Editing Forensic engineering (section)

==Analysis==
[[File:Spectroscopy overview.svg|thumb|379x379px|This picture shows the mechanics of the spectroscopy machine]]
There are two of the main types of analysis done in forensic engineering, there is root cause analysis and failure analysis. Root cause analysis is defined as looking at the system as a whole and what led to the system failing, and is done with large scale object, for example a building collapse.<ref name=":12"/> Failure analysis is defined as the analysis of one part in the system that failed to operate, an example of this would be a car failure causing an accident.<ref name=":12"/> These two types of analysis are the initial assessments done when forensic engineering investigators start their investigation.<ref name=":12"/>

[[Failure mode and effects analysis]] (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 rate]]s, and precise identification, of the failure modes involved.

There is some common ground between forensic science and forensic 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 microscope]]s, for example. They also share common use of [[spectroscopy]] ([[infrared]], [[ultraviolet]], and [[nuclear magnetic resonance]]) to examine critical evidence. [[Radiography]] using [[X-ray]]s (such as [[X-ray computed tomography]]), or [[neutron]]s is also very useful in examining thick products for their internal defects before destructive examination is attempted. Often, however, a simple [[Magnifying glass|hand lens]] may reveal the cause of a particular problem.

[[Trace evidence]] is sometimes an important factor in reconstructing the sequence of events in an accident. For example, tire 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 slip and may show how the accident occurred. When a product fails for no obvious reason, [[scanning electron microscope|SEM]] and [[Energy-dispersive X-ray spectroscopy]] (EDX) performed in the microscope can reveal the presence of aggressive chemicals that have left traces on the fracture or adjacent surfaces. Thus an [[polyoxymethylene plastic|acetal resin]] water pipe joint suddenly failed and caused substantial damages to a building in which it was situated. Analysis of the joint showed traces of chlorine, indicating a [[stress corrosion cracking]] failure mode. The failed fuel pipe junction mentioned above showed traces of [[sulfur]] on the fracture surface from the [[sulfuric acid]], which had initiated the crack.

Extracting physical evidence from digital photography is a major technique used in forensic accident reconstruction. [[Match moving|Camera matching]], [[photogrammetry]], and [[Image rectification|photo rectification]] techniques are used to create three-dimensional and top-down views from the two-dimensional photos typically taken at an accident scene. Overlooked or undocumented evidence for accident reconstruction can be retrieved and quantified as long as photographs of such evidence are available. By using photographs of the accident scene including the vehicle, "lost" evidence can be recovered and accurately determined.<ref>{{Cite web |last1=Danaher |first1=David |last2=Ball |first2=Jeff |last3=Kittel |first3=Mark |date=June 15, 2012 <!-- version archived in 2014 says "6-15-12" and "Copyright ©2012" --> |title=Extracting Physical Evidence from Digital Photographs for use in Forensic Accident Reconstruction |trans-title=Photogrammetry Reconstruction White Paper |url=https://www.veritecheng.com/white-paper-forensic-accident-reconstruction/ |url-status=live |archive-url=https://web.archive.org/web/20140325204255/http://www.veritecheng.com/white-paper-forensic-accident-reconstruction |archive-date=2014-03-25 |access-date=2024-09-09 |website=Veritech Consulting Engineering, LLC |type=Publication White Paper |publication-place=Castle Rock, CO}}</ref>

[[Forensic materials engineering]] involves methods applied to specific materials, such as [[metal]]s, [[glass]]es, [[ceramic]]s, [[composite material|composites]] and [[polymer]]s.