Journal articles: 'Flying shear'

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Song, Jin Chun, Chang Zhou Wang, and Dong Xu. "Dynamic Simulation and Control Strategy of Centrifugal Flying Shear." Applied Mechanics and Materials 16-19 (October 2009): 278–82. http://dx.doi.org/10.4028/www.scientific.net/amm.16-19.278.

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Centrifugal Flying Shear is one of the most advanced equipments, which is widely used in tandem mill production lines because of its simple structure and high shearing precision. In this paper, the working principle of the centrifugal flying shear was introduced; the three-dimensional model of the centrifugal flying shear was established; the structural analysis and the dynamic simulation of the flying shear, with the movement rule and trajectory, were made based on MATLAB/SimMechanics and Solidworks/COSMOS Motion; and the control strategy of realizing scale shearing was proposed. The results obtained provide theoretical basis for design of the electronic control system, and facilitate further analysis of the shearing process and parameter optimization design of similar flying shears.

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Peric, N., and I. Petrovic. "Flying shear control system." IEEE Transactions on Industry Applications 26, no. 6 (1990): 1049–56. http://dx.doi.org/10.1109/28.62386.

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Chen, Tao, Ya Ping Hu, and Jing Peng Zhu. "Solid Modeling and Optimization Design of Crank Rocking Flying Shear." Applied Mechanics and Materials 608-609 (October 2014): 7–13. http://dx.doi.org/10.4028/www.scientific.net/amm.608-609.7.

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Flying shear is the equipment that steel enterprises make shearing process on metal preform body for further processing. Crank flying shear has the advantages of high efficiency and good shearing quality, which makes it widely applied. The paper analyzes and studies crank rocking flying shear evolved from IHI rocking shear. And the paper makes kinetic analysis on crank rocking flying shear, applies Solid works software to make three-dimensional modeling, assembly and animation of working process on crank rocking flying shear, and makes optimized analysis and design on spare parts of flying shear combined with kinetic analysis results.

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Li, Yu Gui, Quan Ye, Gao Ping Wang, and Fei Fan. "The Analyze of Shear Force Calculation Model of Drum Type Linear Blade Flying Shear." Advanced Materials Research 503-504 (April 2012): 785–89. http://dx.doi.org/10.4028/www.scientific.net/amr.503-504.785.

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In this paper, the shear force in the shearing process of the drum type linear blade flying shear is done. Two different approaches were taken to establish the shear force formula, and then the finite element simulation. The comparison results of the calculated values and simulated values can be seen that as the thickness increases, the maximum shear force calculated by the pure shear force formula increases rapidly, the shear force calculated by the energy release rate formula is relatively small, and the finite element simulation values and calculated values close to each other when the plate thickness is small. The derived formula in this paper not only can be applied to complex engineering problems, but also has provided a theoretical basis for drum type linear blade flying shears on the shear force calculations and equipment design.

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Xia, Jun Yong, Wen Hong Ding, and Zhang Yi Li. "Calculation of Cutting Force for Drum Type Arc Flying Shear." Advanced Materials Research 145 (October 2010): 434–42. http://dx.doi.org/10.4028/www.scientific.net/amr.145.434.

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Taking drum type flying shear as the subject, this paper firstly analyzes the position relation between shear blade and strip. Then it deduces the formula for calculating contacting arc length between shear blade and strip, formula for calculating blade inclined angle and formula for calculating blade gap. Then, cutting force of drum arc flying shear is calculated with the formula, which was used for calculating cutting force of slanting blade. Program is made with help of MATLAB software to realized parameterized design of drum type flying shear.

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Wang, Jiun-Yaw, Mao-Lin Chen, and Ching-Long Shih. "Generalized Predictive Control in Flying Shear Equipment." Journal of Advanced Computational Intelligence and Intelligent Informatics 11, no. 9 (November 20, 2007): 1144–48. http://dx.doi.org/10.20965/jaciii.2007.p1144.

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To develop and evaluate improved on-line flying-shear equipment control tasks, we introduces a Generalized Predictive Control (GPC) PID controller for positioning control of a flying-shear cutter. After successful trials and excellent regulation results, the GPC-based PID control algorithm with constraints is proved to be very robust.

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Shi, Jia Lian, Chang Qi Zhu, and Ming Zhao. "The Analysis of the Fly Shear Head Motion Track." Advanced Materials Research 605-607 (December 2012): 110–13. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.110.

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Study the equation of motion of cut head on flying head, and get the trajectory curve.According to the analysis about trajectory curve,build a baffle on the bell mouth behind the guide groove of flying shear , and determine the position of the baffle, solve the problem that steel head often inserting into the guide groove behind flying shear, which affect the process of steel inserting into the following mill group, and even cause run steel accident.

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Zhang, De Li, and Lai Shui Zhou. "The Track Motion Control of the Flying Shear Based on Quintic Spline Curve." Advanced Materials Research 468-471 (February 2012): 2613–19. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.2613.

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If the acceleration and deceleration of the flying shear track motion is constant, the acceleration and jerk of the tracking algorithm are not continuous, these result in a mutation of the force on moving parts and a great impact on the abrasion and service life of the equipment. Moreover, these affect the following effect of the servo system, make the cutting precision decreased. To improve the shear precision and cross section quality, an algorithm of the synchronous motion tracking of the flying shear is proposed. This algorithm directly uses the quintic spline curve profile to track the strip feed without any cam profile table. The quintic spline curve trajectory of the flying shear can make the velocity and acceleration of the blade rotation movement smooth. According to the length that user inputs, the control system uses iteration method to calculate the initial waiting length of the feed to carry out long cutting or short cutting automatically. Nonlinear synchronous movement is carried out to synchronize the horizontal speed of the flying shear with the feed speed of the strip on the cutting zone, which ensures the high-precision cutting length and smooth cutting cross section.

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Luo, Bowen, Chunming Xu, Chao Xu, and Qiang Yin. "Modal analysis of flying shear crankshaft system architecture." International Journal of Wireless and Mobile Computing 17, no. 4 (2019): 393. http://dx.doi.org/10.1504/ijwmc.2019.10024346.

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Xu, Chunming, Qiang Yin, Bowen Luo, and Chao Xu. "Modal analysis of flying shear crankshaft system architecture." International Journal of Wireless and Mobile Computing 17, no. 4 (2019): 393. http://dx.doi.org/10.1504/ijwmc.2019.103118.

