Bottom Joint Research Articles

An approach on ultrasonic testing of surface flaws in buttwelded bottom plate joint with covered coating in oil tank

An approach on ultrasonic testing of surface flaws in buttwelded bottom plate joint with covered coating in oil tank

Microstructure and Properties of Joint Interface of Semisolid Stirring Brazing of Composites

Stirring assisted brazing of SiCp/A356 composites in air was investigated. A stirring was applied on one of the samples to be bonded at 455 °C during brazing. The filler metal was extruded and impacted intensively on the two surfaces of the base materials during stirring. It can be found that oxide film on the surface of the composites can be disrupted and removed through the observation by scanning electron microscopy (SEM). The metallurgical bonds formed between the filler metal and the base materials. However, continuous residual oxide film was found at bottom joint interface, which limited the lift of joint strength. A stirring was applied once more after the samples were continuously heated up to 470 and 500 °C, respectively. At this time, residual oxide film after the first of stirring can be broken by once more stirring. The bonds are mainly composed of a new alloy, which have a higher content of aluminum and are free of continuous oxide film, showing higher shear strength of 113 MPa than that of the base materials.

Experimental Research of Bottom Chord Splice Joints with Variable Cross-Section in Steel Roof Truss

A workshop’s roof is designed to use steel tube trusses with the span of 24m. There are three kinds of variable cross-section splice joints of the roof truss bottom chord. Nine splice joint specimens, three for each kind, were tested to obtain their tension capacity and failure modes. A special test setup is designed to introduce the tension load to the splice joint specimen. The paper detailed introduced the test setup and method, discussed the failure load and failure mode of the joints. Experimental research indicated that the bottom chord splice joint with variable cross-section of the roof is safe, reliable, having high bearing capacity. The research also validated the correctness of the design and calculation, and provided the basis for the application of such joints in the engineering practice.

Microstructures and high temperature mechanical properties of electron beam welded Inconel 718 superalloy thick plate

The microstructures and high temperature mechanical properties of whole and slices in Inconel 718 thick plate joint obtained by electron beam welding (EBW) were studied. The results show that, in the joint welded by full and cosmetic penetration, dendrites preserve in the top and bottom of welding center and columnar crystals emerge in the middle. The grain size in heat affected zone (HAZ) becomes smaller and smaller from top to bottom of welding line. The δ-phase precipitate in grain boundary and γ-phase is obtained inside the grain of EBW joint, which was heat-treated with solution and double aging. The most of δ-phases appear in the weld center and the less turn up in HAZ and base material zone (BMZ). The tensile strength σ b, yield strength σ s and elongation δ of the whole joint at 650°C are 1 100 MPa, 800 MPa and 18%, which reach 90%, 80% and 80% of base material's, respectively. The maximum σ b, σ s and δ lie in the bottom of joint and attain 1 170 MPa, 870 MPa and 18%, separately, while the minimum σ b, σ s and δ appear in the top of joint and reach 1 080 MPa, 780 MPa and 7%, respectively. The fracture of top weld is brittle; however, the ones of middle and bottom joint are flexible. The microhardness in HAZ and BMZ is higher than that in weld center. The value of microhardness tends to be lower as more δ-phase.

Parametric Study of Static Strength of Multiplanar KK-Joints：Square Chords and Circular Braces

Pre-stressed spatial tubular truss system is adopted in steel roof truss structures of China International Exhibition Center New Venue. Bottom chord joints are multiplanar KK-joints consisting of chord with square hollow section and brace with circular hollow section. However, not only that relatively little research has been carried out on such joints, but also that no detailed design guidance on KK-type joints consisting of chord with square hollow section and brace with circular hollow section can be found Current design code for steel structure (GB 50017-2003). This paper reports the study into the strength of this type of KK-joints under axial loading. The numerical models were adopted, and several various geometric parameters which affect the strength and failure modes, were investigated. It was indicated that the geometric parameters affects significantly the ultimate capacity and failure modes of the joints. The varied relationship of the strength and failure mode with parameter varying was studied in detail. The results of the work presented provide initial discussion on behavior of this type of KK-joints and lay the foundation for a future large-scale parametric study and put out design formula.

