UNIT V

OTHER
TESTING
 OVERVIEW
 Materials testing, measurement of the
characteristics and behaviour of such
substances as metals, ceramics, or plastics
etc. under various condition.
 Investigators may construct mathematics
models that utilize known material
characteristics and behaviour to predict
capabilities of the structure.
 TYPES OF MATERIALS
TESTING
 Mechancial testing & Non destructive
testing
 Testing for physical& chemical properties
 Testing for thermal properties
 Testing for electrical properties
 Testing for resistance to corrosion,
Radiation and Biological deterioration.
 THERMAL PROPERTIES
 Thermal analysis is a form of analytical
technique most commonly used in the
branch of materials science where changes
in the properties of materials are examined
with respect to temperature.
 It is a group of techniques in which
changes of physical or chemical properties
of the sample are monitored against time
or temperature, while the temperature of
the sample is programmed.
 The temperature program may involve
heating or cooling at a fixed rate, holding
the temperature constant(isothermal), or
any sequence of these.
 The sample is subjected to a predefined
heating or cooling program.
 The sample is usually in the solid state
and the changes that occurs on heating
includes melting, phase transition,
sublimation, and decomposition.
 THERMAL PROPERTIES
 THERMAL CONDUCTIVITY – To
determining temperatures as a function of
time along the length.
 SPECIFIC HEAT – Heat absorbed per unit
mass per degree changes in temperature.
 THERMAL EXPANSION – Changes in a
unit length of a material caused by a one-
degree changes in temperature.
 THERMALSTRESS – The stress
experienced by a body due to either thermal
expansion .
 THERMALTESTING
 Thermal testing involves testing a
product at the extremes of its intended use
thermal environment for heating rate,
temperature and airflow or gaseous
atmosphere or vacuum with measuring
case temperatures on individual
components to determine the effect on
product performance and long- term
reliability.
 MAJOR MOTHODS OF
THERMAL TESTING
 Differential thermal analysis
 Dilatometer
 Differential scanning calorimetry
 Dynamic mechanical analysis
 Thermogravimetric analysis
 Thermo mechanical analysis
 Thermo optical analysis
OTHER COMMON METHODS

 Dielectric thermal analysis

 Evolved gas analysis
 Laser flash analysis
 Derivatography
 PARAMETERS OF THERMAL
TSETING
METHOD PARAMETER TESTING
Thermogravimeteric Analysis Mass changes
Differential Thermal Analysis Temperature Difference
Differential Scanning Heat Difference
Calorimetry
Evolved Gas Analysis Gas Decomposition
Thermo Mechanical Analysis Deformation And Dimension
Dilatometer Volume
Dielectric thermal analysis Electrical properties
Thermo optical analysis Optical properties
 THERMOGRAVIMETRIC
ANALYSIS(TGA)
 The Thermogravimetric analysis(TGA) is a
type of thermo analytical testing performed
on materials to determine changes in weight
in relation to changes in temperature.
 The TGA relies on a high degree of precision
in three measurements: weight, temperature,
and temperature changes.
 The TGA is commonly employed in research and
testing to determine characteristics of materials.
 To determine degradation temperature, absorbed
moisture content of materials, the level of
inorganic and organic components in materials,
decomposition points of explosives and solvent
residues.
 DIFFERENTIAL SCANNING
CALORIMETRY
 DSC measures the energy absorbed or
released from a sample as a function of
time or temperature profile.
 DSC is useful to make the measurements
for melting points, heats of reaction,
glass transition, and heat capacity.
 PRINCIPLE
 Differential scanning calorimetry (DSC) is
based on the principle; sample and reference
and maintained at the same temperature,
even during a thermal event (in the sample).
The energy required maintaining zero
temperature different between the sample
and the reference is measured.
 By calibrating the standard
material(reference materials), the unknown
sample quantitative measurement is
achievable.
 TYPES
 There are four different types of DSC
instrument
 Heat flux DSC
 Power compensated DSC
 Modulated DSC
 Hyper DSC
 Pressure DSC
 The most common methods are Heat flux
DSC and Power compensated DSC.
POWER COMPENSATION DSC

