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Volume 77, 1948-49
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Address By the Chairman

Engineering Research at Auckland University College.

Abstract:

While the present conditions at the Schools of Engineering are not favourable for regular research, a limited amount is being done. Unfortunately delays due to excessive teaching burdens tend to dampen enthusiasm and restrict the publication of work. However, some work which has been carried out at the School of Engineering, Auckland University College, was described.

Engineering Materials.

(a) Dependence of mechanical strengths of materials upon the surface tension of wetting media: Recent experiments conducted in Sweden revealed the anomalous behaviour of materials when stressed to their ultimate strengths in the presence of wetting agents such as water and oils. A review at the Auckland University College revealed that the surface tension of the wetting medium affected the mechanical properties. This question is now being examined in detail.

(b) The capping of concrete-compression-test specimens: In recent years the technique of testing concrete-compression specimens has been the subject of occasional comment and criticism. Last year the matter was examined systematically and a satisfactory technique has been worked out.

(c) Photo-elastic examination of models of reinforced concrete construction: The usual assumptions made in the design of reinforced concrete design are at the best rough approximations. Economy in design can be effected by a close study of the transfer of stress from the concrete to the steel. It is proposed to use doubly refracting materials to represent both concrete and steel, and to subject models of typical structures to examination by means of polarized light.

Structures.

(a) Analysis of grain-bin pressures under vertical seismic accelerations: The current codes governing the design of structures provide for horizontal seismic loadings. In general this is adequate, but in the case of tall grain bins theoretical treatments show that small vertical accelerations modify substantially the pressure distribution. In addition to the theoretical analysis, endeavours are being made to examine the problem with the aid of models and a universal shaking table. The proposed table will permit of any vertical or horizontal acceleration being applied within wide limits, and the pressures will be recorded by piezo-electric methods.

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(b) Prefabricated reinforced-concrete floor tests: In collaboration with the Department of Scientific and Industrial Research, the School has conducted a number of investigations into the efficiency of a number of suggested schemes for prefabricated reinforced-concrete floors for housing construction.

Fluid Mechanics.

(a) Aerodynamic method of rating current meters: For some time current meters have been rated in an aerodynamic wind tunnel. The rating so obtained can readily be converted for use in the gauging of rivers by the methods of similarity. The aerodynamic method has the advantages of convenience and accuracy as compared with the conventional water method.

(b) Determination of stream rating curves by means of hydraulic models: A scheme for the rapid determination of stream-rating curves by means of hydraulic models has been worked out. In this way information collected in the laboratory over a period of a few weeks provides a rating curve which otherwise could be obtained only after the elapse of many years.

(c) Fluid tunnel: Through the courtesy of Messrs. Mason Bros., of Auckland, the School has been provided with a fluid tunnel which can function as a high-speed channel for tests upon model ships, a water tunnel for cavitation studies and a wind tunnel for aerodynamic experiments. It is believed that the combination is unique. Trials have shown it to be successful.

(d) Trans-sonic wind tunnel: The conventional high-speed wind tunnels use air, which, in order to obtain velocities approximating that of sound in air, require very large power inputs. A modified wind tunnel using dense gases—e.g., dichloro-difluoromethane (freon) or trichlorethylene, has been designed in which the corresponding sonic conditions can be reproduced with approximately one-third of the power.

Conclusion.

It is hoped with the appointment of additional staff and a decrease in student enrolments that research will receive more attention.