Search

Abstract: The influence of a monotonic predeformation at room temperature on the very high cycle fatigue (VHCF) behaviour was studied in polycrystalline nickel-based superalloys (Nimonic 75 and Nimonic 80A) in three characteristic precipitation conditions (precipitation-free, peak-aged and overaged) after various degrees of predeformation. Isothermal fatigue tests were executed at temperatures up to 800°C. In the intermediate temperature range (400–600°C) the effect of predeformation becomes weaker with increasing temperature. This can be partially explained by the beginning of recovery. However, additional effects not related to the strain-hardened microstructure play a role, such as the formation of oxide layers and the decrease in notch sensitivity. The latter effect is important because of the surface roughening resulting from prestraining. Even for the overaged condition, 4% predeformation led to a higher VHCF fatigue resistance at 600°C, due to the relatively stable recovered dislocation arrangement. Isothermal cyclic deformation at 800°C revealed a pronounced decrease in cyclic lifetime for all precipitation conditions with or without a mechanical prehistory. Transmission electron microscopy was carried out in order to characterize the influence of the microstructure, the resulting dislocation slip behaviour and the relevant dislocation/particle interaction mechanisms on the VHCF behaviour. Furthermore, scanning electron microscopy observations revealed that all precipitation conditions show, independent of their predeformation condition, a transition from transgranular (room temperature to 600°C) to intergranular (600–800°C) microfatigue crack formation in the emerging oxide layers at the surface after VHCF tests. [Copyright &y& Elsevier]

Participants practiced short sequences of key presses; sequence length and response-effect mapping were the independent variables. Contingent, distinct key-effect relations were contrasted with either contingent but uniform or no response effects. In Experiment 1, tone effects were relevant as response-specific stimuli and also as effects. The sequence length effect for the tones group was reduced. In Experiment 2, participants were informed about the sequences to be executed and then given varying amounts of preparation time before the start signal. A reduction in the sequence length effect was observed, and initiation times and mean interresponse time (IRTs) were generally reduced in the tone group. Preparation time could compensate for some but not all of the latency reducing influence of the tone effects. The results are discussed with reference to ideomotor approaches to motor control, i.e., the notion that actions are represented in sensory format. [ABSTRACT FROM AUTHOR]

Participants performed a serial reaction time task, responding to either asterisks presented at varying screen locations or centrally presented letters. Stimulus presentation followed a fixed second-order conditional sequence. Each keypress in the experimental groups produced a contingent, key-specific tone effect. The critical variation concerned the mapping of tones to keys. In Experiment 1, keypresses in one control condition produced noncontingent tone effects, while in another control condition there were no tone effects. In Experiment 2, three different key–tone mappings were compared to a control condition without tone effects. The results show that tone effects improve serial learning when they are mapped to the response keys contingently and in a highly compatible manner. The results are discussed with reference to an ideomotor mechanism of motor sequence acquisition. [ABSTRACT FROM AUTHOR]

A non-spatial variant of the Simon effect for the stimulus–response (S–R) feature of duration is reported. In Experiment 1 subjects were required to press a single response key either briefly or longer in response to the colour of a visual stimulus that varied in its presentation duration. Short keypresses were initiated faster with short than with long stimulus duration whereas the inverse was observed with long keypresses. In Experiment 2 subjects were required to press a left or right key (according to stimulus form) either briefly or longer (according to stimulus colour). The stimuli concurrently varied in their location (left or right) and duration (short or long), which were both task irrelevant. Approximately additive correspondence effects for S–R location and S–R duration were observed. To summarize, the results suggest that the irrelevant stimulus features of location and duration are processed automatically and prime corresponding responses in an independent manner. [ABSTRACT FROM AUTHOR]

Abstract: Previous research has shown that subliminally presented stimuli accelerate or delay responses afforded by supraliminally presented stimuli. Our experiments extend these findings by showing that unconscious stimuli even affect free choices between responses. Thus, actions that are phenomenally experienced as freely chosen are influenced without the actor becoming aware of the manipulation. However, the unconscious influence is limited to a response bias, as participants chose the primed response only in up to 60% of the trials. LRP data in free choice trials indicate that the prime was not ineffective in trials in which participants chose the non-primed response as then it delayed performance of the incongruently primed response. [Copyright &y& Elsevier]