Journal of Manufacturing Processes最新文献

The adverse effect on ground surface of workpiece during the grinding process is caused by poor lubrication. Improving the utilization rate of the grinding fluid has become an urgent problem. To prevent airflow disturbance from obstructing the grinding fluid flow, this paper proposes a combinatorial bionic structure grinding wheel that incorporates fish-scale shape and phyllotaxis-arrangement. This study analyses and compares the surface structure of different grinding wheels based on the surface quality of the workpiece, the grinding fluid utilization rate and the surface condition of the grinding wheel. We propose a ground surface model for workpieces based on structural grinding wheels. By combining the model calculations with the results of the grinding experiments, the combinatorial bionic structure grinding wheel was found to produce the smallest surface roughness on the workpiece, with a maximum reduction rate of 34.2 %. Then, the anti-disturbance performance of the combinatorial bionic structured grinding wheel is analyzed by studying the hydrodynamic properties of the grinding fluid during the grinding process. The utilization of the combinatorial bionic structured grinding wheel resulted in a grinding fluid utilization of 146.7 % compared to the other structured grinding wheels. The combinatorial bionic structure grinding wheel effectively guides the flow of grinding fluid on the basis of ensuring the surface quality of the workpiece. This reduces the waste of grinding fluid and achieves effective cleaning of the grinding zone, contributing to green manufacturing.

Weld bead models are crucial in the process planning phase for wire arc additive manufacturing. By simulating the overlap between weld beads, the toolpath can be optimized to obtain a high-quality production process. The creation of datasets covering all possible combinations of process parameters and boundary conditions is hindered by a high and costly experimental effort. Accurate and numerically efficient modelling approaches that can be derived from simple and cost-effective experimental campaigns are needed. This article introduces a new weld bead footprint model to address this challenge. The proposed footprint locus model is used to predict the weld bead footprint, which is afterwards used to predict the weld bead shape. A calibration procedure is introduced, which allows for calibrating the model parameters for a reference situation. The geometrical interpretation of the model parameters is exploited for estimating how they should change when welding parameters or boundary conditions different from the nominal ones are used. The model is validated with experimental data and compared to a baseline model derived from assumptions commonly found in the literature. The deposition of two parts produced with different processing conditions could be predicted with an error inferior to 2% the deposited height.

Laser Power Bed Fusion (L-PBF) is one of the sought-after Additive manufacturing methods for manufacturing metallic parts with complex geometries and functionally efficient porous materials. This has opened avenues of applications in aerospace, medical and automotive industry. The geometric parameters of these miniaturely architectured metamaterials can be varied to engineer the mechanical properties according to the applications. This paper has critically studied the geometric feasibility, surface features and resultant microstructure of struts, the basic building block of strut-and-node based lattice architectured metamaterials. The struts under focus are circular in cross-sections with diameters from 0.1 mm to 1 mm with various angles of inclination ranging from 10° to 90°. The studies have revealed that the inclination of these strut components not only affect the surface texture but also influences the microstructure of the material. Laser profilometric studies and SEM studies revealed that the best surface finish can be obtained roughly between 40° and 60° of inclination angles. The change in the angle of inclination influences the solidification kinetics along the same layer. Micro-structural studies using SEM and EBSD reveal that the architecture of the XY plane along which the load would be applied varies from an equiaxed structure for a 90° strut to a near to columnar structure for a 10° strut.

The Vat-Photopolymerization (VPP) additive manufacturing process excels in producing intricate components via layering. This study employs an inter-stage stirring method during layering to create composite parts, especially in bottom-up VPP setups with high filler density. Samples with 2–8 % short glass fiber volume fractions in a photopolymer matrix are manufactured using Digital Light Processing-based VPP. Dynamic Mechanical Analysis is utilized to examine the viscoelastic properties and heat deflection temperature (HDT) of these photopolymer composites (PPC) under static and oscillatory conditions, generating a time-temperature-superposition (TTS) master curve for storage modulus (E'). Results show the highest glass transition temperature (T_g ∼ 60 °C), HDT ∼ 85 °C, and E' ∼ 4500 MPa in the 4 % PPC under preloaded static stress. Analysis reveals efficient force transfer in glassy and rubbery zones, indicating improved moduli with 4 % PPC. A Prony series material model accurately replicates the TTS-derived master curve, suggesting enhanced short- and long-term mechanical properties.

