The manufacturing of complex parts can be easily achieved by additive manufacturing (AM), which has attracted a significant attention from both academia and industry. Regardless of the shape of the ...model, the 3-axis AM techniques slice the model into a series of sections along the Z-axis and then use a fixed direction filling algorithm to plan the interiors of the sections. This approach greatly simplifies the planning of manufacturing processes. However, this directional construction method can lead to a series of problems, such as staircase effect, supporting effect, anisotropic mechanical property, and sizing limitation. In order to address these issues, both academia and industry have investigated multi-axis AM technology. Multi-axis AM dynamically constructs parts through redundant degrees of freedom, thus overcoming the problems of 3-axis AM process. This paper analyses the limitations of 3-axis AM process, summarizes the potential of multi-axis AM technology and describes methods for implementing multi-axis AM. The paper concludes with a discussion of the new opportunities and current challenges of multi-axis AM technology.
A revised version of Table 2 of Nanao et al. J. Synchrotron Rad. (2022). 29, 581–590 is provided.
Corrections to Table 2 of Nanao et al. J. Synchrotron Rad. (2022). 29, 581–590 are reported.
The maintenance works (e.g. inspection, repair) of aero-engines while still attached on the airframes requires a desirable approach since this can significantly shorten both the time and cost of such ...interventions as the aerospace industry commonly operates based on the generic concept “power by the hour”. However, navigating and performing a multi-axis movement of an end-effector in a very constrained environment such as gas turbine engines is a challenging task. This paper reports on the development of a highly flexible slender (i.e. low diameter-to-length ratios) continuum robot of 25 degrees of freedom capable to uncoil from a drum to provide the feeding motion needed to navigate into crammed environments and then perform, with its last 6 DoF, complex trajectories with a camera equipped machining end-effector for allowing in-situ interventions at a low-pressure compressor of a gas turbine engine. This continuum robot is a compact system and presents a set of innovative mechatronics solutions such as: (i) twin commanding cables to minimise the number of actuators; (ii) twin compliant joints to enable large bending angles (±90°) arranged on a tapered structure (start from 40mm to 13mm at its end); (iii) feeding motion provided by a rotating drum for coiling/uncoiling the continuum robot; (iv) machining end-effector equipped with vision system. To be able to achieve the in-situ maintenance tasks, a set of innovative control algorithms to enable the navigation and end-effector path generation have been developed and implemented. Finally, the continuum robot has been tested both for navigation and movement of the end-effector against a specified target within a gas turbine engine mock-up proving that: (i) max. deviations in navigation from the desired path (1000mm length with bends between 45° and 90°) are ±10mm; (ii) max. errors in positioning the end-effector against a target situated at the end of navigation path is 1mm. Thus, this paper presents a compact continuum robot that could be considered as a step forward in providing aero-engine manufacturers with a solution to perform complex tasks in an invasive manner.
•A novel slender continuum robot is introduced for in-situ repair/inspection of jet engines.•A new kinematic model is introduced for the new tapered design.•Modes of control for the continuum robot were developed, including tip-following, feeding-in/out, Machining commands.•Navigation and inspection/machining tests in engine model were introduced.
In this study, we focus on topology optimization considering the accessibility constraint, which is a constraint that removes inaccessible regions from multiple linear directions. To detect ...inaccessible regions, we propose a method using a fictitious anisotropic diffusion equation. The proposed equation can simultaneously consider access from a bi-direction, which means one access direction and its 180-degree rotated direction, contributing to computational efficiency improvements. Additionally, we formulate a representative optimization problem with the accessibility constraint from multiple bi-directions and perform sensitivity analysis based on a coupled fictitious physics model. The model can resolve the difficulty in converging to a single optimal shape in the previous formulation method. Furthermore, through various numerical examples, we verify whether the numerical result converges to the optimal structure satisfying the accessibility constraint.
The current global energy crisis necessitates a shift to renewable energy sources to mitigate climate change impacts. Wave energy emerges as a promising renewable resource to fulfill increasing ...energy demands. This energy can be extracted using wave energy converters (WECs), with multi-axis WECs (MA-WECs) being more effective than single-axis versions due to their capacity to harness energy from waves in various directions. The challenge lies in determining the ideal geometric design for MA-WECs, that can be tackled through multi-objective optimization (MOO) techniques. This research focuses on evaluating different MOO algorithms for the optimal geometric design of MA-WECs. To assess the structural response of different geometries and sizes, the study utilized the NEMOH boundary element method solver, aiming to maximize power output, lower the levelized cost of energy (LCOE), and optimize the geometry configuration. Findings indicate that the choice of optimization algorithm considerably influences the MA-WEC's optimal design, enhancing power efficiency, reducing device volume, and cutting costs more effectively than the initial design.
