Hot stamping of aluminum alloy is an important manufacturing method to achieve the goal of automobile lightweight,and scrat-ches and cracks of sheets caused by friction and wear in the production process are the main obstacles to mass production.In order to study the applicability and lubrication mechanism of lubricants in hot stamping process,based on the pin-disk friction experimental equip-ment,the experimental conditions of hot stamping were studied by reasonable experimental design,and a water-based release agent with similar working condition was selected for friction experiment to evaluate its lubrication performance under the hot stamping condition and explore its lubrication mechanism.Furthermore,through experiments,it is found that the water-based siloxane lubricant could obtain a long time low friction factor state by isolating the die from the workpiece.So it is feasible to use water-based lubricant to achieve stable and low friction factor state in hot stamping process of aluminum alloy.
Abstract. In this paper, the forming process research of the front opening and closing mechanism hatch for multiple units was carried out, and the industrial grade 5083 aluminum alloy was selected as the original material. The uniform rapid superplastic forming process combined with hot stamping and direct-reverse superplastic forming was used to form the hatch body skin, the cold stamping and argon arc welding process were used to produce the connection support, and the hatch integral part was obtained by argon arc welding finally, which solved the problem of poor environmental protection and high ratio of traditional FRP hatch and high precision forming of the large complex thin-walled structural part that cannot be achieved by the traditional forming process. After process research and development, finite element analysis, and forming tests, the aluminum alloy hatch with good forming quality was successfully manufactured. The ultimate thinning rate of the part was 23.8%, the overall wall thickness was evenly distributed, the deviation of shape was controlled within 1 mm, and the mechanical properties met the relevant technical requirements.
The room temperature forming ability of 5A06 aluminum alloy is limited,and it is prone to cracking in stamping,for this prob-lem,the warm forming of 5A06 aluminum alloy sheet was researched,and based on the M-K groove theory,the formability of 5A06 alu-minum alloy sheet was predicted.Firstly,a constitutive model of 5A06 aluminum alloy under the conditions of 200-300℃and 0.01-1 s-1 was established by combining theoretical calculation and experiment.Then,the Swift material strengthening model was introduced into the derivation of forming limit,the forming limit diagram and the initial thickness unevenness predicted by the M-K groove theory were obtained by the Newton-Raphson iteration method.Finally,the Nakajima test was conducted on the 5A06 aluminum alloy sheet to verify the accuracy of theoretical prediction results.The results show that the M-K groove theory can effectively predict the formability of 5A06 aluminum alloy within the experimental temperature range.
For the riveting forming of two layers of 5052 aluminum alloy sheets with the thickness of 1.5 mm in the battery pack of new energy vehicles,a new structural rivet was designed based on the waterproof requirement after riveting of sheets.Then,the sheet metal riveting forming process was simulated based on finite element software DEFORM-2D,and the simulation results were verified by installing the die and riveting equipment.The simulation results show that the simulation values of head penetration,residual thickness,interlocking length between rivet and upper plate,and interlocking length between lower plate and upper plate are 0.038,0.210,0.526 and 0.505 mm respectively.The relative errors between numerical simulation and experimental values are 7.89%,7.14%,6.08%and 12.67%respectively.Therefore,the reliability of DEFORM simulation applied to the riveting is verified by experiments.In addition,through simulation analysis it is known that the interlock length increases with the increasing of riveting speed and die installation width,while it decreases with the increasing of die installation depth.
In order to solve the lubrication problems in vacuum isothermal forging,for two glass lubricants RD-1 and GR-2,the wetting angle was measured by the seat drop method,the linear expansion coefficient was measured by the differential method,the high-tempera-ture viscosity was measured by the rotation method,and the combination of coating and substrate was observed by the trial firing method combined with scanning electron microscopy.Then,vacuum isothermal compression tests were conducted under different process condi-tions to explore the relationship between friction factor and process parameters.The experimental results show that RD-1 glass lubricant has better wettability property and lower high-temperature viscosity in the vacuum isothermal forging.The linear expansion coefficients of the two glass lubricants are similar,and the thicknesses of the interface coating are both 40-50 μm.In the forging temperature range of 950-1000℃,the friction factor of RD-1 glass lubricant is lower,which shows better lubrication performance and is more suitable for the vacuum isothermal forging process below 1000℃.
