This document summarizes a seminar on how the ductile to brittle transition temperature (DBTT) can affect ships. It discusses how the Titanic's steel structure failed due to brittle fracture from low temperatures. The DBTT is the temperature at which a material changes from ductile to brittle behavior. Several factors can influence a material's DBTT curve, including crystal structure, grain size, heat treatment, and composition. Modern steels have lower sulfur contents and smaller grains, leading to higher transition temperatures than the steel used for the Titanic. Understanding how materials behave at low temperatures helps make ships safer by considering fracture risks during design.

1. SEMINAR ON
EFFECT OF DUCTILE TO BRITTILE
TRANSITION TEMPERATURE ON
SHIP
SEMINAR ON
EFFECT OF DUCTILE TO BRITTILE
TRANSITION TEMPERATURE ON
SHIP
SANJAYA KUMAR SAHOO
METALLURGICAL AND MATERIALs ENG.
ROLLNO…… 25628
REGD NO….0601105153
Presented By
GUIDED By
MR. P. k. MALLICk

2. SUBJET OF INTEREST
• Objective
• Introduction
• What is DBTT
• Problem on ship due to DBTT
• Factors affecting DBTT
• Remedy of upcoming problem
• Conclusion

3. OBJECTIVES
• The awareness of brittle fracture under
service conditions will be made by the
use of ductile to brittle transition
temperature curve.
• This chapter provides an understanding
of characteristics and causes that effect
on ship.

4. Introduction
• Big failure of Titanic in 10th April 1912
• Failure of different material due to DBTT
• Commitment to safety pervades all deep sea
shipping operations
• An alternative to increasing the component
reliability is to provide redundancy in a part of
the system

5. WHAT IS DBTT
Ductile to brittle transition
temperature curve
• The absorbed energy (Joule) is plotted
again testing temperature, giving a
ductile to brittle transition temperature
curve (DBTT curve).
• The curve represents a change in
fracture behavior from ductile at high
temperature to brittle at lower
temperature
Lower shelf
Transition – mixed mode
Upper shelf
DBTT curve
Upper shelf
Transition
Lower shelf

6. contd….
1. As temperature decreases a ductile material can
become behave brittle - ductile-to-brittle transition
2. FCC metals remain ductile down to very low
temperatures.
3. For ceramics, this type of transition occurs at much
higher temperatures than for metals.
4. The ductile-to-brittle transition can be measured by
impact testing: the impact energy needed for fracture
drops suddenly over a relatively narrow temperature
range – temperature of the ductile-to-brittle
transition.

7. Charpy impact test
The energy absorption is a
measure of the impact energy
The results are qualitative in
nature and are useful in
making comparisons
Determine whether or not a
material experiences a ductile
brittle transition with decreasing
temperature and, if so, the range
of temperatures over which occur

8. Transition temperature
Different criteria are used to determine
the transition temperature, depending
on the purpose of the application
Various criteria of transition temperature
obtained from Charpy test
1) T1 transition temp is the
Temp at which fracture is
100% ductile (fibrous).
2) T2 transition temp is the
Temp at which fracture is
50% cleavage and 50%
ductile.
3) T3 transition temp is the
Temp at the average energy
absorption of upper and
lower shelves.
4) T4 transition temp is the
Temp defined at Cv = 20J.
5) T5 transition temp is the
Temp at which fracture is
100% cleavage
Note: FTP is fracture transition plastic

9. The brittle-fracture problems
Failure of Liberty Ships during services in
World War II.
The cause of failure was due to crack of
materials to brittle behavior.
initiated from defects in the welded area
and subjected to subzero temperature

10. Material failures
• When the Titanic collided with the iceberg,
the hull steel and the wrought iron rivets
failed.
• Brittle facture is a failure of a metal by rapid
crack propagation and without any
significant deformation.
• The steel and the wrought iron rivets failed
by brittle fracture.

11. What caused the brittle fracture
• What caused the brittle fracture?
• What was the effect of the impact with the
iceberg?
• Did the sulphur content play a role in the failure?
• Temperature for the steel used to construct the
hull of Titanic?
• Did the water temperature experienced by the
Titanic ( -20degreeC ) play a role?

