Titanium Alloy Thin-walled Parts Research Articles

Optimization of process parameters for minimizing the temperature field of high-speed milling of titanium alloy thin-walled parts

Optimization of process parameters for minimizing the temperature field of high-speed milling of titanium alloy thin-walled parts

Study on milling flatness control method for TC4 titanium alloy thin-walled parts under ice fixation

Thin-walled parts are characterized by weak rigidity and are very prone to deformation during machining, which directly affects the machining accuracy and performance of the parts, so controlling the machining deformation of thin-walled parts is an urgent process problem to be solved. To address such problems, this paper proposes a flatness control machining method based on ice holding of workpieces. The method uses frozen suction cups to solidify liquid water to achieve stress-free clamping of workpieces. We conducted a low-temperature tensile test to investigate the low-temperature mechanical properties of the material. Comparative tests of ice-free and low-temperature ice-fixed milling were conducted to compare and analyze the changes of flatness and milling force in the two working conditions, to investigate the influence of machining parameters on the flatness of thin-walled parts, and to reveal the mechanism of low-temperature milling of ice-fixed workpieces. In addition, the low-temperature milling performance of titanium/aluminum alloy based on ice-fixation was compared. The results show that TC4 has good plasticity, high flexural strength ratio and strong resistance to deformation at low temperatures. Compared with no ice-holding, ice-holding machining effectively improves the flatness of the workpiece, and the order of the machining parameters affecting flatness is: feed rate > milling depth > spindle speed. The milling forces under ice-holding conditions were all greater than those without ice holding. The stiffness and hardness, resistance to damage and deformation of titanium alloy at low temperature are greater than those of aluminum alloy. This method provides a new method for high-precision machining of thin-walled parts.

Milling performance of cryogenic cooled titanium alloy thin-walled parts based on cantilever sheet

Milling performance of cryogenic cooled titanium alloy thin-walled parts based on cantilever sheet

High surface quality additive manufacturing process of titanium alloy with composite heat source

In order to solve the problems of high surface roughness and low dimensional accuracy of titanium alloy metal-wire fuse additive manufacturing, this paper proposes a high surface quality and dimensional accuracy of titanium alloy additive manufacturing with composite heat source process. On the basis of orthogonal experiments, titanium alloy wires with diameter of 0.3 mm Ti-6Al-4V were deposited in a small molten pool by laser and Joule heat source. Thin-walled titanium alloy parts with high surface quality and dimensional accuracy were obtained, and the quality, microstructure, and mechanical properties were tested. The measurement areas are shown that the average roughness Ra is 1.65 μm in the direction deposition, and the dimensional accuracy error is less than 0.28 mm. On this basis, the microstructure and mechanical properties of titanium alloy thin-walled were analyzed. The microstructures are net-like, with microhardness of about 330HV. The ultimate tensile strength of titanium alloy thin-walled parts is 917.56 MPa, and the elongation can reach 20.68%, which is comparable to the strength of casting and forging fracture. The results show that the proposed additive manufacturing process of metal-wire with composite heat source has the potential of further metal AM in high surface quality parts.

Side-Milling-Force Model Considering Tool Runout and Workpiece Deformation

With the development of Industry 4.0, hard-cut materials such as titanium alloys have been widely used in the aerospace industry. However, due to the poor rigidity of titanium alloy parts, deformation and vibration easily occur during the cutting process, which affects the accuracy, surface quality and efficiency of part machining. Therefore, in this paper, tool runout and workpiece deformation are introduced into the milling process of flat-end mills. Based on the tool’s hypocycloid motion, a geometric parameter model of the milling process is established, and the undeformed cutting thickness model is obtained considering the tool runout and workpiece deformation. Finally, the milling force model for side-milling titanium alloy thin-walled parts was established. The accuracy of the force model is verified through experiments. The error of the proposed model is far less than that of the traditional basic method. The maximum error of the traditional basic method is 87.09%. However, the maximum error of the proposed model is only 66.54%. The results show that the proposed force model considering tool runout and workpiece deformation can provide more accurate milling force prediction.

