List of articles (by subject) welding
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Open Access Article
1 - Optimizing Friction Stir Welding Process for Enhancing Strength and Hardness using Taguchi Multi-Objective Function Method
Sajjad Khaki Ali Heidari Amin KolahdoozAs a solid-state welding method, friction stir welding is widely employed for welding aluminium alloys. An important subject in this regard is the optimal adjustment of the parameters to maximize the ultimate tensile strength and the surface hardness. Four parameters ha MoreAs a solid-state welding method, friction stir welding is widely employed for welding aluminium alloys. An important subject in this regard is the optimal adjustment of the parameters to maximize the ultimate tensile strength and the surface hardness. Four parameters have been selected for the multi-objective optimization of the 6061-T6 aluminium alloy, namely the rotational and the linear speed of the tool, the variation of the shoulder diameter with respect to the pin diameter (D⁄d ratio), and the shoulder base angle. The Taguchi's L9 Orthogonal Array has been employed for designing experiments. The experimental results have been examined using the Taguchi signal-to-noise (S/N) method, the analysis of variance, and regression. Optimization using the multi-objective Taguchi function revealed that a rotational speed of 800 rpm, a D⁄d ratio of 18/6, a shoulder base angle of 7°, and a linear speed of 80 mm/min yield both maximum strength and surface hardness. The results of the S/N analysis suggested the rotational speed of the tool and the linear tool speed have the most significant impact on the tensile strength with the average of 44.07 dB. On the other hand, the linear speed and the ratio of the diameters have the most significant impact on the surface hardness (around 36.91 dB). The results showed that using this optimization method, simultaneous improvement of tensile strength and surface hardness occurs. In fact, the tensile strength and hardness of the sheet surface were improved by 17.3% and 6.2%, respectively. Manuscript profile -
Open Access Article
2 - Optimization of AZ61 Mg Alloy Resistance Spot Welding using Response Surface Method
Afshin Lotfi Davood Afshari Zuheir BarsoumThe purpose of this study is to investigate the effect of resistance spot welding (RSW) parameters on nugget size and ultimate strength of Magnesium alloy sheets AZ61 under tensile-shear test. In this study microstructural examination and hardness measurements were carr MoreThe purpose of this study is to investigate the effect of resistance spot welding (RSW) parameters on nugget size and ultimate strength of Magnesium alloy sheets AZ61 under tensile-shear test. In this study microstructural examination and hardness measurements were carried out on the welded samples. The results show that the weld nugget zone is divided into two separate parts: the equiaxed dendritic zone (EDZ) perched at the center of the weld nugget and the columnar dendritic zone (CDZ) situated around the fine-grained zone having it surrounded. The effect of the following three parameters: electric current, welding time and electrode force on the dimensions of the weld nugget and the welded ultimate strength is investigated. The response surface method (RSM) is employed to examine the effects of welding parameters and to attain optimum parameters. The analysis of variance (ANOVA) results of RSM model shows that however the tensile-shear strength and nugget size are improved with increasing the welding current and welding time, the welding current is the most influential parameter. In addition, the optimal values for the welding parameters are calculated to achieve the maximum nugget size and the ultimate strength of welded joint. Finally, a regression model is proposed in order to predict the peak load and the nugget size as function of the mentioned welding parameters. Manuscript profile -
Open Access Article
3 - Effect of Burr Grinding on Fatigue Strength of Steel Butt-Welded Connections
