,
,Draw graph for this tensile test?
5mins
,Identify the straight line part of the graph.
, Learning Objectives
At the end of this session, you should be able to:
Define failure
Describe how failure occurs
Describe various mode of failure
Discuss how to prevent or minimise failure in service.
Evaluate a case study and recommend why failure was not prevented
, Class Activity 1- 5mins
Failure of Metallic Materials
• Why is it that we do not want metallic materials to fail
in service?
, Solution
• We don’t want engineering materials to fail because……they
can cause loss of life, economic loss or a loss of products or
services.
• The usual causes of material failure are incorrect materials
selection, incorrect processing, incorrect manufacturing
procedures, inadequate design or incorrect use.
, How do Materials Break?
• Ductile vs. brittle fracture
• Principles of fracture mechanics
• Stress concentration
• Impact fracture testing
, Mode of failures
• Fatigue (cyclic stresses)
• Cyclic stresses, the S—N curve ( a plot of stress (S) against the
number of cycles to failure (N),
• Crack initiation and propagation
• Factors that affect fatigue behaviour
• Creep (time dependent deformation)
• Stress and temperature effects
• Alloys for high-temperature use
, Definition of key terminologies
• Fracture: separation of a body into pieces due to stress, at
temperatures below the melting point.
Steps in fracture:
• crack formation
• crack propagation
Depending on the ability of material to undergo plastic
• deformation before the fracture two fracture modes can be
• defined - ductile or brittle
,Draw graph for this tensile test?
5mins
,Identify the straight line part of the graph.
, Learning Objectives
At the end of this session, you should be able to:
Define failure
Describe how failure occurs
Describe various mode of failure
Discuss how to prevent or minimise failure in service.
Evaluate a case study and recommend why failure was not prevented
, Class Activity 1- 5mins
Failure of Metallic Materials
• Why is it that we do not want metallic materials to fail
in service?
, Solution
• We don’t want engineering materials to fail because……they
can cause loss of life, economic loss or a loss of products or
services.
• The usual causes of material failure are incorrect materials
selection, incorrect processing, incorrect manufacturing
procedures, inadequate design or incorrect use.
, How do Materials Break?
• Ductile vs. brittle fracture
• Principles of fracture mechanics
• Stress concentration
• Impact fracture testing
, Mode of failures
• Fatigue (cyclic stresses)
• Cyclic stresses, the S—N curve ( a plot of stress (S) against the
number of cycles to failure (N),
• Crack initiation and propagation
• Factors that affect fatigue behaviour
• Creep (time dependent deformation)
• Stress and temperature effects
• Alloys for high-temperature use
, Definition of key terminologies
• Fracture: separation of a body into pieces due to stress, at
temperatures below the melting point.
Steps in fracture:
• crack formation
• crack propagation
Depending on the ability of material to undergo plastic
• deformation before the fracture two fracture modes can be
• defined - ductile or brittle
