Faying Surface Research Articles

Enhanced interfacial joining strength of joined high chromium gray cast iron/low carbon steel joint via graphite coating

Liquid-state bonding is one of the most crucial methods in joining dissimilar materials to manufacture composites with structural design. The high chromium gray cast iron (HCGCI)/low carbon steel (LCS) composite structure is attractive in mining industries due to its superior mechanical properties and low density. However, the decarburization of the faying surface of HCGCI leads to the formation of a coarse-grained brittle interlayer between HCGCI and LCS which seriously deteriorates the mechanical properties of welded joints. In this work, high chromium gray cast iron/low carbon steel composite was fabricated by diffusion bonding via graphite coating layer. The results showed that the graphite coating on the fusion surfaces prevented the decarburization of HCGCI and the growth of coarse grains which improved the bonding quality. The ultimate tensile strength and total elongation of the graphite-free sample are 335.6 MPa and 8.9%, respectively. In contrast, the ultimate tensile strength and total elongation of the graphite-contain sample are 435.6 MPa and 17.9%, separately. This work opens a new strategy for fabricating high chromium gray cast iron/low carbon steel composite, and the flexibility to achieve complex structures through liquid-state bonding is extended.

Characteristics of Solidification Cracking for Ni-P Coated Cu-Al5052 Single-Mode Fiber Laser Welds

This study fundamentally examines the characteristics of solidification cracking in Cu-Al5052 single-mode fiber laser welding by utilizing uncoated and Ni-P coated Cu plates for the high durability busbar welding of pouch-type lithium-ion battery packs. Weld solidification cracking was confirmed regardless of Ni-P coating for both weld materials. However, there were differences in the regions of crack occurrence. Unlike the uncoated Cu-Al5052 welds where cracks occurred randomly within the fusion zone, for the Ni-P coated Cu-Al5052 welds, solidification cracks were concentrated near the faying surface of the upper and lower materials, particularly near the fusion line. The effect of the Ni and P components on the solidification cracking susceptibility, i.e., the welding solidification temperature range, was considered. Diffusion-controlled Scheil’s solidification calculations revealed that the mushy zone range enlarged with the use of a Ni coating layer. It was confirmed that an extremely wide mushy zone range of 1060 K was calculated at the solidification cracking region. Furthermore, P was also identified as an element that expands the solidification temperature range based on the Cu-P binary system. Consequently, during the laser welding of Cu-Al5052 dissimilar materials, the behavior of solidification cracking in the welds is influenced by the composition of the coating material and the incorporated composition within the weld fusion zone. Hence, it is necessary to select the optimal coating material and layer thickness considering weld solidification cracking susceptibility.

Offset-stoichiometric reflowable composite bonding method with adhesive for mitigating strict faying surface tolerances

Inherent susceptibility of adhesive bonds to miniscule quantities of contamination can cause undetectable weakened bonds. For this reason, the Federal Aviation Administration (FAA) places strict regulations on adhesively bonded joints in primary aircraft structures. To meet certification requirements aircraft manufactures resort to redundant load paths in the form of fasteners which inherently add weight to the structure and increase manufacturing time. In prior work, a secondary bonding technique called AERoBOND was developed, which utilized off-stoichiometric epoxy-matrix resins to facilitate reflow and diffusion of the resin within the joint interface during a secondary bonding/cure process, thus achieving a bond similar to a co-cured joint. However, the AERoBOND process required tight spatial tolerances between the two parts being joined. This study examined the utilization of conventional adhesive with the AERoBOND method to act as a filler in the joint line, effectively reducing the need for tight tolerances on the joining parts and serving as a flexible alternative for existing manufacturing processes. Ultrasonic inspection, optical microscopy, and ASTM International standard tests were performed to analyze the joints for defects and to quantify the mode-I and mode-II interlaminar fracture toughness and short beam strength of the proposed methodology with varying manufacturing parameters. The comprehensive results indicate that the AERoBOND+ method with and without surface preparation performs comparably to co-cured and conventional, adhesively bonded joints when secondary cured in an autoclave with 791 kPa of pressure. As an example, the AERoBOND+ panel without surface preparation bonded with 791 kPa of pressure (referred to as AB+3 throughout paper) had a mode-I fracture toughness (GIc) of 0.643 kJ/m2 and a mode-II fracture toughness (GIIc) of 4.000 kJ/m2 in the non-precracked condition and 4.218 kJ/m2 in the precracked condition at the adhesive-to-prepreg interface. These results were 96 %, 142 %, and 217 %, respectively, of a co-cured baseline panel (referred to as C1 throughout paper).

