Content uploaded by Suresh Bhalla
Author content
All content in this area was uploaded by Suresh Bhalla on Nov 02, 2014
Content may be subject to copyright.
9th International Symposium on Advanced Science and Technology in Experimental Mechanics, 1-6 November, 2014, New Delhi, India
Virtual Smart Structures and Dynamics Lab: Towards Teaching Advanced Concepts Online
Suresh BHALLA1, Naveet KAUR and Susmita NASKAR
1Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016
Abstract
This paper presents an overview of the Virtual Smart
Structures and Dynamics Lab (VSSDL) at the Department
of Civil Engineering, IIT Delhi. VSSDL has been set up as
a part of the ‘Virtual Labs’ project sponsored by the
Ministry of Human Resource Development (MHRD),
Government of India, under the National Mission on
Education through Information and Communication
Technology (NMEICT). The aim of the lab is to be emerge
as an effective medium of learning for those students who
do not have access to specialized lab in the area of smart
materials and structures or those who wish to take up and
R&D career in this field. The lab covers experiments
concerning interdisciplinary applications of smart materials
and structures concerning structural dynamics. The lab
provides two types of experiments- trigger based and
simulation based, both of which can be effectively used for
learning purposes. Students from all over the world can
take advantage of the facilities to master advanced
concepts thorough online experiments of VSSDL.
Key words
Virtual Lab, Simulation, Trigger, Smart Materials, Smart
Structures
1. Introduction
For a normal engineering college in India, lack of
resources in terms of sophisticated instruments is a major
hurdle, especially when the experiments involve concepts
very different from the routine curriculum. At the same
time, they also face human resource problem. Qualified
and competent teachers are a scare resource, especially for
tier two or three engineering colleges in India. The ‘Virtual
Labs’ project initiated by the MHRD is a major step to
overcome the above issues to great extent. It enables good
institutions such as IITs to share their instruments and
human resources through the internet. The lab is available
online to the users through the link:
http://ssdl.iitd.ac.in/vssdl/home.html
2. Smart Materials and Structures
A ‘smart material’ is defined as a material which exhibits
stimulus-response characteristics [1]. Piezoelectric
materials, shape memory alloys, fibre optic materials and
electro-rheological fluids are some of the commercially
available smart materials. Similarly, ‘smart structure’ is
defined as a structural system having built-in sensors,
actuators and a control mechanism, whereby it is capable
of sensing a stimulus, responding to it in a predetermined
manner and extent, and reverting to the original state as
soon as the stimulus is removed [2].
VSSDL provides a platform to inquisitive students to
perform basic experiments related to smart materials and
structures involving structural dynamics, both remotely
and through simulation. The trigger based experiments
involve remote operation of equipment (physically present
at IIT Delhi) to obtain experimental data. The simulation
based experiments, on the other hand, are based on
mathematical or numerical models running in a server to
simulate the process intended to be taught to the student.
The main smart material focused in the VSSDL is
“piezoelectric material”. This material shows the stimulus-
response characteristics in terms of the generation of
charges under the influence of stress, and conversely, the
generation of strain under the influence of and applied
electric field. The fundamental relationships for a piezo-
patch under small field conditions may be expressed as
(1)
331
11
1
1Ed
Y
T
SE+=
(2)
1313333 TdED T+=
ε
where S1 is the mechanical strain, D3 the electric charge
density over piezo-element and d31 the piezoelectric
constant. )1( jY EE
η
+= 1111
Yis the complex Young’s modulus of
the PZT patch at zero electric field, η being the mechanical
loss factor. Similarly, )1(
3333 j
TT
δεε
−= is the complex
permittivity of the PZT material at zero stress,
δ
being the
dielectric loss factor. For d31, the first subscript signifies the
direction of the electric field and the second subscript
signifies the direction of the resulting stress or strain.
