The ultimate tensile strength is a basic quality indicator when nuclear fuel is produced from uranium dioxide powder. Generally, it is determined by testing samples dozens of times bigger than the fuel pellets, which are not more than 6-8 mm in length and diameter.
The "Brazilian test" involves testing a short cylinder, which is placed on its side for compression. This method has a long and successful record in testing rock specimens not less than 50 mm in diameter and 0.2-0.75 diameters thick. However, the method cannot be used when there is a hole in the centre of the specimen, which is the case with fuel pellets.
"We have made a design analysis of the specimen's stress-deformed state at various points, using the finite-element method in the ANSYS software package. It has shown how the distribution of tension over the cylinder base surface and over the section along the plane of symmetry and load depends on the hole," said Vladimir Goltsev, an associate professor at the university's Strength Physics Department.
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"The research has led us to the conclusion that the Brazilian test can be used successfully to test small-sized samples of fragile materials and it has also made it possible for us to propose our formula for calculating nuclear fuel tensile strength," Goltsev said.
These research results have been presented at the 16th International School-Conference "New Materials: Tolerant Nuclear Fuel" held at the University at the initiative of the ion-beam materials treatment school of the university's Material Science Department.