• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.8
• /
• pp.1458-1467
• /
• 1992

Recently, the composite materials have been researched actively by many researchers because of its useful properties. Especially, an interface crack on the dissimilar material exposes the behavior of the mixed mode crack even though under only the tension stress. In the previous papers, crack energy density(CED) was shown as the crack behavior evaluation parameter which can be expressed consistently from the onset until a final fracture. In a present paper, the basic properties of CED on the interface crack are examined because the results by CED at the homogeneous material above are also expected to be held at the dissimilar material. And we proposed that the contribution of each mode of CED can be separated and be evaluated. Furthermore, the total CED and contribution of each mode are evaluated by domain integral through a finite element analysis at the elastic crack model and the basic examination are carried out.

• Geomechanics and Engineering
• /
• v.12 no.3
• /
• pp.399-415
• /
• 2017

A series of direct shear tests were conducted to investigate the frictional properties of the interface between structures and the filling soil of Chongqing airport fourth stage expansion project. Two types of structures are investigated, one is low carbon steel and the other is the bedrock sampled from the site. The influence of soil water content, surface roughness and material types of structure were analyzed. The tests show that the interface friction and shear displacement curve has no softening stage and the curve shape is close to the Clough-Duncan hyperbola, while the soil is mainly shear contraction during testing. The interface frictional resistance and normal stress curve meets the Mohr-Coulomb criterion and the derived friction angle and frictional resistance of interface increase as surface roughness increases but is always lower than the internal friction angle and shear strength of soil respectively. When surface roughness is much larger than soil grain size, soil-structure interface is nearly shear surface in soil. In addition to the geometry of structural surface, the material types of structure also affects the performance of soil-structure interface. The wet interface frictional resistance will become lower than the natural one under specific conditions.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.33 no.2
• /
• pp.82-93
• /
• 1991

The objective of this paper is to show that the soil-geotextile interaction needs to he addressed in addition to the usual tensile and modulus properties when the geotextile is being designed for a specific application. The soil-geotextile interaction can be directly assessed by standard direct shear test. The data presented here show that the shear strength paramaters describing the soil-geotextile interface can he greatly influenced by the type of the geotextile. In this investigation, we examined nine different geotextiles of varying construction and surface textures with two standard soil, under five loading conditions, and compared the shear strength and the frictional resistance with the corresponding values of soil itself The following conclusions were drawned from this study. 1. The shear stress-strain curve shows that there are the residual shear stresses at the soil-geotextile interface. Because of the hydraulic gradient between the soil and the geotextile, the excessive pore water can migrate into the geotextile and among the filaments and dissipate through the soil-geotextile interface. 2. The shear strength of the soil-geotextile interface is affected by the moisture content of the soil. At moisture content lower than the optimum water content of the Proctor compaction test, the shear strength of the soil-geotextile interface is greater. 3. The type and surface roughness of the geotextile have the greatest influence on the interface friction angle between the soil and the geotextile.

• Journal of Adhesion and Interface
• /
• v.17 no.2
• /
• pp.56-61
• /
• 2016

This study was to investigate the effect of main monomer, butyl acrylate instead of 2-ethylhexyl acrylate, of acrylic PSAs on adhesive properties. The copolymers of butyl acrylate, acrylic acid and 2-hydroxyethyl acrylate were synthesized and their adhesive properties were investigated after crosslinking with two different agents. Comparing to 2-hydroxyethyl acrylate-based one which has branch-like side groups, butyl acrylate-based PSA with linear side groups show poor adhesive properties. In case of crosslinking agent, epoxy-typed agent than isocyanate-typed one showed better properties than isocyanate-typed one because epoxy-typed agent has more crosslinking sites and produces more flexible bonds, ester and ether, than isocynate-typed one. Most adhesive properties of PSAs were increased with acid content.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.471-474
• /
• 1999

An interface always appears when a repair is applied to an aged infrastructure system for repair. These repaired structures have the high chance to fail along the interface because of the stress concentration/discontinuity along the interface. So, mechanical properties of the interface have much influence on the behavior of repaired structure systems. In this paper, numerical tool that can predict effectively the interfacial fracture behavior is developed using axial deformation link elements, and this numerical technique is applied to the interfacial failure behavior. The results coincide with the ultimate strength and failure profile on the interfacial behavior of carbon fiber sheets for strengthening with epoxy adhesion. Thus, the mechanical behavior of the interface up to failure can be predicted using numerical technique with the proposed axial deformation link elements.

