Gradient nanostructure was introduced to enhance the strength and ductility via deformation incompatibility accommodated by geometrical necessary dislocations for most metallic materials recently.However,few intensive...Gradient nanostructure was introduced to enhance the strength and ductility via deformation incompatibility accommodated by geometrical necessary dislocations for most metallic materials recently.However,few intensive researches were carried out to investigate the effect of gradient structure on the deformation twin evolution and resulting performance improvements.In the present paper,we produced gradient-structured AZ31 Mg alloy with fine-grain layers,parallel twin laminates and a coarse-grain core from two upmost surfaces to the center of plate.Surprisingly,this architected Mg alloy exhibited simultaneous enhancement of strength and ductility.Subsequent microstructural observations demonstrated that abundant twin-twin interactions resulting from higher strength and multi-axial stress state could make great contributions to the increase of work-hardening capability.This was further proved by the measurement of full-field strain evolution during the plastic deformation.Such a design strategy may provide a new path for producing advanced structure materials in which the deformation twinning works as one of the dominant plasticity mechanisms.展开更多
The detonation wave-aiming warhead can effectively enhance the lethality efficiency. In the past, rules for casing rupture and velocity distribution under asymmetrical initiations were not adequately investigated. In ...The detonation wave-aiming warhead can effectively enhance the lethality efficiency. In the past, rules for casing rupture and velocity distribution under asymmetrical initiations were not adequately investigated. In this study, X-ray photography and numerical modelling are used to examine the casing expansions under centre point, asymmetrical one-point, and asymmetrical two-point(with central angles of 45° and 90°) initiations. The results indicate that early casing ruptures are caused by local high pressures, induced by the initiation, detonation wave interaction, and Mach wave onset. The fragment shapes are controlled by the impact angle of the detonation wave. The fragment velocity distributions differ under different initiation types, and the end rarefaction waves can affect the velocity distribution.This study can serve as a reference for the design and optimization of high-efficiency warheads.展开更多
Locoregional spread of abdominopelvic malignant tumors frequently results in peritoneal carcinomatosis(PC). The prognosis of PC patients treated by conventional systemic chemotherapy is poor, with a median survival of...Locoregional spread of abdominopelvic malignant tumors frequently results in peritoneal carcinomatosis(PC). The prognosis of PC patients treated by conventional systemic chemotherapy is poor, with a median survival of < 6 mo. However, over the past three decades, an integrated treatment strategy of cytoreductive surgery(CRS) + hyperthermic intraperitoneal chemotherapy(HIPEC) has been developed by the pioneering oncologists, with proved efficacy and safety in selected patients. Supported by several lines of clinical evidence from phases Ⅰ, Ⅱ and Ⅲ clinical trials, CRS + HIPEC has been regarded as the standard treatment for selected patients with PC in many established cancer centers worldwide. In China, an expert consensus on CRS + HIPEC has been reached by the leading surgical and medical oncologists, under the framework of the China Anti-Cancer Association. This expert consensus has summarized the progress in PC clinical studies and systematically evaluated the CRS + HIPEC procedures in China as well as across the world, so as to lay the foundation for formulating PC treatment guidelines specific to the national conditions of China.展开更多
AIM:To investigate the current status of peritoneal carcinomatosis(PC) management,as well as the usage of cytoreductive surgery(CRS) and hyperthermic intraperitoneal chemotherapy(HIPEC) in China's Mainland.METHODS...AIM:To investigate the current status of peritoneal carcinomatosis(PC) management,as well as the usage of cytoreductive surgery(CRS) and hyperthermic intraperitoneal chemotherapy(HIPEC) in China's Mainland.METHODS:A potentially curative therapeutic strategy for selecting patients with PC,known as "Techniques",consists of CRS in combination with HIPEC.A systemic search of published works and clinical trials was performed.Additional papers were retrieved by crosschecking references and obtaining information from Chinese oncologists and relevant conferences.One hundred and one papers and one registered clinical trial on HIPEC were included.RESULTS:A