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In this paper, the optimum linear/nonlinear spring and linear/nonlinear damper force versus displacement and force versus velocity characteristic functions, respectively, are determined using simple lumped parameter models of a quarter car front independent suspension and a half car rear solid axle suspension of a light commercial vehicle. The complexity of a nonlinear function optimisation problem is reduced by determining the shape a priori based on typical shapes supplied by the car manufacturer and then scaling it up or down in the optimisation process. The vehicle ride and handling responses are investigated considering models of increased complexity. The linear and nonlinear optimised spring characteristics are first obtained using lower complexity lumped parameter models. The commercial vehicle dynamics software Carmaker is then used in the optimisation as the higher complexity, more realistic model. The performance of the optimised suspension units are also verified using this more realistic Carmaker model.

In order to study the effects of a steel spring floating slab track (SSFST) on the vibration and noise of rail transit overhead box-girders, a train–track system coupling model in the frequency domain was established. Two numerical models – a finite-element model to analyse the vibration and a boundary-element model for predicting structure-borne noise – were then built. Based on a field test of one 30 m long simply supported box-girder paved with ordinary slab track (OST) in an urban rail transit system, the models were verified to be effective at predicting the vibration and noise of the box-girder. Meanwhile, both the vibration- and noise-reduction effects of SSFST were assessed in comparison with OST. After substituting SSFST for OST, the maximum reductions of the overall vibration acceleration level and overall sound pressure level of the box-girder were 34·7 dB and 25 dB, respectively. Finally, the effects of the SSFST's parameters on the noise of the box-girder were investigated. The results showed that the isolator stiffness is the primary factor that affects the noise characteristics of the box-girder, followed by the floating slab thickness. However, the floating slab length and fastener stiffness were found to have little influence on the noise radiation.

The power capture performance of an adaptive bistable point absorber wave energy converter (WEC) in irregular waves is investigated in this paper. Based on the linear potential flow theory and Cummins equations, the equation of motion for the WEC is established in time domain. Then a parametric study is performed on the power capture performance of the WEC by considering the influences of different wave and system parameters such as the spring combination parameter, the stiffness of auxiliary springs and main springs, the original length value of the main spring, damping coefficient of the PTO systems and the significant wave height. The results show that in an irregular wave, each parameter will have a certain impact on the performance of the device. Appropriate device parameters need to be selected according to actual environmental parameters to ensure that the adaptive bistable WEC has better power capture performance than its linear and conventional bistable counterparts.

This experimental study aimed to obtain the actuation properties of Shape Memory Alloy (SMA) spring actuators available under the commercial names of Biometal® NiTiCu and KRL® NiTi NiTiCu, NiTiFe. An objective is to characterize the electro-thermo-mechano-electro behavior of shape memory spring through experimentation via simultaneous measurement techniques. These measurements are synchronized by embedding an impedance analyzer and data acquisition module through a unique program. Moreover, to obtain the mathematical model by parts of the SMA spring and equivalent circuit analysis of active spring through their electro-thermo-mechano-electro characteristics exhibited during shape memory effect. Based on the experimental results, the SMA spring's equivalent circuit is considered a series resistance - inductance​ circuit. It was found from the experimental results that the Biometal® actuator produced more resistance, inductance variation and offered more displacement as compared to KRL® actuators.

The effect of bearings on the vibrational behavior of machine tool spindles is investigated. This is done through the development of a calibrated dynamic stiffness matrix (CDSM) method, where the bearings flexibility is represented by massless linear spring elements with tuneable stiffness. A dedicated MATLAB code is written to develop and to assemble the element stiffness matrices for the system’s multiple components and to apply the boundary conditions. The developed method is applied to an illustrative example of spindle system. When the spindle bearings are modeled as simply supported boundary conditions, the DSM model results in a fundamental frequency much higher than the system’s nominal value. The simply supported boundary conditions are then replaced by linear spring elements, and the spring constants are adjusted such that the resulting calibrated CDSM model leads to the nominal fundamental frequency of the spindle system. The spindle frequency results are also validated against the experimental data. The proposed method can be effectively applied to predict the vibration characteristics of spindle systems supported by bearings.

Throughout evolution, organisms repeatedly developed elastic elements to power explosive body motions, overcoming ubiquitous limits on the power capacity of fast-contracting muscles. Seahorses evolved such a latch-mediated spring-actuated (LaMSA) mechanism; however, it is unclear how this mechanism powers the two complementary functions necessary for feeding: rapidly swinging the head towards the prey, and sucking water into the mouth to entrain it. Here, we combine flow visualization and hydrodynamic modelling to estimate the net power required for accelerating the suction feeding flows in 13 fish species. We show that the mass-specific power of suction feeding in seahorses is approximately three times higher than the maximum recorded from any vertebrate muscle, resulting in suction flows that are approximately eight times faster than similar-sized fishes. Using material testing, we reveal that the rapid contraction of the sternohyoideus tendons can release approximately 72% of the power needed to accelerate the water into the mouth. We conclude that the LaMSA system in seahorses is powered by two elastic elements, the sternohyoideus and epaxial tendons. These elements jointly actuate the coordinated acceleration of the head and the fluid in front of the mouth. These findings extend the known function, capacity and design of LaMSA systems.

