Research of precise pulse plasma arc powder welding technology of thin-walled inner hole parts

The inner hole parts played an oriented or supporting role in engineering machinery and equipment,which are prone to appear surface damages such as wear,strain and corrosion. The precise pulse plasma arc powder welding method is used for surface damage repairing of inner hole parts in this paper. The working principle and process of the technology are illustrated,and the microstructure and property of repairing layer by precise pulse plasma powder welding and CO2 gas shielded welding are tested and observed by microscope,micro hardness tester and X-ray residual stress tester etc. Results showed that the substrate deformation of thin-walled inner hole parts samples by precise pulse plasma powder welding is relatively small. The repair layer and substrate is metallurgical bonding,the transition zones( including fusion zone and heat affected zone) are relatively narrow and the welding quality is good. It showed that the thin-walled inner hole parts can be repaired by this technology and equipment.

Optimization of material removal strategy in milling of thin-walled parts

The optimal material removal strategy can improve a geometric accuracy and surface quality of thin-walled parts such as turbine blades and blisks in high-speed ball end milling.The dominant conception in the material removal represents the persistence of the workpiece cutting stiffness in operation to advance the machining accuracy and machining efficiency.On the basis of theoretical models of cutting stiffness and deformation,finite element method (FEM) is applied to calculate the virtual displacements of the thin-walled part under given virtual loads at the nodes of the discrete surface.With the reference of deformation distribution of the thin-walled part,the milling material removal strategy is optimized to make the best of bracing ability of still uncut material.This material removal method is summarized as the lower stiffness region removed firstly and the higher stiffness region removed next.Analytical and experimental results show the availability,which has been verified by the blade machining test in this work,for thin-walled parts to reduce cutting deformation and meliorate machining quality.

Initial residual stress experiment and simulation of thin-walled parts for layer removal method

Thin-walled parts have low stiffness characteristic. Initial residual stress of thin-walled blanks is an important influence factor on machining stability. The present work is to verify the feasibility of an initial residual stress measurement of layer removal method. According to initial residual stress experiment for casting ZL205 A aluminum alloy tapered thin-walled blank by a common method,namely hole-drilling method,three finite element models with initial residual stress are established to simulate the layer removal method in ABAQUS and ANSYS software. By analyzing the results of simulation and experiments,the cutting residual stress inlayer removal process has a significant effect on measurement results. Reducing cutting residual stress is helpful to improve accuracy of layer removal method.

Research on the Influence of Cutting Condition on the Surface Microstruct ure of Ultra-thin Wall Parts in Ultrasonic Vibration Cutting

In many fields of high-tech industry the ultra-t hi n wall parts are employed. In this paper the experiments were carried out to dis cuss the surface microstructure of the camera’s guided drawtube by applying ult rasonic vibration cutting device to the traditional lathe. The influence rule of the cutting condition on the surface roughness was put forward, which was drawn by comparing the ultrasonic cutting with the common cutting by use of the cemen ted carbide tool and the polycrystalline diamond (PCD) tool. The test results sh owed that the ultrasonic cutting performs better than the common cutting in the same condition. According to the test results analyzing, the surface characteriz ation is influenced clearly by the rigidity of the acoustic system and the machi ne tool, as well the setting height of the tool tip. Otherwise, the dense regula r low frequency vibration ripples will be scraped on the machined surface. When the tool tip is set higher than the rotating center of the work piece by three t imes of the amplitude of ultrasonic vibration, the vibration ripples behave alig ht; they turn light and shade alternatively when the tool tip is lower than the rotating center of the work piece by three times of the amplitude of ultrasonic vibration. According to the test result analyzing, the following conclusions are put forward: 1) The surface roughness in ultrasonic cutting is better than that in common cutting. Under a one third critical cutting velocity, the value of th e surface roughness in ultrasonic cutting rise slightly along with the cutting v elocity, while in common cutting it decreases contrast to the cutting velocity; the curves of the surface roughness in ultrasonic cutting and common cutting see m to be alike, both increase along with the feed rate and the cutting depth, but the value in ultrasonic cutting is smaller in the same condition.2) The influen ce of the coolant on the surface roughness cannot be ignored. The kerosene can b e employed to improve the surface roughness in ultrasonic machining.3) In ultras onic cutting process of aluminum alloy ultra-thin wall work piece, the PCD tool performs better than the cemented carbide tools.4) The vibration ripples result from the not enough rigidity of the acoustic system and the improper setting he ight of the tool tip. The departure of the tool tip from the rotating center of the work piece to some extent causes the vibration ripples on the machined surfa ce.

