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Ball screws are subjected to complex loads during machining processes, which affects the position accuracy of the feed shaft of machine tools. The lack of a reliable model for analyzing the deformation of the ball screw, coupled with the unclear relationship between the deformation of the ball screw and the position error of the feed shaft, makes it challenging to accurately predict and compensate for the position error. The objective of the present research is to investigate the correlation between the deformation of the ball screw and the position error of the feed shaft to improve the accuracy of the machine tool. First, this paper establishes a FEM model to explore the loading and deformation of the ball screw. Secondly, a method for predicting position errors based on the deformation of the ball screw is proposed. Finally, the ball screw-loading test device is used for the position error compensation experiment to verify the reliability of the prediction method. This paper serves as a reference for understanding the generation mechanism of position errors in machine tool feed systems. [ABSTRACT FROM AUTHOR]

The heat transfer coefficient, including interfacial heat transfer coefficient (IHTC) and convective heat transfer coefficient (CHTC), plays a pivotal role in the thermal dynamics of hot gas forming processes. This parameter can determine the temperature field, thereby affecting the deformation and mechanical properties of the material to improve productivity. In this paper, we present an innovative experimental apparatus designed to measure the temperature evolutions of the aluminum specimen and the die during the hot gas forming processes. This apparatus is capable of simultaneously measuring IHTC and CHTC. Using the inverse finite element method, the simulated temperature histories are matched with empirical data and the best-fit values are adopted as indicative of IHTC and CHTC. This study identified the effects of contact pressure and die temperature on IHTC, as well as the impact of gas pressure on CHTC. In addition, a predictive model was developed to forecast the IHTC and CHTC at varying contact pressures and die temperatures with a prediction accuracy surpassing 0.95. By leveraging the predictive model presented in this paper, users can modulate contact pressure and die temperature based on specific production needs to achieve a targeted temperature profile. This method offers enhanced precision in managing the temperature field of the workpiece during hot gas forming experiments, thereby refining the temperature distribution. Moreover, it optimizes the formability and microstructural attributes of the material, ultimately leading to improved mechanical characteristics. [ABSTRACT FROM AUTHOR]

Integral blisk blades are typical complex curved structures with small thickness, low stiffness, and complex boundaries. Due to the high material removal rate during the machining process, they are prone to force-induced deformation, resulting in significant machining errors. This seriously contradicts the requirements for high design accuracy and surface accuracy in the aerospace industry. Therefore, accurately predicting the distribution pattern of deformation caused by dynamic milling forces during the machining process and proposing reasonable error compensation strategies are urgent issues to be solved in the manufacturing of integral blisk blade. Firstly, this paper establishes a prediction model for the deformation distribution during the milling process of the integral blisk blade. Secondly, based on the finite element deformation prediction model of blades, the selection of blade milling processing methods and parameters was completed with the goal of minimizing machining deformation. Finally, a reverse reconstruction geometric modeling compensation strategy is proposed, and the tool path program containing the deformation error compensation amount is regenerated. The prediction model and compensation strategy proposed in this paper were validated through milling experiments and profile accuracy measurement experiments on a certain aeroengine integral blisk blade. The results showed that the prediction model has high reliability, with an average error of 7.96%; the new compensation strategy can reduce the tool-yielding error to within the tolerance range. This study will provide technical support for improving the machining accuracy and efficiency of integral blisk blade. [ABSTRACT FROM AUTHOR]

Cutting toolholders, with designed in-built compliant mechanisms, are frequently used for machining microfeatures. In this paper, compliant structures are designed using trusses as they exhibit a superior strength-to-weight ratio. Systematically stacked two-stage truss structures along with flexure hinges are designed to yield the desired precise cutting motion. The materially reduced efficient design amplifies the output force and greatly assists in overcoming cutting resistance during machining. The characteristics of the designed compliant tool holder are analysed by considering the output force and displacement for a given input. Both mathematical modelling to determine the force and finite element analysis to identify the critical stress regions when subjected to a prescribed input displacement are presented. As part of dynamic analysis, modal analysis and harmonic response studies were performed to determine how the trussed compliant structure deforms when subjected to dynamic loadings. The designed tool holder was additively manufactured using functionally rigid polyamide-12-glass-bead (PA12-GB) material. The performance of the developed cutting tool holder is then verified by machining radially graded surfaces following which, the machining results are presented in this paper. [ABSTRACT FROM AUTHOR]

In order to reduce the machining deformation of thin-walled parts during milling, a non-uniform allowance planning method for thin-walled parts based on the workpiece deformation constraint with the idea of adding materials in reverse material removal sequence is proposed in this paper. This method does not require accurate deformation prediction and extensive experiments compared to traditional error compensation methods. It strives to maximize the allowance to enhance the stiffness of the in-process workpiece. First, a cutting force threshold calculation method is proposed according to the finite element method. The cutting force threshold at different positions is calculated by obtaining the local stiffness characteristics at the cutter-contact point under the constraint of allowable deformation. And then, the maximum machining allowance at the cutter-contact point is calculated depending on the cutting force model. Considering that the stiffness of the workpiece is position-dependent and affected by material removal, the stiffness of the workpiece is updated by adding elements in the reverse cutting direction, and the finishing stock is obtained by surface fitting. Experimental results show that compared with the traditional uniform allowance method, the error of the proposed method is reduced by about 83%, which can effectively reduce the deformation and improve the machining accuracy. [ABSTRACT FROM AUTHOR]

As the first study in the field regarding CB, this paper investigates the implications of interchanging between RDB and CB through manufacturing bends with various angles and investigates the difference between the two methods in form of springback, cross section compression and widening, cross section shape and wall thinning/thickening. The experiments conducted consists of aluminum alloy 6060-T4 round tubes of 60 mm diameter and 3 mm wall thickness, bent around 222 mm radius tooling with various bend angles. In this case, we have found that CB is capable of manufacturing bends with quality near those manufactured by RDB with less springback, however with a dimensional penalty regarding increased deformation of the cross section. [ABSTRACT FROM AUTHOR]

The design of pressure hull structures plays an essential role in the research and development of underwater operation equipment such as deep-sea submersibles. As a bionic structure, an egg-shaped shell has apparent advantages in the application of an underwater pressure hull. Still, the egg-shaped shell is a positive Gauss surface, so it is difficult to control the manufacturing accuracy and quality. In this paper, the technology of solid particle flexible medium forming and the principle of high-pressure bulging in tubes is proposed to manufacture high-precision egg-shaped shell parts. By optimizing the shape of the punch structure, optimizing the process parameters, improving the stress and strain distribution of the egg-shaped shell, and analyzing the deformation mechanism in the bulging process, we have mastered the deformation and quality control methods of the granular medium flexible bulging of non-equal curvature tubular structures in some aspects. [ABSTRACT FROM AUTHOR]

