Pengelasan pada Stainless Steel dengan Tipe yang Berbeda Menggunakan Resistance Spot Welding untuk Aplikasi Gerbong Kereta

Salah satu jenis proses pengelasan yang banyak digunakan di dunia industri Kereta Api adalah proses <em>resistance spot welding</em>. Proses pengelasan ini mempunyai banyak keunggulan pada pengelasan pelat tipis dengan menggunakan sambungan tumpang yang diaplikasikan pada <em>side wall</em> kereta api. Penelitian ini dilakukan dengan tujuan untuk mengetahui pengaruh variasi parameter pengelasan yang meliputi <em>current</em>, <em>weld time</em>, dan <em>pulsation</em> terhadap <em>shear strength</em>, struktur mikro dan diameter <em>nugget</em>. Material yang digunakan adalah material SA-240 tipe 304 dan SA-240 tipe 201 dengan ketebalan 2 mm untuk material SA-240 tipe 304 dan tebal 3 mm untuk material SA-240 tipe 201. Pengujian <em>shear strength</em> diperoleh parameter<em> resistance spot welding</em> semakin tinggi, maka nilai <em>shear strength </em>juga semakin tinggi. Strukturmakro didapatkan semakin tinggi <em>current</em>, <em>weld time</em>, dan <em>pulsation</em>, maka <em>nugget</em> semakin lebar. Sedangkan pada hasil uji mikro pada daerah <em>base metal</em> struktur yang tebentuk adalah <em>austenite</em>, sedangkan pada daerah HAZ dan <em>weld metal</em> adalah struktur <em>ferrit</em> dan <em>austenite</em>. Ukuran butir pada daerah HAZ yang semakin mendekat ke daerah <em>weld metal</em> ukuran butirnya menjadi semakin besar. Struktur mikro yang terbentuk pada <em>weld metal</em> bentuknya memanjang (<em>columnar grains</em>) ke daerah yang mengalami pembekuan paling akhir.

Analysis of the oscillation behavior during ultrasonic welding of EN AW-1070 wire strands and EN CW004A terminals

For fulfilling the demand of durable yet lightweight electrical connections in transportation industries, ultrasonic metal welding (USMW) sees widespread use in these branches. As the ultrasound oscillations utilized in the welding procedure occur at a range of only a few micrometers at frequencies of 20–100 kHz for an overall duration of only 50–1500 ms, it is not possible to observe the compaction behavior with the bare eye. This paper focusses on investigating the oscillation behavior of the horn, the anvil, and the joining partners during the welding procedure by utilizing an array of synchronized laser vibrometers and performing welds with incrementing time stages. The oscillation data is correlated with temperature measurements in the welding zone as well as tensile testing results. Inter alia the formation of sidebands at the fundamental frequency as well as 2nd- and 3rd-order harmonics has been observed for the anvil, terminal, and wire front face when exceeding optimal weld time which would lead to maximum joint strength. Following the assumption of other research groups, the cause of these sidebands could be a change in relative motion of these components. As the terminal is slipping with increasing weld time, it could be assumed that the reason for the sidebands is low-frequency movement of the anvil, modulated onto the fundamental frequency, additionally indicating successful bonding of the stranded wire and the terminal. Furthermore, this slipping of the terminal on the anvil could lead to increased wear of the anvil knurls.

The Effect of a Hollow Fixture on Energy Dissipation of Ultrasonic Welded Carbon Fiber/Polyamide 66 Composite

In this study, the effect of the fixture configuration on ultrasonic welding of 4-mm-thick carbon-fiber-reinforced polyamide 66 (CF/PA66) composite with 30% mass fiber was evaluated. An analytical model to estimate the energy dissipation in the welding zone of lapped CF/PA66 samples was derived. Calculation analyses showed the energy dissipation at the faying interface of joints made from hollow-fixture ultrasonic welding (HFUSW) was about 25% higher than those made from conventional ultrasonic welding (CUSW) under the given process variables. This was primarily attributed to the almost total reflection at the workpiece-to-fixture interface in HFUSW. Experimental results indicated that the HFUSW joints exhibited a greater peak load and weld area than CUSW joints when the weld time was less than 2.1 s. The optimal weld time for CUSW and HFUSW processes were 2.1 and 1.7 s. When the weld time exceeded the optimal time, the joints occurred with a porous region, which was caused by thermal decomposition of the material, resulting in the decrease in peak load. Experimental and simulation results demonstrated the HFUSW process changed the propagation behavior of the ultrasonic wave and enhanced the energy dissipation at the faying interface. This study enriched the understanding of energy dissipation during ultrasonic welding of polymers.

