Tee Joint Research Articles

An Improved Plasticity-Based Distortion Analysis Method for Large Welded Structures

The plasticity-based distortion prediction method was improved to address the computationally intensive nature of welding simulations. Plastic strains, which are typically first computed using either two-dimensional (2D) or three-dimensional (3D) thermo-elastic-plastic analysis (EPA) on finite element models of simple weld geometry, are mapped to the full structure finite element model to predict distortion by conducting a linear elastic analysis. To optimize welding sequence to control distortion, a new theory was developed to consider the effect of weld interactions on plastic strains. This improved method was validated with experimental work on a Tee joint and tested on two large-scale welded structures—a light fabrication and a heavy fabrication—by comparing against full-blown distortion predictions using thermo-EPA. 3D solid and shell models were used for the heavy and light fabrications, respectively, to compute plastic strains due to each weld. Quantitative comparisons between this method and thermo-EPA indicate that this method can predict distortions fairly accurately—even for different welding sequences—and is roughly 1-2 orders of magnitude faster. It was concluded from these findings that, with further technical development, this method can be an ideal solver for optimizing welding sequences.

Research on Welding Repair for Tee Joint Crack of Final Superheater Header of 300MW Station Boiler

Through methods, such as microscope analysis, metallographic examination, the crack located nearby the fusion line between tee joint and outlet steam pipe of subcritical power station boiler final superheater header is reheat crack (the main crack occurred in the heat affected zone and extended along the fusion line and grain boundary in HAZ. There are many small cracks paralleling with main crack). The base metal material (12Cr1MoV) and excessive welding residual stress are the primary inducement of crack. In repair crack, the measures of reducing residual stress, such as lower welding heat input, reducing thickness of welding layer, hammer blowing, assigning reasonably heat treatment power ,lengthening holding time and so on, were taken. The welding repair succeeded greatly.

Correction of flow metering coefficients by using multi-dimensional non-linear curve fitting

Flow disturbances can significantly affect flow metering because the downstream flow of flow disturbances can become unstable and asymmetric, thus resulting in measurement errors in the flow meter. A clamp-on type ultrasonic flow meter is an example of a flow meter that is susceptible to flow disturbances given its diametrical configuration of ultrasonic paths. Several flow rate correction formulas have been suggested to mitigate the effect of flow disturbance for improved flow metering. As a novel method, a multi-dimensional non-linear correction formula is suggested to overcome limitations in flow metering that are attributed to the non-linearity of flow disturbances. The non-linear correction formula comprises n-th order polynomials with multiple variables. To validate the usefulness of the non-linear correction formula, the standard error of estimate (SEE) is introduced. Four types of flow configurations, namely, downstream of a contraction pipe, an expansion pipe, a single elbow joint, and a tee joint, are used to show the effect of the non-linear correction formula. The expanded uncertainty based on the SEE indicates estimated values of 1.29%, 11.14%, 1.07%, and 6.31% for the four upstream flow configurations, respectively. Thus, the effect of the non-linear correction formula is limited according to the upstream flow conditions. In the downstream flow of the contraction pipe and of the single elbow joint, the non-linear correction formula not only harmonizes the distribution of the flow rate deviations but also removes the biases of flow rate deviations with respect to the flow velocity, the installation location, and the diameter ratio.

Influence of the Notch Rounding Radius on Estimating the Elastic Notch Stress Concentration Factor in a Laser Welded Tee Joint

In recent years an increased interest of industry in sandwich-type metal structures can be observed. These structures consist of thin plates of 2.5 mm in thickness separated by stiffeners of different shapes and forms. Welds joining the plates and stiffeners are made on the outer side of the plates using laser welding technique. A locally focused source of heat causes the plate to melt creating a very narrow and elongated joint. As a result, sharp geometric notches are formed on the side of the root of a weld – a place which is inaccessible and cannot be checked. Geometries of individual welded joints vary, sometimes considerably, and this makes their analysis even more complicated. Additionally, the use of laser welding technique influences the formation of untypical distribution of changes in material properties in weld zones. The effect is a joint whose behaviour under load is significantly different from the behaviour of a welded tee joint made with the use of classical methods. Fatigue strength calculations for this type of joints can be conducted based on local stress values in notches, which can be determined with the use of Finite Element Method (FEM). This article analyses the influence of the notch rounding radius on the elastic notch stress concentration factor Kt The aim of the analysis is to evaluate the notch stress concentration according to local notch stress approach.

