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The world cannot counter climate change without the automobile industry becoming far more environmentally sustainable than it is today. With the realization that electrified mobility will take decades, not years, and that internal combustion engines (ICE) will continue to power vehicles in the near future, we need to step up the focus on improving fuel efficiency of ICE vehicles. In this report, we have confirmed that, in timing chains for automobile engines, the sliding area can be reduced by changing the arrangement of the arms & guides from continuous contact to a segmented one and by using an aromatic polyimide (PI) that can withstand the high contact surface pressure, thereby reducing friction loss. Through bench test monitoring, we confirmed that the friction loss was reduced in comparison to that by the conventional arms & guides in ICEs. The conventional arms & guides in the layout of the timing chains are placed with a curvature of ~ R2000 mm (at least R500 mm). In this study, the layout of the arms & guides was investigated. Each arm or guide is divided into two or three segments in the direction of travel and each curvature is reduced to about R100 mm. In addition, the material has been changed from polyamide (PA66) to PI. By these changes, the contact surface is decreased, and the surface pressure is increased. This means that on the Stribeck diagram, the lubrication conditions move in the direction of the smaller Sommerfeld number and the friction loss decreases. The use of the high compressive modulus material reduces the amount of deformation of the arms & guides contact surface, leading to the reduction of the friction loss.

Marine structures are supposed to simultaneously possess high stiffness bearing high loadings and large damping dissipating dynamic energy. Structural impact protection and stiffening approach is achieved via assembling a pre-compressed negative stiffness component and linear members, which not only exhibits high initial stiffness but also dissipation capacity approaching the theoretical limit under small deformation. The effects of design parameters on the energy dissipation characteristics are investigated by the combination of quasi-static, dynamic and finite element analysis. For potential applications, the dynamic responses and vibration suppression of a representative grille structure optimized by the novel design are studied via FE simulations. [ABSTRACT FROM AUTHOR]

In this paper, a biped robot system for dynamic walking is presented. It has two 2-degree-of-freedom (DOF) lightweight legs and a 6-DOF hip. All the joint pulleys of the legs are driven by motors that are placed at the hip using steel cables. Since all the heavy motors are mounted at the hip, the biped robot has remarkably low-mass legs beyond the hip, which guarantees low inertia during walking at high speeds. Utilizing cable-amplification mechanisms, high stiffness and strength are achieved, resulting in better control performance compared to conventional direct-driven methods. Techniques are developed to estimate joint-angle errors caused by the elastic deformation of the cables. To achieve smooth control, we introduce the concept of a virtual leg, which is an imaginary leg connecting the hip joint and the ankle joint. A robust control approach based on the "virtual leg" is presented, which considers the variances of the virtual leg length during walking. Experiments are conducted to validate the effectiveness of the mechanical design and the proposed control approach. [ABSTRACT FROM AUTHOR]

In the pursuit of sustainability and reduced dependence on new plastic materials, this study explores the upcycling potential of high-density polyethylene (HDPE) milk bottles into high-stiffness, high-heat-distortion-temperature (HDT) composites. Recycled high-density polyethylene (rHDPE) sourced from used milk bottles serves as the composite matrix, while reinforcing fillers are derived from dried pineapple leaves, comprising fibers (PALF) and non-fibrous materials (NFM). A two-roll mixer is employed to prepare rHDPE/NFM and rHDPE/PALF mixtures, facilitating filler alignment in the resulting prepreg. The prepreg is subsequently stacked and pressed into composite sheets. The introduction of PALF as a reinforcing filler significantly enhances the flexural strength and modulus of the rHDPE composite. A 20 wt.% PALF content yields a remarkable 162% increase in flexural strength and a 204% increase in modulus compared to neat rHDPE. The rHDPE/NFM composite also shows improved mechanical properties, albeit to a lesser degree than fiber reinforcement. Both composites exhibit a slight reduction in impact resistance. Notably, the addition of NFM or PALF substantially elevates HDT, raising the HDT values of the composites to approximately 84 °C and 108 °C, respectively, in contrast to the 71 °C HDT of neat rHDPE. Furthermore, the overall properties of both the composites are further enhanced by improving their compatibility through maleic anhydride-modified polyethylene (MAPE) use. Impact fracture surfaces of both composites reveal higher compatibility and clear alignment of NFM and PALF fillers, underscoring the enhanced performance and environmental friendliness of composites produced from recycled plastics reinforced with pineapple leaf waste fillers. [ABSTRACT FROM AUTHOR]

