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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]

Thin-walled square tube with longitudinal rib (TWSTILR) is a key structural component widely used in aerospace field. However, there are still critical problems in the preparation of large-scale TWSTILR component due to their complex shapes and structures. Components prepared by traditional low-efficiency, high-cost separate manufacturing, and cutting forming processes are difficult to meet service requirement. Therefore, this article proposes to break through the technical bottleneck of the integral forming of such TWSTILR components by preformed rib method and multi-pass rolling-extrusion process. This article mainly elaborated the design method of preformed rib and the principle of multi-pass rolling-extrusion. And the metal flow deformation behavior and equivalent strain distribution of typical region of TWSTILR workpiece during multi-pass rolling-extrusion process were revealed by finite element simulation. In addition, the effects of different process parameters on TWSTILR forming were discussed. Finally, the physical forming experiment was designed and implemented, which fully verified the feasibility of the forming process for preparing TWSTILR component. [ABSTRACT FROM AUTHOR]

Triaxial braided composites employed as structural components need to be drilled for mechanical connections. This study is to investigate the thrust force, temperature elevation, and drilling-induced damages with varying machining parameters in the drilling of triaxial braided CFRP. A high-resolution infrared thermography was carried out to capture the temperature of the panel side surface and the drill-exit surface of CFRP. The damage characteristic of drilled hole was evaluated, and a relationship between force, temperature, and hole damage was established. The obtained results indicate that the temperature of triaxial braided CFRP was mainly transferred along the fiber direction. The temperature isothermal at the drill-exit surface developed from polygonal to roughly circular with the increase of drilling depth. The braided yarns tended to deflect, and induced poorly cut fibers due to the more heat generation with the low feed, making the matrix behaved from brittle to ductile and therefore resulting in more burrs. The increase of spindle speed could restrain the burrs. A larger thrust force with high feed will result in fiber-resin debonding and more tearing defects. The delamination occurred at the interface of fiber bundles at the outermost layer with high thrust force and cracks propagated along the yarn direction. [ABSTRACT FROM AUTHOR]

Compared with traditional structures, lattice structures show more excellent mechanical properties, e.g., higher rigidity and lighter weight. The additive manufacturing (AM) technology enables complex lattice structure to be realized. The path planning problem of AM for lattice structures faces new challenges that have been barely explored before now, because the lattice structures have unique characteristics of complex geometrical features and high-precision processing requirements. Despite many efforts toward path generation, the printing efficiency problem of the lattice structures is more than one single printing path can resolve. Using machine learning method based on a support vector machine (SVM) system, the goal of this paper is to automatically determine a suitable filling path for each sub-domain of the slicing layer of the lattice structures. Moreover, a route is found to traverse every scattered sub-domain by solving a traveling salesman problem (TSP). We demonstrate various testing examples and the experimental results to show the superiority and effectiveness of our method in terms of classification accuracy, filling effects, and linking path length. [ABSTRACT FROM AUTHOR]

The increasing substitution of metallic structural components by carbon fibre reinforced polymers (CFRP) in aerospace applications results in a growing need for drilling metal and CFRP in one operation, the so-called stack machining. The different material properties of the stack components in combination with high geometrical tolerance requirements result in large challenges for the drilling tool and the process strategy. Focussing on the process strategy, this paper deals with an extensive comparison of conventional and low-frequency vibration-assisted drilling (LF-VAD) of CFRP/aluminium stacks. The influence of the cutting speed, the feed rate and the amplitude of the superimposed oscillation in LF-VAD on the resulting bore quality is analysed. For the bore quality, three separate aspects are considered, namely, damages at the CFRP entrance, burr formation at the aluminium exit and deviations from the nominal diameter in both materials. Online temperature and force measurements enable interpretation of the influence on the bore quality. Based on experimental data, a clear dependency of the bore quality and the chip transport on both, the process parameters and the drilling strategy are identified. Based on high-speed recordings, the dynamic loading situation due to the superimposed oscillation in LF-VAD is found to be crucial for the formation of peel-up delaminations. [ABSTRACT FROM AUTHOR]

This paper provides a novel integrated approach for designing customized milling machines. Static stiffness matching design of milling machine is carried out according to the static stiffness requirement at TCP. Rapid evaluation approach of milling stability of milling machine with position-dependent has been developed. The theoretical model which can describe the relationships between and among milling stability, dynamic stiffness, and natural frequency has been established. Dynamic characteristics' simulation of milling machine has been carried out based on CAD/CAE co-simulation analysis platform. The structural component mass can be changed by changing the critical dimension, and then, the rule of structural component mass influence on the natural frequency of the milling machine can be obtained by optimal Latin hypercube experimental design method. The lightweight design of milling machine has been achieved according to the rule. The approach improves the rapidity, parameterization, and digitization of customized milling machine design. [ABSTRACT FROM AUTHOR]

