Effects of selective laser melting process parameters on 3D-printing of Ti6Al4V/ST316L composite material and their optimization using response surface methodology

The mechanical properties of Ti6Al4V and ST316L bone implants make them superior to natural bone, which results in fewer contact points with the bone. Different manufacturing processes, such as selective laser melting (SLM), may result in different mechanical properties between Ti-6Al-4V and ST316L implants. Sustainable development for the composite implants was optimized (SLM) in this study to minimize their compressive strength and Young's modulus. A three-dimensional printing process using SLM was optimized based on laser power, hatch distance, laser velocity, and ST316L weight percentage. Composite implants made from titanium alloys and steel alloys were evaluated using response surface methodology (RSM). ST316L composition has been found to influence the mechanical properties of composites in a significant manner, based on the results of parameter optimization. Using Ti6Al4V/ST316L as a biomaterial in knee joint prostheses is possible

Fixed and rotary wing transonic aerodynamic improvement via surface-based trapped vortex generators

A novel passive flow control concept for transonic flows over airfoils is proposed and examined via computational fluid dynamics. The control concept is based on the local modification of the airfoil's geometry. It aims to reduce drag or to increase lift without deteriorating the original lift and/or drag characteristics of the airfoil, respectively. Such flow control technique could be beneficial for improving the range or endurance of transonic aircraft or for mitigating the negative effects of transonic flow on the advancing blades of helicopter rotors. To explore the feasibility of the concept, two-dimensional computational fluid dynamics simulations of a NACA 0012 airfoil exposed to a freestream of Mach 0.7 and Re = 9 × 106 as well as of a NASA SC(3)−0712(B) supercritical airfoil exposed to a freestream of Mach 0.78 and Re = 30 × 106 were conducted. The baseline airfoil simulations were carefully verified and validated, showing excellent agreement with wind tunnel data. Then, 32 various local geometry modifications were proposed and systematically examined, all functioning as a trapped-vortex generator. The surface modifications were examined on both the upper and lower surfaces of the airfoils. The upper surface modifications demonstrated remarkable ability to reduce the strength of the shockwave on the upper surface of the airfoil with only a small penalty in lift. On the other hand, the lower surface modifications could significantly increase the lift-to-drag ratio for the full range of the investigated angles of attack, when compared to the baseline airfoil

Investigating the impact of using CFD generated unsteady mach number dynamic stall data for numerical rotor analysis of helicopter forward flight

This paper investigates whether the accuracy of the blade airload prediction by current comprehensive rotor analysis methods are compromised by the exclusion of the unsteady nature of the freestream velocity in semi-empirical dynamic stall models. First, the current industry practice of rotor analysis utilizing semi-empirical dynamic stall models is reviewed, and the deficiencies in the accuracy of this method is demonstrated by comparing its results to the flight test data obtained from the UH-60A Airloads Program. To study the impact of including the unsteady nature of the freestream in dynamic stall, Computational Fluid Dynamics (CFD) was used to generate the unsteady 2D dynamic stall aerodynamic data representative of the conditions in the steady-level flight validation case (CT/σ = 0.129, μ = 0.24) from the UH-60A Airloads program whose counter designation is c9017. The CFD data served as inputs to the in-house rotor analysis code called Qoptr to generate blade airload results. The Qoptr blade airload results generated with the unsteady CFD dynamic stall data showed considerably better agreement with the flight test data than the results generated with semi-empirical dynamic stall models, especially in the sectional moment results