Strength Of Welded Joints Research Articles

Large depth to width ratio friction stir welding joint obtained by novel designed tool with double pin

A novel welding tool with a double pin structure was proposed to solve the problem of difficult weld formation with a large depth to width ratio (DWR). Experiments revealed that the novel welding tool could achieve non-defect joints for four common engineering aluminum alloys (2A12-T6/5052-H32/6013-T6/7075-T6), with a DWR of 0.59–0.67. Due to the difference in the direction of material flow between the upper pin and the pin effect, impact slow flow zone was formed in the joint center. The maximum ultimate tensile strength of the 7075-T6 aluminum alloy double pin friction stir welding (DPFSW) joint reached 450.38 MPa, which was 85.8% of the base material. Analysis of the tensile fracture location revealed that the stirring zone of the advancing side and weld nugget zone occurred local blockage, resulting in joint failure. • In this paper, a novel welding tool with a double-pin structure is proposed, and it is demonstrated through experiments that the novel welding tool can achieve defect-free joints with DWR of 0.59–0.67 for four common engineering aluminum alloys. • The DPFSW joint can be divided into seven zones, where the ISFZ is caused by the different flow directions of the upper and lower layers of the DPFSW material, and the interior of this zone consists of a mixture of fine and coarse grains. • The numerical simulation results are consistent with the actual tensile results and the modeling is reasonable. PA and PB are the locations where partial blockage occurs in SZ-AS and UWNZ/DWNZ, which are the weak zones of the joints. • DPFSW joints are greatly influenced by the welding speed. At a welding speed of 100 mm/min, the joint strength was the highest, reaching 450.38 MPa, or 85.8% of BM.

Influence of biological pretreatment of wooden dowels on strength of rotary welded joints

Welding wood achieves joints whose strength is comparable with the strength of glued joints. When welding, the top of the dowel is not welded because of the lack of melted lignin. To achieve satisfactory strength of a welded joint, it is necessary to optimize the main welding factors such as interference fit, frequency of dowel rotation, welding depth, welding duration, etc. There are also other ideas to increase the strength of welded joints. One of these ideas involves pre-treatment of dowels with wood decaying fungi to increase the proportion of lignin on the surface of the dowels and thus in the melt. This paper presents the results of the impact of pretreatment of beech wood dowels with the brown-rot fungus Gloeophyllum trabeum. Results showed that biological pretreatment of the dowels had a significant impact on the pull-out force of the joint. Pretreatment for 4 weeks caused a substantial increase in pull-out force, while pretreatment for 2 weeks did not have a positive effect on the strength of the welded joint. Grooved dowels exhibited an increase in pull-out force of 26.9%, while smooth dowels had an increase of 21.1% of pull-out force. Research also determined additional vibrations during welding.

Evaluation of hardness and impact toughness of drawn arc stud weldments on different structural steel grades

The drawn arc stud welding (DASW) procedure is usually qualified by visual examinations and practical destructive tests of the joint according to international standards. An assessment of the material properties in specific weld zone regions is not requested under consideration of their limited areas or the general joint dimension although the press welding process implies a complex metallurgy. Nonetheless, there is a need of knowledge regarding the heterogeneous material properties in the weld zone, especially when welding on base materials with specified strength and toughness behavior that might be significantly diminished. In this study, the local strength and toughness properties in welded joints of non-alloyed steel studs (Ø20 mm) on plates of different generic structural steel grades are investigated by hardness test and Charpy impact testing. A non-alloyed normalized structural steel (nominal yield strength 355 MPa) and a thermomechanically rolled fine grain structural steel of same strength as well as a quenched and tempered structural steel with high nominal yield strength of 690 MPa were examined. In the weld metal region, relatively similar hardness and low impact energy were determined despite of the different base plate steel grades. The base plate heat-affected zones suffer a strong embrittlement due to the DASW thermocycle.

