Dual Clearance Research Articles

Influence of Cutting Tool and Drilling Process on the Machinability of Inconel 718

Nickel-based superalloy is a kind of metal material that is widely used to manufacture high-temperature parts in the fields of aviation and aerospace, but it is also a typical difficult-to-machining material. The precision cutting of nickel-based superalloy has always been an important manufacturing problem. Based on the tests of conventional drilling with three kinds of twist drills, the machinability of Inconel 718 was evaluated comprehensively by drilling force, tool wear and machining quality, and the cutting tools suitable for drilling nickel-based superalloy were chosen. Then the experiments of peck-drilling for Inconel 718 were carried out, and the process effect under different peck depth Q was deeply researched. The results showed that the HSS-Co (high speed steel with cobalt) twist drill can meet the needs of low-speed drilling of nickel-based superalloy, while the coated carbide twist drill has better service performance. The drill tip structure of dual clearance angle is beneficial to decrease the cutting friction and improve the machining accuracy. Compared with conventional drilling, the peck-drilling can reduce the cutting force and improve the dimensional accuracy and surface quality. However, it is very important to choose a suitable peck depth Q for fully exploiting the advantages of peck-drilling.

Numerical and Experimental Investigation of the Effect of Cavitation on Dual Clearance Squeeze Film Damper

A new dynamic model is developed for the dual clearance squeeze film damper (DCSFD) considering the effect of cavitation in this paper. The relationship between the eccentricities of the inner and outer films is achieved based on the equations of motion. The Reynolds equation and Rayleigh–Plesset equation are employed to describe the kinetic properties of DCSFD and the cavitation effect of film, respectively. Under the assumption of compressible fluid, the pressure distribution of DCSFD is finally obtained by the numerically iterative method. The film pressure distribution in the outer layer (including the positive and negative pressure zones) obtained from the experimental test agrees well with the numerical prediction, which verifies the validity of the proposed numerical model. In Section 5, the effects of oil temperature, inlet pressure, eccentricity, and whirling frequency on the cavitation in the film are investigated systematically and experimentally. The experimental results indicate that cavitation mainly affect the pressure in the negative pressure zone of the inner and outer film of DCSFD, but has little influence on the pressure in the positive pressure zone. The area of cavitation increased with eccentricity; when the inner eccentricity reached 0.1 or above, the area near the injection hole of film also generated a small zone of negative pressure. The numerical model and the experimental results in this paper are valuable for further research and engineering applications of DCSFD.

Study on the Vibration Mitigation Characteristic of Dual Clearance Squeeze Film Damper

In this paper, a novel model of dual clearance squeeze film damper (DCSFD) was constructed considering convection effect and the vibration mitigation characteristic of DCSFD was researched. The DCSFD film force linearity r FSFD was proposed. The response characteristics of rigid rotor containing DCSFD were studied based on the DCSFD model. A response experiment of the DCSFD was arranged, and the model was verified. A good consistence was achieved between the simulation and experiment. The experiment and simulation result manifests that the unbalance response of DCSFD was smaller than that of SFD at every excitation frequency. The DCSFD could inhibit the nonlinear vibration such as the bistability and bifurcation due to big mass eccentricity, and nonlinear film force for the DCSFD film force linearity was bigger than that for SFD. The thickness ratio of inner and outer film, pressure loss coefficient, and inner film thickness were the important parameters that have great influence on DCSFD vibration mitigation characteristic.

Step responses of a torsional system with multiple clearances: Study of vibro-impact phenomenon using experimental and computational methods

Abstract Recently Krak and Singh (2017) proposed a scientific experiment that examined vibro-impacts in a torsional system under a step down excitation and provided preliminary measurements and limited non-linear model studies. A major goal of this article is to extend the prior work with a focus on the examination of vibro-impact phenomena observed under step responses in a torsional system with one, two or three controlled clearances. First, new measurements are made at several locations with a higher sampling frequency. Measured angular accelerations are examined in both time and time-frequency domains. Minimal order non-linear models of the experiment are successfully constructed, using piecewise linear stiffness and Coulomb friction elements; eight cases of the generic system are examined though only three are experimentally studied. Measured and predicted responses for single and dual clearance configurations exhibit double sided impacts and time varying periods suggest softening trends under the step down torque. Non-linear models are experimentally validated by comparing results with new measurements and with those previously reported. Several metrics are utilized to quantify and compare the measured and predicted responses (including peak to peak accelerations). Eigensolutions and step responses of the corresponding linearized models are utilized to better understand the nature of the non-linear dynamic system. Finally, the effect of step amplitude on the non-linear responses is examined for several configurations, and hardening trends are observed in the torsional system with three clearances.

