Wafer curvature method has been applied to determine the internal stress in the films using Stoney＇s equation.During the film deposition,the wafer fixation on the sample holder will restrict the deformation of the re...Wafer curvature method has been applied to determine the internal stress in the films using Stoney＇s equation.During the film deposition,the wafer fixation on the sample holder will restrict the deformation of the rectangle-shaped wafer,which may result in the stress datum difference along length and width direction.In this paper,the effect of wafer size and the wafer fixation on the TiN film internal stress measured by wafer curvature method was discussed.The rectangle-shaped wafers with different length/width ratios（L/W=1：1,2：1,3：1 and 4：1） were fixed as a cantilever beam.After the TiN films deposition,the profiles of the film/wafer were measured using a stylus profilometer and then the internal stress was calculated using the Stoney equation in the film.The results showed that the fixed end of the wafers limited to some degree the curvature of the wafers along the width direction.For film internal stress measured by wafer curvature method,the wafer profile should be scanned along the length direction and the scan distance should be greater than or equal to half of wafer length.When the length/width ratio of the wafer reached 3：1,the wafer curvature and the calculated stress were basically the same at different positions along the length direction.For film internal stress measured by wafer curvature method,it was recommended that the length/width ratio of wafer should be considered to be greater than or equal to 3：1,and the deformed profile was scanned along the length direction.展开更多
Considering the variable cross section thickness of longitudinal profiled plate and the dynamic reductions of straightening rolls,an analytical model combining curvature integral method with linear decreasing straight...Considering the variable cross section thickness of longitudinal profiled plate and the dynamic reductions of straightening rolls,an analytical model combining curvature integral method with linear decreasing straightening scheme was proposed to investigate the longitudinal profiled plate straightening process.Moreover,the calculation flow and solution algorithm of longitudinal profiled plate straightening process were presented.To verify the proposed model,calculated straightening forces were compared with the measured values,and very good agreements were achieved.Then,the reduction,contact angle,reverse bending curvature,residual curvature,straightening force and straightening moment of longitudinal profiled plate in the straightening process were calculated and analyzed,and the calculated results show that the curvature integral method can be used to reveal the mechanism of longitudinal profiled plate straightening.展开更多
Damage detection and localization analysis have gained increasing importance over the years,due to the growing number of catastrophic events and the associated risks that small,undetected cracks in structures may evol...Damage detection and localization analysis have gained increasing importance over the years,due to the growing number of catastrophic events and the associated risks that small,undetected cracks in structures may evolve into severe failures if not identified in time.In this context,vibration-based methods have been extensively investigated for structural damage detection.Among them,one of the most widely used approaches since its introduction is the curvature method.It has been successfully employed in numerous studies,consistently providing reliable results.However,the use of second-order or higher-order derivatives can be challenging when dealing with experimental data,as these are highly sensitive tomeasurement noise.Conversely,using the first derivative may simplify the analysis while maintaining robustness.Therefore,the present work introduces and experimentally demonstrates an extension of the curvature-based approach,focusing on the integration of the first derivative for damage localization.In particular,both methods based on the use of the second and first derivatives were applied to detect their capability in detecting and localizing the damage.This was tested on a slender truss structure,with induced damages at different locations,equal to just 1.069%of the structure volume.The results,obtained from this real-world case study,show that for certain structures,like slender ones,the use of the first derivative can achieve equal or even superior damage detection performance compared to the traditional second derivative method.Specifically,the comparison was evaluated based on the accuracy in localizing the damage with the twomethods,both froma visual and quantitative point of view,since a deviation index δ was also introduced.展开更多
To make the large-scale helium cryogenic system of fusion device EAST （experimen- tal advanced super-conducting tokamak） run stably, as the core part, the helium turbine expander must meet the requirement of refrige...To make the large-scale helium cryogenic system of fusion device EAST （experimen- tal advanced super-conducting tokamak） run stably, as the core part, the helium turbine expander must meet the requirement of refrigeration capacity. However, previous designs were based on one dimension flow to determine the average fluid parameters and geometric parameters of impeller cross-sections, so that it could not describe real physical processes in the internal flow of the tur- bine expander. Therefore, based on the inverse proposition of streamline curvature method in the context of quasi-three-dimensional flows, the all-over-controlled vortex concept was adopted to design the impeller under specified condition. The wrap angle of the impeller blade and the whole flow distribution on the meridian plane were obtained; meanwhile the performance of the designed impeller was analyzed. Thus a new design method is proposed here for the inverse proposition of the helium turbine expander impeller.展开更多
