A pine wood specimen was prepared with actual dimensions of 50 x50 x 250 (mm) an
ID: 1940487 • Letter: A
Question
A pine wood specimen was prepared with actual dimensions of 50 x50 x 250 (mm)and grain parallel to its length. The deformation was measured over a gauge length of 200 mm. The specimen was subjected to compression parallel to the grain to failure. The load–deformation results are as shown in Table P10.25.
Table P10.25
Load (Kn) Deformation (mm)
0 0
8.9 0.457
17.8 0.597
26.7 0.724
35.6 0.838
44.5 0.965
53.4 1.118
62.3 1.270
71.2 1.422
80.1 1.588
89.0 1.765
97.9 1.956
106.8 2.159
111.3 2.311
a. Using a computer spreadsheet program, plot the stress–strain relationship.
b. Calculate the modulus of elasticity.
c. What is the failure stress?
Explanation / Answer
A)
In order to calculate Stress we use the equation:
=F/A
=Stress F=Force(Kn)
A=cross sectional area(mm) 50mmx50mm = 250mm
Ex. @point 2 =8.9/250=0.0356 (compute the entire column down)
In order to calculate Strain we use:
=L'-L/L L'=Final length L=Length initial
=(2.457mm)-(2.0mm)/2.0(mm)
=0.2285 (compute the entire column down)
B)
Modulus of Elasticity=Stress/Strain
C) Failure Stress?
You need to analyze the graph created using excel or another graphing program. Failure stress is where the material breaks and trace it down to your X-axis.
Judging by a glance at the deformation data the sample has not gone beyond the plastic deformation point yet.
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