Multidisciplinary Engineering Laboratory Experiments by warwar123

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									                     Multidisciplinary Engineering Laboratory Experiments

                        R. King, T. Parker, T. Grover, J. Gosink, and N. Middleton
                Engineering Division, Colorado School of Mines (CSM), Golden, CO 80401
Abstract - CSM is developing a series of three laboratory       motion, vibration, displacement, data analysis, and error
courses that is horizontally integrated to replace              analysis. More details are available in [2]. Experiments
traditional discipline specific laboratory courses in           utilize computer data acquisition, thermistors, strain gages,
electrical circuits, fluid mechanics, and mechanics of          pressure transducers, flow meters, power supplies, digital
materials. The objective is to provide a more realistic,        multimeters, oscilloscopes, filters, amplifiers, and linear
industrial experience by integrating components from            displacement transducers. As small systems are developed
several engineering disciplines and develop life long           with these topics, students specializing in electrical,
learning skills. This paper describes the multidisciplinary     mechanical and civil areas begin to understand the
experiments in the first course and the student’s               commonalties in and relationships between their
assessment. Experiments are also vertically integrated into     disciplines.
complex systems over a three-course sequence. This                    These topics, devices, and skills were chosen to
vertical sequence moves students from a controlled              represent inherent components of more sophisticated
engineering science laboratory environment to less              systems that will be covered during the three semester
controlled engineering design environments while data           course sequence. For example, thermistors, strain gages,
analysis sophistication increases. Even though controlled       pressure transducers, flow meters and linear displacement
conditions are used in some experiments in the first course,    transducers will simultaneously provide system data in
students are not led sequentially through the steps             MEL III to monitor performance of a testing machine while
necessary to complete the experiment. Rather they are           determining the stress/stain properties of a specimen.
encouraged to develop the skills which foster life long               The sequence also moves students from a controlled
learning. In the vertical integration, the first course         engineering science laboratory to less controlled
bridges basic science and engineering science, the second       engineering design environments while data analysis
transitions between engineering science and engineering         sophistication increases.     For example, strain gages,
design, and the third prepares students for industrial          accelerometers, data acquisition and data analysis are
projects.                                                       studied in MEL I experiments. Later they will be used to
                                                                gather data from off road paths to improve suspension
                      Introduction                              designs for the mini-baja student-competition vehicle.
                                                                      Even though controlled conditions are used in some
The Fund for the Improvement of Secondary Education             experiments, students are not led sequentially through the
(FIPSE) within the Department of Education along with           steps necessary to complete the experiment. Rather, they
several companies is providing resources to develop a           are given a group of objectives to accomplish, training in
multidisciplinary engineering laboratory (MEL) for              the skills necessary to use the required tools, and
engineering students [1]. The series of three laboratory        encouraged to design their own experimental procedure and
courses (MEL I, II, & III) replaces traditional laboratories    to be inquisitive. The instructor moves around the room,
in electrical circuits, fluid mechanics, and mechanics of       coaching the students through the experiments. This
materials in order to provide a more realistic, industrial      encourages higher level thinking skills that make students
experience by integrating components from several               life long learners.
engineering disciplines.                                              We connect each experiment to one or more lecture
     Our goal is to prepare students for the real practice of   courses common to a variety of engineering disciplines.
engineering by integrating disciplines, skills (wiring,         Consequently, the introductory experiments bridge basic
programming, experimentation, data analysis and                 science and engineering science. The second laboratory
modeling), and methods (discovery, evaluation and               transitions between engineering science and engineering
investigation) on a foundation of underlying principles         design, and the third laboratory prepares students for
(laws of conservation, continuity and equilibrium). We          industrial projects they might see in their first full time
integrate disciplines horizontally and build experimentation    employment.
and thinking skills vertically.                                       To accomplish the above, we set the following
     This paper describes the MEL I horizontally integrated     guidelines for MEL experiments:
experiments in bridge circuits, amplifiers, filters, thermal
properties, stress and strain, pressure, flow, harmonic
N All experiments should use systems.           Even when a    limited solutions so sophomore level students are not
  component is learned, it is learned in an applications       overwhelmed in this one credit hour course.
