Characteristics Of Welded Joints Research Articles

A Study on Crack Initiation and Propagation of Welded Joints under Explosive Load

Welded joints in naval ship hull structures are weak areas under explosive load, but there are relatively few studies investigating the failure characteristics of welded joints through dynamic fracture and explosion tests. In order to explore and predict the failure characteristics of welded joints under explosive load, instrumented Charpy impact tests, explosion tests, and numerical simulations were carried out. The dynamic fracture toughness of ultra-high strength ship hull structural steel welded joints was obtained, and the dynamic stress intensity factors, together with the correlation between stress wave and crack propagation at different positions, were acquired. The results showed that the stress state at the crack tip of a Charpy impact specimen was consistent with that of a welded joint under explosive loads, and the crack initiated when the dynamic stress intensity factor exceeded the dynamic fracture toughness. The results indicated that the dynamic fracture toughness obtained by instrumented Charpy impact tests could be used to predict the crack initiation characteristics of welded structures under explosive load, and the stress wave at the crack tip was basically perpendicular to the crack propagation surface and promoted the rapid propagation of cracks.

Investigating the weld joint characteristics of AZ31 and AZ91 magnesium alloys produced by friction stir welding

ABSTRACT In this work, FSW was used to join AZ31 and AZ91 magnesium (Mg) alloys to investigate the mechanism behind joint formation and its mechanical performance. The cross-sectional microstructure of the weld zone clearly indicated a strong metallurgical bonding between AZ31 and AZ91 sheets in addition to the mechanical interlocking due to the mixing of both base materials. Uniform hardness (62.9 ± 4.5 HV) was recorded in the weld joint and the values were between AZ31 (59.8 ± 2.4 HV) and AZ91 (78.7 ± 19.5 HV). Tensile test results demonstrated decreased strength (145 ± 4.2 MPa) compared with the base alloys (265 ± 7.3 MPa and 190 ± 4.8 MPa for AZ31 and AZ91, respectively. Ductility was noticed as decreased as reflected by the lower % of elongation for the weld joint compared with both AZ31 and AZ91 base materials. The fractography studies of the samples suggest a brittle mode of fracture in the weld joint similar to that of AZ91 base material.

Explosive weld joint characteristics of Copper-Tantalum via simulation

This report aims to examine the effects of impact velocity, impact depth, and impact orientation on the Cu–Ta weld joint of the explosive welding process via MD simulation. The findings indicate that the residual shear stress in the welded block mostly increases as the impact velocity rises. The bottom Ta block is more severely distorted than the higher Cu block due to the impact direction. During the tensile test, three stress zones can be identified including the low-stress Cu block, the high-stress Ta block, and the medium-stress weld joint in the middle of the samples. The weld joint position is lower than the median line of the welded block. The Cu–Ta welded block with 500 m/s impact velocities had the highest ultimate tensile strength (UTS) value of 6.49 GPa. With increasing impact depth, the atomic strain level, residual shear stress, and weld joint dimensions all noticeably increase. The Cu–Ta welded block with an impact depth of 7.5 Å has the greatest UTS values, measuring 11.65 GPa, because of its well-crystal structure. Changing the impact orientation does not result in a dramatic change in atomic strain. Orientation (001) vs (001) has the highest strain and stress rates. With an impact orientation of (110) vs. (111), the Cu–Ta welded block gets the highest UTS value of 8.03 GPa compared to other orientations.

Development of a novel fabricating thin-walled TA2 titanium tube via high-frequency induction welding