Machinability analysis of micro-milling thin-walled Ti-6Al-4V micro parts under dry, lubrication, and chatter mitigation conditions

Micro-milling technology is an efficient method for machining titanium alloy thin-walled micro parts. However, the machinability of thin-walled microstructures can be greatly affected by chatters due to their weak stiffness, especially in difficult-to-machine materials like titanium alloys. In order to obtain high-quality thin-walled micro parts, a chatter mitigation strategy is presented and its mechanism is analyzed in this paper. The titanium alloy workpiece is submerged into a kind of high-viscosity fluid, which can improve machining stability by increasing the damping of the micro-milling process. The stability lobe diagrams (SLD) are established, and the machinability is analyzed and compared under different machining conditions. The cutting force, surface roughness, micro-tool wear, and dimension accuracy of thin-walled micro parts are selected as the evaluation criteria for the machinability assessment. Well-designed micro-milling experiments are carried out under dry, lubrication, and chatter mitigation conditions using the same cutting process parameters. The results show that the use of cutting fluid can effectively improve machinability under stable cutting processes, but the effect of cutting fluid is weakened under chatter machining. The proposed chatter mitigation strategy can suppress regenerative chatter throughout the micro-milling process for thin-walled micro parts and improve their machinability comprehensively.

Finite Element Simulation of Bending Thin-Walled Parts and Optimization of Cutting Parameters

Aiming at the problems of large elastic deformation and low machining accuracy in cutting titanium alloy thin-walled parts, this paper establishes the finite element model of milling titanium alloy thin-walled parts, and simulates and analyses the milling process of titanium alloy thin-walled parts by the statics analysis module of ANSYS 15.0 software. The maximum deformation point of the workpiece in the milling process is determined. Then the combination of cutting parameters that can minimize the deformation is determined by the orthogonal experiments of four factors and four levels. This paper designs the single factor experiments, which study the distribution of the milling force and the deformation law of the parts in the milling process. Moreover, this paper carries out the optimal design of the cutting parameters by orthogonal experiments, which provides a reference for the selection of the cutting parameters for the bending thin-walled parts of titanium alloy.

Milling chatter detection of thin-walled parts based on GA-SE-SCK-VMD and RCMDE

In the milling process, it is easy to produce chatter due to the low rigidity of the thin-walled structure, which leads to the deterioration of workpiece surface quality and reduces the service life of cutting tools and machine tools. Therefore, a new chatter detection method for thin-walled parts based on optimal variational mode decomposition (OVMD) and refined composite multi-scale dispersion entropy (RCMDE) is proposed in this paper. Firstly, to solve the problem that the decomposition effect of the variational mode decomposition (VMD) algorithm is greatly affected by its parameter, a genetic algorithm (GA) is used to iteratively optimize the parameter of the VMD algorithm, and a new index, square envelope spectral correlated kurtosis (SE-SCK), is introduced as the fitness function of the genetic algorithm. Then, the energy ratio of the decomposed signal is calculated as the principle of selecting sub-components, and the sub-components with rich chatter information are selected for signal reconstruction. To solve the problem that the multi-scale dispersion entropy (MDE) will miss some information in the multi-scale process, RCMDE is introduced to detect milling chatter. Finally, the experiment of the variable cutting depth in side milling of titanium alloy thin-walled parts is carried out. The experimental results show that the OVMD algorithm proposed can solve the problem of difficult separation of chatter frequency bands caused by mode aliasing and lay a foundation for subsequent chatter feature extraction. RCMDE is more conducive to chatter detection than the single-scale DE when the scale factor is 4. The distinguishing effect of RCMDE on the machining state is more than 50% higher than that of MDE when the scale factor is 4.

Investigation on an in-process chatter detection strategy for micro-milling titanium alloy thin-walled parts and its implementation perspectives

Thin-walled micro parts are widely used in many fields, such as aviation, aerospace, precision engineering, and even micro-molds. Compared with other micro-fabrication technology, micro-milling can be considered as one of the most efficient 3D fabrication techniques. However, due to the vulnerable stiffness of thin-walled micro parts and micro tools, regenerative chatter is prone to occur during the micro-milling process. Severe chatter can lead to large fluctuations in cutting forces, resulting in deterioration of surface roughness/integrity and decreasing in tool life. Therefore, an in-process chatter detection strategy based on the feature extraction of micro-milling forces is proposed in this paper. Micro-milling force signals are measured and processed by advanced algorithms developed. After variational mode decomposition (VMD) for each group of cutting forces, the optimal intrinsic mode function (IMF) is adopted based on the Laplacian score (LS). The multi-scale permutation entropy (MSPE) values of the optimal IMF of each group are calculated, wherein the scale factor s, the embedding dimension m, and the delay time t are obtained by the genetic algorithm (GA). The obtained MSPE values are used as input vectors to train the support vector machine (SVM) classifier, which is used to monitor the stability states of the micro-milling processes. The effectiveness of the proposed strategy is compared with the other classic chatter detection methods and indicators in the micro-milling experiments of thin-walled parts. The results show that the method resulted from the strategy can extract cutting force features effectively and in-process detect chatters accurately in micro-milling thin-walled parts processes.

