Weld Shear Research Articles

Pushout tests on demountable bolted angle shear connectors for steel-concrete composite structures

Welded connectors are commonly utilized in steel-concrete composite construction. However, these connectors lack demountability, hindering the recycling or reuse of steel sections. In response to this limitation, high-strength bolts have been proposed as alternatives to traditional welded shear connectors to facilitate demountability. Nevertheless, the use of numerous high-strength bolts may negatively impact construction costs due to their limited capacity. This paper introduces a novel solution: the bolted angle shear connector. Comprising a standard angle section, a smaller size angle section functioning as a hat, and a high-strength bolt, this connector aims to balance the demountability advantage while avoiding the drawbacks associated with high-strength bolts. To assess its performance, the proposed connector was embedded into a solid concrete block, and horizontal pushout tests were conducted on 31 specimens. Variables considered included the angle section size, bolt diameter, bolt grade, concrete compressive strength, loading direction, and bolt thread condition. The findings reveal that the proposed connectors demonstrate a ductile response, meeting the mandated slip capacity of at least 6 mm according to EN 1994–1-1. Two distinct failure modes were observed: bolt fracture and a combination of concrete crushing and angle bending. The shear resistances at 6 mm slip ranged from 146 kN to 280 kN, influenced by the angle size and concrete compressive strength. Capacities were formulated as functions of these variables, leading to the development of design recommendations, which are presented in this paper.

Enhancement mechanism of shear properties for SiO2 ceramics by laser welding with Al2O3/SiO2 powder

The laser direct fusion welding of SiO2 ceramics was a global challenge in the manufacture of radome. The paper explored the laser direct fusion welding of SiO2 ceramics, investigated the influence of filling powder addition and welding material composition on the formation of weld. The findings revealed that the addition of welding material effectively addressed the issue of weld formation in laser direct fusion welding SiO2 ceramic. However, the abundance of internal bubbles within the weld emerged as a significant impediment to further enhancing weld strength. The addition of SiO2/Al2O3 mixed powder not only significantly reduced the quantity and size of internal bubbles within the weld but also generated the strengthening phase Al2SiO5, leading to a substantial increase in weld shear strength, reaching a maximum of 106 % of the base material. The research results provided a new solution for direct melting welding of ceramics.

Interface enhancement and distribution of carbon fibers in injection welding

AbstractInjection welding is an excellent adhesive‐free bonding method for thermoplastic resins, demonstrating outstanding connection effectiveness. The incorporation of carbon fibers (CFs) significantly enhances the weld shear strength at the injection interface. This study aims to investigate the reinforcement effect of CF‐reinforced thermoplastic composites (CFRTP) during the injection welding process. And explore the influence of the amount of added CFs on the weld shear strength. Polyamide 6 (PA6)/CF composites with CF contents of 10 wt% and 30 wt% were subjected to injection welding for the first and second molding cycles, respectively. It was observed that the reinforcement effects varied considerably depending on the combinations studied. Under the optimal combination and process parameters, the weld shear strength of PA6/CF composites reached 63 MPa, equivalent to 90% of the shear strength (70 MPa) of the original PA6/CF material. Polarized light microscopy and scanning electron microscopy were utilized to analyze the distribution of CFs at the interface and the reinforcing mechanism during tensile fracture. The significance of maintaining uniform CF content during the welding process of PA6/CF composites was emphasized.Highlights Preparation of PA6 composite materials with different carbon fiber contents. Achieving high welding shear strength of composite materials through injection welding. Identified the optimal injection welding conditions to achieve the highest strength. The positive effect of specific fiber distribution on welding strength was analyzed.

