Simple Spring Research Articles

Seismic performance of light steel-natural timber composite beam-column joint in low-rise buildings

Current timber structures or steel-timber composite structures are made of thick steel and glued laminated timber (glulam) with beams and columns connected by high-strength bolts used in high-rise and large-span structures. However, there is no high strength requirement for low-rise buildings in villages and towns. The composite action of thin-walled steel and fast-growing timber is selected to constitute the structural members together, which are connected using plain bolts for a structural system suitable for residential houses in villages and towns. Thin-walled steel can be used to minimize the initial defects and material variability of fast-growing timber. To meet the requirements of the light steel-fast-growing timber composite structural system, a fully bolted joint is designed in this paper. The quasi-static tests of seven joints are carried out to analyze their seismic performance. The results show that the seismic performance of joints can meet the requirements of low-rise residential buildings in villages and towns. The finite element simulation of the test specimens is also carried out, and the modeling approach is described in detail to analyze similar structures further. Finally, the component-based expression was used to propose a simplified spring model to calculate the joints' initial rotational stiffness and ultimate capacity and compared with the experimental results for practical applications.

Rolling resistance model for estimation of friction fluctuation in linear ball guideways

Linear ball guideways are widely employed in machine tool drive systems. Friction fluctuation of linear ball guideways causes fluctuations in the feed rate that results in contour errors in synchronous motions while using several feed drives. In this study, a practical model of rolling resistance is proposed for a model-based design of the raceway profile that realizes a smooth feed motion. In the proposed model, the rolling resistance is obtained from the preload and two contact angles at the upper and lower raceways. The preload variation is represented by a simplified spring model. The validity of the proposed model is experimentally verified. The variation in the rolling resistance is influenced by the phase difference between the upper and lower raceway profiles. The resistance variation can be decreased by setting the phase difference to the half period of the profile component. The experimental results indicate that the fluctuation components of the rolling resistance, with a wavelength longer than the contact diameter between the ball and raceway, can be correctly estimated. The estimation error for the shorter-wavelength component is not a crucial issue because the rolling resistance fluctuation is small for such a component. The verification results show that the proposed model can provide an effective guideline for the raceway profile design to reduce the rolling resistance fluctuation to an acceptable level.

Non-linear vibration analysis of specially orthotropic tapered micro-plates with arbitrary located crack: A non-classical analytical approach

The present work aims to study the non-linear vibrations in a cracked orthotropic tapered micro-plate. Linear and parabolic variation in the plate thickness is assumed in one as well as two directions. The partial crack is located in the centre, and it is continuous; this crack’s location is arbitrary and can be varied within the centre-line. Based on classical plate theory, the equilibrium principle is applied, and the governing equation of tapered orthotropic plate is derived. Additionally, the microstructure’s effect has been included in the governing equation using the non-classical modified couple stress theory. The simplified line spring model is used to consider the impact of partial crack on the plate dynamics and is incorporated using in-plane forces and bending moments. The introduction of Berger’s formulation brings the non-linearity in the model in terms of in-plane forces. Here, Galerkin’s method has been chosen for converting the derived governing equation into time-dependent modal coordinates, which uses an approximate solution technique to solve the non-linear Duffing equation. The crack is considered along the fibres and across the fibres to show the effect of orthotropy. Results are presented for an orthotropic cracked plate with non-uniform thickness. The effects of the variation of taper constants, crack location, crack length, internal material length scale parameter on the fundamental frequency are obtained for two different boundary conditions. The non-linear frequency response curves are plotted to show the effect of non-linearity on the system dynamics using the method of multiple scales, and the contribution of taper constants and crack parameters on non-linearity is shown with bending-hardening and bending-softening phenomenon. It has been found that vibration characteristics are affected by the taper parameters and fibre direction for a cracked orthotropic plate.

The Mechanical Behavior of a Multispring System Revealing Absurdity in the Relativistic Force Transformation

The mechanical motion of a system consisting of simple springs is investigated from the viewpoint of two inertial observers with a relativistic relative velocity. It is shown that the final displacement of the springs is not measured the same by the observers. Indeed, it is demonstrated that there is an incompatibility between kinematics and dynamics in Einstein’s relativity regarding the force transformation.

Force Plate with Simple Mechanical Springs and Separated Noncontact Sensor Elements.