Effect of faying surface treatments and bolt tightened levels on fretting fatigue performance of slip critical connections with high strength bolts

The experimental investigation focuses on the fretting fatigue performance of M24 high-strength bolt slip critical connections (SCC) under shear load, taking into account the influence factors of faying surface treatments and bolt tightened levels. A novel extensometer supporting device for measuring micro-displacement between connection plates is proposed. The μ-N curves are obtained. Three-dimensional surface morphology scanning and fracture morphology analysis are conducted on the specimens. The results showed that the SCC contact area can be divided into stick, partial slip, and gross slip, with distribution ranges determined for each zone. Meanwhile the fretting fatigue life decreases with the increase of μ and pre-tension. Finally, a prediction of fretting fatigue life is made based on a multiaxial fatigue critical plane model.

Solid-state diffusion bonding for INCONEl 617 superalloy using field-assisted sintering technology (FAST) guided by CALPHAD approach

This study investigates solid-state diffusion bonding between two INCONEL 617 alloy samples using field-assisted sintering technology (FAST). The study focuses on analyzing the faying surface validating the theoretical alloy design modeling done by the CALculation of PHAse Diagrams (CALPHAD) approach followed by experimental validation. Varying kinetics’ limitations enabled phase stability and phase control governed by the CALPHAD approach alloy design. The alloy design contains a pseudo-binary phase diagram assisted with thermal mapping of a property phase diagram to obtain the optimum temperature of solid-state diffusion bonding while understanding phase fields and their evolution through Molybdenum (Mo) increasing content and temperature increase. The FAST parameters recommended by CALPHAD were 800 °C under 10 MPa pressure with a holding time of 30 min. The investigation observations were promising in a way that the faying surface contains gamma (γ) only, while the further region on the alloy contains γ and gamma prime (γ′). It is worth mentioning that FAST joining resulted in fine faying surface thickness of around 10 μm and a controlled heat affected zone (HAZ) leading to relevant reduction in the recrystallization zone yielding an average grain size of 60–100 μm before and after diffusion bonding. Furthermore, two modes of metal carbide (MC) have been found; MC formed under the faying surface and micro-MC pools formed around the faying surface.

Fatigue of 1.5 Single-Shear Lap Joints with Sealant and Corrosion-Inhibiting Compounds

Corrosion-inhibiting compounds (CICs) are a secondary protection method used with aircraft that can reduce the rate of corrosion development. However, CICs can also affect the fatigue life of fastened lap joints. This study uses a 1.5 single-shear lap joint design to investigate fatigue life changes with CIC application. Hi-Lok and rivet fastener types are compared, along with the inclusion of faying surface sealant. It was found that without sealant, the application of CICs increased the fatigue life due to prolonging the crack initiation process. The presence of faying surface sealant led to a reduction in fatigue life for the rivet samples. The Hi-Lok samples saw no change in life due to the squeeze-out of the sealant around the fastener holes. This study provides a foundational understanding of the mechanisms and significance of the change in fatigue life with the presence of CICs and faying surface sealant in a fastened lap joint.

Effect of innovative faying surfaces on dissimilar metal welds made with friction rotary joining

Effect of innovative faying surfaces on dissimilar metal welds made with friction rotary joining

Fabricating carbon steel/Ti composites through forge-welding via in-situ interfacial reaction of Ni coating

Solid-state bonding is paramount in joining dissimilar materials, often combined with metal forming, such as forging, rolling and extrusion, to fabricate composites with a designed structure. Owing to its superior mechanical properties and low density, the carbon steel/Ti composite structure is attractive in automotive and aerospace industries but is difficult to fabricate due to the decarburization of carbon steel's faying surface. In this work, a carbon steel/Ti6Al4V composite structure was first fabricated via a forge-bonding method with the assistance of a Ni coating layer. Results show that the Ni layer on the faying surfaces precludes the decarburization of the steel and the growth of the TiC phase so as to improve the bonding quality. Meanwhile, the in-situ eutectic reaction between the Ni layer and β-Ti was observed. As a result, a seamless bonded interface with the total elimination of the Ni layer can be obtained. The bonding strength was examined to establish the relationship between bonding windows, microstructure and the resulting mechanical properties. An experimentally validated thermal-mechanical finite element model was also developed to understand the process-dependent interface evolution. This work opens a new avenue for fabricating carbon steel/Ti6Al4V composite, extending the flexibility of achieving complex structures by combining solid-state bonding with other metal-forming technologies.

