TRANSACTIONS
2016, 22: 525-535
OF TIANJIN UNIVERSITY
DOI 10.1007/s12209-016-2806-8
Accepted date : 2016-01-12. * Supported by the National Natural Science Foundation of China (No. 51205284 and No. 51575384).
Ren Chengzu, born in 1962, male, Dr, Prof.
Correspondence to Chen Guang, E-mail: guangchen@https://www.doczj.com/doc/cc5129654.html,.
Modeling of Tool -Chip Contact Length for Orthogonal
Cutting of Ti -6Al -4V Alloy Considering
Segmented Chip Formation *
Ren Chengzu (任成祖)，Ke Zhihong (柯志宏)，Chen Guang (陈 光)，Wu Jing (吴 靖)
(Tianjin Key Laboratory of Equipment Design and Manufacturing Technology, Tianjin University, Tianjin 300072, China )
? Tianjin University and Springer-Verlag Berlin Heidelberg 2016
Abstract ：In this work, the orthogonal cutting experiments on Ti-6Al-4V alloy were conducted at different cutting speeds (10—160 m/min )and feed rates (20—160 μm/rev ). The tool-chip contact length was measured by the track of tool rake face; meanwhile, the chip morphology caused by the localized and overall chip deformation was char-acterized by the degree of segmentation and the chip compression ratio, respectively. These parameters were ana-lyzed and calculated according to the segmented chip morphology. In addition, three modified models considering the overall chip deformation and the localized deformation of adiabatic shear band were proposed, and the constants of the models wer e calculated by the genetic algor ithm optimization. Consider ing the over all and localized chip deformation, the value and variation trend of the tool-contact length predicted by these three models agreed well with the experimental results.
Keywords ：tool-chip contact length; segmented chip; Ti-6Al-4V alloy; localized shear deformation
Titanium alloys have been widely used for the fabri-cation of the products in many fields such as aerospace, biomedical and automotive industries in recent years be-cause of their excellent corrosion -resistance, heat -resistance and strength -to -weight ratio [1]. However, these characteristics also bring difficulties to the machining process. Ti -6Al -4V, as a typical α＋β titanium alloy, is difficult to be machined due to its low thermal conductiv-ity, low elastic modulus and high chemical activity [2]. When machining Ti -6Al -4V alloy, the localized stress increases and the temperature rises significantly at the tool -chip contact zone. Besides, the process often gener-ates excessive vibration for the tool and the workpiece. That is, the tool -chip contact behavior at the interface contributes to the chip formation, tool wear as well as the surface quality.
The tool -chip contact length is an important parame-ter to characterize the tool -chip contact state. The chip contacts with the tool rake face during the chip move-ment along the rake face, and remains a distance on the tool rake face from the cutting edge of the tool [3]. The distance is defined as the tool -chip contact length, which
can directly reflect the friction state of the cutting proc-ess, and signi?cantly affect the cutting force, cutting temperature, tool wear, chip formation and machined surface quality [4,5]. Therefore, the accurate prediction of the tool -chip contact length is useful to control the ma-chining process.
In recent years, several researchers have studied the tool -chip contact length. To measure the tool -chip contact length through experiments, one common and easy way is microscopic examination of cutting tool. Friedman and Lenz [6] used this method to examine the traces left by the sliding of the chip on the tool face. Tasdelen et al [7] in-vestigated the tool -chip contact length under dry and minimum quantity lubrication (MQL ) machining based on the optical microscopy images and scanning electron microscope (SEM ) images of tool inserts. To measure the chip characteristics during orthogonal cutting, Sut-ter [8] used a numerical high -speed camera located near the cutting zone to record the tool -chip contact length. The method makes it possible to obtain the tool -chip con-tact length during the machining process.
To model the tool -chip contact length, some re-