I. Background
A steel mill has been asked to produce high strength low alloy steel (H.S.L.A.) that has a
minimum yield strength of 60,000 psi. You are the quality control supervisor for the steel mill.
As the steel is produced, each coil is tested for strength. The data shown at the end of the case
study has been obtained.
The product is a thin sheet steel that is several feet wide and several thousand feet long. The
strip has been rolled into coils to make them easier to handle. The samples are taken from the
outside ends of each coil. The samples are nominally 0.5 in width, 0.030 in thick and 2.0 in
length. The samples are tested to yield in tension and the load at yield is read directly from the
load displacement plot produced by the testing machine. The yield point can normally be
determined within +/- 3 pounds.
II. Your Task
Your job is to decide whether or not to ship any of the coils of steel A-E based on the sample
tests and the following applications:
• Aircraft manufacturer
• Non-critical restaurant equipment supports
• Unknown manufacturer
There are three testing options you can pick from: Option #1 assumes that you only make one
test per coil; option #2 assumes you make three tests per coil, but this increases the cost of
each roll by 10%; and option #3 assumes you make five tests per coil, but this increases the cost
of each roll by 20%.
Your selection of the number of tests and data analysis methods is not neutral, since it may
change your decision as to which coils can be shipped. Using the wrong methods could result in
you shipping bad coils. This could have safety implications, as well as damaging your own and
your company’s reputation. On the other hand, if you do not ship coils that are actually good,
then you are costing your company money and not fulfilling your obligation to be a faithful
trustee for your company’s resources. The tests also take time and have associated costs that
should be considered.
Carry out any numerical calculations necessary to ensure that the steel shipped satisfies the
minimum requirements of 60,000 psi yield strength. The production control department has
put you under pressure to ship all of the coils, since they all were produced from the same heat
of steel (same batch) and have all been processed in the same manner, thus all should have the
same nominal properties.
1. Decide which test method should be used for each application. You can use a different
method for each application. Justify your answer with appropriate analysis and/or
reasoning. Just picking one method because you think it is best is not sufficient! You
cannot use the test data to decide which method to use! That would be like having data
from 5 samples for all coils before you decided how many samples to actually test.
2. Once you have selected a test method, identify which coils should be shipped for each
application based only on the data from the method(s) selected in question 1. Support
your decisions using appropriate analysis, etc.
You should consult the ASME Code of Ethics and identify which canons apply to this
situation in preparing your answers to questions 1 and 2.
III. Data
The tables below provide the failure load data for the test sample(s) from each coil using the
three possible test methods.
Data for Option 1 (one test per coil):
Coil Load where yielding begins (lbs)
A 938
B 903
C 899
D 890
E 843
Data for Option 2 (three tests per coil):
Coil Load for test 1 (lbs) Load for test 2 (lbs) Load for test 3 (lbs)
A 970 943 947
B 925 888 894
C 884 898 910
D 872 871 901
E 832 838 864
Data for Option 3 (five tests per coil):
Coil
Load for
test 1
(lbs)
Load for
test 2
(lbs)
Load for
test 3
(lbs)
Load for
test 4
(lbs)
Load for
test 5
(lbs)
A 966 968 960 932 931
B 877 907 917 926 918
C 905 919 889 917 914
D 884 885 893 888 880
E 825 819 868 862 869