Distribution and reinforcement effect of carbon fiber at the interface in injection welding of polyamide 6 composites

AbstractTo meet the lightweight production requirements of automobiles and achieve high strength, reinforced thermoplastic composite materials are gradually replacing metal materials. Injection molding is the preferred manufacturing method to enable the production of complex‐shaped parts, facilitate production, and reduce costs. In this study, carbon fiber (CF) was added to the commonly used resin‐reinforcing material, polyamide (nylon) PA6, to create a CF‐reinforced thermoplastic composite (polyamide 6 [PA6]/CF) that was welded using injection molding. This study not only investigates the impact of different welding conditions on shear strength but also discusses the sequence of welding. Achieving 85% of the shear strength of the PA6 base material under ideal circumstances. The CF distribution and reinforcement mechanism were analyzed by observing the connection interface and cross section using a polarizing microscope and a scanning electron microscope. When PA6/CF was used as the secondary molded body, the welding results were better. The addition of CF had a significant strengthening effect on the strength of the PA6 injection welding.Highlights Carbon fiber‐reinforced thermoplastic composite materials were prepared, and welding with PA6 was achieved using the injection molding method. The optimal welding parameters were determined by varying the mold, injection speed, injection temperature, and order of injection. The maximum welding shear strength reached 85% of the base material shear strength. The positive effect of specific fiber distribution on welding strength was analyzed by observing the interface using a scanning electron microscope and a polarizing microscope. This study provides valuable insights into the optimization of welding processes for carbon fiber thermoplastic composite materials, offering possibilities for connecting dissimilar materials with poor compatibility.

Experimental, numerical and analytical investigation of bending performance of bolted demountable composite beams with profiled steel decking

This paper presents the results of a detailed experimental, numerical and analytical study to investigate the flexural bending performance of prefabricated demountable composite beams (PDCBs) with bolted shear connectors. Four full–scale tests were carried out for two profiled steel decking configurations (parallel and perpendicular to the steel section) with two different degrees of shear connection. The experimental results were used to validate a numerical simulation model established by the ABAQUS platform. A detailed parametric study was then performed using the validated numerical model to evaluate the effects of using different numbers of bolted shear connectors. The experimental results show that the final failure modes of the demountable composite beams are the same as conventional composite beams using welded shear studs, and the demountable composite beams behavior is ductile. The results of a comparison of load carrying capacity and elastic stiffness of the demountable beams calculated using the analytical equations for conventional composite beams against the experimental and numerical simulation results for the demountable composite beams confirm that the conventional composite beam theory can be used for the demountable composite beams. However, the experimental results indicate that longitudinal cracking in the grout between concrete slabs along the steel beam can happen, due to unsymmetrical location of the shear studs. Anti-cracking mesh would be necessary in practical applications for crack control.

High strength injection molding welding and interface crystal phase changes in polyamide 6

AbstractInjection molding is a widely used method for production of plastic components, offering both simplicity and high strength. In this study, secondary injection molding was utilized to weld polyamide 6 (PA6). The welded samples were evaluated for the welding strength via a shear tensile test. Three process parameters of mold temperature, injection temperature, and injection speed were varied to determine the optimal conditions for welding. A polarizing microscope analysis of the welding interface revealed formation of a shish kebab layer (SKL) structure, which significantly contributed to the welding strength. A differential scanning calorimetry analysis of the welded samples showed that changes in the crystallinity at the interface were closely related to the welding strength under different injection molding conditions. To analyze the crystal phase of the interface after welding, we propose the use of Fourier‐transform infrared spectroscopy area scanning to obtain the relationship between the phase transformation and welding strength. Additionally, microhardness testing is proposed as a means of evaluation of the welding effect. Overall, this study highlights the importance of optimization of process parameters in secondary injection molding to achieve strong welds in PA6, where the SKL structure and crystallinity changes at the interface have crucial roles.Highlights The high welding shear strength reaches 80% of the base material. The interfacial crystalline structure has a significant impact on the strength. The crystalline changes were analyzed using FTIR region scanning. The relationship between microhardness and welding strength was obtained. The wide‐ranging conditions have reference value for industrial production.

