Fatigue failure analysis of anti-vibration rubber spring

The stress-endurance (S-N) method has been widely used in metal fatigue in the railway industry over many years. However, when this method is applied to rubber-like materials, it seems not as successful as when it is applied to metallic materials. Recently, an integrated fatigue evaluation programme has been carried out with the aim of improving the design of antivibration components in response to the increasing demands of the rail operating environment. This programme will also make simulations more reliable and relevant to industrial applications, especially for the fatigue design of rubber springs used in rail vehicle suspensions. The continuum mechanics (total life) approach has been used to characterize the fatigue life in terms of the cyclic stress range (S-N curve). It is suggested that the effective stress, sigma(f), can be used as a parameter (taking three principal stress ranges into consideration) to evaluate fatigue failure. The initial verification of this approach has been carried out on two types of rubber spring. The results have shown good agreement between the fatigue test of the components and the simulation based on this approach.

An approach to evaluate the service life of rubber springs used in rail vehicle suspensions

Fatigue failure investigation on anti-vibration springs

The temperature of rubber or rubber-metal springs increases under cyclic
 loading, due to hysteresis losses and low rubber thermal conductivity.
 Hysteresis losses correspond to energy dissipation from the rubber, which is
 primarily converted into heat. This well-known phenomenon, called heat
 build-up, is the primary reason for rubber aging. Increase in temperature
 within the rubber compound leads to degradation of its physical and chemical
 properties, increase in stiffness and loss of damping capability. This paper
 presents a novel procedure of heat generation prediction in rubber or
 rubber-metal springs. The procedure encompasses the prediction of hysteresis
 loss, i. e. dissipated energy within the rubber, by finite element analysis
 and application of a modern visco-plastic rubber constitutive model. The
 obtained dissipated energy was used as an input for transient thermal
 analysis. Verification of the proposed procedure was performed by comparison
 of simulation results with experimentally obtained data during the dynamic
 loading of the rubber specimen. The proposed procedure is highly
 computationally efficient and it enables time integration, which can be
 problematic in coupled mechanical thermal analysis.

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Prediction of heat generation in rubber or rubber-metal springs

Rubber and Rubber-Like Materials, Finite Element Analyses and Simulations, An Addendum : A Bibliiography (1997-2003)

Rubber and rubber-like materials, finite-element analyses and simulations, an addendum: a bibliography (1997?2003)

Rubber-to-metal bonded springs are vital antivibration components for rail vehicles. Metacone rubber springs are widely used as a primary spring on a rail vehicle fitted at the wheel axle b...

Fatigue design of rubber springs used in rail vehicle suspensions

This paper reports on an integrated real-time simulation and experimental program that was carried out on a rubber spring anti-vibration part used as a rail vehicle component. This work was designed to ensure that any temperature rise inside an anti-vibration part does not exceed the design requirement in accelerated fatigue tests. Results from both testing and simulation indicate that the energy loss per cycle of the rubber spring, under fixed dynamic amplitude, does not depend on the loading frequency. Therefore, the energy loss per cycle can be more easily obtained using a conventional quasi-static loading procedure than from conducting more complicated dynamic tests. The method presented here is shown to be reliable for evaluating the temperature effects caused by dynamic loading. A detailed thermal stress analysis can also be carried out by feeding back the thermal effects. Key rubber parameters obtained from the authors' material testing laboratory are presented here as references for similar applications in railroad industries.

A method to predict the heat generation in a rubber spring used in the railway industry

SYNOPSIS A case study is reported on the design of a Metacone mounting used as a primary spring fitted at the wheel axle box on a railway vehicle. In use the rubber layers are loaded in shear and compression and the Metacone mounting provides controlled complicance along three axes. Requirements for increased service life and dimensional limitations (implying high strain levels) have led to an ever closer focus on suspension spring design. (In the current example the general space envelope was 250 mm in diameter by 250 mm high.) Furthermore, as was the case here, end of life is often defined in terms of clearly noticeable cracks or changes in stiffness rather than final failure. The location, formation and early stage development of fatigue cracks are therefore key issues in such cases. Design methods involving finite element (FE) and fatigue life analysis (FLA) were used to redesign the Metacone. As a result the life of the Metacone undergoing customer-specified (single axis) fatigue testing was increased more than ten-fold.

Fatigue Life Investigation in the Design Process of Metacone Rubber Springs

Over many years of design and application experience, our products have fulfilled the customers required service life with very few fatigue failure problems. Recently an integrated fatigue evaluation programme has been carried out at the company aiming at improving the design of our anti-vibration component. This programme will also enable the FE simulation more reliable and directly associated to the industrial applications. Continuum mechanics (total life) approach has been used to characterise the fatigue life in terms of the cyclic stress range (S-N curve). It is suggested that an effective stress sigma(f) can be used as a parameter (as a function of three principal stresses) to evaluate fatigue failure based on the uniaxial fatigue test. The initial verification of this approach has been carried out on one of our products (Metacone mountings). The results have shown a good agreement between the uniaxial fatigue test and the real component test.

W X Wu

Papers

An approach to evaluate the service life of rubber springs used in rail vehicle suspensions

Fatigue design of rubber springs used in rail vehicle suspensions

A method to predict the heat generation in a rubber spring used in the railway industry

Fatigue Life Investigation in the Design Process of Metacone Rubber Springs

Fatigue life prediction and verification of rubber to metal bonded springs