Fatigue life improvement of similar and dissimilar aluminum friction stir welds by deep rolling

At the moment, high production costs prevent the friction stir welding (FSW) process from further industrial applications even if comparable high fatigue strength of the joints can be reached. Higher welding speed may reduce the production costs but decrease the fatigue strength of the manufactured FSW joints. A potential solution is a mechanical post weld treatment directly after welding to increase the fatigue strength of the FSW joint again. In this study, hydrostatic deep rolling was applied for fatigue strength improvement of similar and dissimilar FSW joints made of EN AW 5083 and EN AW 6082 alloys manufactured with different welding speed. Additionally, the fatigue strength was directly compared to conventional joints manufactured by metal inert gas (MIG) welding and to base material specimen made of EN AW 5083. The surface state in as-welded condition was characterized by surface roughness and residual stress measurements. Fatigue tests were performed to quantify the fatigue strength of the FSW joints. Similar compressive residual stresses were determined after deep rolling for similar and dissimilar joints. No fatigue life improvement was determined for deep-rolled similar joints made of EN AW 5083. However, in this condition, the fatigue life of the specimen was within the range of the base material. Thus, significant lower fatigue life and a high fatigue life improvement by deep rolling were reached for dissimilar joints. An increase of the welding speed from 300 to 800 mm/min strongly decreased the fatigue strength of dissimilar welded joints in the investigated case.

Experimental investigation and numerical analysis using Taguchi and ANOVA methods for underwater friction stir welding of aluminium alloy 2017 process improvement

The effect of under water friction stir welding for 5 mm AA2017 aluminum alloy plaque on mechanical properties has been examined and optimized. Nine different tests were designed according to Taguchi orthogonal array without changing the welding tool. Three variable operating parameters (Welding velocity, rotational velocity and axial force) have been used with three levels for each parameter. The effects of each FSW parameters on the weld joint were discussed and analyzed, the analysis of variance (ANOVA) is adopted to identify the contribution of each FSW underwater parameters. Moreover, the statistical Taguchi method (TM) was employed to pridect the optimal combination of welding parameters to improve the tensile properties such astensile strength (TS) of welded joints. In addition, the experimental tests show good agreement with that obtained by the proposed mathematical model. Wherethe obtained validation results confirm the robustness of the optimization method as a useful tool to improve the quality responses of underwater friction stir welding.

Investigation of cold cracking resistance of HSLA 950A steel by taguchi optimization technique

Cold cracking is one of the major issues during welding High Strength Low Alloy (HSLA) 950A steel. The aim of the present research work is to optimize preheating temperature, the addition of oxide particles, and heat input using the Taguchi design of experiments for bead on plate, especially on the improved impact strength of weld metal. The experiments are carried out at three levels of mentioned parameters and Charpy impact strength is considered as a response. L27 orthogonal array is selected for experimentation in the present investigation using three parameters. An addition of vanadium oxide (V2O5) has acted as a nucleation site for acicular ferrite and enhanced the cold cracking resistance of investigated steel. The experimental results suggested that the impact strength of weldment is strongly influenced by pre-heating temperature (74.5%) and less influenced by oxide particle concentration (12.7%), and heat input (12.2%). Microstructure at HAZ revealed the presence of a small proportion of acicular ferrite of Widmanstatten morphology and upper bainite near weldment causes the reason for enhancement in cold cracking resistance. Fractographic examination revealed the presence of both ductile and brittle fracture modes, which attributed to higher and lower impact strength of weld joint respectively.