Considering the horizontal vibration,vertical vibration and dynamic rolling process parameters of work roll,a CNN-LSTM dy-namic rolling force model based on a combination of one-dimensional convolutional neural network(1D CNN)and long short-term memory network(LSTM)was established.Then,aiming at the problems of unsteady state and variable working conditions such as multiple product specifications and frequent roll changes in the hot rolling process,the dynamic rolling force prediction of small sample target data was en-hanced by the transfer learning method.The results show that the CNN-LSTM model has better generalization ability.With 10354 sets of da-ta,the prediction accuracy of the CNN-LSTM dynamic rolling force model is 96.7%,and the relative error is within 0.3%.For variable working conditions,the transfer learning model needs 600 sets of data to achieve the prediction accuracy of more than 90%.The time of data training and parameter adjustment is saved by the transfer learning method,the prediction accuracy of small sample target data is improved to better adapt to the actual production,which provides a new idea for the rapid prediction of dynamic rolling force and vibration suppression.
The 5750 mm×5750 mm×380 mm ultra-wide shield cutter head square plate forgings have large width,low height,heavy ton-nage and strict technical indicators,and it is extremely difficult to control the purity of steel ingot,select the forging scheme and formulate the heat treatment process.Therefore,in the aspect of melten steel smelting,the process scheme of"preferred steel plate + vacuum de-gassing + vacuum pouring"was proposed.In the aspect of lengthening and drawing,the forging forming scheme of"dimension control for blank making + drawing and speading with rotary anvil + four-sided trimming"was put forward for the first time.In the heat treatment process,combined with material characteristics and part structure,the process measures of"uniform spray for forced cooling in normali-zing stage + support pad height control + time-controlled flipping"was put forward.Furthermore,by establishing a finite element analysis model,the multi-scheme simulation comparison analysis for forging was conducted,and the compressive stress at the core and the forging compaction effect of various forming schemes were predicted and verified,which provides the theoretical basis for the formulation of process scheme and parameters.Through the trial production,the rationality of the process scheme is verified.
The stamping process and springback of left and right side beam reinforcement plates for automobile were simulated by finite el-ement software Autoform.Then,taking blank holding force,friction factor,stamping speed and die clearance as the optimization varia-bles,and the maximum thinning rate and the maximum springback amount as the evaluation indexes,the orthogonal test scheme was de-signed,and the optimal process parameters combination was determined to be the blank holding force of 450 kN,the friction factor of 0.13,the stamping speed of 1500 mm·s-1 and the die clearance of 1.04 mm.Furthermore,based on the optimal process parameters,the stamping and springback of parts were simulated,and on the premise that the thinning rate of part was reduced to 22.7%and the forming quality was met,the reverse springback compensation design was conducted on the facade and flange of part.Finally,the spring-back simulation results of the compensated parts and the test results of the actual production parts were compared.The results show that the simulation results are basically consistent with the actual production results,and the final stamping quality and the springback amount of parts meet the technical requirement,which provides useful guidance for the research on the stamping of similar parts.
In order to study the contact bonding and fracture characteristics of particles during the dense forming process of mushroom resi-due,the uniaxial compression mechanical experiment and the detection of acoustic emission signals were carried out.Then,the simula-tion analysis was conducted by using the discrete element software PFC,and the contact bonding fracture of the mushroom residue parti-cles,the characteristics of forcechain network,the stress-strain curves under different porosities,and the changes of particle structure were investigated.The results show that the acoustic emission counts increase with the increasing of stress,and at least 88.28%of the a-coustic emission counts is contributed by tensile bonding fracture.When the strains are 0.2,0.3,0.4 and 0.5,the number of force chains increases to 6304,7076,8080 and 9258,respectively,and the continuous pressure enhances the bonding between particles.When the porosies are 0.36,0.38 and 0.40,the number of contacts increases by 64.78%,66.55%and 70.39%,respectively.The number of tensile fractures accounts for the total number of 85.67%,90.20%and 88.28%respectively,which are much larger than the number of shear bonding fractures,and the particles are more inclined to fracture in the vertical direction of about 90°.
In order to further study and improve the influence laws of pulse current on the plastic processing process of magnesium alloy and improve its plastic deformation ability,the electroplastic tensile test of AZ31 magnesium alloy plate was carried out to study its influ-ence laws on mechanical properties and microstructure evolution of plate under different current densities.The results show that with the increasing of current density,the elongation of magnesium alloy plate increases first and then decreases.After the introduction of pulse current,the deformation activation energy Q of magnesium alloy electroplastic tensile is 79.447 kJ·mol-1.With the increasing of current density,the tensile fracture of AZ31 magnesium alloy plate changes from brittle fracture to ductile fracture,and finally melts due to the in-creasing of current density and the occurrence of necking.It is found that the addition of current has the effect of reducing the flow stress,which is conducive to recrystallization nucleation and dynamic recrystallization,so as to improve the plasticity of magnesium alloy.
