Increase Of Speed Ratio Research Articles

Analytical and experimental investigations on the mechanisms of surface generation in micro grinding

Micro grinding is an emerging technology for producing structured surfaces on hard and brittle materials. A micro pencil grinding tool (MPGT) consists of a layer of superabrasive grits, bonded to a solid cylindrical surface. Randomly distributed and geometrically undefined grits interact with the workpiece surface at random positions. These random grit positions and protrusions lead to a difference in the size of undeformed chips. This study presents an analytical method to understand the undeformed chip geometry, that considers grit kinematics. Kinematic simulation of grit trajectory paths in longitudinal direction showed a reduced number of active grits in micro grinding with an increase in speed ratio and with reduced tool dimensions. MPGTs with different diameters, grit sizes, and planar grit densities have been used to perform the experiments on a 16MnCr5 hardened steel material. The influence of maximum radial height grits on surface generation in micro grinding has been verified experimentally for up and down grinding modes. Microscopic observations of ground surfaces have shown the distinct differences between up and down grinding modes, which are similar to the surface generation in milling processes. Moreover, the formation of linear grooves with uniform depth and width unlike conventional surface grinding at lower speed ratios indicated the influence of individual grits on surface generation. Trajectory path simulation results have also shown the same observation.

Conditions for Wall Thickness Reduction in Hollow Sinking of SUS304 Tubes With Drawing Speed Control in Entrance and Exit Sides of Die

Abstract In this study, the conditions for wall thickness reduction in hollow sinking were obtained by tube drawing experiments in which the drawing speed ratio was controlled under three conditions (1.09, 1.11, and 1.14). These conditions have not been found in the history of hollow sinking. The results of the experiment and the theoretical formulas indicate that the geometric condition is obtained from the figure of the ratio of inner diameter to outer diameter after drawing against that ratio before drawing. Furthermore, the ratio of the inner diameter to the outer diameter after drawing must be above the constant wall thickness line derived from the cross-sectional change. To satisfy this geometric condition, the drawing speed ratio must be larger than the threshold value, which is obtained from the ratio of the inner diameter to the outer diameter before drawing, and the reduction of the die. However, the value of the back stress approaches that of the strength of the tube when the drawing speed ratio increases. A simple dynamical model shows that parameters other than the drawing speed ratio do not significantly decrease the back stress during drawing. Therefore, the drawing speed ratio should be set such that the tube does not break.

NO Removal from Simulated Diesel Engine Exhaust Gas by Cyclic Scrubbing Using NaClO2 Solution in a Rotating Packed Bed Reactor

Experiments were conducted to remove NO from simulated flue gas in a rotating packed bed (RPB) reactor with NaClO2 as wet scrubbing oxidant and diesel exhaust gas as carrier gas. The effects of various operating parameters (rotational speed, solution pH, NaClO2 concentration, liquid-gas ratio, and NO and SO2 concentrations) on NO removal performance were investigated preliminarily. The results showed that with the increase of rotational speed, oxidant concentration, and liquid-gas ratio, NO removal efficiency increased obviously. NO removal efficiency increased largely with the decrease of solution pH, and a complete removal of NO could be attained at pH 4. NO concentration imposed little effect on NO removal efficiency while coexisting SO2 in exhaust gas could enhance NOx removal greatly.

Effect of Asymmetric Rolling on the Microstructure, Mechanical Properties and Texture Evolution of Mg–8Li–3Al–1Y Alloy

Asymmetric rolling was applied to dual phase Mg–8Li–3Al–1Y alloy with different speed ratio and rolling reduction. With increasing reduction at the same speed ratio the population of β-Li grains decreased with a feature of fibered grains along the rolling direction. As for different speed ratio under the same reduction, β-Li grains kept equiaxed, but α-Mg phase was first elongated and fibered and then transited to equiaxed small grains. The enhanced yield strength and tensile strength were achieved with the increase of rolling reduction and speed ratio. In particular, when speed ratio reached to 1:1.3 under the same rolling reduction (30%), the optimal mechanical properties were obtained. As for texture evolution, we found the basal texture was obviously weakened and some new weak texture was formed after asymmetric rolling. Interestingly, it was noted that the texture on the side of slow roll is distinct from that on the side of the fast roll due to the different rolling speed.