Mandrel is an indispensable tool for manufacturing hollow curved components with large diameter by rotary draw bending. In this paper, an analytical model of mandrel parameters in numerical control (NC) rotary bending of a large diameter tube using a spherical hinge mandrel was proposed, and then the mandrel extension length and core number were preliminarily determined. A nonlinear 3D elastoplastic finite element (FE) model for simulating the NC rotary bending was established. The influences of mandrel-cores on the tangential stress, strain, and bending deformation characteristics were systematically studied. The results show that the maximum prediction errors of wall thicknesses and cross-section distortion are all less than 10%, and the simulated wrinkling position and number also showed good agreements with experimental ones, which indicate that the established FE model is accurate and reliable. Compared with the tube bending without mandrel-cores, the difference between maximum tangential tensile and compressive stresses, as well as the shift of stress and strain neutral layers, was smaller for tube bending with mandrel-cores, which had a good inhibitory effect on cross-section distortion and wrinkling. During tube bending with mandrel-cores, the compressive deformation zone was only located within the zone from the bending tangent point to the section position of 30°, and the tangential compressive strain reached peak value at the section position of 30°. Among the mandrel parameters, core number has a significant influence on cross-section distortion, while mandrel extension length is more sensitive to the wall thickness thinning. The cross-section distortion decreased while the wall thinning rate increased with increasing mandrel extension length, core number, and decreasing the clearance between mandrel and tube. A low friction between the mandrel and tube can decrease cross-section distortion and wall thinning rate. The appropriate mandrel extension length, core number, and clearance between mandrel and tube in NC rotary bending of ⌀ 76 × 1.2 × R150 mm tube were 9 mm, 3, and 0.2 mm, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a new deformation model for analyzing the asymmetric sheet rolling process in plane strain conditions. In the proposed deformation model, similar to the symmetric sheet rolling process, the sheet material between the upper and the lower rolls is divided into two deformation zones, i.e., entry and exit zones. The entry and exit zones are separated from each other by the line that connects the upper and lower neutral points. The mathematical equations of the two deformation zones are defined in a cylindrical coordinate system. The origin of the cylindrical coordinate system is located at the intersection of two inclined and vertical lines where the inclined line passes through the upper and lower neutral points and the vertical line passes through the first contact points of the sheet with the rolls. The proposed analytical model is based on the slab method for the analysis of asymmetric sheet rolling. The governing equations on the slabs are derived from the cylindrical coordinate system, and the roll force and the roll torque are calculated. The validity of the proposed model is discussed by comparing the theoretical predictions of the rolling force and the rolling torque with the results of other researchers and the FE simulation data obtained by the finite element analysis software DEFORM. [ABSTRACT FROM AUTHOR]

Forming limit curves (FLC) at high temperatures under plane-stress states are beneficial for guiding the process parameter design of hot forming superalloy sheets. Constrained by the high deformation temperatures, the establishment of FLCs of superalloy sheets at high temperatures is extremely difficult. This paper conducts an experimental and modelling research to establish the physical-based model with the accurate prediction of hot flow behavior as well as micro grain sizes, using which, the forming limit curves can be predicted. First, the uniaxial tensile tests under different temperatures and strain rates and electron backscattered scattering detection (EBSD) observations of typical conditions were conducted to obtain the hot flow behavior and grain evolution. Second, the dome test at room temperature was performed, and the corresponding simulation was further carried out to obtain the forming limit at room temperature under plane-stress states. Using the above results, a plane-stress constitutive model for GH3128 superalloy was established enabling plane-stress test results under typical hot conditions to be accurately predicted. The prediction accuracies of hot uniaxial and biaxial stretching results are 94.2% and 95.4%, respectively. [ABSTRACT FROM AUTHOR]

In dissimilar friction stir welding (FSW), the influence of tool position with respect to the weld interface (tool-offset) on the microstructural evolution and its effect on joint formation, particularly considering the difference in deformation behavior of the two joining materials, has not been fully explored. This investigation highlights the influence of tool position in friction stir welding of titanium to aluminum and the mechanisms of microstructural evolution that leads to joint formation. It was observed that the tool position controls the deformation behavior and the mixing mechanism of the two metals in the weld nugget. In titanium, the deformation mechanism changed from the formation of "continuous flakes" to "finely distributed particles" when the tool offset was more toward the aluminum side. The deformation and fracture mechanism in titanium is mediated through the formation of adiabatic shear bands (ASBs). Furthermore, the amount of intermetallic phases formed is affected by tool offset. At the optimum tool offset the presence of Ti particles, intercalated particles, interfaces without defects, and controlled diffusion gives rise to improved tensile properties. The mechanisms involved in the joint formation process, such as deformation and distribution, are also discussed in this paper. [ABSTRACT FROM AUTHOR]

Electromagnetic punching (EMP) is a dynamic, high-energy and high-speed hole-processing method. In this paper, the EMP specimens under different discharge energies (11–19 kJ) was prepared. By numerical and experimental methods, the deformation characteristic was analyzed, and hole-quality assessments (including morphology observation, dimensional measurements and microhardness test) were implemented. Results showed that the deformation process of sheet consisted of electromagnetic induction, elastic deformation, plastic deformation and separation stage, and the duration of the entire process was within 100 μs. For 11–15 kJ, the sheet had not completed the entire EMP process (no separation stage), and the deformation degree was aggravated with the increase of discharge energy. For 16 kJ, the incomplete punching occurred owing to the insufficient of electromagnetic force and uneven force. As discharge energy continued to increased, the dimensional accuracy of punching improved, the proportion of rollover zone (η) decreased, the slant angle of fracture zone (β) increased (gradually perpendicular to the sheet plane), the surface morphology of hole wall was more regular, and the micro hardness value of cross section increased, indicating that the punching quality of punched hole was improved. In addition, this work can provide a scientific guidance for the engineering application of EMP technology in automobile industry. [ABSTRACT FROM AUTHOR]

Hot gas forming (HGF) is an advanced technique for fabricating complex-shaped hollow tubular parts. Practically, multi-step pre-forming involving pre-deformation is often necessary prior to HGF. This paper performs an experimental investigation to simulate the pre-forming operation evaluating the effect of pre-strain on the subsequent HGF. Firstly, the dislocation density was accumulated with uniaxial pre-stretching with different strains (5%, 10%, and 15%) at room temperature, simulating the pre-forming operations. Secondly, the sub-sized specimen from the pre-stretched sample was characterized at different temperatures (350, 400, and 450 °C) to evaluate the effect of pre-strain on successive hot deformation for simulating practical HGF. The experimental results proves the coupled influence of pre-strain and temperature on the flow stress and stress-strain variations. To thoroughly understand the micro-mechanisms, EBSD analysis of grains and grain boundary angles was carried out under different pre-deformation levels and temperatures, which shows the recrystallization phenomenon at 15% pre-strain and 450 °C temperature. Finally, a physical mechanism constitutive model is established based on the determined macro and micro results where the pre-strain effect shows the accurate modeling of stress flow behavior of the material. [ABSTRACT FROM AUTHOR]

