FAILURE MECHANICS FINAL REPORT GROUP 11

© Dept. of Mechanical Engineering Technology, All rights reserved.
Mechanical Engineering Technology
Fatigue Characteristic Analysis of 1018 Cold Rolled
Steel Involving Pre and Post Annealed States
Name of Principal Author: Ryan Schwartz
Names of Contributors: Austin Allessio
Kathy Feinberg
Stephanie Ulman
Tyler Peterson
Instructor Signature: __________________________ Date: ____________
0610-403 Failure Mechanics Project
Technical Report #: _20121-403-01.11__
Date of Submission:
November 9, 2012
Abstract:
This project determined the fatigue characteristics of AISI 1018 Cold Rolled Steel
with a 95% confidence level. The published value was placed in an SN diagram with
appropriate correction factors for the samples. Fatigue, hardness, and tensile tests were
run on the samples, resulting in a remarkably higher vale for ultimate tensile strength than
what is published for AISI 1018 CRS. After annealing the samples, the fatigue, tensile and
hardness tests were repeated, finding that the annealed parts showed an ultimate tensile
strength within 4.95% of published values.

0610-403 Failure Mechanics Project 20121-403-01.11
Professor Leonard Mechanical Engineering Technology 11/12/2012
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Table of Contents
EXECUTIVE SUMMARY .........................................................................................................................................3
OBJECTIVE................................................................................................................................................................4
DISCUSSION...............................................................................................................................................................4
CONCLUSION............................................................................................................................................................9
APPENDIX A.............................................................................................................................................................10
1 PRE-ANNEAL FATIGUE TESTING ..........................................................................................................................10
2 PRE-ANNEAL HARDNESS TESTING ......................................................................................................................13
3 PRE-ANNEAL TENSILE TESTING ..........................................................................................................................16
4 SPARK TESTING....................................................................................................................................................20
5 COMBUSTION TESTING ........................................................................................................................................25
6 PRE-ANNEAL METALLOGRAPHY TESTING...........................................................................................................28
7 POST--ANNEAL FATIGUE TESTING ......................................................................................................................34
8 POST--ANNEAL HARDNESS TESTING ...................................................................................................................37
9 POST--ANNEAL TENSILE TESTING .......................................................................................................................40
10 POST--ANNEAL METALLOGRAPHY TESTING .......................................................................................................43
APPENDIX B.............................................................................................................................................................49
1 VOC/CTQ.........................................................................................................................................................49
2 PROJECT CHARTER ............................................................................................................................................50
3 Gantt Chart.........................................................................................................................................................52
4 SIPOC ................................................................................................................................................................53
5 Fatigue Test Flow Chart.....................................................................................................................................54
6 Ishikawa Cause & Effect Diagram.....................................................................................................................55
7 Pareto Diagram ..................................................................................................................................................56
8 Boxplot of Pre-annealed Fatigue, Hardness, Tensile, & Published Data ...........................................................56
9 ANOVA of Pre-annealed Fatigue, Hardness, Tensile, & Published Data..........................................................57
10 T-test Pre-Annealed vs. Post-Annealed Tensile.................................................................................................57
11 Boxplot of Post-annealed Fatigue, Hardness, Tensile, & Published Data..........................................................58
12 ANOVA of Post-annealed Fatigue, Hardness, Tensile, & Published Data ........................................................58
13 PDCA.................................................................................................................................................................59
14 Cost Analysis .....................................................................................................................................................60
BIBLIOGRAPHY......................................................................................................................................................61
ACKNOWLEDGEMENTS ......................................................................................................................................61

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Executive Summary
The objective was to determine the fatigue characteristics of 1018 Cold Rolled Steel. The DMAIC
process for Lean Six Sigma was used to determine the Ultimate Tensile Strength of the material
within a 95% confidence interval. The samples underwent fatigue, hardness, tensile, metallography
and combustion tests to gain multiple bases of confirmation for this data. The fatigue data for pre-
annealed samples returned a mean value of Sut=113.2 kpsi with a standard deviation of 8.7 kpsi,
resulting in a variance of 77.4% from published values. The hypothesis formed as a result of this
data is as follows: The cold working process has produced a higher Ultimate Tensile Strength than
that of accepted published values.
In the interest of affirming the hypothesis, metallography testing was performed on the pre-
anneal specimens in order to investigate the material’s grain structure, as well as IMR and spark
testing to ascertain the material’s carbon content. Though the carbon content of the material proved
to be within acceptable ranges of 0.18% ±0.03%, the grain structure was found to be aligned along
the long axis of the part, confirming the proposed hypothesis. In order to prove this hypothesis an
annealing process was performed to return the material’s grain structure to a normalized state,
wherein the original testing was repeated.
Post anneal values for the tensile tests show a mean value of Sut=60.64 kpsi with a standard
deviation of ±0.92 kpsi, a 4.95% difference from the accepted published value of Sut=63.8 kpsi. The
fatigue tests however yielded an Sut value of Sut=79.0 kpsi, showing that the fatigue test did not
provide conclusive results. It is clear that the annealing process has returned the samples’ UTS to
within acceptable ranges of published values ± 5.0%.
10
100
1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08
Strength(kpsi)
Cycles N
Stress-Life Diagram of AISI 1018 CRS
Adjusted Theoretical
Group 11 Pre Anneal
Class Data post
Annealed
SUT=63.8
SUT=124.2
SUT=79.0
SM=111.8
SM=71.1
SM=57.4
SE=31.6
SE=23.5
SE=20.3
LCF HCF