Abstract In order to solve the problem of weak stiffness of the existing fully decoupled parallel mechanism, a new synthesis method of fully decoupled three translational (3T) parallel mechanisms (PMs) with closed-loop units and high stiffness is proposed based on screw theory. Firstly, a new criterion for the full decoupled of PMs is presented that the reciprocal product of the transmission wrench screw matrix and the output twist screw matrix of PMs is a diagonal matrix, and all elements on the main diagonal are nonzero constants. The forms of the transmission wrench screws are determined by the criterion. Secondly, the forms of the actuated and unactuated screws can be obtained according to their relationships with the transmission wrench screws. The basic decoupled limbs are generated by combination of the above actuated and unactuated screws. Finally, a closed-loop units construction method is investigated to apply the decoupled mechanisms in a better way on the high stiffness occasion. The closed-loop units are constructed in the basic decoupled limbs to generate a high-stiffness fully decoupled 3T PM. Kinematic and stiffness analyses show that the Jacobian matrix is a diagonal matrix, and the stiffness is obviously higher than that of the coupling mechanisms, which verifies the correctness of the proposed synthesis method. The mechanism synthesized by this method has a good application prospect in vehicle durability test platform.

In order to solve the problem of weak stiffness of the existing fully decoupled parallel mechanism, a new synthesis method of fully decoupled three translational (3T) parallel mechanisms (PMs) with closed-loop units and high stiffness is proposed based on screw theory. Firstly, a new criterion for the full decoupled of PMs is presented that the reciprocal product of the transmission wrench screw matrix and the output twist screw matrix of PMs is a diagonal matrix, and all elements on the main diagonal are nonzero constants. The forms of the transmission wrench screws are determined by the criterion. Secondly, the forms of the actuated and unactuated screws can be obtained according to their relationships with the transmission wrench screws. The basic decoupled limbs are generated by combination of the above actuated and unactuated screws. Finally, a closed-loop units construction method is investigated to apply the decoupled mechanisms in a better way on the high stiffness occasion. The closed-loop units are constructed in the basic decoupled limbs to generate a high-stiffness fully decoupled 3T PM. Kinematic and stiffness analyses show that the Jacobian matrix is a diagonal matrix, and the stiffness is obviously higher than that of the coupling mechanisms, which verifies the correctness of the proposed synthesis method. The mechanism synthesized by this method has a good application prospect in vehicle durability test platform. [ABSTRACT FROM AUTHOR]

In the spin-off acceleration stage during high-speed rotation in space, the deployable arm of the space gravity simulation device must withstand a large axial centrifugal force and a driving torque. In this paper, a large-scale high-speed rotating deployable arm is proposed, and the relevant characteristics during the rotation process are analyzed. A new driving mode of towed deployment is proposed that can lead to the rapid and efficient deployment of a large-scale deployable arm. First, an optimized configuration of a deployable arm is proposed. Second, the deployment driving process of the deployable arm under several different drag driving modes is simulated and analyzed, and a comparative analysis is performed to select a simple and reliable drag deployment driving scheme. Then, the effects of various disturbances on the posture of the deployable arm during the rotation process are explored, guiding the posture control of the deployable arm. Finally, a 10 m four-unit prototype is developed for the stiffness and rotation tests, which verify that the theoretical analysis in this paper is correct. [ABSTRACT FROM AUTHOR]

In this paper, a biped robot system for dynamic walking is presented. It has two 2-degree-of-freedom (DOF) lightweight legs and a 6-DOF hip. All the joint pulleys of the legs are driven by motors that are placed at the hip using steel cables. Since all the heavy motors are mounted at the hip, the biped robot has remarkably low-mass legs beyond the hip, which guarantees low inertia during walking at high speeds. Utilizing cable-amplification mechanisms, high stiffness and strength are achieved, resulting in better control performance compared to conventional direct-driven methods. Techniques are developed to estimate joint-angle errors caused by the elastic deformation of the cables. To achieve smooth control, we introduce the concept of a virtual leg, which is an imaginary leg connecting the hip joint and the ankle joint. A robust control approach based on the “virtual leg” is presented, which considers the variances of the virtual leg length during walking. Experiments are conducted to validate the effectiveness of the mechanical design and the proposed control approach.

