External Flange Research Articles

Study of the influence of technological parameters on the mechanics of shaping of billets using roll stamping processes

The article presents the results of development and research of technological schemes of planting flanges on tubular (ring) workpieces by stamping by rolling cylindrical and conical rolls. It is shown that the achievement of significant dimensions of the various elements of the workpiece is possible by providing a directed flow of metal by changing the relative position of the roll and the workpiece. Planting of external flanges is one of the most effective operations of stamping by rolling, as it allows you to form a wide range of products with advanced geometric elements. To assess the technological capabilities of the flange landing operation, the most dangerous from the destruction positions of the workpiece zone was identified and the analysis of the stress strain state of the material using the method of grids, hardness measurement and microstructural analysis. According to the results of the research, the ways of deformation of the particles of the material of the peripheral surface of the flange in the coordinates "intensity of deformations - an indicator of the stress state" are schematically constructed. These deformation paths are given against the background of curves of ultimate deformations of steels, which are built on the results of uniaxial compression and torsion of cylindrical specimens and using tested approximations. A mathematical model of deformation trajectories is constructed, for which a one-parameter function is taken as a basis, which is "glued" from the elementary function of the sine and tangent to it at some point in the line. To determine the used plasticity resource, a damage summation model with a power approximation of the damage function was adopted. As a result, we have for the first time described the general expression of the linear damage summation model for the case of the parametric deformation path problem. The graphical representation on the constructed model of accumulation of damages in material of a dangerous zone of a flange at landing by a method of rolling stamping (SHO) is resulted. Based on the constructed model, it is possible to model the accumulation of damage by changing the values of the model parameters for different materials and deformation paths, which, in turn, depend on the relative geometric parameters of the workpiece and its location relative to the rolling roll.

EVALUATION OF DEFORMABILITY OF MATERIAL DURING PLANTING OF ELEMENTS OF PREPARATIONS BY ROLLING STAMPING METHOD

The article presents the results of development and research of technological schemes of planting flanges on tubular (ring) workpieces by stamping by rolling cylindrical and conical rolls. It is shown that the achievement of significant dimensions of the various elements of the workpiece is possible by providing a directed flow of metal by changing the relative position of the roll and the workpiece. Planting of external flanges is one of the most effective operations of stamping by rolling, as it allows you to form a wide range of products with advanced geometric elements. To assess the technological capabilities of the flange landing operation, the most dangerous from the destruction positions of the workpiece zone was identified and the analysis of the stress-strain state of the material using the method of grids, hardness measurement and microstructural analysis. According to the results of the research, the ways of deformation of the particles of the material of the peripheral surface of the flange in the coordinates "intensity of deformations - an indicator of the stress state" are schematically constructed. These deformation paths are given against the background of curves of ultimate deformations of steels, which are built on the results of uniaxial compression and torsion of cylindrical specimens and using tested approximations. A mathematical model of deformation trajectories is constructed, for which a one-parameter function is taken as a basis, which is "glued" from the elementary function of the sine and tangent to it at some point in the line. To determine the used plasticity resource, a damage summation model with a power approximation of the damage function was adopted. As a result, we have for the first time described the general expression of the linear damage summation model for the case of the parametric deformation path problem. The graphical representation on the constructed model of accumulation of damages in material of a dangerous zone of a flange at landing by a method of SHO is resulted. Based on the constructed model, it is possible to model the accumulation of damage by changing the values of the model parameters for different materials and deformation paths, which, in turn, depend on the relative geometric parameters of the workpiece and its location relative to the rolling roll.

Cold forging of a hollow flanged part by an unconventional extrusion method

This paper presents a numerical analysis of a new cold forming process for a hollow part with an external flange. The following techniques were used: forward extrusion, an unconventional method of extrusion with a moving sleeve, and upsetting in a tapered die cavity. The billet (42CrMo4 steel tube) was formed at ambient temperature. The study aimed to investigate the proposed method in terms of forged part accuracy. The following are examined and discussed: material flow, process force parameters in relation to tool strength, energy consumption of individual operations, as well as the distributions of strains, stresses, temperature and Cockcroft-Latham integrals in the produced part. The study has confirmed that hollow forged parts with external flanges of relatively large diameters and heights can be cold formed in several operations using different techniques.

