Related Experiment Video
Updated: Nov 20, 2025
05:30
Crack Monitoring in Resonance Fatigue Testing of Welded Specimens Using Digital Image Correlation
Published on: September 29, 2019
8.5K
Detection and tracking of cracks based on thermoelastic stress analysis
C A Middleton1, M Weihrauch1, W J R Christian1
1School of Engineering, University of Liverpool, The Quadrangle, Brownlow Hill, Liverpool L69 3GH, UK.
Royal Society Open Science
|January 25, 2021
Summary
A new method uses image decomposition to analyze thermoelastic stress, enabling early detection of cracks as small as 1 mm. This advance in structural health monitoring utilizes low-cost sensors for improved crack detection and tracking.
Area of Science:
- Materials Science
- Mechanical Engineering
- Non-Destructive Testing
Background:
- Thermoelastic stress analysis is promising for structural health monitoring.
- Low-resolution sensors and complex loading conditions pose challenges for traditional data evaluation.
- Existing methods struggle with precise crack detection and tracking.
Purpose of the Study:
- To develop an alternative method for evaluating thermoelastic stress data from low-cost sensors.
- To enable accurate detection and tracking of crack initiation and propagation.
- To advance structural health monitoring capabilities using cost-effective sensors.
Main Methods:
- Image decomposition to generate feature vectors characterizing the thermoelastic effect.
- Data collection using photovoltaic and microbolometer detectors under various loading conditions.
- Calculating Euclidean distance between feature vectors to detect damage.
Main Results:
- Successfully detected and tracked cracks as small as 1 mm.
- Identified an increase in the rate of change of Euclidean distance indicating critical crack propagation.
- Demonstrated the effectiveness of the differential feature vector method with low-cost sensors.
Conclusions:
- The differential feature vector method offers a substantial advancement for monitoring crack initiation and propagation.
- This technology is suitable for both structural testing and in-service monitoring.
- Low-cost sensors can be effectively utilized for precise structural health monitoring.
Related Concept Videos
01:20Microcracking in Concrete
290
Microcracking in concrete refers to the tiny cracks that can form within the material even before any external load is applied. These microcracks typically occur at the interface between the coarse aggregate and the hydrated cement paste, often as a result of differential volume changes prompted by variations in stress-strain behavior, as well as thermal and moisture movement. Initially, these microcracks remain stable and do not grow substantially until the concrete is stressed to about 30...
290
01:09Thermal Stress
3.1K
If the temperature of an object is changed while it is prevented from expanding or contracting, the object is subjected to stress. The stress is compressive if the object expands in the absence of constraint and tensile if it contracts. This stress resulting from temperature change is known as thermal stress. It can be quite large and can cause damage. To avoid this stress, engineers may design components so they can expand and contract freely. For instance, on highways, gaps are deliberately...
3.1K
01:19Thermal Strain
2.6K
Thermal strain is a concept that arises when we consider how temperature changes affect structures. Unlike the conventional assumption that structures remain constant under load, real-world scenarios often involve temperature fluctuations that can significantly impact these structures. Consider a homogeneous rod with a uniform cross-section resting freely on a flat horizontal surface. If the rod's temperature increases, the rod elongates. This elongation is proportional to the temperature...
2.6K
01:27Thermal expansion and Thermal stress: Problem Solving
1.8K
San Francisco's Golden Gate Bridge is exposed to temperatures ranging from -15 °C to 40 °C. At its coldest, the main span of the bridge is 1275 m long. Assuming that the bridge is made entirely of steel, what is the change in its length between these temperatures?
To solve the problem, first, identify the known and unknown quantities. The initial length (L) of the bridge is 1275 m, the coefficient of linear expansion (α) for steel is 12 x 10-6/°C, and the change in temperature (ΔT) is 55...
To solve the problem, first, identify the known and unknown quantities. The initial length (L) of the bridge is 1275 m, the coefficient of linear expansion (α) for steel is 12 x 10-6/°C, and the change in temperature (ΔT) is 55...
1.8K
01:20Elastic Strain Energy for Shearing Stresses
366
As discussed in previous lessons, strain energy in a material is the energy stored when it is elastically deformed, a concept crucial in materials science and mechanical engineering. This energy results from the internal work done against the cohesive forces within the material. When a material undergoes shearing stress and corresponding shearing strain, the strain energy density, which is the energy stored per unit volume, is calculated. Within the elastic limit, where the stress is...
366
01:29Three-Dimensional Analysis of Strain
443
Three-dimensional strain analysis is crucial for understanding how materials deform under stress, particularly in elastic, homogeneous materials. This method employs principal stress axes to simplify complex stress states into more understandable forms. Subjected to stress, a small cubic element within a material either expands or contracts along these axes, transforming into a rectangular parallelepiped. This transformation effectively illustrates the material's deformation. The principal...
443