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Objective of This Document
The objective was to determine the fatigue characteristics of 1018 Cold Rolled Steel. The
DMAIC process for Lean Six Sigma was used to determine the Ultimate Tensile Strength of the
material within a 95% confidence interval by week 10.
Discussion
After obtaining the Voice of the Customer (VOC), the team was assembled and parts
were obtained from the supplier, the machine shop manager. The parts were marked for
identification then measured individually. An SN diagram was created using published values.
The Sut was used to estimate the uncorrected graph. Average correction factors were used to
estimate a corrected SN diagram. Correction factors were calculated for each part’s individual
measurements when calculating the stresses within the materials. Fatigue testing was
performed on the samples of AISI 1018 cold rolled steel to determine the materials fatigue
characteristics. The samples were tested in a fatigue testing machine which put them in fully
reversed bending. The data from the samples was used to calculate a best fit line and create a
SN curve. The test data was compared to published data for the same material and a difference
between the values as shown on the SN graph on page 3. At this point the project goal switched
to finding the source of the difference between the two values for the ultimate tensile strength
between the published data and the test data.
The most likely causes for the unexpected data was brainstormed by the team and
displayed on a cause & effect diagram using the Ishikawa format displayed in Appendix B6.
These potential causes for variation were then weighted by the team and displayed in the
Pareto Chart displayed below. From the Pareto Chart the team hypothesized that the machine
was causing the data variation and both hardness and tensile testing were performed to prove
this theory.
Pareto Chart

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The ultimate tensile strength test results of the hardness and tensile tests were
compared to the fatigue test and published data in the boxplot from Appendix B8, also seen
below.
The results from this chart show the maximum difference between hardness, tensile, and
fatigue data to be 19 ksi. This is data doesn’t show statistical significance that the tests yielded
the same results as illustrated by the ANOVA below but it does confirm that all three tests vary
from published values by a minimum of 30 ksi. This concludes the previous hypothesis that the
fatigue testing machine was the cause of the data variance to be false.

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Since the material was identified as the second highest possible source of data variance
it was investigated first. The carbon content of steel can vary from .1% to over 1.2% and the
strength of the steel will increase in accordance with the increased carbon content. The samples
could have had an increased ultimate tensile strength because the material actually had higher
carbon content then stated. The 1018 cold rolled steel should have had .18% carbon with a
tolerance of +/- .03%. A new hypothesis was formed that the carbon content of the material was
the cause of the higher ultimate tensile strength. To prove this hypothesis the team decided to
test carbon content of the material with a spark test and a combustion test.
The spark test results displayed in Appendix A4 determined that the material was a low-
carbon steel, the expected result for 1018 steel. Another team had a combustion test performed
on one part and resulted in a carbon content of 0.15%, within tolerance for 1018 steel. The
team brainstormed new causes for variation of the mechanical properties of the material. After
investigating other possibilities of changes in the material process which could increase the
strength of the material the team decided that the cold rolling process which the material went
through could be a possible cause for this variance. Cold rolling or cold forming of round parts
like the samples involves the material being pulled through a die which decreases its diameter.
The more the diameter is deceased the more the material strength can be increased. The
graph below illustrates this behavior. The drawing process elongates the normally isotropic
grain structure of the metal. The elongated grains have more surface area and are all oriented
in the same direction. The increase in surface area allows for more bonds to be formed between
the grains which makes the material stronger in the direction of the grain orientation. In the cold
forming process of round stock the grain structure would be aligned with the material’s long
axis. The increase in this direction would increase the ultimate tensile strength in the direction
which the material was loaded. A new hypothesis was formed that the material underwent
strengthening through the cold-working process. To prove this hypothesis the team performed
metallography testing displayed in Appendix A6 to view the grain structure in line with and
perpendicular to the axis.

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The grain structure was found to be both elongated and oriented along the material’s
long axis. The results of this test proved the team’s hypothesis. The team discussed and
decided to fully anneal the parts to reform the grain structure without the grain elongation and
lower the ultimate tensile strength. The final hypothesis of the team was that the material would
show the expected properties after fully annealing the parts.
The team obtained 3 more parts from the supplier, physically marked them, annealed
them fully in a nitrogen atmosphere at 5psi and was set to cool in the nitrogen for 8 hours. The
parts then underwent the same processes for fatigue, hardness, tensile, and metallography
testing. The T-test displayed below was performed to statistically confirm the difference between
the pre-annealed and post-annealed tensile tests.
Two-sample T for Pre Tensile Sut vs Post Tensile Sut
N Mean StDev SE Mean
Pre Tensile Sut 65 94.43 2.31 0.29
Post Tensile Sut 28 60.641 0.939 0.18
Difference = mu (Pre Tensile Sut) - mu (Post Tensile Sut)
Estimate for difference: 33.791
95% CI for difference: (33.122, 34.460)
T-Test of difference = 0 (vs not =): T-Value = 100.34 P-Value = 0.000 DF = 90
The post-annealed metallography displayed in Appendix A10 confirms that there has
been a change made by the annealing process. The Boxplot displayed below and in Appendix
B11 visually confirms that ultimate strength estimated from the post-annealed fatigue, hardness,
and tensile tests were closer to published values than pre-annealed tests.

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One-way ANOVA: Post Fatigue Sut, Post Tensile Sut, Post Hardness Sut, Published
Source DF SS MS F P
Factor 3 2170.27 723.42 188.18 0.000Error 50 192.22 3.84
Total 53 2362.49
S = 1.961 R-Sq = 91.86% R-Sq(adj) = 91.38%
Individual 95% CIs For Mean Based on
Pooled StDev
Level N Mean StDev --------+---------+---------+---------+-
Post Fatigue Sut 4 70.383 5.433 (--*---)
Post Tensile Sut 28 60.641 0.939 (*)
Post Hardness Sut 19 49.842 2.106 (*-)
Published 3 63.800 0.000 (--*---)
--------+---------+---------+---------+-
54.0 60.0 66.0 72.0
Pooled StDev = 1.961
The ANOVA displayed above measures the statistical similarity between the tests. The
results of this analysis indicate that there is not enough statistical evidence to say that the
annealing process yielded the same ultimate tensile strength as published values. While
statistical significance cannot be proven from the results of the annealed testing practical
significance can. The most accurate test results, the tensile test, were within 4.95%, an
acceptable value for use in engineering calculations.

