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I. RYU,Y. LIM 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.2
Quasistatic fractures at high joint angles constitute a chronic quality problem in CV joints. This type of fracture occurs when a driver unintentionally depresses the brake and accelerator simultaneously under a full-turn retreat condition. In general, the cage in a ball joint can be broken only at these high joint angles. Here we present a flexible quasistatic simulation model developed to simulate fracture in a CV joint. The cause and process of the quasistatic fracture were analyzed using simulations and physical tests. Static fracture simulations and tests at high joint angles showed that, initially, only one of the six cage posts was damaged. In a simulation of one revolution at constant torque, we found that an imbalance in ball loads generated an excessive cage load. Moreover, if this high cage load was applied when the cage protruded outward, the cage post was subjected to severe shear loading. The cage post was damaged in this specific rotational range. Quasistatic fracture simulations and tests at high joint angles showed that all six cage posts were damaged sequentially. Because entire cage posts were damaged, the quasistatic fracture torque was approximately half of the static torque. The plastic strain in each cage post displayed one step-like jump per revolution in the quasistatic simulations. The ball indentation created by a high ball load was interrupted by the cage-window edges as the ball joint rotated. This hindrance by ball indentation triggered the final breakage of the cage, although it was not the major cause of cage fractures.
Lindahl, P.,Asami, R.,Iryu, Y.,Worsfold, P.,Keith-Roach, M.,Choi, M.S. Pergamon Press ; Elsevier Science Ltd 2011 Geochimica et cosmochimica acta Vol.75 No.5
The Pu isotopes, <SUP>239</SUP>Pu and <SUP>240</SUP>Pu, were determined in annually-banded skeletons of an accurately dated (1943-1999) modern coral (Porites lobata) from Guam Island to identify historical Pu sources to the tropical Northwest Pacific Ocean. Activity concentrations of <SUP>239+240</SUP>Pu and <SUP>240</SUP>Pu/<SUP>239</SUP>Pu atom ratios were determined in the dated coral bands using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Close-in fallout from the former US Pacific Proving Grounds (PPG) in the Marshall Islands and global fallout were identified as the two main sources. The Guam site was dominated by PPG close-in fallout in the 1950s, with an average <SUP>240</SUP>Pu/<SUP>239</SUP>Pu atom ratio of 0.315+/-0.005. In addition, a higher <SUP>240</SUP>Pu/<SUP>239</SUP>Pu atom ratio (0.456+/-0.020) was observed that could be attributed to fallout from the ''Ivy Mike'' thermonuclear detonation in 1952. The atom ratio decreased in the 1960s and 1970s due to increase in the global fallout with a low <SUP>240</SUP>Pu/<SUP>239</SUP>Pu atom ratio (∼0.18). Recent coral bands (1981-1999) are dominated by the transport of remobilised Pu, with high <SUP>240</SUP>Pu/<SUP>239</SUP>Pu atom ratios, from the Marshall Islands to Guam Island along the North Equatorial Current (NEC). This remobilised Pu was estimated to comprise 69% of the total Pu in the recent coral bands, although its contribution was variable over time.