Deformation Of Workpiece Research Articles

Integrated optimisation of multi-pass cutting parameters and tool path with hierarchical reinforcement learning towards green manufacturing

Five-axis machining, especially flank milling, is popular in machining thin-walled freeform surface parts with high energy consumption. Reducing the machining energy consumption is paramount for advancing green manufacturing. Therefore, this paper proposes an energy-efficient integration optimisation of cutting parameters and tool path with hierarchical reinforcement learning (HRL). Firstly, a novel multi-pass machining energy consumption model is developed with cutting and path parameters, based on which the integrated optimisation problem is modelled considering a dynamic workpiece deformation constraint. Secondly, HRL with a Soft Actor Critic agent (HSAC) decouples the model into two Markov Decision Processes at different timescales. The higher-layer plans cutting parameters for each pass on a macro timescale, while the micro-timescale lower-layer performs multiple tool path expansions with the planned cutting parameters, and provides feedback to the higher layer. By hierarchical optimisation and non-hierarchical interaction, the model is efficiently solved. Moreover, curriculum transfer learning is applied to expedite task completion of the lower layer, enhancing interaction efficiency between the two layers. Experiments show that, compared with two benchmarks, the proposed method improves machining energy consumption by 35.02 % and 30.92 %, and reduces machining time by 38.57 % and 27.17 %, providing a promising paradigm of green practices for thin-walled freeform parts and the broader manufacturing industry.

Dual flexible contact material removal model for robotic disk grinding

High-precision machining of flexible materials, such as rubber, presents a challenge in manual grinding. The implementation of robotic grinding has the potential to significantly enhance machining precision and efficiency. Normally, an accurate material removal model is needed for precise planning of the robotic grinding parameters. Existing models are mostly built for metal materials, and neglect the large deformation of flexible workpieces, resulting in deficiencies in accuracy and generalization. To this end, a nonlinear dual flexible contact force model is presented, considering the significant deformation of both the tool and the workpiece, to characterize the dual flexible contact mechanism. Then, the contact force model is combined with the Preston equation, yielding the material removal model. The effectiveness and superiority of our contact force model and material removal model are substantiated by force–displacement experiments and robotic grinding experiments, respectively. These experiments show a remarkable reduction of 68.17% in the root-mean-square error (RMSE) for the contact force model and a noteworthy 29.31% decrease in RMSE for the material removal model.

Effect of crystal orientation on the scratching behavior of γ-TiAl alloy nanowires by molecular dynamics simulation

In micro-and-nanomachining, crystal orientation effects significantly influence the plastic deformation, mechanical response, and temperature profile of nanowire materials. This study utilizes molecular dynamics simulation to investigate the process of surface scratching on γ-TiAl alloy nanowires under six different crystal orientations. The results reveal that the evolution of internal microscopic defects during the surface scratching process is heavily affected by crystal orientation, resulting in distinct dislocation motion-induced shear deformation and extrusion removal by the tool. These factors determine variations in both the shape of the nanowire's surface pile-up and the overall degree of workpiece deformation. Among all cases examined, (001)[1‾1‾0] crystal orientation exhibits easier removal of atoms with minimal internal defects, while (110)[11‾0] crystal orientation shows maximum atom removal without significant overall deformation, both cases demonstrate superior surface morphology and subsurface quality. Furthermore, stress and temperature profiles within abraded atoms and inside the workpiece depend on crystal orientation. These findings provide valuable insights for characterizing surface damage in γ-TiAl alloy nanowires as well as facilitating the preparation of surface nano-channels.

Quality control of NiCr-Cr3C2-hBN@Ni coating on thin-walled GH4169 alloy surface prepared by plasma spraying

As equipment lightweight trends progress, thin-walled structures have seen extensive application in critical aerospace components. Nevertheless, the aero-engine tail nozzle flaps are exposed to the harsh operating conditions of high-temperature friction, so there is an urgent requirement to prepare wear-resistant, self-lubricating coatings with a wide range of temperatures for their protection. Due to the poor rigidity and weak strength of thin-walled workpieces and complex forms of structural stresses, the processing is extremely difficult. In order to solve the thermal deformation problem of coating workpieces prepared by spraying on the surface of thin-walled workpieces, the effects of spraying path, cooling airflow, and spraying interval on the thermal force field of thin-walled workpieces to prepare NiCr-Cr3C2-hBN@Ni coating are investigated in this study using finite element simulation. As a result, the deformation and stress of thin-walled workpieces can be minimized by adding back-side cooling air during the spraying process and moving the cooling air with the gun in a set interval, with the maximum warpage and maximum stress being less than 2.366 mm and 0.177 GPa, respectively. During the spraying process by simulating the optimum spraying process, no significant warpage of the substrate occurred and the coating was sprayed with uniform thickness. Typically, the thickness error rate is 16.7 %, and the coating hardness reaches 15–20 GPa, with excellent tribological properties in a wear rate of 10−5 mm3·N−1·m−1 and 10−6 mm3·N−1·m−1, which protects the workpiece effectively.

