SEM

RESUME

C. Kendall Clarke
Ph.D., P.E.

President and Principal Engineer

Don Halimunanda
M.S., P.E.

Mechanical Engineer

FAILURE ANALYSIS

Failure of automotive leaf spring was the result of pre-existing crack.

Metallurgical Consulting's engineers have many years of experience evaluating failures. Metal components sometimes fail to perform as expected. Metallurgical Consulting has a variety of testing methods which can give you insight into how to prevent future failures by helping you to understand the cause of the failure.

Failure analysis to determine a root cause requires an engineering evaluation that goes beyond simple determination of the failure mode and compliance with specifications. This type of failure analysis has been conducted on machined parts, castings, weldments, and non metals. Metallurgical Consulting utilizes a procedure for mechanical failures which involves a comparison of estimates of the operating stress at failure from fracture surface analysis as well as estimates of design and or operating stresses. A root cause explanation for the failure has been made when the two stresses agree. Failure of the stresses to be similar points to the need to determine other factors affecting the failure.

Old crack in individual wire from wire rope failure.

Corrosion failure analysis usually begins with a visit to the site to determine plant operating conditions and maintenance history. Process chemistry and flow information is also obtained. This information provides a basis for determining all of the possible corrosion problems. Specimens from damaged equipment and undamaged equipment, if possible, are taken and evaluated to determine the mode of corrosion. This information usually yields a hypothesis that is then tested by potentiodynamic corrosion tests.

Some Examples:

• A leaf spring on a vehicle broke forward of the axle and caused the driver to lose control. Analysis of the failure involved spring tests, extensive fracture analysis, and stress analysis. The spring was found to have been cracked before the owner picked up the new vehicle.

Failure analysis of fatigue cracked bolts such as this one lead to reconstruction of a ship crane collapse.

• Wire rope bridle line failed in the launch of a new ship. Examination of the individual wires revealed evidence for old cracks. These old cracks plus dynamic loads accounted for premature failure.

• The collapse of a pedestal mounted hydraulic crane on a ship was reconstructed by analyzing the failure of bolts and performing a finite element analysis of the boom structure.