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Wang, Yong Qin, Li Li, Yuan Xin Luo, and Xing Chun Yan. "Study on the Dynamics Performance of the Drive Train of Flying Shear Machine." Applied Mechanics and Materials 121-126 (October 2011): 1397–401. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.1397.

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Flying shear machine is widely used in continuous rolling mill production line, and its performance is largely depended on the transmission system. Here a model is established with multiple backlashes, time-varying mesh stiffness and error excitation to investigate the dynamics performance of the transmission system during the process. Also, effects of parameters are discussed. It’s believed that it will be helpful for the design of the flying shear machine

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Gao, Zhen Xing, and Hong Bin Gu. "Safety Analysis of Aircraft Flying through Low Altitude Wind Shear." Applied Mechanics and Materials 97-98 (September 2011): 817–20. http://dx.doi.org/10.4028/www.scientific.net/amm.97-98.817.

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Low altitude microburst wind shear would do harm to aircrafts’ takeoff and landing. In order to analyze flight safety and advise better escape strategies, a mathematical model was built with high fidelity by a vortex ring based microburst model and a flight dynamics model with wind effects. A human pilot model which can describe characteristics of pilots such as skills, experiences, emotion, etc was embedded into the dynamics model. Since the key parameters of the microburst wind shear model and pilot model were set to be stochastic, the Monte Carlo method was adopted to obtain a numerical approximation of the probability density function of the minimum altitude and the F-factors for flight safety analysis.

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Zhou, Lin, Zun Feng Ke, Ying Biao Zhao, Wei Wei He, and Li Ping He. "Technology Innovation of Short Stress Path Mill and Flying Shear." Advanced Materials Research 572 (October 2012): 43–48. http://dx.doi.org/10.4028/www.scientific.net/amr.572.43.

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In order to improve the accuracy and performance of long products, increase the metal yield, more better ensure high speed and continuous rolling, the structure and principle of short stress path mill and flying shear which are the key equipments in rolling line are emphasized in our research work. Some new technology method and rational mechanical structure are proposed and has been applied to optimize equipments. The requirements of various products and high quantity production in long milling products are ensured.

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Gao, Zhen Xing, and Zheng Qiang Li. "Predictive Controller for Aircraft Landing under Wind Shear." Applied Mechanics and Materials 587-589 (July 2014): 2030–35. http://dx.doi.org/10.4028/www.scientific.net/amm.587-589.2030.

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Low altitude wind shear badly threatens aircrafts’ flight safety. Since flight states change rapidly during flying through wind shear, it is deficient to design an optimization controller by off-line analyse. A ring-vortex microburst wind shear model and B747 aircraft flight dynamics model were built. For glide slope tracking under wind shear, an off-line controller was designed by linear quadratic method. Furthermore, a model predictive controller with sequential optimization was designed. Simulation results show the on-line sequential optimization controller possess better tracking performance.

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Liu, Dong Ye, An Rui He, Wei Gan, and Long Jun He. "Research on Precision Compensation of Cross-Cutting Flying Shear Based on BP Neural Network." Advanced Materials Research 753-755 (August 2013): 1078–83. http://dx.doi.org/10.4028/www.scientific.net/amr.753-755.1078.

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In allusion to the numerous nonlinearity factors affecting precision in the cut process of cross-cutting line modeling shear and the difficulties to build precision mathematical model controlled by shear, the essay adopts BP neural network to build model of shear precision compensation system. By Matlab simulation experiment, the data demonstrates nonlinearity complex system can be identified fast and effectively by neural network. The predicted time of the model is 97ms with the control precision within 0-2mm hitting 89%, proving that the model can fully fulfil production demands regarding precision and pace and prove that probability that BP neural network is used in precision compensation of cross-cutting line modeling shear.

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Li, Hui, Shengnan Shen, Kensuke Amemiya, Bo Liu, and Hejun Du. "Simulation of Piezoelectric Flying Height Control Slider Using Shear-Mode Deformation." Physics Procedia 16 (2011): 101–10. http://dx.doi.org/10.1016/j.phpro.2011.06.115.

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17

Shen, Shengnan, Hui Li, Bo Liu, Hejun Du, and Nobutoshi Sagawa. "Parametric simulation of piezoelectric flying height control slider using shear-mode deformation." Microsystem Technologies 18, no. 9-10 (June 28, 2012): 1481–86. http://dx.doi.org/10.1007/s00542-012-1576-z.

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18

Kelso, R. M., T. T. Lim, and A. E. Perry. "An experimental study of round jets in cross-flow." Journal of Fluid Mechanics 306 (January 10, 1996): 111–44. http://dx.doi.org/10.1017/s0022112096001255.

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The structure of round jets in cross-flow was studied using flow visualization techniques and flying-hot-wire measurements. The study was restricted to jet to freestream velocity ratios ranging from 2.0 to 6.0 and Reynolds numbers based on the jet diameter and free-stream velocity in the range of 440 to 6200.Flow visualization studies, together with time-averaged flying-hot-wire measurements in both vertical and horizontal sectional planes, have allowed the mean topological features of the jet in cross-flow to be identified using critical point theory. These features include the horseshoe (or necklace) vortex system originating just upstream of the jet, a separation region inside the pipe upstream of the pipe exit, the roll-up of the jet shear layer which initiates the counter-rotating vortex pair and the separation of the flat-wall boundary layer leading to the formation of the wake vortex system beneath the downstream side of the jet.The topology of the vortex ring roll-up of the jet shear layer was studied in detail using phase-averaged flying-hot-wire measurements of the velocity field when the roll-up was forced. From these data it is possible to examine the evolution of the shear layer topology. These results are supported by the flow visualization studies which also aid in their interpretation.The study also shows that, for velocity ratios ranging from 4.0 to 6.0, the unsteady upright vortices in the wake may form by different mechanisms, depending on the Reynolds number. It is found that at high Reynolds numbers, the upright vortex orientation in the wake may change intermittently from one configuration of vortex street to another. Three mechanisms are proposed to explain these observations.

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Roh, Jeong U., and Woo I. Lee. "Manufacturing of MWNT Filled Carbon Fiber Reinforced Polypropylene with Gelatin." Advanced Materials Research 845 (December 2013): 868–72. http://dx.doi.org/10.4028/www.scientific.net/amr.845.868.

