244 lab 1
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Department of Building, Civil, & Environmental Engineering
ENGR 244: Mechanics of Materials Experiment No.1: Brinell Hardness Test
Luis Alberto Alvarado Bravo 40193230 Group member: Erica Sciotto Section: CC-CM-X
Summer 2022
July 4th, 2022
1 OBJECTIVE The purpose of the following experiment is to determine how resistant are steel and aluminum under different loads. INTRODUCTION In order to be efficient in their line of work, an engineer must be able to understand and apply many of the scientific concepts and processes that they have learned throughout their studies. One such process is the hardness test. There are four tests that measures hardness: Brinell Hardness; Rockwell Hardness; Vickers Hardness; Mohs Hardness. For this experiment, the focus was on the Brinell Hardness test. Hardness has different definitions based on the context it is being used in. In the case of the Brinell Hardnes
s test where an indent is made onto a material, the definition is “resistance to permanent indentation under static or dynamic loads”. Developed by J.A. Brinell back in early 1900’s, this hardness test uses a small 10 mm steel ball that is pressed against a flat surface for 15 seconds under a certain load. The Brinell hardness (HB) value is found dividing the load in kilograms by the area of the indentation. However, this test is not recommended with materials that have HB values higher than 627 because it can cause the steel ball to deform, making the indentation not accurate. For this experiment, the test materials are flat surfaced steel and aluminum discs.
2 PROCEDURE To perform the test the following materials were used: •
Compression machine •
10 mm steel ball •
Microscope (0.02 mm) •
Steel and aluminum flat discs The compression machine is connected to a hydraulic pump and a digital load reader. At the center of it is a small platform that can be moved up and down to adjust for the size of the specimen. At the top of the machine, the 10 mm is fixed in position so that when the platform moves, the ball can create an indent. To perform the test, the steel disc was placed on the platform and moved as close to the steel ball as possible. With the specimen in position, we started increasing the load until it reached 10000 N. After keeping the load constant for 15 seconds, the load was released, and the specimen was removed from the platform. With the microscope, the indent is measured horizontally and vertically to the nearest 0.1 mm to be able to find the average diameter of the indent. This process was performed 3 times. Given that aluminum is a weaker metal, the load was reduced to 5000 N, and as well, was performed 3 times. RESULTS This were results of the experiment. dx
dy
d = 0.5(dx+dy)
in Newton (N)
in kg (N/9.81)
1
3.30
3.30
3.30
10022.00
1021.61
0.28
8.80
116.10
2
3.30
3.30
3.30
10004.00
1019.78
0.28
8.80
115.89
3
3.40
3.30
3.35
10006.00
1019.98
0.29
9.08
112.38
1
2.40
2.40
2.40
5010.00
510.70
0.15
4.59
111.24
2
2.30
2.40
2.35
5006.00
510.30
0.14
4.40
116.00
3
2.30
2.30
2.30
5009.00
510.60
0.13
4.21
121.25
114.79
116.16
Diameter of impression
Load (P)
Depth of indentation, t (mm)
Area of indentation, A (mm^2)
Brinell Hardness, HB (kg/mm^2)
Average Brinell Hardness, HB (kg/mm^2)
No. of trial
Ball diameter, D (mm)
10.00
10.00
Table 1 - Brinell Hardness test results
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3 As shown on Table #1, the diameter of the indent was determined using the following formula: ? =
1
2
(?
?
+ ?
?
)
So, in the case where ?
?
= 3.40 ??
and ?
?
= 3.30 ??
, the diameter was ? =
1
2
(3.4 + 3.3) = 3.35 ??.
With the value of the diameter, the depth of the indentation t can be found using this formula: ? =
𝐷 − √𝐷
2
− ?
2
2
For a trial run where the diameter of the indent ? = 2.4 ??
, the depth of indentation was ? =
10−√10
2
−2.4
2
2
= 0.146 ??
. To find the Brinell Hardness value we use the formula, 𝐻? =
𝑃 (𝑘𝑔)
? (??
2
)
where P is the load of the pump in kg and A is the area of the indent that can be found using: ? = 𝜋𝐷?
With a load of 𝑃 = 1019.77 𝑘𝑔
and a depth ? = 0.28 ??
, the HB value is 𝐻? =
1019.77
𝜋(10)(0.28)
= 115.89𝐻?
. At the end, the average hardness of the trials is found, giving a final hardness value for each metal: •
Steel ℎ𝑎?????? = 114.79 𝐻?
10/10.01/15 •
Aluminum ℎ𝑎?????? = 116.16 𝐻?
10/5.08/15
4 Discussion and Conclusion After having performed the Brinell Hardness test, we can see that it has some practical uses in engineering because it can help engineers determine if a material is strong enough and suitable for a certain task, or even perhaps they might need a material that does not necessarily have to be strong. For example, the test can be used to determine the hardness of a railroad and a train’s wheel. By finding the different hardness values, engineers can determine which of the two parts should be the weakest to make it easier to repair. A common use of this test is to simply test aluminum and copper alloys under heavy loads. As mentioned before however, this test is not suitable for materials that have HB values larger than 627, which is why other test like the Rockwell hardness test; or if more accuracy was needed for softer materials, the Vickers hardness test is perfect for that situation. When performing the test, it was important to keep track of two things: that the indentations were performed away from the tes
t material’s edge; and that the indentations were performed far from each other. If the indentations had been too close to the edge, there was a risk that the specimen could have tilted just enough for the indentation to not be accurate, as well as it could have caused the specimen to fly out and potentially hurt somebody. On the other hand, if the indentations had been too close to each other, the risk there was that while performing and indentation, the marks could have slightly touched and merged, making it difficult to measure them. Additionally, a source of error that might have affected the results could have been the digital readers. In previous runs performed before the ones of this experiment, the reader started measuring a negative value, slowly going up to positive load values. Another source would be the ruler on the microscope, since it is accurate to 0.1 mm. Lastly, the specimen themselves, that although were flat surfaced, were not completely straight, making taking measurements inaccurate as well.
5 References [1] Lab Manual, Mechanics of Materials, Concordia University, 2022
. [2] A. Velling, “Material hardness - from types of hardness to testing & Units,” Fractory
, 30-Dec-2021. [Online]. Available: https://fractory.com/material-
hardness/#Different_Hardness_Units. [Accessed: 03-Jul-2022]. [3] “Brinell hardness testing,” Buehler United Kingdom - Metallography Equipment & Supplies for Sample Preparation
, 17-Nov-2021. [Online]. Available: https://www.buehler.com/uk/blog/brinell-hardness-testing/. [Accessed: 03-Jul-2022].
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