Test of ITER conductors in SULTAN: An update

The ITER Toroidal Field (TF) conductor qualification phase has been carried out by testing short sample prototype conductors in the SULTAN test facility. This phase, started in 2007, has been substantially completed after minor adjustment of the conductor specification and test procedures. All the parties involved in the TF conductor procurement passed the qualification phase. Starting 2010, the samples for TF process qualification phase are tested in SULTAN. A summary of the results for all the ITER Qualification samples and an updated statistics are presented for the V– I and V– T characteristics of the cable-in-conduit conductors (CICC), including Nb 3Sn and NbTi samples assembled with either a “bottom joint” or a “U-bend”. The technical improvements of the test facility are reported, including the enhanced cyclic loading rate and the calibration of the current meter. An outlook of the ITER conductor tests in the coming years is also presented.

Test results and analyses of conductor short samples for China first PF conductor

The first China PF conductor sample (CNPF1) which was made of one single cable section with hairpin configuration and without bottom joint was fabricated with Chinese NbTi strands and assembled at ENEA and CEA according to the requirements of the SULTAN test facility. The sample was equipped with temperature sensors and voltage taps at CEA according to the test program. The test program included DC performance, cyclic loading, AC loss, and MQE test. The sample exhibited a good performance which fit well with the requirement in the procurement arrangement (PA). But most of the current sharing temperature ( T cs ) tests showed a suddenly voltage take-off or fast voltage transition with take-off electric field below the threshold of 10 μV/m. The temperature could be considered as quench temperature ( T q ) but not exactly T cs . At 35 kA and background field of 3.5 T, the temperature T q was 6.94 K. Even after 2000 cycles at the condition of 6.5 T and 19 kA, the T q remained unchanged.

The JT-60SA Toroidal Field Conductor Reference Sample: Manufacturing and Test Results

In the framework of the JT-60SA design activities, EU home team has defined a reference layout for the Toroidal Field conductor: it is a slightly rectangular Cable-In-Conduit NbTi conductor, operating at 25.7 kA with a peak field of 5.65 T. ENEA has assigned LUVATA Fornaci di Barga the task to produce the strands and to perform cabling, whereas jacketing and compaction have been carried out in its own labs. The sample, successfully tested at the CRPP SULTAN facility, has been assembled in such a way as to avoid the bottom joint between the two legs, thus using a single conductor length (about 7 m). An ad-hoc developed solution to restrain the U-bent conductor section (where jacket is not present), consisting in a stainless steel He-leak tight box with an inner structure designed in order to completely block the cable, has been also developed and manufactured by ENEA, where the sample has been also assembled. Instrumentation installation and final assembly of the sample have been performed by the SULTAN team. The main aspects of the sample manufacturing and characterization are here presented and discussed.

Tests and Analyses of Two TF Conductor Prototypes for JT-60SA

In the framework of the JT-60SA project, included inside the Broader Approach agreement, EU is expected to provide to JA the totality of the toroidal field (TF) magnet system. It consists in 18 coils, evenly shared for in-kind procurement between France and Italy while the TF conductor providing is under the responsibility of Fusion for Energy. The conductor is a rectangular-shaped, NbTi-based, cable-in-conduit (CICC) and will be wound in double-pancake inside the TF casing. In the paper, the experimental approach of conductor design validation process and the associated analyses of conductor samples test campaign in the SULTAN facility are shown. A design and manufacture action on full-size SULTAN-type short samples for the TF conductor have been launched in 2007 to allow an early gathering of relevant information enabling to proceed onto the conductor design qualification process. A series of two pre-prototypes was realized, based on a former conductor design which even if slightly different from the most up-to-date layout, includes all its important relevant features: square-shaped section, superconducting strands segregation with copper, no subwrapping. The samples are designed to allow comparative studies on shape influence (two types of sections) and on joint influence (presence or not of a bottom joint), and to provide a consolidated baseline for making decisions on conductor final design. A descriptive part of the samples manufacturing activity is included. The samples TFCS1 and TFJS1 were then characterized in the SULTAN facility (Villigen, CH) respectively in 2008 and 2009, experiencing DC tests, AC tests, mechanical cycling, and stability tests. The corresponding results and the associated analyses are shown and statements regarding the contribution of the present results to the assessment of the actual JT-60SA TF conductor design are also drawn.

