열 하중 기반의 리츠벡터와 순차적 센서위치 선택방법을 이용한 강건하고 효율적인 열 오차 모델링

현재엽(Jaeyub Hyun),유동윤(Dongyoon Yoo),이선규(Sun-Kyu Lee),왕세명(Semyung Wang) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

Thermal deformations are among the most significant factors to errors generation of machine tool, this degrades the performance and accuracy of the machine tool. There are many methods to reduce the thermal deformation, such as structural designs to minimize thermal deformation, approaches to block and/or suppress thermal source, and thermal error compensation techniques to estimate and control thermal deformation. Among these, thermal error compensation techniques have been realized as the most successful method and actively studied. Securing of robustness and effectiveness of the thermal error modeling is directly correlated to the better compensation results. Most of the current thermal error modeling methods is highly dependent on measured data, and cannot consider mechanisms of the thermal deformation due to the thermal-structural interaction effect. In this paper, therefore, a novel and innovative strategy that can select the optimized thermal sensor placement and thermal error modeling method are proposed based on thermal load dependent ritz vectors. Operation state of the actual machine tool and thermal source variation are continuously changing according to the time. Thus, the various boundary conditions are applied to properly deal with these variations. The Wilson’s Ritz algorithm is used for generating the thermal load dependent Ritz vectors. Finally, for various 2D and 3D systems such as heat pipe and spindle, both existing thermal errors modeling method to use the eigenvectors and proposed method to use thermal load dependent ritz vectors are compared and investigated. Through this, the robustness and effectiveness are verified.

열변형 해석을 위한 허니컴 샌드위치 평판의 열 및 탄성 물성치 예측에 관한 연구

홍석민(Seok Min Hong),이장일(Jang Il Lee),변재기(Jae Ki Byun),최영돈(Young Don Choi) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.4

전자장치들의 소형화 및 박형화가 됨에 따라 전자장치의 수명과 직결되는 열적문제가 중요해지고 있다. 열적문제를 해결하기위해 열확산과 단열을 통한 열적 안정성 연구가 필요하다. 허니컴 샌드위치 평판은 이방성의 열전도계수를 갖는다. 허니컴 샌드위치 평판이 적용된 시스템에 대해 온도분포와 열변형을 해석하기 위하여 열 및 탄성 물성치가 필요하다. 본 연구에서는 허니컴 코어의 크기, 두께 그리고 구성된 재료에 따라 허니컴 샌드위치 평판의 물성치가 변하기 때문에 허니컴 샌드위치 평판의 열전도 계수, 열팽창계수, 탄성계수, 전단탄성계수, 푸아송비와 같은 열 및 탄성 물성치를 예측하였다. Thermal problems that are directly related to the lifetime of an electronic device are becoming increasingly important owing to the miniaturization of electronic devices. To solve thermal problems, it is essential to study thermal stability through thermal diffusion and insulation. A honeycomb sandwich plate has anisotropic thermal conductivity. To analyze the thermal deformation and temperature distribution of a system that employs a honeycomb sandwich plate, the thermal and elastic properties need to be determined. In this study, the thermal and elastic properties of a honeycomb sandwich plate, such as thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson"s ratio, and shear modulus, are predicted. The properties of a honeycomb sandwich plate vary according to the hexagon size, thickness, and material properties.

금속복합재 TiC-SUS431을 사용한 공작기계 주축 열변형 억제에 대한 연구

서지원(Ji Won Seo),배원준(Won Jun Bae),김성태(Sung Tae Kim),김양진(Yang Jin Kim),이상관(Sang Kwan Lee) 대한기계학회 2020 大韓機械學會論文集A Vol.44 No.7

공작기계에서 주축의 열변형은 가공 오차의 주요 원인이다. 이러한 열적 오차를 억제하는 근본적인 해결책은 기존의 주축 재료를 뛰어난 기계적 성질을 갖는 재료로 대체하는 것이다. 이에 적합한 금속 복합재 TiC-SUS431은 우수한 가공성과 내마모성, 내산화성을 갖고 있으며 본문에서 균일한 열확산율과 낮은 열팽창 계수를 확인하였다. 유한요소 해석을 이용하여 TiC-SUS431과 SUS431, 기존 주축 재료인 GC300을 각각 사용한 주축에서 열변형을 비교한 결과, TiC-SUS431을 사용한 주축에서 변형이 가장 작은 것을 확인하였다. 이를 통해 TiC-SUS431의 열변형 억제 능력을 확인하여 주축의 재료로서 적용 가능성을 제시하였다. The thermal deformation of a spindle is one of the sources of errors in machine tools. A fundamental solution to this thermal error problem involves replacing the conventional material used in producing spindles with an advanced material. TiC-SUS431 is a metal composite that exhibits satisfactory machinability, wear resistance, and oxidation resistance. The experimental tests conducted in this study confirmed the excellent thermal properties of the TiCSUS431 composite, including a uniform thermal diffusivity and low thermal expansion coefficient. We conducted finite element analysis (FEA) of a spindle using TiC-SUS431, SUS431, and GC300 based on the variation of the generated heat and time. The FEA results indicated that the thermal deformation of a spindle fabricated from TiC-SUS431 is minimal when compared with those of SUS431 and GC300. This suggests the potential of using TiC-SUS431 composite as an alternative material for manufacturing spindles due to its low thermal expansion coefficient. Hence, this in turn can decrease the thermal strain in a spindle.

