• 제목/요약/키워드: critical residual stress

검색결과 125건 처리시간 0.024초

ESTIMATION OF RESIDUAL STRESS IN CYLINDER HEAD

  • KIM B.;EGNER-WALTER A.;CHANG H.
    • International Journal of Automotive Technology
    • /
    • 제7권1호
    • /
    • pp.69-74
    • /
    • 2006
  • Residual stresses are introduced in aluminum cylinder head during quenching at the end of the T6 heat treatment process. Tensile residual stress resulted from quenching is detrimental to fatigue behavior of a cylinder head when it is overlapped with stresses of engine operation load. Quenching simulation has been performed to assess the distribution of residual stress in the cylinder head. Analysis revealed that in-homogeneous temperature distribution led to high tensile residual stress at the foot of the long intake port, where high stresses of engine operation load are expected. Measurements of residual stress have been followed and compared with the calculated results. Results successfully proved that high tensile residual stress, which was large enough to accelerate fatigue failure of the cylinder head, are formed during quenching process at the end of heat treatment at the same critical position. Effect of quenching parameters on the distribution of residual stress in cylinder head has been investigated by choosing different combination of heat treatment parameters. It was demonstrated that changes of quenching parameters led to more homogeneous temperature distribution during cooling and could reduce tensile residual stress at the critical region of the cylinder head used in this study.

Dislocation Injections by a Localized Stress Field in a Strained Silicon

  • Yoon, Ju-Il
    • International Journal of Safety
    • /
    • 제7권2호
    • /
    • pp.27-30
    • /
    • 2008
  • In the 21st century, safety issues in the strained silicon industry, such as dislocation injection, should be carefully considered. This is because a microelectronic device usually contains sharp features (e.g., edges and corners) that may intensify stresses, inject dislocations into silicon, and ultimately cause the failure of the device. In this paper, critical residual stresses in various strained structures are calculated. It is confirmed that this model correctly predicts trends and the order of magnitude of critical residual stresses.

AJM을 이용한 HDM에 의한 잔류응력 계측에 관한 연구 1

  • 이택순
    • Journal of Welding and Joining
    • /
    • 제6권3호
    • /
    • pp.37-42
    • /
    • 1988
  • The Hole Drilling Method(HDM) is widely used to measure residual stresses in the welded structures. The purpose of this study is to evaluate the accuracy fo measuring residual stresses when drilling the hole by Air-abrasive Jet machine(AJM). Simulated residual stresses wre introduced by applying known stresses to steel bars. These known streses were then compared with measured stresses relaxed from hole drilling. the obtained results are summarized as follows; 1) It was possible to obtain well defined holes with the nozzle designed for this study. 2) If the hole shape is not cylindrical, critical may occur. 3) In the uniaxial strain field, the measurement error of the maximum principal stress was within .+-.10 percent. The orientation angle of the maximum principal stress was within 8.deg. from the given directioin. 4) meausrements were made varying hole depths. Little or no change of stresses occurs since holse were drilled more than the depth of the 0.6 times diameter. 5) The air-abrasive jet machining for drilling holse does not cause appreciable apparent stresses which si critical to measure residual stresses.

  • PDF

용접 구조물의 사용중 적합성 평가를 위한 잔류응력 해석절차 개발 (Development of Residual Stress Analysis Procedure for Fitness-For-Service Assessment of Welded Structure)

  • 김종성;진태은
    • 대한기계학회논문집A
    • /
    • 제27권5호
    • /
    • pp.713-723
    • /
    • 2003
  • In this study, a state of art review of existing residual stress analysis techniques and representative solutions is presented in order to develope the residual stress analysis procedure for fitness-for-service (FFS) assessment of welded structure. Critical issues associated with existing residual stress solutions and their treatments in performing FFS are discussed. It should be recognized that detailed residual stress evolution is an extremely complicated phenomenon that typically involves material-specific ther-momechanical/metallurgical response, welding process physics, and structural interactions within a component being welded. As a result, computational procedures can vary significantly from highly complicated numerical techniques intended only to elucidate a small part of the process physics to cost-effective procedures that are deemed adequate for capturing some of the important features in a final residual stress distribution. Residual stress analysis procedure for FFS purposes belongs to the latter category. With this in mind, both residual stress analysis techniques and their adequacy for FFS are assessed based on both literature data and analyses performed in this investigation.

고 탄소 미세 강선의 기계적 특성에 미치는 잔류 응력과 표면 결함의 영향 (Effects of Residual Stress and Surface Defect on the Mechanical Properties of the High Carbon Steel Filaments)

  • 양요셉;배종구;박찬경
    • 한국소성가공학회:학술대회논문집
    • /
    • 한국소성가공학회 2008년도 추계학술대회 논문집
    • /
    • pp.134-137
    • /
    • 2008
  • The effects of residual stress and surface defects on the mechanical properties of the high carbon steel filament used for the automotive tire have been experimentally investigated. The samples were fabricated with annealing temperature. The residual stress was measured by focused ion beam and strain mapping software which has advantages, such as data with high accuracy and fast data acquisition time. Mechanical properties, such as tensile strength and fatigue resistance, were gradually increased up to $200^{\circ}C$ and then slightly decreased. From the measurement of residual stress and level of surface defect, it was revealed that the critical factor was varied with different temperature region. That is, the fatigue resistance increased due to decreasing the residual stress and decreased due to increasing the size and distribution of surface defect.

