Materials Mechanics
Monocular 3D Video Extensometer
I. Working Principles of the Two Types of Non-Contact Extensometers
Laser Extensometer
A laser/scan spot tracks two markers or edge positions and computes the distance change between the two points — point-to-point displacement measurement.DIC video extensometer（Video/DIC Extensometer）
A camera captures images; digital image correlation (Digital Image Correlation) tracks the texture displacement of speckles or markers, and can output multi-gauge or even full-field displacement/strain contour maps.
II. Core Differences at a Glance (Table Comparison)
dimension | DIC video extensometer | Laser extensometer: | Description& applicable |
Measured objects | texture/speckle area, markers, boundaries | Two laser tracking points/boundaries | DIC is friendlier to complex surfaces/deformation modes |
Output dimensions | Point measurement, multi-gauge, full-field displacement/strain | Mainly point-to-point displacement | mechanism research/strain concentration: DIC recommended |
Sample restrictions | shapes/few material restrictions | Recognizable edges required/markers, strongly affected by reflectivity | Strong reflection/smoke is more sensitive to the laser |
Surface preparation | Requires speckle or labels (sprayable/film) | Reflective markers can be applied or edges recognized | Conventional metals also workQuick start with light speckle |
accuracy/stability | High precision in the elastic stage; full-field has consistency advantages | High point accuracy, short link | Both can satisfy JJG762-2007 class 0.5 models (depending on the model) |
Frequency response | Determined by camera frame rate; high-speed cameras available | Continuous tracking, suitable for high frequency | fatigue/high-speed: both work, but the solutions differ |
high-/low-temperature adaptability | through-window imaging+optics/algorithm heat-disturbance suppression | Direct optical path, affected by airflow/thermal blooming influence | For high-temperature chambers, window and field-of-view evaluation is recommended first |
Multi-gauge/transverse | Naturally supports multiple gauge lengths/transverse/Poisson's ratio | Usually requires multiple channels or repeated measurement | transverse strain and reduction of area,DIC is simpler |
Assembly and calibration | Requires camera alignment, calibration and gauge length setup | Quick alignment, intuitive process | DIC calibration is done once and easy to reuse |
Data value | Can replay and export strain contour maps and trajectories | Curve-dominated, small data volume | Fault tracing/research publication: DIC wins |
compatibility | easy to pair with testing machines/force synchronized output | Simple synchronization | Both can communicate with mainstream testing machines |
O&M and cost | camera/lens/lighting integrated, routine maintenance | Simple optical path and marker maintenance | Weigh project frequency and expansion needs comprehensively |
III. Selection Advice Under Different Working Conditions
Standard metal tension (room temperature, single gauge):Both are suitable; for quick setup and point measurement, laser is an option; for transverse/multi-gauge and subsequent mechanism analysis, DIC is recommended.
High/low temperature (environmental chamber):Both work; first confirm window material/size, thermal radiation and sight distance. If you later want to see necking-area strain concentration or crack evolution, DIC is easier.
Large strain (rubber, films, soft materials):Non-contact first. DIC is more stable for large deformation and local stretching, facilitating parallel long/short gauge settings.
Fatigue/high-frequency loading:Both can do it. Laser has a simple chain for high-frequency point measurement; high-speed DIC can obtain cross-cycle full-field evidence when needed.
Irregular/curved/multi-axis:DIC is friendly to curved surfaces, boundary changes and multi-gauge, facilitating post-processing alignment and statistics.
Need Poisson's ratio/Reduction of area：DIC's axial plus transverse combination is more direct; laser requires extra channels or repeated alignment.
IV. Frequently Asked Questions（FAQ）
Q: Is DIC Necessarily More Complex Than Laser?
A: Initial DIC setup requires calibration and optical configuration, but one set of parameters can be reused among similar specimens; in the long run, multi-gauge/full-field needs can significantly save repeated setup time.
Q: Can laser do full-field?
A: Laser is mainly point-based; if you need full-field or parallel multi-gauge, a DIC solution is more suitable.
Q: Which Is More Stable at High Temperature?
A: It depends on heat disturbance, windows and the optical path. Both solutions can work stably, but DIC more easily combines filtering/image-stabilization algorithms to suppress thermal blooming while preserving image evidence.
Q: How to compare accuracy?
A: It depends on the specific model and gauge length. Compliant models can all meet class 0.5 or equivalent for material tests; the most objective comparison is a standardized specimen comparison at the same gauge length under the same conditions.
V. Product Introduction: Haytham Video Extensometer (DIC)
The Haytham video extensometerBased on single-camera 3D DIC, it supports multi-gauge and transverse measurement, with an optional full-field displacement/strain module; it achieves force-displacement-strain synchronized output with mainstream testing machines, meeting material testing requirements for accuracy and stability (covering JJG762-2007 class 0.5 corresponding models). It adapts to common high/low-temperature, fatigue and large-strain scenarios, facilitating research publication and quality verification.
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