Усталостная прочность сварных соединений сталей 30ХГСА–40ХМФА, полученных ротационной сваркой трением

Rotary friction welding (RFW) is used in the production of drill pipes for solid mineral prospecting. The need for the creation of the lightened drill strings for high-speed diamond drilling of ultradeep wells dictates the necessity of a greater focus on the study of a weld zone and setting the RFW technological parameters. This paper presents the results of experimental studies of a welded joint of a drill pipe of the H standard size according to ISO 10097, made of the 30ХГСА (pipe body) and 40ХМФА (tool joint) steels under the cyclic loads. The authors evaluated the influence of the force applied to the workpieces in the process of friction of the contacting surfaces (force during heating), and postweld tempering at a temperature of 550 °С on the cyclic life of welded joints, under the conditions of alternate tension-compression at the cycle amplitude stress of ±420 MPa. The study determined that with an increase in the force during heating, the microstructure changes occur in the zone of thermomechanical influence, contributing to an increase in the fatigue strength of welded joints. The authors identified the negative effect of postweld tempering on the fatigue strength of welded joints, which is expressed in the decrease in the number of cycles before failure by 15–40 %, depending on the magnitude of the force during heating. The optimal RFW mode of the specified combination of steels is determined, which provides the largest number of cycles before failure: the force during heating (at friction) Fh=120 kN, forging force Ffor=160 kN, rotational frequency during heating n=800 Rpm, and upset during heating l=8 mm. A series of fatigue tests have been carried out at various values of the cycle amplitude stress of the welded joint produced at the optimal mode and the 30ХГСА steel base metal; limited endurance curves have been plotted. It is shown that the differences in the limited endurance curves of the pipe body material (30ХГСА steel) and the welded joint are insignificant. The obtained results are supplemented by the microhardness measurement data and fractographs of fractured samples, revealing the mechanism of crack propagation under the cyclic loads.

Implementation of a nominal stress approach for the fatigue assessment of aluminium naval ships

Fatigue analysis is an important part of the structural design of weight-optimised naval ships, because they are often constructed from aluminium alloys or high tensile steel. Due to the low fatigue strength of these metals, the welded joints are vulnerable to cracking. Furthermore, naval ships can be required to operate in demanding environments, and remain in service longer than assumed during design. Thus, ship designers and in-service managers require efficient fatigue evaluation approaches. One industry-accepted and relatively quick method, documented in design codes, to assess the fatigue strength of welded joints is the nominal stress or S-N curve approach. However, there are uncertainties associated with using a design code; if all of the conditions for its applicability are not met, the analyst must reliably interpret the code. Further, different specifications for the use of S-N curves leads to different fatigue life estimates. In this paper, a refinement of the nominal stress approach for joints, typical of aluminium welded ship details, is proposed. The goal is to inject rigour and practicality into the fatigue analysis of naval ships. The refinement process leverages both in-service maintenance information and long-term strain measurements of a 56 m aluminium patrol boat. The sensitivity of the predicted fatigue life of welded details to the choice of S-N curve, available from a structural design code, and stress parameter extraction is investigated. Finally, recommendations for future work are provided.

ОПРЕДЕЛЕНИЕ ОПТИМАЛЬНЫХ РЕЖИМОВ СВАРКИ ЁМКОСТЕЙ ДЛЯ ХИМИЧЕСКОЙ ПРОМЫШЛЕННОСТИ С УЧЁТОМ ПРОИЗВОДИТЕЛЬНОСТИ ПРОЦЕССА

The paper studies the influence of the heat input value on the weld metal quality in manufacturing tanks for the chemical industry of corrosion-resistant steel 12H18N10T. The results of metallographic studies and welded joint strength tests are given. They are used as the basis for developing technological solutions (welding modes are determined) to obtain a high-quality welded joint ensuring maximum process performance.

