Active control of high frequency chatter with machine tool feed drives in turning

This paper presents a new active vibration control strategy to mitigate high frequency regenerative chatter vibrations using machine tool feed drives. Rather than modal damping, proposed approach aims to control regenerative process dynamics to shape the Stability Lobe diagram (SLD) and attain higher material removal rates. The controller is designed as a feedback filter whose parameters are optimized to compensate regeneration. The proposed strategy is applied to actively control orthogonal (plunge) turning dynamics where >2.5 [kHz] chatter vibrations are suppressed by a fast tool servo (FTS) drive system. Stability lobes are shaped locally to reach up to 4x higher material removal rates.     

A Study of Different Microstructural Effects on the Strain Hardening Behavior of Hadfield Steel

The effects of the initial texture, velocity gradient, strain increment and type of interaction tensor on the strain hardening response of Hadfield steel were investigated. To observe their influences on mechanical response, crystal plasticity computations were carried out with the aid of the Visco-Plastic Self-Consistent (VPSC) algorithm. Specifically, uniaxial deformation response of Hadfield steel was modeled based on the experimental deformation response at a strain rate of 1×10^?1 s^?1 and corresponding Voce hardening parameters were calculated. The same Voce hardening parameters were utilized with different boundary conditions in the VPSC simulations to identify the roles of the aforementioned microstructural properties. The current results demonstrate the importance of these microstructural properties for reliable predictions of the strain hardening response of Hadfield steel and constitute an important guideline for the proper selection of them.     

Structural Characterization of Sputtered Fe70Pd30 Thin Films During Ex Situ and In Situ TEM Heating

Magnetic shape memory (MSM) thin films have been investigated for their use as actuators and sensors in micro‐electro‐mechanical systems (MEMS). Here, we report on the fabrication of polycrystalline Fe₇Pd₃ thin films by magnetron sputtering. Two‐dimensionally structured, freestanding films can be obtained by the use of different lift‐off techniques and optical lithography. The effect of different heat treatments is discussed. In situ transmission electron microscopy of the as deposited films up to 850 °C shows intermediate phases during heating. Significant changes in magnetic properties of the intermediate phases are observed in complementary investigations on ex situ annealed freestanding films.     

Coupling stochastic occupant models to building performance simulation using the discrete event system specification formalism

When applying occupant models to building performance simulation (BPS), it is common practice to use a discrete-time approach requiring fixed time steps. Consequently, a simulated occupant's decisions do not increase in frequency in response to rapid changes in environmental conditions. Furthermore, as illustrated in this study through the analysis of a discrete-time EnergyPlus simulation, changing the time step between simulation runs may have a dramatic effect on BPS predictions. It is therefore necessary to adhere to a prescribed time step, which may complicate the synchronization of events when models of different domains are coupled. The main contribution of this study is an investigation of the viability of employing the discrete event system specification (DEVS) formalism to represent occupant behaviour without fixed and prescribed time steps. Results indicate that using an adaptive time advancement scheme, the DEVS formalism permits realistic patterns of decision-making while facilitating the coupling of stochastic occupant models with thermal and heating, ventilation and air-conditioning models.     

Pulse Suppression Technique for Mitigating Digital Clock Noise

A practical digital clock noise mitigation technique based on pulse removal is presented. Clock frequency is increased to generate an excess pulse, which is removed in order to match the number of pulses in an average time frame. The location of the excess pulse is selected as the same time point or randomly selected in every time frame. Mathematical analyses are presented for both methods. The circuit is implemented using a state machine on a FPGA. Measurement results indicate more than 40 dB improvement on the digital noise level within a band of interest.     

Gaussian beam to spatial soliton formation in Kerr media

We present a detailed analysis of the generation and propagation of bright spatial soliton beams in nonlinear Kerr media, in which an input beam is assumed to be of a Gaussian or hyperbolic secant form. The problem is solved by the use of the inverse-scattering transform (IST). The analysis of the discrete spectrum obtained from the direct-scattering problem gives exact information about the parameters of the generated soliton. A condition of soliton appearance in the spectrum as a function of the complex width of the initial Gaussian beam is given numerically. The similarities and differences between the hyperbolic secant and Gaussian beams entering the Kerr medium are analyzed in detail. A case is found in which almost all (approximately 99.5%) the total intensity of the Gaussian beam entering the Kerr medium is transformed into the soliton beam. However, this analogy to the self-trapping of soliton beams occurs for higher total-intensity values than in the case of the soliton input profile. The evolution from the Gaussian to the soliton envelope is studied and the condition of self-trapping in the near field is found. The numerical method based on the IST of the solution to the nonlinear Schr?dinger equation is refined.     

Understanding the Effect of Handedness on Both-Handed Task Performance: An Experimental Study based on a Haptic-Controlled,Simulation-Based Surgical Skill Training Scenario

Understanding the performance on both-handed tasks, such as endoscopic surgery, is critical to better organize and develop appropriate instructional systems to improve the necessary skills of surgeons. However, in the literature, only a limited number of studies have investigated the effect of handedness on both-handed task performance. This study aimed to provide an understanding of the participants’ performance differences while performing both-handed tasks through a haptic user interface in a simulated virtual environment specifically developed for surgical training purposes. Twenty-four surgeons attending a medical school in Turkey voluntarily participated in the study. The duration, accuracy, and collision measures were automatically recorded by software. The results revealed that the left-handed participants performed the both-handed tasks (camera: nondominant hand, tool: dominant-hand) in a significantly shorter time than the right-handed participants. This study also showed that haptic-controlled simulation-based surgical skill training systems can potentially provide measures for better understanding the individual behaviors and deliver alternative training environments specific to individual requirements.     

Effect of groove-type chip breakers on twist drill performance

This paper proposes the use of grooves placed on the rake face of a twist drill to facilitate chip breaking and reduce drilling forces and chip clogging. A procedure to design grooves including groove geometry and orientation is discussed. Two sets of experiments are presented that determine the effect of grooves on the forces, chip morphology, and critical depth, and compare the life of the grooved and ungrooved drills. The grooves are found to be very effective in breaking chips and preventing chip clogging. Experiments show the positive effects of the grooves including lower drilling torque and thrust, lower chip evacuation forces, lower cutting forces, increased critical depth and increased drill life.     

Surface Segmental Mobility and Adhesion—Effects of Filler and Molecular Mass

The adhesion of thin films of poly(methyl acrylate) (PMA) on glass slides in contact with tape has been measured as a function of thickness, molecular mass, and amount of silica-based filler. In all cases studied the polymer thin-film, tape-peel tests resulted in linear force-velocity plots. The best-fit lines were extrapolated to find the fracture energies at zero velocity. For thin layers of rubbery PMA on glass slides the PMA-tape fracture energies were found to decrease (from 55–20 J/m²) with increasing PMA thickness (50–1000 nm). Thin films made from glassy poly(methyl methacrylate) (PMMA) were found to have no thickness dependence and much higher fracture energies (～ 140 J/m²). The effect of PMA molecular mass was found to be smaller than the effect of film thickness. Including silica in the films at low levels dramatically increased the fracture energies, with a maximum (182 J/m²) found with 5.2% silica. With larger amounts of silica, the fracture energy declined significantly.