Papers by Keyword: Slip

Abstract: The bridge plug is a staple tool used in downhole operation and the performance of the slips has a directly influence on the oil well productivity and production safety. We raised an optimize method based on BP network and genetic algorithm to make sure the slips satisfy the high temperature and high pressure demands. Establishing the slips system and making finite element analysis by ANSYS, abtaining sixteen group datas to constitute the BP network training samples, establishing the BP simulation model reflecting curvature radius of the slip fluke, dip angle of the fluke, angle of the fluke and distance between flukes using nonlinearity mapping ability of the neural network, applying optimize design for the simulation model using global optimization ability of the genetic algorithm and abtaining the optimum structure parameters of the slip. The optimized results indicate the whole performance of the slips system has increased notably.

Abstract: In engineering, the excessive slip of shear connectors will arouse the failure of the beams, and cracks in the brittle material element can increase the slip. In this paper, composite beam is composed of the brittle and ductile material elements and there are cracks in the brittle material element. Based on the relation between the slip strain and flexural rigidity, defining rigidity coefficient as there are cracks in the brittle material element, the total change in the slip strain at a given section due to cracking of the brittle material is obtained. The end slip that incorporates the effects of the brittle material cracking is calculated by integrating the slip strain. Letting the end slip equaled to the ultimate slip of shear connectors, the ultimate load formation of composite beam is gotten.

Abstract: In order to study the bonding characteristic of the BFRP(Basalt Fiber Reinforced Plastics for short) bars and the basalt fiber reinforced concrete, the BFRP was embedded into the cubic concrete specimen which mixed the basalt fiber sized the edge length 150 mm. By changing the diameter of the BFRP, the bonding length of the BFRP and the basalt fiber volume content of the basalt fiber reinforced concrete, the experimental results indicate that the average bonding strength decreased while the bonding length increased and it become weaker while the diameter of the BFRP was bigger, and it shows the best effect of the bonding strength when its fiber content was 0.1% comparing with three kinds of fiber content. The bond-slip constitutive model of BFRP bar and the basalt fiber concrete corresponded to the continuous curve model.

Abstract: According to the demand of exploiting the poor-thin oil layer in Daqing oilfield, Y422 retrievable fracture bridge plug is designed. Match usage of this bridge plug and other instruments can fracture multiple oil reservoirs with one-trip string, which is characterized by simple technology and safety operation. This bridge plug has realistic significance and practical value for improving oilfield economic benefits and provides an extensive application prospect. After setting process, the slips brace the bridge plug whose performance have a directly influence on the oil well productivity and production safety. In order to make sure that the bridge plug slips can meet the anchoring requirement, the actual working state of the slips system was analyzed by using finite element software, and the stress distribution rules were obtained. The results provide theoretical basis for optimizing slip structure and improving working reliability.

Abstract: The efficiency of continuously variable transmission for vehicle is an important factor impacting on its performance, many kinds of power loss in process of shifting down and up are analyzed by means of theoretical and experimental ways, it can be seen that the power loss between metal-belt and pulley, which includes three items of loss: the entering and out of pulley; the slip between elements and surface of pulley; the slip of between steel bands and elements, is a major one. The calculating formulas are founded. The comparison of calculating results with experimental results under the different ratio, it is good coherence between them which has a guiding function for the design of TCU.

Abstract: {10 2} twin is common in pure hcp metals. In this study, initiation and development of {10 2} twin in hcp metal was simulated by molecular dynamics (MD) method. Two types of model crystals were stretched along the y-axis by applying displacement of 0.005a (a is lattice constant of the basal plane) every 1000 MD steps and relaxed atoms by molecular dynamics method. The Y-boundary of the model was applied fixed boundary condition and the X and the Z-boundary were free boundary condition. The Lennard-Jones type interatomic potential was employed in this simulation. In the single crystal, {10 1} pyramidal slip initiated at the crack tip and the pyramidal slip was stopped at Y-boundary atoms. After that, a {10 2} twin was initiated at a front of the slip. With increasing external strain, the twin grew with increasing external strain. In the bi-crystal, {10 0} prismatic slip occurred at the crack tip in Crystal 1 and a-dislocation of the slip stopped at a grain boundary between the Crystal 1 and 2. With increasing applied strain, {10 2} twin was initiated in the Crystal 2 at the grain boundary. From the simulation results, the ‘shuffling’ process of twin deformation was estimated.