Due to the problems of low welding efficiency, large heat-affected zone, and poor welding quality in the process of welding thin-walled titanium tubes by argon arc welding, there are few studies on the use of high-frequency induction welding (HFIW) of thin-walled titanium alloy tubes. The evolution law of weld microstructure and mechanical properties of the thin-walled titanium tube needs to be further studied because of rapid welding speed and the small heat-affected zone of HFIW. Therefore, a novel manufacturing method via high-frequency induction welding is proposed in this paper to solve the existing problems. With an industrial-grade titanium TA2 tube (wall's thickness is 0.5 ​mm) as the research object, a comparative study is conducted in this research to examine the morphology, microstructure, microhardness, and tensile characteristics of welded joints at different welding power. The findings demonstrated a significant efficacy of HFIW in resolving these challenges. The mechanical properties and microstructue of heat-affected zone (HAZ) were characterized. The lowest hardness is measured at 202 HV, while the base material was recorded as 184 HV, when the welding speed of HFIW is set at 50 ​m/min. Meanwhile, the heat-affected zone has the highest hardness at 224 HV, a tensile strength of 446.8 ​MPa and a post-fracture elongation of 16%. The results showed that HFIW can not only greatly improve the welding efficiency, significantly improve the microstructure of weld joint and HAZ, and improve the mechanical properties of thin-walled titanium pipe, but also provide a highly feasible welding method for welding ultra-thin-walled pipes.

A Study on Mechanical/Metallurgical Characteristic of Welded Joints According to Heat Input and Gap in Al/Cu Laser Welding

The electrical connectivity and tensile strength between battery components are crucial factors for enhancing battery performance in electric vehicles. In this study, the welding characteristics of aluminum-copper welded joints manufactured using the multi-core laser welding process were studied according to the output power of core/ring laser. Moreover, the tensile strength change behavior according to various welding processes, such as single/two-line welding, and welding gap distance were measured. The results revealed that increasing the output power of the ring beam led to an increase in the tensile strength. However, excessive laser power would increase convection between aluminum and copper during welding and cause defects owing to the difference in the solidification temperature between the two materials. In addition, the mechanical properties were improved by increasing the distance between the two lines of straight laser welding. As the spacing increased, the fraction of the equiaxed microstructure increased, and grain growth was suppressed to improve mechanical properties.

Mechanical characteristics of welded joints of high-strength titanium alloys produced by various welding methods

Mechanical characteristics of welded joints of high-strength titanium alloys produced by various welding methods

Влияние геометрии наконечника сварочного инструмента на характеристики растяжения соединений сплава АА8011, полученных сваркой трением с перемешиванием

Introduction. Aluminum alloys are in abundant demand of shipbuilding and aircraft industries. This study emphasizes on the effects of two different tool pin profiles on the tensile characteristics of welded joints made of AA8011 aluminum alloy welded joints. The joining technique used is friction stir welding (FSW) due to its unique characteristics such as very low heat affected zone when joining in a solid state. The microstructure and mechanical properties of the welded joint are influenced by the geometry of the tool and such parameters as rotational speed and traverse speed of the tool. The methods of investigation. The experiments on FSW were performed on universal milling machine with taper cylindrical and cylindrical threaded tool pin profiles using the three different combination of tool rotational and traverse speed (a) 320 rpm, 45 mm/min; b) 400 rpm, 50 mm/min; c) 575 rpm, 60 mm/min.). To analyze the joint characteristics, tensile tests were conducted and ultimate tensile strength as well as joint efficiency was calculated for individual joint. Results and Discussion. Based on the revised results, it is evident that higher RPM values have a positive impact on joint efficiency and tensile strength for both the taper cylindrical pin profile and the threaded cylindrical pin profile. The findings show that the joint efficiency and tensile strength are consistently higher for the threaded cylindrical pin profile compared to the taper cylindrical pin profile, regardless of the RPM and feed rate. From the results, it was found that joint efficiency and tensile strength is maximum at higher RPM irrespective of the tool pin profile i.e. 73.6 % and 123 MPa for taper cylindrical pin profile and 85 % and 142 MPa for threaded cylindrical pin profile at 575 rpm, 60 mm/min. These are the highest in comparison to 72.5 % and 119 MPa at 320 rpm, 45 mm/min and 70.1 % and 115 MPa at 400 rpm, 50 mm/min for taper pin profile tool and 82.6 % and 138 MPa at 320 rpm, 45 mm/min and 77.8 % and 130 MPa at 400 rpm, 50 mm/min for threaded cylindrical pin profile. Overall, the study demonstrates that joints obtained using the threaded cylindrical pin profile demonstrate higher joint efficiency and tensile strength than those prepared using the taper cylindrical pin profile. The highest joint efficiency and tensile strength of 84.5 % and 142 MPa, respectively, were achieved using the threaded cylindrical pin profile at 575 rpm and 60 mm/min.

