Flange Material Research Articles

Plain and threaded bearing strengths for the design of bolted connections with pultruded FRP material

Presented are results from testing 28 batches of 5 or 10 nominally identical specimens to characterise the laterally unrestrained pin-bearing strength when bolting is with and without thread. For the test series flange material is taken from a 254x254x9.53 mm Pultex® SuperStructural 1525 series shape. Strengths are measured with the Fibre Reinforced Polymer (FRP) material oriented at either 0° or 90° to the direction of pultrusion. Four steel bolt sizes of M10, M12, M16 and M20 are used, and when threaded there are different standard teeth (pitch) geometries. To remove this variable in a comparison with plain pin strengths a unique test series of 12 batches was carried out with three non-standard thread profiles. The effect on pin-bearing strength of having a threaded bolt is evaluated using mean and characteristic strengths, the latter determined in accordance with EN 1990. A key finding is that the proposed reduction factor of 0.6 in a forthcoming American LRFD standard to calculate a thread characteristic strength from the plain value is acceptable. Other findings are important to the determination of pin-bearing strength, and to us having knowledge and understanding to prepare a universal design procedure for resistances in bolted connections when the mode of failure is bearing.

Failure investigation of 321 stainless steel pipe to flange weld joint

Abstract Failure investigation was conducted on a refinery pipe-to-flange weld joint that suffered cracking. Both the pipe and flange are made of AISI 321 stainless steel. The flange was circumferentially welded to the pipe which is seam welded. The investigation revealed that both the circumferential and seam welds were in sound conditions, namely no evidences of sensitization, lack of weld penetration, and voids or porosities. Thus, welding practices were not suspected to be the cause of failure. The failure of the weld joint was found to have started at the δ-ferrite phase in the flange material and propagated through the circumferential and seam welds. The failure mode was concluded to be chloride stress corrosion cracking synergized by the presence of H 2 S. The presence of corrosive compounds in the refinery stream and the residual stresses at the weld joint triggered active anodic dissolution of the δ-ferrite precipitates, resulting in cracking of the material.

Feasibility of electromagnetic pulse-assisted incremental drawing with a radial magnetic force for AA-5052 aluminum alloy sheet

In the conventional drawing process, the predominant failure modes of a sheet metal are wrinkling and fracture. Wrinkling during the forming process can often be treated as a recoverable defect as it can be eliminated though the appropriate control of the blank holding force. Fracture, however, is a fatal flaw. When the fracture occurs, the drawing process cannot continue. We propose a new forming method that can handle large height/diameter ratios. The new method uses electromagnetic pulse-assisted incremental drawing (EMPAID) together with radial magnetic force and a suitable auxiliary coil structure and size. Both the calculated and experimental results indicate that the magnetic force generated by the auxiliary coils can increase the flange material flow and significantly improve the ability of the sheet metal to resist fracture. When only the auxiliary coil is used in the experiment, the drawing depth increases by 21.8 % (with respect to conventional drawing) if the auxiliary coils discharge once. The drawing depth can be increased by as much as 36.7 % when multiple discharges are applied. When the auxiliary coil is used in combination with other electromagnetic forming coils in the experiment, the maximum drawing height of the cylinder cup increases by 141.6 %, after multiple discharges.

Ultimate strength of singly symmetrical I-section steel beams with variable flange ratio

Long steel beams in entrances of hotel lobbies and halls often support a masonry wall and are laterally unsupported. These beams do not reach their in-plane flexural capacity due to the occurrence of elastic or inelastic lateral–torsional buckling (LTB). Designers usually select doubly-symmetrical sections for these beams. In this paper the ratio of the compression flange size to the tension flange size is increasingly varied to obtain a higher resistance to lateral buckling of the compression flange. However, increasing the size of the compression flange and decreasing the size of the tension flange leads to the limiting case of a T-section which is weak in in-plane bending. Code provisions usually refer to generalized cases and special cases are always embedded in these and are not directly addressed. One of these special cases is the singly symmetric I-section. Special direct solutions for such problems are becoming more popular based on accurate inelastic ultimate load analysis. This paper develops a three dimensional finite element model, using ANSYS for the elastic and inelastic flexural–torsional buckling of I-beams, which is used to investigate the effect of varying the ratio of the flange sizes on the optimum performance of the beam. Slender webs are proposed and a study is made on the material of this web and the performance of its local and global buckling and its correlation to the total ultimate load of the beam system. The flange material consumption is kept constant and only the shares to the tension and compression flanges are varied to achieve the most economical system for design. The main goal of this research is to present a direct solution system that is simplified for the use of inexperienced designers, which provides the most economic system selection for design.