This paper reports on a force plate (FP) using mechanical springs and noncontact distance sensors. The ground reaction force (GRF) is one of the factors for clarify biomechanics, and FPs are widely used to measure it. The sensor elements of conventional FPs are mainly strain gauges. Thus, the mechanical properties of FP depend on the sensor element performance. If the FP performance must change, we must redesign the FP, including changing the sensor elements. Here, we proposed an FP that uses a measuring principle based on simple springs and noncontact sensors. The shape and performance of the proposed FP are expected to change easily. As a prototype device, we designed and fabricated an FP installed with 12 springs and four sensors for human walking. A planar coil and magnet were used as the sensor elements, and the sensor output was proportional to the vertical and horizontal displacements. The FP resonance frequency was 123 Hz, which was larger than the required specification. The calibration experiments showed that vertical and horizontal forces and moments could be measured independently. The FP’s resolutions were 1.9 N and 1.4 N in the anterior–posterior and vertical directions, respectively. Furthermore, the fabricated FP measured GRF similarly to the commercial FP when a human walked on the plate. These results suggest that the proposed method will be helpful for FPs with custom-made requirements.

Development of resilient friction beams and application to moment-resisting frames

This paper proposes the concept of resilient friction beams (RFBs) and investigates how RFBs can be economically implemented in moment-resisting frames (MFs) to improve seismic performance. The RFBs mainly consist of two T-shaped beams and four cap plates, resulting in a cost-effective configuration that employs less steel than previous self-centring beam designs. The mechanics of the RFB are first explained, and the equations predicting its responses are given. Two numerical methods are presented for modelling RFBs. The results from a finite element model (FEM) confirmed the sliding behaviour of the RFBs. Then a simplified spring model was created for performing nonlinear dynamic analysis. Finally, a set of steel framed buildings with different heights were designed and computationally subjected to two seismic levels of ground motions. The results suggest that residual interstory drift, peak base shears and peak absolute accelerations can be effectively limited by providing RFBs at the lower storeys.

Architected material analogs for shape memory alloys

Architected material analogs for shape memory alloys

A Simplified Spring winder For Clinical Application

Introduction: The fabrication of coils using heavy gauge stainless steel wire for use in appliances such as the Churro Jumper can be a tedious task and can often result in spaced coils that lead to more flexibility than can be desired, leading to a decreased force application and hence overall lengthened treatment time. Using well placed, tightly adherent coils the force of which can be controlled by placement of the desired number of coils can help to mitigate this shortcoming. Technique: The spring winder described here is easy to fabricate using easily available stationary articles which can be repurposed to form an efficient winder that can coil springs with reduced effort as compared to that would have been required when using orthodontic pliers only. The stationary repurposed for this winder is the electric etching pen which provides a good framework for fabricating the winder. In addition, clear acrylic is used along with a syringe body to hold the winding components. The syringe is filled up with clear acrylic and winding rods are laid down within the acrylic which holds it firmly in place. In addition, the syringe body is embedded into the electric pen handle which allows for easy turning the winder so as to exert effective force while reducing operator effort and fatigue. This also allows for winding of heavy gauge orthodontic wire with little effort. Conclusion: A simplified spring winder can be best indicated for the fabrication of coils for fixed functional appliances like Churro Jumper.

A novel configuration for high power-output and highly efficient vibration energy harvesting

The most commonly used vibration energy harvesting system is the single-degree-of-freedom (SDOF) system. However, the power output of the SDOF system is limited by the mechanical damping ratio and the efficiency is only 50% at the maximal power output. In this paper, we modified the SDOF configuration by adding a spring in series with the energy transducer, which results in a configuration where a parallel energy-harvesting damper and inerter are in series with the spring, similar to the Maxwell model. The parameters of the proposed configuration are analyzed and optimized. The optimization results show the new configuration can produce many times more power output compared with the conventional SDOF system if the primary spring is relatively soft and the added spring is properly selected. In addition, the energy-harvesting efficiency can be significantly increased at the maximal power output. A lab experiment of backpack setup demonstrated 82% power increase and an efficiency of 83%. Lab test using a bridge vibration induced by freight train finds out that the proposed configuration can double the power output compared with the conventional SDOF system. With the augment of a simple spring, the proposed configuration disrupts the fundamental limit on the power and efficiency of the conventional SDOF energy-harvesting system, which opens a new perspective in the energy-harvesting field.

