Increase In Arc Length Research Articles

Measurement and analysis of arc pressure in two-TIG welding

The distributions of the arc pressure at the anode surface along the directions of the tungsten electrode alignment (x-axis) and that perpendicular to the x-axis (y-axis) in two-TIG welding were measured and analyzed with the aid of the numerical results. The influences of the electrode spacing, the proportion of the current through the electrodes with the same total current, the total current and the arc length on the arc pressure were investigated. The results showed that the two-TIG arc pressure is significantly lower than the single-TIG arc under the same conditions, and the distribution range is noticeably reduced. As the tungsten electrode spacing increases, the arc pressure decreases, and the direction in which the arc pressure distribution extends changes from the x-axis to the y-axis. When the currents through the two tungsten electrodes are different, the arc pressure distribution in the x-axis is not symmetrical but symmetrical in the y-axis. As the current ratio or the total current increases, the maximum arc pressure increases and the deviation of the maximum arc pressure from the central point becomes more pronounced. The arc pressure decreases as the arc length increases, and its distribution range extends more along the y-axis.

Survey of Welding Voltage from Welding Current and Arc Length in SMAW Process

The relationship between welding voltage, welding current and arc length was investigated in this study. Shielded metal arc welding (SMAW) process was used to weld API 5L X65 line pipes at welding current of 80 – 200A and arc length of 1.5 – 3.5mm. First and second order polynomial equation and Amson models were also used to study the welding voltage as a function of current and arc length. The results revealed that increase in current and arc length lead to corresponding increase in voltage. The welding voltage increased from 19.48 – 23.82V at constant arc length of 1.5mm and from 22.25 – 26.77V at 3.5mm arc length, as current increased from 80 – 200A. Voltage increase was more influenced by increase in arc length than increase in current. Welding currents between 140A and 180A and arc length between 2mm and 3mm are recommended for optimum quality welded joints. The analysis of the model performance showed that there was high correlation between the predicted and the measured welding voltage values (R2 up to 99%). However, the predictions from the second-order polynomial model slightly edged the Amson and the first-order polynomial models. Therefore, using either of these models could be helpful in making a decision on the range of welding input parameters that can be used to optimise welding quality and productivity in the SMAW process

Analysis of droplet transition features and weld formation in laser-MIG hybrid welding

The image of laser-MIG hybrid welding process was collected by high-speed camera, the arc area and the barycenter of droplet were extracted by image processing method, the weld width and weld height were extracted from the 3D point cloud of weldment surface, and the relationship between droplet transition features, droplet velocity and weld formation were analyzed. Results show that the extremum of arc area and droplet transition period have the same change trend. The change of droplet velocity can effectively reflect the change of weld width. The decrease of arc length can increase the droplet transition frequency, speed up the droplet velocity and increase the weld width. The abrupt increase of arc length will increase the ratio of height to width, which reduce the welding quality.

Observation of Arc Behaviour in TIG/MIG Hybrid Welding Process

In this project, the influence of TIG currents’s variation on arc stability of TIG/MIG hybrid welding was studied by comparing with MIG welding process. The welding current-voltage waveform was analyzed to characterize the arc stability of the MIG arc. From the observations, the introduction of TIG arc as low as 60 A of current significantly change the MIG arc stability in TIG/MIG hybrid welding. The length of MIG arc in TIG/MIG welding increased with the introduction of the TIG arc as compared with MIG welding. The increase of arc length was due to the arc interaction between the TIG arc and MIG arc, which is affecting the wire melting rate. At the maximum TIG current, the diameter of the molten droplet decreased with the increment of droplet transfer frequency.

Effects of Arc Length Adjustment on Weld Bead Formation and Droplet Transfer in Pulsed GMAW Based on Datum Current Time

The characteristics of weld bead formation and droplet transfer in pulsed gas metal arc weld (GMAW) with different arc lengths were studied by changing the base current time in this work. The results showed that it was easier to cause short circuits and spatters with a short arc. However, the deviation between the deepest point of penetration and the center of bead will be aggravated with the increase of arc length. In addition, more than 90% “one drop per pulse” (ODPP) transfer mode can be obtained when the pulse parameters were selected properly. However, the short arc trended to rise the proportion of “multiple drops per pulse” (MDPP), and the long arc trended towards increasing the proportion of “one drop per multiple pulses” (ODMP). Additionally, with the growth of the arc in the projected transfer zone, the penetration tended to become shallower because of the increase of arc heat dissipation, the fall of arc energy density, and droplet impact force. Overall, the strategy of choosing suitable arc length of pulsed GMAW was summarized: in order to obtain high-quality bead formation and weld joints, a shorter arc in the projected transfer zone was recommended.

