What is a puncture/penetration test?
In a penetration or puncture test a probe is made to penetrate into the test sample and the force necessary to achieve a certain penetration depth or the depth of penetration in a specified time, under defined conditions, is measured and used as an index of e.g. hardness, firmness, toughness.
Both test principles cause an irreversible change in the sample and assume that the sample being investigated is of larger area than the contact area of the probe in use; a sample smaller than the probe contact area would assume compression principles.
The higher the force reading (or the smaller the penetration depth – if measuring in constant force), the more resistant is the material.
Why perform a puncture/penetration test?
Puncture and penetration tests are commonly used in the testing of the ripeness and bioyield point of fresh fruits and vegetables, the ripeness/hardness of cheese, hardness of confectionery and the spreadability of butter and margarine. They are suitable tests for those products that are not-self supporting or are contained.
Penetration tests have also been used extensively for testing the rigidity of gels. The best known is the Bloom test, a standard test for measuring the gelling power of edible gelatin. There are many consumer products that need a measure of the force required to puncture packaging or the force required to actuate a product and deliver its contents.
Penetration testing may sometimes be the only possible means of testing a hard product if the force capacity of the instrument is limited.
Typical properties that can be measured within a puncture/penetration test
Puncture/penetration tests are typically chosen to measure:
Firmness, gel strength, dipping consistency, product toughness, fracture force, 'cake' breaking strength, semi-solid consistency, actuation force
To understand how these properties are measured visit the Textural Properties page
Typical probes/fixtures used for puncture/penetration tests
Penetration tests usually employ cylinders (2mm – 10mm diameter), cones, ball probes or needles. Small probes are particularly recommended for the assessment of rupture force or for the testing of multiple structure products e.g. measuring skin/crust/coatings and continuing to test the underlying material.
Ball probes are recommended where the surface of the sample is not flat or the sample is extremely thin.
Hemispherical probes are recommended for imitating a finger when assessing actuation force.
Standard cylinder, cone, needle, ball and hemispherical probes are available in delrin, stainless steel or aluminium but bespoke probes in other materials and dimensions can be designed and made to order.
Multiple penetration tests
Using multiple penetration probes within a test is recommended for products with variable structure either due to nature (fruits, vegetables, meat) or design (marmalade, petfood, confectionery) and is sometimes the only means of being able to acquire repeatable data from inherently variable products.
To understand how these probes are designed and manufactured click here. Other probes/fixtures and accessories are available to accommodate many specialist needs, or can be designed and manufactured to a specific customer brief.
Items with codes prefixed 'HDP/' must be used with the HDP/90 Heavy Duty Platform.
Items tagged * are Community Registered Designs.