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).
Page detailing test procedures for hard composite insulating materials, including cross-breaking strength and crushing tests.
| Identifier | ExFiles\Box 24\2\ Scan213 | |
| Date | 21th February 1922 guessed | |
| HARD COMPOSITE DIELECTRICS (INSULATING MATERIALS). 571 hot, the height shall be re-measured. With the weight on, the unsupported end shall not have yielded more than 10 mm. Another specimen shall then be set up and tested in the same manner, except that the test shall be carried out at grade temperature, at which temperature the yield shall not exceed 2.5 mm. When it is impracticable to obtain a specimen in accordance with the dimensions shown in Fig. 9, the smaller alternative specimen shown in Fig. 11 may be used. The smaller specimen shall be set up as shown in Fig. 12 and tested as described above, except that the load applied shall be 72 grammes. increased at the rate of 10 kilogrammes per minute until the specimen breaks. If the unsupported end yields 20 mm before fracture occurs the specimen shall be deemed to have failed, and the value of the load causing this deflection shall be taken in computing the cross-breaking strength. The cross-breaking strength at grade temperature shall be computed in the same manner as in (a) above. When it is impracticable to obtain a specimen in accordance with the dimensions shown in Fig. 9, the smaller alternative specimen shown in Fig. 11 may be used. The smaller specimen shall be set up generally in the manner indicated in Fig. 12 and tested as described above, except that the specimen shall be deemed to have failed when the unsupported end yields 8 mm before fracture occurs. [Image of a testing apparatus] Clamp 20m/m 60m/m Stirrup W Fig. 12.—Arrangement of Specimen in Fig. 11 set up for Plastic Yield with Temperature Test and Cross-breaking Strength Test. 8. Cross-breaking Strength. (a) Cross-breaking strength at normal temperature. The material shall be tested at a temperature from 15° C. to 20° C. The specimen shall be of the shape and dimensions shown in Fig. 9, and shall be set up for testing generally in the manner indicated in Fig. 10. The load shall be increased gradually at the rate of 10 kilogrammes per minute until the specimen breaks. The cross-breaking strength at normal temperature shall be expressed in terms of the constant k in the following formula :— W = kBD²/L where B, D and L are in centimetres and W in kilogrammes, B being the breadth of the specimen, D the depth, and L the distance between the edge of the clamp and centre of the notch. (b) Cross-breaking strength at grade temperature. The specimen employed for the Plastic Yield Test at grade temperature shall be tested as follows :— With the specimen set up for test under Clause 7, and immediately after the height of the unsupported end has been re-measured as described in Clause 7, and whilst the specimen is still hot, the load shall be gradually 9. Crushing. The ability of the material to resist crushing shall be proved at a temperature from 15° C. to 20° C. in a testing machine on a specimen moulded or machined to the shape and dimensions shown in Fig. 13. The end faces of the specimen shall be truly square, plane and parallel, being rubbed down on fine emery paper if necessary, with due precaution against rounding. If a specimen of the size shown in Fig. 13 cannot be cut from the material available, a smaller cylinder, geometrically similar, may be used, but not less than 10 mm long and 10 mm diameter. [Image of a cylindrical specimen] 15 m.m. 15 m.m. Fig. 13.—Specimen for Crushing Test. | ||