Measurement and analysis on the thermal and mechanical transfer characteristics of GTA arc affected by arc length

Arc length is an important factor affecting the thermal and mechanical transfer characteristics of GTA arc. Arc calorimeter and arc pressure sensor were used to study the thermal and mechanical transfer characteristics. The influence mechanism of the thermal and mechanical characteristics on the morphology of metal deposition is explained. The experimental results revealed that the increase of arc length will increase the effective power output, arc heat and its action range, but will decrease the peak value of arc pressure. Accordingly, the short arc length will lead to a smaller molten pool and smaller metal droplets. Instead, a long arc length will lead to a larger molten pool and larger metal droplets. The single deposition layer formed by short arc length is high and narrow, and the single deposition layer formed by long arc length is low and wide. Therefore, the arc length can be controlled according to the product structure requirements to obtain different morphology of droplet deposition layers.

The metal transfer behavior and the effect of arcing mode on metal transfer process in twin-arc integrated cold wire hybrid welding

In response to the demands of high-efficient welding, twin-arc integrated cold wire hybrid welding technology was proposed in this paper. In order to realize a stable welding process, the research was focused on the effect of welding electrical parameters on the metal transfer process of simultaneous arcing to find a proper range of process parameters. In addition, the experimental research found a new factor to affect the metal transfer mode, i.e., arcing mode, and its effect mechanism was discussed in greater detail. The results showed that both the leading wires kept simultaneous arcing with in-phase pulse currents supplied to two wires. The metal transfer modes were divided into two types: one is one droplet per pulse, and the other is one droplet multiple pulses, which highly depended on arc voltage. At first, the main metal transfer was one droplet multiple pulses at lower arc voltage. Then the metal transfer mode started to change to one droplet per pulse with the increase of arc voltage. Finally, when arc voltage continuously increased to a certain value, one droplet multiple pulses once again occurred. This was mainly because the great increase of arc length restricted the expansion of arc root. What is more important, through the comparison between the metal transfer processes of simultaneous arcing and alternative arcing, it was found that the arcing mode had a significant effect on the metal transfer mode, and the main reason was the arcing mode affected the electric field intensity of arc column.

18 Propagation of arterial dissection

We compute and study critical pressures (Pc) for the initiation of the propagation of an existing arterial dissection, which in general depends on the residual stress and pre-stretch of the artery, and the length and depth of the tear, using the Holzapfel-Gasser-Ogden mathematical model for the walls of the large arteries. For the simple case of a 2D tissue sample, increasing the length of the initial dissection lowers the value of Pc, but when the strip is supported by connective tissue, arrest of the dissection is obtained. A peeling test on a disc-shaped sample demonstrates that the orientation of collagen fibres plays an important role in the direction of propagation. To study the effects of residual stress on arterial dissection, we include residual stress, quantified by the opening angle when an artery is subject to a longitudinal cut. We show that Pc is approximately proportional to the opening angle, so that the observed loss of residual stress associated with ageing increases the likelihood of dissection. Finally the effects of the circumferential (arc) length and radial position of the initial tear in a cylindrical model of an artery are investigated. Pc decreases as arc length increases and as the initial dissection is placed closer to the lumen. Prolapse of the dissection into the lumen occurs when the initial tear close to the lumen and the arc length is large.

On Conductivity of Cold Gas Layer Separating Arc Column and Nozzle in Nontransferred Plasma Arc (Anode Reattachment Process in Plasma Spray Systems)

The nozzle serves as an anode in systems for plasma arc spraying. In these systems, the anode attachment moves downstream along the nozzle under the influence of the gas flow. The arc length increases and the arc voltage rises. At a specific arc voltage, the anode attachment jumps upstream and the arc voltage drops: reattachment occurs. The frequency of reattachment and the location of the new anode spot are determined by the conductivity of the cold gas layer that separates the extended arc column and the metallic anode. The conductivity of this layer in calculated in this paper. Two important effects are taken into account: 1) the difference between the electron and the heavy particle temperatures and 2) deviation from ionization equilibrium. Disregarding these effects leads to, practically, a completely insulating characterization of the cold gas layer. Calculations for an argon plasma showed that as opposed to the frequently accepted opinion, the electrical conductivity of the layer in the arc trail remains at a very substantial level. They also showed, in accordance with experiments, that admixing even small amounts of helium to argon decreases the layer conductivity that leads to reattachment delay and high voltage fluctuations. Analysis of the spatial distribution of the layer conductivity allows one to predict the new location of the anode spot after reattachment.