Study on the Properties of a 2219 Aluminum Alloy Friction Stir-Welded Joint under the Biaxial Stress State

Friction stir welding (FSW) has been considered ideal for aluminum alloy structures. The performance of FSW joints under unidirectional stress state has been widely tested, but there is still a lack of experimental data under a biaxial stress state. For accurate characterization of the mechanical properties of 2219 aluminum alloy FSW joints under a biaxial stress state, this article conducted biaxial tests. The FSW joint was tested using scanning electron microscopy (SEM) to obtain its microscopic properties and obtain the partition results of the welded joint. The stress–strain relationship and yield characteristics of welded joints under different loading ratios were studied using biaxial tensile tests of cruciform specimens combined with digital image correlation technology. By comparing it with the existing yield criteria, the yield criterion suitable for FSW joints of 2219 aluminum alloy under a biaxial tensile load was determined.

Experimental Analysis and Weld Joint Characteristics Study on Friction Stir Welded Dissimilar Joints Fabricated by Novel Hybrid Pin Profiles

Experimental Analysis and Weld Joint Characteristics Study on Friction Stir Welded Dissimilar Joints Fabricated by Novel Hybrid Pin Profiles

Multi-objective optimization of FSW aviation-grade AA8090 alloy: an RSM-based design approach

Purpose This study aims to determine the effect of different friction stir welding (FSW) parameters on mechanical and metallurgical characteristics of aviation-grade AA8090 alloy joints. Design/methodology/approach Response surface methodology with central composite design is used to design experiments. The mechanical and microstructure characteristics of the weld joints have been studied through a standardized method, and the influence of threaded pins on the joint microstructure has also been assessed. Findings From a desirability strategy, the optimum parameters setting of the friction stir welding was the tool rotational speed (TRS) of 800, 1,100 and 1,400 rpm; tool traverse speed (TTS) of 20, 30 and 40 mm/min; and tilt angle 1°, 2° and 3° with different tool pin profiles, i.e. cylindrical threaded (CT), square threaded and triangular threaded (TT), for achieving the maximum tensile strength, yield strength (YTS) and % elongation as an output parameter. The TRS speed was the highest weld joint characteristics influencing parameter. Peak tensile strength (378 MPa), percentage elongation (10.1) and YTS (308 MPa) were observed for the optimized parametric value of TRS-1,400, TTS-40 mm/min and TA (3°) along with CT pin profile. Microstructure study of the welded surface was achieved by using scanning electron microscope of output parameters. When the tool rotation speed, tool transverse speed, tilt angle and tool profile are set to moderately optimal levels, a mixed mode of ductile and brittle fracture has been seen during the microstructure analysis of the welded joint. This has been aided by the material’s plastic deformation and the small cracks surrounding the weld zone. Originality/value From the reported literature, it has been observed that limited work has been reported on aviation-grade AA8090 alloys. Further thermal behavior of welded joints has also been observed in this experimental work.

An investigation of the effect of sensitization on the metallurgical characteristics of dissimilarly welded austenitic-ferritic stainless steel

Purpose The purpose of this study is to examine the effects of sensitization on the metallurgical characteristics of weld joints made up of austenitic stainless steel (AISI 316L) and ferritic stainless steel (AISI 430), using the gas tungsten arc welding (GTAW) process with ER316L filler wires. Design/methodology/approach A non-consumable tungsten electrode with a diameter of 1.6 mm was used during the GTAW procedure. The filler wire, ER316L, was selected based on the recommendation provided in literature. To explore the interconnections among the structure and properties of these weldments, the techniques including scanning electron microscopy and optical analysis have been used. In addition, the sensitization behaviour of the weldments was investigated using the double loop electrochemical potentio-kinetic reactivation (DLEPR) test. Findings Microstructural analyses revealed the occurrences of coarsened grains with equiaxed columnar grains and migrating grain boundaries in the weld zone. The results of the DLEPR test demonstrated that heat affected zone (HAZ) of AISI 430 was more susceptible to sensitization than HAZ of AISI 316L. Microstructure analysis also revealed the precipitation of large amounts of chromium carbide at the grain boundaries region of AISI 430 welded steel, causing more sensitization and, as a result, more failure or breaking at the side of AISI 430 weld in the dissimilar weldment of AISI 316L–AISI 430. Originality/value The present work has been carried out to determine the appropriate welding conditions for joining AISI 316L and AISI 430, as well as the metallurgical properties of the dissimilar weldment formed between AISI 316L and AISI 430. Owing to the difficulties in measuring the performance of these types of dissimilar joints given their unique mechanical and microstructural characteristics, research on the subject is limited.

