This document is for all crusious learners who want to learn about various tests of materials on "Universal Testing Machine" ie. UTM. it is also beneficial for engineering students studying mechanical engineering or civil engineering at any institute.

1. EXPERIMENT No. 6
Objective: - (i) To study universal testing machine.
Apparatus: - 1.Universal testing machine
UNIVERSAL TESTING MACHINE
Applicability and Range of Application:
Universal Testing Machine serves for conducting tests in tension, compression, bending and
shearing for metals and other materials. The testing machine is operated hydraulically. Driving is
performed by the help of an electrical motor. The machine is equipped with pendulum
dynamometer, a recording device for registering load-deformation diagram.
Description of Arrangement:
Technical Data: Measuring Ranges, Maximum Capacity 40 Tons
Construction:
The machine consists of two units viz. the loading unit A and the control panel B. shown in fig.1
The Loading Unit:
Consists of robust base (l-p1). The main hydraulic cylinder is fitted in the centre of the
base and the piston slides in the cylinder. Special materials used for the cylinder and the piston
and their careful precise machining including individual lapping have increased the accuracy of
the machine to a great extent.
A motor is fitted to the left-hand side of the base. The chain and sprocket drive by the
motor rotates two screwed columns (8-p1) mounted in the base with bearings. These screws pass
through the two main nuts (16-P4&P4) fitted in the lower cross head. Lock nuts (17-P4&P4)
avoid the loosening of the main nuts. The additional back-lash removing nuts (18-P4) are
provided to remove the back-lash screws (8p1) and the main nuts while lowering of the lower
cross-head, and avoids sudden jerk when the specimen breaks. In the long run, it can also
compensate for the wear of the screws and the nuts. The screws (I9-P4&P4) provided on the
backlash removing nut assembly are used to adjust the back-lash.

2. Fig.1 (P 1)
The lower table (6-P1) is connected to the main piston through a ball and ball seat joint. This
joint ensures axial loading. This lower table (6-P1) is rigidly connected to the upper cross-head
(20-P1) by two straight columns (9-P1).
The lower table and upper cross-head assembly moves up and down with the main piston. The
up and down movement of this assembly is guided by eight bearings which slide over the screw
columns. Four bearings are fitted in one bearing holder (24-P4) and two such holders are fixed
on the upper cross head with the two screwed columns (8-Pl) at their respective centre. The jaws
inserts for tensile test specimen along-with the rack jaws slide in the lower and upper cross-
heads. The sliding motion of the rack jaws is achieved by rotating the helical toothed pinion by
the operating hand wheel (22-P4&P4) provided. Jaw locking handle (2-Pl &P4) is provided to
lock the jaws of the lower cross-head after the specimen is clamped. This arrangement ensures

3. firm clamping of the specimen and easy take out of the broken specimen. Separate jaw pieces are
provided for different ranges of specimen diameters. Users should confirm that the correct jaw
pieces are inserted in the rack jaws before testing the specimen.
For changing the jaw pieces first take out the rack jaws. For taking out the rack jaws, remove the
top plate (21-P1&P4) from the top of the upper cross-head. Now rotate the pinion and take out
the rack jaws by hand from the top. For taking out the jaws from lower cross-head, lock the
handle and take out the lower plate (12-P1) from the bottom. The jaws will come out from
bottom if you release the handle slowly by un-locking. Take care that the jaws do not fall down
on the lower table. After taking out. the rack jaws, removed the clamping strips from the rack
jaws, which are screwed to it. Now insert the correct jaw pieces and fix the clamping strips in
their position. The jaw pieces must be inserted in the direction of the arrow marked on it.
Insert the lower rack jaws from the bottom of the lower cross-head. Care should be taken that
both the jaws are inserted at .a time and their top faces come in the same plane when those are
taken up to touch each other. Rotate the handle, take up the jaws in the chuck and confirm the
piston of the rack jaws. Lock the operation handle in its uppermost piston.
Then fix up the lower plate (12-P 1), similarly insert the upper jaws ham the top of the upper
cross head and fix up the top plate (21-P 1).
Note: The jaws should always be released slowly.
The upper and lower jaws are non-interchangeable.
Two compression plates viz, upper (11-P1) and lower (7-P1) are provided for conducting
compression test. The lower compression plate (7-P1) is to be kept on the lower table (6-P1) in
the location hole provided and the upper compression plate (11-P1) is to be clamped to the
bottom of the lower cross head. For clamping this plate, take the jaws in the lower cross head to
their bottom most position (no head of removal) - keep the top plate (3-P1) on the top lower
cross-head, place in such a position that its projected portion fits correctly in the chuck bolt,
resulting in the correct position of the control hole. Now insert the clamp stud from the top
through the hole of the top plate. The clamp stud will come out from the centre hole of the lower
plate (12-P1). Now screw the upper compression plate (II-PI) to the clamp stud and tighten it
against the lower plate (12-P1) by the nut (15P1&P4) from above.
The space between the lower table and the lower cross head is used from compression, bend and
shear tests, and the space between the lower and upper cross heads is used for tension test. In any
test, the up and down motion of the lower table and upper cross-head assemble performs the
loading action. The mechanical up and down motion of the lower cross-head (10-P1) is provided
for rapid initial space adjustment depending on the length or height of the tension and
compression test specimen respectively.

