Welding velocity

The translation of the heat source is defined by the process parameter of welding velocity and direction, whereas the characteristics of heat input (heat source dimension, power... 

The efficiency rj depends on the material thickness d, the gap width s, the welding velocity v, or the laser type (e.g. CO2- or solid-state-laser). In the present case, i.e., for butt welding with C02-laser, experiments show the following empiric relation, (Kotowski, 1998) ... 

A.l) Defining and fine discretizing of an area at X = L/2 with normal vector parallel to the welding velocity. 

Welding parameters important in determining the quality of the weld include the hot air temperature, hot air flow velocity and volume, welding velocity, geometry of the weld shoe, and temperature, flow rate, and pressure of the extruded material. Weld velocity is dependent on the flow velocity of the extrudate, which is... 

Besides taking into accoiuit specific material properties, the developed model for a quasi-simultaneous welding process is capable for the first time to consider directly welding pressure, scan welding velocity and scan length to calculate temperature and melt displacement profiles. 

Second corner reflection The first corner reflection appears as usual when the transducer is coupled to the probe at a certain distance from the V-butt weld. The second corner reflection appears if the transducer is positioned well above the V-hutt weld. If the weld is made of isotropic material the wavefront will miss (pass) the notch without causing any reflection or diffraction (see Fig. 3(a)) for this particular transducer position. In the anisotropic case, the direction of the phase velocity vector will differ from the 45° direction in the isotropic case. Moreover, the direction of the group velocity vector will no longer be the same as the direction of the phase velocity vector (see Fig. 3(b), 3(c)). This can be explained by comparing the corresponding slowness and group velocity diagrams. 

Figure 3 Snapshots of the shear wavefronts for different types of weld material to show the direction of the wave unit vector k (a phase velocity unit vector Cp ) and the group velocity unit vector...

Figure 4 Slowness and group velocity diagrams for isotropic weld material...

Then, the weld depths penetration are controlled in a pulse-echo configuration because the weld bead (of width 2 mm) disturbs the detection when the pump and the probe beams are shifted of 2.2 mm. The results are presented in figure 8 (identical experimental parameters as in figure 7). The slow propagation velocities for gold-nickel alloy involve that the thermal component does not overlap the ultrasonic components, in particular for the echo due to the interaction with a lack of weld penetration. The acoustic response (V shape) is still well observed both for the slot of height 1.7 mm and for a weld depth penetration of 0.8 mm (lack of weld penetration of 1.7 mm), even with the weld bead. This is hopeful with regard to the difficulties encountered by conventional ultrasound in the case of the weld depths penetration. 

For defect sizing by TOED, use of L waves involves a penalty in resolution of almost a factor of two at a given frequency because of difference in velocity as compared to shear waves and use of SV waves runs into difficulties because of the mode conversion problems. Further, problems due to couplant thickness variations, surface roughness affects, beam skewing and distortion problems in anisotropic welds can also be expected. On the contrary, SH waves are not affected... 

The University developed a method of determination of the material residual strength, based on measurement of the change of phase velocity of ultrasonic waves, as well as an ultrasonic flaw detector-tomograph with multi-element transducers of the type of phased acoustic array. It enables control of the internal structure of materials and products of up to 300 mm thickness, with the resolution of up to 0.5 mm. In the same university, work on NDT is also carried out in the welding and electro-acoustic departments. 

An approximate equilibrium is set up in the plasma, with the electrons, ions, and atoms having velocity distributions similar to those of a gas that has been heated to temperatures of 7,000 to 10,000°C. Since the plasma is ignited toward the end of the concentric tubes from which argon gas is issuing, the plasma appears as a pale-blue-to-lilac flame coming out of the end of the tube, which is why the system is referred to as a torch, as in a welding torch. 

Both ultrasonic and radiographic techniques have shown appHcations which ate useful in determining residual stresses (27,28,33,34). Ultrasonic techniques use the acoustoelastic effect where the ultrasonic wave velocity changes with stress. The x-ray diffraction (xrd) method uses Bragg s law of diffraction of crystallographic planes to experimentally determine the strain in a material. The result is used to calculate the stress. As of this writing, whereas xrd equipment has been developed to where the technique may be conveniently appHed in the field, convenient ultrasonic stress measurement equipment has not. This latter technique has shown an abiHty to differentiate between stress reHeved and nonstress reHeved welds in laboratory experiments. 

Severe corrosion by turbulent mill coolant was found generally throughout a rolling-oil system. Hose couplings were severely wasted in as little as 8 weeks (Fig. 7.23A and B). Turbulence caused by high-velocity flow through nozzles accelerated attack. Attack at bends, elbows, intrusive welds, and discharge areas was also severe. 

This corrosion is most pronounced in locations of high velocity, turbulence, and impingement, such as at elbows, weld reinforcements, pump impellers, steam injection nozzles, and locations where freshly condensed fractions drip upon or run down metal surfaces. 

Released at low velocity into moderately still air Spray booths Intermittent container filling Low-speed conveyor transfers Welding Plating Pickling 0.51-1.02... 

Release at low velocity into moderately still air Container filling, low-speed conveyor transfers, welding 0..5 to 1.0... 

Released at Imv velocity into rnodcTarciv srill air Spray booths, intermittent container filling, low-speed conveyor transfer, welding, plating, pickimg 0,5- l. 0... 

Downdraft tables are available for welding, but the efficiency could be quite low due to low suction velocities and large work pieces. 

Use of warm processes on a downdraft table should be avoided since the air velocity created by the exhaust is often lower than the velocity due to buoyancy effects. Effective use of a downdraft table for welding requires velocities high enough to counteract the buoyancy, which could result in disturbances of the welding process. 

Note that if 28-inch O.D. X -inch wall pipe is available this could be used with weld cap ends, or dished heads. The percent design velocity would be = 71.8%. 

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