a[mm]/l - Memorial University of Newfoundland DAI

cmclung. called process zone. The rze of he zone of mncm-craclung dcpndtng on the
velocity of the crack. A faster crack has a larger zone of mzm-cnclung ahead of 11. At a
hlghei nrerr nle that crack propagates faster, and therefore the pmess zone will be
htggcr. Thar ,"creased mem-craelung may crpliun the h~gher fracture energy
Rqulremenrr at hlgher rtress rates.
The prcvlour ursumenr seems to contnd!ct wrth the argument presented above
The rubsnl>cal cnrk gmwB. predmcrs less mmm-crackmg ~n htgh-rrrerr rrlc loading
rltual!onr However, these two phenomena occur on $he oppornrs rldsr of Ihe pnk lxd.
The concept of rubcntlcal crack gmwth ~s applncable pnor to the pak load whtle the
concept of larger pmerr zone appl~es for orhc pan-peak load regnon where the unrtable
crack propagason commencer.
5.7. Dynamic Fracture Energy
When the pmjectnle htls the rpclmen. a sudden transfer of energy fmm the pmject!le to
the specmen occurs. The energy lost by the pmjeculc Ir panly mnsfemd to the
rpeclmen and panly rrayr wrthtn the pmjccrnic tn the form of slasue rlrrlns and
vlbrauons. The energy mewed by the rpcnmen from the pmjecttie 19 the energy even
by the area under bendrng load versus deflectton curve. as dexnbed m the follow~ng
cqurtmn:
GI(') = ~~PIl)du 15.27)
where. GJ It) =bending energy -wed by the spcrmsn
PI!) = punchmg load