Experiment Overview: Report Examples

Lab report

Viscosity measurement

Viscosity is an important property of a fluid and by this property fluid’s resistance of flow is measured. In other words, viscosity is a quantification of resistance of fluid to gradual deformation by shear stress. So, by this property shear stress in a fluid and angular rate of deformation are correlated. The resistance in a fluid is offered by intermolecular friction applied while layers of fluid slide by one another. Highly viscous fluid resist its flow and low viscous fluid like gas flows easily.

Objective:

Purpose of this lab experiment was to quantity viscosity, shear stress, strain rate and shear rate of oil motor and grease with Physica MCR 300 rheometer.

Materials

Materials used to carry out this lab experiment, were Castrol GTX 15W-40, Lithium grease and Physica MCR 300 rheometer - a stress controlled rheometer that is capable to perform a wide range of steady and dynamic tests e.g. flow curves, time-dependent tests, temperature-dependent tests, creep tests etc. The experiment setup was arranged for rheo-optic analysis.

Method:

Whole experiment procedures contained two steps. In first step viscosity and shear stress of motor oil were measured and in second step the same of grease were quantified with help of Physica MCR 300 rheometer.

Procedure to measure viscosity and shear stress of Motor Oil

Before starting the test, the Physica MCR 300 rheometer was set up by following steps. At first, a measuring system was installed and Plate-Plate (PP 50) was used. Temperature was set on 24 degree Celsius. The zero gap was calibrated and the gap on 0.5 mm was set. After this, the moto oil (Castrol GTX 15W-40) was loaded and the top plate was moved down to the trim position. Then the edges of the oil motor was trimmed carefully to get perfect situation and best results. In the next step, the top plate was moved down to the measuring position (the gap distance) and allowed the normal force to be stable. Then pressing OK button the test was started. Finally, results and charts were copied to Excel file.

Procedure to measure viscosity and shear stress of Lithium grease

Prior starting the test, the Physica MCR 300 rheometer was set up in the same way. At first, a measuring system was installed and parallel plane (PP 50) was used. Temperature was set on 24 degree Celsius. The zero gap was calibrated and the gap on 1 mm was set to reduce poples. After this, the lithium grease was loaded and the top plate was moved down to the trim position. Then the edges of the grease was trimmed carefully. Then the gap on 0.5 mm was again set and the top plate was moved down to the trim position. Then the edges of the lithium grease was trimmed carefully in the next step, the top plate was moved down to the measuring position (the gap distance) and allowed the normal force to be stable. Then pressing OK button the test was started. Finally, results and charts were copied to Excel file.

Result:

Results of measure a viscosity and shear stress of motor oil (Castrol GTX 15W-40) with Physica MCR 300 Rheometer:
Results of measure a viscosity and shear stress of grease (lithium) with Physica MCR 300 Rheometer:
Discussion
The experiment was carried out safely. It has been found that the viscosity of Lithium grease was quite high. Possible reason for this was existence of friction between a top plate and bottom plate with different speeds. When each layer of fluid sample was moving, friction force was generated between them and viscous force was generated. For Castrol Oil 15W-40, the viscosity of oil was found very low, as resistance of oil to gradual deformation by shear stress is quite low and less friction force is generated between two consecutive layers.

References

White, F. M. (2003). Fluid Mechanics. New York, NY: McGraw Hill.