In a joint, how is joint penetration defined?

Joint penetration refers specifically to the depth at which the weld metal fuses with the base metal in a joint. This definition emphasizes the important aspect of the weld's effectiveness: the weld metal must adequately penetrate the base material to ensure a strong, cohesive bond that meets structural integrity requirements.

When considering the context of welding processes, joint penetration is crucial because insufficient penetration can lead to weak welds that might fail under load. The measurement of how far the weld metal extends from the weld face into the joint is a critical factor in determining the quality and strength of the weld.

The other choices focus on different aspects of a joint or welding but do not accurately capture the specific definition of joint penetration. For example, discussing the depth of a joint or the thickness of the material does not reflect the interaction between the weld metal and the base material. Understanding joint penetration enables welders to assess and control weld quality effectively.