is now on the World Wide Web, with its new homepage. You can find
us at http://www.flask.com/mei. We are also indexed throughout the
web and can be found through search engines and on the ASM International
home page of materials related companies.
the debut of our homepage this August, we became the first metallurgical
or materials engineering company in Illinois or Wisconsin to be on
talking to many of our engineering customers, we found they often
search the web looking for information about companies, products and
answers to technical questions. We were surprised to find out just
how many of our customers are on line. The decision to develop our
home page fell naturally out of our desire to provide faster, better
service to our customers.
home page provides information on our capabilities, experience and
expertise. It also gives anyone the opportunity to ask us technical
questions via e-mail. These questions will then be answered and posted
in a section of the page called "Yes Virginia, there is a free
lunch." We have always given our customers information and advice
on the phone; now this same service is available on line. We feel
this level of service differentiates us from other metallurgical and
engineering companies. We are committed to assisting you, and we believe
that we all benefit from a greater understanding of materials, processing
and engineering principles.
our site, and e-mail us (email@example.com) to let us know what you think!
If you have considered
putting together a home page, give us a call and we'll tell you about
our experiences, and about Flask Productions and designer Dan Wykes,
who worked with us putting our home page together.
past summer, the crash investigation of TWA flight 800 and of ValuJet
airlines drew the country's attention to the teams of engineers and
scientists who are investigating the mystery of why these jets crashed.
This field, Forensic Engineering or Failure Analysis, is one of the
primary services provided by engineers at MEi. We have many years
of experience working on the failures of products, ranging from the
space shuttle, to consumer products.
steps followed by the FAA, NTSB and FBI labs are identical to the
steps that we follow when we conduct a failure investigation. No matter
how big or how small, the same basic thinking process is used to come
to the conclusion of what happened and why.
failure investigation can be divided into several steps:
Usage Information: "Looking At The Black Boxes"
The most important
feature of an investigation is having accurate and inclusive information.
The airplane black boxes provide information on exactly what the plane
was doing at and just before the time of failure. In our investigation,
it is important to know exactly what the product was doing at the
time of failure.
About The Event: "Interviewing The Witnesses"
the last piece of information as to what was happening as the unit
failed. Were there noises or flashes of light? But the information
provided by eyewitnesses is not always accurate. This is understandable,
as most failures are unexpected, and rarely are people carefully observing
the unit looking for signs of distress in anticipation of a failure.
Gathering The Evidence: "Sorting Through
When a plane crashes,
it leaves tons of debris. All the hardware has to be carefully gathered,
so that no information is left behind at the sight. The whole picture
can be misleading if a critical piece to the puzzle is missing. For
our investigations, it is often desirable to look not only at the
failed components, but at the entire assembly for signs of distress
and supporting evidence.
The Design: "Talking To The Manufacturers"
When a plane crashes,
the investigation team always includes technical representatives from
the companies that manufacture the airplane, the engines and key subsystems.
The investigation is conducted by a team. We consider your technical
staff to be a key part of our failure investigation team, providing
us with information about the design, design changes, failure history
and performance expectations. While as engineers, we have a good understanding
of how systems operate, the details that your staff provide on the
unique features of the product are often invaluable to us in getting
the job done efficiently.
Examination Of The Hardware: "Deciding What And Where To Examine"
Just as the NTSB
does not microscopically examine every inch of the failed aircraft,
it is not a wise use of resources to start with a detailed examination
of large components. We always begin with a macroscopic examination
of the components at magnifications up to 90x using optical microscopes.
Our experience allows us to sort the wheat from the chaff, and to
determine which areas will provide the most information through detailed
Detailed Scientific Examination
Of The Hardware: "Sending It Back To The Lab"
We use the same
tools that the NTSB labs use to determine the cause of failure. The
scanning electron microscope (SEM) is the key instrument. In fact,
many in the forensic engineering field divide the history of failure
analysis into two eras: before the invention of the SEM and after
the invention of the SEM. Other techniques, such as metallographic
examination, chemical analysis and mechanical testing also provide
Defining The Failure
Mode: "Determining The Cause"
and microscopic examination, the failure mode can be determined. This,
coupled with understanding of the design and information about what
was happening at the time of failure, allows a failure scenario to
be developed, which proposes exactly what happened during the failure.
Making Sure All The Pieces Fit: "Tracking
Once a failure
scenario is defined, all the hardware and information must be re-examined
to insure that all the pieces support the failure sequence. Cause
and effect logic must be carefully thought through to insure no evidence
contradicts the proposed failure scenario. If the pieces don't fit,
it's time to rethink and gather more information.
Of The Information: "Press Conference"
Just as the NTSB
will call a press conference once they have an understanding of the
failure, we will call you and let you know our findings. We will discuss
all the findings to insure you clearly understand the failure scenario,
and to further verify all the pieces fit.
And Implementing Corrective Action: "Making Sure It Doesn't Happen
We all want
to be perfectly safe when we fly. We want what ever happened to the
ValuJet or TWA planes to be prevented on all future flights. Likewise,
we want your products to offer high performance and long life in the
marketplace. We will work with you to determine what can be done from
a design, materials or usage viewpoint to insure safety and reliability
in your product. Sometimes this is just a simple suggestion, other
times it involves complex analysis. Our experience in product design
and understanding of failure scenarios makes us a valuable member
of your team to prevent future failures.
