Summary of ch 7 Materials Engineering

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00:00:00 - 01:00:00

This video explains the basics of materials engineering, focusing on dislocations and how they can be used to improve the strength of materials. It discusses the different types of slip systems that can exist in a crystal structure, and how this affects the material's behavior. Additionally, the video explains how the shear stress required to initiate slip varies depending on the material.

00:00:00 In Chapter 7 of Materials Engineering, the dislocations and strengthening mechanisms are discussed. The relationship between dislocation and deformation is explained, and how heat treatments can affect the mechanical properties of a material.
00:05:00 In this video, the author explains the Slip process and how it causes a change in the shape of a material. She also mentions the importance of applying shear stresses in order to start the Slip process. Once the Slip process has started, plastic deformation will take place.
00:10:00 In this video, the different types of dislocations in materials are explained, and how they are formed. Additionally, the effects of processing and thermal heat on the dislocation density are discussed.
00:15:00 This video explains how materials science deals with dislocations, which are the tiny breaks in the atomic bonds that hold atoms together in a material. Materials scientists often attempt to weaken these bonds by increasing the stress levels in the material, which allows the dislocations to move more easily and break fewer bonds. This can lead to an increase in the strength of the material.
00:20:00 The video discusses the different types of slip systems that can form in crystalline structures, and how this affects the ease with which dislocations can move. The video also provides examples of slip systems in FCC, BCC, and SBCC structures, and explains how these systems are determined by the plane and direction of the highest linear density of atoms.
00:25:00 In this video, the author explains the various slip systems that can exist in a crystal structure, and how this affects the material's behavior. FCC and BCC crystals are relatively ductile, while HC medals are brittle.
00:30:00 The video discusses materials engineering, focusing on how shear stress is generated and exposed in a material when a tensile force is applied. Shear stress is perpendicular to the stress direction in a single crystal, but can be generated in other planes in a material.
00:35:00 In this video, the components of a force are explained, and the shear stress associated with this force is shown.
00:40:00 The video discusses the shear stress required to initiate slip in materials. It explains that the critical resolved shear stress, or the stress level at which the material yields, is different for different materials. It also explains that there are multiple slip systems in a material, and that one of these slip systems is the most favorable.
00:45:00 The material engineering topic of ch 7 discusses the effects of different angles on the result shear stress, yielding, and critical shear stress. The video explains that the maximum result shear stress occurs when the angles are 45 degrees to the applied force, and that yield strength occurs when the shear stress reaches the critical volume.
00:50:00 The shear stress required to yield a material is determined by the resolved shear stress (cos lambda) and cos P. The normal stress required to yield is equal to the critical resolved shear stress divided by cos lambda. The maximum yield stress is greater than the critical resolved shear stress for polycrystalline materials, due to the random crystallographic orientation of the grains.
00:55:00 In this video, boundaries are discussed and it is explained that there are no differences in orientation in single crystals, but in polycrystalline metals there are many obstacles to the dislocation motion, starting from the grain boundaries and different orientation in grains. When deformed, the initially acquiesced grains becomes elongated along the direction of deformation and we are seeing this in these microscopic images. Solid solution strengthening and cold working are introduced as ways to prevent dislocation motion and strengthen the material.

01:00:00 - 01:40:00

This video discusses how the various properties of materials are affected by temperature, grain size, and the presence of dislocations. It also explains how cold working can be used to achieve a desired level of deformation.

01:00:00 In this video, the effect of grains on the strength of a material is explained. The video also discusses the stresses that are created due to the presence of dislocations. These stresses cause the material to become stronger.
01:05:00 In Materials Engineering, dislocation not in and far away from the dislocation okay, so when small impurities are introduced, they create tensile strains around atoms. These strains can be neutralized if the impurity particle moves close to the dislocation line, but if the impurity particle is large, it will introduce compression stresses in neighboring atoms. These stresses need to be increased to overcome the obstacle of the small impurities.
01:10:00 The video discusses how nickel can increase the strength and ductility of alloyed metals, and how dislocations can interact to produce these effects.
01:15:00 In this video, the author explains how strain-hardening occurs when materials are subjected to cold working. Higher dislocation density results in increased distance between dislocations, which inhibits their motion and results in a decrease in strength.
01:20:00 This video discusses the effects of cold work on metals, and the various steps involved in heat treating them. It explains that cold work can make a metal stronger and more ductile, but that it must be heat treated carefully to prevent it from becoming brittle. The video also provides a brief introduction to annealing, and discusses the three stages of annealing.
01:25:00 Through discussing the effects of temperature on materials, this video discusses how grains will elongate, how dislocations will increase, and how recrystallization will occur. It also explains how heat treatment can affect these processes.
01:30:00 The video discusses the effects of recrystallization on metal properties, including how grain size affects these properties. The video also provides links to additional information about grain growth and creep resistance.
01:35:00 This video discusses the effects of temperature on materials, and how it can affect the plastic deformation that occurs during creep. The video also provides an equation that can be used to calculate the amount of cold work that must be done in order to achieve a desired level of deformation.
01:40:00 In this video, the presenter discusses the various factors that affect the strength of materials, including the effect of grain size, dislocations, and temperature. The presenter also explains how to cold work the material to achieve a desired reduction in cross sectional area.