Joint Quality Research Articles

Numerical investigation of the impact of thermoelectric effect on electron beam welding of dissimilar materials

Electron beam welding of GH4169 and Ni is required in the manufacture of the regenerative cooling system of the liquid rocket motor. The thermoelectric effect is observed during the welding of dissimilar metals; however, there has been a lack of investigation into the influence of this effect on electron beam welding joint formation and its dependence on test plate thickness. The thermoelectric effect of electron beam welding between GH4169 and Ni with varying thicknesses, as well as the influence of induced magnetic fields on electron beam trajectories, are investigated through the establishment of a numerical model incorporating thermal-electric-magnetic coupling.The results show that when the test plate increases from 2.5 mm to 10 mm the peak current density increases from 5.1 × 106 A/m2 to 7.6 × 106 A/m2, and the maximum magnetic flux density increases from 1.49× 10−2 T to 1.77 × 10−2 T. The increase in magnetic flux density results in a greater displacement of the electron beam spot away from the interface between the two materials, thereby causing incomplete fusion defects in the joints. This study elucidates the fundamental physical principles underlying the occurrence of incomplete fusion defects in electron beam welding joints, thereby furnishing essential theoretical underpinnings for enhancing the quality of dissimilar metal electron beam weld joints.

Simulation of temperature and weld growth mechanism in ultrasonic welding of carbon fiber reinforced polyamide 66 composite: Employing the high frequency real-time horn vibration

Ultrasonic welding (UW) of carbon fiber reinforced polyamide 66 (CF/PA 66) composite is a very promising process for assembly of automobile component. Simulation of the temperature distribution and weld growth in UW process remains a difficulty issue. In this study, a high frequency sensor is equipped in the welder to collect the real-time horn vibration during UW. Then the real-time horn vibration is applied on tip of the horn and integrated into the finite element model in Abaqus. The simulation results are validated with experimental tests of temperature and weld evolution in UW of CF/PA 66. Results showed the ultrasonically welded CF/PA 66 joint made with a weld time of 2.7 s consisted of five distinct stages and the characteristics in stage 3 determined the quality of the weld. An index Q based on the amplitude and duration of T3 was proposed to evaluate the joint quality. The accuracy of Q was also verified through extensive experiments.

Transmission laser welding of thermoplastics: Influence of welding parameters and rib dimensions on the strength of welded joints

Laser transmission welding of injection moulded thermoplastics is commonly used in industrial applications such as electronic packaging, textiles, biomedical devices, windows, signs, food and medical packaging, visual displays and automotive components due to very precise control of the process parameters, including the amount of energy delivered and its location, which results in high joint quality. In this article, the influence of laser transmission contour welding parameters and geometry of welding rib on joint force is investigated. Velocity with which the laser beam moves on the sample, temperature applied, clamp force, laser beam size and number of laser passes were studied for various dimensions of the rib with rectangular and triangular cross section. Samples of different thermoplastic materials, PMMA and PC/ABS, were produced and then joined by transmission laser welding and after that were subjected to tensile tests, in order to measure strength of the joint between the plastic parts. Initially, optimal welding conditions were found for each studied rib and their influence on the force of the joint was analysed. Afterwards, a comparison between the best results obtained for each rib was performed, in order to define the dimensions of the rib that result in the highest joint force. It was observed that samples with triangular ribs achieved higher joint strength. For both studied geometries of rib cross section, an increase of the width of the ribs improves the joint strength, while an increase of the height worsens it.

Determining the technological parameters of electron-beam welding of high-strength titanium alloys

It is usually quite difficult to carry out deep penetration of thick-walled products from titanium alloys using conventional welding technologies. In this study, it was proposed to use electron beam welding under high vacuum conditions for the realization of 40 mm thick melting of VT23, VT3-1 alloys. This paper considers the possibility of obtaining high-quality welded joints from high-strength titanium alloys having (a+β) two-phase structures. For the implementation of research works, samples were made from selected materials, samples were welded according to the specified modes, metallographic analysis was performed, and the level of mechanical properties was determined. The research results were verified under laboratory conditions. The technological features of the processes of electron-beam welding of products with a thickness of 40 mm were considered; the parameters affecting the weldability of titanium alloys and their structure were determined. The welded samples were checked by X-ray non-destructive testing, the microstructure of the welds was studied, and the physical and mechanical properties of the welded joints were checked. It was established that a feature of titanium alloys VT3-1, VT23 is the need for heat treatment after welding under the base metal regimes to improve the characteristics of the welded joint. The resulting strength limit of the alloys after heat treatment reached values of 1250 MPa and more, while the impact toughness was at the level of 48–50 J·cm-2. Modeling the welding process has made it possible to ensure the reproducibility of the characteristics of the welded joint at a level close to that of the base metal, to increase the quality indicators of welded joints, and to reduce the time required to test the technology. The studies of simulator samples showed compliance of the quality of welded joints with the predefined parameters.

