Weld Length Research Articles

WITHDRAWN: Evaluation of welding strength and optimization on seam welding of domex steel

Abstract The quality of the welded joints is difficult to achieve in manufacturing industries. Gases and fumes are spoiling the welding quality. This problem can be rectified through seam welding process. It is a green and clean welding without affect the environment. At the same time, it can be easily automated and reduce the processing time. It can produce the better welding structure throughout the welding length. The aim of the work is to increase the welding strength of the domex steel. The welding current, electrode force and welding time are used to estimate the welding strength. The optimal welding factor and their contribution have been found through Taguchi technique and variance analysis respectively.

Optimizing the mechanical properties of Al-SS joint using the numerical and experimental investigation of electromagnetic welding

In this research, the influence of electromagnetic welding (EMW) parameters such as voltage (V), standoff distance (D s) and distance between spacers (S d) on ultimate tensile strength (UTS), elongation (El), weld length (Wl) and hardness (HV) of Al-SS joint has been investigated. Formation of Al-SS weld was predicted using the finite-element analysis (FEA) in combination with the weldability window. The experimental tests were performed using the response surface methodology (RSM) to develop the regression equations based on the significant parameters. For evaluating the quality of joints, the microstructure of weld interface was studied by optical and scanning electron microscopy (SEM). It was observed from the results that the maximum ultimate tensile strength (UTS), elongation (El), weld length (Wl) and hardness (HV) of Al-SS weld can be obtained simultaneously by the voltage of 11.2 kV, standoff distance of 1.9 mm and distance between spacers of 22.5 mm.

Evaluation of the slotted-hidden-gap (SHG) connection for square HSS brace members

Hollow structural section (HSS) braces of concentrically braced steel frame structures are often connected using a knife connection, which creates a net area in the brace due to the slot. Tensile rupture of the brace's net section is the controlling failure mode unless reinforcing schemes are utilized. The “Slotted-Hidden-Gap (SHG)” connection, in which a notch is created in the gusset plate to overlap the gross area of the tube to eliminate the net area, represents an attractive alternative to traditional connection reinforcements; however, no design guidelines exist for the SHG connection for square HSS braces. A laboratory testing program and finite element modelling were carried out to determine the minimum overlap length required to develop the yield resistance of a square HSS brace. The test program included monotonic tensile loading tests on short conventional- and SHG- connection specimens, and one reversed cyclic loading test on a 4.86 m long brace specimen with SHG connections. An overlap length of 5% of the weld length was sufficient to develop the yield resistance of the braces with SHG connections. For those specimens, the HSS eventually fractured on their gross area away from the connections, after experiencing extensive yielding along their length. Conversely, braces with the conventional connections suffered localised yielding and fracture at the net section. The long brace with SHG connections attained its yield tensile resistance, including a 15% increase due to strain hardening, while sustaining an axial deformation corresponding to a storey drift of 3.14%.

Experimental Investigation of TIG Welding Input Parameters Effects on Mechanical Characteristics

Tungsten inert gas (TIG) welding process is one of the complex production methods. The reason is the drastic changes in the metallurgical structure of welding parts due to the heating and cooling cycle during welding. These changes cause various metallurgical and mechanical defects of the parts and weaken the mechanical properties of the parts. Many parameters in welding have different effects on the quality of welding parts. To create a suitable weld, it is necessary to identify the effect of these parameters and to be able to estimate it and select the appropriate and optimal conditions. Accordingly, In this study, an experimental investigation were conducted on determining the mechanical characteristics of the pieces through variation of three main welding parameters including advance speed, welding amperage and preheating temperature. Due to the difficulty of changing the rate of advance speed in manual welding, a robotic welding arm was designed for welding 316 stainless steel in the current paper, in which a microcontroller tuned the speed and welding length. By collecting the practical data, the effect of the input data (advance speed, welding amperage and preheating temperature) investigated in durability and strength of the joints. In other words, the tension and durability of the joints for stainless steels are proposed for various welding parameters to enhance the optimal conditions based on the experimental results. In samples with low advance speed, in addition to increase the solidification time, the coarseness of the structure and the burning of the edges of the welded parts due to the low speed and high amps, reduce the tensile strength. Also, the results showed that by increasing the amperage, the strength of welding parts decreases due to the burn defect of the plate edges, which can be minimized by increasing the welding speed and reducing the effect of extreme heat on the edges. Finally, by analyzing the effect of the input parameter on the output, the best conditions of the adjustment parameters in butt-welding were acquired among existed samples for welding 316 stainless steel.

