δ0为3.0、锥度为1∶3能够更有效地降低平盖的边缘应力。     

Thermal non-linear elastic stress analysis of an adhesively bonded T-joint

Adhesive joints consist of adherends and an adhesive layer having different thermal and mechanical properties. When they are exposed to uniform thermal loads the mechanical-thermal mismatches of the adherends and adhesive layer result in uniform but different thermal strain distributions in the adhesive and adherends. The thermal stresses arise near and along the adherend-adhesive interfaces. The present thermal stress analyses of adhesively bonded joints assume a uniform temperature distribution or a constant temperature imposed along the outer boundaries of adhesive lap joints. This paper outlines the thermal analysis and geometrically non-linear stress analysis of adhesive joints subjected to different plate edge conditions and varying thermal boundary conditions causing large displacements and rotations. In addition, the geometrically non-linear thermal stress analysis of an adhesively bonded T-joint with single support plus angled reinforcement was carried out using the incremental finite element method, which was subjected to variable thermal boundary conditions, i.e. air streams with different temperatures and velocities parallel and perpendicular to its outer surfaces. The steady state heat transfer analysis showed that the temperature distribution through the joint members was non-uniform and high heat fluxes occurred inside the adhesive fillets at the adhesive free ends. Based on the geometrically non-linear stress analysis of the T-joint bonded to both rigid and flexible bases for different plate edge conditions, stress concentrations were observed at the free ends of adhesive-adherend interfaces and inside the adhesive fillets around the adhesive free ends, and the horizontal and vertical plates also experienced considerable stress distributions along outer surfaces. In addition, the effect of support length on the peak thermal adhesive stresses was found to be dependent on the plate edge conditions, when a support length allowing moderate adhesive stresses was present.     

Effect of adhesive free-end geometry on the initiation and propagation of damaged zones in adhesively bonded lap joints

In this study the effect of adhesive free-end geometry on the initiation and propagation of damaged zones in adhesively bonded single- and double-lap joints was investigated considering the material non-linear behaviour of both adhesive and adherends and the geometrical non-linearity. The damaged adhesive and adherend zones exceeding the specified ultimate strains were determined based on the modified von Mises criterion for adherends and the failure criterion, including the effects of the hydrostatic stress states for the epoxy adhesives proposed by Raghava and Cadell. The stiffness of each finite element in the damaged zones was reduced to a negligible value, thus not contributing to the overall stiffness of the adhesive joint. This simple method provides useful information on the initiation and propagation of damaged zones in both the adhesive layer and adherends. The damaged adhesive zones due to a tensile load were observed to initiate around the rounded adherend corners inside the adhesive fillets and to propagate first towards both the free surface of the adhesive fillet and across the adhesive layer, and later along the adherend–adhesive interface. The damaged adhesive zones initiate at the left free-end of the adhesive-upper adherend interface and at the right free-end of the adhesive-lower adherend interface and propagate along these interfaces in the large adhesive fillets. In the bending test, the damaged adhesive zones appeared only at the left free-end in tension of the adhesive-upper adherend interface for the large adhesive fillets, but around the lower adherend corner for the smaller adhesive fillets. Later, it propagated with a similar mechanism as in the tensile load. In a double-lap joint subjected to a tensile load, the damaged zone appeared around the upper adherend corner inside the right adhesive fillet in tension, and propagated first towards the free surface of the adhesive fillet and through the adhesive layer towards the adhesive-middle adherend interface, and later along this interface. For all loading conditions, increasing the adhesive fillet size caused the damaged zone initiation to occur at a larger load level. The SEM micrographs of fracture surfaces around the adhesive fillets showed that the damaged zones initiated around the adherend corner inside the adhesive fillet and propagated through the adhesive fillets.     

Geometrically Non-Linear Analysis of Adhesively Bonded Double Containment Corner Joints

In cases where adhesively bonded joints may experience large displacements and rotations whilst the strains remain small, although all joint members behave elastically the small strain-small displacement (SSSD) theory cannot correctly predict the stresses and deformations in the adhesive joint members. Previous studies have shown that the small strain-large displacement theory considering the non-linear effects of the large displacements in the stresses and deformations has to be used in the analysis of adhesively bonded joints. In this study, the geometrical non-linear analysis of an adhesively bonded double containment corner joint was carried out using the incremental finite element method based on the small strain-large displacement (SSLD) theory. The objective of the study was to determine the effects of the large displacements on the adhesive and adherend stresses of the corner joint. Therefore, the corner joint was analysed for two different loading conditions; a compressive applied load, P_x, at the free end of the horizontal plate and one normal to the plane of the horizontal plate, P_y. The plates, support and adhesive layer were assumed to have elastic properties. In practice, the adhesive accumulations, called spew fillets, arising around the adhesive free ends were taken into account in the analysis since their presence results in a considerable decrease in the peak stresses around the free ends of the adhesive. The SSLD and SSSD analyses showed that the stress concentrations occurred around the free end of the adhesive, thus at the adherend (slot) corners inside the right vertical and the lower horizontal adhesive fillets, and inside the left vertical and the upper horizontal adhesive fillets for the loading conditions P_x and P_y, respectively. In addition, the plate regions around the adherend (slot) free ends along the outer fibres of the vertical and horizontal plates undergo very high stress concentrations. The SSLD analysis predicted a non-linear effect in the displacement and stress variations at the critical adhesive and plate locations, whereas the SSSD analysis showed their variations were lower and proportional to the applied incremental load. This non-linear effect became more evident for the loading condition P_x, whereas both analyses predicted very close displacement and stress variations in the adhesive fillets and in the horizontal plate for the loading condition P_y. As a result, the geometrical non-linear behaviour of the corner joint is strictly dependent on the loading condition and the large displacements affect the stress and deformation states in the joint members, and result in higher stresses than those predicted by the SSSD theory.     

