Showing papers in "Science and Technology of Welding and Joining in 2008"
TL;DR: In this article, the fracture paths within the joint microstructure of spot welded AHSS, including dual phase (DP), transformation induced plasticity (TRIP), and ferritic-bainitic (FB), were compared to new high strength low alloy steels.
Abstract: Evaluating the impact performance of resistance spot welded joints in advanced high strength steels (AHSS) is critical for their continued integration into the automotive architecture. The effect of strain rate on the joint strength and failure mode is an important consideration in the design of welded structures. Recent results suggest that the failure mode is dependent upon the strength, chemistry, and processing of AHSS. Current literature, however, does not explain the effects of weld microstructure and a comprehensive comparison has yet to be conducted. The present study details the fracture paths within the joint microstructure of spot welded AHSS, including dual phase (DP), transformation induced plasticity (TRIP) and ferritic–bainitic (FB), in comparison to new high strength low alloy steels. Quasi-static and impact tests were conducted using a universal tensile tester and an instrumented drop tower respectively. Results for elongation, failure load and energy absorption for each material ...
138 citations
TL;DR: In this article, resistance spot welds were produced in dissimilar combinations of advanced high strength steels, and the microstructure and mechanical properties were characterised using metallurgical techniques and lap shear and cross-tension testing.
Abstract: Resistance spot welds were produced in dissimilar combinations of advanced high strength steels. A 600 MPa dual phase (DP) steel was welded to a high strength low alloy, a 780 MPa DP, and a 780 MPa transformation induced plasticity steel. The microstructure and mechanical properties were characterised using metallurgical techniques and lap shear and cross-tension testing. The results show that a pullout failure mode with improved mechanical properties is obtained when DP600 is paired with other advanced high strength steels, compared to the DP600 welded to itself, which is prone to interfacial failure and poor mechanical properties, given the same weld size. An in depth comparison of the interfacial to pullout failure transition in similar DP600 and DP780 and dissimilar DP600–DP780 welds was performed. The results show that the interfacial to pullout transition for the DP600–DP780 welds is significantly lower than with DP600 welded to itself. Increased fusion zone strength through dilution with th...
123 citations
TL;DR: In this article, a comprehensive, three-dimensional heat transfer and fluid flow model is developed and tested by comparing three different models of the weld pool and the fluid flow in order to understand the temperature fields, cooling rates and mixing in the welding pool.
Abstract: In order to understand the temperature fields, cooling rates and mixing in the weld pool, a comprehensive, three-dimensional heat transfer and fluid flow model is developed and tested by comparing ...
107 citations
TL;DR: In this article, a feasibility investigation was carried out of the formation of surface composite by uniformly distributing SiC particles 1˙25 µm in size into a surface layer of an A 1050-H24 Al plate through friction stir processing.
Abstract: A feasibility investigation has been carried out of the formation of surface composite by uniformly distributing SiC particles 1˙25 µm in size into a surface layer of an A 1050-H24 Al plate through friction stir processing (FSP). The SiC particle was filled into a groove cut on the Al plate, covered by an Al sheet 2 mm thick, and a rotating tool was penetrated from the cover sheet so that the probe tip reached a depth beyond the groove bottom. The effects of process parameters (rotation speed and travelling speed) and applying multiple passes on the distribution of SiC particle in the nugget zone were investigated. The effects of groove size and its position relative to the tool probe were also investigated. Applying multiple passes had a great effect on the homogeneity of the SiC particle distribution. At rotation speeds of 2000–3000 rev min−1, the SiC particles tended to cluster in some places in the nugget zone. By decreasing the rotation speed to 1000–1500 rev min−1, the SiC particle was distr...
107 citations
TL;DR: In this article, the effects of weld nugget size and expulsion on the performance of low carbon steel resistance spot weld have been investigated in the presence of voids and porosity as well as electrode indentation associated with expulsion.