Microstructure and mechanical property improvement of X70 in asymmetrical thermomechanical rolling

Asymmetrical thermomechanical rolling (ATMR) process of API X70 microalloy steel was investigated to evaluate of rolling force and distribution of material property in the roll gap. Applying a user-defined VUMAT subroutine, the equations of material flow and microstructure kinetics, as material genome package, were implemented into finite element (FE) solver of ABAQUS for simulation of X70 multi-pass rolling. A rough rolling schedule was carried out to verify the accuracy of the material genome by evaluation of the computed rolling force of FE model and experimental results. Considering the interaction of the asymmetrical parameters such as rolls speed ratio (VA), pass height (PH) and rolls diameter ratio, it was found that coinciding of the high level PH with high range of rolls speed ratio and diameter ratio lead to a rise of the rolling force. Strain distribution of the roll gap indicated that an increase of the rolls speed ratio can improve the dislocation density and the strength of rolled material. The study of strain distribution contour in the length of slab thickness revealed that the homogeneity of deformation can be enhanced in the mechanism of asymmetrical rolling of microalloy steel. Experimental test reveals that in asymmetry condition in TMR process of X70, increase of the speed ratio (1.02–1.05) in roughing passes leads to a considerable grain refinement and growth of yield strength and ultimate tensile strength of 3.12 and 2.05% of final plate structure, respectively.

Mechanical and Fatigue Strength Assessment of Friction Stir Welded Plates of Magnesium Alloy AZ31B

Abstract Light-alloys play a significant role in saving weight in automotive and aerospace industries; however, a few joining methods guarantee mechanical and fatigue strengths for high performance application. Even conventional arc welding processes do not offer constant quality joints. Therefore, this study uses an alternative solid-state welding process, friction stir welding (FSW), to analyze post processing microstructures and assess mechanical and fatigue strength. Magnesium alloy AZ31B plates were welded using different welding parameters in a dedicated FSW machine. The effect of the spindle speed (ω) and welding speed (ν) on the microstructure, the tensile strength and fatigue were studied. The stirred zone (SZ) at the FS-welded joints presented a microstructure composed by homogeneous equiaxial grains, refined by dynamic recrystallization. A rise in grain size, weld bead width, tensile and fatigue strengths with the increase of speed ratio (ω/ν) were observed. Results of the fatigue and mechanical strength here presented outperformed results from welds made with conventional milling machines.

Analysis of strain variation in cross shear zone of plate during snake hot rolling

In order to study the distribution of equivalent and shear strain of aluminum alloy plate during snake hot rolling, several coupled thermo-mechanical finite element models (FEM) are established. Effects of speed ratio and offset distance on strain distribution of the plate are analyzed. The length of cross shear zone is defined to have a better understanding of the deformation characteristic in cross shear zone, which is the essential difference from symmetrical rolling in deformation zone. The results show that the equivalent strain and shear strain of lower part both increase with the increase of speed ratio, while the upper part decreases; the equivalent strain through the whole thickness decreases with ascending offset distance, while the shear strain of lower part increases. The length of cross shear zone quickly increases with ascending speed ratio and slightly decreases with ascending offset distance. The “positive” and “negative” cross shear zones are formed with the increase of speed ratio and offset distance, respectively. The value of the sensitivity coefficient of speed ratio is an order of magnitude bigger than the offset distance. However, the shear strain at center point increases with the ascending speed ratio and offset distance for different mechanism. As speed ratio increases, the asymmetry of the distribution of equivalent is becoming larger and the shear strain is generated in the same direction in cross shear zone. The FEM results agree well with experimental results.