Metallurgical Analysis on a Cracked Super Duplex Stainless Steel Flange

A flange-to-pipe weldment in a seawater-intake-return-line suffered from cracking on its flange portion after in service for 4 months. The flange was fabricated from S32750 super duplex stainless steel. The cracked flange was investigated by visual inspection and fractographic examination on the crack surface, metallographic examination, hardness measurement, and chemical composition analysis of the flange-to-pipe weldment. The results of laboratory analysis showed that the flange had cracked in a brittle manner resulting from the presence of large amount of sigma phase in the flange material. Formation of such brittle second phase precipitates in the flange material was due to improper heat treatment.

In situ analysis of impurities deposited on the tokamak flange using laser induced breakdown spectroscopy

The impurity materials deposited on the plasma exposed surface of the flange in Aditya tokamak have been identified using laser induced breakdown spectroscopy. The spectral lines of Fe, Cr, Ni, Mn, Mo, Cu and C are detected in the coated layer of the flange. Intensity variation of spectral lines with successive number of laser shots has been studied. The concentrations of elements present in successive laser shot (1st to 12th) have been determined using CF-LIBS technique. Although, the intensity of the spectral lines in 1st and 12th laser shots are entirely different but relative concentration of constituents are similar. This anomalous behavior may be due to different nature of the matrices of 1st (coated layer) and 12th laser shot (flange material). Present study clearly demonstrates the capability of CF-LIBS to study the two different natures of the samples but having similar relative concentration of the constituents.

A non-linear stiffness composite twisting I-beam

A classic structural component of mechanical engineering, the I-beam, is re-designed by adding a morphing twist functionality to the high bending stiffness inherent to the geometry of the component. The beam, as with its conventional counterpart, is made of two flanges separated by a web. Here, bi-stability is introduced from a combination of flange pre-stress, web geometry and material properties, yielding a highly non-linear twist morphing structure while keeping the low weight and the high bending stiffness of the beam. The present case study offers two twisted stable shapes and can be morphed from one stable configuration to the other by applying a snap-through twist moment to the ends of the structure. Correlation is found between tests results, finite element model data and analytical predictions, validating the modelling assumptions. A sensitivity study is also performed to understand the influence of the design parameters of the beam and loading condition on the stability of the structure. As a result, the three conflicting requirements of adaptive structures are met in a single structural entity: low mass, load-carrying capability and compliance.

Fatigue Analysis of MW Wind Turbine Top Flange

On the basis of the finite element analysis model of the wind turbine flange, this paper studies the fatigue damage of the MW wind turbine flange, analyzing the fatigue stress of the wind turbine flange with MSC.Marc/Mentat software, realizing load simulation of flange fatigue case with Bladed software, and calculating the fatigue loading spectrum of the flange with the method of rain flow circulation count. The fatigue damage calculation method which combines the rain flow circulation count method with Palmgren-Miner linear cumulative damage law, is proposed to modify the S-N curve of the flange material according to GL standard. The result shows the method feasible and reliable which provides one more accurate analysis idea for the fatigue life of the wind turbine generator system top flange.

해상풍력발전용 타워플랜지 소재의 잉고트 파쇄공정설계

The ingot-breakdown scheme of a tower flange material (low-alloy steel) for offshore wind turbine was investigated using finite element (FE) simulations and experimental analyses. Based on compression test results of the low-alloy steel, a deformation processing map was generated using the superposition approach between the dynamic materials model (DMM) and Ziegler's instability criterion. The deformation processing map allowed determination of the optimum process conditions for the tower flange material. Within the FE simulations of the ingot breakdown process, the Cockcroft-Latham criterion, which considers ductile fracture, was used to predict the possibility of forming defects during the hot working process. In general, the critical value for the ductile fracture of steel is 0.74. During the ingot-breakdown under optimum process conditions, the actual tower flange forgings exhibited a relatively uniform shape without any forming defects.

