This paper derives a mathematical description of the complex stretch processor’s response to bandlimited Gaussian noise having arbitrary center frequency and bandwidth. The description of the complex stretch processo...This paper derives a mathematical description of the complex stretch processor’s response to bandlimited Gaussian noise having arbitrary center frequency and bandwidth. The description of the complex stretch processor’s random output comprises highly accurate closed-form approximations for the probability density function and the autocorrelation function. The solution supports the complex stretch processor’s usage of any conventional range-sidelobe-reduction window. The paper then identifies two practical applications of the derived description. Digital-simulation results for the two identified applications, assuming the complex stretch processor uses the rectangular, Hamming, Blackman, or Kaiser window, verify the derivation’s correctness through favorable comparison to the theoretically predicted behavior.展开更多
The stretch flanging process is significantly affected by various geometrical,material and process parameters.The punch-die clearance and initial flange length are main parameters which have major effects on the edge ...The stretch flanging process is significantly affected by various geometrical,material and process parameters.The punch-die clearance and initial flange length are main parameters which have major effects on the edge crack location and strain distribution along die profile radius in the flange.Non-axisymmetric stretch flanging process of AA-5052 sheet metal blanks was carried out by numerical simulation to predict the deformation behavior of flange,location and propagation of crack in flange and to investigate the effect of punch die clearance,flange length,die and punch profile radius and friction in the stretch flanging process.The experimental investigations were made to validate the simulations results.The results reveal that the crack length increases with the increase in the flange length.It is found that the flange length has a significant effect in circumferential direction as compared with the radial direction.The punch die clearance has the most significant effect in crack propagation in comparison with flange length.The circumferential strain is found to be larger in the case of punch having the profile radius less than the die profile radius,which leads to faster edge crack propagation.A close agreement is found between simulation and experimental results in terms of location of edge crack and forming load.展开更多
This study presents a parameter selection strategy developed for the Stretch-Blow Molding (SBM) process to minimize the weight of preforms used. The method is based on a predictive model developed using Neural Network...This study presents a parameter selection strategy developed for the Stretch-Blow Molding (SBM) process to minimize the weight of preforms used. The method is based on a predictive model developed using Neural Networks. The temperature distribution model of the preform was predicted using a 3-layer NN model with supervised backpropagation learning. In addition, the model was used to predict the uniform air pressure applied inside the preform, taking into account the relationship between the internal air pressure and the volume of the preform. Parameters were validated using in situ tests and measurements performed on several weights and lengths of a 0.330 Liter Polyethylene Terephthalate (PET) bottles. Tests showed that the model adequately predicts both the blowing kinematics, mainly zone temperatures and blowing and stretching pressures along the walls of the bottle while maintaining the bottle strength and top load requirements. In the second step, the model was combined to automatically compute the lowest preform weight that can be used for a particular 330 ml bottle design providing a uniform wall thickness distribution.展开更多
Young＇s modulus of biaxially oriented polypropylene （BOPP） films prepared with homemade film stretcher was investigated, which can be used to indicate the softness of films. It was found that the modulus of films w...Young＇s modulus of biaxially oriented polypropylene （BOPP） films prepared with homemade film stretcher was investigated, which can be used to indicate the softness of films. It was found that the modulus of films was decreased by about 69% as the content of polyethylene （PE） added into polypropylene （PP） reached 30%. Also, increasing draw temperature can induce lower stress level during stretching, which may lead to the formation of crystals with low orientation level and thus decreased modulus of films. Based on laboratory study, BOPP films produced on commercial line were studied by differential scanning calorimetry （DSC）, wide and small-angle X-ray scattering （WAXS, SAXS） with varying contents of PE. SAXS results show that the crystals are oriented in both machine direction （MD） and transverse direction （TD）, and the crystals are more oriented in TD than MD according to the WAXS results for all films. Also, the orientation parameter of crystal along TD increases from 0.68 to 0.83 as the contents of PE increase from 0% to 25%. Meanwhile, the modulus of films in MD declines with increase of PE contents generally, improving the film softness. Orientation of crystals is thus an effective structure parameter to adjust the film softness. The relationship of processing-structure-property is also established.展开更多