Experimental and Numerical Investigation of Stress Concentration at Rib-to-Crossbeam Joint

In orthotropic steel decks (OSDs), the rib-to-crossbeam joint is the most vulnerable detail that has not been drawn enough attention. The failure mode of cracks initiate from the lower weld end on rib wall is governing its fatigue performance. However, relevant detail categories are still missing in prevailing codes. This paper mainly focuses on the stress concentrations at the rib-to-crossbeam joint induced by rib distortions. A series of static load tests were first performed on a full-scale OSD specimen with different weld length between the ribs and the crossbeam. Then, corresponding numerical simulations were finished. Several possibilities that may cause the differences between the measurements and the calculations are investigated. At last, fatigue assessments based on influence lines of structural hot spot stress (SHSS) are completed. Research results reveal that the measurement results of reference points for SHSS method would be very sensitive to the exact location of strain gauges. Due to the manual welding, the deviation of strain gauge positions induced by the irregular weld shape is thought to be the main reason that causes the differences between measurements and calculations. Raising the location of cope hole terminations would decrease distortional stresses. However, the influence of this parameter on fatigue lives is rather small. The fatigue lives of points along the lower weld toe are very close. Hence, the point at the middle plane of crossbeam could be used as the reference point for fatigue assessments. Meanwhile, the center between ribs could be used as the reference transverse load position for fatigue assessments of this joint.

Friction stir welding machine “Malakhit”

Friction stir welding unit is described, designed for experimental works on the welding technology of large-sized items. Structural diagrams of the main units of the installation are presented. Technical characteristics of unit make it possible to obtain prototypes of weld made of aluminum AMg5 type alloy with thickness of up to 20 mm, with weld length of 2000 mm in the longitudinal direction and 1500 mm in the transverse direction. The maximum trans verse dimensions of the welded structures is 1500 Ѕ800 mm. The parameters of the welding process in real time are displayed on the control panel and recorded in the report: the values of the vertical force on the tool, the power consumed by the electric drive of the spindle and the horizontal force on the welding table in the direction of welding.

Non-linear FEA of mechanical properties of modular prefabricated steel-concrete composite joints

This paper study the seismic performance of modular prefabricated SRC column to steel beam composite joint (MPCJ) under static loading. Numerical modeling of MPCJs with three different beam-end connections was carried out in ABAQUS. Results of the numerical calculation were compared with existing quasi-static test results to verify the feasibility of the numerical model. The model was then used to analyze changes in the moment-rotation relation, failure mode, ductility, stiffness, and bolt stress in the joint between the column and joint module. Besides, stress distributions in the joints were analyzed along different stress paths. Under monotonic loading, the mechanical performance of the MPCJ is significantly affected by the beam end connection mode. Failure of the MPCJ mainly occurs at the beam end connection, thus, the aim of keeping the plastic hinge away from the joint core and preventing shear failure is achieved. Furthermore, the maximum story drift ratio is 3.9–5 times greater than the recommended limit, which indicates good ductility and deformation performance. The MPCJ of the three-beam end connection methods is all semi-rigid connections. The beam end structure will have a large influence on the bolt tension and stress distribution. According to the test research results, a nonlinear model with three parameters including joint cover plate cantilever section length, flange connecting plate thickness and flange connecting plate weld length was established. The theoretical calculation results was consistent with the results of the numerical simulation. MPCJs can be designed based on the proposed theoretical calculation formula.