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The aims of this study were to investigate the effect of gelatin coating on the mechanical property of the polypropylene (PP) composites by the addition of Multi-walled nanotube (MWNT) and gelatin coated carbon fibers. The morphology of surface of carbon fiber filament on the fracture surface was examined by field-emission scanning electronic microscopy (FE-SEM). The Iosipescu shear test was done to determine the ultimate shear strength of the PP reinforced with MWNT/gelatin composite layer coated carbon fibers. The gelatin coated carbon fibers resulted in an increase in the ultimate shear strength compared to plain carbon fibers. In addition, the ultimate shear strength was improved through the addition of MWNTs with the gelatin. Also, with gelatin acting as a binder, flying CNT particles could be minimized.

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20

Andrews, Ian A. "Broadaxe to Flying Shear: The Mechanization of Forest Harvesting East of the Rockies." Technology and Culture 40, no. 1 (1999): 166–67. http://dx.doi.org/10.1353/tech.1999.0039.

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BROOKS, D. A. "DESIGN AND DEVELOPMENT OF FLOW BASED ELECTRO-RHEOLOGICAL DEVICES." International Journal of Modern Physics B 06, no. 15n16 (August 1992): 2705–30. http://dx.doi.org/10.1142/s0217979292001389.

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The foundations for the design of electro-rheological (ER) actuating devices that use Poiseuille flow are laid. Systems of measurement to assess ER fluids are described including a high pressure flow apparatus. This was used to examine alternative valve geometries and fluids. A method is shown for the reduction of basic flow data to excess shear stress and shear rate. Standard actuator arrangements are reviewed before the design of a flying control surface servomechanism is discussed. The evaluation of this validates the methods and indicates that the forces developed are within striking distance of those required for operational systems.

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Torres, Hector, Markus Varga, Dieter Horwatitsch, Karl Adam, and Manel Rodríguez Ripoll. "The Role of Tool Geometry and Process Parameters during Fly Shearing in Hot Rolling of Steel." Advanced Materials Research 966-967 (June 2014): 184–95. http://dx.doi.org/10.4028/www.scientific.net/amr.966-967.184.

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Sheet metal shearing takes place immediately after hot rolling of steel. Due to the extreme operating conditions, flying shear blades suffer from severe wear and need frequent repair, significantly increasing the maintenance costs for steel producers. In order to optimise the shearing process and increase the tool lifetime, a finite element model was applied for performing a systematic variation of the blade geometry and process parameters. In the model, friction is taken into account by implementing a hybrid friction equation, which is suitable for the simulation of metal forming processes. Tool geometry and process parameters such as the vertical overlapping between the two shearing blades were varied in the simulation, in order to identify optimum process parameters. The results obtained show in particular that the variation of the vertical overlapping between both blades has a limited influence on the maximum calculated stresses, leading to the assumption that no significant changes in tool wear may be achieved by modifying it. On the other hand, it was found that higher cutting edge radii lead to significantly lower stresses for both flying shear blades, thus suggesting the possibility of decreasing tool wear through increasing values of the cutting edge radius.

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Feng, J., P. Y. Huang, and D. D. Joseph. "Dynamic simulation of the motion of capsules in pipelines." Journal of Fluid Mechanics 286 (March 10, 1995): 201–27. http://dx.doi.org/10.1017/s002211209500070x.

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In this paper we report results of two-dimensional simulations of the motion of elliptic capsules carried by a Poiseuille flow in a channel. The numerical method allows computation of the capsule motion and the fluid flow around the capsule, and accurate evaluation of the lift force and torque. Results show that the motion of a capsule which is heavier than the carrying fluid may be decomposed into three stages: initial lift-off, transient oscillations and steady flying. The behaviour of the capsule during initial lift-off and steady flying is analysed by studying the pressure and shear stress distributions on the capsule. The dominant mechanism for the lift force and torque is lubrication or inertia or a combination of the two under different conditions. The lift-off velocity for the ellipse in two dimensions is compared with experimental values for cylindrical capsules in pipes. Finally, the mechanisms of lift for capsules are applied to flying core flows, and it is argued that inertial forces are responsible for levitating heavy crude oil cores lubricated by water in a horizontal pipeline.

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Bousquet, Gabriel D., Michael S. Triantafyllou, and Jean-Jacques E. Slotine. "Optimal dynamic soaring consists of successive shallow arcs." Journal of The Royal Society Interface 14, no. 135 (October 2017): 20170496. http://dx.doi.org/10.1098/rsif.2017.0496.

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Albatrosses can travel a thousand kilometres daily over the oceans. They extract their propulsive energy from horizontal wind shears with a flight strategy called dynamic soaring. While thermal soaring, exploited by birds of prey and sports gliders, consists of simply remaining in updrafts, extracting energy from horizontal winds necessitates redistributing momentum across the wind shear layer, by means of an intricate and dynamic flight manoeuvre. Dynamic soaring has been described as a sequence of half-turns connecting upwind climbs and downwind dives through the surface shear layer. Here, we investigate the optimal (minimum-wind) flight trajectory, with a combined numerical and analytic methodology. We show that contrary to current thinking, but consistent with GPS recordings of albatrosses, when the shear layer is thin the optimal trajectory is composed of small-angle, large-radius arcs. Essentially, the albatross is a flying sailboat, sequentially acting as sail and keel, and is most efficient when remaining crosswind at all times. Our analysis constitutes a general framework for dynamic soaring and more broadly energy extraction in complex winds. It is geared to improve the characterization of pelagic birds flight dynamics and habitat, and could enable the development of a robotic albatross that could travel with a virtually infinite range.

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Dreissigacker, Marc, Ole Hoelck, Joerg Bauer, Tanja Braun, Karl-Friedrich Becker, Martin Schneider-Ramelow, and Klaus-Dieter Lang. "A numerical study on mitigation of flying dies in compression molding of microelectronic packages." International Symposium on Microelectronics 2018, no. 1 (October 1, 2018): 000355–60. http://dx.doi.org/10.4071/2380-4505-2018.1.000355.

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Abstract Compression molding with liquid encapsulants is a crucial process in microelectronic packaging. Material properties of highly filled systems of reactive epoxy molding compounds (EMC) depend on process conditions in a complex manner, such as shear-thinning behavior, which is superimposed by a time- and temperature-dependent conversion rate, both strongly affecting viscosity. The focus is set on forces exerted on individual dies during encapsulation in Fan-Out Wafer Level Packaging (FOWLP). The presented framework consists of an analytical approach to calculate the melt front velocity and simulations carried out to capture the nonlinear kinematics, chemo-rheology, as well as to extract forces exerted on individual dies. It offers separate evaluation of pressure and shear-contributions for two cases, 0 ° and 45 ° between the dies' frontal area and the melt front. Process parameters, such as compression speed and process temperature, are determined to minimize flying dies and thereby maximize yield. The approach is easily scalable and is therefore well suited to face the challenges that come with the current efforts towards the transition from FOWLP to FOPLP (Fan-Out Panel Level Packaging).