STUDY ON COEFFICIENT Bi IN N VALUE CALCULATION METHOD ABOUT COLUMN'S TOP AND BOTTOM JOINTS

According to the moment resistance frame substitution model, the assumed stress state about the N value calculation method to estimate the required tensile force of column's top and bottom joints was explained. The general solution about the tensile force of column's top and bottom joints was derived with the moment resistance frame substitution model and the shear panel substitution model in which the bending stiffness of the beams and the axial stiffness of the joints were considered. It was found by using the general solution with these substitution models that the coefficient “Bi”, which is multiplied by the shear wall magnification factor in N value calculation method, was affected by the bending stiffness of the beams and the shear wall length. As a result, the validity and coverage of the coefficient “Bi” became clear. In addition, the approximated values of “Bi” corresponding to each shear wall length were shown in Table 3 for the practical structural calculation as the result of this theoretical study. The tensile force of column's top and bottom joints in various conditions can be obtained accurately by the calculation method of this theoretical study.

JackPot: A novel model to study the influence of current non-uniformity and cabling patterns in cable-in-conduit conductors

JackPot is a new model that is used to analyse how and to what extend current non-uniformity among strands in a cable-in-conduit conductor (CICC) affects its performance. The joints at the extremities of the CICCs in coils and short samples introduce a non-uniform current distribution among the strands. A detailed and quantitative study down to strand level is required to explain the involved phenomena, to understand their implications on short sample and coil tests and to provide adequate solutions for improvements. The model can be used to evaluate the influence of the joint design and to define its baseline requirements for short-sample qualification testing, and for optimum magnet performance of for example the ITER coils. JackPot is an electrical network model that simulates the interaction between the superconducting strands in the cable (following their precise trajectories), the interstrand contact resistances, the conduit, and the cable’s connection to the joints. The backbone of JackPot is its cable geometry model, from which all relevant properties are derived. All parameters are derived from well defined experimental measurements on conductor sections and joints, except the axial strain for Nb 3Sn strands, which is the only free parameter in the model. The simulations demonstrate that the current non-uniformity is the source for a number of observed phenomena. Another conclusion is that completely filling the bottom joints and upper terminations of a short sample with solder, opposed to only (partly) soldering the cable surface, improves short-sample testing significantly for qualifying the ITER type CICCs. This paper describes the model and gives a few examples of applications for its validation.

Physicomechanical properties of lining materials before and after use in an electrolyzer

Lining materials for metallurgical plant undergo substantial changes during use, which influences their operating parameters.We have examined the changes in composition and property of materials for lining aluminum electrolyzers after various working times by the use of special measuring systems. Measurements are presented on the properties of bottom blocks and joints, refractory and heat-insulating materials in the lining, and results are given on the phase composition after use. These properties are necessary for the simulation of physical fields on upgrading existing and future electrolyzers.

Analysis of the current distribution in the ITER CS-insert model coil conductor by self field measurements

Non-uniformities in the paths of the currents in a cable-in-conduit conductor (CICC), resistive or inductive, will result into an unbalanced current distribution. The current nonuniformity may affect the performance of a magnet system and it is therefore essential to evaluate this phenomenon. The current distribution in the Central Solenoid Insert Coil (CSIC) from the Central Solenoid Model Coil (CSMC) experiment is reconstructed from the four Hall-sensor voltages at the top and bottom joint of the CSIC. Four Hall sensors are used, near both joints at the extremities of the cable, to measure the self-field of the conductor. The inverse identification problem is solved in order to find the currents that match as close as possible to the set of measured data. Solutions are found for the current amplitudes in the six petals of the cable from the set of measurements of the tangential field component. Differences in the petal currents are found which rate up to a factor of two.

