Jim S. J. Chen

An experimental study of process behavior in planar flow melt spinning

A parametric study concerning the process behavior in planar flow melt spinning (PEMS) of Pb−Sn alloy ribbons is presented in this article. Experiments were conducted to develop correlations between the produced ribbon thickness and process variables, including wheel speed, crucible pressure, nozzle-wheel gap, and melt superheat. The ribbon thickness was found to vary with the wheel speed to the power of −2/3 and the crucible pressure to the power of 1/3. Puddle lengths were found to increase linearly with crucible pressure. The ribbon thickness behaved in a two-term exponential manner in relation to the melt superheat. A processing window for the production of high-quality ribbons was determined using dimensionless parameters. Five distinct ribbon patterns were identified, and their respective surface roughnesses were measured and reported.

The Effect of an Embedded Heat Pipe in a Cutting Tool on Temperature and Wear

This paper presents the fundamental understanding of the effect of an embedded heat pipe in a cutting tool on temperature and wear in machining. In particular, the technique can effectively minimize pollution and contamination of the environment caused by cutting fluids and the health problems of skin exposure and particulate inhalation in manufacturing. The temperature of a tool plays an important role in thermal distortion and the machined part’s dimensional accuracy, as well as in tool life in machining. A new embedded heat pipe technology has been developed to effectively remove the heat generated at the tool-chip interface in machining, thereby reduce tool wear and prolong tool life. Experiments were carried out to characterize the temperature distributions when performing turning experiments using a cutting tool installed with an embedded heat pipe. The ANSYS simulations show that the temperature near the cutting edge drops significantly with an embedded heat pipe during machining. Temperature measurements at several locations on the cutting tool insert agree with the simulation results both with and without the heat pipe. The effect of the heat pipe on reducing the cutting tool temperature was further supported by the observations of cutting tool material color, chip color, and chip radius of curvature.Copyright

Prediction of Heat Transfer Behavior of Carbide Inserts With Embedded Heat Pipes for Dry Machining

The temperature of a tool plays an important role in thermal distortion and the machined part’s dimensional accuracy, as well as in tool life in machining. The most significant factors in tool wear are temperature and the degree of chemical affinity between the tool and the workpiece. This research focuses on developing a clear understanding of the temperature distribution with cutting tool inserts embedded with heat pipes to eliminate the use of cutting fluids and reduce tool wealr in machining. A novel approach using the finite element analysis was developed to simulate the thermal behavior of a carbide cutting tool in three-dimensional dry machining. The carbide tools possess high material strengths at room temperature, but they cannot retain useful hardness at temperatures above 900°C (1700°F). Therefore, the reduction of tool wear typically requires maintaining the temperature of cutting tool inserts below some critical values. The particular temperature distribution depends on density, specific heat, thermal conductivity, shape and contact of the tool and heat pipe. Finite Element Analysis (FEA) shows that the temperature drops greatly at the tool-chip interface and that the heat flow to the tool is effectively removed when a heat pipe is embedded.Copyright

The melt spinning of gamma titanium aluminides

Rapid solidification shows great promise for the production of gamma titanium aluminides, and one of the most interesting rapid solidification techniques is melt spinning. In this work, melt-spun Ti-5SAl and Ti-48Al-2Cr-2Ta (atomic percent) were produced; the resulting alloys had uniform microstructure and composition. In addition, the investigation showed the utility of a model developed to describe heat transfer and fluid flow in melt spinning.

Analytical Study of the Effect of Heat Pipe Cooling in Machining

Tool wear of machine tools and large usage of cutting fluids is one of the major problems in manufacturing. Cutting fluids are used to cool down the tool and have been shown to cause environmental problems in machine shops. Tool life and temperature have an inverse relationship, namely that the higher the temperature at the tool-chip interface is, the lower the tool life will be, and vice-versa. In this paper an innovative approach was taken to create an analytical solution to the effect of the embedded heat pipe on temperature of the tool and tool life. It has been well documented in the industry that the major factors that contribute to tool wear are the material properties of the tool insert and the work piece, cutting speed, depth of cut and feed rate. The analytical approach taken in this project is unique because it does not only take into account the complex boundary conditions of heat transfer but also the aforementioned factors and variety of possible cutting conditions. The analytical solution is in the form of set of equations which were developed to simulate the behavior of the tool insert under normal cutting conditions. Both cases, with and without heat-pipe were considered. The predicted temperature data was then compared to the existing experimental data, with very good results. In the end the project yields a quantitative evaluation on influence of mechanical properties of insert, work piece, heat pipe and cutting conditions on tool wear.Copyright