In the pursuit of sustainability and reduced dependence on new plastic materials, this study explores the upcycling potential of high-density polyethylene (HDPE) milk bottles into high-stiffness, high-heat-distortion-temperature (HDT) composites. Recycled high-density polyethylene (rHDPE) sourced from used milk bottles serves as the composite matrix, while reinforcing fillers are derived from dried pineapple leaves, comprising fibers (PALF) and non-fibrous materials (NFM). A two-roll mixer is employed to prepare rHDPE/NFM and rHDPE/PALF mixtures, facilitating filler alignment in the resulting prepreg. The prepreg is subsequently stacked and pressed into composite sheets. The introduction of PALF as a reinforcing filler significantly enhances the flexural strength and modulus of the rHDPE composite. A 20 wt.% PALF content yields a remarkable 162% increase in flexural strength and a 204% increase in modulus compared to neat rHDPE. The rHDPE/NFM composite also shows improved mechanical properties, albeit to a lesser degree than fiber reinforcement. Both composites exhibit a slight reduction in impact resistance. Notably, the addition of NFM or PALF substantially elevates HDT, raising the HDT values of the composites to approximately 84 °C and 108 °C, respectively, in contrast to the 71 °C HDT of neat rHDPE. Furthermore, the overall properties of both the composites are further enhanced by improving their compatibility through maleic anhydride-modified polyethylene (MAPE) use. Impact fracture surfaces of both composites reveal higher compatibility and clear alignment of NFM and PALF fillers, underscoring the enhanced performance and environmental friendliness of composites produced from recycled plastics reinforced with pineapple leaf waste fillers.

Naval architectures are required to simultaneously have high stiffness and high damping to bear periodic loading and suppress resonance that is possibly caused by ship self-excitation vibration. A protection approach, namely, metal members stiffened by bistable components, is proposed. This approach not only achieves high stiffness but also exhibits excellent energy dissipation compared to that of traditional approaches under periodic loading. A two-degree-of-freedom (2-DOF) model of a Euler beam stiffened by a bistable component is derived and characterised by two potential wells. The influence of the structural parameters and energy dissipation mechanisms of the coupled bistable-linear (CBL) beam on the laws of the potential energy wells are studied via theoretical model. In the end, a panel stiffened by optimally designed CBL beams, according to the parametric studies, effectively dissipate the dynamic energy and protect the structure by staying within the elastic range found in the finite element model (FEM). [ABSTRACT FROM AUTHOR]

Steel jacket structures exposed to environmental impacts can experience intense dynamic responses, leading to potential localized fatigue failure, plastic deformation, and even catastrophic collapse. Therefore, the jacket structure needs to possess both high stiffness and large damping to cope with impacts and dissipate dynamic energy. A novel damper with programmable mechanical behaviors and damping performance has been designed by using the contact interaction between two columns. Analytical models have been derived to investigate the effect of design parameters on mechanical behaviors and dissipation capacity of the damper and provide guidance for practical applications. Experiments and finite element analysis indicate that the stiffness-damping comprehensive performance of the damper is far superior to the general materials and other nonlinear structures that rely on elastic buckling to achieve energy dissipation. For potential engineering applications, the vibration decay responses of a three-dimensional jacket structure installed with the damper were simulated using ABAQUS software. The results indicate that the damper can serve as a potential candidate for achieving simultaneously high stiffness and large damping in marine engineering structures. • A novel damper with multi-step snap-through energy dissipation enhanced characteristics. • Investigating the complex contact interaction and elastic buckling configurations of columns. • Exploring the engineering applications of the novel damper in the field of vibration suppression. [ABSTRACT FROM AUTHOR]

Physically cross‐linked hydrogels have great potential for tissue engineering because of their excellent biocompatibility and easy fabrication. However, physical cross‐linking points are typically weaker compared to chemical ones and therefore cannot form robust hydrogels with excellent water stability, which greatly hinder their further applications. In this work, a novel hydrogel with high stiffness and outstanding antiswelling performance cross‐linked by hydrophobic polymer chains entanglements is reported. The hydrophobic polymer polyimide (PI) is mixed with the hydrophilic polymer poly‐(vinyl pyrrolidone) (PVP) to form cross‐linking points between the chains. At the equilibrium swelling state, tensile modulus of the hydrogel can be up to 22.57 MPa (higher than most existing hydrogels) and the equilibrium water swelling ratio (ESR) can be as low as 125.0%. By decreasing the PI mass ratio, tensile modulus and ESR of the hydrogel can be tuned in a wide range from 22.57 to 0.005 MPa and 125.0% to 765.6%, respectively. Using PVP/PI solutions as inks, uniform structures and multi‐material structures are fabricated having mechanical properties close to cartilage through a direct ink writing 3D printing platform. This current work demonstrates that entangled PVP/PI hydrogels have excellent tailoring capabilities and are promising candidates for tissue engineering applications. [ABSTRACT FROM AUTHOR]

