http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Thermal shear behavior in deformation phase of axisymmetric upsetting
황병복,노정훈 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.12
The generalized energy equation was investigated for an incompressible fluid film in homogeneous deformation phase of axisymmetric upsetting process with a perfectly plastic material. A reduced form of energy equation was used for the heat transfer problem of convection coupled with conduction mode in the lubricant film. The effect of convection denoted by Peclet number and the temperature difference between tool and workpiece was parametrically investigated on the temperature distribution and inhomogeneous shear motion in the film. The results of present model problem indicate that the localized thermal shear across the lubricant film depends mainly on the reduction in height and the degree of convection induced by sliding motion between tool and workpiece.
Numerical analysis of tool geometry effect on the wear characteristics in a radial forward extrusion
노정훈,황병복 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.8
The finite element analysis has been performed to investigate the tool wear characteristics in forming a central hub component with radialprotrusion by a radial forward extrusion process. The main objective of this study is to investigate the influence of tool geometries onthe wear characteristics of the mandrel and container surfaces. Two major process parameters such as annular gap height and mandreldiameter were adopted to examine the wear characteristics. SCM415H steel was selected as a model material in simulation by adoptingthe Archard’s wear model, which was verified by comparing with experimental results in the literatures. The results of present study weresummarized quantitatively in terms of wear profiles on the tool surfaces such as container and mandrel in terms of wear depth, contactpressure and sliding velocity. The localized wear depth is more sensitive to the variation of annular gap height with increase in mandreldiameter.
Work Efficiency in a Double Cup Extrusion Process
노정훈,황병복 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.3
A double cup extrusion process (DCEP) has been analyzed numerically to investigate the characteristics of energy consumptions for a selected model material, AA 2024 aluminum alloy. The forming energy in a double cup extrusion process was analyzed in terms of ideal, redundant and frictional energy or work, which constitute of a total forming energy in metal forming process. Ideal and theoretical forming or deformation efficiencies were also examined for various process parameters chosen for analysis. The objective of this study is to investigate the influence of geometrical process parameters in DCEP on the characteristics of energy consumption or dissipation. It was revealed from this study that frictional energy was expected to be more dissipated for high reductions and low thickness ratios. It was also found that the theoretical work efficiency would decrease as the thickness ratio increases and the reduction decreases.
Influence of punch geometry on surface deformation and tribological conditions in backward extrusion
노정훈,황병복 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1
The main goal of this study is to examine the influence of process conditions such as reduction and punch face angle in backward extrusion, especially for surface stresses such as surface expansion, contact pressure and sliding velocity and distance. Extensive analysis has been performed for the forming efficiency and flow mode. The simulation has been conducted by applying rigid-plastic finite element method. It was found that the relative movement at the contact interface increases with decrease in punch face angle and with increase in reduction such that sliding mode is expected for smaller punch face angles with larger reductions.
Characteristics of tool wear in a combined double cup extrusion process
노정훈,황병복 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.1
This paper is to investigate the wear characteristics of a tool in a double cup extrusion process (DCEP). The main objective of thisstudy is to examine the influence of geometrical process parameters on the tool wear characteristics in DCEP. Two major design factorsinclude the reduction in area in backward direction (RAB) and the wall thickness ratio of extruded can (TR). In order to verify the applicabilityof Archard’s wear model to massive deformation such as metal forming processes, two cases of experimental observations werecompared with numerical predictions. A sequential operation has been also simulated to compare the tool wear with those in a combinedoperation. The simulation results were summarized quantitatively in terms of wear profiles such as contact pressure, sliding distance, andwear depth. It can be concluded from the results that severe wear occurs in regions near the punch or mandrel corner and the wear depthincreases as the TR increases. This trend is intensified with increase in RAB.
Stress profiles at contact surface in ring compression test
노정훈,김민태,황병복 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.8
A perfectly plastic material has been employed as a model material in simulation to analyze numerically the ring compression process,especially to examine the deformation patterns along the die/workpiece interface, which is strongly related to the frictional condition at the contact boundary. The main objective is to provide the deformation characteristics in detail in ring compression, especially at the tool/workpiece interface. The surface flow patterns at the contact boundary in ring compression are summarized and analyzed in terms of surface expansion, surface expansion velocity, pressure distributions exerted on the die surface, relative sliding velocity between die and workpiece, and sliding distance along the die surface. Movement of neutral positions and folding phenomenon are also investigated to see the effect on the deformation patterns at the interface, that is, geometrical change, which is important to measure the frictional condition at the interface using calibration curves. Finite element (FE) simulation using rigid-plastic finite element code has been performed for analysis. The results of this study reveal that surface expansion as well as other surface flow patterns, such as sliding velocity and so on, shows different and distinctive characteristics between low and high frictional conditions at the interface. This is directly related to the movement of neutral positions and folding, which affects the sensitivity of dimensional changes to tribological conditions at the interface.