عنوان مقاله
دریل کاری کامپوزیتهای کربنی به کمک مته «Oneshot» بخش اول : تشریح مراحل پنج گانه حفاری و فاکتورهای تأثیرگذار بر بیشترین میزان نیرو و گشتاور پیچشی
فهرست مطالب
چکیده
مقدمه
شرایط آزمایشی
نیروی پیشروی، گشتاور پیچشی و مراحل دریل کاری
اثر سطح پوششی ابزار آلات
نتیجه گیری
بخشی از مقاله
مرحله آغازین I
در مرحله اول مته دریل به قطعه کار نزدیک می گردد . با استفاده از قلم و قرار گرفتن نوک آن بر روی قطعه کار و فشار دادن آن بر روی نمونه اثر ایجاد می گردد . در طول این مرحله به سرعت نیروی پیشروی افزایش می یابد . همچنین میزان گشتاور پیچشی نیز افزایش می یابد ، البته میزان رشد گشتاور پیچشی نسبت به نیروی رانشی کمتر می باشد .
کلمات کلیدی:
Drilling of carbon composites using a one shot drill bit. Part I: Five stage representation of drilling and factors affecting maximum force and torque Marta Fernandesa,*, Chris Cookb a School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Northfields Avenue, 2522, NSW Australia b Faculty of Engineering, University of Wollongong, Australia Received 23 September 2004; accepted 22 March 2005 Available online 6 June 2005 Abstract The thrust force and torque produced during drilling contain important information related to the quality of the hole and the wear of the drill bit [1]. In this paper, the force and torque produced during drilling of carbon fibre using a ‘one shot’ drill bit is investigated. The signals in the time domain were divided into stages and common problems and defects associated with each stage discussed. It is also shown how tool wear and thickness of the workpiece affect the thrust force and torque throughout the drilling process. The findings of this paper are used to develop a mathematical model of the maximum thrust force and torque as described on Part II of this paper and are a valuable reference for future optimisation of drilling carbon composites with a ‘oneshot’ drill bit. q 2005 Elsevier Ltd. All rights reserved. Keywords: Drilling; Carbon composite; Tool wear 1. Introduction Although carbon fibre is not metal, for many years industry has applied the theory: ‘cut it like metal’. The results of this theory were often poor finish quality and excessive tool wear. For the applications where the quality demand was higher, special drill bits have been designed for drilling composites, to improve performance compared with twist drills [2–5]. There are several common problems associated with drilling carbon fibre, with delamination and excessive tool wear usually reported as the biggest concern [6]. Melting and softening of the matrix, fibre pull-outs and scorching of the surface can also be concerns. Delamination usually occurs when the last plies of the material do not withstand the force exerted by the drill bit’s chisel edge. Several authors have studied this phenomena [7–9] and some avoid delamination by means of controlling the thrust force at breakthrough [2,5,10]. The chip produced during drilling of carbon composites is a very abrasive dry dust. The ineffective extraction of the chip is one of the major reasons for high tool wear rates. Tool wear is also related to delamination, as the force necessary to cut the material increases with tool wear [11–13]. Many authors have studied the tool wear process for drilling carbon composites as well as the effect of tool wear on the drilling forces and quality of the holes produced [14–19]. Mostly, these studies are done using twist drills. A better understanding of the drilling of carbon composites with other shaped drill bits is still necessary for further improvement and optimization of the drilling process. In this paper, the drilling process of carbon composite using an ‘one shot’ drill bit will be analysed. The thrust force and torque produced during drilling are investigated, divided into stages and each stage related to common defects. The effect of tool wear on the forces will also be studied. This provides the foundation for more accurate modelling of this process, as outlined in part 2 of this work, leading to the improvement of quality and productivity of the drilling process.