Chlorotetracycline and Sodium Chloride Treatment Effects on Some Micro-Organisms and Unsaponifiables of Bolti Fish Fillets

The effects of chlorotetracycline (CTC),brine (NaCI) and combination of them on Bolti unsaponifiables and associated micro-organisms were studied under different storage conditions. Lipolytic and psychrophilic bacterial counts in cold stored fillets with combined employment of NaCl and CTC were much lower than either NaCl or CTC. The data for partial freezing indicated that lipolytic bacteria increased much lower than that of psychrophilic bacteria. NaCl had a synergistic effect on CTC and this phenomenon was superior in decreasing lipolytic bacterial counts to that of psychrophilic bacteria. The hydrocarbons of the fresh Bolti fillets were fractionated by GLC into 10 different components of which 7 were completely characterized. The detected sterols were cholesterol, campesterol and β-sitosterol with cholesterol being the most predominant. With cold storage, slight interconversion might occur between hydrocarbons or sterols and not between these lipid classes. On the contrary, remarkable amounts of sterols were converted to hydrocarbons in partially frozen fillets. The employment of NaCl, CTC and in combination lead to enormous, slight and noticeable conversions from hydrocarbons to sterols of Bolti fillets, respectively.     

Dietary Fatty‐Acid Compositions Are more Strongly Reflected in Fatty than Lean Dorsal Fillets of Common Carp (Cyprinus carpio L.)

In this fish‐feeding study, we tested similarity patterns between fatty acids (FA) in diets and common carp (Cyprinus carpio) of fish ponds used for semi‐intensive aquaculture, containing naturally occurring pond zooplankton and different feeds (marine or terrestrial feeds) until carp reached market size. We evaluated if and how total lipid contents in dorsal fillets can reflect dietary FA compositions in farm‐raised common carp and hypothesized that increasing total lipid contents in dorsal fillets significantly increase the similarity between dietary and dorsal fillets’ FA compositions. Results of this study showed that carps had higher total lipids when supplied with marine feeds and dietary FA compositions were indeed more strongly reflected in fatty (i.e. high total lipid contents) than in leaner dorsal fillets (low total lipid contents). Increasing total lipid contents in dorsal fillets significantly increased the similarity between the dietary and dorsal fillets’ FA compositions. In contrast, leaner dorsal fillets had FA patterns that were more distinct from dietary FA. Total lipid contents higher than ~60 mg/g dry weight in dorsal fillets had only limited effects on increasing the similarity between FA compositions of diets and dorsal fillets, and were independent of feed sources. It is thus suggested that higher total lipid contents in dorsal fillets can be used as a proxy to predict dietary FA profiles in common carps, or perhaps even in farm‐raised fish in general.     

Vacuum Frying of Desalted Grass Carp (Ctenopharyngodon idellus) Fillets

The objective of this study was to investigate the effects of vacuum frying on the product quality of desalted grass carp fillets. Parameters of included moisture content, oil content, color values, and textures (hardness, chewiness, and springiness) were used to evaluate the product quality. Results showed that with increasing vacuum frying temperature and time, the moisture content of fillets decreased while the oil content increased, and hardness increased quickly. The hardness and chewiness values of vacuum-fried samples were both higher than those of atmospheric fried samples. However, there was no significant change in L* among four different temperature/vacuum-frying combinations. The results also indicated that vacuum frying at 0.08 MPa and 100°C–110°C for 15 min can produce crisp grass carp fillets with lower moisture and oil contents as well as good color and texture quality.     

Effects of Lupin Oil on Carp Lipids during Chilling 2. Changes in Fatty Acid Composition

Rearing carp for 6 weeks on diets containing 5% lupin oil slightly affected the composition of the component fatty acids in various lipid classes of the fillets. On the other hand, the incorporation of lupin oil in the diet did not affect the trend in the changes occurring in the component fatty acids of the different lipid classes during chilling storage of the carp fillets. Thus, the percentage of saturated and monounsaturated fatty acids increased whereas the percentages of polyunsaturated fatty acids decreased during storage.     