Analytical investigation of rectangular steel pipe shear connector

Rectangular steel pipe (RSP) which is a new kind of connector in a composite slab of steel–concrete has been proposed. Research on the shear properties of RSPs is limited, but such data are needed if RSPs are to be used as shear connectors in composite slabs. Here, a nonlinear finite-element (FE) model that accounts for the nonlinear material properties and the RSP–concrete interface is proposed. A comparison between the finite element method (FEM) results and the static push-out test data showed good agreement in terms of shear stiffness, shear capacity, and failure mode. This verified FE model was then used in a parametric study to investigate the effects of constraint in push-out test, concrete stiffness, concrete compressive strength, RSP dimensions, RSP thickness, and RSP welding length on RSP shear capacity. The analytical results showed that constraint, concrete strength, RSP dimensions, RSP thickness, and welding length all affected RSP shear capacity, whereas concrete stiffness showed light effects. The shear capacity obtained using the FE model was compared with the calculated result using the Japan Society of Civil Engineers (JSCE) equations for the shear capacity of L-shaped channels.

Mechanical behaviour of longitudinal lap-welded joints of high strength steel: Experimental and numerical analysis

Mechanical behaviour of twenty-eight longitudinal lap-welded joints made of high strength steels (HSS) under tension load was investigated by experimental and numerical study. Weaknesses due to traditional deformation measurements for fillet welded joints can be perfectly solved by digital image correlation techniques (DIC). Distribution and development of strain field throughout the specimens along the whole loading process were recorded by DIC measurement. The effect of parameters (e.g. weld size, weld length and mismatch ratio) on mechanical properties (e.g. ultimate strength, failure modes, weld ductility and fracture angle) of longitudinal fillet welds and transverse fillet welds, which was introduced in detail in previous work by the authors, were compared. Generally, because of the difference on the combination of shear force and tension force, the fracture angle of longitudinal welded specimens (around 50∘) were much more divergent from transverse welded specimens (around 20∘) even though both of them failed at welded zone (welded zone only refers to weld metal in this paper), resulting that the mean strength of longitudinal welded specimens were only 0.58 time of transverse welded specimens. Conversely, the mean deformation capacity of longitudinal welded specimens was almost 4.0 times of transverse welded specimens. All longitudinal welded specimens have “platform” or “decline” feature while all transverse welded specimens have “rise” or “platform” feature load-deformation curves. Generally, the specimens with “rise” feature load-deformation curve are more likely to suffer sudden fracture, while specimens with “decline” or “platform” feature have satisfactory ductility performance. Based on the strain distribution and development features provided by DIC measurement, a new strength criterion, in which the ultimate strain obtained in relevant coupon tests was an indicator, was proposed and through the comparison between the numerical results and test results, its validation was verified by FE simulation. Moreover, it was confirmed that the predicted loads of EC3 and AISC Specification were close and slightly conservative for all specimens.

Fatigue life of the welding seam of a tracked vehicle body structure evaluated using the structural stress method

The supporting roller is an important component in the driving systems of tracked vehicles. Through the bracket structure, the supporting roller is bolted to the vehicle body welded with a reinforced metal plate, providing vertical support and lateral guidance of the track. The strengthening weld structure between the bottom plate and the vehicle body is the root of the cantilever beam, where stress is concentrated and fatigue damage is easily accumulated. The fatigue life of the whole vehicle is affected by the fatigue damage in this part. This paper proposes a structural stress method to evaluate the fatigue life of the welding seam of a tracked vehicle body. Further, the proposed method is evaluated under typical road-load spectra. Initially, the base-metal and weld structures were subjected to monotonic tensile and cyclic plastic deformation tests. The tensile strength of the weld sample was approximately half of that of the base metal. Next, the welded structure of the supporting roller bracket was simulated using a finite element model. The calculated stresses were consistent with the fatigue crack locations in the welded structure. The structural stress was not dependent on the grid density. Subsequently, multibody dynamic simulations of the whole tracked vehicle were performed on four standard road surfaces constructed using the harmony superposition method. The road-load spectra at the axle head of the supporting roller were calculated under four pavement conditions, and the fatigue life of the weld structure of the supporting roller bracket was determined. The calculated fatigue life was considerably lower than the designed fatigue life. Finally, the initial weld structure was redesigned by increasing the size of the strengthening metal plate and the weld length. The fatigue life of the redesigned structure was considerably longer than that of the original structure, indicating that the proposed method can effectively analyze the fatigue life of the welding seam and that it can be used to optimize the design scheme.

