{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T23:10:33Z","timestamp":1791241833326,"version":"4.1.0"},"reference-count":17,"publisher":"ASME International","issue":"9","content-domain":{"domain":["asmedigitalcollection.asme.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2009,9,1]]},"abstract":"<jats:p>Biaxial testing has been used widely to characterize the mechanical properties of soft tissues and other flexible materials, but fundamental issues related to specimen design and attachment have remained. Finite element models and experiments were used to investigate how specimen geometry and attachment details affect uniformity of the strain field inside the attachment points. The computational studies confirm that increasing the number of attachment points increases the size of the area that experiences sensibly uniform strain (defined here as the central sample region where the ratio of principal strains E11\/E22&lt;1.10), and that the strains experienced in this region are less than nominal strains based on attachment point movement. Uniformity of the strain field improves substantially when the attachment points span a wide zone along each edge. Subtle irregularities in attachment point positioning can significantly degrade strain field uniformity. In contrast, details of the apron, the region outside of the attachment points, have little effect on the interior strain field. When nonlinear properties consistent with those found in human sclera are used, similar results are found. Experiments were conducted on 6\u00d76\u2002mm talc-sprinkled rubber specimens loaded using wire \u201crakes.\u201d Points on a grid having 12\u00d712\u2002bays were tracked, and a detailed strain map was constructed. A finite element model based on the actual geometry of an experiment having an off-pattern rake tine gave strain patterns that matched to within 4.4%. Finally, simulations using nonequibiaxial strains indicated that the strain field uniformity was more sensitive to sample attachment details for the nonequibiaxial case as compared to the equibiaxial case. Specimen design and attachment were found to significantly affect the uniformity of the strain field produced in biaxial tests. Practical guidelines were offered for design and mounting of biaxial test specimens. The issues addressed here are particularly relevant as specimens become smaller in size.<\/jats:p>","DOI":"10.1115\/1.3148467","type":"journal-article","created":{"date-parts":[[2009,8,28]],"date-time":"2009-08-28T18:37:09Z","timestamp":1251484629000},"update-policy":"https:\/\/doi.org\/10.1115\/crossmarkpolicy-asme","source":"Crossref","is-referenced-by-count":75,"title":["Strain Uniformity in Biaxial Specimens is Highly Sensitive to Attachment Details"],"prefix":"10.1115","volume":"131","author":[{"given":"Armin","family":"Eilaghi","sequence":"first","affiliation":[{"name":"Department of Mechanical and Industrial Engineering, and Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, M5S 1A1"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"John G.","family":"Flanagan","sequence":"additional","affiliation":[{"name":"Department of Ophthalmology and Vision Sciences, University of Toronto; School of Optometry School, University of Waterloo, Waterloo, Ontario, N2L 3G1"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"G. Wayne","family":"Brodland","sequence":"additional","affiliation":[{"name":"Department of Civil and Environmental Engineering, and Department of Biology, University of Waterloo"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"C. 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