Vibrations of Flexible Structures
Assessment: Having already undertaken the actual experiment and submitted a short experimental report, this document spells out the requirements for a longer formal report to be done by the Mechanical, Aerospace and Medical cohorts. The report should not be longer than 8 pages.
The purpose of this report is to develop the reporting skills of the student, as well as to enhance the ability to undertake analysis of experimental data and validate against theory. As such, the format of the report is very important, as well as the reporting structure and clarity of results and discussion.
Requirements for Formal Report
1) Complete coversheetwith name, student id, group number
2) Summary - Executive Summary of report
3) Objectives - Bullet list of objectives
4) Health & Safety - List the health & safety procedures followed during the lab
5) Experimental Procedure - 1) Give a description with photo/sketch of the experimental equipment. Describe the procedures/protocol used during your experiment to gather the raw experimental data for each type of measurement.
6) Results(Free vibration test)- Download the file EG268_formalreport_decay.xlsx. The diagram shows the time-trace of a decay test, similar to that used in question (d) in your previous report. A matlab script has been used to identify the beginning each cycle of oscillation, by noting where the time signal crosses zero (note this is differen to defining a peak as the start of a cycle, but should give similar results). The amplitude A and periodT of each cycle can then be automatically evaluated on a cycle-by-cycle basis. Furthermore, we can then calculate the apparent natural frequency ffor each cycle, and by comparing the amplitude of consecutive cycles we can evaluate the logarithmic decrementδ and damping ratio ζfor each cycle using formulas in the labsheet. All of this data is provided in the table.
a. Using the data table in the file provided, calculate the mean and standard deviation of the damped natural frequency f. Comment on the accuracy with which we have established the natural frequency.
b. Our modelling assumes that the damped natural frequency f is independent of the amplitude of vibration. Plot a graph of f against the amplitude A. Is this assumption justified?
c. Using the data table in the file provided, calculate the mean and standard deviation of the damping ratio ζ. Comment on the accuracy with which we have established this damping ratio.
d. Similarly, we assume linear damping that is independent of the amplitude A. Plot a graph of ζ against the amplitude A, and comment on whether any apparent relationship exists between these two variables, and therefore on whether our assumption is justified.
7) Results(Receptance FRF from Broadband) This shows ten runs of the experiment used in question (f) of the previous report; however all data has been converted to a receptance FRF (instead of accelerance as in the raw data), and the mean for each frequency has also been calculated.
a. Starting with the data from the given file, add an additional column containing the Standard Deviation (Excel function STDEV) of the data for each frequency.
b. Comment on the relevance of including the Standard Deviation when analyzing data
c. From the data provided in the filecreate a FRF graph as you did during the experimental report. However, this time add error bars to demonstrate the spread of results from the ten reputations of the experiment (note - if you are having difficulty producing error bars in excel, use dashed lines indicating the mean result plus 1 standard deviation and mean result minus 1 standard deviation).
8) Marks) Conclusion (max half a page)
This section should summarise key findings of the work
In the conclusion section it is important to concisely summarize points from your discussion - bulleting helps to keep the conciseness, but you can use paragraphs instead if you wish - but keep it all within half a page. Also, you need to make sure that your statements in your summary align with your experimental results.
9) References
10) Personnel reflection
The final section should include short answers to set questions
a. What have you learnt about experimental testing?
b. What could have been done to improve the learning experience of the module?
Attachment:- Vibrations of Flexible Structures.zip