3. Structure and Operation of VSSDL
Fig. 1 A physical overview of VSSDL
The VSSDL is basically the online extension of the existing
“Smart Structures and Dynamics Lab” (SSDL), at the
Department of Civil Engineering, IIT Delhi
(http://ssdl.iitd.ac.in). Fig. 1 shows a physical overview of
the VSSDL at the Department of Civil Engineering, IIT
Delhi. It consists of the experimental set-ups of four trigger
based experiments, cameras to provide real-time
9th International Symposium on Advanced Science and Technology in Experimental Mechanics, 1-6 November, 2014, New Delhi, India
visualization to the user and data acquistion systems
operating through the local area network (LAN). All the data
acquisition systems are VXI compliant and can be easily
controlled through the internet. The four trigger based
experiments are:
(a) Exp 1:Vibration Characteristics of Cantilever
Beam Using Piezoelectric Sensors
(b) Exp 2:Identification of High Frequency Modes of
Beam in “Free-Free” Conditions Using Electro-
Mechanical Impedance (EMI) Technique
(c) Exp 3:Forced Excitation of Steel Beam Using
Portable Shaker
(d) Exp 4:Photogrammetry for Displacement
Measurement
Except (d), all trigger based experiments involve piezo
material, specifically lead zirconate titanate (PZT) based
patches. Fig. 2 and 3 show the typical camera view and the
graphical user interface available to the user for experiment
1. In this experiment, the user can get real audio-visual
feeling of a hammer striking a cantilever beam. The website
provides the user all resources such as the manual, pre-
experiment quiz (to check readiness of the student to
perform experiment with understanding) and post-
experiment quiz (to check the understanding of the student
post experiment). The user is given control of few
parameters such as the sampling rate and the total duration
of data acquisition.
Fig. 2 Camera view of Experiment 1
Fig. 3 GUI available to user for Experiment 1
Fig. 4 Camera view of Experiment 3
Fi
T
g. 4 shows the camera view of Experiment 3. Here, a
portable dynamic shaker does a sweep excitation of a large
steel beam, whereby the user is able to obtain the resonant
frequency and the structural damping of the system. The
user can physically experience resonance of the structure
through audio interface.
he four simulation experiments are :
(a) Exp 5: Modes of Vibration of Simply Supported
Beam
(b) Exp 6:Modes of Vibration of Simply Supported
Plate
(c) Exp 7:Damage Detection and Quantification Using
Electro-mechanical Impedance (EMI) Technique
(d) Exp 8:Dynamics of Bandra Worli Sea Link Bridge.
The simulation based experiments 5 and 6 concern
simple structural dynamics related experiments for the
beginners. Fig. 5 shows the typical plot of the simulation
experiment number 6, where the student understands about
the modes of vibration of a simple plate through simulation.
Similarly, experiment 7 uses the measurement data to
simulate damage in a typical structure and observe the
changes in the conductance signatures. Experiment 8
demonstrates to the user typical modes of vibration of a
cable-stayed bridge through finite element simulation.
Unlike the trigger based experiments, the simulation based
experiments are available round the clock to the users. This
gives an opportunity to the inquisitive students to learn
advanced concepts at their own pace.
2.1 Structure of paper
Fig. 5 Simulation covered by Experiment 6
Cantilever
Hammer
9th International Symposium on Advanced Science and Technology in Experimental Mechanics, 1-6 November, 2014, New Delhi, India
4. Conclusions
The VSSDL has something to offer to inquisitive
undergraduate as well as post graduate students. For
undergraduate students, it offers basic experiments on
structural dynamics. For post graduate level students, it
offer advanced trigger based experiments. Of course, the
undergraduate students too can attempt the trigger based
experiments. The VSSDL also offers online resources and
video lectures involving smart materials and structures to
the users who wish to take up further higher studies in this
field of research. It is the endeavor of the developers that
more and more student be motivated of taking up higher
studies in this important field of research.
Acknowledgement
The authors gratefully acknowledge the financial support
of the MHRD for the VSSDL project.
References
[1] Gandhi, M.V and Thompson, B.S: Smart Materials
and Structures, Chapman and Hall (1992).
[2] Ahmad I.: Smart Materials, Structures and
Mathematical Issues, Proc. US Army Research
Workshop (1988), 13-16.
[3] Bhalla, S.: A Mechanical Impedance Approach for
Structural Identification, Health Monitoring and Non-
Destructive Evaluation Using Piezo-Transducers
(2004), School of Civil and Environmental
Engineering (CEE), Nanyang Technogogical
University (NTU), Singapore.
