• 품질경영학회지
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• 제20권2호
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• pp.33-43
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• 1992

Items are assumed to fail by degradation. An appropriate stochastic model of such item is a cumulative process in which an item can fail only when the total amount of wear exceeds a prespecified failure level. This paper presents replacement policy in which an item is replaced at a certain level of wear before failure or at failure, whichever occurs first. Yet, when measuring the item wear level is very expensive, destructive or time-consuming, it may be economical to use substitutive characteristics that are correlated with the item wear level and relatively inexpensive to measure. The item's wear level could usually be estimated by monitoring such substitutive characteristics only except for a breakdown, which may be observed immediately at its occurrence. The purpose of this paper is to find an optimal periodic replacement policy based on such substitutive characteristics that balance the cost of replacement with the cost of failure and result in a minimum total long-run average cost per unit time. The optimal level of substitutive characteristics to replace the item is obtained. Numerical example illustrate how the model can be used to determine the optimal replacement policy.

• 품질경영학회지
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• 제24권2호
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• pp.44-53
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• 1996

This paper deals with the problem of selecting optimal wear limit and initial process mean in a wear-out process. Consider a material removal processing machinery where 1)there are deffective items by linear shift in the mean of the diameter of to be processed with varing process variance and 2)there can be any failure in the machine tools or to be processed. In the previous studies, the one is analyzed by 'Model of Producing Goods' in quality control area and the other, any failure, is analyzed by 'Model of Producing Services' in reliability area. We propose a new integrated maintenance model, considering the percent defective and the failure rate. A numerical example for the model is given.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.219-220
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• 2002

To establish a thermodynamic basis for degradation, a hypothesis was made on the potential correlation between entropy and degradation for wear of machinery components. This paper reports an experimental study of wear of model machinery component pairs, on an accelerated testing basis. Measured were wear, friction, temperatures, and entropy flow. Results show a strong correlation between the referenced wear and the production of entropy flow. The hypothesis linking wear to entropy led to formulations consistent with the Archard/Holm wear law.

• 대한기계학회논문집A
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• 제27권11호
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• pp.1881-1888
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• 2003

This study show a numerical method to predict roll wear in the roll forming process. Archard's wear model was reformulated in an elemental form to predict volume of roll wear and then wear depth on the roll was calculated using the results of finite element analysis. Abrasive wear occurs at contact area in the roll forming process and the results of simulation are compared with experimental data in production line. The wear simulation approach with 3-D FEM program for roll forming process, SHAPE-RF is in good agreement with it in tendency.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.61-66
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• 1994

Tool condition monitoring is one of the most important aspects to improve productivity and quality and to achieve intelligent machining system. The tool state is classified into three groups as chipping, wear and fracture. In this study, wear of a ceramic cutting tool for hardened die material (SKD11) was investigated. Flank wear was occured more dominant than crarer wear. Therefore, to predict flank wear, the modeling of cutting force has been performed. The modeling of cutting force by an assumption that act the stress distribution on the tool face obtained through a numerical analysis. The relationships between the cutting force and the tool wear can be constructed by machining paraneters with cutting conditions. Experiments were performed under the various cutting conditions to ensure the validity of force models. The theoretical predictions of the flank wear is approximately in good agreement with experimental result.

• 대한기계학회논문집A
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• 제32권11호
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• pp.930-936
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• 2008

This paper studies the effect of pad at initial stage and wear during braking on the dynamic contact pressure distribution. Wear is influenced by variable factor (contact pressure, sliding speed, radius, temperature) during dynamic braking and variation in contact pressure distribution. Many researchers have conducted complex eigenvalue analysis considering wear characteristic with Lim and Ashby wear map. The conventional analysis method is assumed the pad has smooth and flat surfaces. The purpose of this paper is to validate that wear rate induced by braking is considered for the precise squeal prediction. After obtaining pad wear from experiment, it is incorporated with FE model of brake system. Finally, the comparisons in fugitive nature of squeal will be carried out between the complex eigenvalue analysis and noise dynamometer experiment.

• Tribology and Lubricants
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• 제28권6호
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• pp.283-288
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• 2012

In this study, a new sliding contact problem involving an elastomeric seal, a spherical particle and a hard coated steel counterface was modeled to investigate the detailed wear mechanisms related to the sealing surface. The model was also used to design the optimum coating conditions. A three-dimensional finite element contact problem was modeled and analyzed using the nonlinear finite element code, MARC. The deformed steel surface and stress distributions are presented for different coating layers and thicknesses. When the coating thickness is relatively small, the entrapped particle produces surface plastic deformations such as groove and torus. In addition, the sealing surface can be damaged by abrasive wear as well as fatigue wear. For a relatively thick and multi-layered coating, on the other hand, surface plastic deformation does not occur, and the amount of abrasive and fatigue wear is reduced. Therefore, the proposed contact model and results can be used in the design of various sealing systems, further intensive studies are required.

• Tribology and Lubricants
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• 제36권4호
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• pp.232-243
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• 2020

It is essential to predict the amount of wear and surface parameters for a surface where relative motion occurs. In the asperity-based model for wear prediction, only the average contact pressure can be obtained. Hence, the accuracy of wear analysis is poor. In this study, DC-FFT is used to obtain the pressure of each node, and wear analysis is performed by considering the effect of the pressure gradient. The numerical surface generation method is used to create Gaussian, negatively skewed, and positively skewed surfaces for wear analysis. The spatial and height distributions of each surface are analyzed to confirm the effectiveness of the generated surface. Furthermore, wear analysis is performed using DC-FFT and Archard's wear formula. After analysis, it is confirmed that all peaks are removed and only valleys remain on the surface. The RMS roughness and Sk continue to decrease and Ku increases as the cycle progresses. It is observed that the surface parameters are significantly affected by the radius of curvature of the asperity. This analysis method is more accurate than the existing average wear and truncation models because the change in asperity shape during the wear process is reflected in detail.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.170.1-170
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• 2001

This paper developed the model for electro hydraulic force control system by identification method via ARMAX model. Implementation of Identification is performed on Pin-On-Disk type tribotester. The wear mechanism is an important mechanic property to select a material´s life and a optimum work condition. Pin-on-disk type tribotester is popular wear analysis experimental equipment and its mechanism is that adding a force on a rotating disk to simplify two surface contact´s wear experimental condition. Material´s rotating velocity and eccentricity rotation makes disturbance and it affects adding constant force. To get a high performance of force adding part, DDV(Direct Drive Valve) which has pressure control loop is used. To obtain a tribotester´ s ARMAX model, prediction error method(PEM) is used in case force adding part and rotating part is ...

• 한국정밀공학회지
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• 제15권11호
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• pp.189-198
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• 1998

Recently, monitoring of tool life is a matter of common interesting because tool life affects precision, productivity and cost in machining process. Especially flank wear has a direct effect on cutting mechanism, so the various pattern of cutting force is obtained experimentally according to variation of wear condition. By investigating cutting force signal, AR(Autoregressive) modeling and correlation dimension analysis is conducted in turning operation. In this modeling and analysis, we extract features through 6th AR model, correlation integral and normalized correlation integral. After the back-propagation model of the neural network is utilized to monitor tool life according to flank wear. As a result. a very reliable classification of tool life was obtained.