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Conclusion
The fatigue test showed the ultimate tensile strength of the specimens to be higher than
the ultimate tensile strength of the published valves by 77.4%. Therefore tensile and hardness
tests were performed in order to conclude whether the fatigue testing machine was properly.
The results from the tensile, hardness and, fatigue tests were higher than the published values
by at least 47.9%, warranting further investigation. Combustion analysis was conducted in order
to determine the material’s carbon content, supported by a spark test; the combustion analysis
returned a content of 0.15%, a value within acceptable industry standards.
The Metallography was done to find the grain structure of the material. The test samples’
grain structure was found to be in an elongated form aligned along the long axis. After an
annealing process, the samples were tested again using fatigue, hardness, tensile, and
metallography tests. The metallography yielded a grain structure that was not aligned as
previously indicated. Being the most accurate, the tensile results of Sut= 60.64 kpsi were chosen
as the basis for comparison against the published value of Sut=63.8 kpsi, yielding a difference of
4.95%, falling within the allowable range for use in engineering practices.

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Appendix A
1.
Fatigue Testing – Pre-Anneal
Lab Info: Materials Testing Lab: GOL (70) – 1190
Testing Machine Used: Gunt Hamburg WP 140 Fatigue Testing Machine
Data Collection Date: 10/1/12 – 10/30/12
Principal Contributors: Austin Allessio, Kathy Feinberg, Tyler Peterson, Ryan
Schwartz, Stephanie Ulman.
Objective:
The objective of this lab is to determine the number of cycles a fatigue sample can withstand
when subjected to fully reversed bending before failure when a specified stress is induced in a
sample. The stress induced in the part and the number of cycles a part undergoes is plotted on a log-
log graph. The points plotted on the graph are used to create a best-fit line to predict the relationship
between the stress induced in a part and the number of cycles it will undergo before failure.
Procedure:
1. Ensure the emergency stop is engaged
2. Turn off the machine power
3. Ensure there is a 1/8” minimum gap between hand nut and rig
4. Loosen 4 quarter-turn screws
5. Remove the protective cage
6. Remove the collar nut and extract the collet from the spindle
7. Place the large end of a fatigue sample into the collet and slide the collar nut over the small
diameter of the sample
8. Ensure the flat face of the bearing is facing away from the motor
9. Slide the small diameter of the sample into the bearing
10. Place the collet into the spindle and loosely screw the collar nut onto the spindle
11. Leave approx. 1/8” (measured with a 1/8” scale) of the small diameter of the shaft protruding
from the flat side of the bearing
12. Tighten the collar nut onto the spindle using the wrenches
13. Replace the cage and fasten the quarter-turn screws until they click
14. Disengage the emergency stop and turn on the machine power
15. Zero both cycle count displays by pressing the “RST” buttons
16. Press the start button and immediately begin loading the rig by turning the hand nut CW
17. Slow turning speed when load is within 10N of the desired load
18. Wait for the sample to break
19. Ensure the machine power is off and the emergency stop is engaged
20. Remove quarter-turn screws and cage

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21. Remove the long piece of the fatigue sample from the bearing
22. Unload the rig by turning the hand nut CCW until there is a 1/8” minimum gap between the
hand nut and the rig
23. Remove the collar nut from the spindle using the wrenches
24. Spin the spindle while gently tapping the fatigue sample stub with a brass mallet until the
sample and collet are released
25. Remove the sample from the collet
26. Label broken parts of fatigue sample
27. Replace the collet and collar nut on the spindle loosely fastening the collar nut
28. Replace the cage
Data/Results:

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Discussion:
The fatigue was test performed to estimate the ultimate tensile strength of the material. To
calculate the ultimate tensile strength of the material from the fatigue test the data is plotted on a log-
log graph of Stress vs. Number of cycles. A best fit line was then created from 106
to 103
, the value at
103
cycles, Sm, is then divided by 0.9 to yield an Ultimate Tensile Strength. This uses the assumption
that the fatigue strength of a material at 103
cycles is 90% of its ultimate tensile strength. The best fit-
line was calculated to be y = 187.26x-0.169
yielding an Sut of 78.7 ksi.
Conclusion:
The best fit-line was calculated to be y = 187.26x-0.169
yielding an Sut of 78.7 ksi.
The fatigue test yielded an Sut of 78.7 ksi.

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2.
Hardness Testing of Fatigue Parts
Lab Info: Materials Testing Lab - 1190
Testing Machine Used: Instron Wilson-Rockwell Series 2000 Hardness Testing
Machine
Data Collection Date: October 11th
, 2012
Principal Contributors: Austin Allessio, Ryan Schwartz, Kathy Feinberg, Tyler
Peterson, Stephanie Ulman.
Executive Summary:
The hardness information of the test pieces was determined in order to get a rough estimate
of the material’s ultimate tensile strength, through use of tables/conversion factors. The test
pieces are speculated to be AISI 1018 Cold Rolled Steel, resulting in the use of the Rockwell B
hardness scale. The samples were found to have an average hardness of 95.2 B, yielding an
ultimate tensile strength of 105.5 ±2.0 kpsi1
.
Objective:
The objective of this lab was to determine the sample pieces hardness. This information is an
indicator of what exactly the material is, and a rough estimator of the ultimate tensile strength. This
information will be used in comparison to the UTS discovered from the fatigue tests to determine if
the hypothesis or an improper material is correct.
Procedure:
1. Gather specimens, and power up test machine.
2. Select appropriate scale, the Rockwell B scale was used.
3. Apply proper corrections due to a round test piece.
4. Test 5 separate spots per specimen.
5. Record data.
6. Compile data in a visual aid, a box plot was well suited.
7. Convert the range and mean hardness to an UTS.