Aiming at the problems of a large amount of material cutting waste or large forming load when large gear profile forming adopts overall cutting or precision forging process, this paper proposed a three-roller bending process (TRBP) for large gear teeth profile, and analyzed the deformation mechanism of the rack bending, meanwhile the gear chain for roll forming was designed. Finite element analysis (FEA) was carried out to numerically simulate the load effects of both the precision forging process and the TRBP for the large gear teeth profile in 17CrNiMo6. The effects of deformation force and strain of TRBP for large gear teeth profile were analyzed. The results showed that as the deformation temperature and speed increase, the deformation force and strain required by the gear profile gradually change. And the reasonable parameter of TRBP is around 750 ∘ C of deformation temperature and 0.5 mm · s - 1 of speed. Compared with the precision forging process under the same boundary conditions, the deformation force of the gear profile TRBP has decreased by about 99 % which could significantly reduce the tonnage requirement of deforming equipment. [ABSTRACT FROM AUTHOR]

In the process of machining aircraft monolithic components, the initial stress in the blank will cause machining deformation. Based on the energy method, an analytical mathematical model of machining deformation is presented in this paper. The key point is to transform the energy in the removed material into the deformation energy of the part after machining. The initial residual stress of 7050-T7451 aluminum alloy blank and single frame part are used as investigated cases in the analytical model. For layer by layer machining, the deformation evolution is closely related to the tensile or compressive properties of the initial stress of removed material. Combined with the change of neutral axis position, the machining deformation is calculated by a theoretical model. Then, utilizing the semi-analytical model of equivalent bending stiffness, FEM simulation is carried out to analyze the influence of stiffening ribs on machining deformation. Furthermore, experiments are set up to verify the validity of the theory and FEM data. The results indicate that the deformation results of the experiment are consistent with that of theory and FEM model. Deformation is determined by energy of removed material. This paper provides a novel theoretical approaches for the further investigation of this issue. [ABSTRACT FROM AUTHOR]

Due to the unique low rigidity of thin-walled parts, significant machining deformation may occur in the milling process. A deformation prediction model is presented in this paper while considering the effect of the removed material on the global stiffness matrix. Aiming at reducing the scale of the global stiffness matrix, the super-element method is firstly used and the scale of the stiffness matrix is significantly reduced about 30%. And then, the stiffness matrix of the in-process workpiece (IPW) is directly obtained by eliminating the contribution of the removed nodes in the global stiffness matrix. This method can avoid re-building the geometric model or re-meshing the finite element (FE) model in the machining process. To improve the inverse calculation efficiency of the stiffness matrix, a novel nodes re-sorting method is proposed based on the calculation order of the matrix blocks in LU decomposition and inverse calculation. Furthermore, the optimal stiffness direction is discussed and applying the cutting force in this direction can minimize the machining deformation. The simulation results verified the existence of the optimal stiffness direction. Finally, the simulation and experiment are carried out to validate the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

With the changes in joint torque and driving state caused by robot postures, the stiffness properties behave differently. However, constant joint stiffness parameters cannot accurately reflect the deformation of different robot postures. To solve this problem, based on the hypothesis of flexible joints, this paper proposes a pose-dependent identification method for joint stiffness. By changing the load at the end of the robot, the laser tracker is used to monitor the slight change of the measuring point on the link near the joint, and the joint deformation monitoring is realized with the analysis of micro displacements. Combined with the external loads monitored by the dynamometer, the change of joint torque is obtained through structural analysis, and then the joint stiffness at a given joint position is identified. Based on the joint stiffness identification results of different joint positions, the joint stiffness is fitted by a polynomial function, and then the varied robot joint stiffness model is obtained. Jacobean transformation and conservative congruence transformation are combined to predict the Cartesian stiffness of the robot. The effectiveness of the stiffness model proposed in this paper is verified by the loading experiments at the end of the robot and robot deformation measurement for milling long aluminum strip. [ABSTRACT FROM AUTHOR]

Thin-walled parts processed by five-axis CNC machine tools are widely used in aerospace and other fields due to their excellent performance. However, due to the weak rigidity of thin-walled parts, they are prone to deformation during milling, which poses great difficulties for efficient and precise machining of thin-walled parts. This paper introduces the classification and corresponding machining methods of thin-walled parts. By analyzing the causes and evolution mechanisms of errors in the machining process of thin-walled parts, and combining modeling methods with factors such as milling force, residual stress, and cutting chatter, the current research status of domestic and foreign scholars on deformation factors is summarized. At the same time, two deformation control methods, adaptive machining and error compensation, were introduced. Finally, the overall research status of thin-walled parts machining was summarized, and prospects for efficient and precise machining of thin-walled parts were proposed based on actual machining conditions. [ABSTRACT FROM AUTHOR]

This paper addresses the problems of easy deformation, difficult dimensional control and difficult accuracy assurance during the production of thin-walled gears for helicopter spoke cutting. It uses finite element simulation technology, metal cutting principles, process optimization and other design and manufacturing technologies to reveal the causes of cutting deformation, effectively predict the deformation of parts during cutting, and develop reasonable deformation control strategies. This study explores the effects of cutting force, residual stress and clamping method on gear machining deformation. The deformation of the spoke plate is analysed by finite element simulation. Abaqus software is adopted to establish a finite element model for 2D turning simulation to predict the machining residual stresses and cutting forces during gear turning machining with different cutting parameters. The simulated cutting forces are compared with the residual stresses and experimentally measured values to verify the accuracy of the finite element model and provide a theoretical basis for model construction in the next simulation study. With Abaqus software, the effect of different cutting forces on the deformation of the spoke plate is simulated, and the effect of the superposition of cutting and clamping forces on the deformation of the spoke plate is simulated using life and death cell technology to simulate the machining of the workpiece. Then, a corresponding fixture is designed to realise the corresponding clamping position for machining experiments, and the deformation of the spoke plate is measured by CMM (coordinate measuring machine) to verify the realism of the simulation. This research provides scientific theoretical guidance and process support for aerospace thin-walled gear spoke plate turning. [ABSTRACT FROM AUTHOR]

High-strength DP980 steel has been used on the automobile to improve the crash safety and lightweight, but serious springback is unavoidable during stamping. In this paper, complicated deformation behaviors during cold stamping of DP980 steel are investigated by combining experiment and simulation in order to promote the accuracy of springback prediction. Deformation behaviors including varied elasticity, anisotropic yield, and cyclic hardening are studied by testing, modelling, and model-programming. Firstly, uniaxial tension, biaxial tension, and in-plane cyclic tension–compression tests are carried out by a self-developed platform to test the mechanical behaviors of DP980 steel in the complicated deformation process. Secondly, elastic, yield, and hardening behaviors are modelled and evaluated. A modified elastic attenuation model by establishing a relation between chord elastic modulus and plastic strain is proposed to describe the elastic behavior. Three yield models, such as BBC2005, Hill-1948, and von-Mises, are presented to compare the description ability to the yield locus and anisotropy. A coupled isotropic and nonlinear kinematic (CINK) hardening model is proposed to accurately describe the hardening behaviors (Bauschinger effect, transient effect and permanent softening) by cyclic tension and compression loads. Finally, U-shaped part is stamped and simulated by using models that can describe actual deformation behaviors. The springback prediction with modified elastic attenuation, anisotropic yield, and CINK hardening models obtains an optimal result, and the overall relative error is only 1.803%. Among three factors, the effect of elastic attenuation on springback is the greatest. The results show that the accurate testing, modelling, and implementing of complicated deformation behaviors of DP980 steel contribute to high-precision simulation results. [ABSTRACT FROM AUTHOR]