Finite Element Analysis of the Milling of Ti6Al4V Titanium Alloy Laser Additive Manufacturing Parts

This study aimed to analyze the defects of large residual stress in laser additive manufacturing metal parts by establishing a milling numerical simulation of Ti6Al4V titanium alloy thin-walled parts based on the Johnson-Cook constitutive model of Ti6Al4V titanium alloy, a modified Coulomb friction stress model, the physical chip separation criterion and other theories, combined with the finite element software ABAQUS. The influences of milling depth, initial temperature and milling speed on the forming quality of the formed part were analyzed. The results show that milling changes the residual stress distribution of the deposition layer, which can reduce or even change the residual tensile stress on the surface of the deposition layer produced by the additive manufacturing process into compressive stress, and the equivalent Mises stress decreases by 47% compared with the original forming surface. When the initial temperature increases from 20 °C to 400 °C, the maximum equivalent Mises stress of the milling surface decreases by 26%.

Prediction and experimental research of abrasive belt grinding residual stress for titanium alloy based on analytical method

As an important material, titanium alloy is widely used in the manufacture of aircraft engine parts, and its processed surface quality is critical to the performance of aircraft engines. Abrasive belt grinding (ABG) is a kind of elastic grinding, which plays a significant role in improving titanium alloys’ surface integrity. To validate the mathematical model’s effectiveness from the grinding parameters to the surface residual stress after grinding, firstly, according to the molecular dynamics theory and ABG process, a physical model of titanium alloy ABG molecular system is proposed, and the embedded atom method is chosen as the interatomic potential of titanium alloy. Secondly, combined with the mathematical expression model of residual stress, the surface residual stress is characterized, and the heat correction coefficient is proposed to modify the mathematical model. Finally, based on molecular dynamics, the simulation of grinding residual stress and the grinding experiment is carried out for titanium alloy thin-walled parts. The results of simulation and experiment show that the trend of simulation results is similar to the experiment results. The simulation model can better represent the change rule of ABG surface residual stress for the titanium alloy material, but the average error rate is up to 15.01% due to the systematic error between the two. After correction, the average error rate between the simulation values and experiment values of residual stress on the surface decreases to 4.44%; the effectiveness of the mathematical model is verified.

Experimental study on surface residual stress of titanium alloy curved thin-walled parts by ultrasonic longitudinal-torsional composite milling

The production of thin-walled titanium alloy curved surfaces is of great significance to aerospace manufacturing industry. The magnitude and distribution of residual stress are one of the important factors affecting the surface integrity of the workpiece. In order to obtain larger surface residual compressive stress, improve the surface integrity of the workpiece, and realize the fatigue-resistant manufacturing, the ultrasonic longitudinal-torsional composite milling method was proposed. Orthogonal and single-factor experiments were carried out on titanium alloy curved thin-walled parts, and the differences of cutting force, cutting temperature, and residual stress between conventional milling and ultrasonic longitudinal-torsional composite milling were compared and analyzed, and the influence of different process parameters on the surface residual stress of titanium alloy thin-walled parts was explored. Compared with conventional milling, the surface residual stress values of ultrasonic longitudinal-torsional composite milling workpiece were negative and significantly increased, with the maximum increase rate of 54.88%.The cutting force was greatly reduced, and Fx and Fy decreased by 31.6% and 45.33%, respectively. The instantaneous cutting temperature was also greatly reduced, the maximum reduction of which is 17.53%. With the increase of ultrasonic amplitude and feed per tooth, the surface residual compressive stress increases gradually but decreases with the increase of spindle speed and curvature. The experimental results show that ultrasonic longitudinal-torsional composite milling is a reliable method for machining titanium alloy curved thin-walled parts, which can obtain larger residual compressive stress and improve the machined surface integrity.

