Objective: For assessment of toughness property of aggregates for the concrete construction
Tools and Equipment
Impact Testing Machine
Description of Machine
Pendulum impact Testing Machine basically comprises of the strong frame structure, the sample sustenance along with the measuring and computing dial. The pendulum shaft is connected in the anti-friction bearings. After that, the pendulum is tightly clamped to the pendulum shaft itself. The pendulum comprises of the pendulum pipe and it also has a pendulum hammer which is designed in U shape. Inside this. the striker is tightly fixed for directing Charpy Impact test. The range in which the pendulum can swing up to is moderately sheltered by the guard. A latch is given for the operation of the latch and suspending the pendulum. There is a dial latched concentrically with the help of a pendulum shaft. The scale is configured and designed in such a way that the Impact energy retained in breaking the sample could be deciphered directly in joules. A distinct striker for Izod test is given.
Theory and Principle
Rigidity and toughness is critically based on the properties of strength and ductility. The characteristics of the material connecting to the work essential to initiate repute is basically known as toughness. In this trial, a sample of definite specific dimensions are exposed to a hammer blow which is initiated by a pendulum of given weight retained at a given height.
Let W -be the weight of hammer (w=21.025kg).
L -the length of the hammer (L=814.44mm)
– Angle restrained from perpendicular up to the original spot of the pendulum weight.
- – Angle measured from the perpendicular up to the position of pendulum after breaking the sample.
Initial potential Energy of the pendulum at A,
Final energy of pendulum at C,
Original position of the pendulum,
After finding the values of w, Land the energy loss can be easily computed for different values of and standardization curve could be illustrated by plotting energy loss on the Y- axis and on the x-axis and on the X- axis.
The Izod Impact test basically comprises of the notched test piece with dimensions of 75mm long, 10mm x 10mm cross section. The piece choses for test is then gripped perpendicularly while the base of the notch in the similar plain.
Attach the proper striker to the foundation of the hammer with the assistance of fastening device. Strongly clamp the latching tube to the bearing housings on all the sides. Fine-tune the pointer along with the pointer carrier on 168.1 reading on the dial while the pendulum is freely being suspended vertically. After that, you have to raise the pendulum manually and latch in with help of manual operation for both. The sample for Izod test is definitely clamped in the sample support with the assistance of clamping screw and the setting gauge. Meticulous care has to be taken so that the notch on the sample will face towards the pendulum striker. Regulate the lever in such a way that so that the pendulum is suspended and the sample is consequently hit. Postpone until the pendulum converses its swing. Now, cautiously retard the swinging pendulum by regulating the brake. Note and mark down the Impact energy. Detach the cracked sample by releasing the fastening bolt.
The Charpy U-notch impact test basically comprises of the test sample jagged in the mid-point and supported at all ends.. The test piece which is machined all over has to be at least 55mm long, 10mm x 10mm cross section and in the midpoint of length of flat, there will be a U notch of 5mm deep with 1mm root range. The plain of equilibrium of notch has to be vertical to the longitudinal axis.
Connect the Charpy striker strongly to the foundation of the hammer with the support of clamping equipment. Now strongly fasten the latching tube to the bearing housing on the sloped side. Raise the hammer partially with manual operation and fasten in. The specimen has to be positioned in such way that the notch is facing to the opposite direction of impact of the pendulum. For correct centering positioning of sample, the end stop is specified and given. Regulate the lever in such a way that the pendulum is suspended and the sample is hit. Wait until the pendulum is retreating its direction of motion and commences to swing slowly. After that, bring the pendulum delicately to a still perpendicular position by exerting the pendulum break. Mark down the impact energy of the test.
Figure: sample of Charpy Test