Material Static Testing_Part 01

1. Mechanical Testing-Static Tests Vishal Easwaran Balakrishnan MANUFACTURING ENGINEERING

2. Mechanical Testing- Static tests • Mechanical testing, also known as destructive testing, reveals the properties of a material under dynamic or static force. • Whether testing to a standard method or developing a custom program, our experts can provide you with accurate, reliable results for projects large and small. • Static testing is performed before code deployment. • Static Testing involves checklist for testing process.

3. Hardness • Hardness is the resistance of a material to abrasion or localized plastic deformation. • It’s adifficult property to describe in terms of first principles ‘Þ’ value depends greatly on method of testing. • It’s a measure of a material’s ability to resist surface indentation or scratching. • Different testing methods provides ‘Þ’different scales and values. • Hardness is not necessarily an indication of strength , although for some materials such as steel, a harder steel is a stronger steel.

4. Hardness Testing • Indentation Hardness used for steel • as opposed to scratch or rebound hardness • It is indicative of ultimate tensile strength • Atoms move out of the way to create indentation • Two main types: Brinell and Rockwell

5. Types of Hardness Testing • Brinell Hardness Test: • 10mm diameter ball with a load of 500, 1000 or 3000kg. • Vickers Hardness Test: • Pyramid shape indenter. • Rockwell Hardness Test: • A cone shape indenter; the depth of penetration is measured. • Micro Hardness Test: • An indentation is made on the specimen by a diamond indenter through the application of a load P.

6. F Brinell’s Hardness Brinell Hardness Test (BHN)

7. D d Brinell Hardness Test (BHN) P from 500 - 3000 kg D= 10 mm

8. Brinell Hardness • A spherical indenter (1 cm diameter) is shot with 29 kN force at the target • Frequently the indenter is steel, but for harder materials it is replaced with a tungsten carbide sphere • The diameter of the indentation is recorded • The indentation diameter can be correlated with the volume of the indentation.

9. Brinell Hardness Test (Animation)

10. Brinell Hardness Test Protocol • Press a 10mm (3/8") diameter ball into material with a known amount of load. • Measure diameter of the indentation. • BHN = Load = 2L • Surface Area D[D-(D2-d2)1/2] • L = Load placed on ball, usually 3000 kg , but 1500 kg, and 500 kg can also be used. • D = Diameter of steel ball ( = 10 mm) • d = diameter of dent, measured by looking thru a Brinell microscope.

11. Brinell Hardness

12. Brinell Hardness • ASTM and ISO use the HB value. It can be HBS (Hardness, Brinell, Steel) or the HBW (Hardness, Brinell, Tungsten) • HBW = 0.102 BHN • Sometimes written as HBW 10/3000 (Tungsten, 10 mm diameter, 3,000 kg force)

13. Mild steel Plastic Elastic H Copper d / D ( % E ) Analysis of Plastic Deformation during Brinell Hardness Test H = Ae-BT

14. Tensile Strength (MPa) Correlations between the Brinell hardness number (BHN) and tensile strength of carbon steels. Hardness (HB) Analysis of Plastic Deformation during Brinell Hardness Test

15. Limitations of Brinell Hardness Test • Sample must be ten times thicker than the indentation depth (sample usually should be at least 3/8" thick) • Test is most accurate if the indentation depth is 2.5 - 5.0 mm. Adjust load to achieve this. • Test is no good if BHN > 650

16. Brinell Hardness Test Pros & Cons • Widely used and well accepted • Large ball gives good average reading with a single test. • Accurate • Easy to learn and use • Destructive • Non-portable • High initial cost (3,74,652.50 INR) • Error due to operator reading Brinell Microscope (10% max)

17. Rockwell Hardness Test (Hrb, HRc, etc.,) • Select Scale - load and indenter depending on the scale • Press a point into material • Diamond Point (Brale) • /16" ball • 1/8" ball • ¼” ball