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Data/Results:
Rockwell B Hardness Data
Part Number Test 1 Test 2 Test 3 Test 4 Test 5 Average
Part 1 95.0 95.4 94.6 95.4 94.5 95.0
Part 2 95.7 96.4 95.5 94.8 95.5 95.6
Part 3 94.5 94.2 94.5 94.2 95.3 94.5
Part 4 94.8 95.1 94.9 94.9 95.6 95.1
Part 5 95.7 95.6 95.3 95.8 96.0 95.7
Part 6 94.6 96.0 95.2 95.1 94.5 95.1
Part 7 95.5 96.0 96.7 94.0 95.4 95.5
Part 8 95.1 95.2 95.6 96.1 95.1 95.4
Overall Average 95.2
97.0
96.5
96.0
95.5
95.0
94.5
94.0
RockwellBHardness
Boxplot of Hardness Testing
Discussion:
The hardness values collected a very low variability, indicating that specific test pieces are
not contaminated. This also gives a very good idea of what value to select as the resultant
Ultimate Tensile Strength. The UTS indicated by the hardness testing does not align with what
was indicated by previous fatigue testing, garnering a need for further testing i.e. tensile test.

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Conclusion:
The hardness data gathered clearly shows an ultimate tensile strength above the published
vales of 1019 Cold Rolled Steel. These results however are not as accurate as other tests, such as a
tensile test. The variance in data, ranging from a Hardness of 94.0 to 96.7 HRB (102.5 to 106.5 kpsi
UTS) is also compounded by the fact that a conversion factor is used from Rockwell to UTS. Not all
sources agree on what exactly this factor is, resulting in some values higher and some lower than
what was chosen to represent the data with.
This variance however, does not condemn the data, which clearly shows that the UTS of the
fatigue tested parts are above standard published values. Many possible factors were discussed,
though the likely cause chosen is a direct result of the cold forming process. This hypothesis will be
confirmed upon the completion of a more accurate Tensile Test, and a Metallography inspection to
determine how the grain structure is oriented.

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3.
Tensile Testing of Fatigue Parts – Pre-Anneal
Testing Machine Used: MTS Universal Test Machine, Tensile Test
, 2012
Objective:
The objective of this lab was to determine the sample pieces’ Ultimate Tensile Strength with
a more accurate method than a hardness or fatigue test. This data aggregated was used in conjunction
with fatigue and hardness test data in order to form a hypothesis as to why the results of these tests
yielded a value for Ultimate Tensile Strength much higher than anticipated with published values.
Procedure:
1. Gather specimens, and power up test machine and
attached computer.
2. Adjust machine clamp heads to fit specimen and ensure alignment.
3. Enter appropriate test data i.e. specimen diameter etc.
4. Place specimen in top jaw.
5. Toggle program to lower testing head, securing bottom jaw on sample once
complete.
6. Attach extensometer to specimen.
7. Start test.
8. Once prompted to or after the part breaks, remove the extensometer.
9. Remove specimen.
10. Repeat as necessary with more sample pieces.
11. Convert test data to Microsoft Word document, and save results.

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Data/Results

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Discussion:
The hardness test garnered a great set of data points. With a mean Ultimate Tensile
Strength (Peak Load) of 94.85 kpsi and a standard deviation of only 0.62 kpsi, the results have
proven to be highly accurate. This is a very reassuring fact, as this UTS value lines up nicely
with the hardness test data, 94.84 kpsi compared to the mean of 95.2 kpsi yielded from the
hardness tests. These data points allow for 3 possible hypothesis for data variance, Machine,
Material and, Process. Further tests are necessary to affirm these hypotheses as viable or not.

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Conclusion:
The tensile test was very conclusive in the proof of a higher Ultimate Tensile Strength than
published values for AISI 1018 Cold Rolled Steel. This data lines up very nicely with the
hardness test’s results for UTS, resulting in a hypothesis needing to be formed for the
discrepancies with the fatigue test. The most likely culprits of these are Material: Carbon content
not to spec, and Process: Cold working changed the material properties in some way.

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4.
Spark Test of Fatigue Parts
Testing Machine Used: Rotary Grinding Wheel
, 2012
Executive Summary:
It is known that the carbon content of steel affects its strength. A spark test was deemed
necessary in order to test for this. This test gives a decent indicator of carbon content, as well as
other alloying elements. It was found that the specimens were in the mild steel range, with
carbon content around 0.15% and 0.25%. Given this data, it was decided that the material’s
carbon content was most likely in the range it should be (0.15%-0.20%), indicating that further
investigation to a more accurate test was unnecessary.
Objective:
The objective of this lab was to roughly determine the sample’s carbon content. A higher
carbon content would produce a material with a higher Ultimate Tensile Strength. Being able to place
the approximate content will allow an educated insight to if the material supplied is to spec. This
gives a good indication of whether or not further investigation is necessary.

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Procedure:
1. Gather specimens, testing machine, and camera.
2. Touch specimen to grinding wheel so that the spray of sparks is visible.
3. Capture images and compare to published data.
Data/Results:
Many charts for carbon/alloying materials content can be found. The chart below was
chosen as a basis for comparison.
Image Courtesy of MechLook (mechlook.com)
The highlighted column shows 1020 Machine Steel, exhibiting extremely similar behavior to the
samples tested (pictured below).

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Image 1

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Image 2

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Discussion:
The testing proved slightly difficult, as only a rotary grinding wheel was available. The
specimens however produced some very telling results. The sparks captured followed
along with an appropriate carbon content, and were of an appropriate color, size, and
amount.
Conclusion:
The specimens tested produced long tails, with a few intermittent bursts. Predominantly
colored orange, with white bursts is indicative of steel with carbon content on the lower range
(0.15%-0.25%). The bursts themselves contained very few mini-bursts and few legs as well. This
is further proof that the material’s carbon content is not higher than 0.50%, as well as ruling out
any other alloying elements out of the ordinary.
The spark test gives reasonable doubt to conclude that that material’s carbon content is not
a concerning factor in the discrepancies between the tested Ultimate Tensile Strength and
published values.

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5.
Combustion Testing
Lab Info: IMR Report Number 201210359
, 2012
Executive Summary:
It is known that the carbon content of steel affects its strength. Since the samples material
composition was in question, specifically the percentage of the materials carbon content, a
sample was sent to an independent material testing laboratory for carbon analysis test. The
results from this test concluded that the carbon content by weight was .15 %, indicating that it is
in the published range of a mild steel, whose carbon content typically is between 0.15% and
0.25%.
Objective:
The objective of this lab report was to determine the carbon content of a fatigue sample.

