• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.171-180
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• 2003

One of the most significant problems in the processing of composite materials is residual stress. The high residual stress may cause cracking in the matrix without external loads and degrade the integrity of composite structures. In this study, thermo-viscoelastic residual stresses occurred in an aluminum liner-inserted polymer composite cylinder are investigated. This type of the structure is used for rocket fuselage due to the convenience to attach payloads and equipment to the metal liner by machining. The time and degree of cure dependent thermo-viscoelastic constitutive equations are developed and coupled with a thermo-chemical process model. These equations are solved with the finite element method to predict the residual stresses in the composite cylinder and also in the interface between the liner and the composite during cure.

• 한국가스학회지
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• 제15권4호
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• pp.21-26
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• 2011

Type-3 용기 라이너는 두께가 5 mm일뿐 아니라 곡률을 가지고 있기 때문에 파괴인성시험을 위한 표준형 시편의 제작에 어려움이 있다. 따라서 용기 라이너의 파괴인성을 평가하기 위해서는 소형시편 시험기법이 도입되어야 한다. 본 연구에서는 용기 라이너의 파괴인성을 평가하기 위해 소형펀치(small punch, SP)시험법을 도입하였다. SP시험으로부터 측정된 하중-변위 곡선 결과에서 라이너 재료는 연성이 소진하여 막신장 영역에서 파손되었다. 라이너 재료는 제작공정 특성에 기인하여 소성변형량이 방향에 따라 다름에도 불구하고 등방성 파괴양상을 보였다. SP시험 데이터를 사용하여 파괴인성을 평가한 결과 $J_{Ic}=13.0kJ/m^2$ 이었다. 이 값은 동종재료의 파괴인성 값과 유사하다. 따라서 SP시험 데이터를 사용하여 평가한 파괴인성은 타당하며, 완성된 용기 라이너는 유효한 파괴인성 값을 유지하는 것으로 확인 되었다.

• Tribology and Lubricants
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• 제28권5호
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• pp.233-239
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• 2012

The engine of a large ship operates under wet conditions using a fuel such as bunker C oil, which includes sulfur and many impurities. A cylinder liner made of cast iron is very susceptible to damage such as scuffing on the surface. This scuffing can reliably be attributed to the destruction of the oil film and the corrosion wear caused by water and sulfur included in the fuel, along with abrasion impurities and poor lubricants. In this study, a reciprocating friction and wear test was carried out with a cast iron specimen, which was used to simulate an engine cylinder in a corrosive environment. Base-oil and stirred oil containing distilled water, NaCl solution, and dilute sulfuric acid were used as lubricants. The friction surface was analyzed using a microscope and EDAX, and the friction coefficient was measured using a load-cell under each experimental condition. We then attempted to investigate the damage to the cylinder liner using the results.

• 한국생산제조학회지
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• 제21권1호
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• pp.1-6
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• 2012

This paper presents a stress safety of a composite pressure cylinder for a hydrogen gas vehicle. The composite pressure cylinder in which is composed of an aluminum liner and carbon fiber wound layers contains 104 liter hydrogen gas, and is compressed by a filling pressure of 70 MPa. The FEM computed results are analyzed based on the US DOT-CFFC basic requirement for a hydrogen gas cylinder and KS B ISO specification. The FEM results indicate that the stress, 255.2 MPa of an aluminum liner is sufficiently low compared with that of 272 MPa, which is 95% level of a yield stress for aluminum. Also, the composite layers in which are wound on the surface of an aluminum cylinder are safe because the stress ratios from 3.46 to 3.57 in hoop and helical directions are above 2.4 for a minimum safety level. The proposed composite pressure cylinder wound by carbon fibers is useful for 70 MPa hydrogen gas vehicles.

• 한국기계가공학회지
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• 제20권10호
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• pp.1-8
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• 2021

Cylinder liners used in diesel engines of combat equipment are prone to cavitation due to wet cooling. The damage caused by erosion and corrosion due to cavitation has a fatal effect on the performance and lifespan of a diesel engine. Therefore, a study was conducted to improve the durability of cylinder liners. Two surface treatment techniques were proposed: nitriding and chrome plating. It was observed that the amount of erosion on the surface of nitride-treated cylinder liners was high because the surface-treated part eroded due to its weak impact resistance against the bubble explosion generated by cavitation. In contrast, the chrome-plated cylinder liner had a lower amount of erosion among the specimens subjected to the accelerated test. These results verified that the resistance of chrome-plated liners against cavitation is high. Therefore, it can withstand the impact of bubble explosion. If the chrome plating thickness is set with reference to the KS standard, an exceptional durability of abrasion, wear resistance, and corrosion resistance can be obtained. If the thickness is set between 120~250㎛, it is expected that the durability of the cylinder liner can be improved. Although a recovery method for corroded cylinder liners is suggested, the proposed method has an inherent risk of crack generation. Therefore, further research is required to solve this problem.