EXPERIMENTAL STUDIES OF THE STRENGTH OF A LONG BASE FLAT WAGONS BY CARRYING OUT ENDURANCE CYCLIC FATIGUE TESTS

The need for experimental validation of structural solutions concerning the frame of long-base flat wagon and assessment of the accuracy of theoretical calculations by carrying out resource cyclic fatigue tests based on the results of the recent studies analysis in the research of the strength of long-base flat wagons, was established. The methodology for carrying out resource cyclic fatigue tests of a long-base flat wagon is presented. The results of theoretical studies on determining the strength of a long-base flat wagon are described. The results of experimental studies of endurance cyclic fatigue tests of the frame of a long-wheelbase flat wagon before and after structural improvement are shown. Structural changes and improvements of the frame of the long-base flat wagon at the stage of experimental endurance cyclic fatigue tests are presented. The place of initiation and development of a crack in the structure of the frame of a long-base flat wagon is shown. Based on the results of the research, the actual strength of the elements of the wagon structure was determined and the design of the long-base flat wagon was chosen in order to prevent fatigue failure and ensure the required operational safety. The need to improve the evaluation methods of fatigue strength of welded joints of the long-wheelbase flat wagons frames at the design stage has been proven. The content of the article will contribute to the construction of new models of long-base flat wagons for mainline railway and the modernization of existing models, as well as to increase their strength and service life while in operation.

Mechanical properties and corrosion behaviour of duplex stainless steel weldment using novel electrodes

Mechanical and corrosion properties of welded duplex stainless steel (DSS) structures are of paramount consideration in many engineering applications. The current research investigates the mechanical properties and corrosion integrity of duplex stainless-steel weldment in a simulated 3.5% NaCl environment using specially developed novel electrodes without the addition of alloying elements to the flux samples. Two different types of fluxes having basicity indexes of 2.40 and 0.40 were used to coat E1 and E2 electrodes respectively for DSS plate welding. The thermal stability of the formulated flux was evaluated using thermogravimetric analysis. The chemical composition, using optical emission spectroscopy, and the mechanical and corrosion properties of the welded joints were evaluated as per different ASTM standards. X-ray diffraction was used to find out the phases present in the DSS welded joints while a scanning electron equipped with EDS was used for microstructural examination of the weldments. The ultimate tensile strength of welded joints made using the E1 electrode was in the range of 715–732 MPa and that of the E2 electrode was found to be 606–687 MPa. The hardness was increased with increased welding current from 90 to 110 A. The welded joint with E1 electrode coated with basic flux has better mechanical properties. The steel structure in 3.5% NaCl environment possesses substantial resistance to corrosion attack. This validates the performance of the welded joints made by the newly developed electrode. The results are discussed on the basis of the depletion of alloying elements such as Cr and Mo observed from the weldments with the coated electrodes E1 and E2 as well as precipitation of the Cr2N in the welded joints made by E1 and E2 electrodes.

