Forensic engineering is the investigation of materials, products, structures or components that fail or do not operate/function as intended, causing personal injury for example. The consequences of failure are dealt by the law of product liability. The subject is applied most commonly in civil law cases, although may be of use in criminal law cases. Generally the purpose of a forensic engineering investigation is to locate cause or causes of failure with a view to improve performance or life of a component, or to assist a court in determining the facts of an accident. It can also involve investigation of intellectual property claims, especially patents. Forensic science (often shortened to forensics) is the application of a broad spectrum of sciences to answer questions of interest to the legal system. ... Engineering is the design, analysis, and/or construction of works for practical purposes. ... Materials science includes those parts of chemistry and physics that deal with the properties of materials. ... Look up Structure in Wiktionary, the free dictionary. ... A personal injury occurs when a person has suffered some form of injury, either physical or psychological, as the result of an accident. ... Product liability encompasses a number of legal claims that allow an injured party to recover financial compensation from the manufacturer or seller of a product. ... Civil law has at least three meanings. ... Criminal law (also known as penal law) is the body of statutory and common law that deals with crime and the legal punishment of criminal offenses. ... A railing accidentally collapses at a college football game, spilling fans onto the sidelines An accident is something going wrong unexpectedly. ... For the 2006 film, see Intellectual Property (film). ... A patent is a set of exclusive rights granted by a state to a patentee for a fixed period of time in exchange for a disclosure of an invention. ...

Failed fuel pipe at right from road traffic accident

Image File history File links Size of this preview: 800 × 546 pixelsFull resolution (858 × 586 pixel, file size: 150 KB, MIME type: image/jpeg) Own photograph (PR Lewis) I, the creator of this work, hereby release it into the public domain. ... Image File history File links Size of this preview: 800 × 546 pixelsFull resolution (858 × 586 pixel, file size: 150 KB, MIME type: image/jpeg) Own photograph (PR Lewis) I, the creator of this work, hereby release it into the public domain. ...

Methods

Methods used in forensic investigations include reverse engineering, inspection of witness statements, a working knowledge of current standards, as well as examination of the failed component itself. The fracture surface of a failed product can reveal much information on how the item failed and the loading pattern prior to failure. Fatigue often produces a characteristic fracture surface for example, enabling diagnosis to be made of the cause of the failure. The key task in many such investigations is to identify the failure mechanism by examining the failed part using physical and chemical techniques. This activity is sometimes called root cause analysis. Corrosion is another common failure mode needing careful analysis to determine the active agents. Accidents caused by fire are especially challenging owing to the frequent loss of critical evidence, although when halted early enough can usually lead to the cause. Fire investigation is a specialist skill where arson is suspected, but is also important in vehicular accident reconstruction where faulty fuel lines, for example, may be the cause of an accident. Reverse engineering (RE) is the process of taking something (a device, an electrical component, a software program, etc. ... In materials science, fatigue is the progressive, localised, and permanent structural damage that occurs when a material is subjected to cyclic or fluctuating strains at nominal stresses that have maximum values less than (often much less than) the static yield strength of the material. ... A root cause is a cause that is at a root of an effect. ... See corrosive for the hazard. ... A failure mode is a characterization of the way a product or process fails. ... A forest fire Fire is a rapid oxidation process that creates light, heat, smoke, and releases energy in varying intensities. ... Fire investigation is the analysis of fire related incidents. ... The Skyline Parkway Motel in Afton, Virginia after an arson fire on July 9, 2004. ... Vehicular accident reconstructions are often conducted by specialized units in law enforcement agencies, to answer questions about automobile accidents, such as who was driving, where were the victims seated, were they using seat belts? Through accident reconstruction, rigorous analysis is done, with expert witnesses that can present results in trial. ...

Close-up of broken fuel pipe from road traffic accident

The broken fuel pipe shown at right caused a serious accident when diesel fuel poured out from a truck onto the road. A following car skidded and the driver was seriously injured when she collided with an oncoming lorry. Scanning microscopy or SEM showed that the nylon connector had fractured by stress corrosion cracking due to a small leak of battery acid. Nylon is susceptible to hydrolysis in contact with sulphuric acid, and only a small leak would have sufficed to start a brittle crack in the injection moulded connector. The crack took about 7 days to grow across the diameter of the tube, so the truck driver should have seen the leak well before it became critical. Image File history File links Size of this preview: 800 × 541 pixelsFull resolution (874 × 591 pixel, file size: 104 KB, MIME type: image/jpeg) PR Lewis own photograph of broken fuel line I, the creator of this work, hereby release it into the public domain. ... Image File history File links Size of this preview: 800 × 541 pixelsFull resolution (874 × 591 pixel, file size: 104 KB, MIME type: image/jpeg) PR Lewis own photograph of broken fuel line I, the creator of this work, hereby release it into the public domain. ... Nylon is a generic designation for a family of synthetic polymers first produced on February 28, 1935 by Wallace Carothers at DuPont. ... Stress corrosion cracking (SCC) is the unexpected sudden failure of normally ductile metals subjected to a constant tensile stress in a corrosive environment, especially at elevated temperature. ... Hydrolysis is a chemical reaction or process in which a chemical compound reacts with water. ... Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ... Injection moulding (United States Injection Molding) is a manufacturing technique for making parts from plastic material. ...