고속이송계의 열변형오차 자동보정에 관한 연구

고해주(Hai-Ju Ko),정윤교(Yoon-Gyo Jung) 한국기계가공학회 2007 한국기계가공학회지 Vol.6 No.4

In the recent years, development of machine tool with high speed feeding system have brought a rapid increase in productivity. Practically, thermal deformation problem due to high speed is, however, become a large obstacle to realize high precision machining. In this study, therefore, the construction of automatic error compensation system to control thermal deformation in high speed feeding system with real time is proposed. To attain this purpose, high speed feeding system with feeding speed 60㎜/min is developed and experimental equation for relationship between thermal deformation and temperature of ball screw shaft using multiple regression analysis is established. Furthermore, in order to analyze thermal deformation error, compensation coefficient is determined and thermal deformation experiments is carried out. From obtained results, it is confirmed that automatic error compensation system constructed in this study is able to control thermal deformation error within 15~20 ㎛.

인공위성 구조모듈의 열변형 해석을 위한 온도 자동 변환 전산프로그램 개발

김도형(Do Hyung Kim),임형은(Hyung Eun Im),이희남(Huinam Rhee),황도순(Do Soon Hwang) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.11

지구궤도 상에서 운용되는 인공위성의 구조체는 태양의 영향으로 각 부품들 위치마다 온도 분포가 다르고 이에 따라 열변형을 하게 되며, 따라서 카메라 및 여러 과학 탑재체에 열지향 오차가 발생하게 된다. 이러한 열지향 오차를 줄이기 위해 위성 구조 설계 단계에서 인공위성 열 변형 해석을 필수적으로 하는데, 상대적으로 덜 상세한 위성 열 해석 모델을 이용하여 구한 3차원 구조체의 온도 분포 데이터를 이용하여 상세한 위성 구조해석 모델에 적합한 온도 분포 입력 데이터로 변화하는 과정이 필요하며, 이것은 매우 복잡하고 어려운 과정이어서 오류를 유발하기 쉽다. 본 연구에서는 내삽 및 외삽법을 이용하여 체계적이고 정확하게 온도 분포 데이터를 자동 변환하여 주는 알고리즘을 개발하였고 이를 기반으로 윈도우 그래픽 기반의 전산프로그램을 개발하였다. 본 연구에서 개발한 방법을 이용하면 다양한 위성구조체의 열변형 해석 시간을 획기적으로 단축시키고 정확성을 대폭 높일 수 있는 장점이 있다. Artificial satellite structures undergo thermal deformation during operation in Earth orbit depending on the temperature distribution. The thermal deformation directly causes thermal pointing errors of cameras and other scientific payloads. Therefore, it is necessary to perform the thermal deformation analysis of satellite structures to minimize thermal pointing errors. Because the thermal model and structural models have different structures, the temperature data generated using the thermal model is not compatible with the structural model. Therefore, there is a need for a temperature-conversion process between two models. In this paper, an effective algorithm is proposed for the automatic conversion process. Finally, a computer program is successfully developed to perform the precise conversion in a relatively short time period.

디스크 브레이크에서 마찰열과 패드에 작용하는 융합 접촉거동에 관한 연구

한승철,이봉구 한국융합학회 2018 한국융합학회논문지 Vol.9 No.1

자동차 디스크 브레이크시스템에서는 열유속 및 열변형 등과 같은 이유로 마찰열이 균일하게 분산되지 않는다. 마찰열에 의한 열탄성 변형이 접촉압력 분포에 영향을 미치게 되고, 접촉하중이 디스크 브레이크 표면상의 작은 영역에 집중되어 열탄성 불안정성을 초래 할 수 있다. 본 연구에서는 실험적 계산식과 Kao 제안한 디스크와 패드의 접촉압력에 대한 해석방법을 참고로 하여 3차원 축대칭 모델을 통하여 실제로 제동 시 발생되는 디스크와 패드의 접촉을 고려한 온도 해석 및 열변형 해석을 하였다. ANSYS를 사용하여 디스크와 패드의 접촉면에서 발생하는 열탄성 불안전성 문제를 열하중과 기계적 하중으로 동시에 고려하여 해석하였다. 디스크와 패드가 직접 접촉하는 3차원 축대칭 모델을 구성하여 디스크의 마찰면 온도, 열변형, 접촉 열응력을 관찰함으로써 디스크에서 일어나는 열적 거동을 보다 정확하게 관찰하였다. In automotive disc brake systems, frictional heat is not uniformly dispersed for reasons such as heat flux and thermal deformation. The thermoelastic deformation due to the frictional heat affects the contact pressure distribution and the contact load may be concentrated on the contact portion on the the disc brake surface, resulting in thermoelastic instability. In this study, thermal analysis and thermal deformation analysis considering the contact between disk and pad occurred during braking through 3D axial symmetry model with reference to the experimental equation and Kao's analysis method of contact pressure of disk and pad. ANSYS is used to analyze the thermal and elastic instability problems occurring at the contact surface between the disk and the pad, considering both the thermal and mechanical loads. A 3D axisymmetric model with direct contact between the disk and the pad was constructed to more accurately observe the thermal behavior of the disk by observing the frictional surface temperature, thermal deformation and contact thermal stress of the disk.

