From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Paper by Sidney M. Cadwell titled 'Rubber of Tomorrow' discussing the testing and fatigue properties of new rubber materials.
| Identifier | ExFiles\Box 178\2\ img056 | |
| Date | 25th March 1940 guessed | |
| RUBBER OF TOMORROW By Sidney M.{Mr Moon / Mr Moore} Cadwell Before beginning a discussion of new materials or new products may I make a few comments on testing? In the accelerated pace which research & development have taken in the last decade or two, we are perhaps too apt to forget the collective part which testing has played in that endeavour. Nowadays testing is so much the partner of our progress that we take it for granted; yet without the continual search for new methods, or necessary revisions in old procedures which your Society has constantly prosecuted, all types of development and production activities would have been handicapped. Your efforts have served as a potent force in substituting the results of experiments and testing for opinion and prejudice. This meeting is devoted to transportation, with emphasis on future developments. Today we are using materials which won their acceptance in tests made only a few short months ago. We continue to test them to see that they maintain the quality by which they merited approval. But the tests which have the greatest interest for us are those on new products or new materials, because in them we hope to discover either the solution to some of our problems, or perhaps the key to a new design we may have been needing, or the chance to make further improvements in quality or reductions in cost. When we find a material or product which passes today's tests better than anything previously available we can be sure we are dealing with tomorrow's product. In some cases the advances are so marked that we must even revise our tests to make them sufficiently critical of the new material. Fatigue: Last year the rubber industry celebrated the 100th anniversary of the discovery of vulcanization, yet in spite of the antiquity of our business we are still finding out new things about it. For example, within the last year we have found that a lot of things we thought we knew about the fatigue of rubber in vibration are not true. If I take a piece of rubber and stretch it back and forth by attaching one end to a vibrating or oscillating member while the other end is fixed, it seems good commonsense to expect that the piece of rubber will last longest if we let it return to the condition of zero strain during each cycle of extension. A lot of rubber parts have been designed with this "commonsense" point of view. However, when we use testing technique and study the life of rubber under the complete range of strains which can be applied, while maintaining the same cycle of extension, we find that rubber apparently has a different common sense from the kind we have. Instead of obtaining the maximum life under the conditions which were outlined, we find that it is almost the worst possible choice of conditions. This will be clearer with a few slides. If we have a piece of rubber between metal plates as shown at the top of slide 2, we can put this thru an oscillation cycle of constant amplitude super imposed on varying conditions of initial strain. The constant amplitude cycle is determined by the throw of the crankpin in the apparatus. The initial strain is varied by changing the position of the fixed support. In the center illustration the rubber is in compression. In the lower picture the rubber is in extension at all times. | ||