Which characteristic indicates wood is less sensitive to repeated loads than iron or steel?

Which characteristic indicates wood is less sensitive to repeated loads than iron or steel?

• A. Orthotropic Behavior
• B. Creep Characteristics
• C. Splits
• D. Fatigue Characteristics

Answer: (D)

The main idea is how materials respond to repeated, cyclic loading—that is, fatigue behavior. Fatigue characteristics describe how a material behaves under many load cycles, including how cracks initiate and propagate until failure. Metals like iron or steel are known to fail at stress levels well below their static strength under repeated loading, so fatigue is a major design concern for them. Wood, by contrast, tends to depend more on moisture, direction, and time-related effects rather than classic metal fatigue, so its response to repeated loads is less pronounced and more variable. Therefore, fatigue characteristics best indicate why wood is less sensitive to repeated loads than iron or steel. The other options describe orthotropic directionality, time-dependent creep under a steady load, and cracking from various causes, none of which directly capture the material’s response to cyclic loading.

The main idea is how materials respond to repeated, cyclic loading—that is, fatigue behavior. Fatigue characteristics describe how a material behaves under many load cycles, including how cracks initiate and propagate until failure. Metals like iron or steel are known to fail at stress levels well below their static strength under repeated loading, so fatigue is a major design concern for them. Wood, by contrast, tends to depend more on moisture, direction, and time-related effects rather than classic metal fatigue, so its response to repeated loads is less pronounced and more variable. Therefore, fatigue characteristics best indicate why wood is less sensitive to repeated loads than iron or steel. The other options describe orthotropic directionality, time-dependent creep under a steady load, and cracking from various causes, none of which directly capture the material’s response to cyclic loading.