• 한국정밀공학회지
• /
• 제22권11호
• /
• pp.111-117
• /
• 2005

The vibration problems associated with gear coupled rotors have been the focus of much engineering work. These systems are complex and difficult to analyze in that they have the problems associated with conventional rotors plus those additional problems associated with the gear couplings. This paper examines the problems peculiar to the gear mesh. Because of the meshing action of gears, the elasticity of the gear teeth introduces time-varying stiffness coefficients into the governing equations of motion. This means that system response must be thought of in terms of Mathieu-type equations, where multiple-frequency response occur due to the periodic coefficients. The meshing action of the gears also couples the lateral and torsional gear motions. Gear errors, such as tooth profile and spacing errors, produce forces and torque that excite the system at multiple frequencies, some of which are much higher than shaft rotational speed. To investigate how to the time-varying stiffness in the gear teeth and the gear errors act one the dynamic response of the gear coupled rotors, a three-dimensional dynamic model with lateral-tortional oscillation is developed. The harmonic balance technique is employed to solve this mathieu-type problem.

• 패션비즈니스
• /
• 제15권5호
• /
• pp.103-114
• /
• 2011

During a wearer's movement, the apparel fabric layers collide each other in a highly complicated manner. The collision involves cloth-cloth, and cloth-body collision. The diversity of the textile fabrics, including silk, wool, cotton, and other synthetic fibers, together with the complex details of the apparel construction, makes the collision and other calculation procedure involved in the 3-dimensional clothing software system much more complicated. Therefore, there is a need to measure the behavior of the fabrics during the fabric collision cycles. In this study, as a first step, static measurements pertinent to the factors governing the appearance of the apparel fabrics were implemented. The drape profile, stiffness(Sd and Sf), tensile properties, thickness, and the air permeability were measured. The correlation between the parameters were calculated and reviewed. It is found that there is a high correlation of 0.97 between the actual fabric drape parameters and the 3D virtual fabric drape parameters. The measured drape coefficients of the fabrics show relatively good correlation with the measured fabric stiffness.

• Structural Engineering and Mechanics
• /
• 제81권6호
• /
• pp.751-767
• /
• 2022

In the hogging bending moment area, continuous composite beams are subjected to the ultimate limit state of lateral-torsional buckling (LTB), which depends on web stiffness as well as concrete slab and shear connection stiffnesses. The design of the LTB and the determination of the elastic critical moment are produced approximately, using the European Standard EN 1994-1-1:2004, for continuous composite steel beams, but is applicable only for those with a plane web steel profile. Also, and from the previous researches, the elastic critical moment of the continuous composite beams with corrugated sinusoidal web steel profiles was determined. In this paper, a finite element analysis (FEA) model was developed using the ANSYS 16 software, to determine the elastic critical moments of continuous composite steel beams with various corrugated web profiles, such as trapezoidal, zigzag, and rectangular profiles, which were evaluated against numerical data of the sinusoidal one from the literature. Ultimately, the failure load of a composite steel beam with various web profiles was predicted by studying 46 models, based on FEA modeling, and a procedure for predicting the elastic critical moment of composite beams with various web steel profiles was proposed. When compared to sinusoidal web profiles, the trapezoidal, zigzag, and rectangular web profiles required an average increase in load capacity and stiffness of 7%, 17.5%, and 28%, respectively, according to the finite element analysis. Also, the rectangular web steel profile has a greater stiffness and load capacity. In contrast, the sinusoidal web has lower values for these characteristics.

• 대한기계학회논문집
• /
• 제18권12호
• /
• pp.3246-3252
• /
• 1994

The vibration of meshing gear system is originated form teeth deformation, teeth contact ratio, profile error, etc. The gear vibration is classified as whine vibration during meshing and as rattle vibration during idling. In this study, the whine vibration is investigated under the assumption of piecewise linearity of elastic stiffness due to the variation of meshing. Numerical, theoretical and experimental investigations show the existence of the superharmonic components of the second and the third order. consistently It can be concluded that the superharmonic components in whine vibration of meshing gear is originated from the stiffness variation. It also shows that the higher order harmonics are reduced on the increase of motor speed.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2005년도 춘계학술대회 논문집
• /
• pp.722-725
• /
• 2005

Recently, ground-borne noise and vibration generated by underground transit system has been recognized as an important environmental problem. This study reviews several of the improved procedures that have been used to predict ground-borne vibration. At first, ground stiffness profile is examined by SASW test which is the most reasonable surface wave test. It is very important to acquire the exact ground stiffness profile at ground response analysis. At second, the train loading to act roadbed is calculated by using the real measured phase angle data. In finite element analysis, averaged acceleration method, infinite element, Rayleigh damping and 2-dimensional wave propagation analysis is performed.

