MECHANICS AND MATERIALS LABORATORY (MEMB221) SEMESTER 2, 2015/2016 EXPERIMENT 2 : TORSION TEST DATE PERFORMED : 3rd DECEMBER 2015 DUE DATE : 11th DECEMBER 2015 SECTION : 05 GROUP : 04 GROUP MEMBERS Mithradassa Nair A/L G Dhamodharan Sorna Kailash A/L Kannan Kurukkal Raveen A/L Thiyagugopal Pragatesh Kumar A/L Ashok Kumar Sarvaisan A/L Muniandy LAB INSTRUCTOR: Cik Nuraslinda Binti Anuar TABLE OF CONTENT I / D NUMBER ME095512 ME095589 ME095572 ME095567 ME095580 G through measurement of the applied torque and angle of twist. The variation of pure shear when a structural member is twisted is called torsion.SUMMARY / ABSTRACT 1 OBJECTIVE 2 THEORY 2-3 EXPERIMENT EQUIPMENT 3-6 PROCEDURE 7-8 DATA AND OBSERVATIONS 10-9 ANALYSIS AND RESULTS 11-12 DISCUSSIONS 13-14 CONCLUSIONS 14-15 REFERENCES 15 ABSTRACT This experiment is performed to study the principle of torsion test and also to determine the modulus of shear. The torsional forces produce a rotating motion about one end to another end of the member. . The test is then performed. 1 Objectives To understand the principle of torsion test. The torque measuring unit is calibrated first by inspecting the read out torque from amplifier to be similar with the applied torque. The results were taken and some calculations is performed using the formula given in the lab manual which is the applied torque. The G value for specimen B theoretically is larger than specimen A. To avoid some measurement errors several measure were taken which can affect the results. The dimension for the both specimen is measured and recorded before the experiment begin. G through measurement of the applied torque and angle of twist. The modulus can be determined when the specimen is still working under the elastic limit. number of revolutions and the percentage error and from the results obtain a graph is plotted. The test specimen is place between the loading device and the torque measuring unit. The torque needed to twist specimen A to the same amount degree of rotation as specimen B is greater.Two different specimens has been used in this experiment. hence it is harder to twist than specimen B. The reading from the amplifier is taken out each time when the load is applied. To determine the modulus of shear. Based on the results obtained. specimen A and specimen B. Specimen A is bright gold in colour whereas Specimen B is silver and much more lighter than specimen A. it is concluded that specimen B is more ductile than specimen A. angle of twist. Theory . 2 EQUIPMENT/DESCRIPTION OF EXPERIMENTAL APPARATUS . in radians. the torque and twisting angle are measured to determine the shear modulus. In each test.Torsion is a force produced when a structural member is twisted . G. torsional forces produces a rotating motion around the object. for a solid round bar is: ∅= Tl GJ Unknow n T J G φ L R D Variable Torque Polar moment of inertia Shear modulus Angle after application of torque Length Radius Diameter The value of the torque in this experiment will be showed in the digital meter or the read out amplifier. The shear modulus G is calculated based on this formula:- T G J L J where r 2 d 4 2 32 The angle of twist. 6. 4. 3. 2. Loading device with scale and revolution counter for twisting angle measurement Torque measurement unit Calibration device Specimen Track base Digital torque meter 3 Technical Data General data:Main dimension: 1400 × 350 × 300 mm Weight: 25 kg .Figure 1: layout of the torsion apparatus Technical description of the apparatus The apparatus consists mainly of: 1. 5. one is the input scale on is output.Loading device:Worm gear reduction ratio: 62 Revolution counter: 5 digit.50° C Power supply: 230 V. LED 14 mm Temperature operating range: 0 . 