• Journal of Environmental Health Sciences
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• v.44 no.3
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• pp.238-243
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• 2018

Objectives: The purpose of this study was to determine skin adhesion rate of children's modeling clay for exposure assessment. Methods: Children's modeling clays were classified into 10 categories as PVA clay, PVA soft clay, starch-based clay, foam clay, rubber clay, oil clay, muddy clay, terra clay, paper clay and slime. A total of 26 children's clay goods was selected. Moisture content (%) and hardness of clays were measured. Five adults aged 20 to 25were recruited for experiment. Gravimetric difference of modeling clay was determined after 3 minutes playing time. Skin adhesion rate ($g/min/cm^2$) was estimated bythe amount of skin adhesion per minute (g/min) and each individual's palm surface area ($cm^2$). Results: Twenty four of the 26 children's modeling clay products were adhesive to skins. Two products of foam and rubber clay were not adhered to skin. For the 24 products, the average skin adhesion rate was $5.5{\times}10^{-4}{\pm}4.0{\times}10^{-4}g/min/cm^2$. The highest skin adhesion rate was $1.3{\times}10^{-3}{\pm}4.4{\times}10^{-4}g/min/cm^2$ for paper clay. The lowest skin adhesion rate was $4.6{\times}10^{-5}{\pm}1.1{\times}10^{-4}g/min/cm^2$ for oil clay. The skin adhesion rate was increased with increase of moisture content. Adhesion rates of some clays were varied by person and testing trials. Conclusion: The study determined skin adhesion rate of children's modeling clay. The adhesion rate is useful for exposure and risk assessments and setting safety guideline to protect children's health.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.108.6-108
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• 2002

It is greatly important to understand the mechanics of AFM-based nanorobotic manipulation for efficient and reliable handling of nanoparticles. Robust motion control of an AFM-based nanorobotic manipulation is much challenging due to uncertain mechanics in tip-sample interaction dominated by surface and intermolecular force and limitations in force and visual sensing capability to observe environment. This paper investigates a nanomechanic modeling which enables simulation for AFM-based nanorobotic manipulation , and its application to motion planning of an AFM-based nanorobot. Based on the modeling of intermolecular and adhesion force in AFM-based nanomanipulation, the behaviors of an AFM ca...

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2436-2441
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• 2002

Finite element technique considering adhesive forces is proposed and applied to analyze the behavior of elastic hemispherical asperity adhesively contacting the plane surface of semi -infinite rigid body. It is demonstrated that the finite element model simulates interfacial phenomena such as jump -to-contact and adhesion hysteresis that cannot be simulated with the currently available adhesive contact continuum models. This simulation aiso provides valuable information on contact pressure, contact region and stress distributions. This technique is anticipated to be utilized in designing a low-adhesion surface profile for MEMS/NEMS applications since various contact geometries can be analyzed with this technique.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1765_1766
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• 2009

In this paper, we propose the mathematical model for the vehicle system and the observer for adhesion force. To model the dynamic properties of vehicle system, we have considered two fundamental parts. The first part is the motion equations for vehicle based on Newton's second law. The second part is the torque dynamics of the traction motor. These parts are affected by outer conditions such as adhesive coefficient, running resistance and gradient resistance. The each parts are presented by the numerical formula. From two equations, we get the observer on adhesion force. Simulation results show that the proposed observer have the good performance compared with the normal observer.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.181-186
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• 2007

UBM (Under Bump Metallurgy) of flip chip assemblies consists of several layers such as the solder wetting, the diffusion barrier, and the adhesion layers. In addition, IMC layers are formed between the solder wetting layers (e.g. Cu, Ni) and the solder. The primary failure mechanism of the solder joints in flip chips is widely known as the fatigue failure caused by thermal fatigues or electromigration damages. Sometimes, the premature brittle failure occurs in the IMC layers. However, these phenomena have thus far been viewed from only experimental investigations. In this sense, this paper presents a method for solid modeling of IMC layers in flip chip assemblies, thus providing a pre-processing tool for finite element analysis to simulate the IMC failure mechanism. The proposed modeling method is CSG-based and can also be applied to the modeling of UBM structure in flip chip assemblies. This is done by performing Boolean operations according to the actual sequences of fabrication processes

• Journal of the Semiconductor & Display Technology
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• v.9 no.1
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• pp.5-10
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• 2010

Among a variety of cleaning processes, the cryogenic carbon dioxide ($CO_2$) cleaning has merits because it is highly efficient in removing very fine particles, innoxious to humans and does not produce residuals after the cleaning, which enables us to extend its area of coverage in the semi-conductor fabrication society. However, the cryogenic carbon dioxide cleaning method has some technical research issues in aspect to particles' adhesion and removal. To resolve these issues, performing an analysis for the identification of particle adhesion mechanism is needed. In this study, a research was performed by a theoretical approach. To this end, we extended the G-T (Greenwood-Tripp) model by applying the JKR (Johnson-Kendall-Roberts) and Lennard-Jones potential theories and the statistical characteristics of rough surface to investigate and identify the contact, adhesion and deformation mechanisms of soft or hard particles on the rough substrate. The statistical characteristics of the rough surface were taken into account through the employment of the normal probability distribution function of the asperity peaks on the substrate surface. The effects of surface roughness on the pull-off force for these particles were examined and discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.197-198
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• 2007

• Structural Engineering and Mechanics
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• v.74 no.6
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• pp.723-735
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• 2020

This study is reported the adhesion failure in adhesive bonded composite and specifically for the T-joint structure. Three-dimensional finite element analysis has been performed using a commercial tool and the necessary outcomes are obtained via an eight noded solid element (Solid 185-element) from the library of ANSYS. The structural analysis input has been incurred through ANSYS parametric design language (APDL) code. The normal and shear stress distributions along different layers of the joint structure have been evaluated as the final outcomes. Based on the stress distributions, failure location in the composite joint structure has been identified by using the Tsai-Wu stress failure criterion. It has been found that the failure index is maximum at the interface between flange and web part of the joint (top layer) which indicates the probable location of failure initiation. This kind of failures are considered as adhesion failure and the failure propagation is governed by strain energy release rate (SERR) of fracture mechanics. The different adhesion failure lengths are also considered at the failure location to calculate the SERR values i.e. mode I fracture (opening), mode II fracture (sliding) and mode III fracture (tearing) along the failure front. Also, virtual crack closure technique (VCCT) principle of fracture mechanics steps is used to calculate the above said SERRs. It is found that the mode I SERR is more dominating compared to other two modes of failure for the joint considered. Finally, the influences of various parametric (geometrical and material) effect on SERR of the joint structure are evaluated and discussed in details.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.2
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• pp.169-178
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• 2009

The presence of low adhesion at the wheel-rail contact point can result in skid of train wheels, and the skid, in turn, results in flats appearing on the wheels. Thus, anti-skid control has a crucial role for safe braking and prevention from flats that could cause a disastrous train accident. This paper presents dynamic modeling of a tilting train and the brake system of the tilting train, and analyzes the anti-skid logic used in the tilting train. The validity of the analysis is demonstrated via simulation study using Simulink for skid and re-adhesion circumstances of the tilting train.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.813-818
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• 2005

In this paper, a re-adhesion control scheme is proposed for 1C2M propulsion system of TTX. The possibility of slip between wheel and rail in railway system is increasing because of the tendency of high speed and a climatic change. This slip results in the decrease of adhesive effort between this wheel and rail, so the control strategy of traction effort which can reduce the speed promptly and make most use of the maximum adhesive force is absolutely necessary. This paper describes the modeling of the TTX system, and this system is verified by the simulation.