Physical characteristics of twin-wire indirect arc plasma

In this study, the behavior of arc in a twin-wire indirect arc welding is simulated for arc lengths of 5.2 mm, 6.2 mm and 7.2 mm. The plasma temperature is measured by spectrometric method. The results showed that increase in arc length increase the arc parameters (plasma temperature, current density, plasma velocity, heat flux and arc voltage) of twin-wire indirect arc (TWIA). The change in arc length was found to have little influence on the distribution and the variation in trend of arc parameters in the whole arc region. As the arc length increases, the arc parameters in cathode region increase at a slower rate than those of anode region. This probably is the reason for self-adjustment of TWIA and for the arc stability in a certain range of arc lengths. The temperature of anode region is slightly higher than that in the cathode region and other arc parameters have similar trends. The isotherms are displaced toward the anode side and the shape of TWIA is similar to an inclined and inverted bell. The displacement increases with increasing arc length. The experimental results of plasma temperatures are in good agreement with calculated results which verifies the accuracy of the calculated results.

Modeling of Engineering Ceramics Grinding Surface Residual Stress

Because of hard and brittle properties of ceramic materials, grinding and polishing the surface is the main processing methods, after grinded and polished, ceramics surface appear residual stresses and resulting in the cracks. Ceramic grinding surface residual stress are caused by machinery and thermal stress, residual stress generation mechanism is due to the combined effection under various stress, the workpiece transient temperature field can be calculated by triangle moving heat source model, the stress-strain relationship can be carried out in plastic region. according to the relationship between displacement increment and strain increment, can calculate element strain rate,in strong grinding, due to heat transfer time increases and the contact arc length increases, the maximum temperature is proportional to the available between the unit width and grinding ratio contact length, two regression method is used in study the effect of grinding parameters on surface residual stresses.

Formula omitted] Hermite interpolation with PH curves by boundary data modification

We show how to create a new class of infinitely many PH Hermite interpolants for a given ordinary C1 Hermite data-set, in a way that ameliorates the rapid shape transitions in PH quintic interpolants that occurs when boundary data has poor geometric compatibility. We first interpolate a Hermite data-set using two asymmetric PH cubics, each of which satisfies the data at one boundary. Then we selectively apply one of three shape improvement techniques to the interpolant, so as to eliminate rapid shape transitions and produce C1 PH curves with lower bending energy, at the expense of a small increase in arc-length.

SINGLE PARAMETER GALAXY CLASSIFICATION: THE PRINCIPAL CURVE THROUGH THE MULTI-DIMENSIONAL SPACE OF GALAXY PROPERTIES

We propose to describe the variety of galaxies from SDSS by using only one affine parameter. To this aim, we build the Principal Curve (P-curve) passing through the spine of the data point cloud, considering the eigenspace derived from Principal Component Analysis of morphological, physical and photometric galaxy properties. Thus, galaxies can be labeled, ranked and classified by a single arc length value of the curve, measured at the unique closest projection of the data points on the P-curve. We find that the P-curve has a "W" letter shape with 3 turning points, defining 4 branches that represent distinct galaxy populations. This behavior is controlled mainly by 2 properties, namely u-r and SFR. We further present the variations of several galaxy properties as a function of arc length. Luminosity functions variate from steep Schechter fits at low arc length, to double power law and ending in Log-normal fits at high arc length. Galaxy clustering shows increasing autocorrelation power at large scales as arc length increases. PCA analysis allowed to find peculiar galaxy populations located apart from the main cloud of data points, such as small red galaxies dominated by a disk, of relatively high stellar mass-to-light ratio and surface mass density. The P-curve allows not only dimensionality reduction, but also provides supporting evidence for relevant physical models and scenarios in extragalactic astronomy: 1) Evidence for the hierarchical merging scenario in the formation of a selected group of red massive galaxies. These galaxies present a log-normal r-band luminosity function, which might arise from multiplicative processes involved in this scenario. 2) Connection between the onset of AGN activity and star formation quenching, which appears in green galaxies when transitioning from blue to red populations. (Full abstract in downloadable version)

