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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers A
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 36, Issue 12 - Dec 2012
Volume 36, Issue 11 - Nov 2012
Volume 36, Issue 10 - Oct 2012
Volume 36, Issue 9 - Sep 2012
Volume 36, Issue 8 - Aug 2012
Volume 36, Issue 7 - Jul 2012
Volume 36, Issue 6 - Jun 2012
Volume 36, Issue 5 - May 2012
Volume 36, Issue 4 - Apr 2012
Volume 36, Issue 3 - Mar 2012
Volume 36, Issue 2 - Feb 2012
Volume 36, Issue 1 - Jan 2012
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A Study of Residual Stress and Plastic Deformation of a Bar with Gap Size Changes Between Rolls in a Two Cross-Roll Straightener
Cho, Hyun-Soo ; Hahm, Ju-Hee ; Lee, Young-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 355~360
DOI : 10.3795/KSME-A.2012.36.4.355
Cold drawn(CD) bars feature superb surface roughness, dimensional precision, and straightness. They are used in the manufacture of automotive parts and home electrical appliances. Two cross-roll straighteners have been used to manufacture CD bars for these industries. This study investigated the variation of the gap size between the two cross-rolls. It was found that changes in the gap size have a large influence on the residual stress and plastic deformation. Finite element method(FEM) simulations were performed to study the influence of the gap size on the residual stress in CD bars, and experiments were performed to verify the FEM results. The residual stresses were measured with X-ray diffraction in both the axial and the hoop directions.
A Non-Uniform Convergence Tolerance Scheme for Enhancing the Branch-and-Bound Method
Jung, Sang-Jin ; Chen, Xi ; Choi, Gyung-Hyun ; Choi, Dong-Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 361~371
DOI : 10.3795/KSME-A.2012.36.4.361
In order to improve the efficiency of the branch-and-bound method for mixed-discrete nonlinear programming, a nonuniform convergence tolerance scheme is proposed for the continuous subproblem optimizations. The suggested scheme assigns the convergence tolerances for each continuous subproblem optimization according to the maximum constraint violation obtained from the first iteration of each subproblem optimization in order to reduce the total number of function evaluations needed to reach the discrete optimal solution. The proposed tolerance scheme is integrated with five branching order options. The comparative performance test results using the ten combinations of the five branching orders and two convergence tolerance schemes show that the suggested non-uniform convergence tolerance scheme is obviously superior to the uniform one. The results also show that the branching order option using the minimum clearance difference method performed best among the five branching order options. Therefore, we recommend using the "minimum clearance difference method" for branching and the "non-uniform convergence tolerance scheme" for solving discrete optimization problems.
An Investigation of Turbine Blade Ejection Frequency Considering Common Cause Failure in Nuclear Power Plants
Oh, Ji-Yong ; Chi, Moon-Goo ; Hwang, Seok-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 373~378
DOI : 10.3795/KSME-A.2012.36.4.373
The objective of this research is to examine the probabilistic approach to evaluating turbine ejection frequency considering common-cause failure. This paper identifies basic turbine ejection mechanisms under high and low speeds and presents a detailed probabilistic methodology (fault tree) for assessing ejection frequency. The alpha factor methodology is applied to common-cause failure evaluations. The frequencies under different test schemes are compared and the propagation of uncertainty through the fault tree model is evaluated. The following conclusions were reached: (1) the turbine blade ejection frequency due to ductile failure under high speed is around 8.005E-7/yr; (2) if common-cause failure is considered, the frequency will be increased by 11% and 33% depending on the test scheme; and (3) if the parameter uncertainties are considered, the frequency is estimated to be in the range of 9.35E-7 to 1.13E 6, with 90% confidence.
