With the rapid development of aerospace, energy, and power technologies, the demand for high-performance parts with complex curved surface is increasingly large, and the multi-axis ...Computer-Numerical-Control (CNC) precision machining technique for such parts becomes a popular and difficult issue in the industrial field. In order to ensure the high-performance of complex curved surface parts, the requirement of the contour accuracy is higher and higher for such parts due to the important role they play in these fields. However, the limitation of dynamic properties for the CNC machine tools, which leads to the contouring-error, becomes a vital issue that affects the machining accuracy of the high-performance parts with complex curved surface. The contouring-error, defined as the orthotropic distance from the actual motion position of machine tool to the desired contour of curved surface in multi-axis contour-following tasks, is caused by the facts such as servo lag, dynamics mismatch, external disturbances, and so forth. The reduction of the contouring-error becomes of great significance for promoting the performance of CNC motion systems thus realizing the high-speed and high-precision machining, and the research on the contouring-error reduction in multi-axis CNC machining is therefore a hotspot issue in the machining engineering. This paper provides a comprehensive review to the state of the art of the contouring-error reduction methods. The massive and complicated studies on constraining the contouring-errors are classified and summarized, and accordingly, the advantages and the disadvantages of different kinds of methods are discussed and compared, which has a guiding significance for selection of the interested contouring-error reduction method. Furthermore, this paper systematically suggests the probable future studies that remain vacant and meaningful based on the discussion of the state of the art. Significantly, it is possible for active promoting and developing to further improve the contouring-error reduction of the complex curved surface parts in multi-axis CNC machining.
•Methods that can be used for contouring-error reduction are reviewed.•Characteristics and range of applications for reviewed methods are analyzed.•Advantages and disadvantages of contouring-error reduction method are compared.•Future development tendency for contouring-error reduction is suggested.•Review is beneficial to improve contour accuracy of multi-axis surface machining.
This paper presents a design of multi-axis tactile force sensor using the fringe effect of an electric field between stationary patterned electrodes. The unique configuration of the electrodes ...consisting of four separate square-shaped sensing electrodes, with each encircled by excitation electrodes, allows to achieve enhanced fringe field effect and hence sensitivity. The proposed sensor can decouple the normal, shear and angular shear applied forces. The sensor is fabricated using low-cost rapid prototyping techniques with flexible Ecoflex 00–30 and silicone rubber RTV-528 as the elastomers for contact with the environment. An analytical model is developed that correlates the nominal capacitance of the sensor with that of the geometric dimensions of the stationary electrodes and air cavity height between the electrodes and elastomer. The force measurement ranges in the normal, shear, and angular axis are 5 N, 1.5 N, and 1 N respectively. The sensor shows a perfectly linear response, repeatability, and a low hysteresis error, thermal stability and robustness to the environmental interferences that makes it suitable to be used for force feedback in minimally invasive robotic surgery.
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•The fringing field effect based tactile force sensor is presented.•High sensitivity is achieved by optimizing electrodes geometric configuration.•The sensor can decouple normal, shear and angular shear forces.•The sensor is fabricated using rapid prototyping techniques for low cost.•The sensor is designed for application in robotic surgical systems.
This paper presents a topology optimization approach that incorporates restrictions of multi-axis machining processes. A filter is defined in a density-based topology optimization setting, that ...transforms an input design field into a geometry that can be manufactured through machining. The formulation is developed for 5-axis processes, but also covers other multi-axis milling configurations, e.g. 2.5D milling and 4-axis machining by including the appropriate machining directions. In addition to various tool orientations, also user-specified tool length and tool shape constraints can be incorporated in the filter. The approach is demonstrated on mechanical and thermal 2D and 3D numerical example problems. The proposed machining filter allows designers to systematically explore a considerably larger range of machinable freeform designs through topology optimization than previously possible.
•Enforce multi-axis machining restrictions within a topology optimization process.•Capable of considering a large set of tool orientations.•Particular cutting tool shapes and maximum insertion lengths can be included.•Adds little computational effort compared to part performance analysis.•Application example shows capability to generate optimized, machinable 3D parts.
Abstract Improving the measurement accuracy and minimising the coupling between directions are the keys to researching the compliant six-axis force sensors. The use of a six-axis force sensor to ...accurately monitor the ground reaction force and centre of pressure during human motion is of great significance in the fields of biomechanics and pathological gait diagnosis. Although complete force information can be obtained using a commercial six-axis force sensor, its high stiffness affects the natural gait and easily leads to human fatigue. A compliant six-axis force sensor based on a flexible optical waveguide is proposed, in which the force and torque of six dimensions are detected by reasonably arranging six modular sensing units, and the mechanical decoupling of some dimensions is realised in theory. For the interdimensional coupling and error caused by machining process factors, as well as the nonlinear relationship between the input and output of the proposed compliant six-axis force sensor, a DE-RBF decoupling algorithm is proposed to decouple the calibration data. Compared with the least squares method (LSM) and the radial basis function (RBF) neural network decoupling algorithm, the obtained type-I errors were reduced by 87.7629%, 43.6265%, respectively, and type-II errors by 35.3312%, 56.9162%, respectively. The decoupling result’s maximum type-I and type-II errors were reduced from 7.7125% and 2.7382% in LSM and 3.1029% and 2.8917% in RBF to 0.5916% and 0.9558%, respectively. The measurement accuracy of the compliant six-axis force sensor was significantly higher; however, the time effectiveness of the proposed DE-RBF decoupling algorithm was slightly lower than that of the RBF neural network by 2.47%. In conclusion, the decoupling accuracy and timeliness of the proposed DE-RBF decoupling algorithm can satisfy the requirements of compliant six-axis force sensors to monitor low-frequency biomechanical signals, such as human motion.
