Large Flange Research Articles

Effects of load height application and pre-buckling deflections on lateral buckling of thin-walled beams

Based on a non-linear model taking into account flexural-torsional couplings, analytical solutions are derived for lateral buckling of simply supported I beams under some representative load cases. A closed form is established for lateral buckling moments. It accounts for bending distribution, load height application and pre-buckling deflections. Coefficients C1 and C2 affected to these parameters are then derived. Regard to well known linear stability solutions, these coefficients are not constant but depend on another coefficient k1 that represents the pre-buckling deflection effects. In numerical simulations, shell elements are used in mesh process. The buckling loads are achieved from solutions of eigenvalue problem and by bifurcations observed on non linear equilibrium paths. It is proved that both the buckling loads derived from linear stability and eigenvalue problem lead to poor results, especially for I sections with large flanges for which the behaviour is predominated by pre-buckling deflection and the coefficient k1 is large. The proposed solutions are in good agreement with numerical bifurcations observed on non linear equilibrium paths.

New forming technologies used in manufacturing large vessels

In this paper, some new forming technologies such as the forming of curved shell using reconfigurable discrete die, the precision bending of large flange with a complicated shape of the cross section, the integrated hydro-bulge forming (IHBF) method for manufacturing LPG spherical tank and the method of machining seal surface of large flange using a multifunction machine tool is introduced. The practical applications of the above-mentioned method in manufacturing different vessels are also given.

The Influence of Two Different Types of Foot Orthoses on First Metatarsophalangeal Joint Kinematics During Gait in a Single Subject

Objective To quantify the effect of two distinct foot orthotic designs on in vivo multisegment foot and leg motion; in particular, the first metatarsal and first metatarsophalangeal (MTP) joint during gait. Methods A 23-year-old man had an excessively pronated foot structure as measured during a clinical orthopedic examination. The Optotrak Motion Analysis System was used to collect three-dimensional position and orientation data from four modeled rigid body segments (hallux, first metatarsal, calcaneus, and tibia) during the stance phase of walking. The subject walked at a self-selected comfortable walking speed, and a minimum of five trials were collected under three different test conditions: no orthosis, semirigid orthosis with a varus post, and a semirigid orthosis with a varus post and a large medial flange. Data were normalized to the stance period, and descriptive statistics were calculated for dependent variables. Results Both orthotic interventions equally modified first MTP joint motion when compared with the no orthotic condition. First MTP joint dorsiflexion was decreased (>2 SD) with the orthosis during terminal stance phase. This decrease was associated with a concomitant increase in first metatarsal plantar flexion. Conclusion A custom-made semirigid orthosis posted medially and made from a neutral position off–weight-bearing plaster cast can alter motion in the forefoot during the propulsive period by increasing first metatarsal plantar flexion and decreasing excessive first MTP joint dorsiflexion.

Characterization of aflatoxin-producing fungi outside of Aspergillus section Flavi

Most aspergilli that produce aflatoxin are members of Aspergillus section Flavi, however isolates of several Aspergillus species not closely related to section Flavi also have been found to produce aflatoxin. Two of the species, Aspergillus ochraceoroseus and an undescribed Aspergillus species SRRC 1468, are morphologically similar to members of Aspergillus section Circumdati. The other species have Emericella teleomorphs (Em. astellata and an undescribed Emericella species SRRC 2520) and are morphologically distinctive in having ascospores with large flanges. All these aflatoxin-producing isolates were from tropical zones near oceans, and none of them grew on artificial media at 37 C. Aflatoxins and sterigmatocystin production were quantified by high-pressure liquid chromatography (HPLC) and confirmed by HPLC-mass spectrometry (LC-MS) detection. Phylogenetic analyses were conducted on these four species using A. parasiticus and Em. nidulans, (which produce aflatoxin and the aflatoxin precursor sterigmatocystin, respectively) for comparison. Two aflatoxin/sterigmatocystin biosynthesis genes and the beta tubulin gene were used in the analyses. Results showed that of the new aflatoxin-producers, Aspergillus SRRC 1468 forms a strongly supported clade with A. ochraceoroseus as does Emericella SRRC 2520 with Em. astellata SRRC 503 and 512.

