1. Experimental Mechanics - assignment
Purpose is to introduce the assignment and discuss how to present data.
How do the laboratory activities fit together?
What is the purpose of comparing the data from the different techniques
Brazilian disc

2. Assignment contents
In the course work assignment a detailed analysis of the data collected in the laboratory classes will be carried out.
The mechanical properties of the aluminium alloy material that was tested will be derived from the different experimental mechanics procedures.
The stresses and strains in the disc will be derived using each technique and the values from each technique compared.
The virtual fields method will be used extract the material properties from the data from the discs obtained using the white light techniques.

3. Marks Coursework title Weighting Brazilian disc analysis 10%
Dog bone tensile test
15%
Camera set up
DIC, Grid and VFM on Brazilian disc
25%
TSA
Comparison of derived stresses
Conclusions

4. Assignment presentation
The findings from the above should be written-up into a formal technical report of no longer than 3000 words (not including tables and figures).
Descriptions of the experiments should be given along with clear discussion.
Marks will be allocated for presentation as well as for technical content, all graphs need gridlines, legend, axes need to be labelled and units must be provided.
In the discussion section each technique must be compared this means you need to present the data in a way that it can be compared. Convert the DIC and Grid technique data to stress sum data and compare with the TSA data and the theory.
The report must finish with at least 10 strong conclusions about the accuracy, precision and applicability of the experimental techniques.

5. Test specimens

6. Mechanical testing
The mechanical tests are conducted using a strain gauge and an extensometer.
The specimens are loaded to below their elastic limit
The data provided gives from the Instron test machine, time, load, displacement, strain (from the extensometer).
Cross sectional area is known so stress is calculated
Calculate E from strain gauge and extensometer data
Calculate E from DIC data

7. Stress-strain curve

8. Theory

9. Stresses (MPa)

10. Calculate the strains

11. Strains

12. Assignment
Use equations (5) and (6) to verify your results along the vertical centre line.
Verify the stress free condition at (x = R, y = 0).
Derive an expression for the strains in the x and y direction along the vertical diameter of the disc.
Derive an expression for (xx +yy) along the vertical diameter of the disc.
Calculate the principal stresses (1 and 2) at each point in the disc and plot as a contour plot. To do this you may wish to consult [2] for a revision of basic solid mechanics.

13. Vertical diameter

14. Matlab code

15. Brazilian Disc - DIC

16. Brazilian Disc - DIC
Displacement field
Strain field
Stress field

17. Brazilian Disc - TSA
The specific challenges addressed in this work

18. Brazilian Disc - comparison

19. Brazilian Disc - comparison