Optimization of resistance spot welding with surface roughness dissimilar mild steel with stainless steel

Resistance spot welding plays a critical role in the manufacture dissimilar material industry. However, there are differences in mechanical properties between mild steel and satinless steel so as to reduce the quality of welded joints. In order for differences in mechanical properties to be corrected, surface roughness was treated. The aim of this study was to optimize the welding parameters of DRSW with surface roughness by analysis using the Taguchi and Anova Methods. In this study discusses about investigates the Resistance spot welding parameters on weld geometry, mechanical properties, and SEM EDS on dissimilar materials of mild steel and stainless steel. The material thickness of the mild steel and stainless steel are 1 mm, respectively. The process parameters of the resistance spot welding joint used, example; surface roughness, current, welding time, and electrode force. Quality welding joint test results include weld geometry, mechanical properties, and SEM EDS. Weld geometry testing to determine the weld nugget profile. The mechanical properties test was shear tensile test, while the SEM EDS included macrostruture and microstructure observations. The results showed the highest nugget diameter 6.65 mm highest shear tensile strength 7.66 kN. The most influential parameter is current by 75.08 %, then surface roughness by 12.35 %. The highest tensile strength has fewer defects. Surface roughness treatment before welding is very good to make welding quality joints between mild steel and quality stainless steel increase. Surface roughness treatment was very good to be included when making welding procedures for welding engineers for welding processes resistance spot welding dissimilar mild steel with stainless steel.

Step phenomenon of intermetallic compounds thickness during laser soldering dependence on laser power

The thickness of CuSn intermetallic compounds (IMCs) plays a crucial role in determining the quality of laser soldering joints. However, there is a lack of research on laser soldering with wire feeding, which is a relatively complicated process of melting and spreading. In this study, we investigated the effect of laser power on IMCs thickness, the maximum temperature of the molten pool, and the spreading behaviors of solder. The results revealed that the thickness of Cu6Sn5 IMCs could be divided into three stages. Notably, a step phenomenon was observed, which is a stable stage between the non-wetting stage and the rapid linear increase stage. Since the phenomenon could not be accurately explained by the temperature-time theory, the actual laser absorptivity (only 20 %–25 %) was calculated during laser soldering by establishing a quantitative relationship between the spreading behaviors and the laser reflectivity. Furthermore, we established the linear relationship (R2 = 98.6 %) between the actual absorptivity and IMCs volume. Finally, the formation mechanism of the step phenomenon is rationally explained in combination with the spreading process of the solder. The findings are of great significance for accurately controlling IMCs thickness, expanding the process window, and enhancing the quality stability of solder joints.

Corrosion behavior of AA3003 friction stir welded joints

This work focuses on the corrosion behavior of the friction stir welded joint of aluminum alloy 3003. In order to quantify the quality of FSW joints, the corrosion in the welded joint and the base metal was compared. A gravimetric and thermodynamic study was carried out to determine corrosion resistance. Three aggressive media based on three solutions (sodium chloride, hydrogen chloride, and ethylene glycol) at four temperatures (25°, 45°, 65°, and 85 °C) were tested. The results showed that temperature has a strong influence on corrosion rates, which are higher in the metal than in the FSW joint. The presence of ethylene glycol considerably reduces the rate of corrosion, its effect is more marked on the FSW joint. The adsorption of ethylene glycol on the surface of the base metal and that of the FSW joint follows the Langmuir isotherm to form a monolayer on the surface of both samples.

