Transcript Fundamentals of Photoelasticity

Photoelastic Stress Measurement and
the DIAS-1600 Digital Image Analysis System
The Strainoptics DIAS-1600 Digital Image Analysis System
CCD Video Camera
(zoom lens optional)
Desktop PC with
Video Frame
Grabber and
DIAS-1600
Software
Optional
Converging Lens
A-100 Senarmont
Analyzer
Adjustable
Immersion
Cell with
Adjustable
Leveling Feet
(Optional)
Polarized light
sources available in
different sizes and
light intensities.
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The Strainoptics DIAS-1600 Digital Image Analysis System
The DIAS-1600 system offers operators a choice of measurement
modes, including single point, line analysis, and full-field stress maps
(not available for all samples). It also features two resolution modes,
standard and high-sensitivity, for maximum flexibility when measuring
samples at the low or high end of the effective range.
Retardation is measured for each point, and stress calculations are
performed automatically, based on thickness and material constant
information provided by the user. Results can be displayed using
retardation (nm), or stress units (psi or MPa).
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The Strainoptics DIAS-1600 Digital Image Analysis System
Digital Image Analysis offers a high degree of accuracy and
resolution, but has a limited range of measurement (<280
nm). It is also somewhat sensitive to ambient light and so
should be used in a dark or dimly lit room.
While not absolutely necessary, for best results, a Digital
Image Analysis system should be calibrated using a stressfree sample of the same composition, color, and thickness
as the sample being measured.
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The Strainoptics DIAS-1600 Digital Image Analysis System
The DIAS-1600 Digital Image Analysis System offers the following
benefits:
• Produces fast, quantitative measurements of
retardation/stress in a user-friendly, menu-driven
Windows-based PC environment
• Permits easy full-field inspection and eliminates decisions
based on the operator's visual judgment
• Standardizes the recording and storage of test results
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The Strainoptics DIAS-1600 Digital Image Analysis System
The DIAS-1600 software permits fast inspection in accordance with
accepted QC procedures with minimal user input required. Operations
include:
• Set-up and calibration
• Data entry (material constants, sample thickness, etc.)
• Line-analysis (linear scan over area)
• Measurement at any cursor-selected point
• Full-field color map of retardation
• Quick Analysis and Area Analysis
• Custom programming features optional;
minor modifications available at no extra charge
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Measurement and Analysis
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Measurement and Analysis
Once setup and calibration is complete, the operator is ready to
measure and analyze any number of identical samples with no further
entries required. Depending on the level of stress in the sample, a highsensitivity mode is available that increases the resolution over a
narrower range of retardation.
The DIAS-1600 offers many types of analysis, including point-by-point,
line analysis, and a Bias On feature that assigns a negative value to
compressive stress and a positive value for tensile stress in a graphic
format. Full-field color mapping (live and captured image) is also
available.
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Measurement and Analysis
Here is an example of the Measurement and Analysis sequence:
1. With the sample in position on the sample stage, the operator
“acquires the image.”
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Measurement and Analysis
2. After selecting “Point Analysis,” the operator uses the mouse to
select any point on the sample, after which a display appears
reporting the results.
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Measurement and Analysis
3. For “Line Analysis,” the operator uses the mouse to
define a line on the sample, after which a display appears
reporting the results in graphic format, stress or retardation vs.
position.
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Measurement and Analysis
4. In Bias Off mode (retardation >100 nm), a color map or a live color
video image can be displayed showing full-field stress distribution in
color-coded levels.
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Measurement and Analysis
Once a measurement is taken, the line analysis results are stored as
both image files and data files that may be retrieved or imported into
other programs for statistical analysis or archiving.
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Optional Features
The DIAS-1600 offers a high degree of flexibility in its software interface and
hardware configuration to allow customization to application requirements:
• A “Quick” analysis feature can be added, generally used with
a sample fixture, to perform fast repetitive measurements at a
designated area or areas on a specific part.
• Stress or retardation thresholds may be entered and the operator
alerted with an on-screen message if any point within a
selected area exceeds an acceptable value.
• For higher resolution of very low stress samples (<50 nm), a high
sensitivity mode is available (requires high-sensitivity cal-bias plate).
• Special models are available for circular polarization, custom
fixturing or sample platforms, macro or micro magnification, highintensity light sources, horizontal mounting, etc.
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About Strainoptics, Inc.
Strainoptics was founded as Strainoptic Technologies, Inc., in 1985 by
Alex Redner, an internationally renowned expert, author, and pioneer in
the field of photoelasticity and stress measurement.
Today, Strainoptics is the world’s largest manufacturer of instrumentation
for measuring residual stress in transparent materials. Based in a suburb
of Philadelphia and represented by a network of representatives and
distributors worldwide, we serve a diverse customer base.
Strainoptics employees play an active role in organizations such as ASTM
and GANA(Glass Association of North America), chairing or participating
in committees devoted to establishing and maintaining standard material
specifications and test methods for the glass and plastics industry.
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A Sampling of Companies Using Strainoptics
Automated Stress Measurement Systems
3M Company
Philips
Bayer Ag (multiple units)
PPG Industries (multiple units)
Celgard
Raytheon
Chrysler Corporation
Rubbermaid
Corning (multiple units)
Samsung
Eastman Kodak
Sandia Laboratories
Ford Motor Company
Sony
SABIC (GE) Plastics (multiple units)
Techneglas
Guardian Industries (multiple units)
Thomson Consumer Electronics
Hoechst Celanese
Unitex (China)
Nam Kwong Electric (China)
U.S. Dept. of Energy
NASA
Visteon
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Strainoptics, Inc.
108 W. Montgomery Ave.
North Wales, PA 19454 USA
Tel: 215.661.0100
Fax: 215.699.7028
[email protected]
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