Dissimilar Thickness Research Articles

High-performance laser welding of thin Al-Si coated press-hardened steel with dissimilar thicknesses

The demand for lightweight, high-strength automotive structures has increased interest in laser welding of dissimilar-thickness sheets. However, conventional Al-Si coated press-hardened steels (25–30 μm) often face challenges like Al segregation and excessive ferrite formation, compromising weld quality. This study examines laser welding of dissimilar-thickness PHS sheets (1.2 and 2.0 mm) with a thin Al-Si coating (∼18 μm). At 3 m/min welding speed, adequate heat input reduces the ferrite fraction to 30%, achieving high tensile strength (1572 MPa) and elongation (6.7%), with fractures in the base metal (BM). The excellent mechanical performance results from the lower ferrite fraction and strengthening effects of work hardening in the narrow weld. However, at 5 m/min, reduced heat input increases the ferrite fraction to 44%, lowering tensile strength (1380 MPa) and elongation (4.0%). sing filler wire at 5 m/min improves aluminum dilution, reducing the ferrite fraction to 32% and shifting fractures back to the BM. These findings highlight the critical roles of heat input and filler wire in controlling microstructure and mechanical performance, guiding optimized welding of PHS components.

The Effect of DLC Surface Coatings on Microabrasive Wear of Ti-22Nb-6Zr Obtained by Powder Metallurgy

Titanium alloys have a high cost of production and exhibit low resistance to abrasive wear. The objective of this work was to carry out diamond-like carbon (DLC) coating, with dissimilar thicknesses, on Ti-22Nb-6Zr titanium alloys produced by powder metallurgy, and to evaluate its microabrasive wear resistance. The samples were compacted, cold pressed, and sintered, producing substrates for coating. The DLC coatings were carried out by PECVD (plasma-enhanced chemical vapor deposition). Free sphere microabrasive wear tests were performed using alumina (Al2O3) abrasive suspension. The DLC-coated samples were characterized by scanning electron microscopy (SEM), Vickers microhardness, coatings adhesion tests, confocal laser microscopy, atomic force microscopy (AFM), and Raman spectroscopy. The coatings did not show peeling-off or delamination in adhesion tests. The PECVD deposition was effective, producing sp2 and sp3 mixed carbon compounds characteristic of diamond-like carbon. The coatings provided good structural quality, homogeneity in surface roughness, excellent coating-to-substrate adhesion, and good tribological performance in microabrasive wear tests. The low wear coefficients obtained in this work demonstrate the excellent potential of DLC coatings to improve the tribological behavior of biocompatible titanium alloy parts (Ti-22Nb-6Zr) produced with a low modulus of elasticity (closer to the bone) and with near net shape, given by powder metallurgy processing.

A novel approach for zero material loss (zero flash) and uniform cross-section during friction stir welding of dissimilar thickness Cu and Al alloys

A novel approach for getting a uniform weld cross-section and flash-free joint with the help of friction stir welding (FSW) is implemented. The influence of the tool tilt angle and rotational speed on the macrostructure, microstructure, and mechanical properties was investigated. Mechanical characterization techniques like an optical microscope, FESEM, profilometer, tensile test, bent test, and XRD analysis were used to evaluate the joint properties. A maximum tensile strength of 108.91 MPa was achieved, which led to a joint efficiency of 96.38 %. A maximum bending angle of 107° was achieved for samples S5 and S6. The Al/Cu mixed region in the stir zone displayed a maximum micro-hardness of 152.26 HV whereas a minimum micro-hardness of 33.57 HV was achieved in the HAZ along aluminium side. Welds prepared at a rotational speed of 540 RPM and a tool tilt angle of 4.5°results in an almost flash-free joint.