A Study of Probabilistic Fatigue Crack Propagation Models in Mg-Al-Zn Alloys Under Different Specimen Thickness Conditions by Using the Residual of a Random Variable
Choi, Seon-Soon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 379~386
DOI : 10.3795/KSME-A.2012.36.4.379
The primary aim of this paper was to evaluate several probabilistic fatigue crack propagation models using the residual of a random variable, and to present the model fit for probabilistic fatigue behavior in Mg-Al-Zn alloys. The proposed probabilistic models are the probabilistic Paris-Erdogan model, probabilistic Walker model, probabilistic Forman model, and probabilistic modified Forman models. These models were prepared by applying a random variable to the empirical fatigue crack propagation models with these names. The best models for describing fatigue crack propagation behavior in Mg-Al-Zn alloys were generally the probabilistic Paris-Erdogan and probabilistic Walker models. The probabilistic Forman model was a good model only for a specimen with a thickness of 9.45 mm.
Pitting Life for RRP System
Kim, Chang-Hyun ; Nam, Hyung-Chul ; Kwon, Soon-Man ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 387~393
DOI : 10.3795/KSME-A.2012.36.4.387
A roller rack pinion (RRP) system, which consists of a rack-bar and a cam pinion, transforms a rotation motion into a linear one. The rack-bar has a series of roller trains, and meshes with the cam pinion. This paper first proposes the exact tooth profile of the cam pinion and the non-undercut condition to satisfy the required performance by introducing the profile shift coefficient. The paper then investigates the load stress factors under various shape design parameters to predict the gear surface fatigue limit, which was strongly related to the gear noise and vibration at the contact patch. The results show that the pitting life can be extended significantly with an increase in the profile shift coefficient.
Study of a Low-Temperature Bonding Process for a Next-Generation Flexible Display Module Using Transverse Ultrasound
Ji, Myeong-Gu ; Song, Chun-Sam ; Kim, Joo-Hyun ; Kim, Jong-Hyeong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 395~403
DOI : 10.3795/KSME-A.2012.36.4.395
This is direct bonding many of the metal bumps between FPCB and HPCB substrate. By using an ultrasonic horn mounted on an ultrasonic bonding machine, it is possible to bond gold pads onto the FPCB and HPCB at room temperature without an adhesive like ACA or NCA and high heat and solder. This ultrasonic bonding technology minimizes damage to the material. The process conditions evaluated for obtaining a greater bonding strength than 0.6 kgf, which is commercially required, were 40 kHz of frequency; 0.6MPa of bonding pressure; and 0.5, 1.0, 1.5, and 2.0 s of bonding time. The peel off test was performed for evaluating bonding strength, which was found to be more than 0.80 kgf.
Improving the Corrosion Resistance of Cold-Rolled Carbon Steel by Treatment with a Hybrid Organic/Inorganic Coating Solution
Kim, Jung-Ryang ; Choi, Chang-Min ; Nam, Ki-Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 405~412
DOI : 10.3795/KSME-A.2012.36.4.405
In the past, a very popular way to reduce the corrosion rate of zinc was the use of chemical conversion layers based on
. However, the use of chromium salts is now restricted because of environmental protection legislation. Previous research investigated the optimum corrosion resistance of galvanized steel treated with an organic/inorganic solution containing Si. The result showed that the optimum corrosion resistance occurred by heat treatment of
in 5 min. In this study, one organic and three hybrid organic/inorganic coating solutions were applied to cold-rolled (CR) carbon steel. The coatings were then evaluated for corrosion resistance under a salt spray test. The coating solutions examined in this study consisted of urethane-only, urethane-Si, urethane-Si-Ti, and urethane-Si-Ti-epoxy. The results of the 7 h salt spray test showed that the urethane-Si-Ti and urethane-Si-Ti-epoxy coating solutions had superior corrosion resistance on CR steel.
