The yield strength of a strand is what percentage of its ultimate strength?

• A. 50%
• B. 70%
• C. 90%
• D. 100%

Answer: (C)

The yield strength of a material is typically defined as the stress at which it begins to deform plastically. In many materials, the yield strength is often expressed as a percentage of the ultimate tensile strength (UTS), which is the maximum stress that a material can withstand before failure.

In metals and other structural materials, it is commonly observed that the yield strength is about 70% of the ultimate tensile strength. This percentage can vary based on the specific material and its treatment, but 70% is a widely accepted standard in engineering and design practices.

Choosing 90% would suggest a material that has very little plastic deformation capability before reaching its ultimate strength, which is not characteristic of most structural materials. The other options, such as 50% and 100%, also do not align with the typical ranges observed in engineering contexts. Therefore, 70% is the most accurate representation of the relationship between yield strength and ultimate strength for a broad range of materials.