• Smart Structures and Systems
• /
• v.20 no.2
• /
• pp.181-195
• /
• 2017

In this study, the severity of damage in tendon anchorage caused by the loss of tendon forces is quantitatively identified by using the PZT interface-based impedance monitoring technique. Firstly, a 2-DOF impedance model is newly designed to represent coupled dynamic responses of PZT interface-host structure. Secondly, the 2-DOF impedance model is adopted for the tendon anchorage system. A prototype of PZT interface is designed for the impedance monitoring. Then impedance signatures are experimentally measured from a laboratory-scale tendon anchorage structure with various tendon forces. Finally, damage severities of the tendon anchorage induced by the variation of tendon forces are quantitatively identified from the phase-by-phase model updating process, from which the change in impedance signatures is correlated to the change in structural properties.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.2
• /
• pp.348-355
• /
• 1992

Casting structures and properties are determined by the solidification speed in the metal mold. The heat transfer characteristics of the interface between the mold and the casting is one of the major factors that control the solidification speed. According to Sully's research, the thermal resistance exists due to the air-gap formation at the mold-casting interface during the freezing process and the interface heat transfer coefficient is used to describe the degree of it. In this study, one-dimensional Stefan problem with air-gap resistance in the cylindrical geometry is considered and heat transfer characteristics is numerically examined. The temperature distribution and solidification speed are obtained by using the modified variable time step method. And the effects of the major parameters such as mold geometry, thermal conductivity, heat transfer coefficient and initial temperature of casting on the thermal characteristics are investigated.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.1
• /
• pp.167-170
• /
• 2012

A test-area molecular dynamics simulation method for the vapor-liquid interface of argon through a Lennard-Jones intermolecular potential is presented in this paper as a primary study of interfacial systems. We found that the calculated density profile along the z-direction normal to the interface is not changed with time after equilibration and that the values of surface tension computed from this test-area method are fully consistent with the experimental data. We compared the thermodynamic properties of vapor argon, liquid argon, and argon in the vapor-liquid interface. Comparisons are made with kinetic and potential energies, diffusion coefficient, and viscosity.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.6
• /
• pp.947-951
• /
• 2005

Rotating compensator multichannel spectroscopic ellipsometry has been employed to determine the optical functions of various liquids used in chemistry. We attempted three different measurement configurations: (1) air-liquid interface, (2) prism-liquid interface, and (3) liquid-sample interface. In prism-liquid interface, we found that the prism surface had roughness and it should be considered in analysis for accurate results. In liquidsample interface, we had much higher reflection, better sensitivity, and less limitation compared to the other two configurations when crystalline silicon was used as reference sample. We discuss the merit of each configuration and present the optical functions of various liquids. Also we demonstrate Bruggeman effective medium theory to determine the optical properties of mixed liquid.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.357-357
• /
• 2010

Using ab initio density functional theory, we study the structural and electronic properties of interface between Cu surface and highly electron withdrawing hexaazatriphenylene-hexanitrile (HAT-CN) known as an efficient hole injection layer for organic light emitting diodes (OLEDs). We calculate the equilibrium geometries of the interface with different HAT-CN coverages. Usually, some of C-N bonds located at the edge of the HAT-CN molecule are deformed toward Cu atoms resulting in the reconstruction of Cu surface. By analyzing the electron charge and the potential distributions over the interface, we observe the formation of surface dipoles, which modify the work function at the interface. Such dipole formation is attributed to two origins, one of which is a geometrical nature and the other is a bond dipole. The former is related to structural deformation mentioned above, whereas the latter is due to charge transfer between organic and metal surface.