Failure Analysis on Tee Joint Crack of Subcritical Power Station Boiler Platen Superheater Header

Failure cause analysis was carried out on tee joint crack of boiler platen superheater header (12Cr1MoV) of subcritical power station applying microanalysis, mechanical properties test, chemical composition analysis, metallography examination and SEM observation etc. Results indicated that the tee joint crack originated at the original defects, connected with reheat cracks during propagation and led to leakage finally. The improper structure, the original welding defects, overhigh welding heat input, and excessive welding residual stress resulted in the leakage failure.

Structure Optimization and Strength Analysis of CBM Special Anti-Clogging Drainage Pump

There are abundant coal bed methane resources in China, and recovery technology is considered a very important part in the development of coal bed methane. At present, coal bed methane production areas are still adopting the tubing liner pump, but because of the special working environment, in the pumping process, the fine breeze (sand) and other solid particles entering into the pump barrel is likely to cause the pump stuck, pipe string buried by sand and other issues. In view of the above problems, based on the ordinary tubing liner pump, through the increase of the anti-litter bypass style traveling valve housing and fixed valve housing, outside liner jacket, sand reservoir and liquid in tee joint measures we developed a new type of CBM special anti-clogging drainage pump and adopted finite element analysis software ANSYS to complete key parts of strength calculation. The use of this pump will effectively reduces the blocking of fine coal particles (sand) and other solid particles, decreases the pump's checking operation and workload of sand bailing, consequently improves efficiency, reduces overall operating costs.

S083025 混合ガス燃焼時の配管強度に関する研究 : 燃焼時の圧力評価用解析

Piping strength evaluation method on combustion of non-condensable gas (stoichiometric hydrogen/oxygen mixture) accumulated in the piping of boiling water reactor (BWR) has been developed. Detonation pressure of non-condensable gas was evaluated by the detonation calculation, then piping strength was calculated using the pressure obtained by the detonation calculation. In this paper, the calculation methods for evaluating the detonation pressure was developed, and the detonation pressure obtained by the calculation was validated using the results of the detonation experiments. It was confirmed that the detonation calculation agreed with the results of detonation experiments on the straight pipe, elbow, tee joint, and so on.

Residual stresses due to gas arc welding of aluminum alloy joints by numerical simulations

This study deals with the numerical simulation of the gas arc welding process of Aluminum tee joints using finite element analysis and evaluation of the effect of welding parameters on residual stress build up. The 3D simulations are performed using ABAQUS code for thermo-mechanical analyses with moving heat source, material deposition, solid-liquid phase transition, temperature dependent material properties, metal elasticity and plasticity, and transient heat transfer. Quasi Newton method is used for the analysis routine and thermo-mechanical coupling is assumed; i.e. the thermal analysis is completed before performing a separate mechanical analysis based on the thermal history. The residual stress build up and temperature history state in a three-dimensional analysis of the tee joint is then compared to experimental results. Hole drilling method is used for measuring the residual stress, while temperature history is measured by thermocouples. After carrying out numerical simulations, the effects of voltage/current, welding speed, material thickness and size of electrode on residual stress build-up and resulting distortions are evaluated.

Failure Analysis on Tee Joint Crack of Subcritical Power Station Boiler Final Superheater Header

Through methods, such as microscope analysis, mechanical analysis, chemical analysis, metallographic examination, the causes resulting in tee joint crack of subcritical power station boiler final superheater header (12Cr1MoV) have been analyzed. The result indicates the tee joint crack is reheat crack, and irrational structure and excessive welding residual stress are the primary inducement of tube joint crack.