literature review identified 86 hospitals in 25 out of all 31 areas of China's Mainland that perform HIPEC.The earliest report included in our survey was published in 1993.Different approaches to HIPEC have been utilized,i.e.palliative,prophylactic,and possiblycurative treatment.Only one center has consistently performed HIPEC according to the "Sugarbaker Protocol",which involves evaluating the extent of PC with peritoneal cancer index and the results of CRS with the completeness of cytoreduction.Positive preliminary results were reported:7 of 21 patients with PC survived,free of tumors,during an 8-43-mo follow-up period.Hyperthermic strategies that include HIPEC have been practiced for a long time in China's Mainland,whereas the "Sugarbaker Protocol/Techniques" has been only rarely implemented in China.The Peritoneal Surface Oncology Group International hosts a biannual workshop with the intent to train more specialists in this field and provide support for the construction of quality treatment centers,especially in developing countries like China,whose population is huge and has a dramatically increased incidence of cancer.CONCLUSION:To popularize Sugarbaker Protocol/Techniques in China's Mainland in PC management arising from gastric cancer or colorectal cancer will be the responsibility of the upcoming Chinese Peritoneal Surface Oncology Group.展开更多
AIM: To collect the evidence to estimate the correlation between smoking and the incidence of dry eye. METHODS: The Pub Med,EMBASE,the Cochrane Central Register of Controlled Trials(CENTRAL,last issue),CBM(Chinese Bio...AIM: To collect the evidence to estimate the correlation between smoking and the incidence of dry eye. METHODS: The Pub Med,EMBASE,the Cochrane Central Register of Controlled Trials(CENTRAL,last issue),CBM(Chinese Bio Medical Literature Database),and CNKI(China National Knowledge Infrastructure/Chinese Academic Journals full-text Database) were searched for eligible studies published from January1964 to December 2015 to investigate the association of smoking with the risk of dry eye.The odds ratio(OR)and 95% confidence interval(CI) were summarized and calculated.The extracted studies were pooled by the fixed-effects model or a random-effects model. RESULTS: Two cohort studies and eight cross-sectional surveys were included in our Meta-analysis.There was no statistically significant relationship between current(OR=1.32; 95% CI: 0.99-1.76; P=0.055)or ever smoking(OR=1.12; 95% CI: 0.98-1.28; P=0.107)and the risk of dry eye among the studies,even when age and gender were adjusted(OR=1.16; 95% CI: 0.83-1.64; P=0.383).In the sensitivity analysis in which only general population were included,the association was significant between smoking and dry eye(OR=1.50; 95%CI: 1.08-2.09; P=0.016).CONCLUSION: This Meta-analysis suggests that smoking may associate with the risk of dry eye in general population.展开更多
Objective:The aim of this study was to evaluate the recent efficacy and adverse reactions of paclitaxel liposome plus nedaplatin in the treatment of advanced non-small cell lung cancer (NSCLC).Methods:Seventeen cases ...Objective:The aim of this study was to evaluate the recent efficacy and adverse reactions of paclitaxel liposome plus nedaplatin in the treatment of advanced non-small cell lung cancer (NSCLC).Methods:Seventeen cases of NSCLC treated with paclitaxel liposome and nedaplatin for 2 to 6 cycles,by infusing paclitaxel liposome 135 mg/m2 for 3 h on d1 and nedaplatin 80 mg/m2 as infusion on d2.Results:Among 17 patients being evaluated for response to treatment,1 achieved complete response (CR),4 achieved partial response (PR),3 achieved stable disease (SD),9 achieved progress disease (PD).The main adverse reaction was haematological toxicities,especially leukopenia and thrombocytopenia.The non-haematological toxicities included nausea,vomiting,mild hepatic dysfunction,alopecia and so on.Conclusion:Paclitaxel liposome plus nedaplatin was effective and well tolerated for treating patients with advanced NSCLC.展开更多
The compressive stress-strain relationships of 6061Al alloy over wide temperatures and strain rates are investigated. The dynamic impact experiments are performed using an improved high temperature split Hopkinson pre...The compressive stress-strain relationships of 6061Al alloy over wide temperatures and strain rates are investigated. The dynamic impact experiments are performed using an improved high temperature split Hopkinson pressure bar apparatus. The experimental results are compared with those obtained by the modified Johnson-Cook constitutive model. It is found that the dynamic mechanical behavior depends sensitively on temperature under relatively low strain rates or on strain rate at relatively high temperatures. The good agreement indicates that it is valid to adopt the parameter identification method and the constitutive model to describe and predict the mechanical response of materials.展开更多