  context.                                                        Some universities have added innovative laboratory
N The exercises have many open-ended elements. Student         courses that cover one technical topic applicable to multiple
  teams are encouraged to learn on their own and bridge the    disciplines. For example, the Optoelectronic laboratory
  gap between experimental resources provided and              course at Bucknell combines elements of electrical
  expected results by developing their own procedures. We      engineering, materials science, optical engineering,
  do not give procedural steps.                                chemistry, and physics [6]. WPI offers a course in
N We don’t attempt to teach students how to use every          communications systems to students from multiple
  instrument, software package, or sensor that they might      programs [7]. The University of Alabama Foundation
  encounter during their working careers.                      Coalition     Program      developed       a    junior    level
N We incorporate reverse engineering.                          multidisciplinary course in dynamic data acquisition and
N We supply manufacturer specification sheets rather than      analysis [8]. The MEL sequence differs by integrating
  extract critical information for the students.               horizontally and vertically without adding new courses.
N Students discover relationships by observing how systems     MEL does not stress one topic throughout the course; each
  react to varying inputs.                                     experiment integrates two or more engineering
N Students evaluate competitive devices.                       fundamentals.
N Students develop models to predict performance.                 Mechatronics is an inherently multidisciplinary topic
N Students diagnose (investigate) unpredicted outcomes.        covered by university laboratory courses [9]. At GMI,
N Students practice communications skills with required
                                                               students explore sensors, motors and electronic components
  reports, results forms, laboratory notebooks, team           and interface a physical system to a personal computer.
  collaboration, and interviewing experts (the lab             MEL I doesn’t cover control, but it will be introduced as
  instructor).                                                 part of the more sophisticated sequence of experiments in
                                                               MEL III.
                                                                  Others have integrated math, physics, and engineering
Comparison with Other Innovative Laboratory                    fundamentals. In the Foundation Coalition program at
                 Courses                                       Arizona State University, students design and calibrate a
                                                               squash-ball slingshot, have a bungee-cord egg drop
Some universities have courses dedicated to data acquisition   competition, identify an unknown shape (cube, cylinder, or
for students in multiple disciplines [3,4]. We considered      hollow cylinder) contained in an opaque spherical plastic
developing several experiments to exclusively teach            shell [10]. These projects are similar to MEL I, except they
computer data acquisition in the initial weeks of MEL I.       are not part of a three course vertically integrated sequence.
However, we chose to integrate data acquisition with              Arizona State University conducts mostly unscheduled
engineering fundamentals, teaching data acquisition along      experiments for 11 electrical engineering courses in a single
with the applications in each experiment. Consequently, we     large room that is open 74 hours each week [11]. We chose
do not increase the number of credit hours required for        scheduled times when faculty are available to coach
graduation, or displace other topics in the curriculum by      students through the difficulties of learning on their own
adding a separate course in data acquisition. Students do      without step by step instructions, and to provide better
not become expert LabVIEW£ (from National Instruments          laboratory equipment security.
Corp.), data-flow, G-language, programmers during MEL I,
but rather develop an adequate skill to gather data. We plan                        Administration
to expand their LabVIEW skills in MEL II and III.
    To encourage higher level thinking skills, some            Twenty-five students were divided into teams of 3 (and one
universities have open-ended project laboratories[5]. At San   of 4). A group of senior students started earlier in the
Jose State University, a class of 24 students majoring in      semester and stayed one or two weeks ahead of the main
EE, Materials Engineering, Chemical, Mechanical, and           pilot group, so our experiments were tested three times,
other Engineering disciplines process device wafers in         once by the seniors, once by the professor, and once by the
student teams. CSM has open ended projects in the              pilot class. Students worked 1-4pm on Wed afternoons.
Freshman and Sophomore projects courses and in our senior      This was a small section of our traditional electrical circuits
capstone design course, so we can focus on technical topics    laboratory course that was asked to volunteer to try MEL I.
in MEL while requiring students to practice and reinforce      All but one student volunteered and he transferred to
their teamwork and open ended problem solving skills.          another section of the traditional lab. A few students in
MEL I contains relatively constrained problems with            other labs heard about MEL and transferred into our pilot
course. Students began working during the third week of         correct, they add a second and observe data from both
the semester, and spent 11, 3-hour meetings on the MEL I        thermistors simultaneously.