Monitoring of friction stirred spot weld quality for dissimilar Al6061 to polycarbonate using tool assisted thrust-torque signatures

Friction stir processing procedures are often found to be an alternative choice for the joining of thermoplastic polymers without melting the base materials. In recent years, dissimilar metallic to thermoplastic assemblies are highly used in aerospace and automotive industries as mechanical fastener or fusion welding techniques are rather inadequate for extreme discrepancy in thermal properties. The present work addresses the feasibility of friction stirred spot welding for non-ferrous aluminium (Al 6061) to polycarbonate using taper cylindrical tool of hardened H13 steel along with machine integrated axial thrust and stirring torque signals. The real-time positional and axial velocity of the rotating tool has been acquired to distinguish between plunging and dwelling stage. The process stability that is, the deviation of thrust-torque in respective phases was processed. The interaction of plunge depth and dwell time on tool pin assisted keyhole with associated material expulsion for different tool revolving speed was established. The weld mechanical behaviour has been scanned using load versus elongation diagram with associated weld pair interface. Lastly, sensors’ based process monitoring extended to weld quality prediction have been made using various significant features of thrust-torque-velocity based approaches. The tool spinning speed followed by dwell time was found to be important on weld quality index. The joint efficiency was significantly upgraded (more than 60%) at intermediate dwell time (40 s) with low tool plunging (0.3 mm) or reversed parametric setting at high tool revolving speed (2500 rpm) due to substantial reduction in axial thrust with higher stirring torque. The local deviation in thrust-torque during plunging was equally responsible with global mean thrust-torque in dwelling to dictate the joint strength and the weld ductility. The material stirring torque was better indicator of weld shear strength while pin assisted slot size highly correlated with tool thrust though tool plunging speed was highly crucial.

Effect of spiral scan distance on the nanosecond-pulsed-laser lap joint of Al/Cu

The T2 Cu with a thickness of 0.2 mm and 6063 Al alloy with a thickness of 0.4 mm were joined via nanosecond pulsed laser welding in an inner spiral scanning mode. The lap configuration was Cu (upper)/Al (under). The influence of spiral scan distance (spiral distance for short) on the weld formation, microstructure and mechanical property was investigated. The results showed that circular holes and arc-shaped cracks formed on the weld surface at the spiral distance of 0.02 mm, and these defects disappeared at higher spiral distances. The tendency of porosity increased initially and decreased afterwards as the spiral distance increased. The interfacial morphology exhibited a wave-shaped structure at the spiral distance of 0.02 mm, and a continuous lump θ-CuAl2 phase was produced at the interface. When the spiral distance was larger than 0.02 mm, the wave-shaped structure disappeared and V-shaped areas were generated due to the invasion of Al element into Cu base metal. α-Al and θ-CuAl2 phases were possibly produced in these areas. The Cu-rich areas generated on the sidewall of the weld could cause the formation of θ-CuAl2. According to the tensile-shear load results, the maximum shear force reached 107.7 N at the spiral distance of 0.04 mm. The satisfactory weld formation and larger effective bounding area contributed to the superior bonding strength. Three fracture modes (button pulling out failure, weld shear failure and interface failure) were observed in this study.

A Rapid Manufacturing Method for Rectangular Splines Based on Laser Cutting and Welding

HighlightsA rapid manufacturing method for internal and external rectangular spline shafts for use in agricultural machinery was developed using a combination of laser cutting and welding.The shear strength of the internal spline welds, extrusion strength of the spline tooth surfaces, and extrusion and shear strength of the external spline pins were tested.Threshold values were obtained for the average diameter of the internal and external splines.Two case studies (light load and heavy load) were performed to verify the feasibility and reliability of the method.Abstract. In recent years, special-sized spline shafts and gears have been widely used in the trial production of new agricultural machinery in China. However, due to the high production cost and long development cycle of these common components, the development of new agricultural machinery has been affected. To solve these problems, this article proposes a method for rapid manufacturing of rectangular internal and external splines using a combination of laser cutting and welding. Through analysis of the weld shear strength of the internal splines, the extrusion strength of the spline tooth surfaces, and the extrusion and shear strength of the external spline pins, it was calculated that the threshold of the average diameter (dm) of the internal splines, commonly used in agricultural machinery, was dm = 31.17 mm, and that of the external splines was dm = 33.45 mm. The feasibility and reliability of the method were verified with two case studies using light and heavy load conditions. The light load case study was the splines of the power input shaft of the pickup platform of a peanut harvester, and the heavy load case study was the splines of the total power input shaft of a peanut no-till planter. The case studies indicated that under the light load conditions (average power of 1.13 kW, average torque of 64.1 N·m, average speed of 168.7 rpm, cumulative working time of 48 h, and harvested area of 46.4 ha) and heavy load conditions (average power of 89.36 kW, average torque of 1029.9 N·m, average speed of 828.6 rpm, cumulative working time of 51.5 h, and planted area of 31.7 ha), no spline failure was observed, and the reliability was 100.0%. This article provides a technical reference for the rapid production of special-sized rectangular splines as single pieces or in small batches for trial production, which requires low processing accuracy, of new agricultural machinery products. Keywords: Agricultural machinery, Laser cutting, Manufacturing method, Rectangular spline, Strength test, Torque.

