• Journal of the Korean Society for Precision Engineering
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• v.18 no.6
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• pp.109-114
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• 2001

Forming pressure of the rupture disc has been analyzed theoretically and verified by experiments. Final shape of the rupture disc after forming process is assumed to be hemi-ellipsoid for small height of the rupture disc. The predicted forming pressures are in good agreement with those by experiment. A new simple model has been proposed to predict the burst pressure of the rupture disc. Experimental results show that the proposed model of burst pressure describes the bursting characteristics of the rupture disc very well.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.991-997
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• 2003

A flow field around a disc in an optical disc drive is invested using numerical methods. The high-speed rotating disc induces a strong flow field around the disc, which causes the pressure distribution on the surfaces of the disc. The pressure difference between the upper and the lower surfaces causes the deformation of the disc. In the first part of this study, flow fields around a rotating disc and a stationary wall are investigated using a similarity solution method, in order to identify the effect of the distance between the disc and the wall on the pressure distribution on the surfaces of the disc. In the second part, flow field in a slim-type optical disc drive is studied using a commercial code in order to consider the effect of the vortices generated by the local geometry of the drive.

• Journal of Biosystems Engineering
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• v.31 no.3 s.116
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• pp.153-160
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• 2006

This study was performed to evaluate some geometrical characteristics of disc type swirl nozzles and to develop nozzles having improved spraying performance for knapsack sprayers. Considered geometrical characteristics of the nozzles were disc thickness, orifice diameter, swirl chamber diameter and shape of the swirl chamber (nozzle chamber). 3 types of nozzle cores were compared. Main results of this study were as follows. 1. Spraying angle (A) was increased with decreasing disc thickness (x), and with increasing orifice diameter (y) or spraying pressure (z). The equation was as a follow. $$A=3.95\frac{1}{x}+73.50\sqrt{y}+18.97\sqrt{z}-60.16$$ 2. Spraying flow rate (F) was increased with decreasing disc thickness (x), and with increasing orifice diameter (y) or spraying pressure (z). The equation was as a follow. $$F=-89.95x+611.09y+620.49\sqrt{z}-868.20$$ 3. Mean spraying droplet size (V) was decreased with decreasing disc thickness (x), with increasing orifice diameter (y) in low spraying pressure, with decreasing orifice diameter (y) in high spraying pressure, and with increasing spraying pressure (z). $$V=148.77x^4-746.85x^3+1311.76x^2-917.31x$$ 4. The spray pattern was compared using CV values. The CV value of the nozzle core type 1 was 26.7% in spraying pressure $3\;kgf/cm^2$, the CV value of the core type 2 was 23.6% in spraying pressure $2\;kgf/cm^2$, the CV value of the core type 3 was 20.6% in spraying pressure $1\;kgf/cm^2$. 5. Minimum spraying pressure was improved from $1.5\;kgf/cm^2\;to\;1.0\;kgf/cm^2$ by changes of nozzle core shape.

• The Journal of Korean Physical Therapy
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• v.13 no.1
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• pp.1-18
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• 2001

Aging has been recognized as the primary cause of disc degeneration. A biomechanical characteristics of disc degeneration has been demonstrated that intradiscal pressure is reduced. With the increasing population of elderly people, disc degeneration and associated problems of nerve entrapment are becoming more prevalent. Presently, research on reduced intradiscal pressure associated with degeneration is insufficient. In this study. we used the Finite Element Method (FEM) of computerized simulations to investigate the effects of variation in intradiscal pressure on mechanical behaviours of L4-5 intervertebral disc degeneration. Degeneration was classified using four grades based on initial intradiscal pressure; Normal (135 kPa), mild(107 kPa), moderate (47 kPa) and severe (15 kPa). The predicted results f3r bending loads were as follows; 1 . Range of motion increased progressively with severity of degeneration with flexion and lateral bending moments, but decreased with extension moments. 2. Discal bulging of posterolateral aspect was larger in lateral bending and extension moment. But bulging was increased with severity of degeneration in lateral bending and torsion(same side).3. The rate of increasing intradiscal pressure was decreased in all bending motions with severity of degeneration. In conclusion, lateral bending and extension moment yield greatest bulging in severe degeneration. In torsion, although bending load produces disc bulging, disc bulging was associated more strongly with severity of degeneration than increasing torsional moments. Clinical Implications: Discal bulging may produce nerve root impingement and irritation. The effect of loading and posture on the varying degrees of disc degeneration has important implications especially in the elderly. In the presence of disc degeneration, avoidance of end range postures, especially extension and lateral bending may help reduce discal bulging and in turn, nerve entrapment.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.188-193
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• 2003

