• Proceedings of the KSME Conference
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• 2001.11b
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• pp.682-687
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• 2001

This study represents effect of exhaust performance by according to active muffler valve spring. The experimental parameter were divided engine speed and torsion coil spring constant. The sound pressure level was generally low at engine speed 2000-2500rpm but That was showed the lowest at spring constant k=0.75. Flow speed of exhaust gas was showed the fast at spring constant k=0.75 but the low value was showed at k=0.97. It was contained a rather low concentration of carbon monoxide(CO) at engine speed 2000-2500rpm and k=0.81, low concentration of hydrocarbon(HC) at spring constant k=0.81 but that was high at spring constant k=0.97. A conclusion based on FFT analysis was generally low concentration value at k=0.79 and k=0.81. The temperature distributions into the muffler was shown similar conditions. Heat transfer was well spreaded at thermocouple No.8 because valve was opened.

• Journal of Ocean Engineering and Technology
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• v.4 no.1
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• pp.101-109
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• 1990

The friction welding has more technical and economic advantages than the other welding processes. As this welding process has the characteristics such as curtailment of production time, materials, cost reduction, etc., it has been widely used in production of various mechanical components which have complex shapes. So, this paper deals with optimizing the friction welding conditions and analyzing various mechanical properties of the friction welded joints of torsion bar material SUP9A bar to bar. The results obtained are summarized as follows; 1) The quantitative relation between heating time($t_{1}$, sec) and total upset(U, mm)can be obtained. The empirical formula obtained is ; U = 3.29$t_{1}$ + 1.6 2) The tensile strength($\sigma_{t}$, kgf/$mm^{2}$) of friction welding joints as post weld heat treated(PWHT) depends upon heating time($t_{1}$, sec) quantitatively and the empirical formula obtained is ; $\sigma$= -5.1$t_{1}\;^{2}$+44.90$t_{1}$+45.2 3) It is certain that the optimum condition for friction welded joints of SUP9A steel bars of diameter 14.5mm is, considering on various properties such as tensile strength, torsional strength, impact energy and strain of the joints after PWTH ; n = 2000rpm, $P_{1}$=8kgf/$mm^{2}$, $P_{2}$=20kgf/$mm^{2}$, $t_{1}$=4sec, $t_{2}$=3sec 4) The tensile strength, torsional strength and hardness were increased with the increased with the increasing carbon equivalent, but toughness was decreased.

• Journal of Korean Neurosurgical Society
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• v.59 no.5
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• pp.425-429
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• 2016

Objective : Rod-screw fixation systems are widely used for spinal instrumentation. Although many biomechanical studies on rod-screw systems have been carried out, but the effects of rod contouring on the construct strength is still not very well defined in the literature. This work examines the mechanical impact of straight, $20^{\circ}$ kyphotic, and $20^{\circ}$ lordotic rod contouring on rod-screw fixation systems, by forming a corpectomy model. Methods : The corpectomy groups were prepared using ultra-high molecular weight polyethylene samples. Non-destructive loads were applied during flexion/extension and torsion testing. Spine-loading conditions were simulated by load subjections of 100 N with a velocity of $5mm\;min^{-1}$, to ensure 8.4-Nm moment. For torsional loading, the corpectomy models were subjected to rotational displacement of $0.5^{\circ}\;s^{-1}$ to an end point of $5.0^{\circ}$, in a torsion testing machine. Results : Under both flexion and extension loading conditions the stiffness values for the lordotic rod-screw system were the highest. Under torsional loading conditions, the lordotic rod-screw system exhibited the highest torsional rigidity. Conclusion : We concluded that the lordotic rod-screw system was the most rigid among the systems tested and the risk of rod and screw failure is much higher in the kyphotic rod-screw systems. Further biomechanical studies should be attempted to compare between different rod kyphotic angles to minimize the kyphotic rod failure rate and to offer a more stable and rigid rod-screw construct models for surgical application in the kyphotic vertebrae.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.1-8
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• 2023