Effect of Different Lateral Reinforcement and its Spacing on Column Reinforced with Hollow Composite Sections

Abstract: Hollow Concrete Columns (HCCs) are one of the preferred construction systems in civil infrastructures including bridge piers, ground piles, and utility poles to minimize the overall weight and costs. HCCs are also considered a solution to increase the strength to mass ratio of structures. However, HCCs are subjected to brittle failure behaviour by concrete crushing means that the displacement capacity and the strength after steel yielding in HCCs are decreasing due to the unconfined concrete core. Absence of the concrete core changes the inner stress formation in HCCs from triaxial to biaxial causes lower strength. A new type of Hollow Composite Reinforcing System (HCRS) has recently been designed and developed to create voids in structural members. This reinforcing system has four external flanges to facilitate mechanical bonding and interaction with concrete. Therefore, providing the inner Hollow Composite Reinforced Sections (HCRS) can significantly increase strength by providing a higher reinforcement ratio and confining the inner concrete core triaxially. The corrosion of steel is also a notable factor in the case of steel reinforced HCCs which became more critical because their outer and inner surfaces exposing more concrete surface area. An alternative reinforcement is Glass Fibre Reinforced Polymer (GFRP) bars, can overcome the brittle behaviour of steel reinforced HCC. In previous studies, HCC shows high strength capacity, when appropriate reinforcement in the form of longitudinal GFRP bars, laterally using GFRP spirals and internally using rectangular HCRS which provide enough inner confinement. However, the spirals laterally restrict the expansion of the concrete core and limit the buckling of the longitudinal bars, allowing the columns to keep resisting applied loads and gives maximum strength. Therefore, in this study, the spirals are replaced by discrete hoops as lateral reinforcement to analyse the effect on structural behaviour of HCC reinforced with rectangle shaped HCRS under axial load using ANSYS software. The results show that column laterally reinforced with spiral attained insignificant increase in strength than their counterpart specimens confined with hoops. So, the circular hoops were found to be as efficient in confining concrete as spirals in a column reinforced internally with rectangle shaped HCRS. The increase in volumetric ratio can be achieved by reducing the spacing between lateral reinforcement. So, this study also investigates the effectiveness of reducing the spiral spacing in HCC reinforced with HCRS, three models with lateral spacing of 50mm, 40mm and 30mm are modelled and analysed. The results show that columns with closer spiral spacing attained more axial stability. Keywords: Hollow Concrete Column, Rectangular Hollow Composite Reinforced Sections, GFRP Spirals, GFRP Hoops, Nonlinear Static Analysis, ANSYS.

Analysis of Concrete Column Reinforced Internally with Hollow Composite Sections

Abstract: Hollow Concrete Columns (HCCs) are one of the preferred construction systems in civil infrastructures including bridge piers, ground piles, and utility poles to minimize the overall weight and costs. HCCs are also considered a solution to increase the strength to mass ratio of structures. However, HCCs are subjected to brittle failure behaviour by concrete crushing means that the displacement capacity and the strength after steel yielding in HCCs are decreasing due to the unconfined concrete core. Absence of the concrete core changes the inner stress formation in HCCs from triaxial to biaxial causes lower strength. A new type of Hollow Composite Reinforcing System (HCRS) has recently been designed and developed to create voids in structural members. This reinforcing system has four external flanges to facilitate mechanical bonding and interaction with concrete. Therefore, providing the inner Hollow Composite Reinforced Sections (HCRS) can significantly increase strength by providing a higher reinforcement ratio and confining the inner concrete core triaxially. The corrosion of steel is also a notable factor in the case of steel reinforced HCCs which became more critical because their outer and inner surfaces exposing more concrete surface area. An alternative reinforcement is Glass Fibre Reinforced Polymer (GFRP) bars, can overcome the brittle behaviour of steel reinforced HCC. In previous studies, HCC shows high strength capacity, when appropriate reinforcement in the form of longitudinal GFRP bars, laterally using GFRP spirals and internally using newly developed HCRS which provide enough inner confinement. Therefore, this study aims to determine the effect of HCRS of different cross sections and also the effect of change in position of its flanges on the axial performance of HCC analytically using ANSYS software. Keywords: Hollow Concrete Column, Hollow Composite Reinforced Sections, GFRP bars, GFRP Spirals, Nonlinear Static Analysis, ANSYS.