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Data/Results:

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Discussion:
The test results provided concrete evidence that the material is indeed 1018 steel and that
the high ultimate strength values were not due to the materials carbon content. Other factors
must now be investigated to see the root cause.
Conclusion:
The IMR report provided conclusive results to conclude that the carbon content is not the
cause of variability in data for the Ultimate Tensile Strength results.

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6.
Metallography Pre-Anneal
Lab Info:
Testing Machine Used:
2012
Principal Contributors: Tyler Peterson, Ryan Schwartz, Kathleen Feinberg, Austin
Allessio, Stephanie Ulman
Executive Summary:
Fatigue testing samples of 1020 cold rolled steel produced higher than expected ultimate
strength values. It is believed that these values are increased because the raw stock of the test parts is
cold drawn when it is manufactured. The cold drawing aligns the metals grain structure and elongates
it along the parts axis. This alignment and elongation of the grain structure increases the materials
strength above the published data for fully annealed 1020 steel. To prove this theory the samples
were polished and etched so that their grain structure could be examined under a microscope. The
grain structure was verified to be both aligned and elongated along the parts axis proving the theory
correct. TO fully validate the theory further a duplicate part from the same stock should be fully
annealed and run through the same test to see if its grain structure no longer shows alignment.
Objective:
Metallography is being performed on the samples to see if the grain structure shows signs of
elongation. Elongation of the grain structure would increase the strength of the material in the
direction which the grain structure is directed. Showing that elongation exists would support the
theory that the material was cold worked which would increase its strength along its axis.

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Procedure:
1. First the round Samples must have a flat milled into them, it is better to mill the surface then
grind it to avoid heating the material which could change the grain structure
a. The flat should be at least .250 inches wide
2. The flat surface needs to be polished starting at a course grit like 200 grit
a. Sand the surface until the whole surface is uniform and has no deep sanding lines
3. Repeat step 2 progressing to finer grit sand paper ex. 320, 400, 600
4. Use commercial metal polish to bring the surface to a mirror finish
a. If at any point there are scratches that can’t be removed with the current grit in use it
may be necessary to drop back to a more coarse grit to remove the scratches.
5. Now the surface must be cleaned with isopropyl, cover the surface with a thin layer and let it
evaporate
6. Next apply a thin layer of Nitol HNO3 to the surface and let it sit for 15 seconds
a. This will etch the grain boundaries making them visible under a microscope.
7. After the 15 seconds quickly remove all the Nitol by covering the surface with more
isopropyl, wait until it evaporates again
8. Now the part may be inspected under the microscope, place it on the base of the microscope
and secure it with the spring foot
9. Turn the microscope lamp on and select the magnification level (80X is a good start)
10. Focus the microscope and observe the grain structure
11. Take pictures to document the grain structure
a. It may be ideal to change the microscope focus and light level to get an ideal picture

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Data/Results:
Material grain structure (80X magnification)
Part is aligned with its axis left to right (side view of part)

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Part is aligned with its axis into or out of the page (end view of part)

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Discussion:
The fatigue test parts were polished and etched so view their grain structure. It was believed
that the grain structure may be altered from a uniform grain structure due to the manufacturing
of the raw stock by cold drawing. Cold drawing is done for round parts by pulling material
through a die which tappers down in size. The part goes in one diameter and is pulled through
to the other side where it now has a decreased diameter. This process tends to align the grain
structure of the material towards the outside of the stock, or in cases where the stock is a small
diameter it may be affected through its entire cross section. Depending on the ratio of diameter
change the part sees, it could have its ultimate tensile strength increased by up to 20%, as
shown by the graph below.
Percent Reduction Graph
The grain structure images above are taken from two different sides of the part. The top
picture is a view of the long side of the part along its axis. This picture shows a common grain
direction, where the grains are going left to right in the same direction as the part axis. These
grains are a shaped like a cigar or elongated oval. This elongated grain has more surface area

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then a uniform grain which would have a more spherical shape. This increased surface area
allows the grain to have more bonds to other grains. Increasing the number of bonds allows the
bond between each individual grain to increase, therefore increasing the material strength along
the direction the grain is pointing. This common grain direction along the part axis is due to the
cold drawing process of the raw stock.
The bottom picture of the end of the part only solidifies the conclusion. The bottom picture
shows that the cross section of the part has a random grain structure showing no alignment
direction. This is expected since there should be no alignment across the part in this direction
and further proves the theory that the grain direction is aligned to the part axis and that axis
only.
Conclusion:
The fatigue test parts have been polished and etched to observe their grain structure. It was
found that the grain structure shows alignment along the parts axis. This grain alignment along
with the elongation of the grains has increased the ultimate tensile strength of the parts. This
grain structure change is due to the cold drawn manufacturing process which the raw stock has
been through. Further testing should be done to anneal another sample of the same stock and
see if the grain structure changes along with the expected drop in ultimate tensile strength.
Citations:
Percent Reduction Graph, http://pmpaspeakingofprecision.files.wordpress.com/2010/06/cold-
work-graph.jpg Graph and data: AISI Cold Finished Steel Bar Handbook, 1968.

