Probabilistic evaluation of the area of coverage of a probe used for eddy current non-destructive inspections

This study proposes a method to probabilistically evaluate the area of coverage of nondestructive inspections to detect defects on a surface of a structure. For the specific problem, this study considers the effect of the distance between two neighboring scanning lines on the detectability of eddy current testing against near-side cracks. Thirty-eight type 316L stainless steel plates having a fatigue crack were prepared, and eddy current examinations were performed with a sufficiently fine scanning pitch. The full width at half maximum of the spatial distribution of the amplitude of the signals was approximated using a Gaussian function. A probability of detection model considering the distance between two neighboring scanning lines is proposed because in actual inspections a scanning line does not always run directly above a crack. The results demonstrated that the proposed model enables a reasonable probabilistic evaluation of the effect of the distance between two neighboring scanning lines.

Surface Roughness Analysis for Radius End Mill in Cross Feed Direction Both Contour and Scanning Line Machinings

An optimum experimental condition, which realize good surface roughness in cross direction both contour and scanning lines, for radius end mill against some inclined surfaces is obtained and some features is these cutting processes is discussed in this paper. The optimum experimental condition, which consists of cutting type (or feed direction), spindle speed, feed rate, depth of immersion, inclination angle, corner radius of end mill and cross feed, is obtained and the influence degree of these parameters is calculated by using Taguchi method. The experiment is carried out based on L18 orthogonal array. Based on the influence degree and geometric contact status due to unique shape of radius end mill, some feature of radius end milling is introduced. As a result of the contour line machining, a scallop height is very influenced by the inclination angle and the corner radius, and surface machined by bottom edge must not be remained. Regarding the scanning line machining, “go-up” is good for the feed direction. Big corner radius is also suitable because side edge does not contact to workpiece. In other words, the cutting force in radial direction becomes small. Furthermore, the surface roughness of the scanning line machining is smaller than the one of the contour line machining.

Effect of Laser Pulse Overlap and Scanning Line Overlap on Femtosecond Laser-Structured Ti6Al4V Surfaces

Surface structuring is a key factor for the tailoring of proper cell attachment and the improvement of the bone-implant interface anchorage. Femtosecond laser machining is especially suited to the structuring of implants due to the possibility of creating surfaces with a wide variety of nano- and microstructures. To achieve a desired surface topography, different laser structuring parameters can be adjusted. The scanning strategy, or rather the laser pulse overlap and scanning line overlap, affect the surface topography in an essential way, which is demonstrated in this study. Ti6Al4V samples were structured using a 300 fs laser source with a wavelength of 1030 nm. Laser pulse overlap and scanning line overlap were varied between 40% and 90% over a wide range of fluences (F from 0.49 to 12.28 J/cm²), respectively. Four different main types of surface structures were obtained depending on the applied laser parameters: femtosecond laser-induced periodic surface structures (FLIPSS), micrometric ripples (MR), micro-craters, and pillared microstructures. It could also be demonstrated that the exceedance of the strong ablation threshold of Ti6Al4V strongly depends on the scanning strategy. The formation of microstructures can be achieved at lower levels of laser pulse overlap compared to the corresponding value of scanning line overlap due to higher heat accumulation in the irradiated area during laser machining.

The Framework of Passable Region Recognition Based on Vanish-Line

For the defect of the traditional vanishing point detection algorithm that is invalid in unstructured environment, a novel vanishing detection algorithm based on Dynamic Template Matching (DTM) is proposed. And a framework of access area recognition is put forward according to the vanishing point line. First, a series of lines are selected from the image in the form of the scanning at the same interval and then calculate the between each line and the previous one. The horizontal position of vanish point is that of the line with the minimum normalized correlation value in all scanning line. Second, a new image is constructed by getting rid of the part above of the viewpoint line, and be divided into several subimages without overlap to extract the multi features. The end, a train set is constructed based on the assumption of no deviation of the vehicle and the test set is classified by multi-kernel learning (MKL) method to obtain passable area. In addition, according to the need of intelligent vehicles during working, a weight-accuracy is delimited by assigning the different weights to the near areas and far areas. This kind of accuracy is more significative than the original one. In the experiments on various environments image sets, the proposed method exhibits favorable performances compared to the other methods.

Detection and Analysis of LED Display System in Large Stadiums

As the mainstream products of flat panel display, LED screen is becoming more and more popular, which has been widely used in the display system of large gymnasium. The detection of LED display system in large stadium is analyzed. Based on the large LED display in Jingzhou stadium, the qualification of LED display system after installation is tested. A scanning line seed filling algorithm is proposed and used to collect the gray value in the connected domain of the lamp and obtain the average gray value of the light point, so that the LED display system of the large gymnasium is detected. The experimental results show that a reasonable LED display and adjustment scheme can ensure the installation of LED display system in large gymnasium in line with the requirements of the national standard.