Bending and Shear Behaviour of Waste Rubber Concrete-Filled FRP Tubes with External Flanges

An innovative beam concept made from hollow FRP tube with external flanges and filled with crumbed rubber concrete was investigated with respect to bending and shear. The performance of the rubberised-concrete-filled specimens was then compared with hollow and normal-concrete-filled tubes. A comparison between flanged and non-flanged hollow and concrete-filled tubes was also implemented. Moreover, finite element simulation was conducted to predict the fundamental behaviour of the beams. The results showed that concrete filling slightly improves bending performance but significantly enhances the shear properties of the beam. Adding 25% of crumb rubber in concrete marginally affects the bending and shear performance of the beam when compared with normal-concrete-filled tubes. Moreover, the stiffness-to-FRP weight ratio of a hollow externally flanged round tube is equivalent to that of a concrete-filled non-flanged round tube. The consideration of the pair-based contact surface between an FRP tube and infill concrete in linear finite element modelling predicted the failure loads within a 15% margin of difference.

DEVELOPMENT OF TECHNOLOGICAL PROCESS OF FORMATION OF WIDE FLANGES ON SHEET PROCUREMENTS BY ROLLING STAMPING METHOD

The article presents the results of development and research of the technological process of forming wide outer flanges of lids of malt and distillation columns on sheet blanks by rolling stamping. For this purpose, equipment has been developed in the form of a rolling device for a lathe and an autonomous rolling unit, which allow to form the outer flanges with a conical roll. The rolling unit to the lathe provides the presence of coil springs for pressing the roll to the workpiece with the mandrel. Both settings provide the ability to change the angle of the axis of the rolling unit relative to the axis of the mandrel with the workpiece. Studies have shown that the technological capabilities of the process are limited by the corrugation of the flange wall. The power calculation of flanging of external flanges by a conical roll by the SHO method is carried out and formulas for determination of deformation forces are received. The acceptable accuracy of these formulas has been experimentally confirmed, and there is a tendency to increase the error with increasing geometric dimensions of the workpiece. To assess and expand the technological capabilities of the process, an analysis of the formation and deformed state of the workpieces. Since the main danger in the formation of external flanges by the SHO method is the loss of stability in the form of corrugations, the paper obtained an expression for determining the maximum width of the flange under the condition of a stable process. If it is necessary to obtain more developed flanges, it is proposed in the second stage to provide thinning of their wall by drawing with the use, if necessary, heating the workpiece by induction method.

DEVELOPMENT OF THE COMBINED TECHNOLOGICAL PROCESS OF BLANK STACKS FLANGES FORMATION BY THE METHOD OF STAMPING BY ROLLING AND ROTARY DRAWING

The article presents the results of the development and research of the combined technological process of forming the outer and inner flanges of the lids of fractional and distillation columns on sheet blanks by the method of stamping by rolling and rotary drawing. For this purpose, equipment has been developed that allows to form both outer and inner flanges of the blank in one run of the conical roll. Studies have shown that technological capabilities of the process are limited by the risk of destruction of the top layers of the outer flange bending center and its corrugation, as well as by the neck formation or destruction of the peripheral areas of the inner flange. To assess the deformability of the outer flange, the stress-strain state of its bending center was investigated. According to the set stress values, the stress state of the material is determined, the maximum value of which on the surface of the bending zone is Formula for determining the minimum radius of the mandrel, which when using the values of the critical ductility of the material allows to prevent destruction. As well, an expression for determining the maximum width of the flange, provided that the destruction of peripheral areas is prevented, is obtained. As corrugations formation is the main danger in forming the external flanges by the stamping by rolling method (SR), the expression for determining the maximum width of the flange under the condition of a stable process is obtained. If it is necessary to get more developed flanges, it is proposed to provide thinning of their walls by rotary extraction at the second stage. When forming the inner flanges of the blank stacks radial compressive stresses and tangential tensile stresses in the material are brought about. The action of tangential stresses causes loss of stability of the flange by way of neck formation. The value of the critical strains increases with the approach to the state of plain-strain deformation. Therefore, it is recommended to develop process parameters based on construction of the critical strains diagrams.

Numerical analysis of a two-stage forming process for a hollow part with external flange

This paper presents the results of a numerical analysis of a two-stage forging process for producing a hollow part with an external flange. The numerical analysis was performed via the finite element method using Deform-2D/3D. The analysed case included a cold forming process. The billet was a tube made of a low alloy steel grade 42CrMo4 with its flow curve described by a constitutive equation. The forming process involved the use of two operations: extrusion and forging in a tapered die cavity. The objective of the study was to determine whether the proposed forming technique could be used for production of hollow flanged parts. The kinematics of material flow, distributions of effective strains and the Cockcroft–Latham ductile fracture criterion, as well as force parameters were examined. The conducted research confirmed the correctness of the proposed method.

