Rubber & tire industry tuning into durability modelling

Belval, Luxembourg – New advances and applications in the field of rubber durability modelling were presented at the Endurica Community Conference held 5-6 May in Belval, Luxembourg.

In general, the conference put a spotlight on how fracture mechanical analysis and simulation modelling are gaining traction across rubber materials and product R&D.

More particularly, the wide-ranging presentations suggested growing adoption of predictive, physics-based approaches to optimising fatigue, wear and ageing properties.

Opening the event, Endurica founder & president Will Mars announced new case studies, including one for automotive OEM Geely: modelling a vehicle suspension structure incorporating 32 bushings along with additional motor mountings.

Working with suppliers, Endurica software was applied to help optimise the performance and durability of the elastomer materials for the NVH elements.

The complex analysis also involved applying road-load data to provide a virtual proving ground for testing of the components, system and vehicle, explained Mars.

Also presented was an offshore, application for Wave Energy Scotland, where Endurica software supported materials characterisation and service-life estimation of combined ageing and fatigue effects in a marine environment.

Led by Tension Technology International – with input from Wacker, ACE Laboratories and Rubber Heart – the Scottish project aims to tap the energy generated by the motion of the sea on flexible materials/structures.

Presentations at the Luxembourg conference included those focused on use-cases in the railway industry, among them a paper by Dr Nina Heinrich, lead structural engineer at Trelleborg Antivibration Solutions.

In Belval, Heinrich reported on a project to assess the 3D loading of a rubber bushing connecting the motor to the gear unit of a railway vehicle. The component, she explained, is subjected to complex fatigue loading comprising multiple load blocks with variable frequency loads in three directions.

<Trelleborg Antivibration Solutions: 3D loading of a rubber bushing connecting the motor to the gear unit of a railway vehicle

According to Heinrich, Endurica's EIE ‘interpolation engine’ proved effective in reconstructing strain histories, in an application where conventional 'pointwise' FEA would have been “computationally inefficient.”

Among other findings, the project showed that EIE could reconstruct the strain effects efficiently, while also tracking the relationship between sample density and modelling accuracy.

Primary railway suspension elements were the focus of a fatigue simulation study by Jose Javier Egurrola, polymers technology director at the Leartiker technology centre, based in the Basque region of Spain.

Integrating specialised programmes, including Abaqus and Endurica, simulated models were produced to represent critical rubber behaviours, including hyperelasticity, the Mullins effect and viscoelasticity.

The precise simulation of fatigue-related properties, said Egurrola, marked a “milestone in enabling the prediction of stiffness evolution in rubber suspensions during the design phase, optimising homologation conditions and offering significant competitive advantage.”

Primary railway suspension elements were the focus of a fatigue simulation study at Leartiker>

Tire applications

Tire applications also featured prominently at the conference, including a talk by Christian Kipscholl, president of Coesfeld Materialstest, a Dortmund, Germany producer of materials testing equipment for various industries.

Noting the growing importance of understanding tire-wear properties, Kipscholl detailed how Endurica simulation tools can support the analysis of wear and abrasion via controlled generation and quantification of materials-loss and wear particles.

Endurica software, he explained, is also being used alongside Coesfeld’s latest fatigue analysis systems, including equipment designed to provide new insights into crack growth – using crack-initiation energy as a key rubber material parameter.

Another conference speaker, Lewis Tunnicliffe, R&D director, rubber carbon blacks, Birla Carbon, majored on the fracture mechanics of natural rubber compounds incorporating standard carbon black and recovered carbon black.

Tunnicliffe's study showed how advanced analysis of crack growth resistance could be used to optimise the filler components to enhance the fatigue life and performance of rubber materials.

CVJ boot study

Challenges around the predicting the fatigue life of constant velocity joint (CVJ) boots was the topic of a paper by Peiter Volgers, manager CAE-EMEA at Celanese Engineered Materials.

<Celanese applied numerical simulation approach to accurately predict the fatigue performance of CVJ boots

While OEMs can typically require testing of the drivetrain components using a loading programme defined in a climate chamber, this approach is both time- and cost-intensive.

Citing an example of a thermoplastic elastomer CVJ boot, Volgers detailed how numerical simulation can accurately predict the fatigue performance of CVJ boots – preventing premature failures.