Weld Strength Research Articles

A review on fracture and fatigue behaviour of FSW joints of Al alloys

Friction stir welding (FSW) is solid state welding process. In this process two similar or dissimilar metallic plates are join using appropriate heat and mechanical forces with the help of rotating tool. Due to mechanical advantages like high strength to weight ratio, aluminium (Al) alloys commonly used in several engineering prospective. Recently, FSW has gained consideration in the automobile, aerospace and marine industries owing various advantages, like high weld strength, low distortion and good fatigue behaviour. This study concentrates on the fracture and fatigue characteristics of Al alloy FSW joints and importance of optimizing FSW process characteristics such as tool rotational speed, travel speed and tool offset, to obtain best joints with improved mechanical properties. This review also highlights the effect of microstructure and residual stresses on the fracture and fatigue behaviour of FSW joints as well as it provides an overall understanding of the fracture and fatigue behaviour of FSW joints of Al alloys.

Microstructure and fracture analysis on MIG welding of Nimonic alloys

Advanced alloy has an essential role in welding process to enhance the performance characteristics. Nimonic alloy has outstanding welding characteristics. The purpose of this work is to analyze the microstructure and fracture analysis of the welded Nimonic alloy joints by employing metal inert gas welding (MIG) welding. In this work, Taguchi analyze was effectively utilized to anticipate the ideal parameters of the input variables such as voltage, welding speed, welding current towards the maximized optimal value of the welded specimen's ultimate tensile strength. In this study, a L9 orthogonal array was employed, and the ultimate tensile strength for the specimen were estimated. The findings reveal that at maximum welding speed and voltage, the specimen has a satisfactory strength bonded joint. Microstructure and fracture analysis were also discussed. The objective of the work is to enhance the ultimate tensile strength of the nimonic welded joints. The optimal welding strength was attained at welding current of 110A, speed of 20 m/s and voltage of 155 V.

Gel-assisted Welding of Epoxy Composite with Ethylene Glycol Mixed Catalyst

Effective and high-strength welding of thermosetting composites is badly in demand and always a challenge in industrial applications. Here, a gel-assisted welding method was proposed for traditional epoxy composites using a gel of 1,5,7-triazabicyclo [4.4.0] dec-5-ene mixed with ethylene glycol (TBD/EG gel) for pretreatment. Firstly, the influence of TBD/EG gel thickness, pretreatment time, pretreatment temperature, and pretreatment after soaking for the welding strength of the epoxy composite was studied. Then, the appropriate TBD/EG gel thickness (2 mm) and TBD/EG gel pretreatment conditions (140 °C for 60 min) were obtained. Compared to the different pretreatment methods for welding, the welding of TBD/EG gel pretreatment is feasible.

Reliable detection of stick welds at resistance spot welding

Resistance spot welding (RSW) of galvanized steel sheets brings a risk of faulty welds in the form of stick-welds. These differ from high-quality spot welds in the way that only the coatings are joined with a material bond, but the base materials are not fused together. Stick-welds can occur, among other things, in critical material combinations with greatly differing sheet thicknesses or with increased wear of the welding electrodes. Due to the significantly different material-specific strengths of zinc and steel, stick-welds do not meet the required weld strengths. Therefore, it is important to reliably prevent or detect the stick-welds. However, the established and most frequently used non-destructive (NDT) method for spot welds by manual ultrasonic testing reaches its limits in this respect, as the fused zinc layers are almost as sound-conductive as proper spot welds. A promising alternative is the method of passive magnetic flux density testing (pMFT) developed at the Technische Universität Dresden, Chair of Joining Technology and Assembly. With this NDT method, the spot welds are first magnetized and their residual flux density on the surface is measured. Due to the different magnetic properties of the used steel alloys and their zinc-coating, clear differences can be measured between correct and stick-welds. This paper shows the experimental design and the developed procedure for evaluating the spot welds on different galvanized steel sheet alloys. In addition, the high potential of integrating this NDT method into fully automated production lines is shown in order to bridge the gap between the highly automated RSW process and NDT, which can only be carried out manually up to now.

Taguchi optimization on friction stir welding of nitinol composite

The alumina welded joints with high quality is fabricated through friction stir welding. Through this experimental investigation, the friction stir welding were made between alumina and carbide based nitinol composite. The boron and titanium carbide based nitinol composite were fabricated through microwave sintering process. The tensile strength of welded joints was estimated and optimized through Taguchi approach. The substance properties of welded joint were evaluated. The interfacial layer formation and morphology of welded joint were investigated through scanning electron microscopy. The analysis of variance was provided the contribution of the friction stir welding factors. The objective of the research work is to enhance the welding strength using different input constrains and their level.