Optimisation of double-tapered rectangular tube with O-shaped diaphragms as energy absorber

In this article, a new double-tapered rectangular tube (DTRT) with diaphragms is introduced as an energy absorber. The material tensile test and impact test were performed to verify the finite element model (FEM) of the tube. Based on the FEM, the Box–Behnken design (BBD) was applied to study the effects of diaphragm geometry on energy absorption (EA) and specific energy absorption (SEA). The weld length between the diaphragm and tube wall has positive effects on the EA and SEA of the DTRT, whereas the hole size on the diaphragms has negative effects. The optimal solution improved the EA and SEA by 12.01% and 9.29%, respectively. The conclusions of this study are based on engineering practice and are expected to aid engineers in designing the diaphragms of tubes as energy-absorbing structures.

An Experimental Study of the Influence of Eccentricity on Shear Lag Effects in Welded Connections

In the 2010 AISC Specification, the shear lag factor for longitudinally welded tension members was applicable only to plate-type members having equal length welds on each side with a minimum length equal to the distance between the welds (AISC, 2010). Fortney and Thornton (2012) used experimental data from three previous research programs consisting of 175 various tension members to develop a generalized shear lag model that addresses the aforementioned limitations. The members comprising this dataset consisted of 158 flat plates with equal weld lengths, 4 single angles with unequal but balanced weld lengths, and 13 other members having equal weld lengths. The shear lag factor presented in the 2016 AISC Specification Table D3.1, Case 4 (AISC, 2016b) is a product of Fortney and Thornton’s work and applies to longitudinally welded plates, angles, channels, tees, and W-shapes having equal or unequal lengths and no length-to-width limitation. This paper presents an experimental study on the shear lag effects in longitudinally welded tension members under both in-plane and out-of-plane eccentricity through the testing of eight 3×1/2 plate sections and twelve 3×3×1/2 single-angle sections having both equal and unequal longitudinal weld lengths. Experimental shear lag factors were determined for each of the 20 tested specimens and compared to three theoretical values: (1) the shear lag factor in the 2010 AISC Specification (AISC, 2010), (2) the shear lag factor based on a bi-planar model (Fortney and Thornton, 2012), and (3) the shear lag factor from Case 4 in the 2016 AISC Specification. The findings of this experimental study confirm that shear lag factor given by Case 4 in the 2016 AISC Specification provides the best prediction of shear lag factors in welded connections subject to both in-plane and out-of-plane eccentricity.

Experimental and numerical studies on gas tungsten arc welding of Ti–6Al–4V tailor-welded blank

