Tensile Shear Fracture Load Research Articles

Optimization investigation of parameters for spot-welding of AA2014 and AISI316 dissimilar alloys

The objective of the research was to determine the exact process parameters required for spot-welding AA2014 and AISI316 alloys. The main focus was on achieving particular welding results, including nugget diameter, hardness, and tensile shear fracture load (TSFL). The central composite rotatable design model within the framework of a Response Surface Methodology (RSM) optimization approach, the study sought to intensify key spot weld process factors. The mechanical characteristics and nugget diameter of the welded joints were analyzed by carefully examining these factors to determine their significant effects. The investigation yielded crucial insights, revealing that the highest strength of welded joints, characterized by a nugget diameter of 5.982 mm, hardness of 149.6 VHN, and TSFL of 2.355 KN, was achieved at 3.4 kgf, when accompanied by 60 W power and a 2.5s duration. Notably, power emerged as the predominant factor driving the spot-welding process. Furthermore, microhardness and TSFL displayed direct correlations with power, while nugget diameter exhibited an inverse relationship. Moreover, rigorous statistical analyses, including F-tests and ANOVA, provided robust validation, indicating that the observed values fell comfortably within a 99.5% confidence interval for hardness, nugget diameter, and TSFL. These meticulously derived conclusions represent a significant stride towards establishing more standardized and efficient spot-welding protocols, particularly beneficial for the manufacturing sectors dealing with mild steel and aluminium materials.

Joining of Al-Alloy Tubes by Carbon Steel Tubes using MPW Technique

Background/ Objectives: Joining aluminum alloys with low carbon steel (DC01) through fusion welding is a challenging task due to the occurrence of solidification defects like porosity, alloy segregation, and hot cracking. However, these issues can be addressed by employing solid-state welding techniques like explosive welding and MPW (magnetic pulse welding). MPW is a cost-effective and high-speed solid state welding method that involves creating joints in an overlap configuration. Methods: The MPW technique was employed to join dissimilar aluminum alloy AL 7075T6 hollow tube and DC01 steel rod in this study. A central composite design model was created to analyze the relationship between key MPW process parameters, including stand-off distance (SoD), overlap length, and discharge energy, and the bonding strength of the joints. Experimental setups were established and correlate with tensile-shear fracture load and interface hardness of the joints with the MPW process parameters. Findings: It is understood that the maximum TSFL of 2.404 kN was obtained under the welding condition of 23kJ discharge energy, 2.25 mm Stand-off distance, 8.5 mm overlap length, which is the optimum MP welding state for AA 7075 T6 with DC01 and confirmed by RSM. In addition, the cultivated connection can be aptly leveraged to anticipate the TSFL of MPW joints with a 95% confidence level. Novelty: The parametric mathematic samples were developed for forecasting TSFL of joints. The MPW parameters were optimized to enhance TSFL of joints. Aluminium alloys with low carbon steel joints were developed using MPW for cars and ships applications without fusion welding defects. Keywords: Magnetic Pulse Welding, Dissimilar Joint, (RSM) Response Surface Methodology, Tensile Shear-Fracture Load

Ultrasonic spot-welding of AA 6061-T6 aluminium alloy: Optimization of process parameters, microstructural characteristics and mechanical properties of spot joints