Machining Deformation Prediction of Thin-Walled Part Based on Finite Element Analysis

For the problems of machining distortion and the low accepted product during milling process of aluminum alloy thin-walled part,this paper starts from the analysis of initial stress state in material preparation process,the change process of residual stress within aluminum alloy pre-stretching plate is researched,and the distribution law of residual stress is indirectly obtained by delamination measurement methods,so the effect of internal residual stress on machining distortion is considered before finite element simulation. Considering the coupling effects of residual stress,dynamic milling force and clamping force on machining distortion,a threedimensional dynamic finite element simulation model is established,and the whole cutting process is simulated from the blank material to finished product,a novel prediction method is proposed,which can availably predict the machining distortion accurately. The machining distortion state of the thin-walled part is achieved at different processing steps,the machining distortion of the thin-walled part is detected with three coordinate measuring machine tools,show that the simulation results are in good agreement with experimental data.

Research on Influence of Cutting Conditions on Roundness of Ultra-thin Wall Parts in Ultrasonic Vibration Cutting

In the paper, the experimental researches were carr ie d out to discuss the roundness forming rule and the influence of cutting paramet ers on roundness by ultrasonic vibration cutting of the camera’s guiding drawtu be with 47.75 mm diameter and 0.6～1.5 mm wall thickness. The research results s h ow that the roundness error of ultra-thin wall parts in ultrasonic vibration cu tting is only one third of that in common cutting. The relations between the rou ndness error and the cutting parameters behave as: (1) The roundness error in co mmon cutting decreases gradually with the rise of cutting speed, while in ultras onic cutting, the roundness changes not obviously till the cutting speed is up t o a value, which is nearly equal to one third of the critical velocity. Then the roundness of workpiece will begin to increase slowly. (2) The roundness error i ncreases along with the feed rate both in common cutting and ultrasonic cutting. (3) Within the range of cutting depth in experiment, the influence of cutting d epth on the roundness error is more obvious in common cutting than that in ultra sonic vibration cutting. The conclusions are useful in machining such precise ul tra-thin wall parts. According to the tests, the following conclusions can be o btained: 1) Compared with common cutting, ultrasonic cutting can decrease effect ively roundness error of the workpiece. Under the same condition, the roundness error of the ultra-thin wall part in ultrasonic turning is about one third of t hat in common cutting. 2) In common cutting, cutting depth and feed rate have mu ch influence on the roundness and the influence of cutting velocity is little. W hile in ultrasonic cutting, the roundness was influenced heavily only when feed rate is more than 0.1 mm/r and cutting speed is more than 1/3 of the critical ro tation speed, cutting depth has little influence on the roundness in the experim ent. 3) Kerosene-oil is an optimum cutting fluid in machining ultra-thin wall workpiece. 4) To machine the ultra-thin wall precision part, ultrasonic cutting is the perfect method which can decrease the roundness error effectively an d ensure high quality of the surface.

Inner and outer pressure forming of nickel based super-alloy thin-walled part with variable diameter sections

A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature,and the principle of the method was provided.Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio(35%).The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet.The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections.The thinning of wall-thickness is less than 4%.This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections.

基于LSO-BP模型的铝合金薄壁零件铣削力预测

铣削力是铝合金薄壁零件铣削加工中很重要的过程参量,其信息的准确反馈对减小工件变形有着十分重要的作用,因而需要实现铣削力的精准预测.首先,通过铝合金薄壁零件铣削加工的仿真实验获得铣削力数据;其次,针对传统BP神经网络的弊端利用狮群算法进行改进,并将铣削力数据导入改进后网络进行训练,从而建立LSO-BP预测模型;最后,分别利用LSO-BP模型、PSO-BP模型和传统BP神经网络模型预测铣削力.均方根误差、平均相对误差和相关系数等评价指标的对比结果表明,LSO-BP模型预测铣削力的性能明显优于PSO-BP模型和传统BP神经网络模型.

