Actions for Predicting the Life and Design Stresses of Medical Plastics Under Creep Conditions

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Predicting the Life and Design Stresses of Medical Plastics Under Creep Conditions / SH. Teoh

Conference Author
Biomaterials' Mechanical Properties (1992 : Pittsburgh, PA)
Physical Description
1 online resource (10 pages) : illustrations, figures, tables
Additional Creators
Teoh, SH., American Society for Testing and Materials, and ASTM International
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Summary
Polymers are finding increasing use in biomedical engineering applications. One of the major problems in designing with polymers is predicting when the material will fail and what stress values should be used in the design of components in order that the material will not fail prematurely. Recent work on modeling the creep rupture behavior of more than 15 polymers has produced a breakthrough in predicting the failure times as well as the upper stress and lower stress limits of the polymers [1,2]. The upper stress relates to the maximum stress that can be applied to the material before instantaneous fracture. The lower stress limit relates to the minimum stress that can be sustained by the material without failure and, in some cases, this also corresponds to the fatigue endurance limit of the polymer. The creep rupture times of some medical plastics such as high density polyethylene (HOPE), polycarbonate (PC), polypropylene (PP), polyoxymethylene (POM), polyvinylchloride (PVC), polysulphone (PSU), and polymethyl-methacrylate (PMMA) were analyzed at 20¿̐ưC in air. In order to optimize the parameters for creep rupture prediction, a nonlinear regression analysis program was used [1]. Special attention was made for Delrin (POM from Du Pont) which is of interest in cardiovascular applications related to wear of mechanical heart valves [3] This matenal was tested in air at 37, 60, and 80¿̐ưC. The effect of saline solution was also studied Here, the lower stress limit was reduced from 20 MPa to 5 MPa. All the specimens brittle fractured This may account why Delrin used in the artificial hip joint prosthesis [4] where the contact stresses exceed this limit was known to wear severely. However, in the disc of the mechanical heart valve [3] no failure occurs because the stresses were probably below the lower stress limit.
Dates of Publication and/or Sequential Designation
Volume 1994, Issue 1173 (January 1994)
Subject(s)
Other Subject(s)
ISBN
9780803152618 (e-ISBN)
9780803118942
0803118945
Digital File Characteristics
text file PDF
Bibliography Note
Includes bibliographical references 13.
Other Forms
Also available online via the World Wide Web. Tables of contents and abstracts freely available; full-text articles available by subscription.
Full text article also available for purchase.
Also available in PDF edition.
Reproduction Note
Electronic reproduction. W. Conshohocken, Pa. : ASTM International, 1994. Mode of access: World Wide Web. System requirements: Web browser. Access may be restricted to users at subscribing institutions.
Technical Details
Mode of access: World Wide Web.
Source of Acquisition
ASTM International PDF Purchase price USD25.
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