Progress on a specification for human tolerance of repeated shocks

615

HUMAN RESPONSE TO VIBRATION

M. J. Griffin and E. M. Whitham. A study of the discomfort produced by dual-axis wholebody vibration. (12 pages, 1 figure, 4 tables, 5 references) Authors’ Abstract. An experiment designed to provide information fundamental to the prediction of the discomfort of multi-axis vibration is summarized. Seated subjects were exposed to various level and phase combinations of 3. I5 Hz vertical (a,) and 3.15 Hz lateral (a,) sinusoidal vibration. One part of the experiment determined the levels of two single-axis vibrations (a, and a,, separately) which provided similar discomfort to a selection of dual-axis vibrations. In another part of the experiment subjects adjusted the level of a 3.15 Hz motion in one of the two axes to produce similar discomfort to each of seven levels of the same frequency in the other axis. The discomfort produced by the dual-axis motions investigated was not greatly influenced by the phase between the single-axis components producing the motions. The results suggest that a meaningful estimate of the relative discomfort produced by dual-axis stimuli can be determined from the levels of a single-axis reference motion appropriately adjusted by subjects. The level of a single-axis motion giving similar discomfort to each of the dual-axis conditions in the experiment was well approximated by the rootmean-square of the two levels of this single-axis motion equivalent to the two separate components of each dual-axis motion. Topics: Complex Vibration (Multiple Axis); Subjective Assessment (Intensity Matching); Non-vertical

Vibration (y-axis).

G. R. Allen. Progress on a specification for human tolerance of repeated shocks. (13 pages, 6 figures, 9 references) Author’s Summary. The first tentative approach to a possible IS0 specification covering repeated shocks is restated, and the reasoning and assumption underlying this approach are explained. A recent elaboration is outlined and discussed. New and as yet, anecdotal evidence from the U.K. is presented and used to prepare a further draft specification. A cri-de-tour is made for the provision of more data and for critical, constructive consideration of the foundations of the approach. Topics : Complex Vibration (Impulse) ; Voluntary Tolerance; Physiological Efects (in General) ; Standardization;

Criteria and Limits; Exposure

Time; Injury and Disease.

C. Ashley. Work vehicle suspension

seating. (27 pages, 32 figures, 14 references) seating is discussed in relation to its primary application in isolating the vertical motion of the vehicle. In many cases the fore and aft and lateral vibration are of equal significance and it is suggested that integral fore and aft isolations used on American truck suspensions could also be applied in Europe. The paper also discusses the design of suspension seats and the need for their correct adjustment by the operator. It is suggested that this area of work is an excellent example of the way in which the scientist researcher, the designer and the production engineer have worked together in order to provide a better environment. Topics: Seating; Complex Vibration (Various); Vibration Measurements (in General); Ride Author’s

Conclusions

(in General);

(edited by M. J. G.). Suspension

Non-vertical

M. E. Johnston. 5 references)

Vibration; Anti-vibration Devices (in General).

The measurement

and analysis

of aircraft

vibration.

(15 pages, 6 figures,

Author’s Summary. Inflight measurements of cockpit vibration in strike aircraft present. special instrumentation problems which arise from the adverse environment and space limitations. Also, the analysis of such vibration measurements requires particular caution if gross errors are to be avoided. The aim of this paper is to point out possible sources of recording error in flight, and to define some analysis errors which may occur particularly if