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1. High Performance Turning Assisted by Chip-Pulling

   Sencer, Burak; Maulimov, Mukhtar (October 2018, American Society for Precision Engineering (ASPE))

   Friction is one of the key factors limiting the achievable productivity and efficiency in most machining processes. Typically, adverse effects of friction in machining has been addressed through better tool material design and use of coolants. This paper presents an innovative technique to significantly increase the efficiency of turning processes by alleviating friction forces using an assistive device. As opposed to breaking the cut chip using chip breakers, in the proposed technique, the chip is not broken but pulled using a system to realize a new turning process so-called the “chip-pulling turning”. By pulling the cut chip externally, the friction force acting along tool’s rake face could be reduced and even cancelled. This, in return, increases the shear angle and leads to efficient material removal with significantly lower process forces and energy. An electro-mechanical chip-pulling device is designed that can pull the guided chip continuously during the turning operation. Design of the chip-pulling system, proposed pulling device and its automatic control are presented. The effect of chip-pulling is validated experimentally through various cutting experiments. Furthermore, orthogonal cutting force models are used to model the effect of chip-pulling on the process. 

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2. Generalized mechanics and dynamics of modulated turning

   https://doi.org/10.1016/j.jmatprotec.2022.117708  

   Eren, Bora; Nam, Soohyun; Sencer, Burak (October 2022, Journal of materials processing technology)

   Budak, Erhan (Ed.)

   This paper presents a generalized cutting force and regenerative chatter stability prediction for the modulated turning (MT) process. Uncut chip thickness is modeled by considering current tool kinematics and undulated (previously generated) surface topography for any given modulation condition in the feed direction. It is found that chip formation is governed by the undulated surface generated in multiple past spindle rotations. Uncut chip thickness is computed analytically in the form of trigonometric functions, and cutting forces are predicted by making use of orthogonal cutting mechanics. Regenerative chatter stability of the process is also modelled. Analytical semi-discretization-based solution is developed to accurately predict the stability lobe diagrams (SLDs) of the MT process. Predicted stability lobes are validated through numerical time-domain simulations and experimentally via orthogonal (plunge) turning tests. It is found that as compared to conventional single-point continuous turning, regenerative stability of MT exhibits multiple (3) regenerative delay loops and long out-of-cut duration in-between tool engagement stabilizes the process to reach up to 2x higher stable widths/depths as compared to the conventional continuous turning. 

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3. Wear Performance Evaluation of Minimum Quantity Lubrication with Exfoliated Graphite Nanoplatelets in Turning Titanium Alloy

   Nguyen, D. (May 2019, Journal of manufacturing science and engineering)

   This paper evaluates the performances of dry, minimum quantity lubrication (MQL), and MQL with nanofluid conditions in turning of the most common titanium (Ti) alloy, Ti-6Al-4 V, in a solution treated and aged (STA) microstructure. In particular, the nanofluid evaluated here is vegetable (rapeseed) oil mixed with small concentrations of exfoliated graphite nanoplatelets (xGnPs). This paper focuses on turning process that imposes a challenging condition to apply the oil or nanofluid droplets directly onto the tribological surfaces of a cutting tool due to the uninterrupted engagement between tool and work material during cutting. A series of turning experiments was conducted with uncoated carbide inserts, while measuring the cutting forces with a dynamometer under the dry, MQL and MQL with nanofluid conditions supplying oil droplets externally from our MQL device. The inserts are retrieved intermittently to measure the progress of flank and crater wear using a confocal microscopy. This preliminary experimental result shows that MQL and in particular MQL with the nanofluid significantly improve the machinability of Ti alloys even in turning process. However, to attain the best performance, the MQL conditions such as nozzle orientation and the concentration of xGnP must be optimized. 

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4. Modeling and Control of Strip Transport in Metal Peeling

   https://doi.org/10.1115/1.4066395  

   Yalamanchili, Aditya; Sagapuram, Dinakar; Pagilla, Prabhakar R (August 2024, Journal of Dynamic Systems, Measurement, and Control)

   Metal peeling refers to the process of forming a thin metal strip from the surface of a rotating feedstock using controlled material removal -- machining under an applied strip tension. In this paper, the mechanics of strip formation process is described, while emphasizing the role of strip tension in ensuring uniformity and quality of the peeled strip. This includes an analysis of the deformation history in the peeling zone and the transport dynamics of the strip as it moves from the cutting edge to the coiler. Using conservation laws, governing equations for strip tension and velocity that incorporate dynamic spatiotemporal interactions between peeling and transport processes are developed. The mechanics of strip formation process is described, while emphasizing the role of strip tension in ensuring uniformity and quality of the peeled strip. This includes an analysis of the deformation history in the peeling zone and the transport dynamics of the strip as it moves from the cutting edge to the coiler. Using conservation laws, governing equations for strip tension and velocity that incorporate dynamic spatiotemporal interactions between peeling and transport processes are developed. Peeling experiments are performed with steel using a prototype experimental platform to evaluate the proposed control approach. Comparisons between two control strategies, with and without tension feedback, are presented and discussed. The importance of real-time tension control for mitigating strip thickness variations and improving other dimensional features of the strip such as flatness and edge waviness is also briefly discussed. 

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5. Silicon Microthermoelectric Coolers for Local Heat Removal in Integrated Circuit Chips

   https://doi.org/10.1109/TED.2023.3304277  

   Dhawan, Ruchika; Edwards, Hal; Lee, Mark. (August 2023, IEEE transactions on electron devices)

   Advancements in electronic device fabrication with increasing integration levels have resulted in very high device densities. This has led to higher power dissipation and heat fluxes, increasing integrated circuit (IC) operating temperature. High and nonuniform heat generation degrades device and system performance. Therefore, thermal management to keep ICs within prescribed temperature limits is an important challenge for reliable and economic performance. Cooling techniques, including liquid coolants and air conditioning (AC), have been utilized to remove heat at the package and system level. However, these techniques must overcome high thermal impedances and require complex integration, while global cooling is generally wasteful, inefficient, and expensive. To improve thermal management, we have developed Si microthermoelectric coolers (μTECs) with areas as small 1E−5 cm^2 that can be integrated on -chip near local hot spots using the standard fabrication processes. While Si μTECs cannot achieve low base temperatures, they can actively pump relatively high heat fluxes directly to a heat sink, thus reducing local temperature increases and allowing targeted rather than global waste heat removal. We demonstrate μTECs that can pump up to 43 W/cm^2 of locally generated excess heat with no increase in chip temperature. 

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