FMEA and fault tree analysis methods also examine product or process failure in a structured and systematic way, in the general context of safety engineering. However, all such techniques rely on accurate reporting of failure rates, and precise identification, of the failure modes involved. Failure Mode and Effect Analysis is a method that examines potential product or process failures, evaluates risk priorities, and helps determine remedial actions to avoid identified problems. ... Safety engineering is used to assure that a life-critical system behaves as needed even when pieces fail. ... Safety engineering is an applied science strongly related to systems engineering. ... Failure rate is the frequency with which an engineered system or component fails, expressed for example in failures per hour. ...

There is some common ground between forensic science and engineering, such as scene of crime and scene of accident analysis, integrity of the evidence and court appearances. Both disciplines make extensive use of optical and scanning electron microscopes, for example. They also share common use of spectroscopy (infra-red, ultra-violet and nuclear magnetic resonance) to examine critical evidence. Radiography using X-rays or neutrons is also very useful in examining thick products for their internal defects before destructive examination is attempted. Often, however, a simple hand lens suffices to reveal the cause of a particular problem. SEM Cambridge S150 at Geological Institute, University Kiel, 1980 SEM opened sample chamber The scanning electron microscope (SEM) is a type of electron microscope capable of producing high resolution images of a sample surface. ... Extremely high resolution spectrogram of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of the interaction between radiation (electromagnetic radiation, or light, as well as particle radiation) and matter. ... A radiograph of a right elbow-joint Radiography is the use of certain types of electromagnetic radiation—usually ionizing—to view objects. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 940 MeV/c² (1. ...

Trace evidence is often an important factor in reconstructing the sequence of events in an accident. For example, tyre burn marks on a road surface can enable vehicle speeds to be estimated, when the brakes were applied and so on. Ladder feet often leave a trace of movement of the ladder during a slipaway, and may show how the accident occurred. Trace evidence is evidence that is found at a crime scene in small but measurable amounts. ...

Applications

Most manufacturing models will have a forensic component that monitors early failures to improve quality or efficiencies. Insurance companies use forensic engineers to prove liability or alternatively non liability. Most engineering disasters (structural failures such as bridge and building collapses) are subject to forensic investigation by engineers experienced in forensic methods of investigation. Rail crashes, aviation accidents and some automobile accidents are investigated by forensic engineers particularly where component failure is suspected. Furthermore, appliances, consumer products, medical devices, structures, industrial machinery, and even simple hand tools such as hammers or chisels can warrant investigations upon incidents causing injury or property damages. The failure of medical devices is often safety-critical to the user, so reporting failures and analysing them is particularly important. The environment of the body is complex, and implants must both survive this environment, and not leach potentially toxic impurities. Problems have been reported with breast implants , heart valves, and catheters, for example. Structural failure refers to loss of the load-carrying capacity of a component or member within a structure or of the structure itself. ... List of rail accidents from 2000 to the present. ... Capt. ... This article or section does not cite its references or sources. ... // European Definition COUNCIL DIRECTIVE 93/42/EEC of 14 June 1993 concerning medical devices defines a ‘medical device’ as: any instrument, apparatus, appliance, material or other article, whether used alone or in combination, including the software necessary for its proper application intended by the manufacturer to be used for human... A life-critical system or safety-critical system is a system whose failure or malfunction may result in a) death or serious injury to people, or b) loss or severe damage to equipment or c) environmental harm. ... The term implant has different meanings: in Scientology, see Implant (Scientology) in medicine, see prosthesis This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Breast implant diagram A breast implant is a prosthesis used in cosmetic surgery to enhance the size and shape of ones breasts or to reconstruct the breast (for example, after a mastectomy). ... In anatomy, the heart valves are valves in the heart that prevent blood from flowing the wrong way. ... Catheter disassembled In medicine, a catheter is a tube that a health professional may insert into part of the body. ...

