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The influence of the machine specific instantaneous current wave forms on weld nugget dimensions and weld strength is investigated over six spot welding machines. It is observed that the nature of the real-time current wave forms corresponding to a common rms value can vary in different ac spot welding machines. The variations exist in the values of peak current and in the current-on and -off times in every ac cycle. It is observed that real-time current wave form involving higher peak current leads to slightly larger weld nugget diameter compared to wave form with smaller peak current even if the overall rms value remains similar The real-time current wave form from a medium frequency dc confirms to a fast rise to the set weld current and remains steady for the complete weld time. A detailed experimental study has depicted that the real-time ac wave forms especially with high peak values and sharp rise characteristics offer a relatively smaller permissible range of weld currents compared to the wave forms with relatively flatter characteristics. The steady instantaneous current wave form confirming to the medium frequency dc machine has facilitated a larger permissible range of weld current. A numerical analysis of the spot welding process based on finite element process is carried out using both the instantaneous current wave forms and the corresponding rms values of weld current. The predicted weld dimensions using instantaneous current wave forms have showed slightly better agreement with the corresponding measured weld dimensions. Keywords: resistance spot welding, instantaneous current wave form, AC and DC welding machines, numerical modeling

The driving behaviour inventory was developed to assess the extent of stress drivers experience. Parameters such as attitudes, anxiety and aggression, human factors in accidents and decision-making styles were used in the survey. Sixty one respondents were involved in the study in the course of five months. The results of the study would be advantageous not only to drivers who ride daily to work, but also for whom driving is a profession. It also has potential use for driving educators, counsellors, therapists, safety engineers, psychologists and automobile ergonomists.

It is argued that the reason that previous evidence apparently did not support the accident proneness hypothesis was faulty methodology and erroneous interpretations of results. Between time periods correlations of traffic accident records actually show an impressive stability over time when restriction of variance is controlled for. However, stability can be caused by stable differences in exposure. Correlations of accident records between time periods were analysed comparing full time and part-time bus drivers. For drivers who worked full time, the amount of exposure was held semi-constant while part-time drivers could be expected to work differing hours. If differential exposure causes stability in crash record, then part-time drivers should yield stronger correlations between time periods for crashes compared with full-time drivers. Between time periods accident correlations for part-time drivers were weaker than the corresponding ones for full time drivers. Correlations increased with increasing variance in the data. Results for all crashes fit in well with other meta-data, while culpable crashes did not, probably due to faulty coding. The current results support the notion of the tendency to cause traffic accidents as a stable trait within individuals as this is apparently not caused by stable differences in exposure. [ABSTRACT FROM AUTHOR]