 A technique in which difference of

thermal energy that is applied to the
sample and the preference materials
separately per unit of times is measured as
a function of the temperature.
 (A) COMPONENTS
 Separate sensors and heaters are used for
the sample and preference.
 SAMPLE HOLDER: Al or Platinum pans.
 SENSORS :Platinum resistance
thermocouples
 FURANCE: Separate blocks for sample
and preference cells.
 TEMPERATURE CONTROLLER:
Differential thermal power is supplied to
the heaters to maintain the temperature of
the sample and preference at the program
value.
 (B) WORKING
 The power needed to maintain the sample
temperature equal to the reference temperature is
measured.
 In power compensation DSC two independent
heating units are employed.
 These heating units are quite small, allowing for
rapid rates of heating, cooling and equilibration .
The heating units are embedded in a large
temperature controlled heat sink.
 The sample and reference holders have
platinum resistance thermometers to
continuously monitor the temperature of the
materials.

 The instrument records the power difference

needed to maintain the sample and reference
at the same temperature as a function of the
programmed temperatures.
 Power compensated DSC has lower
sensitivity than heat flux DSC, but its
response time is more rapid. It is also
capable of higher resolution then heat flux
DSC.
 This makes power compensated DSC well
suited for kinetics studies in which fast
equilibrations to new temperature settings
are needed.
 HEAT FLUX DSC
 The difference in heat flow into the sample
and reference is measured while the sample
temperature is changed at constant rate.

 Sample and reference are connected by a low

resistance heat flow path.

 The assembly is enclosed in a single furnace.

 COMPONENTS
SAMPLE HOLDER :-
 Al or platinum pans placed on constantan
disc
SENSORS:-
 Chromel alumel thermocouples furnace
are used
ARRANGEMENT OF HEAT
FLUX DSC
 WORKING
 The main assembly of the DSC cell is
enclosed in a cylindrical, silver heating
black, which dissipates heat to the
specimens via I constantan disc which is
attached to the silver block.
 The disc has two raised platforms on
which the sample and reference pans are
placed.
 WORKING
 A chromel disk and connecting wire are
attached to the underside of each platform
and the resulting chromel constantan
thermocouples are used to determine the
differential temperatures of interest.
 Alumel wires attached to the chrome disc
provide the chromel-alumel junctions for
independently measuring the sample and
reference temperature.
 DSC MEASURES
 Glass transistion
 Melting and boiling points
 Crystallization time and temperature
 Present crystallinity
 Heats of fusion and reactions
 Specific heat capacity
 Purity
 DSC CURVE
 A plot between heat flow and temperature. It
shows various peak of measurement.
 FACTORS AFFECTING DSC
CURVE
INSTRUMENTAL FACTORS SAMPLE CHARACTERISTIC
FACTORS