Effect of welding speed on butt joint quality of laser powder bed fusion AlSi10Mg parts welded using Nd:YAG laser

Abstract The invention of additive manufacturing technology, such as laser powder bed fusion, was initiated by the aerospace industries’ growing need for lightweight alloy components with intricate geometries. However, widespread adoption of lightweight alloy components is limited by size restrictions. Currently, only relatively small and simple-shaped objects can be efficiently produced using lightweight alloys. Thus, this research aims to investigate the effect of welding speed on butt joint quality of laser powder bed fusioned AlSi10Mg parts welded using an Nd:YAG laser. Laser beam welding is a method for welding small parts manufactured by laser powder bed fusion together to build large-scale and complex-shaped objects. Using a 2 kW continuous wave solid-state Nd:YAG laser with three different weld scan speeds (150, 175, and 200 mm min−1), autogenous, single-pass, square butt joints were created from 3 mm thick plates. Crystal orientation mapping and fractography results showed that the laser beam welding scan speed significantly impacts plastic deformation and fracture behavior. A significant amount of grain refinement and an Si-particle morphology change was realized in the weld zone’s microstructure, attributed to the increase in weld scanning speed. The transverse tensile test demonstrates that increasing the weld scan speed from 150 to 200 mm min−1 leads to significant growth in the efficiency of the weld joint, from 70 % to 77 %, arising from grain refinement (13–8 µm). However, a significant decrease in ductility is observed with increasing scan speed. In addition, it was determined that pores have substantial effect on tensile strength and ductility.

Joint status, pain and quality of life in elderly people with haemophilia: A case-control study.

Elderly people with haemophilia (PwH) develop haemophilic arthropathy, pain, and reduced health-related quality of life (HR-QoL). The condition of elderly mild haemophilia patients have rarely been evaluated. This study aimed to compare joint status, pain, and HR-QoL between elderly with mild, moderate/severe haemophilia and healthy elderlies. Knee/ankle abnormalities were assessed by ultrasound (HEAD-US) and physical examination (HJHS 2.1). Pain severity and pain interference were investigated using the Brief Pain Inventory. Pressure pain thresholds (PPTs) were obtained at knees/ankles and forehead. Functional limitations were evaluated using the 2-Minute-Walking-Test, Timed-Up-and-Go and HAL. The EQ-5D-5L questionnaire evaluated HR-QoL. Healthy controls (HCs) and elderly individuals with moderate/severe and mild haemophilia were compared using Kruskal-Wallis and Mann-Whitney U tests. From the 46 elderly PwH approached, 40 individuals (≥60 years) with haemophilia A/B (17 moderate/severe; 23 mild) and 20 age-matched HCs were recruited. Moderate/severe PwH displayed worse joint status, lower PPTs, and poorer HR-QoL than mild PwH and HCs (p-value=.010-<.001). HEAD-US abnormalities were observed in 100% of knees and 94% of ankles in moderate/severe PwH, versus 50% of knees and 61% of ankles in mild PwH. Pain was reported by 80% and 57% of moderate/severe and mild PwH, respectively. Low PPTs, functional limitations, and poor HR-QoL scores were likewise observed in some mild PwH, yet without significantly differing from HCs. This study highlights poor joint/functional status, pain, and HR-QoL outcomes in elderly with moderate/severe haemophilia. A few mild haemophilia subjects presented joint abnormalities, pain, functional limitations, and poor HR-QoL, without significantly differing from HCs. Elderly individuals with mild haemophilia have not yet been extensively studied, whereas moderate/severe haemophilia individuals have proven to suffer from haemophilic arthropathy, pain, and poor health-related quality of life (HR-QoL). Using a case-control design, joint status, pain, and HR-QoL outcomes were examined in elderly haemophilia individuals and compared with those of healthy controls (HCs). Elderly moderate/severe haemophilia individuals exhibited worse joint status, increased joint pain sensitivity, and reduced HR-QoL compared with both mild haemophilia subjects and HCs. A subset of mild haemophilia subjects exhibited poor joint status, pain, and HR-QoL outcomes, without any differences noted when compared with HCs.

Clinical value of ankle flexion and extension exercises combined with a psychological intervention in knee osteoarthritis.