12. Metallurgical factors affecting
DBTT curves
• The shape and position of the DBTT curve is
important because it determines the
transition temperature, which indicates where
it is safe to use for the required application.
• There are several factors affecting the DBTT
curve
• Crystal structure
• Interstitial atom
• Grain size
• Heat treatment
• Specimen orientation
• Specimen thickness

13. Effect of crystal structure
Relationship between energy absorption
and test temperature
• Only BCC structure materials
experience ductile to brittle
transition
temperature. be careful to select
the service temperature.
• This is due to limited active slip
systems operating at low
temperature. very low plastic
deformation.
• Increasing temperature allows
more slip systems to operate
more plastic deformation.
• FCC and HCP metals do not
experience ductile to brittle
transition, therefore they give the
same energy absorption at any

14. Effect of interstitial atom
Ex: in steel
• Mn: C ratio should be at least
3:1 to satisfy notch toughness.
• P, Si, Mo, O raise the transition
temperature while Ni is beneficial
to notch toughness.
• Carbon and manganese contents have been observed to
change the DBTT curve
Carbon
content
Smoother curve
Higher Transition temp
Become ductile at
higher temperature

15. Effect of grain size
• Grain size has a strong effect on transition
temperature
• Grain size
Transition tempt
• Reducing grain size shifts the DBTT curve to the left
has a wider range of service temperatures.
• Heat treatments that provide grain refinement
such as air cooling, recrystallisation during hot
working help to lower transition temperature.

16. Effect of heat treatment
• Tempered martensitic
structure steel produces
the best combination of
strength and impact
toughness
Tempering temperature
Energy absorption

17. Effect of specimen orientation
For impact test, anisotropic properties are also observed in rolled
or forged products, giving different energy absorption according
to specimen orientations
• Longitudinal (B) shows the
best energy absorption because
the crack propagation is across
the fiber alignment.
• Transverse (C) gives the worst
energy absorption because the
crack propagates parallel to the
rolling direction.

18. Effect of specimen thickness
• Larger specimen size (in-service components) provides
higher constraint more brittle
If large size specimens are
used, the transition
temperature will increase
Large scale tests
Effect of section thickness on
transition temperature

19. Effect of sulfur
http://db1.wdc-
jp.com/isij/pdf/199107/is310712.pdf
The presence of
relatively high amounts
of P and S embrittles the
steel at low
temperatures

20. Composition comparison
Titanic steel Modern steel
c 0.21 0.20
Mn 0.47 0.55
p 0.045 0.012
S 0.069 0.01 to0.04
Si 0.017 0.007
Cu 0.024 0.01
O 0.013 -
N 0.0035 0.032
Mn:S ratio 7:1 15:1(typical)

21. Ductile-brittle transition temperature
Titanic Steel Modern Steel
Longitudinal
Direction
Traverse
Direction
Longitudinal
Direction
Traverse
Direction
Impact energy
at –2 °C
4 J 4 J 325 J 100 J
Ductile-brittle
Transition
Temperature
30 °C -42 °C -42 °C -42 °C
The steel used for the Titanic hull
was not suited for service at
low temperatures
H. P. Leighly, B. L. Bramfit, and S. J.
Lawrence. Practical Failure Analysis

22. Remedy of upcoming problem
• Analysis of titanic failure
• Effect of grain size
• How does the grain size affect strength?
• Hall-Petch equation: YS= a + bd-1/2
• Yield strength of a steel with 26 micrometer grain
is higher
• redundant ship navigational radar system is
performed
• prototype tool has been implemented that allows
selective failure of system resources on the fly
during testing.

23. conclusion
• By analysis of the factor affecting the DBTT we
can take the approach
• Finally, a quantitative comparative reliability
analysis of the two-component standby
redundant ship navigational radar system is
performed
• Both directly through safer construction designs
and indirectly through intelligence and
surveillance
• The enhanced characteristics of materials will
allow us to create new and innovative devices
to protect all of us from failure of ship

24. reference
1.Dieter, G.E., Mechanical metallurgy, 1988, SI metric
edition ,McGraw-Hill, ISBN 0-07-100406-8
2.a b c
Rich, Jack C. (1988), The Materials and Methods of
Sculpture, Courier Dover Publications, p. 129, ISBN
0486257428
3.John, Vernon. Introduction to Engineering Materials, 3rd
ed.(?) New York: Industrial Press, 1992. ISBN
0831130431
4.Standard Methods for Notched Bar Impact Testing of Metallic
Materials, E 23, Annual Book
of ASTM Standards, v. 03.01, ASTM, Philadelphia, 1984, pp. 210-
233

25. Thank youThank you