Arc sensor is a conventional technique so as to compensate the aiming deviation which causes from the heat distortion or unevenness of work piece. But, at present, only less than 5% of arc welding robot equips arc sensing function. It is hard to use in actual welding line because of occurring of miss sensing. So we began to reconsider over arc sensing in the meaning of reliability. Our approach is separating arc welding process into several physical phenomena, and research how the unstable factors act to the sensing results. And we try to find the countermeasures toward miss sensing. Our final target is short arc welding. As the road to that target, this report shows the effect of unstable factors to the arc plasma phenomena. So the experiment is performed with TIG welding on copper plate so as to ignore the melting of electrode and workpiece. By analyzing the effect of unstable factor, we proposed the several countermeasures toward miss sensing.
Friction stir welding (FSW) is a solid phase process which can produce high quality dissimilar joints. However, due to the difference of material properties between A6N01 aluminum alloy and AZ31 magnesium alloy, optimization of process parameter is difficult for dissimilar FSW. In this study, the relationship between process factors (material arrangement, tool offset and probe diameter) and quality of the joint was investigated. After the optimization of these process factors, the AZ31 and A6N01 dissimilar joints with high joint efficiency could be obtained at circumferential velocity of the probe from 0.147 to 0.183m/s regardless of probe diameter. This result indicates that the circumferential velocity is one of the most important factors for AZ31 and A6N01 dissimilar FSW.
Bondability of thermosonic flip chip bonding using ramp bond force profile was investigated. Compared with a conventional method using constant bond force profile, ramp bond force profile achieved higher bond strengths with same amount of bump deformation. This was because that expansion amount of contact area between bump and electrode under applying ultrasonic vibration increased. Furthermore, we found out that pressure in bonding process at interface between bump and electrode of ramp bond force profile became lower than constant bond force profile. Bondability was considered to have been improved by incrementation of slip between bump and electrode cause by lower pressure.
In this study, the oxygen contamination and the heat input on the anode surface were investigated by experimental measurements in order to guarantee a high-quality welding in TIG welding with a constricted nozzle. As a result, it was clarified that the energy density which was one of the heat source characteristics became higher at the center of the anode surface by attaching the constricted nozzle. Moreover, the oxygen concentration on the anode surface during TIG welding with constricted nozzle was as low as that during a conventional TIG welding. In addition, the oxygen concentration on the center of anode surface was changed by operating conditions such as a welding current and a shielding gas flow rate. Finally, the suitable welding condition was proposed from the tendency of the oxygen concentration on the anode surface, in which the oxygen concentration on the anode surface kept low.
For the purpose of higher welding speed and lower force in friction-stir-welding (FSW), we investigated the feasibility of preheating using gas-tungsten- arc-welding (GTAW). It can be expected to assist heat input for the plastic flow by using GTAW with high energy density. Defect-free bonding by a GTAW-FSW hybrid process was successfully achieved at a welding speed less than 8.3mm/s, while normal FSW left a defect at welding speed of 5.0mm/s. The axial forces during friction stirring in the GTAW-FSW process were lower than 40% of that in the normal FSW. The joints of GTAW-FSW had stir zones with fine grains similar to the FSW joints. This process could obtain higher productivity, that is, higher welding speed and lower force than the conventional FSW. It is also possible to obtain a high strengthen and unique structure with fine grains of FSW.
Current work deals with investigation of the effect of the use of low transformation temperature welding wire (LTT welding wire) on distortion reduction of parts made by wire and arc additive manufacturing technique (WAAM). LTT welding wire and SUS308L wire, which was austenitic stainless steel wire, were used for making WAAM test pieces. Distortion of base plates of test pieces were evaluated by 3D non-contact coordinate measurement system. As a result, longitudinal bending distortion of the base plates of test pieces in which LTT welding wire was partially or fully used was smaller than those of the test piece which was made only by SUS308L wire. Especially, longitudinal bending distortion of the base plates of test pieces which was made only by LTT welding wire was reduced drastically from those of the test piece which was made only by SUS308L wire. However, angular distortion of the base plates were not reduced drastically even if the test piece was made only by LTT welding wire. The difference of the reduction effect of the use of LTT welding wire was discussed by considering the position of neutral plane of each distortion mode.