Investigation of proper specimen geometry for mode I fracture toughness testing with flattened Brazilian disc method

Investigation of geometrical parameters for flattened Brazilian disc method is important, since this is a simple and attractive method for mode I fracture toughness testing on rock cores. Evaluating numerical modeling results, a parametric equation in terms of principal stresses at the center of the disc and the loading angle of the flattened end was developed. An equation was proposed for maximum stress intensity factors at critical crack lengths around stable to unstable crack propagation. Comparing fracture toughness results of flattened Brazilian disc method to the results of the suggested cracked chevron notched Brazilian disc method, geometrical parameters for flattened Brazilian discs were investigated. Diameter, loading angle of flattened ends, and thickness of andesite rock core specimens were changed to obtain comparable results to the suggested method. The closest results to the suggested method were obtained by 54 mm diameter discs with loading angles larger than 32°, and thicknesses between 19 and 34 mm. Results were confirmed by the flattened Brazilian disc tests on a marble rock. In flattened Brazilian disc tests with smaller loading angles and larger diameters, larger fracture toughness values than the results of the suggested cracked chevron notched were obtained. However, excluding tests with large loading angles over 27°; specimen size was less effective on the results of these tests. Critical crack length parameters computed from modeling and experiments were close to each other for the flattened Brazilian disc specimens with smaller loading angles around 20° and thickness/radius ratio equal or less than 1.1.     

Laser cutting of small diameter hole in aluminum foam

The International Journal of Advanced Manufacturing Technology - Laser cutting of a small diameter hole into aluminum foam is carried out, and thermal stress field developed in the cutting section...     

EDTriangles: a high-speed triangle detection algorithm with a false detection control

We present a high-speed method for triangular object detection. The proposed method utilizes the recently developed, real-time edge segment detection algorithm, Edge Drawing; hence, the name EDTriangles, which consists of a detection stage and a validation stage. In the detection stage, EDTriangles extracts edge segments from the image using Edge Drawing and converts these edge segments into line segments, which are then converted into line pairs according to the angles between the line segments and the distance between their endpoints. Next, the line pairs are combined together using some heuristics to generate many triangle candidates, some of which are valid detections and some invalid. Finally, in the validation stage the candidate triangles are validated using the Helmholtz principle and number of false alarms computation to eliminate false detections. Experimental results show that EDTriangles runs very fast, detects various types of triangular objects ranging from narrow to wide-angled triangles and offers a higher detection performance compared to some of the well-known triangle detection algorithms found in the literature.     

Effect of anisotropy on axisymmetric dynamic response of thick-walled cylinders

Effect of anisotropy on the free and forced vibration behavior of hollow cylinders under dynamic internal pressure is investigated. The material is assumed to be cylindrically orthotropic. Laplace transform method is used and the inversion into the time domain is performed exactly using calculus of residues. Complex Laplace parameter in the free vibration equation has directly given natural frequencies and the results are listed in tabular form. On the inner surface various axisymmetric dynamic pressures are applied and hoop stresses are presented in the form of graphs for different values of an anisotropy parameter and wall thickness. The anisotropy parameter which essentially indicates the degree of anisotropy is the square root of a modulus ratio defined as the ratio of circumferential modulus to radial modulus. Increasing the anisotropy parameter provides a stress-amplification effect for thick-walled cylinders. Closed-form solutions obtained in the present paper are tractable and they allow for further parametric studies. The anisotropy constant is a useful parameter from a design point of view in that it can be tailored for specific applications to control the stress distribution. The numerical values used are chosen arbitrarily and do not necessarily represent a certain material     

A regression study on the solid particle erosion of copper and copper alloys by angular and spherical particles at normal incidence

A regression analysis is presented on the solid particle erosion results of copper and copper alloys impacted by angular and spherical silica particles at normal incidence. Particle shape, particle size, and zinc content of materials were selected as factors. Also, three levels were assigned to each factor. Experiments were performed under 50 mTorr vacuum utilizing an electrostatic accelerator erosion tester. A total of 10 g particles were sent to each substrate material in 10 increments. At the end of the experiments, the extent of erosion was calculated by dividing weight loss to the amount of particles sent. A regression analysis was conducted on the erosion data to see the individual and interaction effects of factors chosen.

Results indicate that quadratic components of zinc content, particle shape, and particle size and linear interaction between particle size and zinc content were effective in defining erosion in this study.     

Magnetic Anomalies and Electronic Structure of Ce<Subscript>2</Subscript>Cu<Subscript>2</Subscript>Mg and Ce<Subscript>2</Subscript>Pd<Subscript>2</Subscript>Mg

The intermetallic compounds RE ₂Cu₂Mg and RE ₂Pd₂Mg (RE=La, Ce) were prepared and characterized by magnetic susceptibility and heat-capacity measurements. They crystallize with an ordered U₃Si₂ type structure (space group P4/mbm) and the cerium compounds contain stable trivalent cerium ions, which undergo antiferromagnetic ordering at ∼7.5 and ∼4 K, respectively. In high magnetic fields Ce₂Cu₂Mg exhibits spin reorientation with critical field strength of 40 kOe at 5 K. The data are compared to the non-magnetic isotypic compounds La₂ T ₂Mg (T=Cu, Ni, Pd) and to the already reported intermediate valent Ce₂Ni₂Mg.     

Study of correlation between specific energy of cutting and physical properties of rock and prediction of excavation rate for lignite mines in Çayırhan area,Turkey

Bulletin of Engineering Geology and the Environment - Laboratory specific energy (SE) is a reliable indicator to evaluate the rock cuttability and efficiency for mechanical excavation in mining and...     

Evaluation of hidden Markov models using deep CNN features in isolated sign recognition

Multimedia Tools and Applications - Isolated sign recognition from video streams is a challenging problem due to the multi-modal nature of the signs, where both local and global hand features and...