A biaxial stretching equipment was designed and constructed to enable fundamental studies of the relationship between film processing conditions and structures of oriented film products. With programmable drive motors...A biaxial stretching equipment was designed and constructed to enable fundamental studies of the relationship between film processing conditions and structures of oriented film products. With programmable drive motors and scissorlike mechanism, all stretching modes, including uniaxial stretching with constant and free width, simultaneous and sequential biaxial stretching, can be applied to a square-shaped sheet. Parameters related to film stretching manufacturing, such as temperature, draw ratio and stretching speed can be set independently to meet the requirement of different polymers. The force information during stretching is recorded by two miniature tension sensors in two directions independently, which can monitor the mechanical stimulus and stress response. Using this equipment, experiments are conducted to investigate the influence of stretching parameters on the structure of polypropylene films, which provides an effective method to tailor the processing conditions to obtain the films with desired properties.展开更多
Comprehensive performances of polytetrafluoroethylene(PTFE) flat filaments used as suture materials in medical field can be affected significantly by morphological and mechanical characteristics.Due to low tensile str...Comprehensive performances of polytetrafluoroethylene(PTFE) flat filaments used as suture materials in medical field can be affected significantly by morphological and mechanical characteristics.Due to low tensile strength and non-uniform morphology,PTFE flat filaments cannot be applied widely as medical sutures.In order to solve flaws above,PTFE flat filaments with constant linear density,550 dtex,are manufactured and dependences of morphology,frictional features and mechanical behaviors on stretching ratio and temperature are also analyzed.The results indicate that PTFE flat filaments with high tensile strength(1 922.0 cN) and excellent apparent performance can be manufactured at optimal stretching ratio and temperature,18.0 and350 ℃,respectively.展开更多
The stretching process,as a key phase of web production system,pursues the target velocities of rollers and the web tensions of spans between the successive rollers to guarantee proper stretching ratios. This requires...The stretching process,as a key phase of web production system,pursues the target velocities of rollers and the web tensions of spans between the successive rollers to guarantee proper stretching ratios. This requires the stable velocities and velocity ratios of large number rollers separated throughout the workshop. To this goal,a distributed cooperative controller is designed to coordinate the velocities of the rollers to the desired values as well as the target ratios between the upper and lower rollers. During the whole evolution,only the neighbor rollers can exchange the working information,and neither global information nor central controller is required. It is proven that all the rollers asymptotically achieve the desired velocity ratios via the proposed control law,which is also demonstrated by numerical simulation.展开更多
文摘This paper derives a mathematical description of the complex stretch processor’s response to bandlimited Gaussian noise having arbitrary center frequency and bandwidth. The description of the complex stretch processor’s random output comprises highly accurate closed-form approximations for the probability density function and the autocorrelation function. The solution supports the complex stretch processor’s usage of any conventional range-sidelobe-reduction window. The paper then identifies two practical applications of the derived description. Digital-simulation results for the two identified applications, assuming the complex stretch processor uses the rectangular, Hamming, Blackman, or Kaiser window, verify the derivation’s correctness through favorable comparison to the theoretically predicted behavior.
基金the Science and Engineering Research Board(SERB)Department of Science & Technology,Government of India for financially supporting this research
文摘The stretch flanging process is significantly affected by various geometrical,material and process parameters.The punch-die clearance and initial flange length are main parameters which have major effects on the edge crack location and strain distribution along die profile radius in the flange.Non-axisymmetric stretch flanging process of AA-5052 sheet metal blanks was carried out by numerical simulation to predict the deformation behavior of flange,location and propagation of crack in flange and to investigate the effect of punch die clearance,flange length,die and punch profile radius and friction in the stretch flanging process.The experimental investigations were made to validate the simulations results.The results reveal that the crack length increases with the increase in the flange length.It is found that the flange length has a significant effect in circumferential direction as compared with the radial direction.The punch die clearance has the most significant effect in crack propagation in comparison with flange length.The circumferential strain is found to be larger in the case of punch having the profile radius less than the die profile radius,which leads to faster edge crack propagation.A close agreement is found between simulation and experimental results in terms of location of edge crack and forming load.
