Straw Test Report

Straw Testing Report

Content

Introduction…………………………………………………………………………….……3

Procedure……………………………………………………………………………………3

Analysis……………………………………………………………………………………5

Data…………………………………………………………………………………………6

Result………………………………………………………………………………………9

Discussion…………………………………………………………………………………11

Conclusion…………………………………………………………………………………12

Introduction

The goal of the experiment is to provide better preparation for designing and building of the final truss project. In this lab, we run test on different lengths of straws and analyze their strength to have an idea about them. Loads are added until straw buckles. By applying this data into the equations given in project description, the buckling strength as a function of the length of the straw can be estimated, which is the goal of the straw testing experiment.

Procedure

1. The group members cut the straws in 9 cm 12 cm and 15 cm before the actual testing lab.
2. On the lab day, The group members are assigned test equipment to test how much weight different lengths of straws can hold. The weight of the tester arm varies on different testers. The group members recorded the masses of the test arms and also the length of center mass. Moreover, the group members measure the length from the straw to the end of the test arm and the distance between the straw to the center of mass. One of the group members draws the free body diagram in the meanwhile.
3. The group members pin holes from both ends with first pin 5 mm from the end and the second 5 mm from the first pin. Both the pins are parallel to each other and perpendicular to the straw. The group members repeat this procedure for all 15 straws. When the straws are placed in the tester, they are oriented vertically. Meanwhile, the hinged lever arm is kept horizontal and perpendicular to the straws.
4. The first three straws of each length are sacrificial tests to get a general idea about the weight they could hold. In the process of adding the weights, the group members wait 30 second between loading. The maximum load is the last one to successfully hold for 30 seconds instead of the one added before the buckling occurs.
5. After obtaining all the needed data, The group share data with another group.

Analysis

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The equation for deviation calculation is

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To fit the data points to a linear curve empirically for buckling load at a given length, use equation:

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where l is the length of the straw.

Data

Table 1. Obtained data (9 cm)

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Table 2. Shared result (9 cm)

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Table 3. Obtained data (12 cm)

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Table 4. Shared data (12 cm)

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Table 5. Obtained data (15 cm)

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Table 6. Shared data (15 cm)

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Table 7. Average & standard deviation of obtained data

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