• 한국기계가공학회지
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• 제21권5호
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• pp.28-33
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• 2022

A pipe is a hollow, long-form part that is primarily used to transport fluids, such as liquids or gases. Pipes are used in a range of applications in different fields from mechanical purposes to architecture and electrical uses. Despite the significance owing to various usability of pipes, few studies have been conducted using the physical property test method. The tensile test is widely used as a method to check the physical properties of the pipe. The existing pipe tension test contains the possibility to cause errors, which are fractures outside the gauge distance and cross-sectional deformation of the pipe. In this study, a novel pipe tension test method using a jig is presented and pipes with various materials are tested. It is expected that the proposed method can reduce errors that occur in conventional pipes and also obtain more accurate values to enable more efficient testing.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1321-1325
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• 2003

Nickel thin film is one of the most important materials used in micromachined structure. To measure the mechanical properties of electroplated nickel thin film, two techniques are adopted and compared quantitatively with. One is nano-indentation test to measure the elastic modulus. The other is tensile test to measure not only elastic modulus but also yield strength and plastic deformation, ultimate strength. To perform the tensile test, the test apparatus was constructed with linear guided servo motor for actuation, load cell for force measurement and dual microscope for strain measurement.

• Earthquakes and Structures
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• 제13권3호
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• pp.299-307
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• 2017

High Damping Rubber bearings (HDR bearings) have been used in the seismic design of bridge structures widely in China. In earthquakes, structural natural periods will be extended, seismic energy will be dissipated by this kind of bearing. Previously, cyclic loading method was used mainly for test studies on mechanical properties of HDR bearings, which cannot simulate real seismic responses. In this paper, Real-Time Substructure (RTS) test study on mechanical properties of HDR bearings was conducted and it was found that the loading rate effect was not negligible. Then the influence of peak acceleration of ground motion was studied. At last test results were compared with a numerical simulation in the OpenSees software framework with the Kikuchi model. It is found that the Kikuchi model can simulate real mechanical properties of HDR bearings in earthquakes accurately.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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• pp.63-64
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• 2012

In case of concrete, it should be deformed by many factors, such as explosive spalling, thermal strain and creep at high temperature. Structural fire design has been proposed to predict fire damage as national standard. It is general safer to use values obtained from tests of unstressed residual test in stead of stressed test. But most of thermal properties on concrete were conducted with normal aggregate. In this study, it evaluated mechanical properties of concrete with aggregate type and loading condition. we use normal and light aggregate to have different thermal properties. Also, we test mechanical properties to use Ø100×200 mm cylinder specimen according to target temperature and 0%, 20%, 40% loading.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.251-252
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• 2006

Tensile and anisotropy test were performed to evaluate the mechanical properties of coated and uncoated steel. These results were used to predict the deference of formability between two sheets. Cup-drawing test was performed to verify formability of two sheets. Also, Cup-drawing test could predict the coefficient of friction and the forming limit. Finite Element Method of cup-drawing was performed to assess the deference between two sheets considering frictional characteristics. This result was compared with the former results.

• Tribology and Lubricants
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• 제39권6호
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• pp.262-267
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• 2023

Research to replace metal mechanical elements with polymer materials has recently accelerated. However, polymers exhibit less favorable mechanical properties than metal materials, and are often easily worn-out owing to frictional heat when their mechanical elements contact while in relative motion. Therefore, research on the polymer tribological properties is required to employ polymer materials in mechanical elements operating under harsh conditions. In this study, we examine the effect of mechanical part operating temperatures on the material friction and wear characteristics of polymer materials. We conduct ball-on-disk friction tests under dry conditions at various temperatures, using a metal ball with high hardness and a polymer as the counter surface. Each test is repeated at least three times to ensure the reliability of the test results. Before the friction test, we analyze the surface hardness and roughness of each polymer specimen; after the friction test, we use a three-dimensional confocal microscope to compare and analyze the polymer specimen wear characteristics. Based on this study, we systematically elucidate the polymer material tribological characteristics. This information should be useful for selecting and utilizing polymer materials at various temperatures.

• 한국정밀공학회지
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• 제33권10호
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• pp.829-835
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• 2016

Electro-Mechanical Actuator installed on the aircraft plays a key role in an aircraft's flight control through flight control computer. Reliable prediction of the actuator is important for the aircraft. To estimate the lifetime of a product, it is necessary to test full target life. However, it is very difficult to perform it due to the long life time of actuator but short period of development time with increasing cost. Therefore, accelerated life test has been used to reduce the test time for various reasons such as reducing product's development cycle and cost. In this paper, to predict the lifetime of the actuator, we analyzed the flight profile of aircraft and adapted the method of accelerated life test in order to accelerate failure modes that might occur under user conditions. We also set up an endurance test equipment for validating the demanded lifetime of an actuator and performed accelerated life test.

• Tribology and Lubricants
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• 제36권2호
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• pp.75-81
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• 2020

In this paper, we present an experimental investigation of the leakage and endurance performances of mechanical face seals in a 75-tonf turbopump for the Korea Space Launch Vehicle II first-stage engine. A mechanical face seal is used between the fuel pump and turbine to prevent mixing of the fuel and turbine gas. However, excessive leakage occurs through the carbon attached to the mechanical face seal bellows. To reduce this leakage, we redesign the mechanical face seal such that the contact area between the fuel and carbon is reduced, height of the carbon nose is reduced, and stiffness of the bellows is increased. Then, we conduct static and dynamic leakage tests and endurance tests to compare the performances of the original and modified mechanical face seals. The investigation of the leakage of the old and new mechanical face seals confirms that the leakage performance is significantly improved, by 80%, in the new design in comparison with the old design. The endurance tests demonstrate that the average wear rate of carbon in the new mechanical face seal is 0.1094 ㎛/s. The service lifetime is predicted to be 4,200 s, which is 28 times greater than the requirement. Finally, we present a new mechanical face seal in a 75-tonf turbopump, and perform a validation test in the real-propellant test facility at the NARO Space Center. Based on the test results, we can confirm that the modified mechanical face seal works well under real operating conditions.

• Journal of Magnetics
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• 제19권3호
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• pp.300-308
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• 2014

This paper develops a moving-magnet electromagnetic actuator for fast steering mirror (FSM). The actuator achieves a reasonable compromise between voice coil actuator and piezoelectric actuator. The stroke of the actuator is between the strokes of a piezoelectric actuator and a voice coil actuator, and its force output is a linear function of air gap and excitation current within our FSM travel range. Additionally, the actuator is more reliable than voice coil actuator as the electrical connection in the actuator is static. Analytically modeling the actuator is difficult and time-consuming. Alternatively, numerous finite element simulations are carried out for the actuator analysis and design. According to the design results, a real prototype of the actuator is fabricated. An experimental test system is then built. Using the test system, the force output of the fabricated actuator is evaluated. The test results validate the actuator analysis and design.

• Journal of Mechanical Science and Technology
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• 제17권7호
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• pp.1016-1025
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• 2003

The rupture of blood vessels in the human brain results in serious pathological and medical problems. In particular, brain hemorrhage and hematomas resulting from impact to the head are a major cause of death. As such, investigating the tensile behavior and rupture of blood vessels in the brain is very important from a medical point of view. In the present study, the tensile characteristics of the blood vessels in the human brain were analyzed using a quasi-static uniaxial tensile test, and the properties of the arteries and veins compared. In addition, to compare the tensile behavior and demonstrate the validity of the experimental results, blood vessels from the legs of pigs were also tested and analyzed. The overall results were in accordance with the histological structures and previous medical reports.