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Intelligent Structural Syst > Exam 2 - Study guide questions > Flashcards

Exam 2 - Study guide questions Flashcards

1
Q

Principles of using martensite SMA and superelastic SMA for passive vibration damping

A

Both have potential for passive vibration control through vibration isolation and energy dissipation

Superelastic is preferred because it is passive (requires no external source) but martensite has greater capacity for damping

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2
Q

Two mechanisms for passive vibration control using SMAs

A

Vibration isolation and Energy dissipation

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3
Q

Why pre-tension is often required when the superelastic SMA is used for passive vibration damping?

A

Pre-tension is applied to avoid the linear elastic region that does not dissipate energy

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4
Q

What is the function of superelastic SMA in the friction damper subject to seismic load?

A

To provide re-centering capacity while the integrated friction device provides the most energy dissipation (superelastic SMAs provide an inherent damping property also)

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5
Q

Effect of nitinol SMA wires in the case of ECC reinforcement

A

To provide energy dissipation and self-repair cracks

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6
Q

Principle of using martensite SMA and superelastic SMA in concrete structure self-rehab

A

Self-rehab property through heating martensite SMA

increased damping

self-sensing ability through monitoring the electrical resistance value of the SMA wire strands

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7
Q

What does monitoring the electrical resistance values of SMA cables tell us in concrete structure?

A

elongation of SMA wires increases electrical resistance thereby monitoring the electrical resistance we can monitor the elongation

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8
Q

MANSIDE project - how the SMA device provides self-centering and energy dissipation

A

re-centering group is based on superelastic SMA wires to re-center the device/building

pre-tension superelastic wires wound around studs dissipate energy by acting as two counteracting springs

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9
Q

Basic principle of using SMA wires for base isolation

A

Two superelastic SMA springs used for passive base isolation provide energy dissipation due to hysteresis and self-centering due to superelastic effect

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10
Q

Why are feedback controllers needed in the operation of SMA wire actuators?

A

Challenges posed by the nonlinear response (hysteresis) feedback controllers help manage this nonlinearity by continuously monitoring the actuators position and adjusting inputs accordingly

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11
Q

Difference in position regulation and position tracking controllers

A

Position regulation: moving from point A to point B - focuses on reaching and maintaining a fixed target position

Position tracking: time dependent - suitable for applications requiring dynamic movement and accurate following of a changing path and also incorporates a feed-forward term which is used to anticipate the desired trajectory and provide initial control input that guides the actuator along its path

The feed-forward term is designed to provide the approximate amount of current required for the SMA actuator to follow the desired path

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12
Q

Liquid vehicle of MR fluids

A

mineral oil, synthetic hydrocarbon oil, silicone oil, water

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13
Q

Polarizable particles of MR fluids

A

Carbonyl iron, powdered iron, iron/cobalt alloys

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14
Q

Size of polarizable MR fluid particles

A

1-10 microns

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15
Q

Yield stress of MR fluids

A

50 - 100 kPa

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16
Q

Power requirements of MR damper/fluid

A

50 watts, 12-24 volts, 1-2 amps

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17
Q

Power requirements of ER damper/fluid

A

50 watts, 2,000-5,000 volts, 1-10 amps

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18
Q

What is a bingham model used for?

A

rheological model used to describe the flow behavior of certain non-newtonian fluids and characterizes materials that behave as a rigid body at low stresses but flow as a viscous fluid at high stress

Slope of stress vs. strain

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19
Q

Key features of the bingham model

A

Yield stress and viscosity

When applied stress exceeds yield stress the fluid will flow

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20
Q

Three common operational modes of MR fluids

A

Pressure driven (valve mode) - fixed poles (servo-valves, dampers and shock absorbers)

Direct shear driven - relatively moveable poles (clutches, brakes, locking devices)

Squeeze film

21
Q

Which operational mode of MR fluids uses disks?

A

Direct shear driven - clutches/brakes

22
Q

Pressure driven flow mode is a result of the sum of what two components?

A

Viscous component and field dependent induced yield stress

23
Q

What is the volume of MR fluid exposed to the magnetic field and thus is responsible in providing the desired MR effect

A

Active fluid volume

24
Q

geometric constraints and necessary aspect ratios for MR devices can be determined from manipulating what equations?

A

Equation for active fluid volume V (eq. 5)

25
Q

The force or torque inputs from actuators are usually used to suppress vibration amplitudes based on on-line measurements from sensors

A

Active vibration control (MR damper)

26
Q

System that combines the best features of active+passive control offering the reliability of passive devices, yet maintaining the versatility and adaptability of active systems

A

Semi-active control (MR dampers)

27
Q

Viscous damper, oil damper, viscoelastic damper, steel damper are all what types of dampers?

A

Passive Damper

28
Q

variable orifice damper, friction controllable braces, friction controllable isolators, variable stiffness devices are all what types of dampers?

A

Semi-Active damper

29
Q

Three models of MR dampers

A

Bingham Viscoplastic, Bouc-Wen, Modified Bouc-Wen

30
Q

What is Bingham Viscoplastic model good for? Bouc-Wen?

A

Bingham for response analysis, but not for control analysis

Bouc-Wen for hysteresis modeling

31
Q

Proper selection of a control algorithm for MR damper may be dependent on what three things?

A

The type of non-linearity present, available feedback measurements, number of devices to be implemented in the structure

32
Q

Simplest and cheapest way to implement a control law and useful for vibration isolation of rotating machines ?

A

Open-loop (on-off) control (sponge damper for washing machine)

33
Q

Working principle of FOSs

A

Total reflection of light rays within the core of the fiber optic cable

34
Q

Main components of a FOS system?

A

Light source, transducer, measurand, detector

35
Q

Four common types of sensors by modulation process

A

Intensity (amplitude), phase, frequency/wavelength, polarization

36
Q

Extrinsic vs Intrinsic FOS

A

Extrinsic - sensing takes place outside of the fiber

Intrinsic - one or more of the physical properties of the fiber undergo a change

37
Q

Modulation of point FOS

A

One point of fiber is a sensor

38
Q

Distributed FOS

A

Whole cable is sensor

39
Q

Quasi-Distributed FOS

A

Periodic portions of fiber act as sensor

40
Q

Mach-Zehnder, Michelson, Fabry-Perot, EFPI skin friction sensor, EFPI acoustic emission sensor are all what type of FOS?

A

Phase modulated

41
Q

Reflective, Fiber displacement, transmission loss, micro/macro bend, evanescent are all techniques to create what type of FOS?

A

Intensity modulated

42
Q

Fiber Bragg and Long Period Grating FOSs are what types of FOSs?

A

Wavelength modulated

43
Q

Guided modes and cladding modes that propagate in the same direction - the results are attenuation bands in the transmission spectrum

A

Long period grating sensors

44
Q

Made by inscribing periodic gratings into the core of the fiber. The gratings are of a different refractive index and will reflect portions of a certain wavelength backwards in phase

A

Fiber Bragg grating sensor

45
Q

Capable of providing measurements along the entire FOC

A

Distributed FOSs

46
Q

Three scattering processes used in DFOS

A

Rayleigh, Raman, Brillouin

47
Q

Brillouin scattering is used to implement what two types of FOSs?

A

Distributed temperature sensor (DTS) and distributed strain sensor (DSS)

48
Q

Two categories of Rayleigh analysis techniques

A

Optical time domain reflectometer (OTDR) and optical frequency domain reflectometer (OFDR)

And is often used for Distributed Acoustic Sensor (DAS)

Intelligent Structural Syst (3 decks)

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