FURNACE HEATING RATE AMOUNT OF SAMPLE

RECORDING OR CHART SPEED NATURE OF SAMPLE

FURNACE ATMOSPHERE SAMPLE PACKING

GEOMETRY OF SAMPLE HOLDER SOLUBILITY OF EVOLVED GASES

SENSITIVITY OF THE RECORDING PARTICLE SIZE

SYSTEM

COMPOSITION OF SAMPLE HEAT OF REACTION

CONTAINERS
 APPLICATION OF DSC
 To observe fusion and crystallization
events as well as glass transition
temperature
 To study oxidation
 The transition from amorphous to
crystalline is known
 The ability to determine transition
temperature and enthalpies
 SOURCES OF ERRORS
 Caliberation
 Contamination
 Sample preparation
 Residual solvents and moisture
 Thermal lag
 Heating/cooling rates
 Sample mass
 ADVANTAGES OF DSC
 Instruments can be used at very high
temperatures
 Instruments are highly sensitive
 Flexibility in sample volume/form
 High resolution obtained
 High sensitivity
 Stability of the material
 DISADVANTAGES
 DSC generally unsuitable for two phase
mixtures
 Difficulties in test cell preparation
 Generally used for thermal screening of
isolated intermediated products
 Does not detect gas generation
 Uncertainity of heats of fusion and
transition temperatures.
 DIFFERENTIAL THERMAL
ANALYSIS
 DTA is a thermo analytical technique
which is used for thermal analysis where
thermal changes can be studied.
 It is used to determine the oxidation
process decomposition and loss of water
or solvent.
 PRINCIPLE
 The sample material and reference
material are made to undergo identical
thermal cycles, while recording any
temperature difference between sample
and reference.
 Changes in the sample, either exothermic
or endothermic can be detected relative to
the inert reference.
 COMPONENTS
 FURNACE – used for heating the sample
(Nickel and Chromium alloy furnace)
 SAMPLE HOLDER – contain the sample
and reference material
 DC AMPLIFIER- low level DC amplifier
 DIFFERENTIAL TEMPERATURE
DETCETOR- to measure differential
temperature
 FURNACE TEMPERATURE
PROGRAMME- increase the temperature
of the furnace at steady rate
 RECORDER- to record DTA curve
 CONTROL EQUIPMENT- maintain
suitable atmosphere of the furnace and
sample holder.
CROSS SECTION OF DTA
 WORKING
 The sample under investigation is loaded
into the container.
 This container is then placed into the
sample pan and it is marked as S
 Same quantity of reference sample is
placed in another container which is then
placed onto the reference pan and it is
marked as R.
 In order to heat the sample pan and the
reference pan at an identical rate, the
dimensions of these two pans should be
nearly identical.
 The sample and the reference should have
equal weights, thermally matched and
should be arranged symmetrically with the
furnace.
➢ The metal block surrounds the pans acts as
a heat sink whose temperature is increased
slowly by using an internal heater.
➢ The sink then heats the sample and
reference material simultaneously.
➢ Two pairs of thermocouples are used.
➢ One pair is in contact with the sample and
the second pair is in contact with the
reference.
DTA CURVE
 FACTORS AFFECTING DTA
CURVE
SAMPLE FACTORS INSTRUMENTAL PHYSICAL
FACTORS FACTORS

Amount of sample Size and shape of Adsorption

holders

Packing density Material of the sample Change in crystal

holder structure

Particle size of the Recording system Crystallization

sample sensitivity

Degree of crystallinity Rate of heating of Desorption

sample

Thermal conductivity Atmosphere around the vaporization

sample
 ADVANTAGES
 It can operated at very high temperatures
 Highly sensitive technique
 Flexibility in crucible volume
DISADVANTAGES
 There is a lot of uncertainty in transition
radiations and heat of fusions upto 20-50%
 Destructive limited range of samples time
consuming.
 APPLICATIONS
 Used to identify minerals both
qualitatively and quantitatively.
 Polymers characterization is easily
characterized
 Degree of crystallinity is assessed
 Melting point, boiling point and
temperatures of decomposition of organic
compounds can be determined.
 THERMO MECHANICAL
ANALYSIS
 A technique in which deformation of the
sample under non-oscillating stress is
monitored against time or temperature while
the temperature of the sample in a specified
atmosphere is programmed.
 TMA easily measures sample displacement
as a function of temperature.
 PRINCIPLE
 TMA is used to measure the dimensional
changes of a material as a function of
temperature by applying stress.
 The stress may be compression, tension,
flexure or torsion.
COMPONENTS
 Transducer- LVDT, optoelectronic or laser
 Probe made up of quartz glass
 Thermocouple furnace
 Force generator
 PROBES ON DIFFERENT
LOADING CONDITIONS
 EXPANSION/ COMPRESSION PROBE
– to measure deformation by the sample
by thermal expansion.
 PENETRATION PROBE
 To measure softening temperature.
 TENSION PROBE
 To measure thermal expansion and
thermal shrinkage of the sample.
 CONSTRUCTIONA ND
WORKING
 The sample is inserted into the furnace
and is touched by the probe which is
connected with the length detector and
force generator.
 The construction of push rod and sample
holder depends on the mode of
measurements.
 The thermocouple for temperature
measurement is located near the sample.
 WORKING OF THERMO
MECHANICAL ANALYSER
 The rate of 5̊ C/min is usually maximum
recommended value for good temperature
equilibrium across the specimen.
 The sample temperature is changed in the
furnace periodically by applying the force
onto the sample from force generator via
probe.
 LVDT is used for length detection sensor.
 APPLICATION
 Measurement of dimensional change
 Coefficient of linear thermal expansion
 Determination of material anistropy
 Softening temperatures and glass
transition
 Linear thermal expansion
 ADVANTAGES
 Compactness and lightness
 Low operation voltage
 Measure large deformation
 Large actuation force
DISADVANTAGES
 Used for only solid samples
 Creep occurring concurrently
 Usage of proper probe
 Low operational speed
 THERMO MECHANICAL
DYNAMIC ANALYSIS
 It is also known as DMA (DYNAMIC
MECHANICAL ANALYSIS)