Abbas Fadaei Annette BetkhooduAmong assembling methods, welding is most widely used in various industries. During the welding operation, material is heated to a temperature above the melting point and melted material forms a weld pool. This leads to the formation of tensile residual stresses in the MoreAmong assembling methods, welding is most widely used in various industries. During the welding operation, material is heated to a temperature above the melting point and melted material forms a weld pool. This leads to the formation of tensile residual stresses in the weld toe. In this paper, effect of burr grinding technique on fatigue strength of butt-welded joint has been evaluated. Burr grinding is one of the weld geometry modification methods that with removing small crack-like defects at the weld toe and increasing weld toe radius leads to reduction of stress concentration factor (SCF) and improvement of fatigue strength of weld. Also, the finite element simulation was performed by using ABAQUS software and stress concentration factor was chosen as a criterion. This factor was calculated using analytical and numerical methods for samples before and after grinding. Burr grinding procedure on welded samples was done using an electric grinder and different conical burrs. Burrs with different radii have been selected in order to provide a better comparison. Fatigue life of samples before and after grinding was determined by fatigue tests under constant amplitude loading. The results show 43.72 percent improvement in stress concentration factor and 50.61 percent improvement in fatigue life of samples. In experimental study, the best result belongs to grinding with a 3 mm tapered burr leading to an improvement of 50.61% in fatigue life while grinding with 1 mm tapered gives the worst result of 8.88% improvement in fatigue life. Manuscript profile -
Open Access Article
4 - Effect of the Number of Welding Passes on the Microstructure and Wear Behavior of St52 Plain Carbon Steel Coated with a High Chromium-Carbon Electrode
Mohsen Barmaki Kamran Amini Farhad GharaviThis study investigated the effect of the number of welding passes on the microstructure, hardness, and wear behavior of St52 plain carbon steel coated with an E10-UM-60R electrode in accordance with the DIN 8555 standard using SMAW method. An optical microscope (OM) an MoreThis study investigated the effect of the number of welding passes on the microstructure, hardness, and wear behavior of St52 plain carbon steel coated with an E10-UM-60R electrode in accordance with the DIN 8555 standard using SMAW method. An optical microscope (OM) and a scanning electron microscope (SEM) were used, and an EDS analysis was carried out to examine the microstructure. The Vickers micro hardness test and a reciprocating wear test were also used to examine the hardness and wear resistance. The results showed that the structure on the surface of the coated specimens is consisted of M7C3 carbides in the eutectic field (). In addition, the volume fraction of carbides increased in specimens that underwent two passes of welding relative to that in one pass-welded specimen. The reason for this was related to the decreased dilution of iron and increased dilution of chromium in the two-pass welded specimen and an increase in the volume fraction of M7C3 carbides. The increased percentage of carbides in the two-pass welded specimen increased the hardness and consequently the wear resistance relative to those in the one-pass welded specimen in a way that the surface hardness and weight loss in the wear test reached from 780 HV and 3.7 mg in the one-pass welded specimen to 910 HV and 2.5 mg in the two-pass welded specimen. Moreover, examining the wear surfaces indicated the occurrence of an adhesive wear mechanism in the specimens in a way that the adhesive wear rate decreased in the two-pass welded specimens. Manuscript profile -
Open Access Article
5 - Effect of TID-dressing on Fatigue Life Stress Concentration Factor in St37-2Butt Weldments
Abbas Fadaei Mostafa Jalalizadeh Faeze Mohammad ZaheriThe researchers have shown that there are cracks in the toe weld and they have an important role in the welding failure. The elimination of these shortcomings and the improvement of the fatigue life have always been a concern for the industrial designers. One method of MoreThe researchers have shown that there are cracks in the toe weld and they have an important role in the welding failure. The elimination of these shortcomings and the improvement of the fatigue life have always been a concern for the industrial designers. One method of improving the fatigue life of the welded joint at its geometry branch is to remelt the toe region of the steel weldments using the Tungsten Inert Gas (TIG) method or TIG-dressing. This method affects the material structure, hardness, stress coefficient and welding shape. In this study, the effectiveness of this method on fatigue and stress concentration at the weld toe was investigated. The experimental results showed that the toe weld form was changed by TIG – dressing and thus increased the radius and decreased the toe weld’s angle, so that the stress was reduced by TIG – dressing. Also, the fatigue tests showed that the fatigue life increased by an average of approximately 30 percent. Finally, the stress concentration factors were obtained using ABAQUS finite element analysis. The amount of stress concentration factors in weldments before and after TIG – dressing were respectively achieved to be 2.4 and 1.3. Manuscript profile -