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7.
Fatigue Testing – Post-Anneal
Lab Info: Materials Testing Lab: GOL (70) – 1190
Testing Machine Used: Gunt Hamburg WP 140 Fatigue Testing Machine
Data Collection Date: 10/1/12 – 10/30/12
Principal Contributors: Austin Allessio, Kathy Feinberg, Tyler Peterson, Ryan
Schwartz, Stephanie Ulman.
Objective:
The objective of this lab is to determine the number cycles a fatigue sample can withstand
when subjected to fully reversed bending before failure when a specified stress is induced in a
sample. The stress induced in the part and the number of cycles a part undergoes is plotted on a log-
log graph. The points plotted on the graph are used to create a best-fit line to predict the relationship
between the stress induced in a part and the number of cycles it will undergo before failure.
Procedure:
1. Ensure the emergency stop is engaged
2. Turn off the machine power
3. Ensure there is a 1/8” minimum gap between hand nut and rig
4. Loosen 4 quarter-turn screws
5. Remove the protective cage
6. Remove the collar nut and extract the collet from the spindle
7. Ensure any scale, from the anneal process, is removed from the surface, utilizing a hand file.
8. Place the large end of a fatigue sample into the collet and slide the collar nut over the small
diameter of the sample
9. Ensure the flat face of the bearing is facing away from the motor
10. Slide the small diameter of the sample into the bearing
11. Place the collet into the spindle and loosely screw the collar nut onto the spindle
12. Leave approx. 1/8” (measured with a 1/8” scale) of the small diameter of the shaft protruding
from the flat side of the bearing
13. Tighten the collar nut onto the spindle using the wrenches
14. Replace the cage and fasten the quarter-turn screws until they click
15. Disengage the emergency stop and turn on the machine power
16. Zero both cycle count displays by pressing the “RST” buttons
17. Press the start button and immediately begin loading the rig by turning the hand nut CW
18. Slow turning speed when load is within 10N of the desired load
19. Wait for the sample to break
20. Ensure the machine power is off and the emergency stop is engaged
21. Remove quarter-turn screws and cage
22. Remove the long piece of the fatigue sample from the bearing

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23. Unload the rig by turning the hand nut CCW until there is a 1/8” minimum gap between the
hand nut and the rig
24. Remove the collar nut from the spindle using the wrenches
25. Spin the spindle while gently tapping the fatigue sample stub with a brass mallet until the
sample and collet are released
26. Remove the sample from the collet
27. Label broken parts of fatigue sample
28. Replace the collet and collar nut on the spindle loosely fastening the collar nut
29. Replace the cage
Data/Results:

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Discussion:
The fatigue was test performed to estimate the ultimate tensile strength of the material. To
calculate the ultimate tensile strength of the material from the fatigue test the data is plotted on a log-
log graph of Stress vs. Number of cycles. A best fit line was then created from 106
to 103
, the value at
103
cycles, Sm, is then divided by 0.9 to yield an Ultimate Tensile Strength. This uses the assumption
that the fatigue strength of a material at 103
cycles is 90% of its ultimate tensile strength. The best fit-
line was calculated to be y = 187.26x-0.169
yielding a Sut of 79.0 ksi.
Conclusion:
The best fit-line was calculated to be y = 291.02x-0.204
yielding a Sut of 79.0 ksi.
The fatigue test yielded a Sut of 79.0 ksi.
Citation:
Data points were collected from Groups 1, 2, 3, 6, 8, and 10.

Page 37 of 61
8.
Hardness Testing of Fatigue Parts - Post Anneal
Testing Machine Used: Instron Wilson-Rockwell Series 2000 Hardness Testing
Machine
Data Collection Date: October 27, 2012
Executive Summary:
The hardness information of three test pieces was required to determine if the annealing
process had an effect and what these effects were on the material’s properties. The initial ten pre-
annealed samples had higher hardness values than what would be expected for AISI 1018 Cold
Rolled Steel, the material under scrutiny. The cold drawing process is thought to have had an
effect on the hardness and strength on these pieces, a hypothesis that previous testing has shown
to be viable. The annealing process was done in order to relax the specimens and release built in
strains 1.
With the utilization of the Rockwell B scale, the samples were found to have an average
hardness of 57.9 B post anneal. Most industrial charts that convert the Rockwell Hardness B
value to the materials ultimate tensile stress do not go as low as this. As a result, a formula 2
was
utilized to convert the Rockwell B Hardness value to an Ultimate Tensile Strength value. For a
mean Rockwell Hardness B value of 57.93 +/-2.7, it was calculated to have an estimated tensile
strength of 58.3 kpsi.
1. Machine Design An Integrated Approach 4ed/ Robert L Norton. Paragraph 4, Page 53.
2. <http://www.ehow.com/how_8759475_convert-rockwell-hardness-tensile-
strength.html>.
Objective:
The objective of this lab was to determine the post-anneal sample pieces’ hardness. This
information will be used to compare the previous non annealed samples to the post annealed samples.
The annealing process was speculated to have lowered the hardness values, which also would
correlate with a lower ultimate tensile strength of the material .This test, in addition to others, should
help in determining if the hypothesis that cold drawing process changes the material’s properties,
specifically Ultimate Tensile Strength.

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Procedure:
1. Gather specimens, and power up test machine.
2. Select appropriate scale, the Rockwell B scale was used.
3. Apply proper corrections due to a round test piece.
4. Test 10 separate spots per specimen, avoiding scale on the material surface.
5. Record data.
6. Compile data in a visual aid, a box plot was well suited.
7. Convert the range and mean hardness to an UTS.
Data/Results:
Part Number Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Test 9 Test 10
Part 11 54.7 55.8 59.2 55.9 55.5 54.5 56.1 60.6 60.5 60.9
Part 12 62.7 57.9 59.2 56.2 57.7 56.5 60.7 56.5 53.6 53.2
Part 13 62 62.5 60 58.1 59.9 56.1 62.4 54.7 58 56.2
57.93Overall Average
Rockwell B Hardness Data

Page 39 of 61
Conversion Formula Used to Convert of Rockwell Hardness B to an approximate
Tensile Strength
TS (kpsi) =c3*RH^3+c2*RH^2+c1*RH+c0
Where RH = Rockwell Hardness B value, the mean value of 57.93 was
used.
Given:
c3 = .0006
c2 = - 0.1216
c1= 9.3502
c0= - 191.89
Discussion:
The grain structures of the pre-anneal samples were found to be elongated in one direction, a
result of the cold drawn process, which changes the material’s properties. To reverse the effects, it
was determined that annealing three new samples was necessary to prove the hypothesis. The thirty
readings were then averaged, with a mean value of 57.93 +/-2.7 Rockwell B Hardness. Utilizing the
conversion formula previously mentioned, the tensile strength of the post annealed samples is
approximately 58.34 kpsi.
Conclusion:
The hardness data gathered does indeed have a much lower value than the non-annealed
specimens. In fact it is closer to published values, validating the hypothesis that the cold forming
process had affected the material properties, specifically Ultimate Tensile Strength, was correct.
Additional Tensile Testing, along with Metallographic inspection will also be performed on these
specimens, aiding in the confirmation of this hypothesis.

