TA15钛合金深孔钻削试验研究

以难加工材料TA15钛合金为研究对象,采用正交试验设计方法,研究内排屑深孔钻削钻头断屑槽圆弧半径、机床主轴转速和进给量在钻削过程中对切屑形态的影响规律。试验表明:钻头断屑槽的圆弧半径是影响切屑形态的主要因素,机床主轴转速和进给量为次要因素;优化后的工艺参数选取断屑槽圆弧半径为0.8 mm,主轴转速为255 r/min,进给量为0.45 mm/r时,切削过程平稳,排屑顺畅。     

Preform design for large-scale bulkhead of TA15 titanium alloy based on local loading features

Large-scale TA15 (Ti–6Al–2Zr–1Mo–1V) titanium alloy bulkhead is a key lightweight load-bearing structure part in an aircraft, which has a large plane view and has a complex shape with high ribs and thin webs. In its forging process, the forming defects, such as folding and under-filling are prone to occurrence. The near-net shape forming with saving force of this large-scale complex component can be realized with proper preform design combining local loading condition. By analyzing isothermal local loading process characteristic of large-scale bulkhead, it indicates that the simple unequal-thickness billet is suitable for small lot manufacture of large-scale TA15 titanium alloy bulkhead. Considering the geometry and forming characteristics, such as large dimension, complex shape, mass data, etc., a design method of unequal-thickness billet using analytical analysis and numerical simulation is proposed. The preform for a large-scale TA15 titanium alloy bulkhead is designed by the proposed method. The basic three-dimensional shape of billet is determined by the analytical models based on local loading features, and the basic billet is modified according to numerical simulation result and considering the local loading forming characteristic, and then the preform without resulting in folding and under-filling can be obtained after two modifications.     

TA15钛合金电子束焊平行焊缝的获得方法

截面平行的焊缝是保证中大厚度焊接结构熔合区组织均匀性及力学性能连续性的重要条件,在工程中有着重要应用。本文在对焊缝形貌进行观察及分析的基础上,研究获得平行焊缝的工艺方法。结果表明,对焊接速度、电子柬流及聚焦电流等焊接参数进行综合调节,可以有效改变焊缝形貌,使焊缝逐步趋于平行。增加编摆扫描并控制扫描的频率和幅度,可以获得一系列具有不同熔宽的平行焊缝。     

Formability analysis on the process of multi-point forming for titanium alloy retiary sheet

The multi-point forming (MPF) process of spherical surface parts of titanium alloy retiary sheet and titanium alloy sheet metal with different thickness and curvature radius was simulated by an explicit finite element software. Contradistinctive analysis between retiary sheet and sheet metal forming parts with different modes were done. The simulation results show that under the same forming conditions, titanium alloy retiary sheet is not easy to wrinkle and springback, whereas it is easy to form. The reason for differences in the formability of above-mentioned sheet metal is also analyzed. A non-wrinkling limited graph and a fracture critical graph for spherical surface parts of retiary metal sheet and metal sheet were obtained. Finally a forming test of titanium alloy cranial prosthesis was done in MPF press. Testing results indicate the customized 3D curved surface of prosthesis can be adequately shaped and the forming quality was guaranteed.     

Study on cutting temperature during milling of titanium alloy based on FEM and experiment

A finite element model of helix double-edge cutting was developed to study cutting temperature during milling of titanium alloy Ti6Al4V. To improve the accuracy of finite element simulation, a new method to construct material constitutive model was presented, and material constitutive model with big strain, high strain rate, and high-temperature characters for aeronautical titanium alloy in cutting process was established. Using this finite element model, milling process of titanium alloy was simulated. Cutting temperature change curves and values were obtained. An analysis indicates that the highest cutting temperature lies in tool-chip interface and is more close to cutting edge; moreover, the temperature is higher in rake face than flank face of the tool. The embedded semi-artificial thermocouple cutting temperature experiment was improved by substituting constantan band for constantan wire. By comparing the results obtained from finite element simulation and cutting temperature experiment results, a good agreement is found, showing finite element simulation analysis of cutting temperature for titanium alloy is correct.     

