Nowadays, people are busier and busier for working and living, and suffer a lot of pressure on their body or mind. Therefore, people are prone to have fatigue activity and decrease their working efficiency and happine...Nowadays, people are busier and busier for working and living, and suffer a lot of pressure on their body or mind. Therefore, people are prone to have fatigue activity and decrease their working efficiency and happiness. It was reported that fatigue is a common symptom in the community, with up to half of the general population complaining of fatigue. More and more researchers devoted themselves to studying natural active ingredients in organism as the anti-fatigue drugs to release fatigue symptom. However, these natural ingredients were difficult to obtain from plants, animals and microorganisms by separating and purifying. In addition, some active substances have many side effects. In our study, we employed tea seed oil as main ingredients blended with bis-(carboxyethylgermanium) sesquioxide (Ge-132) to investigate the effects of anti-fatigue on mice by administrating mice with low dose, intermediate dose and high dose of tea seed oil complex for 0, 2 or 4 weeks. The specific tests of studying effects of anti-fatigue were body weight, weight-loaded force swimming, blood urea nitrogen, blood lactic acid and hepaticglycogen. And the results showed that appropriate level of tea seed oil complex could decrease the body weight and prolong the weight-loaded swimming time, and had an active effect on the bloodurea nitrogen, hepatic glycogen and blood lactic acid level mice, which significantly embodied the anti-fatigue activity of tea seed oil complex.展开更多
The adoption of cold-extrusion forming for internal thread net forming becomes an important component of anti-fatigue processing with the development of internal thread processing towards high performance, low cost an...The adoption of cold-extrusion forming for internal thread net forming becomes an important component of anti-fatigue processing with the development of internal thread processing towards high performance, low cost and low energy consumption. It has vast application foreground in the field of aviation, spaceflight, high speed train and etc. The internal thread processing and anti-fatigue manufacture technology are summarized. In terms of the perspective of processing quality and fatigue serving life, the advantages and disadvantages of the processing methods from are compared. The internal thread cold-extrusion processing technology is investigated for the purpose of improving the anti-fatigue serving life of internal thread. The superiorities of the plastic deformation law and surface integrity of the metal layer in the course of cold extrusion for improving its stability and economy are summed up. The proposed research forecasts the develop- ment tendency of the internal thread anti-fatigue manufacturing technology.展开更多
In this paper, ultrasonic （20 kHz） fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue （VHCF） regime. Experimental results showed that for most tested specimens failed in ...In this paper, ultrasonic （20 kHz） fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue （VHCF） regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area （FGA） centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.展开更多
Studies were made of the symmetric tensile-compressive low cycle fatigue behaviour and the influence of dynamic strain aging(DSA)pre-treatment of 18-8 austenitic stainless steel. Within the testing amplitude range of ...Studies were made of the symmetric tensile-compressive low cycle fatigue behaviour and the influence of dynamic strain aging(DSA)pre-treatment of 18-8 austenitic stainless steel. Within the testing amplitude range of strain.±0.5 % to±1.5 %,the three processes of cyclic hardening,cyclic saturation and cyclic softening were observed.In the same amplitude of strain,the peak stress of the samples pre-treated by DSA is higher than that of solid-solu- tion and cold working pre-treatment,but no remarkable differences of the fatigue lives of them were found.TEM observation shows that the uniform and stable dislocation networks with high density form after DSA pre-treatment,which increases the cyclic peak stress.The cyclic softening results from the low dislocation density and elongated cell structure with low energy.展开更多
Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and d...Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and damage evolution criteria. Furthermore,damage evolution equations of time rate are established by the generalized Drucker＇s postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations,and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise,for notched specimens under the repeated loading with constant strain amplitude,the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus,the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1,2 and 3.展开更多
Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some ...Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some of them were modified by the ceramic coating deposition surface treatment. The effects of ceramic coating, on the fatigue crack growth behaviour of hollow shaft specimens, were experimentally investigated. Fatigue crack growth rates, da/dN, were characterised, using the power law relationship between da/dN (in mm/cycle) and the stress intensity factor range, ΔK (in MPa∙m0.5). The two constants of the correlation are 7.9768 × 10−9 and 2.8107 for the parent material, and those for the coated material are 2.4391 × 10−9 and 3.1990, respectively. Microstructural analyses were carried out on the tested specimens, which shows that the maximum hardness of the ceramic coating is higher than that of substrate by a factor of ~3.2. The dimple fracture dominates the final fracture mechanism for the parent material, and the combination of fatigue, ductile fracture and cleavage dominates the final fracture mechanism for the coated material, based on the SEM analyses. EDS tests’ results reveal that the parent material specimen shows higher levels of C at matrix regions along with Fe- and O-rich regions, compared with the coated material specimen.展开更多
Vitamin C and taurine (TR) are well known as active components for fatigue recovery. However, the mechanism of the anti-fatigue effects of vitamin C and TR is still unclear. Our study was designed to evaluate the anti...Vitamin C and taurine (TR) are well known as active components for fatigue recovery. However, the mechanism of the anti-fatigue effects of vitamin C and TR is still unclear. Our study was designed to evaluate the anti-fatigue activities of vitamin C and TR in an animal test for fatigue and to compare the activities between vitamin C and TR. Materials and Methods: Vitamin C, TR or their combination were orally administrated to mice once daily for 15 days, and then metabolic activities such as blood glucose, triglyceride (TG), lactate, and lactate dehydrogenase (LDH) as well as antioxidant activities such as malondialdehyde (MDA) and superoxide dismutase (SOD) were determined (evaluated) after forced swimming test (FST). Results: Compared with the control group, C100, C200, and T50 showed a tendency to decrease mobility in FST. Moreover, TG (C100, C200, T200), LDH (C200), lactic acid (C100) and MDA (C50, C100, C200) levels were inhibited by vitamin C and TR. Conclusions: These results suggest that vitamin C and TR have anti-fatigue activities in mice, with vitamin C providing a stronger effect.展开更多
利用Arnol'd的Legendrian理论,对三维Anti de Sitter空间中Lorentzian曲面进行了研究.引入光维高度函数概念研究了三维Anti de Sitter空间Lorentzian曲面的S1t×S1s-值、光锥Gauss映射的奇点,进行了奇点分类,揭示了类光Causs-kr...利用Arnol'd的Legendrian理论,对三维Anti de Sitter空间中Lorentzian曲面进行了研究.引入光维高度函数概念研究了三维Anti de Sitter空间Lorentzian曲面的S1t×S1s-值、光锥Gauss映射的奇点,进行了奇点分类,揭示了类光Causs-kronecker曲率之间的关系;并研究了Lorentzian曲面的一些基本几何性质.展开更多
文摘Nowadays, people are busier and busier for working and living, and suffer a lot of pressure on their body or mind. Therefore, people are prone to have fatigue activity and decrease their working efficiency and happiness. It was reported that fatigue is a common symptom in the community, with up to half of the general population complaining of fatigue. More and more researchers devoted themselves to studying natural active ingredients in organism as the anti-fatigue drugs to release fatigue symptom. However, these natural ingredients were difficult to obtain from plants, animals and microorganisms by separating and purifying. In addition, some active substances have many side effects. In our study, we employed tea seed oil as main ingredients blended with bis-(carboxyethylgermanium) sesquioxide (Ge-132) to investigate the effects of anti-fatigue on mice by administrating mice with low dose, intermediate dose and high dose of tea seed oil complex for 0, 2 or 4 weeks. The specific tests of studying effects of anti-fatigue were body weight, weight-loaded force swimming, blood urea nitrogen, blood lactic acid and hepaticglycogen. And the results showed that appropriate level of tea seed oil complex could decrease the body weight and prolong the weight-loaded swimming time, and had an active effect on the bloodurea nitrogen, hepatic glycogen and blood lactic acid level mice, which significantly embodied the anti-fatigue activity of tea seed oil complex.
基金Supported by National Natural Science Foundation of China(Grant No.51672241)International Cooperation Foundation of Ministry of Agriculture of China(Grant No.20162003)+2 种基金Collaborative Innovation Program of Industry University Research of Jiangsu Province China(Grant No.BE2015113)Young and Middle-aged Academic Leaders of Universities‘‘Qinglan Project’’of Jiangsu Province 2016Foundation of Key Laboratory of Modern Agricultural Equipment Ministry of Agriculture,China(Grant No.201604003)
文摘The adoption of cold-extrusion forming for internal thread net forming becomes an important component of anti-fatigue processing with the development of internal thread processing towards high performance, low cost and low energy consumption. It has vast application foreground in the field of aviation, spaceflight, high speed train and etc. The internal thread processing and anti-fatigue manufacture technology are summarized. In terms of the perspective of processing quality and fatigue serving life, the advantages and disadvantages of the processing methods from are compared. The internal thread cold-extrusion processing technology is investigated for the purpose of improving the anti-fatigue serving life of internal thread. The superiorities of the plastic deformation law and surface integrity of the metal layer in the course of cold extrusion for improving its stability and economy are summed up. The proposed research forecasts the develop- ment tendency of the internal thread anti-fatigue manufacturing technology.