A propylimidazole functionalized coumarin derivative (IPC) was fabricated for the first time and applied as a dual responsive fluorescent chemoprobe for sensitive and selective recognitions of picric acid (PA) and Fe3+. Strong fluorescence quenching phenomena of the IPC were observed in H2O/ACN (5/95, v/v) medium (λem=408 nm) upon the additions of Fe3+or PA. The fabricated dual responsive IPC offered good selectivity and sensitivity with the low limit of detection values (0.92 µM for PA and 0.22 µM for Fe3+) lower than the acceptable amounts of Fe3+ and PA by the international official authorities. The interaction phenomena of IPC with PA and Fe3+ based on the findings of a range of experiments were considered and DFT computations were done to verify their recognition mechanisms. The sensing phenomena of IPC towards PA (1:1) and Fe3+ (3:1) were confirmed by the MALDI TOF–MS, FT–IR, 1H–NMR titration and Job's methods. Furthermore, the compound IPC was effectively applied as a fluorescent sensor for Fe3+ and PA detection in real natural spring water samples.

This paper proposes a new version of a variable gravity compensation mechanism (CVGC-II) for mobile manipulation robots such as mobile manipulators and exoskeletons. CVGC-II, which incorporated an energy-free variable mechanism in a smaller design space, exhibited improved performance with a wider range of variable torque. These enhancements were achieved by adopting an optimal curved lever and hybrid spring system. First, the mechanism concept and specifications of the CVGC mechanism are described. Next, the contribution of the curved lever and hybrid spring system to the performance enhancement of CVGC-II is explained. Subsequently, the design methodologies for the main mechanical elements, including the lever, hybrid spring, and cam, are introduced. In the lever design, Hermite spline and B-spline curve model based optimization is performed to generate optimal curved shape of the lever. The hybrid spring system, consisting of compression coil springs and layered leaf springs, helps achieve a wider variable range by maximizing the storable energy in a limited design space. Finally, the enhanced performance of CVGC-II is evaluated experimentally. The results showed that CVGC-II exhibited a 6.8 times wider variable range and energy-free variable mechanism under a 1.5 and 1.3 times smaller size and weight, respectively.

Numerical analysis of collision is an important aspect of bridge seismic research. This paper introduces precise integration to the numerical analysis of seismic collision. Firstly, the collision forces of four contact element models were expressed in a unified form, including linear spring model, Kelvin-Voigt model, Hertz model, and Jan-Hertz-Damp model, and then the precision integration formula was derived for solving the collision force. Next, a collision time search method was proposed under the linear acceleration hypothesis, and the seismic collision was divided into a collision phase and a non-collision phase. Different time steps were adopted for the two phases. This strategy was verified by comparing simulation results with the data of theoretical analysis and shaking table test. The results show that precision integration ensures the accuracy of numerical calculation for bridge structure collision under seismic action, and achieves a high calculation efficiency; the contact element model and model parameters should be selected reasonably to analyze seismic collision of bridges; the Jan-Hertz-Damp model of contact elements boasts the highest simulation accuracy among the commonly used models.

This paper proposes a novel differential kinematics of elastic tendons for tendon-driven manipulators where tendons transmit actuator force/torque to remote links via a train of pulleys. The local variability of tension and longitudinal speed in each tendon is carefully investigated in terms of the rest lengths of the virtually partitioned tendon segments along the tendon. A significant attention is paid to building a proper friction-tension mechanic model between the pulleys and tendons to identify the no-slip points that are important to be used as kinematic constraints. The kinematic relations of tendon are obtained for two possible types of tendon-pulley transmission, i.e., free-free ended and fixed-free ended types, and then a complete kinematics of tendon is formulated by augmenting all the kinematic relations existing in the entire system. Simulation and experimental results are provided to validate the proposed kinematics of tendon by comparing with a previous simple spring model where the tension was determined by the relative positions of consecutive pulleys.

A calculation method for workpiece profile variation during double-sided lapping was developed in this study. In this method, shell element in FEM deformation was used to formulate elastic deformation of workpiece, and spring element was used to formulate the contact between workpiece and platens to calculate distribution of their contact pressure considering workpiece elastic deformation. First, the developed method of the contact pressure distribution was evaluated by comparing with a method using a FEM software and the existing methods, and was confirmed to be quite valuable in terms of applicable process and calculation time. Subsequently, the workpiece profile variation was calculated using the developed method for several workpiece conditions, and it was clarified that the uneven workpiece thickness can be modified by the process, but it is difficult to modify the bow shape when the workpiece is not small. Furthermore, the decrease of the load applied to the workpiece was suggested to modify the bow shape of the workpiece.

An automatic protection guard for bikes reduces the impact to the side panels, engine, and the rider's leg when the bike collides with the ground, which follows the reverse quick return mechanism. Include a tilt sensor to monitor the bike's lean angle to activate the system and a wave spring inside the hollow bars to absorb the impact. A tilt sensor will be installed and will set a lean angle to the system. When the bike crosses the calibrated lean angle, the system activates and releases the bars from the system installed onto the bike frame and will take the first contact with the ground surface. To match real-life situations, the time taken for the protection guards to move from initial position to extreme position has been calculated using solid Works motion analysis with an average time taken is 0.14 s, and to find the total deformation different loads and different spring constants have been applied using Ansys software the average deformation is 12 mm. The system helps the rider to ride the bike in a safe mode. The total design system is dynamic and varies with the bike segment but follows the same mechanism.

In the ongoing world, everyone has been using the shock absorber as an essential component in most places like load carriers, large structures, and automobiles. This shock absorber plays a crucial role in the vehicle suspension to absorb the major shocks. So, if we absorb the shocks more efficiently, we can reduce the damage to the vehicle body, passenger and also, we can give a comfortable drive to the driver. In the suspension system, spring is the major part to absorb shocks through spring energy. So, if we use different springs or if we can modify the existing spring with better efficiency then we can increase the shock-absorbing capacity. Based on these ideas, I worked on the comparative analysis between coil spring shock absorber and wave spring shock absorber using stainless steel material under static structural and random vibrational analysis. Through these results, we can understand how effectively the wave spring shock absorber can replace the coil spring absorber in terms of load and deformation. In the end, we can find the effectiveness of springs under different random obstructions using the PSD concept in Ansys. This work can be helpful to mono shock absorber bikes and in other places where springs are required at low space areas. If we replace the coil spring with a wave spring with the same length, we can absorb more vibrations at a more comfortable level for the drivers.

