Zhenyuan Jia

Characteristics forecasting of hydraulic valve based on grey correlation and ANFIS

Accurate prediction is crucial for the synthesis characteristics of the hydraulic valve in industrial production. A prediction method (G-ANFIS for short) based on grey correlation and adaptive neuro-fuzzy system (ANFIS) to forecast synthesis characteristics of hydraulic valve is devised and the utilizing of the method can help enterprises to decrease the repair rate and reject rate of the product. Grey correlation model is used first to get the main geometric elements affecting the synthesis characteristics of the hydraulic valve and thus simplifies the system forecasting model. Then use ANFIS to build a prediction model based on the above mentioned main geometric elements. To illustrate the applicability and capability of the devised prediction method, a specific hydraulic valve production was used as a case study. The results demonstrate that the prediction method was applied successfully and could provide high accuracy. The method performed better than artificial neural networks (ANN) to forecast the synthesis characteristics of hydraulic valve.

Hybrid of simulated annealing and SVM for hydraulic valve characteristics prediction

Accurate prediction for the synthesis characteristics of hydraulic valve in industrial production plays an important role in decreasing the repair rate and the reject rate of the product. Recently, Support Vector Machine (SVM) as a highly effective mean of system modeling has been widely used for predicting. However, the important problem is how to choose the reasonable input parameters for SVM. In this paper, a hybrid prediction method (SA-SVM for short) is proposed by using simulated annealing (SA) and SVM to predict synthesis characteristics of the hydraulic valve, where SA is used to optimize the input parameters of SVM based prediction model. To validate the proposed prediction method, a specific hydraulic valve production is selected as a case study. The prediction results show that the proposed prediction method is applicable to forecast the synthesis characteristics of hydraulic valve and with higher accuracy. Comparing with Adaptive Neuro-Fuzzy Inference System (ANFIS) and Artificial Neural Networks (ANN) are also made.

Improved camera calibration method based on perpendicularity compensation for binocular stereo vision measurement system

High-precision calibration of binocular vision systems plays an important role in accurate dimensional measurements. In this paper, an improved camera calibration method is proposed. First, an accurate intrinsic parameters calibration method based on active vision with perpendicularity compensation is developed. Compared to the previous work, this method eliminates the effect of non-perpendicularity of the camera motion on calibration accuracy. The principal point, scale factors, and distortion factors are calculated independently in this method, thereby allowing the strong coupling of these parameters to be eliminated. Second, an accurate global optimization method with only 5 images is presented. The results of calibration experiments show that the accuracy of the calibration method can reach 99.91%.

The interaction between the cutting force and induced sub-surface damage in machining of carbon fiber-reinforced plastics:

Carbon fiber-reinforced plastics (CFRPs) have the characteristics of non-homogeneity and anisotropy. Damage occurs frequently in machining of CFRPs, and it can seriously influence the performance of work piece. This study builds a finite element model for machining of CFRPs based on the constitutive relation with damage, the Hashin failure criterion, and the damage evolution. The continuous cutting processes of unidirectional CFRPs with various fiber orientations are simulated. Cutting forces and sub-surface damage are determined from simulations. Furthermore, machining experiments on unidirectional-CFRPs are performed. Cutting processes are monitored, and cutting forces are measured. An artificial neural network (ANN) force model is proposed by using the experimental data, and then simulation results of the cutting forces are validated by these of the ANN model. Cutting force increases when the fiber orientation varies from 0° to 135°. Fiber orientation is the critical factor affecting the cutting force and the sub-surface damage. More sub-surface damage occurs in a fiber orientation range of 90–135°. The primary reasons for the induced sub-surface damage include the damage evolution and the crack propagation of matrix caused by the cutting force. In addition, the effects of cutting parameters and tool geometries on the cutting force and the damage are discussed by simulations. The cutting force thus can be reasonably controlled to reduce the damage.

Pose measurement method and experiments for high-speed rolling targets in a wind tunnel.

High-precision wind tunnel simulation tests play an important role in aircraft design and manufacture. In this study, a high-speed pose vision measurement method is proposed for high-speed and rolling targets in a supersonic wind tunnel. To obtain images with high signal-to-noise ratio and avoid impacts on the aerodynamic shape of the rolling targets, a high-speed image acquisition method based on ultrathin retro-reflection markers is presented. Since markers are small-sized and some of them may be lost when the target is rolling, a novel markers layout with which markers are distributed evenly on the surface is proposed based on a spatial coding method to achieve highly accurate pose information. Additionally, a pose acquisition is carried out according to the mentioned markers layout after removing mismatching points by Case Deletion Diagnostics. Finally, experiments on measuring the pose parameters of high-speed targets in the laboratory and in a supersonic wind tunnel are conducted to verify the feasibility and effectiveness of the proposed method. Experimental results indicate that the position measurement precision is less than 0.16 mm, the pitching and yaw angle precision less than 0.132° and the roll angle precision 0.712°.