Investigation of Weld Forces and Strength of Friction Stir Welded Polypropylene

Friction stir welding (FSW) is an advanced joining technology specifically developed for welding materials that are difficult to weld (e.g. polymers). Over the last two decades, more and more research has been published on the applicability and development of the technique on polymeric materials. The aim of the present study is to investigate the applicability of the method for welding polymeric materials and to analyse the effect of the parameters of FSW. In the tests, 4 mm thick polypropylene sheets were welded by varying two welding parameters (tool speed (n) and feed rate (vf)) in four levels. Thus, a complete experimental design with 16 measurement points was created. During the welding process, the force components on the tool/workpiece were measured, from which the resultant welding force was calculated and the strength of the joints was characterized by tensile testing. The ratio of the tensile strength of the joints and the tensile strength of the material were used to characterise the process in terms of joint efficiency. During welding, the axial force component (Fz) was the dominant force value. The resultant forces (Fe) decreased with increasing n, while they increased with increasing vf. The tensile strength of the joint, and hence the bonding efficiency, improved with increasing n, while it deteriorated with increasing vf. The ratio derived from the ratio of n to vf was also analysed, with an increase in the ratio showing a decreasing trend in the resulting weld strength and an improving trend in the bonding efficiency.

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.

Investigation Parameters of Resistance Spot Welding For AA1050 Aluminum Alloy Sheets

The parameters of resistance spot welding (RSW) performed on low strength commercial aluminum sheets are investigated experimentally, the performance requirements and weldability issues were driven the choice of a specific aluminum alloy that was AA1050. RSW aluminum alloys has a major problem of inconsistent quality from weld to weld comparing with welding steel alloys sheet, due to the higher thermal conductivity, higher thermal expansion, narrow plastic temperature range, and lower electrical resistivity. Much effort has been devoted to the study of describing the relation between the parameters of the process (welding current, welding time, and electrode force) and weld strength. Shear-tensile strength tests were performed to indicate the weld quality. A weld lobe diagrams were constructed to evaluate the weldability of three sheet thicknesses of this alloy. Most appropriate welding time and electrode force are 5 cycles and 1.75- 2.25 kN respectively. The ranges of the weldability are 14-28, 18-30, and 22-32 kA for 0.6, 1.0, and 1.5 mm sheet thicknesses respectively. A statistical regression analysis was used to demonstrate the relationship of the process parameters and the strength of the weldments. Two empirical equations for each thickness were proposed to estimate the shear tensile strength of the weldments, one for quadratic and the other linear relationship between the process parameters and the strength. There are no significant differences between the equations when applied to the available data.

A Predictive Model for Weld Properties in AA-7075-FSW: A Heterogeneous AMIS-Ensemble Machine Learning Approach

This study addresses the research gap in materials science by developing an integrated predictive model for Ultimate Tensile Strength (UTS), Maximum Hardness (MH), and Heat Input (HI) in AA-7075 Friction Stir Welding (FSW). The aim is to enhance welding procedures, particularly in high-precision industries like aerospace and automotive. By incorporating four control parameters (Tilt Angle, Rotation Speed, Welding Speed, and Shoulder Diameter) and utilizing a Long Short-Term Memory (LSTM) machine learning model, a Heterogeneous Ensemble Machine Learning (He-EM) approach is developed. The Artificial Multiple Intelligence System (AMIS) optimizes the decision fusion strategy of each technique, ensuring the model's effectiveness. Validated using diverse experimental design methods and three datasets, the proposed AMIS He-EM model outperforms existing techniques (GPR, SVM, HE-UWE, and HE-WEDE) by significant margins (35.12%, 24.92%, 22.31%, and 15.48% respectively). The model's robustness is demonstrated, as its performance remains consistent across different experimental design methods. The key finding of this research is the remarkable improvement in accuracy for predicting UTS, MH, and HI in AA7075 FSW. This study highlights the importance of incorporating four control parameters and utilizing the D-optimal design for efficient exploration of the input parameter space. The implications of this research are profound, offering opportunities to optimize welding procedures, improve product performance, and streamline manufacturing processes in industries relying on AA7075 FSW.

