• Tribology and Lubricants
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• 제40권4호
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• pp.133-138
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• 2024

This study evaluates the structural safety of wind turbine blades, analyzes the behavior of composite laminate structures with and without defects, and assesses surface erosion wear. The NREL 5 MW standard is applied to assign accurate composite material properties to each blade section. Modeling and analysis of the wind turbine blades reveal stable behavior under individual load conditions (gravity, motor speed, wind speed), with the web bearing most of the load. Surface erosion wear analysis in which microparticle impacts are simulated on the blade coating shows a maximum stress and maximum displacement of 14 MPa and 0.02 mm, respectively, indicating good initial durability, but suggest potential long-term performance issues due to cumulative effects. The study examines defect effects on composite laminate structures to compare the stress distribution, strain, and stiffness characteristics between normal and cracked states. Although normal conditions exhibit stable behavior, crack defects lead to fiber breakage, high-stress concentration in the vulnerable resin layer, and decreased rigidity. This demonstrates that local defects can compromise the safety of the entire structure. The study utilizes finite element analysis to simulate various load scenarios and defect conditions. Results show that even minor defects can significantly alter stress distributions and potentially lead to catastrophic failure if left unaddressed. These findings provide valuable insights for wind turbine blade safety evaluations, surface protection strategies, and composite structure health management. The methodology and results can inform the design improvements, maintenance strategies, and defect detection techniques of the wind energy industry.

• 한국표면공학회지
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• 제46권2호
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• pp.68-74
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• 2013

For the coating of diamond films on WC-Co tools, a buffer interlayer is needed because Co catalyzes diamond into graphite. W and Ti were chosen as candidate interlayer materials to prevent the diffusion of Co during diamond deposition. W or Ti interlayer of $1{\mu}m$ thickness was deposited on WC-Co substrate under Ar in a DC magnetron sputter. After seeding treatment of the interlayer-deposited specimens in an ultrasonic bath containing nanometer diamond powders, $2{\mu}m$ thick nanocrystalline diamond (NCD) films were deposited at $600^{\circ}C$ over the metal layers in a 2.45 GHz microwave plasma CVD system. The cross-sectional morphology of films was observed by FESEM. X-ray diffraction and visual Raman spectroscopy were used to confirm the NCD crystal structure. Micro hardness was measured by nano-indenter. The coefficient of friction (COF) was measured by tribology test using ball on disk method. After tribology test, wear tracks were examined by optical microscope and alpha step profiler. Rockwell C indentation test was performed to characterize the adhesion between films and substrate. Ti and W were found good interlayer materials to act as Co diffusion barriers and diamond nucleation layers. The COFs on NCD films with W or Ti interlayer were measured as less than 0.1 whereas that on bare WC-Co was 0.6~1.0. However, W interlayer exhibited better results than Ti in terms of the adhesion to WC-Co substrate and to NCD film. This result is believed to be due to smaller difference in the coefficients of thermal expansion of the related films in the case of W interlayer than Ti one. By varying the thickness of W interlayer as 1, 2, and $4{\mu}m$ with a fixed $2{\mu}m$ thick NCD film, no difference in COF and wear behavior but a significant change in adhesion was observed. It was shown that the thicker the interlayer, the stronger the adhesion. It is suggested that thicker W interlayer is more effective in relieving the residual stress of NCD film during cooling after deposition and results in stronger adhesion.

• 한국세라믹학회지
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• 제39권9호
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• pp.851-856
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• 2002

산화몰리브덴($MoO_3$)이 첨가된 산화크롬 용사코팅층을 제조하여 산화몰리브덴의 첨가에 따른 고온(450$^{\circ}C$)에서의 플라즈마 용사코팅층에 마찰, 마멸특성을 조사하였다. 마찰, 마멸 특성에 대한 실험을 위하여 왕복동 마멸시험장치를 사용하였다. TEM을 이용하여 코팅층의 미세 구조와 각 상들의 조성을 살펴보았다. 분석 결과에 의하면 산화몰리브덴이 입계로 분산되어 있어 코팅층의 경도와 밀도의 증가가 발생하였다. 마멸시험후 마멸면의 물리적 변화와 화학적 조성의 변화를 SEM와 XPS를 통하여 살펴보았다. 산화몰리브덴이 첨가된 코팅층에서 마찰계수의 감소를 관찰할 수 있었다. 산화몰리브덴이 첨가된 코팅의 마멸된 표면에 마찰, 마멸에 유리한 보호막의 형성이 광범위하게 일어남을 알 수 있었다. 이러한 보호막에 몰리브덴이 산화몰리브덴의 형태로 존재하는 것을 XPS 분석을 통하여 알 수 있었다. 보호막에 산화몰리브덴의 존재가 마찰계수를 감소시키는 것으로 생각된다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.111-112
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• 2009

