Multi-leaf Spring Research Articles

Precise estimation of individual leaf camber and stepping in symmetrical 65Si7 leaf springs

The term symmetrical multi-leaf spring is generally applied to springs of constant width, properly stepped leaves and each leaf of constant thickness and equal cantilever lengths. The main leaf is under the action of longitudinal and lateral forces during its operation, hence it is not desired that the maximum stress is induced in it. To reduce this stress, leaves with different unassembled cambers are assembled by pulling against each other and a common curvature is established. This causes stress concentration or set assembly stress in the assembled leaf springs. The assembly stress is subtractive from load stress in the master leaf, while it is additive to load stress in short leaves. It is possible to distribute the stress in a desirable manner among the leaves by a suitable combination of assembly stresses and stepping. The work presented in this article provides a design procedure for the number of leaves, stepping, individual leaf camber and no load assembly camber of leaf springs used in a light commercial vehicle. A proper combination of stepping and camber has been proposed by taking leaf spring design parameters into consideration, so that the stress in the leaves does not exceed maximum design stress. The leaf springs with the proposed parameters have been manufactured and tested on a full-scale leaf spring testing machine. The analytical stepping, no load assembly camber and individual leaf camber were compared with actual leaf spring for validation.

EXPERIMENTAL INVESTIGATIONS OF DOUBLE MULTI-LEAF SPRING SUBJECTED TO IMPACT LOAD

EXPERIMENTAL INVESTIGATIONS OF DOUBLE MULTI-LEAF SPRING SUBJECTED TO IMPACT LOAD

Mechanical Property Testing of Woven Roven Glass Fiber Specimen and Structural Analysis of a Composite Leaf Spring

A Composite material has been fabricated by laying epoxy resin over woven roven fiber mat and carbon fiber combination and its mechanical properties were attained in the Material testing Laboratory. Based on the material properties achieved, A multi-leaf steel spring used in the rear suspension system of light vehicles is designed and analyzed using ANSYS software. The finite element results showing stresses and deflections, verified the existing analytical and experimental solutions. Using the results of the steel leaf spring, a composite one made from Woven glass fiber with epoxy resin was designed and optimized using ANSYS. Main consideration was given to the optimization of the spring geometry. The objective is to obtain a spring with minimum weight that is capable of carrying given static external forces without failure. The design constraints were stresses and displacements. The results show that an optimum spring width decreases hyperbolically and the thickness increases linearly from the spring eyes towards the axle seat. Compared to the steel spring, the optimized composite spring has stresses that are much lower, the natural frequency is higher and the spring weight without eye units is lower and the cost of the composite leaf spring that has been fabricated is comparatively less.

Design, Fabrication, and Analysis of a Hybrid FIBER Composite Monoleaf Spring Using Carbon and E-Glass Fibers for Automotive Suspension Applications

The leaf spring is an important component that provides suspension and plays a vital role in automotive applications. As a vehicle travels, a tremendous force, mostly in terms of a fatigue load, is applied to the leaf spring assembly, particularly to the eye point of the rear axle. In a vehicle with rear-wheel drive, the leaf spring is subject to twisting forces that are opposite in direction and magnitude during the acceleration of drive wheels. A multileaf spring provides an additional strength, but lacks the flexibility and increases the overall weight of the vehicle. Considering the loading conditions, the availability of space in a vehicle, and geometrical considerations, a composite monoleaf spring is designed. In due consideration of the tensile behavior, fatigue resistance, chipping resistance, and base part resistance, a hybrid laminated spring is constructed for the purpose. The present study focuses on an analysis and behavior of a monoleaf spring made of hybrid composite materials, i.e., carbon and E-glass fibers. It is observed that the natural frequency of a hybrid composite leaf spring is twice the frequency of a conventional leaf spring, particularly in the vertical direction, which means that the occurrences of resonance will be less. Also, it is observed that the stress produced in it is lower than that in a conventional leaf spring. The hybrid composite monoleaf spring proved to have better impact and tensile behavior than a steel one.

