Experimental Evaluation of Cutting Kinematics and Chip Evacuation in Drilling With Low-Frequency Modulation-Assisted Machining

2017 ◽  
Author(s):  
Yang Guo ◽  
James B. Mann
Keyword(s):  
Kinematic Model ◽  
Low Frequency ◽  
Chip Morphology ◽  
Process Efficiency ◽  
Low Frequency Oscillation ◽  
Gun Drill ◽  
Chip Size ◽  
Cutting Kinematics ◽  
Cutting Regimes ◽  
Intermittent Cutting

Modulation assisted machining (MAM) superimposes a low-frequency oscillation onto the cutting process. The otherwise continuous cutting is transformed into a series of discrete, intermittent cutting events. A primary benefit of this process is to form discrete chips of small sizes and hence to improve chip evacuation. For applications in drilling the ability to control the chip size offers a direct route to improving process efficiency and stability. In this paper, the MAM process is evaluated for drilling applications via systematic experiments in drilling copper and Ti6Al4V with a two-flute twist drill and a single-flute gun drill. Based on the measurement of thrust force and examination of chip morphology, the continuous cutting and intermittent cutting regimes of MAM are determined experimentally in the normalized frequency and amplitude parameter space. The results are compared with those predicted by the kinematic model of MAM. Furthermore, the results clearly demonstrate the effect of chip morphology control on chip evacuation and process stability in drilling. The modulation conditions leading to the best performance in chip evacuation are discussed. The study shows that MAM is a promising process for enhancing the efficiency and stability in drilling difficult-to-cut materials and/or holes with high length-to-diameter ratio.

Control of Chip Formation and Improved Chip Ejection in Drilling With Modulation-Assisted Machining

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Yang Guo ◽  
James B. Mann
Keyword(s):  
Chip Formation ◽  
Kinematic Model ◽  
Low Frequency ◽  
Hole Drilling ◽  
Drilling Process ◽  
Low Frequency Oscillation ◽  
Thin Sections ◽  
Gun Drill ◽  
Chip Size ◽  
Cutting Regimes

Abstract Drilling with modulation-assisted machining (MAM) superimposes a low-frequency oscillation onto the drill feed motion. The otherwise continuous cutting in the drilling process is converted into a series of discrete cutting events. The result is a discrete chip formation process and concurrent improvement in chip ejection. The discrete chip formation and ejection in drilling with MAM were investigated via systematic experiments in OFHC Cu and Ti6Al4V using a two-flute twist drill and a single-flute gun drill. Drilling thrust force and chip morphologies for various modulation conditions are examined. The continuous cutting and discrete cutting regimes of modulation-assisted drilling are compared with conditions determined by a kinematic model. The results show that chip formation in the continuous cutting regime with MAM can influence chip breakage by random fracture at thin sections of the chip, but in this regime the resulting chip size is variable and not controlled. In contrast, when MAM conditions operate in the regime of discrete cutting, the deformed chip size can be directly controlled. The ability to control the chip size improves chip ejection and drilling process stability. A set of modulation conditions for enhanced performance of chip ejection are proposed. The study shows that modulation-assisted machining offers distinct advantages as a method for deep-hole drilling applications.

ANALYSIS OF STAND RESEARCH RESULTS OF AXIAL DYNAMIC FORCE IN DRILLING BY THREE ROLLER CONE BIT

2019 ◽  
pp. 81-93
Author(s):  
В. М. Мойсишин ◽  
M. V. Lyskanych ◽  
R. A. Zhovniruk ◽  
Ye. P. Majkovych
Keyword(s):  
Low Frequency ◽  
Maximum Energy ◽  
Dynamic Force ◽  
Low Frequency Oscillation ◽  
Drilling Tool ◽  
Rock Destruction ◽  
Frequency Components ◽  
Harmonic Components ◽  
Experimental Values ◽  
Harmful Effects

The purpose of the proposed article is to establish the causes of oscillations of drilling tool and the basic laws of the distribution of the total energy of the process of changing the axial dynamic force over frequencies of spectrum. Variable factors during experiments on the classical plan were the rigidity of drilling tool and the hardness of the rock. According to the results of research, the main power of the process of change of axial dynamic force during drilling of three roller cone bits is in the frequency range 0-32 Hz in which three harmonic frequency components are allocated which correspond to the theoretical values of low-frequency and gear oscillations of the chisel and proper oscillations of the bit. The experimental values of frequencies of harmonic components of energy and normalized spectrum as well as the magnitude of the dispersion of the axial dynamic force and its normalized values at these frequencies are presented. It has been found that with decreasing rigidity of the drilling tool maximum energy of axial dynamic force moves from the low-frequency oscillation region to the tooth oscillation area, intensifying the process of rock destruction and, at the same time, protecting the tool from the harmful effects of the vibrations of the bit. Reducing the rigidity of the drilling tool protects the bit from the harmful effects of the vibrations generated by the stand. The energy reductions in these fluctuations range from 47 to 77%.

Low-frequency-oscillation characteristics of ionization distribution in Hall thruster channels

Vacuum ◽  
2021 ◽  
pp. 110320
Author(s):  
Tianyuan Ji ◽  
Liqiu Wei ◽  
Haifeng Lu ◽  
Shangmin Wang ◽  
Ning Guo ◽  
...  
Keyword(s):  
Low Frequency ◽  
Hall Thruster ◽  
Frequency Oscillation ◽  
Low Frequency Oscillation ◽  
Oscillation Characteristics

A Parametric Study of Low-Frequency Damping of Mooring System

2014 ◽  
Author(s):  
Minglu Chen ◽  
Shan Huang ◽  
Nigel Baltrop ◽  
Ji Chunyan ◽  
Liangbi Li
Keyword(s):  
Low Frequency ◽  
Structure Design ◽  
The Body ◽  
Body Motion ◽  
Mooring Line ◽  
Offshore Structure ◽  
Frequency Oscillation ◽  
Low Frequency Oscillation ◽  
Line System ◽  
Irregular Wave

Mooring line damping plays an important role to the body motion of moored floating platforms. Meanwhile, it can also make contributions to optimize the mooring line system. Accurate assessment of mooring line damping is thus an essential issue for offshore structure design. However, it is difficult to determine the mooring line damping based on theoretical methods. This study considers the parameters which have impact on mooring-induced damping. In the paper, applying Morison formula to calculate the drag and initial force on the mooring line, its dynamic response is computed in the time domain. The energy dissipation of the mooring line due to the viscosity was used to calculate mooring-induced damping. A mooring line is performed with low-frequency oscillation only, the low-frequency oscillation superimposed with regular and irregular wave-frequency motions. In addition, the influences of current velocity, mooring line pretension and different water depths are taken into account.

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