The effect of gas tungsten arc welding (GTAW) process parameters and its impact on the titanium TWB was studied experimentally as well as using numerical simulation. Bead characteristics of BoP trials (bead on plate) were analyzed based on Taguchi L27 orthogonal array by taking welding current (115 A, 125 A, 135 A), welding speed (4.1 mm/s, 5.8 mm/s, 7.5 mm/s) and arc length (3 mm, 4 mm, 5 mm) as process parameters. The bead width and depth of penetration for all trials were measured by using the weld expert system. Based on the bead characteristics, optimized GTAW process parameters (135 A, 4.1 mm/s and 3 mm) were identified for making the TWB by joining 2–1.6-mm-thick Ti–6Al–4V sheets. The tensile test of the prepared Ti–6Al–4V TWB was conducted in the universal testing machine. The COMSOL and ABAQUS software packages were used for the numerical simulation of TWB to assess the bead profile and tensile properties. The prediction made from the temperature distribution curve related to phase change near weld zone, exactly matched with the experimental work. The joint strength of TWB observed to be around 982 MPa and 1005 MPa was evaluated experimentally and conducting ABAQUS simulation work. The tensile test results were comparable with each other within the acceptable error level.

FEM analysis of residual stress induced by repair welding in SUS304 stainless steel pipe butt-welded joint

Abstract Repair welding is widely used to repair defects such as fatigue crack and stress corrosion crack in metal structures for prolonging their service lives. However, the residual stress induced by repair welding potentially threatens the safety of the repaired weldments, especially stainless steel pipe structures and pressure vessels used in nuclear power plants. Based on the MSC. Marc software, a thermal elastic plastic finite element method with the consideration of full 3-D model, moving heat source and advanced material model was developed to simulate residual stress distribution induced by repair welding. In the current study, the effectiveness of the developed computational approach was verified by a two-pass thin-walled butt-welded SUS304 steel pipe mock-up at first. Then, the residual stress distributions in a medium thickness SUS304 steel pipe butt-welded joint before and after repair welding were investigated numerically. The simulation results show that the peak value of axial residual stress after repair welding was significantly increased, while the variation of the maximum value of hoop residual stress was limited. In addition, the effect of repair length on the feature of residual stress distribution was studied numerically. The numerical results indicate that the peak value of repair-induced residual stress decreases with the repair length. The main reason is that the longer the repair welding length is, the less local constraint will be. The residual stress distribution in the repair area at service temperature was also discussed in this study. The results obtained from the current study will be helpful in evaluating the structural integrity of repaired weldments.

Evaluating the Electromagnetic Welding Parameters for Improving the Mechanical Properties of Al–Cu Joint

The aim of this study is to simultaneously improve ultimate tensile strength, elongation, weld length and hardness of Al–Cu welded sheets by optimizing the electromagnetic welding parameters such as voltage, standoff distance and distance between spacers. Finite element analysis was conducted for the electromagnetic welding of Al–Cu sheets, and the results were used to predict the formation of weld. The experimental tests were then executed by response surface methodology in order to extract the regression models for predicting the optimal values of the parameters. The assessment of the weld quality was performed by observation of the microstructure of weld interface using the optical and scanning electron microscopes. The mechanical properties of Al–Cu weld were improved simultaneously using the desirable values of parameters as validated by confirmation experiments. It was also observed from the weld microstructure that the most important potential sources for reducing the weld length and weld strength are the high thickness intermetallic layers with micro-cracks and the entrapped oxides in the weld interface.

Experimental study and numerical simulation of a new prefabricated SRC column to steel beam composite joint

This study investigated the influence of different beam end connection modes on the seismic performance of joints. Three prefabricated steel–concrete composite joints were tested by quasi-static test. Based on the experimental results, the refined finite element model was established by ABAQUS, and its reliability was verified. The influence of different parameters on the seismic performance of the joint was analyzed. The parameters include the length of the joint cover plate (lj), the thickness of the flange connection plate (tf), and the weld length of the flange connection (lw). The results show that different beam end connections significantly impact the seismic performance of the joint. The hysteresis curves of the three joints are relatively full, and the degradation performance of strength and stiffness is stable, thus achieving better energy dissipation capacity and ductility performance. Comparative analysis verified the correctness of the finite element model. lj has little influence on the bearing capacity and energy consumption, but has an obvious influence on ductility. tf and lw significantly influence the bearing capacity, ductility, and energy consumption of the joint. Under the influences of different lj, tf, and lw, the strength and stiffness degradation remain relatively stable.