Failures which occur early in the life of a new product are vital information for the manufacturer to improve the product. New product development aims to eliminate defects by testing in the factory before launch, but some may occur during its early life. Testing products to simulate their behaviour in the external environment is a difficult skill, and may involve accelerated life testing for example. The worst kind of defect to occur after launch is a safety-critical defect, a defect which can endanger life or limb. Their discovery usually leads to a product recall or even complete withdrawal of the product from the market. Product defects often follow the bath-tub curve, with high initial failures, a lower rate during regular life, followed by another rise due to wear-out. National standards, such as those of ASTM and the British Standards Institute, and International Standards can help the designer in increasing product integrity. In business and engineering, new product development is the complete process of bringing a new product to market. ... A life-critical system or safety-critical system is a system whose failure or malfunction may result in a) death or serious injury to people, or b) loss or severe damage to equipment or c) environmental harm. ... A product recall is a request to return to the maker a batch or an entire production run of a product, usually due to the discovery of safety issues. ... The bathtub curve hazard function A bathtub, whence the term is derived The bathtub curve is widely used in reliability engineering, although the general concept is also applicable to humans. ... ASTM International is an international voluntary standards organization that develops and produces technical standards for materials, products, systems and services. ... British Standards is the new name of the British Standards Institute and is part of BSI Group which also includes a testing organisation. ... Standards are produced by many organisations, some for internal usage only, others for use by a groups of people, groups of companies, or a subsection of an industry. ...

Publications

It is unfortunate that product failures are not more widely published in the academic literature or trade literature, partly because companies do not want to advertise their problems. However, it then denies others the opportunity to improve product design so as to prevent further accidents. However, a notable exception to the reluctance to publish is the journal Engineering Failure Analysis, which publishes case studies of a wide range of different products, failing under different circumstances. There is also an increasing number of textbooks becoming available. Academic publishing describes the subfield of publishing which distributes academic research and scholarship. ...

See also

• Catastrophic failure
• Forensic chemistry
• Forensic electrical engineering
• Forensic evidence
• Forensic photography
• Forensic Science
• Mechanics of materials
• Reverse engineering
• Strength of materials
• Stress analysis
• Structural failure
• Structural analysis
• Trace evidence

Catastrophic failure is a sudden and total (or near total) failure which not only cannot be recovered from (the system which experiences it may be destroyed beyond any reasonable possibility of repair), but also frequently causes injury, death, or significant damage to other, often unrelated systems. ... Forensic chemistry applies the principles of chemistry to law enforcement. ... Forensic electrical engineering is a branch of forensic engineering, and is concerned with investigating electrical failures and accidents in a legal context. ... This article or section should be merged with Forensic science Forensic evidence consists of anything that can be used in a court of law to convict a person of a crime. ... Forensic photography (sometimes referred to as forensic imaging or crime scene photography) is the art of producing an accurate reproduction of a crime scene or an accident scene for the benefit of a court. ... Crime Scene, done by the United States Army Criminal Investigation Command Forensic science (often shortened to forensics) is the application of a broad spectrum of sciences to answer questions of interest to the legal system. ... A field of study at the boundary of two disciplines, Applied mechanics and Materials Science and Engineering, focussing on relations between the mechanical behavior of materials and their microstructures. ... Reverse engineering (RE) is the process of taking something (a device, an electrical component, a software program, etc. ... Strength of materials is materials science applied to the study of engineering materials and their mechanical behavior in general (such as stress, deformation, strain and stress-strain relations). ... Stress analysis is an engineering discipline that determines the stress in materials and structures subjected to static or dynamic forces or loads (see statics and dynamics). ... Structural failure refers to loss of the load-carrying capacity of a component or member within a structure or of the structure itself. ... Structural analysis comprises the set of physical laws and mathematics required to study and predict the behavior of structures. ... Trace evidence is evidence that is found at a crime scene in small but measurable amounts. ...

References

• Introduction to Forensic Engineering (The Forensic Library) by Randall K. Noon, CRC Press (1992).
• Forensic Engineering Investigation by Randall K. Noon, CRC Press (2000).
• Forensic Materials Engineering: Case Studies by Peter Rhys Lewis, Colin Gagg, Ken Reynolds, CRC Press (2004).
• Peter R Lewis and Sarah Hainsworth, Fuel Line Failure from stress corrosion cracking, Engineering Failure Analysis,13 (2006) 946-962.

External links

• http://materials.open.ac.uk/mem/index.html; for virtual museum of failed products
• http://www.elsevier.com/wps/find/journaldescription.cws_home/30190/description; the journal Engineering Failure Analysis