Carbon fiber reinforced epoxy composites are typically difficult to machine due to their anisotropic properties which cause delamination and other damages. Introducing a backup plate beneath the workpiece during drilling has proven to be an efficient and cost-effective strategy to circumvent this problem. With a view to reduce the serious fiber pull-out and delamination problems that occur during conventional drilling of CFRP composites, a novel method of active spring restoring backup force is introduced at the bottom side of the workpiece. The thrust force and delamination are determined experimentally during the drilling of holes at various drilling parameters, with and without back-up force. This spring restoring active backup force technique aids in the continuous hole making process and is found to be a simple, inexpensive and versatile technique to adopt for reducing drilling damages. The applied active backup force contributes in the reduction of delamination even at higher thrust force. The optimal backup force is found to be 321.6 N which results in reduced delamination in drilling of composite laminate.

Traditional oscillating water column (OWC) devices are mostly fixed with almost no components allowed to move. To complement the research of OWC consisting of moving components, the capability in extracting wave energy for a device with a surging front and back lip-wall restricted by different spring stiffness values is investigated. A theoretical model is developed based on potential flow theory and solved by the matched eigenfunction method, and the pros and cons between the proposed model and the traditional fixed model are compared. The influential factors, including the wall drafts and chamber breaths, are explored to study the effects on the interested hydrodynamic parameters. To make full use of the inclusion of surging motion of lip-walls, a progressive optimized process of spring stiffness is proposed to obtain a superior efficiency curve. The results show that a relatively larger lip-wall draft and wider chamber breadth is more beneficial for the improvement of absorption efficiency for the dual-surging-motion model but the peak efficiency remains unchanged. An appropriate combination of the employed two stiffness values can expand the high-efficiency frequency bandwidth, and the peak efficiency can be improved to a better extent in contrast to the traditional fixed device.

Belleville springs are frusto-conical in shape, can support high load with small deflection. Load-Deflection characteristics of a Belleville spring can be altered by stacking of springs. In this research work, Finite Element Analysis (FEA) of Belleville spring was carried out and compared against experimental analysis using strain gauge. FEA was carried out on a plain spring and results were compared with theoretical analysis. Experimental investigation was carried out using strain gauges for different configuration of Belleville springs such as plain spring and spring with stacking. From the studies it was concluded that theoretical, Finite Elemental and Experimental analyses were in good agreement. Spring stacking was done up to 6 numbers, and deflection was significantly altered from 1.46 mm to 8.14 mm (Deflection from one spring to six springs). With the stacking of springs, change in the magnitude of maximum stress was 1.5%. Thus, required load- deflection characteristics can be achieved by stacking of springs when space is not a constraint and large deflection is required.

Sheathed Cold-formed Steel (CFS) wall framed buildings provide various advantages such as speed of construction, environmentally green, high strength-to-weight ratio etc. over construction with conventional materials. In this type of construction, walls are the main load-bearing elements. It has been observed in literature that sheathing significantly influences the load-carrying capacity of CFS wall frame. However, limited studies are available on axial behaviour of calcium silicate board (CSB) sheathed CFS wall panels. Fibre cement board (FCB) sheathed wall panels are proposed in the present study and the same are investigated for their performance under axial loading. A detailed series of experiments on full-scale sheathed perforated CFS single-studed wall panels are carried out and load factors which may be adopted by designers or researchers for evaluating axial strength of sheathed CFS panels, are proposed. Sheathings using FCB and CSB boards are applied on the specimens. Effect of variation of parameters such as type of sheathing, sheathing thickness, layer configuration of sheathing (number of layer on either side) on the load factors are also investigated in the present study. ‘Differential equation of equilibrium’ based analytical method is validated with the experimental results in the present study. In the adopted analytical method, the stud is assumed as channel section restrained by sheathing based springs. The value of spring stiffnesses is obtained analytically as specified in the literature, using modulus of elasticity, obtained through experiments. Suitable modification factor is recommended for panels with sheath on one side, while predicting axial strength of CFS panels with sheath, analytically. The proposed factor may be used with confidence as the experimental results agree well with the analytical results.

In this paper, a novel meshfree approach is proposed for the free vibration analysis of laminated closed conical, cylindrical shells and annular plate with a hole. The theoretical formulation for free vibration analysis is based on the first order shear deformation theory (FSDT) and the field functions are approximated by a Tchebychev-radial point interpolation method (TRIPM) shape function using various radial functions augmented with Tchebychev polynomials as the basis. A laminated closed shell with a hole is decomposed into five open shells without holes, and continuous conditions of displacement are applied at the interfaces between the open shells. The governing equations and boundary conditions for the laminated open shells without hole are derived using Hamilton’s principle. The boundary and continuous conditions are generalized by the introduction of an artificial spring technique, and the type of the conditions is selected according to the spring stiffness values. A comparison with the results of the literatures and finite element software ABAQUS is conducted to verify the accuracy and reliability of the proposed method. The investigation of the vibration characteristics of the laminated closed conical, cylindrical shells and annular plates with a hole according to various radial functions, geometric dimensions and boundary conditions is presented through numerical examples.

