Connecting rod fasteners are preloaded during assembly such that the resulting tightening stress_________________?
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Answer: B. approaches yield point
Explanation
Connecting rod fasteners are preloaded during assembly to tension levels approaching yield point. High preload prevents joint separation and cyclic fatigue failure under alternating inertial loads. Engineers specify precise tightening torques to achieve the required high stress without yielding. Connecting rods experience severe tensile and compressive forces during every engine cycle. Bolt preload creates a clamping force that exceeds the external separating loads on the joint. Yield point represents the stress threshold where permanent plastic deformation begins in steel.
High performance racing and diesel engines rely on properly torqued rod bolts for reliability. Connecting rod bolt failure can cause catastrophic engine destruction at high operating speeds. Mechanics use torque-angle measurement methods to achieve accurate high-stress bolt preloads. Holding parts together with minimal stress would lead to joint separation and fatigue failure. Stopping at fifty percent of yield underutilizes the potential clamping force of the fastener. Dividing yield by a safety factor provides working stress limits for static parts, not rod bolts.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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