There are two rules of thumb that have been given in comparing the density of materials i.e. titanium is nearly half the density of steel and that of aluminum is about one third the density of steel. Any heavy and weak material is considered bad but for a strong and light material is considered good.

Stress and strain

Stress has been described as the amount of force applied to a certain material divided by the cross sectional area of the material to the direction of the force. Strain properties, on the other hand, indicate how much a material lengthens under stress.

Tensile and comprehensive strength

The strength of a material can be measured by putting a material sample in a powerful materials testing machine, which pulls the materials apart and then records the force required to do so, plus the deformation to the material. Compression strength is determined by subjecting the material under pressure until it breaks i.e. heat, impact, et cetera. Tensile and compressive indicators are then recorded. These are good measure of how much impact the building materials can withstand without breaking if subjected to certain pressures (James, 2011, 35).

Elastic and plastic deformation

As explained in the stress strain diagrams above, elasticity and plastic deformation occurs prior and after application of a certain amount of stress on a certain material. In figure 2 above, below point A, we find that steel goes back to its original state hence it is elastic. Beyond point B, the steel cannot go back to its original length hence it is deformed or inelastic. Permanent elongation of a material is called plastic deformation. The same case applies to other building materials under different stress conditions. Below is the load deformation curve: Modulus of elasticity This is a coefficient which denotes the ratio of stress per unit area acting on, to cause deformation on a material to the resulting deformation therefrom. The elastic modulus, E, is usually determined after the compression tests are done on buildings. It differs in various types of materials for building. Elasticity modulus for steel is determined during manufacture while that of a concrete wall is calculated depending on the building dimensions. Task II Figure three: Graph of load against extension See the excel attachment Modulus of elasticity, E E = 2G(r+1) where G is the modulus of rigidity and r is the Poisson’s ratio. E= (F) (L1)/ (A) (L2) where F is the force or load, L1 is the original length of material (in this case mild steel), L2 is the amount the length changes on application of the load, A is the cross section area that the force is applied on the material. Area of the rod steel is given by the formula:, then A= 22/7* 12.52 = 491.07 mm2 E = {[50*195] / [491.07*0.09] + [100*195] / [491.07*0.19] + [150*195] / [491.07*0.29] + [160*195] / [491.07*0.34] + [165*195] / [491.07*0.46] + [170*195] / [491.07*0.78] + [180*195] / [491.07*0.84] + [190*195] / [491.07*0.91] + [200*195] / [491.07*0.98] + [210*195] / [491.07*1.07] + [220*195] / [491.07*1.24]
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