全耳内镜下耳屏软骨-软骨膜复合体在上鼓室外侧壁重建中的临床应用

目的探究全耳内镜下耳屏软骨-软骨膜复合体在上鼓室外侧壁重建中的临床应用。方法选取2020年6月~2023年6月间徐州市中心医院收治的58例进行上鼓室外侧壁重建的胆脂瘤患者,根据采用修复材料的不同分为对照组及观察组各29例。对照组采用耳屏软骨膜进行上鼓室外侧壁重建,观察组采用耳屏软骨-软骨膜复合体进行上鼓室外侧壁重建,两组患者均于全耳内镜下进行手术。统计患者术中出血量、手术时间,术后3个月复查听力情况、干耳情况及耳道功能改善情况,术后随访6个月鼓膜愈合情况。结果与术前比较,术后3个月气导听阈、气骨导差降低(P<0.05),与对照组比较,观察组气导听阈、气骨导差降低(P<0.05);与对照组比较,观察组干耳率、耳道功能良好率、听力提高成功率均升高,干耳时间缩短,但耳屏愈合时间增加(P<0.05);与对照组比较,观察组手术时间缩短,术中出血量减少(P<0.05);观察组、对照组术后并发症总发生率分别为13.79%、24.14%,二者比较差异无统计学意义(P>0.05);观察组愈合良好率高于对照组(86.21%vs.62.07%)(P<0.05),两组患者耳膜穿孔(10.34%vs.24.14%)、鼓膜移位(3.45%vs.6.90%)及鼓膜回缩(0.00%vs.6.90%)发生情况比较,差异无统计学意义(P>0.05)。结论全耳内镜下耳屏软骨-软骨膜复合体在上鼓室外侧壁重建中有利于改善患者听力,有利于术后恢复。

3003Al-H14薄壁微小通道扁管波形冲压成形尺寸对截面变形的作用规律

薄壁微小通道波形扁管是建设新能源汽车锂电池组恒温系统的绝佳材料,成形尺寸是影响其冲压成形截面变形的关键因素。建立了实验验证的3003Al-H14微小通道薄壁扁管的波形冲压-回弹有限元模型。基于所建模型,研究了截面高度、管坯壁厚、内外面相对弯曲半径缩放系数等成形尺寸,对截面变形率和平均截面变形率的作用规律。研究发现:①横截面上边缘孔的截面变形率通常较大,其余孔的截面变形率相对较小且大小一致;纵截面上孔的截面变形率呈现波峰波谷高、中间段低的分布特点。②扁管的截面变形率随着截面高度增大而增大,当截面高度超过4 mm时,扁管内的筋显著弯折,横截面塌陷严重。③扁管的平均截面变形率随着壁厚增大呈指数函数下降;当壁厚等于0.1 mm时,所有截面都畸变严重,而当壁厚超过0.3 mm时,最大截面畸变率下降至24.71%。④内外面相对弯曲半径的缩放系数越大,则内外面的实际弯曲程度越小,平均截面变形率也越小。研究成果对薄壁微小通道波形扁管的精确成形具有科学意义和工程价值。

Numerical analysis of flow-thermal coupling in micro-plasma welding pool of thin-wall part

The formed characteristics of thin-wall part is studied when it is in the process of MPAW. Finite element method is used to sinmlate the temperature field coupling flow field in the welding of thin-wall part. It is found that because of the obvious effect of heat accumution in cross-section, where the distribution of temperature field area presents trapezoidal inverted approximately in the molten pool and the non-molten pool area presents level. The surface tension, the electromagnetic force and buoyancy are considered for analyzing the effects on the fluid flow of welding-pool. It can be obtained that the surface tension is the main driving force in the welding pool, which is far greater than electromagnetic force and buoyancy.