FEM을 이용한 벤틸레이티드 디스크 브레이크 열응력 해석에 관한 연구

김성모(Sung Mo Kim) 한국생산제조학회 2009 한국생산제조학회지 Vol.18 No.5

Thermal brake judder caused by the high friction heat of the brake disk. Hot thermal judder makes serious problems such as to be unstability to drivers or to decrease braking force of automobile. Because thermal judder vibration makes high vibration occurrence and thermal deformation of brake disk. Therefore it is necessary to reduce or eleminate thermal judder phenomenon by understanding and investigation. This paper introduces the thermal deformation arising from friction heat generation in braking and proposes the FEM analysis to predict the distribution of temperature and thermal deformation. the results of the FEM analysis show the deformed shape and temperature distribution of the disk brake. The optimization is performed to minimize the thermal judder of ventilated disc brake that is induced by the thermal deformation of the disk brake.

열변형으로 인한 틸팅패드 저널베어링의 예압 변화

서준호(Junho Suh),황철호(Cheolho Hwang) 한국트라이볼로지학회 2016 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.32 No.1

This paper focuses on the thermal deformation induced preload change in the tilting pad journal bearing, using a three-dimensional (3D) thermo-hydro-dynamic (THD) approach. Preload is considered as a critical factor in designing the tilting pad journal bearing. The initial preload measured under nil external load and nil thermal gradient is influenced by two factors, namely, the thermal deformation and elastic deformation. Thermal deformation is due to a temperature distribution in the bearing pads, whereas the elastic deformation is due to fluid forces acting on the pads. This study focuses on the changes induced in preload and film clearance due to thermal deformation. The generalized Reynolds equation is used to evaluate the force of the fluid and the 3D energy equation is used to calculate the temperature of the lubricant. The abovementioned equations are combined by establishing a relationship between viscosity and temperature. The heat transfer within the bearing pads, the lubricant, and the spinning journal is calculated using the heat flux boundary condition. The 3D Finite Element Method (FEM) is used in modeling the (1) heat conduction in the spinning journal and bearing pads, (2) thermal gradient induced thermal distortion of the spinning journal and pads, and (3) viscous shearing, and heat conduction and convection in a thin film. This evaluation method has an increased fidelity, and it can prove to be a cost-effective tool that can be used by designers to predict the dynamic behavior of a bearing.

소재변경에 따른 차량용 스크롤압축기의 열변형 해석

이형욱(Lee Hyoungwook),이근안(Lee Geunan),김정배(Kim Jeongbae) 한국태양에너지학회 2014 한국태양에너지학회 논문집 Vol.34 No.6

An inverter scroll compressor is used for the air conditioning in cars. Scrolls would be changed from the aluminum material to the magnesium material in order to satisfy the light weight trends of cars. The material changing influences on the scroll dimensions particularly the gap between two scrolls. Since the larger gap declines the performance of the compression, the gap between wraps of scrolls or the gap between wraps of scrolls to the plate of the opposite scroll is regarded as an important design variable. This paper is focused on the effects of the thermal stress due to the materials changing. The temperature difference between the inlet and the outlet is about 60 degrees and the highest operating temperature in the compressor is less than 110 degrees. The level of thermal stresses in the magnesium scroll is less than the result from aluminum one. The trend of the deformation is revealed that the normal directional deformation is 2 times lager than the in-plane directional deformation. Therefore the gap between the top of the wrap to the plate of the opposite scroll become more important than the other gaps. The orbiting scroll deforms larger than the fixed scroll by the thermal stresses. The deformation of the magnesium scroll is about 10% lager than that of the aluminum scroll. This value is similar to the ratio of the coefficients of thermal expansion of two materials. At the initial design stage, the results give many useful guides to engineers to propose gaps between parts.

고출력 레이저 시스템의 반사경 열변형에 관한 연구

하태광 한국기계기술학회 2024 한국기계기술학회지 Vol.26 No.2

The laser power has been continually increased since the laser was developed in the mid-20th century. Achieving higher laser power requires not only enhancing the cooling performance of laser systems but also addressing the potential degradation of optical characteristics due to thermal deformation induced by laser beam absorption in a mirror. This study delves into the thermal deformation characteristics of mirrors in high-power laser systems. To minimize thermal deformation by heat absorption, Zerodur, known for its low coefficient of thermal expansion, was employed as the mirror material. Various configurations including circular, rectangular, and spline shapes were implemented on a solid mirror structure. Furthermore, two different diameter of a mirror, 300mm and 400mm, were considered to investigate the size effect of the high-power laser beams. Also, three different transmitted beam power were adopted: 50W, 250W, and 500W. Based on the finite element analysis for the thermal deformation, the deformation characteristics of the different types of mirror structures were investigated and analyzed for high-power laser systems.