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08A- Tensile Testing of Engineering Materials 

What is it? 

Different types of materials have different microstructures (structure at the sub-millimetre level), which directly control their different mechanical properties. 
Three broad categories of materials are commonly used in engineering: metals, ceramics and polymers, as well as combination of those (composite materials). This experiment aims to study mechanical properties of the three materials and also to demonstrate the factors that affect the mechanical strength of the materials. 

What is the theory behind it? 

This experiment is based on some fundamental theories regarding the mechanical properties of materials.

Interesting video that exposes your mind to the various different types of Tensile Tests (different materials): 

08B - Scanning of the Electron Microscope

How did it come about?
Electron Microscopes were developed due to limitations of Light Microscopes which are restricted by the physics of light to 500x or 1000x magnification and a resolution of 0.2 micrometers, where human hair is around 0.1 micrometers.

The signals generated by interaction of the electron beam with the sample are collected by a variety of detectors, which provide us the topography (the surface feature and its texture), morphology (the shape and size of the particles making up the object) and composition (the chemical elements and compounds) of the sample.

What is the theory behind it? 
In a typical SEM, an electron beam is emitted from an electron gun. The electron beam, which typically has a high energy, is focused onto the surface of the samples. The beam passes through pairs of coils or pairs of deflector plates in the electron column, typically in the final lens, which deflect the beam in the x and y axes so that it scans in a raster fashion over a rectangular area of the sample surface.

When the primary electron beam interacts with the sample, the electrons lose energy. The remained electrons will be reflected back and these electrons will be detected by specialized detectors according to their atomic number and density. The beam current absorbed by the specimen can also be detected and used to create images of the distribution of specimen current.

The detected signals are processed and the resulting image is, in modern machines, digitally integrated and displayed on a computer monitor and saved to a computer's hard disk. 

Videos to illustrate how it works: 

08C - Composite Material Processing

What is it?
Composite material is a combination between two or more materials. It has the desirable properties which cannot be obtained by either of the constituent materials acting alone. T herefore, composites are developed in transportation industries especially airplanes and also sports equipment. 

What is the theory behind it? 

Composite materials are mixtures of distinctly different materials which, in combination, produce a material that has useful properties. Concrete and asphalt are aggregate composites and wood is a natural cellulose fiber/resin composite. Most of the composite materials are composed of two phases i.e. the matrix and the reinforcing/dispersed phase. Matrix is the one which holds the fibres/particles/sheets together in a structural unit. Besides, it transfers and distributes the applied load to the reinforcement. In addition, it protects them from external damage. This reinforcing/dispersed phase will improve the mechanical properties of the material. Sometimes, there may be a third constituent material called the filler. Fillers are used to enhance some other aspects of composite behaviour such as reduce weight; reduce cost, protection against UV radiation.


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