基于BAS-BP的铝合金弱刚性零件铣削力的预测

为减少薄壁零件的加工变形,实现对铝合金薄壁零件铣削力的精准预测,通过响应曲面法设计相关试验获得铣削力试验数据。针对传统BP神经网络预测精度不高的弊端,将天牛须寻优算法(BAS)与BP神经网络结合,优化BP神经网络初始权值和阈值,建立BAS-BP神经网络预测模型。结果表明,改进后的神经网络预测模型具有更高的预测精度,对铝合金零件加工中铣削力的预测有较为理想的效果。

Flow behavior in microchannel made of different materials with wall slip velocity and electro-viscous effects

In a microfluidic system, flow slip velocity on a solid wall can be the same order of magnitude as the average velocity in a microchannel. The flow-electricity interaction in a complex microfluidic system subjected to joint action of wall slip and electro-viscous effect is an important topic. This paper presents an analytic solution of pressuredriven liquid flow velocity and flow-induced electric field in a two-dimensional microchannel made of different materials with wall slip and electro-viscous effects. The Poisson- Boltzmann equation and the Navier-Stokes equation are solved for the analytic solutions. The analytic solutions agree well with the numerical solutions. It was found that the wall slip amplifies the fow-induced electric field and enhances the electro-viscous effect on flow. Thus the electro-viscous effect can be significant in a relatively wide microchannel with relatively large kh, the ratio of channel width to thickness of electric double layer, in comparison with the channel without wall slip.

薄壁件铣削颤振特征提取的GA-PE-VMD和MSE方法

在高速铣削航空零件时,由于薄壁结构刚度较低,容易产生颤振,颤振导致表面质量差,尺寸误差,降低刀具和机器寿命,是性能的主要限制之一。因此,需要一种可靠的检测方法来识别颤振。针对薄壁结构铣削过程中的颤振检测问题,提出一种基于优化变分模态分解和多尺度样本熵的薄壁件颤振特征提取方法。首先,为了解决变分模态分解参数选择问题,提出一种基于遗传算法优化和最小排列熵的参数自适应方法。其次,计算分解信号的能量比作为挑选IMFs的原则,从而进行信号重构。为了解决单尺度样本熵不能很好地反映颤振发生时铣削力信号特征,引入多尺度样本熵对铣削颤振进行检测,并进行了实验验证。结果表明,采用优化变分模态分解算法对信号进行处理,可以避免因模态混叠而造成的颤振信号难以分离的问题。多尺度样本熵比单尺度样本熵更加有利于颤振检测,随着尺度因子的增大,铣削信号的MSE有减小的趋势,且尺度因子为10时的MSE更有利于颤振检测。

Determination of <i>α</i>-1,3-Linked Mannose Residue in the Cell Wall Mannan of <i>Candida tropicalis</i>NBRC 1400 Strain

To investigate the chemical structure of cell wall mannan obtained from pathogenic yeast, Candida tropicalis NBRC 1400 (former antigenic standard strain, IFO 1400). As a result of two-dimensional NMR analysis, it was shown that the mannan of this strain is composed of α-1,6-, α-1,3-, α-1,2- and β-1,2-linked mannose residues. In this research, the mannan was subjected to three degradation procedures, acid-treatment, α-mannosidase, and acetolysis under two conditions in order to determine the chemical structure of the antigenic oligomannosyl side chains in this molecule. The 1H-nuclear magnetic resonance spectra of resultant oligosaccharides, pentaose and hexaose, demonstrated the existence of the oligomannosyl side chains corresponding to Manα1-3Manα1-2Manα1-2Manα1-2Man and Manα1-3Manα1-2Manα1-2Manα1-2Manα1-2Man, respectively, which have previously also been found in Candida albicans serotype A strain mannans. These findings indicate that C. tropicalis and C. albicans serotype A have no significant difference in the chemical structure of these cell wall mannans. Therefore, it can be interpreted that it is extremely difficult to distinguish both species by targeting the antigenic group in these mannans.

铝合金半球壳拉深-旋压复合成形工艺仿真

针对航天铝合金半球壳传统拉深成形精度差的问题,引入旋压成形,提出铝合金半球壳拉深-旋压复合成形新思路,充分发挥拉深成形和旋压成形的技术优势,实现该构件厚度均匀性好和贴模精度高的成形加工.建立了铝合金半球壳复合成形过程有限元仿真模型,实现了铝合金半球壳复合成形过程仿真,分析了不同旋压占比复合成形件的壁厚分布和贴模度变化规律.结果表明,旋压占比为50%的复合成形铝合金半球壳壁厚均匀性改善明显;强力旋压可改变成形构件应力状态,显著提高复合成形构件尺寸精度.同时,进行了直径1 m级铝合金半球壳复合成形工艺试验验证,实现了构件厚度均匀性和贴模精度的提高.