Emphasis of Weld Time, Shielding Gas and Oxygen Content in Activated Fluxes on the Weldment Microstructure

The activated-TIG (A-TIG) process is a recognised process for achieving higher depth-of- penetration (DoP) and it could be used for various stainless-steel grades welding. The oxygen content of oxide based activated fluxes provide the extra heat during decomposition of flux and result into deep penetration. This study reveals the effect of short weld time of 2 sec in stationary arc, shielding environment (Ar and Ar + 2.5 % H2) and an effect of oxygen element in activated flux (CrO3 and SiO2) on the microstructure and weld metal micro-hardness. Use of hydrogen mix shielding gas during A-TIG process has significant impact on the dilution rate, grain size and dendrite arm spacing. The fraction of oxygen in the flux and the presence of silicon in SiO2 flux play a significant role in achieving higher DoP. To evaluate the impact of different shielding environment on grain growth, the samples were investigated with weld pool morphology, depth of penetration, weld chemistry, optical microscopy and SEM analysis. The extra heat produced due to oxygen fraction in activated flux and H2 induced shielding have been quantified in the study. The ferrite and austenite grain growth as well as the dendrite arm spacing found to be increased due to presence of H2 in shielding gas.

The Extent of Interlayer Bond Strength during Fused Filament Fabrication of Nylon Copolymers: An Interplay between Thermal History and Crystalline Morphology

One of the main drawbacks of Fused Filament Fabrication is the often-inadequate mechanical performance of printed parts due to a lack of sufficient interlayer bonding between successively deposited layers. The phenomenon of interlayer bonding becomes especially complex for semi-crystalline polymers, as, besides the extremely non-isothermal temperature history experienced by the extruded layers, the ongoing crystallization process will greatly complicate its analysis. This work attempts to elucidate a possible relation between the degree of crystallinity attained during printing by mimicking the experienced thermal history with Fast Scanning Chip Calorimetry, the extent of interlayer bonding by performing trouser tear fracture tests on printed specimens, and the resulting crystalline morphology at the weld interface through visualization with polarized light microscopy. Different printing conditions are defined, which all vary in terms of processing parameters or feedstock molecular weight. The concept of an equivalent isothermal weld time is utilized to validate whether an amorphous healing theory is capable of explaining the observed trends in weld strength. Interlayer bond strength was found to be positively impacted by an increased liquefier temperature and reduced feedstock molecular weight as predicted by the weld time. An increase in liquefier temperature of 40 °C brings about a tear energy value that is three to four times higher. The print speed was found to have a negligible effect. An elevated build plate temperature will lead to an increased degree of crystallinity, generally resulting in about a 1.5 times larger crystalline fraction compared to when printing occurs at a lower build plate temperature, as well as larger spherulites attained during printing, as it allows crystallization to occur at higher temperatures. Due to slower crystal growth, a lower tie chain density in the amorphous interlamellar regions is believed to be created, which will negatively impact interlayer bond strength.

Resistance Spot Welding of Dissimilar Alloys 1008 Low Carbon Steel- 1100 Aluminum Alloy

The resistance spot welding is adopted to joint dissimilar alloys such as aluminum alloy 1100 , and low carbon steel alloy 1008 by using cover plate. This study aims to optimization the best conditions of dissimilar welding of Aluminum with low carbon steel by RSW, and improving the properties of joints by many method. three different variables were used for the welding process: welding current (5, 6 ,7 and 8 KA), weld time (0.5, 1 and 1.5 sec) and electrode force (13.2 and 15.5 N).The welding joints are ―examined by a scanning electron microscope SEM and a X-ray diffraction‖ for the purpose of discussing the causes of the improved characteristics. The results revealed that the best welding conditions were under welding current 7 KA , weld time 1 sec and electrode force 13.2 KN, where the joint possessed the maximum shear force (4.8KN) and after improvement the tensile shear force become (6.02 KN), in addition to presence of the intermetallic compounds at optimum condition , such as AlFe3,Al5Fe4 and Al13Fe4, in the joint layer between dissimilar metal improves of the tensile shear forces and hardness in fusion zone.

