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 Metallurgy is the science and technology of metals. Go ahead, introduce yourself as a “forensic expert”. Now, prove it. The forensic metals expert must exhibit excellent knowledge and communication skills to argue the case before peers, as well as a pleasing demeanor toward the authority who will render a verdict on the findings. The expert must supply a curriculum vitae, methodology, photographs and testimony to convince an audience about the facts in the case.
Metal failures are not always just accidents or acts of God. Failures may be from man-made catastrophes, operating error, equipment malfunction, or natural disasters. The Forensic Expert deeply cares why a metal failed and knows how to study and examine a broken metal part. One test may be worth a thousand expert opinions. The forensic expert who does not study history is doomed to repeat it. The forensic expert uses many bits of practical information that are not found in handbooks or taught in classes. Practical education, experience and the truth continue to be the answers for long-term success of the forensic expert. Your audience cares about metal.
It is as simple as be true to your-self.
The registration law permits the practicing PE to determine areas of personal competency and provide services accordingly. Be ethical, and be true to your-self. If you are an expert on a topic, then you are. If you are not, then just say so. Carefully select your topic. It is acceptable to reply with an “I don’t know”. If you don’t know the answers, then perhaps you can find out.
Nowadays, the recognized Forensic Expert probably has a background, education, training and a recognized academic degree from a prestigious university. A Forensic Expert is: an investigator of materials, products, structures or components that fail or do not operate/function as intended, causing personal injury or damage to property. The consequences of metal failures may be significant or insignificant. The purpose of a Forensic Expert investigation is to locate cause or causes of a failure with a view to improve performance or life of a component or to assist a court in determining the facts of an accident.
- FOCUS on the specific metal failure.
- “Reverse engineering”, CHOICES made by the originators of the item.
- Personal inspection of the part and surroundings for trace evidence, use a good LIGHT.
- Statements from eye-witnesses of the incident, Communicate with proper DEFINITIONS / Terms.
- A working knowledge of current standards, Study in a metals LIBRARY.
- A case review of similar failures, Study HISTORICAL RECORDS.
- Accident reconstruction, what really could have happened?
- Examination of the subject failed component and an exemplar item, TALK to the failed part.
 Metal failures are often the result of human errors originating from unrealistic delivery schedules, oversight, carelessness, ignorance or greed. With the advance of design sophistication and fast-track methodologies came the proliferation of metal failures. Early savings in design and construction costs can easily boomerang as later and larger costs of repair and litigation. The vulnerable metal structures of the late 20th century can provide “bread and butter” to Forensic Experts of the 21st century.
Metal failures are receiving increased attention over the past 30 years, primarily because of concerns related to public safety and equipment reliability. In addition, metal failures have a strong impact on economic changes and pressure exerted by expanded competition on the global market. In the United States, increases in litigation have forced commercial entities to investigate metal failures and identify the root causes to avoid repeated events and potential liability. It is a common statement in industry that a metal was intact and fully met the designer’s specifications until the fabricator performed welding on the metal.
Considerable developments in failure analysis techniques and reliability are emerging with legal community acceptance of new methodologies in metals alloy analysis, fatigue, fracture mechanics and metallurgy. Actual metal properties can be determined without affecting an in-service component’s integrity through portable alloy analysis, infield metallography and hardness testing. Laboratory optical emission spectrometry (OES) techniques provide reliable metal alloy determinations. Mechanical tests assess changes in metal bending and tensile properties, toughness, and metallurgical grain structures. Nondestructive tests provide accurate surface and sub-surface flaw detection and defect sizing. Metal life prediction and fitness-for-service analysis are achieving wider acceptance by the engineering profession and legal community. The economic advantages of avoiding business interruptions, extending equipment life and saving time required to build replacement components justifies the use of advance Forensic Expert metal examination techniques.
Owners, purchasing agents, attorneys and in-experienced project managers don’t understand the factors and conditions that have lead to past metal failures. After a failure occurs, there is a “hurry-up meeting”, examination of a dirty metal piece, and a resounding question, “Why did it fail?”
