Curves of △Kth vs.△ath and △Kcl·th vs.△ath for aluminum-lithium alloy 2090 have been determined and compared with those for traditional aluminum alloy 2024.The growth resistance of short fatigue cracks for al...Curves of △Kth vs.△ath and △Kcl·th vs.△ath for aluminum-lithium alloy 2090 have been determined and compared with those for traditional aluminum alloy 2024.The growth resistance of short fatigue cracks for aluminum-lithium alloy 2090 is quantitatively evaluated.The essential reason resulting in stronger short cracks effect has been ascertained.Influence of cerium on the growth behavior of short fatigue cracks for aluminum-lithium alloy 2090 was investigated.The results show that by adding cerium into this alloy a significant improvement in △Ki can be achieved and at the same time △Kcl·th is increased.Consequently,the essential factor resulting in lower growth resistance of short fatigue cracks for this alloy is removed and the growth resistance of long and short fatigue cracks is increased.展开更多
Threshold of fatigue for short through cracks for Al-Li alloy 8090 was evaluated to be lower than that of long cracks,and to decrease with the shortening of the crack length.The correla- tion among the threshold,crack...Threshold of fatigue for short through cracks for Al-Li alloy 8090 was evaluated to be lower than that of long cracks,and to decrease with the shortening of the crack length.The correla- tion among the threshold,crack wake,and crack tip shielding of the short fatigue cracks was discussed.The super demarcation length and lowest theoretical threshold of short through fa- tigue cracks were presented.展开更多
The effects of environmental media,both in atmosphere and in 3.5% NaCl aqueous solution, on the growth of short cracks in comparison with the long ones have been investigated under fatigue loading on the specimens of ...The effects of environmental media,both in atmosphere and in 3.5% NaCl aqueous solution, on the growth of short cracks in comparison with the long ones have been investigated under fatigue loading on the specimens of single-edge crack about 0.05—0.15 mm for A537CLI steel.The growth rate of short cracks is faster than those of long ones around the threshoht stress intensity.The threshold stress intensity for short crack growth decreases with de- creasing crack length.The acceleration effect of the salt water,as compared with atmosphere environment,on the growth of short cracks under fatigue is much greater than that on the growth of long cracks.展开更多
The material parameter ρ~*=4c/σ_(-1)~3 is put forward, which represents the crack tip radius independent of crack length under the action of the fatigue limit stress. According to the fatigue notch factor of the cra...The material parameter ρ~*=4c/σ_(-1)~3 is put forward, which represents the crack tip radius independent of crack length under the action of the fatigue limit stress. According to the fatigue notch factor of the crack propagation, K_t=K_t^(1/(3+n))=(4d/ρ~*)^(1/3), the fatigue limits of sharp notch, long crack and short crack are calculated, which are very close to the measurements. The calculated results make it clear that for surface crack the transition point from long crack to short crack is a~*=(ΔK_(th)~3/12.8c)~2, the range of physical short crack (a_s) is ρ~*/4≤a_s≤a~*, the threshold of the fatigue crack initiation is ΔK_(th(i))=0.66 Δσ_(-1) (πρ~*/4)^(1/2), the material parameter that indicates the fatigue crack sensitivity is ρ~*/a~*, which represents the blunting condition of crack tip under the action of the fatigue limit stress.展开更多
文摘Curves of △Kth vs.△ath and △Kcl·th vs.△ath for aluminum-lithium alloy 2090 have been determined and compared with those for traditional aluminum alloy 2024.The growth resistance of short fatigue cracks for aluminum-lithium alloy 2090 is quantitatively evaluated.The essential reason resulting in stronger short cracks effect has been ascertained.Influence of cerium on the growth behavior of short fatigue cracks for aluminum-lithium alloy 2090 was investigated.The results show that by adding cerium into this alloy a significant improvement in △Ki can be achieved and at the same time △Kcl·th is increased.Consequently,the essential factor resulting in lower growth resistance of short fatigue cracks for this alloy is removed and the growth resistance of long and short fatigue cracks is increased.
文摘Threshold of fatigue for short through cracks for Al-Li alloy 8090 was evaluated to be lower than that of long cracks,and to decrease with the shortening of the crack length.The correla- tion among the threshold,crack wake,and crack tip shielding of the short fatigue cracks was discussed.The super demarcation length and lowest theoretical threshold of short through fa- tigue cracks were presented.
文摘The effects of environmental media,both in atmosphere and in 3.5% NaCl aqueous solution, on the growth of short cracks in comparison with the long ones have been investigated under fatigue loading on the specimens of single-edge crack about 0.05—0.15 mm for A537CLI steel.The growth rate of short cracks is faster than those of long ones around the threshoht stress intensity.The threshold stress intensity for short crack growth decreases with de- creasing crack length.The acceleration effect of the salt water,as compared with atmosphere environment,on the growth of short cracks under fatigue is much greater than that on the growth of long cracks.
基金Fourth Term of ‘333 Engineering’ Program of Jiangsu Province(Project No.BRA2011116)Youth Foundation of Jiangsu Province(Project No.BK2012095)The Natural Science Foundation of Jiangsu Province of China(Project No.BK2012696)
文摘The material parameter ρ~*=4c/σ_(-1)~3 is put forward, which represents the crack tip radius independent of crack length under the action of the fatigue limit stress. According to the fatigue notch factor of the crack propagation, K_t=K_t^(1/(3+n))=(4d/ρ~*)^(1/3), the fatigue limits of sharp notch, long crack and short crack are calculated, which are very close to the measurements. The calculated results make it clear that for surface crack the transition point from long crack to short crack is a~*=(ΔK_(th)~3/12.8c)~2, the range of physical short crack (a_s) is ρ~*/4≤a_s≤a~*, the threshold of the fatigue crack initiation is ΔK_(th(i))=0.66 Δσ_(-1) (πρ~*/4)^(1/2), the material parameter that indicates the fatigue crack sensitivity is ρ~*/a~*, which represents the blunting condition of crack tip under the action of the fatigue limit stress.