Diamond-like carbon (DLC) is a convenient term to indicate the compositions of the various forms of amorphous carbon (a-C), tetrahedral amorphous carbon (ta-C), hydrogenated amorphous carbon and tetrahedral amorphous carbon (a-C:H and ta-C:H). The a-C film with disordered graphitic ordering, such as soot, chars, glassy carbon, and evaporated a-C, is shown in the lower left hand corner. If the fraction of sp3 bonding reaches a high degree, such an a-C is denoted as tetrahedral amorphous carbon (ta-C), in order to distinguish it from sp2 a-C [2]. Two hydrocarbon polymers, that is, polyethylene (CH2)n and polyacetylene (CH)n, define the limits of the triangle in the right hand corner beyond which interconnecting C-C networks do not form, and only strait-chain molecules are formed. The DLC films, i.e. a-C, ta-C, a-C:H and ta-C:H, have some extreme properties similar to diamond, such as hardness, elastic modulus and chemical inertness. These films are great advantages for many applications. One of the most important applications of the carbon-based films is the coating for magnetic hard disk recording. The second successful application is wear protective and antireflective films for IR windows. The third application is wear protection of bearings and sliding friction parts. The fourth is precision gages for the automotive industry. Recently, exciting ongoing study [1] tries to deposit a carbon-based protective film on engine parts (e.g. engine cylinders and pistons) taking into account not only low friction and wear, but also self lubricating properties. Reduction of the oil consumption is expected. Currently, for an additional application field, the carbon-based films are extensively studied as excellent candidates for biocompatible films on biomedical implants. The carbon-based films consist of carbon, hydrogen and nitrogen, which are biologically harmless as well as the main elements of human body. Some in vitro and limited in vivo studies on the biological effects of carbon-based films have been studied [$2{\sim}5$].The carbon-based films have great potentials in many fields. However, a few technological issues for carbon-based film are still needed to be studied to improve the applicability. Aisenberg and Chabot [3] firstly prepared an amorphous carbon film on substrates remained at room temperature using a beam of carbon ions produced using argon plasma. Spencer et al. [4] had subsequently developed this field. Many deposition techniques for DLC films have been developed to increase the fraction of sp3 bonding in the films. The a-C films have been prepared by a variety of deposition methods such as ion plating, DC or RF sputtering, RF or DC plasma enhanced chemical vapor deposition (PECVD), electron cyclotron resonance chemical vapor deposition (ECR-CVD), ion implantation, ablation, pulsed laser deposition and cathodic arc deposition, from a variety of carbon target or gaseous sources materials [5]. Sputtering is the most common deposition method for a-C film. Deposited films by these plasma methods, such as plasma enhanced chemical vapor deposition (PECVD) [6], are ranged into the interior of the triangle. Application fields of DLC films investigated from papers. Many papers purposed to apply for tribology due to the carbon-based films of low friction and wear resistance. Figure 1 shows the percentage of DLC research interest for application field. The biggest portion is tribology field. It is occupied 57%. Second, biomedical field hold 14%. Nowadays, biomedical field is took notice in many countries and significantly increased the research papers. DLC films actually applied to many industries in 2005 as shown figure 2. The most applied fields are mold and machinery industries. It took over 50%. The automobile industry is more and more increase application parts. In the near future, automobile industry is expected a big market for DLC coating. Figure 1 Research interests of carbon-based filmsFigure 2 Demand ratio of DLC coating for industry in 2005. In this presentation, I will introduce a trend of carbon-based coating research and applications.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1989년도 제10회 학술강연회초록집
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• pp.41-58
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• 1989

