Search

The article presents results of experimental studies using a bi-axial servo-control system to apply load on samples with extensional and compressional en echelon faults. During the experiments, variations of temperature and thermal images were recorded synchronously by a multi-path contact-type thermometric apparatus and a thermal image system, respectively. A digital CCD camera was employed to synchronously collect images of specimens’ surfaces. The digital speckle correlation method (DSCM) was utilized to analyze the images and to define displacements and strain fields. Our experimental results show that temperature fields have clear responses to opposite stress states in the jog areas of both types of the en echelon faults. Prior to failure of the jog area, its temperature is the highest at the compressional en echelon faults and the lowest at the extensional en echelon faults. Records by DSCM give evidence that mean strain of the jog area is the highest at compressional en echelon faults and the lowest at the extensional en echelon faults. It is revealed that deformation of the en echelon faults occurs in two stages, developing from stress build-up and fault propagation in the jog area to unstable sliding along the fault. Correspondingly, the mechanism of heating-up converts from strain heating into friction heating. During the period of transformation of the temperature rising mechanism, three events are observed in the jog area and its vicinity. Analyses of our experimental results demonstrate that variations of temperatures in the jog area can be indicative of fault sliding and suggest sliding directions. Observations and studies of temperature changes during transformation of the temperature rising mechanism at sensitive portions of faults are of great importance for early detection of precursors of unstable slip on active faults.

A new type of marker locating method based on the gray centroid algorithm is developed. The new algorithm takes higher resolution and less computational complexity. A verification experiment is completed and the results are presented that a 2% error can be obtained if the resolution large than 0.05 pixel. Two application examples of this new algorithm of marker locating method are described in this paper.

An automatic human face sculpture is presented in this paper. The system is consisted of a 3D shape measurement unit and a reconstruction or process unit. Some key techniques are adopted and a flow chart of this technology is described. A statuary example is displayed and the future improving is discussed.

Moiré technique is often used to measure surface morphology and deformation fields. CCD moiré is a special kind of moiré and is produced when a digital camera is used to capture periodic grid structures, like gratings. Different from the ordinary moiré setups with two gratings, however, CCD moiré requires only one grating. But the formation mechanism is not fully understood and also, a high-quality CCD moiré pattern is hard to achieve. In this paper, the formation mechanism of a CCD moiré pattern, based on the imaging principle of a digital camera, is analyzed and a way of simulating the pattern is proposed. A universal period formula is also proposed and the validity of the simulation and formula is verified by experiments. The proposed model is shown to be an efficient guide for obtaining high-quality CCD moiré patterns.

The systematic strain measurement error in digital image correlation (DIC) induced by self-heating of digital CCD and CMOS cameras was extensively studied, and an experimental and data analysis procedure has been proposed and two parameters have been suggested to examine and evaluate this. Six digital cameras of four different types were tested to define the strain errors, and it was found that each camera needed between 1 and 2 h to reach a stable heat balance, with a measured temperature increase of around 10 ?C. During the temperature increase, the virtual image expansion will cause a 70?230 ?? strain error in the DIC measurement, which is large enough to be noticed in most DIC experiments and hence should be eliminated.