基金Funded by National Scholastic Athletics Foundotion(NSAF)(No.U1330113)National Natural Science Foundation of China(No.81271953)
文摘Wafer curvature method has been applied to determine the internal stress in the films using Stoney＇s equation.During the film deposition,the wafer fixation on the sample holder will restrict the deformation of the rectangle-shaped wafer,which may result in the stress datum difference along length and width direction.In this paper,the effect of wafer size and the wafer fixation on the TiN film internal stress measured by wafer curvature method was discussed.The rectangle-shaped wafers with different length/width ratios（L/W=1：1,2：1,3：1 and 4：1） were fixed as a cantilever beam.After the TiN films deposition,the profiles of the film/wafer were measured using a stylus profilometer and then the internal stress was calculated using the Stoney equation in the film.The results showed that the fixed end of the wafers limited to some degree the curvature of the wafers along the width direction.For film internal stress measured by wafer curvature method,the wafer profile should be scanned along the length direction and the scan distance should be greater than or equal to half of wafer length.When the length/width ratio of the wafer reached 3：1,the wafer curvature and the calculated stress were basically the same at different positions along the length direction.For film internal stress measured by wafer curvature method,it was recommended that the length/width ratio of wafer should be considered to be greater than or equal to 3：1,and the deformed profile was scanned along the length direction.
基金The authors are grateful for the supports of the National Key Research and Development Program of China(No.2017YFB0306404)Key Project of Hebei Education Department(No.ZD2018203).
文摘Considering the variable cross section thickness of longitudinal profiled plate and the dynamic reductions of straightening rolls,an analytical model combining curvature integral method with linear decreasing straightening scheme was proposed to investigate the longitudinal profiled plate straightening process.Moreover,the calculation flow and solution algorithm of longitudinal profiled plate straightening process were presented.To verify the proposed model,calculated straightening forces were compared with the measured values,and very good agreements were achieved.Then,the reduction,contact angle,reverse bending curvature,residual curvature,straightening force and straightening moment of longitudinal profiled plate in the straightening process were calculated and analyzed,and the calculated results show that the curvature integral method can be used to reveal the mechanism of longitudinal profiled plate straightening.
文摘Damage detection and localization analysis have gained increasing importance over the years,due to the growing number of catastrophic events and the associated risks that small,undetected cracks in structures may evolve into severe failures if not identified in time.In this context,vibration-based methods have been extensively investigated for structural damage detection.Among them,one of the most widely used approaches since its introduction is the curvature method.It has been successfully employed in numerous studies,consistently providing reliable results.However,the use of second-order or higher-order derivatives can be challenging when dealing with experimental data,as these are highly sensitive tomeasurement noise.Conversely,using the first derivative may simplify the analysis while maintaining robustness.Therefore,the present work introduces and experimentally demonstrates an extension of the curvature-based approach,focusing on the integration of the first derivative for damage localization.In particular,both methods based on the use of the second and first derivatives were applied to detect their capability in detecting and localizing the damage.This was tested on a slender truss structure,with induced damages at different locations,equal to just 1.069%of the structure volume.The results,obtained from this real-world case study,show that for certain structures,like slender ones,the use of the first derivative can achieve equal or even superior damage detection performance compared to the traditional second derivative method.Specifically,the comparison was evaluated based on the accuracy in localizing the damage with the twomethods,both froma visual and quantitative point of view,since a deviation index δ was also introduced.
文摘To make the large-scale helium cryogenic system of fusion device EAST （experimen- tal advanced super-conducting tokamak） run stably, as the core part, the helium turbine expander must meet the requirement of refrigeration capacity. However, previous designs were based on one dimension flow to determine the average fluid parameters and geometric parameters of impeller cross-sections, so that it could not describe real physical processes in the internal flow of the tur- bine expander. Therefore, based on the inverse proposition of streamline curvature method in the context of quasi-three-dimensional flows, the all-over-controlled vortex concept was adopted to design the impeller under specified condition. The wrap angle of the impeller blade and the whole flow distribution on the meridian plane were obtained; meanwhile the performance of the designed impeller was analyzed. Thus a new design method is proposed here for the inverse proposition of the helium turbine expander impeller.