Analysis of FSW welding parameters on mechanical welding properties in aluminum alloy AA 5083 plates using different tool geometries

Friction welding is based on a rotating tool that penetrates the line of union of the previously fixed and pressed pieces and moves along this line. It is a process of joining materials at low temperatures, in the solid state of metals, below their melting point. The heat generated by the friction of the tool at high rotation further dilutes the base material and flows towards the center of the tool, causing mechanical mixing, the shoulder of which causes the final stage of this material, already cooled. This article proposes to study the influence of the different parameters of FSW welding on the thermal characteristics of weld joints in aluminum and magnesium alloys, numerically. The simulation results confirmed that the temperature distribution is high from shoulder towards the borders of the parts and it was symmetrical with respect to the middle plane. The calculated maximum temperatures for magnesium and aluminum were 843.7 K & 702 K, respectively.

Insights into the microstructure evolution and mechanical behavior of dissimilar friction stir welded joints of additively manufactured AlSi10Mg and conventional 7075-T651 aluminum alloys

Metal 3D printing through laser powder bed fusion (L-PBF) has revolutionised the manufacturing industry. However, size limitations and production costs persist as challenges for the 3D printing of metallic alloys. Thus, joining L-PBF components to other parts becomes a vital aspect to produce composite structures for engineering applications. Among the dissimilar joining of various non-ferrous alloys, the integration of L-PBF components with difficult-to-join materials, such as aerospace-grade AA-7XXX aluminum alloys, still remains an unaddressed industrial problem. To address this problem, the current study was carried out to investigate the feasibility of joining L-PBF manufactured AlSi10Mg alloy with a traditionally rolled AA7075-T651 alloy using friction stir welding process. In this study, the influence of the base material positioning and heat input on the mechanical and metallurgical characteristics of welded joints was examined, followed by their interrelationships for more efficient adoption of this technology. The results revealed that the base material placement significantly influenced the joint strength at low heat input but showed negligible impact at high heat input. The joints fabricated at high heat input exhibited higher hardness within the nugget zone owing to the higher concentration of MgZn2 and β-Mg2Si secondary-phase particles as compared to the joints fabricated at low heat input. Texture analysis of welds showed that the C {001} <110> shear component dominated the nugget zone when AA7075-T651 was placed on the retracting side. Whereas, the A1*/ A2* {111} <1‾12‾ >/{111} <112‾ > simple shear component was prominent when AA7075-T651 was placed on the advancing side of the joint. Finer grains and high dislocation density in the nugget zone at low heat input resulted in the maximum joint efficiency of 77% with respect to the AlSi10Mg alloy. In contrast, a coarse grain structure at high heat input reduced the joint efficiency to 74%. The findings from this research suggest friction sir welding to be an efficient method for dissimilar joining of additive components with conventionally manufactured parts.

