Effect of coating material and lubricant on forming force and surface defects in wire drawing process

A pilot wire drawing machine as well as wire end-pointing roller was developed. Using these machines, a wire drawing test for four different coating materials and two different lubricants was performed as the reduction ratio increased from 10% to 30%. Materials used for a substrate in this study are plain carbon steel （AIS11045） and ultra low carbon bainite steel. To compute the friction coefficient between the coating layer of wire and the surface of die lbr a specific lubricant, a series of finite element analyses were carried out. SEM observations were also conducted to investigate the surface defects of wire deformed. Results show that the behavior of drawing force varies with the lubricant-type at the initial stage of drawing. The powder-typed lubricant with a large particle causes the retardation of lull lubrication on the entire contact surface and the local delamination of coating layer on the wire surface. As the flow stress of a substrate increases, the delamination becomes severe.

Design and Experiment of the High Speed Wire Drawing with Ultrasound

The previous experiments of wire drawing with ultrasonic vibration were mostly carried out on self-made machine or drawing test machine and the drawing speed didn＇t conform to practical production. In order to promote the practical application of the technology, the ultrasonic vibration system was designed and manufactured by using the classical dynamics method. The dynamic characteristic of the ultrasonic vibration system was analyzed. The performance parameters of the system were measured on the resistance analyzer. The oxygen-free brass wire drawing with ultrasonic vibration at the approximate speed of practice was carried out on the LH-200/17 drawing machine. By comparing the wire drawing through ultrasonic vibration and the conventional wire drawing, the experimental results show that the drawing process with ultrasound was steady at the high drawing speed of 1 126 mm/s, while the broken wire often occurs at the speed of 980 mm/s during the conventional wire drawing; the ultrasonic vibration reduced the drawing force by 7 %; and the ultrasound also reduced the uneven deformation of the wire and greatly improved the surface quality of the wire. The research results provide theoretical and experimental support for the practice and application of the wire drawing by ultrasonic vibration.

Modeling asymmetric fracture mechanics of Mg alloy wire in drawing process

In this study,a numerical analysis was conducted on the ductile fracture of a 2-mm diameter Mg-1Zn-0.5Mn-0.5Sr-0.1Ca alloy wire during drawing.The hexagonally close-packed crystal structure of Mg alloys causes asymmetric fracture behavior,especially in the compression region.The aim of this study is to develop a comprehensive damage model for Mg alloy wire that accurately predicts ductile fracture,with a focus on the compression region.A novel experimental method was introduced to measure the ductile fracture of Mg alloy wires under different stress states.The wire drawing process was simulated using the Generalized Incremental Stress-State dependent damage(GISSMO)Model and the Semi-Analytical Model for Polymers(SAMP)model.The damage model's prediction and the experimental results were found to be in excellent agreement,especially in determining crack initiation.Computational analysis established a safe zone diagram for die angle and reduction ratio,and experimental validation confirmed the feasibility of this approach.The proposed damage model can provide a practical and reliable analysis for optimizing the drawing process of Mg alloy wire.

EFFECTS OF HIGH-DENSITY CURRENT PULSES ON WORK HARDENING BEHAVIORS OF AUSTENITE STAINLESS STEEL IN WIRE-DRAWING DEFORMATION

The influence of high-density pulsing current on the work-hardening behaviour of H0Cr17Ni6Mn3 and 1Cr18Ni9 stainless steels in wire-drawing deformation processes has been studied. It was found that the drawing stress and the work-hardening rate of wires were significantly reduced by applying current pulses in drawing process. The work-hardening behavior of the multi-courses drawing deformation can be well described by Hollomon formula σ=κΕn. With the application of current pulses in drawing deformation, the work-hardening exponents of H0Cr17Ni6Mn3 steel wires and 1Cr18Ni9 stainless steel wires were reduced by 33% and 45%, respectively, and their work-hardening coefficients were reduced by 41% and 47%, respectively. It was also found that the work-hardening coefficient of wires was reduced with the increment of the frequency of current pulses, while the work-hardening exponents of both steels were insensitive to the pulsing frequency.