Abstract: The effects of weld nugget size and expulsion on the performance of low carbon steel resistance spot weld have been investigated in the present paper. Failure mode, peak load and failure energy obtained in tensile–shear test have been used to describe the performance of spot weld. The influence of voids and porosity as well as electrode indentation associated with expulsion on peak load and failure energy is discussed. The results showed that although expulsion does not reduce the load carrying capacity of spot welds, it decreases their energy absorption capability which was attributed to the change of failure location due to excessive electrode indentation associated with expulsion.
98 citations
TL;DR: In this article, the authors obtained a fundamental knowledge of generation behaviour and ionised state of a plume or plasma induced during bead on plate welding of a 20 mm thick type 304 stainless steel plate with a 10 kW fibre laser beam of 0˙9 MW mm-2 power density, on the basis of 10 000 to 40 000 flames s-1 high speed video observation and spectroscopic analysis.
Abstract: The objective of this research is to obtain a fundamental knowledge of generation behaviour and ionised state of a plume or plasma induced during bead on plate welding of a 20 mm thick type 304 stainless steel plate with a 10 kW fibre laser beam of 0˙9 MW mm–2 power density, on the basis of 10 000 to 40 000 flames s–1 high speed video observation and spectroscopic analysis. The high power fibre laser produced a partial penetration weld of 12 mm in depth at 50 mm s–1 welding speed. According to the high speed observation pictures, the laser induced plume was repeatedly generated from a keyhole at the interval of about 0&dot5 ms period to reach 12 mm in maximum height. The spectroscopy indicated the line spectra of neutral atoms of alloying elements of type 304 such as iron (Fe), chromium (Cr) and manganese (Mn). However, ionised spectra of alloying elements and line spectra of argon (Ar) neutral atom were not apparently detected under these welding conditions. Furthermore, the temperature and the i...
91 citations
TL;DR: In this article, the joining of DC04 steel to 6016-T4 Al alloy is achieved by laser braze welding using a 4047 (Al-12Si) filler wire and a brazing flux.
Abstract: The joining of DC04 steel to 6016-T4 Al alloy is achieved by laser braze welding using a 4047 (Al–12Si) filler wire and a brazing flux. The dissimilar joining is obtained both by welding the parent 6016 alloy to the 4047 filler wire, producing a continuous bonding without apparent macroscopic flaws, and by reactive wetting of the molten Al alloy on the solid steel, resulting in the formation of a thin layer of Fe–Al–Si intermetallic compounds at the steel/bead interface. The linear strength of the assemblies can be as high as 190 N mm−1, with a failure generally located in the reaction layer of the steel/bead interface. Last, the strength of the assemblies is shown to increase linearly with the reaction layer width.
87 citations
TL;DR: In this article, material flow and intermixing during dissimilar friction stir spot welding and friction stir seam welding are investigated, and it is suggested that the onion ring structures observed in similar and dissimilar FSS welds mad...
Abstract: Material flow and intermixing during dissimilar friction stir spot welding and friction stir seam welding are investigated. During friction stir spot welding, a ribbon of contiguous dissimilar lamellae is produced during each rotation of the tool and the number of intermingled lamellae contained in the intermixed region is determined by the tool rotational speed setting and the dwell time applied. When the rotating tool moves across the component, the ribbon of dissimilar contiguous lamellae continues to be produced and the linear distance in the traversing direction between dissimilar lamellae corresponds with the pitch distance [the travel speed (mm s−1) divided by the tool rotational speed (Hz)]. The material flow pattern produced when a threaded tool moves across a component is therefore a variant of that produced during the touch down period when the rotating tool is held stationary. It is suggested that the onion ring structures observed in similar and dissimilar friction stir seam welds mad...
84 citations
TL;DR: In this article, the influence of shielding gas composition on arc properties including temperature, voltage, heat flux and shear stress at the anode and also the weld depth as indicated by the maximum temperature of a water cooled anode is investigated.