The influence of the torsional restraint of crane column brackets on their critical load capacity

The paper presents the results of numerical parametric studies conducted on laterally restrained steel I-columns with a single stepped asymmetric change in their cross-section. Such elements are used as a part of the outermost columns in the transversal system of steel halls with cranes. The columns are usually braced along their length with wall girts, which in a properly structured hall system have a significant effect on the columns’ load bearing capacity and determine their axis of rotation. The main aim of the presented studies is to determine the impact of parameters, such as longitudinal load distribution on the upper and lower segment of the column, the number of pointed lateral bracings and their distance to a column's external flange, and also the application of torsional restraint on the critical load capacity. Results are presented as surfaces or contour maps, in which the ordinates represent the critical loads with regards to the analysed parameters. The paper ends with practical conclusions.

Numerical and Experimental Study of Producing Two-Step Flanges by Extrusion with a Movable Sleeve

Abstract The paper presents a new metal forming process for producing two-step external flanges on hollow parts. With this method, the flange is extruded by a movable sleeve, which moves in the opposite direction to the punch. This reduces the phenomenon of buckling of the tube wall, which allows extruding flanges with relatively large volumes. The new method was applied to produce a two-step flange on the end of a tubular billet made of 6060 aluminum alloy. This cold metal forming process was designed based on numerical simulations and experimental tests. The effect of the basic technological parameters on metal flow was investigated and limitations of the process were identified. The experimental results confirmed the possibility of forming a two-step flange with a diameter that is approximately twice as big as the external diameter of the tubular billet.

The Relative Performance of External Casing Impingement Cooling Arrangements for Thermal Control of Blade Tip Clearance

As a key way of improving jet engine performance, a thermal tip clearance control system provides a robust means of manipulating the closure between the casing and the rotating blade tips, reducing undesirable tip leakage flows. This may be achieved using an impingement cooling scheme on the external casing. Such systems can be optimized to increase the contraction capability for a given casing cooling flow. Typically, this is achieved by changing the cooled area and local casing features, such as the external flanges or the external cooling geometry. This paper reports the effectiveness of a range of impingement cooling arrangements in typical engine casing closure system. The effects of jet-to-jet pitch, number of jets, and inline and staggered alignment of jets on an engine representative casing geometry are assessed through comparison of the convective heat transfer coefficient distributions as well as the thermal closure at the point of the casing liner attachment. The investigation is primarily numerical, however, a baseline case has been validated experimentally in tests using a transient liquid crystal technique. Steady numerical simulations using the realizable k–ε, k–ω SST, and EARSM turbulence models were conducted to understand the variation in the predicted local heat transfer coefficient distribution. A constant mass flow rate was used as a constraint at each engine condition, approximately corresponding to a constant feed pressure when the manifold exit area is constant. Sets of local heat transfer coefficient data generated using a consistent modeling approach were then used to create reduced order distributions of the local cooling. These were used in a thermomechanical model to predict the casing closure at engine representative operating conditions.

A Simulator for System-Level Analysis of Heat Transfer and Phase-Change in Thermal Batteries: II. Multiple-Cell Simulations

We present the application of our thermal battery system-level simulator [J. Electrochem Soc., 156, A442 (2009)] in novel multiple-cell thermal analyses. Several model batteries are chosen to demonstrate the simulator's versatility and robustness in developing advanced thermal battery designs. The heat transfer phase-change model and supporting mass balance are modified to improve model consistency. Simulation results are presented from several case-studies covering different battery structures and operating conditions, including low and high current densities, different number of electro-active cells, various internal and external battery geometrical details, the use of salt buffers, external flanges, and inhomogeneous initial conditions in the battery stack. These results show the simulator to be a highly user-friendly and powerful tool for development of complex thermal batteries. Investigation of heat of reactions and joule heating effects unfold insights regarding dominant processes in multiple-cell batteries. Furthermore, these detailed analyses emphasize the need to track solidification dynamics at the sub-cell level and, at the same time, show that thermal battery design should include a significant ingredient of multiple-cell analysis. Altogether, this study presents a first-in-its-kind portable simulator with great flexibility and a capability for supporting the analysis and development of most thermal battery structures and designs.

