Influence of Cusp External Magnetic Field on Deposition Rate of Two-electrode TIG Welding

Experiments have been conducted to investigate the influence of the cusp external magnetic field (EMF) on deposition rate of two-electrode tungsten insert gas (T-TIG) welding. T-TIG arc parameters such as arc shape, arc voltage, arc pressure and arc plasma information were acquired respectively. Results showed compared to TIG, a higher welding current could be allowed for T-TIG, due to its low arc pressure characteristic. Under the effect of the cusp EMF, the arc shape was compressed along x-axis of T-TIG, while elongated along y-axis of T-TIG. Besides, the peak arc pressure of T-TIG was not significantly increased by the cusp EMF. Moreover, with the action of the cusp EMF, the maximum values of the electron temperature (Te) and electron density (Ne) of T-TIG were not significantly increased, but along y-axis, the increments of the two parameters were gradually increased and their distributions were widened. Therefore, more arc energy was allocated on y-axis of T-TIG by the cusp EMF, which could improve the preheating and the melting of the filler wire along y-axis, so the deposition rate of T-TIG could be increased by 17.6% under the effect of the cusp EMF.

Arc Plasma Flow Variation by Obstruction Structures between Anode and Cathode

Arc plasma flow between electrodes has been investigated in several studies. However, in the industrial field, arc plasma flow between electrodes is hindered by interfering materials such as filler metal in arc welding, substrates in chemical vapor deposition, and powders in sintering. Therefore, in this study, high temperature arc plasma flow analysis via three obstruction structure shapes was performed to understand the inter-electrode interference phenomena. COMSOL Multiphysics was used for the analysis; COMSOL interface such as electric field, magnetic field, heat transfer, and fluid flow (laminar flow) was applied and Multiphysics such as plasma heat source and temperature coupling were considered. The temperature and velocity of the arc plasma were determined and the energy transfer between the electrodes was analyzed. We confirmed that the concave shape has a lower average heat flux than the other shapes, with the arc pressure evenly distributed in the anode. It is concluded that the concave shape can reduce the flow of the plasma from the anode and obtain even distribution of the arc plasma in the radial direction.

Study on Time Characteristics of Coupling Discharge in Pulsed Laser Induced Double-TIG Welding

Based on the dynamic behavior of laser keyhole, the time characteristics of coupling discharge of heat source in pulsed laser induced double-TIG welding (LIDTW) are studied. The behaviors of arc plasma and laser keyhole were directly observed by high-speed camera and auxiliary illumination source. The physical characteristics of arc plasma were analyzed by spectrometer and arc quality analyzer. A physical model is established to reveal the regulation mechanism of time characteristics of coupling discharge. It is found that after laser pulse action the coupling discharge between keyhole plasma and double-arc plasma does not end immediately, and its time depends on the existence time of keyhole. During hybrid welding, when the combined force of arc pressure and Marangoni force can overcome the gravity, the liquid metal is forced out of the keyhole and the keyhole remains open. Improving the electron density of arc plasma and arc voltage and reducing the diameter of arc conductive channel by selecting appropriate parameters to is the key to prolong the existence time of keyhole, which is beneficial to improve the welding penetration. The coupling enhancement of double-arc electromagnetic field in LIDTW can effectively suppress keyhole backfill and increase the duty ratio of coupling discharge. When the total current intensity is 200 A, compared with laser induced single-TIG welding (LISTW), the existence time of keyhole in LIDTW increases by 77 %, the duty ratio of coupling discharge increases by 12 %, and the weld penetration increases by 29.2 %.

Numerical Analysis of Keyhole and Weld Pool Behaviors in Ultrasonic-Assisted Plasma Arc Welding Process

The acoustic radiation force driving the plasma jet and the ultrasound reflection at the plasma arc-weld pool interface are considered to modify the formulas of gas shear stress and plasma arc pressure on the anode surface in ultrasonic-assisted plasma arc welding (U-PAW). A transient model taking into account the dynamic changes of heat flux, gas shear stress, and arc pressure on the keyhole wall is developed. The keyhole and weld pool behaviors are numerically simulated to predict the heat transfer and fluid flow in the weld pool and dynamic keyhole evolution process. The model is experimentally validated. The simulation results show that the acoustic radiation force increases the plasma arc velocity, and then increases both the plasma arc pressure and the gas shear stress on the keyhole wall, so that the keyholing capability is enhanced in U-PAW.

Arc Characteristics and Weld Bead Microstructure of Ti-6Al-4V Titanium Alloy in Ultra-high Frequency Pulse Gas Tungsten Arc Welding (UHFP-GTAW) Process

To resolve the problem of grain coarsening occurring in the fusion zone and the heat-affected zone during conventional gas tungsten arc welding(C-GTAW) welded titanium alloy, which severely restricts the improvement of weld mechanical properties, welding experiments on Ti-6Al-4V titanium alloy by adopting ultra-high frequency pulse gas tungsten arc welding (UHFP-GTAW) technique were carried out to study arc characteristics and weld bead microstructure. Combined with image processing technique, arc shapes during welding process were observed by high-speed camera. Meanwhile the average arc pressure under various welding parameters were obtained by adopting pressure measuring equipment with high-precision. In addition, the metallographic samples of the weld cross section were prepared for observing weld bead geometry and microstructure of the fusion zone. The experimental results show that, compared with C-GTAW, UHFP-GTAW process provides larger arc energy density and higher proportion of arc core region to the whole arc area. Moreover, UHFP-GTAW process has the obviously effect on grain refinement, which can decrease the grain size of the fusion zone. The results also revealed that a significant increase of arc pressure while increasing pulse frequency of UHFP-GTAW, which could improve the depth-to-width ratio of weld beads.