Abstract: The influence of shielding gas composition on arc properties including temperature, voltage, heat flux and shear stress at the anode and also the weld depth as indicated by the maximum temperature of a water cooled anode is investigated. It is found that the additions of helium, hydrogen and nitrogen to argon all increase the arc and anode temperature. For helium, this is due to the lower electrical conductivity; in the other cases, it is due to the higher specific heat.
78 citations
TL;DR: In this article, an overview of the physical background of the resistance welding process is presented, followed by the main problems concerning the appurtenant control theory and solutions to these problems are presented primarily according to the measured signals used and to the type of control strategies.
Abstract: This paper presents an overview of resistance spot welding control. The presentation of the physical background of the resistance welding process is followed by the description of the main problems concerning the appurtenant control theory. Solutions to these problems are presented primarily according to the measured signals used and to the type of control strategies.
76 citations
TL;DR: The morphology and structure of the weld interface in magnetic pulse welding of similar and dissimilar metals were investigated in this paper, where extensive characterisation techniques were used, including the focused ion beam (FIB) method, to prepare a cross-section of the Al-Mg interface for TEM characterisation.
Abstract: The morphology and structure of the weld interface in magnetic pulse welding of similar and dissimilar metals were investigated. The interface zone of dissimilar metal couples such as Al–Mg, was studied in comparison to Al–Al welds. It was found that intermetallic phases (IMP) of different compositions are created during welding of the Al–Mg couple by rapid solidification of a thin melted layer at the interface. According to the calculated energy balance of magnetic pulse welding (MPW), there is enough energy to melt a thin interfacial layer and create IMP. Intensive characterisation techniques were used, including the focused ion beam (FIB) method that was used to prepare a cross-section of the Al–Mg interface for TEM characterisation. It was established that the jet action plays an important role in the melting process at the bonding zone.
TL;DR: In this paper, an artificial neural network based system to predict weld bead geometry using features derived from the infrared thermal video of a welding process is proposed The multilayer perceptron and radial basis function networks are used in the prediction model and an online feature selection technique prioritises the features used in prediction model.
Abstract: In this article an artificial neural network based system to predict weld bead geometry using features derived from the infrared thermal video of a welding process is proposed The multilayer perceptron and radial basis function networks are used in the prediction model and an online feature selection technique prioritises the features used in the prediction model The efficacy of the system is demonstrated with a number of welding experiments and using the leave one out cross-validation experiments
TL;DR: Friction stir spot welding (FSSW) was applied to a lap joint of Al alloy 6061 sheets, 1 mm in thickness, to clarify its micro-mechanical properties as discussed by the authors.
Abstract: Friction stir spot welding (FSSW), which was recently developed as a spot joining technique, has been applied to a lap joint of Al alloy 6061 sheets, 1 mm in thickness, to clarify its micro...
TL;DR: In this paper, continuous drive friction welding of AA6061 Al alloy to AISI 304 austenitic stainless steel was carried out by incorporating Cu, Ni and Ag as diffusion barrier interlayers.
Abstract: Aluminium austenitic stainless steel joints find application in cryogenic engines, spacecrafts and automobiles. This dissimilar material combination is unweldable by conventional fusion welding due to a tendency for brittle intermetallic formation. Solid state welding processes such as friction welding are reported to be employed in such situations. This paper deals with continuous drive friction welding of AA6061 Al alloy to AISI 304 austenitic stainless steel. Direct welding of this combination resulted in brittle joints with 0° bend angle due to the formation of Fe2Al5. To alleviate this problem welding was carried out by incorporating Cu, Ni and Ag as diffusion barrier interlayers. The interlayer was incorporated by electroplating. Welds with Cu and Ni interlayer were also brittle due to the presence of CuAl2 and NiAl3. Ag acted as an effective diffusion barrier for Fe avoiding the formation of Fe2Al5. Therefore welds with Ag interlayer were stronger and ductile and could be bent to an angle o...