50/60 Hz Calibration device:Maximum load: 30 Nm Load increment: 2. There are two revolution scales. At the input side there is a rotating gear which is used to turn the specimen with an angle. . with reset Output scale: 360° Input scale: 360° Indicator: Adjustable Torque measurement unit:Range: 0 – 30 Nm Display: 6 digit.5 Nm 4 Loading Device The torsional loading is transmitted to the specimen by a worm gear and a hand wheel. The error can be reduced by. The torque applied to the specimen will produce shear stresses which are detected by the strain gauges. The signal of the gauges is conditioned by a measuring amplifier with a digital read out. 5 Specimen . Compensation can be controlled by a dial gauge which is located at the side of the specimen holder. Strain gauges can only measure strain. In the case of pure torsion the maximum of principal stress will occur at a 45 to the axial axis of the torsion rod which then causes Slight deformation of the torsion rod .Thus this will cause an error in the twist angle calculation.Torque Measurement Unit The specimen is mounted at one side to the loading device and the other side to the torque measurement device. moving the specimen holder of the torque measurement unit. The output signal of the strain gauge can be obtained from the amplifier. Calibration Calibration process was carried out before carrying out the experiment.Specimen A ( brass ) Specimen B (aluminium) 6 Procedure: I. The calibration component is made up of a lever and a load weight. Range of torque set was . For calibration purpose of the torque measurement unit a defined load torque was used as reference where it was generated by a calibration unit. Weight of the lever was balanced by a certain weight which enables the load torque to solely depend on the load weight. 7. The materials were mounted in between the loading device and torque measurement unit. The read out values should relate to the applied torque. 1. Offset was checked after reload and it has to be set zero when necessary. Notified data of read out and load torque can be graphed. the curve will show. Calibration of torque measurement unit. 4. Hexagon socket of 19mm was used. 2. If nonlinearities exist. Measurement amplifier at the back plane was switched on. 7 II. 7. V button was held and P was pressed to set the read outs to zero. 2. 6. Read out of the amplifier was set to zero. Dial gauge of the compensation unit was calibrated to zero. . The load weight was increased by stages using weight of 5N to 60N.between 0 and 30 Nm.5 Nm. Carrying out the experiment: Specimen attachment: 1. The calibration unit was fixed by the specimen holder of the torque measurement unit. Both the units were connected by a 15mm hexagon socket. Resolution used was 2. The load torque was increased by stages using torque of 5Nm and read out was tabulated. if not. Hand wheel at the input can be turned if necessary until amplifier read out shows zero. Both indicators at the input and output shaft of the worm gear was set to zero. Two specimens namely specimen A and B are used. it can be used as a calibration curve. 5. 3. There should not be a preload on the specimen. 4. 3. Shifting holder of the load device has to be in mid position. 5. 6. Torque measurement unit was connected to the measurement amplifier. ∅ Applied Load Torque Read out Torque (Nm) (Nm) 5 4. Specimen loading and tabulation 1.70 15 14. 2. Hand wheel at the input of the gear was turned clockwise to load the experimental material. For the second and third rotation of a half quarter (180’) was chosen and for the fourth to tenth rotation (360’) was chosen. Li Diameter.0061m Table 2: Dimensions of specimens . It shows only turned for a defined angle increment.5m LOAD (N) 10 20 30 40 50 60 Outer length. 8 DATA AND OBSERVATIONS Length of lever = 0. Results were tabulated. 8. For the first rotation. The deformation of the measuring torsion rod after each angle increment was compensated.8.40 25 24. an increment of quarter rotation (90’) was chosen. The twist angle was calculated at the specimen by dividing the rotations at the input by the reduction ratio of 62. Torque values were read from the display of the amplifier and were noted with the indicated angle twist. 7. fracture will occur.0061m Specimen B (Alluminium) 0. 6. Lo Inner Length. The hand wheel of the compensation unit shows turned to achieve this until the dial gauge indicated zero. Revolution counter was reset. 4.50 10 9.15 m 0. Experiment was repeated with specimen B.0662m 0.15 m 0.55 20 19. Between 100 and 200 rotation. 5.30 30 Table 1: Reading for calibration process Specimen A (Brass) 0. 3.0662 m 0. 52 1080 9.40 (degree) 1.45 9th 3240 10.15 46.60 29. θ Angle at gear input (degree) Read out torque (Nm) 90 1.65 8th 2880 10.26 No.40 23.42 4th 1440 9.95 4.80 34.50 3600 58.84 7th 2520 9.61 900 8.23 5th 1800 9. of Rotation st 1 2nd 3rd 10 th 10.25 8.35 360 4.35 52.81 540 7.90 270 3.45 2.70 14.75 5.06 Table 2: Shows the values obtained and calculated for Specimen A. 9 .20 11.45 180 2.71 720 8.03 6th 2160 9.90 40.00 17.Angle of twist. 