The ultrasonic spot welding (USW) is used to develop the lap joints of AA 6061-T6 aluminium alloy because it is difficult to spot weld using resistance spot welding (RSW) and laser beam spot welding (LBSW) processes due to its high electrical conductivity, thermal conductivity and light reflectivity respectively. The main objective of this investigation is to optimize the USW parameters specifically welding time (s), amplitude (%) and pressure (bar) for enhancing the tensile shear fracture load (TSFL) bearing capability of AA 6061-T6 aluminium alloy lap joints for automotive applications. The statistical response surface methodology (RSM) was utilized for generating strength prediction models (SPM) and validated using analysis of variance (ANOVA). The RSM is widely used for optimizing the process parameters as it provides greater information such as optimum conditions, direct effect of process parameters and performance prediction from limited number of experiments compared to other optimization techniques. The response surfaces were created using RSM and analyzed. The effect of USW parameters on macrostructure, microstructure and TSFL of USW joints was studied. From the results, it was observed that the USW joints created using the welding amplitude of 100%, welding time of 21 s and welding pressure of 6 bar exhibited greater TSFL capacity of 5.08 kN. The SPM accurately predicted the TSFL of USW joints within 5% error on 95% confidence. Welding pressure disclosed major effect on TSFL of USW joints followed by welding amplitude and time. The greater TSFL of USW joints is imputed to the better coalescence of weld surfaces and refined microstructure.

EFFECTS OF PRE-OXIDATION ON HOT CORROSION RESISTANCE OF Al–Si COATINGS

The joining of aluminium (Al) and copper (Cu) is an essential spot weld for renewable energy applications due to its excellent thermal and electrical conductivity. It is challenging to produce a high-quality Al-Cu spot weld using traditional techniques and the durability of a weldment is also uncertain. A new welding technique that is effective and suitable for spot welding Cu and Al is friction-melt-bonding (FMB) spot welding. The process parameters employed during welding have a strong impact on the quality of a weld. The strategy for integrating the FMB process characteristics, such as tool rotational speed and dwell time, into a mathematical model that may be used for predicting the process parameters of dissimilar spot joints, was the focus of this study. The findings showed that the tensile shear fracture load (TSFL) was significantly influenced by the tool's rotational speed and dwell time. Optimization was carried out using the response surface methodology (RSM) to find the best FMB process parameters for making a dissimilar spot weld of AA 6061-Cu.

Tensile shear fracture load bearing capability, softening of HAZ and microstructural characteristics of resistance spot welded DP-1000 steel joints

Abstract The main objective of this investigation is to enhance the tensile shear fracture load (TSFL) bearing capability and minimize softening in heat affected zone (HAZ) of resistance spot welded DP-1000 steel spot joints for automotive applications. The lap tensile and cross tensile shear fracture load tests (LTSFL and CTSFL) were conducted. The process parameters were optimized using numerical and graphical optimization techniques to maximize the TSFL capability of spot joints. The microstructure of spot joints was studied using optical microscopy and correlated to TSFL and hardness of spot joints. Results showed that DP-1000 steel spot joints made using the welding power of 70 W, welding time of 1.0 s, electrode pressure of 4.25 MPa showed maximum LTSFL of 22 kN and CTSFL of 9.1 kN. The parametric optimization showed 46.66, 45.77, 22.33 and 9.87% increase in LTSFL, CTSFL, nugget zone hardness and HAZ hardness of DP-1000 steel spot joints. The higher TSFL and nugget hardness of spot joints is mainly attributed to the evolution of finer martensitic sandwiching ferrite phases in nugget zone and lower softening of HAZ than other joints. Welding power showed significant influence on TSFL of spot joints followed by welding time and electrode pressure.

The Effect of Resistance Spot Welding Parameters on Microstructure and Strength of DP800 Steel Joints Using Response Surface Methodology

Abstract The main objective of this paper is to analyze the direct and interaction effect of resistance spot welding (RSW) parameters on microstructure and strength of DP800 steel joints using response surface methodology (RSM). The DP800 steel sheets were spot welded in straight lap and cross lap joint configuration using RSW. The relationship between the RSW parameters, tensile shear fracture load (TSFL) and nugget zone hardness (NZH) was established employing statistical regression analysis and validated using Analysis of Variance (ANOVA). The DP800 steel joints made using welding current of 5.0 kA, electrode pressure of 4.0 MPa, and welding time of 1.50 s displayed maximum STRAIGHT-TSFL of 21.7 kN, CROSS-TSFL of 17.65 kN, and NZH of 589 HV0.5 respectively.

