Papers by Keyword: Ring Specimen

Abstract: Ring-shaped specimen is commonly used in tests for determination of mechanical properties for arteries in hoop direction, especially for small mammals such as rats or mice. Although ring test is a lot more convenient than the tests concerning strip specimens, interpretation of the experimental data might be inconclusive – it is difficult distinguish whether it's still straightening up or the actual tension begins. The basic problem is to properly define initial length of specimen, which is essential for strain calculation. The purpose of this study was to evaluate various methods for strain evaluation. Ten Wistar Albino Glaxo male rats (3 months old, body weight about 200g) were sacrificed by decapitation and arteries were immediately removed. Three specimens, each approximately 2–3mm long, from each rat were excised adjacent to the aortic arch. Couple different initial lengths, as well as Digital Image Correlation based extensometer results were used for strain-stress response calculations. In addition a 3D Finite Element model, with an Ogden constitutive model based material, was made for deeper investigation of specimen behavior. This study has shown that the testing procedure for determination of mechanical properties of arteries, based on ring-shaped specimen, is prone to errors. Stiffness calculations are very sensitive to the choice of initial length of the specimen. As the use of DIC proved to give very good correlation with experimental data this method will be used in further studies.

Abstract: In this paper, a ring shaped numerical specimen is used to studying the failure process in brittle materials. The ring specimen is subjected to a compressive diametral load and contains two angled central cracks. Numerical modeling in this study is performed. It is shown that the obtained numerical results are in a very good agreement with the experiments. Effect of the crack orientation angle on the failure modes and loading-displace responses is discussed. In the range of 0°~40°, the fracture paths are curvilinear forms starting from the tip of pre-existing cracks and grow towards the loading points. For the crack orientation angle 90°, vertical fractures will split the specimen and the horizontal cracks do not influence the fracture process.

Abstract: A burst rupture test has been mainly used for evaluating the burst properties of internal pressurized tubes. Although the burst creep test provides accurate results, its complicated and material-wasting process makes it difficult to perform this test. In the burst test, it is known that the hoop stress is a main reason of burst, so it can be expected that the burst rupture properties are strongly related with the hoop creep rupture properties. A ring test is occasionally used for obtaining the hoop directional properties of tube-shaped structures. In this study, the creep rupture properties of Zirlo tubing are investigated at temperature ranging from 365 to 570
using the ring specimens. An analysis of the fractography was performed and the estimation of service life with Larson-Miller parameter was conducted. Finally, In view of the Dorn equation of power-law, the creep mechanism was determined and discussed.