Abstract: Measurements of strain rate sensitivity (SRS) provide a key link between dislocation-based interpretations of plastic deformation and macroscopic measurements made in mechanical tests. It is well known that plastic deformation of hexagonal close-packed (hcp) metals is achieved not only by dislocation glide but also by twinning and that the atomic rearrangement underlying the latter mode is different from that of slip. This leads to an expectation that co-activation of twinning may affect SRS of hcp metals. This assumption was tested in the present work where strain rate jump tests in both tension and compression were conducted on highly textured AZ31 plate. It was found that the SRS of the alloy in tension decreased with strain whereas that in compression increased with strain, exhibiting negative values at low strain and positive values at higher strain. Microstructure analyses revealed that the strain regimes where negative SRS or decreasing trend in SRS with strain was observed correspond to extensive twinning, implying a negative SRS of twinning. It is concluded that dislocation model alone cannot explain the strain rate dependence of flow stress in metals whose deformation is assisted by twinning.

Abstract: A mathematical model for the hydrodynamic lubrication of finite slider bearings with velocity slip and couple stress lubricants is presented. A numerical solution for the mathematical model using finite element scheme is obtained using four node linearly interpolated quadrilateral elements. Stiffness integrals obtained from the weak form of the governing equations were solved using Gauss Quadrature to obtain a finite number of stiffness matrices. The global system of equations was obtained for the bearing and solved using Gauss Seidel iterative scheme. The converged pressure solution was used to obtain the load capacity of the bearing. Numerical experiments reveal the existence of an optimum velocity slip for which maximum benefit is obtained for the slider bearing in terms of bearing load. Increase in the slip parameter beyond this optimum value was shown not to augment the bearing load. Computations put forth also affirm that the bearing load is augmented with increase in couple stress parameter. An optimal film thickness ratio was also obtained for which load capacity is maximized with or without the application of slip to the bearing surfaces.

Abstract: Effects of carboxymethyl cellulose from papaya peel (CMCp) on the properties of ceramics were investigated. Cellulose was extracted from papaya peels by NaOH and then it was modified by chloro acetic acid to obtain carboxymethyl cellulose. The prepared CMCp was applied as a binder in ceramic slip in order to increase its viscosity. Sodium silicate was also added into the slip for providing a dispersion of slip and protecting the sedimentation of clay particles. Various concentrations of CMCp and commercial CMC (CMCc) (0.05, 0.1, 0.15, 0.2 and 0.25% w/w of dry weight of clays) were added into the slip. Effect of CMC on viscosity of the slip and the ceramic density were studied. The relationship between the ceramic properties such as, shrinkage, porosity, casting rate and bending strength (both green strength and fired strength), and CMC concentration was also observed. As increasing both CMCp and CMCc, viscosity increased while density decreased. The prepared ceramics (green ware and fired ware) added with CMCp were found to have higher strength and lower in %shrinkage than that of adding with CMCc. The thickness of the ceramic wall adding CMCc increased with increasing CMCc concentration, and time in contrast to that of CMCp as the thickness decreased with increasing CMCp concentration. However, the ceramics with addition of CMCp possessed higher strength than that of the commercial one.

Abstract: Metals exposed to small charge explosions, even in absence of overall deformation, show characteristic and permanent microstructural features, that can be related to blast wave properties, e.g. to the charge mass and the charge-to-target distance. In particular, Face Centered Cubic (FCC) alloys with low stacking fault energy may exhibit mechanical twinning due to the high strain rate caused by an explosion, even if in slower processes they mainly deform by slip. In some forensic science investigations, these crystallographic modifications, and particularly the occurrence of twinning, may be among the few remaining clues of a small charge explosion, and may be useful to hypothesize the nature and location of the charge. A wide experimental campaign was performed to correlate the blast wave properties with the ensuing modifications of FCC metal targets, and to investigate the microscopic deformation mechanisms leading to these modifications. In particular, it was attempted to identify the threshold conditions (charge-to-target distance, charge mass, and hence applied stress) that yield barely detectable microstructural modifications, and to study the transition from slip to twinning. FCC metal alloys, with low (α-brass, stainless steel), intermediate (copper, gold alloy), or high (aluminum alloy) stacking fault energy, were exposed to blast waves (caused by 50 or 100 g plastic explosive charges located at increasing charge-to-target distances) and then analyzed by X-ray diffraction, optical microscopy, scanning electron microscopy, and electron backscattered diffraction imaging. A comprehensive review of the most significant findings of the whole research, together with theoretical considerations on the slip and twinning deformation mechanisms, is here presented.