Compression Test of Concrete Lab Report

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Hardness Testing






EAS 213 Lab #
3

Professor Chien Wern


10
-
28
-
2005









Prepared by:

David Scuito
















Background:


Hardness testing is one of the more common testing processes for identifying material properties
and is considered a non
-
de
structive test. Although deformations are made in the material, the
tests are considered non
-
destructive in that the part is still considered usable.


There are several methods of testing for hardness as well as how the test results measure various
effe
cts that the material has been subjected too, such as heat treatment or cold flashing. The
Rockwell and Brinell Hardness tests are two of the most common forms of hardness testing.


Objective:


To evaluate the hardness of various materials using the Roc
kwell and Brinell hardness test
methods and understand what the hardness values mean and represent.


Equipment:


Marshall Furnace

Vertical Tube Furnace

S/N: 637516

Max Rated Temp : 1550
˚F


Jominy Quench Tank

PSU# 66047


Wilson Rockwell Hardness Machine

Model #3JR


Wilson Brinell Tester

(Wilson scope included)

Model #J
-
Brinell


Leco Rockwell Tester

S/N: LCR0010


Milutoyo dial caliper

Model: 505
-
637
-
50


Materials:


4140 to be tested as th
e Jominy sample.

2024T4 Aluminum Sample to be tested using the Brinell Method.

Brass sample to be tested using the Brinell Method.

A Grade 2 bolt

to be tested using the Rockwell B method.

A Grade 5 bolt

to be tested using the Rockwell C method.

A Grade 8 b
olt

to be tested using the Rockwell C method.











Procedures:


General procedures are given below for each test:


Rockwell Hardness Testing:

1.

Select sample to be tested.

2.

Configure the Test Machine to the appropriate Rockwell Test (test B or C).

3.

Place s
ample on stage.

4.

Raise stage to point of contact.

5.

Preload sample with the stage using the preload dial as an indicator.

6.

Adjust the read dial to “zero” the readings for the required test scale.

7.

Apply the load by pressing the load handle.

8.

Wait until the load
release handle and read out dial stop moving.

9.

Pull load release handle.

10.

Record the hardness value for the scale used.

11.

Lower stage to clear sample from test.

12.

Repeat test to acquire 6 readings per sample.


Brinell Hardness Testing:

1.

Select sample to be tested
.

2.

Ensure Test machine is properly configured.

3.

Place sample on stage.

4.

Raise stage to point of contact.

5.

Raise load lever to apply load.

6.

Wait approximately 10 seconds.

7.

Pull load lever to relieve load.

8.

Lower stage to clear sample.

9.

Repeat test to acquire 6 read
ings per sample.


Jominy Hardenability Test:

1.

Heat Treat sample to
1550
˚C for 60 min. in an Argon gas chamber.

2.

Place heated sample in Jominy quenching tank and begin quenching.

3.

After sample has cooled, prepare sample for testing by removing the suspension bolt,
washer and grinding a flat surface along one side of the sample.

4.

Use the Leco Rockwell tester to perform tests along sample’s flat surface in
approximately 1/8
th

inch increments.

5.

After approximately 20 readings, remove sample, measure and record the locations of test
sites.



















Data:

The Raw Data is posted i
n Appendix A

Grade 2 Bolt

Grade 5 Bolt

Grade 8 Bolt

Rockwell B Test

Rockwell C Test

Rockwell C Test

67.5

HR
B

(avg)

26.75

HR
C

(avg)

31.10

HR
C

(avg)

Table 1: Bolt Test Data and Average Hardness Values (Rockwell).


Brinell Test: (3,000Kg Load)

Aluminum S
ample

Brass Sample

Impression diameter
(mm)

Brinell Hardness #

Impression diameter
(mm)

Brinell Hardness #

5.3 (avg)

126
(avg.)

6.28

(avg.)

86

(avg.)

Table 2: Sample Data and Average Hardness Values (
Brinell
).




Jominy Test Sample:

Jominy Hardenability Sample
0
10
20
30
40
50
60
0
500
1000
1500
2000
2500
3000
3500
Distance from Quenched End (1/1000th inch)
Hardness (HRc)
Figure 1: Jominy Hardenability Test Graph















2
2
2
d
D
D
D
P
BHN








Calculation:


All of the Rockwell test machines used dial scales and configuration parameters to automatically
provide a hardness value for the test being performed. Calculations were only nec
essary to
determine the Brinell Hardness number. That formula is provided below

and a calculation is
performed under the raw data section.






BHN = Brinell Hardness Number P = A
pplied Load in Kg

D = Diameter of steel ball in mm. d = Diameter of impression in mm.