One factor that plays an important role in the aerodynamic performance of aeroengines is the shape of the blades, which is vulnerable to change resulting from the plastic deformation and the residual stresses induced by the complex manufacturing processes, especially the shot peening. However, few studies were focused on the detailed strategies of shot peening on the complex profile and the superposition effects of residual stresses during the entire manufacturing processes. In this paper, based on the concept of eigenstrains, we investigated the effect of shot peening on residual stresses and deformation of the blade by combining the experimental measurement and the local-global simulation. The results show that the initial residual stresses induced by the previous milling process could be neglected. After the shot peening, the blade has the largest deformation if considering the initial residual stresses during milling with large amount of material removal, compared with the case without considering initial residual stresses and the case considering initial residual stresses after dynamic milling of blades. Furthermore, the in-out sequence of shot peening results in the smallest deformation and the pre-deformation of the blade can effectively offset this deformation. Finally, the shot peening intensity should not be too high in practical blade manufacturing for small thickness in order to avoid compromising the reliability and safety of blades. [ABSTRACT FROM AUTHOR]

This paper presents a simulation method for predicting thermo-elastic behaviours of spindle-bearing system and an optimization procedure for housing design parameters in relation to various spindle-bearing operating and surrounding conditions such as assembling tolerance, geometric dimension, cooling condition and thermal deformation. The numerical formulation of transient thermo-elastic behaviours as a function of major spindle-bearing system design parameters is developed using the design of experiment methodology. The spindle-bearing analysis program has also been suggested in this paper. The suggested modelling and optimization method not only considers thermal deformation or heat transfer, but eventually it includes the nature of thermo-elastic interaction within spindle, bearing, housing and surrounding conditions in terms of formulating theobjective functiondescribing thermo-elastic characteristics such as friction moment, heat generation, contact mechanism, thermal displacement, assembly tolerance change, bearing internal clearance and spindle stiffness change and the dynamically changing operating conditions of the spindle. In order to substantiate the method, this paper shows a numerical example of formulation and optimization results for spindle housing design parameters with consideration of thermo-elastic behaviours as the thermal displacement, the preload increase, and the preload fluctuation. [ABSTRACT FROM AUTHOR]

Due to the low rigidity, the milling process of cantilever thin-walled structure (CTWS) inevitably generates machining-induced deformation, ultimately resulting in poor surface quality and thickness accuracy. In this paper, to avoid these issues, a novel and green ice-based fixture (IBF) is innovatively proposed to hold CTWS firmly to suppress machining deformation during the whole processing. Firstly, a stair-step model is established to express machining-induced deformation of CTWS with/without IBF. Next, IBF is designed to clamp CTWS steadily. Secondly, finite element model (FEM) for CTWS is utilized to simulate milling deformation with/without IBF to reflect the effect of IBF on eliminating CTWS deformation. Finally, the experiment of CTWS milling is carried out, and the experiment results show that IBF can achieve a reliable and stable holding for CTWS, and hence suppress machining-induced deformation and improve thickness accuracy. In this paper, research on IBF for CTWS processing provides reference and guidance for the application and promotion of IBF in industry. [ABSTRACT FROM AUTHOR]

During the machining process of large-scaled and thin-walled parts such as aircraft structural parts, the deformation is a relatively common phenomenon which seriously affects the machining quality of the parts and may lead the parts to be scrapped. In this paper, interim machining states of workpiece are considered in addition to final machining states for deformation control so as to improve the machining quality and part correct rate. It is very important for large-scaled and thin-walled parts to consider the interim machining states, as considerable deformation has always occurred in interim machining states. The difficulties of deformation control of interim machining states contain two aspects: (1) how to assess whether interim machining states can satisfy process requirements for further machining and (2) how to adjust the tool paths adaptively for further machining so as to make the final machining states correct. In order to address the above difficulties, an adaptive machining approach based on in-process inspection of interim machining states for large-scaled and thin-walled complex aircraft structural parts is proposed in this paper. The actual interim machining state is obtained based on in-process inspection of machining states during the machining process; the essential idea of this paper is that the final machining state of the workpiece can be guaranteed by adjusting the tool path based on the inspection of interim machining states, which is realized by coordinating the dimensional tolerance and geometrical tolerance. In order to realize the new idea, the criterion for determining whether the interim machining state is suitable or not for further machining and the concept of expected final state are introduced. Eventually, the large-scaled and thin-walled complex aircraft structural parts can be machined adaptively according to process requirements. A typical large-scaled and thin-walled complex aircraft structural part is used as a case to validate the proposed approach. The results show that the dimensional error is 0.10 mm and the profile error is 0.06 mm, which can meet the machining requirement of large-scaled and thin-walled complex parts. [ABSTRACT FROM AUTHOR]

Bend tubes have been widely used in aerospace equipment due to their excellent mechanical properties and chemical properties. However, elliptic deformation will occur in the process of bending, which will reduce the pressure bearing capacity and service life of the bend tube. In order to ensure the production quality of the bend tube, a method of detecting elliptic deformation based on the spine line of the tube is proposed in this article. Firstly, the spine line reconstruction method, which employs scanning points of the tube is proposed. Specifically, a voting points inspired spine line initialization method, and a bend part identification preferred spine line shape analysis method are designed. Secondly, the contour extraction method based on the natural coordinate system of the spine line is studied. Thirdly, the contour integrity assessment method based on the maximum center angle of the missing contour line is proposed. Contours satisfying the integrity will be used for ellipse fitting to determine the ovality of the tube. Finally, various bend tubes and standard elliptical cylinders are used to illustrate the effectiveness of the proposed method. Extensive experimental results show that our proposed method can extract the contour of the bend tube and analyze its deformation in only 7 s, and the ovality error is about 0.039%. Therefore, the method proposed in this paper can quickly and effectively analyze the elliptic deformation of the bend tube and can be used for online detection. [ABSTRACT FROM AUTHOR]