An Experimental Investigation of Parameters Influencing Dimensional Accuracy in Rotary Stretch Bending

The rapid application of alternative materials is vital to the environmental and sustainable development of the European manufacturing industry. In many cases, companies seek using ‘old’ materials, such as aluminum alloys, magnesium, titanium, composites and plastics, for new applications in order to improve customer value; i.e., the perceived product benefits subtracted its price. For a subset of manufacturing companies, one of the most viable strategies is to offer weight savings at an affordable price by replacing steel with aluminum alloys, typically providing added value in the 0.25 - 0.5 kg/€ range, depending on application. Hence, weight savings shave to come with minimum cost penalty, which calls for a balanced optimization of manufacturing process and material consumption. For formed products, the latter optimization is driven by the performance characteristics of the final product as well as its quality capabilities relating to dimensional accuracy. The former is closely related to the attributes of the particular forming method. In this study, an industry-like rotary stretch bending set-up has been equipped with two different modular die inserts to determine how process characteristics impact dimensional accuracy of the product, as represented by local cross-sectional distortions and global elastic springback in industrial practice. A number of cross-sectional profile geometries with different wall thickness, depth, width and number of internal chambers have been simultaneously stretched and bent into the shapes provided by two die different configurations. The extruded profiles were made in different heat treatable alloys within the AA6xxx and AA7xxx series and formed according to industrial practices, which for the latter included solution heat-treatment immediately before forming. The results show that the slenderness of the external flange of the cross section is the main parameter with regard to the magnitude of local cross-sectional distortions. In practice, therefore, wall-thickness is the critical quality control parameter. The material’s yield characteristic proved to have limited impact on local distortions, although this is usually a major concern with regard to springback variations. The results from the experimental series have been structured into a design relationship for assessment of local distortions where the problem is reduced to the use of a proposed dimensionless bendability parameter as input.

Research on Bonding Strength of Steel and Concrete with Different Bonding Interfaces

For the purpose of researching the natural bonding behavior of different interfaces between steel and concrete in SRC structures, four specimens are designed to launch the monotonic push-out loading test. Each specimen is used to consider one case, including the bonding of the external flange, internal flange, web and whole cross-sections with the concrete. Failure process and modes of these specimens were observed during the test. Load-slip curves and ultimate bond strength are obtained and the bonding strength between different interfaces of steel and concrete was analyzed. The results show that the bonding strengths of different interfaces in SRC members are not equal. The minimum bonding strength occurs in web, the bonding strength of external flange is higher, and the maximum bonding strength occurs in internal flange, the ratio of the strength is 1:1.39:1.59.

A Model Dipole for FAIR SIS300: 3D Design of the Mechanical Structure

The FAIR facility, under development at GSI, includes the synchrotron SIS300 (300 Tm rigidity). In order to reach the required high intensities of proton and heavy ion beams, the bending dipole magnets have to be pulsed from the injection magnetic field of 1.5 T up to 4.5 T maximum field at the rate of 1 T/s. These 7.8 m long magnets have cos-theta shaped coils with a 100 mm bore with the particular characteristic to be geometrically curved (the sagitta is 114 mm). The 2D mechanical cross section has been designed in detail: it consists of 3 mm thick laminated stainless steel collars, assembled through keys, and 1 mm thick iron yoke laminations, assembled through large stainless steel C-shaped clamps. This paper analyses some aspects that are intrinsically 3-dimensional: the mechanical behavior of the ends, the effect of the longitudinal pre-stress, the design of the external flange and outer shell.

Stress concentration factor and minimum hub length predictions for hollow tubes with internal and external flanges subjected to axial loading

This paper presents equations for estimating the elastic stress concentration factor Kt and minimum hub length δ in hollow tubes with internal and external flanges subjected to symmetrical axial pressure over the flat section of the flanges. Results from an extensive finite element study are supported by a limited number of experimental tests. The experimental Kt values are compared with data obtained numerically by the present authors and very good agreement was found between the two methods. Minimum hub lengths, which are an important parameter for fabrication, have been derived on the basis of Saint Venant's principle. It is seen that Kt and δ follow similar trends, being functions of several geometric parameters. Kt and δ values for the internal and external flange-tube intersections contained in this paper cover the most common practical range of geometries. The effect of tube wall radial pre-load (which can result from the compressive radial interface pressure established in the shrink-fitting process, compressive radial residual stress due to the autofrettage process or any other reinforcing process) on Kt and δ has also been studied. Furthermore, the effect of eccentric loading has been studied, using an experimental approach with one geometry. The extensive range of Kt and δ values obtained from the analyses is used to obtain useful prediction equations, using a statistical multiple non-linear regression model and a high level of accuracy is demonstrated. Finally, a direct relationship between elastic stress concentration factor, which is readily available, and minimum hub length, which usually requires a complex numerical analysis, is provided.

