The research of forming parameters on the ultrasonic vibration single-point incremental forming of magnesium alloy plastic deformation can provide a theoretical basis for the establishment of the forming parameters.Ac...The research of forming parameters on the ultrasonic vibration single-point incremental forming of magnesium alloy plastic deformation can provide a theoretical basis for the establishment of the forming parameters.According to the forming characteristics of magnesium alloy sheet,a new method of ultrasonic vibration-as sis ted single-point incremental forming was proposed.The influence of forming parameters on the plastic deformation of magnesium alloy was studied by finite element simulation and experimentation.The influence of vibration frequency,amplitude,friction coefficient,and tool head size on stress and thinning rate of magnesium alloy during ultrasonic vibration-as sis ted single-point asymptotic forming was studied.The results show that the vibration frequency of 20 kHz and forming tool radius of about 5 mm are beneficial for plastic deformation magnesium alloy in ultrasonic vibration-assisted single-point incremental forming.With vibration amplitude increasing,the maximum shear stress tends to decrease as a whole,but at the amplitude of 0.16 mm,the thinning rate is large and fracture occurs easily.With friction coefficient increasing,the maximum shear stress tends to increase,and there is a good linear relationship between the maximum thinning rate and the friction coefficient.展开更多
The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empi...The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empirical formulas for the growth of significant wave height and period. The main features of spectrum growth as specified by these parameters agree with those of the JONS-WAP experiments. For given wind speed and fetch, the high frequency parts beyond the peaks of shallow water spectra almost coincide with that of the corresponding deep water spectrum, whereas the low frequency parts differ appreciably. The method developed in this paper predicts smaller significant wave height as well as smaller wave period for shallow water spectra in contrast to the theoretical result of Kitaigorodskii ef al, in which the peak frequency, and consequently the significant wave period, remains basically unchanged for different water depths. Spectra are further reduced to a form in which only significant wave height and period are left as parameters, the peakness factor being replaced by the wave steepness through an empirical relation between them. Spectra in this form have been verified by observations.展开更多
This study performs single point incremental forming(SPIF)on two aluminum alloys(i.e.AA5754 and AA6061),and analyzes their post forming mechanical properties and microstructure evolution.The forming parameters namely ...This study performs single point incremental forming(SPIF)on two aluminum alloys(i.e.AA5754 and AA6061),and analyzes their post forming mechanical properties and microstructure evolution.The forming parameters namely wall angle(35°-55°),feed rate(1-4 m/min),spindle rotational speed(50-1000 r/min),and lubricant(grease and hydraulic oil)are varied to probe detailed processing effects.The pre-and post-SPIF mechanical properties and microstructures are characterized by conducting tensile tests and optical microscopy,respectively.It is shown that an increase in the wall angle,feed rate and rotational speed causes microscopic variations in the alloys such that the grains of AA5754 and the second phase particles of AA6061 elongate.As a result,the ultimate tensile strength of the formed parts is increased by 10%for AA5754 and by 8%for AA6061.And,the ductility of AA5754 is decreased from 22.9%to 12%and that of AA6061 is decreased from 16%to 10.7%.Regarding the lubricant effect,it is shown that the mechanical properties remain insensitive to the type of lubricant employed.These results indicate that SPIF processing modifies the microstructure of Al alloys in a way to enhance the strength at the cost of ductility.展开更多
A method based on the semi-empirical Miedema model and a geometrical model was used to study the glass forming abili-ties （GFA） and the amorphous forming ranges of Al-Fe-Nd-Zr system and its constituent ternary syst...A method based on the semi-empirical Miedema model and a geometrical model was used to study the glass forming abili-ties （GFA） and the amorphous forming ranges of Al-Fe-Nd-Zr system and its constituent ternary systems. The amorphous forming composition ranges were analyzed based on different criteria such asΔGam-ss and PHSS （PHSS=ΔHchem （ΔSC/R）（ΔSσ/R）） for Al-Fe-Nd system. The predicted amorphous forming range was in good agreement with the experimental results. The results showed that the criterion ofΔGam-ss was more accurate, and agreed well with the experiment results. The Gibbs free energy differenceΔGam-ss and pa-rameter PHSS were then used to predict the amorphous forming composition range for the rest of the constitutive ternary systems of Al-Fe-Nd-Zr. In addition, the amorphous forming composition ranges of the （Al-Fe-Zr）100-xNdx （x=50, 60, 70） systems were predicted byΔGam-ss and the modified parameter PHSS. The Gibbs free energy of Al10（Fe1-xZrx）30Nd60 were also calculated. The GFA parameter PHSS indicated that the composition with the highest GFA was Al33.5Fe13.5Zr3Nd50 for the （Al-Fe-Zr）50Nd50 system, Al28.8Fe10Zr1.2Nd60 for the （Al-Fe-Zr）40Nd60 system and Al22.8Fe6.9Zr0.3Nd70 for the （Al-Fe-Zr）30Nd70 system, and the results suggested that those alloys with high content of Al had higher GFA. The appropriate content of neodymium and zirconium resulted in the lower value of PHSS and increased the GFA obviously.展开更多
