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3D DIC vs. Strain Gauge
A Comparative Case Study
Strain gauges have long been the standard for analyzing strain in tensile testing. However, the advent of 3D Digital Image Correlation (DIC) has introduced a non-contact alternative that offers increased accuracy and flexibility. In this case study, conducted in collaboration with our Japanese distributor, NobbyTech, we compare the performance of a strain gauge and 3D DIC to verify their differences and advantages.
Objective
The goal of this study is to compare strain results obtained from a traditional contact strain gauge with those from a non-contact 3D DIC system during a tensile test on an aluminum specimen.
Advantages of 3D DIC and Strain Gauges
Advantages of 3D DIC:
❖ Non-contact measurement: No need for physical attachment to the specimen.
❖ Full-field mapping: Provides strain and displacement distribution across the entire surface.
❖ Versatile results: Offers a variety of outputs, including principal strain, Poisson’s ratio, and shear strain.
❖ Post-processing: Analyze data after the test for deeper insights.
❖ Direct measurements: Provides specific strain and displacement data.
Advantages of Strain Gauges:
❖ No speckle pattern required: Simplifies the preparation process.
❖ Inaccessible locations: Can be used in areas that are hard to reach optically.
Testing Conditions
A tensile test was conducted on an aluminum sheet specimen measuring 25 x 60 x 2 mm using a Shimadzu Autograph testing machine. A strain gauge was attached to the middle of the specimen for traditional measurements, while 3D DIC provided non-contact strain data.
Setup Specifications
❖ Camera: Basler (5 MP, resolution: 2,472 x 2,064 px).
❖ Lens: 25 mm (C-Mount).
❖ Lighting: Halogen light (200 W).
❖ Frame Rate: 20 fps.
❖ Exposure Time: 10 ms.
❖ Measurement Location: Marked by a red circle on the specimen (see Fig. 1).
Results
As shown in Fig. 3, the strain values from 3D DIC closely match those obtained from the strain gauge. Using the trapezoid rule to calculate the area under the curve, the data sets revealed an error margin of only 2.116%. This demonstrates the high accuracy of 3D DIC as a reliable alternative to strain gauges.
Key Insights
❖ 3D DIC Provides Comprehensive Data: Unlike strain gauges, which offer localized data, 3D DIC captures strain and displacement across the entire surface, enabling full-field analysis.
❖ High Accuracy: With an error margin of just 2.116%, 3D DIC delivers results comparable to strain gauges while offering additional flexibility.
❖ Flexibility and Versatility: The non-contact nature of DIC eliminates limitations associated with physical attachment, making it ideal for fragile or dynamically loaded specimens.
Conclusion
This case study highlights the benefits of using 3D Digital Image Correlation as a modern alternative to traditional strain gauges. While strain gauges remain useful for specific scenarios, 3D DIC provides a broader range of data, higher flexibility, and comparable accuracy, making it a powerful tool for material testing.
Discover more about how MercuryRT enables advanced 3D analysis by visiting our Applications pages.
For more information about 3D DIC and AMEE 3D or AMEE 3D Vex (3D Extensometer), please Contact us through email info@mercury-dic.com.
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