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Papers by Daniel Branagan

Materials Science Engineering a Structural Materials Properties Microstructure and Processing, 2008

Metallurgical and Materials Transactions A, 2006

The Palmqvist fracture toughness method was applied in a new fashion to measure the fracture toug... more The Palmqvist fracture toughness method was applied in a new fashion to measure the fracture toughness of a new wear-resistant alloy in both a powder product for plasma-transferred arc (PTA) welding and a wire product for metal inert gas (MIG) welding. Cracks were observed at high loads with a linear relationship between load and crack length indicating that only Palmqvist cracks occurred in the alloys. The fracture toughness for the no-preheat and preheat PT40 welds are 15.6±0.3 Mpa m1/2 and 17.6±0.1 MPa m1/2, respectively, and for the no-preheat and preheat MG40 welds are 12±1 MPa m1/2 and 20.5±0.2 MPa m1/2, respectively. Observations of the cracks show evidence of ligaments indicating that the toughness mechanism is due to crack bridging. The microstructural scale and morphology correlates with the fracture toughness, and as the structural scale decreases, the fracture toughness increases.

Materials Science and Engineering: A, 2009

Abstract One of the largest controversial issues of mechanical testing is the interpretation of s... more Abstract One of the largest controversial issues of mechanical testing is the interpretation of scaling laws on materials strength and ductility. With a general trend towards miniaturization based on recent development in nanomaterials and metallic glasses, the challenges confront not only with preparation, handling and testing of small volumes of materials, but, also with clear understanding of test results. The main question is whether mechanical behavior of small volumes is controlled by mechanics or by sample geometry. Analysis of mechanical behavior of well-known Ti–6Al–4V alloy at different length scales is presented in this study. The results are compared to that of metallic glasses at the same scale and the general trends are highlighted.

Journal of Magnetism and Magnetic Materials, 2004

A Nd-Dy-Fe-B alloy was designed to exhibit high coercivity and optimum loop shapes utilizing a co... more A Nd-Dy-Fe-B alloy was designed to exhibit high coercivity and optimum loop shapes utilizing a combination of intrinsic and extrinsic alloy design principles. After achieving these initial goals, conventional structural analysis using X-ray and TEM could explain the salient features of the observed hysteresis behavior. However, greater understanding could be gained on the complex dynamic behavior of hysteresis through the exploitation of a new recoil technique that was developed, which focuses on switching field distributions arising from irreversible magnetic behavior. Utilizing this approach, we have successfully linked specific magnetic reversal behavior with distinct magnetic phases that have characteristic microstructural length scales. This new approach may become a powerful tool for the study of the structure-property-hysteresis behavior of hard magnetic materials.

IEEE Transactions on Magnetics, 2001

In this study, the structural state and microstructural scale of Pr 2 Co 17 and Sm 2 Fe 17 were m... more In this study, the structural state and microstructural scale of Pr 2 Co 17 and Sm 2 Fe 17 were modified by rapid solidification and alloying. Partial suppression of the dumbbell ordering was accomplished by melt spinning, and more effective suppression, leading to the formation of the TbCu 7-type structure, was accomplished by the addition of Ti or Ti and C. Annealing recovered the order, although Ti and TiC significantly affected the kinetics in the Sm-Fe system. The addition of Ti and C refines the grain size in both Pr-Co and Sm-Fe. The degree of order was found to influence the coercivity in the nitrided Sm-Fe alloys. The Pr-Co alloys were found to have a planar easy magnetization direction at all levels of ordering.

Journal of Testing and Evaluation, 2018

Reliable tensile data are crucial in the automotive design process, particularly for the implemen... more Reliable tensile data are crucial in the automotive design process, particularly for the implementation of new Advanced High Strength Steel grades that can be used in new intricate shapes. The property evaluation of specific subsections of a complex part, such as a metal stamping, requires deviation from standard-sized specimens because of material quantity limitations which force the use of smaller specimens. A new tensile geometry is introduced for testing regions within parts that were previously difficult to characterize. However, the specimen size effect is not consistent between different steels, as demonstrated for this new geometry herein. Tensile property measurements taken with noncontact extensometers from specimens of three different sizes from three different sheet steels showed varying material responses to changes in specimen geometry.

