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Machine vision is a desirable non-contact measurement method for hot forgings, as image segmentation has been a challenging issue in performance and robustness resulting from the diversity of working conditions for hot forgings. Thus, this paper proposes an efficient and robust active contour model and corresponding image segmentation approach for forging images, by which verification experiments are conducted to prove the performance of the segmentation method by measuring geometric parameters for forging parts. Specifically, three types of continuity parameters are defined based on the geometric continuity of equivalent grayscale surfaces for forging images; hence, a new image force and external energy functional are proposed to form a new active contour model, Geometric Continuity Snakes (GC Snakes), which is more percipient to the grayscale distribution characteristics of forging images to improve the convergence for active contour robustly; additionally, a generating strategy for initial control points for GC Snakes is proposed to compose an efficient and robust image segmentation approach. The experimental results show that the proposed GC Snakes has better segmentation performance compared with existing active contour models for forging images of different temperatures and sizes, which provides better performance and efficiency in geometric parameter measurement for hot forgings. The maximum positioning and dimension errors by GC Snakes are 0.5525 mm and 0.3868 mm, respectively, compared with errors of 0.7873 mm and 0.6868 mm by the Snakes model.

A computational scheme is presented in this paper to simulate dynamical behavior of multiple degrees of freedom (MDOF) systems with multiple bilinear springs. In the proposed scheme, a bilinear spring is modeled using by two parallel springs - a primary spring and a secondary spring. The primary spring is an ordinary linear spring having identical stiffness in tension and compression, and is active for tension and compression. The secondary spring, whose stiffness characterizes the bilinearity, is active only during compression. It is employed in connection with the Newmark integration method and the linear complementarity problem (LCP) formulation to obtain time-domain responses of dynamical systems with bilinear springs due to initial disturbances and harmonic excitations. The scheme described in this paper is effective in dealing with the sudden transition from tension to compression and vice versa simultaneously for all bilinear springs. Numerical results for bilinear oscillators with finite bilinearity ratios and impact oscillators with an infinite bilinearity ratio show that the proposed bilinear spring model is accurate, generic and valid for bilinearity ratios ranging from zero to infinity. Orderly and chaotic behavior of viscously damped 3-DOF system under harmonic excitation is studied for a wide range of excitation frequencies and bilinear ratios to demonstrate the effectiveness and applicability of the proposed model for MDOF bilinear systems.

This paper presents the new synthesis models of spatial linkages for designing measurement motion functions and ranges and identifying the actual dimension parameters. The spatial five-bar linkage is first introduced for the kinematic model of a double ball bar test of a two-axis rotary table. To design the ideal measurement motion and motion range of the double ball bar test, a novel saddle synthesis model of a spatial four-bar linkage RRSS is readily presented. Based on the output data measured from the double ball bar test, a new saddle synthesis model of a spatial five-bar linkage RRSPS is logically proposed for identifying their actual dimensions. Finally, three test cases and their results indicate that the new synthesis models presented in the paper can conveniently and efficiently calculate the measurement motion function and range and accurately identify the actual dimensions of the double ball bar test, which provides a suitable mathematical model for improving the accuracy of the double ball bar tests of a two-axis rotary table of machine tools.

In this paper, resource flow variables are extracted from the internal structural features of the logistics distribution process and a new method for optimizing the internal structure of the logistics distribution system by using the characteristic state space is proposed. The characteristic state equation is constructed to represent the input and output resources of each basic logistics activity. The basic logistics activity equation is iterated according to the resource flow, and the implementation of the basic logistics process is visually and quantitatively expressed in the form of the characteristic state matrix. According to the nature of the characteristic state space, the optimization problem of the logistics distribution system is transformed into a critical path-planning problem, the gradient calculation of the objective function is solved, and an improved genetic algorithm is proposed. This accelerates the convergence speed of the algorithm and reduces the running time of the optimization process. Taking a listed logistics distribution enterprise as an example, the optimization algorithm is verified, which proves the advantages of the algorithm and provides a new method and theoretical basis for the analysis and optimization of the logistics distribution system.

Machine vision measurement is an ideal method for real-time non-contact measurement of hot forgings, where image segmentation is the most important issue in extracting contours and effective areas. However, existing image segmentation methods have limitations of poor performance or complex algorithms with high computational costs, thus are not suitable for real-time processing of hot forging images in industrial processing. This paper proposes an efficient and robust passive visual image segmentation approach by extracting edges of forging images based on discrete grayscale surface continuity, by which experiments on forging positioning and dimension measurement are conducted to prove the performance and feasibility of the image segmentation approach. In this paper, three types of edges by the geometric continuity of the equivalent grayscale surface for forging images are proposed, so that segmentation can be realized by extracting feature edges directly, or combined with the Snakes model. Continuity edges directly related to the geometric characteristics of grayscale surface for forging images, the extracted primary and secondary edges, subsequently the edge-based segmentation approach, can be identified as suitable and stable for forgings with different thermal radiations and dimensions. The experimental results show that the proposed image segmentation approach based on continuity edges works well for segmenting forging images of different temperatures and dimensions, which provides good results in real-time dimension and positioning measurement experiments for hot forging.

