Visual Testing (VT) Practice Exam 2025 – Comprehensive All-in-One Guide for Exam Success!

Creep is the phenomenon that illustrates how metals can become weaker when they undergo continuous deformation under steady stress at elevated temperatures. As materials are exposed to high temperatures and maintained under a constant load, they will slowly deform over time. This gradual and time-dependent deformation occurs as the metal's internal microstructure undergoes changes, such as movement of dislocations and grain boundaries.

The result of creep is that the material can lose its ability to bear loads effectively, leading to a reduction in its strength and potentially resulting in failure. This is particularly important in applications involving high-temperature environments, such as in turbines or pressure vessels, where metals are subjected to prolonged stress and heat.

In contrast, the other options like thermal fatigue and stress corrosion cracking refer to different phenomena. Thermal fatigue is related to cyclic thermal stresses that cause cracking, while stress corrosion cracking is the result of chemical processes that weaken a material when it is subjected to tensile stress in a corrosive environment. Corrosion reduction also does not address the specific mechanism of deformation and strength loss due to sustained stress at high temperatures.