This document discusses heat resistance in materials and its effects. It covers 6 main topics: 1) Melting points of common materials and the transition from solid to liquid. 2) Thermal expansion and contraction as materials change size with temperature. 3) Thermal conductivity and how heat is transferred through materials. 4) Changes in microstructure that can occur from temperature changes. 5) Variations in material strength at different temperatures. 6) Warping and distortion that may happen due to uneven heating or cooling.

1. MACHINE DESING
PRESENTATION – 2
HEAT RESISTANCE
D.M.Gamage
Institute of Technology
(NDT)
University of Moratuwa
Sri Lanka

2. WHAT IS THE HEAT RESISTANCE
•Ability to withstand change of heat
•Various materials exhibit different properties at
different temperature

3. EFFECTS OF TEMPERATURE ON
MATERIALS PROPERTIES
Melting
Thermal expansion and contraction
Thermal conductivity of materials
Changes in microstructure
Variation of strength
Warping or distortion

4. 1.MELTING
Melting, is a physical process that results in the phase transition of a substance from
a solid to a liquid. This occurs when the internal energy of the solid increases,
typically by the application of heat or pressure.
• Melting point is the temperature at which a substance changes from solid to
liquid state.

5. Metal
Melting Point
(oC) (oF)
Admiralty Brass 900 - 940 1650 - 1720
Aluminum 660 1220
Aluminum Alloy 463 - 671 865 - 1240
Aluminum Bronze 1027 - 1038 1881 - 1900
Antimony 630 1170
Babbitt 249 480
Beryllium 1285 2345
Beryllium Copper 865 - 955 1587 - 1750
Bismuth 271.4 520.5
Brass, Red 1000 1832
Brass, Yellow 930 1710
Cadmium 321 610
Chromium 1860 3380
Cobalt 1495 2723
Copper 1084 1983
Cupronickel 1170 - 1240 2140 - 2260
Gold, 24K Pure 1063 1945
Hastelloy C 1320 - 1350 2410 - 2460
Inconel 1390 - 1425 2540 - 2600
Incoloy 1390 - 1425 2540 - 2600
Iridium 2450 4440
Iron, Wrought 1482 - 1593 2700 - 2900
Iron, Gray Cast 1127 - 1204 2060 - 2200
MELTING POINTS OF SOME
COMMON MATERIALS

6. Iron, Ductile 1149 2100
Lead 327.5 621
Magnesium 650 1200
Magnesium Alloy 349 - 649 660 - 1200
Manganese 1244 2271
Manganese bronze 865 - 890 1590 - 1630
Mercury -38.86 -37.95
Molybdenum 2620 4750
Monel 1300 - 1350 2370 - 2460
Nickel 1453 2647
Niobium (Columbium) 2470 4473
Osmium 3025 5477
Palladium 1555 2831
Phosphorus 44 111
Platinum 1770 3220
Plutonium 640 1180
Potassium 63.3 146
Red Brass 990 - 1025 1810 - 1880
Rhenium 3186 5767
Rhodium 1965 3569
Ruthenium 2482 4500
Selenium 217 423
Silicon 1411 2572
Silver, Coin 879 1615
Silver, Pure 961 1761
Silver, Sterling 893 1640
Sodium 97.83 208
Steel, Carbon 1425 - 1540 2600 - 2800
Steel, Stainless 1510 2750
Tantalum 2980 5400
Thorium 1750 3180
Tin 232 449.4
Titanium 1670 3040
Tungsten 3400 6150
Uranium 1132 2070
Vanadium 1900 3450
Yellow Brass 905 - 932 1660 - 1710
Zinc 419.5 787
Zirconium 1854 3369

7. 2.THERMAL EXPANSION AND CONTRACTION
• Introduction
• Thermal expansion is the tendency of matter to change in shape, area, and volume in response
to a change in temperature[1]
• Thermal contraction is the opposite of thermal expansion. When the temperature drops, atoms
calm down and shrink. They aren't bouncing so aggressively off of each other and don't need
that much space to coexist. When they shrink, the boundaries of the material shrink. The
material contracts.
• most solid materials expand upon heating and contract when cooled
The change in length with temperature for a metal may be expressed as follows.
𝛼(Tf -T0)=
Lf −L0
L0

8. USUALLY THERE ARE THREE TYPE OF EXPANSIONS

9. Our formula for linear expansion is;
∆L=L0.α. ∆T
Where; ∆L is the amount of change in the length of the rod, L0 is the initial
length of the road, α is the coefficient of linear expansion and ∆T is the change
in the temperature of the matter
Volume Expansion: If the objects expand in volume with the gained heat, we call
this volume expansion and find it with the following formula;
• ∆V=V0.3α. ∆T
• Where; ∆V is the amount of change in the volume of the cube, V0 is the initial
volume of the cube, 3α is the coefficient of volume expansion and ∆T is the change
in the temperature of the matter.

10. EFFECT OF THERMAL EXPANSION
• The expansion and contraction of materials
must be considered when designing large
structures.

11. 3.THERMAL CONDUCTIVITY OF MATERIALS
• The ratio of the amount of heat energy conducted peer unit area of cross section
per seconed to the temperature gradient.
• Therefore ,the thermal conductivity
• Q=-k
𝑑𝑇
𝑑𝑥
• Where, of heat energy conducted per unit area of cross section
k= coefficient of thermal conductivity.
Q= amount of heat energy conducted per unit area of cross section in one
second
𝑑𝑇
𝑑𝑥
= temperature gradient
The negative sign shows that heat flows from the hot end to cold end.

12. MECHANISUMS OF HEAT CONDUCTION
• Heat is transported in solid materials by lattice vibration waves and free electrons.
• A thermal conductivity is associated with each of these mechanism and total
conductivity is ,
KTotal =kelectron+kphonons

13. THERMAL SHOCK RESISTANCE OF MATERIALS
• The capacity of a material to withstand failures is termed its thermal shock
resistance.

14. 4.CHANGES IN MICROSTRUCTURE
• The microstructure of materials can be changed by changing the temperature .

15. 5.VARIATION OF STRENGTH
• Strength of materials, also called mechanics of materials, is a subject which deals
with the behaviour of solid objects subject to stresses and strains.
• When changes temperature strain and stress of a material also change.
thermal stress
thermal stress are stresses incluced in a body as a result of changes in temperature.
Where,
E = modulus of elasticity
𝛼 = linear coefficient of thermal expansion
𝜎= E𝛼(T0 -T1)

16. 6.WARPING OR DISTORTION
.
DEFINITION:
Warp in engraving material is a distortion of the sheet from a desired
flatness. The degree that the sheet deviates from the specification or
desired flatness is the result of many factors.

17. • HOW TO MINIMIZE WARP AND ITS EFFECTS
• Many cases of warp can be eliminated through proper handling and
processing of the material. To minimize warp and its effects, the
• following suggestions are offered:
• 1. Never store sheets in extreme temperatures. For best results, store
and use sheet material at ambient room temperature.
• 2. Store sheets flat at all times. Sheets stored vertically will take a set
over time. A warped sheet should be placed flat. In some cases, some
of the damage can be removed.
• 3. Remove the protective mask and allow the material to relax
naturally over time. Place the sheet on a flat surface and place in a
room temperature environment. If possible, place an even weight over
the entire surface by using additional sheets or pieces of material to
hold the material in place.
• 4. Apply adhesive tapes prior to using. Sheets stored for prolonged
periods of time with adhesives previously applied will tend to warp as
the adhesive materials dry out. Once this damage has occurred,

18. THANK YOU