Compression Testing – Lab Report Example

The paper "Compression Testing" is a good example of a lab report on formal science and physical science. A sample of polymer, in a compression test, was tested for compressive strength and stiffness. The study was conducted with a Compression method from “BlueHill 3 tensile test program” at a test speed of 1.3mm/min and a limit of the strain of 0.3mm/mm in accordance with ASTM Standard D695-96. Data were collected while carrying out this experiment calculating for material properties. The compressive modulus was calculated as 21.27 whereas ultimate compressive strength recorded 8.68MPa. Value of ultimate compressive strength depicted proximity to similar value for silicon fume mortar at 9.62MPa thus the likely identity of the test sample.  Introduction
Properties of various engineering materials in construction determine the life of structures as they influence their ability to serve for long periods before failure. Failure of structures can be through collapse or reduction in serviceability as well as durability (Ward & Sweeney, 20-25). Economically, the collapse of structures leads to loss of funds by stakeholders thus necessitating thorough testing to determine suitable materials for construction. Compression testing is a procedure for defining behavior exhibited by various engineering materials under loads of compressive nature.
Additionally, such tests aid in determining limits of proportionality and elasticity, points of yielding, material strength at yield. Compressive strength and elasticity modulus are other properties that classify the type of engineering materials. Ultimate compressive strength refers to the extreme pressure a material can resist prior to fracturing whereas elastic modulus refers to the gradient of the stress-strain curve. Brittle materials possess definite values for strength while the strength of ductile materials relies on the extent of alteration during testing.
This test serves to identify the type of polymer sample through testing of material properties.
Formulae:
Stress = Load (N)/Area of cross-section (mm2)
Compressive modulus = slope of the linear portion of the stress-strain curve
Strain = extension/ original length
Length reduction (%) = (initial length-original length) %/ original length
Materials and Methods
Materials:
Polymer
Method
1. Dimensions of the sample were measured twice are different points to obtain average length (height) and average diameter.
2. Compression method from “BlueHill 3 tensile test program” was utilized in this experiment labeling test sample as “Compressio_SEC#_Sample@” for each section number (SEC#) and sample number (Sample@).
3. Dimensional properties of the sample were fed into the program.
4. The specimen was uprightly placed on the lowest salver of the compressive machine.
5. Under instructions, test speeds of 1.3 mm/min and strain limits of 0.3 mm/min were set.
6. Soft keys were used to reset extension before loading.
7. Crossheads were lowered until loading meters registered a 10 N pre-load.
8. The extension was reset before loading again; repeating the process until failure of load.
Analysis of material properties utilizes the formula for calculating strain, stress and Compressive modulus stated earlier. Material properties matching values recorded literature identifies the type of sample polymer.
Results/Analysis
The original height of specimen = 15.49mm
The final height of specimen = 15mm
% reduction in length = 30%
Diameter of specimen = 13.84mm
Compressive modulus = 21.27
Yield strength = 0.265 MPa
Ultimate compressive strength = 8.68 MPa
Figure 1: A graph of stress versus strain for a test sample
The value of ultimate compressive strength for sample specimen compares with values for silica fume mortar (a by-product of alloys of ferrosilicon) which yields 9.62MPa surpassing mortar strength of 8.68MPa (Ward & Sweeney, 11-14). Analysis of material properties utilizes specifications for determining strength and ductility.
Discussion
Materials exhibit unique stiffness and compressive strength typical to their respective properties. In this experiment, the properties of materials were investigated with a vision of identifying types of sample polymers. Civil engineers work closely with chemical engineers to manufacture polymers with beneficial properties for design practices. These polymers possess both high compressive strengths and modulus-weight ratios. The specimen recorded yield strength of 0.265MPa and ultimate strength of 8.68MPa thereby portraying ductility. Additionally, specimen reduced by 30% of its original length whereas compressive modulus was 21.27.
Results obtained in this experiment depict compressive strength and stiffness of sample polymer. The probable source of experimental error lies in safety stop prior to determining ultimate compressive strength. Owing to errors in timing safety stops, the actual value of ultimate compressive strength may be unattainable.
Conclusion
The sample tested in this study exhibited statistically momentous stiffness and compressive strength typical of silica fume mortar.