4. Bending table (25-P4), Bending Rollers (28-P4) and bending pan (29-P2) are provided as an
attachment for carrying out bend test.
An elongation scale (30-P4) is kept sliding on the scale rod (31-P4) which is fixed between the
lower table and the upper cross-head. Elongation indicating pointer (32-P4) is fixed to the lower
cross-head. The scale can slide on the rod when the screw at its back is loosened and can be set
to indicate zero before starting the loading on the specimen. Limit switch x 4 provided below the
lower table for limiting the maximum stroke of the piston.
The Control Panel:
The main units in the control panel are:-
The oil tank (33-P2) which contains the hydraulic oil level sight class (34-P2) for checking the
oil level is fitted to the oil tank. The fitted to the oil tank cover (35-P2) filtrs the incoming oil, to
the tank. Drain cock (36-P2) is provided to take out the oil while cleaning the tank.
The pump is a positive displacement type pump. This assures continuous high non-pulsating oil
current for the smooth application of the load on the specimen. The pump is fitted to the tank
cover (35-P2) from bottom which makes it easily assessable. The electric motor is fitted on the
plate hinged at the bottom (38-P2). Belt tightening or loosening can be achieved very easily as
shown in the fig and the motor can be locked at the desired position by the check nuts.
Two valves on the control panel, one at the right side and the other at the left side are used to
control the oil flow in the hydraulic systems. The right side valve (39-P2&P2) is a pressure
compensated flow control valve. The overload relief valve is adjusted and is locked.
The left side valve (4-P2) is a return valve. This valve allows the oil from the cylinder to go back
to the tank, there-by reducing the pressure in the cylinder and then the working piston comes
down. The rate of oil returns and so the speed of piston return can be adjusted by this valve. If
the return valve is closed, oil delivered by the pump passes through the flow control valve (39-
P2) (if in open position) to the cylinder and the piston goes up. If it comes across any resistance
(i.e. resistance of any test piece), pressure starts developing until either the specimen break of the
load reaches the maximum value of the range adjusted. Pressure compensation of the flow
control is an unique design which keeps a constant rate of straining regardless of the total load on
the specimen and you need not adjust the control knob again and again if it is once adjusted for a
particular rate of straining. High pressure oil connection is given from the valve (39-P2) to the
cylinder at its centre. This high pressure oil supplied at the cylinder centre serves as a" hydraulic
bearing for the piston and reduces the friction, thereby increasing the accuracy. It also helps in
getting the pressure compensation effect.

5. Fig. 2 (P2)
The confine control valve (41-P2) is specially provided and set by the manufacturer so as to
control the rate of loading very precisely by means of the right control valve only. So the
adjustment of the needle valve is not to be disturbed by the users. .
The needle valve (45-P2) is a damper speed control valve. It controls the return peed of the
pendulum when the specimen breaks and the pendulum tries to come down suddenly due to
sudden pressure drop in the main cylinder. It obstructs to the return flow of the oil and thus
avoids sudden jerks to the dynamometer piston and the indicating mechanism.
Dynamometer is a unit which measures and indicates the load on the specimen. The overall
accuracy of the machine depends mainly on the accuracy of this unit. It is a pendulum
dynamometer consisting of a cylinder in which the piston reciprocates. The cylinder top is

6. connected to the main hydraulic cylinder. So the oil pressure under the work pi ton is transmitted
to the small measuring piston in the dynamometer. The displacement of the measuring piston
causes the pendulum to deflect as far as the equilibrium point. This deflection represents the
measurement of the load on the specimen. The deflection is registered by a pointer on a dial. The
pendulum weight is subdivided into several detachable weight discs. Thus various measuring
ranges, from full load up to 1/10 of the full load can be obtained. The dynamometer piston is
kept rotating at a slow speed. The drive is taken from the same motor (38-P2) driving the pump
with worm wheel reduction (14-P2) in between the rotating piston assures dynamic friction
conditions and increases the measuring accuracy. The dynamometer is also equipped with an
integral check valve. When the specimen breaks, this valve avoids the return oil flow from the
measuring cylinder and the oil has to bypass through the damper control valve (45-P2) getting
the damping effect. In addition to the accurate load indication on the scale a recording instrument
automatically registers the load elongation diagram. A pen (43-P1) fixed to pen holder (44-P1)
which is fixed to the main rack, moves across the recording drum (42-P1) as the load increases.
At the same time the drum is rotated through small gears by taking movement of the lower table.
The movement of the lower table is taken through chain and sprockets without slip and friction
as the specimen under test is elongated. Thus an automatic graph of load against elongation is
plotted. A big size load indicating dial (46-Pl), fitted with a glass cover (47-Pl) is mounted at the
front side of the control panel. The range indicating dial, located at the back side of the load
indicating dial is to be adjusted for the particular range selected. A range adjuster knob (48-P1) is
provided for this adjustment. A zero adjusting knob (l3-Pl) provided at the right hand side serves
for initial zero adjustment.