PENETRATION FRACTlJRE OF SEA ICE PLATE: SIMPLIFIED ANALYSIS AND SIZE EFFECT

ABSTRACT: Vertical penetration of an ohjectthrough a floaling ela~tic-hrillle platc frolll thc hOIlOIll up or Ihe top dllwn is studied. Based on field ohservations. it i~ assulllcd Ihal many symllletric nacks grow radially f r(lm a small loaded area. and Ihe maximulIl load is achieved at Ihe inilialion of circumferenlial nacks. Nevel's approximation. in which the plate wedges between the r.. dial cracks <trt:analyzed as narrow floating heams of linearly varying widlh, is adopled. This makes an analYlical Solulion possihle. The rale of energy release due 10 Ihe radial u<lck growth is calculated according 10 linear elastic fracture mechanics alld the theory of Ihin plates. This yields Ihe dependence of Ihe radial nack length on Ihc lo;ul. which is consideled to he IInifOlnlly dislrihulcd along;, slllall circle. It is conlilllll·d thai Ihere is a size c!fect sllch Ihal Ihe nominal slress (lo'ld divlllcd hy icc Ihicknc\s squared) that causes similar naeks til grow is proportional to (icc thickncss) II" or, c(luivalenlly. to (flcxural wavelengths) II!. Iloweyer. the maximullI load docs nol follow this size effect. hecause it is allained at the initialion of circumfercnlial cracks. which is governed hy a ~trenglh type of criterion and causes no size died. When Ihe sizc of the loadet.i area is fixed, Ihere is a size dfed dul ' 10 an increase of load conCl?nlralion. Ihat is. a deuease of the ralio of Ihc loaded circle diamcter to Ihe thickness. This size effed is inlcnsified hy Ihe size depellllcncc llf Ihe J'uplllle modulus (or hending. hul in the normal Sill ' r'lIIge. Sill h a SilC effect is nol ~ignil ican!. The leI'ltion h.;tween thc length of the radial l'I'lcks and the applied load calculated hy fladull ' IIlcchanics is also usdllilor other mclhods III pledictillg thc penelralion load