Applied Mechanics and Materials Vols. 52-54

Abstract: As the energy distribution in each frequency band of rolling bearing acoustic emission (AE) signal is related to its fault type, so we can use the redundant lifting wavelet packet to decompose the rolling bearing AE signal of different fault into different frequency band, combine energy in each frequency band together to be a feature vector of the Support Vector Machines (SVM), then being applied to identify the fault through SVM. This paper also compared the redundant lifting wavelet packet and Daubechies wavelet packet as well as the SVM and neural networks. The experimental result shows that for the fault pattern identification, the method that combines redundant lifting wavelet packet decomposition and SVM together can be effective.

Abstract: As the energy distribution in each frequency band of rolling bearing acoustic emission (AE) signal is related to its fault type, so we can use the harmonic wavelet packet to decompose the rolling bearing AE signal of different fault into different frequency band, combine energy in each frequency band together to be a feature vector of the Support Vector Machines (SVM), then being applied to identify the fault through SVM. This paper also compared the Harmonic wavelet packet and Daubechies wavelet packet as well as the SVM and neural networks. The experimental result shows that for the fault pattern identification, the method that combines harmonic wavelet packet decomposition and SVM together can be effective.

Abstract: The effects of injection velocity on propulsive droplets sizing and efficient mass fraction in a three dimensional side-dump combustor with dual opposite curved side-inlet duct are numerically investigated in the present paper. The mass of fuel vapor inside the flammability limit is named efficient mass fraction. The air flow comes from side-inlet ducts into the cylindrical combustor and four nozzles which are located in the top of the cylinder have the duties of fuel injection. The injection velocity is varied as 20, 40, 60 and 80 [m/s] respectively to examine its effects on propulsive droplets sizing and efficient mass fraction which provides worthwhile information for the combustor design work. As well, by increasing entrance air flow velocity from 35 to 100 and 280[m/s] correspondingly, these computations are repeated. To fulfill the calculations a modified version of KIVA-3V code which is a transient, three-dimensional, multiphase, multicomponent code for the analysis of chemically reacting flows with sprays, is used.

Abstract: The grinding wheel wear status is an important guarantee for the processing efficiency and processing quality of precision and super precision grinding. In this paper, a USB acoustic emission signal acquisition system is designed for online monitoring of grinding wheel status. In the system, CPLD is used as the controller, and a high-speed A/D converter is used to implement the synchronous acquisition of acoustic emission array signals. The collected data are sent into FIFO, and CY7C68013A is used for USB data transmission with upper computer. The sampling frequency of the system can be 10 MHz, and USB transmission speed can reach 40M/S. It is proved that it can meet the monitoring requirements of grinding wheel wear status well by the grinding processing.

Abstract: A bisphenol-A glycidol ether epoxy resin was toughened in cryogenic temperature using reactive macroglycol as modifiers. The properties of modified epoxy resin were characterized by SEM and DMA. Phase-separated structure formed during curing process in the PPG and PTMG modified epoxy resins system, and did not occurred in the PEO modified epoxy resins system. The impact strength of epoxy resin increased at both room temperature (RT) and cryogenic temperature (CT, 77 K) using PEO as modifier. The DMA results confirm that the introduction of PEO chains in the structure of the epoxy increases the mobility of the molecular segment of epoxy network at both RT and CT.

Abstract: Fiber optic interferometry pressure sensor is an excellent diaphragm-base measurement system. It is in-vivo medical device to measure local blood pressure by using endoscopic procedures via the blood vessels and the heart. The sensor must smaller than the size of human artery. This paper has concentrated on the MEMS technology in order to build the sensor tip using micromachining process to the proposed Fabry-Perot Interferometry (FPI) micro-pressure sensor. The feasibility of bulk, surface and hybrid micro-machining as viable proposition for sensor fabrication are reviewed. This paper will address the various factors involved in the manufacturing of FPI sensors, which gives high yield with a specific level of performance. The reliability of the sensor tip has been discussed.