• 한국가스학회지
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• 제17권6호
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• pp.46-51
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• 2013

복합재 압력용기는 높은 비강성과 비강도 그리고 내피로성으로 수소연료전지자동차와 천연가스자동차에 사용된다. 이음매가 없는 일체형 라이너를 갖는 복합재 압력용기는 고강도 탄소섬유와 에폭시 레진으로 라이너 전체를 감싼다. 본 연구에서는 구조적으로 취약한 너클 부위와 압축잔류응력을 고려하여 필라멘트 와인딩 패턴과 자긴압력 설계 기법을 제시하였다. 복합재 압력용기 시제품에 대한 압력반복시험을 통해 제안된 방법을 검증한다.

• 한국자동차공학회논문집
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• 제1권2호
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• pp.89-102
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• 1993

In this experimental investigation, various plasma-sprayed zirconia contained coatings and a kind of alumina-zirconia coating were studied to gain a better understanding of their tribological behaviour under dry contact condition in a reciprocating motion at temperature of 200℃. Particular attention was made for finding appropriate coatings in cylinder liner/piston ring application with an emphasis on the antiwear property. In order to identify the wear mechanism, SEM(Scanning Electron Microscope), optical micrograph, and roughness tester were used. Alumina-zirconia and 8% yttria-zirconia were found to be most appropriate for the application to the cylinder liner/piston ring and, especially, alumina-zirconia exhibited highest wear-resistance and also showed good friction characteristics. Wear mechanisms of ceramic coatings identified.

• 열처리공학회지
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• 제20권2호
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• pp.72-77
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• 2007

Abrasive wear between piston ring face and cylinder liner is an extremely unpredictable and hard-to-reproduce phenomenon that significantly decreases engine performance. Wear by abrasion are forms of wear caused by contact between a particle and solid material. Abrasive wear is the loss of material by the passage of hard particles over a surface. From the pin-on-disk test, particle dent test and scuffing test, abrasive wear characteristics of diesel engine cylinder liner-piston ring have been investigated. Pin-on-disk test results indicate that abrasive wear resistance is not simply related to the hardness of materials, but is influenced also by the microstructure, temperature, lubricity and micro- fracture properties. In particle dent test, dent resistance stress decreases with increasing temperature. From the scuffing test by using pin-on-disk tester, scuffing mechanisms for the soft coating and hard coating were proposed and experimentally confirmed.

• 오토저널
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• 제2권1호
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• pp.39-50
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• 1980

This paper presents the variations obtained in heat flow rate and engine performance of a four-stroke cycle Diesel engine when there were changes in the temperature of cooling water, compression ratio, injection timing of fuel, and other factors. Heat dissipation of engine cylinder was calculated by the heat transfer coefficient of Nusselt's empirical equation and the analysis of distribution of temperature in cylinder barrel was obtained by the finite element method of two-dimensional steady state heat conduction. In this experiment, the out side temperature of cylinder liner was measured by the data logger, and the temperature distribution of liner was computed by the analysis of triangular finite element model under the assumption due to surface heat flux of cylinder inner surface. The results obtained by this study are as follows. Under the given operating condition, the temperature distribution of cylinder liner by using finite element method shows that the mean temperature of barrel is in accordance with the experimental results of Eichelberg and temperature difference is lower than 4.23.deg. C. The heat dissipation of engine decrease in accordance with the decrease of piston mean velocity, compression ratio, and the increase of coolant temperature. Influence on the delay of injection timing of fuel brings about the decrease of heat rejection over the cylinder at constant test conditions.

• Tribology and Lubricants
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• 제30권6호
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• pp.356-363
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• 2014

Marine diesel engines operate in environments in which damage easily occurs from corrosion. Recently, damage to cylinder liners has increased from corrosion wear caused by increased engine power. This damage can cause serious problems in the economy. Thus, many researchers have treated and studied damaged cylinder liners. However, a method is necessary for real-time monitoring of damage to cylinder liners during operation of the engine, before serious damage can occur. This study carries out reciprocating friction and wear tests on a cast iron specimen under various corrosion atmospheres and verifies the variations of friction coefficient and friction surface. Additionally, the friction coefficient and friction status are predicted by using a neural network that learns the vibration and frequency spectrum data from an acceleration sensor. According to our conclusions, amplitude is distributed highly at high frequencies, and values of standard deviation and kurtosis are high when damage to the friction surface is serious. The accuracy rate of the friction coefficient predicted by the neural network is over 80% of the real measured value without NaCl, and application of the neural network is very effective for diagnosing the friction condition and damage to the cylinder liner.