35 360 0.80 3600 58.23 5th 1800 12.0662m Diameter.0061m Angle at gear input (degree) Read out torque (Nm) 90 0 (degree) 1.52 1080 8.71 720 3.84 7th 2520 12. it was observed that the read out torque value increases linearly as the weight of the load increases. of Rotation st 1 2nd rd 3 9 10th Angle of twist.03 6th 2160 12. 10 ANALYSIS AND RESULTS .26 No.55 40.40 34.42 4th 1440 11.90 23. Besides. when the experiment was first conducted to test the calibration.25 4.95 8.15 2.45 180 0. 12.81 540 1. Observations: In the beginning.61 900 5. the value of offset in the digital torque meter varies after each time the load was removed. It was also observed that it was quite harder to twist Specimen A compared to Specimen B while conducting this experiment.65 5.2mm = 0. Li = 66.65 8th 2880 12.85 14.1mm = 0.90 270 0.06 Table 3: Shows the values obtained and calculated for Specimen B.35 17.75 52. ∅ = 6.Specimen B (Silver Colour Material) Outer Length.60 46.45 th 3240 12.15m Inner Length. Lo = 115mm = 0.15 11.25 29. 0662 156.359 10 10 m 4 Shear Modulus.133 0.40 5. G for Brass = 39GPa 39. J = TL 0.322 0.359 10 10 m 4 32 32 Polar moment of inertia.00 0.85 0.359 10 10 m 4 32 32 Polar moment of inertia.79MPa J 1.00614 1.322 34.85MPa J 1.359 10 10 m 4 Shear Modulus. G for Brass = 27GPa .00.00614 1.I.00 |× 100 =3.83% 39. But the theoretical gradient value should be 1.133 46. Value – Experimental Value |TheoreticalTheoretical |×100 Value – 0.9651 |1.49 FOR SPECIMEN A T 10.81 Gradient from the graph.15 4. J = TL 0. Percentage Error = = II. % = FOR SPECIMEN B T 12. d 4 0.75 0.84 14. G = Theoretical Value.00 Percentage error.001.9651.45 5. FROM CALIBRATION CURVE The gradient value obtained from the calibration curve is 0.52 Gradient from the graph.0662 64. d 4 0.06479 100 99. G = Theoretical Value. 42% 27.1569 100 99.00 11 Graph of Read Out Torque vs Angle of Twist 12 10 8 Read Out Torque (Nm) 6 4 2 0 0 10 20 30 40 50 60 70 Angle of Twist (deg) .00 0. % = 27.Percentage error. For Specimen B 12 Discussion . For Specimen A Graph of Read Out Torque vs Angle of Twist 14 12 10 Read Out Torque (Nm) 8 6 4 2 0 0 10 20 30 40 50 60 70 Angle of Twist (deg) 2.1. The usage of torsion in real life engineering is very important. The value of the percentage error turned error obtained for specimen A is out to be high for both specimen.1062. 2.83% 99. this is because it involves things that rotate. The percentage 99.9651X +1. The shear stress varies from zero in the axis to a maximum at the outside surface of the shaft. One common mechanical part that are subject to torsion are the shafts. Bolts are very important in all types of applications. This is due to random errors. which means as the applied load increase there will be an increase in read out amplifier.42% whereas for specimen B is . the shear modulus.Whereas the shear modulus for material B is . there is no secure connection between the body parts of the ship. From the graph of read out torque vs angle of twist it can be seen that at a angle of 40 specimen A has a higher torque because it is a more brittle material while specimen B has a lower torque value because it is a more ductile material. and this is due to human error. 4. When a shaft is subjected to a torque or twisting. The equation of the graph is Y= 0. material A and B has an increase of torque when the number of rotation of the hand gear increases. Another mechanical part is the bolt. Based on the results of this experiment. It is clear that specimen A is less ductile compared specimen B. 16 . The torsion that generates friction which holds up the bolt so that it does not become lose.79MPa 156. 3. We can also say ships need bolts. 