Analytical modeling of chatter stability in turning and boring operations - Part II: Experimental verification

In this part of the paper series, chatter experiments are conducted in order to verify the proposed stability models presented in the first part (Ozlu, E., and Budak, E., 2007, ASME J. Manuf. Sci. Eng., 129(4), pp. 726–732). Turning and boring chatter experiments are conducted for the cases where the tool or the workpiece is the most flexible component of the cutting system. In addition, chatter experiments demonstrating the effect of the insert nose radius on the stability limit are presented. Satisfactory agreement is observed between the analytical predictions and the experimental results

Thermomechanical modeling of orthogonal cutting including the effect of stick-slide regions on the rake face

An orthogonal cutting model including the primary and secondary shear zones is pre-sented in this study. The primary shear zone is modeled by a thermomechanical model where the rake contact is represented by two regions of respectively sticking and sliding friction. The model is compared with experimental results in terms of shear stress, shear angle, and cutting force predictions. Overall a good agreement is observed

Analytical prediction of stability limit in turning operations

Unstable cutting due to chatter vibrations is one of the most important problems during metal cutting operations. Chatter can be a limitation for productivity and surface quality in turning operations, especially when long and slender tools and parts are involved. In this study, an analytical stability method for turning process is presented. The model takes the cutting geometry into consideration, and proposes a new solution procedure for the dynamic chip thickness at the insert nose. The analytically calculated absolute stable depth of cuts are compared with the chatter test results, and a good agreement is observed

Analytical stability models for turning and boring operations

In this paper an analytical model for stability limit predictions in turning and boring operations is proposed. The multi-dimensional model includes the 3D geometry of the processes. In addition a model for the chip thickness at the insert nose radius is also proposed to observe the effect of the insert nose radius on the chatter stability limit. Chatter experiments are conducted for both turning and boring in order to compare with analytical results and good agreement is observed

Analytical modeling of chatter stability in turning and boring operations: a multi-dimensional approach

In this study, an analytical model for the stability of turning and boring processes is proposed. The proposed model is a step ahead from the previous studies as it includes the dynamics of the system in a multidimensional form, uses the true process geometry and models the insert nose radius in a precise manner. Simulations are conducted in order to compare the results with the traditional oriented transfer function stability model, and to show the effects of the insert nose radius on the stability limit. It is shown that very high errors in stability limit predictions can be caused when the true process geometry is not considered in the calculations. The proposed stability model predictions are compared with experimental results and an acceptable agreement is observed

Experimental analysis and modeling of orthogonal cutting using material and friction models

In this study, a process model for orthogonal cutting processes is proposed. The model involves the primary and secondary deformation zones. The primary shear zone is modeled by a Johnson-Cook constitutive relationship and a shear plane having constant thickness. The secondary deformation zone is modeled semi-analytically, where the coefficient of friction is calibrated experimentally. The cutting forces predicted using the calibrated sliding friction coefficients are in good agreement with the measurements. The experimental investigation of sliding friction coefficients also show promising results for the proposed model, which is still under development

Monetary policy communication under inflation targeting: Do words speak louder than actions?

This paper assesses the effectiveness of monetary policy communication of the Central Bank of Turkey (CBT) by quantifying the information content of the policy statements released right after the monthly Monetary Policy Committee meetings. First, we quantify the signal regarding the next interest rate decision and ask whether CBT’s words match its deeds, i.e., whether communication improves predictability using the Autoregressive Conditional Hazard model. Our findings suggest that the role of statements in predicting the next policy move have strengthened following the adoption of full-fledged inflation targeting (IT) regime. Second, we identify the surprise component of policy communication directly from market commentaries and assess its impact on the term structure of interest rates. We find that the response of the yield curve to policy statements have become highly significant for the unanticipated changes in the monetary policy communication and the relative importance of communication in driving market yields has increased through time.Central Bank Communication, Predictability, Transparency

Toplumsal çelişki ve Sabahattin Ali

Taha Toros Arşivi, Dosya No: 218-Sabahattin Aliİstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

“Değnekçilik” in Ottoman Empire in the 19th Century

Değnekçiler; hamal ve kayıkçı esnafının sorunlarını kethüdaya iletmek, bu esnafın vermekle yükümlü olduğu vergileri (rüsûm) toplamak, denetlemek, hamal ve kayıkçıların ihtiyaç duyulan alanlarda istihdamını sağlamak gibi muhtelif görevleri üstlenmişlerdir. Lonca sisteminde esnaf ile kethüda arasındaki iletişim genel olarak yiğitbaşılar tarafından sağlanmışken, hamal ve kayıkçı esnafı içerisinde kethüda-esnaf koordinasyonunu sağlayan görevli değnekçi olarak adlandırılmıştır. Değnekçiler; klasik dönemde lonca sistemi çerçevesinde faaliyetlerini yürütürken, 19. yüzyılda İhtisab veya Hububat Nezâreti, Şehremâneti kurulduktan sonra ise başkentte Şehremâneti veya Altıncı Daire Müdüriyeti, taşrada ise taşra belediye teşkilatları tarafından faaliyetlerini yürütmüşlerdi

Modeling dynamics and stability of 5-axis milling processes

5-axis milling is an important machining process for several industries such as aero-space, automotive and die/mold. It is mainly used in machining of sculptured surfaces where surface quality is of extreme importance. Being one of the most important prob-lems in machining, chatter vibrations must be avoided in manufacturing of these com-ponents as they result in high cutting forces, poor surface finish and unacceptable part quality. Chatter free cutting conditions for required quality with higher productivity can be determined by using stability models. Up to now, dynamic milling and stability models have been developed for 3-axis milling operations; however the stability of 5-axis proc-esses has never been modeled. In this paper, a stability model for 5-axis milling opera-tions is proposed. The model can consider the 3D dynamics of the 5-axis milling proc-ess including effects of all important process parameters including lead and tilt angles. Due to the complex geometry and mechanics of the process, the resulting analytical equations are solved numerically in order to generate the stability diagrams