Geometrically non-linear analysis of adhesively bonded modified double containment corner j oints - II

In this study, the geometrical non-linear analysis of an adhesively bonded modified double containment comer joint, which is presented as an alternative to previous comer joints, was carried out using the incremental finite element method based on the small strain-large displacement (SSLD) theory. The analysis method assumes the joint members such as the support, plates, and adhesive layers to have linear elastic properties. Since the adhesive accumulations (spew fillets) around the adhesive free ends have an important effect on the peak adhesive stresses, their presence was taken into account by idealizing them as triangular in shape. The joint was analysed for two different loading conditions: one load normal to the horizontal plate plane, P_y, and one load horizontal at the horizontal plate free edge, P_x. Finally, small strain-small displacement (SSSD) analysis of the joint was carried out and the results of both analyses were compared in order to determine the capability of the two theories in predicting the effects of large displacements on the stress and deformation states in the joint members. Both analyses showed that the peak stress values appeared at the slot comers inside the adhesive fillets and at the upper and lower longitudinal fibres (top and bottom longitudinal surfaces) of the horizontal and vertical plates corresponding to the horizontal and vertical slot free ends. In the case of the load P_y, the right vertical adhesive fillet and both plates were the most critical joint regions, whereas the lower horizontal fillet and both plates were determined to be the most critical regions for the load P_x. The SSLD theory predicted a non-linear effect on the variations of the displacement and stress components at these critical adhesive and plate locations for the load P_x, whereas the stress components at the critical adhesive locations presented variations very close to those determined by the SSSD theory for the load P_y, but this non-linear effect appeared on the displacement and stress variations at the critical locations of both plates. In addition, the SSSD theory predicted that the displacement and stress components would have lower variations proportional to the increasing load for both loading conditions. The stress and deformation states of all joint members are strictly dependent on the boundary and loading conditions. In addition, whereas the SSSD theory may be misleading for some loading conditions, the SSLD theory gives more realistic results, since it takes into account the non-linear effect of large displacements and rotations.     

Lipid Composition and Antioxidant Capacity Evaluation in Tilapia Fillets Supplemented with a Blend of Oils and Vitamin E

Since the nutritional value of farm‐raised fish fillets is directly related to the diet provided, we supplemented the diet of Tilapia (Oreochromis niloticus) with a blend of chia (Salvia hispanica L.) oil, tung (Aleurites fordii) oil, and conjugated linoleic acid (CLA) to evaluate the effects on the fatty acid composition. Vitamin E was also added to the diet to improve the antioxidant capacity of tilapia fillets. We observed an increase in α‐linolenic acid content (from 6.56 to 19.03 mg g^?1 of total lipids), as well as the incorporation of CLA and conjugated linolenic acid (CLnA) isomers in the fillets. The addition of vitamin E resulted in the antioxidant capacity improvement of the fillets and higher values were found after 15 feeding days (39.25 µmol TE g^?1 in the Ferric Reducing Ability Power assay). Supplementation proved to be an excellent tool to improve the nutritional value of fish fillets.     

Geometrically non-linear analysis of adhesively bonded corner joints

When adhesively bonded joints are subjected to large displacements, the small strain-small displacement (linear elasticity) theory may not predict the adhesive or adherend stresses and deformations accurately. In this study, a geometricaly non-linear analysis of three adhesively bonded corner joints was carried out using the incremental finite element method based on the small strain-large displacement (SSLD) theory. The first one, a corner joint with a single support, consisted of a vertical plate and a horizontal plate whose left end was bent at right angles and bonded to the vertical plate. The second corner joint, with a double support, had two plates whose ends were bent at right angles and bonded to each other. The final corner joint, with a single support plus angled reinforcement, was a modification of the first corner joint. The analysis method assumes that the joint members, such as the support, plates, and adhesive layers, have linear elastic properties. Since the adhesive accumulations (spew fillets) around the adhesive free ends have a considerable effect on the peak adhesive stresses, they were taken into account. The joints were analyzed for two different loading conditions: one loading normal to the horizontal plate plane P_y and the other horizontal loading at the horizontal plate free edge P_x. In addition, three corner joints were analyzed using the finite clement method based on the small strain-small displacement (SSSD) theory. In predicting the effect of the large displacements on the stress and deformation states of the joint members, the capabilities of both analyses were compared. Both analyses showed that the adhesive free ends and the outer fibres of the horizontal and vertical plates were subjected to stress concentrations. The peak stresses appeared at the slot corners inside the adhesive fillets and at the horizontal and vertical plate outer fibres corresponding to the locations where the horizontal and vertical adhesive fillets finished. The SSLD analysis predicted that the displacement components and the peak adhesive and plate stress components would show a non-linear variation for the loading condition P_x, whereas the SSSD analysis showed smaller stress variations proportional to the applied load. However, both the SSLD and the SSSD analyses predicted similar displacement and stress variations for the loading condition P_y. Therefore, the stress and deformation states of the joint members are dependent on the loading conditions, and in the case of large displacements, the SSSD analysis can be misleading in predicting the stresses and deformations. The SSLD analysis also showed that the vertical and horizontal support lengths and the angled reinforcement length played an important role in reducing the peak adhesive and plate stresses.