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Dreissigacker, Marc, Ole Hoelck, Joerg Bauer, Tanja Braun, Karl-Friedrich Becker, Martin Schneider-Ramelow, and Klaus-Dieter Lang. "A Numerical Study on Mitigation of Flying Dies in Compression Molding of Microelectronic Packages." Journal of Microelectronics and Electronic Packaging 16, no. 1 (January 1, 2019): 39–44. http://dx.doi.org/10.4071/imaps.763387.

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Abstract Compression molding with liquid encapsulants is a crucial process in microelectronic packaging. Material properties of highly filled systems of reactive epoxy molding compounds depend on process conditions in a complex manner, such as shear-thinning behavior, which is superimposed by a time- and temperature-dependent conversion rate, both strongly affecting viscosity. The focus is set on forces exerted on individual dice during encapsulation in fan-out wafer-level packaging (FOWLP). The presented framework consists of an analytical approach to calculate the melt front velocity and simulations carried out to capture the nonlinear kinematics, chemorheology, and to extract forces exerted on individual dice. It offers separate evaluation of pressure and shear contributions for two cases, 0° and 45° between the dice' frontal area and the melt front. Process parameters, such as compression speed, thus cycle time, and process temperature, are determined to keep the forces on the dice below the critical level, where drag forces exceed adhesive forces. As a result, process parameters are determined to minimize flying dice and thereby maximize yield. The approach is easily transferable to arbitrary geometries and is therefore well suited to face the challenges that come with the current efforts toward the transition from FOWLP to larger substrates.

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Bi, Junxi, Wenze Fan, Hongzhong Huang, and Bin Liu. "Reliability Design of an Electronic Cam Curve for Flying Shear Machine in Short Materials Cutting." Journal of Shanghai Jiaotong University (Science) 25, no. 2 (July 29, 2019): 246–52. http://dx.doi.org/10.1007/s12204-019-2106-2.

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De Bruyne, Frank A., and D. B. Bogy. "Numerical Simulation of the Lubrication of the Head-Disk Interface Using a Non-Newtonian Fluid." Journal of Tribology 116, no. 3 (July 1, 1994): 541–48. http://dx.doi.org/10.1115/1.2928878.

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The prospect of contact and near-contact recording in magnetic hard disk files naturally leads to reduced flying heights of the read-write head over the rigid disk. To avoid dry contact at these low head-to-disk spacings, a lubricant should be used to minimize wear and maximize reliability. Since fluids generally have a much greater viscosity than air and very large shear rates develop under the slider, it is believed that a fully flooded interface can only be practically possible if the fluid possesses a non-Newtonian character with a significant amount of shear-thinning. In this paper, we present results from extensive numerical simulations of the fully flooded head-disk interface using the finite element technique. This approach has proven very successful in calculating a wide variation of slider geometries for various fluid nonlinearities.

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Ebrahimi, Abbas, Majid Hajipour, and Kamran Ghamkhar. "Dual-position excitation technique in flow control over an airfoil at low speeds." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 9 (December 6, 2018): 4141–54. http://dx.doi.org/10.1108/hff-05-2018-0195.

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PurposeThe purpose of this paper is to control flow separation over a NACA 4415 airfoil by applying unsteady forces to the separated shear layers using dielectric barrier discharge (DBD) plasma actuators. This novel flow control method is studied under conditions which the airfoil angle of attack is 18°, and Reynolds number based on chord length is 5.5 × 105.Design/methodology/approachLarge eddy simulation of the turbulent flow is used to capture vortical structures through the airfoil wake. Power spectral density analysis of the baseline flow indicates dominant natural frequencies associated with “shear layer mode” and “wake mode.” The wake mode frequency is used simultaneously to excite separated shear layers at both the upper surface and the trailing edge of the airfoil (dual-position excitation), and it is also used singly to excite the upper surface shear layer (single-position excitation).FindingsBased on the results, actuations manipulate the shear layers instabilities and change the wake patterns considerably. It is revealed that in the single-position excitation case, the vortices shed from the upper surface shear layer are more coherent than the dual-position excitation case. The maximum value of lift coefficient and lift-to-drag ratio is achieved, respectively, by single-position excitation as well as dual-position excitation.Originality/valueThe paper contributes to the understanding and progress of DBD plasma actuators for flow control applications. Further, this research could be a beneficial solution for the promising design of advanced low speed flying vehicles.

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Badran, O. O., and H. H. Bruun. "Comparison of Flying-Hot-Wire and Stationary-Hot-Wire Measurements of Flow Over a Backward-Facing Step." Journal of Fluids Engineering 121, no. 2 (June 1, 1999): 441–45. http://dx.doi.org/10.1115/1.2822229.

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This paper is concerned with measurements of the flow field in the separated flow region behind a backward-facing step. The main instrument used in this research was Flying X Hot-Wire Anemometry (FHWA). Stationary (single normal) Hot-Wire Anemometry (SHWA) was also used. Comparative measurements between the SHW probe and the FHW system were conducted downstream of the step (step height H = 120 mm) and results are presented for axial locations of 1H and 2H. Two step configurations were considered; (i) a blunt leading edge with flow underneath (Case I) and (ii) a blunt leading edge with no flow underneath (Case II). It is observed from the results presented that the two Hot-Wire methods produce significantly different mean velocity and turbulence results inside the separation bubble. In particular, the SHWA method cannot detect the reverse flow velocity direction, while the Flying Hot-Wire clearly identifies the existing reverse flow. Also, in the shear flow region, the results presented indicate that measurements with a SHW probe must be treated with great caution.

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Yao, Junkai, Haibo He, Danjie Zhou, Zhiwei Shi, and Hai Du. "Effects of Plasma Actuator Discharge on Lift-Enhancement and Flow Patterns of Flying Wing Aircraft." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 36, no. 5 (October 2018): 963–69. http://dx.doi.org/10.1051/jnwpu/20183650963.

