The optic nerve is a viscoelastic solid-like biomaterial.Its normal stress relaxation and creep properties enable the nerve to resist constant strain and protect it from injury.We hypothesized that stress relaxation a...The optic nerve is a viscoelastic solid-like biomaterial.Its normal stress relaxation and creep properties enable the nerve to resist constant strain and protect it from injury.We hypothesized that stress relaxation and creep properties of the optic nerve change after injury.Moreover,human brain-derived neurotrophic factor or umbilical cord blood-derived stem cells may restore these changes to normal.To validate this hypothesis,a rabbit model of optic nerve injury was established using a clamp approach.At 7 days after injury,the vitreous body received a one-time injection of 50 μg human brain-derived neurotrophic factor or 1 × 106 human umbilical cord blood-derived stem cells.At 30 days after injury,stress relaxation and creep properties of the optic nerve that received treatment had recovered greatly,with pathological changes in the injured optic nerve also noticeably improved.These results suggest that human brain-derived neurotrophic factor or umbilical cord blood-derived stem cell intervention promotes viscoelasticity recovery of injured optic nerves,and thereby contributes to nerve recovery.展开更多
This paper presents the creep-fatigue interaction life consumption of industrial gas turbine blades using the LM2500+ engine operated at Pulrose Power station, Isle of Mann as a case study. The linear damage summation...This paper presents the creep-fatigue interaction life consumption of industrial gas turbine blades using the LM2500+ engine operated at Pulrose Power station, Isle of Mann as a case study. The linear damage summation approach where creep damage and fatigue damage are combined was used for the creep-fatigue interaction life consumption of the target blades. The creep damage was modelled with the Larson-Miller parameter method while fatigue damage was assessed with the modified universal slopes method and the damage due to creep-fatigue interaction was obtained from the respective life fractions. Because of the difficulty in predicting the life of engine components accurately, relative life consumption analysis was carried out in the work using the concept of creep-fatigue interaction factor which is the ratio of the creep-fatigue interaction life obtained from any condition of engine operation to a reference creep-fatigue interaction life. The developed creep-fatigue interaction life consumption analysis procedure was applied to 8 most of real engine operation. It was observed that the contribution of creep to creep-fatigue interaction life consumption is greater than that of fatigue at all ambient temperatures. The fatigue contribution is greater at lower ambient temperatures as against higher ambient temperatures. For the case study, the overall equivalent creep-fatigue factor obtained was 1.5 which indicates safe engine operation compared to the reference condition. The developed life analysis algorithm could be applied to other engines and could serve as useful tool in engine life monitoring by engine operators.展开更多
The creep crack propagation in superalloy René80 of two different microstructures,i.e., equiaxed grain structure by conventional casting and columnar grain by directional solidification,was investigated under sta...The creep crack propagation in superalloy René80 of two different microstructures,i.e., equiaxed grain structure by conventional casting and columnar grain by directional solidification,was investigated under static load at 1123 K.The creep crack growth rate, da/dt,seems to be correlated with the stress intensity factor,K.The creep crack growth rate in the directionally solidified alloy is lower than that in the conventional cast alloy,owing to the elimination of transverse grain boundaries.The effect of microstructure on creep crack propagation has also been discussed.展开更多
