Research On The Ultrasonic-assisted Shear Processing Of Fe-based Amorphous Alloy Strips

At a time when the country strongly advocates green manufacturing to promote highquality economic development,Fe-based amorphous alloy strip has excellent soft magnetic properties and obvious technical advantages,but its long-range disorderly structural characteristics and physical and mechanical properties lead to processing problems in shear processing and molding,and its processing accuracy also directly affects the comprehensive performance of amorphous alloy products.In this thesis,it is proposed for the first time that ultrasonic-assisted method is applied to shear processing of Fe-based amorphous strip and the process is studied in depth.Firstly,the production defects of Fe-based amorphous alloy strips are summarized from practical research,and the macroscopic manifestations of defects are summarized into two microscopic indicators of strip shear section quality and tool wear,then the structure of ultrasonic oscillator is designed through simulation,and the ultrasonic-assisted shear experimental platform is built based on the modification of existing equipment for experimental research.Secondly,based on the ultrasonic scratching test and bending test,the influence of ultrasonic vibration on the processing process of Fe-based amorphous alloy strips was analyzed in depth from the processing mechanism.The result of ultrasonic scratch test shows that the Fe-based amorphous alloy strip has certain plasticity,and the ploughing and cutting processes are the two ways to produce real microscopic plastic deformation on the surface of the Fe-based amorphous alloy strip,and the ultrasonic vibration causes the decrease of internal tensile stress of the Fe-based amorphous alloy strip,which plays an important role in suppressing the crack expansion.It was found by bending tests that during the ultrasonic energy enhancement,the shear bands at the crease of the Fe-based amorphous alloy strip became denser,and multiple secondary shear bands accompanied by primary shear bands crossed to form a strong interactive expansion mode,which made it show stronger plastic deformation ability.Thirdly,based on the ultrasonic-assisted shear experiment,the effect of ultrasonic vibration on the tool wear process and wear forms under different friction states and different ultrasonic amplitude conditions was investigated,and it was found that the HSS tool wear during shear is mainly frictional wear by mechanical action.Ordinary shear makes the tool surface plastic deformation as well as chipping breakage,which is abrasive wear;ultrasonic assisted shear is mainly slight bond wear and chipping;liquid lubricated shear and wet ultrasonic shear keep the tool edge straight and intact,and the wet ultrasonic shear shows the best friction reduction effect.When the number of shears reached 1000,the tool edge radius was reduced by 13.79%,8.52%,and 5.76% under wet ultrasonic shear compared with normal shear,liquid lubricated shear,and ultrasonic assisted shear conditions,respectively.By establishing the force model of Fe-based amorphous alloy strip during ultrasonic-assisted shearing and the lubrication contact interface model during wet ultrasonic shearing,the mechanism of the effect of different shearing methods on shear force was theoretically analyzed.The wet ultrasonic transverse shear process forms fluid lubrication on the strip surface with the help of the flip angle when the tool is dropped,and the lubricant is fully spread and wetted at the contact interface with the pumping effect when the section is created,forming boundary lubrication,which indirectly reduces the shear force by reducing the friction factor.Finally,based on the ultrasound-assisted shear experiment,the influence of ultrasonic vibration on the shear section quality of Fe-based amorphous alloy strip under different friction states and different ultrasonic amplitudes was investigated.Shear zone cracks may appear on the surface of Fe-base amorphous alloy strip after punching and shearing.The cracks can be divided into parallel crack layered shear zone and dendrite crack aggregation zone.Compared with ordinary shear,ultrasonic vibration can reduce the surface crack width of Fe-based amorphous strip,and the larger ultrasonic amplitude can restrain the crack propagation.The oil film of the lubricant can absorb the impact energy and provide a certain buffer effect.The crack width of wet ultrasonic shear band decreases by 42.9% and 20%,respectively,compared with ordinary shear and lubrication shear.The ultrasonic-assisted cross-shearing process of Fe-based amorphous alloy strips formed a unique processing process with the participation of ultrasonic vibration.Ripple traces of the strip section being sheared several times can be observed,and ultrasonic shearing replaces one-time-shear with multiple micro-shears.The strip section is subjected to more uniform forces during the shearing process,and the section quality is significantly improved,proving that ultrasonic vibration can improve the processing plasticity of room-temperature brittle amorphous strips.