Analysis of the Effects of Polarity Variations, Electrode Types, and Cooling Media on the Tensile Strength of ASTM A36 Steel Welded Joints

This research investigates the pivotal role of welding in manufacturing and construction, specifically in the context of material joining for ASTM A36 steel. The study aims to determine the impact of polarity, electrode type, and coolant on the maximum tensile strength of welds. A total of 54 specimens were welded using Shielded Metal Arc Welding (SMAW) with DCEN and DCEP polarities, employing electrode variations of E6013, E7016, and E7018, along with different coolants—Air, Oil, and Saltwater. The results reveal that E7018 welding at a speed of 100 mm/s exhibited the highest tensile strength of 529 MPa, with an average maximum load of 37.35 kN. Conversely, the lowest tensile strength was observed in E6013 welding at 100 mm/s, recording 339 MPa with an average maximum load of 25.84 kN. Additionally, E7018 welding at a speed of 100 mm/60 s showed the highest elasticity of 22.08% with a maximum load of 37.55 kN. These findings contribute valuable insights for optimizing welding processes, thereby enhancing the mechanical integrity of ASTM A36 steel in various industrial applications.
 Highlights:
 
 Significance of Polarity: Investigating the impact of DCEN and DCEP polarities on welded material strength. 
 Electrode Influence: Understanding how E6013, E7016, and E7018 electrodes affect the mechanical properties of welds.
 Coolant Consideration: Analyzing the role of Air, Oil, and Saltwater as coolants in optimizing welding outcomes.
 
 Keywords: Welding, ASTM A36 steel, Polarity, Electrode, Coolant

Structural performance of cold metal transfer welding technique on cold-formed steel flare v-groove welds

The performance and feasibility of a recent welding technique called Cold Metal transfer (CMT) welding technique for Cold-Formed Steel (CFS) welded sections is presented in this paper. The study focuses on understanding the behaviour of flare v-groove welds on back-to-back connected CFS sections subjected to longitudinal shear. A total of thirty lap shear specimens were fabricated and the parameters such as length of the weld and thickness of the weld were varied and tested under longitudinal loading. The weld geometry was observed under an optical microscope after polishing and chemical etching of the weld cross-section to determine the thickness of the weld for CMT flare v-groove welds. Based on the weld cross-section profiles, a set of calibrated welding parameters for 1.5mm CFS section is presented in the paper. The lap shear specimens failed in either transverse plate tearing of the individual cross-section or fracture of the weld at the weld contours. The test results show that AISI design standard yield over-conservative strength prediction and inaccurate failure modes for longitudinal flare v-groove welds. Therefore, a limiting ratio constituting of length of the weld, outstanding flange length, ultimate strength of parent material, and ultimate strength of wire electrode is proposed in the paper to accurately predict the failure mode. Additionally, a modified and reliable design equation is recommended to determine ultimate shear strength of CMT flare v-groove welds subjected to longitudinal loading.

Acoustic monitoring of weld strength in ultrasonic metal welding by tracking welding stages

Ultrasonic metal welding (USMW) is a welding technique often used in the electronic and automobile industries. However, the strength of the welds it produces is influenced by a large number of variables, making USMW difficult to monitor. There is therefore a need for monitoring parameters which can be used across a large number of influencing variables. Such parameters should be closely related to the welding process and the evolution of the weld strength during welding. The goal of this paper is to investigate the usability of the horn and anvil vibrations at the welding frequency as such monitoring parameters. In this study, the horn and anvil vibrations were tracked during welding of copper sheets using laser vibrometers, compared to results in the literature to identify welding stages, and compared to the evolution of the weld strength. To avoid any low sample size bias, 120 welds were used. Their envelopes and their rate of change were extracted and used to identify welding stages. The results showed that the strength of a weld plateaus when it reaches its stage of maximum strength, and that this stage can be identified by both the horn and anvil vibrations using features derived from the envelopes and their rate of change.