Ballistic impact tests were carried out with examined projectiles of the Ti-6Al-4V titanium alloy to investigate the impact response of the 2618 aluminum plates at a nominal velocity of 210 m/s. The influence of proje...Ballistic impact tests were carried out with examined projectiles of the Ti-6Al-4V titanium alloy to investigate the impact response of the 2618 aluminum plates at a nominal velocity of 210 m/s. The influence of projectile forms and oblique angles on damage formation was particularly discussed by applying different loading conditions such as multiple projectile forms and oblique angles. Additionally, the numerical simulation method was employed to provide further insight into the characteristics of damage and target responses. The Johnson-Cook(J-C)constitutive model with revised failure parameters was used to support the simulations to assess target responses and characteristics of the damage created from different impact conditions. Results show that there is a significant transition in the deformation mode as changes of the projectile form are applied. Moreover, the cracks on the back of the 2618 aluminum alloy plates impacted by the solid plate projectile and the hollow blade projectile tend to locate at different positions, which are supposed to be influenced by local bending and stretching. The work in this paper may provide guidance for the design of fan blade containment systems.展开更多
In the present work, we explore the strain hardening behaviors as well as the effect of temperature on the plastic deformation of ultrafine grained aluminum. The temperature sensitivity is determined and compared with...In the present work, we explore the strain hardening behaviors as well as the effect of temperature on the plastic deformation of ultrafine grained aluminum. The temperature sensitivity is determined and compared with that of coarse grained material. The results indicate that the flow stress of ultrafine grained aluminum displays enhanced sensitivity to temperature. The reduction in activation volume is suggested to be the major reason for the enhanced temperature sensitivity as grain size is refined into the sub-micrometer regime. Finally, a phenomenological constitutive model is proposed to describe the post-yield response of ultrafine grained aluminum.展开更多
Lean alloy(low alloyed)is beneficial for long-term sustainable development of metal materials.Creating a nanocrystalline microstructure is a desirable approach to improve biodegradability and mechanical properties of ...Lean alloy(low alloyed)is beneficial for long-term sustainable development of metal materials.Creating a nanocrystalline microstructure is a desirable approach to improve biodegradability and mechanical properties of lean biomedical Mg alloy,but it is nearly impossible to realize.In the present study,the bulk nanocrystalline Mg alloy(average grain size:~70 nm)was successfully obtained by hot rolling process of a lean Mg-2wt.%Zn(Z2)alloy and both high strength((223 MPa(YS)and 260 MPa(UTS))and good corrosion resistance(corrosion rate in vivo:0.2 mm/year)could be achieved.The microstructure evolution during the rolling process was analyzed and discussed.Several factors including large strain,fine grains,strong basal texture,high temperature and Zn segregation conjointly provided the possibility for the activation of pyramidal<c+a>slip to produce nanocrystals.This finding could provide a new development direction and field of application for lean biomedical Mg alloys.展开更多
The adiabatic shear instability of ductile materials has attracted more and more attentions of researchers and groups,who have been sparing no effort in further understanding of the underlying mechanism since the firs...The adiabatic shear instability of ductile materials has attracted more and more attentions of researchers and groups,who have been sparing no effort in further understanding of the underlying mechanism since the first experimental depiction of adiabatic shear instability by Zener and Hollomon.As for the adiabatic shear instability,many factors account for its occurrence,including heat conduction,inertia effect,microstructure effect and so on.However,lots of experimental evidence has shown that metal materials display a strong size effect when the characteristic length scale is in the order of microns.The size effect has also been observed in the analysis of shear band in the ductile materials because the order of the bandwidth stays within the microscale range.However,a comprehensive understanding of the whole