Handbook of Forensic Services (pdf) - FBI
Handbook of Forensic Services (pdf) - FBI
Handbook of Forensic Services (pdf) - FBI
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<strong>Handbook</strong> <strong>of</strong> Forens c Serv ces 2007<br />
Metallurgy Examinations<br />
Comparison<br />
Comparat ve exam nat ons can determ ne whether<br />
two metals or metall c objects came from the<br />
same source or from each other. Metal<br />
compar sons can dent fy var ous surface and<br />
m crostructural character st cs— nclud ng<br />
fractured areas, acc dental damage, and<br />
fabr cat on marks—to determ ne whether the<br />
objects share a common or g n. Moreover, the<br />
manufactur ng methods used to produce an object<br />
can be determ ned. These manufactur ng<br />
techn ques can nclude cast ng, forg ng, hot and<br />
cold roll ng, extrus on, draw ng, swag ng, m ll ng,<br />
gr nd ng, sp nn ng, blank ng, ron ng, deep<br />
draw ng, and others. Exam nat ons can determ ne<br />
mechan cal propert es, such as the response <strong>of</strong> a<br />
metal to an appl ed force or load. Exam nat ons<br />
also can determ ne chem cal compos t on,<br />
nclud ng alloy ng and trace elements.<br />
Broken or Mechanically Damaged Metal<br />
The causes <strong>of</strong> fa lure or damage—such as the<br />
appl cat on <strong>of</strong> stress exceed ng the tens le<br />
strength or y eld l m t <strong>of</strong> the metal; a mater al or<br />
manufactur ng defect; or corros on, crack ng, or<br />
excess ve serv ce usage (fat gue)—can be<br />
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