Fatigue life, fatigue crack propagation and fracture toughness study of 7075 aluminum alloy subjected to thermomechanical processing Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/nv9356277

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • Due to its high strength/weight ratio, 7075 aluminum alloy has been widely used as an aerospace material. However, it has relatively low fatigue strength and low fracture toughness in the T6 condition. Thermomechanical processing, including pre-cyclic loading and stretching at high and ambient temperatures, has been investigated with the aim of improving these properties. Fatigue life tests show that all four thermomechanical processes investigated increase the fatigue life at low stress levels, but cause a reduction at high stress levels. The effect of the precipitate free zone (PFZ) width on the fatigue crack propagation rate and fracture toughness has also been investigated. The fatigue crack propagation rate of the alloy with a wide PFZ was found to be approximately the same as that of the alloy with a narrow PFZ under similar conditions of cyclic loading. The alloy with the wide PFZ demonstrated a greater value of fracture toughness than that shown by the alloy with the narrow PFZ. These experimental results have been analyzed taking recently proposed theoretical models into account. Transmission electron microscopy showed that a large number of dislocations were generated within the soft PFZ areas as a result of the cyclic pre-loading. This is believed to contribute to the increase in fatigue life at low applied stress levels. Scanning electron microscopy has shown an intergranular fracture mode for the alloy with the narrow PFZ and a dimple rupture mode for the alloy with the wide PFZ.
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Academic Affiliation
Non-Academic Affiliation
Subject
Rights Statement
Peer Reviewed
Language
Digitization Specifications
  • File scanned at 300 ppi (Monochrome, 8-bit Grayscale) using ScandAll PRO 1.8.1 on a Fi-6670 in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-07-01T16:51:36Z (GMT) No. of bitstreams: 1 LeeMoonH1985.pdf: 3214659 bytes, checksum: e1dcf84777a4360056e2ff977df3c82f (MD5)
  • description.provenance : Submitted by Katy Davis (kdscannerosu@gmail.com) on 2013-06-27T20:43:40Z No. of bitstreams: 1 LeeMoonH1985.pdf: 3214659 bytes, checksum: e1dcf84777a4360056e2ff977df3c82f (MD5)
  • description.provenance : Made available in DSpace on 2013-07-19T17:51:34Z (GMT). No. of bitstreams: 1 LeeMoonH1985.pdf: 3214659 bytes, checksum: e1dcf84777a4360056e2ff977df3c82f (MD5) Previous issue date: 1984-08-14
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-07-19T17:51:34Z (GMT) No. of bitstreams: 1 LeeMoonH1985.pdf: 3214659 bytes, checksum: e1dcf84777a4360056e2ff977df3c82f (MD5)

Relationships

Parents:

This work has no parents.

Last modified

Downloadable Content

Download PDF

Items