抄録
The logarithmic strain, which is sometimes called as "true strain" or "natural strain", is defined as the sum of each differential change in specimen length divided by its current length. This paper proposes a new interpretation, that is, the logarithmic strain is the difference of Eulerian displacement of the specimen measured at two separate reference points, which are fixed in space, divided by the distance between them. An Eulerian type displacement meter which gives Eulerian description of the displacement directly is also proposed and it is shown that PC mouse, which is now an indispensable input device of computers, is by itself an excellent Eulerian displacement transducer. While in computer environments, mouse moves on the fixed pad and it measures its own movement, in this study, the movement of the object is measured by the mouse fixed in space. It is analytically and experimentally shown that the logarithmic strain is obtained by dividing the difference of the readings of two Eulerian displacement meters by their separation distance.
