🔍 Key Concepts

• Radiographic testing (RT) – how different types of discontinuities (cracks vs. porosity) show up on film • Difference between light (less dense) and dark (more dense) areas on a radiograph and what that means about material thickness or voids • Effect of crack orientation vs. radiation direction on detectability in radiography

💭 Think About

• How would a void or gas pocket (porosity) affect the amount of radiation passing through the metal compared to solid metal? Should that make the film lighter or darker in those spots? • Think about a crack: is it more like missing material (a void) or extra material? How does that affect the shading on the film, and would it show as a light line or a dark line? • If a crack is oriented at an angle to the radiation beam, does that make it easier or harder for the beam to see the full extent of the crack? Would detection be guaranteed in that case?

✅ Before You Answer

• Review how areas of less metal (thinner or voids) appear on film compared to thicker/denser areas • Confirm what porosity actually looks like on a weld radiograph (shape and film density) • Consider whether radiographic detection of cracks is ever “certain” for all orientations of the crack relative to the radiation beam