TL;DR: In this article, the effect of process parameters (cycle time, tool speed and axial force) on the specimen temperature measured 2 mm away from the weld in spot friction welding (SFW) of Al 6111-T4 is investigated.
Abstract: The effect of process parameters (cycle time, tool speed and axial force) on the specimen temperature measured 2 mm away from the weld in spot friction welding (SFW) of Al 6111-T4 is investigated. The temperatures were correlated to the lap shear load. Results revealed that, to achieve a good joint strength with the maximum lap shear load >2˙5 kN, temperatures should be greater than a threshold value, which is 350°C at a location close to the SFW joint in this study. By studying the specimen macrographs, two internal weld geometric features based on the cross-section area were identified and correlated to the shear and mixed failure modes of the lap shear tested specimens. A model was developed and validated using experimental data of the cross section area of SFW joint with either shear or mixed mode fracture. The model predicts that the SFW joint strength is maximised at the transition region between the shear and mixed mode fracture.
TL;DR: In this article, the formability of YAG and diode laser welded blanks of a dual phase (DP) steel with banded martensite was investigated by using limiting dome height (LDH) testing method.
Abstract: In this paper, the formability of YAG and diode laser welded blanks of a dual phase (DP) steel with banded martensite was investigated by using limiting dome height (LDH) testing method. One high strength low alloy (HSLA) steel with equiaxed ferrite matrix was included for comparison. Both steels had a ferrite matrix and dispersed secondary phase, namely martensite and carbide. The failure mode and dome height at fracture were examined on both parent metals and welded blanks. It was found that the failure pattern of DP parent metal was determined by its rolling direction. With increasing plastic strain, voids initiated along interfaces between ferrite/martensite due to decohesion between two phases and propagated preferentially along the interface. For DP welded blanks, dome test failures occurred within the softened zone in the heat affected zone (HAZ) regardless of the orientation between weld and rolling direction. Voids formed at the interfaces between ferrite and tempered martensite. The presence of the softened HAZ zone led to dramatic LDH decrease compared to the parent metal. The diode laser welded blanks had a lower dome height than that of YAG laser welded blanks due to their more severe HAZ softening. In comparison, HSLA parent metal and welded blanks exhibited almost the same LDH values and showed insensitivity to welding process. The failure of HSLA welded blanks initiated from the weld and propagated perpendicular to the unaffected base metal.
TL;DR: In this paper, a gas tungsten arc in helium and argon was modelled taking into account the contamination of the plasma by metal vapour from the weld pool, and the transient distribution of the temperature, velocity of plasma flow and iron vapour concentration were predicted, together with the weld penetration as a function of time for a 150 A arc current at the atmospheric pressure.
Abstract: A gas tungsten arc in helium and argon was modelled taking into account the contamination of the plasma by metal vapour from the weld pool. The whole region of gas tungsten arc atmosphere including the tungsten cathode, arc plasma and weld pool was treated using a unified numerical model. A viscosity approximation was used to express the diffusion coefficient in terms of viscosity of shielding gas and metal vapour. The transient two-dimensional distributions of the temperature, velocity of plasma flow and iron vapour concentration were predicted, together with the weld penetration as a function of time for a 150 A arc current at the atmospheric pressure, both for helium and argon welding gases.It was shown that the thermal plasma in gas tungsten arcs is influenced by iron vapour from the weld pool surface and that the concentration of iron vapour in plasma is dependent on the temperature of the weld pool.
TL;DR: In this paper, a keyhole gas tungsten arc welding (K-GTAW) was used to join commercially pure zirconium and the mechanical properties and the microstructure of the resulting joints were characterised.
Abstract: Keyhole gas tungsten arc welding (K-GTAW), a novel variant of GTAW, has been used to join commercially pure zirconium. The process enables single pass welding of 6˙35 mm thick zirconium using conventional GTAW equipment and a high current torch, without expensive filler metal addition or joint preparation. The mechanical properties and the microstructure of the resulting joints were characterised. It is concluded that the K-GTAW process, with its high productivity combined with low capital investment requirements, can be successfully used for welding relatively heavy section zirconium.
