Spring Structure Research Articles

A new L-shaped rigid beam FBG acceleration sensor

Acceleration detection is an important technology in the fields of seismic monitoring, structural health monitoring and resource exploration. A FBG acceleration sensor with the combination of L-shaped rigid beam and spring structure based on bearings is proposed against the low sensitivity that predominates in the low-frequency vibration measurement by FBG acceleration sensors, where L-shaped rigid beam is utilized to amplify the vibration signal, and is fixed by the bearings at both ends to effectively suppress the transverse crosstalk. The effects of structural parameters on the sensitivity and natural frequency of the sensors were analyzed using Origin theory, and such parameters were optimized; next, static stress and modal simulation analysis was made using COMSOL; in the end, a test system was built to test the performance of the real sensors. According to the findings, the acceleration sensor, whose natural frequency is 57 Hz, is of a flat sensitivity response in the low frequency range of 1–35 Hz, with the dynamic range being 89.83 dB, the acceleration sensitivity being up to 1241.85 pm/g, the coefficient of determination R2 for the sensitivity fit is 0.9997, and the transverse crosstalk being -26.20 dB within the operating frequency band. The findings offer a reference for improving the low-frequency vibration measurement capability of FBG acceleration sensors.

The vibration isolation characteristics of torsion bar spring with negative stiffness structure

Nonlinear stiffness systems are an effective way to achieve low frequency vibration isolation. To improve the support capacity and ride comfort of nonlinear stiffness systems, this paper proposes a quasi-zero stiffness (QZS) vibration isolator composed of the torsion bar spring and negative stiffness structure (NSS) and investigates its vibration isolation characteristics. The influence of the system parameters on the static nonlinear stiffness peculiarities of the vibration isolator is delved. The motion equation of the isolator under the harmonic excitation from the base can be expressed as Helmholtz–Duffing equation due to an offset distance from zero stiffness point to the equilibrium position. The primary resonance response of the QZS system is approximately analytically predicted by Harmonic Balance Method (HBM). The absolute acceleration transmissibility of the QZS system considering the effect of excitation amplitude and system parameters is investigated and compared with the equivalent linear system to evaluate the isolation performance of the nonlinear system. Then, the numerical simulation is investigated and good agreement with theoretical analysis. The validity of the proposed model is verified by finite element method (FEM) and an experiment. Based on the numerical simulation and experiment results, the proposed nonlinear system possesses a better vibration isolation performance of heavy equipment in the low-frequency region.

Fully 3D-printed spring metasurface loaded with dielectric substrate

This article presents the design, construction and measurement of a 3D-printed spring metasurface loaded with a dielectric 3D-printed substrate. The spring-like metasurface is constructed using a high-conductive filament for the conductive parts and a low-cost polylactic acid (PLA) filament as a dielectric substrate. The addition of the dielectric substrate lowers the frequencies where the stopband is generated, when compared to the same spring metasurface without the substrate. The possibility to add a dielectric substrate thanks to 3D-printing allows a reduction of the overall size of the spring structure in terms of the operating wavelength. Measurement results show good match with the simulated structures, confirming the feasibility of implementation for this 3D-printed metasurface topology.

Static and Dynamic Analysis of 6-DOF Quasi-Zero-Stiffness Vibration Isolation Platform Based on Leaf Spring Structure

Multi-degree-of-freedom isolator with low stiffness is a fair prospect in engineering application. In this paper, a novel 6-DOF QZS vibration isolation platform based on leaf spring structure is presented. Its bearing capacity is provided through four leaf springs, and the quasi-zero-stiffness is realized by the force balance between the central spring and the suspension spring. 6-DOF vibration isolation is realized by the ball-hinge fixed design of a leaf spring. Through static and dynamic analysis, the following conclusions are brought. The stiffness of the leaf spring and the deformation of the central spring under static load are directly proportional to the bearing capacity of the isolation table. Besides, in order to ensure that the stiffness of the system is close to zero, the stiffness of the suspension spring and the inner spring should be as similar as possible. The vertical and horizontal displacement transmissibility tests of the isolation platform are carried out, in which the jumping phenomenon in the QZS vibration isolation platform is analyzed. By improving the damping of the structure and the length of the suspension spring, the dynamic vibration isolation process of the system can be more stable, the transmissibility can be reduced, and the vibration isolation effect can be enhanced.

A novel whisker sensor with variable detection range for object positioning.