Aiming at the problems of complex processing technology, uneven deformation, and poor forming accuracy of multi-curvature positive Gaussian slewing egg-shaped shells, it is proposed to use unidirectional loading rubber flexible medium bulging technology to improve the tube deformation distribution and enhance the processing accuracy of plastic forming of bionic egg-shaped shells. By analyzing the structure and manufacturing method of egg-shaped shells, this paper explores the optimization problems in the rubber bulging technology of non-homogeneous deformation egg-shaped shells. The simulation analysis and experimental verification methods are used to study the different technological parameters and forming accuracy of rubber bulging of egg-shaped shells under unidirectional loading and to master the deformation mechanism of rubber bulging of egg-shaped shell structural components under unidirectional loading. The study shows that optimizing technological parameters in unidirectional loading mode can effectively improve the uniformity of strain distribution and thickness distribution during the forming of egg-shaped shells, thus improving the processing accuracy of plastic deformation of bionic egg-shaped thin-walled parts. Furthermore, the simulation of the rubber bulging technology of the egg-shaped shell after the optimization of technological parameters is in good agreement with the experiment. [ABSTRACT FROM AUTHOR]

Traditional punch and die stamping process are not capable of fabricating micro channels with high aspect ratio due to stress concentration and large thickness reduction. A thin sheet metal roll forming process using involute gears as rollers was proposed as a method to fabricate micro channels with high aspect ratio in this paper. Corresponding relations of gear-rollers and formed channel's geometrical morphology were firstly established as designing guidelines. Then, process characteristics, material deformation behavior, and process mechanism were studied by experiments and simulation. Micro channels with aspect ratios up to 1.0 was formed with thickness reduction lower than 18.7% using 0.1-mm SS316L metal sheets. And both experiments and simulation reveal that thickness reduction can be further lowered down by reducing friction. The forming process of a micro channel consists of two chronological states-forming stage and quitting stage which, respectively, determines the formability and dimension accuracy. Furthermore, process parameters and assembly errors were demonstrated to have great influences on the process' formability. This paper provides designing guidelines and process mechanism for thin sheet metal roll forming process as a promising method to fabricate micro channels with high aspect ratio. [ABSTRACT FROM AUTHOR]

Shot peening is widely used in the aeronautical industry to enhance the fatigue life of the parts and form large, thin, and complex components, such as wing and fuselage skins. Previous research on peen forming simulation has rarely considered the influence of the shot peening sequence on the resulting deformed shape. In particular, the study on the mechanics mechanism of asymmetry in double-sided sequential (un-simultaneous) shot peening is not enough. In this study, therefore, experiments based on symmetrical plane strips (Almen-sized Al7075 strip and Almen strip) show that the final deformation is often asymmetrical with the same shot peening parameters in sequence. As the symmetrical surfaces are peened in sequence, the final bending direction is always consistent with the later shot peening effect. To explain this interesting phenomenon, the double-sided symmetrical sequential shot peening process was simulated by finite element method (FEM). The simulation and experiment results verified the universality of asymmetric deformation in double-sided symmetrical sequential shot peening process. A theory analytical model of the stiffness reduction proposed in this paper was used to explain the asymmetric deformation mechanism, and it is verified by three-point bending tests. Some new results obtained by the experiment and simulation are presented. The influences of the strip thicknesses and shot peening pressures on the asymmetric deformation are discussed in double-sided symmetrical sequential shot peening. [ABSTRACT FROM AUTHOR]

In this paper, the strain-induced martensite transformation (SIMT) process of 304 stainless steel tubes under the action of a high shear stress state (HSSS) in the deformation zone of a new spinning process is studied and analyzes the changes in the microstructure and mechanical properties of each tubular workpiece obtained after continuous cold spinning under HSSS. Firstly, the contact equations and stress–strain state equations for the external cold extrusion spinning (ECES) were established and combined with the stress state criterion to find that ECES has a higher softening coefficient than conventional spinning (CS) in the deformation zone. To study the performance of the workpiece at each stage of processing, a longitudinal unidirectional tensile test was carried out on 304 stainless steel tubes. The material was obtained by cold spinning 5 times in succession for each pass of the tube, while X-ray diffraction (XRD) analysis was performed to measure the phase volume fraction of the workpiece at each stage, which provides a reference for subsequent transmission electron microscope (TEM) observation of the microstructure. The results show that the martensitic phase changes gradually after the volume fraction of martensite grows to a peak of 35% and gradually refines and fractures in tension, forming ultra-fine grain size laths of martensitic phase, while the tensile limit increases by 2.1 times, at which time the elongation at break is less than 5%. [ABSTRACT FROM AUTHOR]

The accurate calculation of the spatial configuration of the tube billet in roll forming process is the theoretical premise of roll pass design. But the currently existing shape function method for calculating the spatial configuration cannot describe the springback of the tube billet after bending deformation, so it cannot be applied to the accurate calculation of the spatial configuration of high strength steel with large springback. For this reason, this paper derived the formulas for calculating the bending moment of springback, proposed a trajectory function G(X) to describe the deformation path of the points on the neutral layer of the tube billet in forming direction, and finally established a new method which is called trajectory function for calculating spatial configuration of high strength steel. To verify the accuracy of the trajectory function method, the ∅120 × 5-mm-high strength steel shaft tube roll forming process was taken as an example in this paper; the spatial configurations in five stages of the breakdown stage were obtained by experimental method, the trajectory function method, and the shape function method respectively. The calculated results of the trajectory function method were compared with those of the shape function method and the experimental method. The comparison shows that the results of the trajectory function method are closer to the experimental ones, and its overall accuracy is higher than that of the shape function method. [ABSTRACT FROM AUTHOR]

Thermal error modeling of the spindle plays an important role in predicting thermal deformation and improving machining precision. Even though the modeling method using temperature as the input variable is widely applied, it is less effective due to severe loss of thermal information and pseudo-hysteresis between temperature and thermal deformation. This paper presents a novel modeling method considering heat quantity as the input variable with theoretical analysis and experimental validation. Firstly, the change of thermal state of a metal part being heated is discussed to reveal the essence of the relationship between heat, thermal deformation and temperature, and the theoretical basis of the modeling method proposed in this paper is elaborated. Subsequently, the relationship between thermal deformation and heat quantity is further studied through modeling the thermal deformations of stretching bar and bending beam using heat quantity as the independent variable, and the stretching model is verified based on finite element method. Then, the thermal error models of the spindle are developed with the heat elastic mechanics theory and the lumped heat capacity method. In succession, the parameter identification of thermal error models is carried out experimentally using the least square method. The average fitting accuracy of these models is up to 91.3%, which verifies the good accuracy and robustness of the models. In addition, these models are of good prediction capability. The proposed modeling method deepens the research of thermal errors and will help to promote the application of relevant research results in the actual production. [ABSTRACT FROM AUTHOR]