Milling Chatter Detection System Based on Multi-Sensor Signal Fusion

The occurrence of chatter in the machining process accelerates tool wear and breakage, reduces the service life of tools and machine tools and the surface accuracy of workpieces. Therefore, how to quickly and accurately detect chatter and adjust process parameters to prevent chatter has become a research hotspot today. This article proposes a new method to detect the machining state in the milling process by using the sensor signal sensitive feature data set and the Mahalanobis-Taguchi System. First, a method for extracting the comprehensive characteristics of nonlinear time-domain signals in the cutting process is proposed. This method can realize the dimensionality reduction of the time-domain data features. Then, time-frequency domain methods such as variable mode decomposition energy entropy, multi-scale power spectrum entropy and multi-scale displacement entropy are used to process the processed signals collected by multiple sensors to obtain the characteristic data set related to flutter. Take the feature data set as the measurement scale to participate in the construction of the Mahalanobis-Taguchi System classifier. Using the experimental data of milling titanium alloy thin-walled parts with end mills, the Mahalanobis space of cutting chatter was constructed, and the chatter detection system was verified. It is found that this method can accurately detect the cutting processing state. The research results can lay the foundation for advancing the industrialization of intelligent cutting processing.

Large Cutting Depth and Layered Milling of Titanium Alloy Thin-Walled Parts

Deformation of thin-walled titanium alloys can occur during the milling process due to the cutting force and chatter vibration, which can influence the precision of the finished parts. In this research, a new milling method without auxiliary support for machining of thin-walled parts was proposed. A large cutting depth and layered milling technology were used during rough machining, with a different machining allowance for each subsequent remaining layer. In the finishing stage, the surface of the previous layer needed to be dressed before processing the next layer. A TiAlSiN-coated, cemented carbide milling cutter was used to machine titanium alloy thin-walled parts, which are characterized by continuous multilayers of unequal thickness. The processing path was simulated using HyperMILL software, and the machining accuracy was detected by the 3D optical scanner. The measurement results indicated that the surface contour accuracy of the parts was ±0.21 mm, within a range of ±0.30 mm. The machining efficiency was increased by 40%, while guaranteeing machining accuracy.

Stability Research Considering Non-Linear Change in the Machining of Titanium Thin-Walled Parts.

Aiming to solve the problem whereby the damping process effect is significant and difficult to measure during low-speed machining of titanium alloy thin-walled parts, the ploughing coefficient of the flank face is obtained based on the frequency-domain decomposition (FDD) of the measured vibration signal and the energy balance principle, and then the process-damping prediction model is obtained. Aiming to solve the problem of non-linear change of dynamic characteristics of a workpiece caused by the material removal effect in the machining of titanium alloy thin-walled parts, a prediction model of dynamic characteristics of a workpiece is established based on the structural dynamic modification method. Meanwhile, the effect of material removal on the process-damping coefficient is studied, and the internal relationship between the process-damping coefficient and the dynamic characteristics of the workpiece is revealed. The stability lobe diagram is obtained by the full discretization in the titanium alloy milling process. The correctness of the model and stability prediction is verified by experiments under different working conditions. It is found that the coupling characteristics of process-damping and workpiece dynamic characteristics control the stability of the milling process. The research results can provide theoretical support for accurate characterization and process optimization of titanium alloy thin-walled workpiece milling.

Modeling machining errors for thin-walled parts according to chip thickness

In the milling process of titanium alloy thin-walled parts, because of its low stiffness, processing deformation easily occurs, which results in in low-dimensional accuracy of machined surface and affecting the workpiece performance. Cutting force is the main factor that causes cutting deformation. Cutting deformation also affects cutting force. There is a coupling relationship between them. To solve the above problems, a method is proposed to predict the surface error by calculating the milling force by varying the chip thickness and by coupling the force with the elastic deformation of the workpiece. Firstly, the analytical model of bending elasticity deformation of thin-walled parts is established. Then, the micro-unit entrance angle and instantaneous chip thickness are calculated by the contact relationship of workpiece deformation and the chip boundary decision conditions. The cutting force and workpiece deformation at random rotating angle are obtained by iterative calculation method. Finally, the surface error is predicted by calculating the deformation matrix and the principle of surface generation mechanism. The simulation results are in good agreement with the experimental results, which verifies the accuracy of the proposed method. The results provide theoretical support for milling process optimization and profile accuracy control of titanium alloy thin-walled parts.

