Category: Material Science and Engineering

Electrical Properties

17) Electrical Properties Electrical Conduction 17.2 Ohm’s Law When an electric potential V is applied across a material, a current of magnitude I flows. In most metals, at low values of V, the current is proportional to V, according to Ohm’s law: I = V/R where R is the electrical resistance. R depends on the…

By Sdbamie 1 May 2020 Off

Composites

16) Composites 16.1 Introduction The idea is that by combining two or more distinct materials one can engineer a new material with the desired combination of properties (e.g., light, strong, corrosion resistant). The idea that a better combination of properties can be achieved is called the principle of combined action. New – High-tech materials, engineered to…

By Sdbamie 1 May 2020 Off

Polymers Characteristics, Applications and Processing

15) Polymers Characteristics, Applications and Processing 15.2 Stress-Strain Behavior The description of stress-strain behavior is similar to that of metals, but a very important consideration for polymers is that the mechanical properties depend on the strain rate, temperature, and environmental conditions. The stress-strain behavior can be brittle, plastic and highly elastic (elastomeric or rubber-like). 1.…

By Sdbamie 1 May 2020 Off

Polymer Structures

14) Polymer Structures 14.1 Introduction Polymers are common in nature, in the form of wood, rubber, cotton, leather, wood, silk, proteins, enzymes, starches, cellulose. Artificial polymers are made mostly from oil. Their use has grown exponentially, especially after WW2. The key factor is the very low production cost and useful properties (e.g., combination of transparency…

By Sdbamie 1 May 2020 Off

Ceramics – Applications and Processing

13) Ceramics – Applications and Processing 13.1 Introduction Ceramics properties that are different from those of metals lead to different uses. In structures, designs must be done for compressive loads. The transparency to light of many ceramics leads to optical uses, like in windows, photographic cameras, telescopes and microscopes. Good thermal insulation leads to use…

By Sdbamie 1 May 2020 Off

Ceramics – Structures and Properties

12) Ceramics – Structures and Properties 12.1 Introduction Ceramics are inorganic and non-metallic materials that are commonly electrical and thermal insulators, brittle and composed of more than one element (e.g., two in Al2O3) Ceramic Structures 12.2 Crystal Structures Ceramic bonds are mixed, ionic and covalent, with a proportion that depends on the particular ceramics. The…

By Sdbamie 1 May 2020 Off

Thermal Processing of Metal Alloys

11) Thermal Processing of Metal Alloys   Annealing Processes 11.1 Introduction Annealing is a heat treatment where the material is taken to a high temperature, kept there for some time and then cooled. High temperatures allow diffusion processes to occur fast. The time at the high temperature (soaking time) is long enough to allow the…

By Sdbamie 1 May 2020 Off

Phase Transformations in Metals

10) Phase Transformations in Metals 10.1 Introduction The goal is to obtain specific micro structures that will improve the mechanical properties of a metal, in addition to grain-size refinement, solid-solution strengthening, and strain-hardening. 10.2 Basic Concepts Phase transformations that involve a change in the micro structure can occur through: Diffusion Maintaining the type and number…

By Sdbamie 1 May 2020 Off

PHASE DIAGRAMS

9) PHASE DIAGRAMS   9.1 Introduction Definitions Component: pure metal or compound (e.g., Cu, Zn in Cu-Zn alloy, sugar, water, in a syrup.)Solvent: host or major component in solution.Solute: dissolved, minor component in solution.System: set of possible alloys from same component (e.g., iron-carbon system.)Solubility Limit: Maximum solute concentration that can be dissolved at a given…

By Sdbamie 28 April 2020 Off

Fundamentals of Fracture

8) Fundamentals of Fracture   Introduction Failure of materials may have huge costs. Causes included improper materials selection or processing, the improper design of components, and improper use.    2. Fundamentals of Fracture Fracture is a form of failure where the material separates in pieces due to stress, at temperatures below the melting point. The…

By Sdbamie 28 April 2020 Off