Papers by Keyword: Flaws

Abstract: The main topic of this paper is finite element analysis of 4-point loaded glulam beams which contain different types of flaws. There were modeled four types of beams. First type was the beam without a flaw, second was the beam with a central crack in the middle of span located at the bottom edge of the beam, third model of beams contained also the central crack but this crack was located 20 mm above the edge and the last model contained a hole in the middle of the span as simulation of a knot. These models were performed and analyzed in ANSYS. Task was considered as two dimensional. There were compared values of stress in different types of beam's models.

Abstract: Detection of damage in rails can be achieved by using ultrasonic guided waves. It is practical that these waves can propagate as lengthy as possible along the rail structure. In this work, the generation of adequate guided waves is considered by performing pertinent laser irradiation of the rail head. Special laser spots were applied through out-of-phase masks collocated on both sides of the rail. Simulation of this excitation configuration was performed by means of the finite element method. It was found that the proposed method enables to trigger sufficiently high stress pulses and generate adequate pattern of waves from a lot of other modes that are likely to exist for a common rail. These waves were found to be sensitive to small localized transverse like defects in the rail system.

Abstract: The paper puts forward a modified eddy current testing method based on the use of miniature eddy current transducers within a localized controlled area of the material surface of up to 50 μm². Measurement results are provided for a model composite material made up of alternating conducting and dielectric layers of system Al-HDPE-Al. Structural flaws are specified as changes in the number and position of layers in the sequence. Prospects of the proposed method and a measuring device operating on its basis for flaw detection in composite aluminum alloy materials are shown.

Abstract: The advent of wireless computing and massive processing power available within portable devices provides organizations with an unprecedented ability to provide flexible computing services on-demand to enable business initiatives and this development has increased the demand for wireless network security, which if unaddressed enables the theft of data, lowers productivity, and causes quantifiable financial losses. Flaws arising from wireless protocol with networking design and implementation errors present challenges to the Wireless Fidelity (Wi-Fi) community of users. In this paper, we attempt to document and classify the flaws in Wi-Fi Protected Setup (WPS), then proving the existence of this flaw with a WPS Pin Cracking Method, and presenting a Reverse Engineering countermeasure to eliminating WPS from an Access Point firmware, including other recommendations to helping the network administrators not repeat the errors that are the root causes of flaws of wireless networking in general from being exploited. By implementing the various techniques discussed in this paper, a better and more secure wireless network will be developed.

Abstract: Many of the NDT methods used for casing, tubing, drill pipe and line pipe are applicable, with some minor modifications, to CT. This article describes the requirements of an ideal in-service inspection. This paper presents a new wall thickness and ovality measuring method engineered for reliable field use. This method based on flux gate testing technology discussed in this paper .This method not only will detect internal flaws and the density of micro-cracks, but also wall thickness measurements will be made. This paper discusses the development of this new method, the detection of eddy current testing program is used in coiled tubing ovality measurements. The key technology is the production of amorphous alloy core. Using this method measure diameter, wall thickness and ovality of CT, is currently being developed.

Abstract: Dynamic response and fracture of high strength boride/alumina ceramic composite were investigated by split Hopkinson pressure bar (SHPB) experiment in this paper. The compressive stress–strain curves and dynamic compression strength of the composites were tested. The surface’s microstructure of fractured composites were examined by using scanning electron microscope (SEM) to investigate the fracture mechanism. The results show that boride/alumina has high dynamic compressive strength and high Young’s modulus. The main fracture mode of the material is the fracture of the ceramic grains. The micro-voids and flaws, generated during the sintering and manufacturing of material and mechanical process of specimen, decrease the strength of the material because they provide the source of crack expansion when the material undergoes the dynamic loadings.

Abstract: Direct tension strength tests were conducted on chemical vapor deposited silicon carbide microspecimens. Three types of specimens were used: straight gage section, tapered gage section, and notched gage section. The average strengths and standards deviations were: 0.42 GPa ± 0.13 GPa; 0.47 GPa ± 0.16 GPa; and 0.68 GPa ± 0.19 GPa, respectively. The fracture origins were identified by fractographic analysis and were cracks in large grains next to surface grooves from the deep reactive ion etch (DRIE) process used to fabricate the specimens.