Suppose it is impossible to use an extensometer on the gauge section of a test specimen. Instead a butt-end specimen (Figure 3.2c) is used and the strain is computed from the cross-head movement. There are two possible sources of error in this procedure. One is that the gripping system may deform elastically and the other is that the butt end may be drawn partly through the collar. How would each of these errors affect the calculated true stress and true strain?