Fossil natural glasses composed of ferric oxyhydroxides: impactites of the 35.5 million year old Chesapeake Bay crater

Many of the pebbles and cobbles found in the ∼5000-km 2 ‘upland deposits’ of eastern Virginia and Southern Maryland (USA) are decorated with external flanges of hard red–brown material with uniform thicknesses ∼5 mm terminated by crisp conchoidal fracture surfaces. Thirteen high-grade sandstone (quartzite) pebbles and cobbles exhibiting such features were cut with rock saws, revealing that the external flanges are contiguous with undulating red–brown bands of about the same thicknesses extending all the way through their interiors and, in several cases, that these interior bands are approximately parallel to spalled surfaces and/or internal fractures. These rocks have been studied by thin-section photomicroscopy, scanning electron microscopy, extended X-ray absorption fine structure (EXAFS), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron-spin-resonance imaging, and Mössbauer spectrometry. The EXAFS, XRF, XRD, and Mössbauer data combine to demonstrate that the hard red–brown materials contain goethite (α-FeOOH) in particle sizes ∼100–150 Å with impurity contents ⩽5%. It is not ruled out that these materials may also include an amorphous-ferric-oxyhydroxide component with short-range order constrained by the EXAFS to be similar to that in goethite. The origin of the upland deposits has long posed a riddle to geologists. And the geometry of the red–brown bands internal to the present rocks (not explainable by aqueous diffusion) now confronts materials scientists with a puzzle. We propose that the solutions to both the riddle and the puzzle may be linked to the effects of the known impact of an extraterrestrial object 35.5 million years ago into the area that is now the Chesapeake Bay (CB) on the US Atlantic Coastal Plain. We strengthen this proposition with (1) critical reconsideration of the previously accepted geological explanation of the upland deposits, (2) an assessment of the probable natures of the materials present in the CB-crater target area that would have become ejecta, (3) a review of the pertinent physics of impact cratering, (4) the detailed studies of the rocks mentioned above, and (5) a preliminary study of a sample of goethite subjected to experimental shocking. Based on these considerations, the hard red–brown materials of the upland deposits are proposed to have been quenched from molten sheets of Fe-oxyhydroxides generated by impact-induced shock waves passing through water rich in suspended ferric-oxyhydroxide particles. A model for the physics of this process is presented. It is reasonably assumed that iron-rich ground waters were present in aquifers extending into the ∼500-m-deep accumulation of quartz-based sediments known to have been in the target area of the CB impactor. Penetration of the molten Fe-oxyhydroxide sheets into the quartzite cobbles is ascribed to opening of interstitial spaces between the constituent sand grains by action of reverberating pressure and rarefaction components of the same shock waves that boosted these rocks to their present-day upland locations.

External flange loads and ‘Koves’-method

Practical implementation of a much more realistic approach for treating external moments for various major flange assessment methods is proposed. First, the question of how to deal with torsion in flange rings weakened by bolt holes is addressed. This aspect was not covered by the original paper of Mr Koves on which our work is based. That our practical implementations result in quite accurate results is shown by an FEM-analysis of a loose flange ring. Correctly dealing with external moments, usually the major part of external loads on flanges, is important because as soon as design pressures are known, flange ratings are selected and initial designs for ‘custom’ flanges are made. Only in the later stages of a project do all loads on flanges become available and then these external flange loads have to be approved. Usually, the margins between internal pressures and maximum allowable pressures are not large and hence one can ill-afford the wasteful ways that flange assessment methods presently treat external loads.

A design for flexible intestinal cannulas.

A design for a cannula made by fixing silicone rubber tubing to rigid internal and external flanges is described. These cannulas have been used to fit simple duodenal, simple ileal and abomasal fistulas in adult lactating cattle for periods up to 1 year and have caused minimal tissue reaction at the site of fistulation.