experiments and one meeting on the final exam. We expand           Because students take an introductory electrical
to 14 meetings in the fall semester.                            engineering course co- or pre-requisite to MEL I, they
      Normally a graduate teaching assistant with help from     design and wire a voltage divider circuit, containing a
a professor teaches lab courses. However, the pilot course      power suply, to interface the thermistor to the computer.
had two professors, Drs. King and Parker. In addition the          Students are required to plot their data and report it and
division engineer, Dr. Grover, prepared equipment and           the value of the constants in the thermistor equation. They
assisted with design and instruction. After MEL I is            are asked to report their procedure, especially as it pertains
modified, graduate students and an adjunct professor will       to exposing both thermistors to the same input conditions,
teach 90 students divided between 3 sections in the fall        covering as large a range as possible, and gathering
semester with help from Dr. King.                               numerous data points within the range. We ask them to
                                                                compare the data from the multimeter and LabVIEW so
  Experiment 1, Computer Data Acquisition,                      they will realize the time dependant nature of the data is
Thermal Measurements, and A Voltage Divider                     much easier to capture with computer data acquisition. We
                                                                ask them what they should do if the data on the computer
                  Circuit                                       monitor graph is difficult to read so they will understand the
                                                                value of the digital indicator and grid line options in a
The initial meeting of the semester involves introducing the
                                                                graphical user interface. To begin thinking about errors in
students to analog to digital conversion with a simple
                                                                measurements, we ask for their opinion of the accuracy of
thermistor and the LabVIEW graphical programming
                                                                their data points. We require that they submit a sketch of
environment.        Programming skills are limited to
                                                                their calibration apparatus emphasizing wiring and
modification of existing programs (Virtual Instruments).
                                                                component interfaces.
The objectives are:
N Wire a simple circuit and make A/D connections,
N Expose students to a simple sensor,
                                                                          Experiment 2, Strain and Bridge
N Introduce calibration,
                                                                The objectives are:
N Integrate thermal concepts and circuits, and
                                                                N Discover how to measure strain
N Practice data acquisition using LabVIEW.
                                                                N Discover differential measurements
    Each team is provided with two thermistors. One is
                                                                N Understand & wire a bridge circuit
precise and we provide its calibration information. The
second thermistor has an unknown response. Students are         N Use an amplifier
asked to calibrate the second over the range from freezing to   N Compare circuit and wiring diagrams
boiling water gathering data with a multimeter and with         N Calculate strain from bridge voltage output
LabVIEW computer data acquisition..                             N Discover higher sampling rate VIs in LabVIEW
    The reference information contains the thermistor           N Learn to save spreadsheet files in LabVIEW
resistance equation:                                                In the material supplied with this experiment, we discuss
1                                 3                             the application to structural design and relate the material
    C1  C 2 ln( R )  C 3 ( (ln R)                             to strength of materials testing and ultimately to a MEL III
T
where: T = temperature (GK), R = thermistor resistance, and     experiment in redesign of our Mini-baja competition vehicle
C1, C2, and C3 are constants.                                   suspension.
    Additional reference material explains the fundamentals         We also make the connection to science courses and
of computer data acquisition, and LabVIEW basics like           provide reference material like: In one dimension, 0=/l/l,
panels, menus, help features, location of example virtual       and Resistance, R = 7l/A, where: 7 = volume resistivity of
instruments: G programs (Vis), editing, tools menu,             the material, l = conductor length, A = cross sectional area.
programming elements: loops, arrays, Graph functions,           0t = -0, 3, where: 3= Poisson's ratio, 0t = transverse strain,
array functions, and a customizing graphs to make a good        and 0, = axial strain.
user interface.                                                 Rnew = 7L(1+0)/(A(1-30)2).
    Student teams are asked to locate an example LabVIEW            The strained and unstrained resistance provide the
virtual instrument (VI) that correctly graphs one channel of    following ratio assuming 7 is constant:
a signal generator output. To learn the use of a function       'R     (1  0 )
                                                                                     1 | (1  0 )(1  230 )  1 | 0 (1  23 )
generator, they are asked to use the function generator as a     R    (1  30 ) 2
known input to test their VI. After they complete one graph     'R                    where Fg = the gage factor
                                                                          Fg0
                                                                  R
    We also provide a manufacturer’s specification sheet for    12. Explain the difference in strain precision with hardware
the strain gages, the pin outs for the amplifier, etc. The          and software amplifiers.
following shows an example of bridge reference material
provided:                                                       Experiment 3, Oscillations and Thermal Expansion

                                                                   The objectives are:
                                                                x Extend strain measurements to the time domain.
