What should the drawing stress in a wire drawing operation never exceed?

In a wire drawing operation, the drawing stress must never exceed the yield strength of the work metal. The yield strength represents the maximum amount of stress that a material can withstand while still being able to return to its original shape when the stress is removed. If the drawing stress exceeds this limit, the material will undergo permanent deformation, which is undesirable in the wire drawing process as it aims to shape the metal without creating defects or altering its properties irreversibly.

Yield strength is a critical parameter that ensures that the wire can be drawn to the desired dimensions while maintaining its structural integrity. Staying within this threshold allows for effective deformation of the material while retaining the necessary mechanical properties, such as ductility and tensile strength, in the final product.

In contrast, exceeding the tensile strength or ultimate tensile strength would lead to fracture or breakage of the material, while compressive strength is not relevant since wire drawing primarily involves tension rather than compression. Therefore, it is crucial to control the drawing stress to not surpass the yield strength during the wire drawing process.