Considering the limited effectiveness of clinical interventions for knee osteoarthritis (KOA), it is necessary to continue to explore appropriate and effective treatment strategies to improve the condition of KOA patients. To clarify the influence of ankle flexion and extension exercises combined with a psychological intervention on the psychological status and activities of daily living (ADLs) of patients with KOA. The research participants were 116 KOA patients admitted to The First Affiliated Hospital of Guizhou University of Traditional Chinese Medicine between May 2019 and May 2022, including 54 patients receiving routine treatment, care and psychological intervention (control group) and 62 patients additionally treated with ankle flexion and extension exercises (research group). The two groups were comparatively analyzed in terms of psychological status (Self-rating Anxiety/Depression Scale, SDS/SAS), ADLs, knee joint function (Lysholm Knee Scoring Scale), pain (Visual Analog Scale, VAS), fatigue (Multidimensional Fatigue Inventory, MFI), and quality of life (QoL; Short-Form 36 Item Health Survey, SF-36). After evaluation, it was found that the postinterventional SDS, SAS, VAS, and MFI scores in the research group were significantly reduced compared with the baseline (before the intervention) values and those of the control group, while the postinterventional Lysholm, ADL and SF-36 scores were markedly elevated. Therefore, ankle flexion and extension exercises are highly effective in easing negative psychological status, enhancing ADLs, daily living ability, knee joint function and QoL, and relieving pain and fatigue in KOA patients, thus warranting clinical promotion.

Modal Analysis of Ultrasonic Spot Welding for Lightweight Metals Joining

Ultrasonic spot welding (USW) represents one of the unique solid-state joining methods for lightweight materials such as magnesium alloy and aluminum alloy. However, the sonotrode vibration may have a detrimental impact on the sheet material and the existing welds, depending on the component geometry and vibration frequency. In this study, a modal analysis tool based on steady-state dynamics was developed for ultrasonic spot welding which features a cyclic load applied to the sheets during the joining process. Through predicting relative motion and shear stress at the faying surfaces, coupon geometry and weld spacing are identified as two major factors that affect the welding reliability and joint quality in USW. The model was validated via welding experiments on aluminum alloy and magnesium alloy and relevant characterization of temperature distribution, joint strength as well as fracture location.

Some Technological Parameters of Construction Joints Formation Using the Self-Compacting Concrete Mixtures

Introduction. The important condition ensuring the monolithicity of the erected massive monolithic reinforced concrete structures, divided in compliance with the standards into the heat-shrinkable blocks, is the quality of construction joints in terms of the new-to-old concrete bonding. The research on the bonding strength dependence on the technological parameters of the construction joints formation using the widely spread in recent years self-compacting concretes is a relevant task, because the number of publications on the respective topic is insufficient. The aim of the present paper is to develop a scientific concept regarding the influence of the certain technological parameters on the new-to-old concrete bonding strength during the construction joints formation.Materials and Methods. The research was carried out using the self-compacting and ordinary heavy vibratory-compacted concretes with the compressive strength ranged from 34.5 to 69.2 MPa. The object of the study was the dependence of the new-to-old concrete bonding strength on the method of standardised surface pre-treatment of the “old” concrete in a joint and the compressive strength of the grade of the “new” self-compacting concrete. The composite Mörsch specimens in which the “old” concrete was cured for up to 3 days were used as the main samples. The construction joint relative strength was considered to be the joint quality evaluation criterion equalling to the ratio of the shear strength of concrete in a composite Mörsch specimen to the minimum axial tension strength values of the “new” and “old” concrete. The quality indicators of the concrete were determined by applying the standard methodology. The specimens were cured under conditions simulating the production of works in the spring-summer season.Results. During the research, the construction joint quality criteria in terms of the “old” to “new” concrete bonding were analysed along with the changes they undergo depending on the studied recipe (concrete grade) and technological (length of the technological break, surface treatment method) factors. The dependences of the proposed construction joint quality criterion on the “new” concrete compressive strength (grade) were obtained and the inefficiency of the surface treatment with a metal brush was shown, especially if accompanied with the technological break extension. The required bonding strength values for B25 ... B35 grade concretes can be for sure provided by the surface pre-milling, whereas the extension of the technological break has negative affect on the bonding strength.Discussion and Conclusions. Due to the revealed low bonding strength of the “old” to “new” concretes, regardless the technological factors, it is expedient to look into the ways of ensuring the construction joint quality by implementing structural solutions such as keyed joints and (or) additional reinforcement.

