1、 System Overview

The structural strain dynamic high-speed testing system is a non-contact full field strain measurement system based on high-speed camera and digital image correlation technology (DIC), mainly used to capture the transient deformation behavior of materials or structures under high-speed dynamic loads (such as impact, explosion, vibration). Its core functions include real-time measurement of displacement, strain, velocity, and acceleration throughout the entire field, providing critical data support for working condition testing in the engineering field.

2、 Detailed explanation of detection methods

1. High speed image acquisition

Hardware configuration:

Ultra high speed camera: The frame rate can reach tens of thousands to millions of frames per second (such as 1 million frames per second), and the resolution is not less than 1280 × 800 pixels, ensuring clear capture of the instantaneous deformation process.

Optical system: equipped with customized lenses and light sources (such as blue light illumination), optimizing image quality, reducing motion blur, and improving speckle feature recognition accuracy.

Testing process:

Synchronize the acquisition of digital images before and after deformation through a high frame rate camera, and output high-resolution speckle patterns.

2. Speckle image processing

Speckle preparation:

Spray random speckles (such as matte paint) on the surface of the specimen or use natural textures as tracking marks to form high contrast patterns. The speckle size needs to be optimized based on the testing distance and lens magnification.

Image matching algorithm:

Based on DIC technology, sub region matching (such as 32 × 32 pixel area) is performed on the images before and after deformation, and the displacement field is determined by calculating the normalized cross-correlation function.

Combining the principle of binocular stereo vision, convert two-dimensional displacement into three-dimensional spatial coordinates, and reconstruct the surface morphology and deformation process of the object.

3D reconstruction:

By using stereo matching algorithm, the three-dimensional coordinate changes of surface points of objects can be calculated with an accuracy of micrometer level.

3. Data processing and result output

Strain calculation:

Perform numerical differentiation (such as least squares method) on the displacement field to obtain the full field strain distribution (including normal strain, shear strain, and principal strain).

Support complex stress state analysis, such as deriving the direction and magnitude of principal stress from strain flower data.

Dynamic analysis:

Vibration modal analysis: Identify the natural frequency and vibration mode of the structure.

Shock response spectrum: Evaluating the energy absorption capacity of materials or structures under dynamic loads.

Fatigue life prediction: Based on strain time history data, combined with fatigue models (such as rainflow counting method) to estimate life.

Visual output:

Generate strain cloud maps, displacement vector diagrams, time history curves, etc., to visually display the deformation evolution process.

Support 3D animation reconstruction and simulate dynamic structural response.

3、 Technical advantages

Non contact measurement:

To avoid interference from the additional mass of sensors on test results, especially suitable for soft materials (such as rubber, biological tissue) or high-temperature environments (such as rocket engine testing).

Full field measurement capability:

Provide continuous spatial deformation data to reveal local stress concentration and crack propagation paths, filling the limitations of traditional single point measurements such as strain gauges.

High spatiotemporal resolution:

By combining high-speed cameras with DIC algorithms, microsecond level temporal resolution and micrometer level spatial resolution can be achieved to capture transient deformation details (such as explosion shock wave propagation).

Adaptable

By replacing the lens and adjusting the testing distance, it is possible to cover measurement requirements from micrometer level components (such as MEMS devices) to meter level structures (such as bridges and aircraft wings).

4、 Application Fields

Aerospace:

Wing deformation measurement, rocket engine ignition impact analysis, and rotor high-speed rotation trajectory tracking in wind tunnel tests.

Automotive industry:

Vehicle collision safety testing (such as evaluating vehicle durability), engine vibration modal analysis, and tire ground contact mechanics research.

Biomechanics:

Assessment of bone impact injuries (such as car accident simulations), study of soft tissue tensile properties (such as ligaments and muscles), and biocompatibility testing of implants.

civil engineering:

Seismic performance testing of bridge bearings, monitoring of wind-induced vibration response of high-rise buildings, and dynamic deformation control of tunnel blasting excavation.

5、 Limitations and Solutions

Environmental sensitivity:

Strong light interference, smoke, or transparent materials may reduce image quality.

Solution: Optimize lighting design (such as polarizer, ring light source), and use backlighting or matte coating on transparent materials.

Computational complexity:

Massive image data (such as tens of thousands of frames per second) requires high processing algorithms and hardware performance.

Solution: Adopt GPU accelerated computing, distributed processing architecture, or focus on key deformation areas through region segmentation (ROI).

Surface requirements:

Smooth or reflective surfaces require additional treatment (such as spraying matte paint) to generate traceable speckles.

Alternative solution: Utilize natural textures of materials such as metal wire drawing and composite fibers as natural speckles.

The structural strain dynamic high-speed testing system achieves precise capture and analysis of dynamic deformation processes through the integration of high-speed cameras and DIC technology, providing key technical support for working condition testing in the engineering field. Its non-contact, full field, and high-precision characteristics make it irreplaceable in fields such as aerospace, automotive industry, and biomechanics.