impact strength
TRANSCRIPT
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Impact Strength
• Impact Strengths the capability of the material to withstand a suddenly applied load and is expressed in terms of energy.• it expressed in j/m or kg cm/cm of notch. • Its a mechanical property of any material.
Significance: impact strength of material determines the toughness of material it means resistance to high speed loading
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Factors affecting the impact strength
• Rate of loading• Temperature• Orientation• Processing condition and types• Degree of crystallinity , molecular weight
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Impact test for plastics can be categorized in three major types: 1.pendulum impact test : charpy, izod ,tensile impact test2.Drop weight impact :
3.Instrumented impact test :
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Test specimen and conditioning
For Izod test : 64.5mm × 12.7 mm × 3.2mmFor charpy test : 127mm × 12.7mm × 3.2mm
Notch : the angel of notch is 45°± 1° with a radius of 0.25 mm.
Laboratory atmosphere is 23 ± 2°C and 50 ± 5 % RH
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Notched Izod Impact Strength Specimen is held as a vertical cantilevered beam and is broken by a pendulum. Impact occurs on the notched side of the specimen.
The test was developed in “1905” by the French scientist Georges Charpy. Charpy Impact Strength Specimen is held as a simply supported beam and is impacted on the side opposite the notch. This method is no longer covered under ASTM D256 but is still reported as such.
Izod / charpy impact test
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Equipment :
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Izod impact
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Charpy Impact
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What we know form impact strength test :
• Shock loading characteristics of material• Test result used for comparison of material, manufacturing condition, material texture design and treatment .
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Factors Affecting Test Result
• Notch
• Specimen thickness
• Specimen preparation
• Temperature
• Filler and other additives
• Limitations
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References
• Handbook of Plastics Testing and Failure Analysis by Vishu Shah• Google books ,Google scholar• Fundamentals of plastics testing by S.K. Nayak• www.polymer-filler.blogspot.com
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