Stress Concentration Factors and Fracture Mechanics in Materials Science, Schemes and Mind Maps of Mechanics

Download Stress Concentration Factors and Fracture Mechanics in Materials Science and more Schemes and Mind Maps Mechanics in PDF only on Docsity! Stress concentration • Transition of cross sections High stresses • More abrupt transition Higher stresses Fillet Abrupt change Stress “flow lines” crowd High stress concentration Smoother change “Flow lines” less crowded Lower stress concentration Figure 6.1 Rectangular plate with hole subjected to axial load. (a) Plate with cross-sectional plane. (b) Half of plate with stress distribution. Text Reference: Figure 6.1, page 221 • Elementary stress equations don’t apply in stress concentrations. ( )hdb P A P avg − ==σ avgcK σσ =max Stress concentration factor from charts Figure 6.3 Stress concentration factor for rectangular plate with fillet. (b) Bending Load. [Adapted from Collins (1981).] Text Reference: Figure 6.3, page 223 Stress Concentrations for Plate with Fillet (cont.) Stress Concentrations for Plate with Hole Figure 6.2 Stress concentration factor for rectangular plate with central hole. (a) Axial Load. [Adapted from Collins (1981).] Text Reference: Figure 6.2, page 222 Stress Concentrations for Plate with Hole (cont.) Figure 6.2 Stress concentration factor for rectangular plate with central hole. (b) Bending. [Adapted from Collins (1981).] Text Reference: Figure 6.2, page 222 Text Reference: Figure 6.6, page 226 Stress Concentrations for Bar with Groove (cont.) Figure 6.6 Stress concentration factor for round bar with groove. (b) Bending. [Adapted from Collins (1981).] Text Reference: Figure 6.6, page 226 Stress Concentrations for Bar with Groove (cont.) Figure 6.6 Stress concentration factor for round bar with groove. (c) Torsion. [Adapted from Collins (1981).] Fracture mechanics • All materials contain cracks. • If crack is bigger than critical dimension, it propagates Catastrophic failure. Figure 6.8 Three modes of crack displacement. (a) Mode I, opening; (b) mode II, sliding; (c) mode III, tearing. • Fracture mechanics predict mode I crack propagation if crack size > 2 a, where 2 1       = nom ci Y K a σπ Fracture toughness, from tables Geometric correction factor