A Review of Optimization and Measurement Techniques of the Friction Stir Welding (FSW) Process

This review reports on the influencing parameters on the joining parts quality of tools and techniques applied for conducting process analysis and optimizing the friction stir welding process (FSW). The important FSW parameters affecting the joint quality are the rotational speed, tilt angle, traverse speed, axial force, and tool profile geometry. Data were collected corresponding to different processing materials and their process outcomes were analyzed using different experimental techniques. The optimization techniques were analyzed, highlighting their potential advantages and limitations. Process measurement techniques enable feedback collection during the process using sensors (force, torque, power, and temperature data) integrated with FSW machines. The use of signal processing coupled with artificial intelligence and machine learning algorithms produced better weld quality was discussed.

Pengaruh Variasi Gerakan Elektroda Pada Pengelasan Smaw Terhadap Uji Kekuatan Bending Baja ST 42

This study aims to determine the effect of straight groove, zigzag groove, and U pattern groove movement on the hardness and mechanical properties of the material in ST42 steel welding. The welding method used is shielded metal arc welding (SMAW) with a current strength of 100 Amperes. The test results show that the movement of the straight groove electrode gives the highest stress value in the bending test with an average of 1,168 MPa. The zig-zag groove electrode movement gave an average stress value of 1.127 Mpa, while the U pattern groove electrode movement gave an average stress value of 1.905 MPa. Microstructural testing showed that all electrode movements produced pearlite and ferrite phases, but straight groove electrode movements had more pearlite phases than the other movements. In addition, the zig-zag groove electrode flow and U pattern. This study provides a better understanding of the effect of electrode movement on the quality of welded joints, as well as providing important information in the development of industrial welding techniques.

Fatigue life simulation of AA7075-T651 FSW joints using experimental data

The friction stir welding (FSW) process is a solid phase type applied in this study to connect AA7075-T651 aluminum alloy plates. This study investigates the impact of welding input quantities such as tool rotational speed, welding speed, shoulder radius, and tool geometry on welding joint quality, including strength, toughness, hardness, fractography, and fatigue behavior. Also, in this study, the fatigue life in the base material (BM) and joints obtained from the simple, threaded, and truncated triangular pyramid pins as an FSW effective input parameter was obtained by the finite element analysis (FEA). The experimental outcomes represented that the mechanical attributes of the threaded pin are higher than that of the simple and truncated triangular pyramid pins with the same input parameters. Also, the outcomes of the numerical simulation with the experimental outcomes of fatigue life for the BM were in acceptable agreement, and the error value of the validation result for σmax=0.5σy for the stress ratio R=-1 was equal to 0.4%. In addition, the FEA results indicated that the fatigue strength of FSW joints in the stir zone for the threaded, simple, and truncated triangular pyramid pins in the fatigue life of 107 cycles was 64%, 63%, and 43% of the BM, respectively.

Elucidating the process mechanism in Mg-to-Al friction stir lap welding enhanced by ultrasonic vibration

The composite structures/components made by friction stir lap welding (FSLW) of Mg alloy sheet and Al alloy sheet are of wide application potentials in the manufacturing sector of transportation vehicles. To further improve the joint quality, the ultrasonic vibration (UV) is exerted in FSLW, and the UV enhanced FSLW (UVeFSLW) was developed for making Mg-to-Al dissimilar joints. The numerical analysis and experimental investigation were combined to study the process mechanism in Mg/Al UVeFSLW. An equation related to the temperature and strain rate was derived to calculate the grain size at different locations of the weld nugget zone, and the effect of grain size distribution on the threshold thermal stress was included, so that the prediction accuracy of flow stress was further improved. With such modified constitutive equation, the numerical simulation was conducted to compare the heat generation, temperature profiles and material flow behaviors in Mg/Al UVeFSLW/FSLW processes. It was found that the exerted UV decreased the temperature at two checking points on the tool/workpiece interface from 707/671 K in FSLW to 689/660 K in UVeFSLW, which suppressed the IMCs thickness at Mg-Al interface from 1.7 µm in FSLW to 1.1 µm in UVeFSLW. The exerted UV increased the horizontal materials flow ability, and decreased the upward flow ability, which resulted in the increase of effective sheet thickness/effective lap width from 2.01/3.70 mm in FSLW to 2.04/4.84 mm in UVeFSLW. Therefore, the ultrasonic vibration improved the tensile shear strength of Mg-to-Al lap joints by 18 %.