Characterization of aflatoxin-producing fungi outside of Aspergillus section Flavi

Most aspergilli that produce aflatoxin are members of Aspergillus section Flavi, however isolates of several Aspergillus species not closely related to section Flavi also have been found to produce aflatoxin. Two of the species, Aspergillus ochraceoroseus and an undescribed Aspergillus species SRRC 1468, are morphologically similar to members of Aspergillus section Circumdati. The other species have Emericella teleomorphs (Em. astellata and an undescribed Emericella species SRRC 2520) and are morphologically distinctive in having ascospores with large flanges. All these aflatoxin-producing isolates were from tropical zones near oceans, and none of them grew on artificial media at 37 C. Aflatoxins and sterigmatocystin production were quantified by high-pressure liquid chromatography (HPLC) and confirmed by HPLC-mass spectrometry (LC-MS) detection. Phylogenetic analyses were conducted on these four species using A. parasiticus and Em. nidulans, (which produce aflatoxin and the aflatoxin precursor sterigmatocystin, respectively) for comparison. Two aflatoxin/sterigmatocystin biosynthesis genes and the beta tubulin gene were used in the analyses. Results showed that of the new aflatoxin-producers, Aspergillus SRRC 1468 forms a strongly supported clade with A. ochraceoroseus as does Emericella SRRC 2520 with Em. astellata SRRC 503 and 512.

Progress in large vessel forming: introduction of some innovations of Prof. Z.R. Wang

Large size vessels are widely used as LPG spherical tanks, elevated water towers, vacuum simulators for the space environment, landmarks and others. Prof. Z.R. Wang has supervised several engineering projects in which he has innovated manufacturing technologies. In this paper, some cases of large vessels manufactured by one of his inventions, integrated hydro-bulge forming, are described. Also the new large flange forming method and the new flexible reconfigurable discrete die for forming curved shell petals are introduced.

Research on the precision bending of a workpiece with a complicated cross-section for manufacturing a large flange

A new technology used for manufacturing large flanges with a complicated cross-section is presented in this paper. It consists of precision bending combined with finish machining. First, the rules of the bending process were determined by experiment. A large flange, 8.5m diameter, is manufactured by using this technology. The results show that it is feasible to manufacture large flanges by this method.

Research on the precision bending of a workpiece with a complicated cross-section for manufacturing a large flange

A new technology used for manufacturing large flanges with a complicated cross-section is presented in this paper. It consists of precision bending combined with finish machining. First, the rules of the bending process were determined by experiment. A large flange, 8.5 m diameter, is manufactured by using this technology. The results show that it is feasible to manufacture large flanges by this method.

CMGC gasket applied to a large reactor vessel

The satisfactory sealing of large reactor vessel flanges in petrochemical plant is a significant problem. It is necessary to accommodate relative flange movement of large pressure vessels and provide a system where adequate bolting can be applied. The leakage from a large flange can be a major contributor to plant emissions. Here a corrugated metal graphite covered gasket has been used to seal a flange 20 feet (6 m) in diameter on a high-temperature (450°C) reactor vessel. This has resulted in a significant reduction in emissions and plant maintenance. This feature is based on the submission by the winning team in the Fluid Sealing Association's 2003 Environmental Achievement Awards.

A study on the development of large aluminum flange using the casting/forging process

In this study, the casting/forging process has been applied in manufacturing a large aluminum flange, in order to reduce press capacity and material costs. Firstly, a hot compression test was performed with cast cylindrical billets in order to determine the optimum forging conditions for the aluminum flange. The optimum range of forging temperature of Al 5083 was from 420 to 450 °C. The suitable strain rate was 1.5/s. In order to find the change in mechanical properties depending on the effective strain of the cast aluminum billets, a hot upsetting test was performed with rectangular blocks and then a uniaxial tensile test was performed with specimens cut from the upsetted billets. The tensile strength and the elongation of cast/upsetted aluminum billets were increased significantly until the effective strain was 0.7. And FE analysis was performed to determine the configurations of the cast preform and die for an aluminum flange. In the FE analysis, the forging load-limit was fixed at 1500 t for low-equipment cost. The cast preform was designed so that the effective stain around the neck of the flange exceeded 0.7. From the result of FE analysis, optimal configurations of the cast preform and the die were designed for a large flange. The filling and solidification analysis for a sound cast preform was carried out with MAGMA soft. In the forging experiment for an aluminum flange, it was confirmed that the optimal configuration of the cast preform predicted by FE analysis was very useful. The cast/forged products using designed preform were made perfectly without any defects.

