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Analysis of the roll hunting force due to hardness in a hot rolling process
임헌봉,양현익,김창완 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.8
A hot rolling operation is performed to alter the thickness of a metal by passing the material through a pair of rollers, forming a gap that is somewhat narrower than the thickness of the material. Therefore, the quality of the product is a function of the pressure applied by the rollers. However, in this process, a roll hunting force occurs in which the rolling force is irregularly changed during the rotation of the rollers due to various complex mechanisms, which include roll surface hardness, difference in rotational speed between rolls, heat treatment conditions, and roll wear. In this study, roll wear tests were conducted to analyze the roll hunting force caused by variation in the hardness of the work roll. The friction coefficient of the work roll was then examined based on hardness. Then, a two-dimensional finite element model was constructed to investigate the roll hunting force as a function of the change in friction coefficient of the work roll. This finite element model was verified in relation to the theoretical rolling expression. Finite element model analysis was performed for three friction coefficients, and the effect of the roll hunting force was determined based on the reduction ratio and temperature. In addition, the wear depth of the work roll by the hardness was predicted. The influence of the abrasion of the work roll on the hunting force was analyzed.
임헌봉,김창완,양현익 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.6
Cold rolling can be described as a processing method that is often used for materials with a small thickness or cross-section, or for finishing work to obtain products with accurate dimensions and clean surfaces. However, as the speed of this process increases to improve productivity, chatter vibration occurs due to the imbalance and eccentricity of the rolling roll, damaging the gear drive unit and the bearing. Therefore, in this study, to analyze the main cause of chatter vibration in the cold rolling system, chatter vibration phenomena according to various rolling conditions were calculated using a multi-body dynamics model. In addition, the experimental design method was used to statistically analyze the calculated data and the interaction effects that could correlate with the main factors causing chatter vibration were investigated. Finally, a simple regression equation model is presented.
임헌봉,양현익 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.6
Chatter vibrations have degraded rolling performances, influencing slab quality, rolling mill performance, and service life. However, chatter vibrations occur under various specific rolling conditions, so its analysis through experimentation is limited. In this study, while chattering occurs vibration data and multibody dynamics are employed to investigate the cause of chatter vibration of a thick plate rolling mill. As a result, it was confirmed that low-frequency chatter vibration is generated during the slab insertion process. The chatter vibration analysis was performed under various rolling conditions to reduce chatter vibration. According to the analysis results, the main design, interaction effect, and optimized rolling conditions were presented using an experimental design.
임헌봉,양현익 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.6
In theory, the maximum allowable working pressure of cast iron, with flange specification PN10 and pressure rating KS B1501, is 1.0 MPa. However, in reality, the maximum allowable pressure can be 1.3 MPa if the strength of the materials used and the stability of the bolted joints are considered. The stability of the flange part of a cast iron pipe was confirmed using function test analysis SPS-KWWA-D111. Next, a D900 (denotes pipe diameter) water pipe was modeled based on the combination of a steel pipe and gray cast iron pipe. Subsequently, the streamline, flow velocity, and pressure distribution, when the valve opened and closed based on the general pipe flow rate and discharge pressure, were calculated. Finally, fatigue analysis was performed using the pressure data for the pipeline, to confirm stability.
임헌봉(H.B. Lim),양현익(H.I Yang),신문균(M.K. Shin) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
국내에서 너클크레인의 설계는 단순 외팔보를 가정한 수치계산에 의한 설계 해석과 소재변경을 통한 강성의 강화 등의 단순설계 방식으로만 수행되고 있다. 본 연구에서는 크레인의 전체 모델을 유한요소화하여 “Optistruct9.0”을 이용한 유한요소 해석을 수행하고, 경량화를 위하여 극단적 하중 조건인 최대 반경에서의 최대 하중을 적용한 구조 최적화를 수행하였다. 결과적으로 과도화된 초기 설계의 강도를 기준 강도에 허용하도록 하였으며, 전체 체적을 감소시킴으로써 중량의 감소를 이루었다.