Elastomers for High Frequency Applications

Presented by Adam Fox CEng MIMechE AMIOA, Director, Mason UK Ltd

This talk discusses these issues but is centred around a particular and current case study where a listed structure is being underpinned and isolated from existing foundations by introducing natural rubber supports. The combination of vibration from an underground rail system and the building structure combine create a high frequency, 100 Hz, for building isolatin challenge.

The nearby underground rail source contributes significant energy at the frequencies of concern. The mechanics of this and the principles of isolation are discussed, in addition to the practical solution derived. This includes details on the rubber formula and moulding process, which is essential for a long-lasting system critical to structural stability. 

Presented by Mark Bauman, Engineering Analyst, Endurica

Fatigue is normally considered with the static application of loads, however, for vibration isolation systems the duty cycle is highly dependant of the properties of the isolators and can have a significant impact on the dynamic loading up to 200 Hz. In the present case, the compressor is mounted on four rubber gromments which partially isolate the basepan from compressor motions. In order to assure adequate grommet durability under typical operation, critial plane analysis has been applied to evaluate the safety factor against fatigure failure. The grommet loading cycle was simulated using the finite element method, and validated against measurements of natural frequency. 

Presented by Brice Taillet, Europe Sales Manager material testing, Merrow Scientific

The measurement of materials viscoelastic properties at high frequency is required in many industrial applications: tires performance prediction and safety, noise and vibration reductions in mechanical engineering, acoustic design in vehicles, new challenges of electric vehicles, industrial process machinery, defense ships and submarines, sport goods...

Dynamic Mechanical Analysis (DMA) is a major technique for measuring viscoelastic properties: easy to operate and giving precise and high reproducible data. This talk focusing on recent advances in the technology moving up upper frequency of 10kHz...

Presented by Aaron Graham, DPhil candidate, University of Oxford

Characterising the mechanical response of ultra-soft materials is challenging, particularly at high strain rates and frequencies. Time Temperature Superposition (TTS) can sometimes be used to mitigate these limitations, however not all materials are suitable for TTS. In the current study, a novel experimental apparatus and methodology was developed and validated using low modulus silicone elastomers as well as biogels as model materials. The full field visco-elastic shear response was characterised over a wide range of deformation frequencies (100-1000 Hz) and amplitudes using Digital Image Correlation (DIC) and the Virtual Fields Method (VFM). This methodology allows for the extraction of full-field material properties that would be difficult or impossible to obtain using traditional engineering techniques.