Assessment of Rotational Speed and Plunge Rate on Lap Shear Strength of FSSW Joints of AA7075/Mild Steel

Friction stir spot welding (FSSW) is an upgraded version of the friction stir welding process. This welding process can be used to replace permanent and temporary fastens such as bolts and nuts, screws, rivets, and welds. FSSW can be utilized to replace steel rivets in aircraft structure fabrication due to the elimination of time required to complete the joints and special tools. Moreover, the joining of dissimilar joints is very difficult due to the formation of different proportions of intermetallic compounds in the weld region. A lot of process parameters may influence the quality of the joints. This investigation analyzes the effect of speed of tool rotation and plunge rate of tensile shear fracture load of AA7075 mild steel dissimilar metal joints. From the observation, the joint fabricated with a speed of tool rotation of 1000 rpm and a plunge rate of 6 mm/min yielded a maximum shear fracture load of 9.86 kN. This weld strength enhancement may be linked to the formation of dynamic recrystallization and density distribution of strengthening precipitates.

Resistance spot welding of advanced high strength steel for fabrication of thin-walled automotive structural frames

This investigation presents the process parameter optimization of resistance spot welded (RSW) advanced high strength steel (AHSS) joints using response surface methodology (RSM) for fabrication of thin-walled automotive structural frames. Resistance spot welding (RSW) is used to minimize solidification cracking, heat affected zone (HAZ) softening and distortion related problems in joining of thin advanced high strength steel (AHSS) sheets. The three factor – five level central composite design (3 × 5 - CCD) matrix pertaining to the minimum number of experiments was chosen for designing the experimental matrix. The polynomial regression analysis was employed to develop the empirical relationships between RSW parameters and performance characteristics of AHSS joints. The 3-dimensional (3D) response surfaces were developed using RSM which shows the optimal process window to enhance the strength of spot joints. The RSW joints made using welding current of 5.0 kA, electrode pressure of 4.0 MPa, and welding time of 1.50 s displayed maximum lap tensile shear fracture load (LAP-TSFL) of 21.7 kN, cross tensile shear fracture load (CROSS-TSFL) of 17.65 kN, and nugget zone hardness (NZH) of 589 HV0.5 respectively. The results of ANOVA indicates that welding current, electrode pressure and welding time significantly influences the LAP-TSFL, CROSS-TSFL and NZH of joints respectively. The superior TSFL and NZH of joints made using optimized RSW parameters is attributed to the evolution of needle/lath martensite in nugget zone .

Investigation on microstructural features and tensile shear fracture properties of resistance spot welded advanced high strength dual phase steel sheets in lap joint configuration for automotive frame applications

Abstract The main objective of this research paper is to study the microstructural features and mechanical properties of resistance spot welded advanced high-strength steel of dual phase grade in lap joint configuration which is mainly employed in sheet form for fabrication of the automotive structure. Resistance spot welding (RSW) being a solid-state welding (SSW) process is used to overcome the problems in fusion welding of AHSS-DP steel such as heat affected zone (HAZ) softening, solidification cracking and distortion which significantly deteriorates the mechanical properties of AHSS-DP800 steel joints. The straight lap (SL-TSFL) and cross lap tensile shear fracture load (CL-TSFL) of spot joints were evaluated. Optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were used to characterize the weld nugget. The X-ray diffraction (XRD) results are also presented for phase identification in the weld nugget. The fracture surface of failed TSFL specimens was analyzed using SEM. The lap joints made using RSW disclosed superior SL-TSFL, CL-TSFL, and WNZH of 21.7 kN, 17.65 kN, and 589 HV0.5 The superior joint strength and hardness of the weld nugget zone are correlated to the evolution of lath martensite in the nugget zone.

