International Journal of Advanced Manufacturing Technology最新文献

In the digital measuring environment, to solve the problem of sampling point planning on the aero-engine blade profile, two requirements should be satisfied: adapting geometry features and keeping the sampling point spacing. Therefore, this paper proposes an adaptive sampling method, which can flexibly increase or decrease the sampling points according to the curvature. Firstly, according to the geometric characteristics of blade profile, an adaptive sampling method based on the equal moment theory is established. Secondly, a parameterized model based on non-uniform rational B-spline (NURBS) is used to represent the geometry of the blade profile, and the Hausdorff distance is used to evaluate the error of the fitting curve. Finally, two cases verify the effectiveness and accuracy of the proposed method. In the simulation, the relationship between the adaptability and the error of the proposed method is analyzed by taking the Sine function as an example. It is obtained by numerical calculations that the error reached the minimum when the adaptive degree r is 0.75. In the actual blade measurement experiment, compared with other methods, the deviation between the reconstructed blade cross-section curve by the proposed method and the theoretical curve is minimum.

In the grinding process of crankshafts, the grinding parameters were improperly selected, which easily caused the high temperature in the grinding zone and led to burns on the crankshaft journal surface. To address this issue, referencing previous studies, the suitability of the Gaussian heat source model was verified by comparing it with three different heat source models. The Gaussian heat source model was applied to predict the temperature on the surface of the crankshaft connecting rod journal. Transient thermal analysis and investigation of material phase transformation were employed to explore the mechanism of grinding burns. The interaction effects among grinding parameters were analyzed using the Box-Behnken design, and a multiple linear regression equation was established for response surface optimization. The results demonstrated that applying the Gaussian heat source model and response surface optimization yielded the optimal solution, with a maximum deviation of 1.37% between the simulation and optimization results. By selecting a grinding depth (a_p) of 0.40 mm, wheel speed (v_s) of 40.00 m/s, and feed rate (v_x) of 0.036 mm/s as the processing parameters, the temperature in the grinding zone was reduced to 659.37 °C, effectively mitigating grinding burns.

A metallic foam specimen was plastically joined with a resin (polymethyl methacrylate, PMMA) sheet by applying friction stir incremental forming (FSIF) process. In FSIF process, a rotating flat-ended (no probe) rod tool was pushed vertically and fed horizontally against the resin sheet which was placed on the foam. The tool operation heated frictionally the resin and deformed incrementally to the resin, while the tool operation did not deform plastically to the cellular matrix of the foam. Due to the plastic flow of the heated resin, the bottom of the resin was interlocked mechanically to the pores near the top surface of the foam. In this study, the relationship between the pore morphology (form and size) and the joining characteristics (joinability, flow thickness of the resin, and joining strength) was investigated using commercial open-cell nickel and closed-cell aluminum foams. According to the experimental investigations, the foam with small size and low depression angle of the surface pore showed better results in relation with the joining strength and the (flow thickness of the resin)/(depth of the surface pore).

Abstract

The laser separation distance (distance between the two lasers in welding direction) in double-sided laser beam oscillation filler welding is difficult to precisely control. To evaluate the effect of laser separation distance on the mechanical properties of T joints, 2219 aluminum alloy double-sided laser beam oscillation filler welding experiments with different laser separation distances were conducted in this work. With laser separation, the symmetry of fusion zone was weakened. The keyhole stability at latter welding side was weakened. The number of pores in the T joint increased. The laser separation distance promoted the formation of porosity at latter welding side and the formation of porosity in the stringer. Most of the cracks in the tensile tests at the weld foot propagated in the partially melted zone. Porosity has no significant influence on the tensile strength of T joints. When laser separation distance was 3 mm, the mechanical performance of T joint was the best. The hoop tensile strength was 370.0 MPa. The T-pull tensile strength was 309.5 MPa. Based on the results of tensile strength testing, the mechanical performance of T joints welded by double-sided laser beam oscillation filler welding did not deteriorate with the laser separation distance less than or equal to 3 mm, which showed a good tolerance of laser separation distance for the welding process.

Roundness error plays an important role of rotating parts in engineering fields and it has a significant influence on the machining quality and accuracy during electrochemical machining (ECM) process. The precision ECM could be processed only if the initial roundness error is decreased or eliminated and the inter-electrode gap (IEG) becomes steady after reaching an equilibrium state. However, a constant voltage is generally used in ECM process. And a long time and a large allowance are required to level the profile error of workblank if the initial profile error is large. In this study, the focus herein is on the acceleration of the leveling process of the rotary workpiece. A counter-rotating electrochemical machining (CRECM) process method with a variable voltage is proposed to improve the leveling ability. For a rotary workpiece with elliptical contours, the machining voltage can be dynamically adjusted based on the IEG through the approximate regulation of sine waves according to modeling-based analysis. The method aims to improve the leveling ability by expanding the difference in the magnitude of electric current between the high and low points on the profile of the anode workpiece under different voltages. The results of experiments confirmed that the proposed method significantly reduced the leveling time from 36 to 7 min (by 81%), and the depth of dissolution of the highest point on the profile from 1.68 to 0.45 mm while reducing the roundness error from 0.5 to 0.05 mm. The leveling ratio increased from 0.26 to 0.99.

