Session 8 Impact Test

7/23/2019 Session 8 Impact Test

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IMPACT TEST

Impact test - Measures the ability of a material to absorb

the sudden application of a load without breaking.

Impact energy - The energy required to fracture a

standard specimen when the load is applied suddenly.

Impact toughness - Energy absorbed by a material,

usually notched, during fracture, under the conditions of

impact test.

Fracture toughness - The resistance of a material tofailure in the presence of a flaw.


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(c)2003 Brooks/Co le, a division of Thomson Learning, Inc. Thomson Learning

is a trademark used herein under license.

Figure 6.26 The impact test: (a) The Charpy and Izodtests, and (b) dimensions of typical specimens


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Properties Obtained from the ImpactTest

Ductile to brittle transition temperature (DBTT) - The

temperature below which a material behaves in a brittle

manner in an impact test. Notch sensitivity - Measures the effect of a notch,

scratch, or other imperfection on a materials properties,

such as toughness or fatigue life.


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(c)2003Brooks/Cole,adivisionofThomsonL

earning,

Inc.

ThomsonLearning

isatrademarkus

edhereinunderlicense.

Results from a series of Izod impact tests for a super-tough nylon thermoplastic

polymer.


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(c)2003Brooks/Cole,adivisionofThomsonL

earning,

Inc.

ThomsonLearning

isatrademarkuse

dhereinunderlicense.

The Charpy V-notch properties for a BCC carbon steel and a FCC stainless steel. The FCC

crystal structure typically leads top higher absorbed energies and no transitiontemperature.


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(c)2003Brooks/Cole,adivisionofThomsonLearning,

Inc.

ThomsonLearning

isatrademarkusedhereinunderlicense.

The area contained

within the true stress-true strain curve isrelated to the tensiletoughness. Althoughmaterial B has a loweryield strength, it absorbs

a greater energy thanmaterial A. The energiesfrom these curves maynot be the same as thoseobtained from impacttest data.


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The data below were obtained from a series of Charpy impact tests

Performed on four steels, each having a different maganese content.

Plot the data and determine (a) the transition temperature (defined

by the mean of the absorbed energies in the ductile and brittle regions)

(b) The transition temperature (defined as the temperature that provides

50 J of absorbed energy)

What would be the minimum manganese allowed in the steel if a part

is to be used at 0 C?


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Choose from the following list of materials, the material that will perform thebest for each case described below.

Materials: Aluminum alloy, SiC, steel1080, steel 0.05% C and 2% de Mn.

a) A material to manufacture a tank for liquid nitrogen at 77 K.b) A Steel to support the structure of a sled.c) A material that could keep high stiffnes at high temperatures with no impact

loads applied.


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Documents

Session 8 Impact Test