EGR2208 Lab Manual.doc - EXPERIMENT 1: IMPACT TESTING...

EXPERIMENT 1: IMPACT TESTING
OBJECTIVE:
To determine the impact strength of Materials
APPARATUS:
Impact Tester Machine STR08
PROCEDURE:
1. The test piece is placed on the supports so that the break indentation faces the
direction of the pendulum swing and that the indent is exactly in the middle of the
supports.
2. Raise the pendulum to the start point.
3. Set the pointer to 50 joules, i.e. straight down.
4. Release the pendulum by turning the black knob, top right. KEEPS HANDS
CLEAR. The test piece is broken off.
5. Stop the pendulum by lifting the friction brake. Be sure that the pendulum is at
standstill before removing the test pieces.
6. The energy consumed when breaking the test piece can now be read directly from
the scale, indicated by the pointer.
1

Influence
of C% on
impact
energy
versus
temperature for steels
(Smith & Hashemi- 4 th Ed)
2

EXPERIMENT 2: MICROSTRUCTURE AND HARDNESS OF Fe-C
ALLOY STEELS
OBJECTIVE:
To examine the microstructure and to measure the hardness of slowly
cooled Fe-C alloy steels containing 3 different wt% of carbon. The wt
% of carbon for each sample will be determined based on the
observation from this experiment.
APPARATUS:
Grinding and Polishing machine, Microscope with Imaging
Workstation and Digital Micro Vickers Hardness Tester.
PROCEDURE:
1. Preparation of steel samples
i. Polish/wash/dry: The three steel samples are mounted individually with
epoxy. Polish, wash and dry specimens, until no gross polishing marks are
visible.
ii. Etch: Delineate the mirror-finish sample using 2% Nital solution (2% by
volume of concentrated nitric acid in methyl alcohol)
2. Microstructure examination
i. After etching, examine the specimens microscopically and identify the
regions of ferrite (light) and pearlite (dark and lamellar).
ii. Estimate the relative amounts of ferrite and pearlite in each sample. Sketch
the microstructures of the three steel samples. Label the different phases
present and quote the total magnification (Objective x Prism (if any) x
Eyepiece).
iii. By applying the Lever Rule, estimate the wt% of carbon in each of the
steels sample based on the Fe-C phase diagram.
3. Hardness measurement
i. Measure the Vikers hardness value of each specimen, taking three readings
for each specimen, and plot into graph with the consideration of
uncertainty in the data using error bars.