In the hot forged steel sleeve method, what causes additional bond and increases tensile strength as the assembly cools?

• A. Contraction of the Sleeve Upon Cooling
• B. Expansion of the Bars Upon Cooling
• C. Rolling of the Sleeve
• D. Cooling Rate Control

Answer: (A)

When the sleeve is heated and expanded to fit around the reinforcing bars, the key bonding effect comes from what happens as it cools. The sleeve contracts around the bars, creating an interference fit that presses tightly on them. This squeeze increases friction and causes a stronger mechanical grip, adding bond strength and thus higher tensile strength for the joint as the assembly cools.

The other ideas don’t drive this bonding mechanism: the bond isn’t primarily from the bars expanding, nor from any rolling of the sleeve, and while controlling cooling rate can influence stresses, it doesn’t itself create the additional bond the contraction provides.