To improve the formability and microstructure of laser powder bed fusion (LPBF) Ti-43Al-4Nb-1Mo-0.1B (TNM) alloy, a circular beam oscillation strategy was employed in this study. The metallurgical defects, microstructure, and mechanical properties of the circularly oscillating and non-oscillating (linear) scanning are first compared. Based on the comparative analysis of solidification and cooling processes during linear and oscillating scanning, the formation and inhibition mechanisms of metallurgical defects were revealed. The lack-of-fusion defects and cracks of LPBFed TNM alloy can be eliminated by circularly oscillating scanning, and the relative density of the crack-free specimen is 99.9 % at an oscillating velocity of 100 mm/s. Compared to linear scanning, circularly oscillating scanning promotes an increase in the α₂ and γ phases, a decrease in the B₂ phase, a uniform distribution of elements, and a relatively random texture. The average microhardness under oscillating scanning (479–507 Hv) is lower than that under linear scanning (584–614 Hv). The yield strength, ultimate strength, and ultimate compression strain of the oscillating LPBFed TNM specimens are ∼1165.65 MPa, ∼1738.03 MPa, and ∼13.21 %, respectively. The inhibition of lack-of-fusion defects is attributed to the more sufficient liquid convection and enhanced liquid diffusion under the prolonged laser action time and solidification time as well as the generation of turbulence. The inhibition of cracks is due to the generation of finer equiaxed grains and a decline in the fraction of brittle phases under the enhanced stirring effect, reduced cooling rate, and more uniform temperature distribution.

In recent years, there has been a growing focus among researchers on enhancing the mechanical performance of Additively Manufactured (AM) polymers. The ultimate goal is to extend their applications beyond prototyping and into real-word scenarios. Within the published literature of this research domain, studies can be broadly categorized into two primary areas of investigation: the reinforcement of AM materials, and the strengthening of AM components. The first category concentrates on enhancing the feedstock material by incorporating additives, drawing on knowledge from traditional polymer-based composites. Additionally, various in- and post-processing methods aimed at improving layer bonding have been explored. These methods seek to strengthen the weakest links in Material Extrusion (MEX) printed parts, thereby enhancing their mechanical performance. Concurrently, other methodologies, primarily involving hybrid manufacturing through the addition of local reinforcement, have been researched with the goal to improve the endurance and mechanical performance of MEX structures. While each of the mentioned techniques can provide some degree of mechanical enhancement, their ease of use and availability may vary. Therefore, a deeper understanding of these methods, along with their pros and cons, can assist users in selecting the most suitable reinforcement technique for improved mechanical performance. This review paper discusses the progress to date in the improvement of mechanical performance of MEX fabricated polymer parts. Towards this objective, the study examines the reported data to identify the fundamental factors influencing the reinforcement process, while also evaluating the efficacy of the suggested techniques. Furthermore, this work duly acknowledges and addresses the research gaps, challenges, and drawbacks associated with the endeavor to strengthen MEX components within the context of the study.

Surface texturing is a technology that effectively controls tribological performance between interacting surfaces, and research is actively being conducted to apply these advantages to cutting tools. However, most of the research has been applied to turning inserts and rarely to twist drills. In addition, the latter research was conducted without reflecting the helical shape of the twist drill. Therefore, the objectives of this study were to create helical grooves on the flutes of twist drills by accurately reflecting the tool shape and then assess their drilling performance. To achieve helical groove texturing, laser micromachining equipment with suitable automatic axes was developed, enabling the creation of uniform helical grooves. Drilling experiments that involved producing closed holes with a depth of 60 mm were performed using both conventional and helical groove textured drills at a cutting speed of 50 m/min and feeds of 0.03, 0.05, and 0.07 mm/rev. Each feed condition was performed three times on aluminum alloy under a wet environment. The results indicated that the textured drills enhanced chip evacuation and machinability by reducing adhesion and friction between the flute surface and the chips compared to conventional drills. When machining with the textured drills, there were different behaviors in terms of thrust force and torque. Excluding cases where chip clogging occurred, the textured drills exhibited higher thrust force and lower torque compared to conventional drills under all feed conditions.

