• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.145-149
• /
• 1997

STEP AP224 includes the information of machining feature and tolerances. Machining features are machined from raw material. Tolerance constrain feasible methods of manufacture, strongly influence the cost of manufacture. And tolerances influence the machining process. We need to decide the precedence between features .tool radius and tool direction for minimum tool changes. This paper deals with the method of decision of precedence between features and process parameters using feature information and tolerances in STEP AP224.

• Proceedings of the KSR Conference
• /
• 1999.05a
• /
• pp.226-231
• /
• 1999

A composition brake shoe composed of iron, graphite, kevlar, barium sulphate, etc. was developed for Diesel locomotives. The density distribution of the shoe depends on groove shapes of the shoe (or punch shape). In this study, we investigated the influence of the punch shape on the density distribution, stresses, etc. The inclination of the groove exerts more influence on the density distribution than the groove filet radius.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.10a
• /
• pp.382-388
• /
• 2005

Soil vapor extraction(SVE) is an effective and cost efficient method of removing volatile organic compounds(VOCs) and petroleum hydrocarbons from unsaturated soils. However, soil vapor extraction becomes ineffective in soils with low gas permeability, for example soils with air permeabilities less than 1 Darcy. Prefabricated vertical drains(PVDs) have been used for dewatering fine-grained soils for more than 25 years. Incorporating PVDs in and SVE system can extend the effectiveness of SVE to lower permeability soils by shortening the air flow-paths and ultimately expediting contaminant removal. The objective of the work described herein was to effectively incorporate PVDs into a SVE remediation system and to demonstrate a PVDs enhanced SVE system at full scale. The finding from this research will facilitate the design of field PVD-SVE systems in terms by providing insight into the optimal spacing between PVDs, the radius of influence of the wells and the flow rates to be used to capture and extract gas phase contaminants.

• Journal of the Korean Society of Groundwater Environment
• /
• v.7 no.1
• /
• pp.24-31
• /
• 2000

Soil air permeability and influence of radius in air injection/extraction tests were estimated. These are important factors in the determination of optimal design for SVE or bioventing system. For evaluation of the effects of air leakage from the ground surface on those factors, Theis (1935) and Hantush (1960) methods were used in the data analysis. The air permeability of the studied area was in the range of 1.64$\times$$10^{-7}$~5.66$\times$$10^{-6}$ $\textrm{cm}^2$, and this result would be used for the design of SVE or bioventing system.

• Transactions of Materials Processing
• /
• v.21 no.6
• /
• pp.348-353
• /
• 2012

Micro-drawn parts have received wider acceptance as products become smaller and more precise. The subject of this study was the deformation characteristics of ultra thin sheet metal in micro drawing of a rectangular shaped part. The influence of drawing speed and blank holding force on the product quality was investigated in micro-drawing of ultra thin sheet of beryllium copper (C1720) alloy. The specimen had a diameter of 4.8 mm and a thickness of $50{\mu}m$. Experiments were carried out in which, different blank holding force and drawing speed were considered. The product quality was evaluated by measuring the thickness and hardness along two specified directions, namely, the side and diagonal directions. The distribution of the thickness strain showed severe thinning especially around the punch radius in both directions. In the diagonal direction, thickening occurred in the flange area due to the axi-symmetric drawing mode. The increase of blank holding force and/or drawing speed was found to cause severe thinning around the punch radius. The blank holding force had a greater effect on thinning of the product than the drawing speed.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.6 no.1
• /
• pp.119-131
• /
• 2014

The phenomenon of cavitation is an unsteady flow, which is nearly inevitable in pump. It would degrade the pump performance, produce vibration and noise and even damage the pump. Hence, to improve accuracy of the numerical prediction of the pump cavitation performance is much desirable. In the present work, a homogenous model, the Zwart-Gerber-Belamri cavitation model, is considered to investigate the influence of the empirical coefficients on predicting the pump cavitation performance, concerning a centrifugal pump. Three coefficients are analyzed, namely the nucleation site radius, evaporation and condensation coefficients. Also, the experiments are carried out to validate the numerical simulations. The results indicate that, to get a precise prediction, the approaches of declining the initial bubble radius, the condensation coefficient or increasing the evaporation coefficient are all feasible, especially for declining the condensation coefficient, which is the most effective way.