Open Access Article
6 - A Novel Technique for Keyhole-Less Reinforced Friction Stir Spot Welding of Polyethylene Sheets
Moosa Sajed S. M. Hossein SeyedkashiTwo main problems exist with friction stir spot welded joints; remaining of a keyhole after welding and low strength of joints. In this paper, a novel method is proposed to address both problems in a simple and cost-effective way. This process is named “Reinforced MoreTwo main problems exist with friction stir spot welded joints; remaining of a keyhole after welding and low strength of joints. In this paper, a novel method is proposed to address both problems in a simple and cost-effective way. This process is named “Reinforced Friction Stir Spot Welding” or “RFSSW” which is based on recently introduced “TFSSW” process. SiC powder was added to the friction stir spot joints of polyethylene sheets with a thickness of 3 mm. First, the sheets were welded using conventional friction stir spot welding tool with a cylindrical pin. Then, the keyhole was filled with SiC powder. In the second stage, for stirring of SiC particles in the nugget and refilling the keyhole as well, a pinless tool was utilized. A homogenized distribution of reinforcing powder was obtained in the nugget. The effect of welding parameters including refilling tool shoulder diameter, refilling dwell time, and refilling tool rotational speed were evaluated in both TFSSW and RFSSW. In both processes, the refilling tool shoulder diameter was the most effective parameter. The strength was increased by 40% applying TFSSW and a further increase by 20% was obtained by reinforcing. Optimized parameter levels are refilling tool shoulder diameter of 24 mm, refilling tool rotational speed of 800 rpm, and refilling dwell time of 50s which result in shear strength of 1079 N. Manuscript profile -
Open Access Article
7 - Microstructure Investigation and Mechanical Properties of Resistance Upset Butt Welded Ti-6Al-4V Alloy
Mahmood SharifitabarIn the present study, resistance upset butt welding was used as a solid-state process for joining Ti-6Al-4V alloy. Results showed that melting and subsequent solidification of the alloy at the joint interface promoted the development of a cast microstructure along with MoreIn the present study, resistance upset butt welding was used as a solid-state process for joining Ti-6Al-4V alloy. Results showed that melting and subsequent solidification of the alloy at the joint interface promoted the development of a cast microstructure along with some pores. However, by applying the constant upset pressure of 1.62 MPa, the pore volume fraction decreased considerably with decreasing the welding current from 110 A/mm2 to 55 A/mm2. Hardness test results showed that the weld interface and the base material had the highest (352 HV) and the lowest (318 HV) values, respectively. The microstructure of the interface consisted of ά martensite and Widmanstätten laths. The tensile strength of the joints varied between 550 and 883 MPa depending on the welding parameters used. In the optimum condition, the maximum strength of the joint was about 94% of the base metal strength. Fractography of samples confirmed that the formation of pores deteriorated the strength of the joints. Manuscript profile -
Open Access Article
8 - Investigation of Pitting Corrosion Rate on Micro Plasma Arc Welded Dissimilar Weld Joints of AISI 304 and AISI 430 Stainless Steel Sheets
Uma Maheswara Rao G Srinivasa Rao ChalamalasettiIn the present paper investigation is carried out to study pitting corrosion rate of Pulsed Current Micro Plasma Arc welded AISI304 and AISI430 dissimilar joint in three different mediums namely 0.5N NaOH, 3.5N NaCl and 0.5N HCl. Linear Polarization method is used and T MoreIn the present paper investigation is carried out to study pitting corrosion rate of Pulsed Current Micro Plasma Arc welded AISI304 and AISI430 dissimilar joint in three different mediums namely 0.5N NaOH, 3.5N NaCl and 0.5N HCl. Linear Polarization method is used and Tafel are drawn, from which corrosion rates are evaluated in Heat Affected Zone (HAZ) of AISI 304, AISI 430 and at Fusion zone (FZ) of the weld joint. Corrosion pits are studied using Scanning Electron Microscope (SEM) images. It is revealed that AISI 304 is subjected to more corrosion when compared to AISI 430. Corrosion rate is higher in HCl when compared to NaCl and NaOH mediums. Corrosion rate is high at FZ, than HAZ of AISI 304 and AISI 430. Manuscript profile -
Open Access Article