Finite element analysis of lap joint based on various geometrical parameters to study the behavior of weld strength

This paper reports on study of lap joint weld shear strength of resistance spot weld. Resistance Spot Welding (RSW) is a very cost effective joining technology in automobile industry used to join sheets or plates. The research papers present the effect of various parameters like welding time, welding current, electrode force and squeeze time on strength of joint formed by spot welding of similar and dissimilar metals and thicknesses. Optimization of these parameters is obtained by the micro-hardness test, tensile shear test and fatigue test and the papers presented the methodologies to increase the fatigue life of the joint. In this paper MSC Nastran software is used to analyze the strength of the joint formed by the resistance spot welding. Steel Plates or sheets are modeled with Shell elements of type CQUAD4 and weld element between two plates (Nuggets) are modeled with 1D element with CBAR elements. Various FE models are generated with the consideration of geometrical parameters like thickness of the plate, nuggets along the span length and edge distance. FE models will be subjected to constant pre-defined loads on the various FE models and the weld shear strength were captured for each model and compared against the other models to study the weld behavior. Outcome of the present study provides the insight towards the selection of the optimized weld spots (nuggets) distribution for the various thicknesses of the plate, location of the nuggets along the length and the selection of optimum edge distance. The present study is used to compare the stresses induced in the plates and nuggets for the given load.

Intermetallic Diminution During Friction Stir Welding of Dissimilar Al/Mg Alloys in Lap Configuration Via Ultrasonic Assistance

This study shows the influence of ultrasonic vibrations on the nature and thickness of intermetallic compounds (IMCs) and the correlation with the weld shear load. An ultrasonic vibration assembly comprised of novel horn attachments and a special welding tool has been developed to impart a thermomechanical-acoustic effect on the stirred zone (SZ). The IMC analysis is made at the SZ and interfaces to portray a complete scenario of their formation mechanism. The outcomes depict a complete elimination of harmful IMC phase Al3Mg2 (β) and the shrinkage of Al12Mg17 (γ) at acoustically treated regions under the optimum parameters. The aforesaid evidence is further supported by elemental mapping, energy-dispersive X-ray spectrometry, and diffraction pattern analysis. With ultrasonic assistance, a maximum reduction in IMC layer thickness up to 56.5 pct has been achieved. The weld shear load and joint efficiency are increased by 26.1 and 26.1 pct, respectively, during the ultrasonic addition. The acoustic assistance helps diminish the IMC thickness, while the morphology and mechanism of their formation remain the same.

Modelling and design method for static resistance of a new connection between steel tubular column and flat concrete slab

This paper presents the results of a numerical and analytical investigation into the punching shear behaviour of an innovative simple and effective shear connection between steel tubular column and flat concrete slab using welded shear studs, steel plates and bent-up rebars. The finite element numerical simulation model was validated against two full-scale physical tests carried out by the authors. The validated numerical simulation model was used to perform extensive numerical parametric studies to investigate the effects of changing different design parameters including flat slab depth, concrete grade, bent-up rebar design, shear stud dimensions (length and diameter) and steel tube size, so as to develop thorough understanding of their punching shear behaviour and to provide comprehensive data for development of an analytical method for design. The developed analytical design method can be used to check capacities of shear studs, bent-up rebars and slab punching shear resistance. For this shear connection system, it is easy to prevent shear stud yield failure and bent-up rebar failure so that the system behaves as an enlarged column for calculating punching shear resistance of the slab. For the enlarged column, punching shear resistance calculation method in Eurocode 2 [2] can be used.