This study investigates the compatibility between the soft deformation and high stiffness through the development of a soft robotic gripper for a human-scale payload. Softness is important for robotic systems that physically interact with the environments, especially for adaptive grasping or manipulation of unknown objects. Pursuing only softness would not achieve them either, and creating a certain stiffness is also an essential function in many human-scale applications. Soft robotics is unique in that it employs soft materials for the structure, and will find a lot more applications if it gains the human-scale specifications of force or the equivalent stiffness. We discuss the compatibility of the soft deformation and high stiffness based on a numerical analysis, and then present the design of a soft robotic gripper actuated by high oil-pressure, reporting its experimental validations. [ABSTRACT FROM AUTHOR]

Background: Typical non-linear vibration isolation systems address the inadequate control of low frequency vibration in linear isolation systems by introducing negative stiffness mechanisms to reduce the overall stiffness of the system and achieve relatively low or zero dynamic stiffness without sacrificing load carrying capacity. In practice, however, adjusting the system stiffness to zero and balancing the loads at the desired equilibrium point can be challenging due to manufacturing and installation defects and changing environments. Purpose: For better application in practical engineering, a simple and easily controlled structure is necessary. This study innovatively designs a sandwich structure with a tristable core comprised of paired columns is innovatively designed to have a high initial stiffness for bearing heavy weights, a quasi-zero intermediate stiffness for isolating vibration and high culminating stiffness for preventing deformation. Method: An experimental prototype of this structure is designed through finite element modelling and fabricated by a 3D printer; then, its variable stiffness is verified. An analytical approach for the post-buckling process is implemented to derive the axial-flexible displacement relation of the tristable pair columns. Averaging and incremental harmonic balance methods are developed to define the relationship between the isolation range and the stiffness characteristics of this tristable system. Results: The lower limit of isolation frequency in this tristable structure is much smaller than that of the linear structure with the same load-bearing capacity. Conclusion: Combining post-buckling and nonlinear dynamic analysis, the design methodology for these sandwich structures is established: according to the excitation, the varied stiffness characteristic of this isolation structure is determined based on nonlinear dynamic analysis; the buckling length and the spacing distance of the pair of beams are determined through post-buckling analysis; and series-parallel pairs of beams can be constructed to fit the dead weight of the equipment and installations. [ABSTRACT FROM AUTHOR]

The high-performance multi-DoF forming process (MDFP) necessitates a 6-DoF forming machine tool with high normal and lateral stiffness to bear large normal and lateral forming force of millions of Newton (MN). However, the payload of parallel kinematic machine (PKM) is generally limited to thousands of Newton (kN), which restricts its application in MDFP. Therefore, this paper aims to develop a novel heavy load PKM with high stiffness for MDFP. To maximise the normal stiffness, a 6-PSS PKM with zero base angle and horizontal driver is proposed. Further, the inner force transfer model of 6-PSS PKM is established, indicating that the normal stiffness will be maximised when the link force approaches to be vertical. Consequently, a design criterion for maximising normal stiffness, i.e., the root mean square error (RMSE) for horizontal projection of all links should be minimised, is established. To maximise the lateral stiffness, general force balance equations of 6-PSS PKM are derived, indicating that lateral force can cause unintended negative force of links, significantly reducing the lateral stiffness. Thus, a novel auxiliary 3-SPS configuration is employed to provide additional force system to mitigate this negative force via hydraulic links. Correspondingly, a design criterion for maximising lateral stiffness, i.e., all link force should remain positive, is proposed. By combining aforementioned design criterion and kinetostatic models, a near-singular 6-PSS PKM with maximising normal stiffness is achieved, and dimension parameters of 3-SPS PKM with maximising lateral stiffness are optimised. On this basis, a novel flexible redundant 6-PSS/3-SPS PKM with both high normal and lateral stiffness is proposed, and a novel heavy load Nonapod with payload of 8 MN and payload-mass ratio of 40 is developed, showing good stiffness performance. The plastic deformation mechanisms of multi-DoF formed aviation bevel gear are revealed, and experimentally formed aviation bevel gear in the new Nonapod achieves good accuracy, microstructure and mechanical performance. This work provides a new methodology for synthesis of heavy load PKM with high normal and lateral stiffness, and has significant application prospect in PKM under heavy load working condition. [Display omitted] • A novel heavy load Nonapod incorporating 6-PSS/3-SPS PKM with payload of 8 MN and payload-mass ratio of 40 is developed. • A novel design criterion for maximising normal stiffness is demonstrated on a near-singular 6-PSS mechanism. • A novel design criterion for maximising lateral stiffness is proposed for a flexible 3-SPS mechanism. • Deformation mechanisms of multi-DoF formed aviation bevel gear are revealed. [ABSTRACT FROM AUTHOR]

