Plastic deformation of magnesium alloy with different forming parameters during ultrasonic vibration-assisted single-point incremental forming

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.

Mechanical properties and microstructure evolution in incremental forming of AA5754 and AA6061 aluminum alloys

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.

Experimental Study on Springback of Sheet Metal Single Point Incremental Forming

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.

Planar morphology and controlling factors of the gullies in the Yuanmou Dry-hot Valley based on field investigation

The plane form of a gully can provide a basis for evaluating the gully volume and erosion rate, acting process, and evolutionary stage. For describing the planar characteristics of a permanent gully and understanding their controlling factors, this study, utilizing a total station and GPS RTK, measured the shoulder lines and channel curves of 112 gullies in six sites of the Yuanmou Dry-hot Valley and then mapped them by Arc GIS software and calculated nine parameters. The results showed that the channel lengths range from 10.88 to 249.11 m; the widths range from 6.20 to 40.99 m; the perimeters range from 54.11 to 541.67 m; the gully areas range from 153.02 to 6,930.30 m2; the left-side areas range from 92.93 to 4,027.20 m2; and the right-side areas range from 63.65 to 3,539.77 m2. The slightly sinuous and straight gullies account for 73.21% of the total gullies; the quantity of the right skewed gullies is 8.93% greater than that of the left skewed ones based on the symmetry ratio; the shape ratios range from 1.12 to 1.40 and the morphology ratios from 0.038 to 1.294; the fractal dimension is 1.192. Gullies in different sites have diverse planar characteristics. Except for the symmetry index, which was close to a negatively skewed distribution, all of the other parameters had the characteristic of positively skewed distribution. The gully area is related to the length and width, but the gully length has a weak correlation with the width. The evolutionary stage, topographic conditions, strata, soil properties, and piping erosion played very important roles in the gully planar morphology. This study could provide useful information for controlling gully erosion and safeguarding human habitation and engineering buildings.

Simulation and formability analysis of drawing process for automotive B-pillar

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.

Amorphous forming ranges of Al-Fe-Nd-Zr system predicted by Miedema and geometrical models

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.