Influence of resistance spot welding process parameters on dissimilar austenitic and duplex stainless steel welded joints

This paper examines the impact of welding parameters on tensile shear fracture load, nugget geometry and microstructure of resistance spot welds (RSW) of austenitic stainless steel AISI 316 L and duplex stainless steel 2205 under lap shear loading condition. The macroscopic examination resulted that many of the nugget lengths were nearer to and higher than the AWS recommended value 4√t and failed at higher tensile shear load. Nugget height for DSS 2205 side was higher in comparison with AISI 316 L due to higher thermal conductivity of duplex stainless steel. Three welding parameters mainly welding current of 9 kA, heating cycle of 9 and electrode tip diameter of 6 mm were discovered as most effectual parameters on the tensile shear load and microstructure of weldments. Heterogeneous hardness was observed in the fusion zone due to the transition of equiaxed to columnar grains takes place in the both sides of nugget edge. DSS HAZ nearby BM observed higher hardness and ASS HAZ nearby BM reported lower hardness. WMZ Microstructure confirmed that thickness of austenite layers increased with heat input. Also, an unmixed zone in the microstructure identified as HAZ which contains delta ferrite. Scanning Electron Microscope (SEM) images in the nugget zone for different welding parameters confirmed that Intra-Granular Austenite (IGA) highly developed at higher welding current. SEM fractrograph for the tensile sheared specimens at higher and lower heat input confirmed the ductile type fracture even failed at Inter-Facial (IF) mode. Nugget area and nugget hardness were positively correlated with Tensile Shear Fracture Load (TSFL).

AN EMPIRICAL RELATIONSHIP FOR ESTIMATING METALLURGICAL AND MECHANICAL BEHAVIOR OF RESISTANCE SPOT WELDED DP800 STEEL JOINTS

Similar joints of DP800 (Dual Phase) steel in lap joint configuration were fabricated using resistance spot welding (RSW) process. The process parameters were optimized using DOE (design of experiments) and the welds joints were fabricated using the obtained DOE matrix. The tensile shear fracture load (TSFL) of joints was evaluated using universal testing machine. Microhardness variations across the weld cross-section was recorded using Vickers’s microhardness tester. Microstructural features were analyzed using optical microscopy (OM) and scanning electron microscopy (SEM). From this investigation, it is understood that increase in welding current increases the nugget zone size and it led to increasing the degrease of softening in the HAZ. The tensile shear strength is found to increase with increase in welding current up to a certain limit and then it decreases. The microhardness profile shows a peak hardness in nugget zone and the hardness is lower in the HAZ. The softening of HAZ is mainly attributed to inter-critical heating during welding.

Comparative study on characteristics of laser welded-brazed AZ31/Ti-6Al-4V lap joints with and without coatings

AZ31B and Ti-6Al-4V were lap welded using laser welding-brazing technique with and without Ni, Cu, and Cu-Ni coatings under similar welding conditions. The effect of the coatings on the appearance, microstructural evolution, and mechanical properties of the joint was studied. For the uncoated joint, only Ti3Al phase formed along the entire brazed interface. In comparison, Ti3Al phase was observed at direct irradiation and middle regions, whereas, Ti2Cu phase was produced at the weld toe region of Cu-added joint. For Ni- and Cu-Ni-coated joints, Ti2Ni mingled with Ti3Al interfacial reaction products evolved from the direct irradiation region to the weld toe region. Interestingly, the thickness of Cu-Ni joint mixed reaction layer was less than the critical thickness of 10 μm. The Cu-Ni-coated joint sustained the highest tensile shear fracture load of 2014 N (which was about 100% higher than that of the uncoated joint), followed by the Ni- and Cu-added joints with 1795 N and 1680 N, respectively. The fracture mode of the uncoated and Cu-added joints was interfacial failure, whereas, FZ fracture with typical dimple feature was observed for both Ni and Cu-Ni joints.