In the spin-off acceleration stage during high-speed rotation in space, the deployable arm of the space gravity simulation device must withstand a large axial centrifugal force and a driving torque. In this paper, a large-scale high-speed rotating deployable arm is proposed, and the relevant characteristics during the rotation process are analyzed. A new driving mode of towed deployment is proposed that can lead to the rapid and efficient deployment of a large-scale deployable arm. First, an optimized configuration of a deployable arm is proposed. Second, the deployment driving process of the deployable arm under several different drag driving modes is simulated and analyzed, and a comparative analysis is performed to select a simple and reliable drag deployment driving scheme. Then, the effects of various disturbances on the posture of the deployable arm during the rotation process are explored, guiding the posture control of the deployable arm. Finally, a 10 m four-unit prototype is developed for the stiffness and rotation tests, which verify that the theoretical analysis in this paper is correct.

This study presents a high-stiffness torque sensor with a strain amplification mechanism for cooperative industrial manipulators. A novel strain amplification mechanism for a torque sensor has been designed to increase the stiffness of the sensor. The mechanism has a single structure composed of trapezoidal beams, flexure structures, and inner and outer frames. In this configuration, the displacement that occurs in the beam is amplified by the flexure structure. The amplified displacement is measured using capacitance sensing technology. As a result, the developed torque sensor has a high stiffness (198.7 kN ⋅ m/rad) and compactness (diameter of 110 mm and a thickness of 9.8 mm) that integrates with all the electronics. Additionally, it has a low cost and it is easy to manufacture. Through several experimental setups, we evaluated the sensing performances of the sensor with regard to accuracy, high stiffness, and repeatability. [ABSTRACT FROM AUTHOR]

It is desirable for naval architectures to simultaneously bear high force and dissipate dynamic energy. A structural protection approach via a specifically designed all-metal stiffened member with bistable components is proposed, which not only exhibits high stiffness but also an order of magnitude increase in the structural damping compared to that of a traditional member under wave impact. As a typical module, a two-degree-of-freedom model of the Euler beam stiffened by bistable component is derived and characterized as a double-well potential, and the theoretical analysis indicates that a unique combination of this coupled bistable-linear (CBL) module's natural vibration and the bistable components' higher frequency oscillation caused by the potential barrier highly enhances the structural damping. The CBL modules are utilized to stiffen a representative grille structure, which effectively mitigates the slamming response within the elastic range in FEM. [ABSTRACT FROM AUTHOR]

Hydrogels are widely used in tissue engineering, soft robotics and wearable electronics. However, it is difficult to achieve both the required toughness and stiffness, which severely hampers their application as load-bearing materials. This study presents a strategy to develop a hard and tough composite hydrogel. Herein, flexible SiO 2 nanofibers (SNF) are dispersed homogeneously in a polyvinyl alcohol (PVA) matrix using the synergistic effect of freeze-drying and annealing through the phase separation, the modulation of macromolecular chain movement and the promotion of macromolecular crystallization. When the stress is applied, the strong molecular interaction between PVA and SNF effectively disperses the load damage to the substrate. Freeze-dried and annealed-flexible SiO 2 nanofibers/polyvinyl alcohol (FDA-SNF/PVA) reaches a preferred balance between enhanced stiffness (13.71 ± 0.28 MPa) and toughness (9.9 ± 0.4 MJ m -3 ). Besides, FDA-SNF/PVA hydrogel has a high tensile strength of 7.84 ± 0.10 MPa, super elasticity (no plastic deformation under 100 cycles of stretching), fast deformation recovery ability and excellent mechanical properties that are superior to the other tough PVA hydrogels, providing an effective way to optimize the mechanical properties of hydrogels for potential applications in artificial tendons and ligaments., (© 2024 Wiley‐VCH GmbH.)

