A rectangular wave shape TIG AC power source with transistorized switches has been developed. The depth of bead penetration of thin Al plates welded by this power source has been examined. Also, butt welding of thin Al plates has been carried out using conditions determined through examination of the depth of bead penetration. The characteristics of this power source is as follows: no-load voltage 72V, maximum welding current 230A, Welding frequency 25 Hz-1k Hz, SP/RP ratios 1-9. Under the conditions of irms 100-230A, welding frequency 25 Hz-1k Hz, SP/RP ratios 2-6, welding speed 500-600 mm/min, arc length 1.5 mm and shielding with Ar gas, the depth of bead penetration of 3.2 mm thick 5052 Al alloy is constant at welding frequency 25 Hz to lk Hz and two times deeper than in the case of sine wave TIG welding, and also increases in proportion to the increase of SP/RP ratio. Welded joints with good mechanical properties are obtained using this power source. The appearance of the beads is excellent with the many regular ripple marks.
Current-voltage characteristic curves for a pair of probes inserted in a low plasma concentration zone surrounding the welding arc column have been measured. The probes made of 1.6 mm φ tungsten wire with holders fixed on the welding torch were set on the right and left side of the arc column. The results obtained are as follows: (1) In a case of the welding arc running along the centre line of the groove, the probe current has the same value for both probes at any probe voltage. Then the characteristic curves for the pair of probes coincide with each other. Otherwise, the running arc deviates left or right of the centre line of the groove. The characteristic curves have different forms intersecting near the floating potential. (2) The deviation of welding arc from the centre line of the groove is detectable indirectly by a difference in the probe current, if any, between the two probes, because the relation of the deviation of the welding arc to the difference in the probe current has certain regularity, which can be depended on as a sign of the positional deviation of the arc column.
Ultrasonic Welding is the method to weld metal specimens clamped between a welding tip and an anvil by ultrasonic vibration energy, and the direction of welding tip vibration is parallel to the specimen surfaces. It is expected that the vibration characteristics of specimens has direct affects on the weld strength. The purpose of the study is to investigate the effects of specimens vibration characteristics on the weld strength. At the experiments, the frequency auto-tracking and constant vibration velocity control type welding equipments are used. The results obtained are as follows; 1) Equivalent circuit of weldment is derived. 2) Weld strength is affected by the resonance and anti-resonance of logitudinal and bending vibration etc ofspecimens. 3) Welding is almost impossible in the case the upper specimen is at anti-resonance of longitudinal vibration. 4) Adequate change of vibration direction is useful to obtain stable weld strength.
The dependence of plastic flow process on temperature and thickness, for slit notched three point bending specimen, was investigated by continuous direct observation, using optical interference method. The relationship between the degree of plastic constraint and plastic flow process or applied load was cleared. Moreover, the cleavage fracture behaviours were discussed based on the observed plastic flow processes. Main results obtained are as follows (1) The plastic flow processes in low temperature region and the degree of plastic constraint, can be estimated by the optical interference method. (2) The state of stress triaxiality is characterized by the transition behaviour from the stage of local yielding to that of hinge type plastic flow. (3) The temperature effect on the size of plastic zone appears only at the stage of hinge type in plastic flow process. (4) In slow bend test of Charpy size specimen, the cleavage fracture occures either at stage of local yielding or after the general yield.