Structural collapse of a wind turbine blade. Part B: Progressive interlaminar failure models

The objective of this paper is to present a geometrical nonlinear and interlaminar progressive failure finite element analysis of a generic wind turbine blade undergoing a static flap-wise load and comparisons with experimental findings. It is found that the predictive numerical models show excellent correlation with the experimental findings and observations in the pre-instability response. Consequently, the ultimate strength of the wind turbine blade studied is governed by a delamination and buckling coupled phenomenon, which results in a chain of events and sudden structural collapse with compressive fibre failure in the delaminated flange material. Finally, a parametric study of the critical load factors with respect to various delamination sizes and positions inside the compressive flange of the wind turbine blade is presented.

ねじり強度を重視した<br>焼入れ軸とフランジの塑性流動結合

Joining two or more parts by forming is an economical method of manufacturing complex-shaped products. In this study, we discuss a form-joining process to provide high torsional strength for shaft products. Experiments to join a shaft of quenched steel and a thick flange of mild steel were carried out. Joining was achieved by forming a hole in the flange with a serrated shaft. The formed serrations had fill-up ratios of 50∼70 % and were 1.4∼1.8 times harder than the machined serrations due to work hardening. The distribution of hardnesses agreed well with those of the fill-up ratios. As a result of torsion tests, the maximum torque increased in proportion to joining length. Torsional strength was estimated using the shear strength of the flange material. Furthermore, the joint was compared with a mechanically fitted joint having the same shape and joining area, which proved that the joint created by forming had higher torsional strength than that created by fitting.

Creep analysis of bolted flange joints

In the petrochemical and nuclear industries, the difficulty in assessing the effect of creep on the tightening load of bolted flanged connections is recognized. Under high temperatures, the leak tightness of bolted joints is compromised due to the loss of the bolt load as a result of creep of not only the gasket and bolt materials but also the flange material. Apart from acknowledgment of this effect, there exists no established design calculation procedure that accounts for creep. This is because the relaxation of the bolt load and the corresponding loss of the gasket contact stress are not easy to assess analytically. The main objective of the work is the development of a simple analytical solution to the creep-relaxation problem encountered in bolted flange connections of the float type. Particular emphasis is put towards relaxation caused by the flange and bolt material creep. The validation of the methodology is carefully checked against the more complex 3D numerical FE method using different size flanges. Based on the creep constants of the different joint elements (bolt, flange and gasket), the implemented analytical method is shown to predict the bolt and gasket load relaxation with reasonable accuracy. In some flange cases, up to 70% of bolt load relaxation is found with both methods depending on the flange creep material and size.

Buckling and debond growth of partial debonds in adhesively bonded composite splice joints

The strains at which buckling and debond growth occur in adhesively bonded composite flanges containing an initial debond were experimentally measured. Test parameters including initial debond geometry, flange material stiffness, and the adhesive critical strain energy release rate (Gc) were investigated. Debond growth was found to be strongly dependent on initial debond length but weakly dependent on flange width; i.e., debonding resistance did not increase in direct proportion with the bonded overlap dimension. Flanges having higher bending stiffness exhibited significantly lower debonding strain. Finally, the effect of Gc was evaluated at three levels by controlling the adhesive cure temperature and bondline thickness. Lower values of Gc (207 and 552 J/m2) allowed debond growth to occur while at the highest value of Gc (1500 J/m2), alternate failure modes occurred prior to debond growth. Ultrasonic C-scans revealed that debond growth occurred along a curved front, as dictated by the post-buckling deformation of the flanges.