Discussion:


As with any lab experiment, deviances from expected results will occur and is typically the result
of errors discovered or made during the testing process.

Although testing machines were used in
many of the calculations, there was also a significant possibility of human factor to be integrated
into each test. During the Rockwell bolt tests as well as the Rockwell portion of the Jominy test
sample, the oper
ator needed to support the bolt as level as possible during stage rising. This
allowed the sample to potentially be at an angle to the testing device rather than be in the
preferred perpendicular position. Due to these kinds of errors, a multiple of read
ings was taken
for each sample and an average was determined.


The Jominy hardenability test also included potential opportunities of error just prior to and
during the quenching stage. Ideally, the heated sample would be immediately placed in a jominy
quenching tank where splashing and overspray of the water would not occur. The lab
environment required the sample to fall to the floor, where a technician would have a minimal
amount of time (under 2 seconds) to grasp the heated sample with tongs and pro
perly place it in
the jominy quench tank. Additionally, the water spray in the tank could have splashed along the
sample sides and introduce regions where the hardness value was outside the expected graphic
behavior.



Results
:


As suggested within the Da
ta section of this report, the average hardness ratings for the tested
samples are given in Table 3. A graph of the Hardness Ratings in Rockwell C scale vs. the
distance from the quenched end is provided in Figure 1.


Grade 2 Bolt

Grade 5 Bolt

Grade 8 Bol
t

Aluminum
Sample

Brass Sample

68

HR
B

27

HR
C

31

HR
C

126

BH

86

BH

Table 3: Summary of Rockwell and Brinell Hardness Test Values.







Appendix A: Raw Data

Calculation:

BHN =


















2
2
283
.
6
10
10
10
3000
2
mm
mm
mm
kg


= 86.0

The calculation was the average of all the tests r
un.

Grade 2 Bolt

Grade 5 Bolt

Grade 8 Bolt

Rockwell B Test

Rockwell C Test

Rockwell C Test

63 HR
B

27 HR
C

32 HR
C

65.5 HR
B

28 HR
C

23.5 HR
C

72.5 HR
B

26 HR
C

33 HR
C

69 HR
B

26 HR
C

33 HR
C

N/A

N/A

34 HR
C

67.5 HR
B

(avg)

26.75 HR
C

(avg)

31.10 HR
C

(avg)

Bri
nell Test: (3,000Kg Load)

Aluminum Sample

Brass Sample

Impression diameter
(mm)

Brinell Hardness #

Impression diameter
(mm)

Brinell Hardness #

5.3

125

6.1

92

5.2

131

6.1

92

5.2

131

6.3

85.4

5.3

125

6.4

82.5

5.3

125

6.3

85.4

5.4

121

6.5

79.6

5.3 (
avg)

126
(avg.)

6.28

(avg.)

86

(avg.)

Quenched steel Rockwell test data

Distance from datum

C Scale reading

0.0045

53.80

0.0760

45.63

0.1280

53.20

0.1870

53.36

0.2440

55.64

0.3530

52.54

0.4930

55.71

0.6030

54.45

0.7810

51.49

0.9600

47.61

1.1520

46.26

1.3410

45.51

1.5720

45.94

1.8270

42.52

2.1470

40.24

2.4720

42.21

2.6320

46.36

2.7800

41.15

2.9800

40.53

3.2400

43.36






Appendix B: Assigned Questions


Questions:

1.

Briefly explain the difference between hardness and hardenability.


Hardness

is the term which defines a material’s ability to resist plastic deformation
from an applied load whereas hardenability is defined as a measure of a material’s
range to which it may be hardened by heating and quenching.


2.

How would you expect the HR
C

vs
. Distance plot to change when carbon content is less
than 0.4%?


With a carbon content of 0.4%, the HR
C

vs. Distance plot would appear more level
as the carbon level decreases. This is due to the overall reduction of carbon
throughout the material’s comp
osition.


3.

Why do you need more than one Rockwell Scale?


The Rockwell Hardness test method employs several different types of indenter
materials as well as geometries. It also employs several ranges o
f load capacities.
These fluctuations allow for a large range of materials to be tested. Additionally,
those materials can be more accurately classified within their hardness ranges.
Softer materials can be more accurately compared to similarly soft mat
erials by
sharing a similar scale. Likewise, harder materials can be more accurately compared
to hard materials using a different scale.


4.

If you want to improve on the HR
C

vs. Distance plot, what hardness test method would
you use?


Using the Brinell T
est Method would produce a plot that appeared more linear and
therefore the range of hardenability could be referenced more accurately in terms of
hardness and distance.