Papers by Keyword: Curvature

Abstract: This paper proposes a method of using the B-spline mathematical model to plan high smoothness curve trajectories with heading condition through given waypoints for autonomous underwater vehicles (AUVs) in particular and ships with rudder systems in general. In addition, this paper examines some of the physical limitations of this vehicle, which lead to some binding conditions of the trajectory. Besides, the paper applies B-spline approximation method to reduce the curvature of the trajectory, when waypoints are too close and we do not need to go through exactly these waypoints in the 2D plane. Finally, this paper also proposes the genetic algorithm application with some modifications to solve the optimization of B-spline path length with constraint in turning radius of the vehicle.

Abstract: Elastoplastic deformation on the presses and high-temperature heating of the steel sheet cause the large residual stresses in the sheet’s and bar’s wall. The technological operations of the obtaining of metal products, their shape and linear dimensions strongly affect on the distribution within the metal and the maximum values of residual stresses. The uneven cooling of various parts of the sheet and bar, obtained by bending, stamping and forging, also leads to the large residual stresses inside the metal. The greatest residual stresses occur in the weld area, where there is a strong heterogeneity of mechanical and physical properties of the metal due to uneven heating and cooling. Below the new analytical method for calculating of the residual stresses of a round steel bar in the elastoplastic bending is obtained. This method takes into account the diameter of the bar, as well as the modulus of elasticity, the yield strength and the hardening modulus of steel’s bar.

Abstract: In the article the results of the eccentrically compressed reinforced concrete element calculation operating under the dynamic loading in fire conditions are shown. The calculation of the compressed reinforced concrete element was carried out, taking into account the conducted experimental studies. The calculation showed that, depending on the temperature effects, the curvature of the reinforced concrete element in stages I and II decreases while the class concrete, which varies from 28.9% to 55%, is increasing. When the temperature reaches 250⁰, the cracking moment and the moment of internal forces at the end of the stage II are reduced to 22% with respect to these forces at normal conditions. With increasing temperature, the dynamic stiffness of the element in the stage I is reduced by 29.3%.

Abstract: The inside profile curves data points of vole’s clawed toes had been analyzed. The least squares fitting method was used to analyze the inside profile curves data points for fitting mathematical model and fitted curves were expressed by polynomial equations. According to the curvature of fitted curves, the geometrical characteristics of the fitted curves were summed up. The variation curvature of inside profile curve from the second clawed toe was similar to the third and fourth. They both had two maximum vales and two minimum vales, and the larger maximum vales were at the tiptoes, the smaller maximum vales were at the end of toes’ babies. The fifth clawed toe had only one maximum vale and two minimum vales. And one of the minimum vales was at the tiptoe, another was at the end of toe’s baby. The maximum vale was in the center of the fifth clawed toe’s body. This concluded that the geometrical characteristics of inside profile curves were very important for vole’s digging ability. This provided design reference of energy-saving and high efficient for structure design of soil contact surface of tillage components.

Abstract: It is of difficulties in measuring welding deformation because of high temperature and the light intensity. In this paper the traditional welding deformation measurement method are reviewed,and the features and limitations of each method were analyzed,and then focused on the non-contact optical measurement method based on the WDIC. In this paper, a noncontact measurement method based on WDIC (weak digital image correlation) is proposed to obtain full-field buckling deformation in the whole welding and cooling process. And the matching difficulties which are caused by weak speckle performance and the large deformation around the solder joint are overcome through the method of piecewise benchmarks based on the continuity of adjacent states. Based on the above methods, the experiment of the sheets welding with three different curvatures was carried on and the following conclusions are summarized based on the analysis of the buckling deformation. The formation mechanisms of out-of-plane deformation in welding area were clarified based on the experimental results. First, low carbon steel occurs buckling deformation with dish shape in welding process and saddle shape in cooling process. Second, the curvature of the sheet has a great influence on the result of the welding. The sheet with a bigger curvature has the smaller displacement in Z direction in the welding process and the smaller transverse strain in the area adjacent to the welding seam. Those measuring results can be used to analyze the influence factors of welding deformation, control the welding deformation and verify the welding numerical simulation.