Lateral Stability of Composite Wood I-Joists Under Concentrated-Load Bending

Three different theoretical beam elastic lateral stability models were combined with the current Load and Resistance Factor Design (LRFD) lateral stability model used for wood I-joist design to identify more accurate predictions of composite wood I-joist buckling behavior. These models were based on Euler, equivalent moment factor (EMF), and Nethercot models. Modifications to account for cross-sectional geometry, load location relative to the cross-section centroid, and lateral bracing were analyzed where applicable within each of the three theoretical models. Material properties of the entire composite wood I-joist cross-section for specimens tested in this research were measured and utilized in the studied lateral stability models. The primary study composite wood I-joists were analyzed in both a cantilevered and simply supported configuration utilizing setups selected to mimic theoretical cases. The results from this analysis were compared to determine the adequacy of the current design effective length equations. The cantilevered composite wood I-joists were tested over nearly the entire range of beam slenderness ratios used in design (RB from 0 to 50). The critical buckling moments (Mcr) recorded from the cantilevered buckling tests were predicted using three lateral stability models. The lateral stability models that provided prediction curves fitting within the 95% confidence interval of the observed cantilevered buckling data were recommended for the lateral stability design of similar composite wood I-joists. Two additional composite wood I-joist types of geometry and flange material different from the primary study I-joists were tested to provide preliminary insight into the robustness of the recommended model for composite wood I-joists. Cantilevered and simply supported beam test configurations yielded similar Mcr values for composite wood I-joists of the same type and geometry having equal RB values. Lateral stability models that included the dimensional, bending stiffness, and torsional rigidity properties of the entire composite wood I-joist cross-section yielded far superior Mcr predictions than the current LRFD design model. However, the current design approach in the LRFD manual can be made to satisfactorily predict Mcr values of composite wood I-joists provided: (1) the I-joist ultimate moment is used; (2) the elastic buckling moment is calculated using either the Euler elastic buckling (EEB) theory or the EMF theory; and (3) the dimensions, flatwise bending stiffness, and torsional rigidity of the entire composite wood I-joist cross-section are used in the calculation of Mcr. When utilized with the current LRFD design approach, the EMF theory appeared to be more adaptable than the EEB theory for predicting the critical buckling moment of composite wood I-joists of varying types and geometries.

Thermally Induced Deflections in Bolted Flanged Connections

Pressure vessel joints operating at high temperature are often very difficult to seal. The existing flange design methods do not address thermal effects other than the variation of flange material mechanical properties with temperature. It is possible to include the effects of temperature loading in joint analysis, however, presently very few guidelines exist for this type of analysis. This paper outlines the theoretical analysis used for the determination of the steady state operating temperature and deflections in bolted flange joints. It details the theoretical equations necessary to predict the temperature profiles and thermal expansion difference between the joint components necessary for the evaluation of the load redistribution for the two cases of a flange pair and a flange with a cover plate. The results from the theoretical models are verified by comparison to finite element results.

1102 スポット溶接されたフランジ材の減衰比評価法に関する研究(GS-10 ダイナミクス計測)

The purpose of this research is to construct the construction machine cab where the dynamic analysis, especially the frequency response can be executed in the conceptual design stage. In this thesis, it proposed the technique for evaluating all factors of the damping of the spot-welded flange material as a linear viscous damping ratio, before the frequency response of the cab model was done. First of all, the impulse excitation experiment was done. Because it was thought that the damping of the vibration had been chiefly generated in the flange section by the friction of the spot welded point. From the experimental result, the damping ratio valuation plan of the flange material was proposed.

Determination of critical load for flange buckling in concentrically loaded pultruded columns

Physical testing and theoretical methods to determine the critical local flange buckling load in concentric pultruded columns are presented. Knowledge of this critical load for wide flange profiles is required in a new universal column design procedure. Because there are too few test results for other profile sizes only the standard 203×203×9.53 mm (8×8×3/8 in.) profile is considered. Reasons are given to explain why the 14 data points give buckling loads between 307 and 406 kN. To obtain a test result corresponding to the true physical situation the minimum column length should be four half-wavelengths of the local instability. The true critical load is about 360 kN. Presented are nine closed form equations that can be used to predict the critical load for the local instability. To use these equations effectively, it is shown that the elastic constants of the flange material must be those of the profile being analysed. Numerical methods, and their closed form equations, that include the rotational stiffness at the web–flange connection are shown to be reasonably accurate. However, without direct access to the software they are difficult to apply, and these equations are therefore unsuitable for application in the preparation of universal design guidance. A simpler equation that predicts the buckling load to within 4% of 360 kN is therefore recommended.

