Papers by Keyword: Attack Angle

Abstract: Various studies have been carried out to understand the properties and the performance of Thermally Stable Diamond Composite (TSDC) when it is used as the rock cutting tools. Existing studies focused on the influences of uncertain TSDC material properties, and randomly varied rock strengths and thickness on the failure probability of cutting tips made of TSDC. It is found that the compressive strength of TSDC cutting tips is much higher than their tensile strength. As a result, the ability of a TSDC cutting tip to bear the resultant force applied along its axis is much greater than its ability to bear the resultant force perpendicular to its axis. However, the resultant angle during rock cutting processes varies greatly. This study focuses on the investigation of the impact of varied resultant force angles on the performance and failure characteristics of TSDC as a rock cutting tip using Monte Carlo simulations. The results show that the varied resultant angle can significantly influence the failure characteristics of the TSDC cutting tip with a fixed attack angle.

Abstract: The shock attack occurs at a railway vehicle circulation in a curve in which a discontinuous bend appears, mathematically represented by an angular point. In this point, shock angle produces an abrupt change of direction of the vehicle, respectively a dynamic shock force.The paper presents a mathematical model used to determine the dynamic force shock and its influence on vehicle guiding safety. The study was applied to the tank wagon on bogies for transportation of petroleum products, because such vehicles generally have derailed at circulation in curves in which have occurred accidentally discontinuous bends.It shows that the dynamic force may lead to an unacceptable increase of guiding force Y at leading axle of the vehicle, and therefore to overcome the (Y/Q)_lim, which defines the limit of derailment, Q being the load on the attacking wheel.The conclusions indicate constructive measures to be taken to ensure the safety of the vehicle guiding at circulation in curves.

Abstract: The wheel/rail profiles in different wear stages are measured using the apparatus of wheel-rail profile. The 3D elastic-plastic FEM contact models are established for the straight line and curves, in which attack angle is considered. Contact problems between the wheels in different wear stages and the worn rail are studied. Contact area, normal contact force, and equivalent Von Mises stress of different cases are analyzed. The obtained results show that the maximum equivalent Von Mises stress reduces and tends to be steady with the independent wheel wearing. Widening the track gauge can have an influence on the variation of wheel wear positions and the wear rules between wheel and rail. When the wheel with a certain attack angle contacts with rail, the maximum equivalent Von Mises stress appears at the contact region between the flange and rail side. The influence of attack angle on the wear between the wheel and rail is quite serious. It is very important to do the research for the further optimization and design of the wheel/rail profiles.

Abstract: The short life due to heavy wear is a bottleneck that limits the usage of mechanical excavators for hard rock cutting. Thermally stable diamond composite (TSDC) tipped cutting tools have the main advantages of good thermal stability, high wear resistance and ability to mine harder deposit compared to the conventional tungsten carbide (WC) tipped cutting tools. Super Material Abrasive Resistant Tool (SMART*CUT) based on TSDC tip has been developed by CSIRO to improve the effectiveness of cutting tools when dealing with hard deposit in mining and civil industries. In this study, the effects of attack angle and depth of cut on the cutting performance of SMART*CUT picks in different cutting orientations were investigated. A tri-axial dynamometer and a data acquisition system were used to measure the cutter forces. Normal force, cutting force and resultant angle were correlated with depth of cut and attack angle. Cutting performances were compared in different cutting orientations. The results would be beneficial to the selection of mechanical excavator motor and the optimization of cutting drum design to some extent.

Abstract: With the variation of the unsteady incoming flow and impeller rotation, when attack angles of the incoming flow is bigger than the critical angle of attack, there are unsteady separation and dynamic stall on the pressure surface of the impeller. Dynamic stalls are of common occurrence during wind turbines operation. And the aerodynamic characteristics and efficiency of wind turbine are largely affected by the dynamic stall.Therefore,the study of dynamic stall has a great significance over the optimization design of the wind turbine. The paper performs numerical simulation in the dynamic stalls of the 1.2MW horizontal-axis wind turbine, comparing the stalling difference between two-dimensional static and rotating condition. Besides, it also contrasts the stalling condition surface pressure coefficient along the different blade spanwise sections in rotating condition of the same attack angle. And the finding is that the attack angles in rotating condition is bigger than that in the two-dimensional static condition; the surface pressure coefficient is almost equivalent in static and rotating condition when attack angle is smaller than stalling angle; the peak of negative pressure at the leading edge of blade in rotating condition is far bigger than the peak of negative pressure in static condition when attack angle is smaller than static stalling angle. Airflow stall delay occurs when near the blade root. Stall delay phenomenon gradually weakened along the direction of blade radius.