STRENGTH OF BUTT WELDED BUTT JOINT OF REINFORCEMENT OF CLASS A500C

The paper presents the results of experimental studies of the strength of cross-shaped welded joints of types К1-Кт and К3-Рр [1] of thermomechanically hardened reinforcement of class A500C [2] for hardening during welding of the main bar [3].
 Experimental studies included testing three series of samples of welded joints and reinforcement samples in the initial state. The first series included testing welded joints of type К1-Кт to strengthen the main bar during welding. Reinforcement Ø14A500С was accepted as the main (working) bar, and reinforcement Ø12A500С and Ø8A240С were accepted as the transverse bar. For each joints, 6 samples were tested on the lower and upper limits of the carbon equivalent values of the grade steel class Ст3пс, 0.245% and 0.346%, respectively. The second series included testing of welded joints of the K3-Pp type to strengthen the main bar during welding. To directly compare the test results of different types of cross-shaped welded joints, the diameter of the main and transverse rods, the number of samples and the value of equivalent were the same as in the first series. The third series included testing welded joints of type К1-Кт for cutting. Reinforcement Ø14A500С was taken as a longitudinal bar, and reinforcement Ø12A500С and Ø8A500С was taken as a transverse rod. For each joints, 12 samples were tested at the lower and upper limits of the carbon equivalent values.
 As a result of testing samples of welded joints of types К1-Кт and К3-Рр of reinforcement A500C for strengthening during welding, it was established that the destruction occurs along the main bar and in the zone of thermal exposure, the amount of hardening was up to 4% for the К1-Кт compound, and for the К3-Рр type connection - 4... 10%.
 Failure of samples of welded joints of type К1-Кт reinforcement A500C with reinforcement Ø12A500C and Ø8A240C during the cut test usually occurred in the zone of thermal exposure, or in some cases, in the presence of both rods from reinforcement of class A500C - directly at the welding site. The average value of cut strength for a sample of 24 samples of reinforcement connections of class A500C with reinforcement A240C was 356.5 MPa, or 0.89 of the temporary resistance of the reinforcement in the initial state, with a coefficient of variation - 0.08 and a span of 107.4 MPa. The average cut strength for a sample of 24 samples of reinforcement connections of class A500C with reinforcement A500C was 541.1 MPa, or 0.80 of the temporary resistance of the reinforcement in the initial state, with a coefficient of variation – 0.152 and a span of 280.0 MPa.
 The first series included fittings Ø12A500C, Ø14A500C, Ø16A500C from steel of the ST3ps brand and Ø18A500C, Ø20A500C, Ø22A500C from steel of the Ст3пс brand. A total of 278 samples of welded joints were tested. The second series included samples of C1-Co welded joints from the rest of the nomenclature of diameters and grades of steel reinforcement class A500C, namely Ø16A500C from steel grade St3ps, Ø20A500C, Ø22A500C from steel grade St3Gps and Ø25A500C, Ø32A500C, Ø32A500C, Ø32A500C. For each of the diameters, 6 samples were tested in the initial state and 6 samples of C1-Co welded joints.
 It was found that the destruction of the butt contact connection type C1-Co thermomechanically reinforced reinforcement class A500C of all diameters, from 12 to 32 mm, and steel grades, takes place in the zone of thermal impact and is plastic.
 Experimental data on the strength of the butt contact weld type C1-Кo reinforcement class A500C for the entire range of diameters and grades of steel produced in Ukraine. It is established that the greatest degree of hardening within 19-20% takes place at diameters of armature of 12… 16 mm from steel of the Ст3пс brand, at diameters of armature of 18… 22 mm from steel of the Ст3Гпс brand of marking made 15-17%, and at diameters of 25… 32 mm from steel of the 25Г2С brand - 2,5… 8%.

Microstructure and mechanical properties of laser welded hot-press-formed steel with varying thicknesses of Al–Si coatings cleaned by nanosecond pulsed laser

The Al–Si coatings are commonly used for hot-press-forming (HPF) steel to prevent oxidation in the automobile industry. However, due to the presence of Al–Si coating, undesirable intermetallic compounds are easily formed in the welds of HPF steel. In this work, an environment-friendly and effective nanosecond pulsed laser cleaning process was used to remove the Al–Si coating, and HPF steel with varying thicknesses of coatings was prepared for laser welding. The microstructure and mechanical properties of laser welded HPF steel with different thicknesses of coatings were further investigated. The results showed that there was a threshold of power to remove the Al–Si coatings in the laser cleaning process. The reduced thickness of coatings not only could improve the stability of the welding process due to the diminishing of metal vapor generated by coating ablation, but also decrease the content of the Fe–Al phase in the welded joint, which is detrimental to weld performance. The tensile strength and cupping test pass rate of weld joints gradually increased with the decreasing thickness of coatings to 5 μm. After that, the Al–Si coating almost had no effect on the mechanical properties of the laser weld joints. The laser weld joint with 5 μm-thick of Al–Si coating showed, a tensile strength of 1435.05 MPa, a microhardness of 488.38 HV and a pass rate of 100% for the cupping test.

