بررسي كمي نيروها در فرايند داخل تراشي و ارائه روش جديد براي محاسبه نيروي نوك ابزار

Quantitative analysis of forces in boring process and providing a new formula for calculation of tool-tip force

فرايند تراش كاري به دليل ديناميك پيچيده اي كه دارد همواره مورد توجه محققان علم ماشين كاري بوده و تلاش هاي زيادي براي تعيين نيروها در آن انجام گرفته است. روش هاي مختلف تجربي و نيمه تجربي براي محاسبه مقادير نيروهاي استاتيكي و ديناميكي برش استفاده شده كه معمولاً مبتني بر ابعاد براده هستند اما هنوز اين موضوع ابعاد ناشناخته ي زيادي دارد كه هدف اين مقاله تعيين ميزان تفاوت فرمول آلتينتاس، مقدار دينامومتر و مقداري است كه از طريق ارائه ي يك روش جديد مبتني بر معادله حاكم بر ارتعاش ابزار، است. براي بررسي صحت نتايج، آزمون هاي عملي انجام مي شوند. آزمون ها براي حالت داخل تراشي و با پارامترهاي مختلف انجام مي شوند و در آن ها به طور همزمان سيگنال نيرو با ستفاده از دينامومتر و شتاب توسط شتاب سنج اندازه گيري مي شود. از نتايج اين دو سيگنال، پارامترهاي مورد نياز براي محاسبه مولفه هاي نيرو در روش آلتينتاس و روش جديد استخراج مي شوند. در نهايت براي دو آزمون، مولفه هاي شعاعي نيروي دينامومتر و اين دو روش مقايسه مي شوند. نتايج نشان مي دهند كه نيروي نوك ابزار، بيشترين دامنه و پس از آن نيرو در انتهاي ابزار و در نهايت نيروي برش كمترين مقدار دامنه را دارد. بنابراين به دليل وجود اين تفاوت مهم نبايد از اين نيروها به جاي يكديگر استفاده كرد.

Due to its complex dynamics, turning process has always been of interest to machining researchers and much effort has been made to determine the forces. Various experimental and quasi-experimental methods are used to calculate the values of static and dynamic cutting forces. The methods are usually based on chip dimensions. Cutting stability amplitude is calculated using these methods. However, there are still a lot of unknown aspects about this subject and the aim of this paper is to clarify one of them which is to define the amount of difference between Altintas formula, dynamometer value, and the value which is obtained by providing a new method based on the equation governing the vibration of tools. Practical tests are done to verify the results. The tests are performed for boring state with different parameters and the force signal is simultaneously measured and determined at the end of the tool using a dynamometer and the new method in which the acceleration of one point of the tool is used. Using the results of these two signals, the parameters needed to calculate the force components in Altintas approach and the new method are derived. Finally, for the two tests, radial components of the derived force of dynamometer and these two methods are calculated and compared. The results show that the tool tip force, resulting from the new method which considered the effects of displacement and acceleration tool, obtains the greatest force amplitude. The force at the end of the tool which is derived by dynamometer has lower amplitude (about 25% of the amplitude in the new approach). Finally, the force resulting from Altintas approach has the lowest amplitude (about 2% of the amplitude in the new approach), in which the cutting force is only considered as a factor of chip dimensions. Therefore, because of their important differences, these forces should not be used interchangeably.