A Review of Friction Welding Research Addressing the Influence, Development, Similar & Dissimilar Welding

This review paper discusses the recent research work carried out in the frictional joining of dissimilar and similar alloys through the friction welding (FW) process with various parameters and modifications. It includes further the latest developments and advances in the research on FW and the influences of FW’s process parameters on the quality of joints and their properties. The specimens’ faying surfaces can also influence the joint properties as the surface modifications stimulate or change the metal joints’ bonding according to the welding parameters selected during FW. Though the rise of friction pressure (FP) during FW improves the strength of the joints, the improper selection of parameters leads to metal damage. It feels better if the axial shortening is less than 30 mm for FW of soft metals. The axial shortening values are less than 25 mm for the hemispherical bowl-type faying surfaces under 18 bar FP and it is noted that the bevel-type tapered faying surfaces increase the shortening. FW provided very narrow weld interfaces with around 5-10 µm width. With a low FP, it was possible to obtain a maximum of 100 % efficiency by modifying their faying surfaces. The small-diameter soft material needs less FP and friction time. The microstructure modification is possible and the weld joint is shown as U and V shapes for the bowl and tapered faying surfaces. It further increases the contact area and thus increases strength.

Simulation Study of Critical Aspects of MIAB Welding for Analysis of Potential Factors Governing the Performance of Weld Formation

Magnetically Impelled Arc Butt (MIAB) welding, is a solid-state welding technique. The magnetic system of this technique is pivotal for the generation of the Lorentz force, which impels an arc to rotate along the periphery of the weld tubes and thus facilitates the heating of faying surfaces. The magnetic arrangement and the arc dynamics significantly impact the effectiveness of the welding process, eventually dictating the efficiency. This study case investigates the impact of the magnetic arrangement on the arc rotation and possible factors that cause irregularities in the (MIAB) welding through COMSOL simulation. The COMSOL simulation has served as a powerful tool to comprehensively analyse various arc dynamics and magnetic systems and extrapolate the observations to analyse the arc dynamics and magnetic systems involved in MIAB welding. By employing simulation studies, the research aims to unravel critical insights for an efficient design of the MIAB welding system. This work includes a study of the effect of magnetic forces on arc dynamics using various models and attempts to develop an analogy to the MIAB welding process. This is further utilized to explain the process variations in the form of arc displacement, electric potential distribution, and the possibility of self-demagnetization of AlNiCo magnets. Thus, it provides a foundation for advancing the technological aspects of MIAB welding to overcome the limitations and irregularities. This research is instrumental in enhancing the understanding of magnetic interactions involved in the MIAB process, which can further pave the way for improved welding machine designs and consequently, enable research on these lines that can help in establishing an optimized parametric window.

Effect of joint configurations on joint strength of different thickness AA6061-T6 friction stir welded blank

This paper presents a comparative study of the mechanical properties and microstructures of three friction stir welded joint configurations, namely square butt (SB), scarf (SC), and double butt lap (DBL) of the aluminium alloy 6061-T6. The experiment was conducted on two aluminium plates of different thicknesses, 2.0 mm on the advancing side and 1.5 mm on the retreating side, at constant welding parameters, such as welding speed, spindle rotation, tool tilt angle, and tool profile. The study compared the joints at different rolling angles, i.e. 0/0, 90/90, 0/90, and 90/0°. Tensile tests were conducted on the joints, and the ultimate tensile strength (UTS) was found to be 6–11% higher in the DBL joint configuration compared to the SC and SB joint configurations. The Vickers hardness values of the SC and DBL joints were also found to be higher than those of the SB joint configuration. The formation of the ‘S’ line was observed to influence the tensile test, hardness, and grain size, which in turn are determined by the shape of the faying surface.

Critical Review on Magnetically Impelled Arc Butt Welding: Challenges, Perspectives and Industrial Applications.

Magnetically Impelled Arc Butt (MIAB) welding is a cutting-edge joining method that replaces the conventional welding procedures such as resistance, friction, flash and butt welding. It is a solid-state process that uses a rotating arc to heat up the butt ends of tubes, being followed by a forging process that completes the joining of the workpieces The magnetic flux density and the current interact to develop the Lorentz force that impels the arc along the faying surfaces. This process is found to produce high tensile strength and defect-free welds in ferrous materials and for this reason, it is predominantly employed in automobile applications for joining metallic tubes. Also, this joining procedure can be applied in the fabrication of boilers, heat exchangers, furnace piping in petrochemical industry and other safety-critical high-pressure machinery parts. The MIAB method has several advantages such as a shorter welding cycle, lower input energy requirement and lower loss of material. Compared to other solid-state welding processes, the MIAB welding has an important advantage in terms of cost-efficient welds with better control and reliability. Moreover, there are researchers who have investigated the joining of non-ferrous dissimilar materials using this welding procedure. The studies have been focused on process parametric analysis that involves optimizing and forecasting the magnetic field and thermal profile distribution. This review article provides competitive insights into various design features, computational methods, tests and material characterization, technical issues and workarounds, as well as automation aspects related to the MIAB-welding process. This work will prove to be a quick reference for researchers, useful to identify the research gaps and conflicting ideas that can be further explored for advancements in joining the similar and dissimilar materials.

