The Effect of Acceleration on the Separation Force in Constrained-Surface Stereolithography

Constrained-surface-based stereolithography has recently attracted much attention from both academic and industrial communities. Despite numerous experimental, numerical and theoretical efforts, the fundamental need to reduce the separation force between the newly cured part and constrained surface has not yet been completely solved. In this paper, we develop a fluid dynamics approach, proposed in our previous work, to theoretically model the separation force in 3D printing of a cylindrical part for flat and patterned windows. We demonstrate the possibility of separation force reduction with an accelerated movement of the printing platform. In particular, we investigate behaviors of transient parameter, its reduction rate, and separation force reduction with respect to elevation speed and time. The proposed approach involves deceleration and acceleration stages and allows to achieve the force reduction for the entire printing process. Finally, we provide implicit analytical solutions for time moments when switching between the stages can be done without noticeable increase of separation force and explicit expression for separation force in case of patterned window.

Criteria of Using Optimum Size Approach for Reduction of Axial Forces in Column in Multi Storied Building under Seismic Zone III

In India, every industry has its own importance to make the country shift towards its future goal. The construction industry plays a very significant role with the introduction of high-rise structures that has been increasing regularly. Beside this, the structure should be strong enough that each element should be economic and strong. The criteria of using optimum size approach for reduction of axial forces in column in multi storied building under seismic zone is a new idea. It reduces the size of beams and columns at the different levels of the building. On other hand, the structural weight should be minimized when the self-weight of the same will be reduced and proved to be an economic structure. In this project a G+13 Storey structure is analyzed using six different cases named as AFR Case A to AFR Case F assumed to be situated in seismic Zone III. The plinth area is in use as 625 m2 and all the cases have compared with each parameter. The project concluded that efficient Case is AFR Case C on comparing 6 maximum axial force reduction cases that ultimately reduce the overall cost of the project. Keywords: Axial forces, Columns, Strength, Durability, Software Models, High-Rise Structures

Teeth Arrangement and Pole–Slot Combination Design for PMLSM Detent Force Reduction

This paper introduces and investigates a new design method that employs both teeth arrangement and pole–slot combination to reduce the detent force of permanent magnet linear synchronous motors (PMLSMs) for precision position control. The proposed topology is a 10-pole, 12-slot-based PMLSM comprising two sections that significantly reduce the detent force without implementing a skewing design. It was analytically and experimentally confirmed that the proposed design effectively reduces detent force with a negligible sacrifice of mover length. The general characteristics and servo performance of the proposed PMLSM were experimentally examined and then discussed.

Tool Downscaling Effects on the Friction Stir Spot Welding Process and Properties of Current-Carrying Welded Aluminum–Copper Joints for E-Mobility Applications

According to the technical breakthrough towards E-Mobility, current-carrying dissimilar joints between aluminum and copper are gaining an increasing relevance for the automotive industry and thus, coming into focus of many research activities. The joining of dissimilar material in general is well known to be a challenging task. Furthermore, the current-carrying joining components in E-Drive consist of pure aluminum and copper materials with relatively thin sheet thickness, which are thermally and mechanically very sensitive, as well as highly heat and electrically conductive. This results in additional challenges for the joining process. Due to their properties, friction stir welding and especially fiction stir spot welding (FSSW) using pinless tools—i.e., as hybrid friction diffusion bonding process (HFDB) is more and more attractive for new application fields and particularly promising for aluminum–copper joining tasks in E-Mobility. However, the feasibility is restricted because of the relatively high process forces required during friction stir welding. Thus, to fulfill the high process and quality requirements in this above-mentioned application field, further research and process development towards process force reduction are necessary. This work deals with the application of the tool downscaling strategy as a mean of process force reduction in FSSW of thin aluminum and copper sheets for current-carrying applications in E-Mobility, where the components are very sensitive to high mechanical loads. The tool downscaling approach enables constant weld quality in similar process time of about 0.5 s despite reduced process forces and torques. By reducing the tool diameter from 10 mm to 6 mm, the process force could be reduced by 36% and the torque by over 50%. Furthermore, a similar heat propagation behavior in the component is observable. These results provide a good basis for the joining of E-Drive components with thermal and mechanical sensitive sheet materials using the pinless FSSW process.