Modeling and improvement for the thermal stability of ring-shaped workpieces with shape boundary constraints

Ring-shaped workpieces are commonly utilized in high-precision measuring instruments, and their thermal deformation affects the instruments’ measuring accuracy. A novel method for establishing the thermal deformation model of ring-shaped workpieces is proposed in this article. The mechanism of thermal deformation caused by shape boundaries is investigated using the principle of molecular dynamics. A mathematical model between deformation degree and height, diameter ratio, or temperature is created using a large-scale atomic/molecular massively parallel simulator. The established model is verified by measuring the thermal deformation of ring-shaped workpieces. The model is used to optimize laser collimation systems, and stability experiments for laser collimation systems in different sizes are performed. The stability of optimized systems can be improved by 50%, 50%, and 48% with temperature increases of 10 °C, 20 °C, and 30 °C, respectively. The experimental results indicate the obtained model can be utilized to improve the stability of instruments.

Tool path generation in pocket machining considering workpiece deformation using Finite Element Method (FEM)

Tool path generation in pocket machining considering workpiece deformation using Finite Element Method (FEM)

Voxel-based end milling simulation of machining error induced by elastic deformation of tool and workpiece

Voxel-based end milling simulation of machining error induced by elastic deformation of tool and workpiece

Adaptive Datum Points Location Optimization Method for Flexible Workpieces based on Centroid Characteristics

This paper proposes a method for adapting the layout of flexible workpieces of various shapes, in order to reduce the difficulty of location design for personalized shapes. Different from the previous location design that relied on the experiences of engineers, this method establishes an optimization model that determines the number of datum points and the optimal solution based on the centroid characteristics of the workpieces. The optimization index of this model is to control the minimum deformation of the overall flexible workpieces and the minimum variance of the deformation at the maximum deformation point. Taking the characteristics of the workpieces as a priori constraints for location determination, this model obtains the optimal solution combined with finite element analysis. Finally, the effectiveness of the method is verified through a numerical example.

Влияние технологии пластического деформирования на механические свойства композитов на основе политетрафторэтилена

This paper presents the results of research on the development of technology for plastic deformation of polymer blanks based on polytetrafluoroethylene (PTFE) and carbon fibers of the UVIS-AK-P brand in order to increase their strength and creep resistance. The dependence of the physico-mechanical, tribotechnical characteristics and structure formation of the obtained composites on the production technology is investigated. It is established that the composites obtained using various schemes of plastic deformation of polymer blanks differ in the nature of deformation under tension, structure formation and the nature of wear of the samples. It is shown that the use of a multidirectional scheme of plastic deformation of workpieces based on PTFE makes it possible to obtain isotropic polymer materials with improved strength properties and increased resistance to deformation under load.

Chatter vibration of workpiece deformation type in cutting thin-walled cylindrical workpiece (Prediction of chatter vibration generation using open-loop transfer function)

Chatter vibration of workpiece deformation type in cutting thin-walled cylindrical workpiece (Prediction of chatter vibration generation using open-loop transfer function)

Kinematic Characteristics of Deformed Porous Structures

Experimental and computational methods of studying the stress state in the plastic region are characterized by various methods and accuracy of measurements, methods of mathematical processing of experimental information, and interpretation of results. The experimentally determined kinematics as a starting point is the most widely used method to study the stress-strain state in the plastic region. When studying the process of plastic deformation of porous blanks, the model of a rigid-plastic isotropic-strengthening porous body with a loading surface that has the shape of an ellipsoid with semi-axes. It depends on the amount of porosity and the ratio of the associated flow law as a mechanical model of the material. In the axisymmetric extrusion of porous blanks, the viscoplasticity method was used to determine the field of flow velocities based on the results of experimental studies. R-functions were applied to approximate experimentally obtained values. The problem of finding approximations was formulated in a variational statement. Cubic splines of one argument were used to interpolate functions. As a result, an approach was proposed, which consists of a particular sequence of calculating the derivatives of the coordinates of the nodes in time in combination with the R-functions approach. All the calculations were performed in Euler variables, eliminating the need to switch from Lagrangian variables and simplifying the solution. Additionally, this method allowed for working with an irregular and non-rectangular grid in areas with any shape of boundaries. This approach is more effective from the point of view of the approximation’s accuracy and the speed of calculations. Finally, the equation for calculating the porosity in the volume of the deformable workpiece based on the information about the distortion of the dividing grid elements was obtained. For stationary axisymmetric processes, a technique was developed that allowed for replacing the calculation of the accumulated deformation of the base material along the deformation trajectory by integration over the region. A technique was developed for determining the stress-strain state at unstable and stable stages of axisymmetric plastic deformation of porous blanks. The calculation results were compared based on the proposed experimental and calculation techniques and the finite element method.

