• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.63-68
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• 1996

In this study, the effect of tool rake angles and the change of cutting conditions on specific cutting pressure in face milling is investigated. The cutting force in face milling is predicted from the double cutting edge model in 3-dimensional cutting. Conventional specific cutting pressure model is modified by considering the variation of tool rake angles. Effectiveness of the modified cutting force model is verified by the experiments using special face milling cutters with different cutter pockets and various rake angles. From the comparison of the pressented model and the specific cutting pressure, it is shown that the axial force can be predicted by the tangential and redial forces without the knowledge of friction angle and shear angle. Also, the relation between specific cutting pressure and cutting cindition including feedrate, cutting velocity and depth of cut is studied.

• Journal of the Korean Society of Visualization
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• v.8 no.1
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• pp.53-60
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• 2010

Experimental investigations were conducted to study the characteristics of turbulent swirling flow in an axisymmetric annuli. Swirl angle measurements were performed using a flow visualization technique using smoke and dye liquid for Re=60,00080,000. Using the two-dimensional particle image velocimetry method, we found the time-mean velocity distribution and turbulent intensities in water with swirl for Re=20,000, 30,000, and 40,000 along longitudinal sections. Neutral points occurred for equal axial velocity at y/(R-r)=0.70.75, and the highest axial velocity was recorded near y/(R-r)=0.9. Negative axial velocity was observed near the convex tube along X/(D-d)=3~23. Another experimental study was performed to investigate heat transfer characteristics of turbulent swirling flow in an axisymmetric annuli. Static pressure, and local flow temperature were measured using tangential inlet condition and the friction factors and Nusselt number were calculated for several Reynolds numbers.

• Tunnel and Underground Space
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• v.3 no.1
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• pp.96-107
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• 1993

This paper deals with the analysis of rock slope stability using the distinct element method. This method consists in analysis of the interaction of discrete block assemblage delimited by elementary joints, which permits to consider the heterogeneous, anisotropic and discontinuous features of the rock mass. In particular, we were able to show that this method, and especially the BRIG3D software, is an outstanding tool which gives informations of greatest interest in order to analyze the toppling mechanisms. We have confirmed the fundamental role of the rock mass structure with different simulations. In the case of toppling phenomena, the essential parameter is the dip of major discontinuities. It has an influence on the intensity and volume of deformations. The anisotropic and heterogeneous features of the rock mass play also an important role. It is proved by insertion of thick rock bars in the structure or varying rock block sizes in the mass. These models modified considerably the stress distribution and the deformation distribution. Finally, we have analyzed the influence of mechanical parameters such as friction angle and tangential stiffness.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.109-117
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• 1993

Force balance method is employed to predict forging information such as forging load, tool pressure and normal stress at the surface of tangential velocity discontinuity. The incipient stages of deformation for the plane strain forging of rectangular billets in V-shaped dies of different semi-angles are analysed. To construct an approximate model for the analysis of deformation by the force balance method in the incipient deformation stages, slip-line field is used. When the deformation mode by slip-line method is the same as that by force balance method, the slip-line method and the force balance method give identical solutions. The effects of die angle, coefficient of friction, billet geometries and deforma- tion characteristics are also investigated. In order to verify the validity of force balance analysis, the rigid-plastic finite element simulation for the various forgig parameters are performed and performed and find to be in good agreement.

• Geomechanics and Engineering
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• v.24 no.4
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• pp.307-321
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• 2021

In an earlier publication (Serrano et al. 2014), the theoretical basis for evaluating the shear strength in rock joints was presented and used to derive an equation that governs the relationship between tangential and normal stresses on the joint during slippage between the joint faces. In this paper, the theoretical equation is applied to two non-linear failure criteria by using non-associated flow laws, including the modified Hoek and Brown and modified Mohr-Coulomb equations. The theoretical model considers the geometric dilatancy, the instantaneous friction angle, and a parameter that considers joint surface roughness as dependent variables. This model uses a similar equation structure to the empirical law that was proposed by Barton in 1973. However, a good correlation with the empirical values and, therefore, Barton's equation is necessary to incorporate a non-associated flow law that governs breakage processes in rock masses and becomes more significant in highly fractured media, which can be induced in a rock joint. A linear law of dilatancy is used to assess the importance of the non-associated flow to obtain very close values for different roughness states, so the best results are obtained for null material dilatancy, which considers significant changes that correspond to soft rock masses or altered zones of weakness.