iezzi webinar

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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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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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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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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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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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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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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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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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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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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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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Partial profile of 1-Euro coin

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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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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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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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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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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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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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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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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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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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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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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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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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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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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

[email protected]

(610) 761-6721

CorrosionPaint TechnologyMetal CoatingsPretreatmentsPlasticsExpert Witness

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