Journal article
Stress concentration sensitivity of pharmaceutical tablets: The concept of an equivalent crack and microstructural considerations
Journal of pharmaceutical sciences, v 115(1), 104055
01 Jan 2026
PMID: 41197802
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
•The applied stress ratio at failure (ASR) as a measure of the stress concentration sensitivity in pharmaceutical tablets.•The concept of equivalent crack is introduced to describe microstructural size effects in the failure of tablets.•ASR in the equivalent crack framework is independent of the fracture toughness of the material.•ASR is numerically estimated using Finite Elements for side pressed specimens with and without a hole.•ASR can be controlled by the particle size of the compacted material and its evolution during compaction.
The sensitivity of the strength of powder compacts to presence of a hole as a stress concentrator has been explored in the past as a parameter that may provide insight to the propensity of these materials to develop defects during the compaction/ejection sequence. In recent work it was shown that the ratio of the strength in side pressing of two specimens of the same overall size with and without a hole depends on the size of the hole and the variation is varied for different materials. Yet the mechanistic explanation of the stress concentration sensitivity has been lacking. In this work we present the concept of an equivalent crack which represents the microstructural effects on the fracture of these materials, and we connect the stress concentration sensitivity with the equivalent crack size. This new approach shows that the stress concentration sensitivity is independent of the fracture toughness of the material and is only a function of geometric characteristics of the specimens and the equivalent crack size. This observation allows us to numerically derive the size of the equivalent crack from the experimental measurement of ratio of strengths of two specimens. In this way we can explain the reduction of the apparent stress concentration sensitivity as the size of the hole is reduced and we prove that the equivalent crack size and the strength ratio scale with the powder size. This new understanding can provide insight into the response of powder compacts in situations where stress concentrations are present.
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Details
- Title
- Stress concentration sensitivity of pharmaceutical tablets: The concept of an equivalent crack and microstructural considerations
- Creators
- Joseph R. Wright - Department of Materials Science and Engineering, University of Connecticut, Science 1 Room 1036, 25 King Hill Rd., Storrs, CT 06278, United StatesPhuong Bui - Department of Materials Science and Engineering, Drexel University, LeBow Engineering 344, 3141 Chestnut St., Philadelphia, PA 19104, United StatesJovana Radojevic - Department of Materials Science and Engineering, Drexel University, LeBow Engineering 344, 3141 Chestnut St., Philadelphia, PA 19104, United StatesEdward Yost - GenentechAntonios Zavaliangos - Drexel University, Materials Science and Engineering
- Publication Details
- Journal of pharmaceutical sciences, v 115(1), 104055
- Publisher
- Elsevier Inc
- Number of pages
- 11
- Grant note
- US Department of Education GAANN program: P200A180026 GenentechNational Science Foundation: NSF-MRI CMMI-2216175
The work performed by Joseph Wright and Phuong Bui at Drexel University was funded by Fellowships from the US Department of Education GAANN program, award No P200A180026. Work by Jovana Radojevic was performed during her doctoral work at Drexel University. Partial support for work performed by Edward Yost was also provided by a grant from Genentech. The tomography work was performed on a Zeiss XRadia 620 purchased through funds provided by the National Science Foundation (NSF-MRI CMMI-2216175) .
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Materials Science and Engineering
- Web of Science ID
- WOS:001629623300001
- Scopus ID
- 2-s2.0-105022834948
- Other Identifier
- 991022130676904721
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- Collaboration types
- Industry collaboration
- Domestic collaboration
- Web of Science research areas
- Chemistry, Medicinal
- Chemistry, Multidisciplinary
- Pharmacology & Pharmacy