Optimization on Spot Weld Parameters in Resistance Spot Welding Process on AISI 304

The spot welding procedure is used in a variety of industrial applications. The most critical elements influencing welding quality, productivity, and cost are the spot welding parameters. This research examines the effect of welding factors such as welding current and welding time on the strength of various welding joint designs. Resistance spot welding (RSW) is used in the automotive industry for manufacturing. This research focused on the optimization of process parameters for resistance spot welding (RSW), as well as the tensile testing and spot weld diameter. The goals of this analysis are to comprehend the physics of the process and to demonstrate the effect of electrical current, weld time, and material type on the resistance spot welding process.

Optimization of ultrasonically welded High density polyethylene with Medium density polyethylene

Ultrasonic welding is a mechanical system whereby high-recurrence ultrasonic acoustic vibrations are privately connected to workpieces being held together compelled to make a strong state weld. It is usually utilized for plastics, and particularly for joining disparate materials. The point of the undertaking is to examine the quality of weld when unique materials are welded together. The sort of weld will rely upon an on-hold time, weld time, weight, and recurrence. Materials utilized will be HDPE (High Density Polyethylene) and a blend of HDPE-LDPE which is termed as MDPE (Medium density polyethylene). Diverse materials have distinctive properties and thus making a joint with wanted properties will give a better outcome. If one material has properties like better elasticity, pressure quality and other material have properties like pliability and flexibility and so forth then the blend of these materials will have properties of both the materials and when these kinds of materials are welded ultrasonically, they give a better outcome. Subsequently we will get a material which will give better quality with ease. Likewise, the material will be increasingly adaptable.

PARAMETRIC STUDY OF MULTI-SPOT WELDED LAP SHEAR SPECIMEN FOR TENSILE AND SHEAR STRENGTH

The effect of number of spots, spot spacing, squeezing force, welding current, weld time, overlapping length and sheet thickness on the tensile and shear strength of two similar galvanized steel sheets are investigated through experiments using RSM method and by using software. Similar sheets of galvanized steel sheets are made by resistance spot welding at different processing conditions and these joint populations were tested under lap-shear loading conditions. Specially fabricated fixture is used to load the lap shear specimen in the universal testing machine Regression analysis is done to obtain relationship between shear strength and selected parameters. The experimental results indicate that the failure loads of spot welds in lap-shear specimens increase when number of spot, squeezing force, welding current and sheet thickness increase for the given ranges

Microstructural Evolution During a Solid State Tube Pinch Weld of Type 304l Stainless Steel

Microstructure development is examined for a specialized spot weld that is used as a solid-state closure process for austenitic stainless steel tubing, referred to as pinch welding. In order to elucidate the microstructural evolution of the weld, a series of test welds were made at nominal conditions using tubing and production like components. These pinch welds normally terminate after twelve cycles of a 60 Hz AC weld process. In this study, production tubes were welded from one to twelve cycles and the microstructure and weld variables after each individual weld cycle number were characterized using radiography and optical metallography. Two electrochemical etchants were used to highlight different microstructural features. The study revealed that: (1) this type pinch weld is largely complete after about six cycles of 60 Hz AC current, half the weld time utilized; (2) the resistance, deformation, and closure length approach “steady-state” conditions after six cycles; and (3) both oxalic and nitric acid electrolytic etchants are useful for highlighting specific microstructural attributes of type 304 L stainless steel. Finally, two distinct microstructural regions can be identified for these welds: the edge of the weld, which is driven by concentrated deformation, recrystallization, and grain growth, and the center region, which is more typical of forge welding and micro-asperity breakdown followed by diffusion and grain-growth.