18. Rockwell Hardness

19. Coefficients in R = C1 – C2 t Symbol Minor(Pre-) Major(Total) Indenter Load, kg Load, kg C1 C2mm-1 Normal Scales RB, 1/16 ball* RC, cone + RA, cone RD, cone RE, 1/8 ball RF, 1/16 ball RG, 1/16 ball Superficial Sales R15N, cone+ R30N, cone R45N, cone R15T, 1/16 ball R30T, 1/16 ball R45T, 1/16 ball • 100 130 500 • 10 150 100 500 • 60 100 500 • 10 100 100 500 • 100 130 500 • 10 60 130 500 • 150 130 500 • 3 15 100 1000 • 3 30 100 1000 • 3 45 100 1000 • 3 15 100 1000 • 3 30 100 1000 • 3 45 100 1000 Load levels and indenter sizes for Rockwell hardness tests

20. Rockwell Test Limitations • Sample must be ten times thicker than the indentation depth (sample usually should be at least 1/8" thick). • Need 3 tests (minimum) to avoid inaccuracies due to impurities, hard spots. • Test is most accurate if the Rockwell Hardness is between 0 and 100. Adjust scale to achieve this. • For Steel: • If HRa > 60, use HRc scale • If HRa < 60, use HRb scale

21. Rockwell Hardness Test Pros & Cons • Widely used and well accepted • Little operator subjectivity • Accurate • Fast • Destructive • Non-Portable • Initial cost (3,74,652.50 INR)

22. Rockwell Readings to Brinell • If -20 < HRc < 40BHN = 1,420,000 (100 – HRc)2 • If 40 < HRc < 100BHN = 25,000(100 - HRc) • If 35 < HRb < 100BHN = 7,300(130 - HRb)

23. P A Vickers Hardness = F/A = 3y Vickers Hardness Testing • P: applied load in kg, 5-120 kg • L: average diagonal length, mm (typically from a few µm to 1 mm) • q: angle between opposite faces of indenter; º 136° • Range: 5 (extremely soft metals) - 1500 (extremely hard materials) DPH/VHN/VPH/VH = 2PSin(/2)/L2

24. Vickers Hardness Testing • Continuous hardness from soft (5 DPH) to hard materials (1500 DPH) • DPH independent on load value unlike BHN • Careful surface preparation required • Slow due to careful measurement • Small indentation compared to BHN • Pin cushion and Barrel indentations possible

25. Vickers to Rockwell Hardness

26. Other types of Hardness Test • Knoop hardness Test: Pyramid shape indenter • Scleroscope: rebound height • Durometer: The resistance to penetration (elastic deformation) • Relationship between Hardness and Strength

27. Knoop Hardness Test • Micro Hardness Tests • Major : Minor = 7 : 1 • P : Applied load = 25 gf- 300 gf • Ap : Unrecovered Proj. area of indentations, mm2 • L : Length of long diagonal, mm • C : A constant supplied by the manufacturer (C=0.07028 for 172° 30' between long edges and 130° 0' between short edges)

28. KnoopHardness Test Pros & Cons • Accurate • Useful for elongated and anisotropic constituents • Requires load to be normal to surface plane parallel surfaces • Can be done on mounted specimens • Slow • Sensitive to surface condition • Subject to error in diagonal measurement

29. Microhardness variation in a 9Cr-1 Mo steel weldment as a function of position. Note the structural changes and the corresponding changes in hardness as the fusion line is traversed. KnoopHardness Test Pros & Cons

30. Shore Tester

31. KnoopHardness Test Pros & Cons

32. KnoopHardness Test Pros & Cons

33. Example Problem on Hardness Testing • The Brinell’s Hardness Test of an alloy steel was measured to be 355. What is the diameter of the indentation if a load of 2000 kg was used. Also compute the tensile strength of the material. • D= 10 mm • d = 2.65 mm • Tensile Strength = 1207 MPa

34. Solution Example Problem on Hardness Testing The Brinell hardness of an alloy steel is 355. Compute the diameter of the indentation if a load of 200 kg was used and estimate the corresponding tensile strength of the material.

35. Thank You…