Effect of Pin Tip Dual Clearance on Flow and Heat Transfer at Low Reynolds Numbers

This paper examines the augmentation of heat and mass transfer due to dual clearances on cylindrical pin fins, relative to a channel between parallel plates, in mini/microchannel reactors at low Reynolds numbers. In this work, diffusion limitations to heat and mass transfer in smooth-walled mini/microchannel reactors were minimized by the implementation of microcylinder pin fins with dual clearances that, (1) promote the production of instabilities in the wakes that enhance mixing and (2) reduce the viscosity dominated regions at pin-wall interfaces. A smooth catalyst coating is assumed on all exposed surfaces of the microchannel interior walls and pin fins. Due to the analogy of heat and mass transfer, augmentation of the Nusselt number is equivalent to the augmentation of the Sherwood number. Heat transfer augmentation is investigated in air (Pr = 0.705) at dual clearances ranging from 0 to 0.4 of the channel height and Reynolds numbers from 10 to 600. The pin fins and the clearance augmented the heat transfer coefficient by a factor of 4.0. The combination of the augmentation of the heat transfer coefficient and the increase in the surface area, by the clearances, results in an increase in the conductance over a plane channel, by a factor of 7.1. The results are extendable to overcoming laminar diffusion with laminar periodic wakes of fuel vapors such as methanol vapor in air where Scfuel ∼ Prair. For turbulent wakes impinging upon downstream pins, the results can be extended to fuel vapors with (Scfuel)turb ∼ (Prair)turb. A large eddy simulation (LES) approach was used in this study.

Two dynamic models of dual clearance squeeze film damper and their verification

Two dynamic models of the dual clearance squeeze film damper (DCSFD) were established. One model was based on the general Reynolds equation and the other model was based on the Reynolds equation of conventional squeeze film damper. To validate the two models, vibration responses of DCSFD were obtained with different exciting frequencies, elastic supports and exciting forces by experiments. Based on the experiment, a dynamic model including DCSFD was established. Excellent consistency of numerical solution was achieved between two different DCSFD models. Good consistency was achieved between the experiment and simulation. These observations provide useful models for further studying DCSFD.

Population pharmacokinetics of CNTO 95, a human anti-αv integrin antibody, in patients with solid tumors

e14593 Background: CNTO 95 is a human anti-αv integrin antibody. The dose-dependent antitumor effect of CNTO 95 has been demonstrated in multiple preclinical studies. The objective of these analyses was to characterize the population pharmacokinetics (PPK) in solid tumor cancer patients treated with CNTO 95 with and without dacarbazine. Methods: Approximately 140 patients with solid tumors from two phase I and one phase II studies were included in this analysis. CNTO 95 was administered via intravenous infusion, with 11 different regimens ranging from 0.1 to 20 mg/kg every 1–4 weeks. Serum CNTO 95 concentrations were determined using a validated enzyme-linked immunosorbent assay. Serum CNTO 95 concentration data were analyzed using noncompartmental analysis (NCA) and a PPK approach. Results: The NCA results indicated that total clearance of CNTO 95 decreased as the dose of CNTO95 increased and approached saturation at 10 mg/kg. Based on the NONMEM analysis, data were best described by a 2-compartment model with dual clearance pathways (linear and nonlinear elimination). The nonlinear elimination process is likely due to the receptor-mediated clearance. Mean estimates of central volume, peripheral compartment volume, intercompartmental clearance and linear clearance, as well as an additional nonlinear clearance, were in agreement with antibodies targeting membrane-bound receptors. No differences in the PPK of CNTO 95 were found in patients treated with and without co-administered dacarbazine. Interindividual variability was moderate (<50%). Conclusions: A PPK model could adequately describe serum CNTO 95 concentration-time profiles. Extensions of this model can be used to assist in the selection of doses in diverse oncology patient populations. [Table: see text]

Dynamic Modeling of a Dual Clearance Squeeze Film Damper—Part I: Test Rig and Dynamic Model with One Damper

This paper presents a description of a dual clearance squeeze film damper (SFD) test rig and a dynamic model of a single SFD. The purpose of a dual SFD is to provide protection at high levels of vibration, when conventional devices are no longer effective. An experimental facility was designed and built for tire study of SFD behavior within mechanically controlled orbits. It can be used for both single and dual squeeze film dampers. In Part 1 of this paper, measured and computed responses are presented while operating as a single squeeze film device. Numerical and experimental results for undamped cases are presented, i.e., when no oil film is present in the damper. Subsequently, the effects of the oil film are considered. Good agreement was obtained between experimental data and predictions. Presented at the 57th Annual Meeting in Houston, Texas May 19–23, 2002

Dual Clearance Squeeze Film Damper for High Load Conditions

Squeeze film dampers are widely used to control vibrations in aircraft turbine engines and other rotating machinery. However, if shaft unbalance rises appreciably above the design value (e.g., due to a turbine blade loss), a conventional squeeze film will be overloaded, and will no longer be effective in controlling vibration amplitudes and bearing forces. This paper describes a new damper concept characterized by two oil films. Under normal conditions, only one low-clearance film is active, allowing precise location of the shaft centerline. Under high unbalance conditions, both films are active, controlling shaft vibration in a near-optimum manner, and allowing continued operation until a safe shutdown can be made.