Aiming at the "light wind start, light wind power generation" of vertical axis wind turbine, a new T-shaped radial passive magnetic bearing with high suspension characteristics is proposed. Passive magnetic bearings used in vertical axis wind turbines usually have small bearing capacity and difficult magnetization. The new T-shaped radial PMB can improve the radial bearing capacity, and the three magnetic rings all adopt simple axial magnetization. The new T-shaped radial PMB is combined with mechanical auxiliary bearing to form the suspension system of wind turbine. In the stable state, the suspension system can realize radial and axial stable suspension. The structure and working principle of the suspension system are briefly described. Through the finite element simulation, the characteristics of the new T-shaped radial PMB, the traditional double-ring PMB and the T-shaped PMBs are compared. Taking the high bearing capacity and high stiffness of the new T-shaped radial PMB as the optimization objective, the multi-objective optimization of the new T-shaped radial PMB was carried out by changing its geometric parameters (inner diameter, magnetization length and air gap). The research results show that: Under the same bearing capacity, the volume of the new T-shaped radial PMB is reduced by about 78.64%. Under the same volume, its bearing capacity increased by about 30.7%, and its stiffness increased by about 96.1%. After optimization, its radial bearing capacity increased to 101.38 N, and its stiffness increased to 202.76 N/mm. [ABSTRACT FROM AUTHOR]

• A class of novel auxetic lattice structures with high stiffness based on the stretchdominant concept has been proposed. • The new concept of structures shows excellent stiffness and obvious negative Poisson's ratio effect along omni-direction. • The tree-like re-entrant structure exhibits controlled anisotropic elastic properties. • Isotropic elasticity with negative Poisson's ratio between -1 and 0 is achievable. Critical drawback of poor stiffness in traditional auxetic materials limits them to be applied where negative Poisson's ratio behavior and excellent load-bearing capacity are simultaneously desired. In this work, a general prescription for designing auxetic lattice structures with high stiffness and controllable isotropic/anisotropic elastic properties is proposed. Based on it, we rationally design a class of novel auxetic lattice structures whose deformation is mainly governed by the stretching mechanisms and conducted an investigation on a tree-like re-entrant structure. A combination of theoretical predictions, numerical simulations and tensile test experiments have been carried out to gain a comprehensive understanding of the structural in-plane elastic mechanical properties along both the principal axes as well as in the off-axis directions. Besides, theoretical model for designing tree-like re-entrant structure with isotropic elastic properties is established and experimentally verified with specimens fabricated with CFRP composite. The results of this research has proven the tree-like re-entrant structure exhibits excellent effective Young's modulus, shear modulus and obvious negative Poisson's ratio effect along omni-direction. Investigation on the directional dependence of structural effective elastic properties has further indicated the proposed structure presents a great potential for designing auxetic material with controllable anisotropic elastic properties. In particular, the proposed structure is capable in achieving isotropic design with any negative Poisson's ratio between −1 and 0. The design philosophy presented in this paper provides a general prescription for solving the challenge of poor stiffness in traditional auxetic materials and paves a new way for isotropic auxetic design. [ABSTRACT FROM AUTHOR]

Structures that are capable of changing shape can increase efficiency in many applications, but are often heavy and maintenance intensive. To reduce the mass and mechanical complexity solid-state morphing materials are desirable but are typically nonstructural and problematic to control. Here we present an electrically controlled solid-state morphing composite material that is lightweight and has a stiffness higher than aluminum. It is capable of producing large deformations and holding them with no additional power, albeit at low rates. The material is manufactured from commercial carbon fibers and a structural battery electrolyte, and uses lithiumion insertion to produce shape changes at low voltages. A proof-of concept material in a cantilever setup is used to show morphing, and analytical modeling shows good correlation with experimental observations. The concept presented shows considerable promise and paves the way for stiff, solid-state morphing materials. [ABSTRACT FROM AUTHOR]

A novel piezoelectric stack for rotary motion using d15 working mode is proposed, fabricated, and tested in this article to achieve the high stiffness and high precision of rotation. This piezoelectric stack is fabricated by bonding process from only two components—lead zirconate titanate ceramics and electrodes, which is beneficial to realize the simple structure. A theoretical model based on the shear deformation theory is established to predict the static output performances. And the simulation with the finite-element method is adopted to evaluate the dynamic characteristics. An experimental system is built to verify the design and study the performances of the piezoelectric stack. The experimental results indicate that the static output angle changes from −13.25 to +13.33 μrad, whereas the exciting voltage changes from −300 to +300 V, with good linear relationship and high repeatability accuracy. Under the condition of changing the exciting voltage by the step of 0.5 V, the stable resolution is measured to be higher than 0.022 μrad. The large load capacity and width frequency response are verified, which reflect the high stiffness of the proposed piezoelectric stack. The proposed piezoelectric stack achieves accurate and stable rotary output motion with high resolution, rapid response, and large load capacity. Besides, the stack has regular shape and simple structure, and therefore, it is suitable to be integrated in the equipment in the fields of micro–nano manipulations, piezoelectric ultrasonic motors, etc. [ABSTRACT FROM AUTHOR]