A PERFORMANCE EVALUATION OF LEAF SPRING REPLACING WITH COMPOSITE LEAF SPRING

The automobile industry has shown increased interest in the replacement of steel spring with fibre glass composite leaf spring due to high strength to weight ratio. Therefore the aim of this work is to reduce the weight and low cost fabrication of complete mono composite leaf spring and mono composite leaf spring with bonded end joints. Also, general study on the analysis and design. A single leaf with variable thickness and width for constant cross sectional area of unidirectional glass fibre reinforced plastic (GFRP) with similar mechanical and geometrical properties to the multi leaf spring, was designed, fabricated (hand- layup technique) and tested. The results showed that an spring width decreases hyperbolically and thickness increases linearly from the spring eyes towards the axle seat. The finite element results using ANSYS software showing stresses and deflections were verified with analytical and experimental results. The design constraints were stresses (Tsai-Wu failure criterion) and displacement. Compared to the steel spring, the composite spring has stresses that are much lower, the natural frequency is higher and the spring weight is nearly 85 % lower with bonded end joint and with complete eye unit.

Dynamics Modeling and Parameter Identification of Leaf Spring Based on RecurDyn

Based on discrete beam principle, a construction method for multi-body dynamics model of leaf spring in Recurdyn system is proposed. The contact force and friction between the interacting spring leaves are effectively simulated by defining the user subroutine translational forces in Recurdyn system. Both stiffness characteristic and hysteretic property of leaf spring are taken into account in the process of model building. The integration of genetic algorithm and the Recurdyn system are realized by using the development tool ProcessNet which provides by Recurdyn system and the reference of the AForge.NET open source framework. Based on the concept that the spring model with two leaves equivalently emulate multi-leaf spring model, the developed application program can effectively identify the parameters of the dynamics model and enable the model to reflect the characteristics of leaf spring more veritably. The correctness of the leaf spring dynamics model and the validity of the application program are verified by an actual example.

Analysis of multi leaf spring based on contact mechanics - a novel approach

A leaf spring, especially the longitudinal type is liable and persistent element in automotive suspension system. In the present scenario the composite materials are widely used in the automobile industries has shown a great interest in the replacement of steel spring due to high strength by weight ratio. Previous investigations focused on stresses and displacement analysis of single leaf spring for different materials. The present work aims to design and analysis of leaf spring for two different cases by considering the Young's modulus to yield strength ratio. In the first case the analysis deals with the design and analysis of a single cantilever solid triangle beam which is an equivalent beam of a spring with three leaves having uniform strength. In the second case a 3-beams of rectangular cross section has been considered which is equivalent to a spring with three leaves. The analysis was carried out based on contact mechanics approach. The results were compared, that the fiberglass composite leaf spring is suitable for high loading capacity, reliability and efficiency.

English

  In the present scenario, composites are widely used in most of the industries in place of steel, due to low weight to strength ratio. In automobile industry, one can think of replacing parts with composites. The aim of this paper is to suggest the best composite material for design and fabrication of complete mono composite leaf spring. A single leaf with variable thickness and variable width for constant cross sectional area of different composite materials, with similar mechanical and geometrical properties to the multi leaf spring, were modeled and analyzed. The finite element results using ANSYS software showing stresses and deflections were verified with analytical results. The design constraints were stresses and displacement. Compared to the steel spring, the composite spring has stresses and deflection that are much lower, and the spring weight is nearly 78% lower.   Key words: Leaf spring, composite, steel spring.

Finite element analysis on the static and fatigue characteristics of composite multi-leaf spring

This paper investigated the static and fatigue behaviors of steel and composite multi-leaf spring using the ANSYS V12 software. The dimensions of an existing conventional leaf spring of a light commercial vehicle were used. The same dimensions were used to design composite multi-leaf spring for the two materials, E-glass fiber/epoxy and E-glass fiber/vinyl ester, which are of great interest to the transportation industry. Main consideration was given to the effects of material composition and its fiber orientation on the static and fatigue behaviors of leaf spring. The design constraints were bending stresses, deflection and fatigue life. Compared to the steel leaf spring, the designed composite spring has much lower bending stresses and deflections and higher fatigue life cycles.

