HELPFUL INFORMATION FOR ATTORNEYS WHEN WORKING WITH
FORENSIC ENGINEERS©
Dr. Robert IezziDocs > Iezzi Webinar.pptx
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OUTLINE
What Do Forensic Engineers Do ? Types of Analytical Tools Commonly
Used Case Studies Summary
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WHAT DO FORENSIC ENGINEERS DO ?
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WHAT DOES A FORENSIC ENGINEER DO ?
Determines reasons why products failWhat went wrong Why it went wrong How it went wrong
Unbiased, accurate, defendable results
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ANALYTICAL TOOLS
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INITIAL SAMPLE OBSERVATION
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ANALYTICAL TOOLS
Optical Microscopy Scanning Electron Microscopy Energy Dispersive X-ray Spectroscopy
(EDS) Metallographic Cross-sections Confocal Scanning Optical Microscopy Atomic Force Microscopy (AFM) X-ray Photoelectron Microscopy (XPS)
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ANALYTICAL TOOLS
Transmission Electron Microscopy (TEM) Auger Electron Spectroscopy Fourier Transform Infrared Spectroscopy
(FTIR) Gas Chromatography Mass Spectrometry
(GC-MS) X-ray diffraction (XRD) X-ray Radiography
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OPTICAL MICROSCOPY
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OPTICAL MICROSCOPY
Optical microscopeOften referred to as light microscope“As-is” samples - need sample to fit under
lensNo surface prep 2-dimensional images Direct link to camera and TV monitorLight filters to see different features –
polarized light shows crystals in polymers
~2X to 2,000X magnificationsResolution ~0.5 micron
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OPTICAL MICROSCOPY
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OPTICAL MICROSCOPY
How Do I UseTake “as-is” photos of every sample I
analyze
Document original condition
Use polarized light to observe structure of plastics
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SCANNING ELECTRON MICROSCOPY (SEM)
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SCANNING ELECTRON MICROSCOPY (SEM)
Produces images of a sample by scanning it with a focused beam of electrons
Electrons interact with atoms in the sample, producing various signals that contain information about the sample's surface features
Resolution better than 1 nanometer - 1 billionth of a meter
Detects the outer few microns of surface
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SCANNING ELECTRON MICROSCOPY (SEM)
More than 500,000 magnification, about 250 times the magnification limit of the best
optical microscope Samples must fit in the specimen chamber
(~6” max) Samples must be in high vacuum and must
be electrically conductive Non-conductive samples must be coated
with ultra-thin conductive coating to prevent surface charging
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SCANNING ELECTRON MICROSCOPE
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SCANNING ELECTRON MICROSCOPY (SEM)
Smooth metal facetscharacteristic of brittle fracture
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SCANNING ELECTRON MICROSCOPE
How Do I UseFrequently
Very high resolution/quality, high magnification images of “as-is” samples
Minimal surface prep – original sample condition preserved
Cost effective
Very high “Bang for the Buck”
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ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS)
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ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS)
EDS is an analytical capability that can be coupled with SEM to determine elemental composition
The impact of the electron beam on the sample produces x-rays that are
characteristic of the elements present on the sample
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ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS)
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ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS)
How Do I UseFrequently
Get elemental analysis results quickly on specific locations noted on SEM
micrograph
Cost included in SEM cost
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METALLOGRAPHIC CROSS–SECTIONS
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METALLOGRAPHIC CROSS–SECTIONS
Cut a “cross-section” of sample to obtain edge view – analogous to cutting
into a steak on the grill to see if its cooked to your liking
“Mount” the cross-section in a plastic material
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METALLOGRAPHIC CROSS–SECTIONS
Sample then grinded and polished using successively finer abrasive particles to produce a scratch-free mirror
finish Analyze the cross-section in SEM or other
methods discussed
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METALLOGRAPHIC CROSS–SECTIONS
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METALLOGRAPHIC CROSS–SECTIONS
How Do I UseFrequently
Particularly to determine why coatings fail or corrosion mechanisms
Used with SEM or other tests methods
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CASE STUDIES USING THESE ANALYTICAL
TECHNIQUES
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CASE #1 CORROSION OF PAINTED ALUMINUM WINDOW &
DOOR FRAMES
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CORROSION OF PAINTED ALUMINUM WINDOW FRAMES
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CORROSION OF PAINTED ALUMINUM FRAMES
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CORROSION OF PAINTED ALUMINUM FRAMES
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CORROSION OF PAINTED ALUMINUM FRAMES
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CORROSION OF PAINTED ALUMINUM FRAMES
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CORROSION OF PAINTED ALUMINUM FRAMES
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CORROSION OF PAINTED ALUMINUM FRAMES