Power transmission shafts in rotary wing aircraft use a hollow shaft to reduce weight. We can apply linear elastic fracture mechanics to predict crack propagation behavior. This paper predicted crack growth life of a hollow shaft with a circumferential through-type crack by finite element analysis. A 2D finite element model was created by applying a torsion and forming elements considering cracks. We defined the initial crack length and performed the finite element analysis by increasing the crack length to derive stress intensity factor at crack tips. We defined the length just prior to the stress intensity factor exceeding the fracture toughness as the crack limit length. We calculated the crack limit length using a handbook and numerically integrated the crack growth rate equation to derive growth life of each crack. The growth life of each crack was compared to verify the proposed finite element analysis method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.33-39
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• 2016

This study investigated the dynamic instability of a ceramic-on-ceramic artificial hip joint system through complex eigenvalue analysis. We examined the mode-coupling mechanism through eigenvalue sensitivity analysis with the variation of system parameters. In addition, we constructed a finite element model including the negative slope of friction curve for investigating the negative-slope mechanism in the hip squeak problem. The numerical results show that the torsion-dominant mode becomes unstable due to the presence of the negative slope while the axial load is the important factor influencing the negative-slope type instability.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.775-787
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• 1996

An optimization procedure is proposed for the design of cylindrically laminated composite shell having midplane symmetry and subjected to axial force, torsion and internal pressure. Tsai-Wu and Tsai-Hill failure criteria are taken as objective functions. The stacking sequence represents the design variable. The optimal design formulation based on state space method is adopted and solution proccedure is described with the emphasis on the method of calculations of the design sensitivities. A gradient projection algorithm is employed for the optimization process. Numerical results are presented for the several test problems.

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.605-618
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• 2014

The effects of variability of the mechanical properties of lead rubber bearings on the response of a seismic isolation system are investigated. Material variability in manufacturing, aging, and operation temperature is assumed, and two variation models of an isolation system are considered. To evaluate the effect of ground motion characteristics on the response, 27 earthquake record sets with different peak A/V ratios were selected, and three components of ground motions were used for a seismic response analysis. The response in an isolation system and a superstructure increases significantly for ground motions with low A/V ratios. The variation in the mechanical properties of isolators results in a significant influence on the shear strains of the isolators and the acceleration response of the superstructure. The variation provisions in the ASCE-4 are reasonable, but more strict variation limits should be given to isolation systems subjected to ground motions having low A/V ratios. For application of seismic isolation systems to safety-related nuclear structures, the variation in the material and mechanical properties of the isolation system should be properly controlled during the manufacturing and aging processes. In addition, special consideration should be given to minimize the accidental torsion caused by the dissimilarity in the stiffness variations of the isolators.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.413-423
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• 1991

Multiaxial loading by combinations of tension-torsion-internal pressure have been applied to the thins-walled tubular specimens prepared from cold drawn tubes of SAE 1020 steel. Prior to the multiaxial loading, each specimen has been twisted to different shear strains. Uniaxial tensile yield stresses measured at different angles to the tube axis clearly show that the initial orthotropic symmetry is maintained during twisting. The orthotropy axes are observed to rotate with shear strains. The plane stress yield locus measured for each twisted specimens show that yield surface shape does not remain similar during twisting and thus anisotropic work hardening is not a function of only plastic work.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.3
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• pp.279-284
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• 2016

Finite element analysis along with DOE scheme has been performed to obtain robust design of crankshaft assembly. This study focused on obtaining optimized fillet radius of crankshaft mainly by statistical approach. 27 design cases using 3 factors with 3 levels are constructed by design of experiment. Changes of design factors and noise factor may influence the durability of crankshaft system. General two stages of robust design may enhance the durability of crankshaft model. Increasing crank arm thickness was adopted as a shrink step and change of fillet radius was used as a shift step. By combining these two steps, the stress concentration at the fillet area is reduced and adequate fillet radius is determined for the robust design of crankshaft.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.3
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• pp.110-115
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• 2010

This paper studies the vibration characteristics of a vehicle seat on several driving conditions. Modal test for a vehicle seat is conducted for the three different boundary conditions: on the rigid jig, BIW and the full vehicle. In driving on various road conditions and speeds, vibration level is measured at several locations including seat mounting and seat-back. The vibration pattern for each driving condition is found where the suspension mode and the 1st bending and torsion modes of the seat make the major contribution on it.