文摘This study presents a parameter selection strategy developed for the Stretch-Blow Molding (SBM) process to minimize the weight of preforms used. The method is based on a predictive model developed using Neural Networks. The temperature distribution model of the preform was predicted using a 3-layer NN model with supervised backpropagation learning. In addition, the model was used to predict the uniform air pressure applied inside the preform, taking into account the relationship between the internal air pressure and the volume of the preform. Parameters were validated using in situ tests and measurements performed on several weights and lengths of a 0.330 Liter Polyethylene Terephthalate (PET) bottles. Tests showed that the model adequately predicts both the blowing kinematics, mainly zone temperatures and blowing and stretching pressures along the walls of the bottle while maintaining the bottle strength and top load requirements. In the second step, the model was combined to automatically compute the lowest preform weight that can be used for a particular 330 ml bottle design providing a uniform wall thickness distribution.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51325301 and 51227801)
文摘Young＇s modulus of biaxially oriented polypropylene （BOPP） films prepared with homemade film stretcher was investigated, which can be used to indicate the softness of films. It was found that the modulus of films was decreased by about 69% as the content of polyethylene （PE） added into polypropylene （PP） reached 30%. Also, increasing draw temperature can induce lower stress level during stretching, which may lead to the formation of crystals with low orientation level and thus decreased modulus of films. Based on laboratory study, BOPP films produced on commercial line were studied by differential scanning calorimetry （DSC）, wide and small-angle X-ray scattering （WAXS, SAXS） with varying contents of PE. SAXS results show that the crystals are oriented in both machine direction （MD） and transverse direction （TD）, and the crystals are more oriented in TD than MD according to the WAXS results for all films. Also, the orientation parameter of crystal along TD increases from 0.68 to 0.83 as the contents of PE increase from 0% to 25%. Meanwhile, the modulus of films in MD declines with increase of PE contents generally, improving the film softness. Orientation of crystals is thus an effective structure parameter to adjust the film softness. The relationship of processing-structure-property is also established.
基金financially supported by the National Natural Science Foundation of China(Nos.51227801,51325301)
文摘A biaxial stretching equipment was designed and constructed to enable fundamental studies of the relationship between film processing conditions and structures of oriented film products. With programmable drive motors and scissorlike mechanism, all stretching modes, including uniaxial stretching with constant and free width, simultaneous and sequential biaxial stretching, can be applied to a square-shaped sheet. Parameters related to film stretching manufacturing, such as temperature, draw ratio and stretching speed can be set independently to meet the requirement of different polymers. The force information during stretching is recorded by two miniature tension sensors in two directions independently, which can monitor the mechanical stimulus and stress response. Using this equipment, experiments are conducted to investigate the influence of stretching parameters on the structure of polypropylene films, which provides an effective method to tailor the processing conditions to obtain the films with desired properties.
基金the Doctoral Fund of Ministry of Education of China(No.CUSF-DH-D-2015012)National Natural Science Foundation of China(No.51403033)Fundamental Research Funds for the Central Universities,China(No.2232014D3-15)
文摘Comprehensive performances of polytetrafluoroethylene(PTFE) flat filaments used as suture materials in medical field can be affected significantly by morphological and mechanical characteristics.Due to low tensile strength and non-uniform morphology,PTFE flat filaments cannot be applied widely as medical sutures.In order to solve flaws above,PTFE flat filaments with constant linear density,550 dtex,are manufactured and dependences of morphology,frictional features and mechanical behaviors on stretching ratio and temperature are also analyzed.The results indicate that PTFE flat filaments with high tensile strength(1 922.0 cN) and excellent apparent performance can be manufactured at optimal stretching ratio and temperature,18.0 and350 ℃,respectively.
基金National Natural Science Foundations of China(Nos.61203073,61134009)Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20120075120008)+2 种基金Foundation of Key Laboratory of System Control and Information Processing,Ministry of Education,China(No.SCIP2012002)Program for Changjiang Scholars and Innovation Research Team in University from the Ministry of Education,China(No.IRT1220)Specialized Research Fund for Shanghai Leading Talents,Project of the Shanghai Committee of Science and Technology(No.13JC1407500)
文摘The stretching process,as a key phase of web production system,pursues the target velocities of rollers and the web tensions of spans between the successive rollers to guarantee proper stretching ratios. This requires the stable velocities and velocity ratios of large number rollers separated throughout the workshop. To this goal,a distributed cooperative controller is designed to coordinate the velocities of the rollers to the desired values as well as the target ratios between the upper and lower rollers. During the whole evolution,only the neighbor rollers can exchange the working information,and neither global information nor central controller is required. It is proven that all the rollers asymptotically achieve the desired velocity ratios via the proposed control law,which is also demonstrated by numerical simulation.
