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    PublicationOpen Access
    A new identification method of specific cutting coefficients for ball end milling
    (Elsevier, 2014) Department of Mechanical Engineering; Khavidaki, Sayed Ehsan Layegh; Lazoğlu, İsmail; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391
    The paper presents a new and accurate strategy for estimation of cutting coefficients for ball-end milling of free form surfaces in 3- and 5-axis operations. Since the cutting coefficients are not constant along the tool axis in the ball part of the cutter, the tool is considered by dividing the ball region into thin disks. In order to find the contribution of each disk to resultant cutting force, an experimental setup is designed to cut the workpiece while only that disk is in engaged with the workpiece. It is shown that this method is more efficient than common methods of mechanistic identification of cutting constants that are available in literature. The derivations are improved by considering the helix angle and cutting edge length to enhance the accuracy of the estimated cutting coefficients. Validation of the proposed strategy is demonstrated experimentally by simulation of cutting forces and comparing the results with conventional methods of identification of cutting coefficients that have been proposed in the literature. (C) 2014 Elsevier B.V.
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    A new magnetorheological damper for chatter stability of boring tools
    (Elsevier Science Sa, 2021) N/A; N/A; Department of Chemistry; Department of Mechanical Engineering; Saleh, Mostafa Khalil Abdou; Nejatpour, Mona; Acar, Havva Funda Yağcı; Lazoğlu, İsmail; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Chemistry; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; N/A; 178902; 179391
    Chatter is a limiting factor during boring of deep holes with long slender boring bars. In this article, a new magnetorheological (MR) damper is introduced to increase the stability of the boring process. The sponge-type configuration of the damper utilizes a minimal amount of MR fluid in the annulus around the boring bar. The MR fluid layer and the electromagnetic circuit are externally applied to the boring bar, which allows easy installation and adjustability in bar length. A custom made, bidisperse MR fluid is used to eliminate particle sedimentation and enhance the lifetime of the damper. The modal analysis of the boring bar with the new MR damper shows improvements in both the damping and the dynamic stiffness of the system. This enhancement significantly increases the chatter-free depth of cut on the stability lobe diagrams. This article presents the experimental validations on the boring of AL 7075 and Inconel 718 workpieces which are materials widely used in many aerospace applications. The damper is installed on a conventional boring bar for a CNC machining center setup, and its performance is tested under various machining conditions.
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    A novel analytical algorithm for prediction of workpiece temperature in end milling
    (Elsevier, 2022) N/A; Department of Mechanical Engineering; Akhtar, Waseem; Lazoğlu, İsmail; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391
    Temperature is a critical parameter in machining as it directly affects the cutting performance, part quality, residual stresses, distortion, tool life, etc. In this article, a novel analytical algorithm for fast temperature predic-tion in intermittent cutting processes like milling is proposed. For the first time, the temperature drop during the noncutting period is taken into consideration for the workpiece side. The model also takes into account time-varying chip thickness due to the trochoidal motion of the milling tool. Validation tests with Ti6Al4V showed the promise of the algorithm in predicting the milling temperature under various cutting conditions.(c) 2022 CIRP. Published by Elsevier Ltd. All rights reserved.
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    Active damping of chatter in the boring process via variable gain sliding mode control of a magnetorheological damper
    (Elsevier, 2021) N/A; N/A; Department of Mechanical Engineering; Saleh, Mostafa Khalil Abdou; Ulasyar, Abasin; Lazoğlu, İsmail; PhD Student; Researcher; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; N/A; College of Engineering; N/A; N/A; 179391
    In this article, a sliding mode control of a magnetorheological fluid damper is presented for active damping of chatter in the boring process for the first time. A boring bar is integrated with an in-house developed magnetorheological fluid damper system. The variable gain super twisting sliding mode control algorithm is designed and implemented for suppressing the chatter in the boring process. Simulations of the controller show its fast response and robustness against disturbances and parametric uncertainties. Validation cutting tests performed under various machining conditions showed that the stability limit can be increased significantly with the sliding mode control of the magnetorheological fluid damper.
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    An enhanced analytical model for residual stress prediction in machining
    (Elsevier, 2008) Ulutan, D.; Engin, S.; Kaftanoglu, B.; Department of Mechanical Engineering; Department of Mechanical Engineering; Lazoğlu, İsmail; Alaca, Burhanettin Erdem; Faculty Member; Faculty Member; Department of Mechanical Engineering; College of Engineering; College of Engineering; 179391; 115108
    The predictions of residual stresses are most critical on the machined aerospace components for the safety of the aircraft. In this paper, an enhanced analytic elasto-plastic model is presented using the superposition of thermal and mechanical stresses on the workpiece, followed by a relaxation procedure. Theoretical residual stress predictions are verified experimentally with X-ray diffraction measurements on the high strength engineering material of Waspaloy that is used critical parts such as in aircraft jet engines. With the enhanced analytical model, accurate residual stress results are achieved, while the computational time compared to equivalent FEM models is decreased from days to secends.