Top burr thickness prediction model in milling of thin-walled workpiece considering tool and workpiece deformation

Top burr thickness prediction model in milling of thin-walled workpiece considering tool and workpiece deformation

An equivalent numerical model for calculating shot peening bending deformation based on the laser forming method

Shot peen forming is an essential method for forming large-size thin-walled structural parts in the aerospace field. However, the complex elastic–plastic deformation involved in the forming process presents a challenge in calculating directly the deformation response under the specified peening parameters. The energy of the shot beam in the shot peen forming process is equivalently converted to that of the laser beam in the laser forming process, enabling the equivalent simulation of macroscopic deformation of the shot-peened workpiece using the laser-induced temperature field. It is proven that the essential factors affecting the laser forming process are the laser power, scanning speed, the width and thickness of the plate. When other parameters remain constant, the equivalent laser energy can be determined by the impact energy of the shot beam and the equivalence factor. The average error of the proposed model is 5.068%, with a maximum error of less than 10%, demonstrating a well agreement between the simulation and test results. Furthermore, the equivalent numerical model is used to examine the influence of process parameters on shot peen forming, indicating that the radius of curvature produced by shot peen forming increases with nozzle speed and plate thickness, but decreases with air pressure.

ANALISIS LAJU DEFORMASI PAHAT CARBIDE PADA SIMULASI PEMBUBUTAN BAJA ST41 DENGAN MESIN BUBUT KONVENSIONAL MENGGUNAKAN SOFTWARE ANSYS

In the machining process, knowledge of the tool and workpiece is required to achieve maximum results between quality and productivity. Tool wear parameters are very important to know because the process of changing or sharpening the tool can be predicted. One thing that influences the tool wear rate is the friction force between the tool and the workpiece. This frictional force will produce vibrations and heat energy, causing the chisel grains to erode so that they will experience wear within certain standards. This research aims to analyze the wear value of carbide-type tool edges in the ST41 material turning process based on the friction force that occurs between the tool and the workpiece. Then, from the wear value, the recommended cutting speed is. The method used is simulation-based research using ANSYS software, especially ANSYS Mechanical, by entering predetermined parameters, including diameter and spindle rotation. From the simulation results, the total deformation of workpieces with diameters of 25 mm, 35 mm and 45 mm is 0.363 μm, 0.155 μm and 0.152 μm, respectively. It can be concluded from the simulation results that the largest total deformation is at a diameter of 25 mm.

Effects of Circular Hydraulic Jump on the Material Removal Characteristics of Jet Electrochemical Machining

Jet electrochemical machining (Jet-ECM) is a potential precision machining method. Due to the advantages of non-stress-free machining and high flexibility, it is widely used in surface finishing and complex structural machining. However, the “w” shaped removal profile and wide removal range caused by inappropriate process parameters reduce the stability and localizability of Jet-ECM. In this paper, the material removal characteristics of Jet-ECM were investigated both theoretically and experimentally. A multi-physics field simulation model for Jet-ECM was established, and the overall shape of the circular hydraulic jump (CHJ), current density distribution and workpiece deformation were calculated. The effects of CHJ on the material removal characteristics were investigated by experiments with jet flow rate and inter-electrode gap (IEG) distance. The results reveal the qualitative relationship between CHJ states and process parameters and give the range of parameters that can form a stable CHJ and ensure a Gaussian shaped removal profile and a narrower removal range. This study provides theoretical guidance on the process parameters of Jet-ECM to improve its processing stability and localizability, which is significant for the accuracy of surface finishing and the controllability of complex structural machining, promoting the further application of Jet-ECM.

