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14 Cards in this Set
- Front
- Back
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heat treatment does what for fracture toughness |
increases both the hardness and the resistance against cracking |
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3 groups of polymers |
thermoplastics thermosetting polymers elastometers |
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thermoplastics |
long coil chains, not crosslinked, low-strength, low-modulus |
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thermosetting polymers |
crosslinked chains to form 3d networks, enhances polymer strength and prevents softening upon reheating |
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elastometers |
rubbers, can be deformed to large strains with most deformation recoverable, do not crosslink and return to coiled config |
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creep occurs |
in polymers exhibiting continued deformation under constant stress |
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Stress relaxation |
attributed to the internal structure reorganization resulting from the movement of polymer chains, the breaking and reforming of secondary bonds between the chains, and the mechanical untangling and recoiling of the chains |
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Cyclic Loading Responses |
-purely elastic -elastic shakedown -plastic shakedown -ratchetting |
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Purely Elastic |
at light loads, the yield condition is not satisfied at any material point and the response is purely elastic |
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Elastic Shakedown |
yielding occurs in some regions during initial loading, but residual stresses produced upon unloading and/or hardening of the material cause a purely elastic steady-state response |
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plastic shakedown |
steady-state response of closed cycle of plastic strain |
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ratcheting |
cyclic loading leads to steady accumulation of unidirectional plastic strain |
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Cyclic Loading |
Stress is applied in one direction for a set amount of time and then applied in the other direction of the same but opposite magnitude |
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if the stress increases with cyclic loading, |
the material exhibits cyclic hardening behavior |
