In general, the test piece is machined and the parallel length shall be connected by means of transition curves to the gripped ends which may be of any suitable shape for the grips of the test machine (see figure 11). The minimum transition radius between the gripped ends and the parallel length shall be:
- — 0,75 d (d being the diameter of the gauge length) for the cylindrical test pieces;
- — 12 mm for the prismatic test pieces.
Sections, bars, etc., may be tested unmachined, if required.
The cross-section of the test piece may be circular, square, rectangular or, in special cases, of another shape.
For test pieces with a rectangular cross-section it is recommended that the width to thickness ratio should not exceed 8:1.
In general, the diameter of the parallel length of machined cylindrical test pieces shall be not less than 4 mm.