In this paper, a novel positioner fixture with a high repeated positioning accuracy and a high stiffness is proposed and investigated. A high-precision end-toothed disc is used to achieve the high repeated positioning accuracy of the designed positioner fixture. The mathematical models of the cumulative error of the tooth pitch, the tooth alignment error and the error of the tooth profile half-angle of the end-toothed disc are analyzed. The allowable tolerance values of the cumulative error of the tooth pitch, the tooth alignment error and the error of the tooth profile half-angle of the end-toothed disc are given. According to the theoretical calculation results, a prototype positioner fixture is fabricated and its repeated positioning accuracy and stiffness are tested. The test results indicate that the stiffness of the proposed positioner fixture is 1050.5 N/μm, which is larger than the previous positioner fixtures of the same type. The repeated positioning accuracy of the proposed positioner fixture in the x, y and z directions are ±0.48 μm, ±0.45 μm and ±0.49 μm, respectively, which is significantly higher than the previous positioner fixtures.

The art of origami has gained traction in various fields such as architecture, the aerospace industry, and soft robotics, owing to the exceptional versatility of flat sheets to exhibit complex shape transformations. Despite the promise that origami robots hold, their use in high-capacity environments has been limited due to the lack of rigidity. This article introduces novel, origami-inspired, self-locking pneumatic modular actuators (SPMAs), enabling them to operate in such environments. Our innovative approach is based on origami patterns that allow for various types of shape morphing, including linear and rotational motion. We have significantly enhanced the stiffness of the actuators by embedding magnets in composite sheets, thus facilitating their application in real-world scenarios. In addition, the embedded self-adjustable valves facilitate the control of sequential origami actuations, making it possible to simplify the pneumatic system for actuating multimodules. With just one actuation source and one solenoid valve, the valves enable efficient control of our SPMAs. The SPMAs can control robotic arms operating in confined spaces, and the entire system can be modularized to accomplish various tasks. Our results demonstrate the potential of origami-inspired designs to achieve more efficient and reliable robotic systems, thus opening up new avenues for the development of robotic systems for various applications.

Environmental impact loading can seriously damage marine structures; thus, it is desirable for structural components to simultaneously bear high force and dissipate dynamic energy. However, the damping properties of structural metals are very low. This paper proposes a structural damping approach via a specifically designed all-metal brace, in which a combination of an asymmetric column with a multistable equilibria (MEQ) mechanism creates a flag-shaped hysteretic loop with an initial modulus similar to that of the parent metal material. The mechanical behavior of the brace is predicted by finite element modeling (FEM). An analytical model is presented for explaining the hysteretic dissipation induced by multistable modes that are transformed through mixed boundary conditions; these hysteretic dissipation behaviors are validated by FEM. A parametric study conducted on the geometric properties illustrates the flexible design of the stiffness and damping configurations of the MEQ brace. The proposed brace effectively mitigates the impact response of a representative jacket platform within the elastic range in the simulation, which utilizes three-dimensional FEM combined with the user-defined material (UMAT) code in ABAQUS. A brace with the MEQ feature is an effective alternative for obtaining high structural stiffness and enhancing damping in marine engineering. • An metal brace with mutli-stable equilibria mechanism introduce hysteretic damping with high modulus. • The transformation of mutli-stable equilibria is predicted by application of an analysis and finite element model (FEM). • Parametric studies using FEM clarify the influence of different geometric properties on the behavior of module. • The proposed brace effectively mitigate the impact response of a schematic jacket platform utilized 3-D FEM. [ABSTRACT FROM AUTHOR]

For the shape memory polymers' (SMPs) applications in demanding, high performance scenarios are usually limited by their poor mechanical performances during shape transformation. In this work, shape memory epoxy composites (SMEPCs) with superior mechanical properties are fabricated by adding various short and continuous carbon fibers (CFs) into neat shape memory epoxies (SMEPs) matrix. The resultant SMEPC's storage modulus (E ') at room temperature is as high as 37 GPa, and the maximum recovery force exceeds 4.4 GPa, with good shape memory capabilities. These properties are at least an order of magnitude higher than those in existing typical SMP systems. The excellent mechanical properties of the fibers and their ability to retard crack propagation in the matrix are believed to play an important role in achieving high moduli below and above the shape-memory triggering temperature. The potential applications of such SMEPCs are demonstrated with wind blades. Experimental results and numerical models regarding air flow velocity variation as initiated by shape change in the blades indicate that our SMEPCs can sustain continuous stable mechanical state and provide variable wind speeds. These CF reinforced SMEPCs can be employed as smart structural materials to automatically switch shapes in response to the change in environment, such as those seen in aero foils and energy harvesters. [ABSTRACT FROM AUTHOR]