Random vibration testing is traditionally performed by means of single-axis testing. However, real operational environment are in general characterized by multi-axis vibration. As a consequence, ...single-axis testing is incapable of reproducing the actual damaging process of a component in the laboratory. In this work the damage inflicted to a cantilever beam by multi-axis and sequential single-axis random excitation is compared. A fatigue testing campaign is carried out to establish the fatigue properties of the specimen under different types of vibration environment. The results of the fatigue testing campaign are used to define a relationship between the damage inflicted by multi-axis and sequential single-axis excitations. In particular, a correction factor is defined that allows to calculate the fatigue damage under multi-axis vibration environment knowing the damage inflicted by single-axis excitations. The correction factor takes into account the different activation of the vibrating modes of the specimen caused by different types of excitations. The correction factor for multi-axis vibration environments may allow to estimate the damage caused by multi-axis vibration with the use of a single-axis shaker, as well as allowing to calculate the required testing time for a multi-axis test starting from single-axis testing procedures, improving laboratory testing in terms of costs and realism.
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.
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A multi-axis force sensor measures forces and moments occurring in more than one spatial direction. In this way, a single multi-axis sensor can perform what is essentially a ...three-dimensional measurement of physical quantities. This feature makes multi-axis sensors popular in a wide range of engineering research including automation, machining processes, aerospace, medical applications and civil engineering. Measurement of multi-directional forces and moments is typically achieved using multiple strain-sensitive elements mounted on an elastic structure. Both the sensitive elements and the elastic structure require careful consideration to design a force sensor for accuracy, reliability and robustness. While the development of multi-axis sensors has been considered extensively in the literature over the past seven decades, a collective resource which collates and examines this information does not exist. This review explores multi-axis force sensor developments across a broad range of disciplines. The salient fundamental sensing techniques adopted for the strain-sensitive elements reported in the literature are discussed and a critical review of elastic structure designs that have featured in the literature is also presented.
•The review focuses on the FDM of discontinuous fiber/polymer composites (FRPC).•The entire FDM-FRPC system (i.e. materials, mechanism and process) is summarized.•As an indispensable technique for ...FDM, hot-melt extrusion process is discussed.•Large-scale FDM and multi-axis FDM are included as the latest advance.•The main challenges and outlook for the future development of FDM is identified.
Fused deposition modeling (FDM) is one of the most widely utilized additive manufacturing techniques by virtue of its numerous merits, such as easy operation, low cost, low energy consumption and little-to-no waste. Based on its simple configuration and extrusion-assisted process, the research and development of this technique is gradually shifting from traditional prototype printing to high-performance composite fabrication. This review provides a panorama for the recent progress of FDM technology in the manufacturing of discontinuous fiber reinforced thermoplastic composites. The entire production chain from the very beginning of FDM filament preparation to the latest stage in large-scale manufacturing process is discussed. The enlightening strategy in multi-axis FDM field is highlighted as it possesses a great potential to manufacture the next-generation composites with superior geometric complexity and flexible fiber alignment. This review also identifies the main challenges and outlook for the future development of this 3D printing technology in fiber reinforced composites.
Density functional calculations with a plane-wave basis set are widely used in materials science. Due to recent developments in high-performance computers, the number of nodes equipped in such ...computers greatly exceeds the number of atoms included in a typical simulation. Thus, it is becoming difficult to perform calculations efficiently even when only a portion of all nodes are used (e.g., 10%). We have developed a multi-axis decomposition scheme in which both G-vectors and band axes are decomposed and 3D-FFT communicators are folded compactly. This proposed scheme retains the inner-most do-loop lengths sufficiently long and restrains the increased MPI communication costs as the number of nodes increases. In an investigation of a wide-gap semiconductor material (SiC), our PHASE/0 DFT code exhibits efficient and strong scaling (up to 82,944 nodes) even for a relatively small system with 3848 atoms, and demonstrates maximum peak performance of 2.25 PFLOPS for a 25,200-atom system despite employing 3D-FFT.
Three-dimensional finite element (FE) models of a non-pneumatic wheel (NPW) with three different honeycomb cell angles are developed and verified to investigate their multi-axis stiffness and road ...contact characteristics. The experiment designs based on L8(27) and L9(34) orthogonal arrays are subsequently formulated to identify influential design factors affecting the wheel response measures and their nonlinear effects. The multi-axis stiffness of the NPW are strongly influenced by the spokes design parameters, although the yaw stiffness is mostly affected by the tread parameters. The road contact properties, however, are dominantly affected by the annular beam and tread design parameters. The results from these experiment designs are effectively used to establish guidance for design tuning of the NPW for realizing desirable stiffness and road contact properties. A L16(215) orthogonal array experiment is further formulated to study the interactions among the influential design factors in view of the multi-axis stiffness and road contact responses of the wheel. The results showed negligible contributions due to interactions among the design factors. It is shown that the NPW design parameters can be tuned to achieve multi-axis stiffness properties comparable to those of the pneumatic tires.
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