Experimental Study on Shear Strength of Geomembrane Welding Seams under Different Inflation Time and Pressure

The shear strength of geomembrane welding seams (GWSs) is one of the key factors for the reliability of geotechnical anti-seepage system. In order to study the evolution law of shear strength of GWSs under different inflation time and pressure, the weld shear strength tests of seven different thicknesses of HDPE geomembrane were carried out under different inflation time and pressure conditions. The test results show that the weld shear strength increases with the increasing geomembrane thickness under the same inflation time (3min or 10min) or the same test inflation pressure (0.1MPa or 0.2MPa). Additionally, the trend of all test curves is similar. The hot-welding method shows good stability in weld shear strength of different thicknesses of HDPE geomembrane. The shear strength values of GWSs of the same thickness under different inflation pressures and inflation times are similar. During the shearing process of the welds, the weakened area of the material at the joint between the edge of the weld and the geomembrane base material is most likely to be destroyed. The corresponding test results can provide reference for GWS inspection and related engineering.

Prediction and optimization in mask-assisted laser transmission microjoining thermoplastic urethane and polyamide 6 through finite-element analysis, Kriging model, and genetic algorithm integrated method

An integrated approach by combining finite-element analysis (FEA), Kriging model, and nondominated sorting genetic algorithm-II (NSGA-II) is utilized to realize modeling and optimization in mask-assisted laser transmission microjoining thermoplastic urethane and polyamide 6 (PA6). First, a three-dimensional FEA model is developed for obtaining the simulation data of the temperature field distribution that can determine the molten pool geometry. Then based on the initial training points generated by the optimal Latin hypercube sampling, the relationships between input parameters (laser power P, scanning speed V, and clamping force F) and weld quality [weld width (WW) and shear strength (SS)] are approximated through the Kriging model. Meanwhile, the main effects and contribution rates of various input parameters on the joint performance are discussed. Finally, the optimal weld quality is characterized as maximum SS and WW with a desired value, the NSGA-II is carried out to solve the multiobjective optimization problem for searching the Pareto-optimal front. The results of validation experiments under the optimal parameters indicate that the corresponding welding joint quality is significantly superior to that under other parameters.

RFID-Based Crack Detection of Ultra High-Performance Concrete Retrofitted Beams.

Ultra-high-performance concrete (UHPC) is a novel material with multiple known uses and many still yet to be discovered. Recently, the use of encasing welded shear studs in UHPC on the web of corroded steel beams was developed. This creates a bearing force transfer mechanism to bypass the corroded web plate. This new material and its uses come with many uncertainties in the short and long term. Structural health monitoring (SHM) can be a tool to observe the development. Specifically, radio frequency technology (RFID) can be used. RFID has existed commercially since the 1960s and has been used as a crack sensor before, but never with UHPC. RFID-based crack sensing is being used to monitor the UHPC retrofit. A crack is simulated on the UHPC specimen and then a commercial, low cost tag is secured. Using backscatter power, the tag reads the crack existence and its increasing volume with every new damage stage. Using a damage index, comparing the uncracked and each cracked stage, this method is not restricted to the raw received signal strength indicator (RSSI), which could be different at each tag. With this sensor, the small cracks that occur in UHPC during its creation can be monitored to ensure the capacity of the retrofitting is maintained. The tested RFID-based crack sensor can be used on various other forms of UHPC.