The design of a whisker sensor, inspired by mammalian whisker characteristics, is presented in this paper. It uses a novel spring structure to transfer the deformation generated by the whisker tip when it touches an object at the base, which drives the permanent magnet installed at the base to change its position. It achieves precise positioning of the object by using the magnetic induction intensity data output from the Hall sensor MLX90393. Based on the results of the finite element model analysis, the detection range of the whisker sensor can be expanded by replacing the artificial whisker material and selecting a permanent magnet of a suitable size. Calibration experiments and positioning tests were conducted on the sensor. The experimental results showed that the detection radius of the sensor was 24, 30, 33, and 39 mm for the carbon fiber, acrylic, acrylonitrile butadiene styrene plastic (ABS), and nylon whiskers, respectively, when they were matched with a NdFeB annular permanent magnet with an aperture of 3 mm and a thickness of 3 mm. The sensor is small and simple to manufacture with good sensitivity, linearity, hysteresis, and repeatability. The maximum positioning errors of the X and Y positions in the detection plane of the sensor were within ±1.3 mm, and the positioning was accurate. The sensor can be used to identify the shape of an object.

3D Printed Spring‐Type Electronics with Liquid Metals for Highly Stretchable Conductors and Inductive Strain/Pressure Sensors

AbstractThe spring structure is stretchable and resilient, enabling electronic devices to be highly stretchable and durable. However, spring objects composed of only soft materials cannot be maintained without a supporting rod inside the coil owing to self‐weight deformation. Therefore, a design strategy should be investigated. In this study, self‐maintaining spring structures with soft materials are designed using physical simulations and soft spring‐type electronic devices (a stretchable conductor, strain sensor, and pressure sensor) with little hysteresis are developed. The spring‐type electronic devices consist of a core–sheath structure, which is a core channel filled with liquid metal and a 3D‐printed elastomeric sheath. The spring‐type conductor can be stretched with a small force (1.25 N) and has a negligible resistance change for up to 400% strain and ≈5.5% resistance increase at 640% strain. Moreover, the inductance induced by the coil structure monotonically decreases in the range of 200% stretching. The device also has high durability with little change in the electrical characteristics during 1000 cycles of 100% stretching. Furthermore, an inductive pressure sensor can measure <250 Pa (50 mN) by compressing the spring. Spring‐type electronic devices composed of soft materials contribute to highly durable and stretchable sensors for robotic applications.

Tough protein based adhesive reinforced by molecular spring strengthening strategy

It is of great importance but still a great challenge to develop bio-based environmental adhesives for industrial applications. In this study, inspired by the adhesion structure of lignin and spring mechanics, a new biomimetic strategy was proposed to prepare high bonding strength, formaldehyde-free and petroleum resource-independent adhesive from biomass. Through Schiff base and Michael addition reaction between the quinone of oxidized demethylated lignin (DL) and the amino and sulfhydryl groups of soybean protein isolate (SPI) with helix chain, SPI was grafted onto DL to form reinforcement structure and crosslinker with molecular spring structure (namely SDL). Cleavage of the disulfide bonds of keratin and introduction of SDL reconstituted a strong cohesive crosslinking network (KPT-SDL), in which the α-helical peptide chain in SDL was stretched and the intramolecular hydrogen bonds were broken under tensile force, thus achieving energy dissipation and significantly improving the shear strength and toughness of the keratin-based adhesives. The maximum wet strength of the wood-based panel prepared by KPT-SDL adhesive reached to 1.22 MPa, which was comparable to the level of industrial adhesives and 197.56% higher than the original keratin-based adhesive. In addition, KPT-SDL presented high adhesion to numerous types of substrates, including steel and ceramic. This study provided a green and effective biomimetic strategy for high value-added keratin to promote the development of strong and tough composites, which had a good value of frontier research and industrial development.

A New Method to Control Intrinsic Localized Mode Using a Variable Magnetic Spring Structure

A special vibration mode called intrinsic localized mode (ILM) in a dispersed multi mass point-nonlinear spring system has been actively studied in solid-state physics and has a high application potential in engineering. Previous studies have only considered parameter-invariant systems; hence, active control of the excited ILM is not possible. Therefore, even though the phenomena are very interesting, there are no applications to devices. In this article, we propose a new paradigm of ILM by designing a dynamic nonlinear vibration system that can treat nonlinear spring properties in a variable manner depending on the applied current. By using variable spring characteristics, the localized vibration energy of the ILM can be freely transferred in unconventional way than before. The spring properties of the variable spring structure with applied current are investigated using finite element analysis. Then, numerical simulations in MATLAB show that the active control of the ILM is possible in a dynamic vibration system with variable spring characteristics.