The non-mandrel hot spinning process of TC4 titanium alloy high-pressure gas cylinders under different process parameter conditions was simulated by DEFORM finite element software,and the influences of spinning temperature,feed ratio and roller fillet ra-dius on the plastic properties during the forming process were studied.The results show that when the spinning temperature increases,the equivalent stress on the gas cylinder surface during the forming process decreases,but the equivalent strains at each sampling point are basically the same at different temperatures.When the feed ratio decreases,the equivalent strain increases,and the effect on the equivalent stress is significant.When the feed ratio is 3 mm·r-1,the stress value changes are relatively uniform between the sampling points.The smaller the fillet radius of roller,the greater the reduction degree of equivalent stress in the depth direction,the change of the equivalent stress caused by the roller on the surface of gas cylinder is great when the radius R is 60 and 80 mm,and the change of the equivalent stress is small when R is 100 mm and the workpiece has better uniformity.In conclusion,the optimal hot spinning process parameters for TC4 titanium alloy high-pressure gas cylinders are the temperature of 950℃,the feed ratio of 3 mm·r-1,and the roller fillet radius of 100 mm.
The hot forging die is subjected to the combined action of alternating thermal stress and mechanical stress during the working process,and it is prone to failure due to wear,cracking and plastic deformation.Aiming at the problem of low service life of hot forging die for a certain type of sliding fork,the main causes of failure were analyzed according to its failure modes.It is found that the failure posi-tion of final forging die is mainly on the end face of punching boss,the hot crack is radial,and the punching boss has a certain degree of plastic bending.Theoretical analysis and numerical simulation results show that the long-term contact of the end face of the punching punch with the hot blank leads to an increase in temperature and a decrease in strength and stiffness.Under the combined action of thermal stress and contact stress for a long time,the end face cracks and bends to a certain extent.By controlling the upsetting amount of blank,impro-ving the rigidity of boss,optimizing the height of punching boss,the rationality of material flow,and using the 3D printing technology and the material with high hot hardness to manufacture the punching boss,the die life is significantly improved.
For the problems that there were a large number of redundant connections between the variables caused by data-based methods and the information loss between the variables caused by knowledge-based methods in the field of the propagation path identification on faults,a new method for the propagation path identification on faults that combined Hidden Markov Model(HMM)and Bayesian Network(BN)was proposed.First,the knowledge of the hot strip rolling process was constructed as a qualitative BN structure,and the dimen-sionality of the data in the hot strip rolling process was reduced by the principal component analysis method to obtain the observation se-quence required for training model.Then,based on the normal historical data after dimensionality reduction and its log-likelihood value,the conditional probability table was established for BN to identify the propagation path.Finally,the fault data and their log-likelihood val-ues were used as the likelihood evidence for BN to identify the fault propagation path.The experimental results show that this method can accurately locate the six variables where the fault occurs,without any misdiagnosis or missed detection,and can accurately identify the propagation path of faults.
A Box-Behnken experimental design was conducted to investigate the influence laws of process parameters such as feeding rate,spindle speed and forming angle of tapered part on the temperature rise in friction spinning process and the interaction between these fac-tors.Based on the experimental design and temperature measurement experiments,the response surface model of the temperature rise rela-tive to the process parameters such as feeding rate,spindle speed and forming angle of tapered part during the aluminum alloy friction spinning process was established,and the causes of different factors affecting the temperature rise in friction spinning were analyzed.The results show that the forming angle has the biggest influence on the temperature rise,followed by the spindle speed and the feeding rate,and the difference of process parameters could affect the value of spinning force and the distance that the tool travels on the workpiece,re-sulting in different processing temperatures.Changing the tool form in the spinning process can significantly increase the temperature of sheet and improve the formability of workpiece.When the feeding ratio is relatively small,not only the temperature rise in the processing process is increased,but the surface quality of the workpiece is also improved.
Based on the analysis of the factors affecting the hot forming performance of Ti6Al4V titanium alloy sheet,the process develop-ment of actual hot forming parts was guided by finite element simulation.Firstly,based on the hot uniaxial tensile experiment,the influ-ences of temperature and average strain rate on flow stress,forming limit and thickness directivity coefficient of Ti6Al4V titanium alloy sheet were summarized.Then,according to the geometrical characteristics of box-shaped parts,the three factors affecting the forming of box-shaped parts,namely,forming temperature,average strain rate and sheet direction,were analyzed by finite element simulation,and the optimal forming parameters were obtained.Finally,referring to the optimal forming parameters obtained by the simulation,the fine-turning was conducted according to the actual forming effect,and the deep drawing of box-shaped part was completed.The results show that the final forming effect and the thinning rate of part are basically consistent with the results of finite element simulation,which proves that the finite element simulation can reflect the actual forming state of part accurately.Thus,it is significant to determine the reasonable process conditions for the hot drawing of box-shaped parts.