Prediction of ultimate tensile strength of friction stir welding joint using deep learning-based-multilayer perceptron and long short term memory networks

Friction stir welding (FSW) is a solid-state joining technique where the joint strength is mainly influenced by three process parameters, namely, spindle speed (N), welding speed (V), and plunge force (Fz). The modelling of complex relationships between the process parameters and joint strength requires many experiments, which is a challenging, time-consuming, and non-economical affair. To tackle this problem, computational mathematical models such as deep learning (DL) can be employed to predict the joint strength reliably. In this paper, DL techniques, namely, deep multilayer perceptron (DMLP) and long short-term memory (LSTM) networks have been proposed for such a purpose. The DL networks were first trained with the FSW experimental data and then, the pre-trained models were used for predicting the weld strength. It was found that the DMLP and LSTM models provided lower prediction errors, which are RMSE of 3.30 and 7.63, respectively, and can be effectively utilized for determining weld quality. The proposed DL-based techniques were further compared with the traditional models – the shallow artificial neural network (SANN) model having an RMSE of 27.11 and the ANFIS model having an RMSE of 5.31. DMLP was found to be superior in determining the weld strength most accurately.

Weld Effective Lengths for Axially Loaded Transverse Plate-to-CHS Connections

Large-scale experimental tests were conducted to evaluate the strength of partial joint penetration (PJP) groove welds in axially loaded transverse plate-to-circular hollow section (CHS) X-connections. Six connections, comprising 12 joints, were designed to investigate the influence of branch-to-chord width ratio and chord slenderness on weld strength. Nonuniform strain distributions were observed in the branches adjacent to the joints, indicating that the welds were only partially effective. Results from the experimental tests were used to evaluate design guidance for PJP welds in the American steel design standard, AISC 360-16, and a weld effective length equation is proposed for axially loaded plate-to-CHS connections.

The Fuel-efficient Vehicle Frame for Energy Saving Competition Design and Analysis Based on ABAQUS

Non-load-bearing body, with an independent frame, is subject to gravity load provided by itself and load-bearing components, and also subject to excitation load from the road and engine, etc. Therefore, the rigidity and strength of the frame must be ensured in the frame design, so the welding strength in the frame fabrication process is extremely important. In this paper, the basic characteristics of the frame are analyzed by using finite element technology, and the welding displacement, stress, and strain of the frame are studied in detail. The main research contents are as follows:The thesis takes the frame of energy-saving racing car as the research object. According to the design requirements of the official committee, firstly, the 3D model software is used to design the geometric model of the racing car and rationalize the spatial layout of the frame. Secondly, the finite element model of the frame of the energy-saving racing car is established by Abaqus software, and through the process of parameter sett and load application, the stress, deformation, and modal performance of the frame under each working condition are derived. Finally, the structural parameters of the frame are compared to see whether the safety factor is achieved, so as to conclude whether the frame is qualified and whether it meets the lightweight design requirements of the racing car.

Development of high strength welding consumable for arc welding carbon steels

High-tensile gas metal arc welding (GMAW) consumables are becoming increasingly common in industries such as Railways, Lifting, and Excavation (L&E) due to the need for superior mechanical performance. AWS ER90S-G grade welding consumable (with a minimum of UTS 620 MPa) is widely used alongside the commonly used AWS ER70S-6 (with a minimum of UTS 480 MPa). However, the microstructure of high-tensile wire rods often contains hard phases such as martensite, making it difficult to draw. To overcome this challenge, ER90S-G grade welding wire development was studied using microstructural analysis, mechanical testing, and physical simulations. The input material (wire rod) underwent mechanical descaling, dry drawing, intermediate annealing, wet drawing, copper coating, and spooling to produce a final wire with a diameter of 1.2 mm. A suitable microstructure (Ferrite + Carbides) is crucial for smooth wire drawing, and it is highly recommended to anneal at the intermediate stage to avoid wire breakages.

STUDY THE INFLUENCE OF WELDING PARAMETERS BY TAGUCHI’S DESIGN ON THE MECHANICAL PROPERTIES OF WELDED MILD STEEL (S235JR)

Gas metal arc welding is a leading process in fusion welding with increased productivity and good quality. The welding parameters are crucial in determining welding quality, cost, and productivity. In this study, mild steel with a 10-mm-thick sheet was welded by gas metal arc welding under predetermined parameters of welding voltage, wire feed speed, and groove shape. The analysis made by Taguchi’s design to investigate the effect of these parameters on tensile strength and Vickers micro-hardness of welding. The microstructure of the fusion zone and heat-affected zone is analyzed to monitor their change concerning the mechanical properties. The results showed that tensile strength decreased with decreased hardness. Also, the tensile strength and hardness were higher (a maximum of 305 MPa and 2170 HVN) at welding made at a lower voltage (20 volts), lower wire feed speed (5.9 m/min), and V-shaped base metal groove. The increased precipitation of perlite structure was shown during welding, which has lower tensile strength and hardness. Widmanstatten ferrite and coarser α-ferrite were presented for welding with a lower cooling time. Taguchi’s design showed that voltage at 20 volts has the highest effect on tensile strength, followed by wire feed speed at 5.9 m/min and V-shaped welding.