                                                                x Integrate experiments 1, 2, and 3.
                                                                x Discover frequency, period and damping properties of a
                                                                  vibrating beam
                                                                x Compare software and hardware amplifiers
                                                                x Measure temperature and strain simultaneously
                                                                    Students study the LabVIEW VI provided using the Help
           Figure 1. Strain Gage Bridge Circuit                 feature. In addition to previous lessons, they learn how to
In balance, R1 + Rpot + R2 = R3+ Rpot + R4. Assume              write data to a file, scan waveforms and use the case
R1 = R2 = R3 = R4 >> Rpot . Current in each branch = I          structure. They add a feature that allows them to view the
I = V / (R1 + R2) = V / 2R.                                     data before deciding to save it to file.
V1 = V / 2R * R = V / 2 and R4 = R + 'R.                            They used the Experiment 2 beam, weights, strain gage,
V2 = V/(2R + 'R) * (2R + 'R) = V/2 * (1 + G)/(1 + G / 2)        bridge circuit, and amplifier. They deflected the beam and
where G = 'R / R,                                               released it, causing oscillation and gathered data with
(1 + G) / (1 + G / 2) | (1 + G) * (1 - G / 2)                   hardware and software amplifiers. They study damping by
V2 = V / 2 * (1 + G / 2)                                        adding weight to the beam. The following reference
V out = (V2 - V1) = V / 4 *G = (V /4) * ('R / R)                material was provided:
      We provide students with a small flexible beam, with      (3EI / l3) G = m dG / dt2 and G = A sin (Z2t + I),
strain gages mounted on top and bottom, to clamp to their       or y = Acos(Zt+G) where:
lab benches. They attached a series of weights to the end of    y = displacement at time = t from an equilibrium position,
the beam to deflect it, and measure the change in strain        A = Initial (maximum) displacement, G = phase constant, Z
gage resistance, then measure the bridge voltage, and           = angular frequency = (k/m)1/2 , where k = force constant
finally the amplified voltage.                                  and m = mass. At a point x on the beam,
    We provided the students with a VI and asked the teams      M=P (l - x), where M = moment and P = Force
to explore it with the Help features and modify it as           Stress at the top of bottom of the beam = V = M c / I,
necessary.                                                      Where: c = h/2, I = bh3 / 12, b = beam width, and
    The student teams verify the linearity of the strain gage   h = beam height
and check the gage factor. We continually ask students to       Strain = H = E V, where E = Modulus of Elasticity or
consider accuracy and errors. In this lab, the reference        Young’s Modulus (Y).
material and the reporting form asks them to consider               Next, students used a pair of strain gages and a
digitizing resolution.                                          thermistor to measure the thermal coefficient of expansion
    The following questions are asked in the report form        for an unknown test specimen. They were given a quartz
submitted after completing the experiment.                      specimen with known thermal expansion coefficient and the
1. Report the resistance data from DVM measurements.            following reference:
2. Should the DVM input impedance be large? why?                'R / R «i = [EG + ( Di - DG) FG] 'T, where:
3. Explain why a voltage is applied to the bridge?              i = unknown or known material, EG = temperature
4. Report the bridge voltage measurements.                      coefficient for resistivity of the strain gage, D = thermal
5. Compare the DVM and the bridge measurements.                 expansion coefficient for the test specimen (i) or the gage,
6. What excitation voltage would be optimum?                    Go.
7. Plot strain precision vs. excitation voltage.                    The results form required the students to:
8. Predict bridge output when gage is moved to other            1. Determine the minimum detectable strain with and
    branches of the bridge. Verify experimentally.                  without the hardware amplifier.
9. Explain how to use the sign of the signal change to          2. Compare data precision in EXCEL or LabVIEW.
    determine which strain gage is on top of the beam.          3. Graph and report the oscillation period and frequency.
10. Show the effect of two gages vs. one in the bridge.         4. Report procedures that would increase accuracy.
11. List and quantify each error.                               5. Evaluate the effect of weight on oscillation.
                                                                6. Relate force constant and frequency.
7. Determine ,.                                                  3.    Give alternatives for 2, and justify their choice.