Computational model for analyzing the kinematics and compliance characteristics of a commercial vehicle’s front suspension system

This paper develops a computational model that can analyze the kinematics and compliance characteristics of the front suspension of a commercial vehicle. This computational model is called the flexible multi-body dynamic model because it is developed by interfacing the finite element model of the multi-leaf spring with the dynamic model of the front suspension. In this paper, the bump mode and roll mode tests are performed with a suspension parameter measuring device (SPMD). An excitation load for creating the bump mode and roll mode motion is applied on the left and right tires slowly in in-phase and out-of-phase modes. In the test, wheel rate, toe angle change, caster angle change, and camber angle change, which together represent the wheel alignment, are measured along with the longitudinal and lateral wheel center loci which together represent the wheel center trajectory change. The reliability of the developed computational model is verified by comparing the simulation results with the SPMD test results. The developed flexible multi-body computational model will provide useful information on kinematics and compliance characteristics in the earliest stages of the commercial vehicle design process.

A new iteration method for the calculation of the multi-leaf spring

A new iteration method for the calculation of the multi-leaf spring

Elasto-plastic leaf spring model

This paper presents a novel approach to the modelling of multi-leaf springs. The proposed leaf spring model is based on a material model analogy, as similar behaviour can be observed between the force-displacement relationship of leaf springs and the stress-strain relationships of engineering materials. The mechanisms governing the behaviour of materials and multi-leaf springs are discussed. Parameters are proposed that are able to describe the mechanical behaviour of the multi-leaf spring. The mechanical properties of the multi-leaf spring are combined with elasto-plastic material models to give the elasto-plastic leaf spring models. The elasto-plastic leaf spring models are implemented and their predictions are compared with experimental data. Good correlation is achieved for both sinusoidal and random displacement inputs.

대형트럭 다판 스프링과 테이퍼 판스프링의 진동특성 비교

대형트럭 다판 스프링과 테이퍼 판스프링의 진동특성 비교

A contact finite element algorithm for the multileaf spring of vehicle suspension systems

This paper presents an innovative finite element (FE) algorithm for the contact problem of the multileaf spring in vehicles. The well-established classic beam theory is adopted to construct the complementary strain energy variational. A piecewise contact stress pattern is approximated to the real contact state between two layered beams. The vector of nodal contact stresses is taken to represent primary state variables. To implement the principle of the least complementary energy, a quadratic programming (QP) problem with equality and unilateral constraints is formulated. The corresponding Kuhn-Tucker condition is equivalent to the linear complementary problem. In this study, Lemke's algorithm is applied to solve for the nodal stress vector and subsequently to determine the contact stress distribution over the contact surfaces between the layered beams. The algorithm is verified against experimental stress analysis, and it is found that the computation and test correlate well.

Influences of leaf shapes on performance of progressive multi-leaf springs

Influences of the shapes of spring leaves in a progressive multi-leaf spring were investigated using the semi-analytic model based on the Euler beam theory and the FEM model using ABAQUS. The trends in shifting of the locations of the contact point are found to change with the shapes of spring leaves. A change in the shapes of the spring leaves causes a change in the transition load of the stiffness of a progressive multi-leaf spring. If there is a quantum jump of the contact point locations a noise, which was absent, can be generated. It is suggested from the analyses based on the models and verified experimentally that the noise is generated by a small collision between the main and the help spring leaves when the contact point between them is shifted to a location at a finite distance. The influences of the leaf shape can be predicted more efficiently with the Euler beam model used in this investigation.