Modelling and Validation of Joint Properties for NVH Simulation Model of an Electrified Passenger Vehicle Drivetrain


 
 
 The constantly changing automotive market, which is characterized by the progressing electrification of vehicles, presents challenges with respect to the acoustic behaviour of powertrains. As indicated frequently, the characteristic noise of electric cars differs from that of conventional drives. In particular, energy dissipation of the assembled housing parts from material and joint damping; is an important aspect. In modelling the NVH behavior of electric vehicles or drivetrains in general, the breakdown of global material and local joint damping is not yet state of the art. Instead, measured global modal damping values from similar constructions are frequently used. Often, a constant degree of damping is defined for all modes. However, moderate changes in the geometry of components or in the load level can lead to severe fluctuations in the damping. In order to improve predictability and to be able to estimate the effects of constructive changes in natural frequency, mode shape, and damping, the goal will be to take into account the global material and local joint damping separately. For that, a local model which is able to take the joint properties into account has to be developed. The analytical based Iwan model for the contact interface was expanded upon to facilitate model updating against forced response measurements on a simple mass spring structure in one dimension and to extend the model from one-dimensional to three-dimensional.
 
 

Addendum

Addendum

Heat and Fluid Flow Analysis and ANN-Based Prediction of A Novel Spring Corrugated Tape

A circular tube fitted with novel corrugated spring tape inserts has been investigated. Air was used as the working fluid. A thorough literature review has been done and this geometry has not been studied previously, neither experimentally nor theoretically. A novel experimental investigation of this enhanced geometry can, therefore, be treated as a new substantial contribution in the open literature. Three different spring ratio and depth ratio has been used in this study. Increase in thermal energy transport coefficient is noticed with increase in depth ratio. Corrugated spring tape shows promising results towards heat transfer enhancement. This geometry performs significantly better (60% to 75% increase in heat duty at constant pumping power and 20% to 31% reduction in pumping power at constant heat duty) than simple spring tape. This paper also presented a statistical analysis of the heat transfer and fluid flow by developing an artificial neural network (ANN)-based machine learning (ML) model. The model is evaluated to have an accuracy of 98.00% on unknown test data. These models will help the researchers working in heat transfer enhancement-based experiments to understand and predict the output. As a result, the time and cost of the experiments will reduce. The results of this investigation can be used in designing heat exchangers.

A numerical survey of nonlinear dynamical responses of discrete pantographic beams

Materials and structures based on pantographic cells exhibit interesting mechanical peculiarities. They have been studied prevalently in the static case, both in linear and nonlinear regime. When the dynamical behavior is considered, available literature is scarce probably for the intrinsic difficulties in the solution of this kind of problems. The aim of this work is to contribute to filling of this gap by addressing the dynamical response of pantographic beams. Starting from a simple spring mechanical model for pantographic beams, the nonlinear equilibrium problem is formulated directly for such a discrete system also considering inertia forces. Successively, the solution of the system of equilibrium equations is sought by means of a stepwise strategy based on a non-standard integration scheme. Here, only harmonic excitations are considered and, for large displacements, frequency-response curves are thoroughly discussed for some significant cases.

Kinematics of Elastic Tendons for Tendon-Driven Manipulators With Transmission Friction

This article 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.

Cation disorder and bond anharmonicity synergistically boosts the thermoelectric performance of p-type AgSbSe2

Atomic bonding with simple 1D spring and ball model for the phonon–phonon interaction, which arises from 5s2 lone pair electrons.

A hierarchical Bayesian approach for calibration of stochastic material models

AbstractThis article recasts the traditional challenge of calibrating a material constitutive model into a hierarchical probabilistic framework. We consider a Bayesian framework where material parameters are assigned distributions, which are then updated given experimental data. Importantly, in true engineering setting, we are not interested in inferring the parameters for a single experiment, but rather inferring the model parameters over the population of possible experimental samples. In doing so, we seek to also capture the inherent variability of the material from coupon-to-coupon, as well as uncertainties around the repeatability of the test. In this article, we address this problem using a hierarchical Bayesian model. However, a vanilla computational approach is prohibitively expensive. Our strategy marginalizes over each individual experiment, decreasing the dimension of our inference problem to only the hyperparameter—those parameter describing the population statistics of the material model only. Importantly, this marginalization step, requires us to derive an approximate likelihood, for which, we exploit an emulator (built offline prior to sampling) and Bayesian quadrature, allowing us to capture the uncertainty in this numerical approximation. Importantly, our approach renders hierarchical Bayesian calibration of material models computational feasible. The approach is tested in two different examples. The first is a compression test of simple spring model using synthetic data; the second, a more complex example using real experiment data to fit a stochastic elastoplastic model for 3D-printed steel.