Experimental study on influence of shielding gas pressure on the quality of pulsed laser welding of thin walled T91 steel clad tube with end plug

Fabrication of metal fuel pins for test irradiation in fast breeder test reactor requires welding of thin wall clad tube with solid end plug of modified 9Cr-1Mo steel material under high pressure helium atmosphere. Autogenous pulsed Gas Tungsten Arc Welding [GTAW] technique is currently used for end cap welding of metal fuel pins inside the glove box. Pulsed laser welding of end plug with clad tube of modified 9Cr-1Mo steel material under inert atmosphere at 1.2 bar gas pressure is under development.Pulsed laser beam welding [PLBW] is considered as alternate welding technique to replace the pulsed tungsten inert gas welding.In the current study the influence of shielding gas pressure on the weld joint characteristics like depth of penetration, bead width, and heat affected zone were investigated to optimize laser welding parameters. Initially experiments were conducted under helium gas at atmosphere pressure to optimize the process parameters to obtain the desired depth of penetration and then repeated the experiment with the optimized parameters at 0.5 bar pressure to study the effect of shielding gas pressure. Laser beam welding parameters like peak power − 1800 to 2400 W, pulse frequency – 5 to 8 Hz and pulse duration – 6 to 10 ms were varied during welding sample coupons. Welded sample coupons were subjected to various NDT techniques and subsequently metallographic examination was carried out to measure the bead width, depth of penetration and delta ferrite distribution in the weld metal. Laser beam welding parameters were optimized at atmosphere pressure to meet the stringent acceptance criteria. Further study was carried out under helium gas atmosphere at 0.5 bar using optimized welding parameters and it reveals that the drastic reduction in heat input due to laser beam attenuation and absorption by quartz window.

Mechanical and Micro-Structural Characterisations of Submerged Arc Welded Steel Plates

The goal of the study is to find out how the welding parameters current (I), voltage (V), and speed (S) affect the mechanical characteristics and mechanical characterization of the submerged arc welding (SAW) process. Tensile strength, Microhardness, Impact load was determined using the universal testing machine (UTM), micro Rockwell Hardness machine and Impact load by Charpy and Izod method. With the help of several Submerged Arc Welding (SAW) factors, notably welding voltage (V), welding current (I), and welding speed, this research aims to examine and analyze the mechanical characteristics of welded connections. (S). The investigation involves cutting and machining samples of welded joints, which are then tested for mechanical qualities using tensile, impact toughness, and hardness methods. Analyses were done on how welding parameters affect the mechanical characteristics of welded joints. It has been noted that when heat input increases, the hardness of the weld first increases up to 100 HRC before declining as heat input continues to increase. The ultimate tensile strength and yield strength of the welded joints increases as the heat input increases, but it decline as the heat input increases more. The slower cooling rate has been achieved with high input heat consequent the coarse grains achieved in the weld metal. In contrast the low input heat results in the faster cooling and finer microstructure.

Ultrasonic inspection technology of welded joints obtained by spot friction welding

Friction stir welding has found wide application in the aircraft and rocket industries, primarily due to the possibility of obtaining welded joints with a strength close to that of the base material. One of the most promising methods of such welding is friction stir spot welding, which can serve as an alternative to electric contact spot welding and riveting of joints. To introduce friction stir spot welding into the production of critical products, it is necessary to consider issues related to non-destructive quality control of welded joints obtained by this welding method. The purpose of this work is to substantiate the applicability of the ultrasonic echo method for quality control of welded joints obtained by friction stir spot welding. The relevance of the work is confirmed by the fact that today there is no sufficiently complete information on the results of experimental studies aimed at analyzing the characteristics of welded joints obtained by friction stir spot welding. The authors of the article proposed to use the ultrasonic echo method of control. The control was carried out using an ultrasonic flaw detector with a separate-combined piezoelectric transducer on samples of welds made using friction stir spot welding. Flaws such as lack of penetration and root sticking were found in three samples as a result of ultrasonic testing, which was confirmed by metallographic studies. Samples in which no defects were found were subjected to mechanical tests, as a result of which it was found that the strength of the obtained welded joints is comparable to the strength of the base metal of the samples. Metallographic studies were carried out on samples after the absence of defects in welded joints was confirmed through mechanical tests. Thus, the relationship between the results of ultrasonic testing, metallographic studies, and mechanical tests is shown, which makes it possible to justify the applicability of the ultrasonic echo method for quality control of welded joints obtained by friction stir spot welding.

