• 대한기계학회논문집A
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• 제24권8호
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• pp.1949-1957
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• 2000

All the loads in the real world act dynamically on structures. Since dynamic loads are extremely difficult to handle in analysis and design, static loads are utilized with dynamic factors. The dyna mic factors are generally determined based on experiences. Therefore, the static loads can cause problems in precise analysis and design. An analytical method based on modal analysis has been proposed for the transformation of dynamic loads into equivalent static load sets. Equivalent static load sets are calculated to generate an identical displacement field in a structure with that from dynamic loads at a certain time. The process is derived and evaluated mathematically. The method is verified through numerical tests. Various characteristics are identified to match the dynamic and the static behaviors. For example, the opposite direction of a dynamic load should be considered due to the vibration response. A dynamic bad is transformed to multiple equivalent static loads according to the number of the critical times. The places of the equivalent static load can be different from those of the dynamic load. An optimization method is defined to use the equivalent static loads. The developed optimization process has the same effect as the dynamic optimization which uses the dynamic loads directly. Standard examples are solved and the results are discussed

• 설비공학논문집
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• 제13권6호
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• pp.490-496
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• 2001

An experimental study on the behavior of the water hold-up by condensation of a fin-and-tube heat exchanger with regard to the surface characteristics, i.e., contact angle, was conducted. The static and dynamic contact angles were measured, and condensation experiments were conducted. Flow patterns on the fins with different surface characteristics were visualized. Results showed that the static contact angle is proportional to the dynamic contact angle within the range of this study. The water hold-up of the heat exchanger increases as the static or dynamic contact angle of its surfaces increases. Existence of transition of flow patterns was found as the static or dynamic angle increase. Due to the transition in the flow patterns, changes in the gradient of the water hold-up is occurred around the static angle of 8$0^{\circ}C$.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.602-607
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• 1998

Rubber materials are extensively used in various machine design application, mainly for vibration/shock/noise control devices. Over the years an enormous effort has been put into developing procedures to provide properties of rubber material for design function. However, there are still a lot of difficulties in the understanding of dynamic characteristics of the rubber components in compression. In this paper, the dynamic characteristics of rubber materials for anti-vibration under compression were investigated. Dynamic and static tests for rubber material with 3 different hardness were performed. In dynamic tests, non-resonance method, impedance method, was used to obtain the complex modulus (storage modulus and loss factor) and the effects of static pre-strain on the dynamic characteristics were investigated. Also, a relation equation between linear dynamic and nonlinear static behavior of rubber material was discussed and its usefulness to predict their combined effects was investigated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.780-783
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• 2003

In this study, As The Tae Yang Metal company manufactured oil tank inserts welding structure bogie, it is Contributed in stability security of freight car of oil tank through static load test, dynamic characteristics analysis. vibration performance test etc. to verify intensity of bogie frame ＆ body structure

• 한국군사과학기술학회지
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• 제12권4호
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• pp.491-499
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• 2009

The determination of response characteristics for pressure sensors is routinely limited to static calibration against a deadweight pressure standard. The strength of this method is that the deadweight device is a primary standard used to generate precise pressure. Its weakness lies in the assumption that the static and dynamic responses of the sensor in question are equivalent. Differences in sensor response to static and dynamic events, however, can lead to serious measurement errors. Dynamic techniques are required to calibrate pressure sensors measuring dynamic events in milliseconds. In this paper, a dynamic calibration using negative going dynamic pressure is proposed to determine dynamic pressure response for piezoelectric sensors. Sensitivity and linearity of sensor by the dynamic calibration were compared with those by the static calibration. The uncertainty of calibration results and the goodness of fit test of linear regression analysis were presented. The results show that the dynamic calibration is applicable to determine dynamic pressure response for piezoelectric sensors.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1011-1016
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• 2004

All the loads in the real world are dynamic loads and it is well known that structural optimization under dynamic loads is very difficult. Thus the dynamic loads are often transformed to the static loads using dynamic factors. However, due to the difference of load characters, there can be considerable differences between the results from static and dynamic analyses. When the natural frequency of a structure is high, the dynamic analysis result is similar to that of static analysis due to the small inertia effect on the behavior of the structure. However, if the natural frequency is low, the inertia effect should not be ignored. Then, the behavior of the dynamic system is different from that of the static system. The difference of the two cases can be explained from the relationship between the homogeneous and the particular solutions of the differential equation that governs the behavior of the structure. Through various examples, the difference between the dynamic analysis and the static analysis are shown. Also the optimization results considering dynamic loads are compared with static loads.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.748-752
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• 2004

Fluid dynamic bearings (FDBs) have been replacing ball bearings of the HDD spindle motor very rapidly. But there are several demerits of HDB, such as high friction torque, variable viscosity of the fluid lubricant depending on operating temperature, low stiffness, and etc. Eccentricity is one of the major parameters which affects the static and dynamic characteristics. As the static eccentricity is larger, the stiffness and the damping coefficients become bigger. But friction torque is relatively unaffected by the static eccentricity. This research proposes a new type of journal bearing with asymmetric journal grooves which results in better dynamic characteristics. The static and dynamic characteristics of the new journal bearing are investigated by solving the Reynolds' equation with FEM, and the transient analysis is performed to predict the dynamic behavior of rotor by solving the equations of motion of a HDD spindle system with Runge-Kutta method. The result shows that the proposed Journal bearings have much bigger stiffness and damping coefficients compared with the conventional symmetric ones. And consequently, it has smaller whirl radius and tilting angle.

• International Journal of Aeronautical and Space Sciences
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• 제2권2호
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• pp.82-94
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• 2001

The purpose of this paper is to analyze the static and dynamic stability-of the unmanned airship under development ; the target airship's over-all length of hull is 50m and the maximum diameter is 12.5m. For the analysis, the dynamic model of an airship was defined and both the nonlinear and linear dynamic equations of motion were derived. Two different configuration models (KA002Y and KA003Y) of the airship were used for the target model of the static stability analysis and the dynamic stability analysis. From the result of analyses, though the airship is unstable in static stability, dynamic characteristics of the airship can provide the stable dynamic stability. All of the results, airship models and dynamic flight equations will be an important basement and basic information for the next step of developing the automatic flight control system(AFCS) and the stability augmentation system(SAS) for the unmanned airship as well as for the stratospheric airship in the future.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.186-194
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• 2004

Experiments were conducted to determine the structural static and dynamic characteristics of air foil bearings. The housing of the bearing on the journal was driven by an impact hammer which was used to simulate dynamic forces acting on the bump loll with various leading condition. Two different bump foils (Cu-coated bump and viscoelastic bump) were tested and the static and dynamic coefficients of two bump foils compared, based on the experimental measurements for a wide range of operating conditions. The static and dynamic characteristics of air foil bearings were extracted 0rpm the frequency response function by least square method and IV(Instrumental Variable) method. The experiment was tested at 0rpm and $10,000\~16,000rpm$, and loaded on $50\~150N$. From the test results, the possibility of the application of high load and high speed condition is suggested.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.895-900
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• 2001

It is very important for impact analysis to reflect the dynamic characteristics of materials as well as the static characteristics. As the dynamic behavior of a material is different from the static(or quasi-static) one due to the inertia effect and the stress wave propagation, an adequate experimental technique has to be developed to obtain the dynamic responses for the corresponding level of the strain rate. To determine the dynamic characteristics of materials, the Hopkinson bar (compression type) experiment is carried out. For using dynamic material properties, Johnson-Cook model is applied in impact analysis with explicit finite element method