Effect of Carbide Morphology on the Susceptibility to Type IV Cracking of a 1.25Cr-0.5Mo Steel

Type IV cracking is considered to be the likely failure mode of ferritic steel welds when operated for long duration. The carbide morphology of the service-exposed 1.25Cr-0.5Mo steel weldment, which is composed of a forged flange and pipe fabricated from plates, has been examined before and after a creep test. Higher susceptibility to Type IV cracking was observed at the Intercritical HAZ (ICZ) on the flange side despite higher creep resistance of the parent material compared with a pipe. The change in carbide morphology during the creep exposure was the most pronounced at the flange ICZ. The coarse bainitic carbide originally existing depleted the intragranular carbides and significant variation in carbide density inside the ICZ was generated. In contrast, carbides at the pipe ICZ were more uniformly distributed. It was interpreted that higher susceptibility of the flange ICZ was accelerated by the heterogeneous distribution of carbide density and the resultant variation of creep strength and would enhance grain boundary sliding associated with creep strain accumulation. It was proved that the susceptibility to Type IV cracking was highly dependent upon the characteristics of a parent material by experiments using simulated ICZ specimens. Significant difference in the effect of heat treatment to simulate the microstructure at the ICZ upon the creep strength was observed between a flange and pipe. The simulated ICZ specimen generated by a pipe parent showed no apparent change due to the heat treatment compared with a parent material. On the contrary, it reduced the time to rupture and changed the fracture mode from transgranular to intergranular for a flange material. The feature of grain boundary cracking was similar to that of actual weldment which took place preferentially at the inclined grain boundaries to the tensile direction, that was to be considered the evidence of grain boundary sliding.

Steel Bridges with Double-Composite Action: Innovative Design

Bridge engineers are continually faced with the challenge of providing efficient and cost-effective structures. In particular, the Florida Department of Transportation has recognized the need to develop economical bridge configurations in the medium-span range of 200- to 400-ft (60.96-to 121.92-m) spans and authorized a research project at the University of South Florida to identify and develop innovative design concepts within this span range. The study identified the concept of a steel bridge with double-composite action as an innovative bridge concept with the potential for significant cost savings compared with conventional modes of construction. This bridge type has been used with good success in Europe, but to the authors’ knowledge it has not been used in the United States. In addition to a composite concrete top slab, the double-composite bridge concept utilizes a composite concrete bottom slab in the negative moment regions. The result is provision of a design meeting compact requirements throughout, increased stiffness with corresponding decrease in fatigue stress range and deflections, savings in cross frames, and savings in flange material. The design implications of this system are examined, including redistribution effects due to creep and shrinkage, implications of different construction sequences, and strength and serviceability issues. Trial designs are presented, including both plate and box girder type structures, and design considerations are discussed. A prototype structure is identified for further development of the double-composite concept.

Tee-Beam Manufacturing Analysis: Producibility of Panel Stiffening Elements

This paper analyzes the manufacturing of tee shapes for stiffening ship structure. The traditional method of deflanging hot-rolled I-beams (producing l/T shapes) has been compared to the practice of fabricating tee-shapes from plate. A group of more than 1700 l/T shapes, used in the DDG-51 class vessel, was used for comparisons. To produce the l/T shapes for one DDG, flanges are stripped from more than 700 tonnes (690 long tons) of I-beams. The flange material removed amounts to 25% of the weight of the original I-beams, totaling approximately 172 tonnes (170 tons). This represents a material loss of 25%, easily in excess of $90 000. Prior review of design criteria for several DDG stiffened plate structures showed that fabricated tees could replace l/T shapes, resulting in weight savings averaging 18%, while still maintaining required strength. An evaluation of methods to produce tee sections was undertaken, and the concept of "net shape" fabrication of tee stiffeners was discussed. Both fabricating and stripping methods were considered, including newer technologies such as plasma cutting and laser cutting and welding. Mock-up testing was performed using several candidate technologies and the results compared. Plasma-arc cutting reduced distortion on 12.2 m (40 ft) test beams by 50% compared to oxyfuel methods. Economic analysis revealed that fabricated tees were less costly to produce than deflanged I-beams, and that handling functions were the greatest cost element of the traditional oxyfuel cutting methodology.