Noise from progressive multi-leaf springs and methods for its reduction

The noise produced by progressive multi-leaf springs was investigated. Experiments on progressive multi-leaf springs indicated that the source of the noise was contact between the main and help springs. The contact between the two leaves was examined by numerical simulations of spring deformation with changes in the applied external load; these simulations were carried out using ABAQUS. The parameters that potentially influence the unexpected noise in the progressive multi-leaf spring were investigated through a review of the structural characteristics of the spring. Two candidates were then selected as potential main parameters influencing the observed noise: impact by an abrupt contact and friction between the main and help spring leaves. Consideration of the results of numerical simulations, noise measurements and other observations led to the conclusion that translational jumping of the contact point between the main and help spring leaves is the main mechanism causing the noises emanating from the progressive multi-leaf spring. Based on this conclusion, modification of the shape of the help spring leaf is proposed to eliminate the abrupt contact caused by a jump of the contact position. Experiments showed that the tapping noise was successfully eliminated by modifying the shape of a help spring leaf without a noticeable change in the spring stiffness.

An efficient method for calculating the nonlinear stiffness of progressive multi-leaf springs

An efficient method for calculating the nonlinear stiffness of a progressive multi-leaf spring is developed and evaluated. This method utilises the interaction between the main and help springs that induces the nonlinearity. The main and the help springs are modelled as multi-leaf cantilever beams, and are then integrated as one by connecting the models for each side of the progressive multi-leaf spring at the centre-bolt. The results from the developed model are evaluated by comparison with those from the commercial FEA programme, ABAQUS. The nonlinear spring coefficients calculated by FEM analysis are very close to those calculated using the developed method. From the comparative evaluations, the developed method is shown to quickly evaluate the nonlinear spring behaviour of progressive multi-leaf springs with acceptable accuracy. Finally, comparison of the model results with those from an experiment measuring the stiffness of a progressive multi-leaf spring show that the model captures the mechanical characteristics of the spring to an accuracy acceptable for design use.

A Study on the Estimation of the Ride Quality of a Large-Sized Truck Using a Computer Model

This paper develops a computational model for estimating the ride quality of a cabover type large-sized truck in a double wheel bumpy ride test. The computational model is developed using ADAMS. To verify the developed model, an actual vehicle double wheel bumpy ride test is performed. In the test, the vehicle maintains a straight course with a constant velocity such that the front two wheels are passed the bump at the same time. The bump has the height of 60mm, and the width of 550mm. In the test, four velocities are used. They are 10kph, 20kph, 30kph and 40kph. Since the large-sized truck's center of gravity location is high, and its weight is heavy, it is a quite severe test condition to perform the test with more than 30kph velocity. In the test, vertical accelerations on the floor of the cab are measured. The measured accelerations are compared to the simulation results. From the comparison, it is shown that the developed model can predict not only the measured acceleration's tendency but also peak accelerations quite well. In this paper, the validated model is utilized to compare the ride quality between a vehicle with a multi-leaf spring and a vehicle with a tapered leaf spring in the front suspension system in a double bumpy ride test.

Analysis of Hysteresis Behavior of Leaf Springs with FEM. 2nd Report, Application of Special Contact Element to Multi-Leaf Spring Modeled by Beam Element.

With the use of a special contact element by which the frictional contact behavior between leaves is systematically expressed in combination with beam finite elements, the load-deflection hysteresis has been analyzed by a finite element method for two kinds of multi-leaf springs i.e., conventional and progressive types. The load-deflection curve obtained by FEM is neally linear for the conventional type, whereas the curve is highly nonlinear for the progressive one. The numerical results are very close to the experiments in both types of leaf springs. In particular, the proposed method can predict well the hysteresis behavior of the spring. Thus, the proposed FEM analysis using beam elements can be used for designing various types of multi-leaf springs.

Fundamental Analysis of Lateral Vibration of a Leaf Spring

The purpose of this paper is to clarify the lateral vibrational characteristics of a leaf spring. The frequency equations are formulated under the assumption so-called "point pressure". For a number of leaf springs, the natural frequencies and their normal modes are calculated, and good agreement with experiments is obtained. Furthermore, for a multi-leaf spring, it is found that the analytical method based on the stepped beam hypothesis fails to predict some of the significant modes in the high-frequency region, while the presented method yields favourable numerical data.