FORENSIC MATERIALS SCIENTIST OR “WHODUNIT” DETECTIVEBeing a forensic materials scientist is being a “whodunit” detective, tasked with

determining why a product or process allegedly failed and who is responsible. Robert S. Carbonara, Ph.D.

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Forensic materials science is a broad technical discipline, that analyzes physical evidence using the principles of physics and chemistry. Before the advent of modern engineering materials, most forensic materials scientists worked with metals and were called metallurgists. Today, forensic materials scientists work with an assortment of materials, including plastics, ceramics, glass, composites, even wood and leather and, of course, metals. Despite the broadening of the materials spectrum, the same scientific principles that apply to metals also apply to other materials.

A portion of the work done by forensic materials scientists deals with the analysis of material failures. However, forensic materials scientists also investigate the production of materials, including raw material and fabrication processes.

Materials impact everythingMaterials scientists investigate issues

regarding:• Transportation — Components used

in trucking, automotive, rail, marine and aero vehicles, oil and gas pipelines

• Consumer and Industrial Products — Valves and fittings, appliances, fastening

devices (bolts, etc.), hoses and piping, amusement rides, firearms, glassware, bicycles, CPVC piping, sprinkler systems, storage tanks, and numerous others

• Material Production and Manufacturing Processes — Recycling precious metal, aluminum and steel furnace operations, metal casting operations, metal forging and rolling production, pipe manufacturing

• Construction — Beams and support structures, welds, safety device material, lifting cables, chains and straps, hoisting devices, and cranes

• Health Sciences — Surgical instruments, fixation devices, implants, patient care and

hospital equipment.

During any investigation, it is important to assess the available information and evidence to identify if there are missing pieces of either or both. One of the major challenges in complex cases is to eliminate the extraneous information and evidence and focus on the “so what” question. The forensic materials scientist not only determines if it corroded, fatigued, or was overloaded, etc., but also must assess the methodology and results for logical consistency with the known facts.

Why the “so what” question mattersTo illustrate the importance and practical

application of answering the “so what,” several complex case profiles are presented.

These cases involved: (1) a serious injury where there was responsibility avoidance by the parties involved, (2) a very complex metal recovery process with a seven-figure loss claim, (3) medical devices that fail and are complicated by issues of patient or doctor conduct, and (4) a pipeline failure that oc-curred many years after installation and with multiple possible technical failure scenarios.

CASE 1. Trucks and semi-tractor trailers traveling at highway speeds can, in some instances, become lethal objects. A wheel, weighing hundreds of pounds, that comes off a semi-tractor trailer can continue down the road close to the speed of the trailer. An oncoming vehicle, also at highway speed, will be approaching the loose wheel with combined speeds of up to and over 100 miles per hour. Due to the small profile of the wheel, the ability of the oncoming driver to adjust course is minimal, especially if the wheel is bouncing, as it often is. This is an extremely dangerous situation, often resulting in serious injury and/or death.

CASE 3. Materials scientists investigate the failure of medical devices, e.g., ortho-pedic fixation devices, implants, pacemak-ers, surgical instruments and patient care apparatuses. A device may fail because a patient did not follow their doctor’s orders, due to doctor error, or for a number of other reasons.

Following spinal fixation device surgery, the patient’s pain was significantly mitigated, and he decided to go bowling. This activity caused him to break several pedicle screws, which he claimed were defective. The investigation revealed the screws failed by fatigue and there were no material defects in them. The fatigue was the result of the loads being put on the screws before they were fully incorporated in the bone structure. Bowling shortly after having back surgery is not recommended!

In some cases, device failures are the result of doctor error. For example, during laparoscopic spinal surgery an instrument was grossly mishandled, due to the doctor’s frustration, causing it to separate and leaving a portion of the instrument in the patient and requiring additional surgery. When the device was examined, the separation was determined to be the result of an overload force administered by the surgeon “exuberantly pulling” on it. In another instance, pedicle screws caps were not properly tightened by the surgeon, which allowed the fixation to come un-done, again requiring additional surgery. Microscopic examination of the two rods used for the fixation showed the marks from the contact of the caps on one rod was significantly different from the other, indicating a different amount of contact force on each one, due to a difference in tightening. There were no design or manufacturing defects in any of the devices used in these instances.