基金supported by the National Basic Research Program of China (Grant 2012CB937500)the National Natural Science Foundations of China (Grants 11172304 and 11202210)
文摘In this paper, ultrasonic （20 kHz） fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue （VHCF） regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area （FGA） centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.
文摘Studies were made of the symmetric tensile-compressive low cycle fatigue behaviour and the influence of dynamic strain aging(DSA)pre-treatment of 18-8 austenitic stainless steel. Within the testing amplitude range of strain.±0.5 % to±1.5 %,the three processes of cyclic hardening,cyclic saturation and cyclic softening were observed.In the same amplitude of strain,the peak stress of the samples pre-treated by DSA is higher than that of solid-solu- tion and cold working pre-treatment,but no remarkable differences of the fatigue lives of them were found.TEM observation shows that the uniform and stable dislocation networks with high density form after DSA pre-treatment,which increases the cyclic peak stress.The cyclic softening results from the low dislocation density and elongated cell structure with low energy.
文摘Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and damage evolution criteria. Furthermore,damage evolution equations of time rate are established by the generalized Drucker＇s postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations,and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise,for notched specimens under the repeated loading with constant strain amplitude,the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus,the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1,2 and 3.
文摘Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some of them were modified by the ceramic coating deposition surface treatment. The effects of ceramic coating, on the fatigue crack growth behaviour of hollow shaft specimens, were experimentally investigated. Fatigue crack growth rates, da/dN, were characterised, using the power law relationship between da/dN (in mm/cycle) and the stress intensity factor range, ΔK (in MPa∙m0.5). The two constants of the correlation are 7.9768 × 10−9 and 2.8107 for the parent material, and those for the coated material are 2.4391 × 10−9 and 3.1990, respectively. Microstructural analyses were carried out on the tested specimens, which shows that the maximum hardness of the ceramic coating is higher than that of substrate by a factor of ~3.2. The dimple fracture dominates the final fracture mechanism for the parent material, and the combination of fatigue, ductile fracture and cleavage dominates the final fracture mechanism for the coated material, based on the SEM analyses. EDS tests’ results reveal that the parent material specimen shows higher levels of C at matrix regions along with Fe- and O-rich regions, compared with the coated material specimen.
文摘Vitamin C and taurine (TR) are well known as active components for fatigue recovery. However, the mechanism of the anti-fatigue effects of vitamin C and TR is still unclear. Our study was designed to evaluate the anti-fatigue activities of vitamin C and TR in an animal test for fatigue and to compare the activities between vitamin C and TR. Materials and Methods: Vitamin C, TR or their combination were orally administrated to mice once daily for 15 days, and then metabolic activities such as blood glucose, triglyceride (TG), lactate, and lactate dehydrogenase (LDH) as well as antioxidant activities such as malondialdehyde (MDA) and superoxide dismutase (SOD) were determined (evaluated) after forced swimming test (FST). Results: Compared with the control group, C100, C200, and T50 showed a tendency to decrease mobility in FST. Moreover, TG (C100, C200, T200), LDH (C200), lactic acid (C100) and MDA (C50, C100, C200) levels were inhibited by vitamin C and TR. Conclusions: These results suggest that vitamin C and TR have anti-fatigue activities in mice, with vitamin C providing a stronger effect.
文摘利用Arnol'd的Legendrian理论,对三维Anti de Sitter空间中Lorentzian曲面进行了研究.引入光维高度函数概念研究了三维Anti de Sitter空间Lorentzian曲面的S1t×S1s-值、光锥Gauss映射的奇点,进行了奇点分类,揭示了类光Causs-kronecker曲率之间的关系;并研究了Lorentzian曲面的一些基本几何性质.
