Investigation of the Processing History during Additive Friction Stir Deposition using In-process Monitoring Techniques

dc.contributor.authorGarcia, Daviden
dc.contributor.committeechairYu, Hangen
dc.contributor.committeememberZhu, Yunhuien
dc.contributor.committeememberReynolds, William T.en
dc.contributor.committeememberSuchicital, Carlos T. A.en
dc.contributor.departmentMaterials Science and Engineeringen
dc.description.abstractAdditive friction stir deposition (AFSD) is an emerging solid-state metal additive manufacturing technology that uses deformation bonding to create near-net shape 3D components. As a developing technology, a deeper understanding of the processing science is necessary to establish the process-structure relationships and enable improved control of the as-printed microstructure and material properties. AFSD provides a unique opportunity to explore the friction stir fundamentals via direct observation of the material during processing. This work explores the relationship between the processing parameters (e.g., tool rotation rate Ω, tool velocity V, and material feed rate F) and the thermomechanical history of the material by process monitoring of i) the temperature evolution, ii) the force evolution, and iii) the interfacial contact state between the tool and deposited material. Empirical trends are established for the peak temperature with respect to the processing conditions for Cu and Al-Mg-Si, but a key difference is noted in the form of the power law relationship: Ω/V for Cu and Ω2/V for Al-Mg-Si. Similarly, the normal force Fz for both materials correlates to V and inversely with Ω. For Cu both parameters show comparable influence on the normal force, whereas Ω is more impactful than V for Al-Mg-Si. On the other hand, the torque Mz trends for Al-Mg-Si are consistent with the normal force trends, however for Cu there is no direct correlation between the processing parameters and the torque. These distinct relationships and thermomechanical histories are directly linked to the contact states observed during deformation monitoring of the two material systems. In Cu, the interfacial contact between the material and tool head is characterized by a full slipping condition (δ=1). In this case, interfacial friction is the dominant heat generation mechanism and compression is the primary deformation mechanism. In Al-Mg-Si, the interfacial contact is characterized by a partial slipping/sticking condition (0<δ<1), so both interfacial friction and plastic energy dissipation are important mechanisms for heat generation and material deformation. Finally, an investigation into the contact evolution at different processing parameters shows that the fraction of sticking is critically dependent on the processing parameters which has many implications on the thermomechanical processing history.en
dc.description.abstractgeneralAdditive manufacturing or three-dimensional (3D) printing technologies have been lauded for their ability to fabricate complex geometries and multi-material parts with reduced material waste. Of particular interest is the use of metal additive manufacturing for repair and fabrication of industrial and structural components. This work focuses on characterizing the thermomechanical processing history for a developing technology Additive Friction Stir Deposition (AFSD). AFSD is solid-state additive manufacturing technology that uses frictional heat and mechanical mixing to fabricate 3D metal components. From a fundamental materials science perspective, it is imperative to understand the processing history of a material to be able to predict the performance and properties of a manufactured part. Through the use of infrared imaging, thermocouples, force sensors, and video monitoring this work is able to establish quantitative relationships between the equipment processing parameters and the processing history for Cu and Al. This work shows that there is a fundamental difference in how these two materials are processed during AFSD. In the future, these quantitative relationships can be used to validate modeling efforts and improve manufacturing quality of parts produced via friction stir techniques.en
dc.description.degreeDoctor of Philosophyen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.subjectmetal additive manufacturingen
dc.subjectfriction stir processen
dc.subjectin situ monitoringen
dc.subjectthermomechanical processingen
dc.titleInvestigation of the Processing History during Additive Friction Stir Deposition using In-process Monitoring Techniquesen
dc.typeDissertationen Science and Engineeringen Polytechnic Institute and State Universityen of Philosophyen


Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
3.51 MB
Adobe Portable Document Format