Currently, most blade repairing methods are primarily oriented for a straight or slightly curved blade; moreover, they are based on non-contact measured point-cloud, resulting in low accuracy and significant uncertainty-related issues on the defective region during repair. Therefore, this study investigates a contact measured point method with a high accuracy to analyze the repairing of a defective twisted blade; in addition, the paper proposes a new repairing method of deforming the reference cross-sectional curves adjacent to defective cross-sectional curves recursively. In order to accomplish the aforementioned, first, an interpolation algorithm of the cross-sectional curves using B-spline is set; thereafter, a criterion of the measured point density based on the size relationship between the defective region and the blade as a whole is determined. Subsequently, the registration algorithm of the reference curve and measured points of the defective cross-sectional curve to facilitate the deforming operation is provided. An iteratively moving distribution algorithm of all control points belonging to the reference curve is proposed by this paper in order to realize curve deformation. The paper presents twisted blade repairing examples and also compares the repairing surface and the designed surface to verify the validity of the proposed method. The blade repairing method proposed in this paper is aimed to guarantee a surface smooth restoration with higher accuracy and offers good conditions for several designing and repairing cases. [ABSTRACT FROM AUTHOR]

Titanium alloy extruded profiles with complex cross-section are usually used to manufacture special-shaped structural parts in the aviation industry. In this paper, a Ti-6Al-4 V profile with asymmetric Y shape was manufactured by a direct extrusion process. A comparative study was conducted at the different lubrication conditions, in which the different process deformation mechanisms, resulting microstructures, and mechanical properties of profiles have been investigated by finite element simulation and a series of experiments, i.e., scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). It was revealed that the metal flow is blocked at the narrow die orifice due to the deterioration of lubrication, resulting in the continuous shrinkage defect. The metal deformation coordination mechanism becomes gradually significant due to poor friction contact, which promotes the internal stress in the cross-sectional center to transfer outward to balance the friction at the edge of the orifice, resulting in the reduction of the effective strain in the center. The heat generated by friction weakens the heat exchange behavior between the metal and the die, which helps the profile retain a more uniform temperature field. In the sectional center of the profiles made from the two different lubrications, extrusion with good lubrication results in greater grain/colony refinement due to greater effective strains, and a slightly greater dislocation density was found due to the uniform deformation. The tensile tests revealed that compared with poor lubrication, due to the improvement of Hall–Petch strengthening and dislocation strengthening in the cross-sectional center with good lubrication, the variation range of yield strength and tensile strength is reduced to 11 MPa and 7 MPa, respectively, and the variation range of microhardness is reduced to 44 HV and 32 HV, respectively. The improvement of lubrication not only helps to reduce forming defects but also can obtain uniform mechanical properties. [ABSTRACT FROM AUTHOR]

The prediction of thermo-mechanical behavior of the spindle is essential for machining precision. Particularly, the characteristics of high-speed spindles depend on their thermal behavior. The heat generated on the bearings transfers to the spindle and surrounding air, thus causing the thermal expansion of spindle elements. This paper presents the thermo-mechanical model of the spindle with ball bearings with angular contact. In this paper, the main source of heat on the spindle occurs due to friction torque on bearings with angular contact. The presented model is based on the mechanical model of the bearing and the numerical model (FEM) of the spindle. The proposed solution considers non-stationary change of temperature, thermal deformation, and bearing stiffness, based on the angular position of the ball. Predicting of bearing characteristics has been used to establish the change in static stiffness of the spindle nose as well as the effect of thermal expansion on the machining accuracy. In order to validate the model, experiments have been performed for different speeds. The paper establishes that the predicted temperatures on the spindle and spindle nose stiffness under different speeds correspond to those measured experimentally. The results of the experiment have shown that the increase of spindle speed causes the increase of bearing temperature, thus leading to the expansion of bearing elements. Additionally, these changes cause increased stiffness of the bearing, which in turn increases the stiffness of the spindle nose. [ABSTRACT FROM AUTHOR]

In this paper, both numerical and analytical method were developed for computing, in strip or plate rolling, the distribution of roll pressure, rolling force, and rolling torque (from which also rolling power can be estimated), assuming an homogeneous deformation of the rolled material. Unlike other similar models present in the literature, which solve the resulting rolling differential equation for the roll pressure, the model presented in this work solves the problem for the horizontal force. In this way, it is possible to avoid the calculation of the derivative of material flow stress curve, which is not always analytically easy and possible (i.e., point material flow stress data). The proposed numerical model is based on the friction law proposed by Chen and Kobayashi while the analytical one is based on the simple shear friction model and brings to useful analytical formulas for a quick calculation of rolling torque and force. Moreover, a relationship between the shear friction factor and Coulomb friction coefficient in rolling was found. The developed models show good agreement with experimental measures, in terms of rolling force and torque, found in literature. [ABSTRACT FROM AUTHOR]

Joint deformation greatly influences machining accuracy for a robotic arm. In this paper, the deformation characteristics of the robotic arm with hybrid kinematic chains are investigated to improve its machining accuracy. Firstly, the deformation model of the joints has been established based on the Strain energy method and Castigliano theorem according to the robot structure. Secondly, the deformation influence coefficient (DIC) is defined to investigate the deformation influence of main components on the end-effector, and the deformation characteristics are evaluated by the simulation. Finally, a small size robotic arm prototype is established and robotic drilling comparative experiments are conducted. The theoretical and experimental results show that the machining method can be selected according to the DIC, in which the force can be applied to the components with better stiffness. On the other hand, the deformation of driving components can also be reduced when the DIC cannot be adjusted to meet the accuracy requirement. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review on the types of machining deformation and mechanism analysis, as well as the machining deformation control methods of aero-engine thin-walled casings. The different types of machining deformation (e.g. deformation caused by positioning and clamping process, cutting forces, residual stress, and chatter) of thin-walled casings are introduced, and the corresponding deformation mechanism of each type is discussed in the first part. Subsequently, the research progress and academic achievements are summarised in terms of the prediction and control of cutting deformation, dynamic modelling and chatter suppression, and adaptive machining and error control in the field of machining deformation control of thin-walled casings. Then, the specific machining deformation control methods, including cutting force prediction, reduction of residual stress, dynamics modelling, chatter suppression, adaptive machining, and error compensation, are explored in detail. Finally, this review implies the existing challenges and future developing tendencies to control the machining deformation of thin-walled casings. [ABSTRACT FROM AUTHOR]

The continuous and synchronous calibration process for straightness and roundness of LSAW (longitudinally submerged arc welding, LSAW) pipes with three rollers is a bidirectional reciprocating bending process. It includes both axial and circumferential directions. It is particularly important to reveal the deformation mechanism, which provides theoretical support for the calibration process to be applied to actual production. Based on this, through the combination of references, theoretical analysis and numerical simulation, the deformation mechanism is analyzed in this paper. The whole deformation process of pipe is modeled and then numerically simulated with FEM software of ABAQUS. The results show that reciprocating bending can eliminate the difference of initial curvature, so that the axial curvature and circumferential curvature are unified to the same direction and value, respectively. The calibration process of LSAW pipes is realized by the synergy between the axial reciprocating bending straightening process and the circumferential reciprocating bending rounding process. The simulation and experimental results support the theoretical results, and the deformation is mainly caused by axial stress and circumferential stress. [ABSTRACT FROM AUTHOR]

