Sompra 2 Practical Guide 2019 PDF

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Strength of materials tests ...

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Practical guide Strength of Materials II Year Module (SOM PRA2) Department of Mechanical and Industrial Engineering Compiled by: EM Kula IMPORTANT INFORMATION: This practical guide contains important information about your practical

SOM PRA2

1. EXECUTION OF THE EXPERIMENTS Each experiment presented in this practical guide is performed according the schedule provided. The order of performance of each experiment is followed unless specified otherwise by the laboratory instructor. In order that the laboratory session is conducted in the most meaningful manner possible, it is imperative that each student read, study and understand the experiment to be conducted prior to coming to the lab. Students will be divided into groups to perform the experiment. Each group is required to work together throughout the practical session. But, each student must do his or her own analysis and compile individual report. Students must come to the lab at their registered schedule. An attendance sheet is circulated and it is the responsibility of the student to sign it at each lab session. The lab instructor is not expected to remember if the student attended the practical session. Any student who arrives late (at the discretion of the instructor) to the laboratory will be deducted 15% on the laboratory report. Students arriving 30 minutes after the start of the experiment is considered absent.

2. LABORATORY REPORT Each student will submit a complete written report covering each experiment performed. The report is to be individual own work. The report will be written in the third person, past tense (for procedures executed, data taken and results obtained), and should be self-sufficient. In other words, the reader should not need to consult the references in order to understand the report. Correct English and spelling should be used. The reports are practice for writing technical reports similar to those, which are required by engineers engaged in industry and engineering practices. The report must be typed using a word processor. All pages, equation, figures, graphs and tables must be numbered. Figures, tables and graphs must have titles. Thy must be neat and clear.

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3. SPECIFICATIONS In order to observe the accepted rules of good writing form, the following specifications for the general makeup of the report are required: 1. 2. 3. 4. 5.

Use A4 white paper. Write the report with a word processor. Consistent fonts and presentation for every section of the report. Use one side of the paper only. Create all drawings and figures using computer drawing and plotting programs. Scanned images are allowed where appropriate. 6. Use the same font font style on drawings and graphs as used in the text. Graphs axes should be clearly labelled, including units where appropriate.

4. REPORT OUTLINE 1. Title page: must include lab title, date performed, student names, student number and submitting date. 2. Aim of the practical: state the objective clearly. 3. Apparatus: draw the apparatus used and clearly label it. 4. Procedure: write the procedure in your own words. And it must be written in the third person, past tense. Note that it is unacceptable to simply use or copy the procedural instruction from the practical guide. 5. Data sheet: tabulate the experimental data. 6. Results: answer all questions posed in practical guide. All observed and calculated data should be tabulated when possible. Heading and subheadings identifying items of data or sets of data should be used a) Sample calculations: show a sample of a complete calculation. b) Graphs: plot graphs using word processor with all the titles. 7. Discussion and conclusion: most important section of the entire report. It should be a complete discussion of the results obtained. Part of this discussion should deal with the accuracy of the results. 8. References: publication or other authorities which help explain the experiment, calculate results, explain errors, draw conclusion etc., should be acknowledged. References should be arranged in alphabetical order according to the last name of the author, or the 3

SOM PRA2

last name of the first-named author for papers with more than one author. 9. Appendices: materials that support the report but are not essential to the reader’s understanding of it are included here.

5. SUBMISSION Students must submit their report to the laboratory instructor at stated date during practical session. Students submitting late reports are not accepted resulting in a zero mark for the practical. 6. CONTACT PERSON Mr. EM Kula Telephone number: (011 471-2887 Email: [email protected] Contact Times 09H00 TO 15H00 (Monday to Friday.)

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SOM PRA2

EXPERIMENT 1

BENDING MOMENT

1. Aim The aim of this experiment is to compare the experimental reactions with theoretical reactions and to draw the shear force and bending moment diagrams. 2. Apparatus

3. Procedure 1. Measure the length of the Beam and measure the weight of mass hanger, silver hinges and the beam. 2. Place the beam on top of the digital gauges. 3. Switch on the digital gauges and set to zero. 4. Place the hinges on the specified distance. 5. Measure the distance from the support to the hinges and the distance between the hinges. 6. Place the mass hangers with the specified weight on the hinges.

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7. Record the readings on the digital gauges as well as the weight on the mass hangers.

4. Experimental Data

RL

RR

W1

X distance from RL

W2

X distance from RR

Where: RL = Left side Reaction RR = Right side Reaction W = weight

5. Calculations 1. Compare the theoretical and experimental reactions 2. Draw the shear force diagram 3. Calculate bending moment at each point 4. Draw bending moment diagram 6. Results Theory RL

RR

Experiment RL

RR

8. Conclusion

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SOM PRA2

EXPERIMENT 2

TENSILE TEST

1. AIM To determine the tensile strength of a material. 2. APPARATUS

3. PROCEDURE 3.1Measure the diameter of the specimen using venier-calliper. 3.2Insert the specimen holders on the top and middle cross members. 3.3Screw the threaded ends of the specimen into the chucks. 3.4Tighten the nut on the upper chuck by hand. 3.5Connect and switch on the interface. 3.6Select the elongation on the interface and press next. 3.7Then press local button. 3.8The jack handle applies load. While doing so, observe the interface. 3.9Set the interface to zero. 3.10 Slowly apply the load and record both load and the elongation from the interface. 3.11 Increases the load, each time record the elongation as well as the load. 3.12 Plot the load vs. elongation on a graph and identify the elastic limit, upper yield point, lower yield point. 4. CALCULATIONS 4.1Calculate the yield strength, 4.2 the tensile strength 4.3 Percentage elongations. 7

SOM PRA2

EXPERIMENT 3

EQUILLIBRUM OF FORCES

1. AIM Is to illustrate the equilibrium of forces acting on an object 2. APPARATUS

3. PROCEDURE Setup a) Setup several pulleys on the frame struts, force board approximately in the middle of frame strut and secure with knobs. Ensure that there is enough space to hang a load underneath each pulley. b) Attach a blank paper sheet on the force board and make sure that it is properly secured and flat against the board. c) Hang the string provided over pulleys and load mass hanger to each open end. d) Slowly add weights to the various load hooks until the connected ends are roughly positioned over the center of the board.

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Measurements e) Using a pencil, trace each string line on the direction of the string. Remember to mark each trace mark line with identification and total weight applied to the string. f) A free body diagram can be sketched in order to “visualize” and identify all the forces and moments acting on a body. Their relative magnitude and direction can be indicated. g) Remove the paper from the board and sketch free body diagram joining all the lines and use protector to measure the angles of forces applied in different directions. 4. EXPIREMENTAL DATA Pulley NO.

Weights (g)

5. CALCULATIONS

a) For both rings, extend the trace lines of one ring to intersect at the common midpoint for that ring, as well as the connecting cord. Specify two sets of perpendicular coordinate axis of which the origins lie on the midpoint of each ring. b) By using the angles measured of each trace and using the weight values, calculate the components of each trace along the specified coordinate axis. c) For both rings, calculate the resultant force that the connecting cord applies to each ring by summing the components of the traces along their respective coordinate axis. 9

SOM PRA2

d) Calculate the resultant forces and discuss any discrepancies.

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