有限体积法研究钛合金叶轮等温精密成形

针对钛合金叶轮形状复杂、受力状况恶劣以及钛合金材料导热率低的特点,研究了叶轮等温锻造工艺中叶片顶部形状的设计、坯料直径的选择以及工艺参数的制订等技术难点.采用有限体积法模拟了Ti-6A1-4V钛合金叶轮的等温精密成形过程,分析了成形过程中金属的流动行为和对模具的充填能力,给出了成形各阶段工件的温度场和应变速率场分布情况.模拟结果表明,等温精密锻造钛合金叶轮,不仅可以获得很好的金属流线和满意的几何形状,而且由于成形的温度和应变速率条件有利于Ti-6A1-4V材料发生超塑性变形,还可以得到分布均匀的等轴细晶组织,提高锻件的力学性能.     

3D FEM simulation of milling process for titanium alloy Ti6Al4V

Milling is used as one of the most important tools with the complex tool geometry in industry. However, the complex milling process cannot be simulated by 2D finite element method. Therefore, a more real 3D finite element model (FEM) for the complex milling process of titanium alloy Ti6Al4V is firstly developed using the finite element software ABAQUS. This model takes into account the dynamic effects, thermomechanical coupling, material damage law, and contact criterion. Firstly, the Johnson–Cook material constitutive equation was proposed, considering the effects of strain, strain rate, and temperature on material properties. Secondly, the damage constitutive law was adopted as the chip separation criterion. Then, the simulation for the milling process of Ti6Al4V was conducted through ABAQUS based on the established 3D FEM. Finally, chip formation, stress distribution, cutting force, and milling temperature were obtained. Further, a series of milling experiments of Ti6Al4V were carried out to validate the simulation results. It confirms the capability and advantage of 3D FEM simulation in the complex milling process of titanium alloy.     

Formability evaluation of a pure titanium sheet in the cold incremental forming process

Owing to its ability to deform a sheet metal locally, the single point incremental forming (SPIF) process produces larger deformations as compared to the conventional forming processes. In the present study, we investigated the effect of some process parameters – pitch, tool diameter, feed rate and friction at the interface between the tool and blank – on the formability of a commercially-pure titanium sheet. Trends between the process parameters and formability are presented in this paper.     

低温MQL技术在TA15铣削加工中的应用研究

通过在冷却液与低温MQL两种方式条件下,对TA15钛合金材料进行切削试验研究发现:低温MQL状态下加工工件使用的刀具切削寿命更长,工件的切削效率更高,加工的表面质量更好,变形更小.但是其在加工过程中,浅切冷却具有不适应性、加工中产生附加产物对环境的影响、深腔结构的加工冷却不充分等方面具有一定局限性,需进一步研究.     

基于正交试验钛合金激光切割工艺参数优化

激光切割质量受各种因素的影响,为了得到高质量的激光切割件,需要根据不同的切割板材进行优化。利用厚度1.5mm的TC1薄板作为研究对象,研究激光功率、切割速度、焦点位置和辅助气体压力主要因素对激光切割质量的影响,采用正交试验方法安排激光切割试验,使用L16(45)正交表,完成十六组激光切割试验。利用测量点轮廓精度的算术平均值作为结果进行分析,采用直观分析法,因素效应曲线图,方差分析对切割参数进行分析研究。结果表明:切割速度和辅助气体压力是主要因素,对切割质量和精度有较大影响,而激光功率对切割后试件的轮廓度影响较之上两个因素小,但是激光功率改变对切割件的表面质量影响显著。     

Flange forming with combined blanking and extrusion process on sheet metals by FEM and experiments

Flange height and lip thickness are generally restricted by the formability of sheet metals in the conventional forming operation. Fracture can easily occur on the edge of the flange, causing it to fold and affecting the sustainability of the application of flange. In the current work, combined blanking and cold extrusion process is applied to manufacture component with the aim to obtain the substantial flange suitable for subsequent assembly with its counterparts. Meanwhile, FEM software DEFORM is utilized to simulate this process and to reveal the deforming features of the combined process and the accuracy of the simulation is experimentally verified. Both the results of simulation and experiment prove that fracture of flange forming mainly occurs in the cutting edge of punch die, which can be predicted by FEM simulation and can be eliminated or avoided by the three following methods: (1) the punch die is modified in the rounded corner of the die as a chamfer connecting the rounded corner and the punch head in an attempt to reduce the flow resistance of the raw material and solve the fracture problem. (2) Sufficient counter-pressure should be applied to bring about the hydrostatic pressure, causing the shear zone to become compressive (negative), and this leads to improvement of ductility of the sheet metals and can restrain fracturing. (3) Suitable combination of blanking and extrusion process should be arranged. Finally, the high-quality components are successfully manufactured through experiment, which confirms that the result of FEM simulation is correct and lays a technical foundation for the design of combined blanking and cold extrusion process on sheet metals.     