Abstract: Most of fracture processes of carbon/carbon composites (C/Cs) have been found to profoundly affected by their interfacial properties. A fiber-bundle pull-out test is utilized to determine the interface strength between fiber bundles and matrix of two kinds of C/Cs. Pre-fracture observations revealed that amount of voids and gaps existed in the interface, which make the interface strength decreases. The interfacial shear strengths of two kinds of C/Cs were all very low. Post-fracture observations revealed that a shear fracture was successfully induced within the carbon matrices at the loaded fiber bundle interface.

Abstract: Polydicyclopentadiene (PDCPD) is a kind of engineering plastic which possesses excellent mechanical performance. It can be made by dicyclopentadiene (DCPD) through Ring-opening metathesis polymerization. In this paper, a supported catalyst of WCl6-phenol on montmorillionite (MMt) was prepared, formed a high efficienct, low-cost and more stable in air, tagether with Et2AlCl as activator, to polymerize the DCPD monomer through ring-opening metathesis polymerization mechanism, and obtained a Polydicyclopentadiene/MMt Nanocomposites. The Molding of PDCPD was finally made by Gusmer-decker’s RIMcell Lt Machine, and the products were characterized by X-ray diffraction, TEM, TGA, SEM, DMA. Mechanical properties were also measured. The result showed that the supported catalyst had good catalytic activity in polymerizing DCPD. MMt was exfoliated in the matrix after the in-situ polymerization, according to the XRD and TEM, which brought about improved properties of PDCPD with small amount MMt dispersed in the matrix.

Abstract: The driving force caused by density difference of slurry and drilling fluid is a function of circumference angle and radius in horizontal well displacing. The closer to annulus bottom, the larger is the driving force, which leads to the displacing interface more easily to extend downward annulus. Based on the mechanics analysis of annular fluid displacing infinitesimal in horizontal well, this paper sets up the calculation model of drilling fluid layer dynamic shearing stress in displacing process. According to the equilibrium condition of displacing interface stability, the boundary position of drilling fluid retention layer at casing and sidewall with different circumference angles for horizontal well is acquired, which will enhance the pertinence of displacing techniques in horizontal well.Calculation results show that with the same circumference angle, the thickness of drilling fluid retention layer at sidewall is far larger than at casing. For this reason, the cement bond quality of the second cementing interface should be used as one of criterions for evaluating horizontal well cementing quality. And the retention at sidewall and casing gradually increases from the lower annulus to the upper part. The retention layer at upper sidewall is thickest. So the oil/gas/water channeling-path is easy to form and special attention should be given to cleaning the upper sidewall drilling fluid . Low permeable horizontal wells generally take subsection fracturing method for exploitation , requirements of cementing quality is higher. The guarantee of higher displacing efficiency is the premise of obtaining high quality of cement quality , in the horizontal well because of dirlling fluid retention and free water precipitation , the oil/gas/water channeling-path is easy to form at the upper wellbore , seriously restricted the implementation[1-2] of the horizontal well stimulation measures. At present technology about improving the displacing efficiency develope rapidly[3-6],but because of drilling fluid retention laws and the retention position is uncleared in horizontal well,which lead to these measures are not well targeted. Analysed by displacing interface dynamic extension process in the process of slurry displace drilling fluid , this article establishes dynamic shearing stress calculation model of horizontal well annular fluid displacing infinitesimal , according to the condition of displacing interface stability, the drilling fluid retention law and retention position in horizontal well is acquired.

Abstract: The potential of recycled wood flour (r-WF) addition to the thermoplastics polypropylene (PP) matrix for the composites in structural application is evaluated. The effects of different r-WF loading to the tensile and impact mechanical structural properties are analyzed. Two types of polypropylene resin which are the virgin and the recycled resin and recycled wood flour as reinforcement materials are utilized as raw materials in the composites fabrication. Various mechanical testing was conducted in accordance to ASTM standard, to study the behavior of the composites mechanical properties to the applied load. The best compounding formulation of enviro-recycled composite was found at 60wt% of PP matrix and 40wt% of the wood flour addition for both of virgin and recycle matrix. Overall experimental results showed that, the increasing of r-WF loading had significantly increased the mechanical properties of produced composite which is suitable to be applied in the application of structural engineering, through the advantage of mechanical properties performance in tensile and impact behavior. Conclusively, this finding is hoped to lead for contribution in the development of newly advanced material that is environmental friendly for the use of structural application.