Journal of Mechanical Science and Technology

Kim, Jong-Dae; Oh, Chae-Youn; Kim, Cheol-Sang

doi: 10.1007/s12206-008-0914-7pmid: N/A

This paper proposes a self-expansion type anterior cruciate ligament fixation device. The proposed fixation device provides graft fixation force by maintaining contact with the bone tunnel. Since the device maintains contact with the bone tunnel by the force that expands by the self-driven elastic force of the device, the main design parameters that determine the performance of this device are the ring thickness and expansion angle. This paper develops the three-dimensional finite element models of the fixation device and bone. By simulation with the developed finite element model, this paper studies the influence of the main design parameters of the device on the maximum stress around the ring when grasping the fixation device. Through the analysis of the stress on the bone tunnel wall when the fixation device comes in contact with the bone tunnel, this paper shows the influence of the main design parameters of the fixation device on the contact condition. In addition, through the analysis of the migration that occur upon application of the pull-out force, this paper studies the influence of the main design parameters on the initial fixation stability of the fixation device.

Lee, Jinyi; Hwang, Jiseong; Jun, Jongwoo; Choi, Seho

doi: 10.1007/s12206-008-0908-5pmid: N/A

Magnetic flux leakage testing (MFLT), which measures the distribution of a magnetic field on a magnetized specimen by using a magnetic sensor such as a Hall sensor, is an effective nondestructive testing (NDT) method for detecting surface cracks on magnetized ferromagnetic materials. A scan-type magnetic camera, based on the principle of MFLT, uses an inclined Hall sensor array on a printed circuit board (PCB) to detect small cracks at high speed. However, the wave forms appear in a direction perpendicular to the scan because the sensors are bonded at different gradients and heights on the PCB despite careful soldering. In this paper, we propose linearly integrated Hall sensors (LIHaS) on a wafer to minimize these waves and to improve the probability of crack detection. A billet specimen is used to determine the effectiveness of the LIHaS in multiple crack detection.

Altan, Gürkan; Topçu, Muzaffer; Bektaş, Numan; Altan, Burçin

doi: 10.1007/s12206-008-0720-2pmid: N/A

An elastic-plastic thermal stress analysis was carried out on an orthotropic aluminum metal matrix composite disc with a hole by using an analytical solution. The thermal load distribution was chosen to vary parabolically from inner surface to outer surface. An aluminum composite disc reinforced curvilinearly by steel fibers was produced under hydraulic press. The mechanical properties of the composite disc were obtained from experiments by using strain gauges. A computer program was developed to calculate the thermal stresses under a parabolic temperature from inner surface to outer surface. The material was assumed to be non-linear hardening. The elastic-plastic solution was performed for the plastic region expanded around the inner surface by an analytical method. The magnitude of the tangential stress component for elastic and elastic-plastic was higher than the magnitude of the radial stress component. Besides, the tangential stress component was compressive on the inner surface and tensile on the outer surface. The magnitude of the tangential residual stress component was the highest on the inner surface of the composite disc. The plastic region began at the inner surface of disc.

Chang, Wen-Tung; Wu, Long-Iong; Liu, Chun-Hsien

doi: 10.1007/s12206-008-0909-4pmid: N/A

The planar-cam type pick-and-place device can clearly and effectively achieve the desired curvilinear motion of its end effector, and it can be designed and fabricated easily. By employing the concept of velocity instant center, the cam profiles, the paths of cutters, the pressure angles and the radii of curvature of the dual cams of the planar-cam type pick-and-place device can be expressed parametrically. The cam profiles may have concave portions, and each minimum radius of curvature of the concave portion of the dual cam profiles is the upper bound of the grinding-wheel radius that may not cause undercutting.

Nam, Jeonghwan; Hawong, Jaisug; Han, Songling; Park, Sunghan

doi: 10.1007/s12206-008-0915-6pmid: N/A

In this paper, photoelastic experimental hybrid methods using the external traction free boundary condition and that using the relative equation of two stress functions in contact problems are developed. The validities of these two methods are confirmed through experiments and discussions. Hertz’s contact theory and the two photoelastic experimental hybrid methods explained are applied to the analysis of the contact stress of an O-ring under 10% or 20% squeeze rate. The photoelastic experimental hybrid method using the relative equation of two stress functions in contact problems was found to be more effective. When the squeeze rates of an O-ring were 10% or 20%, the maximum of absolute σ x was greater than the maximum of absolute σ y , but was almost equal. Maximums of absolute τ xy were 1/8 of absolute σ x and 1/5 of absolute σ x when the squeeze rates of the O-ring were 10% and 20%, respectively.

