Vickers Hardness Test 

thank you science for that

Answer to "HOW TO CHECK SOFT METAL LIKE GOID,.SILVER, CPPER BERILUM ETC": The Vickers hardness of soft metals can also be measured by using very low test forces. There is actually no limit towards low hardness.

Answer to "How does it measure the indent size? Do we need to feed in the distance between the microscope lens and the test specimen as how big or small the indent looks depends on how far it is from the lens? or does it do optics calculations automatically to understand the size?" It's your second point: the optics are carefully calibrated, and if the focus is correct, the conversion of the camera's pixel size to the actual distance on the sample is known exactly.

@@MaterialsScience2000 I got it. Thank you for your reply. :)

Answer to "Thanks for this video , can I use this video for my teaching purpose": I'm afraid our videos are under RU-vid's standard license. This means that it is not allowed to download the videos. However, you can always present the videos in your classes with a direct internet link to RU-vid.

Answer to "Pls guide ,what is the force need to apply. And dwell time." Forces and can be varied in a wide range from 0.01 kp to about 100 kp. The lower end of the range is limited by the smallness of the indent and the difficulty to measure the diagonals. The upper end is limited by the size of the diamond. The dwell time is usually 10 s, sometimes 30 s.

Answer to "Hi can we change the dwell time?": The dwell time (time during which the test load is kept constant) can reasonably be varied between 5 and 30 seconds. If one deviates from 10 seconds, one has to include the dwell time in the result, for example 70 HV1/30. 70 is the hardness, 1 the test force in the old units kp, 30 the dwell time in seconds. A dwell time of 30 s is only used in the case of materials which show creep during the test.

Answer to "how do you find the area of the indentation?" The area of the indentation is calculated from the measured diagonals using the appropriate equation.

Answer to "whats the measurement, its sounds like kilo pond ?": The forces in hardness testing still refer to the old force unit "kilopond". It is an old story, it has to do with the problem of omitting the real units in the test result and the change to the international units long ago ...

Answer to "Question! How do we know what value of the force to set?: You may use almost any force that leads to an reasonable indent. If the force is too low, the indent is very small and difficult to measure. If the force is too high, the diamond indenter may be damaged or completely pressed into the sample, not good either.

@@MaterialsScience2000 so basically the value depends on previous studies right?

@@nurulnadiabintimdshah9007 Hi! i am currently studying aviation engineering and as part of the course we are learning hardness testing, this is some info i found on the book we are reading: VICKERS HARDNESS TEST. In this test, a small pyramidal diamond is pressed into the metal being tested. The Vickers Hardness number (HV) is the ratio of the load applied to the surface area of the indention. This is done with the following formula. HV = P / . 0 5393 d 2 a. The indenter is made of diamond, and is in the form of a square-based pyramid having an angle of 136 degrees between faces. The facets are highly-polished, free from surface imperfections, and the point is sharp. The loads applied vary from 1 to 120 kg; the standard loads are 5, 10, 20, 30, 50, 100, and 120 kg. For most hardness testing, 50 kg is maximum. hope that helps!

@@skraak9276 thx a lot for the info, really appreciate that!!! ;)

Answer to "Can i convert vicker hardness to GPa and compare with nanoidentation result in the literature??? Is it reasonable??? a simple question from a master in china..." This is by no means a simple question, it has a long tradition, which is little known. Originally, the Vickers hardness was calculated (not quite correctly) by "mass in kg / area of indentation in square millimetres", including the unit kg/mm>2. Since mass is not correct here, it was later changed to "force in kp / area of indentation in square millimetres", including the unit kp/mm>2. Later, the units were omitted (not at all a good idea), and the hardness was just given as a number. In the 1970s, the old units of force (kp) were changed to the modern SI system (N), and since the units had been dropped, the old and new units could no longer be distinguished, and there was a problem. So even today, the old kiloponds (kp) are still used in Vickers hardness calculations (without units) - a real mess. So if you take the (official) Vickers hardness value and multiply it by 9.81, you get the result in N/mm>2 (or MPa). And if you divide that result by 1000, you get the answer in GPa. A mess, a mess, why didn't they ask me. I am afraid I was not yet born then ... But be careful: The Vickers hardness at low test forces depends on the magnitude of the force. Thus, a different result is obtained at low test forces. General rule: The lower the force, the higher the Vickers hardness value.

@@MaterialsScience2000 Thank you so much to answer my problem. so what ur mean is that I couldn't just convert the vickers hardness into GPa and compare it with my nanoindentation result. Anyway, I prefer not to touch such a complex question which could let me in trouble.

Answer to "You needed to clean the part first make a smooth surface and then test it. You can see the part has a lot of lines which is not accurate when measurements are made by the lines. It’s all uneven lines.": In principle, you are right. But the specimen was finely ground and cleaned before the test. What you see in the microscope is the typical surface structure after fine grinding. This surface quality is absolutely acceptable in this case, where a comparatively large indentation has been made. Only in the case of very small indentations does the surface need to be polished before the hardness test.

que parte no entendiste?