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The nanosecond pulsed plasma discharge actuator is used on a flying wing aircraft. At the angles of attack rang from -4° to 28°, the impact of plasma actuator arrangement position and discharge frequency on lift-enhancement effect is tested. Oil flow visualization is used to investigate the surface flow pattern varies with angles of attack for the plasma actuator turned on and off. The result indicates that lift-enhancement can be achieved through the actuator discharges at large angles of attack on flying wing aircraft. The arrangement position and discharge frequency both have a significant impact on lift-enhancement effect. The actuator which arranged at the leading edge of the aircraft could get the best lift-enhancement effect. There exists an optimal discharge frequency, flow separation under this frequency can be effectively suppressed, which results the best lift-enhancement effect. The flow visualization test shows that the control mechanisms of the plasma actuator are to inject energy to the shear layer, thus increased the vortex strength. The vortices strengthen the mixing of the outer high-speed fluid with inner low-speed fluid, which effectively restrains the separation.

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Ghosh, Kingshuk. "A Study on Kinematic Analysis of Crank-Type Flying Shear Mechanism for Production-Oriented Design and Motion Control." Journal of The Institution of Engineers (India): Series C 100, no. 6 (October 22, 2018): 851–58. http://dx.doi.org/10.1007/s40032-018-0495-x.

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Grishin, V. I., M. A. Glebova, Yu I. Dudarkov, E. A. Levchenko, and M. V. Limonin. "Strength analysis of structural elements and metal-composite joints of a flying vehicle." Spacecrafts & Technologies 4, no. 4 (December 4, 2020): 191–200. http://dx.doi.org/10.26732/j.st.2020.4.01.

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The strength and load-bearing capacity analyses results for flying vehicle typical structural elements and joints are presented in the paper. Calculations were made with the use of nonlinear finite element method, implemented in software NASTRAN and ABAQUS. Structural composite panels and metal-composite joints in attachment points of moving components under consideration for research. Employed computational models and procedures, obtained results analysis process are presented. Numerical strength estimations of structural panels and joint strength confirmed with test results. On the example of a virtual test simulation of composite panels’ strength test in a shear frame, the effect of experimental conditions on obtaining results is evaluated. It is shown that boundary conditions realized in such tests cannot always give correct values of panels’ global buckling critical stress. The computation results of buckling and strength of metal-composite joints in attachment points of moving components are presented. The computation performed on a detailed model with employing solid elements and taking into account contact interaction between joint parts, geometrical and physical nonlinearities. Composite strength in bolted joints is made based on Nuismer criterion. The formed recommendations for improvement made it possible to avoid earlier failure of the considered joint in strength tests.

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Tao, Yang, Zhongliang Zhao, Junqiang Wu, Zhaolin Fan, and Yi Zhang. "Pitching effect on transonic wing stall of a blended flying wing with low aspect ratio." Modern Physics Letters B 32, no. 12n13 (May 10, 2018): 1840040. http://dx.doi.org/10.1142/s0217984918400407.

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Numerical simulation of the pitching effect on transonic wing stall of a blended flying wing with low aspect ratio was performed using improved delayed detached eddy simulation (IDDES). To capture the discontinuity caused by shock wave, a second-order upwind scheme with Roe’s flux-difference splitting is introduced into the inviscid flux. The artificial dissipation is also turned off in the region where the upwind scheme is applied. To reveal the pitching effect, the implicit approximate-factorization method with sub-iterations and second-order temporal accuracy is employed to avoid the time integration of the unsteady Navier–Stokes equations solved by finite volume method at Arbitrary Lagrange–Euler (ALE) form. The leading edge vortex (LEV) development and LEV circulation of pitch-up wings at a free-stream Mach number M = 0.9 and a Reynolds number Re = [Formula: see text] is studied. The Q-criterion is used to capture the LEV structure from shear layer. The result shows that a shock wave/vortex interaction is responsible for the vortex breakdown which eventually causes the wing stall. The balance of the vortex strength and axial flow, and the shock strength, is examined to provide an explanation of the sensitivity of the breakdown location. Pitching motion has great influence on shock wave and shock wave/vortex interactions, which can significantly affect the vortex breakdown behavior and wing stall onset of low aspect ratio blended flying wing.

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Jing, Guo Qing, Lei Shao, Ya Di Zhu, and Liang Gao. "Micro-Analysis of Railway Ballast Bond Effects." Advanced Materials Research 446-449 (January 2012): 2492–96. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.2492.

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Ballast glue is a material to adjust ballast stiffness and stabilize ballast from flying due to high speed train winds; its ballast-glue system is less of microscopic mechanism research. In this paper, 3D DEM method is used to produce sleeper-ballast box model, ballast is made of real size irregular clumps, the ballast glue is represented by bonds to simulate the tensile and shear strength, it works at the ballast-ballast particles interaction contacts physically. The sleeper induced monotonic loadings results show the ballast-sleeper microscopic contact force chain distribution is altered due to ballast glue bonding effects, the glue results in tension forces among ballast system. The ballast-box bearing ability is improved with ballast global stiffness increase; ballast-box global stiffness increases with the glue bonding layer depth non-proportional, and is governed by the top 10cm layer.

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Henningsson, Per, Dirk Michaelis, Toshiyuki Nakata, Daniel Schanz, Reinhard Geisler, Andreas Schröder, and Richard J. Bomphrey. "The complex aerodynamic footprint of desert locusts revealed by large-volume tomographic particle image velocimetry." Journal of The Royal Society Interface 12, no. 108 (July 2015): 20150119. http://dx.doi.org/10.1098/rsif.2015.0119.

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Particle image velocimetry has been the preferred experimental technique with which to study the aerodynamics of animal flight for over a decade. In that time, hardware has become more accessible and the software has progressed from the acquisition of planes through the flow field to the reconstruction of small volumetric measurements. Until now, it has not been possible to capture large volumes that incorporate the full wavelength of the aerodynamic track left behind during a complete wingbeat cycle. Here, we use a unique apparatus to acquire the first instantaneous wake volume of a flying animal's entire wingbeat. We confirm the presence of wake deformation behind desert locusts and quantify the effect of that deformation on estimates of aerodynamic force and the efficiency of lift generation. We present previously undescribed vortex wake phenomena, including entrainment around the wing-tip vortices of a set of secondary vortices borne of Kelvin–Helmholtz instability in the shear layer behind the flapping wings.

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Xie, Fei Ming, Yang Liu, Yan Lin Wang, and Qing Zhang. "The Production Technology in High-Performance and Economical Hot-Rolled Ribbed Wire Rod." Advanced Materials Research 746 (August 2013): 539–42. http://dx.doi.org/10.4028/www.scientific.net/amr.746.539.