TL;DR: In this paper, the grain boundary misorientations of magnetic pulse welded (MPW) AA6061-T6 in linear and tubular configurations were examined using the electron backscattered diffraction (EBSD) technique.
Abstract: The grain boundary crystallographic misorientations of magnetic pulse welded (MPW) AA6061-T6 in linear and tubular configurations were examined using the electron backscattered diffraction (EBSD) technique. A refined structure of heavily deformed grains with higher grain boundary angles was observed in linear welds. Significant spalling was observed away from the welded region, in the interior of tubular welds. The results show the complex interaction of shock waves with the materials during this impact welding process.
TL;DR: In this article, the optical interaction between a fiber laser beam and a weakly ionised plasma was investigated in stainless steel welding with a 10 kW laser beam at the ultra high power density of ∼1 MW mm-2 in Ar shielding gas.
Abstract: A weakly ionised plasma can be generated in stainless steel welding with a 10 kW fibre laser beam at the ultra high power density of ∼1 MW mm–2 in Ar shielding gas. The objectives of this study are to obtain a fundamental knowledge of optical interaction between a fibre laser beam and the weakly ionised plasma, and to evaluate effects of the plasma on weld penetration. The optical interaction was investigated by the high speed video observation or the power meter measurement of another probe fibre laser beam, which passed horizontally through the weakly ionised plasma induced during bead on plate welding of a 20 mm thick type 304 plate with a 10 kW fibre laser beam of 0˙9 MW mm–2 in power density. The probe laser observed was refracted at 0˙6 mrad angle in average, which was much lower than the 90 mrad divergence of the focused fibre laser beam. The attenuation of the probe laser was measured to be ∼4%, which was not mainly caused by Inverse Bremsstrahlung but by Rayleigh scattering. Moreover, a s...
TL;DR: In this article, a series of CO2 laser-metal inert gas arc hybrid welding experiments was carried out to investigate the effects of laser/arc energy ratio and groove parameters on the shape and microstructure of hybrid weld.
Abstract: A series of CO2 laser–metal inert gas arc hybrid welding experiment was carried out to investigate the effects of laser/arc energy ratio and groove parameters on the shape and microstructure of hybrid weld The results showed that increasing arc current and groove cross-section area can reduce dimension difference of laser zone and arc zone by enhancing the uniform of energy distribution in molten pool The arc current can speed the melted metal flow to the pool root and drive more heat to the pool below by the arc pressure, and groove area can reduce the resistance of melted metal flowing to the pool root The microstructure of hybrid weld is simultaneously determined by the total line energy of hybrid welding and energy ratio of laser/arc (ER LA), and only under the proper or relatively smaller total line energy ER LA has obvious effects on microstructure Increasing the ER LA can increase the tendency of hybrid weld to obtain structure with higher hardness Furthermore, the mechanical performan
TL;DR: In this paper, the authors made dynamic observations of the nucleation and growth of acicular ferrite at inclusion sites using a high temperature laser scanning microscope, and the formation of a multiphase type of inclusions and the existence of titanium enriched layers on the interface between the inclusions, and nucleated ferrite were clarified by an electron diffraction analysis and an energy disperse X-ray spectroscopy (EDS).
