در این مقاله به تخمین همزمان شار حرارتی ورودی به قطعه کار و ضریب انتقال حرارت جابجایی در عملیات فرزکاری پرداخته شده است. دو مدل حرارتی صفر بعدی و سه بعدی گذرا برای قطعه کار از جنسAISIH13 در نظر گرفته شده است. دماها در پنج نقطه در داخل قطعه کار با استفاده از ترموکوپل برای دو سرعت برشی mm/min50 و mm/min100 اندازه گیری شده است و برای تخمین مجهولات از روش جستجوی الگویی و روش اف مین سرچ استفاده شده است. نتایج حاصل از دو مدل حرارتی برای مجهولات متفاوت و تقریبا مستقل از الگوریتم معکوس می باشد. دیده شد با افزایش سرعت برشی، شار حرارتی افزایش می یابدو ضریب انتقال حرارت جابجایی ، در مدل حرارتی اول افزایش و در مدل حرارتی دوم کاهش می یابد. همچنین هر دو الگوریتم با دقت خوبی مقادیر مجهول را بر اساس دماهای اندازه گیری شده و مدل حرارتی برآورد نموده اند.
Simultaneous Estimation of Heat Flux into Work Piece and Convective Heat Transfer Coefficient in Milling Process
نویسندگان [English]
somayeh farahani
arak university of technology
چکیده [English]
In this paper simultaneously estimation of heat flux input to the work piece and convective heat transfer coefficient in milling operations are discussed. The material of the work piece is AISIH13. Temperatures in 5 points inside the work piece using thermocouples (K-type) were measured. Two thermal models for the work piece were considered to solve the direct problem. Both thermal models are considered:n1.Heat is added through milled surface at once. nb.Heat flux and convective heat transfer coefficient are constant. nc.Workpiece material is isotropic.nd. Thermal property of work piece is constant.n In first thermal model, it is assumed that temperature changes only with time. This model uses the mean temperature of all thermocouples. For direct problem solving, the code of this model is written in MATLAB software. The second thermal model is a transient 3D problem and temperature in inside work piece change with time and location. This model uses the temperature of each thermocouple. For direct problem solving, the code of this model is written in ANSYS software. Heat flux and convective heat transfer in two thermal models are unknown. Thus, inverse heat transfer method is used to estimate the unknowns. This problem will not solve by using the standard inverse algorithms. Thus, Pattern search algorithm and Nealder-mead method is used. For both of algorithms, MATLAB toolbox was used. In this study, two cutting speed: 50mm / min and 100mm / min were considered. The estimated values for the unknowns by using two thermal models are different due to the assumptions are considered for models. The obtained results from two thermal models are independent of the inverse algorithms. The results show that heat flux input to the work piece with increasing the cutting speed increases. Convective heat transfer coefficient increases with increasing the cutting speed in the first thermal model but this parameter decreases with increasing the cutting speed in the second thermal model. The main reason of this behavior is in the second thermal model temperature gradient in all directions (XYZ) inside the work piece was considered. Estimated temperatures are in good agreement with measured temperatures.
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