Surface microstructure of titanium alloy thin-walled parts at ultrasonic vibration-assisted milling

Milling of the titanium alloy thin-walled workpiece is a critical challenging task and the machining vibration is a major effect on the accuracy of the final part due to difficult machining properties and low stiffness. The common milling (CM) is very hard for titanium alloy thin-walled parts to get high-quality machined surface microstructure, so finding an effective way of processing to obtain better surface microstructure is particularly important. In this article, the longitudinal-torsional composite ultrasonic vibration-assisted milling (LTCUVM) is proposed to overcome the problems of the common milling. The cutting method of the high-frequency vibration separation of a workpiece and the tool reduces an average cutting force. Thereby suppressing the tool relieving and further providing a good machined surface. In this study, firstly, the kinematic model of LTCUVM was established and the variations of the movement of the cutting edge flank with the spindle speed change were analyzed. Then the finite element model (FEM) of the two processing methods was developed and significant differences between the CM and LTCUVM in the micro-milling were revealed. Further, related experiments were designed and conducted. Finally, the experimental analysis showed that the LTCUVM effectively reduced an average cutting force, and further reduced surface roughness and height of chatter marks compared to the CM with the same processing parameters.

Investigation of mechanics and machinability of titanium alloy thin-walled parts by CBN grinding head

A force model of machining TC4 titanium alloy thin-walled part is developed based on the actual geometry and abrasive characteristics of CBN grinding head in this paper. Then, the single factor experiment illustrates that the grinding force increases with the increase of the grinding depth and feed rate, while it decreases with the increase of the spindle speed. And the contrast experiment results show that new improved grinding head is beneficial for reducing the force compared with common grinding head. On the basis of the mechanics analysis, the chatter stability of grinding thin-walled parts is studied based on the modal tests of titanium alloy thin-walled parts and grinding head, and the stability lobe diagrams are finally drawn as well by considering the radial grinding depth. In addition, further research indicates that the surface roughness of vertical side wall surface and surface micro-hardness is determined by several key parameters including spindle speed, feed rate, and cutting depth in grinding process based on analysis of experiments. An optimal combination of these parameters is of great benefit to achieving better surface of the parts.

Research on Milling Deformation in Ultrasonic Vibration Assisted End Milling of Titanium Alloy Thin-Walled Parts

The hard machinability of titanium alloy material and the poor stiffness of thin-walled parts hindered the extensive application of titanium alloy thin-walled components in aerospace engineering. In order to heighten the geometric accuracy in the processing, the ultrasonic vibration assisted (UVA) end milling technology with workpiece vibrating in feed direction was put forward in this paper, and characteristics of the milling deformation in UVA milling of titanium alloy TC4 thin-walled workpieces were researched. Through the theoretical analysis, the cutting force and deformation characteristics in UVA milling were clarified. Based on the range analysis of orthogonal experiment, the effects of milling parameters and ultrasonic amplitude on the deflection displacement and the milling deformation of workpieces are obtained. Research results show that the deflection displacement in the process of UVA milling affects the thickness error of the thin wall. Ultrasonic parameters as well as milling parameters should be optimized to obtain higher machining accuracy. The research provides a certain reference for the precision milling of titanium alloy thin-walled parts.

Research on Milling Force in Ultrasonic Assisted End Milling of Titanium Alloy Thin-Walled Parts

Hard machinability of titanium alloy material and poor stiffness of thin-walled part restricted the extensive applications of titanium alloy thin-walled component in aerospace engineering. In order to increase geometric accuracy, a method of ultrasonic vibration assisted (UVA) end milling technology with workpiece vibrating in feeding direction was put forward in this paper, and the corresponding milling force characteristics in UVA milling of titanium alloy TC4 thin-walled workpiece were researched. Through theoretical analysis, the path of cutter tooth in UVA milling was analyzed. The important factors that affect milling force are obtained with the signal to noise ratio analysis. Results show that the radial cutting force in UVA milling is smaller than that in traditional milling. Cutting force fluctuate in high frequency when treated ultrasonic vibration. And the axial cutting feed is the core factor that affects the milling force. The research provides a certain reference for the precision milling of titanium alloy thin-walled parts.