• Geomechanics and Engineering
• /
• v.24 no.5
• /
• pp.479-490
• /
• 2021

Pre-drainage of groundwater in the roof aquifer by boreholes is the main method for prevention of roof water disaster, and the drop in the water level during the drainage leads to the variation of the local stress in the overlying strata. Based on a multitude of boreholes for groundwater drainage from aquifer above the 1303 mining face of Longyun Coal Mine, theoretical analysis and numerical simulation are used to investigate the local stress variation in the process of borehole drainage. The results show that due to the drop in the water level of the roof aquifer during the drainage, the stress around the borehole gradually evolved. From the center of the borehole to the outside, a stress-relaxed zone, a stress-elevated zone, and a stress-recovered zone are sequentially formed. Along with the expansion of drainage influence, the stress peak in the stress-elevated zone also moves to the outside. When the radius of influence develops to the maximum, the stress peak position no longer moves outward. When the coal mining face advances to the drainage influence range, the abutment pressure in front of the mining face is superimposed with the high local stress around the borehole, which increases the risk of stress concentration. The present study provides a reference for the stress concentration caused by borehole drainage, which can be potentially utilized in the optimal arrangement of drainage boreholes in underground mining.

• Transactions of Materials Processing
• /
• v.18 no.4
• /
• pp.336-341
• /
• 2009

Hydroformed parts have higher dimensional accuracy, structural strength, and dimensional repeatability. Particularly in the automotive industry, manufacturing of parts with complex shapes from tubular materials sometimes requires one or more pre-forming operations such as bending before the hydroforming process. The pre-bending process is an important process for the successful hydroforming in the case where the perimeter of the blank is nearly the same as that of final product. The bendability of a tube depends on the parameters such as the bending radius, welding methods, mechanical properties and hardness. Through the stainless steel tubes bent by rotary draw bending machine, this study shows the following : (1) The influence on spring back ratio variation with stress level in the welded bent tube. (2) The Cross-section ovality variation with weld seam position and bending radius. (3) The relation between elongation and thickness reduction of tension zone with weld seam position and bending radius. (4) Workability evaluation of bent stainless steel tubes through the hardness of materials and hardness increment. The results of this study may help to understanding of characteristics on bendability of stainless steel tubes.

• Advances in concrete construction
• /
• v.9 no.6
• /
• pp.569-576
• /
• 2020

Employment of the wave propagation approach with the combination of Pasternak foundation equation gives birth to the shell frequency equation. Mathematically, the integral form of the Lagrange energy functional is converted into a set of three partial differential equations. A cylindrical shell is placed on the elastic foundation of Pasternak. For isotropic materials, the physical properties are same everywhere, whereas the laminated and functionally graded materials, they vary from point to point. Here the shell material has been taken as functionally graded material. The influence of the elastic foundation, wave number, length and height-to-radius ratios is investigated with different boundary conditions. The frequencies of length-to-radius and height-to-radius ratio are counter part of each other. The frequency first increases and gain maximum value in the midway of the shell length and then lowers down for the variations of wave number. It is found that due to inducting the elastic foundation of Pasternak, the frequencies increases. It is also exhibited that the effect of frequencies is investigated by varying the surfaces with stainless steel and nickel as a constituent material. MATLAB software is utilized for the vibration of functionally graded cylindrical shell with elastic foundation of Pasternak and the results are verified with the open literature.

• Transactions of Materials Processing
• /
• v.16 no.8
• /
• pp.582-589
• /
• 2007

This paper is related to an analysis on the surface expansion in backward can extrusion process using spherical punches. It is generally known that the backward can extrusion process usually experiences severe normal pressure and heavy surface expansion. This is a reason why the backward can extrusion process is one of most difficult operations among many forging processes. Different punch nose radii have been applied to the simulation to investigate the effect of punch nose radius on the surface expansion, which is a major effort in this study. AA 2024 aluminum alloy is selected as a model material for investigation. Different frictional conditions have also been selected as a process parameter. The pressure applied on the punch has been also investigated since heavy surface expansion as well as high normal pressure on the tool usually leads to severe tribological conditions along the interface between material and tool. The simulation results are summarized in terms of surface expansion at different reduction in height, deformation patterns including strain distributions and maximum pressure exerted on the workpiece and punch, the effect of punch nose radius and the frictional condition on the surface expansion and the location and magnitude of maximum pressure exerted, respectively.