The cross-sectional method is undoubtedly the most widely used method of measuring cylindricity. The method consists of measurements of roundness profiles in several cross-sections of the cylindrical surface. Usually, the distance between subsequent cross-sections is equal. The number of cross-sections used depends on the required accuracy of the assessment of the cylindricity deviation. If one wants to get only rough estimation of the cylindricity deviation, then the measurement can be made in a few cross-sections only. However, if the required measurement accuracy is high, measurements should be carried out in a large number of cross-sections. The consequence of taking the measurements in a large number of sections is significant extension of the measurement time. In this work, an adaptive method of measuring cylindricity is proposed, the purpose of which is to ensure the required measurement accuracy while reducing the necessary number of cross-sections in which roundness profile measurements should be conducted. The proposed strategy is iterative and it is based on carrying out measurements in the cross-sections of the measured part. The proposed method implies two criteria: the correlation coefficient and the predicted values of the form deviations in the non-measured areas of the measured part. The paper presents the fundamentals of the method and the selected results of its practical verification. The experimental results show the ability of the new method to measure the form deviations of cylindrical parts.

In order to address the existing challenges in the filling clamping methods of metal honeycomb core, such as slow efficiency, difficult post-processing, easy damage to the honeycomb wall, and lack of environmental friendliness, a new method called integral immersion ice fixation clamping for metal honeycomb core was proposed. This study conducted analytical calculations and test analysis on the mechanical properties of superalloy honeycomb core and artificial ice. It elucidated the mechanism of the metal honeycomb core with ice fixation constraint action and verified the effectiveness of ice fixation clamping through cutting tests and finite element simulation methods. The results indicate that introducing the ice fixation clamping method in metal honeycomb core machining provides sufficient support and adhesive strength for the honeycomb wall, reducing the maximum vibration amplitude by approximately 32.77 to 50.57%. When the height of the machined honeycomb core specimen is h ≥ 3 mm, it can prevent axial displacement of the honeycomb wall under the action of cutting force. The ice fixation clamping method improves the ability of the honeycomb core side wall to resist radial deformation and machining stability, and enables the machining quality of the honeycomb core with low damage, and low roughness. This research provides a new method and basic guidance for the reliable clamping of thin-walled porous metal components.

Productively reducing the time required to cut numerous through holes in automotive workpieces is crucial for enhancing parts manufacturing in the 3D laser cutting process. However, the conventional cutting strategy, in which the laser beam maintains a stationary posture along the hole path, lacks flexibility and fails to effectively leverage processing tolerances. In this study, we conduct a thorough analysis of the kinematics of a six-axis redundant laser cutting machine and resolve through a decoupling method with singularity management. We propose an innovative conic posture cutting strategy for 3D laser hole-cutting with thin materials. This approach adopts the geometry of a cone as the posture while cutting the hole path. In order to obtain the optimal vertex of the cone while minimizing the taper error generated by the conic posture and kinetic energy consumption of the actuators during motion, we formulate a multi-objective optimization problem and solve it using a genetic algorithm. Furthermore, we enhance the optimization by adopting a time minimization approach. Through the implementation of a B-pillar workpiece cutting experiment, we have successfully validated the credibility of our proposed cutting strategy, thereby demonstrating an enhancement of time on 26 hole-cutting paths.

Reliable prediction of the grinding force is essential for improving the grinding efficiency and service life of the grinding head. To better optimize and control the grinding process of the grinding head, this paper proposes a grinding force prediction method of the grinding head that combines surface measurement, statistical analysis, and finite element method (FEM). Firstly, a grinding head surface measurement system is constructed according to the principle of focused imaging. The distribution model of abrasive grains in terms of size, spacing, and protruding height has been established by measuring and counting the characteristics of abrasive grains on the surface of a real grinding head. Then, the undeformed chip thicknesses when the abrasive grains are cut are analyzed in depth, the material model of abrasive grains and workpiece is established, and the cutting process of abrasive grains with different characteristics on the surface of the grinding head is analyzed by finite element simulation. A single abrasive grain grinding force model is obtained. Finally, the grinding force prediction of the grinding head was realized by combining finite element simulation with grinding kinematics analysis. In addition, grinding experiments with different grinding parameters were conducted to verify the grinding force prediction model. The results show that the predicted grinding force of the grinding head is in good agreement with the experimental values. The average error of tangential grinding force is 7.42%, and the average error of normal grinding force is 9.77%. This indicates that the grinding force prediction method has good accuracy and reliability.

The demand for surface wear-resistant metal components is increasing, but the current traditional preparation method of surface heat treatment for forgings and castings can hardly satisfy the trend of green development. In this study, we developed wire arc additive manufacturing laser cladding (WAAM-LC) hybrid manufacturing technology for the integrated preparation of 304 component with Ni60B reinforced coating. The microstructure and mechanical properties of 304 WAAM entity and Ni60B coating were systematically investigated. The results show that a good metallurgical bond is achieved between the Ni60B coating and 304 substrate. Both γ-Fe and δ-Fe phases appear in the 304 WAAM region, and γ-(Ni,Fe), FeNi₃, (Cr,Fe)_mC_n, and Ni_mSi_n phases are detected in the Ni60B LC coating. Slender columnar crystals and cellular crystals coexist in the 304 bonding region, while the bottom of the Ni60B coating consists of plane crystal and columnar crystals. Both molten pools appear to have a haphazardly growing dendrite structure inside. Compared to the 304 substrate, the hardness of Ni60B coating increases by 2.76 times, and the friction and wear mass loss is only 10.54% of the 304, significantly improving the wear resistance of the 304 substrate. This work indicates that WAAM-LC hybrid technology is expected to become a promising new solution for manufacturing surface wear-resistant metal components.

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