Lateral post-buckling analysis of thin-walled open section beams

Thin-walled beams with open sections are studied using a nonlinear model. This model is developed in the context of large displacements and small deformations, by accounting for bending-bending and bending-torsion couplings. The warping and shortening effects are considered in the torsion equilibrium equation. The governing coupled equilibrium equations obtained from Galerkin’s method are solved by a Newton–Raphson iterative process. It is established that the buckling loads are highly dependent on the pre-buckling deformations of the beam. The bifurcated branches are unstable and strongly influenced by shortening effects. Some comparisons are presented with the solutions commonly used in linear stability, like in the standard European steel code (Eurocode 3). The regular solutions appear to be very conservative, especially for I sections with large flanges.

Experimental Study on Shear Splitting Failure of Full-Scale Composite Concrete Encased Steel Beams

Presented herein is an experimental study that focuses on the shear splitting failure concrete encased steel beams. Nine full-scale specimens were constructed and tested in this study. Significant horizontal cracks along the interface of steel flange and concrete, referred to as the shear splitting failure, appeared in five tested specimens. Observations from the experiments indicate that the steel flange width ratio, defined as the ratio of steel flange width to gross section width, has a dominant effect on the shear splitting failure of composite beams. The tests results reveal that the shear splitting failure occurs when the steel flange width ratio of a composite beam reaches 0.67. The test results also show that the application of shear studs has a positive effect on preventing this type of failure for beams with large steel flange ratio. In addition to the experimental study, a new method for predicting the failure mode of composite beams is proposed. The proposed method gives satisfactory predictions as compared to the test results. Finally, a new equation is derived for the design of the stirrups to prevent shear splitting failure of naturally bonded composite beams.

Re-Examination of I-Girder/Pier Connection in Jointless Bridges

Elimination of expansion joints in bridge decks results in initial economy and long-term durability. It provides a smooth riding surface, minimizes maintenance cost caused by water leakage, and provides a relatively high span-to-depth ratio of the superstructure. This paper presents a summary of the results of a project whose dual objective was to reduce the cost of bearing devices used in jointless bridges and to optimize the girder/pier joint details for economy, constructability and aesthetics. Criteria for selection of bearing devices as a function of load levels, translational and rotational capacities, simplified diaphragm details, and enhancements of bridge aesthetics are presented. Cases where a sharp skew exists in the bridge are covered. With the large bottom flange of modern l-girder shapes, it is shown how girder ends are produced with a skew to minimize the pier width.

A Study on the Development of Large Aluminum Flange Using Casting/Forging Process

The significance of the casting/forging process for reducing the production cost of large components is being noted in these days. This casting/forging process is a method of forging a workpiece preformed by casting into the final shape. In this study, the casting/forging process has been applied in manufacturing a large aluminum flange in order to reduce press capacity and material cost. Firstly, a hot compression test was performed with cast cylindrical billets in order to determine the optimum forging condition of the aluminum flange. The optimum range of forging temperature of Al 5083 was from 420 to 450. The suitable strain rate was 1.5 sec(sup)-1. The deformation amount of a preform of a preform in a forging process is a key role in the mechanical properties of casting/forging products. In order to find the change of mechanical properties according to effective stain of cast aluminum billets, a hot upsetting test were performed with rectangular blocks and then a uniaxial tensile test was performed with specimens cut from the upsetted billets. The tensile strength and the elongation of cast/upsetted aluminum billets were increased largely until the effective strain was 0.7. FE analysis was performed to determine the configurations of case preform and die for an aluminum flange. In the FE analysis, the forging load-limit was fixed 1500ton for low equipment cost. The cast preform was designed so that the effective stain around the neck of a flange exceeded 0.7. From the result of FE analysis, optimal configurations of the cast preform and the die were designed for a large flange. The filling and solidification analysis for a sound cast-preform was carried out with MAGMA soft. In the forging experiment for an aluminum flange, it was confirmed that the optimal configuration of the cast preform predicted by FE analysis was very useful. The cast/forged products using designed preform were made perfectly without any defects.