8. Show how an additional thermistor reduces error in ,.         4.    Redesign the gage for a range of 250 psi.
9. Explain why quartz was a good thermal reference               5.    Redesign the gage to provide 1% accuracy.
    material.                                                    6.    Redesign the gage to build a transducer.
10. Describe the data acquisition program.                       7.    Explain their calibration procedure.
                                                                 8.    Calculate the mass of air in the calibration system.
       Experiment 4, Pressure Transducers                        9.    Report data in EXCEL tables.
                                                                 10.   Submit calibration curves for each transducer.
The objectives are:                                              11.   Specify linearity, sensitivity, hysteresis, zero (null), and
                                                                       repeatability errors.
N Reverse engineer and redesign a gage
                                                                 12.   Report the errors in the calibration system.
N Calibrate a pressure transducer                                13.   Define the damage point of the tuna can transducer.
N Discover hysteresis                                            14.   Explain the damage mechanism and effect on errors.
N Analyze Errors                                                 15.   Compare predicted and actual strain of can transducer.
N Understand gage and absolute pressure                          16.   Calculate Vout of the bridge at 1.0 psi.
N Understand different methods of describing accuracy            17.   Calculate appropriate dimensions and sensitivity error
   The reference material explains the common units of                 of a 100-psia-aluminum transducer.
pressure, and that the compressibility of a fluid is:            18.   Report measurements from the manometer experiments
k = -(V/V)/P, where: k = compressibility,                             and plot error vs. depth.
V/V = fractional change in volume, and P = pressure.            19.   Report the data from the differential measurement
Pressure from the weight of a column of liquid:                        experiment.
P = Po + 7gh where: Po is initial pressure at the top of the     20.   Calculate specific weight for water and salt water from
column (usually atmospheric pressure), 7 = density of the              absolute and differential measurements.
fluid, and g = gravitational acceleration = 9.81 m/s2.
    Additional reference material explains that pressure                   Remaining Experiments in MEL I
measurement device accuracy is presented as zero level
(null), sensitivity, linearity, hysteresis, and repeatability.   The above provided details from 4 of 9 experiments. To
      Students disassemble and reverse engineer a low            comply with FIE page limitations, we refer you to [2] for
accuracy vacuum dial gage that uses a Bourdon tube. They         details of experiments on:
receive a box of parts including a tuna can with strain gage
                                                                 N Accelerometer, function generator, Nyquist
mounted to an aluminum plate, a long plastic pipe, some
                                                                 N Microphone - filters, oscilloscope
hose, a valve, a yard stick, a manufactured pressure
                                                                 N Flowmeters, Hall Effect, Scaling Laws
transducer, and some Teflon £ tape. They are asked to
assemble these pieces into a system that will calibrate both
                                                                 N Rotary and Linear Transducers
pressure transducers and determine linearity, zero (null),
                                                                 N Final Exam
sensitivity, hysteresis, and repeatability errors. Reference
materials contain the approximate stress on the cylindrical                               Assessment
surface of the can:
8 = 0.75pa2/h2, where p = pressure, a = radius and               Our assessment data comes from multiple sources:
h = thickness                                                    N Survey Instrument (see [2] for list of questions)
    Students determine the pressure that damages the tuna        N Exam Questions
can transducer. They also estimate the dimensions and            N Independent Evaluator Classroom Observation
accuracy of a transducer made from aluminum instead of           N Focus Groups Led by Independent Evaluators
steel, with a range of 0 to 100 psia.                            N CSM Student Evaluation Forms
    Students also investigate manometers and differential           The independent assessment team of faculty from other
manometers to measure the specific weight of water, salt         departments at CSM Dr. Pavelich, Chemistry, Dr. Olds,
water, and an unknown fluid, using a variety of depths.          Liberal Arts, and Dr. Pang, International Studies, used
They plot the error in measurement as a function of depth in     focus groups, classroom observations and a student survey
the fluid, consulting an extensive reference on random and       to gather comparative data between MEL and EG383 ( the
systematic errors to determine how different errors in an        traditional electrical circuits laboratory). They concluded
experiment should be combined into a total error estimate.       that MEL I definitely met its goals; it caused more and
    The students:                                                deeper learning, with obvious integration of topics and
1. Explain the vacuum gage working mechanism.                    student excitement about the experience. However, they
2. Show how make it into a positive pressure gage.               were concerned that MEL may be at the extreme end of
what students can handle. Specific statements heard by the
three assessors were:                                                                 References
N MEL is open-ended, EG383 is cookbook,
N MEL forces critical thinking and deeper learning,             1.  Middleton, N., S. Glaser, J. Gosink, T. Parker, and R.