Evaluation of ultrasonic spot welded Al-Cu dissimilar sheets: Mechanical performance, microstructural changes and thermal analysis

Automotive lithium-ion battery manufacturing industries are increasingly using ultrasonic welding (USW) to join thin dissimilar metals and foils. USW has good joint efficiency, no formation of the heat-affected zone, high production rate, shorter welding time, and sustainability over conventional fusion welding techniques. However, this process is less distinct and precise control of weld surface conditions to get good quality welds. In this regard, experimental and thermal analysis significantly helps to control the state of the weld interface during the joining process. In this study, the objective is to enhance the mechanical performance of aluminum (Al) and copper (Cu) joints under different surface conditions such as lubricating, normal, electrolytically, and emery polished. According to the lap shear tensile load result, the joint strength decreases significantly with the rise in weld time after 0.7 s. The lubricating surface provides the maximum lap shear tensile load of 1507 N among all other surface conditions. Fracture surface analyses are conducted to determine the quality of welds under varying surface conditions. Additionally, a three-dimensional (3D) finite element model (FE) for ultrasonic welding of two highly conductive metal sheets is also being investigated for the purposes of analysing the thermal behaviour around the weld interface. It reveals that the thermal profile of the interface differs depending on the surface condition. The numerical framework is confirmed by comparing the predicted interface temperature variations at different faying surface conditions with the experimental results.

Microwave joining of SS-430 with a nano SS-316L powder

In this study, a hybrid microwave heating (MH) approach was employed to fabricate SS-430 to SS-430 joints using a nano-based SS-316L powder as a binding agent. The microstructural aspects of the developed fusion zone (FZ) revealed the perfect diffusion bonding between the faying surfaces through the fully melting of the filler material. The formation of martensite was observed at the diffused zone/heat-affected zone along both interfacing surfaces of the SS-430 base metals to be butt welded. The phase analysis of the developed reaction layer in the FZ showed the presence of small amounts of carbide particles (mainly chromium carbides) along with the presence of the main Ni-Fe-Cr enriched solid solution matrix. The hardness of the diffused zone/heat-affected zone is significantly high (760 ± 15HV) due to the presence of martensite followed by FZ hardness (410 ± 8HV) and then followed by base metal hardness (190 ± 4HV). The tensile properties of the fabricated weldment were evaluated by employing a computer-controlled universal testing machine. The tested weldment exhibits 475 MPa with an elongation of about 35%.

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.

Flash joining of BaTiO3 ceramic to NiCrFe medium-entropy alloy by using an electric field

Joining of barium titanate (BaTiO3, BT) ceramics to metals plays an important role in their wide applications. However, conventional joining methods, including solid state diffusion joining and liquid state joining, have several drawbacks. In this paper, BT ceramic was flash joined to NiCrFe medium-entropy alloy (MEA) in seconds with an electric field (E-field) using current density of 10–80 mA/mm2 at 700–1000 °C. Shear strength of the joint first increased with applied current density and dwell time of the E-field and then decreased. It exceeded 40 MPa when the temperature was above 900 °C with current density of 60 mA/mm2 for 60 s. Both the real part (ε’) and imaginary part (ε”) of complex permittivity of the joined sample were larger than those of the as-sintered BT ceramic at high frequency range. Microstructure of the joint suggests that a layer of chromium oxide was formed at faying surfaces, achieving effective bonding of BT and MEA. This research provides an efficient method for the manufacturing of BT based devices.