Stresses analyses of shell structure with large holes

The strength, deformation and buckling of a large engineering structure consisting of four ellipsoidal shells, two cylindrical shells with stiffening ribs and large holes, one conical shell and three pairs of large flanges under external pressure, self weight and heat sinks have been analysed by using two kinds of five different finite elements - four assumed displacement finite elements (shell element with curved surfaces, axisymmetric conical shell element with variable thickness, three dimensional eccentric beam element, axisymmetric solid revolutionary element) and an assumed stress hybrid element (a 3-dimensional special element developed by authors). The compatibility between different elements is enforced. The strength analyses of the top cover and the main vessel are described in the paper.

Metal-to-metal full face taper-hub flanges: Finite element model evaluation and preliminary plastic analysis results

The stress analysis of the flange problem is found to be sensitive to the way in which the component is modelled, particularly so when a finite element program is used to analyse the flange and bolt contact faces. The validity of a number of these finite element models are examined, by comparing the predicted maximum axial bending stress at the intersection of the taper-hub and the cylindrical vessel, with those measured on a large taper hub flange. It is found that a well-thought-through simple model can produce accurate results. In this type of flange it is considered that the magnitude of this stress is critical since, if the bending stress at this intersection reaches yield and subsequently a plastic hinge develops, then undue rotation of the flange could cause leakage. Using an appropriate finite element model, the development of plasticity is studied, from which it is shown that the use of a cylindrical shell yield surface provides a more realistic approach than the simple beam criterion which is unconservative despite its wide use in the existing pressure vessel standards.

Determination of the gasket load drop at large size welding neck flange joints in the case of nonlinear gasket model

This paper deals with the calculation of gasket load drop caused by internal pressure at flange joints. The method published here makes it possible to take into consideration the nonlinearity of gasket material and the stiffness effect of the integrated part of the flange ring. The equations published refer to large size welding neck flanges but the method itself can be applied at any other types of flange joint too. The preciseness of this method, as well as the convergence of trial-and-error calculations used, are proved by results of calculations carried out on a flange joint.

A fundamental approach to establishing a rule base for the design of tools for pressworking

Software is being developed for use in the design of tools for the multi-stage drawing of small cylindrical cups with some emphasis on cups with medium to large flanges often produced in progression tools; the software is also being used for the rapid estimation of the manufacturing and tooling costs. Attempts are being made to generate the rules from fundamental data on material properties such as the workhardening and plastic anisotropy and the limiting draw and redraw ratios rather than relying completely on data on safe diameter reductions normally elicitated from tool designers and obtained from standard tool design reference books. Computer models which take into account workhardening and planar anisotropy have been developed to estimate the drawing loads in the presence of ironing and to predict forming limits. This paper presents the theory involved in the development of the program for the first stage drawing of plain and flanged cylindrical cups with some results from use of the model.

Recent Progress of Rolling Technologies in Japan.

After the Plaza Agreement of G5, which was held in September 1985, the Yen was highly appreciated, and the Japanese government changed its policy from the encouragement of exports to the expansion of the domestic market. Fortunately, the government policy has been a success, and the production of hot and cold strip, large wide flange beam, wire and rod has recovered. Investment for equipment is under way and there are plans for renewing mills. However, the steel tube mills are highly dependent on the foreign market, the production of steel tube was drastically cut due to the sharp drop of the dollar and sharp rise of the yen. Nevertheless, research and development has been actively promoted and many marvelous results have been reported in every field. Iron and steel industries in Japan are still confident and innovative.

Fracture toughness and defect assessment of low-temperature carbon steel flanges

A quantitative fitness-for-purpose assessment has been performed for a range of large carbon steel flanges for use at low temperatures (to ASTM A350 LF2 specifications). Toughness has been measured using fracture toughness tests and Charpy impact tests and results have been related qualitatively to microstructure. The presence of Widmannstatten ferrite has been found to be particularly deleterious to toughness. Local stresses have been predicted using both elastic and elastic-plastic finite element methods (FEMs). Point-loading methods have been used to study the behaviour of cracks in these non-uniform stress fields and to establish critical defect sizes. A critical tensile stress criterion has been invoked to characterise the onset of cleavage fracture. Although under worst-case operating conditions tolerable defect sizes (according to PD6493) are below nominal acceptance limits, for lower bound toughness values, δ c = 0·009 mm and K Q = 39 MPa m 1 2 , reassessment using point-loading methods suggests in many instances that the material may still be fit for purpose. To guarantee fitness for purpose, δ c values of approximately 0·020 mm may be required, and the study appears to suggest that the impact toughness requirements of ASTM A350 LF2 could be relaxed.