Dissimilar materials joining of metal/carbon fibre reinforced plastic by resistance spot welding

ABSTRACTDissimilar materials joining of metal to carbon fibre reinforced plastic (CFRP), which consisted of PA6, modified polypropylene (PP) or polyphenylene sulphide (PPS) as matrix polymer with short carbon fibre, was performed using series resistance spot welding (series-RSW). The metal plate was placed on CFRP plate as the lap joint, and electrodes of series-RSW were pressed only on the metal plate side. The metal around the electrode was heated by electrical resistance heating, and the thermoplastic near the interface was slightly melted by the heat conduction from heated metal. The objectives of this research are to confirm the possibility of direct joining of CFRP and metal, and to investigate the effects of the heat input during series-RSW, silane-coupling treatment and chemical structure of matrix plastics on the joint properties.The direct joint formations of SUS304 to CFRP (PA6) and CFRP (PP) were accomplished, and CFRP (PPS) was not. The joining area, which corresponding to the melted area of CFRP, enlarged with increasing the welding current and welding time, therefore, the tensile shear fracture load also increased. The silane-coupling treatment for metal surface was highly effective to increase the joining strength. The maximum tensile shear strength of about 13 MPa was obtained for SUS304/CFRP (PA6) joint.

Effect of silane coupling on the joint characteristics of friction lap joined Al alloy/CFRP

ABSTRACTDissimilar materials joining of an A5052 plate and a carbon fibre reinforced thermoplastic (CFRTP), which consisted of polyamide 6 (PA6) with 20 wt% carbon fibre addition, was performed using friction lap joining (FLJ) with the Al alloy plate as a top and the CFRTP plate as a bottom. The joint characteristics were evaluated to investigate effects of the surface treatment by the silane coupling treatment for A5052 and the joining speed on the joining properties. The joint strength was increased by inducing the silane coupling treatment for the A5052 plate surface. The tensile shear fracture load of the silane coupling treated FLJ joint increased by increasing the joining speed up to 6.67 mm/s and then decreased. The maximum tensile shear fracture load of 5.0 kN was obtained at the joining speed of 6.67 mm/s, and the fracture occurred at the CFRTP base plate with the joint efficiency of 97%. The shear strength of the joint interface of the joint formed at the joining speed of 1.67 mm/s, which fractured at the joining interface by the tensile shear test, was estimated to be about 19 MPa. The covalent bondings between the A5052 plate and the silane coupling layer, and the silane coupling layer and the CFRTP plate were indicated by inducing the silane coupling treatment.

Resistance spot welding of metal/carbon-fibre-reinforced plastics and applying silane coupling treatment

ABSTRACTDissimilar materials joining of SUS304 and carbon-fibre-reinforced plastics consisting of short fibres and thermoplastics was performed. The materials were joined by series resistance spot welding. The electrodes were pressed on the metal plate of the lap joint of metal/carbon-fibre-reinforced plastics. The SUS304 plate was heated by resistance heating, causing the thermoplastic near the interface to melt slightly because of heat conduction. SUS304 could be joined directly to carbon-fibre-reinforced polyamide and modified polypropylene, but not to polyphenylene sulphide. The joining area increased with an increase in the welding current and welding time, so did the tensile shear fracture load. Furthermore, the silane coupling agent treatment of SUS304 was highly effective in increasing the joining strength.

Identifying combination of friction stir welding parameters to maximize strength of lap joints of AA2014-T6 aluminium alloy

AA2014 aluminium alloy (Al–Cu alloy) has been widely utilised in fabrication of lightweight structures like aircraft structures, demanding high strength to weight ratio and good corrosion resistance. The fusion welding of these alloys will lead to solidification problems such as hot cracking. Friction stir welding is a new solid-state welding process, in which the material being welded does not melt and recast. Lot of research works have been carried out by many researchers to optimise process parameters and establish empirical relationships to predict tensile strength of friction stir welded butt joints of aluminium alloys. However, very few investigations have been carried out on friction stir welded lap joints of aluminium alloys. Hence, in this investigation, an attempt has been made to optimise friction stir lap welding parameters to attain maximum tensile strength using statistical tools such as design of experiment, analysis of variance, response graph and contour plots. By this method, it is found that maximum tensile shear fracture load of 12.76 kN can be achieved if a joint is made using tool rotational speed of 900 rpm, welding speed of 110 mm/min, tool shoulder diameter of 12 mm and tool tilt angle of 1.5°.