Materials Science Engineering a Structural Materials Properties Microstructure and Processing, 2008

Metallurgical and Materials Transactions A, 2006

The Palmqvist fracture toughness method was applied in a new fashion to measure the fracture toug... more The Palmqvist fracture toughness method was applied in a new fashion to measure the fracture toughness of a new wear-resistant alloy in both a powder product for plasma-transferred arc (PTA) welding and a wire product for metal inert gas (MIG) welding. Cracks were observed at high loads with a linear relationship between load and crack length indicating that only Palmqvist cracks occurred in the alloys. The fracture toughness for the no-preheat and preheat PT40 welds are 15.6±0.3 Mpa m1/2 and 17.6±0.1 MPa m1/2, respectively, and for the no-preheat and preheat MG40 welds are 12±1 MPa m1/2 and 20.5±0.2 MPa m1/2, respectively. Observations of the cracks show evidence of ligaments indicating that the toughness mechanism is due to crack bridging. The microstructural scale and morphology correlates with the fracture toughness, and as the structural scale decreases, the fracture toughness increases.

Materials Science and Engineering: A, 2009

Abstract One of the largest controversial issues of mechanical testing is the interpretation of s... more Abstract One of the largest controversial issues of mechanical testing is the interpretation of scaling laws on materials strength and ductility. With a general trend towards miniaturization based on recent development in nanomaterials and metallic glasses, the challenges confront not only with preparation, handling and testing of small volumes of materials, but, also with clear understanding of test results. The main question is whether mechanical behavior of small volumes is controlled by mechanics or by sample geometry. Analysis of mechanical behavior of well-known Ti–6Al–4V alloy at different length scales is presented in this study. The results are compared to that of metallic glasses at the same scale and the general trends are highlighted.

Journal of Magnetism and Magnetic Materials, 2004

A Nd-Dy-Fe-B alloy was designed to exhibit high coercivity and optimum loop shapes utilizing a co... more A Nd-Dy-Fe-B alloy was designed to exhibit high coercivity and optimum loop shapes utilizing a combination of intrinsic and extrinsic alloy design principles. After achieving these initial goals, conventional structural analysis using X-ray and TEM could explain the salient features of the observed hysteresis behavior. However, greater understanding could be gained on the complex dynamic behavior of hysteresis through the exploitation of a new recoil technique that was developed, which focuses on switching field distributions arising from irreversible magnetic behavior. Utilizing this approach, we have successfully linked specific magnetic reversal behavior with distinct magnetic phases that have characteristic microstructural length scales. This new approach may become a powerful tool for the study of the structure-property-hysteresis behavior of hard magnetic materials.

IEEE Transactions on Magnetics, 2001

In this study, the structural state and microstructural scale of Pr 2 Co 17 and Sm 2 Fe 17 were m... more In this study, the structural state and microstructural scale of Pr 2 Co 17 and Sm 2 Fe 17 were modified by rapid solidification and alloying. Partial suppression of the dumbbell ordering was accomplished by melt spinning, and more effective suppression, leading to the formation of the TbCu 7-type structure, was accomplished by the addition of Ti or Ti and C. Annealing recovered the order, although Ti and TiC significantly affected the kinetics in the Sm-Fe system. The addition of Ti and C refines the grain size in both Pr-Co and Sm-Fe. The degree of order was found to influence the coercivity in the nitrided Sm-Fe alloys. The Pr-Co alloys were found to have a planar easy magnetization direction at all levels of ordering.

Journal of Testing and Evaluation, 2018

Reliable tensile data are crucial in the automotive design process, particularly for the implemen... more Reliable tensile data are crucial in the automotive design process, particularly for the implementation of new Advanced High Strength Steel grades that can be used in new intricate shapes. The property evaluation of specific subsections of a complex part, such as a metal stamping, requires deviation from standard-sized specimens because of material quantity limitations which force the use of smaller specimens. A new tensile geometry is introduced for testing regions within parts that were previously difficult to characterize. However, the specimen size effect is not consistent between different steels, as demonstrated for this new geometry herein. Tensile property measurements taken with noncontact extensometers from specimens of three different sizes from three different sheet steels showed varying material responses to changes in specimen geometry.