Flexural behaviour of asymmetric composite beam with low degree of shear connection

This paper outlines an experiment on a 12m long composite beam subjected to uniformly distributed loading. Although composite beams are widely used, current Eurocode design guidelines for these types of members can be over-conservative, particularly in relation to the required degree of shear connection. The tested beam comprised a concrete slab supported by profiled metal decking, connected to an asymmetric fabricated steel I-beam using welded shear studs. The specimen was assembled using unpropped construction methods and had a degree of shear connection equal to 33%, significantly lower than the minimum required amount specified in Eurocode 4. A uniformly distributed load was applied to the specimen, which was increased until the failure occurred characterized by yielding of the steel beam. The maximum bending moment of the composite beam obtained from the test was close to the plastic bending resistance according to the Eurocode 4. No concrete crushing or shear stud failure was observed and the end slips exceeded 6mm, the limit for ductile behaviour in Eurocode 4. The test demonstrated the merits of unpropped construction, which are currently not fully exploited in Eurocode 4. The comparison and analysis suggest that the design limits governing the minimum degree of shear connection might be revised.

03.27: Punching shear behaviour of an innovative connection between steel tubular column to flat concrete slab

ABSTRACTThis paper presents the results of an experimental investigation into the punching shear behaviour and resistance of a simple and effective method of connection between steel tubular column and concrete flat slab using welded shear studs. The shear stud used is the same type as used in conventional steel/concrete composite beams. A major difference between the shear stud behaviour in the proposed system and in composite beam is that in the proposed system, the amount of concrete available to resist punching shear is limited due to small depth of the flat concrete slab. The experimental studies have investigated the effects on punching shear behaviour and resistance of the proposed shear connection system under different design variables including concrete depth above the shear stud, concrete grade, and shear stud dimensions (length and diameter). The results indicate that it is possible to use the proposed simple connection system to provide sufficient punching shear resistance in realistic flat slab construction. Punching shear resistance is dependent on the concrete depth above shear stud. Concrete grade is also important, however, it is the concrete tensile strength that directly determines punching shear resistance. The dimensions of shear stud have relatively minor influences.

쉬어탭 공유 접합부를 갖는 비내진중심가새골조의 내진거동

Special concentrically braced frames(SCBFs) have distinctive advantages in considerable seismic performance, which make engineers widely use SCBFs as lateral-load resisting systems in buildings and have researchers to develop SCBFs design methods. Compared to the extensive research of SCBF, comparatively little information is currently available on the performance of SCBFs designed and constructed before the early 1990`s. Prior to 1988, concentrically braced frames(CBFs) design requirements were substantially less restrictive. As a result, many existing structures designed to these requirements may not ensure ductility and pose a significant concern in current buildings. In this study, these older frames are referred as non-seismic braced frames(NCBFs). In order to investigate the seismic behavior of NCBFs, finite-element(FE) models of SCBF and NCBF were suggested and verified using case investigation of NCBF conducted on the University of Washington. Using these models, the seismic behavior of NCBF with shared welding shear tab, which is the representative of the types of connections, was established and compared with the seismic performance of SCBF.

Effect of Concrete Strength and Stud Collar Size to Shear Capacity of Demountable Shear Connectors

AbstractIn this paper, a group of demountable shear connectors have been developed and tested to assess their potential and suitability in terms of replacing welded shear studs. The experiments showed that these demountable shear connectors can be easily demounted after testing and have similar capacity and behavior to those of welded shear connectors. After the numerical simulation method had been validated against experimental observation, a parametric study was carried out to understand the effect of concrete grades and stud collar sizes on the shear resistance of demountable shear connections. Simple design calculation methods for welded shear connections or anchoring connections provided in European and American standards were checked to the suitability for assessment of this headed demountable shear connector.

Estimation of friction contribution in the behavior of steel-concrete composite beams with flexible shear connectors

A shear connector, developed to be applied to a composite beam whose steel profile is a thin-walled box profile, displayed much greater flexibility than the conventional welded shear connector, leading to particular issues in the composite beam behaviour. One of these issues is the role played by friction at the interface between the steel profile and the slab which, under particular circumstances, may be relevant for serviceability limit states and also for ultimate limit states. The Brazilian and American Standards do not yet recognize the friction contribution in the behaviour of composite beams, though they recognize this contribution in composite slabs. This paper presents the experimental tests carried out with and without friction contribution on simple supported composite beams with flexible connectors and the numerical models developed to simulate the behaviour of the tested beams. The experimental tests revealed significant increases in strength and stiffness of the composite beam due to friction contribution and the comparisons between numerical and experimental results displayed good correlations.