• 한국안전학회지
• /
• 제21권3호
• /
• pp.87-93
• /
• 2006

When a structure is constructed at the site composed of soil, the behavior of a structure is much affected by the characteristics of soil. Therefore, the effect of soil-structure interaction is an important consideration in the design of a structure at the site composed of soil. Precise analysis of soil-structure interaction requires a proper description of soil profile. However, most of approaches are nearly unpractical for soil exhibiting material discontinuity and complex geometry since those cannot consider precisely complicated soil profiles. To overcome these difficulties, an improved integration method is adopted and enables to integrate easily over an element with material discontinuity. As a result the mesh can be generated rapidly and highly structured, leading to regular and precise stiffness matrix. The influence of soil profile on the response is examined by the presented method. It is seen that the presented method can be easily used on soil-structure interaction problems with complicated soil profile and produce reliable results regardless of material discontinuities.

• Journal of Mechanical Science and Technology
• /
• 제14권3호
• /
• pp.283-290
• /
• 2000

To maintain the specific volumetric efficiency of a heavy-duty diesel engine, an understanding of the behavior of each part of the valve train system is very important. The stiffness of the valve train system has a strong influence on the behavior of the valve train than valve clearance, heatresistance, or the durability of parts. In this study, a geometrical cam design profile using a finite element model of the valve train system is suggested. The results of the valve behavior according to the change in stiffness is analyzed for further tuning of the valve train system.

• 한국정밀공학회지
• /
• 제13권4호
• /
• pp.129-135
• /
• 1996

The area of gear vibration and noise, has recently been the focus of many studies. The proper kinematic and geometric design of gears, the mathematical modeling of gear system are essential for a good design. This work present a gear disign for reducing noise, and practical approaches used for machinery noise reduction slong with the summary of methods available for predicting gear noise in terms of the transmis- sion error, and show a comparative study with other methods. A new tooth profile modification is proposed for reducing vibration and noise of involute gears. The method is based on the use of cubic spline curves. The tooth profile is constrained to assume an involute shape during the loaded operation. Thus the new gear profile assures conjugate motion at all points along the line of action. The new profile is found to result in a more uniform static transmission error compared to not only standard involute profile but also modificated profile therby contributing to the improvement of vibration and noise characteristics of the gear.

• 한국지반공학회지:지반
• /
• 제6권4호
• /
• pp.43-52
• /
• 1990

수평방향의 조화진동을 받는 말뚝주변의 지반특성에 관한 각종 계수들의 효과를 연구하였다. 그리고 비선형 해석을 위하여 말뚝주변의 흙을 성질이 같은 여러개의 동심고리 모양으로 나누어 지반반력 또는 흙의 강성을 계산하였으며 다음과 같은 결론을 얻었다. 1) 강성의 실수와 허수부분은 무차원 주파수가 증가함에 따라 전단 계수비, 포아슨비, 그리고 외부영역까지의 거리의 비에 대하여 큰 변화를 나타냈고 그 차이는 강성의 허수부분에 더 현저하게 나타났다. 2) 흙의 강성의 외부영역까지의 거리가 증가할수록 현저하게 감소하였는데 강성의 실수부분은 주파수가 작을수록 크게 나타났다. 반면에 허수부분은 작게 나타났다.

• 한국생산제조학회지
• /
• 제21권1호
• /
• pp.130-136
• /
• 2012

Dynamic as well as static and geometric design parameters such as inertia, tooth profile, backlash and clearance can be directly considered via multi-body dynamic analysis along with contact analysis. However, it is time consuming to use finite elements for the consideration of the tooth flexibility in the multi-body dynamic analysis of gears. A computationally efficient procedure, so called, Gear Stiffness Module, is suggested to resolve this calculation time issue. The characteristics of gear tooth compliance are discussed and rotational stiffness element concept for the Gear Stiffness Module is presented. Transmission error analyses for a spur gear system are carried out to validate the reliability and efficiency of the module. Compared with the finite element model, the Gear Stiffness Module yields considerably similar results and takes only 3% of calculation time.