The paper by G. I. Taylor, titled "The Mechanism of Plastic Deformation of Crystals. Part I.—Theoretical," explores the plastic deformation of single crystals, focusing on metals and rock salt. The author defines the shear strain and the resistance to shear, denoted as \( s \) and \( S \) respectively, and discusses how these parameters are related in the stress-strain curve. The curves for different metals show a general characteristic where a small stress produces a small plastic deformation, but as the deformation increases, the stress required also increases. The paper also examines various theories of strain hardening, including the idea that misfit surfaces or faults in the crystal structure contribute to strength, and the role of temperature in the movement of dislocations. Taylor then delves into the atomic model of dislocations, explaining how they move and interact under external shear stress. He introduces the concept of positive and negative dislocations and their mutual repulsion or attraction. The paper calculates the stress distribution around a unit dislocation and the equilibrium conditions for different arrangements of dislocations, such as rectangular and diagonal lattices. Taylor derives a theoretical stress-strain relationship and compares it with experimental data, providing insights into the mechanisms of plastic deformation in crystals. The results suggest that the least shear stress at which plastic flow occurs is influenced by the arrangement of dislocations and the temperature of the crystal.The paper by G. I. Taylor, titled "The Mechanism of Plastic Deformation of Crystals. Part I.—Theoretical," explores the plastic deformation of single crystals, focusing on metals and rock salt. The author defines the shear strain and the resistance to shear, denoted as \( s \) and \( S \) respectively, and discusses how these parameters are related in the stress-strain curve. The curves for different metals show a general characteristic where a small stress produces a small plastic deformation, but as the deformation increases, the stress required also increases. The paper also examines various theories of strain hardening, including the idea that misfit surfaces or faults in the crystal structure contribute to strength, and the role of temperature in the movement of dislocations. Taylor then delves into the atomic model of dislocations, explaining how they move and interact under external shear stress. He introduces the concept of positive and negative dislocations and their mutual repulsion or attraction. The paper calculates the stress distribution around a unit dislocation and the equilibrium conditions for different arrangements of dislocations, such as rectangular and diagonal lattices. Taylor derives a theoretical stress-strain relationship and compares it with experimental data, providing insights into the mechanisms of plastic deformation in crystals. The results suggest that the least shear stress at which plastic flow occurs is influenced by the arrangement of dislocations and the temperature of the crystal.