In this paper, a novel impact load model for a tool-changer mechanism of spindle system in machine tool is proposed to determine the impact load of tool-changer during unclamping tool. The tool-changer mechanism is composed of cam (frame), shift fork, headstock, and spindle system with cutter bar. In order to build the model, the working principles of the tool-changer and the spindle system structure are briefly introduced, and the load transmitting path of spindle system is analyzed. By combining the kinetostatic behavior and energy conservation law, the computational model to calculate the impact load of tool-changer mechanism is established to obtain the theoretical result. Moreover, a transmitting model of the impact load is set up to collect the experiment result in the light of bolted connection equivalent model, which is in agreement with the impact load transmitting path. With the computational model, the theoretical result of impact load can be determined based on the motion of shift fork and cutter bar system constrained by both headstock movement and cam contour curve. Using the transmitting model, the experimental result of impact load can be calculated by measuring check ring strain. From the comparison of the theoretical and experimental results, it is found that the experimental measurement agrees well with theoretical analysis. This means that the built model is valid, which can be used to predict the impact load during the unclamping tool process. This work aims to provide some fundamental analysis for both the design of the spindle system and the selection of the spindle bearings of high-performance machine tools.

With a pioneering methodology, the book covers the fundamental aspects of kinematic analysis and synthesis of linkage, and provides a theoretical foundation for engineers and researchers in mechanisms design. The first book to propose a complete curvature theory for planar, spherical and spatial motion Treatment of the synthesis of linkages with a novel approach Well-structured format with chapters introducing clearly distinguishable concepts following in a logical sequence dealing with planar, spherical and spatial motion Presents a pioneering methodology by a recognized expert in the field and brought up to date with the latest research and findings Fundamental theory and application examples are supplied fully illustrated throughout.

The temperature difference method is used for the assembly and disassembly of cylindrical interference fit in aircraft engines, which is prone to causing scratches on the contact surfaces. To improve maintainability, this study optimized the design of a conical interference fit with an oil groove, which not only maintains torque transmission capability comparable to that of the prototype but also achieves non-destructive assembly and disassembly. The similarity criteria for the torque transmission capacity of interference fit and the design requirements for taper were derived, forming a design methodology for the conical interference fit. By reducing the distortion of the similarity criterion, an optimized conical interference fit with an oil groove and a taper of 1:15 was designed for aircraft engines. Based on finite element analysis, the torque transmission capability prediction coefficient between the optimized structure and the prototype was 0.972, demonstrating that the optimized structure can effectively represent the torque transmission capability of the prototype. Hydraulic assembly and disassembly, as well as torque transmission tests, were conducted on conical interference fit specimens with oil grooves. The theoretical and test results of torque transmission capability were compared, and the mating surfaces were analyzed for scratches after torsional loading and disassembly, thereby verifying the validity of the non-destructive assembly and disassembly interference fit design. The design method has engineering applicability and offers a reference for the structural optimization and analysis of interference fit.

A Multi-degree-of-freedom (M-DOF) nonlinear dynamic model for n -pinion Planetary gear train (PGT) is presented in this paper to investigate load sharing behavior of planet gears. In this dynamic model, manufacturing and assembly errors, elastic deformation and time-varying mesh stiffness are considered. Two sets of elastic compatibility equations are proposed to describe compatibility relationship between displacements, errors and elastic deformations. By means of Ishikawa formula, time-varying mesh stiffness of the gear pair is determined. The dynamic motion equations are solved with Runge-Kutta numerical integral method, which yields the displacements and deformations of each component. With the model, dynamic load sharing behavior of planet gears is evaluated. An example of 3-pinion PGT dynamic modeling is included, for which the influence of floating sun gear and adding flexible planet pin on the load sharing characteristics is analyzed.

In aero-engine, interference fit is employed as the assembly method between the gear bushing and the front journal, where the magnitude and distribution of the contact pressure on the mating surface are critical factors influencing the fatigue failure of the interference fit. Current methods predominantly adopt stress relief groove and chamfer to optimize the contact pressure distribution. However, the associated design parameters lack a solid theoretical foundation and require multiple finite element simulations, which considerably reduces computational efficiency. Therefore, this paper proposes an interference fit profile modification method based on super-element. Based on the equilibrium equations and constitutive equations of the interference fit mating surface, the modifying generatrix of the mating surface is efficiently designed through forward optimization to mitigate edge effect and improve the contact state. Subsequently, the interference fit of a real aero-engine was taken as a case study for profile modification design. Finite element results demonstrated that, after profile modification, the contact pressures at both edges of the mating surface were reduced by 83.6% and 87.3%, respectively. The effective contact length increased by 247.8%, thereby significantly improving the contact state. Finally, ultrasonic testing was conducted to measure the contact pressure distribution of interference fit components without profile modification and with profile modification, and the experimental results verified the effectiveness of the profile modification method. The profile modification method proposed in this study effectively improves the contact interface performance of interference fit and provides a theoretical basis for its structural design.