A Case Study of a Laser Beam Welding Model for the Welding of Inconel 718 Sheets of a Dissimilar Thickness

Laser beam welding (LBW) is a highly demanded process for premium-quality joints in aeronautic, energy, or industrial sectors, where flexibility and low-heat-affected zones are required. One of the main applications of LBW in the near future is expected to be the welding of new turbine engine components, which are typically made of Nickel-based superalloys. However, parameter setup is time- and resource-consuming, where experiment-based methods are typically employed. Therefore, the process development is far from an efficient resource utilization. In the present work, an LBW numerical model is developed and experimentally validated through a machine-integrated monitoring system. The LBW model is based on solving the heat transfer problem produced by the laser and provides the resulting temperature field, as well as the weld bead dimensions. The model includes a variable heat source that automatically adapts to the welding regime, conduction, or keyhole. For the model validation, two Inconel 718 sheets of different thicknesses are butt-welded and an error of around 10% is obtained, which ensures the validity of the model.

Systematic approach to improve overlap laser welding of AA5052-H32 with dissimilar thickness by evaluation of mechanical performance, undercut, and welding penetration

Systematic approach to improve overlap laser welding of AA5052-H32 with dissimilar thickness by evaluation of mechanical performance, undercut, and welding penetration

Laser beam oscillation welding for fatigue properties enhancement of tailor-welded blanks

Dissimilar thickness laser welded tailored blanks of two low-alloyed carbon steel grades were fabricated. Laser welds made without beam oscillation exhibited serious root undercuts. Although these notches did not degrade the tensile strength, they were detrimental to the fatigue lifetime of a weld joint. Therefore, laser welds with three different beam oscillation modes to modify the root were examined. Application of beam oscillation improved fatigue properties in all tested cases. The best results were achieved with line oscillation, even though this mode did not suppress weld root notches, suggesting other factors, besides joint geometry, contributing to the resulting fatigue properties.

Laser butt welding of thin stainless steel 316L sheets in asymmetric configurations: A numerical study

Laser butt welding of thin metal sheets is a widely used fusion-based joining technique in industrial manufacturing. A comprehensive understanding of the complex transport phenomena during the welding process is essential for achieving high-quality welds. In the present work, high-fidelity numerical simulations are employed to investigate the influence of various symmetric and asymmetric welding configurations on the melt-pool behaviour in conduction-mode laser butt welding of stainless steel sheets. The analysis focuses on the effects of laser power density, heat source misplacement and different welding scenarios, including plates with a root gap, high-low mismatches, and dissimilar thicknesses, on the molten metal flow and heat transfer. The results show that advection is the dominant mechanism for energy transfer in the melt pool, and its contribution increases with higher laser power. The non-uniform temperature distribution over the melt-pool surface induces Marangoni shear forces, driving the flow of molten metal and leading to the formation of vortices and periodic flow oscillations within the pool. The effects of various types of asymmetries on the thermal and molten metal flow fields, as well as the process stability, are thoroughly examined and compared with symmetrical welding configurations. These comprehensive simulations provide valuable insights into the fluid flow dynamics and thermal field evolution during laser butt welding of thin metal sheets. The knowledge gained from this study can facilitate process optimisation and guide the improvement of weld quality in practical applications.

Effect of strain rate on tensile behavior of tailor welded blanks

The demand for weight reduction, cost savings, more fuel efficiency, and reduced greenhouse gas has led to the increasing application of tailor welded blanks (TWBs) in the automotive industry. The purpose of this study is to investigate the strain rate effect on the tensile behavior of TWB consisting of dissimilar thickness sheets. Hence, a fiber laser was used for welding St14 steel sheets. The weld zone was examined using metallographic and microhardness tests. For investigating the tensile properties, uniaxial tensile tests were performed at strain rates ranging from 0.001 to 10 s−1. It has been found that the presence of Bainitic microstructure in the weld zone increases its hardness. Tensile test results indicate that yield strength and ultimate tensile strength of base metals and TWB enhanced with increasing strain rate. The yield and ultimate tensile strength of TWB are higher than base metals at different strain rates. As the strain rate increases, the total elongation of the TWB decreases, but in base metals, it decreases first and then increases at higher strain rates. In TWB and base metals, by increasing strain rate, uniform elongation decreases, but post-uniform elongation increases. For analysis of plastic deformation of thick and thin parts of TWB, indexes of limiting thickness ratio and difference of ratios (DR) were used. DR decreases with increasing strain rate, which indicates a decrease in the plastic deformation of the thick part of TWB and is consistent with the experimental findings.