A Novel Approach for the Detection of Geometric- and Weight-Related FSW Tool Wear Using Stripe Light Projection

Friction stir welding (FSW) has become an up-and-coming joining method with a wide range of industrial applications. Besides the unique weld seam properties, recent investigations have focused on the process-related tool wear of shoulder and probe, which can have detrimental economic and technological effects. This paper presents a systematic quantitative characterization of FSW tool wear using stripe light projection as a novel method to detect weight and form deviations of shoulder and probe. The investigations were carried out with a robotic welding setup in which AA-6060 T66 sheets, with a thickness of 8 mm, were joined by weld seams up to a total length of 80 m. During the experimental tests, geometrical deviations of the tool induced by wear were detected for varying weld seam lengths and different measuring points on the probe and shoulder. It was shown that wear depended on welding length which in turn caused significant deviations and weight losses on shoulder and probe. Furthermore, it was demonstrated that the wear on shoulder and probe can be considered separately. It was found that there is a progressive wear rate on the shoulder and a degressive wear rate on the probe depending on the weld seam length. To demonstrate the negative impact of tool wear on shoulder and probe after 80 m weld seam length, visual and metallographic inspections and tensile tests were carried out to detect resultant irregularities in the weld seam.

Wear of ZhS6U Nickel Superalloy Tool in Friction Stir Processing on Commercially Pure Titanium

The use of electric arc or gas welding in the manufacture of titanium components often results in low quality welded joints due to large residual stresses and strains. A successful solution to this problem can be found in the application of friction stir welding. However, friction stir welding (FSW) of titanium alloys is complicated by rapid tool wear under high loads and temperatures achieved in the process. This paper studies the durability of a tool made of ZhS6U Ni-based superalloy used for friction stir processing of commercially pure titanium and the effect of the tool wear on the weld quality. The total length of the titanium weld formed by the tool without failure comprised 2755 mm. The highest wear of the tool is observed at the base of the pin, which brings about the formation of macrodefects in the processed material. The tool overheating causes an increase in the dendrite element size of ZhS6U alloy. The transfer layer contains chemical elements of this alloy, indicating that the tool wear occurs by diffusion and adhesion. As a result of processing, the tensile strength of commercially pure titanium increased by 25%.

The Effect of Weld Length on the Tension Capacity of Hollow Structural Section (HSS)

The non-uniform stress distribution occurs in a tension member adjacent to a connection, in which all elements of the cross-section are not directly connected. This effect reduces the member’s design strength because the entire cross-section is not fully effective in the critical section’s location. That's why an experimental study has been done to investigate the effect of the weld length on the tension capacity, two specimens (hollow structural sections) have been tested by using Instron 8800 machine with two weld lengths, 46 mm and 56 mm. The 46 mm size is the minimum requirement of the sufficient size of the tension connection depending on United States Steel Standard. The Result proved that there has been too much effect on the connection carrying tension capacity. The result of the 46 mm weld length is about 155 KN and about 180 KN for the 56 mm weld length. While the ABAQUS simulation results were about 168 KN for the 46 mm weld length and about 172 KN for the 56 mm weld length.

Heatproof Relaxation of Welding Stresses Openwork Designs of Large Size Ultrasonic Field

Designed experimental setup, and a prototype of the original devices for athermic relaxation of thermal residual stresses in openwork welded constructions of large dimensions for the rational use of energy high-frequency acoustic (ultrasonic) fields, conducted laboratory studies and pilot tests in real conditions of production. Ultrasonic relaxation when welding thin-walled constructions standard openwork rolled steel profiles 10 large dimensions (up to 3 x 10 m). It has been established that with a decrease in the time of ultrasonic relaxation, the efficiency of its use decreases somewhat. Therefore, in an industrial environment, it is advisable to use the duration of ultrasonic treatment in the range of 0.02-0.04 min per mm of weld length.