The needle of the industrial sewing machine is its most important part. During the sewing process, the needle is subjected to various actions and interactions between these actions. One of the factors that are most related to these interactions is the lateral elastic resistance – spring effect – of the sewn fabric on the needle during its penetration in the layers of fabric. In the present work, this effect has been investigated via a special formula, where the spring constant is incorporated. It was found that the equivalent length coefficient of the sewing needle ( γ ) ranged between 0.7, where the lower end of the needle still has not penetrated the fabric and 2, where the lower end has already penetrated the fabric. The elastic stability factor (η) was changed from 2.46 to 20.35, to create a critical axial compressive load P cr = 5 for a 39 cN of the sewing needle. This means that the spring constant (S) changed from S = 0 to S = ∞ , which enhanced the critical load by 8 folds. For S = 0 , the angle has two options, the first is ≤ π 2 λ l o and the second ≥ π 2 λ l \ o . The values of γ , η, and P cr for ( λ l ) o were not reasonable, while values of these variables for λ l \ o were acceptable. The future vision of the present work is to design and construct a stand to experimentally check the theoretical work suggested in this paper and to find its experimental values.

To face the demand for applications in which robots have to safely interact with humans and the environment, the research community developed new types of actuators with compliant characteristics. To embody compliance into the actuator, elastic elements with fixed or variable compliance can be used. Among the variable stiffness mechanisms, a popular approach is based on the agonistic-antagonistic (A-A) layout, where two prime movers are elastically connected to the output shaft of the actuator. Notwithstanding the conceptually simple realization of the A-A layout, one limitation is that, due to the nonlinear torque/deflection characteristic of the elastic transmissions and to the limited spring elongation, the stiffness range achievable at the output shaft reduces as the external torque increases. In this work, a novel layout, based on the A-A principle, is proposed to increase the torque/stiffness capability of the actuator. To achieve this result, we combine elastic transmissions with linear and nonlinear torque/deflection characteristics. The mathematical model of the new layout and a possible implementation are analyzed. Then, the design of a novel variable stiffness actuator is presented and experimental validations are shown to compare the new device with the benchmark.

The mechanical properties of reinforced concrete (RC) structures are closely related to the bond stress-slip relationship of rebar-concrete interface. In this paper, a novel bond stress-slip model under monotonic and cyclic loading is proposed. For interfacial behaviour under monotonic loading, an innovative micro-element model, consisting of a spring element, a friction element and a switch element, is proposed to effectively characterize the interfacial micro-damage mechanical behaviours in a physical sense. By adopting a parallel system of micro-elements and setting the fracture threshold of individual spring element as a random variable, the expressions of the bond stress-slip relationship and interfacial damage variable are derived. Subsequently, succinct practical expressions for the bond strength, peak slip under monotonic loading are formulated. The bond stress-slip model for rebar-concrete interface under monotonic loading are further established. For cyclic constitutive model of rebar-concrete interface, a new method of cyclic correction factor for the degradation law of bond strength is developed. The bond strength degradation under cyclic loading affected by the number of cycles, maximum slip value and opposite loading can be reflected with reasonable accuracy. Furthermore, the predictions calculated by the proposed model under monotonic and cyclic loading are in favorable agreement with experimental results. All parameters in the model have clear physical meaning.

Recently, many buildings have originally been designed as base-isolated to mitigate the structural vibration. However, buildings with base isolation systems can undergo displacement/amplification demand due to the inherent nonlinear behaviour of the base isolators, especially in earthquake-prone regions. Hence, in some cases it could be necessary to control the seismic response of the base-isolated buildings using supplemental damping device. This paper investigated the effectiveness of nonlinear fluid viscous damper (NFVD) considering design parameters for the base-isolated buildings with lead rubber bearing (LRB). For this, 10-storey benchmark steel moment resisting frame isolated with LRB having a series of isolation periods (T) of 3, 3.5, 4, and 5 s was used. These base-isolated frames consist of three bays and NFVDs having different damping exponents (α) of 0.15, 0.30, 0.50, and 0.70 were inserted in the mid, corner, and all bays of each base-isolated frame at the ground level. The case studied frames were modelled with a finite element program in which LRB elements were characterized by bi-linear hysteretic behaviour while NFVD elements were represented considering the Maxwell model having an elastic spring and a viscous dashpot in series. The nonlinear response of the frames with LRB and NFVD were evaluated by the nonlinear time history analyses using five ground motion records. The analysis of the results were comparatively evaluated considering certain engineering demand parameters such as the storey, bearing, and relative displacements, roof and inter-storey drift ratios, absolute acceleration, base shear, base moment, input energy, and hysteretic curves. One of the main findings of this study is that the base-isolated building with the passive damping device as control attenuation satisfactorily responded when associated with appropriated design parameters.

Increasing use of renewable energy sources to combat climate change comes with the challenge of power imbalance and instability issues in emerging power grids. To mitigate power fluctuation arising from the intermittent nature of renewables, electric spring has been proposed as a fast demand-side management technology. Since its original conceptualization in 2011, many versions and variants of electric springs have emerged and industrial evaluations have begun. This paper provides an update of existing electric spring topologies, their associated control methodologies, and studies from the device level to the power system level. Future trends of electric springs in large-scale infrastructures are also addressed.

