ASM Materials Solutions Conference and Exposition

October 15-19, 2006

The conference held in Duke Energy Center, Cincinnati, Ohio was attended by Graduate Students:
Xiaoshu Dai, Olly Karabelchtchikova, Cheri Geiger and Lei Zhang
Professors: Md. Maniruzzaman and Richard Sisson, Jr.

Papers presented:

Estimation of Surface Heat Transfer Coefficients for Quenching Process Simulation
Gas Quenching - An Environment Friendly Heat Treatment Process
Hybrid Analogs for the Production of Porous Calcium Phosphate Scaffolds
Numerical Simulation on Solidification and Thermal Stress of Continuous Casting Billet in Mold Based on Meshless Methods
Optimization of Carburization Process Using Numerical Simulation
Role of Solvent in the Development of Nanofibrous Structures during Electrospinning

Estimation of Surface Heat Transfer Coefficients for Quenching Process Simulation

Authors:

Md. Maniuzzaman
Aparna Varde
Richard D. Sisson, Jr.

With the advent of faster computer and better numerical algorithm, quenching process simulation to determine residual stress, distortion and microstructure evolution is now becoming reality. But accuracy of simulation results largely depends on the boundary condition and thermophysical properties of materials being supplied during simulation. Surface heat transfer coefficients as a function of temperaure are very important boundary condition for quenching process simulation. Various techniques for heat transfer coefficients estimation are discussed in this paper. Effects of nonuniform surface heat extraction on distortion and microstructure evolution of a steel part are simulated using a Finite Element Simulation code. An alternative data-mining technique is also discussed to estimate surface heat transfer coefficients from and existing quenching heat transfer database.

Gas Quenching - An Environment Friendly Heat Treatment Process

Authors:

Md. Maniruzzaman
Richard D. Sisson, Jr.

Abstract

Safety and environmental considerations make gas quenching an attractive alternative to conventional liquid quenching heat treatment process. But up to now, it has not experienced wide spread implementaiton due to some issues restricting the introduction of this technology. Compared with liquid quenching, the specific advantages of gas quenching include cleaner product surfaces, avoidance of need for washing the parts after quenching, and minimization of environmental problems associated with the handling and disposal of liquid quenching fluids, all these lead to lower the operating costs of a hardening heat treatment process. In this paper advantages and disadvantages of gas quenching process are presented. Effectiveness of gas quenching process is demonstrated in terms of heat extraction rate and compared with that of liquid quenching process.

Hybrid Analogs for the Production of Porous Calcium Phosphate Scaffolds

Authors:

Xiaoshu Dai
Satya Shivkumar

Abstract

A polymer-inorganic sol mixture has been used to develop interconnected and highly porous calcium phosphate networks. The inorganic sol was developed based by reacting Triethyl Phosphite and Calcium Nitrate. The sol was directly added to an aqueous solution of PVA with molecular weights between 31000 to 124,000 g/mol. This mixture was electrospun at a voltage of 20 kV to produce fibers, whose diameter was on the order of 2 um. This electrospun structure was calcined at 600⁰ C obtain to highly interconnected sub-micron fibrous network (fiber size- 200nm) of calcium phosphate. The crystal size is on the order of 30 50 nm. Micropores could be introduced in each of the fibers by controlling the polymer molecular weight and the polymer/sol ratio. Such structures can have many potential uses in the repair and treatment of bone defects and in drug delivery.

Numerical Simulation on Solidification and Thermal Stress of Continuous Casting Billet in Mold Based on Meshless Methods

Authors:

Lei Zhang
Yiming Rong
Houfa Shen
Tianyou Huang

Abstract

In this paper, meshless method is investigated into the simulation of continuous casting. An integrated meshless thermal-mechanical analysis packaage is developed: a meshless solidificatin model based on Finite Point Method (FPM) is constructed; and meanwhile, Meshless Local Petrov-Galerkin (MLPG) is used to build the MLPG based thermal elastic-plastic analysis model. The package is applied to simulate solidification and thermal stress of continuous casting billet in mold. The results are consistent with the measurement and satisfy the characteristic of stress and strain distribution and the formation mechanism of the off-corner defects, with the same accuracy as that of FEM is achieved. These observations show that meshless method is a potent numerical analysis tool, and it is worth for the analysis of the continuous casting process.

Optimization of Carburization Process Using Numerical Simulation

Authors:

Olga Karabelchtchikova
Md. Maniruzzaman
Richard Sisson, Jr.

Abstract

Industry often faces prpblem in maintaining uniform case depth from one batch to other during gas carburization heat treatment process. Two important process parameters influence the carburization of steel; environmental reaction rate that causes carbon to be absorbed at the surface and the carbon diffusion rate from surface to the interior of the part. In this study a computer model is developed to investigate the effect of temperature on mass transfer coefficients at the boundary and the effect of carbon contents and temperature on the carbon diffusion rate in the low and medium carbon steels. A series of computer experiments are performed to determine the potential route to reduce the cycle time. The model is then used for a process optimization to reduce the variability in the process and the cycle time.

Role of Solvent in the Development of Nanofibrous Structures during Electrospinning

Authors:

Cheri Geiger
Satya Shivkumar

Abstract

Electrospinning is a technique that has received considerable attention in the biomaterials field for the development of sub-micron, highly interconnected porous networks. Such structures are highly desirable in drug delivery and tissue engineering. The properties of the network that can be produced depend strongly on factors such as polymer molecular weight, branching and the type of solvent used. In this contribution the results of the range of structure that can be produced with good solvents and poor solvents will be presented.

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