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According to the production actual situation of the hot-rolled ribbed wire rod in Fangda special steel technology Co., Ltd, Through optimizing the rolling process to improve rolling organization , and with low alloy composition, which can greatly save resources and production cost. The results show that the yield strength of hot-rolled ribbed wire rod is 510MPa, the tensile strength is 622MPa, and the elongation is 23.35%, but the content of Mn can be decreased 58.13%, the content of Si can be decreased 67.50% compared with the national standard upper limit value in HRB400; The grain size scale of edge microstructure is 9.0 at the 1# flying shear in the rolling process, the grain size scale of core microstructure is 8.5, and the edge microstructure of hot-rolled ribbed wire rod after rolling is the tempered sorbite, the grain size scale is 13.5, the core microstructure is the ferrite-pearlite, the grain size scale is 12.0, and the depth of hardening is 0.50mm.

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Bramberger, Martina, Andreas Dörnbrack, Henrike Wilms, Florian Ewald, and Robert Sharman. "Mountain-Wave Turbulence Encounter of the Research Aircraft HALO above Iceland." Journal of Applied Meteorology and Climatology 59, no. 3 (March 2020): 567–88. http://dx.doi.org/10.1175/jamc-d-19-0079.1.

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AbstractStrong turbulence was encountered by the German High-Altitude Long-Range Research Aircraft (HALO) at flight level 430 (13.8 km) on 13 October 2016 above Iceland. In this event the turbulence caused altitude changes of the research aircraft of about 50 m within a period of approximately 15 s. Additionally, the automatic thrust control of the HALO could not control the large gradients in the horizontal wind speed and, consequently, the pilot had to switch off this system. Simultaneously, the French Falcon of Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE), flying 2 km below HALO, also encountered turbulence at almost the same location. On that day, mountain-wave (MW) excitation and propagation was favored by the alignment of strong surface winds and the polar front jet. We use a combination of in situ observations, ECMWF and empirical turbulence forecasts, and high-resolution simulations to characterize the observed turbulent event. These show that a pronounced negative vertical shear of the horizontal wind favored overturning and breaking of MWs in the area of the encountered turbulence. The turbulent region was tilted upstream and extended over a distance of about 2 km in the vertical. The analyses suggest that HALO was flying through the center of a breaking MW field while the French Falcon encountered the lower edge of this region. Surprisingly, the pronounced gradients in the horizontal wind speeds leading to the deactivation of the automatic thrust control were located north of the breaking MW field. In this area, our analysis suggests the presence of gravity waves that could have generated the encountered modulation of the horizontal wind field.

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Ágústsson, Hálfdán, and Haraldur Ólafsson. "Simulations of Observed Lee Waves and Rotor Turbulence." Monthly Weather Review 142, no. 2 (January 24, 2014): 832–49. http://dx.doi.org/10.1175/mwr-d-13-00212.1.

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Abstract On 18 November 2008 a commercial aircraft encountered severe turbulence while flying in westerly flow along the southeastern coast of Iceland and descending from 2500 m down to the ground for a safe landing. Numerical simulations at horizontal resolutions of 9, 3, and 1 km are compared to the available observations. The simulations reproduce the situation, with an observed severe downslope windstorm at the ground as well as associated amplified lee waves and a rotor aloft, while climate data indicate that all observed westerly windstorms in the region are of the same type and occur in a similarly structured atmosphere. Strong shear turbulence is simulated at the interface of the lee wave and the rotor, as well as inside the rotor. The lee waves and the turbulence patterns are not stationary and as the upstream vertical wind shear increases, the lee wave becomes less steep, but the turbulence increases temporarily while the rotor circulation breaks down. From a forecasting perspective, this event could have been foreseen quite accurately, but not with the NWP tools that were in use for aviation forecasts, as their resolution was simply not adequate for resolving hazardous features of flow in and above complex terrain on the scale of this event. This event underlines the urgency of delivering products from finescale simulations over complex terrain to pilots and forecasters. Such products need to be developed taking into account the transient nature of the flows and the hazards.

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Liu, Lu Ning, Zhen Yu Shi, and Zhan Qiang Liu. "FEM Analyzing Effect of Tool Body Materials on Security Reliability for Face-Milling Cutter." Advanced Materials Research 797 (September 2013): 161–65. http://dx.doi.org/10.4028/www.scientific.net/amr.797.161.

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Face milling is the most common milling operation and can be performed using a wide range of different tools. Tool life is an important indicator of the milling operation in manufacturing process. In high speed machining, there are two forms of security lapse including cutter body rupture and flying out to effect face-milling cutter life. This study investigates the influence of cutting tool body material on the distribution of stress field by utilizing finite element simulations (FEM). Two kind of cutting tool body materials including Al alloys and 40CrMo tool steels were used for simulation. The cutting tool was set to be idling under different rotation speed including 5000r/min, 10000r/min, 15000r/min, 20000r/min and 30000r/min, respectively. Results show that for the two kinds of materials, the security cutting speed is 15000r/min to Al alloys and 20000r/min to 40CrMo tool steels respectively. Under the same cutting condition, 40CrMo tool steels have higher shear stress than that of Al alloys, in hence they have higher security rotation speed.

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Kim, Jung-Hoon, and Hye-Yeong Chun. "A Numerical Simulation of Convectively Induced Turbulence above Deep Convection." Journal of Applied Meteorology and Climatology 51, no. 6 (June 2012): 1180–200. http://dx.doi.org/10.1175/jamc-d-11-0140.1.

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AbstractAt 1034 UTC 2 September 2007, a commercial aircraft flying from Jeju, South Korea, to Osaka, Japan, at an altitude of approximately 11.2 km encountered severe turbulence above deep convection. To investigate the characteristics and generation mechanism of this event, the real atmosphere is simulated using the Weather Research and Forecasting model with six nested domains, the finest of which is a horizontal grid spacing of 120 m. The model reproduces well the observed large-scale flows and the location and timing of the turbulence along the evolving deep convection. Three hours before the incident, isolated deep convection with two overshooting tops develops in a warm area ahead of the cold front in the southwestern region of the turbulence. As the deep convection moves with the dominant southwesterly flow toward the incident region, its thickness shrinks significantly because of weakening of upward motions inside the convection. Twenty minutes before the incident, the dissipating convection disturbs the southwesterly flow at the incident altitude, enhancing local vertical wind shear above the dissipating convection. The leading edge of the cloud stretches toward the lee side because of shear-induced y vorticity, finally overturning. This activates turbulence and vertical mixing at the cloud boundary through convective instability in the entrainment process. While the dissipating convection, its thickness still shrinking, continues to move toward the observed turbulence region, the turbulence generated at the cloud interface is advected by the dominant southwesterly flow, emerging about 1–2 km above the dissipating convection and intersecting the aircraft’s flight route at the incident time.