Conclusions
Premature corrosion Not due to aluminum substrate, window manufacturer, or paint
company Was due to poor pretreatment process by company who painted
the product Paint lifted from the pretreatment layer
Poor pretreatment layer likely due to Use of tap process water, not de-ionized water Contaminated water Poor process control
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CASE #2CORROSION OF COPPER ROOFING COATED WITH
LEAD
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LEAD-COATED COPPER
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LEAD-COATED COPPER
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LEAD-COATED COPPER
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LEAD-COATED COPPER
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LEAD-COATED COPPER
Conclusion Premature corrosion caused by porosity
and non-uniformity of the lead coating
The porosity exposed the copper substrate, creating an electrochemical
corrosion cell which accelerated the corrosion of the lead
Poor LCC manufacturing
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CASE #3MANGANESE PHOSPHATE
COATING
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MANGANESE PHOSPHATE
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MANGANESE PHOSPHATE
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MANGANESE PHOSPHATE
Conclusions The premature failure of the
compressorswas due to the alternate MnP coating, which:
-was very rough, non-uniform, and porous
-wore away the compressor seals at an accelerated rate, causing the compressor to lose pressure and not pump refrigerant
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CONFOCAL SCANNING OPTICAL MICROSCOPY
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CONFOCAL SCANNING OPTICAL MICROSCOPY
Recent development in last 20 years Evaluate “as is” sample - no sample prep
or vacuum chamber Filters out out-of-focus blur from 3-
dimensional samples Permits imaging of 3-dimensional
samples or very rough surfaces Gives quantitative measurements of
height, surface profiles, and 3-dimensional image reconstruction
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CONFOCAL SCANNING OPTICAL MICROSCOPY
Partial profile of 1-Euro coin
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CONFOCAL SCANNING OPTICAL MICROSCOPY
How Do I UseRarely – only when I need extreme detail
about the surface features of surface sample
Very few test labs have this equipment - relatively new and expensive
Long time to process the sample = high cost per sample
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ATOMIC FORCE MICROSCOPY (AFM)
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ATOMIC FORCE MICROSCOPY (AFM)
AFM Analysis provides visual images with atomic resolution of surface features
Capable of quantifying surface roughness of samples down to the nanometer scale
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ATOMIC FORCE MICROSCOPY (AFM)
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ATOMIC FORCE MICROSCOPY (AFM)
How Do I Use
When I need extreme detail about the surface features of a flat sample
Use confocal scanning optical microscopy if surface is not flat
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X-RAY PHOTOELECTRON MICROSCOPY (XPS)
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X-RAY PHOTOELECTRON MICROSCOPY (XPS)
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X-RAY PHOTOELECTRON MICROSCOPY (XPS)
How Do I Use
When I need to know the chemical compounds present on the surface
(top 0 - 10 nm) of a material – not just chemical elements
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TRANSMISSION ELECTRON MICROSCOPY (TEM)
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TRANSMISSION ELECTRON MICROSCOPY (TEM)
Provides an image of a sample by transmitting beam of electrons through an ultra-thin sample
Image resolutions about 0.1 nm are produced
TEM has better spatial resolution/images than SEM or optical microscopy, but requires much more sample
preparation
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TEM
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TRANSMISSION ELECTRON MICROSCOPY (TEM)
Provides extremely fine detail - even as small as a single column of atoms, which is thousands of times smaller than the smallest resolvable object
in a light microscope
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TRANSMISSION ELECTRON MICROSCOPY (TEM)
How Do I Use
Rarely use because I usually do not need details down to the atom size
TEM more suitable for basic material research at atomic level
Sample prep tedious – very thin samples needed to transmit electrons through it
Very few labs have TEM
High cost per sample
Overkill for most of my work
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AUGER ELECTRON SPECTROSCOPY
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AUGER ELECTRON SPECTROSCOPY
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AUGER ELECTRON SPECTROSCOPY
How Do I Use
Use when I need visualization of spatial distribution of chemical elements on the top
few atom layers of sample surface
Ideal for metals but polymers may degrade during analysis
Very few labs have this equipmentHigh cost per sample
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FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
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FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
Chemical analysis Identifies organic materials - plastics,
lubricants, adhesives and cleaning agents
Ideal for the direct, in situ, analysis of organic contaminants on metallic surfaces
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FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
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FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
How Do I Use
Frequently for chemical analysisof organic material (paints, plastics, etc.)