In this paper, the deformation behavior of circular hole-flanging obtained by electromagnetic forming (EMF) and stamping is investigated. Numerical simulations are performed to analyze the deformation of the 5052 aluminum alloy sheet and the stress–strain characteristics obtained by the two forming processes. The correctness of the simulation results is verified experimentally. It has been found that with the increase of the discharge voltage, the sheet flanging area gradually changes from an inclined plane to a vertical plane. The sheet deformation is not synchronous due to the uneven electromagnetic force distribution, while four special nodes collide with the die successively at a discharge voltage of 9 kV. The maximum contact error by EMF at 9 kV is less than 0.3 mm. The forming accuracy obtained by stamping is poor. The maximum gap between the sheet and mold is 1.1 mm when the punch diameter is equal to 75.2 mm. After both electromagnetic flanging and stamping, the maximum principal strain appears at the sheet edge region, which is prone to rupture. [ABSTRACT FROM AUTHOR]

Large-sized thin-walled composite structure has been widely used in aircraft due to favorable strength-to-weight ratio and stiffness-to-weight ratio. The deformation has great influence on assembly quality of aircraft. So, deformation prediction is essential for guaranteeing the assembly quality. The structure with complicated geometry is difficult to discretize into regular quadrilateral or hexahedron. However, the above types of element are required when using the available conventional laminate shell and continuum laminate shell elements in the commercial software. To cope with this issue, an efficient trans-scale and multi-stage approach is proposed to predict deformation of large-sized thin-walled composite structure in this paper. Firstly, the large-sized composite is divided into several sub-regions based on its lay-ups. Multi-scale homogenizations were adopted to compute the macroscale material properties of each sub-region. Then, deformation analysis on the homogenized model is conducted. During simulation, micro-stress distribution in each element is investigated by stress projection. Damage analysis was conducted with failure criteria. An assembly experiment was conducted to validate the proposed model. The numerical results are in agreement with the experiment. Deformation behaviors of composite panel under different working pressures of 0.03 MPa and 0.09 MPa are evaluated. [ABSTRACT FROM AUTHOR]

Electric-pulse triggered energetic materials forming (ETEF) is a high-speed manufacturing process, which utilizes the chemical energy released by energetic materials (EMs) triggered by underwater wire discharge to plastically shape metals. ETEF is not fully understood, particularly in research on the discharge characteristics of energetic materials triggered by metal wires and the deformation process of metal sheets. The above two problems were investigated in this paper using experimentation and numerical simulation. For the pulse discharge characteristics, the peak values of voltage and current were reduced during the triggering process of energetic materials, and the triggering energy consumption of energetic materials was quantified to be about 200 J. The matching parameters of different capacitor-voltage devices may be insensitive to triggering the energy release of energetic materials. The maximum major strain and thinning rate of the bulged specimen under ETEF conditions were significantly reduced when compared to the quasi-static specimen with the same bulging height, and the specimen's deformation uniformity and strain distribution were improved. The simulation results showed that the addition of energetic materials significantly improved the plastic strain energy of the blank. The deformation of the blank in ETEF can be divided into two stages: the initial chemical energy action stage and the inertia action stage. The bulging height of sheet metal increased by nearly 301% in inertia action stage, accounting for 80% of the total deformation time, and the effective plastic strain distribution was more uniform. [ABSTRACT FROM AUTHOR]

Due to their good mechanical and technological performances, thin substrate-supported metal layers are increasingly used as functional components in flexible electronic devices. Consequently, the prediction of necking, and the associated limit strains, for such components is of major academic and industrial importance. The current contribution aims to numerically investigate the respective and combined effects of strain rate sensitivity of the metal layer and the addition of an elastomer layer on localized necking in substrate-supported metal layers. To this end, strain rate-dependent forms for the flow theory of plasticity and the deformation theory counterpart are used to describe the mechanical behavior of the metal layer. As to the substrate layer, it is made of elastomer material whose mechanical response is described by a neo-Hookean hyperelastic model. The two layers are assumed to be perfectly adhered. Necking limit strains are predicted by the Marciniak-Kuczynski (M-K) imperfection approach. Various numerical results, corresponding to freestanding metal layers as well as substrate-supported metal layers, are presented and extensively discussed in this paper. The significant effect of strain rate sensitivity on the retardation of localized necking is first emphasized. Then, the combined and positive influence of strain rate sensitivity of the metal layer and characteristics of the elastomer layer (thickness and stiffness) on the enhancement of the ductility of the whole bilayer is analyzed and discussed. [ABSTRACT FROM AUTHOR]

Under the load conditions of clamping force and riveting force, the part deformation problems are induced in the assembly process. For the component deformation problems of the thin-wall part assembly, in this paper, from the viewpoint of micro-aspect, the fractal theory model is proposed to analyze the relationship between the part deformation, loads, and contact area for rivet-joint parts; the micro-deformation values for different stages are solved and obtained through theoretical analysis. According to the self-similarity of fractal theory model, the change of the micro-convex body for contact surface will be researched to reflect the macro-deformation properties. Through the measuring experiment for thin-wall parts, the actual three-dimensional coordinate value of each measuring point is obtained before and after riveting assembly, and then, the wavelet neural network method (WNNM) is adopted to predict experiment deformation value based on the obtained deformation value after processing the coordinate value through fitting surface method. Hereby, according to the deformation value for every thin-wall part after processing experiment data, the fractal dimension value will be determined based on the fractal statistic method to analyze the deformation status of different stages. Through analysis and comparison, the results show that the variation regularity of deformation value based on two or three fractal deformation stages is well conformed to and similar to the experimental value and prediction value, which also verify the correctness and effectiveness of the theoretical model, and provide a theoretical basis for further research on thin-wall part assembly deformation from a micro-perspective and improving assembly accuracy quality in future. [ABSTRACT FROM AUTHOR]

This paper proposes a new sheet forming method that combines electromagnetic forming (EMF) with hydraulic forming called electromagnetic hydroforming (EMHF). Finite element models of both the EMF and EMHF processes were established using ANSYS and ABAQUS. Then, dynamic free bulging deformation of 5052 aluminum alloy during the forming processes was analyzed. The EMF process results in a deformed sheet profile with an uneven conical shape, whereas EMHF leads to a deformed profile with a regular circular shape. This is because during the EMHF process, electromagnetic impact energy is transformed into liquid pressure that is evenly distributed on the sheet surface. When the discharge voltage is 4.5 kV, the maximum deformation speed and strain rate reached 70.6 m/s and 2176.8 s−1, respectively. Thus, EMHF can be considered a high-speed forming method. The simulation results for both EMF and EMHF were verified by experiment at two different discharge voltages. The maximum error was less than 7.4%. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for removing out-of-plane deformation in stretched metal interconnects by adding a fractal structure to the original meander shape and using an optimized fabrication stack. In thermoformed electronics, in cases where copper is used as conductor, the twisting of meander-shaped structures caused by excessive mechanical stress can cause a non-uniform surface, delamination of the metal interconnect from the substrate, and in some cases, a short circuit to the adjacent tracks. Typically, designers of stretchable electronics use various shapes and widths of the copper interconnect to tackle this issue. Using conventional meander shapes such as horseshoes and U-shapes is not universally practical, especially when stretching is higher than 30 percent leading to significant out-of-plane buckling. Limiting this out-of-plane buckling by reducing the track width is not always applicable, as a minimum width is needed from a technology and conductivity perspective. The presented approach is inspired by computational and experimental studies of multiple meander shapes and fabrication methods. A geometry- and fabrication-based approach is presented, reducing the mechanical stress of almost all possible meander shapes by increasing the meander's path length to accommodate the metal track's produced torque during stretching. An analytical approach is provided for calculating the optimal meander parameters and the optimal fabrication stack is achieved based on simulation results. Experiments and finite element modeling for a case study show the improvement in the stress distribution and reduction of out-of-plane buckling. [ABSTRACT FROM AUTHOR]