Frictional mid‐spliced shear links for eccentrically braced frames

AbstractAccording to the AISC Seismic Provisions for Structural Steel Buildings (AISC341‐16) and EC8, the inelastic rotation demand at the design story drift is limited to 0.08 rad for I‐shape shear links in eccentrically braced frames (EBFs). Numerical studies on EBF archetypes show that the single‐sided inelastic rotation demands can be much higher than the limiting value. In addition, these links can fail due to low‐cycle fatigue (LCF) which depends on the loading history. A mid‐spliced end‐plated detachable replaceable link has recently been developed to promote easy replacement of end‐plated links. In this paper, a frictional mid‐spliced shear link is developed to increase the inelastic link rotation capacity and LCF life of shear links. The proposed link utilizes a splice connection at the mid‐length, where frictional faying surfaces are introduced to dissipate energy. Slip at the mid‐splice connection causes a relative vertical displacement between the link ends which eventually reduces the rotation demands on the I‐shape members. Experimental and numerical studies were conducted to study the proposed link concept. Three conventional and eight frictional mid‐spliced links were tested using a nearly full‐scale test setup. The results showed that the proposed links have a pinched link shear versus link rotation response. The links were able to sustain a link rotation demand of 0.23 rad together with a significant increase in their LCF life. Numerical studies were conducted to investigate the link rotation, interstory drift, and residual interstory drift of EBF archetypes equipped with the proposed frictional link.

Numerical study on thermal-electrical-mechanical coupling mechanism of electrical connectors considering contact resistance

Electrical connectors are widely used in electromechanical equipment. Their rough surfaces inevitably induce electrical contact resistance (ECR) and thermal contact resistance (TCR), which generates a significant influence on electricity and heat conducting at the faying surface and affects the accuracy of the thermal-electrical-mechanical coupling (TEMC) numerical calculation. Thus, a TEMC model with ECR and TCR of a parallel groove clamp is necessary to investigate the TEMC mechanism. Firstly, appropriate ECR and TCR models are created based on the available experimental results. Secondly, a refined TEMC finite element model is established by optimising the mesh size at the faying surfaces, and the cyclic coupling calculation method is adopted to achieve efficient and consistent numerical calculations. Meanwhile, the validity of the simulation model is verified by experimental results. Finally, the transient real contact area, current density, and heat generation rate (HGR) are obtained to analyse the TEMC mechanism during temperature rise. The results indicate that the mechanical characteristics during temperature rise are different under two loading conditions of tight and loose, thereby resulting in different changing laws in terms of the maximum current density and HGR. In addition, two coupling mechanisms exist until the steady-state temperature is achieved.

A New Method of Predicting the Parameters of the Rotational Friction Welding Process Based on the Determination of the Frictional Heat Transfer in Ti Grade 2/AA 5005 Joints.

The article presents an original approach to determining the basic parameters of rotational friction welding (RFW) based on the analysis of friction heat transfer at the faying surfaces. Dissimilar Ti Grade 2/AA 5005 joints were used to demonstrate the method. The work established that for the analyzed joint, the optimum temperature at the faying surface that allow for a good quality weld to be obtained should be ~505 °C. On this basis, a map of optimal parameters was developed to achieve this temperature. This approach could potentially allow for more precise control of the welding process, leading to better joint quality and performance. The paper includes both a description of the technological process of friction welding and an attempt to explain the mechanism of the phenomena occurring in the welding area. The numerical calculations presented in the article were carried out using the ADINA System v. 9.8.2, which allows for the consideration of heat friction in the axial symmetric thermo-mechanical model. Frictional resistance was determined by the temperature-dependent friction coefficient. The assumed thermo-mechanical model required the determination of elastic-plastic properties versus temperature for the analyzed materials. The simulations of the friction welding were carried out for the different welding parameters and time. The different variants of friction welding were modelled.

The Effect of Electrode Geometry and Pre-heating Treatment on Resistance Spot Welding Strength

Resistance spot welding (RSW) is one of the most significant and common metal joining methods used in industries. The present paper discusses the comparative performance of resistance spot welding electrodes of nontraditional design with the traditional one of 8 mm contact diameter in welding a 1.5 mm thick low carbon steel sheet used in automobile structural bodies and bridges. The modified electrode tip surface center was machined to have three different holes of 2, 3, and 4 mm depth and three different diameters of 2, 4, and 6 mm producing nine different hollow electrode dimensions. As well as the influence of pre-heating temperature on the mechanical properties of the weld joint was investigated by considering the other main parameters of welding time, current, and force are constant. The shear tensile test and torsion test examinations are carried out to investigate the mechanical properties. Also, to interrupt the results, a macrograph examination was conducted to determine the nugget size formation. The results show that the increase or decrease in the strength of the weld joint is greatly influenced by the proper selection of the modified electrode geometries. Also, the results indicated that the maximum improvement in shear tensile strength and torsional strength is about 140% and 150% compared to the traditional one. Furthermore, pre-heating processes helped decrease the contact resistance at the faying surfaces and improve the weld tensile strength and torsional strength to about 141% and 171% at 200 oC. Moreover, improvement may be achieved by slightly increasing pre-heating temperatures