현재 자동차엔진유를 비롯한 각종윤활유에 마찰마모방지제 및 산화방지제로 사용되고 있는 유용성 몰리부덴계 화합물은 윤활제의 첨가제로서 주목받고 있다. 이와 같은 유용성 몰리부덴계 화합물은 윤활제의 첨가제로서 마찰부분의 고온에 의해 열분해함으 2 유화몰리부덴($MoS_2$)을 생성하기 위해서 합성한 것이다. $MoS_2$는 마찰마모 감소제로서 잘 알려져 있지만 고체이기 때문에 마찰면에 COATING 하거나 윤활유에 분산시켜 사용하고 있다. 그러나 윤활유에 분산시키는 것과 마찰면에 흡착시키는 것과는 계면화학적 반대현상이므로 문제가 발생하게 된다. 그러므로 윤활유중에 안정한 분산계를 만들어 사용시에는 비교적 안정한 COLLOID 계가 파손되지 않아야 한다. 그러나 열가학적으로 불안정한 COLLOID 계를 유지하기는 어려운 문제이다. 그러므로 유용성인 몰리부덴계 화합물을 윤활유에 용해시켜 열적 혹은 TRIBOCHEMICAL 적으로 분해해 줌으로서 마찰표면에 $MoS_2$의 생성이 필요하다. 이와같은 목적으로 개발된 유용성 몰리부덴화합물은 마찰마모감소작용 및 산화방지작용의 메카니즘에 관해서는 불투명한 점이 많다. 본 논문은 유용성 몰리부덴계 화합물중 Molybdenum dialkyl dithiocarbamate (이후 MoDTC로 명함)를 윤활유 첨가제로 사용해 마찰실험을 통하여 마찰감소작용의 메카니즘을 해명하고, 특히 마찰표면에 생성될 $MoS_2$막의 효과에 관해 중점을 두고 분위기의 효과로 부터 MoDTC의 마찰감소작용의 인자에 대한 고찰을 행하였다.

• 대한기계학회논문집A
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• 제20권10호
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• pp.3095-3104
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• 1996

The tribological characteristics of TIN and DLC coated VCR drums were compared to conventional aluminum drums using a custom built accelerated testing set-up under varying temperature and humidity. It is found that the coated drums exhibit superior frictional properties at elevated temperature and high humidity compared to bare aluminum drum. Futhermore, the coated drums maintained their initial surface conditions over a wider range of temperature and humidity variation. As for the damage incurred to the tape, DLC coated drum was the most favorable of the three types of drums.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.346-353
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• 2001

Zirconia powder containing 3 mol% yttria(3Y-PSZ) with and with out Fe$_2$O$_3$ addition was coated on tile cast iron substrate by plasma spraying method. The erosion experiments were performed at temperatures from $25^{\circ}C$ to $600^{\circ}C$. A gas blast type erosion tester was used to examine erosion behavior of the specimens. The results of 3Y-PSZ coatings showed that tile erosion rate had maximum value at 40$0^{\circ}C$. It coincided with tile results of phase transformation tetragonal phase to monoclinic phase caused by low temperature thermal degradation. The tensile stress relaxation and the micro-hardness improvement significantly influenced on the erosion rate at $600^{\circ}C$. In the case of Fe$_2$O$_3$ added 3Y-PSZ coatings, the erosion rate of tested at $25^{\circ}C$ showed maximum value at 5.0 mol% Fe$_2$O$_3$ added coating. This tendency is caused by the improvement of mechanical properties and the tensile residual stress. The erosion rate at 200'c and 400'L showed significantly decrease by Fe203 addition. This decrease is believed to be the stabilization of the tetragonal phase and the increase of micro-hardness.

• 한국표면공학회지
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• 제53권6호
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• pp.271-279
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• 2020

Non-ferrous metals, widely used in the mechanical industry, are difficult to machine, particularly by drilling and tapping. Since non-ferrous metals have a strong tendency to adhere to the cutting tool, the tool life is greatly deteriorated. Diamond-like carbon (DLC) is one of the promising candidates to improve the performance and life of cutting tool due to their low frictional property. In this study, a sacrificial DLC layer is applied on the hard nitride coated drill tool to improve the durability. The DLC coatings are fabricated by controlling the acceleration voltage of the linear ion source in the range of 0.6~1.8 kV. As a result, the optimized hardness(20 GPa) and wear resistance(1.4 x 10-8 ㎣/N·m) were obtained at the 1.4 kV. Then, the optimized DLC coating is applied as an sacrificial layer on the hard nitride coating to evaluate the performance and life of cutting tool. The Vickers hardness of the composite coatings were similar to those of the nitride coatings (AlCrN, AlTiSiN), but the friction coefficients were significantly reduced to 0.13 compared to 0.63 of nitride coatings. The drilling test were performed on S55C plate using a drilling machine at rotation speed of 2,500 rpm and penetration rate of 0.25 m/rev. The result showed that the wear width of the composite coated drills were 200 % lower than those of the AlCrN, AlTiSiN coated drills. In addition, the cutting forces of the composite coated drills were 13 and 15 % lower than that of AlCrN, AlTiSiN coated drills, respectively, as it reduced the aluminum clogging. Finally, the application of the DLC sacrificial layer prevents initial chipping through its low friction property and improves drilling quality with efficient chip removal.