Functionality and design of mechanical springs are simple and limited due to manufacturing constraints of conventional fabrication methods being used for making helical and wave springs. In recent era, design for additive manufacturing has proven its great worth to design and manufacture optimal, complex as well as intricate structures with better mechanical and lightweigting properties. This study aims to investigate the mechanical behavior of functionally gradient wave springs as a function of variation in thickness and morphology of each wave. Functionally gradient wave springs incorporated with different morphology and cross-sections including circular, rectangular and combination of both were designed and printed by keeping mass and height constant to investigate their mechanical properties. Loading–unloading experimentation was conducted within the elastic range (90% of compressible distance) in order to study energy absorption/loss, load-bearing capacity and stiffness of all designs. The experimental results were validated by finite element anaylsis (FEA) by providing the identical boundary conditions of experimental setup. The results revealed that the stiffness of wave spring having rectangular cross-section is increased significantly, while energy absorption is almost 90% increased due to circular cross-section of waves. Overall, the design with combination of round and rectangular cross-sectional waves has better stiffness and energy absorption properties. For further investigation of mechanical properties due to variation in cross-section of waves, more designs including semi-circular and filleted waves were designed, and FEA of those showed that 786 N of load-bearing capacity is achieved in the wave spring having semicircular cross-section of waves which is double than the wave spring having variable circular cross-section of waves.

As a complementary way to traditional wave-equation-based forward modeling methods, lattice spring model (LSM) is introduced into seismology for wavefield modeling owing to its remarkable stability, high-calculation accuracy, and flexibility in choosing simulation meshes, and so forth. The LSM simulates seismic-wave propagation from a micromechanics perspective, thus enjoying comprehensive characterization of elastic dynamics in complex media. Incorporating an absorbing boundary condition (ABC) is necessary for wavefield modeling to avoid the artificial reflections caused by truncated boundaries. To the best of our knowledge, the perfectly matched layer (PML) method has been a routine ABC in the wave-equation-based numerical modeling of wave physics. However, it has not been used in the nonwave-equation-based LSM simulations. In this work, we want to apply PML to LSM to attenuate the boundary reflections. We divide the whole simulation region into PML region and inner region, PML region surrounds the inner region. To incorporate PML to LSM, we establish elastic-wave equations corresponding to LSM. The simulation in the PML region is conducted using the established wave equations and the simulation in the inner region is conducted using LSM. Three simulation examples show that the PML scheme is effective and outperforms Gaussian ABC.

The improvement of the energy utilization rate of a hydraulic vibration-excitation system is critical to the research and development of hydraulic vibration equipment. In this paper, a hydraulic vibration-excitation system controlled by a new type of shock rotary vibrator is proposed. A system model considering the pipeline effect was established for the hydraulic shock phenomenon. In addition, the model was compared with the one that does not consider the pipeline effect. The effectiveness of the proposed model was verified experimentally. Finally, the shock phenomenon during the process of switching the working state of the vibrator and the influence of certain important parameters of the system on the vibration output were investigated based on the proposed model. The results showed that (1) the hydraulic shock phenomenon occurred when the working state of the hydraulic vibrator was switched and (2) the hydraulic shock wave could effectively improve the excitation force of the system. The excitation force increased with an increase in the oil supply pressure, spindle speed, and load. However, it was negatively correlated with the spring stiffness. The amplitude of the vibration waveform output was positively correlated with the oil supply pressure and negatively correlated with the spindle speed and load. The amplitude first increased and then decreased as the stiffness of the vibration spring increased. The only influence of the precompressed length of the spring on the system output was its alteration of the vibration center of the system output vibration.

Liquid storage tanks are lifeline structures and strategically very important. Heavy damages or even collapse of these facilities subjected to strong earthquakes may cause disastrous consequences. In this paper, the seismic response of a multistage series liquid storage tank was simulated by a finite element method and verified by a scaled-down experiment. The structural flexibility of the tank and the liquid-structure coupling characteristics between the liquid and tank wall were considered in the research. A multimass-block and spring model was employed to be equivalent to the longitudinal vibration of the liquid in the storage tank. The relationships between the connection springs and the elements of the stiffness matrix were explicitly deduced. The seismic response analysis of a four-stage series liquid tank was carried out, and the acceleration response, the stress response of the tank, and the vertical vibration of the liquid were obtained. The experimental results are in good agreement with the simulation results, which verifies the effectiveness of the modeling method in this paper.

This paper aims to show through a factorial experimental design significant factors on the polymeric bushing wear PA66, including their amplitude, frequency and spring height, when interacting with a steel axle SAE1018 (from Society of Automotive Engineers - SAE) in a tension belt applied. It was verified that factors as amplitude and frequency are significant and it was possible to propose a mathematical model to predict this wear behaviour for the proposed test. Moreover, an adhesion wear behaviour was verified, whereof a polyamide film was observed on the axle transferred by the bushing. Through the microscopy report analysis, it was possible to see the transfer film topology characterisation for a better comprehension of the adhered polyamide film from the bushing to the axle surface.

The dynamic mechanical properties of rubber spring have great influence on the vehicle dynamic performance, so the accurate description of the mechanical properties of rubber spring has always been the focus of the train dynamics. Among the mechanical properties of rubber springs, the study of non-hyperelastic properties are the most difficult and complex. Therefore, this paper mainly studies non-hyperelastic forces. Based on the experimental data of rubber springs, an elliptic analysis model is derived to describe the non-hyperelastic properties of rubber springs. On the basis of this model, a modified model based on time change and a modified model based on displacement change are also proposed. The results show that the ellipse analysis model is simple, but the error of calculation is large; the calculation precision of time correction model is high, but the calculation process is complex; the displacement correction model is between the previous two models, with both accuracy and convenience. Compared with other models, the displacement correction model has great advantages, which can improve the accuracy of the calculation of train dynamics. It is suggested to adopt the rubber spring displacement correction model in engineering application.

