Engineering aspects of natural rubber: Finite element analysis and fracture mechanisms
Dr. A. Stevenson, Managing Director of the Materials Engineering Research Laboratory (MERL) UK
Natural rubber has proven to be a versatile and durable material for a wide range of engineering applications. Its main advantage over synthetic elastomers is its high tear strength and fatigue resistance for application that do not require prolonged service at elevated temperatures. Low cost is also a considerable advantage for high volume applications, although of less concern for many critical engineering components where the engineering costs outweigh the cost of materials.
Natural rubber components continue to hold an important place in non-tyre automotive components as well as the material usage in tyres. Natural rubber has also found an important niche in demanding offshore engineering components and in one recent case laminated natural rubber flexelements were installed as primary load bearing components in a deep-water offshore platform for the Norwegian sector of the North Sea, after fatigue testing up to 5000 tonnes.
The first part of this lecture will review the basic properties of natural rubber that are important for engineering applications. This will be illustrated by a number of engineering applications from the past 150 years.
In the second part of the lecture some new advances will be presented from research at MERL on finite element and fatigue life analyses and multiaxial testing.
New computer software has been developed that integrates fracture mechanics and fatigue life calculations to enable the number of service cycles to a certain depth of crack to be calculated. Current research is also underway to integrate this approach with the long term effects of chemical ageing. For many modern engineering components it is important to characterise the combined effects of loading in different directions simultaneously (eg. combined shear with compression).