Testing and Evaluation of Metal-Plate-Connected Wood Truss Joints

Abstract Five different types of metal-plate-connected (MPC) wood joints from a scissors truss were tested to evaluate their behavior. All joints were tested in a unique testing apparatus where in-plane loads along with moments were applied to simulate loads carried by the truss members. Strength, stiffness, and failure modes for bottom chord splice joints at web (BSJ), heel joints (HJ), crown joints (CJ), bottom chord ridge joints (BRJ), and top chord splice joints at web (TSJ) were reported. The average strengths of the BSJ, HJ, CJ, BRJ, and TSJ were 51 200 N, 49 800 N, 33 000 N, 52 300 N, and 43 100 N, respectively. The average values of the rotational stiffness were 245 440 kNmm/rad, 249 600 kNmm/rad, 103 700 kNmm/rad, and 33 800 kNmm/rad for BSJ, HJ, BRJ, and TSJ, respectively. Average transitional stiffness values were 61.7 kN/mm for BSJ, 29.2 kN/mm for HJ, and 40.2 kN/mm for BRJ. The majority of bottom chord joints failed in plate tearing, whereas top chord joints generally failed in a web member withdrawal mode. The joint stiffness data were used in a preliminary finite element (FE) analysis of the same truss, and the analytical results compared well to actual full-scale truss test results. Stiffness and strength data will be used in a future FE study.

Destructive Testing of Metal‐Plate‐Connected Wood Truss Joints

Load-displacement characteristics and failure modes of metal-plate–connected wood truss joints are presented. Tension splice, heel, and web at the bottom chord joints are fabricated using southern pine (SP) no. 2 lumber and 20-gage punched metal plates. These joints are tested with a newly developed testing apparatus that allows the testing of all three joints without major modifications. In-plane loads are applied to simulate the loads carried by truss members. The computerized testing apparatus and methods show potential as an efficient testing procedure to assess joint behavior. The average strength of tension splice, heel, and web at the lower chord joints is 27.0 kN, 22.7 kN, and 16.7 kN, respectively. The failure of the heel joint is characterized as ductile, and that of the tension splice and web at the bottom chord joints as brittle. The failure of the joints is a combination of wood and teeth failure. The results are useful for semirigid joint analysis and design of metal-plate–connected wood trusses.

Interaction of shear and tension in welded truss connections

By present design procedures bottom chords of welded structural steel trusses are designed as simple tension members. Little regard is given to the interaction of shear and tension stresses that occur at the bottom chord joints. A study of this interaction on the ultimate capacity of a truss joint consisting of a structural tee tension chord and double angle web members is presented. Based on theoretical considerations and experimental results, an interaction equation is suggested as a design aid to determine the allowable tensile stress at critical joints with transverse shear present.

Failures in the Bottom joints of Surface and Intermediate Casing Strings

Abstract The drilling industry long has been plagued by failures in the bottom few joints of surface and intermediate casing strings. This paper presents an analysis of the various possible causes of failure and concludes that failures are caused by short-lived, high-energy torque impulses delivered from the drill string through the bit while drilling out the cementing plugs, cement and floating equipment. The magnitude of these torque impulses is shown to be a function of the rotational momentum of the drill string, and a method is derived to calculate the magnitude of these impulses. The available methods of strengthening the bottom joints are reviewed. It is concluded that, while present methods are ineffective, a combination of improved procedures for strengthening and minor restrictions on drillout practices will prevent failures. Introduction In most cases, failure in the bottom few joints of casing strings is not discovered until electric logs record that the bottom one, two or three joints have parted from the casing string and slipped down the hole. However, in some cases the parted section of casing uncovers a high-pressure or lost circulation zone, or shifts laterally restricting the passage of drilling equipment. In these instances extensive remedial work is required to realign the parted pieces and seal the exposed formations. Several methods used to strengthen the bottom joints of casing strings include locking set screws in the couplings, putting wedges in special collars, welding straps across the couplings, welding the couplings and, most recently, using epoxy resin-based, thread-locking compounds. Since none of these techniques has eliminated the problem, this study was initiated to find the cause of failures and to evaluate the available methods of prevention. Mechanics of Casing Failures An analysis of the various possible causes of failure indicates that the casing is unscrewed rather than broken and that therefore failure must occur before the shoe is drilled. Since there is no general agreement as to the causes of casing failure, some possible mechanisms were considered in this analysis. Failure of the bottom joints of casing can occur by only one of three types of stress: tension, torsion or bending. The possible mechanisms of failure were evaluated by determining the forces required to cause casing failure by each of the stresses; and, where applicable, the possibility of failure by fatigue was considered. For casing to part under tension requires a downward load of more than the tensile strength of the casing. The lightest API weight H-40 grade casing requires a bit load on the bottom of the casing of 27,000 to 34,000 lb per inch of bit diameter (Table 1). Since maximum drill collar weights seldom exceed 10,000 lb per inch of bit diameter, it is apparent that casing strings cannot be parted by the downward load of the drill string. The second mechanism considered was failure by bending. This mechanism requires that the lowermost casing joints be free to be deflected laterally until the bending stress exceeds the strength of the pipe. To fail, the casing (at a height L above the shoe) requires a force and deflection at the shoe of (1) (2) To deflect the casing shoe with the drill string obviously requires a dog-leg at the casing shoe. This dog-leg must have a rate of change equal to or greater than the change in curvature of the deflected casing, which is given by (3) or (4) TABLE 1 - TENSILE LOADS REQUIRED TO PART THE MINIMUM API WEIGHT H-40 GRADE CASING IN TENSION Required Casing Parting Load Bit Weight per Size Weight ST and C Bit Diameter (in.) (lb) Casing (lb/in.)7 17 160,000 27,3007 5/8 24 227,000 34,0008 5/8 28 252,000 32,0009 5/8 32.3 279,000 32,000 10 3/4 32.75 265,000 27,000 11 3/4 42 336,000 30,600 13 3/8 48 352,000 28,700 JPT P. 93ˆ