Robotized welding of butt and T-welds of metal sheets 3.0 mm thick made of Al–Mg alloys

This article presents the results of studies on joints connecting 3 mm-thick aluminium–magnesium alloy sheets. The joints were manufactured on a robotized welding station by means of the GTA method (butt joints) and the GMA method (tee joints with fillet welds). Butt joints were tested by means of X-ray, mechanical, and metallographic methods, whereas tee joints were examined using metallographic methods as well as a break test. The results of these studies validated the high quality of the joints. The welding rate with the GMA method is nearly two times higher than with GTA welding, which explicitly indicates that the GMA method is more efficient, even in welding relatively thin metal sheets.

Numerical Study of Welding Sequence on the Residual Stress Field in a Thick-Walled Tee Joint

Finite element simulation is an efficient method for studying factors affecting weld-induced residual stress distributions. In this paper, a validated three-dimensional finite element model consisting of sequentially coupled thermal and structural analyses was developed. Three possible symmetrical welding sequences, i.e. one-welder, two-welder and four-welder sequence, which were perceived to generate the least distortion in actual welding circumstances, were proposed and their influences on the residual stress fields in a thick-walled tee joint were investigated. Appropriate conclusions and recommendations regarding welding sequences are presented.

Nonlinear finite element analyses of tee joints of laminated composites

Geometrically nonlinear finite element analysis is conducted to determine three dimensional stress components of a composite tee joint, which is formed when a right angled plate is adhesively bonded to a base plate. Two different boundary conditions of the tee joint, such as assuming the base plate of the tee joint as rigid and flexible, have been considered. The stress components of the tee joint with three different laminate stacking sequence viz. unidirectional [0]8, cross ply [(0/905)s]2 and angle ply [(+45/−45)s]2 laminates have been evaluated when it is subjected to an out-of-plane loading through the right angled plate, and the effects of laminate stacking sequence on three-dimensional stresses have been studied. Conclusions about the stresses of the composite tee joint with different boundary conditions, stacking sequence, and ply styles are drawn.

Determination of Strains near the Welded Seams

This paper suggests a new method of determining residual strain in the welding seals. Method is based on the speed of Rayleigh waves with measurements of strain changes σ1 + σ2. According to results of experiments described in the paper, author finds correlations for the two types of steels. The paper also reports on the experimentally obtained values of strain in the areas around welding seals and tee joints. Research indicates that under the influence of external loadings, residual strain doesn’t cause significant changes in the epures of strain.

SCF analysis of a pressurized vessel–nozzle intersection with wall thinning damage

A three-dimensional finite element analysis is carried out of a pressurized vessel–nozzle intersection (tee joint), with wall thinning damage. A convergence-validation study is first carried out for undamaged intersections, in which comparisons are made with previously published work for the stress concentration factor (SCF), and good agreement is observed. A study is then carried out for specific tee joints to examine the effect on the SCF of varying the extent of the wall thinning damage. Finally, a parametric study is conducted in which the SCF is computed for a wide range of tee joints, initially considered undamaged, and then with wall thinning damage.

Weldability of Low Carbon Transformation Induced Plasticity Steel

Transformation induced plasticity (TRIP) steel exhibited high or rather high carbon equivalent (CE) because of its chemical composition, which was a particularly detrimental factor affecting weldability of steels. Thus the weldability of a TRIP steel (grade 600) containing (in mass percent, %) 0. 11C-1. 19Si-1. 67Mn was extensively studied. The mechanical properties and impact toughness of butt joint, the welding crack susceptibility of weld and heat affected zone (HAZ) for tee joint, control thermal severity (CTS) of the welded joint, and Y shape 60° butt joint were measured after the gas metal arc welding (GMAW) test. The tensile strength of the weld was higher than 700 MPa. Both in the fusion zone (FZ) and HAZ for butt joint, the impact toughness was much higher than 27 J, either at room temperature or at −20 °C, indicating good low temperature impact ductility of the weld of TRIP 600 steel. In addition, welding crack susceptibility tests revealed that weldments were free of surface crack and other imperfection. All experimental results of this steel showed fairly good weldability. For application, the crossmember in automobile made of this steel exhibited excellent weldability, and fatigue and durability tests were also accomplished for crossmember assembly.