Identifying Combination of Friction Stir Welding Parameters to Maximize Strength of Lap Joints of AA2014-T6 Aluminum Alloy

Abstract AA2014 aluminum alloy (Al-Cu alloy) has been widely utilized in fabrication of lightweight structures like aircraft structures, demanding high strength to weight ratio and good corrosion resistance. The fusion welding of these alloys will lead to solidification problems such as hot cracking. Friction stir welding is a new solid state welding process, in which the material being welded does not melt and recast. Lot of research works have been carried out by many researchers to optimize process parameters and establish empirical relationships to predict tensile strength of friction stir welded butt joints of aluminum alloys. However, very few investigations have been carried out on friction stir welded lap joints of aluminum alloys. Hence, in this investigation, an attempt has been made to optimize friction stir lap welding (FSLW) parameters to attain maximum tensile strength using statistical tools such as design of experiment (DoE), analysis of variance (ANOVA), response graph and contour plots. By this method, it is found that maximum tensile shear fracture load of 12.76 kN can be achieved if a joint is made using tool rotational speed of 900 rpm, welding speed of 110 mm/min, tool shoulder diameter of 12 mm and tool tilt angle of 1.5°.

Optimization of Electrical Resistance Spot Welding and Comparison with Friction Stir Spot Welding of AA2024-T3 Aluminum Alloy Joints

Electrical resistance spot welding (ERSW) is an ideal process for joining sheet metal assemblies. Nowadays, aluminum alloys are increasingly being used in automotive industries in order to minimize the inertia. It is known that the process parameters play a vital role to determine the desired weld strength. In this study, an empirical relationship was established to predict the tensile shear fracture load (TSFL) of electrical resistance spot welded AA2024-T3 aluminum alloy joints with sheet thickness of 2.7 mm. A central composite rotatable design with four factors and five levels was chosen to minimize the number of experiments. Response surface methodology was used to optimize the process parameters. And TSFL of optimized electrical resistance spot welded joint was compared with TSFL of optimized friction stir spot welded AA2024-T3 aluminum alloy joint. However, ERSW could be used for joining of aluminum alloys; FSSW exhibited the maximum TSFL at the optimized condition.

Optimizing the Friction Stir Spot Welding Parameters to Attain Maximum Strength in Dissimilar Joints of Aluminum and Carbon Steel

The present investigation is aimed at optimizing the friction stir spot welding (FSSW) process parameters such as tool rotational speed, plunge rate, dwell time and tool diameter ratio, to attain the maximum strength in dissimilar joints of AA6061 aluminum and carbon steel. Experiments were conducted according to the four factor, five level central composite rotatable design matrix. Strength of the joints was evaluated by means of single lap shear test. Optimization was done by response surface method (RSM). A maximum tensile shear fracture load (TSFL) of 9.46 kN was exhibited by a joint welded using following parameters: tool rotational speed of 1000 rpm, plunge rate of 4 mm/ min, dwell time of 5 sec and tool diameter ratio of 3.0.

Optimizing the Friction Stir Spot Welding Parameters to Attain Maximum Strength in Al/Mg Dissimilar Joints

This paper discusses the optimization of friction stir spot welding (FSSW) process parameters for joining Aluminum alloy (AA6061-T6) with Magnesium alloy (AZ31B) sheets. Prior to optimization an empirical relationship was developed to predict the Tensile Shear Fracture Load (TSFL) incorporating the four most important FSSW parameters, i.e., tool rotational speed, plunge rate, dwell time and tool diameter ratio, using response surface methodology (RSM). The experiments were conducted based on four factor, five levels central composite rotatable design (CCD) matrix. The maximum TSFL obtained was 3.61kN, with the tool rotation of 1000 rpm, plunge rate of 16 mm/min, dwell time of 5 sec and tool diameter ratio of 2.5.