•Performance evaluation of multi-objective evolutionary algorithms for WEC geometry.•Enhanced design solutions for multi-axis WECs using evolutionary algorithms.•Multiple geometries for multi-axis WECs are presented to find optimal geometry.•Optimal geometries found while minimizing the LCOE simultaneously.
This paper presents a multi-axis low-cost soft magnetic tactile sensor with a high force range for force feedback in robotic surgical systems. The proposed sensor is designed to fully decouple the ...output response for normal, shear and angular forces. The proposed sensor is fabricated using rapid prototyping techniques and utilizes Neodymium magnets embedded in an elastomer over Hall sensors such that their displacement produces a voltage change that can be used to calculate the applied force. The initial spacing between the magnets and the Hall sensors is optimized to achieve a large displacement range using finite element method (FEM) simulations. The experimental characterization of the proposed sensor is performed for applied force in normal, shear and 45° angular direction. The force sensitivity of the proposed sensor in normal, shear and angular directions is 16 mV/N, 30 mV/N and 81 mV/N, respectively, with minimum mechanical crosstalk. The force range for the normal, shear and angular direction is obtained as 0-20 N, 0-3.5 N and 0-1.5 N, respectively. The proposed sensor shows a perfectly linear behavior and a low hysteresis error of 8.3%, making it suitable for tactile sensing and biomedical applications. The effect of the material properties of the elastomer on force ranges and sensitivity values of the proposed sensor is also discussed.
The lateral wind load applied to high-rise buildings results in movements that can cause creaking noises in drywall partitions with suspended ceiling systems. These noises can be disruptive to the ...residents and impair the structure’s serviceability. In this study, a sequence of large-scale three-dimensional (3D) experiments was conducted on two assemblies of drywall partitions with a suspended ceiling system to address this serviceability issue. The goal was to explore the 3D response of these assemblies, with a key emphasis on validating the effectiveness of adhesives in mitigating noise introduced by screw fixings, not only for individual walls but also when interacting with neighbouring walls and ceilings, which represent the real-world conditions. The six-degree of freedom (6-DOF) Multi-Axis Substructure Testing (MAST) system at Swinburne University Technology was used to simulate realistic wind load conditions. Two sets of test specimens were constructed using different methods to fix the plasterboard wall lining to the cold-formed steel (CFS) frame, which was rigidly bolted to both the MAST crosshead and the floor below. The first set of specimens (Assembly 1) had the plasterboards screw-fixed to the steel frame, while the second set (Assembly 2) used adhesive-only or a combination of adhesive and screw-fixing methods. Additionally, the instrumentation employed for acoustic measurements was strategically chosen to capture the noise generated by the overall system-level response. This served as a means of validating the serviceability noise experienced by users/occupants. Sound pressure level measurements and an acoustic camera were used simultaneously to identify the noise sources. The creaking noise measurements were compared for different specimens of Assemblies 1 and 2 and the effects of different construction details (e.g. fixing method, plasterboard ceiling lining, etc.) on wind-induced creaking noises were discussed. The results of this study can provide valuable insights for manufacturers and designers to minimize creaking noises in drywall partition systems and propose new construction techniques to improve the serviceability of high-rise buildings.
•Wind-induced creaking noises in drywall partitions were assessed.•Multi-axis substructure testing (MAST) system was used for 3d full-scale experiments.•Two different methods of screw vs adhesive fixing plasterboards to steel frames were evaluated.•Adhesive fixing significantly reduced wind-induced creaking noises.
Small‐radius curved bridges are mostly used for overpass ramps, that are spatially irregular and usually have very complex seismic behavior. It is not easy to reproduce such behavior because of the ...need for large‐scale shaking tables. The hybrid test is one of the most effective approaches for solving this problem by considering the structural elements of interest as physically tested substructure while the rest is numerically simulated. In this paper, a hybrid test system was first developed based on the OpenFresco framework, where one of the piers was considered as the tested substructure, and the rest was simulated by OpenSees. A novel spatial loading device (SLD), configured as the Stewart pattern, was then developed to achieve the boundary conditions between substructures. The control schemes to perform the force‐displacement mixed control, conduct the geometric transformation while considering the load point offset, and achieve an external displacement control were proposed and validated through several rounds of hybrid testing. The experimental results indicate that the experimental system including loading control subsystem and hybrid control subsystem can realize the loading command accurately.
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