Optimization of spring-back in creep age forming process of 7075 Al-Alclad alloy using D-optimal design of experiment method

This paper attempts to model and predict the spring-back for creep age forming of a 7075 Al-Alclad alloy using statistical analyses based on a design of experiments method. Time and temperature were chosen as effective variables for determining spring-back in the creep age-forming process. The D-optimal design of experiments method facilitated statistical analyses and the extraction of a mathematical model for determining spring-back in the experimental variables domain. The spring-back of the specimens was calculated using a numerical procedure based on the pure bending theory. Analysis of the variances for spring-back showed that temperature was the most effective variable in the creep-age forming process. Additionally, a mathematical model and the response surface of the spring-back showed that to decrease spring-back, the significant variables should be in the upper level. The spring-back in the creep age-forming process was optimized for a 7075 Al-Alclad alloy in the optimum mechanical properties region.     

基于单因素实验的钛合金砂带磨削砂带寿命研究及分析

采用ck918x碳化硅砂带和kk712x氧化铝砂带,对钛合金进行了磨削工艺试验,对磨削后砂带形貌进行了观测.研究了砂带线速度、工作移动速度、磨削深度等磨削参数对砂带寿命和相对金属去除率的影响情况.     

Forming process optimization for non-axisymmetrical complex component based on FEM simulation and experiment

Numerical and experimental investigations were carried out in order to reduce the forming load and defects for non-axisymmetrical complex components. The component with intricate shape and V-type high ribs was widely used as key load-bearing structures. Single-step integral loading with different billet shapes and two-step local loading schemes were used to simulate the forming process and study the metal flow laws. Forming processes of preforming and finisher were analyzed to predict the detail characteristics of material flow using the 3D finite element method models. The simulated results showed that the two-step local loading schemes significantly reduced the forming load and improved the metal filling formability without defects, the required forming load obviously lower than single-step integral. The occurrences of defects, forming loads, and velocity vector distributions were studied and a suitable preform and corresponding die designs were obtained. The experimental results also showed that the component could meet the requirements of dimensional accuracy and mechanical properties.     

Determination of the friction factor of Ti-6Al-4V titanium alloy in hot forging by means of ring-compression test using FEM

The friction factor of Ti-6Al-4V titanium alloy under hot forging situation was determined by the combined approach of ring-compression tests and finite element (FE) simulations. It is noticed in particular that the heat-transfer (HT) coefficient has significant effects on the metal flow and calibration curves, thereby affects the measurement of interfacial friction factor. Moreover, the HT coefficients are different for glass lubricant and dry friction conditions. Therefore, different HT coefficients should be employed to generate the calibration curves when both of the lubricant conditions were applied for determining the interfacial friction coefficients in hot ring-compression of Ti-6Al-4V titanium alloy.     

Determination of the friction factor of Ti-6Al-4V titanium alloy in hot forging by means of ring-compression test using FEM

The friction factor of Ti-6Al-4V titanium alloy under hot forging situation was determined by the combined approach of ring-compression tests and finite element (FE) simulations. It is noticed in particular that the heat-transfer (HT) coefficient has significant effects on the metal flow and calibration curves, thereby affects the measurement of interfacial friction factor. Moreover, the HT coefficients are different for glass lubricant and dry friction conditions. Therefore, different HT coefficients should be employed to generate the calibration curves when both of the lubricant conditions were applied for determining the interfacial friction coefficients in hot ring-compression of Ti-6Al-4V titanium alloy.     

Friction of composites based on titanium carbide produced by the process combustion method

The method of SHS force compaction is used to produce composites that include TiC + 50 vol % inert. Copper, iron, nichrome, and steel G13 served as the inert. It is noted that the lattice parameter, the TiC grain size, and the mass ratio Ti/C in TiC grains are practically independent of the inert composition. It is shown that some of the composites possess high mechanical properties. The friction of the composites that contain Ni-Cr is characterized by a friction coefficient of up to 0.5 and a high wear owing to their strong adhesion to the counterbody. The materials whose compositions are TiC + (Cu, Fe) and TiC + (Cu, G13) are effective under a pressure of about 100 MPa and can serve as a basis for developing tribological materials.