Jang, T.; Sung, H.; Han, S.; Kwon, S.

doi: 10.1007/s12206-008-0822-xpmid: N/A

The primary aim of the paper is to identify the loading source of infinite beams on an elastic foundation from given information of vertical deflection of infinite beams. An integral equation is obtained for the relationship between loading distribution and vertical deflection. It is shown that the inverse identification of a loading source is one-to-one but ill-posed. Because of ill-posedness, the usual numerical schemes produce arbitrarily large errors. A method for the solution is proposed by using Tikhonov’s regularization. L-curve criterion is introduced for the determination of optimal regularization parameter. Numerical experiments show that the present methodology is accurate and robust in the inverse determination of loading source.

Ahn, Hyeong-Joon

doi: 10.1007/s12206-008-0930-7pmid: N/A

A passive vibration isolator using a negative stiffness mechanism (NSM) is being considered for small precision instruments since it does not need any outer power supply and pressurized air, and its fundamental frequency can be lowered down to 0.5 Hz. Although the working principle of the NSM and its patents are well known, neither the isolation performance limit related to the lowest fundamental frequency nor its nonlinear behavior have been studied. This paper discusses the performance limit of the passive vertical isolator using the NSM and presents the design guidelines for the isolator based on that performance limit. First, a nonlinear dynamic model of the passive isolator is derived through solid approximations, and the fundamental frequency or performance limit is obtained using nonlinear analysis, which entirely explains the nonlinear behavior of the isolator. In addition, the approximate design equations of the isolator are derived to analyze its performance limit. Finally, an approximate expression of the lowest fundamental frequency of the isolator is derived using nonlinear analysis and design equations, which provide substantial design guidelines to improve isolator performance.

Sohn, Jeong-Hyun; Lee, Seung-Kyu; Yoo, Wan-Suk

doi: 10.1007/s12206-008-0712-2pmid: N/A

Although the linear model was widely used for the bushing model in vehicle suspension systems, it could not express the nonlinear characteristics of bushing in terms of the amplitude and the frequency. An artificial neural network model was suggested to consider the hysteretic responses of bushings. This model, however, often diverges due to the uncertainties of the neural network under the unexpected excitation inputs. In this paper, a hybrid neural network bushing model combining linear and neural network is suggested. A linear model was employed to represent linear stiffness and damping effects, and the artificial neural network algorithm was adopted to take into account the hysteretic responses. A rubber test was performed to capture bushing characteristics, where sine excitation with different frequencies and amplitudes is applied. Random test results were used to update the weighting factors of the neural network model. It is proven that the proposed model has more robust characteristics than a simple neural network model under step excitation input. A full car simulation was carried out to verify the proposed bushing models. It was shown that the hybrid model results are almost identical to the linear model under several maneuvers.

Kim, Bong; Kim, Young; Choi, Jungwoon

doi: 10.1007/s12206-008-0505-7pmid: N/A

The purpose of system analysis using fluid induced vibration is to identify the problems of the system in advance by analyzing the vibration behavior of the system excited by fluid flow. Fluid-induced vibration analysis methods, developed so far, generally use the numerical analysis method to analyze the fluid flowing inside the pipe and the infinitesimal elements at normal temperature on the basis of the governing equation obtained by applying Newton’s Second Law and the momentum equation. However, as the fluid temperature changes greatly at low temperature, fluid-induced vibration analysis methods for normal temperature cannot be applied. This study investigated methods of analyzing fluid-induced vibration in consideration of the cooling effect. In consideration of the changes in the properties of the fluid and system relative to temperature, vibration behavior was analyzed numerically by means of the equation of motion. As a result, the natural frequency of the system tends to change because of the changes of the properties of materials even when the flux is constant inside the pipe, and the vibration behavior of the system was compared to that in case of normal temperature to analyze how much influence the cooling effect has on the vibration behavior of the system.

Kim, Jae-On; Lee, Kee-Seok; Lee, Jin-Woo

doi: 10.1007/s12206-008-0823-9pmid: N/A

Problems related to the stability and behavior of a cantilevered beam with a tip mass on an elastic foundation and subjected to a distributed follower force are addressed. The stability of a beam partially attached to an elastic foundation is also considered. The dynamic stability of a beam subjected to a distributed follower force is formulated by using finite element method to get a general eigenvalue problem. The influence of the modulus on the elastic foundation and the ratio of the cantilevered beam’s mass to the tip mass on the critical flutter are investigated. Finally, the stability of the cantilevered beam is found to depend on both the modulus of the elastic foundation and the ratio of the cantilevered beam’s mass to the tip mass.