What stress magnitude is required to initiate plastic yielding_________________?
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Answer: A. considerably greater than that necessary to continue it
Explanation
Static friction or initial yielding requires greater stress to start than to continue. Overcoming initial molecular bonding and static stiction demands higher peak force thresholds. Once plastic flow or motion is initiated, lower stress levels sustain ongoing movement. Materials exhibit yield drop phenomena where upper yield points exceed lower yield values. Dislocation movement in crystal lattices requires more energy to break free initially. Static friction coefficients are traditionally higher than kinetic friction coefficients.
Manufacturing metal forming processes require high initial press loads to start plastic deformation. Understanding yield behavior prevents unexpected structural distortions during sheet metal stamping. Machine tool designers account for breakaway torque requirements in heavy industrial drives. Stating initial stress is lesser contradicts established static friction and yield phenomena. Options mentioning stopping stress are irrelevant to the initiation of plastic yielding. Equal stress levels fail to account for the higher threshold needed to start yielding.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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