BMEN 3399 HW4
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University of Texas *
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Course
3399
Subject
English
Date
Apr 3, 2024
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5
Uploaded by ChancellorManateePerson1055
BMEN 3399 HW4 Spring 2024 Instructions:
Please complete the assignment on a separate piece of paper and upload a PDF copy to eLearning. Include your name, and clearly mark your final answers. Answers should include units and go to three significant figures. Graded Problem: Question 1 and 7 Question 1:
A tension test was performed on 3 different dog bone specimens. The data from the test are given in the excel file provided with this assignment. i.
For each sample plot the stress
–
strain diagram. Stress should be in MPa. ii.
Determine approximately the modulus of elasticity, the ultimate strength, at percent elongation at failure. iii.
State which sample is the stiffest, most brittle, and most ductile. Question 2:
Determine the elongation of the square hollow bar when it is subjected to the axial force P = 100 kN. If this axial force is increased to P = 360 KN and released, find the permanent elongation of the bar. The bar is made of a metal alloy having a stress
–
strain diagram which can be approximated as shown. LSBI10003
Land
Barakat
on
google
document
e
Graph 1
(Brittle)
Young’s Modulus:
Find slope
Around
1.13953
Ultimate Strength:
Highest amount of stress-
0.7385
Percent Elongation
Lf-L0/L0
=(0.02995-0.00000381)/0.00000381*100
=785989%
Graph 2
(Ductile)
Young Modulus
Around
39.57488
By finding slope
Ultimate Strength:
Highest amount of stress-
0.975
Percent Elongation:
Lf-L0/L0
= (0.19731-0.000006096)/0.000006096*100
=3236612.598%
Graph 3
(Stiffest)
Young Modulus:
Around
72.17155
By Finding slope between two earlier
points
Ultimate Strength:
Highest amount of stress- 2.0227
Percent Elongation
Lf-L0/L0
=(0.010866374-0.000001524)/ 0.000001524*100
=712916.67%
2) State which sample is the stiffest, most brittle, and most ductile.
Sample 3 is the stiffest due to its highest young modulus and linear slope. Sample 2 is the most
ductile due to how the graph extends the most. Sample 1 is the most brittle due to small strain
vs stress difference and how the graph ends at a smaller strain value.
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BMEN 3399 HW4 Spring 2024 Question 7: The two rods form a simple truss. These rods are made of a material that has the stress
–
strain diagram shown. If P = 6 kip determine the following: i.
Solve for the magnitude of forces developed in members AB and BD of the truss and state whether they are in tension or compression. ii.
Using the ultimate tensile strength of the rod as the failure criteria and a safety factor of 5, determine the minimum diameter of each rod.