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Influence of Feed Velocity on Nonlinear Dynamics of Turning Process
An Wang,Wuyin Jin 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.6
A more comprehensive orthogonal turning model is developed in order to further study the influence of feed velocity on frictional chatter. Nonlinear dynamic behavior of the cutting tool in two directions is presented by using bifurcation diagram, phase portrait, and Poincare section. It can be found that the cutting tool has a variety of dynamic behaviors at different feed velocity and cutting velocity, such as periodic motion, quasi-periodic motion, and chaotic motion. Furthermore, the vibration displacement of the cutting tool is affected by the feed velocity, especially for relatively high feed velocity which will result in the cutting tool vibration displacement increase in the cutting direction but a decrease in the feed direction. In addition, it is clear that the stick–slip phenomenon only appears in the cutting direction in our work.
Quantitative Metallographic Analysis of GCr15 Microstructure Using Mask R-CNN
Reuben Agbozo,Wuyin Jin Korean Society for Precision Engineering 2020 한국정밀공학회지 Vol.37 No.5
Quantitative metallographic analysis is significant in predicting the mechanical and physical properties of materials. This paper presents an alternate method to the approach used by Zhao, et al. (2016) in the paper “Metallographic Quantitative Analysis for GCr15 by Digital Image Process” in identifying carbide particles present within GCr15 bearing steel. GCr15 bearing steel is classified as a quality alloy; high carbon, chromium and manganese. This study quantitated the proportion of carbide particles in GCr15 bearing steel microstructure using the Mask Region-Based Convolution Neural Networks (Mask R-CNN) approach. The approach precisely located carbide particles, using bounding box indicators based on the concept Region of Interest (ROI) as used in the Mask R-CNN approach and masked the carbide particles within the ROIs. With this approach, we accurately located and masked more than 90% of the target particles, labeled and calculated the area and perimeter of each corresponding blob within the microstructure of GCr15.
Impact of numerical choices on water conservation in the E3SM Atmosphere Model version 1 (EAMv1)
Zhang, Kai,Rasch, Philip J.,Taylor, Mark A.,Wan, Hui,Leung, Ruby,Ma, Po-Lun,Golaz, Jean-Christophe,Wolfe, Jon,Lin, Wuyin,Singh, Balwinder,Burrows, Susannah,Yoon, Jin-Ho,Wang, Hailong,Qian, Yun,Tang, Q Copernicus GmbH 2018 Geoscientific model development Vol.11 No.5
<P><p><strong>Abstract.</strong> The conservation of total water is an important numerical feature for global Earth system models. Even small conservation problems in the water budget can lead to systematic errors in century-long simulations. This study quantifies and reduces various sources of water conservation error in the atmosphere component of the Energy Exascale Earth System Model.</p> <p>Several sources of water conservation error have been identified during the development of the version 1 (V1) model. The largest errors result from the numerical coupling between the resolved dynamics and the parameterized sub-grid physics. A hybrid coupling using different methods for fluid dynamics and tracer transport provides a reduction of water conservation error by a factor of 50 at 1<span class='inline-formula'><sup>∘</sup></span> horizontal resolution as well as consistent improvements at other resolutions. The second largest error source is the use of an overly simplified relationship between the surface moisture flux and latent heat flux at the interface between the host model and the turbulence parameterization. This error can be prevented by applying the same (correct) relationship throughout the entire model. Two additional types of conservation error that result from correcting the surface moisture flux and clipping negative water concentrations can be avoided by using mass-conserving fixers. With all four error sources addressed, the water conservation error in the V1 model becomes negligible and insensitive to the horizontal resolution. The associated changes in the long-term statistics of the main atmospheric features are small.</p> <p>A sensitivity analysis is carried out to show that the magnitudes of the conservation errors in early V1 versions decrease strongly with temporal resolution but increase with horizontal resolution. The increased vertical resolution in V1 results in a very thin model layer at the Earth's surface, which amplifies the conservation error associated with the surface moisture flux correction. We note that for some of the identified error sources, the proposed fixers are remedies rather than solutions to the problems at their roots. Future improvements in time integration would be beneficial for V1.</p> </P>