Comparison of force decay pattern in orthodontic elastomeric chains and NiTi closed coil springs, affected by five different mouthwashes: An in vitro Study

Background: The aim of this study was to compare the force decay pattern of elastomeric chains and NiTi coil springs which were exposed to five different commercially available mouthwashes.Methods: In this in vitro study, 60 pieces of elastomeric chain (EC) and 60 NiTi closed coil springs (CS) were divided into 6 groups. The specimens were exposed to one of these mouthwashes twice a day for 60 seconds: Listerine, chlorhexidine, Orthokin, Persica, fluoride and artificial saliva as the control group. The elastomeric chains and NiTi springs were stretched so that they exert the initial force of 250 gr. Their force was measured on the 1, 7, 14 and 28 following days by means of a digital gauge.Results: Elastomeric chains and coil springs had force decrease over time, but EC' force reduction was greater with the highest reduction rate in the first week. However, in the CS group, the force decrease wasn't statistically significant in the first two weeks. After 28 days in the control groups, 49.8% of the initial force was remained in ECs while the value was 93.3% for CSs. In comparison between mouthwashes, in EC groups, in all mouthwashes except Persica, the remained force was statistically less than control group.Conclusion: Force degradation of elastomeric chains could be exacerbated by use of mouthwashes. About coil springs, force decay was also observed. However, it was not statistically significant. Force reduction was detectable after four weeks of coil springs usage, but in EC groups, the greatest reduction was after the first week.

Modelling of Drag Force Reduction for a Waterjet Propulsion System

The paper provides simulation results for SUP (Stand Up Paddle) board appendage resistance. Additional propulsion is added to the SUP board. It is equipped with a waterjet. The waterjet is attached to the board rudder. This increases the drag coefficient for rudder five times. To reduce the drag variable, design options for the waterjet duct were proposed. The simulation tests were performed using SolidWorks Flow software using two types of simulations, namely, the pressure on the body and the flow around the body. The objective was to streamline the bluff duct of the waterjet and thus to create the appendage design with minimum drag force from fluid flow and possibly greater Inlet Velocity Ratio. Calculations showed that rounding-off the edges of waterjet duct resulted in 35 % of drag coefficient reduction, while further streamlining reduced it by additional 10 %.

Simulations of flow over a bio-inspired undulated cylinder with dynamically morphing topography

Inspired by the geometric properties of seal whiskers, the addition of spanwise undulations on a cylinder have been shown to lower the mean and oscillatory forces and modify the frequency of flow-induced vibration when compared to smooth cylinders. Previously, computational fluid dynamics (CFD) has been used to characterize the hydrodynamic response with respect to specific geometric features. However simulations are time intensive due to complex three-dimensional meshing and computation time, limiting the number of geometric perturbations explored. A method is proposed in which the specific geometric features of this complex topography can be modified during a simulation thereby decreasing the time per geometric modification and removing the need for manual meshing of the complex structure. The surface of the seal whisker inspired geometry is parameterized into seven defining parameters, each of which is directly controlled in order to morph the surface into any realization within the defined parameter space. Once validated, the algorithm is used to explore the undulation amplitudes in the chord and thickness directions, by varying each independently from 0 to 0.3 thicknesses in increments of 0.05 at a Reynolds number of 500. The force and frequency response are examined for this matrix of geometric parameters, yielding detailed force trends not previously investigated. The impact of the bio-inspired morphing algorithm will allow for further optimization and development of force-mitigating underwater devices and other engineering applications in need of vibration suppression, frequency tuning, or force reduction.

Topological Characteristics of Obstacles and Nonlinear Rheological Fluid Flow in Presence of Insulated Fins: A Fluid Force Reduction Study

In this work, a comprehensive study of fluid forces and thermal analysis of two-dimensional, laminar, and incompressible complex (power law, Bingham, and Herschel–Bulkley) fluid flow over a topological cross-sectional cylinder (square, hexagon, and circle) in channel have been computationally done by using finite element technique. The characteristics of nonlinear flow for varying ranges of power law index 0.4 ≤ n ≤ 1.6 , Bingham number 0 ≤ Bn ≤ 50 , Prandtl number 0.7 ≤ Pr ≤ 10 , Reynolds number 10 ≤ Re ≤ 50 , and Grashof number 1 ≤ Gr ≤ 10 have been examined. Considerable evaluation for thermal flow field in the form of dimensionless velocity profile, isotherms, drag and lift coefficients, and average Nusselt number Nu avg is done. Also, for a range of Bn , the drag forces reduction is observed for circular and hexagonal obstacles in comparison with the square cylinder. At Bn = 0 corresponding to Newtonian fluid, maximum reduction in drag force is reported.