薄壁易碎圆柱内壁工件的内撑式机械手抓取接触-碰撞仿真与实验研究

针对工业生产中抓取薄壁易碎件的作业需求,提出了一种具有指掌协同特征的内撑式机械手构型。为了寻找合适的机械手手指作业参数,探索抓取过程中接触-碰撞时应力的变化规律,采用HyperMesh、LS-PrePost等软件集成建模的方法建立了机械手指的有限元模型,对有限元模型施加相应的约束、载荷、接触类型后,计算得到了手指与易碎件接触碰撞过程中的应力、应变云图。仿真结果表明:随着手指冲击速度的增大,易碎件所受的应力呈线性增大。速度在0.5~2.5 mm/ms变化时,应力增大为原来的3~4倍;随易碎件壁厚的增大,易碎件所受的应力逐渐减小。而在较小壁厚阶段,应力变化明显,壁厚0.5~1.0 mm时的平均应力变化是壁厚1.0~2.5 mm时应力的6~7倍;在机械手抓取易碎件的碰撞瞬间施加不同的加速度时,随加速度的增大,接触应力也相应增大,加速度在1.0~2.5 mm/ms^(2)时的平均应力变化是加速度0.5~1.0 mm/ms^(2)时的8~9倍。根据已有的仿真结果,通过建立Kriging代理模型,计算得到的不同壁厚、抓取速度条件下接触应力大小的预测模型,为确定不同状态下的机械手抓取参数、设计和优化手指结构建立了基础。通过构建实验系统,对相关仿真结果进行了实验验证,证明了仿真结果的正确性。

基于PSO-BPNN和NSGA的薄壁件定位布局优化

为提高装夹布局优化计算的效率,同时考虑加工过程中振动对变形的影响,提出了融合改进的反向传播神经网络(back propagation neural network,BPNN)与快速非支配排序遗传算法(nondominated sorting genetic algorithms,NSGA-Ⅱ)的优化模型。首先,基于“N-2-1”定位原理,以定位点坐标为设计变量,薄壁件装夹变形和主振型位移为优化目标,通过有限元仿真建立了神经网络训练样本集;其次,引入粒子群算法(particle swarm optimization,PSO)改进神经网络,通过对有限样本集训练,构建了定位布局与装夹变形和振动位移之间的代理模型。实例结果表明,改进后的神经网络对装夹变形的预测精度提高了93%,对振动变形的预测最大误差仅为1.8%;最后,通过遗传算法求解预测模型得到了定位布局帕累托解集,进一步提高了优化效率。

Structural model for the first wall W-based material in ITER project

The preparation, characterization, and test of the first wall materials designed to be used in the fusion reactor have remained challenging problems in the material science. This work uses the firstprinciples method as implemented in the CASTEP package to study the influ ences of the doped titanium carbide on the structural sta bility of the WTiC material. The calculated total energy and enthalpy have been used as criteria to judge the structural models built with consideration of symmetry. Our simulation indicates that the doped TiC tends to form its own domain up to the investigated nanoscale, which implies a possible phase separation. This result reveals the intrinsic reason for the composite nature of the WTiC material and provides an explanation for the experimen tally observed phase separation at the nanoscale. Our approach also sheds a light on explaining the enhancing effects of doped components on the durability, reliability, corrosion resistance, etc., in many special steels.

框类薄壁件装夹布局与加工参数研究

针对航空隔框类薄壁件在铣削加工中极易产生变形等问题,通过有限元软件ABAQUS研究了铣削过程中装夹布局和铣削参数对薄壁件加工变形量的影响。首先根据装夹有限元模型,分析装夹位置和夹紧顺序对薄壁件变形量的影响,并在装夹仿真的基础上建立了铣削加工模型,设计正交试验得到不同铣削加工参数下薄壁件的变形量;其次以仿真数据为样本,使用BP神经网络和遗传算法对装夹布局和铣削参数进行优化;最后对优化结果进行实验验证,结果显示仿真与实验数据比较符合,最小偏差为4.38%,最大偏差为9.35%。研究结果表明:通过有限元仿真试验辅助选取薄壁件的铣削加工参数,能充分地提高航空薄壁件的加工质量。