This paper addresses the determination of the response of beams under static loads, in presence of multiple cracks. The crack is modeled as a rotational internal spring. Both the amplitude and position of the spring are taken as uncertain variables. In particular, its random position characteristic has been modeled as Poisson law distribution along the axial coordinate. By using the theory of generalized functions, the probability transformation method (PTM) has been easily applied to the beam equilibrium equations. The PTM, employing the space transformation laws of random vectors, allows determining the probability density function (PDF) of the system response directly and easily. The results of some numerical applications have confirmed the goodness of the proposed stochastic procedure.

In order to avoid the damage of piezoelectric vibrator due to excessive deformation during resonance, an amplitude-limiting rotational piezoelectric energy harvester excited by a radially dragged magnetic force was presented in this paper. The amplitude-limiting device consisted of two springs and a wedge cam to limit deformation of the piezoelectric vibrator. Simulation analysis and tests were carried out to obtain the influence of system parameters on the response characteristics of the piezoelectric vibrator. The results showed that the amplitude-limiting device could effectively limit the maximal deformation and output voltage of the piezoelectric vibrator. The maximum generated voltage increases with the increases of the wedge cam lift, but the optimum speed range decreases. The effective speed range increased with the decreasing number ratio of exciting magnets and the rising spring stiffness. Moreover, a combination of a high-stiffness return spring and a low-stiffness buffer spring is helpful to enhance the effective speed range and to decrease the fluctuation of output voltage. Therefore, the energy generation capability and bandwidth of the energy harvester could be effectively improved through reasonable parameter matching. Under the load resistance of 40 kΩ, the maximal output power of 2.3424 mW is achieved at the rotating speed of 183.7 rpm.

The equation for prediction of the spring-in angle of a cylindrically orthotropic segment is shown to be independent of all material properties except for the anisotropic coefficients of thermal expansion and a stress-free state is insured for the corresponding unconstrained deformation. In contrast, the complete cylindrical geometry is shown to provide constraint to thermal deformation and thereby induce thermal residual stresses in the form of a moment. The method of superposition is demonstrated whereby traction-free conditions yield stress-free cylindrical elements with corresponding angular displacements at the element free boundaries. The first derivation of the spring-in equation is attributed to Radford, in contrast to the widely accepted view that the equation was first developed by Spencer et al. Finite-element methods, combined with the superposition approach, further validate the accuracy of the Radford equation for cylindrically orthotropic segments and explore its limitations for multiaxial composite laminates.

Premature failure of the spring diaphragm of coupling in wind power generator has been frequently reported. The cause of the failure spring diaphragm was analyzed by chemical composition, mechanical property, and microstructure morphology. The results showed that the fatigue failure mode initiated on the surface of the spring diaphragm resulting from cyclic loading conditions during operation. The fatigue was the main reason for failure of the spring diaphragm. The micro-crack was initiated on the spring diaphragm due to the slightly loosed and the cyclic bending fatigue. Meanwhile, the brittleness was increased, and the resist ability of crack was reduced due to the overtop yield strength ratio. Therefore, the micro-crack was extended until the spring diaphragm was broken on the combined action of fatigue and the material's high yield strength ratio. Suggestions to prevent the similar failure were proposed based on the analysis results.

In this technical note, a consistent finite element formulation of the Hyperstatic Reaction Method (HRM) for tunnel linings design is proposed by introducing a variational consistently linearized formulation. It permits to consider a nonlinear interaction between a lining structure and the surrounding ground. Recent advances of the HRM in regard to the consideration of the nonlinear response of the segmented tunnel lining exposed to design loads use an iterative algorithm for solving the nonlinear system of equations. In the proposed Variationally consistent Hyperstatic Reaction Method (VHRM), a distributed nonlinear spring model representing the interaction between the lining and the ground soils is considered in a variationally consistent format. Computing the tangential spring stiffness via consistent linearization, and using Newton-Raphson iteration, requires significantly smaller number of iterations as compared to the original HRM model based on nodal springs. Furthermore, the method is applicable for simulations using solid finite elements (2D and 3D), as well as beam or finite shell elements, respectively.

Spiral springs have a wide range of applications in various fields. As a result of the complexity of friction, few theoretical analyses of spring belts under static loading have been carried out. Considering the piecewise smooth property of the whole contact area, a simplified static model of spiral springs under loading is established in this paper. Besides, three main stress and friction distribution areas of the spring belt are proposed, namely, internal, transitional, and external regions. Since the outermost side of the spring is not subject to any pressure, a recursive method is adopted from the outside to the inside. The model provides the parameter conditions, i.e., the internal and external forces are independent or dependent. Therefore, the case that the whole contact region of the spring belt has one subregion, two subregions, and three subregions is obtained. The model gives a theoretical basis for the parameter optimization of spiral springs.

In general, the suspension systems are used to absorb vibrations, bump, rolls, dip from shock loads due to road surface irregularities. It performs its major role without affecting the vehicles’ stability and overall handling during operation. Coil springs are used as suspension element in light vehicles to attenuate unwanted vibrations. A spring is an elastic object used to store mechanical energy and it can be twisted, pulled or extended by some force and can return to its initial position when the force is released. In this study, mild steel material was taken into consideration in designing and fabricating coil springs. Theoretical and experimental investigations were conducted to calculate springs’ stiffness and to make validation between them. Three model of springs having coils 10, 11, 14 respectively are designed which have slight stiffness difference both theoretically and experimentally. The models were analyzed to determine mechanical behaviors for randomly chosen loading conditions ranging from 29.4 N to 176.4 N which are better suited with spring size. It is noted from both numerical and experimental investigations that deflection is high when the stiffness is less and vice-versa. In addition, shear stress formation increases with the increment of stiffness and applied load. Hence, springs having high stiffness are used in suspension system to reduce vibration and other disturbances. This study shows springs of having high stiffness are comparatively compact in size and cost economic as well.