Spindle Speed Selection for High-Speed Milling of Titanium Alloy Curved Surface

The development of high-speed milling technology provides an effective processing method for titanium alloy curved surface with high quality, and the spindle speed is an important machining parameter for the high-speed milling of titanium alloy curved surface. The variation of the geometric features of the titanium alloy curved surface results in the sharp fluctuation of the cutting force as well as the vibration of machine tool, which not only makes a severe impact on the surface machining quality and the tool life but also greatly affects the efficiency of the high-speed milling. An experimental study is carried out to determine the spindle speed for high-speed milling of the titanium alloy curved surface based on the cutting force. The experimental results indicate that in high-speed milling process, the cutting force is associated with the geometric feature of the curved surface and the change of cutting force is relatively smooth when the spindle speed is in the range from 9000 to 13,000 rpm for the machining of titanium alloy curved surface.

Model of the instantaneous undeformed chip thickness in micro-milling based on tooth trajectory:

Instantaneous undeformed chip thickness is one of the key parameters in modeling of micro-milling process. Most of the existing instantaneous undeformed chip thickness models in meso-scale cutting process are based on the trochoidal trajectory of the cutting edge, which neglect the influences of cutter installation errors, cutter-holder manufacturing errors, radial runout of the spindle and so forth on the instantaneous undeformed chip thickness. This article investigates the tooth trajectory in micro-milling process. A prediction model of radial runout of cutting edge is built, with consideration of the effects of the extended length of micro-milling cutter and the spindle speed. Considering the effects of cutting-edge trochoidal trajectory, radial runout of cutting edge and the minimum cutting thickness, a novel instantaneous undeformed chip thickness model is proposed, and the phenomenon of single-tooth cutting in micro-milling process is analyzed. Comparisons of cutting forces under different chip thickness models and experimental data indicate that this new model can be used to predict cutting forces.

Tool wear appearance and failure mechanism of coated carbide tools in micro-milling of Inconel 718 super alloy

Purpose – The paper aims to study the wear and breakage characteristics of coated carbide cutting tools through micro-milling slot experiments on superalloy Inconel 718. Design/methodology/approach – During the micro-milling process, the wear and breakage appearance on the rake face and flank face of the cutting tools, as well as the failure mechanism, have been studied. Furthermore, the wear and breakage characteristics of the micro-cutting tools have been compared with the traditional milling on Inconel 718. Findings – The main failure forms of the micro tool when micro-milling Inconel 718 were tool tip breakage and coating shed on the rake and flank faces of the cutting tool and micro-crack blade. The main causes of tool wear were synthetic action of adhesive abrasion, diffusion wear and oxidation wear, while the causes of abrasive wear were not obvious. Practical implications – The changing trend in tool wear during the micro-milling process and the main reasons of the tool wear are studied. The findi...

A study of electrode compensation model improvement in micro-electrical discharge machining milling based on large monolayer thickness

Micro-electrical discharge machining (EDM) milling with a simple-shaped electrode is an effective machining method to fabricate three-dimensional micro parts and micro structures. However, the serious electrode wear occurring in the machining process significantly deteriorates the geometrical accuracy of the products. Since the electrode wear in micro-EDM milling is inevitable and hard to model accurately, it is difficult to conduct effective electrode compensation. To enhance the machining quality and efficiency of micro-EDM milling, a large layer thickness milling method is introduced and the improved electrode compensation model for large monolayer thickness milling is proposed based on modification of the conventional compensation model. First of all, proper machining parameters are obtained from processing tests without compensation. The wear law of the micro-electrode is then investigated and the conventional electrode compensation model is modified taking into consideration the changes of electrode shape during machining. Moreover, a new relative volume wear ratio measurement method is also presented through material composition analysis and the improved compensation model based on large monolayer thickness is finally established. Experiments demonstrate that the improved electrode compensation model can achieve accuracy when machining micro structures with large monolayer thickness and this method is an effective way to ensure the quality of micro products. Meanwhile, the use of large monolayer thickness in micro-EDM milling can enhance the machining efficiency significantly.

Pre-compensation for continuous-path running trajectory error in high-speed machining of parts with varied curvature features

Parts with varied curvature features play increasingly critical roles in engineering, and are often machined under high-speed continuous-path running mode to ensure the machining efficiency. However, the continuous-path running trajectory error is significant during high-feed-speed machining, which seriously restricts the machining precision for such parts with varied curvature features. In order to reduce the continuous-path running trajectory error without sacrificing the machining efficiency, a pre-compensation method for the trajectory error is proposed. Based on the formation mechanism of the continuous-path running trajectory error analyzed, this error is estimated in advance by approximating the desired toolpath with spline curves. Then, an iterative error pre-compensation method is presented. By machining with the regenerated toolpath after pre-compensation instead of the uncompensated toolpath, the continuous-path running trajectory error can be effectively decreased without the reduction of the feed speed. To demonstrate the feasibility of the proposed pre-compensation method, a heart curve toolpath that possesses varied curvature features is employed. Experimental results indicate that compared with the uncompensated processing trajectory, the maximum and average machining errors for the pre-compensated processing trajectory are reduced by 67.19% and 82.30%, respectively. An easy to implement solution for high efficiency and high precision machining of the parts with varied curvature features is provided.