scholarly journals Build Orientation Optimization Based on Weighted Analysis of Local Surface Region Curvature

2020 ◽  
Vol 11 (1) ◽  
pp. 304
Author(s):  
Hongshuai Guo ◽  
Jinghua Xu ◽  
Shuyou Zhang ◽  
Guodong Yi
Keyword(s):  
Surface Quality ◽  
Error Function ◽  
Surface Region ◽  
Eigenvalue Decomposition ◽  
Build Orientation ◽  
Weighted Analysis ◽  
Average Curvature ◽  
Printing Cost ◽  
Shift Strategy ◽  
The One

Build orientation becomes a hot issue in 3D printing, which has a significant impact on the surface quality, support structure and final cost of the fabricated model. In this paper, we focus our attention on the surface quality of the part when fabricated by a 3D printer under certain specific build orientation. A novel method using curvature shift is proposed to search local regions with obvious curvature changes of the model printed. Based on curvature shift strategy, the model is divided into separate regions which can be treated differently. Every triangle facet of the regions is given different weight factor by calculating the average curvature of each region. Weighted facets is introduced in building volume error function. Candidate build orientation can be obtained by the eigenvalue decomposition and the optimal build orientation is the one which leads to the minimal error of the function. From the case study, the method proposed gets a smaller error with a lower printing cost and time, which means the model surface in higher weighted regions gets a higher surface quality when printed.

scholarly journals Detection and characterization of extreme wind speed ramps

2019 ◽  
Vol 4 (3) ◽  
pp. 385-396 ◽  
Author(s):  
Ásta Hannesdóttir ◽  
Mark Kelly
Keyword(s):  
Wind Speed ◽  
Rise Time ◽  
Error Function ◽  
General Pattern ◽  
Analytical Form ◽  
Direction Change ◽  
Extreme Wind Speed ◽  
Time Variables ◽  
The One ◽  
Speed Fluctuations

Abstract. The present study introduces a new method to characterize ramp-like wind speed fluctuations, including coherent gusts. This method combines two well-known methods: the continuous wavelet transform and the fitting of an analytical form based on the error function. The method provides estimation of ramp amplitude and rise time, and is herein used to statistically characterize ramp-like fluctuations at three different measurement sites. Together with the corresponding amplitude of wind direction change, the ramp amplitude and rise time variables are compared to the extreme coherent gust with direction change from the IEC wind turbine safety standard. From the comparison we find that the observed amplitudes of the estimated fluctuations do not exceed the one prescribed in the standard, but the rise time is generally much longer, on average around 200 s. The direction change does however exceed the one prescribed in the standard several times, but for those events the rise time is a minute or more. We also demonstrate a general pattern in the statistical behaviour of the characteristic ramp variables, noting their wind speed dependence, or lack thereof, at the different sites.

scholarly journals Experimental Study on the Effects of Coolants on Surface Quality and Mechanical Properties of Micromilled Thin-Walled Elgiloy

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1497 ◽  
Author(s):  
Da Qu ◽  
Peng Zhang ◽  
Jiadai Xue ◽  
Yun Fan ◽  
Zuhui Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Surface Quality ◽  
Lower Surface ◽  
Work Piece ◽  
Dry Machining ◽  
Core Component ◽  
The Core ◽  
Thin Walled ◽  
The One

In this study, minimum quantity coolant/lubrication (MQCL) is found to have significant impact on the surface quality and mechanical properties of the micromilled thin-walled work piece that is the core component of an aeroaccelerometer. Three kinds of coolants were used in the micromilling process to analyze their effects on surface quality and mechanical properties of the component. The experiment results show that an appropriate dynamic viscosity of coolant helps to improve surface roughness. The high evaporation rate of the coolants can enhance the cooling performance. Comparing with the dry machining case, MQCL has better performance on improving tool wear, surface quality, and mechanical properties of the micromilled work piece. It yielded up to 1.4–10.4% lower surface roughness compared with the dry machining case in this experiment. The machined work piece with the best mechanical properties and the one with the worst mechanical properties appeared in the ethyl alcohol and the dry machining case, respectively. The reasons for deteriorating surface quality and mechanical properties in dry machining cases are also analyzed. For improving the micromilling process, the penetration and cooling effect of the coolants are more important. This paper gives references to obtain better service performance of the component by improving the micromilling process.

scholarly journals A WCSPH Particle Shifting Strategy for Simulating Violent Free Surface Flows

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3189
Author(s):  
Abdelkader Krimi ◽  
Mojtaba Jandaghian ◽  
Ahmad Shakibaeinia
Keyword(s):  
Free Surface ◽  
Surface Region ◽  
Free Surface Flows ◽  
Sph Method ◽  
Surface Flows ◽  
Weakly Compressible ◽  
Shifting Strategy ◽  
Long Time ◽  
The One ◽  
Stability And Consistency

In this work, we develop an enhanced particle shifting strategy in the framework of weakly compressible δ+-SPH method. This technique can be considered as an extension of the so-called improved particle shifting technology (IPST) proposed by Wang et al. (2019). We introduce a new parameter named “ϕ” to the particle shifting formulation, on the one hand to reduce the effect of truncated kernel support on the formulation near the free surface region, on the other hand, to deal with the problem of poor estimation of free surface particles. We define a simple criterion based on the estimation of particle concentration to limit the error’s accumulation in time caused by the shifting in order to achieve a long time violent free surface flows simulation. We propose also an efficient and simple concept for free surface particles detection. A validation of accuracy, stability and consistency of the presented model was shown via several challenging benchmarks.