Abstract: Mechanical excavators play an important role in mining and construction. An excavation machine cuts rocks using its cutterhead which is normally composed of a large number of cutting picks. These picks are installed on a drum with certain attack angles, tilt angles and skew angles. These angles, especially attack and tilt angles, will affect the forces acting on individual picks and the cutterhead. To ensure the reliability and productivity of the excavation machine, these angles have to be kept in their optimal values. However, in manufacturing, these three types of angles cannot be set simultaneously. They have to be respectively set one after another. As a result, the angle which is set previously will be changed by the angles which are determined after it. Understanding the relationship between the values of the final angle and the designed angle is important for optimizing drum and pick design. This paper develops a formula for quantitatively analyzing this relationship, with the research scope limited to attack angle and tilt angle only as the first stage of the study.

Abstract: In this paper, we investigate an underwater vehicle with two rudders suitable for working in Kuroshio near the eastern Taiwan, where the flow field of ocean current is less than 1.0m/sec. Lift and drag forces of the underwater vehicle submerged in the sea were calculated at different attack of angles and rudders by using finite element method. An on-site experiment with a prototype vehicle was also conducted located on Hsinta Fishing Harbor. Results show that lift force for the rudder of prototype vehicle near the sea surface is only 60% of theoretical calculations. To reduce the turbulence effect, the position of rudders in the front and the rear for the underwater vehicle should not be at the same level. Drag forces increase tremendously with increasing attack of angles compared with the effect of rudder’s quantity. The power-free underwater vehicle has been built and controlled steadily at 0.6~0.7m/sec flow velocity, suitable for carrying generators in Kuroshio.

Abstract: The purpose of this paper is to find the optimum design attack angle for fixed-pitch variable-speed wind turbine blade design, given the base-line wind turbine and the blade airfoil. Aerodynamic characteristics, i.e. lift and drag coefficients and lift to drag ratio, of the wind turbine, are analyzed. Two design attack angles along with the base-line attack angle (with maximum lift to drag ratio) are selected for the wind turbine blade design exercise. Blade design outcomes are analyzed and compared along with load performance and power performance. This paper is possibly the first attempt to determine the optimized design attack angle for maximizing annual energy production, given the base-line wind turbine and the blade airfoil.

Abstract: In order to analyze the performance of a certain FSAE racing car with rear wing at different attack angles by virtual prototyping technology. The multi-body model of a FSAE racing car which takes non-linear factors into consideration was built by applying ADAMS/Car. The correctness of the model is verified by comparison with the actual experiment result. By the simulation of the air resistance and lift characteristics of the rear wing, a feasible method to building the aerodynamic characteristics of the rear wing in multi-body model was proposed. Based on these, the crosswind stability of FSAE racing car with rear wing at different attack angles was analyzed, the result shows that the effect of crosswind is reduced with the increase of the attack angle of the rear wing.

Abstract: Flow forming is one of the cold forming process which is used for hollow symmetrical shapes. In this paper, the forward flow forming process is simulated using the finite element method and its results are compared with the experimental process. The variation of thickness of the sample is examined by the ultrasonic tests for the five locations of the tubes. To simulate the process, the ABAQUS explicit is used. The effects of flow forming variables such as the angle of rollers and rate of feeding of rollers, on the external variables such as internal diameter, thickness of tube and roller forces are considered. The study showed that the roller force and surface defects were reduced with low feeding rate and low rollers attack angles. Moreover, the sample internal diameter increased at low feeding rate and low rollers attack angles. The optimum variables for flow forming process were also obtained.