Mechanised and automated welding of tee joints with butt welds

Mechanised and automated welding of tee joints with butt welds

T継手部の脆性き裂伝播停止挙動に及ぼす未溶着寸法の影響

In the large heat input weld joint of heavy gauge steel plate used for large container carrier, a brittle crack possibly propagates straightly along a weld joint without diverging to base metal. This phenomenon is being discussed for its application to the large heat input weld of heavy gauge plate to ship structures. In this study, to arrest a brittle crack at Tee joint embedding un-welded face, the effect of un-welded face on behavior of brittle crack propagation/arrest in Tee joint structure was investigated and analyzed. The ESSO test of Tee joint structure was carried out, supposing that a brittle crack which propagates along a weld joint of hatch coaming rush into Tee joint of hatch coaming and strength deck. The test results exhibited that the brittle crack arrested at the Tee joint embedding un-welded face, and the brittle crack arrested easier, the longer un-welded face was. The results of static FEM analysis showed that stress intensity factor of brittle crack was increased by un-welded face, until brittle crack reached a flange. However, when brittle crack propagate into the flange, stress intensity factor of brittle crack was decreased by un-welded face for instance. The crack-arrest effect of un-welded face appears remarkably after brittle crack propagates into the flange.

New API RP2A Tubular Joint Strength Design Provisions

The development of the new API RP2A (22nd edition) parametric static strength prediction equations for planar circular hollow section tubular joints is described. Prediction equations are presented for brace axial, brace in-plane bending, and brace out-of-plane bending loads. The prediction equations are based on screened test databases, augmented, and extended by an extensive new series of validated nonlinear finite element simulations for nonoverlapping K joints, double tee (DT/X) joints, and T joints. The increased reliability (reduced scatter) provided by the new static strength formulation was used to justify a reduction of the load factor of safety to 1.6 from the previous value of 1.7.

Modeling Multi-phase Flow Using CFD WithRelated Applications

Concurrent liquid-gas flow manifests itself into different flow regimes depending on fluid properties, flow rates, heat inputs and geometry. The Baker chart has identified at least seven flow regimes, viz. stratified, wavy, plug, slug, annular, dispersed and bubbly flow. Each flow regime exhibits a unique flow pattern and may transition from one to another depending on the flow conditions in the pipe. Computational Fluid Dynamics (CFD) with multiphase flow equations add a capability by which these flow regimes can be visualized and understood. In this paper stratified and slug flow regimes are studied by using CFD modeling. The modeling results are validated by comparison with published experimental data. The benchmark comparison shows that CFD is successful in predicting the following aspects in two-phase flow: • Quantitative prediction of stream-wise velocities in both phases. • Qualitative prediction of flow regime, phase distribution and pressure distribution. • Transition between certain, but not all, flow regimes. On the other hand, more research and development is needed to accurately predict pressure drop and vapor/liquid interface location when the velocity difference between phases is relatively large. The application of the validated CFD model is extended to the same flow regime in a tee joint distributor system. The results demonstrate that the mal-distribution of flow can occur in complex piping systems with sudden transition.

Improved Seismic Design Procedure for Concrete Bridge Joints

Experimental investigation and subsequent analytical studies have shown that the external strut force transfer method of design is insufficient for reinforced concrete bridge joints and overly conservative for prestressed joints, particularly under in-plane seismic loading. Despite these findings, this design method is widely endorsed for use in seismic design practice in the United States. In consideration of the shortcomings of the currently used force transfer model for bridge joints, an improved design model, referred to hereafter as the modified external strut force transfer model, is introduced in this paper. Use of the modified model for bridge tee and knee joints, design equations, a set of prescriptive design steps in a readily applicable form, and reinforced and prestressed concrete bridge joint design examples are also presented.