Technikatörténeti szemle 11. (1979)
TANULMÁNYOK - Petik Ferenc: The development of material testing machines
steel wires was determined by Pieter van Musschenbroek (1692—1761) on the tensile testing machine shown in Fig. 5. His strength data were utilized by strengthening the dome of St. Peter’s Cathedral in Rome, showing cracks in consequence of soil displacements. To this end a retaining-chain encircling the dome was employed. Musschenbroek had built also compression and bending testers. Strength data published by him had been used for a long time by engineers. The building (of another early material testing machine is similarly connected with a dome, that of the Pantheon in Paris. The architect, Soufflot, decided to try a new structural scheme, when building was begun in 1757. To convince traditionally-minded opponents, he determined the strength of selected stone specimens on the compression tester constructed by Gauthey in 1770 (Fig. 6). The frame was built of wood, the lever producing the load was made of iron. Lever length was 2,3 m, transmission ratio 1 : 24. For loading, weights were placed on the pan, what means an increase in .steps, not continuously. Later Rondelet, who completed the work of Soufflot, improved the machine by providing a knife-edge instead of a bolt at the fulcrum, by making an iron frame and by employing a screw-jack to apply the load, so that the beam could be kept level while the specimen was compressed. At the turn of the 18th and 19th centuries the testing of metals was even less developed than that of building materials of mineral origin. The British House of Commons discussed in 1799—1800 a scheme of replacing Old London Bridge. According to this plan the new bridge should have an arch of cast 6. Gauthey’s compression testing machine 221
