Yuhua Wu

Infrared radiation of rock impacted at low velocity

Impact is one of the issues in dynamic mechanics, the impacting velocities ranging from low to hypervelocity. Usually, the reaction of the impacted material is the main purpose of research on high-velocity or hypervelocity impacts [1–3], such as piercing and blasting. Recent research on low-velocity impact emphasizes the dynamic change of material parameters and the transient processes [4]. However, research on solid impact, whatever the velocity, has common features:

Infrared Imaging Detection of Water Permeation on Field Large-Scale Rock Relics

Although thermal infrared (TIR) imaging technology has been successfully applied in the thermographic inspection of engineering defects and landmines, its use for detecting water permeation on field large-scale rock relics is new. Huashan Rock Painting, a world-famous field large-scale rock relic in Guangxi Province, China, was used as a case for TIR imaging detection of water permeation on field large-scale rock relics. This paper introduced detection methods, a key parameter, and a gradation model for TIR imaging. Three detection methods were specially designed and used in two experiments performed during the drought and rainy seasons, respectively. Thermographic features were comprehensively analyzed, and temperature variation curves of water-permeation places were quantitatively compared with those of places unaffected by water permeation. Water-permeation places can be precisely identified based on thermographic features and temperature variation curves. Physical interpretation was conducted based on the heat transfer equation and on the Stefan-Boltzmann law. The minimum temperature of solar irradiated water-permeation places was selected as the key parameter, and a -based model was established for water-permeation gradation. To strengthen the differences between water-permeation places and places unaffected by water permeation, TIR imaging should also be conducted during a sunny day after the rains, particularly during an intermittent sunny day after heavy rains in the rainy season. It is the best time for TIR-imaging-based water-permeation detection and gradation.

Experimental study on infrared anomaly of tectonic earthquake

Many scientists believe that the earthquake cannot be predicted. But, the fact that there were positive infrared (IR) anomalies in satellite remote sensing images 15 - 60 days before some moderate-strong tectonic earthquakes in Asia is changing the situation. To reveal the mechanism and to seek for the spatio-temporal laws of IR anomaly evaluation before tectonic earthquakes, a series of fundamental experiments detecting the surface IR radiation images on loaded rock samples, which were designed to model the incubation of tectonic earthquakes, were conducted. This article introduced the spatio-temporal evaluation laws of IR anomaly from rock surface for the condition of compressively sheared rock, bi-axial loaded en echelon faults, compressively-sheared sliding faults and compressively loaded intersected faults, respectively simulating the four gestation mechanisms of tectonic earthquake. The experiments concluded that the tectonic earthquake is predictable, and the satellite IR remote sensing is a prospecting technique for earthquake prediction, especially in the condition that remote sensing is assisted with analyzing to rock properties of regional crust and locations of active faults.

Comparisons of thermal radiation characteristics between rocks and PMMA subjected to free-fall impacts

Utilizing the Thermal Infrared (TIR) imaging technology, the transient process of solids (Three kinds of rocks and one kind of PMMA) impacted by free-falling steel balls are monitored with an infrared camera. It is discovered that: (1) as for rock materials, the increments of IR temperature (both the maximum and average, i.e., ΔTmax and ΔTavr) are all linear related to the impacting height, the difference are the statistical correlation coefficients (R): relatively homogeneous rock (marble, R=0.93~0.95); non-homogeneous rocks (granite: R=0.88~0.92; gabbro: R=0.80~0.84); while for PMMA, there exists a critical height (h≈5m), within this height, ΔTmax is quadratic related and ΔTavr is linear related to the impacting height, and when above this critical height, both ΔTmax and ΔTavr are linear related, comparison to rocks, the statistical correlation coefficients are somewhat higher (R=0.94~0.96); (2) the amplitude of IR temperature increments are different, it is somewhat less of IR temperature variations for relatively hard rocks (granite) than others (gabbro, marble and PMMA), for example, when impacted at a height of 2 meter with a standard ball (1 inch in diameter), the higher ΔTmax≈2~4K, while others are within 1K, and (3) it is verified that the parameters about the impaction could be well inversed qualitatively to quantitatively, not only the type of rocks can be identified exactly, but also the impacting height can be accurately estimated especially for the relatively homogenous materials, as for marble rock and PMMA, the relative mean errors of inversion are less than 11.3% and 6.2%, respectively.

Gauss-filtration-based feature extraction for IR image analysis

Infrared (IR) image analysis is important for extracting IR anomaly features in the fundamental experiments of Remote Sensing Rock Mechanics (RSRM) and for identifying omen for tectonic earthquake based on satellite remote sensing monitoring. Transferring the IR image into a raster contour map is very useful, but usually a raster contour map transferred is not smooth enough for the disturbance of noise and the limitation of spatial resolution of the image. A Gauss filter, G(i,j) ≡ ke i2+j2/σ2, is selected for generating raster contour map. The practical appplication cases in image analysis and feature extraction for RSRM experiments suggest that the raster contour map is smooth enough for quantitative analysis, and is helpful for IR feature extraction and for anomaly identification. As compared to mean filter and median filter, the Gauss filter is effective both in filtering speed and in contour maps quality for the condition that filter width be 9~15 and σ be 0.2~0.6.