Mechanical Response of Additively Manufactured Composite Joints

This paper aims to assess the quality of composite joints made with the Fused Filament Fabrication (FFF) additive manufacturing technique through strength tests. The first part of this paper details the design of different test sample versions with standardised geometry and the methods of joining plastics by application of 3D printing. The details cover the test apparatus used in the research, sample preparation methodology, as well as tensile and impact testing methodology. The test sample versions were selected according to the test types to have the results fully reproduce the mechanical response of the composite materials to the input forces. The second part of this paper analysis of the test results, presenting the fabrication accuracy of the test samples and their mechanical response recorded during the tests. Five test specimens of each version were produced to enable statistical analysis of the test results, which was indispensable for a reliable data analysis. The tests made it possible to determine how the proposed joints of plastic materials responded to the input forces, the maximum transmitted force limit, and the flaws of each version’s design. The test results made it possible to adapt the suggested solutions in the design engineering of programmable energy-absorbing structures.

On the Optimization of Resistance Projection Welding Process

The resistance projection welding process for weld nuts has several parameters to reach good joint quality. In this study, three welding parameters were chosen, such as electrode force, welding period and welding current to examine the process. Design of experiments was prepared to optimize the conditions. The three above mentioned parameters were changed systematically with Response Surface Method, where the linear and the quadratic effects of the parameters can be estimated. During the experiments three output parameters, such as ultimate torque, weld spatter and inspection of screw were determined, and optimization were performed for the resistance projection welding process of the weld nut

Human Osteoblasts' Response to Biomaterials for Subchondral Bone Regeneration in Standard and Aggressive Environments.

Osteochondral lesions, when not properly treated, may evolve into osteoarthritis (OA), especially in the elderly population, where altered joint function and quality are usual. To date, a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold (OC) has demonstrated good clinical results, although suboptimal subchondral bone regeneration still limits its efficacy. This study was aimed at evaluating the in vitro osteogenic potential of this scaffold, functionalized with two different strategies: the addition of Bone Morphogenetic Protein-2 (BMP-2) and the incorporation of strontium (Sr)-ion-enriched amorphous calcium phosphate (Sr-ACP) granules. Human osteoblasts were seeded on the functionalized scaffolds (OC+BMP-2 and OC+Sr-ACP, compared to OC) under stress conditions reproduced with the addition of H2O2 to the culture system, as well as in normal conditions, and evaluated in terms of morphology, metabolic activity, gene expression, and matrix synthesis. The OC+BMP-2 scaffold supported a better osteoblast morphology and stimulated scaffold colonization, cell activity, and extracellular matrix secretion, especially in the stressed culture environment but also in normal culture conditions, with increased expression of genes related to osteoblast differentiation. In conclusion, the incorporation of BMP-2 into the Col/Col-Mg-HAp scaffold also represents an improvement of the osteochondral scaffold in more challenging conditions, supporting further preclinical studies to optimize it for use in clinical practice.

Local Plastic Deformation and Quality of Cu-Cu Joints Obtained by Ultrasonic Welding

Joints of copper sheets with a thickness of 0.8 mm were produced by ultrasonic welding. To assess the quality of the joints, tensile lap-shear strength, area fraction of bonding, distributions of normal strains in the cross sections of welded samples, linear weld density at a magnification of ×1000, and the microstructure and microhardness of welded samples were analyzed. It was proved that the arrangement of microbonds and length of gaps in joint zones significantly depended on the local normal strains of welded samples caused by the penetration of tool ridges under the clamping pressure. Joint regions with a linear weld density of more than 70% were observed if the local compression strains of the sample exceeded 15%. The appearance of local tensile strains was accompanied by a drop in the linear weld density of the joints in some regions, down to 5%. The distribution of normal strains depends on the mutual positions of the ridges of the welding tip and anvil. It is concluded that in order to improve the quality of joints obtained by ultrasonic welding and reduce the scatter of their strength values, welding tools should provide sufficiently high normal compression strains in the weld spot area.