Effects of root radius and pitch difference on fatigue strength and anti-loosening performance for high strength bolt–nut connections

The fatigue strength improvement and anti-loosening performance are studied experimentally and analytically for JIS M16 bolt–nut connections. Three different root radii are considered coupled with three different pitch differences. The enlarging the bolt root radius improves the fatigue limit of the bolt by more than 30% because both stress amplitude and mean stress can be reduced. Furthermore, suitable pitch difference improves the fatigue limit by more than 25%. This is because under no pitch difference the crack initiation always occurs at No.1 or No.2 threads close to the bolt head causing the final failure; however, under a suitable pitch difference the crack initiation occurs at No.6 or No.7 threads far away from the bolt head. Good anti-loosening performance can be expected for the bolt–nut connections having enlarged root radius because the prevailing torque [Formula: see text] = 19 Nm and the residual prevailing torque [Formula: see text] are not smaller compared to other special bolt–nut connections.

Involuntary Markers of Saliency and Surprise Revealed by Oculomotor Inhibition in Response to Auditory Sequences

Our eyes move constantly but are often inhibited momentarily in response to external stimuli. The properties of this Oculomotor-Inhibition (OMI) depend on the stimulus saliency, anticipation, and attention. Previous studies have shown prolonged saccadic inhibition for auditory oddballs; however, they required active counting of the oddballs. Here we investigated whether the OMI response to auditory deviants can provide a quantitative measure of deviance strength (auditory pitch difference) and investigated its dependence on the Inter-Stimulus Interval (ISI), without requesting a voluntary attention to the deviant stimulus. Observers fixated on a central fixation stimulus and passively listened to repeated short sequences of pure tones that contained a deviant tone either regularly or with 20% probability (the Oddball paradigm). The results showed, as in previous studies, prolonged microsaccade inhibition following the deviant tone. Moreover, the inhibition onset latency was shorter in proportion to the pitch deviance (the saliency effect) and the release was significantly longer for rare deviants (the surprise effect) as long as the ISI was short (<2.5s). Taken together, these results suggest that OMI provides involuntary markers of saliency and surprise, which can be obtained without the observer’s response.