Delamination Limit of Aluminum Foil-Laminated Sheet During Stretch Forming
Lee, Chan-Joo ; Son, Young-Ki ; Lee, Jung-Min ; Lee, Seon-Bong ; Byun, Sang-Deog ; Kim, Byung-Min ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 413~420
DOI : 10.3795/KSME-A.2012.36.4.413
An aluminum foil-laminated sheet is a laminated steel sheet on which aluminum foil is adhesively bonded. It is usually used on the outer panel of home appliances to provide an aluminum feeling and appearance on the surface of the product. The delamination of aluminum foil is one of the main problems during the stretch forming process. The purpose of this study is was to determine the delamination limit of an aluminum foil-laminated sheet in the stretch forming process. The delamination was dependent on the bonding strength between aluminum foil and steel sheet. The fracture behavior of the interface between the aluminum foil and the steel sheet was described by a cohesive zone model. A finite element was conducted with the cohesive zone model to analyze the relationship between the delamination limit and the bonding strength of the interface. The interface bonding strength was evaluated by lap shear and T-peel test. The delamination limit of the aluminum foil-laminated sheet was determined by using the bonding strength of the steel sheet. The delamination limit was also verified by the Erichsen test.
Effect of Oxide Film Formation on the Fatigue Behavior of Aluminum Alloy
Kim, Jong-Cheon ; Cheong, Seong-Kyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 421~428
DOI : 10.3795/KSME-A.2012.36.4.421
In this study, the effects of surface oxide film formation on the fatigue behavior of 7075-T6 aluminum alloy were analyzed in terms of the corrosion time of the alloy. The aluminum material used is known to have high corrosion resistance due to the passivation phenomenon that prevents corrosion. Aluminum alloys have been widely used in various industrial applications such as aircraft component manufacturing because of their lighter weight and higher strength than other materials. Therefore, studies on the fatigue behavior of materials and passivation properties that prevent corrosion are required. The fatigue behavior in terms of the corrosion time was analyzed by using a four-pointing bending machine, and the surface corrosion level of the aluminum material in terms of the corrosion time was estimated by measuring the surface roughness. In addition, fractographic analysis was performed and the oxide films formed on the material surface were studied by scanning electron microscopy (SEM). The results indicated that corrosion actively progressed for four weeks during the initial corrosion phase, the fatigue life significantly decreased, and the surface roughness increased. However, after four weeks, the corrosion reaction tended to slow down due to the passivation phenomenon of the material. Therefore, on the basis of SEM analysis results, it was concluded that the growth of the surface oxide film was reduced after four weeks and then the oxide film on the material surface served as a protection layer and prevented further corrosion.
Investigation of Unbalanced Mass of a Work Roll in a Cold Rolling Mill
Kim, Young-Deuk ; Kim, Chang-Wan ; Park, Hyun-Chul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 429~435
DOI : 10.3795/KSME-A.2012.36.4.429
An abrasion due to continuous friction between a work roll and strip causes the mass of the work roll to be unbalanced in the rolling process. We developed a mathematical model for the rolling mill considering the unbalanced mass and verified the model experimentally. The work roll was approximated as a rigid rotor with eccentricity, and the effect of the unbalanced mass on chatter vibration was investigated. The joint forces computed by quasistatic analysis were applied to the work roll in the rolling mill. Transient responses were obtained, and frequency analysis was performed by solving equations of motion using a direct integration method. Horizontal vibrations were more strongly affected by eccentricity than vertical vibrations. In the horizontal direction, a small eccentricity of 1% of the work roll radius considerably increased the amplitude of the chatter frequency.
An Implicit Integration Method for Joint Coordinate Subsystem Synthesis Method
Jo, Jun-Youn ; Kim, Myoung-Ho ; Kim, Sung-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 437~442
DOI : 10.3795/KSME-A.2012.36.4.437
To analyze a multibody system, this paper proposes an implicit numerical integration method for joint coordinates subsystem synthesis method. To verify the proposed method, a multibody model for an unmanned robot vehicle, which consists of six identical independent suspension systems, is developed. The symbolic method is applied to compute the system Jacobian matrix for the implicit integration method. The proposed method is also verified by performing rough terrain run-over simulation in comparison with the conventional implicit integration method. In addition, to evaluate the efficiency of the proposed method, the CPU time obtained by using this method is compared with that obtained by using the conventional implicit method.