Microstructure and texture evolution in fully pearlitic steel during wire drawing

The evolution of morphology of pearlite and crystallographic texture of ferrite matrix in fully pearlitic steels during wire drawing were quantitatively investigated. The study revealed that a fiber structure of the pearlite morphology and a 〈110〉 fi- ber texture of the ferrite matrix begin to take shape and develop gradually with increasing strain. The growth rates of the fiber structure and the 〈110〉 texture are different in different regions within the wires with increasing drawing strain. There is a close relationship between the pearlite morphology and the crystalline texture during wire drawing. The pearlite interlamellar spacing （ILS） and thickness of cementite lamellae （To） decrease gradually both in longitudinal and transverse sections. The definition of pearlite colony should be reconsidered for describing microstructure of the wire drawing deformed pearlitic steels.

Advanced simulation of die wear caused by wire vibrations during wire-drawing process

An advanced simulation that considers the effect of wire vibrations was proposed for predicting accurately wear profiles of a die used in a wire-drawing process.The effect of wire vibrations,the changes in the wear profiles,and the generation of ringing during die approach were investigated by this simulation.Wire vibrations occurring between the die and the drum are governed by a partial differential equation called the wave equation,which is a function of the wire length,tension,density,and initial wire velocity.The wire-drawing process was simulated by the commercial code Abaqus FEA,and the die wear profiles were predicted by Archard’s wear model.The predicted profiles were compared with measured profiles of a worn drawing die after producing 5 t of AISI 1010 wire;the die was made of tungsten carbide with a Brinell hardness of HB 682.The profiles predicted by considering the effect of wire vibrations are in good agreement with the experimental data,indicating that the advanced simulation can be used to accurately predict the die wear profiles when ringing is observed during die approach.

Deformation bands in fully pearlitic steel during wire drawing

The deformation of fully pearlitic steels during wire drawing has been investigated for botb longitudinal section and transverse section by back-scattered electron imaging （BSEI）, electron back-scattered diffraction （EBSD）, and transmission electron mi- croscope （TEM）. The results show that a large number of deformation bands （DBs） composed of a mixture of kink-like bands and shear-like bands were observed both in the longitudinal section and the traverse section of the drawn wires. The formation of such bands involves two aspects： heterogeneous deformation in the scale of pearlite colonies and instability of fer- rite-cementite interfaces due to stress concentration during wire drawing. The development of suck bands in fully pearlitic steels dominates the formation of metallograpbic texture, reduces the pearlite interlamellar spacing and promotes the development of 〈 110〉 fiber crystalline texture of ferrite matrix during wire drawing.

Rectifying control of wire diameter during dieless drawing by a deformation measuring method of interframe displacement

A deformation measurement method of interframe displacement was proposed in this paper. By online monitoring the shape di- mensions of both the deformation zone and its adjacent zone by machine vision, the initial and terminative positions of deformation were dynamically identified during dieless drawing, and the global monitoring and online closed-loop control of the deformation zone were achieved. The dieless drawing process was systematically carried out on NiTi shape memory alloy wires. It is shown that the deformation measurement method of interframe displacement can track the axial displacement of the wires, but this cannot be achieved by traditional machine vision. The initial and terminative positions of deformation can be accurately identified by this method. The proposed rectifying control technology can effectively decrease the wire diameter fluctuation during dieless drawing, that is, the standard deviation of the wire diameter fluctuation could be decreased fi＇om 0.30 to 0.08 mm after three passes of dieless drawing, indicating that the control system has a good rectifying ability.

Effect of drawing speed on microstructure distribution and drawability in twinning-induced plasticity steel during wire drawing