Experimental investigation on high-temperature tensile behavior of cold metal transfer pulse multi-control welding of Inconel 617 alloy

To improve the efficiency of the advanced steam power plants, both the pressure and temperature of the steam are increased. The Inconel 617 alloys are a candidate material for these applications. The microstructural features and tensile characteristics of welded joints made using the cold metal transfer (CMT) plus pulse multi-control (PMC) by varying the wire feed speed (8.9, 9.4, and 9.9 m/min) at room and high temperatures (650 °C, 700 °C, and 750 °C) are examined. An optical microscope (OM) and Field emission scanning electron microscope (FESEM) were used to examine the microstructure and fracture surfaces of the alloy. The mechanism of strengthening and the effects of precipitates on tensile strength and % elongation in both Base metal (BM) and weld bead are discussed in detail. The mechanical behavior was analyzed in terms of impact strength and bending strength in detail by varying the wire feed speed (WFS). Indications for porosity and cracks were not reported in the X-ray radiography test. The macrographs revealed that bead width, penetration depth, the metal deposited on the weld, and HAZ are in direct proportion with wire feed speed. Bend test results showed that the weld joints exhibit good ductility without cracks.

Исследование свариваемости полуфабрикатов из сплава системы Al – Mg – Si – Cu

The features of the formation of the microstructure of welded joints of sheets of aluminum alloy V-1381 of the Al – Mg – Si – Cu system, obtained with various parameters of automatic argon-arc welding, were studied. Welding modes were selected that provide a high-quality welded joint and strength at a level not lower than 0.8 of the strength of the base metal. It has been established that welding without filler wire leads to cracking without applying tensile deformation, the use of Sv1221 filler wire compared to SvAMg61 and SvAK5 leads to an increase in the strength characteristics of welded joints by 15 – 20 %. Corrosion resistance of welded joints of sheets from V-1381 alloy was determined. Various experimental modes of laser welding were tested, the microstructure and mechanical properties of welded joints were studied. Parameters have been selected that ensure high quality of welds. The possibility of using laser welding for semi-finished products from alloy V-1381 has been established. The new V-1381 alloy can be recommended for use in aircraft fuselage structural elements, including as an alternative to less corrosion-resistant non-weldable alloys of the D16 type, which will increase the weight efficiency of structures both due to increased strength and through the use of welded joints instead of riveted ones.

Investigating the Microstructure and Mechanical Properties of Materials Joined using Advanced Welding Techniques

The science of materials joining has witnessed the emergence of advanced welding techniques, which have become crucial operations. These techniques provide improved manipulation and regulation of the microstructure and mechanical characteristics of welded joints. The primary objective of this work is to examine the complex correlation between the microstructure and mechanical characteristics of materials that have undergone joining processes utilising sophisticated welding methods. The present research provides insight into the development of many microstructural characteristics, including grain growth, phase transitions, and defect creation, and their influence on the mechanical properties of welded joints. The mechanical characteristics being examined span a broad spectrum of factors, such as tensile strength, toughness, hardness, and fatigue resistance. The evaluation of these qualities is conducted by subjecting specimens obtained from the welded joints to a variety of mechanical tests. Through the correlation of microstructural traits with the observed mechanical behaviour, a more profound comprehension of the structure-property link in advanced welding is attained. In addition, this study investigates the impact of welding parameters, including welding speed, heat input, and shielding gas composition, on the microstructure and mechanical characteristics. The objective of this inquiry is to optimise the welding parameters in order to get the specified material characteristics in the welded connections, while simultaneously minimising the development of faults and ensuring the maintenance of structural integrity.

Assessment of the possibility of using RFW for the production of composite joints from steel X10CRNITI18-10

An effective way to avoid heat treatment in the production of pipe beams of heat exchange apparatuses is to replace tungsten inert gas (TIG) welding with rotary RFW (RFW), but at the moment there is no information on the characteristics of welded joints of steel X10CRNITI18-10 obtained by RFW. In this article, the possibility of using RFW to obtain composite joints of a changed design was evaluated. To do this, studies were carried out on the structure of the metal, tests for static tension and impact bending of samples of X10CRNITI18-10 steel obtained by RFW.