Abstract: Microdamage, viscoplastic and viscoelastic strain development in 90-layers of cross-ply laminates subjected to tensile loading is studied on unsymmetrical GF/EP laminates measuring the thermal curvature change. All three phenomena partially compensate for the effect of the thermal mismatch reducing the residual stress (specimen curvature). The viscoplastic strain contribution to curvature change is the largest whereas the effect of transient viscoelasticity is the smallest. Damage is included in the analysis through its effect on the effective transverse modulus of the 90-layer.

Abstract: The main goal of the investigation is to determine key technological parameters, necessary for producing required curvature of sheets up to 4000 mm in width with the required mechanical properties. Investigation into dynamics of the process' main technological parameters allowed it to define its three characteristic stages: asymmetric rolling, asymmetric rolling in combination with initial unsettled plastic bending, and asymmetric rolling combined with settled plastic bending. It was found out that the intensity of the deformations changes unevenly, depending on the height of the deformation zone, on all three stages, with its highest value being in the lower part of the sheet, and with the lowest value being in its center. In the second stage, the intensity of the deformation abruptly increases, and a significant asymmetry on the sheet thickness occurs. In the third stage, the non-uniformity of the intensity deformations fields decreases. Similar results can be also observed for stress intensities. Casings on two converters were produced and installed in the oxygen-converter plant.

Abstract: The prescribed surface curvature distribution blade design (CIRCLE) method optimises aerofoils and blades by controlling curvature continuity and slope of curvature distribution along their surfaces. The symmetrical NACA0012 exhibits a surface curvature discontinuity at the leading edge point, and the non-symmetrical E387 exhibits slope-of-curvature discontinuities in the surface. The CIRCLE method is applied to both aerofoils to remove both surface curvature and slope-of-curvature discontinuities. Computational fluid dynamics analyses are used to investigate the curvature effects on aerodynamic performance of the original and modified aerofoils. These results are compared with experimental data obtained from tests on the original aerofoil geometry. The computed aerodynamic advantages of the modified aerofoil are analysed in different operating conditions. The leading edge singularity of NACA0012 is removed and it is shown that the surface curvature discontinuity affects the aerodynamic performance near the stalling angle of attack. The discontinuous slope-of-curvature distribution of E387 influences the size of the laminar separation bubble at lower Reynolds numbers, and it affects the inherent profile of the aerofoil at higher Reynolds numbers. It is concluded that the surface curvature distribution of aerofoils has a significant effect on aerofoil aerodynamic performance, which can be improved by redesigning the surface curvature distribution of the original aerofoil geometry.

Abstract: An experiment sturdy has been carried out for jet impingement cooling on the spherically convex surface is the development of mechanism. The effect of curvature, Space between jet exit and target surface, and Reynolds number on heat transfer is investigated for around air jet on hemispherical surface. The flow at the jet exit has fully developed velocity profile. A uniform heat flux boundary is created on the heated surface. The experiments are performed for 5000<Re<25000, 2<L/d<10, and jet diameters ranging from 1.3, 2.1, 3.4, 4.0 and 5.2 cm. In the mean time effect of curvature on local heat transfer is negligible at the wall jet region corresponding to r/d>0.5. From the experimental results the variation of the D/d ratio with local Nusselt number (Nu_st) for various Reynolds numbers and various L/d ratios are plotted. The results show that Nu_st increase with increase in curvature and the effect of the curvature will high at high Reynolds number. i.e. Nu_st at Re=25000 is 25% higher than at Re= 5000 This may be attributed to an increase in curvature increases acceleration, & size of three dimensional counter rotating vortices at stagnation point and the increment of Reynolds number increases the jet momentum, and also enhances the vortices creation. Nu_st is peaking in the L/d ratio of 6 because of high turbulence intensity as this distance.

Abstract: Thin metal films on polymeric materials have been widely used in electronic devices. Their total mechanical performance is determined by the mechanical property of each material, the thickness and size of film and substrate, their interface properties in addition to the temperature change during production and use. In this paper, stress and strain distribution of gold thin film on polycarbonate substrate subjected to tension and cooling was analyzed using the finite element method. The effect of cracking in thin film on the stress and strain distribution was also discussed.