Altun, Barış
Frequency Response Functions (FRFs) are utilized for analyzing vibrations created during milling process. FRFs obtained with external excitations are often not sufficient as machine-tool dynamics are position-dependent (to machine-tool axes, workpiece placement) and frequency domain to be identified requires specialized equipment. In this thesis, an identification method based on operational excitation addressing these problems is proposed. A single rectangular workpiece is processed and acceleration measurements are taken. FRF is calculated according to the proposed method of sampling engagements individually and force calculation based on mechanistic models. Results are compared with tap test results. Force coefficients to be used are identified by tap tests obtained from a different spot and mechanistic force model by processing a similar rectangular workpiece. Results are confirmed with FRF obtained in the same location.


Prediction of frequency response function (FRF) of asymmetric tools from the analytical coupling of spindle and beam models of holder and tool
Özşahin, Orkun (2015-05-01)
The prediction of chatter stability diagrams in milling requires accurate frequency response functions (FRF) at the tool - workpiece contact zone. Traditionally, the most accurate FRFs are best obtained through the experimental modal testing of each tool, which is costly. This paper presents analytical modeling and coupling procedures for spindle-holder-tool assemblies with asymmetric tools. Tools and holders are analytically modeled with continuous Timoshenko beams, while considering variation of the cross...
Quantitative electrostatic force measurement in AFM
JEFFERY, Steve; Oral, Ahmet; Pethica, John B. (2000-04-02)
We describe a method for measuring forces in the atomic force microscope (AFM), in which a small amplitude oscillation(similar to 1 Angstrom(p-p)) is applied to a stiff(similar to 40 N/m) cantilever below its first resonant frequency, and the force gradient is measured directly as a function of separation. We have used this instrument to measure electrostatic forces by applying an ac voltage between the tip and the sample, and observed a variation in contact potential difference with separation. We also sho...
Analytical modeling of the machine tool spindle dynamics under operational conditions
Özşahin, Orkun; Özgüven, Hasan Nevzat (null; 2012-07-27)
Chatter is an important problem in machining operations, and can be avoided by utilizing stability diagrams which are generated using frequency response functions (FRF) at the tool tip. In general, tool point FRF is obtained experimentally or analytically for the idle state of the machine. However, during high speed cutting operations, gyroscopic effects and changes of contact stiffness and damping at the interfaces as well as the changes in the bearing properties may lead to variations in the tool point FR...
Calculation of the raman frequency, damping constant (Linewidth) and the relaxation time near the tetragonal-cubic transition in PbTiO3
KİRACI, ALİ; Yurtseven, Hasan Hamit (2017-01-01)
Frequencies, damping constants and the relaxation times of some Raman modes including the two soft modes are calculated as a function of pressure near the tetragonal-cubic transition in PbTiO3. Calculation of the Raman frequencies is performed using the observed volume data from the literature by means of the mode Gruneisen parameter at various pressures. Pressure dependence of the damping constant and the relaxation time is predicted using the pseudospin-phonon coupled model and the energy fluctuation mode...
Investigation of subsynchronous resonance risk in the 380 kv Turkish electric network
Ozay, N.; Güven, Ali Nezih (null; 1988-12-01)
Subsynchronous resonance (SSR) occurs when a resonant frequency of a series compensated transmission system interacts with a natural frequency of the turbine prime mover. This form of SSR is referred to as torsional interaction which, under certain conditions, may become self-excited and cause serious damage to electrical equipment and turbine shafts. The presence of a thermal power plant (Kangal) in the close vicinity of a group of series capacitors in Eastern Turkey necessitated a careful investigation of...
Citation Formats
B. Altun, “IDENTIFICATION OF POSITION-DEPENDENT WORKPIECE DYNAMICS IN MILLING PROCESS,” M.S. - Master of Science, Middle East Technical University, 2022.