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    Analysis of thermal fields in orthogonal machining with infrared imaging
    (Elsevier Science Sa, 2008) Department of Mechanical Engineering; Department of Mechanical Engineering; Department of Physics; Lazoğlu, İsmail; Serpengüzel, Ali; N/A; Faculty Member; Faculty Member; Department of Mechanical Engineering; Department of Physics; Manufacturing and Automation Research Center (MARC); Manufacturing and Automation Research Center (MARC); N/A; College of Engineering; College of Engineering; College of Sciences; N/A; 179391; 27855
    The validation of a previously developed finite difference temperature prediction model is carried out for orthogonal machining process with a high precision infrared camera set-up, considering the temperature distribution in the tool. the thermal experiments are conducted with two different materials; al 7075, AISI 1050, with two different tool geometries; inserts having a rake angle of 6 degrees and 18 degrees, for different cutting velocities and feedrates. an infrared camera set-up is utilized for the thermal experiments. the results of the high precision infrared thermal measurements are compared with the outputs of the finite difference temperature model, considering the maximum and the mean temperatures in the tool-chip interface zone and the temperature distributions on the tool take face. the maximum tool-chip interface temperature increases with increasing cutting velocity and feedrate. the relationship between the maximum tool-chip interface temperature and the rake angle of the tool is not distinctive. the experimental results show good agreement with the simulations. (c) 2007 Elsevier B.V. all rights reserved.
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    Analytical modelling of residual stresses in machining
    (Elsevier Science Sa, 2007) N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Ulutan, Durul; Alaca, Burhanettin Erdem; Lazoğlu, İsmail; Master Student; Faculty Member; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 115108; 179391
    An analytical model is developed for prediction of residual stresses in machining. In the thermo-mechanical model of residual stresses both the thermal field of the workpiece and mechanical cutting forces are coupled. The shear energy created in the primary shear zone, the friction energy produced at the rake face-chip contact zone, the heat balance between the chip, tool and workpiece are considered based on the first law of thermodynamics. The temperature distributions on the workpiece, tool and chip are solved by using finite difference method. The calculated workpiece temperature field is used in thermal load calculations. Stresses resulting from thermal and mechanical loading are computed using an analytical elasto-plastic model and a relaxation procedure. The model is verified with experimental measurements of residual stresses on bearing steel 100Cr6 (JIS SUJ2) in the literature. With the analytical model presented here, substantial reduction in computational time is achieved in the predictions of residual stresses.
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    Five-axis additive manufacturing of freeform models through buildup of transition layers
    (Elsevier Sci Ltd, 2019) N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Isa, Mohammed A.; Lazoğlu, İsmail; Researcher; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); College of Engineering; College of Engineering; N/A; 179391
    Acclaimed for enabling the fabrication of complex parts, additive manufacturing is confined to established processing and planning methods that contribute impediments to its industrial adoption. The requirement of support structures and poor quality of produced surfaces are some of these impediments. Extension of the manufacturing method to accommodate variable tool orientation can introduce new approaches in process planning that can resolve these obstacles. Therefore, a new 5-axis 3D printer is designed, built and programmed to facilitate implementation of novel 3D curve paths. Common layering methods in additive manufacturing are centered around the idea of intersection of a CAD model with parallel planes or offset surfaces without regards to the form of the part. The use of these inflexible layering patterns leads to staircase effect on the surfaces, inefficient toolpaths and low load-bearing capacity. This article suggests and develops new 5-axis path planning model that takes into account the surface profiles of the freeform part. Path and tool orientation conditions are reexamined to propose planning schemes that prevent staircase effects on shell and solid components. To accomplish this, the material is deposited on successive transition surfaces whose infra-layer thickness varies to allow changes in the form of the surfaces.
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    Improving cycle time in sculptured surface machining through force modeling
    (Elsevier, 2004) Budak, E.; Department of Mechanical Engineering; N/A; Lazoğlu, İsmail; Güzel, Birhan Ufku; Faculty Member; Master Student; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; 179391; N/A
    In this paper, an enhanced mathematical model is presented for the prediction of cutting force system in ball end milling of sculptured surfaces. This force model is also used as the basis for off-line feed rate scheduling along the tool path in order to decrease the cycle time in sculptured surface machining. As an alternative for setting a constant feed rate all along the tool path in rough machining of sculptured surfaces, resultant cutting forces are aimed to be kept under a pre-set threshold value along the tool path by off-line scheduled piecewise variable feed rates. In this paper, it is shown that machining time, depending on complexity of sculptured surfaces, can be decreased significantly by scheduling feed rate along the tool path. The model is tested under various cutting conditions and some of the results are also presented and discussed in the paper.
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    Investigation on the performance of SiAlON ceramic drills on aerospace grade CFRP composites
    (Elsevier, 2015) Celik, Ali; Kara, Alpagut; Kara, Ferhat; Department of Mechanical Engineering; Lazoğlu, İsmail; Faculty Member; Department of Mechanical Engineering; College of Engineering; 179391
    Carbon fiber reinforced polymer (CFRP) composites are widely used in aircraft structure due to their outstanding physical and mechanical properties. Drilling is one of the most critical operation in the handling of CFRP composites, since the delamination free holes with high dimensional accuracy are required for assembly. The quality of the machined holes strongly depends on machining conditions, tool geometry and tool wear. There are a limited number of tool materials which can survive in the abrasive cutting conditions formed by the fractured carbon fibers during drilling. SiAlONs are promising materials for the machining of CFRP composites due to their superior abrasive wear resistance. SiAlON ceramics have been reported for the first time in the literature as cutting tool materials for drilling of CFRP composites in this study, where alpha/beta-SiAlON drilling tools with four different sets of common drill geometries were manufactured and tested extensively on drilling of aerospace grade CFRP composites. The effects of cutting parameters and geometrical features of novel alpha/beta-SiAlON drilling tools on the cutting forces and the peel-up delamination of the machined holes were investigated. It was observed that the point angle and chisel edge length of the novel SiAlON drilling tools are the main parameters that affect the maximum thrust force and delamination during drilling. The thrust force exhibited an increase during drilling tests, indicating that an abrasive wear occurs at the cutting edges of the SiAlON drilling tools.