Advantages of an All-Welded Freight Car Bogie Side Frame

Purpose. Railway safety during the operation of freight cars largely depends on the reliability, fatigue resistance and durability of the cast bearing elements of the three-element bogie, especially the side frames. Premature failure of cast frames occurs mainly due to undetected latent defects in the foundry. To eliminate these problems, it is advisable to develop an alternative native all-welded side frame for a bogie with an axle load of 23.5 tnf, which can be interchangeable with the cast structure. Methodology. Mathematical modelling approaches were used to determine the stress-strain state of an all-welded structure under the influence of regulated loads and to assess its strength in accordance with current national and modern world standards. Findings. Prototypes of the all-welded side frame structure were subjected to accelerated fatigue tests. The tests have experimentally proved that the cyclic durability of the developed side frame is significantly (2...4 times) higher than the cyclic durability of cast side frames. Originality. A comparative analysis of the permissible stress amplitudes in different zones of the all-welded side frame during long-term operation based on 107 load cycles in accordance with the current standard for the strength of railway cars and modern approaches to determining the fatigue resistance of welded joints showed the insufficient conservatism of the national standard for assessing the fatigue strength of welded joints, which was taken into account when developing a new design of the all-welded side frame. Practical value. In addition to increasing reliability, possible increase in overhaul mileage and warranty period of side frames by ensuring a high level of fatigue resistance and durability, the welded structure can ensure the accuracy of the base frame size, reduce the weight of unsprung masses, which should reduce wheel wear and improve the running characteristics of railway carriage bogies. Reducing the cost of introducing all-welded side frames into mass production compared to the use of foundry technology for the manufacture of these structures and the fact that the cost of manufacturing an all-welded side frame is generally competitive with a cast structure is also one of the important advantages of our developme

Optimization of friction stir welding process parameters using MCDM method

Friction Stir Welding (FSW) is categorized into a solid-state welding process which is preferred to join aluminum-based materials effectively. Generally, aluminum-based materials are welded using solid state welding than fusion-based welding due to the chance of hot cracking, loss of elements and porosity. Process parameters and its selection in FSW process are important and it leads to efficient of weld quality. Taguchi concept is a standard optimization procedure but it has a limitation of not capable to solve multi objective problems simultaneously. Multi Criteria Decision Making (MCDM) method can be used for solving multiple objectives simultaneous effectively. Al-6061 T6 alloy is used as workpiece and carbon steel, H13 tool steel and high carbon high chromium steel is used as tool materials. The important process parameters considered are rotational speed of tool and welding speed. Response parameters selected are tensile strength and microhardness of welded joints. Process parameters are optimized using MCDM method and the optimum values obtained are rotational speed of 700 rpm and welding speed of 35 mm/min. It is understood that better tensile strength and microhardness of FSW joints at optimized condition due to adequate material flow, fine grain size and pulsating action. MCDM method has simple calculation procedure and easier solving methodology for machining parameters optimization.

Resistance welding of thermoplastic composites with nanofiber films prepared by electrospinning technique

In resistance welding of thermoplastic composites, a stainless-steel (SS) heating element (HE) is usually applied with current to provide heat to melt the thermoplastic polymer and remains at the joint. In this study, electrospinning technique was proposed to produce nanofiber films on the SS HE to achieve the hole pre-filling in the mesh and to provide a resin-rich zone in the bondline to enhance resin impregnation and void reduction, which improved the mechanical interlocking of the joints. The lap shear strength (LSS) of welded joints with nanofiber films was increased by 2.3 times to 36.98 MPa in comparison to the film-free joints and the indefinite fatigue life of the joint was reported at 20% of the static LSS. Taguchi method and Analysis of Variance approach were used to investigate the influence of the process parameters on the LSS. A comparative analysis of the welding curves, defects distributions, and fractographic evolutions was carried out for welded joints with and without the nanofiber films. With nanofiber films, the main failure modes of the joints changed from HE debonding to interlayer debonding.

