CIVENG 303
Section 804
Stress Concentrations
Performed
October 24th, 2013
Today’s Date:
November 7th, 2013
Tim Hendrickson
OBJECTIVE
The objective of this lab is to determine a set of changes due to the stress in geometric irregularities in an axially loaded bar. Some of the irregularities include certain features such as holes and notches.
QUESTIONS:
-The following are formulas are for stress and strain that are biaxial.
Sample Material
Steel
Testing Machine
INSTRON 3369
Capacity
11K
Measuring Device
Load Cell
1.
a.
b. Poisson’s ratio in the book Mechanics of Materials and Integrated Learning System the calculated value for Structural Steel is 0.26 and our calculated value is 0.196629. This is a difference of 0.063371. This ratio only varies slightly so our values are accurate. In the book the elastic modulus is 29 ksi and ours is 27.219 ksi, which is a difference of 1.781 ksi. Our values seem comparable and accurate.
c. We were asked to calculate the values for the material properties at locations far away from the geometric discontinuities because if the calculations were done on the gages close to the discontinuities, the data would not be a baseline for the material, it would take into account the stress concentrations due to geometric discontinuities.
2. Data Table of Recorded Data
RECORDED DATA
GAGE #
READING W/O LOAD
READING W/ LOADING
UNIAXIAL OR BIAXIAL STRESS εx εy σx(psi) σy(psi)
1
2162
2340
Uniaxial
178
0
4844.982
0
2
2023
1988
Biaxial
0
-35
0
-952.665
3
2607
2767
Uniaxial
160
0
4355.04
0
4
2155
2258
Uniaxial
103
0
2803.557
0
5
1616
2297
Uniaxial
681
0
18536.14
0
6
1976
2664
Uniaxial
688
0
18726.67
0
7
x x x x x x x
8
x x x x x x x
9
1450
1916
Uniaxial
466
0
12684.05
0
10
4150
4591
Uniaxial
441
0
12003.58
0
-The equations that we used to solve this excel table were using