The influences of continuous extrusion plate sizes on the microstructure and properties of C19210 alloy were investigated,and the extruded plates with three sizes were prepared by continuously extruding the cast rod.Then,the three extruded plates were rough rolled,aged and finished rolled,respectively,the microstructure of extruded and rolled plate was observed by metallographic micro-scope and transmission electron microscope,and its mechanical properties and electrical conductivity were tested by using universal ten-sile machine,hardness tester and eddy current conductivity meter.The experimental results show that the larger the sizes of extrusion plate,the more deformation heat is generated during the continuous extrusion process,and the better the solution effect,which promotes the precipitation of the smaller second phase particles during aging,so that the prepared finished product has smaller grain size,higher mechanical properties and softening resistance property.Compared with the finished product prepared by the small-size extruded plate,the tensile strength of the finished product prepared by the large-size extruded plate increases from 404.1 MPa to 414.6 MPa,and the an-ti-softening hardness increases from 98.7 HV to 102.3 HV.
In order to optimize the structure and size of cross-section rib for micro-channel corrugated flat tube,the cross-section distortion rules under fifteen size-type models during the stamping process were studied by the finite element simulation,and the optimal structural style to resist the cross-section distortion was obtained.It is found that the average cross-section distortion rate of wave crest cross-section first increases and then decreases with the increasing of longitudinal rib height,and with the increasing of transverse rib width,the average cross-section distortion rate of wave crest cross-section and edge hole longitudinal cross-section decreases.When the longitudinal and transverse ribs are connected to the cross-section respectively,the cross-section distortion rate is minimum.Compared with the transverse rib,the cross-section distortion rate is more sensitive to the longitudinal rib.The smaller the number of longitudinal rib N1,the more con-ducive to reduce the cross-section distortion rate.When N1=0,the bigger the number of transverse rib N2,the more conducive to reduce the distortion rate.However,when N1≥1 and the value is fixed,the smaller N2,the more conducive to reduce the distortion rate.Among the fifteen size-style models,the corresponding cross-section distortion rate of model IV-1(h=0,N1 =0,N2=2,transverse rib width of 0.6 mm)is the smallest.
For the problems of low production efficiency,high cost and poor performance of a type of automotive flange connection part,the multi-station automatic precision hot forging technology was attempted to apply to the production.Then,based on the forming theory,a 3-station forging plan of pre-forging,final forging and punching was formulated,and three different shapes of pre-forgings were de-signed.Furthermore,the rheological curve of forging material 40CrNiMo steel was obtained by hot compression test,and the constitutive equation was fitted.The forming processes of flange connection part under different schemes were simulated by using software Deform-3D,and the reliability of each process was analyzed based on the streamline situation of metal grid and the filling quality.The forming load and temperature distribution of forgings under different schemes were compared,and the wear of forging mold was predicted based on the mold wear model,and the optimal scheme was determined.Finally,a multi-station hot forging test of flange connection part was conducted,and the test results are consistent with the predicted results,the forgings at each station are well formed without defects,the dimensional performance meets the requirements,and the forging process is stable and fast.
The precision extrusion forming process of a Φ215 mm caliber projectile body was studied by finite element simulation software DEFORM-3D.Then,the process difficulties of large aspect ratio and variable cross-section during the projectile body forming process were analyzed,and the cross-sectional shrinkage rate of projectile body was calculated.It was clear that the projectile body could be formed by the precision extrusion process.Furthermore,the precision extrusion forming process mold was designed,and the dimensions of punch and die were optimized and analyzed to reduce the forming load.By setting three sets of experiments with the wall thicknesses of 6,7 and 8 mm for projectile body,respectively,the distribution characteristics of flow velocity field and temperature field and equivalent strain field,and the changing rules of forming load for metal billets with different wall thicknesses were obtained.The results show that the form-ing load decreases with the increasing of wall thickness,and the temperature distribution and metal deformation during the forming process of the metal billet with the wall thickness of 7 mm are relatively uniform,which is the optimal wall thickness.The forming load of the metal billet with the wall thickness of 7 mm is 84.0 MN,and the equipment with the nominal pressure of 90.0 MN should be selected for the trial production.
第 21 届国际制造研究会议 (21st International Conference on Manufacuring Research, ICMR 2024) 将于2024 年8 月28-30 日于英国苏格兰格拉斯哥举办, 同期召开第 38 届英国制造研究全国会议.