N MEL focuses on how to learn, EG383 on what to learn,              King, 1996, “An Integrated Engineering Systems
N Only MEL integrates circuits, fluids and strengths;               Laboratory,” FIE Proceedings paper 7c2.5, 1996.
N MEL students have an excitement about the experience          2. King, R., T. Parker, J. Gosink, “A Multifaceted
    that EG383 students do not,                                     Engineering systems Laboratory,” FIPSE Annul
N MEL is perceived as much more "real-world",                       Report, Dept. of Education, 1997.
N MEL students use teamwork in a more sophisticated             3. Eaton, J. K., “Computer-Based, Self-Guided Instruction
    fashion,                                                        in Laboratory Data Acquisition and Control,” FIE
N MEL teaching is more Socratic (coaching, not telling)             Conference Proceedings, 1992, 5pgs.
N MEL open-endedness requires much more teacher time            4. Ojha, A. K., “Data Acquisition Experiments,”
N MEL creates a higher frustration level than needed.               IEEE SOUTHEASTCON Proceedings, 1996, p 533-
N The background supplied at the start of a MEL                     536.
    assignment often seems overwhelming.                        5. Allen E.L., A.J. Muscat and E.D.H. Green,
N Information may have been incomplete or inaccurate in             “Interdisciplinary Team Learning in a Semiconductor
  some MEL assignments.                                             Processing Course, FIE Proceedings Paper 6a3.1,
N Non-Engineering students felt their background was                1996.
  inadequate for MEL and it was inappropriate to their          6. Lord, S. M., “An Innovative Multidisciplinary Elective
  needs.                                                            on Optoelectronic Materials and Devices,” FIE
N There may be too much depth expected or too many                  Proceedings Paper 3a4, 1996.
  assignments for success with less devoted faculty.            7. Orr, J. A., D. Cyganski, and R. Vaz, “A Course in
N All students learned in MEL but many seemed disturbed             Information Engineering Across the Professions,” FIE
  by their rate of learning being slower than that of others.       Proceedings Paper 6b1.1, 1996.
  They lacked confidence that they could do the work on         8. M c Inerny S. A., H. P. Stern, and T. A. Haskew, “A
  their own.                                                        Multidisciplinary Junior Level Laboratory Course in
                                                                    Dynamic Data Acquisition,” FIE Proceedings Paper
                       Conclusion                                   7c2.2, 1996.
                                                                9. Mariappan, J., T. Cameron and J. Berry,
Because MEL caused more and deeper learning, with                   “Multidisciplinary      Undergraduate      Mechatronic
obvious integration of topics and student excitement, the           Experiments,” FIE Proceedings Paper 6b1.2, 1996.
CSM Undergraduate council approved MEL I to replace the         10. Roedel, R., M. Kawski, B. Doak, M. Politano, S.
traditional circuits lab. We plan to improve MEL I and              Duerden, M. Green, J. Kelly D. Linder, D. Evans,
enhance the connection with physics over the summer of              “An Integrated, Project-based, Introductory Course in
1997to address the assessment concerns. MEL I will be               Calculus, Physics, English, and Engineering, FIE
offered in fall 1997 to 90 students divided into three              Proceedings, 1996.
sections. We will pilot and assess MEL II, fall 1997, and       11. Palais, J. and C. G. Javurek, “Arizona State University
MEL III spring, 1998.                                               Electrical     Engineering     Undergraduate     Open
    Planned topics for MEL II are:                                  Laboratory, IEEE Transactions on Education, v 39, n
                                                                    2, May 1996, p 257-264.
N earthquake simulation
N fluids network
N organ pipe
N acoustic velocities in different media
N strengths test machine hydraulics and electrical power
N total station surveying
  Planned topics for MEL III include:
N Mini-baja suspension
N Mini-baja GPS and digital mapping
N Pathway Bridge
N Fluids Processing Circuit Control
N Strength of Materials Testing System

								
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