A typical stress-strain testing apparatus is shown in the figure above, along with the typical geometry of a tensile test specimen. During a tensile test, the sample is slowly pulled while the resulting change in length and the applied force are recorded. Using the original length and surface area a stress-strain diagram can be generated.
Now that I have introduced stress, please go to your e-textbook and read the first two sections (pages 65 to 70 in Chapter 4 of Materials for Today's World, Custom Edition for Penn State University) of this lesson's reading. When finished with the reading proceed to the next web page.