Tolga ASA_030070177_Week7

1. Harmonic Motion(Motion)

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Harmonic motion:Oscillaratory motion may repeat itself regularly, as in the balance wheel of a watch, or display considerable irregularity, as in earthquakes . When the motion is repeated in equal intervals of time (T), it is called periodic motion. The repetition time T is called the period of oscillation, and its reciprocal, f=1/T, it is called the frequency. If the motion is designed by the time function x(t), then any periodic motion must satisfy the relationship x(t) = x(t +T). The simplest form of periodic motion isharmonic motion. It can be demonstrated by a mass suspended from a light spring. If the mass is displaced from its rest position and released, it will oscillate up and down. By placing a light source on the oscillating mass, its motion can be recorded on a light-sensitive filmstrip, which is mado to move past it at a constant speed.The motion recorded on the film strip can be expressed by the equation x = A.sin2(pi).t/T where A is the amplitude of oscillation, measured from the equilibrium position of the mass, and T is the perion. The motion is repeated when t=THarmonic motion is often represented as the projection on a straight line of a point that is moving on a circle at constant speed as shown in Fig 1.1-2. ( Theory of vibration with applications- Willia Thomson- page 6)

New Answer

Simple harmonic motion and its characteristics

A motion in which the accelaration of the body is proportional to its displacement from the mean position and is always directed towards the mean position is known as the simple harmonic motion It has following characteristics:

Motion is on both sides of mean postion. The maximum displacement on one side of mean position is known amplitude.

The body repeats its motion in a definite interval of time.

Acceleration is always proportional to the displacement and is directed opposite to it.

The motion of foot of perpendicular dropped from the particle moving in a circle on the horizontal and vertical diameters is called S.H.M

(Sharma S., Physics, p. 236)

2. Semi-active Actuators (Tranducers)

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Semi-active actuators:

The power at the output port of the actuator can be expressed as a function of the conjugate variables as:

PTrans =F. v

for translational output mechanical energy, and:

PRot = T . w

for rotational mechanical energy.

Semiactive actuators are those whose output mechanical power is not positive: PTrans <0 or Prot <0. This means that the energy level in the plant is reduced. Semiactive actuators dissipate the energy of the plant they are coupled to.

Semiactive actuators can actively modulate power dissipation, but the effort they supply (whether a force or a torque) can only oppose the flow in the plant (whether a velocity or an angular rate)

(Pons J. L., Emerging actuator technologies: a micromechatronic approach, Ed. 1st, p. 33, 34)

New Answer

Semi-active actuators behave basically as passive elements, capable of storing or dissipating energy. These actuators are adaptive since their passive mechanical properties can be adjusted by applying control signals. Electrorheological fluids, magnetostrictive actuators, electrostatic devices or shape memory alloys can be used in the fabrication of these semi-active actuators. Amongst these different options, piezoelectric transducers offer several distinctive advantages in active control applications because they are lightweight, can be of any shape and can even be microsized and are easily driven by a voltage. These actuators are flat, thin piezoceramic devices bonded to the surface of a structure.

(Sujatha, Vibration and Acousticsi p. 101)

 3. Rivet Bonding (Structural Adhesive)

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Rivet Bonding : (08.04.2011 03:06)

Rivet-bonding is a hybrid of adhesive bonding and mechanical joining employing rivets as fasteners. Shown schematically in Figure 10.9, the combination of rivets driven and set though structural adhesive has been used to considerable advantage in helicopter manufacturing as an example. The rivets tend to carry andy transient out-of-plane loads (whether anticipated or unexpected) to protect the adhesive from failing in peel. On the other hand, the adhesive acts to spread loading and soften stress concentrations added energy needed to open the bonded plus welded or fastened joint area), which improves both the crashworthiness of automobiles and their ride quality (through vibration damping and noise abatement) and (10) complete interface bonding to improve load transfer.
(Messler R.W., Joining of materials and structures: from pragmatic process to enabling, 2004, p.514)


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Rivet Bonding - the combination of a small number of rivets and a structural adhesive can usually give a much stronger assembly than a large number of rivets used alone. This process has been widely used in the assembly of school buses for many years.


( Dunn D., Adhesives and Sealants: Technology, Applications and Markets, p. 77)


Rivet bonding is defined as a method of joining metals which involves the installation of structural rivets used in conjunction/combination with a structural adhesive.


(Lord, Procedure for Rivet Bonding With Lord Fusor Adhesives, p. 1 )

4. Tape Forming (manufacturing method)

Old Answer

Tape Forming

Tape formingis used to make thin ceramic parts like alumina substrates for integrated circuit chips and special capacitor. A thin layer of slip is laid on a flat carrier which can be a paper sheet or polymer film. A doctor blade controls the slip thickness, resulting in a tape that can be stamped into small shapes. These can be stacked or coiled for subsequent sintering.

(Ohring M., Engineering Materials Science, Part I, pg.420, Kayra Ermutlu)

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Tape Casting 

This process shown in figure 3.20D

( Fischer T., Material Science for Engineering Students,p. 232)

Tape casting is a forming technique for producing thin, flat ceramics. The method was 

originally developed for producing electronic ceramics, including substrates, packages and 

multilayer capacitors. The tape thickness that can be achieved is generally in the 

micrometre-to-millimetre range.

(Pardo L., Multifunctional Polycrystalline Ferroelastic Materials, p. 45)