Magnetoelectric effect in layered composites with arc shape

Magnetoelectric (ME) layered Ni/PZT/Ni composites with arc shape have been prepared by using electroless deposition. The ME effect is measured by applying both constant and alternating magnetic fields in longitudinal and transverse directions. The longitudinal ME voltage coefficient is much larger than the transverse one. With the increase of arc length or decrease of curvature, the resonance frequency of layered arc Ni/PZT/Ni composites gradually decreases, while the maximum of the ME voltage coefficient of the composites increases monotonously. The influence of the arc length and the curvature on ME coupling is discussed. The flat interface between the ferromagnetic and the piezoelectric phases in layered ME composites is believed to provide large ME voltage coefficient.

HUBBLE SPACE TELESCOPE ASTROMETRY OF TRANS-NEPTUNIAN OBJECTS

We present 1428 individual astrometric measurements of 256 trans-Neptunian objects made with Hubble Space Telescope (HST). The observations were collected over three years with two instruments, the Wide Field Planetary Camera 2 and the Advanced Camera for Surveys High Resolution Camera, as part of four HST programs. We briefly describe the data and our analysis procedures. The submission of these measurements to the Minor Planet Center increased the individual arc length of objects by 1.83 days to 8.11 years. Of the 256 total objects, 62 (24.2%) had arc length increases of ≥3 years. The arc length for 60 objects (23.4%) was increased by a factor of 2 or greater.

A bathymetric overview of the Mariana forearc

Bathymetric data at a 200‐m contour interval for the entire Mariana forearc, from south of 13°N to 25°N, permits the first comprehensive overview of this feature. The Mariana forearc represents a sediment‐starved end‐member. The forearc in its southern and central sections is divisible into a structurally complex eastern province and a less‐deformed western province. Despite the absence of an accretionary complex the Mariana forearc has a well‐defined outer‐arc high; this probably results from a greater concentration of low‐density serpentinized mantle lithosphere beneath the outer forearc relative to the inner forearc. This serpentinization gradient is coupled with differing deformational styles of thinner and more brittle lithosphere beneath the outer forearc compared to thicker and more ductile lithosphere beneath the inner forearc. The bathymetric data also support models calling for extension along‐strike of the forearc, reflecting an increase in arc length accompanying the crescent‐shaped opening of the Mariana Trough back‐arc basin. Both northeast and northwest ridges and grabens can be identified, with the latter restricted to the southern part of the forearc and the former widely distributed in the central and northern forearc. Northeast‐oriented extensional structures are supplanted northward by long, linear northwest‐trending structures that are interpreted as left‐lateral strike–slip faults. These variations in deformation along‐strike of the forearc manifest a transition from nearly orthogonal convergence in the south to highly oblique convergence in the north.

Laser-arc treatment of steels

1. The laser-arc method of thermal hardening makes it possible to obtain hardened layers 2–3.5 thicker than in laser hardening with maintenance of a high microhardenss of 700–740 H (surface hardness 56–62 HRC). 3. Laser-arc treatment makes it possible to obtain hardened layers 4–6 mm wide and up to 1.0 mm deep with treatment rates up to 10 mm/sec and 3–4 mm wide and 0.4–0.6 mm deep with a rate of movement of the laser beam of 20–30 mm/sec. 3. An increase in arc length from 2 to 5 mm has practically no influence on the depth, width, and geometry of the laser action zone. 5. Defocusing of the laser beam (dL=2.0–4.0) with an increase in the rate of laser-arc treatment above 3.6 mm/sec is undesirable since in this case a high level of hardness is not obtained and localization of the beam is poorer.

熔接アークの比熔着熱について

The specific deposited heat or the specific Let transfer number, i e. the ratio of heat atsorbed by the base metal to the weight of deposited metal is measured for various kinds of electrodes, the core diameter being 4 mm The value varies from 12 to 25 Ka' per gram for ordinary arc length.The value is independent of the current employed but increases as the arc length increases, because the melting speed of electrod metal is proportional to the current while the thermal efficiency is independent of the current, and the total heat input increases as the arc length increases (3), (4)It will be higher for those electrodes and polarity which have lower melting speeds.Fig. 3, 4 shov those relations.