In double-sided grinding, the material removal on the surface of the workpiece is non-uniform. The thermal deformation of the material may be one of the influencing factors. However, it is difficult to predict and measure the temperature field distribution in the workpiece in double-sided grinding. In this paper, based on the grain trajectory model, a single effective abrasive grain is regarded as a moving point heat source, and the new model of temperature field and workpiece thermal deformation is established based on the thermal–mechanical coupling effect. The distribution characteristics of the temperature field in the workpiece and the axial deformation of the workpiece under different processing parameters are calculated. Finally, a double-sided grinding experiment is carried out to measure the surface profile of the workpiece under different processing parameters to verify the accuracy of the established model. This article solves the problem of the unpredictable temperature field of the workpiece in double-sided grinding and has guiding significance for improving the surface quality of the workpiece in double-sided grinding through the optimization of processing parameters. [ABSTRACT FROM AUTHOR]

In the two-step cutting process, due to the combined effects of mechanical and thermal deformation, the microstructure and residual stress of the workpiece are changed with the change of roughing parameters, which affects the machined surface quality. In this paper, the two-step milling (roughing and then finishing) experiments of Ti-6Al-4V titanium alloy were designed to analyze the effect of different roughing parameters on the cutting force of roughing and finishing, the residual stress of finishing surface, and the microstructure. The microstructural characteristics in terms of residual stress, XRD patterns, phase composition and content, and nano-scale crystallite size of machined surface layer were characterized to reveal the machined surface layer quality adjustment and controlling mechanism from the prospective of the microscopic scale. The experimental results showed that the cutting force and compressive residual stress were larger at low roughing cutting speed than that at high roughing cutting speed because of the combined effects of mechanical and thermal deformations. In the two-step machining process, with the increase of roughing cutting speed, the β phase on the finishing surface firstly increased and then decreased. Meanwhile, the high roughing cutting speed weakened the microcrystal refinement of the finishing surface because of the work hardening effect. Therefore, the appropriate roughing machining parameters will contribute to the improvement of finishing machined surface quality in the terms of lower cutting force, higher compressive residual stress, and better grain refinement, phase content, and preferred crystallite orientation, thus increasing the microscopic mechanical properties of machined surface layer. This provides a reference for optimizing the cutting parameters to adjust and control the quality and integrity of the machined surface layer in two-step milling of Ti-6Al-4V alloy. [ABSTRACT FROM AUTHOR]

In the investment casting process of castings with complex structures, due to shrinkage deformation, the casting accuracy and pass rate are low, which largely limits the application scope. In this study, a convolutional neural network (CNN) was used to predict and analyze the shrinkage deformation of complex castings in a investment casting process, which provides a new method to improve the precision of investment casting and cavity design. Through the establishment of a hollow thin-walled structure model, simulation calculations, mathematical modeling, and nonlinear fitting analyses of the shrinkage rate were performed, and a mapping model between the shrinkage rate and the structural parameters was constructed. The CNN model was constructed based on the structural characteristics of the model. Finally, experimental verification was carried out to analyze actual hollow turbine blades. The average error for the training set was 0.04%, and the average error for the test set was 0.03%. The experimental results showed that the CNN model proposed in this paper could accurately predict the shrinkage deformation and trends of complex castings in the investment casting process, which has important practical significance for improving the accuracy of castings and mold cavity design. [ABSTRACT FROM AUTHOR]

In order to produce the mechanical assemblies with the high quality, the finest functionality, and the low cost, the optimal tolerance synthesis can be a useful tool in the design stage. The degradation of components due to some operational or environmental factors (such as the thermal cycling, the mechanical deformation, and the wear) can lead to dimensional variations in components and fall-off of the functionality of the product. In addition, different manners of the degradation on the internal and external dimensions can cause asymmetric deviations in the dimensions. On the other hand, the effect of degradation on the product quality has not been considered in most researches. In this paper, a new multi-objective framework is proposed for optimal asymmetric tolerance synthesis of mechanical assemblies with degrading components. In this method, the optimal tolerances are allocated based on ensuring the fulfillment of the product's functional requirements, maximizing the product quality, and minimizing the total cost over the lifetime of the product. To incorporate the degradation effect into the loss function concept, the present worth of the expected quality loss (PWL) is formulated in terms of asymmetric tolerances. Accordingly, the functional process capability and manufacturing cost are developed based on asymmetric tolerances and the degradation effects. In order to extract Pareto fronts of optimal solutions, the elitist Non-dominated Sorting Genetic Algorithm II as an evolutionary generating methodology is utilized. In solving multi-criteria tolerance synthesis problem by a generating method, selecting the best tolerances from the obtained optimal Pareto solutions is a significant challenge. In this paper, to find the best asymmetric tolerances from Pareto solutions, a combined Shannon's entropy-based TOPSIS algorithm is used. Finally, a bi-directional non-back drivable roller clutch assembly as an industrial case study is considered to illustrate the efficiency of the proposed method, and the obtained results are compared and discussed for verification. [ABSTRACT FROM AUTHOR]

In this paper, a prediction model of the material removal depth for the polishing process is developed from the microscopic point of view. Based on the statistics analysis, and by the use of the elastic contact theory and the plastic contact theory, the relationship between the pressure and the depth of indentation is obtained. Moreover, the calculation equation for the linear removal intensity, which is the material removal depth per unit contact length along the polishing path, is presented. Finally, by integrating the linear removal intensity, the micro-model of the material removal depth for the polishing process is developed. Analyzed from the perspective of the abrasive grains, the model takes the grit designation and the structural number as the two basic variables for abrasive grains characteristics, and it is assumed that the shape of an abrasive grain is conic with spherical tip and the distribution of its protrusion heights is taken to be Gaussian distribution, which fully takes into account the impact of the abrasive grains characteristics on the depth of removal. In the model, different stages of the polishing process are decomposed in detail, and the reality that the plastic deformation is accompanied by the presence of elastic deformation is taken into consideration, which makes the model more realistic. Experimental results are compared with the prediction results to verify the theoretical model. The model can be used as the theoretical foundation for the selection of abrasive grains and the process parameters. [ABSTRACT FROM AUTHOR]