Variation of Fatigue Properties in Nanoskinned Ti-6Al-4V - Rotating Bending and Axial Loading Tension-Compression Cycle -
Suh, Min-Soo ; Pyoun, Young-Shik ; Suh, Chang-Min ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 443~449
DOI : 10.3795/KSME-A.2012.36.4.443
Nanoskins were fabricated on a Ti-6Al-4V material by carrying out various surface treatments, i.e., deep rolling, laser shot peening, and ultrasonic nanocrystal surface modification (UNSM). These surface treatments are newly developed techniques and are becoming more popular for industrial applications. Fatigue tests were carried out using material test system (MTS); these tests included the axial loading tension-compression fatigue test (R = -1, RT, 5 Hz, sinusoidal wave) and rotating bending fatigue test (R = -1, RT, 3200 rpm). The analysis of the crack initiation pattern in the UNSM-treated material indicated that the crack was interior originating in the axial loading tension-compression cycle, and was surface originating in the bending fatigue test. UNSM treatment significantly improved the fatigue strength for the regime of above
cycles that S-N curve of rotating bending stress clearly show the performance of a 5 mm titanium specimen after UNSM treatment is similar to that of an untreated 6 mm titanium specimen.
Application of Saint-Venant's Principle to Anisotropic Beams
Kim, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 451~455
DOI : 10.3795/KSME-A.2012.36.4.451
Asymptotic analysis is a powerful tool for the mathematically rigorous design and analysis of anisotropic beam structures. However, it has a limitation in that the asymptotic approach requires asymptotically correct boundary conditions for higher-order solutions, which are often needed for beams weak in shear. A method utilizing Saint-Venant's principle was proposed in a previous work to improve the stress state of isotropic beams and plates. In this paper, such a method is generalized for anisotropic beams, so that one does not need to consider the asymptotically correct boundary conditions for higher-order solutions. Consequently, solving the recursive system equations is not necessary, which makes the method very efficient in terms of accuracy and computational effort.
A Simulation Study of Artificial Cochlea Based on Artificial Basilar Membrane for Improving the Performance of Frequency Separation
Kim, Tae-In ; Chang, Seong-Min ; Song, Won-Joon ; Bae, Sung-Jae ; Kim, Wan-Doo ; Cho, Maeng-Hyo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 457~463
DOI : 10.3795/KSME-A.2012.36.4.457
The basilar membrane (BM), one of organs of cochlea, has the specific positions of the maximum amplitude at each of related frequencies. This phenomenon is due to the geometry of BM. In this study, as the part of the research for the development of fully implantable artificial cochlea which is based on polymer membrane, parametric studies are performed to suggest the desirable artificial basilar membrane model which can detect wider range of frequency separation. The vibro-acoustic characteristics of the artificial basilar membrane are predicted through finite element analysis using commercial software Abaqus. Simulation results are verified by comparing with experimental results. Various geometric shapes of the BM and residual stress effects on the BM are investigated through the parametric study to enable a wider detectable frequency separation range.
Co-simulation of MultiBody Dynamics and Plenteous Sphere of Contacted Particles Using NVIDIA GPGPU
Park, Ji-Soo ; Yoon, Joon-Shik ; Choi, Jin-Hwan ; Rhim, Sung-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 4, 2012, Pages 465~474
DOI : 10.3795/KSME-A.2012.36.4.465
In this study, a dynamic simulation model that considers many spherical particles and multibody dynamics (MBD) entities is developed. Plenteous spherical particles are solved using the Discrete Element Method (DEM) technique and simulated on a GPU board in a PC. A fast algorithm is used to calculate the Hertzian contact forces between many spherical particles, and NVIDIA CUDA is used to increase the calculation speed. The explicit integration method is applied to solve the many spheres. MBD entities are simulated by recursive formulation. Constraints are reduced by recursive formulation, and the implicit generalized alpha method is applied to solve the dynamic model. A new algorithm is developed to simulate the DEM and MBD models simultaneously. As a numerical example, a truck car model and gear model are developed. The results show that the proposed algorithm using a general-purpose GPU in a PC has many advantages.