A novel method is presented to evaluate the complicated fatigue behavior of gears made of20Cr2Ni4 A.Fatigue tests are conducted in a high-frequency push-pull fatigue tester,and acoustic emission（AE）technique is used...A novel method is presented to evaluate the complicated fatigue behavior of gears made of20Cr2Ni4 A.Fatigue tests are conducted in a high-frequency push-pull fatigue tester,and acoustic emission（AE）technique is used to acquire metal fatigue signals.After analyzing large number of AE frequency spectrum,we find that：the crack extension can be expressed as the energy of specific frequency band,which is abbreviated as F-energy.To further validate the fatigue behavior,some correlation analysis is applied between F-energy and some AE parameters.Experimental results show that there is significant correlation among the Fenergy,root mean square（RMS）,relative energy,and hits.The findings can be used to validate the effectiveness of the F-energy in predicting fatigue crack propagation and remaining life for parts in-service.F-energy,as a new AE parameter,is first put forward in the area of fatigue crack growth.展开更多
Carbon fiber reinforced polymer(CFRP)has many remarkable merits.It is lightweight and has great rigidity and high intensity. High-durability cable produced from CFRP as reinforcement material is widely used in bridge ...Carbon fiber reinforced polymer(CFRP)has many remarkable merits.It is lightweight and has great rigidity and high intensity. High-durability cable produced from CFRP as reinforcement material is widely used in bridge construction projects.However, there is a dearth of studies regarding damage types and mechanism under fatigue load of CFRP bridge cables.In this paper,we adopt acoustic emission(AE)technology to monitor fatigue damage and failure of the CFRP bridge cables,specifically by monitoring the bridge cable’s fatigue test process and using wavelet transformation to analyze data.Results show that damage on the CFRP cable is divided into three stages.Based on wavelet singularity theory,in each stage of AE,the burst signal is obtained and its time-frequency distribution is achieved through wavelet analysis.According to the analysis results,failure modes in each phase and type of acoustic emission source are easy to determine.The characteristics of waveform,types of damages, and frequency distribution of CFRP bridge cable in different damage phases are collected.Research shows that the method used to determine the types of fatigue damage on the CFRP cable is feasible according to the range of distribution characteristic parameters for acoustic emission signal and type of waveform.展开更多
The accumulated damage process of rolling contact fatigue （RCF） of plasma-sprayed coatings was investigated. The influences of surface roughness, loading condition, and stress cycle frequency on the accumulated dama...The accumulated damage process of rolling contact fatigue （RCF） of plasma-sprayed coatings was investigated. The influences of surface roughness, loading condition, and stress cycle frequency on the accumulated damage status of the coatings were discussed. A ball-on- disc machine was employed to conduct RCF experiments. Acoustic emission （AE） technique was introduced to monitor thc RCF process of the coatings. AE signal characteristics were investigated to reveal the accumulated damage process. Result showed that the polished coating would resist the asperity contact and remit accumulated damage. The RCF lifetime would then extend. Heavy load would aggravate the accumulated damage status and induce surface fracture. Wear became the main failure mode that reduced the RCF lifetime. Frequent stress cycle would aggravate the accumulated damage status and induce interface fracture. Fatigue then became the main failure mode that also reduced the RCF lifetime.展开更多
基金Supported by the National Natural Science Foundation of China(50975030)
文摘A novel method is presented to evaluate the complicated fatigue behavior of gears made of20Cr2Ni4 A.Fatigue tests are conducted in a high-frequency push-pull fatigue tester,and acoustic emission（AE）technique is used to acquire metal fatigue signals.After analyzing large number of AE frequency spectrum,we find that：the crack extension can be expressed as the energy of specific frequency band,which is abbreviated as F-energy.To further validate the fatigue behavior,some correlation analysis is applied between F-energy and some AE parameters.Experimental results show that there is significant correlation among the Fenergy,root mean square（RMS）,relative energy,and hits.The findings can be used to validate the effectiveness of the F-energy in predicting fatigue crack propagation and remaining life for parts in-service.F-energy,as a new AE parameter,is first put forward in the area of fatigue crack growth.
基金supported by the National Natural Science Foundation of China(Grant No.50808030)the Doctoral Fund of Ministry of Education of China(Grant No.200801411102)
文摘Carbon fiber reinforced polymer(CFRP)has many remarkable merits.It is lightweight and has great rigidity and high intensity. High-durability cable produced from CFRP as reinforcement material is widely used in bridge construction projects.However, there is a dearth of studies regarding damage types and mechanism under fatigue load of CFRP bridge cables.In this paper,we adopt acoustic emission(AE)technology to monitor fatigue damage and failure of the CFRP bridge cables,specifically by monitoring the bridge cable’s fatigue test process and using wavelet transformation to analyze data.Results show that damage on the CFRP cable is divided into three stages.Based on wavelet singularity theory,in each stage of AE,the burst signal is obtained and its time-frequency distribution is achieved through wavelet analysis.According to the analysis results,failure modes in each phase and type of acoustic emission source are easy to determine.The characteristics of waveform,types of damages, and frequency distribution of CFRP bridge cable in different damage phases are collected.Research shows that the method used to determine the types of fatigue damage on the CFRP cable is feasible according to the range of distribution characteristic parameters for acoustic emission signal and type of waveform.
基金This study was financially supported by the Distinguished Young Scholars of National Natural Science Foundation of China （Grant No. 51125023）, the 973 Project （Grant No. 2011CB013405）, the National Natural Science Foundation of China （Grant Nos. 51305397 and 51375457）, and the Open Foundation of the State Laboratory of Fluid Power Transmission and Control （GZKF-201411） （Grant Nos. 2014C31099 and EM2015042003）.
文摘The accumulated damage process of rolling contact fatigue （RCF） of plasma-sprayed coatings was investigated. The influences of surface roughness, loading condition, and stress cycle frequency on the accumulated damage status of the coatings were discussed. A ball-on- disc machine was employed to conduct RCF experiments. Acoustic emission （AE） technique was introduced to monitor thc RCF process of the coatings. AE signal characteristics were investigated to reveal the accumulated damage process. Result showed that the polished coating would resist the asperity contact and remit accumulated damage. The RCF lifetime would then extend. Heavy load would aggravate the accumulated damage status and induce surface fracture. Wear became the main failure mode that reduced the RCF lifetime. Frequent stress cycle would aggravate the accumulated damage status and induce interface fracture. Fatigue then became the main failure mode that also reduced the RCF lifetime.
