The need for joining dissimilar materials is increasing rapidly in manufacturing industries.
Therefore, a successful weld of dissimilar metals by Friction Stir Welding (FSW) process
becomes a topic of interest for many investigators. FSW research topics have been used for Manufacturing Engineering students at Virginia State University as undergraduate research projects. The purpose of this study was to investigate intermetallic characteristics between aluminum and copper at the transition zone in the FSW process. The effects of process parameters on heat affected zone (HAZ) have been examined to find the optimal tool rotational speed, axial force, and transverse speed. A metallographic study was conducted to investigate the quality of intermetallic bonding at the interfaces. It was observed that using optimized process parameters for experimental setup resulted in a very good quality of the welds.
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Investigation of Relationship Between Microhardness and Charpy Impact Energy for Temper Bead Welding Qualification: Part 1
Temper bead (TB) welding is often used as an alternative to post weld heat treatment (PWHT) for repair of pressure vessels and piping in the nuclear power industry. Historically, qualification of TB welding procedures has employed the Charpy V-notch test to ensure acceptable heat-affected-zone (HAZ) impact properties. The 2004 Edition of ASME Section IX provided a new provision in QW-290 that allows temper bead qualification using a peak hardness criterion. The peak hardness provision is appropriate for industries such as oil and gas, where peak allowable hardness is specified to ensure adequate resistance to sulfide stress cracking in sour service environments. However, a peak hardness criterion is not appropriate where impact properties are specified for resistance to brittle fracture during low temperature conditions that can occur during certain postulated accident scenarios at a nuclear power plant.
Work at the Electric Power Research Institute (EPRI) and The Ohio State University (OSU) show that a hardness drop protocol can be used to demonstrate acceptable impact properties in the HAZ of a temper bead weld. This paper presents a quantitative correlation between hardness measurements and HAZ microstructures with presumed optimum impact properties using a hardness drop approach. The overarching goal is to develop a hardness test protocol for temper bead weld procedure qualification for applications where impact properties are specified.
more » « less- Award ID(s):
- 1822144
- NSF-PAR ID:
- 10175964
- Date Published:
- Journal Name:
- ASME 2019 Pressure Vessels & Piping Conference
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Sub-surface voids and material heterogeneities resulting from the friction stir welding (FSW) process often necessitate post-weld inspection to ensure the quality of weld obtained from this solid-state welding process. In this context, in-process void detection techniques can potentially help in optimizing the process conditions and thereby reduce expensive and time-consuming post-process inspection of welds. Current in-process void detection techniques rely on approaches that try to directly correlate the part-scale welding quality to void formation, without a fundamental understanding of the underlying mechanics and materials physics that modulate void evolution. In this work, we demonstrate an effective in-process numerical technique that uses process force signals to detect volumetric void formation and connect the variations in the force signals to interactions between the tool probe and the underlying material voids. Our approach relies on a high-fidelity finite element analysis simulation of the FSW process and on correlation of numerically obtained process force signals with the corresponding void structures. This correlation is obtained in the phase-space relating in-plane reaction forces on the tool to the tool rotation angle. We focus on the interactions of the tool geometry and tool motion with the surrounding material undergoing plastic deformation and deduce novel insights into various correlations of tool motion and void formation. Through this approach, we can identify tool-related process conditions that can be optimized to minimize void formation and demonstrate a potential in situ force-based void monitoring method that links to the underlying plastic flow and void structures during the FSW process.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1115/PVP2019-93950