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Saengsaen, Sirada, Chawin Chantharasenawong, and Tsung-Liang Wu. "A 2–D Mathematical Model of Vortex Induced Vibration Driven Bladeless Wind Turbine." MATEC Web of Conferences 291 (2019): 02007. http://dx.doi.org/10.1051/matecconf/201929102007.

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Bladeless wind turbine (BWT) is a flexible cylindrical structure that extracts energy from wind by utilising vortex-induced vibration (VIV) - aerodynamic forces and the resulting structural vibration. This work focuses on taking possible advantage of the increase in lift forces in the similar fashion to birds flying in a V-formation. The purposes of the present study are 1) to study the flow pattern and characteristic around two BWTs which are cylindrical structures in the same flow field and 2) to study the extra lift force generation of the system. 2–D CFD models are used to simulate flow of stationary cylinder of BWTs at Re = 105. The two different turbulent models, Reynolds Averaged Navier-Stokes shear-stress transport k(RANS–SST k) and Detached Eddy Simulation shear-stress transport k(DES–SST k) are investigated. The results show that only DES–SST kgives converged results, therefore, DES–SST kis selected for the additional studies of two cylindrical structures. From 2–D CFD simulation, the one BWT in flow field case produces lift coefficient 0.851. In the case of two BTWs in same flow field (BWT no.2 is located at x = 3D, y = 0D, directly downstream of two cylinders), BTW no.1 and BWT no.2 show greater lift coefficients of 0.893 and 1.841, respectively. This result indicates that the kinetic energy generation of the downstream BWT in the two BWTs system in this study is greater than the baseline BWT with an increase of 116% of lift. Further work is needed to determine the optimum location of the behind wind turbine for greater lift and result to increasing of energy produce of the system.

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Foloni-Neto, Herminio, Rolf Lueck, Yoshiro Mabuchi, Hisato Nakamura, Masakazu Arima, and Hidekatsu Yamazaki. "A New Quasi-Horizontal Glider to Measure Biophysical Microstructure." Journal of Atmospheric and Oceanic Technology 31, no. 10 (October 1, 2014): 2278–93. http://dx.doi.org/10.1175/jtech-d-13-00240.1.

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Abstract This study describes the development of a new tethered quasi-horizontal microstructure profiler: the Turbulence Ocean Microstructure Acquisition Profiler–Glider [TurboMAP-Glider (TMG)]. It is a unique instrument, capable of measuring ocean microstructure (temperature and turbulent velocity shear), chlorophyll, and turbidity simultaneously through a quasi-horizontal perspective. Three field experiments were carried out near Joga-shima, Japan, to test the TMG flight performance, and those results as well as comparisons with a laser-based vertical profiler, TurboMAP-L (TM), are described here. The TMG was capable of flying with an angle of attack of less than 25° and was reasonably stable for up to 300 m horizontally over 100-m depth. Some new and relevant empirical results about quasi-horizontal application of high-resolution chlorophyll-a fluorescence sensors are presented. The ratio between the Thorpe length scale and the Ozmidov length scale was used as a tracer to demonstrate that most of the TMG density inversions are due to horizontal variability and not to vertical overturning. These waveform structures are probably due to the horizontal inhomogeneity of the density field and are likely caused by internal waves.

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Gawron, Valerie J., and Jeff Peer. "Evaluation of Airplane Upset Recovery Training." Aviation Psychology and Applied Human Factors 4, no. 2 (July 1, 2014): 74–85. http://dx.doi.org/10.1027/2192-0923/a000059.

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Loss of control is one of the leading factors in hull losses and fatalities in airline aircraft. To reduce the risk of this type of accident, four types of airplane upset recovery training have been developed (ground-based flight simulation, aerobatic flight, ground-based flight simulation with aerobatic flight, and in-flight simulation). These were evaluated during in-flight reenactments of fatal, hull loss airline airplane accidents. A between-subjects design, with five groups of eight nonmilitary pilots flying in their probationary year for airlines, was used to evaluate these types of training. Each group had received a different type of training, including one group that had received no training. Each pilot completed a 1.4-hr evaluation flight in which eight airplane upsets were introduced. For some scenarios, training clearly works – specifically, 39 evaluation pilots recovered from the wind shear upset. But few evaluation pilots used bank to change the direction of the lift vector to recover from nose-high upsets. Further, very few used differential thrust to recover from rudder- or aileron-induced roll upsets (use of alternate controls). Finally, recovery attempts from icing-induced stalls were generally inadequate.

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Tsukagoshi, Hideyuki, and Yuichi Osada. "Soft Hybrid Suction Cup Capable of Sticking to Various Objects and Environments." Actuators 10, no. 3 (March 5, 2021): 50. http://dx.doi.org/10.3390/act10030050.

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A universal suction cup that can stick to various objects expands the areas in which robots can work. However, the size, shape, and surface roughness of objects to which conventional suction cups can stick are limited. To overcome this challenge, we propose a new hybrid suction cup structure that uses the adhesive force of sticky gel and the suction force of negative pressure. In addition, a flexible and thin pneumatic balloon actuator with a check valve function is installed in the interior, enabling the controllable detachment from objects. The prototype has an outer diameter of 55 mm, a weight of 18.8 g, and generates an adsorption force of 80 N in the vertical direction and 60 N in the shear direction on porous walls where conventional suction cups struggle to adsorb. We confirmed that parts smaller than the suction cup and fragile potato chips are adsorbed by the prototype. Finally, the effectiveness of the proposed method is verified through experiments in which a drone with the prototypes can be attached to and detached from concrete walls and ceilings while flying; the possibility of adsorption to dusty and wet plates is discussed.

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Martin, Samuel, and Bharat Bhushan. "Discovery of riblets in a bird beak ( Rynchops ) for low fluid drag." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2073 (August 6, 2016): 20160134. http://dx.doi.org/10.1098/rsta.2016.0134.

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Riblet structures found on fast-swimming shark scales, such as those found on a mako shark, have been shown to reduce fluid drag. In previous experimental and modelling studies, riblets have been shown to provide drag reduction by lifting vortices formed in turbulent flow, decreasing overall shear stresses. Skimmer birds ( Rynchops ) are the only birds to catch fish in flight by flying just above the water surface with a submerged beak to fish for food. Because they need to quickly catch prey, reducing drag on their beak is advantageous. For the first time, riblet structures found on the beak of the skimmer bird have been studied experimentally and computationally for low fluid drag properties. In this study, skimmer replicas were studied for drag reduction through pressure drop in closed-channel, turbulent water flow. Pressure drop measurements are compared for black and yellow skimmer beaks in two configurations, and mako shark skin. In addition, two configurations of skimmer beak were modelled to compare drag properties and vortex structures. Results are discussed, and a conceptual model is presented to explain a possible drag reduction mechanism in skimmers. This article is part of the themed issue ‘Bioinspired hierarchically structured surfaces for green science’.