  • PDF

Estimation of residual stress in welding of dissimilar metals at nuclear power plants using cascaded support vector regression

  • Koo, Young Do;Yoo, Kwae Hwan;Na, Man Gyun
    • Nuclear Engineering and Technology
    • /
    • 제49권4호
    • /
    • pp.817-824
    • /
    • 2017
  • Residual stress is a critical element in determining the integrity of parts and the lifetime of welded structures. It is necessary to estimate the residual stress of a welding zone because residual stress is a major reason for the generation of primary water stress corrosion cracking in nuclear power plants. That is, it is necessary to estimate the distribution of the residual stress in welding of dissimilar metals under manifold welding conditions. In this study, a cascaded support vector regression (CSVR) model was presented to estimate the residual stress of a welding zone. The CSVR model was serially and consecutively structured in terms of SVR modules. Using numerical data obtained from finite element analysis by a subtractive clustering method, learning data that explained the characteristic behavior of the residual stress of a welding zone were selected to optimize the proposed model. The results suggest that the CSVR model yielded a better estimation performance when compared with a classic SVR model.

PECVD 에 의해 형성된 TiCN 박막의 형상 및 밀착성 (The Morphology and Adhesion of TiCN Film formed by PECVD)

  • 허정;남태운
    • 열처리공학회지
    • /
    • 제15권3호
    • /
    • pp.118-126
    • /
    • 2002
  • TiCN thin films were deposited on tool steels at $510^{\circ}C$ by PECVD from a $TiCl_4+N_2+CH_4+H_2+Ar$ gaseous mixture. The microstructures and preferred orientation were investigated. The micro-scratch tests were performed using a system equipped with an acoustic emission sensor. Critical loads were determined to evaluate the adhesion of TiCN to substrate. The influences of the microstructures of substrates, double layered coatings, and coatings after nitriding(duplex coating) were investigated. The experimental results showed that the microstructures of substrates and double layered coating did not affect the critical loads considerably. By the duplex coating, critical loads were not always increased. In some cases, duplex coatings decreased critical loads significantly despite of absence of black layer. In this study, we tried to relate the results of scratch test to the residual stress analysis. Nitriding before the coating reduces the tensile residual stress in the film, which gives rise to low critical load in scratch test.

사출성형 디스크의 진동특성 향상을 위한 공정조건 제어 (Control of Processing Conditions for Improvement of vibration Characteristics of Injection Molded Disk)

  • 신효철;남지근
    • 대한기계학회논문집A
    • /
    • 제30권6호
    • /
    • pp.615-621
    • /
    • 2006
  • Increased application of optical disks requires more improved dynamic stability of rotating disks. In this study, a new concept of controlling the processing conditions of injection molded disks was developed to improve vibration characteristics. The critical speed, which shows stiffness and dynamic stability of disk, is affected by the residual stress distribution; this varies as functions of distance from the gate and processing condition. The critical speed of disk was calculated with the initial stress taken into consideration, which was determined from injection molding simulation. Choosing melt temperature, mold temperature, filling speed and packing pressure as design parameters, critical speed is maximized with the method of response surface. It is shown that the stability of injection molded disk has been improved for the new condition obtained as a result of the study proposed.

철도차량 차륜의 잔류응력 평가 (Evaluation of Residual Stress of railway wheel)

  • 서정원;구병춘;이동형;정흥채
    • 한국철도학회:학술대회논문집
    • /
    • 한국철도학회 2002년도 추계학술대회 논문집(I)
    • /
    • pp.208-213
    • /
    • 2002
  • Railway wheel and axle are the most critical components in railway system. A wheel and axle failure can cause a derailment with its attendant loss of life and property. The service conditions of railway vehicles have become severe in recent years due to a general increase in operating speeds. Therefore, more precise evaluation of wheelset strength and safety has been desired. Damages of railway wheel are a spatting by wheel/rail contact and thermal crack by braking heat etc. One of the main source of damage is a residual stress. therefore it is important to evaluate exactly. A Residual stress of wheel is formed at the process of heat treatment when manufacturing. it is changed by contact stress developed by wheel/rail contact and thermal stress from heat induced in braking. The objective of this paper is to estimate the variation and magnitude of the residual stress of railway wheel.

  • PDF

상수도용 도복장강관의 용접 및 외부하중에 의한 응력 특성에 관한 연구(I) - 후열처리에 의한 용접부의 잔류응력 특성 - (A Study on the Stress Distribution of Steel Water Pipes(I) - Characteristics of Residual Stress Distribution by PWHT -)

  • 윤석환;이승기;나석주;고명환
    • Journal of Welding and Joining
    • /
    • 제19권3호
    • /
    • pp.285-291
    • /
    • 2001
  • Large steel water pipes are joined prevalently by the bell end method, and are welded both at inside and outside of lapped parts. In practice, welded joints of water pipes are very critical, because in most cases failure of pipes causing leakage occurs at the welded joint. Therefore some methods have been developed to ensure the soundness of welded joints of water pipes, like leakage tests and nondestructive tests (NDTs). But one of the major characteristics that affects the soundness of welded Joints is the stress distribution caused by welding and external forces. Some studies have been carried out on the residual stress of steel water popes, but complex stress distributions by welding and external forces are rarely studied. In this study, temperature and stress distributions in steel water pipes produced by welding are predicted by a three-dimensional finite element method(FEM). Also, stress values are measured from real steel water pipes by the hole-drilling methods, and compared with predicted ones. The influence of some typical post weld treatments on residual stress distribution was also investigated by residual stress measurements.

  • PDF