CASE 4. Why do pipelines fail? Some pipelines have failed due to improper backfill, some have failed (even years later) after being hit by excavating equipment and some fail from corrosion. The long-term failures are usually complicated by issues of who did what and when. One case involved a dispute regarding a very old (+100 years) gas line that was surrounded by a sewer manhole. At issue was, which came first, the pipeline or the manhole? Was the manhole put around the pipe or was the pipe run through an existing manhole? By analyzing the steel pipe composition and microstructure, and searching historical

This wheel-off case involves a semi-trailer that was found to have a fractured axel that had a weld repair. Welding is not a permissible repair to an axle, so none of the several- involved parties would admit to making the repair. Using a scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS), a concentration of a specific element was found in the weld slag. This element is only present in a certain class of welding rods. S-E-A asked for a discovery request for the welding rod purchase orders of the potential welder(s). The purchase order records were the most reliable way to establish which welding rod each company used. Once the purchase orders for welding rods from each of the involved parties were reviewed, the one purchaser of that class of welding rods was identified and the identity of the welder was revealed.

CASE 2. A large international chemical company was recycling product that contained precious metals. After scaling up the induction smelting furnace it used for recovering the precious metal, the company realized a sudden shortfall in its accounting of the precious metal output. The company’s insurance policy had coverage for any loss of precious metals. If the company could show a physical loss, perhaps by theft, the insurer had to pay. The dollar amount of the loss was in the seven-figure range. The insurer requested S-E-A to investigate if there was a physical loss of precious metals.

The recovery process had numerous steps and complex relationships between the steps. The investigation showed that when some steps in the process were scaled up, the relationships between the steps did not scale in a linear fashion. When all the processes were analyzed, it was found that the scaled-up smelting process did not directly measure the smelting furnace dross or slag, which still had residual precious metal content. Two assumptions were made by the chemical company: (1) that the concentration of precious metal in the old process slag held for the new scaled-up process, and (2) it was unnecessary and/or inconvenient to measure the amount of dross or slag produced by the new scaled-up furnace. S-E-A showed these assumptions were erroneous and the company did not have a physical loss of precious metals. Instead, the metals were in the slag. This analysis saved the insurance company millions of dollars.

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records for steel-making processes in the late 1800’s and early 1900’s, it was possible to establish that the pipe was made and installed in 1895, while the sewer manhole was installed in 1921. The manhole surround-ing the pipe allowed moisture from the water running through the sewer to cause the pipe to corrode and fail at the manhole location. Even though it was over 100 years old, when examined by S-E-A, the remain-der of the pipe was in remarkedly good condition with very little corrosion. This is not unusual since there is very little active oxygen underground, if water is not present.

Forensic materials scientists deal with issues where someone’s (personal or corporate) actions have resulted in a loss. Using the scientific method and knowledge of the materials involved, the forensic materials scientists will establish a basis for establishing “whodunit.”

Author Robert S. Carbonara, Ph.D, is a Materials Scientist / Metallurgist who has been performing materials forensic analysis for 40 years. He has been with S-E-A for 31 years.

Dr. Carbonara received his Bachelor of Science degree in Physics from the University of Pittsburgh, and his Doctor of Philosophy degree in Materials Science from the University of Cincinnati.

He did Graduate Studies in Physics at the University of Pittsburgh and Graduate Studies in Metallurgy at Carnegie-Mellon University.

Dr. Carbonara is responsible for performing and supervising the testing and evaluation of samples, as well as analyzing the results. Areas of activity include forensic analysis of metals, glass, ceramic, and polymeric materials, and general failure analysis.

He has provided testimony in state and federal courts of law and in the Canadian federal court.

Know.