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Yasmin Ahmed Salem
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Scientific Events

Scientific Events

Month:

Gordon Research Conference “Thin Film and Small Scale Mechanical Behavior”

17693 1550059291

Gordon Research Conference “Thin Film and Small Scale Mechanical Behavior”

Mini‐symposium “Experimental Micromechanics and Nanomechanics” at the “10th edition of the European Solids Mechanics Conference”

17692 1550059316

Mini‐symposium “Experimental Micromechanics and Nanomechanics” at the “10th edition of the European Solids Mechanics Conference”

MPIE Colloquium

14224 1527505386

Martensitic Microstructure: Modern Art or Science?

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Additive Manufacturing, 3D Printing, Porosity and Synchrotron Experiments

13791 1523952360

Additive Manufacturing, 3D Printing, Porosity and Synchrotron Experiments

3D printing of metals has advanced rapidly in the past decade and is used across a wide range of industry. Many aspects of the technology are considered to be well understood in the sense that validated computer simulations are available. At the microscopic scale, however, more work is required to quantify and understand defect structures, which affect fatigue resistance, for example. Synchrotron-based 3D X-ray computed microtomography (µXCT) was performed at the Advanced Photon Source on a variety of AM samples using both laser (SLM) and electron beam (EBM) powder bed; this showed systematic trends in porosity. Optical and SEM characterization of powders used in additively manufacturing (AM) reveals a variety of morphologies and size distributions. Computer vision (CV), as a subset of machine learning, has been successfully applied to classify different microstructures, including powders. The power of CV is further demonstrated by application to detecting and classifying defects in the spreading in powder bed machines, where the defects often correspond to deficiencies in the printed part. In addition to the printed material, a wide range of powders were measured and invariably exhibited porosity to varying degrees. Outside of incomplete melting and keyholing, porosity in printed parts is inherited from pores or bubbles in the powder. This explanation is reinforced by evidence from simulation and from dynamic x-ray radiography (DXR), also conducted at the APS. DXR has revealed a wide range of phenomena, including void entrapment (from powder particles), keyholes (i.e., vapor holes) and hot cracking. Keyhole depth is linearly related to the excess power over a vaporization threshold. Concurrent diffraction provides information on solidification and phase transformation in, e.g., Ti-6Al-4V and stainless steel. High Energy (x-ray) Diffraction Microscopy (HEDM) experiments are also described that provide data on 3D microstructure and local elastic strain in 3D printed materials, including Ti-6Al-4V and Ti-7Al. The reconstruction of 3D microstructure in Ti-6Al-4V is challenging because of the fine, two-phase lamellar microstructure and the residual stress in the as-built condition. Both the majority hexagonal phase and the minority bcc phase were reconstructed. [more]

MPIE Colloquium

13920 1525694664

Quantum Chemistry in Position Space and Chemical Bonding in Intermetallic Compounds

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Symposium “Mechanical Properties and Adhesion 45th ICMCTF (International Conference on Metallurgical Coatings and Thin Films)

17708 1551253843

Symposium “Mechanical Properties and Adhesion 45th ICMCTF (International Conference on Metallurgical Coatings and Thin Films)

 
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