Ultrasonic shot peeing (USP) is a random and uniform peening process that has advantage to strengthen the complex surface of fir-tree shaped groove. However, due to the complexity of the groove geometry, it is difficult to accurately predict the shot dynamics and surface integrity along the profile during USP treatment. In this paper, a coupled discrete element method (DEM) and finite element method (FEM) has been established to predict the ultrasonic shot peening process of the fir tree shaped groove. DEM simulation model is established with a real groove to obtain the velocity field of the shots. The shot dynamic field is coupled as an input to the FEM model to obtain the surface integrity. The USP experiment verifies that the proposed coupled method can predict the surface integrity of grooves. The compressive residual stress (CRS), maximum CRS, and roughness of each region obtained in the DEM-DEM model are relatively uniform (fluctuating within ±60 MPa). Further, the roughness of each area of the groove is below Ra0.6 μm, and the values is closely corresponded to the velocity field of the shot impact. This study provides an effective method and potential application in uniform surface strengthening of complex components.

Online inspection of welding defects is of great help for welding quality assessment, rapid process optimization, and production efficiency improvement. However, in-situ detection is difficult due to the noisy environments, real-time changes in light, diverse weld forms, and requirements for rapid detection. Traditional defect detection methods face many challenges, such as complex processes, slow speed, insufficient information, and weak adaptability. In this study, an online fast detection method based on laser scanning and a lightweight network is proposed. Firstly, high-precision point clouds of weld surfaces are acquired using a laser displacement sensor. Secondly, equal-interval splitting divides the point cloud of a long-seam weld into equal-resolution subframes for online detection. An image processing algorithm combining radius filtering, Sobel convolution, normalization, and Gaussian enhancement is proposed to convert the split point clouds into high-contrast gray-scale images. With the gray-scale images as input and pixel-level classification of the background and three types of defects as output, a semantic segmentation model, VGG16-UNet, is trained through transfer learning, achieving 88.77 % precision and 92.03 % recall. Based on the prediction result and its mapping point cloud, 3D reconstruction and visualization of defects are realized using Delaunay triangulation. 3D location and geometry dimensions of defects are calculated for defect assessment. Compared with the alternative segmentation models, VGG16-UNet performs better while having a smaller weight (94.95 MB) and a faster inference speed (26.8fps), making it suitable for online industrial applications. The work provides strong support for achieving online automated evaluation of weld surface quality.

Controlling thermal cycles during arc-based Directed Energy Deposition (DED), typically known as Wire Arc Additive Manufacturing (WAAM), is crucial to reduce heat buildup and prevent issues such as distortions, formation of brittle microstructures, grain growth, anisotropy, and consequent reduction in mechanical properties. In-situ interlayer hot forging coupled with WAAM (HF-WAAM) provides grain refinement and pore closure. The effect of HF-WAAM can be combined with the control of peak temperature and cooling rates, benefiting the material's microstructure and mechanical properties. In this context, the aim of this work was to evaluate the effect of direct cooling on the mechanical and microstructural properties of a high-strength low-alloy (HSLA) steel manufactured by WAAM and HF-WAAM. A pneumatically actuated system with a cooling system was specifically designed, where two pumps with a flow rate of 1.8 kg/min each were used to pump G13 antifreeze fluid at approximately −25 °C. In the actuator design, a double counterflow cooling system was used, as it promotes greater thermal homogenization and higher heat transfer rate, thus allowing greater thermal energy removal. Analyses of the mechanical and microstructural properties of the parts were carried out through uniaxial tensile testing, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Thermal cycles and cooling system control were conducted using a thermal imaging camera and thermocouples installed at the inlet and outlet of the actuator's cooling ducts. The results showed that samples manufactured with HF-WAAM had a greater number of less hard structures in their microstructure than those manufactured by conventional WAAM. The fabricated samples exhibited high tensile and yield strength values, with calculated anisotropy below 2 %. All samples showed ductile fracture characteristics after the tensile test, confirmed by fractography.