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9.
Tensile Testing of Fatigue Parts – Post
Anneal
Testing Machine Used: MTS Universal Test Machine, Tensile Test
, 2012
Objective:
The objective of this lab was to prove that the hypothesis of annealing in order to return to
published values is true. The tensile test is most accurate at determining the Ultimate Tensile
Strength of the samples, and so was chosen as a go-to test for proving the effectiveness of this
annealing.
Procedure:
1. Gather specimens, and power up test machine and attached computer.
2. Adjust machine clamp heads to fit specimen and ensure alignment.
3. Enter appropriate test data i.e. specimen diameter etc.
4. Place specimen in top jaw.
5. Toggle program to lower testing head, securing bottom jaw on sample once
complete.
6. Attach extensometer to specimen.
7. Start test.
8. Once prompted to or after the part breaks, remove the extensometer.
9. Remove specimen.
10. Repeat as necessary with more sample pieces.
11. Convert test data to Microsoft Word document, and save results.

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Data/Results
Specimen # Specimen
Comment
Diameter
in
Peak Load
lbf
Peak Stress
psi
Modulus
psi
Stress At
Offset Yield
psi
Break Stress
psi
1 Sample 13 0.312 4664 61009.3 4.993e+007 3.852e+004 4.297e+004
2 Sample 11 0.311 4651 61230.5 3.789e+007 3.857e+004 4.376e+004
3 Sample 12 0.311 4627 60911.2 3.043e+007 3.668e+004 4.244e+004
Mean 0.311 4648 61050.4 3.942e+007 3.792e+004 4.306e+004
Std. Dev. 0.001 19 163.5 9.839e+006 1.079e+003 6.634e+002
Specimen # Strain At
Break
%
Total
Energy
Absorbed
ft*lbf/in^2
1 33.335 2340
2 34.379 2473
3 31.731 2151
Mean 33.148 2321
Std. Dev. 1.334 162

Page 42 of 61
Discussion:
The annealed parts showed a great drop in the Ultimate Tensile Strength from the previous
pre-annealed tests. This is a great indicator that the hypothesis of material deformation having
an effect on the test sample’s properties. The Tensile test returned a mean value of 61.05 kpsi
with a standard deviation of 0.16 kpsi, giving an extremely accurate result that is only 4.3%
difference from published values. This, alongside with the post anneal hardness data is an
extremely good indicator that the cold working process to form the stock from which the
samples were made had a drastic effect on the material’s physical properties.
Conclusion:
The tensile test proved that the annealing process had an effect at reducing the sample’s
Ultimate Tensile Strength to near published values. This is proof that the hypothesis of the cold
drawing process raising the material’s Ultimate Tensile Strength is very likely to be true. The
tensile test returned UTS values within 4.3% of the published values, 61.05 kpsi for the test and
63.8 kpsi for published values.

Page 43 of 61
10.
Post-Anneal Metallography
Lab Info:
Testing Machine Used:
Data Collection Date: November 1st
, 2012
Principal Contributors: Tyler Peterson, Ryan Schwartz, Kathleen Feinberg, Austin
Allessio, Stephanie Ulman
Executive Summary:
Fatigue testing samples of 1020 cold rolled steel produced higher than expected ultimate
strength values. It is believed that these values are increased because the raw stock of the test parts is
cold drawn when it is manufactured. The cold drawing aligns the metals grain structure and elongates
it along the parts axis. This alignment and elongation of the grain structure increases the materials
strength above the published data for fully annealed 1020 steel. This was proven through earlier
testing which observed the grain being elongated and aligned with the part axis. To fully validate the
theory r a duplicate part from the same stock was fully annealed and run through the same etch and
observed. This fully annealed sample showed no sign of having elongated or aligned grain structure.
This proves that the change in grains structure was modified by manufacturing the stock. The new
grain structure has no bias and therefore the material would have the same strength in all directions.
Objective:
To prove that the 1020 cold rolled steels grain structure was changed through the
manufacturing of the stock a copy of the part made from the same stock was fully annealed. This full
anneal should let the grain structure relax and become isotropic so that the material has the same
properties in every direction. This annealed material will be polished and etched so that its grain
structure can be observed and verified to be random without elongation or orientation.

Page 44 of 61
Procedure:
1. First the round Samples must have a flat milled into them, it is better to mill the surface then
grind it to avoid heating the material which could change the grain structure
a. The flat should be at least .250 inches wide
2. The flat surface needs to be polished starting at a course grit like 200 grit
a. Sand the surface until the whole surface is uniform and has no deep sanding lines
3. Repeat step 2 progressing to finer grit sand paper ex. 320, 400, 600
4. Use commercial metal polish to bring the surface to a mirror finish
a. If at any point there are scratches that can’t be removed with the current grit in use it
may be necessary to drop back to a more coarse grit to remove the scratches.
5. Now the surface must be cleaned with isopropyl, cover the surface with a thin layer and let it
evaporate
6. Next apply a thin layer of Nitol HNO3 to the surface and let it sit for 15 seconds
a. This will etch the grain boundaries making them visible under a microscope.
7. After the 15 seconds quickly remove all the Nitol by covering the surface with more
isopropyl, wait until it evaporates again
8. Now the part may be inspected under the microscope, place it on the base of the microscope
and secure it with the spring foot
9. Turn the microscope lamp on and select the magnification level (80X is a good start)
10. Focus the microscope and observe the grain structure
11. Take pictures to document the grain structure
a. It may be ideal to change the microscope focus and light level to get an ideal picture

Page 45 of 61
Data/Results:
Part is aligned with its axis left to right (side view of part)

Page 46 of 61
Part is aligned with its axis into or out of the page (end view of part)

Page 47 of 61
Discussion:
The annealed fatigue test parts were polished and etched so view their grain structure. It
was believed that the grain structure may be altered from a uniform grain structure due to the
manufacturing of the raw stock by cold drawing. Cold drawing is done for round parts by pulling
material through a die which tappers down in size. The part goes in one diameter and is pulled
through to the other side where it now has a decreased diameter. This process tends to align
the grain structure of the material towards the outside of the stock, or in cases where the stock
is a small diameter it may be affected through its entire cross section. Depending on the ratio of
diameter change the part sees, it could have its ultimate tensile strength increased by up to
20%, as shown by the graph below.
Percent Reduction Graph
The grain structure images above are taken from two different sides of the part. The top
picture is a view of the long side of the part along its axis. This picture shows no common grain
direction. These grains are not elongated. The random grain shape and direction would give the
part similar strength in all directions. This annealed part proves that the grain direction and
shape was caused by the stock being manufactured by cold drawing.