Fatigue analyses and life predictions of copper laser-welded lap-shear samples

This study experimentally and numerically investigated the fatigue response of laser-welded (LW) lap-shear samples in copper (Cu) sheets of dissimilar thicknesses. Fatigue tests were first conducted, and the resulting fatigue data and failure modes were recorded. To investigate the failure processes and mechanisms, microscopic examinations, including microhardness tests for Cu LWs, were conducted before and after the failure. The experimental results showed the interfacial failure under high-load-range and low-load-range conditions and the top sheet separation under median-load-range conditions. Next, finite element analyses for LW lap-shear samples were conducted to calculate the global stress intensity factors (GSIFs) and local stress intensity factors (LSIFs) for interfacial and kinked cracks, respectively. The GSIFs, LSIFs, and Paris law were further used to derive the two fatigue models to analyze the evolution of interfacial and kinked cracks, respectively. Finally, two fatigue models estimated a series of fatigue lives that matched the general trends of experimental data.

A Uniformed Calculation Criterion on Heat Band Width of Local PWHT on Welded Joint with Dissimilar Thickness

Local post-weld heat treatment is used to reduce welding residual stresses. The existing standards have great differences in the selection of the width of the heated band, and the heating width, as an important control parameter of the local heat treatment, will directly affect the quality of the heat treatment. In this paper, the numerical simulation method is used to simulate the welding and heat treatment process of unequal-thickness joints. The stress and deformation of the joint with different thickness ratios under different heating widths are studied by finite element simulation, focusing on the influence of the width of the heated band on the residual stress relief of the joint. Based on these studies, the criteria for determining the optimal width of the heating zone are consistent. Finally, the formula HB=HB1+HB2=3RT+1+k2RT for calculating local heat treatment heating width based on the thickness of welded joint for SA738Gr.B steel is established. Among them, HB1 is the width of the main heating zone, HB2 is the width of the auxiliary heating zone, k is the thickness ratio of the thick plate to the thin plate, and t is the wall thickness of the thin plate.

Effect of compensating aluminium alloy during friction stir welding of Al-Cu alloys having dissimilar thicknesses

Effect of compensating aluminium alloy during friction stir welding of Al-Cu alloys having dissimilar thicknesses

Effect of plate placement on nugget shape in joining dissimilar thickness automotive steel thin sheets using resistance spot welding

The automotive products are adopting modern design dynamics to meet the market demands. One of the challenges that the automotive industries are facing is joining dissimilar thickness steel panels. The current study is an attempt to understand the formation of nugget shape during the resistance spot welding process in joining dissimilar thickness automotive steel AISI 4340. Steel plates with two different thickness of 2 mm and 1.5 mm are considered in the current investigation. The numerical simulation of the resistance spot welding process is carried out in FEM based commercially available software package. The study revealed that the temperature and the shape of the nugget is not same with the alteration of the positioning of the steel plates having dissimilar thickness. The shapes of the nuggets are different when the plate with higher thickness is at the top than the nugget formed when the plate is placed at the bottom.

New Self-Clinching Fasteners for Electric Conductive Connections

This paper presents new rotational and longitudinal symmetric self-clinching fasteners to fabricate reliable connections in busbars with low electrical resistance for energy distribution systems. Connections consist of form-closed joints that are hidden inside regions where two busbars overlap. The investigation into the fabrication and performance of the new self-clinched joints involved finite element modelling and experimentation to determine the required forces and to evaluate the electric current flow and the electrical resistance at different service temperatures. The original design of the joints that was proposed in a previous work was modified to account for busbar strips of copper and/or aluminum with similar or dissimilar thicknesses, connected by means of self-clinching fasteners made from the same materials of the busbars, instead of steel. The effectiveness of the new self-clinched joints was compared to that of conventional bolted joints that are included in the paper for reference purposes. The results show that rotational symmetric self-clinching fasteners yield lighter fabrication and more compact joints with a similar electrical resistance to that of bolted joints. They also show that longitudinal symmetric self-clinching fasteners aimed at replicating the resistance-seam-welding contact conditions yield a reduction in electrical resistance to values close to that of ideal joints, consisting of two strips in perfect contact and without contaminant or oxide films along their overlapped surfaces.

