Surface and microstructure characterization of low-frequency vibration-assisted drilling of Ti6Al4V

Hussein, Ramy; Sadek, A.; Elbestawi, M.A.; Attia, Helmi

doi:10.1007/s00170-019-03608-2

Cited by 19 publications

(32 citation statements)

References 26 publications

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“…The measured cutting forces for VAD did not show any change over the 50 drilled holes, as shown in Figure 5. However, the thrust forces increased with amplitude due to the cyclic tool-workpiece impact [40]. All VAD tests at Am = 0.1 mm, 0.16 mm, and 0.25 mm experienced a negligible increase of the thrust force with a number of holes.…”

Section: Effect Of Tool Wear On the Thrust Forcementioning

confidence: 91%

“…The maximum drilled number of holes reached was 10 for A m = 0.1 mm, which was doubled for A m = 0.25 mm, before the observation of tool-chips welding process as shown in Figure 4B,C. Increasing the number of holes drilled with higher amplitude can be attributed to the lower thermal load, small chip radian, and enhanced evacuation efficiency [38,40,41,43]. Digital Microscope, the hole diameter error was calculated by taking an average of ten points on the top and bottom surfaces for both materials using a Mitutoyo Coordinate Measuring Machine (CMM).…”

Section: Effect Of Tool Wear On the Thrust Forcementioning

confidence: 91%

“…Consequently, the drill tool material maintained its hardness with a sharp cutting edge geometry at low cutting temperature. Also, the low reduction percentages of cutting forces for high modulation amplitude can be attributed to the higher impact load [40]. For f = 0.075 mm/rev, the CD drilling process was stopped after drill hole number 2, due to the observation of the tool-chip welding process as shown in Figure 4A.…”

Section: Effect Of Tool Wear On the Thrust Forcementioning

confidence: 99%

“…Advanced machining process such as vibration-assisted drilling (VAD) where the axial feed is superimposed by a harmonic motion [38,39], can be seen as a promising candidate to attain better machining quality. This is possibly due to the significant benefit of changing the chip morphology from continuous to segmented [40][41][42] and the efficient chip evacuation mechanism [40,43].The experimental investigation of low-frequency vibration-assisted drilling (LF-VAD) of CFRP/Ti6Al4V showed promising results compared to the conventional drilling (CD) [38,44]. The utilization of 1.5 cycle/rev frequency with minimum quantity lubrication (MQL) resulted in a 43% reduction in the cutting temperature with improved surface integrity [44].…”

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confidence: 99%

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confidence: 99%

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An Investigation into Tool Wear and Hole Quality during Low-Frequency Vibration-Assisted Drilling of CFRP/Ti6Al4V Stack

Hussein

Sadek

Elbestawi

et al. 2019

JMMP

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The use of lightweight material such as CFRP/Ti6Al4V in stacked structures in the aerospace industry is associated with improved physical and mechanical characteristics. The drilling process of nonuniform structures plays a significant role prior to the assembly operation. However, this drilling process is typically associated with unacceptable CFRP delamination, hole accuracy, and high tool wear. These machining difficulties are attributed to high thermal load and poor chip evacuation mechanism. Low-frequency vibration-assisted drilling (LF-VAD) is an advanced manufacturing technique where the dynamic change of the uncut chip thickness is used to manipulate the cutting energy. An efficient chip evacuation mechanism was achieved through axial tool oscillation. This study investigates the effect of vibration-assisted drilling machining parameters on tool wear mechanisms. The paper also presents the effect of tool wear progression on drilled hole quality. Hole quality is described by CFRP entry and exit delamination and hole accuracy. The results showed a significant reduction in the thrust force, cutting torque, cutting temperature, and flank wear-land.This wear mechanism was attributed to hard and soft abrasion modes [14]. The hard mode is located at WC grains due to the generated dynamic stresses from the broken fiber, material reinforcement, and powder like chips [15]. Consequently, the WC grains suffer crack initiation and propagation fracture [16]. On the other hand, the relatively low hardness Co binder is more easily damaged by carbon fibers (CF) in a process known as soft abrasion mode [14,17,18]. Hence, WC grain spalling is more rapid under the cyclic machining load.High cutting temperature, poor chip evacuation mechanism, and burr formation are of the common issue during the drilling process of Ti6Al4V [19][20][21]. These problems resulted in a higher probability of flute-chip accumulation, progressive tool wear, and poor surface integrity [19,20,22]. Low thermal conductivity and high chemical affinity to the majority of tool materials are due to the adverse titanium characteristics, which resulted in a significant reduction in the tool life with a high probability of catastrophic failure [20,23,24]. This effect contributed to the cutting stress concentration on the tool cutting edge where the maximum cutting temperature is located. Therefore, the machining process of Ti6Al4V is typically associated with the formation of built-up-edge (BUE). The formation of BUE has a significant drawback on the machined surface integrity and the tool life [25,26]. Thus, adding more limitations in the aerospace production procedure [27].Despite, the extensive to optimize separate machining process of both materials, the machining process suffers when it comes to production time, cost, and assembly positional error. Single process drilling of the CFRP and Ti6Al4V materials in situ, also known as stacked drilling shows considerable benefits to overcome separate drilling issues [1][2][3]28,29]. However, the stack drilling o...

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Section: Effect Of Tool Wear On the Thrust Forcementioning

confidence: 91%