Hello again from the teaching laboratories here in Campor Hall. In this segment, we're going to talk about stress versus strain and a set of mechanical properties that come from that simple experiment are extremely important in understanding the basic structural integrity of so many of the materials that we use in everyday life. [MUSIC] So now I'm doing a stress strain experiment, which gives us, as I said, the big four mechanical properties of a very important understanding of the nature of the structural materials that we use very broadly throughout the engineering profession. Especially metallic samples. We'll be defining Elastic modulus, Yield strength, Tensile strength, and Ductility or Strain at failure. And in doing so, we're going to see that we begin by simply measuring, in this Instron machine, the load on the sample, as we pull it slowly in uniaxial tension, and monitor the increasing length as a result of that pulling of the sample. So, we'll first of all monitor the load versus length. And then by dividing the load by the cross section area of the sample and the length by the initial length of the sample under zero load, will convert that load elongation curve into a stress string curve. And then as we monitor that stress strain curve in its various aspects, first of all a straight line portion with the slope that we call the elastic modulus and that slope is a definition of the Famous Hooke's law that many of you have seen in various engineering courses. That the stress is directly proportional to the strain in that elastic deformation region. And then that's followed by the nonlinear breaking away from elastic deformation, and the beginning of plastic deformation. And that point of breaking away is defined as the E of the strength. And then the ultimate tensile strength is sometimes simply called tensile strength. And then as the sample is taken to complete failure and breaks, that total amount of elongation at that point of break is the elongation of failure or the ductility. And so now let's do the experiment. We're going to take a sample again, through elastic deformation, plastic deformation to ultimate failure, and our teaching assistant, Andrew, is going to operate the Instron machine. So, Andrew, let's begin. [MUSIC] [SOUND] And there you have it. We've measured elastic modulus, yield strength, tensile strength, and elongation of failure all in one fairly simple experiment.