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Static and dynamic strength tests were performed on spot welded specimens made of dual-phase (DP) 780 and mild steels (DQSK). Lap-shear (LS) and cross-tension (CT) as well as a new mixed mode specimen were studied using MTS hydraulic universal testing machine for static tests and drop weight tower for dynamic tests. Three weld nugget sizes were made for each steel and CT and LS. DP780 with one weld size was also tested in mixed mode. Load and displacement as functions of time and fracture mode of the spot welds were recorded. Representative data are reported in this paper.

Inertia force during dynamic testing exists in any testing system. A generic system is analyzed using the principle of rigid body dynamics. It is shown that the load recorded by a load cell includes both the load experienced by the test specimen and the inertia force from the mass between the specimen and the load cell, when the load cell is placed on the fixed side of the test specimen. An impact fixture designed for spot weld strength test was then studied as an example. Test data were collected and analyzed to show the effect of inertia on the impact strength of the spot weld.

In the friction stir welding (FSW) process, heat is generated by friction between the interfaces between the tool and the workpiece. The amount of heat conducted into the workpiece determines the quality of the weld. In this paper, 37.6 mm (1.48 inch) thick plates made of aluminum alloy 6061-T6 were welded using the FSW process. We report (a) welding parameters such as tool RPM, welding speeds, (b) power and heat input to the welding process, (c) a complete temperature history from 27 thermocouples. Data are reported for one weld with a full-length pin and two welds with a short pin. In conjunction with the measurement, finite element analyses were also performed to study (1) the heat inputs from the tool shoulder as well as from the probe pin, and (2) temperature distribution and history in the workpiece. The analysis results are also compared with the measured data.

As the automotive industry becomes more concerned with the crash performance of automobiles, the behavior of used vehicles becomes an interesting subject. In this work, the effect of aging on spot welded joints was simulated by applying fatigue loading to the samples. Samples were then subjected to quasi-static and impact tests to measure the effect of fatigue aging to the strength of the samples. The results show (a) a reduction in the strength of the test samples under impact conditions, (b) no obvious reduction in quasi-static conditions, and (c) significant reduction in strength if cracks in the welds were initiated during the fatigue aging process.