• 한국레이저가공학회지
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• 제9권1호
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• pp.9-16
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• 2006

Glass is one of brittle materials. Generally, brittle material is weak for tensile stress but strong for compression stress. Laser breaking of glass used this brittle characteristics. Laser breaking of glass was simulated to optimize breaking condition by using commercial FEM code MARC which is applicable to thermo-mechanical coupling analysis. Various shapes of heat sources were applied to the analysis and the distance between heating and cooling source were varied for each simulation. The shapes of heat sources were circle, single and double ellipse and the distance was varied from 0mm to 30mm. Moving heat sources were designed on the basis of experimental condition. As a result, double elliptic shape of heat source was the most suitable among them in laser breaking of glass. And it should be useful to determine optimal condition of laser breaking for glass.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.191-201
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• 2019

Finite element analysis is one of the most used tools for studying femoral neck fracture. Nerveless, consensus concerning either the choice of material characteristics, damage law and /or geometric models (linear on nonlinear) remains unreached. In this work, we propose a numerical quasi-brittle damage model to describe the behavior of the proximal femur associated with two methods to evaluate the Young modulus. Eight proximal femur finite elements models were constructed from CT scan data (4 donors: 3 women; 1 man). The numerical computations showed a good agreement between the numerical curves (load - displacement) and the experimental ones. A very encouraging result is obtained when a comparison is made between the computed fracture loads and the experimental ones ($R^2=0.825$, Relative error =6.49%). All specific numerical computation provided very fair qualitative matches with the fracture patterns for the sideway fall simulation. Finally, the comparative study based on 32 simulations adopting linear and nonlinear meshing led to the conclusion that the quantitatively results are improved when a nonlinear mesh is used.

• 한국정밀공학회지
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• 제33권1호
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• pp.11-16
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• 2016

Lithography techniques are generally used to manufacture nano-patterns on silicon, however, it is difficult to make a V-shaped pattern using these techniques. Although silicon is a brittle material, it can be treated as a ductile material if mechanically machined at extremely low force scale. The manufacturing technique of nano-patterns on single crystal silicon using a mechanical method was developed in this study. First, the linear pattern was machined on the silicon with increasing thrust force. Then, the correlation between measured cutting force and machined pattern was analyzed. Based on the analysis, the critical thrust force was quantitatively determined, and then the silicon was machined at a force lower than the critical thrust force. The machined pattern was observed using SEM and AFM to check for the occurrence of brittle fractures. Finally, the sharp V-shaped nano-pattern was manufactured on the single crystal silicon.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.533-534
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• 2007

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.105-110
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• 2000

The Micromechanics test is new test method which uses comparatively smaller specimen than that required in conventional material tests. There are several methods, such as small-specimen creep test, the continuous indentation test, and small punch(SP) test. Among them, the small punch(SP) test method has been applied to many evaluation fields, such as a ductile-brittle transition temperature, stress corrosion cracking, hydrogen embrittlement, and fracture properties of advanced materials like FGM or MMC. In this study, the small punch(SP) test is performed to evaluate the mechanical properties at high/low temperature from $-196^{\circ}C$ to $650^{\circ}C$ and the material degradation for virgin and aged materials of 9Cr1MoVNb steel which has been recently developed. The ${\Delta}P/{\Delta}{\delta}$ parameter defined a slope in plastic membrane stretching region of SP load-displacement curve decreases according to the increase of specimen temperature, and that of aged materials is higher than the virgin material in all test temperatures. And the material degradation degrees of aged materials with $630^{\circ}C$ -500hrs and $630^{\circ}C$ -1000hrs are $36^{\circ}C$ and $38^{\circ}C$ respectively. These behaviors are good consistent with the results of hardness($H_v$) and maximum displacement(${\delta}_{max}$).

• 한국기계가공학회지
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• 제16권6호
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• pp.1-6
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• 2017

Recently, the brittle materials such as ceramics, glass, sapphire and textile material have been widely used in semiconductors, aerospace and automobile owing to high functional characteristics. On the other hand, it has the characteristics of difficult-to-cut material relative to all materials. In this study, diamond electro-deposited band-saw machine was developed to operate stably using water-coolant type through relative motion between band-saw tool and $Al_2O_3$ material. High densified $Al_2O_3$ material was manufactured by spark plasma sintering method. The bulk density was observed by the Archimedes law and the theoretical density was estimated to be $3.88g/cm^3$ and its hardness 14.7 MPa. From the dicing sawing test of $Al_2O_3$ specimen, behavior of surface roughness and band-saw wear are dominantly affected by the increase of the band-saw linear velocity. Additionally, an continuous pattern type of diamond band-saw was a very effective due to entry impact as a one-off for brittle material.

• Computers and Concrete
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• 제9권1호
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• pp.35-50
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• 2012

The 2D representative volume element (RVE) for softening quasi-brittle materials like concrete is determined. Two alternative methods are presented to determine a size of RVE in concrete subjected to uniaxial tension by taking into account strain localization. Concrete is described as a heterogeneous three-phase material composed of aggregate, cement matrix and bond. The plane strain FE calculations of strain localization at meso-scale are carried out with an isotropic damage model with non-local softening.

• 한국군사과학기술학회지
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• 제5권2호
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• pp.207-216
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• 2002

In this paper, the study on the behavior of the deformation of brittle material, such as concrete, ceramic, was peformed by comparison of Lagrangian technique and Smoothed Particle Hydrodynamics using commercial nonlinear hydrodynamic numerical program, Autodyn_2D. The effect of SPH technique was proved by investigating the behavior of material deformation, velocity profile and pressure profile.

• 한국농공학회지
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• 제41권3호
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• pp.73-80
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• 1999

The objective of this study were to investigate the properties and to improve the disadvantages of the polymer concrete such as brittle fracture, large hardening shrinkage . In this paper, steel fiber reinforced polymer concrete is prepared with various steel fiber aspect ratios(ι/d), contents(vol.%), and their material characteristics were investigated experimentally . The aspect ration (ι/d) of the steel fiber was reversly proportional to slump value, and slump value tended to decrease as increase of steel fiber content . And harding shrinkage and impact resistance tended to be improved as the steel fiber content and aspect ration were increased.

• 한국생산제조학회지
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• 제20권4호
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• pp.382-385
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• 2011

There is an immense need to obtain nanometric surface finish on optical glass owing to the advantage of improved performance of the components. But owing to brittleness and hardness, optical glass is one of the materials that is difficult to ultra-precision turning. According to the hypothesis of ductile mode machining, regardless of their hardness and brittleness, will undergo a transition from brittle to ductile machining region below a critical undeformed chip thickness. Below this threshold, it is suggested that the energy required for plastic formation. Thus, plastic deformation is the predominant mechanism of material removal in machining these materials in this mode. An experimental study is conducted diamond cutting for machining BK7 glass. The investigation presents the feasibility of achieving nanometric surface and the understanding the mechanism of cutting glass, proving the cutting edge radius effect.