The effect of drawing speed on temperature rise and microstructure distribution in twinning-induced plasticity(TWIP)steel during wire drawing has been investigated to improve drawability for wire rod applications.Although wire drawing process is performed at room temperature,heat is generated due to the plastic deformation and friction at the wire-die interface.The steel wires subjected to the low drawing speed(LD)of 0.5 m/min and the high drawing speed(HD)of 5.0 m/min were analyzed using the numerical simulation and electron backscatter diffraction techniques.Interestingly,the specimens subjected to the HD had a higher drawability by about 18%compared to the LD,which is totally different from the general behavior of plain carbon pearlitic steels.The LD wire had uniform temperature distribution along the radial direction during wire drawing.In contrast,the HD wire had a temperature gradient along the radial direction due to the higher frictional effect at surface:the minimum temperature of 58℃ at center area and the maximum temperature of 143 C at surface area.The higher stacking fault energy of HD wire at the surface area due to the high temperature rise retarded twinning rate,resulting in the prevention of fast exhaustion in ductility in comparison with the LD wires since the earlier depletion of twins at surface area is known as the main reason for the fracture of TWIP steel during wire drawing.Consequently,HD process delayed the fracture strain of wire and increased the uniformity of microstructure and mechanical properties along the radial direction.

DRAWING OF ALUMINUM-CLAD STEEL WIRE BY FORCE-FEED LUBRICATION

The force feed lubrication method is used for drawing aluminum clad steel wire. It is studied how deformation of wire and aspect of the lubricant film are influenced by the die angle, the reduction, the drawing speed and the gap between pressure die and wire. It has been concluded that when the factors above mentioned promote to thicken lubricant film, the drawing force is reduced and this favors the homogenous deformation of aluminum coating and steel core.

A novel Hf-Si-O wire drawing phenomenon after ablation of SiC_(nws)/ HfC-SiC coating on C/C composites

A SiC_(nws)/HfC-SiC coating was fabricated by a two-step chemical vapor deposition.After introducing SiC nanowires,the fracture toughness of HfC-SiC coating increases by 228%.After ablation under oxyacetylene torch for 60s,a bone-like HfO_(2) reticular structure was formed in the central ablation area.Interestingly,a novel Hf-Si-O wire-drawing phenomenon was happened in the transition area of ablated SiC_(nws)/HfC-SiC coating,providing a new toughness mechanism under ablation environment.Moreover,HfO_(2) precipitated from Hf-Si-O glass wires to generate nanocrystalline grains during ablation,which explains the formation of bone-like HfO_(2) reticular structure observed from central ablation area.

Wear Behavior of Diamond-Coated Drawing Dies

The failure behavior of diamond-coated die was investigated experimentally and analytically through finite element method (FEM) simulation in the present work. Diamond coatings were fabricated by straight hot filament chemical vapor deposition (CVD) passing through the interior hole of the drawing die using a mixture of hydrogen and acetone as source gases. The performance tests were made under real drawing condition. Scanning electron microscopy (SEM) was used for the study of coating wear after die service. The coating wear appears on two regions of the reduction zone: one is near the entrance where the contact begins, and the other is at the end of the reduction zone. FEM simulation was made for calculating the von Mises stresses distribution on the coating and substrate during the drawing process. The present work was of great practical significance for the improvement of drawing performance of diamond-coated drawing dies.

Geometric Calibration Method of Robot Based on Measurement System Including Position and Orientation Parameters

Industrial robot which can acquire high accuracy has been widely used in automatic assembly.Usually,the geometric parameter of industrial robot should be inspected during manufacturing and application.High precision measurement equipment was utilized to acquire the position and orientation of robot’s end⁃effector,when calibrating the geometric parameter of robot.A kind of measurement system based on a draw⁃wire encoder was presented,since the current measurement equipment has some disadvantages,such as the cost and the requirements of working environment are high.According to this kind of measurement system,a sort of geometric calibration method of robot was presented including position and orientation parameters.The uncertain arc length of the cable length between robot end⁃effector and the measurement can be exactly acquired according to the position and orientation parameters.The pose⁃solving model of robot end⁃effector was associated with the kinematic model of robot,and robot’s geometric parameter can be computed by using the least⁃squares methods.Validate instance was conducted,the result showed that the optimal number of the calibration pose was 47 with little improvement in accuracy,even if increasing the number of calibration pose.Robot calibration experiment was performed and the results showed that the absolute accuracy of robot decreased from 4.32 mm to 0.87 mm after calibration,which improved the robot’s absolute accuracy effectively.

DEVELOPMENT OF MATERIAL USED FOR AVIATION APPARATUS AXLE JOURNALS

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