Reconstruction of a fluttering flag from a single image

Reconstructing a 3 D object from a single image is a challenging task because determining useful geometric structure information from a single image is difficult. In this paper, we propose a novel method to extract the 3 D mesh of a flag from a single image and drive the flag model to flutter with virtual wind. A deep convolutional neural fields model is first used to generate a depth map of a single image. Based on the Alpha Shape, a coarse 2 D mesh of flag is reconstructed by sampling at different depth regions. Then, we optimize the mesh to generate a mesh with depth based on Restricted Frontal-Delaunay. We transform the Delaunay mesh with depth into a simple spring model and use a velocity-based solver to calculate the moving position of the virtual flag model. The experiments demonstrate that the proposed method can construct a realistic fluttering flag video from a single image.

Diabetes and Reactive Balance: Quantifying Stepping Thresholds With a Simple Spring Scale to Measure Fall-Risk in Ambulatory Older Adults.

Fall-risk assessments for patients with diabetes fail to consider reactive responses to balance loss. The purpose of this study was to assess the feasibility of using a simple clinical tool to evaluate the impact of diabetes and fall history on reactive balance in older adults. We recruited 72 older adults with and without diabetes. Postural perturbations were applied by a waist-mounted spring scale. Stepping thresholds (STs) in the anterior and posterior directions were defined as the lowest spring-loads that induced a step. Balance was assessed via the National Institutes of Health Toolbox Standing Balance Test, and lower extremity sensation was assessed using vibratory perception threshold and Semmes-Weinstein monofilaments. Fall history over the past year was self-reported. Cox regressions and analysis of variance were used to compare hazard rates for stepping and observed STs between groups. Anterior STs were elicited in 42 subjects and posterior STs in 65 subjects. Hazard rates for posterior ST were significantly affected by diabetes, with greater hazards for fallers with diabetes versus control fallers and nonfallers, after accounting for balance and sensory loss. For those who stepped, ST was lower in the posterior direction for the diabetes group. Additionally, anterior but not posterior ST was lower in all fallers vs all nonfallers. The waist-mounted spring scale is a clinically implementable device that can assess ST in older adults with diabetes. Using the device, we demonstrated that ST was affected by diabetes and could potentially serve as a fall-risk factor independent of balance or sensory loss.

Research on Squeak Noise from Polypropylene in Frictional Contact with Leather for Automotive Interior Assembly

To explore the mechanisms of squeak generation in automotive interiors, stick–slip experiments on polypropylene versus leather were conducted under various conditions. The friction properties were researched with changes in normal force, velocity, and temperature and static friction coefficients were generally lower at low temperature, higher at room temperature, and intermediate at high temperature and generally increased with an increase in velocity from 1 to 4 mm/s except in some individual cases. The dynamic friction coefficients as a whole presented a significant decrease but displayed similar trends in comparison with the static values. A simplified spring–mass model was built to illustrate the stick–slip physics of movement of polypropylene versus leather. The concomitant squeak characteristics are discussed. Risk priority indexes were acquired to evaluate the level of squeak noise. The inverse of the impulse rate obtained from stick–slip tests was perceived as the crucial threshold for squeak evaluation. A finite element simulation was developed to study the squeak problems of a trimmed vehicle door, and some risk locations were identified by comparing the maximal peak-to-peak amplitude of relative displacement in the main direction with the inverse of the tested impulse rate. The weak area where the squeak originated can be located from the modal contribution analysis for enhancement in the design phase.

Estimation of Structural Parameters Using Transfer Matrices and State Vectors

A new system identification (SI) method based on Transfer Matrix (TM) concept is proposed here to identify structural stiffness. Transfer matrices based on lumped mass and the more accurate consistent mass models are used here, based on displacement measurements in the time domain. The consistent mass based TM is derived from the dynamic stiffness matrix of a beam element. The state vector at a location is the sum of the internal and external contributions of displacements, forces and moments at that point - when multiplied with the (TM), we obtain the adjacent state vectors. The method of identification proposed here involves predicting the displacements at certain locations using the TM, and comparing them with the measured displacements at those locations. The mean square deviations between the measured and predicted responses at all locations are minimized using an optimization algorithm, and the optimization variables are the unknown stiffness parameters in the TM. A non-classical heuristic Particle Swarm Optimization algorithm (PSO) is used, since it is especially suited for global search. Different strategies for calculating the initial state vector, as well as two identification processes viz., simultaneous and successive methods, are discussed. Numerical simulations are carried out on four examples ranging from a simple spring mass system to a nine member framed structure. The speed and accuracy of identification using this method are good. One main advantage of this method is that it can be applied at any portion of the structure to identify the local parameters in that zone without the need to model the entire global structure.