Experimental study on material flow in cold rolling

Abstract Material flow in roll bite occurred during symmetric or asymmetric rolling of thin sheet was investigated by model rolling experiment in this study. The sheet samples with fine grids drawn by laser processing on longitudinal-thickness cross-section at the middle of the sheet width were used for the experiment to visualize material flow. By measuring the changes of roughness in the cross section after rolling, it was confirmed that the rolling was conducted practically in plane strain conditions in the cross section. Also the changes of vertical ruled lines before and after rolling reflect material flow throughout the roll bite. It clearly shows the characteristic that the inclination angle of the ruled line due to rolling increases monotonically as the different speed ratio increases. To compare the material flow of model rolling experiment, two dimensional steady-state rolling analyses using rigid plastic finite element (FE) method have been conducted. The profiles of the ruled line observed in the experiments have a good agreement with the calculated results. Also the calculated results of equivalent plastic strain reveal non-monotonical relations between the strain and the different speed ratio (i.e. maximal of the strain observed at certain different speed ratio). This qualitative discrepancy observed between the measured angles and the calculated strains in relation to the different speed ratio suggests that measurement of the angle of the ruled lines is not sufficient to characterize plastic strain.

Experimental investigation of fibre particles in a turbulent stirred tank with DPIV

In this paper, the experiments of fibre particles in turbulent solid-liquid two-phase flow fields using Digital Particle Image Velocimetry (DPIV) were conducted in a baffled tank stirred by standard six-blade Rushton. Fibre particles with different aspect ratios of 18.8, 25.0 and 37.5 are experimented with impeller speed from 100 to 400rpm, respectively. Both the orientations and the velocities of the fibre particles in the stirred tank under different conditions are obtained, as well as the turbulent velocity field. It is found that velocity of solid phase is very close to that of liquid phase. In the range of investigated solid concentration, liquid velocity exhibits close agreement at different solid concentrations. The velocities of two-phase flow are slightly greater than those of single phase. The influences of impeller speed, aspect ratio and solid concentration of fibre particles on the velocity field are discussed. With the increase of impeller speed, radial and axial particle velocities increase accordingly. With the increase of impeller speed and aspect ratio, orientation decreases slightly. Orientation seldom has any change with the increase of solid concentration. Meantime, the velocity profiles of solid-liquid two-phase flow with spherical particles are also compared with those of fibre particles. There is little discrepancy between velocities of fibre particle and spherical particle. All these can be used as the basis for industrial design as well as further simulation.

Analysis of temperature asymmetry of aluminum alloy thick plate during snake hot rolling

In order to study the temperature distribution of aluminum alloy thick plate during snake hot rolling, several coupled thermo-mechanical models using finite element method (FEM) were established. Effects of different factors on temperature distribution of the plate and the bending behavior due to temperature difference were analyzed. Temperature asymmetry coefficient was defined in this study. The results show that the temperature distribution of plate is asymmetrical and the temperature of the lower surface is higher than the upper surface during snake hot rolling, in which the maximum α can gd reach 58 °C/m. The asymmetric coefficient was increased with the increase of rolling velocity and speed ratio. Different ways of heat exchange play different roles in the temperature distribution. Friction heat and deformation heat play dominant role in hot rolling process and pass interval time and their weight influences were 47 and 69 %, respectively. The bending curvature is increased with the increase of temperature difference and pass reduction and decreased dramatically with the increase of initial thickness. The FEM results agree well with experimental results.

Measurement of the flow field around straight-bladed vertical axis wind turbine

The flow field around a vertical axis wind turbine (VAWT) is very complicated mainly due to the continuous variation of the geometrical angle of attack and resultant flow velocity to blade during rotation. This paper has attempted to compile the assessment study the flow field around a small straight-bladed VAWT. Two dimensional unsteady flows around the VAWT are investigated through the use of the Laser Doppler Velocimeter (LDV) system, operating at three different tip speed ratios in wind tunnel experiments. Meanwhile, the geometrical angles of attack and the resultant flow velocities are calculated using local wind velocity and direction. From the results of these experiments, it has been found that a wide low wind velocity field emerges in the wind turbine׳s internal region and continues into the downstream region. As the tip speed ratio increases, the area of low wind velocity also expands. Furthermore, moving from the upstream to the downstream region, the velocity deficit becomes greater in the free stream direction. Finally, large turbulence intensity is generated in the plane of wind turbine rotation.

Effect of Shear Deformation on Closure of a Central Void in Thin-Strip Rolling

Central voids or voids at the middle layer are often found in thin strips produced by twin-roll casting. These strips are in general so thin that they are unable to take a required reduction in thickness to close the voids. In the present investigation, equal-speed rolling and differential-speed rolling were compared to assess the effect of differential speed on closure of the voids by the rigid-plastic finite-element analysis. As a result, shear deformation developed in differential-speed rolling was found to reduce the reduction in thickness required for void closure. An increase in speed ratio, length of deformation zone, or friction coefficient at the interface expedited the progress in void closure. However, as the speed ratio exceeded thickness ratio, a portion of rolling power was dissipated extensively by excessive slip at the interface. Moreover, tensile stress developed which would cause cracks in the strip.

