Failure Analysis Engineering Firm, Metallurgical Associates, Plans Atlanta Area Expansion

Metallurgical Associates, a leading engineering firm providing Material Testing and Failure Analysis, today announced plans for a new office in the Atlanta area to better serve manufacturing and industrial clients in the Southern United States.

Atlanta, GA May 15, 2012 – Metallurgical Associates (MAI) today announced that it has secured a location in the Atlanta suburb of Acworth for its new Southern Office. The new Atlanta-area office will allow MAI’s engineers to better serve their clients by providing immediate response to manufacturing interruptions when parts fail.

Rob Hutchinson, Managing Director of MAI, stated “MAI has experienced significant growth by working with clients to provide practical cost effective solutions to their unique failure analysis and manufacturing process challenges. Our new Atlanta-area office will allow us to work closely with our many clients in the Southern US”.

MAI provides materials engineering and analytical services to clients throughout the United States and North America, as well as Europe, the Middle East, the Far East and Central America. MAI South will provide a presence and accelerated response for our clients in Georgia, North Carolina, South Carolina, Alabama, Tennessee, Mississippi, Louisiana and Florida.

Contact details, as well as the official opening date, will be announced shortly. In the interim, please contact Rob by phone or email with any questions or testing requirements that MAI South can assist you with.

Metallurgical Associates
Rob Hutchinson
Managing Director
262 -798-8098

or visit www.metassoc.com

Metallurgical Associates is a Testing Laboratory that provides Engineering services including expert Failure Analysis, Manufacturing Process Problem Solving and Improvement, and Metals & Materials Testing, Analysis and Engineering.

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Welds are also tested using a similar procedure called a guided bend test. This test uses one of several types of fixtures to bend the welded test coupon to determine the ductility and integrity of the weld. This test is specified for welder qualification and welding procedure requirements under ASME IX, EN 287 and 288, and ISO 15614 Part 1.

Machined Round Tensile Specimen

Typical Hydraulic Tensile Test Machine

To perform the test, the bar is placed in the test fixture, with clamps securing each end. Using mechanical or hydraulic force, the bar is then “stretched” or pulled and the “stretching” response of the bar is recorded. The test is usually continued, with the amount of force increased, until the bar breaks. The tensile strength of chain, wire, and wire rope can also be determined by tensile testing as well as the tensile strengths of plastics, rope, and other materials. In addition to tensile strength, tensile testing can determine properties such as yield strength, elongation, and reduction in area.

The tensile stress that contributes to SCC is typically significantly lower than that required to produce a tensile fracture, however, the continuing corrosion process weakens the metal at the advancing crack front to the point at which it fractures under this tensile stress.

Naturally, a corrosive environment is required for stress corrosion cracking to occur. This environment may be extremely subtle and can range from mildly acidic rain to the highly concentrated chloride road salts. Different types of material are affected differently by various environments. Stress corrosion cracking occurs in carbon, alloy and stainless steels, from exposure to chlorides. Copper alloys such as brass and bronze are susceptible to SCC in chloride or ammonia environments.

Stress Corrosion Cracking is easily mistaken for other failure modes Analysis of SCC should be performed by engineers with Failure Analysis experience in this fracture mechanism.

An optical microscope uses light to illuminate a sample for examination. A scanning electron microscope uses a beam of electrons. Sophisticated electronic circuitry is utilized to generate a stable electron beam which is then focused on the sample with electro-magnetic lenses. Additional circuitry transfers the focused image of the sample to a monitor for viewing.  Images are then collected and saved in digital format. The beam and sample are under extreme vacuum during the examination process.

The AMRAY 1830i Scanning Electron Microscope is shown at the top of the page (right). The image to the immediate right, while not a typical materials engineering subject, demonstrates the high magnification and depth of focus capabilities of the SEM. The object at the upper left (A) is a human red blood cell. A white blood cell is shown at left center (B). The smaller spherical object at lower left is a bacteria. Magnification of this image is 20,000X.

Engines undergo extensive dynamometer testing lasting weeks or even months. This testing continues in order to identify further reliability and performance improvements, even after an engine design has gone into production. In a recent extended dyno testing program, an engine manufacturer in Michigan encountered a rash of connecting rod bolt failures in multiple test engines as they reached the equivalent of 30,000 miles in dyno time. Engine production immediately stopped while an urgent investigation was implemented. Thread “laps” – seams in the bolt threads resulting from defective manufacturing – were identified as the cause of the fractures. The bolt vendor brought the manufacturing process back to specified parameters, eliminating the lap defect. A new lot of bolts was quickly brought in, tested to confirm that no defects were present, and engine production resumed.

A major problem remained, however. The auto manufacturer had no idea how many defective lots of connecting rod bolts had been introduced into the system and assembled into engines prior to their discovery during dynamometer testing. To further complicate the issue, it appeared that only one in every 200 or 300 bolts was defective. Each V-6 engine contained twelve connecting rod bolts. This meant that on average, between one-in-16 to one-in-25 previously installed engines could have been assembled with a defective bolt. Depending on how far back the problem went, cars with defective engines could be waiting delivery to dealerships, at dealerships awaiting sale or sold to customers and on the road. Fortunately, the manufacturer had set aside a percentage of each lot of connecting rod bolts for possible “post assembly analysis” in case just such a situation occurred. Unfortunately, the set asides from previously assembled lots constituted just over 5000 bolts.

Immediate analysis of these bolts and identification of when defective bolts first entered the supply stream was required. The manufacturer didn’t have the staff to perform these analyses in the required time, and called Metallurgical Associates Inc. We received the bolts at our Milwaukee materials analysis lab at 4PM on a Friday afternoon. Our metallurgical engineers and technicians went into immediate “round the clock” shifts, visually examining each of the 5000 bolts by stereomicroscopy to sort potentially defective bolts. These were then examined by Scanning Electron Microscopy to confirm the presence of thread laps. Bolts with confirmed laps were then sectioned, mounted, polished, and metallographically examined to document the extent and depth of the thread laps to critical “pass/fail” criteria. By Monday morning at 8AM, 72 hours after receiving the first lot, all 5000 bolts had been examined, the percentage of defects in each lot calculated, and the date on which the first defective lot had entered the production stream, identified.

With the test results provided by Metallurgical Associates Inc. materials analysis engineers, the auto manufacturer was able to quickly identify the production dates of engines with potentially defective connecting rod bolts. Several thousand had already been installed in cars and had left the assembly plants. These were diverted from the supply chain before delivery to dealerships and retro-fitted with replacement bolts, an expensive and time consuming process. This expense, however, was a fraction of the cost of a nation wide recall both financially and to the manufacturer’s public image.

Residual stresses are cumulative. In other words, if a beam has the capacity to carry a load of 1000 pounds and contains residual stresses in the same orientation as that load carrying capacity of 100 pounds, then any load applied to the beam that exceeds 900 pounds will overload (100 pounds residual + 900 pound load = 1000 pounds) the beam’s carrying capacity and cause it to fail. This is an obvious factor to consider in the design and manufacture of load carrying parts.