Abstract: The strength and toughness in low carbon low alloy steel welds is improved by the refinement of microstructures resulting from the formation of acicular ferrite. The behaviour of the nucleation and growth of acicular ferrite has been extensively studied and the weld metal of refined acicular ferrite is practically used in industry. It is known that inclusions in weld metal strongly contribute to the nucleation of acicular ferrite. The present authors made dynamic observations of the nucleation and growth of acicular ferrite at inclusion sites using a high temperature laser scanning microscope. In the steel weld metal of a Ti–B system, the formation of acicular ferrite is reported to be controlled by the weight ratio of aluminium and oxygen (Al/O ratio) which is an index of oxygen potential after the completion of deoxidisation by aluminium. The proper control of the Al/O ratio results in the formation of MnAl2O4 oxide of a spinel structure whose capability of the acicular ferrite nucleation is governed by a specific lattice misfit between nucleated ferrite and this oxide. It is considered that the addition of titanium is essential because titanium assists the formation of MnAl2O4. 8 However, there are reports depicting that there is no specific lattice orientation between ferrite and oxides of a spinel structure. As to the role of titanium, the researchers reported that it brings about catalysis or acts as the first nuclei for acicular ferrite nucleation. In spite of the fact that the acicular ferrite production technology is practically used in industry, the mechanisms of the acicular ferrite nucleation have been not completely clarified yet and thus, the development of nucleation control technologies for a further improvement of weld metal toughness is hindered. In the present study, the inclusions were formed by varying Al/O ratios. Thus formed inclusions were directly sliced into thin foils and crystallographic analyses were performed using a transmission electron microscopy (TEM). The formation of a multiphase type of inclusions and the existence of titanium enriched layers on the interface between the inclusions and nucleated ferrite were clarified by an electron diffraction analysis and an energy disperse X-ray spectroscopy (EDS). Experimental
TL;DR: In this article, the martensite start and bainite start temperatures have been determined in reheated, high strength weld deposits, with each result associated with 95% coincidence limits.
Abstract: The martensite start and bainite start temperatures have been determined in reheated, high strength weld deposits, with each result associated with 95% coincidence limits. This helped define isothermal transformation temperatures where bainite can be obtained without the risk of unintentional transformation to martensite. It has been demonstrated, therefore, that coalesced bainite, which is detrimental to mechanical properties, can be generated isothermally without the possibility of confusion with autotempered martensite.
TL;DR: In this article, the effect of welding consumables on tensile and impact properties of high strength, quenched and tempered (Q&T) steel joints was investigated using a shielded metal arc welding (SMAW) process.
Abstract: Quenched and tempered (Q&T) steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking in the heat affected zone (HAZ) after welding and HAZ softening. The use of austenitic stainless steel (ASS) consumables to weld the above steel was the only remedy because of higher solubility for hydrogen in austenitic phase. Recent studies proved that high nickel steel (HNS) and low hydrogen ferritic (LHF) steel consumables can be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits. In this investigation an attempt has been made to study the effect of welding consumables on tensile and impact properties of high strength, Q&T steel joints. Three different consumables, namely ASS, LHF steel and HNS have been used to fabricate the joints by shielded metal arc welding (SMAW) process. The joints fabricated using LHF steel electrodes showed superior transverse tensil...
TL;DR: In this article, the authors investigated the thermomechanically affected zone (TMAZ) region during friction stir spot welding of AM60 and AZ91 materials and found no evidence of liquation cracking in the stir zone or the TMAZ region when AM60 was the lower sheet in the dissimilar sandwich.
Abstract: Cracking during dissimilar friction stir spot welding of thixomoulded AM60 and AZ91 sheet materials is investigated. Liquation cracking occurs in the thermomechanically affected zone (TMAZ) region during friction stir spot welding when AZ91 material is the lower sheet in the dissimilar AM60/AZ91 sandwich. A TMAZ microstructure comprising elongated α-Mg grains and aligned Mg17Al12 is created during the tool penetration stage in spot welding and melted eutectic film formation is facilitated since the temperature in the stir zone (504°C) is much higher than the α-Mg+Mg17Al12 eutectic temperature (437°C).There is no evidence of liquation cracking in the stir zone or the TMAZ region of AM60 sheet when it is the lower sheet in the dissimilar sandwich. However, liquation cracking is observed in the upper sheet material (AZ91) in the location beneath the tool shoulder close to its periphery.