The mechanical properties of dissimilar/similar polymer materials joined by friction stir welding

Joining dissimilar materials is important in engineering studies to reduce costs, lighten structures, and take advantage of the superior properties of the materials. However, the different chemical compositions, physical, and mechanical properties of dissimilar materials make the joining process difficult. To overcome the limitations of traditional joining techniques, there is an increasing interest towards innovative welding methods such as ultrasonic welding, laser welding, friction stir welding, and so on. In this study, friction stir welding was used to join different types of polymer materials. Polylactic acid (PLA Plus) plates were 3D printed and welded with High Density Polyethylene (HDPE) to create PLA Plus/PLA Plus, HDPE/HDPE, and PLA Plus/HDPE connection pairs. Two different pin profiles (triangle and square), rotational speed (1000 and 1500 rpm) and feed rate (30 and 50 mm/min) were used in the FSW process. Tensile tests were performed to determine the weld strength after FSW. In addition, the hardness changes in the heat-affected zone and in the weld zone were evaluated. Finally, optical inspections were made on the welded samples to identify welding defects. The results showed that the highest weld strength was obtained with the triangular pin profile in PLA Plus/PLA Plus and PLA Plus/HDPE material pairs, and while with the square pin profile in HDPE-HDPE pairs. PLA Plus has been found to be a more suitable material for Friction Stir Welding compared to HDPE. Welding defects caused by changes in welding speed and tool rotation speed were identified in the material pairs.

STUDY OF WELD SEAM STRENGTH PARAMETERS

   In the scientific work, the study of the strength parameters of an ultrasonic weld on the example of artificial fur is considered. A characteristic trend in the change in the raw material base of the textile industry in all developed industrial countries of the world is the steady growth in the production and consumption of chemical fibers. This is due to a number of advantages of chemical fibers, in particular, the cheapness and availability of the raw material base, and the important properties of chemical fibers. Despite the foregoing, the use of new, chemical fiber-containing textile materials in the production of clothing by the traditional filament method has caused a number of problems, to eliminate which it has become expedient to use welding methods for the manufacture of garments. products from fabrics containing chemical fibers, which are based on the thermoplasticity of these materials. In this scientific article, the strength of an ultrasonic weld of artificial fur, changes in the structure of the area surrounding the weld, and the reasons for the decrease in the strength of the weld were studied by X-ray diffraction analysis. The results of the study showed that the reason for the decrease in the strength of the artificial fur weld is the uneven structure of the area surrounding the weld, a sharp transition from the weld to the base material. This can be eliminated by improving the design of the working bodies of the apparatus used for ultrasonic welding.

Online evaluation of resistance spot welding quality and defect classification

Resistance spot welding (RSW) is widely used in industrial product manufacturing, and weld quality is critical to ensure the safety and reliability of mechanical structures. With product quality improvement, the online monitoring of weld quality has become an urgent issue. Therefore, a method for online evaluation of RSW quality and automatic classification of welding defects based on mild steel is proposed. By acquiring the welding current and electrode voltage signals of the welding process in real time, a finite impulse response low-pass filter based on the Blackman window function is designed to perform zero-phase filtering of the dynamic resistance (DR). The influence of three welding parameters on the nugget diameter and shear strength of spot welding of DC01 mild steel was studied through the control variable method to determine the optimum welding parameters. Since the main defects of the RSW process are classified as expulsion defects and incomplete fusion defects, minor adjustments were made to the welding parameters to produce expulsion and incomplete fusion defects. Features in the time domain are extracted from the DR curves signals of normal, expulsion, and incomplete fusion welding spots, and the performance of the extracted features in the classifier is analyzed. Improvements are made to classify normal and expulsion spots with low accuracy, a new method is proposed that can accurately classify the quality of the welding spots. Through online evaluation tests of quality on 200 welding spots, the online evaluation test showed results that closely matched the validation test results. The results of the classification performance tests show that this study can be used for online evaluation of RSW quality and automatic classification of the welding spot defects of the DC01.