To predict changes in biomechanical parameters such as intradiscal pressure, and the shock absorbing mechanism in the spinal motion segment under different impact duration/loading rates, a three dimensional L3/L4 motion segment finite element model was modified to incorporate the poroelastic properties of the motion segment. The results were analyzed under variable impact duration for normal and degenerated discs. For short impact duration and a given maximum compressive force, relatively high cancellous pore pressure was generated as compared with a case of long impact duration, although the amount of impulse was increased. In contrast relatively constant pore pressure was generated in the nucleus. Disc degeneration increased pore pressure in the disc and decreased pore pressure in the cancellous core, which is more vulnerable to compressive fracture compared with intact case.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.211-218
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• 1999

This paper describes the application of a coupled finite element-boundary element method (FE-BEM) to obtain the steady-state response of a piezoelectric transducer. The particular structure considered is a PZT4 disc-typed projector. The projector is three-dimensionally simulated to transduce applied electric charge on axial surfaces of the piezoelectric disc to acoustic pressure in air or in water. The directivity pattern of the acoustic field formed from the projected sound pressure is also simulated. And the displacement of the disc caused by the externally applied electric charge is shown in temporal motion. The coupled FE-BE method is described in detail.

• The Journal of Korean Physical Therapy
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• v.12 no.3
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• pp.455-467
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• 2000

The purpose of this study was to analyse the effects of disc degeneration on the biomechanical behaviors of the intervertebral disc in term of axial displacement, intradiscal pressure. disc bulge at the 1.4-1.5 functional spinal unit(FSU). The degeneration is divided 4 grade by initial intradiscal pressure: normal: 135kPa. mild: 107kPa. moderate: 47kPa, severe: 15kPa, The predicted results were follows: 1. The magnitude of the bulge is found to be maximum at the anterior, minimum at the postero-lateral portion. The bulge of lateral, postero-lateral is found to be maximum in severe grade. followed by moderate. mild, normal grade. 2. Tho displacement was increased with increasing compressive load in all four grades.'rho stiffness of disc was found to be reduced by progressing from normal to severe grade. 3. The intradiscal pressure was increased nearly linearly with increasing compressive load in normal and mild grade. But the increasing rate in moderate and severe grade was showed apparently different from nomal and mild grade. Specially, it was increased very slightly in severe grade. In conclusion, decreased intradiscal pressure resulted in increase of axial displacement and disc bulge with compressive load increasing. these may compromise the nerve root impingement or irritation. Therefore posture and activities must be focus to reduce compressive load applied on the back or disc.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.481-487
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• 2011

This paper provides a comparison between finite element analysis results and test data of rupture disc. Rupture disc is safety device of high pressure equipment. Rupture disc of solid rocket motor is a device to control rupture pressure. Rupture discs were made of AISI 316L. By the elastic-plastic analysis, the stress limit of rupture discs were compared to the test results. The results can be used to control the rupture pressure by the change of the disc size.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.93-100
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• 2003

This paper describes the thermoelastic instability arising from friction heat generation in braking and proposes the finite element methods to predict the variation of temperature and thermal deformation. In a conventional disc brake analysis, heat generation is only related with wheel speed and friction material and the interface pressure between disc and pad is assumed constant. But under dynamic braking conditions, the frictional heat causes the thermoelastic distortion that leads to more concentrated contact pressure distribution and hence more and more non-uniform temperature. In this paper, to complete the solution of the thermomechanically coupled problem, the linear relation model between pressure and temperature is proposed and demonstrated in examples of a simple two dimensional contact problem. And the two dimensional model has been extended to an annular three dimensional disc model in order to consider more realistic geometry and to provide a more accurate critical speed for automotive brake systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.10
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• pp.979-986
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• 2009

This paper presents a dynamic modeling of a military vehicle suspension featuring disc spring and MR valve. Firstly, the dynamic model of the disc spring is established with respect to the load and pressure. The nonlinear behavior of the spring is incorporated with the model. Secondly, the dynamic model of the MR valve is derived by considering the pressure drop due to the viscosity and yield stress of MR fluid. The governing characteristics of the proposed suspension system are then investigated by presenting the field-dependent pressure drop of the MR valve and spring force of the gas spring.