Maximum wind turbine performance at low tip speed ratio

Wind turbines can approach the Betz-Joukowsky limit on maximum power only at sufficiently high tip speed ratio: in practice, for ratios in excess of about seven. This paper analyses the performance of a turbine with an infinite number of blades as the tip speed ratio decreases to zero, beginning with the two traditional ways of determining the maximum power. The first is the “Glauert” optimization of the power extracted at every radius and the second is the “Betz-Goldstein” optimization of the whole rotor with the wake represented as a rigid helicoidal sheet of constant pitch. At high tip speed ratio, the two methods give very similar power and both asymptote to the Betz-Joukowsky limit. As the ratio approaches zero, the differences become significant. It is shown that Glauert's analysis does not account for effect of the varying pitch on the axial velocity. In addition, there is a large and unphysical energy extraction by a stationary rotor, and an unphysical constant circumferential velocity. Glauert's analysis, however, gives positive torque on a stationary rotor, which is necessary to start a wind turbine, but the torque at very low tip speed ratio seems too high. In contrast, the Betz-Goldstein analysis implies no torque on a stationary rotor but the circumferential velocity is zero on the axis of rotation. A modification is proposed to the Betz-Goldstein analysis to yield positive torque on a stationary rotor. The modified Betz-Goldstein torque coefficient never exceeds 1/2 and the power is less than the Glauert optimum. Finally, the analysis for varying pitch is corrected and the power maximized numerically. The modification applied to the Betz-Goldstein rotor is required to produce torque on the stationary rotor. The maximum torque coefficient was 0.55, and the maximum power was again less than the Glauert maximum. As tip speed ratio increases, the power from all methods asymptotes to the Betz-Joukowsky limit.

Bending analysis and control of rolled plate during snake hot rolling

In order to study the bending behavior of aluminum alloy 7050 thick plate during snake hot rolling, several coupled thermo-mechanical finite element (FE) models were established. Effects of different initial thicknesses, pass reductions, speed ratios and offset distances on the bending value of the plate were analyzed. ‘Quasi smooth plate’ and optimum offset distance were defined and quasi smooth plate could be acquired by adjusting offset distance, and then bending control equation was fitted. The results show that bending value of the plate as well as the extent of the increase grows with the increase of pass reduction and decrease of initial thickness; the bending value firstly increases and then keeps steady with the ascending speed ratio; the bending value can be reduced by enlarging the offset distance. The optimum offset distance varies for different rolling parameters and it is augmented with the increase of pass reduction and speed ratio and the decrease of initial thickness. A proper offset distance for different rolling parameters can be calculated by the bending control equation and this equation can be a guidance to acquire a quasi smooth plate. The FEM results agree well with experimental results.

DEVELOPMENT OF A SUGAR BEET TOPPER

The aim of this research is to develop and evaluate a topper unit for sugarbeet suitable for Egyptian conditions. Field experiments were carried out at El-Serw Agric. Res. Station, Damietta Governorate during 2013/2014 season. The performance of the developed topper unit was evaluated at different speed ratios of 0.007, 0.0076, 0.0080 and 0.0085 under knives positions; faced (F) and edged (E) and flails number solo (S) and doubled (D). Different flail lengths of 15, 20, 25 and 30 cm were tested. Over topping, under topping beets, un-topped beets, damaged beets, topping efficiency, actual field capacity, field efficiency, energy requirement and total costs were estimated. Due to increasing speed ratio increased actual field capacity and field eff. Both doubled and faced flails showed the best results under all treatments. Generally, the results recommended that topper unit should be used at speed ratio of 0.0085 with doubled-faced-flail (DFF) that recorded highest value of topping eff. (97.30%). On the other hand, the lowest value for over topping beet (2.4%), undertopping beets (2.8%), un-topped beets (2.2%) and damaged beets (2.77% ) were recorded. Hence, the best value of actual field capacity (0.92 fed/h) and field eff.(83.4%) were recorded at speed ratio of (0.0085). Energy requirement decreased by 13.22 % while total costs decreased by 78.27% comparing to manual topping costs. Flail length of 25 cm showed the desirable results with all treatments. Doubling and facing flails position had a high significant effect on all treatments.

