grammar

List of Tables

List of Figures

ABSTRACT

For this lab we studied the accuracy of the Tinius and Olsen machine using the proving ring; and we found the error of the T&O machine to be 0.054%. This is in the acceptable range as per the verification methods section of our handout.

Keywords: Morehouse Proving Ring, UTM, T&O machine, accuracy, % error

INTRODUCTION

A proving ring is a device which is used to measure force by being subjected to compressional or tensional loads. The ring is circular shaped, and usually made out of a steel alloy, with a measuring system. The measuring system consists of a vibrating reed, internal and external bosses and a micrometer screw-gauge. The detailed description of the ring is shown in figure 1.

Figure 1. Proving Ring

BACKGROUND AND METHODOLOGY

The Tinius and Olsen Machine, shown in figure 2, is used for testing compressions of different objects be applying loads to find deformation and other material characteristics. The load is produced by hydraulics inside the machine and can be manipulated within a few pounds accuracy. It has a capacity of 60,000 pounds. This machine is calibrated and verified by using the Morehouse proving ring that is shown in Figure 1 as specified by the ASTM. It has a capacity of 100,000 pounds

The following steps were followed to obtain the values we were given by our instructor:

1. Make sure all items are off the table and the machine is ready for start-up.

2. Then, Power ON; wait for “clicking” to stop before proceeding any further.

3. Zero the “LOAD” and “UNLOAD” knobs in the lower left-hand side.

4. Turn Pump ON. Allow machine to warm up for about 15 minutes.

5. Switch to Manual Control. Make sure that the Lower Head is in an approachable position.

6. Leave machine in ‘FAST’ mode to Zero table. Switch to ‘SLOW’ for Experiments.

7. Zero all Channels. Verify proper range on loading.

8. Depress “LOAD” and rotate “LOAD” knob to approx. 70 (up to 100 is OK) to raise table to 6” according to readout. 2” is Fine.

9. Decrease “LOAD” to zero. Then hit STOP.

10. Press and hold “FAST UNLOAD” to allow table to return to neutral position.

11. When pitch of motor changes, then release “FAST UNLOAD” button and allow table to return to equilibrium.

12. Switch to “SLOW.”

13. Re-Zero all channels and reset Max load with the “CLEAR” button.

14. Place Proving Ring on the table; center is approximately.

15. Obtain “Temperature” and “No-Load” reading. Rotate dial away from reed 4 revolutions.

16. Lower the lower head to close to top of the Proving Ring. Demonstrate Momentum of head.

17. Verify that knobs are at Zero and press “LOAD.”

18. Increase load slowly until Ring contacts lower head. Approx. 20% should be sufficient.

19. Once load starts registering, watch only the load reading.

20. Monitor Proving Ring during loading to ensure reed clearance.

21. Reduce loading rate when the desired load is approached. Null range is at approx. 12 on the dial.

22. At desired load(s), take reading on the ring dial while another maintains static load.

23. Once all loads have been recorded (from Ring and machine), prepare to unload.

24. To unload, decrease “LOAD” dial to zero. If unloading stops, press “STOP.” Then press “UNLOAD” and increase “UNLOAD” dial until ring is unloaded.

25. When table movement (down) is observed, press “STOP.”

26. Obtain ‘NO-LOAD’ reading from Proving Ring and Machine.

27. Remove Ring from the machine and return it to the cabinet.

28. Depress “FAST UNLOAD” to allow table to return to neutral position.

29. Shut OFF machine.

Equations

After the data was collected from the experiment we had to derive a few equations which would help us understand the data and compare it to the accepted values for the Morehouse Ring.

Zero Error Adjusted

This took into account the point at which the vibrating reed was in contact with the screw gauge which was not necessarily the zero point of the screw gauge reading. For this lab the zero error was 2 divisions.

Zero Error adjusted = Actual reading – 2 divisions

Temperature adjusted Reading (

The accredited values that came with the proving ring were retrieved at a temperature of 23 degrees Celsius. It is also known that metals have properties that will be affected by temperature. The purpose of deriving the temperature adjusted reading is so that we can make very accurate comparisons with the original readings, by simulating the same conditions.

Actual Load

The actual load is what the corresponding load should be for the micrometer reading you get. This value is derived by using a correction factor. For our experiment the correction factor at 23 degrees is 138.5.

Percent Error

Correction Factor

RESULTS AND DISCUSSIONS

All of the following data was collected at the constant temperature of 25°C. The fact that

temperature stayed the same throughout the experiment decreases the chance for unwanted error. Table 1 shows all the measurements and calculations from the experiment.

Table 1. Calculations of the Tinius Olsen UTM using a Proving Ring at 25°C

Figure 2 shows the plotting of actual load versus machine load, and Figure 3 shows the percent error graph from the results. Figure 3 gave a linear regression line for the actual load readings compared to the machine load readings. They were slightly off from one another, but not too much to be noticeable in this graph.

Figure 2. Actual load vs. Machine Load

Figure 3. Error (lb.) vs. Proving Ring Load (lb.)

CONCLUSIONS AND RECOMMENDATIONS

We never got to perform the actual experiment ourselves but from the given data and by working the results ourselves. We determined that the T&O machine was accurately calibrated and therefore fit for normal use. We did have sources of random error, of which the major one was getting the deflection reading to be as precise as possible. The best way to minimize this error would be to take several more readings as well as practicing getting the readings from the dial.

SOURCES

Design and Construction of the Proving Ring. (n.d.). Retrieved February 28, 2016, from http://www.nist.gov/pml/div684/grp07/provingringdesign.cfm

APPENDIX A RAW DATA and ORIGINAL HANDOUT

APPENDIX B DETAIL CALCULATIONS

Actual load vs. Machine Load

Machine Load (lb)

Actual Load (lb)

Error (lb) vs. Proving Ring Load

Proving Ring Load (lb)

Error (lb)

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