scholarly journals Estimates for the Effective Permeability of Intact Granite Obtained from the Eastern and Western Flanks of the Canadian Shield

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 667
Author(s):  
A. P. S. Selvadurai ◽  
A. Blain-Coallier ◽  
P. A. Selvadurai
Keyword(s):  
Effective Permeability ◽  
Computational Models ◽  
Granitic Rock ◽  
Geometric Mean ◽  
Surface Region ◽  
Canadian Shield ◽  
Surface Permeability ◽  
Experimental Values ◽  
The One ◽  
High Level

Granitic rock from the western part of the Canadian Shield is considered as a potential host rock for the siting of a deep geological repository for the storage of heat-emitting high-level nuclear fuel waste. The research program focused on the use of surface permeability measurements conducted at 54 locations on a 300 mm cuboid of granite, obtained from the Lac du Bonnet region in Manitoba, to obtain an estimate for the effective permeability of the cuboid. Companion experiments are conducted on a 280 mm cuboid of granite obtained from Stanstead, Quebec, located in the eastern part of the Canadian Shield. The surface permeabilities for the cuboids of granite are developed from theoretical relationships applicable to experimental situations where steady flow is initiated at a sealed annular surface region with a pressurized central domain. The experimental values for the surface permeability are used with a kriging procedure to estimate the permeability variations within the cuboidal region. The spatial variations of permeability are implemented in computational models of the cuboidal regions to determine the one-dimensional permeabilities in three orthogonal directions. The effective permeability of the granite cuboids is estimated by appeal to the geometric mean. The research provides a non-destructive methodology for estimating the effective permeability of large specimens of rock and the experiments performed give estimates for the effective permeability of the two types of granitic rock obtained from the western and eastern flanks of the Canadian Shield.

Effect of build orientation on surface quality of selective laser melted Ti-6A1-4V

2017 ◽  
Author(s):  
Peter C. Serles ◽  
O. Remus Tutunea-Fatan ◽  
Evgueni V. Bordatchev
Keyword(s):  
Surface Quality ◽  
Build Orientation

Pressure Renormalization for Premelting Phenomena

1998 ◽  
Vol 05 (02) ◽  
pp. 479-491 ◽  
Author(s):  
Grzegorz Wiatrowski ◽  
Leszek Wojtczak
Keyword(s):  
Surface Region ◽  
Generalized Equation ◽  
Melting Transition ◽  
Layered System ◽  
Global Instability ◽  
Hamiltonian Description ◽  
Melting Temperatures ◽  
The One ◽  
Increasing Temperature ◽  
Pseudoharmonic Approximation

We develop the pressure renormalization of a phonon potential for atoms interacting anharmonically, starting from a fully dynamical Hamiltonian description in pseudoharmonic approximation. We derive a generalized equation for the correlation function of atom–atom displacement across a thin film, which under certain conditions reduces to the one previously discussed in the literature. Our theory yields expressions for a series of melting temperatures in terms of the microscopic parameters of a layered system using Lindemann's argument. The global instability temperature is obtained due to the distribution of displacement correlations in the surface region while the local melting transition is recognized as a process of surface premelting which expands into the stable bulk with increasing temperature. The pressure dependencies of instability and premelting temperatures are mainly discussed.

scholarly journals Analysis of an Electrical Circuit Using Two-Parameter Conformable Operator in the Caputo Sense

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 771
Author(s):  
Ewa Piotrowska ◽  
Łukasz Sajewski
Keyword(s):  
Classical Method ◽  
Error Function ◽  
Electrical Circuit ◽  
Constant Voltage ◽  
Conformable Derivative ◽  
The One ◽  
Voltage Dynamics ◽  
Theoretical Considerations ◽  
Two Parameter ◽  
Better Than

The problem of voltage dynamics description in a circuit containing resistors, and at least two fractional order elements such as supercapacitors, supplied with constant voltage is addressed. A new operator called Conformable Derivative in the Caputo sense is used. A state solution is proposed. The considered operator is a generalization of three derivative definitions: classical definition (integer order), Caputo fractional definition and the so-called Conformable Derivative (CFD) definition. The proposed solution based on a two-parameter Conformable Derivative in the Caputo sense is proven to be better than the classical approach or the one-parameter fractional definition. Theoretical considerations are verified experimentally. The cumulated matching error function is given and it reveals that the proposed CFD–Caputo method generates an almost two times lower error compared to the classical method.

Radiation Adhered with Conduction Heat Transfer Adopting Finite Volume Method

2014 ◽  
Vol 592-594 ◽  
pp. 1746-1750
Author(s):  
Prerana Nashine ◽  
Ashok Kumar Satapathy
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Control Volume ◽  
Error Function ◽  
Discrete Ordinates ◽  
Participating Media ◽  
Promising Alternative ◽  
Transfer Method ◽  
The One ◽  
Volume Method

This article considers a radiative transport problem coupled with conduction in the one dimensional slab in the presence of participating media. The finite volume method of computation is presented to discretize the radiative transfer equation over the control volume and by using the error function, conduction term is being computed. In the mathematical derivation the RTE is integrated with respect to control volume and control angles with the freedom in choosing number of angular nodes. The results reveals that the proposed method is a promising alternative to the well-established practices like the discrete ordinates method (DOM), discrete transfer method (DTM), monte-carlo method and many more.

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