Nonlinear analysis of chatter in turning process using dimensionless groups

Proceedings of the Institution of Mechanical Engineers, Part C:

Emami

2016

Self Cite

Chatter phenomenon is one of the essential problems in metal machining processes. It causes cutting tool wear and increase of production costs. Chatter vibration is an unstable self-excited vibration that the regenerative chatter is its most common type. In this paper, regenerative chatter in turning process is investigated. A three-dimensional nonlinear dynamic model of the turning process including both structural and cutting force nonlinearities and gyroscopic effects is presented. The workpiece is modeled as a rotating clamped–free beam which is excited by cutting forces. Using the method of multiple-scales, analytical approximate response of the system is obtained. To validate the model its responses are compared with the experimental results. Using this model the influences of tool longitudinal position, workpiece diameter, depth of cut, and rotational speed of workpiece on the stability results are studied. Using these results, turning velocity intervals for stable and unstable cuts are determined.

Section: Department Of Mechanical Engineering Yazd Iranmentioning

confidence: 99%

“…Substituting equation (22) in equation (21), the relation for nonconservative forces can be expressed as Substituting equations (5), (17), and (19) in equation (2), equations of motion in two directions y and z can be derived as…”

Section: Virtual Work Of the Nonconservative Forcesmentioning

confidence: 99%

Analytical solution for nonlinear oscillation of workpiece in turning process

Proceedings of the Institution of Mechanical Engineers, Part C:

Emami

2016

Self Cite

“…3–12 A number of investigations have focused on the continuous structure for macro-machining operation. 13–16 For micro-machining operation, most of the researchers modeled the tool using classical continuum theory, 17–24 and some few others developed the tool model by applying non-classical continuum theory. 25,26…”

Section: Introductionmentioning

confidence: 99%

Optimization of different parameters related to milling tools to maximize the allowable cutting depth for chatter-free machining

Mokhtari

Proceedings of the Institution of Mechanical Engineers, Part B:

Mazidi

2020

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Determination of optimal parameters of cutting tool is one of the most significant factors in any operation planning of metal elements, especially in micro-milling process. This article presents an optimization procedure, based on genetic algorithms, to optimize some parameters related to micro-milling tool including number of teeth, shank diameter, fluted section diameter, shank length, taper length, and length of fluted section. The aim of this optimization is maximizing the minimum value of cutting depth on the border of stability lobe diagrams, which is called allowable cutting depth, for chatter-free machining. Cutting tool is modeled as a three-dimensional spinning cantilever Timoshenko beam based on strain gradient elasticity theory. Structural nonlinearity, gyroscopic moment, rotary inertia, and velocity-dependent process damping are also considered in the cutting tool model. The values of natural frequency, damping ratio, and material length scale of the micro-milling tool are calculated using a system identification based on genetic algorithm to match the analytical response with recorded experimental vibration signal. Using beam model, the allowable cutting depth is increased in the optimization process for a specific range of spindle speed to avoid the chatter phenomenon. Analytical study of micro-milling process stability is carried out to determine the cost function of the genetic algorithm. A plot of the greatest fitness in each generation is sketched. In addition, stability lobe diagrams before and after optimization process are presented to show the efficiency of the optimized micro-milling tool. In the presented examples, the results of genetic algorithm may lead to design or find a micro-milling tool that its acceptable cutting depth increases up to 1.9313 times.

“…Tajalli et al 28,29 presented the formulations of a micro end-mill tool by considering strain gradient and Timoshenko beam theories regardless of twist effects and any verification of their results by experimental articles. Tavari et al 30 derived a novel 3D nonlinear representation of self-generated fluctuation in turning operation. They modeled the workpiece as a spinning cantilever Euler-Bernoulli beam.…”

Section: Introductionmentioning

confidence: 99%

“…Tavari et al. 30 derived a novel 3D nonlinear representation of self-generated fluctuation in turning operation. They modeled the workpiece as a spinning cantilever Euler–Bernoulli beam.…”

Section: Introductionmentioning

confidence: 99%

Investigation of rotary inertial dynamic effects on chatter boundary in milling process using three-dimensional Timoshenko tool model

Mokhtari

Mazidi

Proceedings of the Institution of Mechanical Engineers, Part K:

2018

Chatter prediction is essential to conduct stable machining. Many of the previous studies made to simulate milling process have not considered gyroscopic and rotary inertial dynamics effects. The aim of this research is to investigate the effects of rotary inertial dynamics on prediction of chatter in the milling operation. For this purpose, a threedimensional rotating cantilever Timoshenko beam is considered for modeling the cutting tool. In the proposed model, cutting forces are applied at the end of the beam. Imposing spectral finite element model, the governing delay partial differential equations of the system reduce to nondelay ordinary differential equations. The main contributions of the current research are modeling the cutting tool as a continuous model by Timoshenko beam theory, finding and solving nondelay ordinary differential equations of the cutter via spectral finite element model, and studying the effects of gyroscopic and rotary inertial dynamics, completely. For validating, the system stability predictions obtained from the presented model are compared with experimental outcomes from the literature. Besides the common stability lobe diagram which is in terms of depth of cut and the spindle speed, other stability diagrams based on cutter length and diameter are illustrated. Using this model, influences of rotary inertial dynamics on these stability diagrams are investigated. The results show that ignoring the rotary inertial dynamics causes significant errors in prediction of chatter boundaries especially in high angular velocity of the tool. In addition, the effect of number of the cutter teeth on the stability of milling process is studied. The presented stability diagram may help a machinist to choose a better set of parameters, such as tool length and diameter, number of cutter flutes, depth of cut, and spindle velocity, for doing a stable milling process.