 Hello, I am Milka Juggle, working as assistant professor in Department of Mechanical Engineering, Valchin Institute of Technology, Solapur. Today, we are going to learn about destructive testing methods. Let's see. Learning outcome. At the end of the session, students will be able to select various destructive methods and its significance. So these are the content, testing of materials, destructive testing methods and references. So as discussed in the last video, the destructive testing methods, it is a test in which the specimen either breathes no longer useful for further purpose. So this is the list of the destructive testing methods, tensile test, hardness test, impact test, creep test and fatigue test. So before going forward for the tensile test, I would like to ask you the question about stress-strain curve. What do you mean by stress-strain curve? So that will be seen in the further video. Tensile testing. In this, the component or the specimen either breathes or remains no longer useful for further testing process. The test is widely used to determine strength, ductility, resilience, toughness and other properties. The test gives idea about behavior of material under tensile load. The specimen may be circular, square or rectangular in cross section. So let's see about the tensile test. The specimen is prepared and the gauge length is measured. The specimen is gripped between the two jaws of UTM that is universal testing machine. One jaw is fixed whereas other jaw is movable. So a record of load versus extension is obtained till fracture which is indicated on SN curve. So this is the test specimen. This is the gauge length. There are different shoulder specimen, threaded specimen, pin and specimen. So this is the schematic illustration of tensile testing machine. The simple diagram which shows the specimen is mounted between the two jaws that is upper and lower. This is the moving cross head. This is the load cell. So let's see a video which describes the tensile testing method. So in this, the specimen is fixed. This is the universal testing machine. Here the behavior is indicated. The behavior of specimen is indicated on this curve. Now the tensile load is applied on the specimen. We observe the change in the cross section of this test specimen. There is change in the cross section at this position. You see there is reduction in the cross section and the neck formation is started at this and the specimen breaks. So all the properties are indicated. The diameter and gauge length is calculated before the test and after the test. So this was the tensile test. Now let us go for hardness test. Name some hardness testing methods you know. I want you to pause the video for few seconds and tell me the hardness testing methods. So these are the hardness testing methods depend on indentation hardness. So these are the methods of indentation hardness, Brinell's hardness test, Rockwell hardness test and Wicker hardness test. Apart from this we have Poldy's hardness test and Rebound hardness test. So in this video we are going to learn about these three tests. So what is hardness? Hardness is resistance of material to plastic deformation. It is the fundamental mechanical property. So hardness depends upon grain size, yield strength, tensile strength, work, hardening coefficient and ductility. So as I said so there are three types of hardness that is indentation test depend upon the resistance offered by the metals to the indentation. This is rebound hardness test and this is scratch hardness test. So principle of indentation test, there is a indenter which is harder than the hardness of the material to be tested is applied with sufficient load and allowed to make an indentation on surface of material. So this is the Brinell's hardness test. So in Brinell's hardness test, indenter is a steel ball of 5 mm to 10 mm diameter. The load applied is for 10 second in ferrous materials for 30 seconds for non-ferrous materials. So the load applied or the load to be applied is calculated by P by d square ratio where P is the load and d is the diameter of indenter. So let's see. So Brinell hardness number is calculated by load upon area of indentation. So Brinell hardness number is calculated in this way. So this is the formula to calculate the Brinell's hardness number. This is the schematic setup of Brinell's hardness test. This is the indenter, the material to be tested. This is after indentation, this is the mark of indentation offered by the indenter. Let's see in this video. This is the Brinell hardness test. This is the indenter steel ball. First for 10 seconds load is applied and then the indentation is measured. That is 2 diameters, diameter d1 and diameter d1 and d2 is calculated and then we find the Brinell's hardness number. So next is Rockwell hardness test. In Rockwell hardness test, the indenter is made up of a diamond cone with included angle of 120 degree and with apex radius of 0.2 mm. The load is applied in two stages here. First is the minor load and the second is the major load. So minor load of 10 kg is applied and the major load of 600 or 150 is applied depending upon the scales, scale A, B, C. So let's see, scale A is for the diamond cone indenter, scale B that is 100 kg that is, it is a ball indenter then C it is a diamond cone indenter. So let's see, this is the Rockwell hardness test. In this the difference is that we have the change in the indenter. Major load of 10 kg is applied for first three seconds and then major load of 150 kg is applied for four seconds. So this was regarding Rockwell hardness test. Next one is Vickers hardness test. It is similar to Brinell's hardness test. Here the indenter is diamond square pyramid with included angle of 136 degree with opposite phases. So let's see here, the load selected for a given test piece should be as large as possible. So here in this as we have the indenter diamond cone base pyramid. So we are going to measure the diagonals, the two diagonals. The Vickers hardness number formula is 1.854 P upon D square whereas D is the diagonals. With this we have square based pyramid. We are going to measure the diagonals and taking the average of the diagonals. So this is D1 and D2 depending on that using the formula we are going to find out the hardness number, Vickers hardness number. So these are the references, thank you.