The Forensic Expert knows that specifying the correct metal and joining process is a fundamental choice by the designer. Bosses make decisions about the resources allocated for metal acquisition, identification and control. The quality assurance employed to track metals through fabrication processes depends upon the consequences of a metal component failing as a traceable result of using an incorrect metal. To protect the public, final product validation often requires a corporate official to sign-off, certifying that all metals used in a product are correct. This can merely be a token gesture. The Forensic Expert knows that metal alloy verification by an independent laboratory testing is the only sure way to confirm the type of metal that was used.
Many experienced engineers know that a great deal of important information and failure experience is locked up in the engineering files of companies fearing adverse publicity of their products. This is unfortunate since this unavailable data could be a great benefit to future engineering designers, metal selection considerations, fabrication techniques and general “know-how”.
Metals are classified by many ways, including appearance, dimensions, weight, magnetic properties, chemical composition, mechanical properties, thermal coefficients and electrical conductivity. There are numerous accepted methods used to select and identify metals.
Numerous types, grades and classes of ferrous and nonferrous metals are available in industry. Potential defects are inherent in metals. Failures have occurred in all types and shapes of metals and will occur again sooner or later. The same causes and failure mechanisms may apply just as much to a ferrous metal as to a non-ferrous metal. The Forensic Expert must study the metal and interpret the conditions involved in each metal failure. Determination of the crack initiation site, propagation driving forces, or type of corrosion conditions are common elements of a Forensic Expert’s analysis of a failed metal. The Forensic Expert knows that though the failure was in a pipe, ship, bridge or airplane, similar metal analysis techniques may be applied to evaluate the failure event.
Fatigue of metals refers to changes in properties resulting from the application of cyclic loads and encompasses many engineering disciplines. Fatigue of metals is a major area of scientific and applied research. The word fatigue originated from the Latin expression fatigare which means “to tire”. The word fatigue is commonly accepted to describe an individual’s physical or mental weariness. Now the term, fatigue, is widely accepted terminology in engineering vocabulary for the damage and failure of metals under cyclic loads. Fatigue applies to changes in properties which can occur in a metal due to the repeated application of stresses or strains, although usually this term applies specifically to those changes which lead to cracking or failure.
The behavior of metals can be predicted. Forecasting the internal actions of metal (steel) during thermal cycles and welding is common. Metallurgists can predict what metal will do as it is heated, cooled and welded. They are challenged to increase the strength of a metal without also increasing the metal’s brittleness. The ability of the metal to be welded in a production environment, with mechanical soundness and the serviceability of the resulting weld-ment is affected by the metal alloying elements. Most welding, brazing or soldering processes require metallurgical compatibility that can be achieved by using clean base metals, controlled thermal conditions, and the addition of filler metal by skilled personnel.
The Forensic Expert‘s confirmation about the type of metal actually incorporated into a failed metal component affirms design considerations, exposes in-service conditions, and reveals flaws that became defects. Numerous catastrophes are the result of incorrect material in the product.
The Forensic Expert recognizes that the performance of any metal member of a structure is dependent on the alloy content and section properties. When the design is based on the efficient use of these two properties, the material selection and connection methods must be functionally acceptable and reasonably conservative.
Applications of metal assessment models and computer simulations must fit real-world choices. The Forensic Expert knows to develop and study the computer analysis as well as consider the published, historical requirements for metals to determine quality, uniformity or interchangeability. These documents may be codes, standards, specifications and professional association with experienced Forensic Experts.
All metal used in commercial business must realistically address the designer’s intent, the installer’s capability, and comply with the codes, standards and specifications.
The Forensic Expert gathers metal samples from the failure site or the failed component for independent alloy validation, nondestructive tests and mechanical tests. Comparison of a failed metal piece with the engineering design documents, specifications and material test reports often reveals clues to the cause of a metal’s failure event.
We cannot be complacent about the integrity of structures. Any accident is of most interest if you or a family member is involved in the occurrence.
Presentation:
Dr. Grantham as the Guest Speaker – ASM Int’l Rocky Mountain Chapter,
November 6th, 2008, at Cinzetti’s in Northglenn, CO
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