process of adiabatic shear banding(ASB),including the early onset and the subsequent evolution,is still lacking.In this work,a gradient plasticity model based on the Taylor-based nonlocal theory feasible for the linear perturbation analysis and convenient for numerical calculation is proposed to investigate the strain gradient on the onset of ASB and the coupling effect of heat conduction,inertia effect and strain gradient at the early stage,as well as on the subsequent evolution process at later stages.As for the onset of ASB,the linear perturbation method is used to consider the effect on the initial formation of ASB.After the investigation of the onset of ASB.the characteristic line method is applied to describe the subsequent nonlinear evolution process of ASB.Three stages of ASB evolution are clearly depicted during the evolution process,and the significance of size effect on the ASB nonlinear evolution process of ASB at different stages is analyzed.With the help of linear perturbation analysis and characteristic line method,a comprehensive description of the role of strain gradient in the ASB from the early onset to the end of the evolution is provided.展开更多
In the present work,the uniaxial compressive mechanical proper\ties of ultrafine grained(UFG)aluminum produced by equal channel angular pressing method were investigated experimentally over a wide temperatures ranging...In the present work,the uniaxial compressive mechanical proper\ties of ultrafine grained(UFG)aluminum produced by equal channel angular pressing method were investigated experimentally over a wide temperatures ranging from 77 to 473 K under both quasi-static and dynamic loading conditions.Based on the experimental results,the strain rate,temperature sensitivity,and the apparent activation volume were estimated.The coupling effects of both experimental temperature and applied strain rate on thermal-activated plastic deformation behavior were also investigated.Based on the thermal activation theory,the rate-controlling mechanisms for the UFG aluminum under both quasi-static and dynamic loading conditions were discussed.展开更多
基金This work was financially supported by National Natural Science Foundation of China(Grant Nos.11772268 and 12025205).The authors would like to appreciate the researchers in Nanjing university of science and technology for their support in preparation of gradient structured materials.
文摘Gradient nanostructure was introduced to enhance the strength and ductility via deformation incompatibility accommodated by geometrical necessary dislocations for most metallic materials recently.However,few intensive researches were carried out to investigate the effect of gradient structure on the deformation twin evolution and resulting performance improvements.In the present paper,we produced gradient-structured AZ31 Mg alloy with fine-grain layers,parallel twin laminates and a coarse-grain core from two upmost surfaces to the center of plate.Surprisingly,this architected Mg alloy exhibited simultaneous enhancement of strength and ductility.Subsequent microstructural observations demonstrated that abundant twin-twin interactions resulting from higher strength and multi-axial stress state could make great contributions to the increase of work-hardening capability.This was further proved by the measurement of full-field strain evolution during the plastic deformation.Such a design strategy may provide a new path for producing advanced structure materials in which the deformation twinning works as one of the dominant plasticity mechanisms.
基金funded by the National Natural Science Foundation of China [Grant No. 12002178]opening project of the State Key Laboratory of Explosion Science and Technology (Beijing Institute of Technology) [Grant No. KFJJ22-17M]the Fundamental Research Funds for Central Universities
文摘The detonation wave-aiming warhead can effectively enhance the lethality efficiency. In the past, rules for casing rupture and velocity distribution under asymmetrical initiations were not adequately investigated. In this study, X-ray photography and numerical modelling are used to examine the casing expansions under centre point, asymmetrical one-point, and asymmetrical two-point(with central angles of 45° and 90°) initiations. The results indicate that early casing ruptures are caused by local high pressures, induced by the initiation, detonation wave interaction, and Mach wave onset. The fragment shapes are controlled by the impact angle of the detonation wave. The fragment velocity distributions differ under different initiation types, and the end rarefaction waves can affect the velocity distribution.This study can serve as a reference for the design and optimization of high-efficiency warheads.
