TENSILE STRENGTH is the measure of the force or stress required to pull something (resistance to lengthwise stress) to the point where it breaks or before permanent deformation results. Usually it is the maximum amount of tensile stress that it can be subjected to before failure, although the definition of failure can vary according to material type and design methodology.
In the fields of material science, mechanical engineering and structural engineering there are three typical definitions of tensile strength:
• Yield strength: the stress at which material strain changes from elastic deformation to plastic deformation, causing it to deform permanently.
• Ultimate strength: the maximum stress a material can withstand.
• Breaking strength: the stress coordinate on the stress-strain curve at the point of rupture.
Tensile Strength can relate to the Toughness of products. The higher the tensile strength a product possesses, the more difficult or tougher it is to stretch. This property can be a positive feature in some products, for example in rope and rubber bands to an extent, but is regarded as unacceptable or negative in chewing gum, mozzarella cheese, noodles or Christmas crackers.
EXTENSIBILITY/ELONGATION is the degree (distance) to which a product can be extended/stretched before breaking. It is related to the 'elasticity' of a product. It is commonly the textural property possessed by raw baked goods (e.g. dough, pastry), cooked baked goods and pasta (e.g. pancakes, tortillas, noodles) but can be a novel property of confectionery products (e.g. liquorice, chewing gum).
Friction can be a limitation to us; for example, the friction of packaging can be a major limiting factor in the speed of packing machines. Additives are often used to improve the lubricity of surfaces; this is known as 'slip'. Polythene is added to packaging to improve slip characteristics.
Typical properties that can be obtained from a texture analyser graph:
Tensile Strength, Burst Strength, Distance to Burst, Resistance to Extension/Toughness, Extensibility, Stretch Quality, Elasticity, Tug Force, Tear Strength, Elongation
Typical Texture Analyser graph with annotated properties of material tension to failure
Typical Probe/Fixture used for Measurement:
Tensile Grips and all fixtures that allow successful holding of a product in order to test in a tensile manner >>
The above are only typical examples of tensile strength measurement. We can, of course, design and manufacture probes or fixtures that are bespoke to your sample and its specific measurement.
Once your measurement is performed, our expertise in its graphical interpretation is unparalleled – no-one understands texture analysis like we do. Not only can we develop the most suitable and accurate method for the testing of your sample, but we can prepare analysis procedures that obtain the desired parameters from your curve and drop them into a spreadsheet or report designed around your requirements.
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