Bar Coliseo, en Sevilla

This bar is situated inside the «Coliseo» building, which houses a cinema, as well as a number of commercial establishments. In order not to break the unity of the total project, no attempt has been made to alter the exterior aspect of the bar. No attempt was made, either, to make it into an intimate, club type of bar, now so much in fashion. Rather has it been given a diaphanous style, seeking the best possible use of the floor space. The windows of the building are elongated, and there is an intermediate floor level, whose detailed structure is metallic. A cleverly designed staircase, of folded sheet metal connects the ground floor, the intermediate floor level and the restaurant. Materials were carefully chosen in accordance with their function. The colour scheme has a sustained unity throughout the building, and care has been taken to avoid surprising or vivid chromatic patterns. Ceramic enamels by the painter Santiago del Campo provide a feature of decoration on the ground floor, and also serve to cover up the return air ducts. On the top floor, the restaurant is fitted with coloured tile facings, the work of the Seville painters Maria Josefa Sanchez, Maria Dolores Sanchez and Emilio Garcia Ortiz. The bottom joints of the timber beams, in conjunction with the tile patterns, is reminiscent of the traditional Sevillian habit of placing ceramic units between the timber framework of buildings. The initial problem of the architect was to combine the optimum functional efficiency and aesthetic quality of the project, and the final solution is undoubtedly successful.

The Strength of Rails with Particular Reference to Rail Joints

This three-part paper describes recent work on rails carried out by the Research Department of British Railways. Part I details the rail sections considered, theoretical considerations of longitudinal bending strength and an analysis of failures in service. Part II describes a site investigation which was made into the dynamic stresses experienced by rail joints under traffic. Stresses in both flat bottom (F.B.) and bull head (B.H.) rail joints have been measured with both normal and abnormal conditions of sleeper packing. Electrical resistance strain gauges were used at the calculated positions of maximum stress in each fishbolt hole, and at other positions in the joint. The work initially covered the effects of steam locomotives and steam hauled stock, but was later extended to a second site so that electric locomotives and multiple unit electric stock could be similarly covered. The investigation brought out the marked influence of speed, wheel diameter and axle load on the magnitude of the stresses induced; and in view of the prospective increase in speeds, and the employment of diesel electric and electric locomotives with heavy axle loads on smaller wheels than as is usual currently, importance attaches to these results and their implications on the life expectancy of rail steel under fatigue loading. Part III describes fatigue tests which have been made on B.H. and F.B. rails, both plain and when drilled with fishbolt holes. The susceptibility to cracks starting at bolt holes, due to shear stresses in the web, is compared for the two rail sections, and some consideration is given to various methods of increasing the resistance to cracking of this type. It is shown that ordinary atmospheric corrosion greatly reduces the fatigue strength of rails, and any proposed method of reducing bolt hole failures must therefore take this into account.