To determine the p & s wave velocity of a given rock sample by using pundit (portable ultrasonic non-destructive digital indicating tester).

SCOPE:-

• With the advent of this apparatus it became very easy and cheap to inspect rocks.
• The world known PUNDIT offers users a reliable and accurate method for determining the sonic properties of materials.

APPARATUS:-

• PUNDIT
• Core sample
• Grease

THEORY

PUNDIT:-

The PUNDIT is a light and portable apparatus, simple to operate and has a high order of accuracy and stability.

WORKING:-

This equipment generates ultrasonic pulses with a frequency of 50kHz and measures the transit time from the transmitting transducer through the sample to the receiving transducer by displaying it in the form of three digits in three numerical indicator tubes

The transmitter converts pulses into mechanical ones which are later converted into electrical pulses by the receivers.

P-WAVES:-

P waves (primary waves) are compressional waves that are longitudinal in nature. P waves are pressure waves that are the initial set of waves produced by an earthquake. These waves can travel through any type of material, and can travel at nearly twice the speed of S waves. In air, they take the form of sound waves, hence they travel at the speed of sound. Typical speeds are 330 m/s in air, 1450 m/s in water and about 5000 m/s in granite.

S-WAVES:-

S waves (secondary waves) are shear waves that are transverse in nature. These waves typically follows P waves during an earthquake and displaces the ground perpendicular to the direction of propagation. Depending on the propagational direction, the wave can take on different surface characteristics; for example, in the case of horizontally polarized S waves, the ground moves alternately to one side and then the other. S waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses. S waves are slower than P waves, and speeds are typically around 60% of that of P waves in any given material.

DYNAMIC MODULUS:-

Dynamic modulus is the ratio of stress to strain under vibratory conditions (calculated from data obtained from either free or forced vibration tests, in shear, compression, or elongation). It is a property of viscoelastic materials.

PROCEURE:-

• Stiffer grease was used as a coupling agent in this study.
• Transducers were pressed to either end of the sample and the pulse transit time was recorded.
• P & S wave velocities were calculated using distance time Equation.

APPLICATIONS:-

Ultrasonic testing can be used for;

• The homogeneity of a material.
• The presence of voids, cracks or other internal imperfections of defects.
• Changes in the concrete which may occur with time (.e, due to the cement hydration or damage from fire, frost or chemical attack).
• The strength or modulus of a material.
• The quality of the concrete in relation to specified standard requirements.

Notes:-

• In most rocks, wave velocity in the saturated conditions is higher than in the dry condition.
• Sample should be oven dried
• A good acoustic coupling between the transducer face and the rock surface is necessary for the accuracy of transit time measurement
• Test was quite easy to perform.
• Our apparatus had some fault that’s why we got wrong values but our main purpose was to learn that how this method works. So we followed those steps.