The numerical simulation on drawing process of automotive B-pillar was carried out on AutoForm software,and dangerous forming areas were discovered.The processing parameters,such as the layout of drawbeads,blank holdi...The numerical simulation on drawing process of automotive B-pillar was carried out on AutoForm software,and dangerous forming areas were discovered.The processing parameters,such as the layout of drawbeads,blank holding force and the shape of blank,were adjusted and optimized according to the simulation results.Results indicate that the quality defects can be forecast and removed,which improves the stability of forming process.The cost of design is decreased and the research cycle is shortened.It is proved that the drawing process and die design of B-pillar forming are feasible in actual production.展开更多
Sheet metal single point incremental forming （SPIF） is a new technology for flexible process. The springback phenomenon in single point incremental forming has been discussed. Effects of forming angle and shape of t...Sheet metal single point incremental forming （SPIF） is a new technology for flexible process. The springback phenomenon in single point incremental forming has been discussed. Effects of forming angle and shape of the part are analysed using simple experimental method. Tool diameter, sheet thickness, step size, material parameters and the interaction of them are also analysed by using orthogonal test. The results show that the primary factor af- fecting springback is forming angle. In addition, springback is decreased when the specimen has a larger forming angle. The order of the four factors that influence springback is tool diameter, sheet thickness, step size and material parameters. The forming precision will increase if springabck is decreased by optimizing the forming parameters.展开更多
基金financially supported by the National Natural Science Foundation of China (No.51305241)the Natural Science Foundation of Shandong Province (No. ZR2014JL040)the Shandong Province Taishan Scholar Construction Project Special Fund (No.tshw20130956)。
文摘The research of forming parameters on the ultrasonic vibration single-point incremental forming of magnesium alloy plastic deformation can provide a theoretical basis for the establishment of the forming parameters.According to the forming characteristics of magnesium alloy sheet,a new method of ultrasonic vibration-as sis ted single-point incremental forming was proposed.The influence of forming parameters on the plastic deformation of magnesium alloy was studied by finite element simulation and experimentation.The influence of vibration frequency,amplitude,friction coefficient,and tool head size on stress and thinning rate of magnesium alloy during ultrasonic vibration-as sis ted single-point asymptotic forming was studied.The results show that the vibration frequency of 20 kHz and forming tool radius of about 5 mm are beneficial for plastic deformation magnesium alloy in ultrasonic vibration-assisted single-point incremental forming.With vibration amplitude increasing,the maximum shear stress tends to decrease as a whole,but at the amplitude of 0.16 mm,the thinning rate is large and fracture occurs easily.With friction coefficient increasing,the maximum shear stress tends to increase,and there is a good linear relationship between the maximum thinning rate and the friction coefficient.
文摘The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empirical formulas for the growth of significant wave height and period. The main features of spectrum growth as specified by these parameters agree with those of the JONS-WAP experiments. For given wind speed and fetch, the high frequency parts beyond the peaks of shallow water spectra almost coincide with that of the corresponding deep water spectrum, whereas the low frequency parts differ appreciably. The method developed in this paper predicts smaller significant wave height as well as smaller wave period for shallow water spectra in contrast to the theoretical result of Kitaigorodskii ef al, in which the peak frequency, and consequently the significant wave period, remains basically unchanged for different water depths. Spectra are further reduced to a form in which only significant wave height and period are left as parameters, the peakness factor being replaced by the wave steepness through an empirical relation between them. Spectra in this form have been verified by observations.
