• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.10a
• /
• pp.27-27
• /
• 2009

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.8
• /
• pp.213-220
• /
• 2003

By the localization of electro-chemical dissolution region, we succeeded in a few micrometer size hole drilling on stainless steel with the radial machining gap of about 1 ${\mu}{\textrm}{m}$. Tens of nanosecond duration voltage pulses were applied between WC micro-shaft and stainless steel in the 0.1 M $H_2SO_4$ solution. Pt balance electrode was used to drill the high aspect ratio micro-hole without generation of Cr oxide layer on the machined surface. The effects of applied voltage, pulse duration, and pulse period on localization distance were investigated according to machining time. We suggested the taper reduction technique especially brought up on blind-hole machining. High quality micro-holes with 8 ${\mu}m$ diameter with 20 ${\mu}m$ depth and 12 ${\mu}m$ diameter with 100 ${\mu}m$ depth were drilled on 304 stainless steel foil. The various hole shapes were also produced including stepped holes and taper free holes.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1052-1058
• /
• 2003

The possibility of micro/nano machining through electro-chemical process is discussed in this research. Electro-chemical dissolution region is localized within 1 ${\mu}m$ by applying ultra short pulses with tens of nanosecond duration. The effects of voltage, pulse duration, and pulse frequency on the localization distance are investigated. Localization distance can be manipulated by controlling the voltage and pulse duration, and various hole shapes are produced including stepped holes and taper free hole. High quality micro-hole with 8 ${\mu}m$ diameter with 20 ${\mu}m$ depth and micro-groove with 9 ${\mu}m$ width with 10 ${\mu}m$ depth are machined on 304 stainless steel.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.11 no.6
• /
• pp.18-25
• /
• 2007

In a plastic metal forming of thermally rate-sensitive material, the localized shear band stems from evolution of a narrow region in which intensive plastic flow occurs. And it give rise to fatal fracture with plastic instability. The objectives of this study are to investigate the localization behavior by using numerical method and predict the failure for WHA(Tungsten Heavy Alloy). In this work, the implicit finite difference scheme is used because of the advantage about convergence and the numerical stability. This study is based on an analysed material with hardening as well as thermally softening behavior which includes isotropic strain hardening and observed the extension of localization within shear band according to material properties.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2012.10a
• /
• pp.151-152
• /
• 2012

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.10a
• /
• pp.311-311
• /
• 2008

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.3
• /
• pp.141-147
• /
• 2018

Recently, interest in customers has shifted to the emotional quality of customers as the driving, handling, and collision stability of automobiles have been greatly improved. The NVH performance of a vehicle is quantified and evaluated from the DPDS. To improve the DPDS, we need to optimize the shape without considering the increases in thickness of the parts or additions to the parts. And at the same time, we need to establish design and analysis processes to satisfy the requirements of the DPDS.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.225-228
• /
• 1999

In a plastically deformed body the formation of a shear band is widely observed in the engineering materials during rapidly forming process for a thermally rate-sensitive material. The localized shear bond stems from evolution of a narrow region in which intensive plastic flow occurs. The shear band often plays as a precursor of the ductile fracture during a forming process. The objectives of this study are to investigate the localization behaivor by using numerical method thus predict the failure. In this work the implicit finite difference scheme is preformed due to the ease of covergence and the numerical stability. This study is based on an analysised material with hardening as well as thermally softening behavior which includes isotropy strain hardening. Furthermore this paper suggests that an anticipated and suggested a kinematic hardening constitutive equation be requried to predicte a more accurate strain level wherein a shear band occurs.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2000.04a
• /
• pp.9-12
• /
• 2000

The importance of the role of plastic spin in the rate-dependent response of materials at large deformations is the main objective of this work. After a brief presentation of a general consitutive framework for visco-rigid plasticity at large strains an isotropic/kinematic hardening and a visco-rigid plastic model are used to analyze the stress-strain response under simple shear. A clear understanding of the role of plastic spin is achieved by obtaining numerical analyzed results for different stress values in which the plastic spin consititutive parameters interrelaste with the strain rate and other more conventional model constants, Especially this paper is concerned with introducing behaviors of Al7075

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.05a
• /
• pp.205-208
• /
• 2001

Localized shear band is investigated through the analysis of one-dimensional model for simple shearing deformation of thermally rate dependent material. Generally mesh size or interval of nodes play an important role in determining the overall flow behavior of the material. In order to observe these size effects we adapted non-local theory by including higher order strain gradients of the equivalent strain into the constitutive equation for the flow stress. for the ease of convergence and numerical stability the inplicit finite difference scheme is employed.