9 - Analysis of Material Flow and Phase Transformation in Friction Hydro-Pillar Processing of 1045 Steel
Moosa Sajed S. M. Hossein SeyedkashiIn the present study, a 3D finite element model was developed using DEFORM commercial software to analyse the material flow and phase transformation, as two key phenomena affecting the joint properties in friction hydro-pillar processing of 1045 steel alloy. The microst MoreIn the present study, a 3D finite element model was developed using DEFORM commercial software to analyse the material flow and phase transformation, as two key phenomena affecting the joint properties in friction hydro-pillar processing of 1045 steel alloy. The microstructure changes significantly due to the high temperature and strain rate. The final microstructure was intergranular pearlite and grain boundary allotriomorphic ferrite. Pearlite was the dominant phase at the final microstructure; thus, its volume fraction was used to validate the model where a good agreement was obtained with the experiment. According to the model, the pearlite volume fraction varies from 100% to 70% moving from the bottom of the stud to the top. The model suggests an inverse relation between the strain rate and pearlite volume fraction. The highest temperature which was experienced in the welding step was 1490 ºC while it dropped to 890 ºC in the forging step. Downward and then radial material flow was detected in the welding step while upward extrusion of material was the dominant material flow pattern during the forging step. Flash was formed mainly in the forging step from stud side material. Manuscript profile -
Open Access Article
10 - Weld Distortion and Residual Stresses in Aluminum Hollow Section T-Joint
Asghar Mahdian Arash Babamiri Behrooz ShahriariWelding is known as one of the most popular attaching methods for different hollow section components. However, local concentrated heating, distortion, and residual stresses at welded joints are unavoidable. In this article, the welding simulation for rectangular hollow MoreWelding is known as one of the most popular attaching methods for different hollow section components. However, local concentrated heating, distortion, and residual stresses at welded joints are unavoidable. In this article, the welding simulation for rectangular hollow (RHS) sections for the front axle carrier of the new BMW series-7 is discussed and weld distortion and residual stresses in its aluminum T-joint for one proposed sequence are investigated. Comparisons of the results of this paper for this recommended sequence with experimental results in some references show good agreement and indicate that characteristics of the welding distortions are fully forecasted. In the following of this paper, the Finite Element Method (FEM) is used to offer a better sequence with smaller weld distortion and residual stresses. Weld distortion and residual stresses are highly influenced by welding strategy. In the proposed strategy, the needed time to perform the welding process decreased, and the total weld distortion and residual stresses decreased by 24% and 4%, respectively. Manuscript profile -
Open Access Article
11 - Effect of Post-Weld Heat Treatment on Microstructure and Mechanical Properties of AA7075 Welds
Alireza Jalil Nasrollah Bani Mostafa Arab Malek Naderi Yaghoub Dadgar AslThe attractive mechanical properties of 7075 alloy, such as its high strength-to-weight ratio and fracture toughness, have received special attention in the automotive and aerospace industries. However, welding as a fabrication process has a detrimental effect on this a MoreThe attractive mechanical properties of 7075 alloy, such as its high strength-to-weight ratio and fracture toughness, have received special attention in the automotive and aerospace industries. However, welding as a fabrication process has a detrimental effect on this alloy’s properties which affects its mechanical performance. In this work, to compensate for the loss in mechanical properties caused by welding, proper heat treatment operations are adopted. To this end, 1.5 mm AA7075 sheets were first preheated and butt welded using the gas tungsten arc welding process. The welded sample was solution heat treated, quenched, and then artificially aged. Microhardness tests showed an increase of hardness in all zones of the aged specimen compared to those of the original welded blank before heat treatment. A maximum microhardness value of 180 HV was recorded in the heat-affected zone of the aged specimen. In addition, elongation at break, and strength (yield, tensile, and fracture) of the original welded blank increased by about 50% after the artificial aging operation. Manuscript profile