This document discusses different methods of hardness testing, including Brinell hardness testing, Rockwell hardness testing, Vickers hardness testing, and Shore hardness testing. Brinell hardness testing involves indenting a material with a 10mm diameter steel ball under a load and measuring the diameter of the indentation. Rockwell hardness testing uses different indenters and loads depending on the scale to measure depth of penetration. Vickers hardness testing uses a pyramid shaped indenter to measure hardness. Shore hardness testing provides an empirical hardness value for rubbers and elastomers using either the Shore A or Shore D scale.
Introduction to Microprocesso programming and interfacing.pptx
MSE 2208 Materials Testing Sessional
1. MSE 2208
Materials Testing Sesssional
Presented by
Md. Abul Gofran Banna
Roll: 2027022
Department of Materials Science and Engineering
Khulna University of Engineering and Technology
1
2. Hardness is the resistance of a
material to abrasion or localized
plastic deformation
2
3. Hardness
Hardness is not necessarily an indication of
strength , although for some materials such as
steel, a harder steel is a stronger steel.
Measure of a material’s ability to resist surface
indentation or scratching.
A difficult property to describe in terms of first
principles Φ value depends greatly on
method of testing.
Different testing methods Φ different scales and
values.
3
4. Hardness Testing
• Brinell Hardness Test: 10mm diameter ball
with a load of 500, 1000 or 3000kg
• Rockwell Hardness Test: A cone shape
indenter; the depth of penetration is measured.
• Vickers Hardness Test: Pyramid shape indenter
4
8. Brinell Test Protocol
1. Press a 10mm (3/8") diameter ball into
material with a known amount of load.
2. Measure diameter of the indentation.
3. BHN = Load = 2L
Surface Area D[D-(D2-d2)1/2]
a) L = Load placed on ball, usually 3000 kg , but 1500 kg, and
500 kg can also be used.
b) D = Diameter of steel ball ( = 10 mm)
c) d = diameter of dent, measured by looking thru a Brinell
microscope.
8
9. Analysis of Plastic Deformation during
Brinell Hardness Test
Elastic
Plastic
H = Ae-BT
Mild steel
Copper
d / D ( % E )
H
9
10. Limitations of the 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
10
11. BHN 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
($5,000)
• Error due to operator
reading Brinell
Microscope (10% max)
11
14. Rockwell Hardness Method
• Select Scale - load and
indentor depending on the
scale
• Press a point into material
– - Diamond Point (Brale)
– - 1/16" ball
– - 1/8" ball
– - ¼” ball
14
16. 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
16
17. PROS & CONS (RHT)
• Widely used and well
accepted
• Little operator
subjectivity
• Accurate
• Fast
• Destructive
• Non-Portable
• Initial cost ($5,000)
17
19. Vickers Hardness Testing
Vickers Hardness = F/A = 3y
A
P
2
1.854P
HV
L
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; 136°
Range: 5 (extremely soft metals) -
1500 (extremely hard materials)
q
DPH/VHN/VPH/VH = 2PSin(q/2)/L2
L
19
20. 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
20
21. Other types of HT
• Knoop hardness Test: Pyramid shape
indenter
• Scleroscope: rebound height
• Durometer: The resistance to penetration
(elastic deformation)
• Relationship between Hardness and
Strength
MPa
45
.
3
lb/in
500 2
in
in
K
where
HB
K
TS h
h
21
22. 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)
2
14.2P
HK
L
22
23. Pros & Cons (KHN)
• 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
23
25. Shore (Durometer) Testing
The Shore (Durometer) test provides an empirical hardness
value that doesn't correlate to other properties or fundamental
characteristics.
Shore Hardness, using either the Shore A or Shore D scale, is
the preferred method for rubbers/elastomers and is also
commonly used for 'softer' plastics such as polyolefins,
fluoropolymers, and vinyls. The Shore A scale is used for
'softer' rubbers while the Shore D scale is used for 'harder'
ones.
Because of the resilience of rubbers and plastics, the hardness
reading may change over time - so the indentation time is
sometimes reported along with the hardness number.
25
27. 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
27
29. 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.
29
31. 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)
31
35. Rockwell Hardness Scales
Scale Code Load Indenter Use
A
HR
A 60 kgf 120° diamond cone
Tungsten
carbide
B
HR
B 100 kgf 1/16 in diameter steel sphere
Al, brass, and
soft steels
C
HR
C 150 kgf 120° diamond cone Harder steels
D
HR
D 100 kgf 120° diamond cone
E
HR
E 100 kgf 1/8 in diameter steel sphere
F HRF60 kgf 1/16 in diameter steel sphere
G
HR
G 150 kgf 1/16 in diameter steel sphere
35