An adaptive clamp system for deformation control of aerospace thin-walled parts

The assembly and service of thin-walled parts are usually threatened by machining deformation. In this study, phase change material (Sn-Bi-Pb-Cd alloy with a melting point of 70 °C) was used to develop an adaptive clamp system, which could adjust the clamping position when the material was liquid to follow the stress-releasing deformation after rough machining. The material's solidification could re-clamp the workpiece, whose internal stress had been minimized. Afterwards, the workpiece deformation could be removed in finishing machining. Comparing to the counterpart using traditional vacuum fixture, the maximum deformation and the flatness tolerance of the web using the adaptive clamp system reduced by 82.0 % and 72.9 %, respectively, thus effectively improving the accuracy of thin-walled parts manufacturing.

Prediction Model for the Evolution of Residual Stresses and Machining Deformation of Uneven Milling Plate Blanks.

During aerospace thin-walled component processing, the prediction and control of machining deformation have gained increasing attention. The initial residual stress in the blank is a major factor leading to the occurrence of machining deformation. This paper proposes the concept of uneven milling during the workpiece machining process, which is caused by the variation in local cutting depth resulting in uneven material removal thickness. Based on the elasticity theory, an analytical model is established to predict the evolution of overall residual stress and machining deformation in beam-like aluminum alloy components under uneven milling conditions. The effectiveness of the model is verified through finite element simulations and experiments. The results are as follows: (1) Under uneven milling conditions, the analytical model can accurately predict the distribution of residual stress and the machining deformation within the ZX section of the workpiece. (2) The uneven distribution of bending stress arises from the different curvature radii of various positions after workpiece deformation, leading to a 1 MPa to 3 MPa difference in stress between the middle and both ends of the workpiece. (3) During the layer-by-layer milling process, the magnitude of workpiece deformation is related to the stress state of the material removed, and there is a deformation superposition effect on the lower surface of the workpiece, further exacerbating the overall machining deformation.

Statistical model comparison based on variation parameters for monitoring thermal deformation of workpiece in end-milling

Statistical model comparison based on variation parameters for monitoring thermal deformation of workpiece in end-milling

Analysis of reaction forces in fixture locating points: An Analytical, numerical, and experimental study

Reaction forces are important parameters in fixture design. They are generated by the clamping forces and machining loads at the fixture locating points. These forces are used as input values in the determination of clamping forces, fixture stiffness, and workpiece deformation. In this paper, an analytical model based on the minimum norm principle was developed to calculate these forces. Numerical simulations and experimental tests were performed on a 3D polyhedral workpiece to validate the model. The simulations were conducted using Abaqus® software and the experimental tests used a fixture and a 3D polyhedral workpiece. The theoretical, numerical, and experimental results showed good agreement for the normal component of reaction forces. The maximum errors of 3.9% and 15% were observed between the theoretical predictions compared to the numerical and experimental results, respectively. The model was also used to study the effects of two influential parameters, the coefficient of friction and clamping force, on the reaction forces. The good agreement between the theoretical, numerical, and experimental results demonstrated the efficiency of the proposed model in the rapid calculation of reaction forces for fixturing 3D polyhedral workpieces.

Optimization of polylactic acid 3D printing parameters based on support vector regression and cuckoo search

Abstract3D printing, also known as additive manufacturing (AM), is evolving from a rapid prototyping tool to a pillar of the Industry 4.0 revolution and widely used in various industries, since it can quickly and efficiently create workpieces with complex structures and integrated functions. After analyzing the 3D printing principle of fused deposition modeling (FDM), this paper proposes a deformation control‐oriented optimization method for process parameters of FDM of the polylactic acid (PLA) materials, based on support vector regression (SVR) and cuckoo search (CS). First, FDM printing principle and its main process parameters were analyzed. Two key parameters, printing temperature and printing speed, were selected for research, with the maximum shrinkage deformation as the workpiece contour accuracy index. Combining Latin Hypercube Sampling (LHS) with Finite Element Analysis (FEA), finite sample sets were generated. Second, learning from the sample data, the SVR surrogate model was built to predict the workpiece contour accuracy, and the nonlinear relationship between FDM process parameters and PLA shrinkage deformation was obtained. Finally, taking the combination of printing temperature and speed as the design variable and minimizing the maximum shrinkage deformation as the optimization objective, the FDM process parameters optimization model was established, and CS was used to search for the optimal parameters combination. Experimental comparison showed that the FEA results and SVR model in this method are correct and effective, and the PLA workpiece shrinkage deformation is smaller under the optimal parameters combination, which effectively improves the shape accuracy of FDM workpieces.Highlights Combining support vector regression (SVR) and cuckoo search (CS) can optimize polymer 3D printing process parameters. Effective finite element model was built for polymer 3D printing. SVR model established by simulation data can predict workpiece deformation. The optimal process parameters were found using CS algorithm.