Fast, inexpensive test
Most chemical test labs have FTIR
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GAS CHROMATOGRAPHY MASS SPECTROMETRY (GC-MS)
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GAS CHROMATOGRAPHY MASS SPECTROMETRY (GC-MS)
Quantifies organic volatile and semi- volatile compounds
Gas chromatography (GC) separates mixtures into individual components
Mass spectrometry (MS) - identifies the various components
Each compound has a unique mass spectrum that can be compared with mass spectral
databases Through use of standards, quantitation is also
possible GC-MS analysis can work on liquids, gases and
solids
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GAS CHROMATOGRAPHY MASS SPECTROMETRY (GC-MS)
How Do I UseFrequently for chemical identification of
volatile compounds of solids, liquids, and gases
Examples – outgassing of plastic food containers or can coatings, composition of
vapors, chemical fumes, etc.
Fast, inexpensive test
Most chemical test labs have GC-MS
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X-RAY DIFFRACTION (XRD)
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X-RAY DIFFRACTION (XRD)
Characterizes crystalline materials Enables quick phase identification for a
large variety of crystalline samples Provides information on structures,
phases, preferred crystal orientations, average grain size, crystallinity,
crystal defects, etc.
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X-RAY DIFFRACTION (XRD)
How Do I UseTo identify the composition & crystalline forms of
metals
Degree of Crystallinity of plastics and paint coatings
Short time to process sample
Low cost per sample
Only useful for crystalline materials, not amorphous materials
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X-RAY RADIOGRAPHY
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X-RAY RADIOGRAPHY
Radiography is an imaging technique that uses x-ray radiation to view the internal structure of an opaque object
The X-rays that pass through the object are captured behind the object by a detector
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X-RAY RADIOGRAPHYX-ray of Broken Handrail Bracket
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X-RAY RADIOGRAPHY
How Do I UseOccasionally used to determine if cracks are prevalent near a corrosion or product failure site, and if the cracks contributed
to the issue
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SUMMARY
SUMMARY
TOOL PRIMARY USE
Optical Microscopy Document original condition (~2,000X)
SEM High quality image of as-is surface (~500,000X)
EDS Elemental analysis of surface
Metallographic cross- section
Edge view of sample
AFM Surface features on atomic scale
XPS Chemical compounds on surface
SUMMARY
TOOL PRIMARY USEConfocal Microscopy Analysis of non-flat surfaceTEM Extreme detail – atomic saleAES Visualization of chemical
elements on top atom layers
FTIR Chemical analysis of organic material
GC-MS Chemical analysis of volatile material – solids, liquid, gas
XRD Composition of crystalline material
X-RAY Internal cracks or defects in material
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SUMMARY
Forensic engineers have many technically-advanced analytical tools at their disposal
Each tool has its own unique capability to help determine why a product failed
Many of the tools are complementary Frequently more than 1 tool is needed to
get the whole story It is to attorneys’ advantage to be aware of
these various tools and capabilities to maximize the value of an expert to the theme of the case
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QUESTIONSBob Iezzi
(610) 761-6721
CorrosionPaint TechnologyMetal CoatingsPretreatmentsPlasticsExpert Witness