5. a shearing stress is produced in the shaft.1. The theoretical value of shear modulus of specimen A is 27MPa and for specimen B is 39MPa. From this we can see that the experimented value of both specimen is higher than its theoretical value.85MPa . Without bolts. From the results obtained at table 1.an example of shaft usage are in cars which is the gear shaft. G for specimen A is 64. Hence the experiments were less accurate for specimen A. When a bolt is tightened it is subjected to tensile stress as preload is introduced but also to torsion stress as a result of friction. More torque is needed to twist the specimen A specimen than specimen B. From the graph of read out amplifier vs applied load torque it can be clearly seen that the graph is linearly proportional. Torsion is the twisting of the bolt when applying the tightening torque. the error we got was calibration error in the torque measuring unit.From this we can state that specimen B is a more ductile material compared to specimen A which has a lesser modulus of shear. From the experiment. Conclusion In conclusion. we concluded that specimen A has a stronger and less ductile property whereas specimen B has a more ductile property and less stronger property compared to specimen A. Also improper loading of the socket may lead to improper data. What we understood from the principle of torsion testing from this experiment is that when a specimen is subjected to torsion it will . The objective of this experiment which is to understand the principles of torsion testing has been achieved. The calculation was mainly based on the shear modulus G and the percentage error. because it’s a hard property. Then we were given two different types of specimen which we have to test its torsion by using a testing device called the WP500 which gives out the value of the torsion of the object at every angle of rotation.First the experiment was tested by using loads to measure the read out torque. Incorrect values from the WP500 is also a very effective error. This can happen due to the wrong loading method of the specimen. This showed the difference in property of the specimen . From this experiment we understood that specimen A is to be Brass whereas specimen B is to be Aluminium . Wrong loading of the specimen can lead to uneven distribution of angle of twist. our understanding was based on the results we obtained which the shear modulus G angle of twist and percentage error. Whereas specimen B twist easily because of its ductility property.Errors and Precautions Graphs of specimen A and B are expected to be same.15. The specimens are first mounted between the device and torque measuring unit. Every angle of rotation was noted. Then the hand wheel was rotated till the 10th rotation was done. this experiment is about torsion test .55 whereas specimen B has a read out torque of 0. This specimen selection was based on their property. then the graph of calibration curve was drawn. From this experiment we understood the effect of torsion test on two different types of specimen. Based on all this calculated values.42% percentage error for specimen A was and for specimen B was at the angle of twist of 2.83% 99.85MPa was and for specimen B was . specimen A is done first followed by specimen B. We had errors that effected our result in a small scale.92. material A has a read out torque of 2.79MPa 156. The modulus of shear of specimen A 64. Make sure the calibration device is tighten properly before starting the experiment. From this experiment. Specimen A needs more rotation to overcome its twisting force. this can be avoided by making sure the socket is properly fixed. we have obtained the values of the torque for both specimen A and B. The 99. .produce an angle of twist which is then calculated to know which specimen is more brittle. pp 147. Reference Ferdinand P. COE. By Torsion testing manufactures are able to simulate real life service condition. Mechanics Of Materials. this is because the effects of torsion applies to small parts such as shafts are used in ships. check product quality. Uniten.Beer. E. . G through measurement of the applied torque and angle of twist has been also achieved. This experiment is very important in every engineering applications as it the small parts like the bolts are the one that gives the biggest effect in the machine. 7th Edition. Whereas bolts and are used in many application for example the body of the ships. 2014. The other objective which is determine the modulus of shear. John T. 14 This experiment plays a very important role in engineering applications. pp 20. Jr. verify designs.DeWolf. MEMB231 Materials Laboratory Manual. and ensure proper manufacturing techniques.Russell Johnston. McGraw Hill. Semester 2 2015/2016. 15 .