Technikatörténeti szemle 11. (1979)

TANULMÁNYOK - Petik Ferenc: The development of material testing machines

5. Tensile testing machine of Musschenbroek (1729)

Leonardo da Vinci (1452—1519), in his notes ,,On the examination of the strength of iron wires of various lengths”, gives also a drawing of his experimental arragement (Fig. 2) [2]. The note gives basic rules on the strength of cantilever and two-support beams.

Galileo Galilei (1564—1642) in the chapter dealing with the strength of materials in his book [1] examines the question, why the dimensions of buildings cannot be increased on the basis of geometrical similitude. He states that similar structures become weaker at proportionally increasing the dimensions. He tried to find the cause by experiments, and found by tensile tests (Fig. 3) that strength depends only on cross section, while independent of the length of the rod. In another figure in his book a wooden cantilever beam fixed in a wall, with a cencentrated load, can be seen (Fig. 4). On the basis of similar tests and of theoretical examinations Galilei already knew that the load carrying capacity of a beam rectangular in cross-section was proportional to its breadth, to the square of its depth, and to the resistance of the material to tension.

Sketches have been conserved of the strength testing devices of Hooke (1635—1703), of Mariotte (1620—1684) and of Coulomb (1736—1806) [2], These scientists tried to prove theoretical hypotheses experimentally. At the same time experiments with practical aims were also being carried out, testing building materials intended for certain applications. Thus the strength of

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