Processing and Manufacturing Flashcards

In metal forming, the flow stress of a material is defined as the:

Answer: Stress required to continue plastic deformation at a given strain and strain rate

Flow stress is the instantaneous stress required for continued plastic deformation, which varies with accumulated strain, strain rate, and temperature.

Shot peening is a surface treatment that improves fatigue life by introducing:

Answer: Compressive residual stresses on the surface

Shot peening bombards the surface with small spherical media, plastically deforming it and introducing compressive residual stresses that retard fatigue crack initiation and growth.

The purpose of normalizing heat treatment in steel is to:

Answer: Refine grain structure and reduce internal stresses by air cooling from above Ac3

Normalizing heats steel above its upper critical temperature (Ac3) and then air cools it, refining grain size and producing a uniform microstructure with slightly higher strength than fully annealed steel.

Electroplating of nickel or chromium on steel parts provides:

Answer: Corrosion and wear resistance with a metallic surface finish

Electroplated coatings provide a functional surface layer with improved corrosion resistance, wear resistance, and cosmetic finish while the substrate provides structural strength.

In die casting, the die material must have high hot hardness and thermal fatigue resistance because:

Answer: Dies experience repeated thermal cycling from injecting hot molten metal

Die casting dies undergo repeated rapid heating and cooling cycles as molten metal is injected and parts are ejected, requiring hot-work tool steels that resist thermal fatigue cracking.

Carburizing is a case hardening process that increases surface carbon content to improve:

Answer: Surface hardness and fatigue strength while maintaining a tough core

Carburizing diffuses carbon into the steel surface to create a hard, wear-resistant case after quenching, while the low-carbon core remains tough and ductile.