Investigation on the Dynamic Behavior of Weld Pool and Weld Microstructure during DP-GMAW for Austenitic Stainless Steel

The influence of heat and droplet transfer into weld pool dynamic behavior and weld metal microstructure in double-pulsed gas metal arc welding (DP-GMAW) was investigated by the self-designed high-speed welding photography system. The heat input, the arc pressure, the droplet momentum and impingement pressure were measured and calculated. It was found that the arc pressure is far less than the droplet impingement pressure. The heat input and droplet impingement pressure per unit time acting on weld pool were proportional to the current pulse frequency, which fluctuated with thermal pulse. The size and oscillation amplitude of the weld pool had noticeable periodic changes synchronized with the process of heat input and droplet impingement. Compared to the microstructure of pulsed gas metal arc welding (P-GMAW) weld metal, that of DP-GMAW weld metal was significantly refined. High oscillation amplitude assisted the enhancement of weld pool convection, which leads to more constitutional supercooling. The heat input and shear force during the peak of thermal pulse causing dendrite fragmentation which provided sufficient crystal nucleus for the growth of equiaxed grains and the possibility of grain refinement. The effects of current parameters on welding behavior and weld metal grain size are investigated for further understanding of DP-GMAW.

ANALISIS KETERAMPILAN MEMANAH BAGI MAHASISWA UIN, SERAMBI DAN UBUDIYAH DI STKIP BINA BANGSA GETSEMPENA BANDA ACEH

The purpose of this article is to increase strength, speed, accuracy, endurance, and coordination and balance are crucial in producing good and correct archery basic techniques, so as to produce good archery accuracy. In line with that, we think that in order to get the automation and effectiveness of arm muscle strength, arrow speed in order to reach the target in archery, in this case it is necessary to have regular and directed physical training, this is felt to be more effectively done through devotion activities carried out by the student . But in its application the field is actually different, isotonic training, which is a form of exercise with shortened and elongated muscle contractions, in this case the chosen form of exercise is bow pulling training, whereas isometric training is a form of training that contracts with no shortening or elongation, in this case the form of exercise used is to hold the arc pressure (balance). The system of implementing the two forms of training is adjusted to the training program that has been planned and established for the achievement of the peak achievements of UIN, Serambi and Ubudiyah students at the STKIP BBG Banda Aceh. The aim is to improve skills, accuracy, right on target when archery, so in this case the solution offered in this service is to conduct training activities based on daily, weekly and monthly training programs. Abstrak Tujuan artikel ini adalah untuk meningkatkan kekuatan, kecepatan, ketepatan, daya tahan, dan koordinasi serta keseimbangan sangat menentukan dalam menghasilkan teknik dasar memanah yang baik dan benar, sehingga menghasilkan ketepatan memanah yang baik. Sejalan dengan itu, kami berpikir bahwa untuk mendapatkan otomatisasi dan efektivitas kekuatan otot lengan, kecepatan anak panah demi mencapai target dalam memanah, maka dalam hal ini perlu latihan fisik secara rutin dan terarah, hal ini dirasa lebih efektif dilakukan melalui kegiatan pengabdian yang dilakukan mahasiswa tersebut. Namun dalam aplikasinya dilapangan justru berbeda, latihan isotonik yaitu suatu bentuk latihan dengan konstraksi otot memendek dan memanjang dalam hal ini bentuk latihan yang dipilih adalah latihan menarik busur, sedangkan latihan isometrik merupakan suatu bentuk latihan yang berkontraksi dengan tidak terjadi pemendekan atau pemanjangan, dalam hal ini bentuk latihan yang dipergunakan adalah menahan tekanan busur (keseimbangan). Sistem pelaksanaan kedua bentuk latihan disesuaikan dengan program latihan yang telah direncanakan dan ditetapkan untuk pencapaian prestasi puncak mahasiswa UIN, Serambi dan Ubudiyah di STKIP BBG Banda Aceh. Tujuannya adalah untuk meningkatkan keterampilan, ketepatan, tepat sasaran saat memanah, maka dalam hal ini solusi yang ditawarkan dalam pengabdian ini adalah dengan melakukan kegiatan pelatihan berpedoman pada program latihan harian, mingguan dan bulanan. Kata Kunci: Keterampilan, Memanah, Mahasiswa.

Prediction of the Weld Pool Stability by Material Flow Behavior of the Perforated Weld Pool

This article presents the application of a computational fluid dynamics (CFD) finite volume method (FVM) model for a thermo-mechanical coupling simulation of the weld pool used in variable polarity plasma arc welding (VPPAW). Based on the mechanism of the additional pressure produced through self-magnetic arc compression and the jet generated from mechanical plasma arc compression, and considering the influence of arc height and keyhole secondary compression on arc pressure, a three-dimensional transient model of variable polarity plasma arc (VPPA) arc pressure was established. The material flow behaviors of the perforated weld pools were studied. The results show that three kinds of flow behavior existed in the perforation weld pools and it is feasible to predict the weld pool stability by the material flow behaviors of the perforated weld pools. The weld pools can exist stably if the material flow in the bottom of the perforated weld pools can form confluences with moderate flow velocities of 0.45 m/s, 0.55 m/s and 0.60 m/s. The weld pools were cut when the material flowed downward and outward with the maximum velocity of 0.70 m/s, 0.80 m/s. When the maximum material flow velocity was 0.40 m/s, the weld pool collapsed downward under the action of larger gravity. The thermo-mechanical coupling model was verified by the comparison of the simulation and experimental results.