Engineering Inc. has many years of failure analysis experience. Let
us work with you to help you solve your "plane crashes".
President and Principal Engineer Bill Durako addressed the Rockford
chapter of the Association of Women in the Metal Industries (AWMI)
at their July dinner meeting. As the name suggests, this is an organization
is of women whose jobs or companies are in the metal industries. They
are a dynamic and diverse organization with membership ranging from
engineers and manufacturing staff to purchasing agents and marketing
topic was "How Hardness and Ductility Affect Manufacturing and
Processing" giving a general overview of how and why ductility
or formability and hardness or strength must be considered to insure
a component is both manufacturable and of sufficient strength for
the application. The talk included a discussion on the principles
of heat treatment and of basic forming processes. Also speaking at
the meeting was Dave Voss of Voss Metals, who discussed the importance
of chemistry in metals and alloys for recycling.
you would like one of our engineers to speak at your company or technical
society, please give us a call.
you are interested in learning more about AWMI, please contact Sue
Lackner of W.A. Whitney at 815-964-6771.
year, a large number of washing machine supply hoses fail, allowing
water to flood into homes and cause large amounts of water damage.
MEi recently completed
an investigation of washing machine hose materials for a major insurance
company. As most of us have washing machines at home, we thought that
sharing these results with you might help to prevent a failure in
your home, and save you the trouble of water damage.
MEi began by looking
at a series of failed hoses from insurance claims. Insurance investigators
had noticed a pattern. The failures were occurring in the rubber hose
portion adjacent to the metal end coupling. Corrosion was often found
in the fitting. The failures were occurring only in the hot water
supply hose and not in the cold water supply hose. Information appeared
to indicate that certain hose manufacturers had a greater incidence
of failure. All standard hoses are manufactured from isoprene, or
natural rubber, with fillers and reinforcing fabric added.
scanning electron microscopy (SEM), energy dispersive spectroscopy
(EDS) and other analytical techniques, it was determined the failures
were a result of a combination of three factors:
Chlorine in the water attacks (oxidizes) the rubber polymer. This
fact has been known for years: in the presence of chlorinated water,
rubber will degrade given enough time. Municipal water supplies contain
up to 3.5 ppm of chlorine.
Elevated temperature accelerates the attack. The oxidation reaction
is kinetic, and the attack becomes more aggressive as temperature
increases. Many hot water heaters operate at 150°F, nearing the
maximum usage temperature for natural rubber of around 170°F.
Bends in the hose
accelerate the attack. When a hose is bent, the polymer chain is subject
to a tensile load, resulting in stress on the polymer. Stressed polymers
are more susceptible to chemical degradation than unstressed polymers.
water supply hoses that are bent or kinked (by pushing the machine
against the wall) will degrade and fail given sufficient time.
conducted on sections of hoses both stretched and unstretched from
four different materials/hose suppliers in chlorinated 150(F water
was able to recreate damage to the rubber, and thus verify the failure
results did show differences between brands of hoses, and types of
rubber. The less expensive natural rubber hoses were the most susceptible
to damage. But surprisingly, even the better materials such as EPDM
and PVC still showed some evidence of degradation.
While it is statistically
unlikely that you will experience a hose failure and resulting water
damage, there are several simple steps that you can follow to help
prevent a hose failure and water damage to your home:
If you can't remember the last time you changed hoses, it has been
Make sure there are no sharp bends or kinks in your hose. Pull the
machine away from the wall a few more inches to eliminate bends. Hoses
with 90∞ elbows in the metal end fittings are useful in preventing
bends or kinks.
Turn down the water heater a few degrees.
When buying hoses, spend a few extra dollars for better hoses. Even
the most expensive hoses are less than $15. While we cannot recommend
a particular brand, the less expensive natural rubber hoses did offer
the least resistance to damage of all the hoses tested. You might
also check with your local appliance parts store, as they may have
experience and opinions on which hoses offer superior performance.
manufacturers have additional recommendations, found in the owners
manual which most of us never read. Change hoses a minimum of every
5 years. Turn off the water supply to the hoses when not using for
long periods of time, especially when you are on vacation.
Remember, only YOU can prevent hose failures.
scanning electron microscope (SEM) is a powerful tool, capable of
magnifications up to 180,000 times. It allows us to reveal information
which is critical to metallurgical investigations, such as fracture
modes and surface characteristics.
SEM can also be fun to play with, because it allows one to view the
surface of anything at high magnification with great depth of field.
All of us have been amazed by the pictures of various insect parts,
especially the eye of a fly.
our contest, we take a look at an object on the SEM that should be
familiar to all of you, and ask you to identify it.
issue, we show you two very similar objects, and ask you
do they differ?
this should be an easy one, no clues will be given this time.
Please fax us or
e mail us (don't call) with your answer. We will draw a winner from
all correct entries received by October 30. The correct answer and
the winner will be published in the next issue Of Materials Interest.
The prize is a
$50 restaurant gift certificate, so put on your thinking caps.