Design and Analysis of a Pneumatic Spring Testing System for Precision Manufacturing.

The vibration isolation effect of the pneumatic spring determines the precision of the manufacturing. In this paper, in order to detect the performance of a pneumatic spring, a multi frequency band testing system with different payload is designed and developed. First, the pneumatic spring structure is analyzed, and the stiffness of the pneumatic spring is obtained based on the ideal gas model, Kelvin–Voigt model, and finite element method. Then, to verify the reliability of the system, a dynamic model of the vibration platform is established. Through an analysis of the simulation using the Simulink environment, critical parameters are determined, and the effective conditions of the vibration isolation are obtained. Based on the results from the simulation and experiment, the transmission rate is around 20% under 40 Hz vibration, and 12% under 100 Hz vibration. The pneumatic spring proves to be effective under vibrations beyond 7 H. This achievement will become an important basis for future research concerning precision manufacturing.

Quality factor control of mechanical resonators using variable phononic bandgap on periodic microstructures

The quality factor (Q-factor) is an important parameter for mechanical resonant sensors, and the optimal values depend on its application. Therefore, Q-factor control is essential for microelectromechanical systems (MEMS). Conventional methods have some restrictions, such as additional and complicated equipment or nanoscale dimensions; thus, structural methods are one of the reasonable solutions for simplifying the system. In this study, we demonstrate Q-factor control using a variable phononic bandgap by changing the length of the periodic microstructure. For this, silicon microstructure is used because it has both periodicity and a spring structure. The bandgap change is experimentally confirmed by measuring the Q-factors of mechanical resonators with different resonant frequencies. The bandgap range varies depending on the extended structure length, followed by a change in the Q-factor value. In addition, the effects of the periodic structure on the Q-factor enhancement and the influence of stress on the structural length were evaluated. Although microstructures can improve the Q-factors irrespective of periodicity; the result of the periodic microstructure is found to be efficient. The proposed method is feasible as the novel Q-factor control technique has good compatibility with conventional MEMS.

Simulation and experimental investigation of contact spot temperature for electrical contact components

The contact spot temperature of electrical contact components substantially affects the reliability and electrical life of any electrical connections within the electrical engineering. In this paper, finite element model of typical spring structure components is built by using COMSOL Multiphysics software. Furthermore, the transient process of contact temperature is simulated by taking account of film resistance on the contact surface. Moreover, a test rig is introduced that makes it possible to measure the electrical contact resistance and temperature within the electrical contact components simultaneously. Finally, correlation between contact resistance and contact spot temperature with different contact force and current levels are investigated explicitly.

Experimental investigation on static and dynamic energy dissipation characteristics of composite sandwich structure with entangled metallic wire materials and disc springs

In this paper, a novel composite sandwich structure with entangled metallic wire materials and disc springs (EMWM/DS) was proposed to improve the high temperature resistance and energy absorption characteristic of disc spring structure (DSS). The performance superiority of the proposed structure was verified by a series of quasi-static and low-velocity impact tests. On the one hand, the static energy dissipation characteristics of the EMWM/DS and DSS are compared through quasi-static test. Furthermore, the influences of the key experimental parameters and the densities of EMWM sandwich layers on the dynamic energy absorption characteristics of EMWM/DS are respectively studied by associating the mechanical properties of EMWM/DS with the helix wires based on curved cantilever beam of variable length. The experimental observations show that by increasing the density of the EMWM sandwich layer or increasing the compression deformation, the energy dissipation characteristics of EMWM/DS can be effectively enhanced. The composite sandwich structures still have good compression resistance and energy dissipation characteristics at high temperatures with increased environmental temperature. On the other hand, the dynamic energy absorption performance of the EMWM/DS and the DSS via low-velocity impact (LVI) is evaluated. The experimental results show that the complete impact energy absorption, specific energy absorption, and impact energy loss rate of the EMWM/DS can be increased by more than 93% compared with the DSS under the low-velocity impact (0.5 m s−1–2 m s−1).