Numerical Modelling of Thermo-Mechanical Effects Developed in Resistance Spot Welding of E304 Steel with Copper Interlayer

Resistance spot welding is a technique applied to join two or more similar or dissimilar metals, by applying pressure and electric current to the spot-weld area. Based on the electrical resistance property of metals, a great amount of heat is generated and used to carry out materials joints, by creating a molten metal nucleus between the components to be welded. The influence of an interlayer material, positioned between the parent materials, on the strength of similar or dissimilar welded joints was studied by researchers worldwide. In most cases, by optimising the process parameters, an increase in the welded joint strength was achieved. In this paper, the resistance spot welding of 1mm thick E304 stainless steel sheets, both with and without a copper foil interlayer, was investigated, by applying, in all cases, the same process parameters. The tensile test of the joints showed a decrease in the strength of joints performed with interlayer metal. A method to control the deterioration level of the joint’ mechanical properties is the Finite Element Analysis which allows to optimise the process parameters so that the negative effects of the process on the joint quality to be limited. It was found that an increase in amperage is needed to compensate for the addition of the interlayer metal and to obtain an adequate melting in the spot-weld area. This modification causes an increase of the molten core diameter that will lead to improvement of the welded joint strength, while no significant influence on the internal stress level was noticed in the processing and numerical analysis of the output data.

Research on root appearance and fatigue life of steel catenary riser (SCR) using GMAW/GTAW-P double-sided root welding process

A steel catenary riser (SCR) is a flexible stand-up pipe that connects a subsea wellhead in the seabed (normally at a depth of more than 1500 m) to a floating platform. Waves, ocean currents, and winds apply substantial loads to SCRs that produce fatigue damage. Hence, the requirements for the appearance of SCR weld joints, particularly the weld root, are extremely strict. This paper proposes a new gas metal arc welding/pulse gas tungsten arc welding (GMAW/GTAW-P) double-sided root welding process for SCRs to obtain a nearly smooth root geometry. Test results show that the average values of root reinforcement, root transition angle, and transition radius achieved with this root welding process are only 169 μm, 6.4°, and 4055 μm, respectively. These values are dramatically lower than those achievable with the best technologies available, such as the surface tension transfer (STT) root welding process and cold metal transfer (CMT) root welding process. The fatigue strength of the double-sided welding joints is improved by at least 45.8% because the root stress concentration is significantly reduced. However, incomplete penetration defects were found when the molten pool position was not appropriate. Solutions for this problem are discussed. The proposed process is believed to be a potential strategy for welding high fatigue life SCRs.

Microstructural and mechanical properties of AlSi10Mg: Hybrid welding of additively manufactured and cast parts

Welding and joining of hybrid components consisting of additively manufactured (AM) parts and conventionally processed parts offer new opportunities in structural design. In the present study, AlSi10Mg specimens were fabricated using two different manufacturing processes, i.e., laser-based powder-bed fusion of metals (PBF-LB/M) and casting, and welded by means of friction stir welding (FSW). Material strength of dissimilar welded joints was found to be governed by the as-cast material, which is characterized by a very coarse microstructure resulting in inferior hardness and tensile properties. During fatigue testing, cast-cast specimens performed slightly better than their hybrid AM-cast counterparts with respect to lifetime, being rationalized by most pronounced strain inhomogeneities in the AM-cast specimens. With the aim of cost reduction, FSW can be employed to fabricate graded large parts as long as the AM as-built material is placed in the region demanding superior cyclic load-bearing capacity.Graphical abstract

Mechanical properties of aluminium alloy 6082-T6 plate and butt weld joint: Experimental test, numerical modelling and application

Aluminium alloy has high mechanical properties and is widely used in manufacturing vehicles to reduce weight. This paper describes an experimental and numerical study of the mechanical properties of aluminium 6082-T6 plates and butt weld joints. Experiments were conducted on three 6082-T6 plates and three butt weld joint specimens, and then stress-strain curves were obtained and analyzed. Finite element (FE) models were developed and validated against the test results. Based on the test and numerical data, the application of the strength analysis of an electrical commercial truck frame with aluminium 6082-T6 using the finite element method was illustrated. The results show that compared with the base metal, the tensile strength of the butt weld joint is significantly reduced since the welding heat affected zone became a weak part of the joint. The results of the case study show that strength analysis of the truck frame with aluminium 6082-T6 using the FE method can be performed based on mechanical performances obtained in this study.