Two-Sided Lid-Driven Cavity Flow at Different Speed Ratio by Lattice Boltzmann Method

In this study, the Lattice Boltzmann method has been used to investigate flow configuration of the two-sided lid driven cavity. The top and bottom lid were moved at the same direction but with different speed ratio which varies from 0 to 1. The range of Reynolds number is 100,400 and 1000. The results show that the increase in both speed ratio and Reynolds number give an effect on flow configuration of the cavity.

Research on Deformation Permeability Changing Law during Snake Rolling Process

In order to refine the microstructure and improve the mechanical properties of the thicker steel plate, the large rolling reduction should be conducted. Confined to the biting angle of rolling mill, the maximum press quantity is constant. The research indicates that shear stress produced in the deformation region during snake rolling process is helpful and the snake rolling method can be used in the thick steel plate production. The effective strain of steel plate with various roller speed ratio, plate thickness, fraction and roller speed was determined by numerical calculation method. By comparison, the effective strain changing law was obtained. The calculation results indicate that compared to traditional rolling process, the effective strain produced in the plate can be improved with the increase of roller speed ratio, and the deformation permeability can also be improved.

Vector modeling of robotic helical milling hole movement and theoretical analysis on roughness of hole surface

To avoid the machine problems of excessive axial force, complex process flow and frequent tool changing during robotic drilling holes, a new hole-making technology (i.e., helical milling hole) was introduced for designing a new robotic helical milling hole system, which could further improve robotic hole-making ability in airplane digital assembly. After analysis on the characteristics of helical milling hole, advantages and limitations of two typical robotic helical milling hole systems were summarized. Then, vector model of helical milling hole movement was built on vector analysis method. Finally, surface roughness calculation formula was deduced according to the movement principle of helical milling hole, then the influence of main technological parameters on surface roughness was analyzed. Analysis shows that theoretical surface roughness of hole becomes poor with the increase of tool speed ratio and revolution radius. Meanwhile, the roughness decreases according to the increase of tool teeth number. The research contributes greatly to the construction of roughness prediction model in helical milling hole.

Field performance of a pneumatic row crop planter equipped with active toothed coulter for direct planting of corn in wheat residue

In this research effects of active toothed coulter on planter penetration in semi-dried soils covered with previous wheat (triticum aestivum) residue was studied. Therefore, effects of three levels of speed ratio (coulter peripheral speed/tractor forward speed; 1.22, 2, 3) at two previous residue levels (baled and non-baled) and two modes of planter attachment (with and without row cleaner) on the corn (zea mays) planting depth and its uniformity, amount of surface residue, emergence rate index and seed spacings indices were investigated. Results showed that planting depth and its uniformity increased significantly with increasing speed ratio, so that desired planting depth was obtained at speed ratio of 2. The emergence rate index decreased with increase in speed ratio mainly due to increase in seeding depth at higher speed ratios. Miss and precision indices decreased in a significant manner with increase in the speed ratio. Other results showed that planting with row cleaner attachment into baled-out residue plots at speed ratio of 2 resulted in 31% decrease in miss and 30% decrease in precision indices as compared to control (inactive coulter). Quality of feed index at same conditions was 72%, the increase was up to 11% as compared to control. No significant difference was found between speed ratios of 2 and 3 for all the parameters studied. The results suggests that the row crop planter equipped with active toothed coulter and row cleaner attachment can be satisfactorily used for direct corn planting in hard soils covered with previous crop residues.

Analysis of Chamber Shape’s Influencing on Axial Force in Hydrodynamic Coupling

In order to research the law of chamber shape’s influencing on Axial Force in Hydrodynamic Coupling, flow field and axial force are numeric simulated at different chamber shapes in full filling rate by using separation solver, realizable k~ε model and PISO algorithm with CFD. The result shows that chamber shape has a greater impact on the axial force, and the influence weaks with the increase of speed ratio.