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Kim, Yoon Keon, and Woo Chun Choi. "Ricochet of steel spheres on sand with varying water content." Advances in Mechanical Engineering 12, no. 12 (December 2020): 168781402097728. http://dx.doi.org/10.1177/1687814020977285.

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The explosion of a building generates plenty of debris that flies far away. The flying debris is hazardous because it contains large amounts of kinetic energy. Therefore, determining the safety distance from the debris is essential. However, debris ricochet that collides onto the ground affects the safety distance because the ricochet phenomenon is influenced by the condition of the medium. In this study, experiments and finite element analysis were performed to investigate the ricochet based on the water content of sand. From a direct shear test, the internal friction angle and cohesion of sand were obtained based on the water content. The effects of internal friction angle and adhesion on the yield stress and ricochet were investigated. The results indicated that as the water content increased, the internal friction angle increased and then decreased, and the cohesion continued to decrease. The yield stress was proportional to the internal friction angle and inversely proportional to adhesion. Therefore, lower yield stress resulted in deeper penetration of debris, leading to higher energy loss, which increased the kinetic energy loss factor. Thus, the condition of the medium should be considered for setting a proper safety distance suitable for the surrounding environment of the building.

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Yaakub, M. F., A. A. Wahab, Mohammad Fahmi Abdul Ghafir, Siti Nur Mariani Mohd Yunos, Siti Juita Mastura Mohd Salleh, Qamarul Ezani Kamarudin, and Mohd Fikri Mohd Masrom. "The Aerodynamics Investigation of Vortex Trap on Helicopter Blade." Applied Mechanics and Materials 225 (November 2012): 43–48. http://dx.doi.org/10.4028/www.scientific.net/amm.225.43.

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During helicopter forward flight, the retreating blade revolves at high angle of attack compared to advancing blade in order to balance the lift and also to stabilise the helicopter. However, due to the aerodynamics limitations of the retreating blade at forward flight, stall may occur at high angle of attack compared with the advancing blade. This phenomenon is dangerous for pilot when controlling and balancing the helicopter while flying against strong wind. This paper investigates the capabilities of introducing multiple vortex traps on the upper surface of the helicopter airfoil in order to delay the stall angle of retreating helicopter blade. Blade Element Theory (BET) was applied to scrutinize the lift force along the helicopter blade. Computational Fluid Dynamic (CFD) analyses using the Shear-Stress Transport (SST) turbulence model was carried out to investigate the effect of groove on delaying the stall and to predict the separation of flow over the airfoil. Based on the CFD analyses, the optimization of the groove was done by analyzing the numbers and locations of the grooves. Finally, the results from both BET and the CFD analyses were utilised to obtain the lift force achieved by the vortex trap. The study showed that the presence of multiple vortex traps has successfully increased the lift coefficient and most importantly, delaying the stall angle.

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Hawkins, Jeffrey D., Jeremy E. Solbrig, Steven D. Miller, Melinda Surratt, Thomas F. Lee, Richard L. Bankert, and Kim Richardson. "Tropical Cyclone Characterization via Nocturnal Low-Light Visible Illumination." Bulletin of the American Meteorological Society 98, no. 11 (November 1, 2017): 2351–65. http://dx.doi.org/10.1175/bams-d-16-0281.1.

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Abstract Global monitoring of tropical cyclones (TC) is enhanced by the unique capabilities provided by the day–night band (DNB), a sensor included on the Visible Infrared Imaging Radiometer Suite (VIIRS) flying on board the Suomi National Polar-Orbiting Partnership (SNPP) satellite. The DNB, a low-light visible–near-infrared-band passive radiometer, can leverage unconventional (i.e., nonsolar) sources of visible light illumination such as moonlight to infer storm structure at night. The DNB provides an unprecedented capability to resolve moonlit clouds at high resolution, offering numerous potential benefits to both operational TC analysts and researchers developing new methods of monitoring TCs occurring within the largely data-void tropical oceanic basins. DNB digital data provide significant enhancements over older nighttime visible data from the Defense Meteorological Satellite Program’s (DMSP) Operational Linescan System (OLS) by leveraging accurate calibration, high sensitivity, and sub-kilometer-scale imagery that covers 2–3 times the moon’s lunar cycle than the OLS. By leveraging these attributes, DNB data can enable the use of automated objective applications instead of subjective image interpretation. Here, the authors detail ways in which critical information about TC structure, location, intensity changes, shear environment, lightning, and other characteristics can be extracted when the DNB data are used in isolation or in a multichannel approach with coincident infrared (IR) channels.

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Wang, Shen, Hani Mitri, Huamin Li, Dongyin Li, and Wen Wang. "Study of SCA-Induced Rock Crack Propagation under Different Stress Conditions Using a Modified Cohesive Element Method." Advances in Civil Engineering 2018 (November 1, 2018): 1–16. http://dx.doi.org/10.1155/2018/7936043.

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When inducing cracks, soundless cracking agents (SCAs) do not generate vibration, harmful gas, dust, nor flying rock fragment, making them suitable for hard rock roof breaking, rock burst prevention, oil or gas reservoir stimulation, and building demolition. In this study, SCA-induced crack initiation and propagation in different stress conditions were modelled using a modified cohesive element method. A new traction-separation law for describing rock compressive shear strength was proposed. The crack length and direction in bidirectional isobaric and unequal stress fields were analyzed in detail. The crack initiation pressure and the incremental ratio of crack length to SCA expansion pressure were proposed as two indicators to evaluate the difficulty in rock breaking in deep underground. Results indicate that (1) the modified cohesive element method used in this study is feasible to model crack propagation in deep rocks; (2) the maximum expansion pressure of SCAs depends on rock elastic modulus and geostress field and should be measured under a condition similar to deep underground prior to SCA borehole spacing design; when using the SCAs with a maximum expansion pressure of 100 MPa in 600 m underground, the suggested borehole spacing is less than 220 mm; and (3) σ3 dominates the crack initiation pressure while the principal stress ratio σ3/σ1 and notch direction control the direction of crack propagation.

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Journal articles on the topic 'Flying shear'

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