"反射式探伤法" can be translated as "reflection flaw detection method" or more specifically in some technical contexts as "reflection ultrasonic flaw detection method" if it specifically refers to ultrasonic testing (a common application of reflection-based flaw detection).
"Reflection flaw detection method" is a general term that can be applied to various non-destructive testing techniques that rely on the reflection of waves (such as ultrasonic waves, electromagnetic waves, etc.) to detect flaws.
"Reflection ultrasonic flaw detection method" is more specific, indicating that the method uses ultrasonic waves and relies on their reflection to identify flaws in materials.