文摘This study performs single point incremental forming(SPIF)on two aluminum alloys(i.e.AA5754 and AA6061),and analyzes their post forming mechanical properties and microstructure evolution.The forming parameters namely wall angle(35°-55°),feed rate(1-4 m/min),spindle rotational speed(50-1000 r/min),and lubricant(grease and hydraulic oil)are varied to probe detailed processing effects.The pre-and post-SPIF mechanical properties and microstructures are characterized by conducting tensile tests and optical microscopy,respectively.It is shown that an increase in the wall angle,feed rate and rotational speed causes microscopic variations in the alloys such that the grains of AA5754 and the second phase particles of AA6061 elongate.As a result,the ultimate tensile strength of the formed parts is increased by 10%for AA5754 and by 8%for AA6061.And,the ductility of AA5754 is decreased from 22.9%to 12%and that of AA6061 is decreased from 16%to 10.7%.Regarding the lubricant effect,it is shown that the mechanical properties remain insensitive to the type of lubricant employed.These results indicate that SPIF processing modifies the microstructure of Al alloys in a way to enhance the strength at the cost of ductility.
基金Project supported by the National Natural Science Foundation of China(51061004)Science Foundation of Guangxi Education Department(2013YB377)
文摘A method based on the semi-empirical Miedema model and a geometrical model was used to study the glass forming abili-ties （GFA） and the amorphous forming ranges of Al-Fe-Nd-Zr system and its constituent ternary systems. The amorphous forming composition ranges were analyzed based on different criteria such asΔGam-ss and PHSS （PHSS=ΔHchem （ΔSC/R）（ΔSσ/R）） for Al-Fe-Nd system. The predicted amorphous forming range was in good agreement with the experimental results. The results showed that the criterion ofΔGam-ss was more accurate, and agreed well with the experiment results. The Gibbs free energy differenceΔGam-ss and pa-rameter PHSS were then used to predict the amorphous forming composition range for the rest of the constitutive ternary systems of Al-Fe-Nd-Zr. In addition, the amorphous forming composition ranges of the （Al-Fe-Zr）100-xNdx （x=50, 60, 70） systems were predicted byΔGam-ss and the modified parameter PHSS. The Gibbs free energy of Al10（Fe1-xZrx）30Nd60 were also calculated. The GFA parameter PHSS indicated that the composition with the highest GFA was Al33.5Fe13.5Zr3Nd50 for the （Al-Fe-Zr）50Nd50 system, Al28.8Fe10Zr1.2Nd60 for the （Al-Fe-Zr）40Nd60 system and Al22.8Fe6.9Zr0.3Nd70 for the （Al-Fe-Zr）30Nd70 system, and the results suggested that those alloys with high content of Al had higher GFA. The appropriate content of neodymium and zirconium resulted in the lower value of PHSS and increased the GFA obviously.
文摘The numerical simulation on drawing process of automotive B-pillar was carried out on AutoForm software,and dangerous forming areas were discovered.The processing parameters,such as the layout of drawbeads,blank holding force and the shape of blank,were adjusted and optimized according to the simulation results.Results indicate that the quality defects can be forecast and removed,which improves the stability of forming process.The cost of design is decreased and the research cycle is shortened.It is proved that the drawing process and die design of B-pillar forming are feasible in actual production.
文摘Sheet metal single point incremental forming （SPIF） is a new technology for flexible process. The springback phenomenon in single point incremental forming has been discussed. Effects of forming angle and shape of the part are analysed using simple experimental method. Tool diameter, sheet thickness, step size, material parameters and the interaction of them are also analysed by using orthogonal test. The results show that the primary factor af- fecting springback is forming angle. In addition, springback is decreased when the specimen has a larger forming angle. The order of the four factors that influence springback is tool diameter, sheet thickness, step size and material parameters. The forming precision will increase if springabck is decreased by optimizing the forming parameters.
基金Supported by the National Basic Research Program of China under Grant No.2002CB312101(国家重点基础研究发展计划(973))the National Natural Science Foundation of China under Grant Nos.60373036,60333010(国家自然科学基金)+1 种基金the Doctoral Program of Higher Education(Specialized Research Fund)of China under Grant No.20050335069(国家教育部高等学校博士学科点专项科研基金)the Natural Science Foundation of Zhejiang Province of China under Grant No.R106449(浙江省自然科学基金)
