Energy changes on deformation of a pneumatic tyre
The major part of this work is concerned with the development of the apparatus and the techniques involved in the measurements of the load-deflection characteristics of a pneumatic tyre and its associated changes in the pressure and volume of the air contained in it. A satisfactory results were obtained from this arrangement. From the measurements of the changes in volume and pressure of the air in the tyre, relationship was derived whereby the volume of the tyre at a particular inflation pressure was determined. The volume obtained by this method agree favourably with the value obtained by the conventional method of filling the tyre with water, and also it has the advantage over the conventional method due to its ease of operation. The most important aspect of this work is to determine qualitatively the amount of work required to deform the tyre structure. This is determined from the relationship that the work done on the structure is the difference between the total work done and the work done on air. An isothermal process was assumed. It was found that the work done on the structure accounts for only 10-20% of the total external work done on the tyre and is independent of the inflation pressure. A simplified quantitative treatment of the result based on the Gent and Thomas theory of air spring was developed and it agrees satisfactorily with the experimental results.
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