基金Supported by Key Project of the National Natural Science Foundation of China,No.81230031
文摘Locoregional spread of abdominopelvic malignant tumors frequently results in peritoneal carcinomatosis(PC). The prognosis of PC patients treated by conventional systemic chemotherapy is poor, with a median survival of < 6 mo. However, over the past three decades, an integrated treatment strategy of cytoreductive surgery(CRS) + hyperthermic intraperitoneal chemotherapy(HIPEC) has been developed by the pioneering oncologists, with proved efficacy and safety in selected patients. Supported by several lines of clinical evidence from phases Ⅰ, Ⅱ and Ⅲ clinical trials, CRS + HIPEC has been regarded as the standard treatment for selected patients with PC in many established cancer centers worldwide. In China, an expert consensus on CRS + HIPEC has been reached by the leading surgical and medical oncologists, under the framework of the China Anti-Cancer Association. This expert consensus has summarized the progress in PC clinical studies and systematically evaluated the CRS + HIPEC procedures in China as well as across the world, so as to lay the foundation for formulating PC treatment guidelines specific to the national conditions of China.
文摘AIM:To investigate the current status of peritoneal carcinomatosis(PC) management,as well as the usage of cytoreductive surgery(CRS) and hyperthermic intraperitoneal chemotherapy(HIPEC) in China's Mainland.METHODS:A potentially curative therapeutic strategy for selecting patients with PC,known as "Techniques",consists of CRS in combination with HIPEC.A systemic search of published works and clinical trials was performed.Additional papers were retrieved by crosschecking references and obtaining information from Chinese oncologists and relevant conferences.One hundred and one papers and one registered clinical trial on HIPEC were included.RESULTS:A literature review identified 86 hospitals in 25 out of all 31 areas of China's Mainland that perform HIPEC.The earliest report included in our survey was published in 1993.Different approaches to HIPEC have been utilized,i.e.palliative,prophylactic,and possiblycurative treatment.Only one center has consistently performed HIPEC according to the "Sugarbaker Protocol",which involves evaluating the extent of PC with peritoneal cancer index and the results of CRS with the completeness of cytoreduction.Positive preliminary results were reported:7 of 21 patients with PC survived,free of tumors,during an 8-43-mo follow-up period.Hyperthermic strategies that include HIPEC have been practiced for a long time in China's Mainland,whereas the "Sugarbaker Protocol/Techniques" has been only rarely implemented in China.The Peritoneal Surface Oncology Group International hosts a biannual workshop with the intent to train more specialists in this field and provide support for the construction of quality treatment centers,especially in developing countries like China,whose population is huge and has a dramatically increased incidence of cancer.CONCLUSION:To popularize Sugarbaker Protocol/Techniques in China's Mainland in PC management arising from gastric cancer or colorectal cancer will be the responsibility of the upcoming Chinese Peritoneal Surface Oncology Group.