TL;DR: In this paper, the authors discussed the longitudinal stress and transverse stress on twin wire welded plate, and a comparison is made with the result of finite element method obtained by Marc Software.
Abstract: The acoustical theory is introduced. Ultrasonic stress measurement experimental installation is established, consisted of a variable angle transducer and an oscillograph with special higher digitiser board. Acoustoelastic coefficient of longitudinal critically refracted waves propagating in Q-235 steel is calibrated by the tensile testing machine. In the present paper are discussed the longitudinal stress and transverse stress on twin wire welded plate, and a comparison is made with the result of finite element method obtained by Marc Software. The present paper also discusses the longitudinal stress distributions of multilayer welded plate and longitudinal residual stress gradient of 2219 Al alloy is obtained in the ultrasonic travel time change expression formal. Instability acoustoelasticity effect in elastic region of welding residual stress field is discovered. The sources of measurement error are pointed out. In conclusion the potential of the ultrasonic method in different industrial cases ...
TL;DR: In this article, the effect of the crystallographic anisotropy of β-tin grains on thermal fatigue properties of lead free solder interconnects was discussed, and three types of microstructures (single crystal-like, fine grain and large grain type) were observed in both solders.
Abstract: An effect of the crystallographic anisotropy of β-tin grains on thermal fatigue properties of Sn–1Ag– 0˙5Cu and Sn–3Ag–0˙5Cu lead free solder interconnects were discussed. From an orientation imaging microscopic observation, three types of microstructures (single crystal-like, fine grain type and large grain type) were observed in both solders. The single crystal-like microstructure disappeared and the large grain type occurred by further fatigue due to recrystallisation. Because single crystal-like microstructure had the {100} plane approximately parallel to strain concentrated areas, recrystallisation could be retarded if the slip systems of {100} or {100} operate and an amount of thermal strain decreases because these slip systems have the larger critical resolved shear stress due to an anisotropic nature of β-tin. One of the reasons Sn–3Ag–0˙5Cu had longer thermal fatigue life than Sn–1Ag–0˙5Cu can be the number of the single crystal-like or the fine grain type microstructures in Sn...
TL;DR: In this article, an integrated computational model was developed by considering microstructural heterogeneity and residual stress of spot welds, which consists of a resistance spot weld process model and a local mechanical model.
Abstract: An integrated computational model was developed by considering microstructural heterogeneity and residual stress of spot welds. The model consists of a resistance spot weld process model and a local mechanical model. The resistance spot weld process model is used to predict residual stress distribution, which is mapped into the local mechanical model. The hardness distribution of a spot weld is measured experimentally, and then converted into the tensile strength which is mapped into the local mechanical model. The local mechanical model is then used to predict the load response functions and failure modes of DP 590 spot welds. The predictions have been compared with DP 590 spot weld experiments.
TL;DR: Tungsten inert gas cladding of steel substrate with copper alloy under different processing conditions was investigated in this paper, with the particular emphasis on the influence of cladding current on the conc...
Abstract: Tungsten inert gas cladding of steel substrate with copper alloy under different processing conditions was investigated with the particular emphasis on the influence of cladding current on the conc...
TL;DR: In this paper, an intelligent system for weld joint strength prediction in a PMIGW process based on the analysis of acquired current signal by wavelet packet transform is introduced. But, it is not suitable for real-time quality control system for the pulsed metal inert gas welding process.
Abstract: The monitoring of welding process is crucial for the development of a real time quality control system for the pulsed metal inert gas welding (PMIGW) process. This work introduces an intelligent system for weld joint strength prediction in a PMIGW process based on the analysis of acquired current signal by wavelet packet transform. A thirteen-dimensional array of process features, i.e. six process parameters and seven wavelet packet features, are used to describe various welding conditions. These process features obtained from a set of experiments are employed as input vectors of an artificial neural network model to predict the corresponding weld joint strengths. The results, i.e. the prediction errors, show that the use of wavelet packet features gives much accurate prediction as compared to the use of the purely time domain features.