A vibrating screen is widely used in raw coal screening, but intensive resonance in the startup and shutdown stages shortens the service life of the vibrating screen and generates vibration damage to surrounding buildings. Therefore, we designed a novel vibration isolator based on a magnetorheological damper, aiming to improve the vibration isolation performance of the vibrating screen. The rheological mechanical model of damping force was analyzed based on the Bingham model, and a magnetic circuit was designed according to electromagnetic theory. Then, an experiment was designed to evaluate the vibration isolation performance of the vibration isolator. The results show that the novel vibration isolator, compared with the metal spring ones, reduces the maximum resonance amplitude by 64 % in the resonance region. In addition, the time of passing through the resonance region in startup and shutdown stages is also reduced by 50 % and 60 %, respectively. This study can provide a new method to improve the vibration isolation performance of vibrating screens.

The present study aims to obtain p-y curves (Winkler spring properties for lateral pile-soil interaction) for liquefied soil from 12 comprehensive centrifuge test cases where pile groups were embedded in liquefiable soil. The p-y curve for fully liquefied soil is back-calculated from the dynamic centrifuge test data using a numerical procedure from the recorded soil response and strain records from the instrumented pile. The p-y curves were obtained for two ground conditions: (a) lateral spreading of liquefied soil, and (b) liquefied soil in level ground. These ground conditions are simulated in the model by having collapsing and non-collapsing intermittent boundaries, which are modelled as quay walls. The p-y curves back-calculated from the centrifuge tests are compared with representative reduced API p-y curves for liquefied soils (known as p-multiplier). The response of p-y curves at full liquefaction is presented and critical observations of lateral pile-soil interaction are discussed. Based on the results of these model tests, guidance for the construction of p-y curves for use in engineering practice is also provided.

A vertical spring had a changeable horizontal stiffness to avoid resonance under a seismic displacement, and a viscous damper had a perfect energy dissipation function to reduce the seismic displacement. They were joined together to achieve a seismic isolation system considerably reducing the seismic acceleration response, however, their displacement should be paid more attentions under an earthquake or in a shaking table test. Because the interface friction in the system affected the scaling process of the system in the shaking table test and the corresponding displacement responses, the system was numerically scaled before a real shaking table test. The comparison between the displacement responses of scaled models and prototype models shows that the spatial friction variation and the gravity distortion are the error sources of the relative and residual displacements of scaled models. The error of scaled relative displacement is reduced by the means of increasing PGA, damping constant, spring constant or reducing vertical spring length with zero stress, however, the error of scaled residual displacement is still chaotic under these means. Only if the error sources above are eliminated fundamentally will the error of scaled models be avoided. The conclusions are validated correct by a real shaking table test.

We developed a robot generating instantaneous force inspired by the smashing mantis shrimp, and conducted dynamic analysis using the mechanistic model. We compared the performance with and without the elastic elements of the exoskeleton to examine the contribution of each spring element. Previously, we confirmed the operation of the proposed mechanism of the shrimp-inspired-system. Because the effectiveness of the mechanism has not fully been examined as an integrated system of elastic components, here we further performed the rigorous numerical simulation using the model otherwise understanding would be limited in the physical robot. From the numerical results, it was confirmed that the proposed mechanism including the spring shortened the time to strike by 0.737 times and increased the impulse at the time of strike by 1.702 times compared with the mechanism using only pneumatic artificial muscles. The results of the simulations demonstrated the interaction between the pneumatic artificial muscles and the elastic elements of the exoskeleton. Our findings can give an insight into the integrative design of the artificial muscles and elastic mechanisms by capitalizing on a design evolved in nature.

Resonators and resonator-based oscillators are used in most electronics systems and they are classified as either mechanical or electrical, with fixed or difficult-to-tune resonant frequencies. Here, we propose an electro-superlubric spring, whose restoring force between two contacting sliding solid surfaces in the structural superlubric state is linearly dependent on the sliding displacement from the balanced position. We use theoretical analysis and finite element methods to study the restoring force and stability. The stiffness of this electro-superlubric spring is proportional to the square of the applied electric bias, facilitating continuous tuning from zero to several megahertz or gigahertz for the microscale or nanoscale resonators, respectively. Furthermore, we propose an electro-superlubric oscillator that is easily operated by varying a pair of harmonic voltages. The resonant frequency, resonant amplitude, quality factor, and maximum resonant speed can be continuously tuned via the applied voltage and bias. These results indicate significant potential in the applications of electro-superlubric resonators and oscillators. Microscale resonators are widely used in modern technology and achieving large tunability of their resonant frequency is highly desirable. Here, a design for electro-superlubric springs, based on a restoring force between sliding solid surfaces, is predicted to have continuously tunable resonant frequencies from zero to several GHz.

Seismic isolation has been a prevalent approach to seismic design of bridges whereas isolation bearings are susceptible to damages in a major earthquake event. A tie-down cable-spring restrainer (TCR) is therefore proposed to protect isolated bridges under near-fault ground motions. The proposed TCR transmits large horizontal force to the substructure under large earthquakes while does not compromise isolation efficiency of the isolator under small ones. The key concepts and theoretical model are provided in this article and a design procedure is put forward for the application of TCR to a bridge with lead-rubber bearings. Case studies show that seismic isolation and ductile behavior develop sequentially under large earthquakes and the isolators are well protected from excessive displacement. It is found that bridges with TCRs have larger displacement capacity and show less sensitivity to near-fault ground motions.