基金Supported by National Natural Science Foundation(No.81370992No.81570812)Research Foundation of Shanghai Science and Technology Committee(No.14411960600)
文摘AIM: To collect the evidence to estimate the correlation between smoking and the incidence of dry eye. METHODS: The Pub Med,EMBASE,the Cochrane Central Register of Controlled Trials(CENTRAL,last issue),CBM(Chinese Bio Medical Literature Database),and CNKI(China National Knowledge Infrastructure/Chinese Academic Journals full-text Database) were searched for eligible studies published from January1964 to December 2015 to investigate the association of smoking with the risk of dry eye.The odds ratio(OR)and 95% confidence interval(CI) were summarized and calculated.The extracted studies were pooled by the fixed-effects model or a random-effects model. RESULTS: Two cohort studies and eight cross-sectional surveys were included in our Meta-analysis.There was no statistically significant relationship between current(OR=1.32; 95% CI: 0.99-1.76; P=0.055)or ever smoking(OR=1.12; 95% CI: 0.98-1.28; P=0.107)and the risk of dry eye among the studies,even when age and gender were adjusted(OR=1.16; 95% CI: 0.83-1.64; P=0.383).In the sensitivity analysis in which only general population were included,the association was significant between smoking and dry eye(OR=1.50; 95%CI: 1.08-2.09; P=0.016).CONCLUSION: This Meta-analysis suggests that smoking may associate with the risk of dry eye in general population.
文摘Objective:The aim of this study was to evaluate the recent efficacy and adverse reactions of paclitaxel liposome plus nedaplatin in the treatment of advanced non-small cell lung cancer (NSCLC).Methods:Seventeen cases of NSCLC treated with paclitaxel liposome and nedaplatin for 2 to 6 cycles,by infusing paclitaxel liposome 135 mg/m2 for 3 h on d1 and nedaplatin 80 mg/m2 as infusion on d2.Results:Among 17 patients being evaluated for response to treatment,1 achieved complete response (CR),4 achieved partial response (PR),3 achieved stable disease (SD),9 achieved progress disease (PD).The main adverse reaction was haematological toxicities,especially leukopenia and thrombocytopenia.The non-haematological toxicities included nausea,vomiting,mild hepatic dysfunction,alopecia and so on.Conclusion:Paclitaxel liposome plus nedaplatin was effective and well tolerated for treating patients with advanced NSCLC.
基金Project supported by the State 973 Program of China (No. 2013CB03570)the National Natural Science Foundation of China (Nos. 11272259, 11002104, 10902090 and 11021202)
文摘The compressive stress-strain relationships of 6061Al alloy over wide temperatures and strain rates are investigated. The dynamic impact experiments are performed using an improved high temperature split Hopkinson pressure bar apparatus. The experimental results are compared with those obtained by the modified Johnson-Cook constitutive model. It is found that the dynamic mechanical behavior depends sensitively on temperature under relatively low strain rates or on strain rate at relatively high temperatures. The good agreement indicates that it is valid to adopt the parameter identification method and the constitutive model to describe and predict the mechanical response of materials.
基金financial support from the National Natural Science Foundation of China (No. 11772268, 11522220, 11627901 and 11527803)
文摘Ballistic impact tests were carried out with examined projectiles of the Ti-6Al-4V titanium alloy to investigate the impact response of the 2618 aluminum plates at a nominal velocity of 210 m/s. The influence of projectile forms and oblique angles on damage formation was particularly discussed by applying different loading conditions such as multiple projectile forms and oblique angles. Additionally, the numerical simulation method was employed to provide further insight into the characteristics of damage and target responses. The Johnson-Cook(J-C)constitutive model with revised failure parameters was used to support the simulations to assess target responses and characteristics of the damage created from different impact conditions. Results show that there is a significant transition in the deformation mode as changes of the projectile form are applied. Moreover, the cracks on the back of the 2618 aluminum alloy plates impacted by the solid plate projectile and the hollow blade projectile tend to locate at different positions, which are supposed to be influenced by local bending and stretching. The work in this paper may provide guidance for the design of fan blade containment systems.