Torque and Power Coefficients of a Vertical Axis Wind Turbine With Optimal Pitch Control

Vertical axis wind turbines (VAWT) have been valued in recent years for their low manufacturing cost, structural simplicity and convenience of applications in urban settings. Despite their advantages, VAWTs have several drawbacks including low power coefficient, poor self-starting ability, negative torque and the associated cyclic stress at certain azimuth angles. Using pitch control ideas, our research is aimed at solving the above problems. In this study, a small-scale Giromill VAWT using three NACA-0015 airfoils with a cord length of 0.09 m and a wind turbine radius of 0.6 m is investigated. During each rotation, the angle of attack depends on the wind velocity, angular velocity and current azimuth angle for each turbine blade. Negative torques at certain angles are attributed to the inherent unsteady aerodynamic behavior at high angles of attack. Without optimal pitch control, the Double-Multiple Streamtube (DMS) model predicts negative torques at certain azimuth angles and very low power coefficients for tip speed ratios below 2.5. The unfavorable negative torques are eliminated using an optimal pitch control strategy, which maximizes the tangential force coefficients and thus the torque coefficients by iterations of all possible relative angles of attack for various tip speed ratios. As a result, the power coefficient is significantly improved especially at low tip speed ratios in the range of zero to three (λ = 0 – 3). Blade pitch control can also solve the self-starting problem and reduce the vibration of vertical axis wind turbines.© 2010 ASME

Transient heat transfer in human endometrium during cryoablation

This paper presents an experimental study and numerical prediction of the transient heat transfer behavior inside the uterus during application of a PFC fluid into the endometrium cavity in order to achieve cryoablation. The numerical prediction is based on a 1-D finite difference method of the bio-heat equation using the Crank Nicolson scheme. The numerical method is first validated by a 1-D physical model by measuring temperature history at several locations within a silicone rubber sheet. Good comparisons are obtained by comparing numerical predictions with the experimental data obtained from eight intact, hysterectomized uteri during cryoablation.

Dry machining characterization simulations and experiments for new cutting tool design with embedded heat pipe

The results of dry machining characterization simulations and experiments for new design technology of using a heat pipe installed in a cutting tool to remove the heat produced at the tool-chip interface which causes thermal damage and tool wear are presented in the paper. Analysis of the results by a heat transfer finite element model indicates that the particular heat pipe used was capable of removing heat with a significant reduction in the rise of the tool-chip interface temperature above the temperature in the surrounding environment at steady operating conditions. Measurements of the variation of the tool insert temperature with time are reported. Both cases, with and without heat-pipe, were considered. In the end the project yields dry machining characterization on influence of embedded heat pipe on mechanical properties of insert and workpiece, tool-chip interface temperature, and tool wear. The results of this study are useful for the cutting tool design and implementation in environmentally conscious manufacturing applications.

An integrated method to determine the stress-strain relationship of beating heart

An integrated computational-experimental method was developed to characterize nonlinear elastic stress-strain behavior of the beating heart. This method combines finite element (FE) simulation with the experimental end-diastolic pressure-balloon volume relationship to characterize the deformation resistance. In the FE simulations, the hyperelastic Ogden strain energy potential was used and geometric nonlinearity was also considered. The elastic moduli for the ex-vivo rat heart obtained through the study vary from 0.003 to 0.577 MPa.

Pharmacokinetics of gentamicin by intravenous and intratracheal administrations

This paper investigates the pharmacokinetics of a drug delivery system for the purpose of understanding the biodistribution of gentamicin delivered to the blood and tissues by intravenous (IV) and intratracheal (IT) administrations. Numerical solutions for both two-compartment (plasma and tissue) and three-compartment (lung + PFC, plasma, and tissue with IV, IT-Top-fill and IT-Slow fill administrations) models are developed using Eulers method. The drug elimination rate and the rate constants describing the first-order transport between compartments are determined by parameter estimation. The numerical solution is validated against the analytical solution for a two-compartment model with IV injection. The numerical results are statistically compared with the experimental data. It is determined that the IT administration provides efficient drug delivery to the lungs while avoiding the toxicity level in the plasma.