Study On The Stress Concentration In Centrifugal Baskets With Perforations

Basket is one of the main parts of a centrifuge. Perforations arranged in the basket will weaken the load-bearing capability and disturb the continuity of the cylinder, so stress concentration around the perforations appears. To gain the precise value of the stress is very important for the engineers to design centrifugal basket and evaluate the strength of the basket.At home and abroad, standards are published to get the maximum circumferential stress of the basket. In this paper, contents of the standards that are used at present are analyzed and compared. JB/T 8051-1996 Standard of strength calculation for centrifugal basket is promulgated in our country. It is proved by using the finite element method in the paper that coefficients for shell perforations in the standard are not very suitable for the centrifugal basket's stress calculation.The stress conditions of centrifugal basket are much complicated because of the existing of holes in the shell, so it is very hard to get the circumferential stress by the theoretical method. In this paper, by using finite element method, how the factors including basket radius, thickness and ligament width influence the circumferential stress is discussed and the results reveal that: for the perforations arranged in regular triangle, square and slanting square arrays, the factor of the basket radius do not have the same effects on stress distribution in the two intervals, which are separated by the coefficient due to perforations and ligament (ratio of perforation diameter and ligament width)γ= 2. Whenγ<2, the factor of thickness has little influence on the change of the membrane stress concentration coefficient K_θ, so it is not right to reduce the stress value by adding basket thickness. In this interval, the curves of K_θvsγare much like the same though the ligament widths are different. Whenγ>2, because the big holes have great effects on the displacement in radial direction of the basket, the differences of the K_θvsγcurves are obvious as the thickness and ligament width change.Several suggestions are proposed in this paper for the revision of JB/T 8051-1996 Standard of strength calculation for centrifugal basket based on the finite element analysis.