The aim of this paper is to investigate the free vibration of functional-graded (FG) cylindrical helical springs. Model differential equations of homogeneous helical springs are extended to the vibration of FG helical springs. The equations are discretized using finite difference method for space. The time dependent equations are solved using a GMRES method. The initial axial and rotational displacements are applied at the free end of the spring manually and then released. The validated numerical model is then adopted to establish the effects of the FG material index on the model natural frequencies obtained by FFT analysis. According to the results, in both homogeneous and FG helical springs, the amplitudes of axial and rotational displacements increase as they approach the free end of the spring. The numerical results indicate that the FG material index strongly affects the dynamic behavior of the cylindrical helical springs. The amplitudes of the oscillations are damped efficiently and by increasing the material gradient index.

The flexible manipulators and related robotic systems have been widely used in minimally invasive surgery (MIS) for enhancing the intraoperative inspection and surgical operation. Although a variety of flexible manipulators using different mechanisms have been developed, most of them are rigid mechanical structures or single function, which lack softness, robustness or in-situ diagnosis and surgical treatment. To enrich the flexibility and therapeutic function of manipulators, we developed a laser endoscopic manipulator with a soft bendable tip. The soft bendable tip is composed of a spring-reinforced soft actuator with multiple channels, which are designed for placing diagnosis and therapy probes to enrich the integrated diagnosis and therapeutic function. Pilot results show that the actuator can bend and elongate in the three-dimensional space and the spring-reinforced structure increases the linearity and consistency of the soft actuator. Experimental outcomes demonstrate that the proposed robotic system has extended bending capability and integrated diagnosis and therapeutic function. The multiple functions with surgical tools and laser fiber realize in-situ therapy. Therefore, it would be an enhancement for future clinical applications such as single-port laparoscopic surgery (SPL) or neurosurgery.

Background Surgical management of otosclerosis is technically challenging with studies demonstrating that outcomes are commensurate with surgical experience. Moreover, experts apply less force on the ossicular chain during prosthesis placement than their novice counterparts. Given the predicted decreasing patient pool and the rising cost of human temporal bone specimens it has become more challenging for trainees to receive adequate intraoperative or laboratory‐based experience in this procedure. As such, there is a need for a low‐cost training model for the procedure. Here we describe such a model. Methods A surgical model of the middle ear was designed using computer aided design (CAD) software. The model consists of four components, the superior three dimensional (3D)‐printed component representing the external auditory canal, a 90° torsion spring representing the incus, a 3D‐printed base with a stapedotomy underlying the torsion spring, and a 3D‐printed phone holder to facilitate video‐recording of trials and subsequent calculation of the force applied on the modeled incus. Force applied on the incus is calculated based on Hooke's Law from post‐trial computer‐vision analysis of recorded video following experimental determination of the spring constant of the modeled incus. Results The described model was manufactured with a total cost of $56.50. The spring constant was experimentally determined to be 97.0 mN mm/deg, resulting in an ability to detect force applied to the modeled incus across a range of 1.2 to 5200 mN. Conclusions We have created a low‐cost middle‐ear training model with measurable objective performance outcomes. The range of detectable force exceeds expected values for the task. Level of Evidence: IV., This manuscript describes a low‐cost training model for ossicular chain reconstruction. Using 3D printing, video footage captured using a smart phone and computer vision software, the authors have created a representative training tool with objective outcome measures. These measures can be trended and improved upon by users.

This article dwells on two technical aspects, the design and implementation of an upgraded version of the differential shape-memory alloy–based revolute actuator/rotary actuating mechanism for stabilization and position control of a two-degree-of-freedom centrally hinged ball on beam system. The actuator is configured with differential and inclined placement of shape-memory alloy springs to provide bidirectional angular shift. The shape-memory alloy spring actuator occupies a smaller space and provides more extensive reformation with justifiable actuation force than an equally able shape-memory alloy wire. The cross or diagonal architecture of shape-memory alloy springs provides force amplification and reduces the actuator’s control effort. The shape-memory alloy spring–embodied actuator’s function is exemplified by the highly dynamic underactuated custom-designed ball balancing system. The ball position control is experimentally demonstrated by cascade control using the control laws that have been unattempted for shape-memory alloy actuated systems; the ball is positioned with linear (integer-order and fractional-order) proportional–integral–derivative controllers optimized with genetic algorithm and particle swarm optimization at the outer/primary loop. Angular control of the shape-memory alloy actuated beam is obtained with nonlinear (integer-order and fractional-order sliding mode control) control algorithms in the inner/secondary loop.

In the design of viscoelastic materials used in rubber products, not theoretical approaches but experimental approaches have been usually employed. This is due to the difficulties in mathematical procedures of the dynamic material characteristics such as the dependencies of strain amplitude, frequency and/or environmental temperature in deformation. In mathematical approach there are two kind of analytical models for a complex module of the material, which are a fractional derivative model and a spring-dashpot model. However there are few papers dealing with the study of the identifications of parameters for the experimental modulus actually obtained not only by using the fractional derivative model but also by using the spring-dashpot model and the discussion of the comparisons of the two models. In the present paper, the complex elastic modulus for a rubber material are obtained experimentally for a wide range of excitation frequency, and the modulus-frequency relations are derived analytically by using the two models, respectively. Finally, the applicability of the models are discussed from the numerical results.

A multi-bolt spring–mass method considering assembly gap and shim was developed to predict the shear stiffness and bolt stiffness of the single-lap composite joints. Based on the premise that the h...