Hybrid Dispersion Model Characterization of PAZO Azopolymer Thin Films over the Entire Transmittance Spectrum Measured in the UV/VIS/NIR Spectral Region.

Notwithstanding the significant optical applicability of PAZO polymer films, there are no accurate data about their optical characteristics. To remedy this shortcoming, in this study three PAZO polymer thin films are characterized, with dissimilar thicknesses, on glass substrates using only one UV/VIS/NIR transmittance spectrum T(λ) per sample and an original hybrid dispersion model (HDM). HDM is based on the Tauc-Lorentz model, the new amorphous dispersion formula, the Tauc-Lorentz-Urbach model of Foldyna and the Tauc-Lorentz-Urbach model of Rodriguez. HDM with two oscillators is employed in characterizations of the PAZO polymer films in the range [300, 2500] nm, whereby the root-mean-square deviation (RMSD) of the fitted transmittance spectrum with respect to T(λ) does not exceed 1.6 × 10-3. Decreasing RMSD by 2.3% to 94.4% is demonstrated by employing HDM compared with the above mentioned four popular dispersion models, for each one of the studied films. HDM is applicable to amorphous films independent of their thickness as well as to cases of non-transparent substrate.

Influence of copper plate positioning, zero tool offset, and bed conditions in friction stir welding of dissimilar Al-Cu alloys with different thicknesses

Friction stir welding of dissimilar thickness aluminum and copper alloys was carried out without offsets by placing the copper at different positions, with horizontal and inclined bed conditions. The influence of the copper plate positions and bed conditions on macro-structure, microstructure, and mechanical properties were investigated. Optical microscopy, FE-SEM, EBSD, Tensile test, bending test, micro-hardness, and XRD analysis were carried out to understand the joint formation mechanism. The joint efficiency of 90% and 80.08% and bending angles of 93˚ and 35˚ were obtained, respectively, when the copper was placed at the middle position with horizontal and inclined bed conditions.

An empirical model for the Backscattering coefficient of 1-30 keV electrons from thin film targets

In this paper, the electron backscattering coefficient for normally incident beams with energy up to 30 keV impinging on thin film targets is stochastically modeled using a Monte Carlo simulation.Accordingly, a generalized model describing the realisticbackscattering behaviortaking into account both the atomic number and the thickness for energy up to 30keV is proposed. The obtained results are compared to the experimental and theoretical data, where an excellent agreement is achieved. Moreover, the usefulness of the proposed model as a probe for investigating the electrons backscattered behavior of several materials is thoroughly discussed. It is revealed that the developedmodel allowsidentifying the critical thickness of thin film exhibiting the same electron backscattering behavior as that of a semi-infinite solid, which contributes to an accurate assessment of surface properties of various thin-films.The use of our empirical model enables reducing the simulation time as compared to that of complicated Monte Carlo time consuming simulation.Therefore, the presented model can be implemented to accurately determinatethe electron backscattering coefficient of various thin-film materials with dissimilar thicknesses, making it appropriate for surface analysis applications.

Fatigue life assessment of dissimilar thickness resistance spot welded C-Mn steel using Weibull distribution

Resistance spot-welding (RSW) is a non-solid-state welding process that is significantly utilized in the self-propelled industry for manufacturing motorized bodies and parts. In this study, current and voltage data were recorded with the help of Miyachi Weld Checker for determining the variation of dynamic resistance over a welding process. Variation in dynamic resistance was analyzed for characterizing the nugget growth. The dynamic contact resistance (DCR) curves delineate that the entire process of nugget progression is composed of contaminants breakdown, asperity softening, resistance increment, growing stage, and stable stage. Further, tensile-shear test and fatigue test were performed for determining peak load and energy absorption, and dynamic behavior of spot-welded samples. Two-parameter Weibull distribution was utilized for statistical analysis of the fatigue test results of the spot-welded joint.