Machining of aircraft structural components can waste up to 90% of the raw material. Therefore, evaluation of alternative manufacturing processes for those components is crucial for reducing the economic and environmental impacts of manufacturing. As the shape and material of a component must match the manufacturing process used, it is necessary to perform a redesign for manufacturing in order to compare manufacturing processes accurately. In this paper, an integrated material-design-process selection methodology is developed. Topology optimization, design for manufacturing (DFM) and design for additive manufacturing (DFAM) are used to design components satisfying the same functional requirements but shaped using different manufacturing processes. New selection criteria such as part weight and buy-to-fly ratio are used to rank material-design-process triplets with the analytic hierarchy process (AHP). The proposed methodology is applied to redesign an aircraft component for machined Al7075-T6 and the same component for selectively melted AlSi10Mg powders. Even though the yield strength of Al7075-T6 is 40% greater than that of AlSi10Mg, optimized components for machining and selective laser melting meet the yield strength security factor while remaining competitive in terms of mass. Although the selective laser melted component is about seven times more expensive to produce than the machined one, it remains competitive considering functional and economic criteria. [ABSTRACT FROM AUTHOR]

In electrochemical machining of aero structural components, the allowance distribution between the blank and the model is generally not uniform, which may influence the final precision of components. However, proper leveling can reduce the negative impacts of this nonuniformity and enhance machining accuracy. This paper proposes a mathematical model for pulse electrochemical machining (ECM) to simulate the corrosion process in order to improve the leveling. Several machining parameters, such as power voltage, pulse duty, and frequency, are considered to optimize the leveling ratio. The optimal parameters are obtained from the simulation. The simulation results show that the leveling ratio improves with the decrease of pulse duty and voltage and the increase of frequency. Furthermore, the pulse duty has a more significant effect on the leveling ability than the voltage and the frequency. In addition, verified experiments are carried out and the results are consistent with the simulation. It indicates that the proposed model is effective and can be used for complex structural components in ECM. [ABSTRACT FROM AUTHOR]

To improve efficiency and cost performance of cast iron machine tool component fabrication, an alternative process must be developed in order to replace the grinding process, which often causes a bottleneck in production. As an alternative manufacturing approach, this research applies cubic boron nitride (CBN) hard milling operations to eliminate the grinding process in order to improve the overall manufacturing process. A variety of hardened cast iron materials with Al and Mg additives and CBN tool types were prepared and tested based on a design of experimentation (DOE) to observe their effect on surface quality and tool life. Al and Mg were added to raw cast iron to achieve generation of oxide layers at the cutting edge during milling to protect the tool from wear. By executing the DOE, the optimal cutting conditions for achieving the best surface quality were introduced. Also, additional machinability tests were conducted with the optimal conditions in order to evaluate tool wear characteristics and surface quality of the machined workpieces. Based on the observation of the used tool by electron probe micro-analyzer (EPMA), a protective oxide layer of additives was observed at the cutting edge. Hardened cast iron with Al and Mg additives is found to show preferable wear and surface quality characteristics. [ABSTRACT FROM AUTHOR]

The current paper describes an apparatus for full-scale vehicle crash test experimentation. This apparatus is referred to as the harp. In brief, the harp may either accelerate a trolley which is impacted into a test vehicle or the test vehicle itself may be accelerated and impacted into an object such as a barrier, a pole, or another vehicle. If a trolley is accelerated, it is equipped with load cells to record the axial crushing force. If a test vehicle is accelerated, it is equipped with a three-axis accelerometer to record the crushing force. At the impact site, high-speed cameras and instrumentation record vital data during the crash. [ABSTRACT FROM AUTHOR]

The positioning accuracy of computer numerical control (CNC) machine tools is mainly limited by the manufacturing accuracy of their linear and circular motion axes and by the long-term dimensional stability of their structures. Maximizing this accuracy can prove to be a particularly challenging task, especially for large-sized systems. In fact, heat-induced deformations, long-period deformation of foundations and the manufacturing process itself, these all cause time-dependent structural deformations of the machine body, which are difficult to model and to predict. The usual approach is a model-based prediction of structural deformations, which is followed by a compensation of positioning errors at CNC level. This approach is often limited by the complexity of the problem from both geometrical (system geometry can be very complex and it can vary in time) and physical (it is difficult to model and consider any possible load type and loading condition) point of view. As a consequence, only limited success has been achieved in active error compensation based on the modelling of the relationship between the generalized dynamic loads and the structural deformation field. This paper illustrates a different approach in active error compensation, which exploits a new measurement system able to provide real-time measurement of the displacement field of a given structural component, without any model about its dynamic/thermal structural behavior. [ABSTRACT FROM AUTHOR]

Geometrical optimization of structural components is a topic of high interest for engineers involved with design activities mainly related to mass reduction. The study described in these pages focuses on the optimization of plates subjected to bending for which stiffness is obtained by a pattern of ribs. Although stiffening by means of ribs is a well-known and old technique, the design of ribs for maximum stiffness is often based on practice and experience. Classical optimization methods such as topological, topographical and parametric optimization fail to give an efficient design with a reasonable programming effort, especially when dealing with many and complex constraints. These constraints are both technical and technological. A most promising technique to obtain optimal rib patterns was to define a set of feasible rib trajectories and then to select the subset with the most efficient combinations. The result is not unique and a method to select the optimal patterns is required. In fact, the stiffening effect increases with increasing rib length, but at a greater cost. A trade-off must be found between structural performance and cost: The tools to guide this selection process is the main objective of the paper, with particular attention in evaluating the stiffening due to the presence of beads on the plate with a close link with the production system and possible technological constraints which can occur during manufacturing processes, such as minimum rib distance or the presence of discontinuities or the presence of holes or other elements on the plate. A special tool with enforced rib cross section is considered, and optimal rib deployment has to be found. Numerical examples attached show the methodology and obtainable results. [ABSTRACT FROM AUTHOR]