7

Moment of Inertia and Mutilation Studies of an Insect Wing

93

Fig. 7.1 Strip method used for calculating wing loading and strip area

The weight of each strip is determined carefully by using a sensitive balance, which

can measure up to 1 mg. The total moment of inertia of the wing is calculated by

summing the moments of inertia of the individual strips. Additional data relating to

the wings in terms of stripwise wing mass and moment of inertia are shown plotted in

Fig. 7.2. The force field operating above the wing is the resultant of the forces acting

on several strips of wings. It may be noted that the wing areas alter slightly during

the downstroke and upstroke since the insect wings are anisotropic and due to the

flexible and membranous nature of the wings. This phenomenon also contributes to

the complex aeroelastic behaviour during insect flight. It should be noted that we are

dealing with chitinous thin, flapping flexible wings whose areas are slightly variable

during the down and upstroke with added rotary and twisting motion of the wings.

This makes the exact analysis of the flight and the wing motion more complex.

In T. javanica, the total wing mass is 6 mg while the total moment of inertia

of each wing is typically 6000 × 10⁻⁶gm cm² with reference to the y-axis passing

through the origin. Preliminary investigations were carried out by Chari and his

research associates at Kakatiya University, Warangal, India. Detailed calculations

for a typical insect such as T. javanica have been carried out by the present authors

at SNIST, Hyderabad. This data forms the basis for the present discussion.



l



= ^√(I/m), where I = Total Moment of Inertia