To: Brandon Saller (Professor)
From: David Quiroz (Student)
Date: 9-29-21
Subject: Studying e ective ways to accurately measure grain size.
Introduction:
Grain sizes are important because they help us analyze a materials structural strength. In this
memo we will bring to light the best way to measure these grain sizes to better know a
materials strength. The way that the grain size numbers were found by 3 di erent measurement
methods. The rst method was a line intercept method, followed by areal and Feret diameter.
The method with the highest accuracy was the Feret diameter method because this was the
only method to account for every grain size.
Body:
To the left is the photo of grains that the data is taken from then to the right is the same chart
but altered. Altercations made were three di erent methods to nd the grain size number.
Using the ASTM E-112 Grain Size Determination chart for the lab to determine the average
grain size and diameter. Below is a table to show the data that the di erent methods give.
Grain Size
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0.0114
fi
10.0
ff
ff
fi
Line Intercept Method
Average Grain Area
(mm2)
Average Diameter
(mm2)
0.1068
Grain Size
Average Grain Area
(mm2)
Average Diameter
(mm2)
Areal Method
3.5
0.00013
0.0112
Feret Diameter
Method
14
0.000008
0.0028
Looking at the table it can be seen that the results are very di erent from each other. Starting
with line intercept method we see that the grain size is 10.0. This method fundamentally should
be the less accurate and be the main source of error because of the steps taken to obtain the
grain size. If random lines happen to be drawn in areas where smaller grains or larger grains are
located then these individual grains are not taken into account when nding the overall grain
size. Areal method did give a grain size of 3.5 which happened to be the lowest. Given that this
method did take into account the every grain size the error could fall onto the person
conducting the measurements. This is because that method takes some estimation in grains
per 1in square, estimation is subject to the individual. Last we had the Feret diameter method,
which is the method with least error. The error is minimized in this method because the
individual grains are being measured from their longest length. Thus accounting for every grain
pictured.
Conclusion
After using the di erent methods to nd grain size from the sample the data shows di erent
grain sizes for each method. The reason for this could be due to the estimation on some grain
sizes while using the areal method, since it was the farthest from the other grain sizes. The
accuracy of the line intercept method is also taken into question as the way to complete the
process calls for placing random lines on the sample. If lines are randomly placed on the line
then certain grains might not be accounted for. The most accurate way to measure and
determine grain size would be Feret Diameter Method. This method accounts for every
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individual grain making it more accurate to nd the grain size of the whole sample.