photoelastic stress measurement and the dias-1600 digital image analysis system

Photoelastic Stress Measurement and the DIAS-1600 Digital Image Analysis System

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The Strainoptics DIAS-1600 Digital Image Analysis System

Desktop PC with Video Frame Grabber and DIAS-1600 Software

Adjustable Immersion Cell with Adjustable Leveling Feet (Optional)

CCD Video Camera (zoom lens optional)

Polarized light sources available in different sizes and light intensities.

A-100 Senarmont Analyzer

Optional Converging Lens



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).



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 stress-free sample of the same composition, color, and thickness as the sample being measured.



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



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


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 high-sensitivity 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.



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.”



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.



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.



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.



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.


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, high- intensity light sources, horizontal mounting, etc.


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.


A Sampling of Companies Using Strainoptics Automated Stress Measurement Systems

3M Company

Bayer Ag (multiple units)

Celgard

Chrysler Corporation

Corning (multiple units)

Eastman Kodak

Ford Motor Company

SABIC (GE) Plastics (multiple units)

Guardian Industries (multiple units)

Hoechst Celanese

Nam Kwong Electric (China)

NASA

Philips

PPG Industries (multiple units)

Raytheon

Rubbermaid

Samsung

Sandia Laboratories

Sony

Techneglas

Thomson Consumer Electronics

Unitex (China)

U.S. Dept. of Energy

Visteon


Strainoptics, Inc.108 W. Montgomery Ave.

North Wales, PA 19454 USATel: 215.661.0100Fax: 215.699.7028

[email protected]

photoelastic stress measurement and the dias-1600 digital image analysis system

Documents

strainoptics dias

line analysis

stress calculations

high end

resolution modes

choice of measurement

stress units psi

field stress maps