Spatial and temporal variabilities of coastal nekton community structure and phylogenetic diversity in Daya and Dapeng Bay, southern China

Coastal areas are important habitats for many species and strongly affected by anthropogenic activities. Management for sustainable coastal ecosystems benefits from a comprehensive assessment of species diversity. Here, we measured the spatio-temporal changes in community and phylogenetic structure of spring and autumn nektonic communities in Daya and Dapeng Bay among 12 sampling sites. We found that both the community structure and phylogenetic facets of nektonic communities in Daya and Dapeng Bay exhibited strong spatial and temporal patterns due which we attribute to fishing intensity and mid-summer fishing moratorium. The relatively larger ratio of unexplained variation in the autumn community resulted from stochastic processes caused by the mid-summer fishing moratorium. Furthermore, the phylogenetic structure of the spring nektonic communities between Dapeng and Daya Bay were significantly different; obvious phylogenetic clustering was found in spring nektonic communities of Dapeng Bay. These results implied that we may consider the current fishing intensity as a strong stress for nektonic communities, which exceeds the effect of natural processes and environmental factors. We speculate that the immediate sweeping fishing efforts may rapidly deplete the recovered fish stocks in a short time as human activities exert great stress on the nektonic communities in the study area. To avoid permanent damage to the ecosystem and a loss of valuable marine resources, urgent attention is required for fishery management.

Alginate/Fish Gelatin-Encapsulated Lactobacillus acidophilus: A Study on Viability and Technological Quality of Bread during Baking and Storage

In the present study, Lactobacillus acidophilus LA-5 was microencapsulated in sodium alginate, followed by fish gelatin coating (0.5, 1.5, and 3%). The survival of L. acidophilus in bread before and after encapsulation in alginate/fish gelatin during the baking and 7-day storage was investigated. Moreover, the effect of alginate/fish gelatin-encapsulated L. acidophilus on the technological properties of bread (hardness, staling rate, water content, oven spring, specific volume, and internal texture structure) was evaluated. Compared with control (free bacteria), encapsulated L. acidophilus in alginate/fish gelatin showed an increase in the viability of bread until 2.49 and 3.07 log CFU/g during baking and storage, respectively. Good viability of (106 CFU/g) for probiotic in encapsulated L. acidophilus in alginate/fish gelatin (1.5 and 3%, respectively) after 4-day storage was achieved. Fish gelatin as a second-layer carrier of the bacteria had a positive effect on improving the technical quality of bread. Furthermore, the staling rate of bread containing encapsulated L. acidophilus alginate/fish gelatin 0.5, 1.5, and 3% decreased by 19.5, 25.8, and 31.7%, respectively. Overall, the findings suggested encapsulation of L. acidophilus in alginate/fish gelatin capsule had great potential to improve probiotic bacteria’s survival during baking and storage and to serve as an effective bread enhancer.

Development of a Hybrid Force-Displacement Sensor Based on Fiber Bragg Grating for Radial Artery Pulse Waveform Measurement

This paper proposes a novel Fiber Bragg Grating (FBG)-based hybrid force and displacement sensor with a high sensitivity to achieve accurate measurement of radial artery pulse waveforms. The proposed sensor prototype mainly consists of a force-sensitive orthogonal planar spring structure, an FBG optical fiber, and a sensor frame. The side-type orthogonal planar spring flexure has been utilized and optimized to achieve an excellent linear force-displacement relationship along the axial direction. It offers other merits in terms of equivalent functions as a parallel mechanism configuration, compactness, and convenient assembly. The employed optical fiber has been tightly stretched to form a suspended configuration vertical to the flexure’s central line. This two-point pasting configuration and the use of the transverse movement property of the suspended fiber can achieve improved sensitivity and resolution, and avoid shortcomings associated with the traditional and direct pasting for the whole FBG element. The theoretical model that corresponds to the sensing principle has been derived. The simulation based on finite element method (FEM) has been adopted to conduct design optimization to determine detailed structural parameters and achieve enhanced sensitivity, as well as performance investigation. The optimized prototype has demonstrated an excellent force resolution of 0.47mN with a small linearity error of 0.98% within the sensing range [0.9N, 2.7N] and a high displacement sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.103\mu \text{m}$ </tex-math></inline-formula> with a linearity error of 4.08% within the sensing range [0.3mm, 0.7mm], and the R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> values are determined as 99.99% and 99.30%, respectively. The experiments for artery pulse waveform measurement have been performed to validate the effectiveness of the proposed sensor design.