基金supported by the National Natural Science Foundation of China(Nos.11272267,11102168 and 10932008)111 Project(No.B07050)of Northwestern Polytechnical University
文摘In the present work, we explore the strain hardening behaviors as well as the effect of temperature on the plastic deformation of ultrafine grained aluminum. The temperature sensitivity is determined and compared with that of coarse grained material. The results indicate that the flow stress of ultrafine grained aluminum displays enhanced sensitivity to temperature. The reduction in activation volume is suggested to be the major reason for the enhanced temperature sensitivity as grain size is refined into the sub-micrometer regime. Finally, a phenomenological constitutive model is proposed to describe the post-yield response of ultrafine grained aluminum.
基金support from the Australian Microscopy and Microanalysis Research Facility node at the University of Sydneysupported by the Australian Research Council(DP190102243)。
基金This work was funded by the National Key R&D Program of China(No.2018YFC1106600)the“Science and Technology Innovation 2025”Major Special Project of Ningbo(No.2019B10064).
文摘Lean alloy(low alloyed)is beneficial for long-term sustainable development of metal materials.Creating a nanocrystalline microstructure is a desirable approach to improve biodegradability and mechanical properties of lean biomedical Mg alloy,but it is nearly impossible to realize.In the present study,the bulk nanocrystalline Mg alloy(average grain size:~70 nm)was successfully obtained by hot rolling process of a lean Mg-2wt.%Zn(Z2)alloy and both high strength((223 MPa(YS)and 260 MPa(UTS))and good corrosion resistance(corrosion rate in vivo:0.2 mm/year)could be achieved.The microstructure evolution during the rolling process was analyzed and discussed.Several factors including large strain,fine grains,strong basal texture,high temperature and Zn segregation conjointly provided the possibility for the activation of pyramidal<c+a>slip to produce nanocrystals.This finding could provide a new development direction and field of application for lean biomedical Mg alloys.
基金the financial support from the National Natural Science Foundation of China(Grant Nos.11522220,11772268,11527803,11390361).
文摘The adiabatic shear instability of ductile materials has attracted more and more attentions of researchers and groups,who have been sparing no effort in further understanding of the underlying mechanism since the first experimental depiction of adiabatic shear instability by Zener and Hollomon.As for the adiabatic shear instability,many factors account for its occurrence,including heat conduction,inertia effect,microstructure effect and so on.However,lots of experimental evidence has shown that metal materials display a strong size effect when the characteristic length scale is in the order of microns.The size effect has also been observed in the analysis of shear band in the ductile materials because the order of the bandwidth stays within the microscale range.However,a comprehensive understanding of the whole process of adiabatic shear banding(ASB),including the early onset and the subsequent evolution,is still lacking.In this work,a gradient plasticity model based on the Taylor-based nonlocal theory feasible for the linear perturbation analysis and convenient for numerical calculation is proposed to investigate the strain gradient on the onset of ASB and the coupling effect of heat conduction,inertia effect and strain gradient at the early stage,as well as on the subsequent evolution process at later stages.As for the onset of ASB,the linear perturbation method is used to consider the effect on the initial formation of ASB.After the investigation of the onset of ASB.the characteristic line method is applied to describe the subsequent nonlinear evolution process of ASB.Three stages of ASB evolution are clearly depicted during the evolution process,and the significance of size effect on the ASB nonlinear evolution process of ASB at different stages is analyzed.With the help of linear perturbation analysis and characteristic line method,a comprehensive description of the role of strain gradient in the ASB from the early onset to the end of the evolution is provided.
基金This work was performed under the financial support from the National Science Foundation of China[grant number 11522220].
文摘In the present work,the uniaxial compressive mechanical proper\ties of ultrafine grained(UFG)aluminum produced by equal channel angular pressing method were investigated experimentally over a wide temperatures ranging from 77 to 473 K under both quasi-static and dynamic loading conditions.Based on the experimental results,the strain rate,temperature sensitivity,and the apparent activation volume were estimated.The coupling effects of both experimental temperature and applied strain rate on thermal-activated plastic deformation behavior were also investigated.Based on the thermal activation theory,the rate-controlling mechanisms for the UFG aluminum under both quasi-static and dynamic loading conditions were discussed.