The aerostatic lubrication model with orifice restriction is built based on finite difference method. The model is solved by combination of flux-error feedback and optimization of grids parameter. The stiffness of aerostatic bearing can be improved by reducing the diameter of the orifice, but the optimum working gas gap is reduced and the processing difficulty of surface throttle is improved. The experiments of load and stiffness are carried out on the slider (50 × 50 mm) with the diameter of orifice at 50 µm. The experimental results and theoretical calculation are in good agreement; thus, the model is verified. The structural parameter of two, three, and four orifice gas-bearings is optimized, respectively, based on the proposed model, and the optimum positions of the orifices are obtained. According to the results, the aerostatic bearing guideways, made up of optical material (K9), are manufactured by some optical ways, and the lubrication of the small gas gap is guaranteed; meanwhile, the straightness accuracy of the aerostatic bearing guideways is 0.1 µm/200 mm. The analysis result verifies that the calculation method and the aerostatic lubrication model are significant to the design of high-precision aerostatic equipment. [ABSTRACT FROM AUTHOR]

• Tristable property of Kresling pattern origami is proposed. • The truss model is corrected based on the tristable property and an established mathematical model. • Energy landscape analysis using the corrected truss model validates the tristable property. • Origami-inspired structures are designed, and the high stiffness of the third stable state is validated. Kresling pattern origami is known for its bistable property, as confirmed by the truss model used to analyze its dynamics. However, our theoretical research and folding experiments reveal that the Kresling pattern origami possesses three stable states during folding motion, with the third state exhibiting high stiffness. These represent exciting new achievements for origami research. Here, Kresling pattern origami is studied using the geometric definitions of triangulated cylindrical origami and triangulated conical origami, and the truss model is corrected based on the proposed tristable property and an established mathematical model of the third stable state. Analysis of the energy landscapes obtained from the corrected truss model reveals various properties of the Kresling pattern origami that confirm its tristable property. In addition, origami-inspired structures are created that exhibit excellent deployability, collapsibility, load-bearing capacity, and multistability. Thereafter, the high stiffness of the third stable state is validated experimentally. These studies can provide new content for constructing multistable metamaterials and improving the load-bearing capacity of deployable structures. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigates the impact behavior of fiber-metal laminates (FMLs) (Carbon FMLs and Glass FMLs), which were fabricated by using high-stiffness steel, carbon prepreg, and glass prepreg through autoclave molding. The mechanical behavior of the FMLs was evaluated by performing tensile, compressive, in-plane shear, and low-velocity impact tests. Drop-weight impact tests were conducted to induce cracking of the FMLs, and the crack initiation along with crack propagation behavior of the different laminate sequences ([0/0], [0/90], [0/90/0], [90/0/90] and [0/90/90/0]) were also studied. The results show that the fabricated FMLs have higher strength and stiffness than conventional FMLs. Their impact strengths increased, and weights decreased simultaneously. The absorption energy was proportional to the crack length that was induced by the low-velocity impact. Moreover, it was found that the fiber orientation mainly affected the direction of crack propagation in the FMLs. This investigation facilitates the design of high-stiffness and lightweight FMLs for automotive parts. [ABSTRACT FROM AUTHOR]

Si wafer diameter tends to be increased from 300 mm to 450 mm in order to increase semiconductor device productivity. To this end, the authors developed a rotary grinding machine with high stiffness, equipped with water hydrostatic bearings. This grinding spindle is designed to govern infeed motion of the grinding wheel. This study investigates the basic design and performance of the grinding spindle system. This system itself is composed of a constant pressure water hydrostatic bearing as a radial bearing and a magnetic actuator as a thrust bearing. The magnetic actuator combine the infeed device and the thrust bearing. The measured results show that the static stiffness, Ks, is 1.06 kN/μm, the natural frequency is 353 Hz, and the positioning accuracy is 0.2 μm. These results meet the performance requirements necessary to grind φ450 mm Si wafer.