Mechanism and Optimization of a Novel Automobile Pneumatic Suspension Based on Dynamic Analysis

Pneumatic suspension is the most significant subsystem for an automobile. In this paper, a simplified and novel pneumatic spring structure with only a conical rubber surface is presented and designed to reduce the influence of external factors besides the pneumatic. The nonlinear stiffness of the pneumatic spring is analyzed based on the ideal gas model and material mechanics. Natural frequency analysis and the transmission rate of the pneumatic suspension are obtained as two effect criteria for the dynamic model. The vibration isolation system platform is established in both simulation and prototype tests. With the results from the simulation, the rules of the pneumatic suspension are analyzed, and the optimal function of mass and pressure is achieved. The experiment results show the analysis of the simulation to be effective. This achievement will become an important basis for future research concerning precise active control of the pneumatic suspension in vehicles.

Discrete scattering and meta-arrest of locally resonant elastic wave metamaterials with a semi-infinite crack

Previous investigations on wave scattering and crack propagation in the discrete periodic structure are concentrated on the conditional mass–spring model, in which the internal mass is not included. In this work, elastic wave metamaterials with local resonators are studied to show the scattering of elastic waves by a semi-infinite crack and the arrest behaviour. The influences of internal mass–spring structure are analysed and the discrete Wiener–Hopf method is used to obtain the displacement solution. Numerical calculations are performed to show that the dynamic negative effective mass and band gaps can be observed owing to the local resonance of the internal mass. Therefore, the scattering of an elastic wave with a specific frequency by a semi-infinite crack can be avoided by tuning the structural parameters. Moreover, the energy release ratio which characterizes the splitting resistance is presented and the meta-arrest performance is found. It is expected that this study will increase understanding of how to control the scattering characteristics of elastic waves by a semi-infinite crack in locally resonant metamaterials and also help to improve their fracture resistance.

An Intermetallic NiTi-Based Shape Memory Coil Spring for Actuator Technologies

Amongst various intermetallic shape memory alloys (SMAs), nickel–titanium-based SMAs (NiTi) are known for their unique elastocaloric property. This widely used shape remembering material demonstrates excellent mechanical and electrical properties with superior corrosion resistance and super-long fatigue life. The straight-drawn wire form of NiTi has a maximum restorable strain limit of ~4%. However, a maximum linear strain of ~20% can be attained in its coil spring structure. Various material/mechanical engineers have widely exploited this superior mechanic characteristic and stress-triggered heating/cooling efficiency of NiTi to design smart engineering structures, especially in actuator technologies. This short technical note reflects the characteristics of the NiTi coil spring structure with its phase transformations and thermal transformation properties. The micro-actuators based on NiTi have been found to be possible, suggesting uses from biomedical to advanced high-tech applications. In recent years, the technical advancements in modular robotic systems involving NiTi-based SMAs have gained speculative commercial interest.

Temperature and size-dependent modeling for predicting mechanical properties of carbon nanotubes

In this paper, a temperature and size-dependent molecular model is proposed to calculate the mechanical properties of carbon nanotubes. The cross section of carbon nanotubes is regarded as a hexagonal ring structure, and the covalent bond between carbon atoms is regarded as a beam of nonlinear spring structure, that is, the molecular structure system is regarded as a "beam-helical spring" structure. For considering the wall thickness of carbon nanotube, the influence of force constant on the molecular structure model is analyzed. On this basis, according to the principle of molecular mechanics, the expressions of calculating surface Young's modulus, Poisson's ratio, shear modulus and bulk modulus are obtained. It is found that due to the wall thickness, the Young's modulus, shear modulus, and bulk modulus of carbon nanotubes decrease with the increase of radius size.

Utilizing mechanical adhesion force as a high contact force in a MEMS relay

High contact force in a microelectromechanical systems (MEMS) relay is known to be the most important factor in achieving low contact resistance. Achieving a high contact force in an electrostatically-actuated MEMS relay usually requires high actuation voltage to exert a high electrostatic force. In this paper, for the first time, we demonstrate the successful use of a mechanical adhesion force as a high contact force for realizing an extremely low contact resistance, even at a low actuation voltage of 3.8 V. To maximize the mechanical adhesion, we designed a suitably-large contact area (100 μm × 100 μm) in the MEMS relay and a detachment spring structure to separate the two electrodes that were in contact with one another by only the mechanical adhesion force, thereby enabling the MEMS switch to perform multiple switching operations. The proposed MEMS relay exhibited an extremely low contact resistance of 4.9 mΩ with only the mechanical adhesion force after we applied an actuation voltage of 3.8 V, and it achieved a retention time of 105 s because of stable mechanical contact. Through this experiment, we verified that the mechanical adhesion force can provide an efficient source for generating high contact force in the MEMS relay.