通过对LY12CZ的平头压痕蠕变和单轴拉伸蠕变行为的比较,主要研究工程材料LY12CZ的压痕蠕变行为。首先对压痕蠕变试验和单轴蠕变试验进行研究,通过试验得出材料蠕变参数及其压痕蠕变参数。其次,通过有限元(fi-nite element method,FEM)...通过对LY12CZ的平头压痕蠕变和单轴拉伸蠕变行为的比较,主要研究工程材料LY12CZ的压痕蠕变行为。首先对压痕蠕变试验和单轴蠕变试验进行研究,通过试验得出材料蠕变参数及其压痕蠕变参数。其次,通过有限元(fi-nite element method,FEM)分析对压痕蠕变进行模拟,也得出材料的压痕蠕变参数,以上都得出相同温度下由压痕蠕变试验和单轴拉伸蠕变试验得出的应力指数是相等的结论,同时利用转化因子验证压痕蠕变试验和单轴蠕变试验的一致性和等效性,从而证实由压痕蠕变试验描述蠕变是合适的,并且能够确定材料的蠕变参数。展开更多
基金supported by a grant from High-Tech Research and Development Program of Jilin Province of China,No.20110492
文摘The optic nerve is a viscoelastic solid-like biomaterial.Its normal stress relaxation and creep properties enable the nerve to resist constant strain and protect it from injury.We hypothesized that stress relaxation and creep properties of the optic nerve change after injury.Moreover,human brain-derived neurotrophic factor or umbilical cord blood-derived stem cells may restore these changes to normal.To validate this hypothesis,a rabbit model of optic nerve injury was established using a clamp approach.At 7 days after injury,the vitreous body received a one-time injection of 50 μg human brain-derived neurotrophic factor or 1 × 106 human umbilical cord blood-derived stem cells.At 30 days after injury,stress relaxation and creep properties of the optic nerve that received treatment had recovered greatly,with pathological changes in the injured optic nerve also noticeably improved.These results suggest that human brain-derived neurotrophic factor or umbilical cord blood-derived stem cell intervention promotes viscoelasticity recovery of injured optic nerves,and thereby contributes to nerve recovery.
文摘This paper presents the creep-fatigue interaction life consumption of industrial gas turbine blades using the LM2500+ engine operated at Pulrose Power station, Isle of Mann as a case study. The linear damage summation approach where creep damage and fatigue damage are combined was used for the creep-fatigue interaction life consumption of the target blades. The creep damage was modelled with the Larson-Miller parameter method while fatigue damage was assessed with the modified universal slopes method and the damage due to creep-fatigue interaction was obtained from the respective life fractions. Because of the difficulty in predicting the life of engine components accurately, relative life consumption analysis was carried out in the work using the concept of creep-fatigue interaction factor which is the ratio of the creep-fatigue interaction life obtained from any condition of engine operation to a reference creep-fatigue interaction life. The developed creep-fatigue interaction life consumption analysis procedure was applied to 8 most of real engine operation. It was observed that the contribution of creep to creep-fatigue interaction life consumption is greater than that of fatigue at all ambient temperatures. The fatigue contribution is greater at lower ambient temperatures as against higher ambient temperatures. For the case study, the overall equivalent creep-fatigue factor obtained was 1.5 which indicates safe engine operation compared to the reference condition. The developed life analysis algorithm could be applied to other engines and could serve as useful tool in engine life monitoring by engine operators.
文摘The creep crack propagation in superalloy René80 of two different microstructures,i.e., equiaxed grain structure by conventional casting and columnar grain by directional solidification,was investigated under static load at 1123 K.The creep crack growth rate, da/dt,seems to be correlated with the stress intensity factor,K.The creep crack growth rate in the directionally solidified alloy is lower than that in the conventional cast alloy,owing to the elimination of transverse grain boundaries.The effect of microstructure on creep crack propagation has also been discussed.
文摘通过对LY12CZ的平头压痕蠕变和单轴拉伸蠕变行为的比较,主要研究工程材料LY12CZ的压痕蠕变行为。首先对压痕蠕变试验和单轴蠕变试验进行研究,通过试验得出材料蠕变参数及其压痕蠕变参数。其次,通过有限元(fi-nite element method,FEM)分析对压痕蠕变进行模拟,也得出材料的压痕蠕变参数,以上都得出相同温度下由压痕蠕变试验和单轴拉伸蠕变试验得出的应力指数是相等的结论,同时利用转化因子验证压痕蠕变试验和单轴蠕变试验的一致性和等效性,从而证实由压痕蠕变试验描述蠕变是合适的,并且能够确定材料的蠕变参数。
