Universal Testing MachineManeeb Masood

M.Tech.Part-1(15152010)IIT(BHU), Varanasi

IntroductionA Universal Testing Machine is a machine

that is used to perform standard tensile and compressive tests on materials, components and structures.

It can be used to perform following tests:Tensile TestCompression TestShear Test

Components.....Loading Unit

Load FrameLoad CellCross Head

Control PanelHydraulic Power UnitLoad Measuring Unit

Control DevicesElectric Control DevicesHydraulic Control DevicesLoad Indicating Devices

Control PanelA Control Panel Comprises of:Power Pack (with drive motor & oil tank)Control ValvesPendulum DynamometerLoad Indicator SystemAutograph Recorder

Working PrincipleIt is a load-controlled machine and works

on the principle of elongation/deformation of material on the application of load.

TESTSTo assess various rock properties we can use different

kind of machines among them universal testing machine is one of the most widely used and versatile machine which can measure compressive/tensile/shear strength, directly or indirectly using sample/specimen of rock mass.

Compressive strength can be assessed directly but for the tensile and shear strength we need to use different kind of cages and calculations.

Tension and Shear tests are conducted by indirect testing.

In the Old UTMs, the lower cross head can be raised or lowered rapidly by operating the screwed columns , thus facilitating ease of fixing of test specimen.

New UTMs have a fixed table and the adjustable cross head moves up and down.

LOAD CELL

TENSION CROSSHEAD

TABLE

ADJUSTABLE CROSS HEAD

SCREW COLUMN

Notched column

Hydraulic cylinderCONTROL

PANEL

OPERTAIONAL PROCEDURECompressive strength:-Specimen: The cross section of the specimen may be

circular, squire, rectangular or in special cases of any other form. Specimens of circular sections are generally be made to the dimensions.

Steps1. Mark the gauge length as per specification and record

it accurately. The gauge length should be symmetrical with the length of the bar.

2. Grip the specimen firmly in the jaw of the Universal testing machine and adjust the machine to read zero.

3. Continue loading at increments each time and this loading should be continued till yield point is reached.

4. Record the load at the yield point. That is uniaxial compressive strength of the specimen.

TENSILE STRENGTH:-Specimen: The cross section of the specimen may be

circular, squire, rectangular or in special cases of any other form. Speimen of circular sections are generally be made to the dimensions

Steps1. Mark the gauge length as per specification and

record it accurately. The gauge length should be symmetrical with the length of the bar.

2. Grip the specimen firmly in the jaw of the Universal testing machine in brazilian cage and adjust the machine to read zero.

3. Continue loading at increments each time and this loading should be continued till yield point is reached.

Brazilian cage

Shear strength:-Steps1. Mark the gauge length as per specification

and record it accurately. The gauge length should be symmetrical with the length of the bar.

2. Grip the specimen firmly in the jaw of the UTM in suitable cage for single shear or double shear and adjust the machine to read zero.

3. Continue loading at increments each time and this loading should be continued till yield point is reached.

4. Record the load at the yield point. That is shear strength of the specimen.

Double shear cageSingle shear cage

PRECAUTIONS1. Apply the load at a uniform rate and without

any jerk.2. Selection of proper dimension of specimen

when testing of different type of strength.