Investigation on failure mechanism of the square clinched joints with different sheet thicknesses

An experimental investigation was carried out to probe into the effect of the thickness arrangement on the failure mechanism and mechanical behaviour of the square joint produced by square clinching tools. Failure mode, geometrical characteristics and absorbed energy of the square joint were investigated to evaluate the quality of the square joint. Full shear and button separation are two major failure types observed in failure tests. The micro morphology of different joint fractures was studied by SEM. Lap shear load and lap tensile load of the square joint were measured during failure process. From the results, the fracture of joints with various sheet thickness arrangements shows typical ductile fracture characteristics. Interlock and neck thickness of the square joints in various thickness arrangements enlarge along with the gain of the top sheet thickness. Greater mechanical load-carrying ability and absorbed energy of the square joint were observed when the thicker sheet is on the top layer. Square clinching process can achieve the joining of Al5052-H32 sheets with dissimilar thickness arrangements reliably. Thicker sheets are suitable for being placed on the top layer during the square clinching process.

Multi-response mathematical model for optimization of process parameters in CMT welding of dissimilar thickness AA6061-T6 and AA6082-T6 alloys using RSM-GRA coupled with PCA

The requirement projected by many industries for stronger, lighter, more efficient and cost-effective combined alloys in the welding of two dissimilar materials or dissimilar thickness. The current industry trend is the coalescence of various aluminium alloys of varying thicknesses. In this research paper, Cold Metal Transfer (CMT) welding process was used for the joining of AA6061-T6 and AA6082-T6 using ER4043 filler wire and inspected the effect of different process parameters on mechanical properties of welded butt joints. Current (I), welding speed or travel speed (TS) and gas flow rate (Q) are the input welding process parameters that are to be optimized. Full factorial central composite face-centered design (CCFCD) was utilized to optimize the tensile properties, microhardness and residual stresses. Grey relation analysis (GRA) with PCA is incorporated with CCFCD for finding out the optimal process parameter by considering multi-response parameters simultaneously. ANOVA was executed to interpret the impact of a process parameter on the mechanical properties of the weldments. Results showed that the most dominant process parameter was found to be the welding speed. The optimal process parameter obtained via the GRA-PCA technique is I3-TS1-Q1 (I - 100 A, TS - 5 ​mm/s and Q - 14 ​L/min having heat input 352 ​J/mm) which produces 226 ​MPa of ultimate tensile strength, 12.6% of elongation, 68.7 HV of microhardness and −152.3 ​MPa of compressive residual stress. The desirability of optimality level obtained through CCFD was 65.99% and significantly improved to 97.07 through GRA-PCA.

Microstructure and Mechanical Properties of Laser-Welded DP Steels Used in the Automotive Industry

The aim of this work was to investigate the microstructure and the mechanical properties of laser-welded joints combined of Dual Phase DP800 and DP1000 high strength thin steel sheets. Microstructural and hardness measurements as well as tensile and fatigue tests have been carried out. The welded joints (WJ) comprised of similar/dissimilar steels with similar/dissimilar thickness were consisted of different zones and exhibited similar microstructural characteristics. The trend of microhardness for all WJs was consistent, characterized by the highest value at hardening zone (HZ) and lowest at softening zone (SZ). The degree of softening was 20 and 8% for the DP1000 and DP800 WJ, respectively, and the size of SZ was wider in the WJ combinations of DP1000 than DP800. The tensile test fractures were located at the base material (BM) for all DP800 weldments, while the fractures occurred at the fusion zone (FZ) for the weldments with DP1000 and those with dissimilar sheet thicknesses. The DP800-DP1000 weldment presented similar yield strength (YS, 747 MPa) and ultimate tensile strength (UTS, 858 MPa) values but lower elongation (EI, 5.1%) in comparison with the DP800-DP800 weldment (YS 701 MPa, UTS 868 MPa, EI 7.9%), which showed similar strength properties as the BM of DP800. However, the EI of DP1000-DP1000 weldment was 1.9%, much lower in comparison with the BM of DP1000. The DP800-DP1000 weldment with dissimilar thicknesses showed the highest YS (955 MPa) and UTS (1075 MPa) values compared with the other weldments, but with the lowest EI (1.2%). The fatigue fractures occurred at the WJ for all types of weldments. The DP800-DP800 weldment had the highest fatigue limit (348 MPa) and DP800-DP1000 with dissimilar thicknesses had the lowest fatigue limit (<200 MPa). The fatigue crack initiated from the weld surface.