Page 48 of 61
Conclusion:
The fatigue test parts have been polished and etched to observe their grain structure. It was
found that the grain structure shows no alignment along the parts axis. The random shape of
the grain and the it’s orientation proves that the grain structure was altered by the cold drawing
of the stock which would have increased its strength along the parts axis.
Citations:
Percent Reduction Graph, http://pmpaspeakingofprecision.files.wordpress.com/2010/06/cold-
work-graph.jpg Graph and data: AISI Cold Finished Steel Bar Handbook, 1968.

Page 49 of 61
Appendix B
1.

Page 50 of 61
2.

Page 51 of 61

Page 52 of 61
3.

Page 53 of 61
4.

Page 54 of 61
5.

Page 55 of 61
6.

Page 56 of 61
7.
8.

Page 57 of 61
9.
One-way ANOVA: Pre Fatigue Sut, Pre Tensile Sut, Pre Hardness Sut, Published
Source DF SS MS F P
Factor 3 9930.5 3310.2 164.24 0.000Error 146 2942.5 20.2
Total 149 12872.9
S = 4.489 R-Sq = 77.14% R-Sq(adj) = 76.67%
Pooled StDev
Level N Mean StDev -+---------+---------+---------+--------
Pre Fatigue Sut 11 113.19 8.71 (*-)
Pre Tensile Sut 65 94.43 2.31 (*)
Pre Hardness Sut 71 105.43 5.13 *)
Published 3 63.80 0.00 (---*--)
-+---------+---------+---------+--------
60 75 90 105
Pooled StDev = 4.49
10.
Two-Sample T-Test and CI: Pre Tensile Sut, Post Tensile Sut
Two-sample T for Pre Tensile Sut vs Post Tensile Sut
N Mean StDev SE Mean
Pre Tensile Sut 65 94.43 2.31 0.29
Post Tensile Sut 28 60.641 0.939 0.18
Difference = mu (Pre Tensile Sut) - mu (Post Tensile Sut)
Estimate for difference: 33.791
95% CI for difference: (33.122, 34.460)
T-Test of difference = 0 (vs not =): T-Value = 100.34 P-Value = 0.000 DF = 90

Page 58 of 61
11.
12.
One-way ANOVA: Post Fatigue Sut, Post Tensile Sut, Post Hardness Sut, Published
Source DF SS MS F P
Factor 3 2170.27 723.42 188.18 0.000Error 50 192.22 3.84
Total 53 2362.49
S = 1.961 R-Sq = 91.86% R-Sq(adj) = 91.38%
Pooled StDev
Level N Mean StDev --------+---------+---------+---------+-
Post Fatigue Sut 4 70.383 5.433 (--*---)
Post Tensile Sut 28 60.641 0.939 (*)
Post Hardness Sut 19 49.842 2.106 (*-)
Published 3 63.800 0.000 (--*---)
--------+---------+---------+---------+-
54.0 60.0 66.0 72.0
Pooled StDev = 1.961

Page 59 of 61
13.

Page 60 of 61
Cost Analysis of Fatigue Testing of AISI 1018 CRSCost Analysis of Fatique Characteristic Testing of AISI 1018 CRS
Test to Perform Rate ($) Burden Rate Cost/Hour Cost of Test Hours
Fatigue Test 25/hour 3x 75 2,475.00$ 33
Tensile Test 150 /test 4x 600 1,200.00$ 2
Hardness Test 100/test 3x 300 1,200.00$ 4
Metallography 100/test 3x 300 600.00$ 2
IMR 60/test 1x 200 60.00$ 1
Spark 12 /hour 3x 36 36.00$ 1
Profilometer 12 /hour 3x 36 36.00$ 1
Any Heat Treatment 100/part 6x 600 1,800.00$ 3
47
7,407.00$Total Cost of Testing
Total # hours
Graphical Analysis-Pie Chart
70%
4%
9%
4%
2% 2%
2% 7%
Cost Analysisof AISI 1018 CRS Fatigue Characteristic Testing
Fatigue Test
Tensile Test
Hardness Test
Metallography
IMR
Spark
Profilometer
Any Heat Treatment

Page 61 of 61
Bibliography
"Rockwell Hardness (HRC, HRB) to Brinell Hardness (HB or BHN) Conversion." Rockwell
Hardness (HRC, HRB) to Brinell Hardness (HB or BHN) Conversion. N.p., n.d. Web. 1 Nov.
2012. <http://www.iron-foundry.com/hardness-hrc-hrb-hb.html>.
Su = 63800 psi
"AISI 1018 Steel, Cold Drawn." AISI 1018 Steel, Cold Drawn. N.p., n.d. Web. 12 Sept.
2012. <http://www.matweb.com/search
Su = 63800 psi
AISI 1018 Cold Rolled Steel
http://www.eaglesteel.com/download/techdocs/Carbon_Steel_Grades.pdf
Su = 63800 psi
AISI 1018 Cold Rolled Steel
http://www.onlinemetals.com/alloycat.cfm?alloy=1018
Acknowledgements
Mike Caldwell
William Leonard
Leslie Gregg
Mike Rodriguez
Steve Parish
Steve Kosicol
Alex Pera
Tom Mordovancey
Groups 1 - 10 of the 20121-403 Class

FAILURE MECHANICS FINAL REPORT GROUP 11

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