potential defects leading to failure
TRANSCRIPT
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8/19/2019 Potential Defects Leading to Failure
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Muhammad Azeem Uddin | ME-4B | me131008
POTENTIAL DEFECTS
LEADING TO
MATERIAL FAILURE
ABSTRACT:
The rising statement about material failure is
that, “Failures do not just happen; they are
caused 1.” So the materials failure urges us to
investigate about the phenomenon undergoing
which they are being failed. The reason for this
enthusiasm is that, if we are unable to figure
out a particular problem then how come wouldwe be able to suggest a remedy for it. Materials
failure may or may not involve fracture. The
defect is result of may be any sort of chemical,
mechanical or thermal influence.
DEFINITIONS:
To understand the defects leading to material
failure we must have to acknowledge few
terms:
Discontinuity: any type of intentional or
unintentional non-uniformity.
Imperfection: non desired behavior of
material; not possessing the proposed
properties.
Flaw: imperfection found by tests.
Defect: flaws whose size, shape,
orientation, location, or properties do
not meet the desired values.
DEFECTS:
Manufacturing defect
Failure to conform to stated
specifications
Non-satisfaction of user requirements
Deviation from the norm
A product leaves the assembly line in
substandard condition, differs from the
1 Failure Analysis of Engineering Structures ASM
manufacturer’s intended result, or
differs from other ostensibly identical
units of the same product line
Design defect
Less safe than expected by the ordinary
consumer
Excessive preventable danger
Marketing defect
Failure to warn or inadequate warning
of hazard and risk involved with use of
a product
Improper Design
Underestimate of service stress
Undesirable geometry
o
Stress concentrators
o Inadequate radii at corners
o Inaccessibility for inspection
o Difficult to fabricate
Improper choice of materials
Improper choice of heat treatment
Environmental effects
Ad hoc modifications
Defective manufacture
Materials
o
Materials mix-up
o Poor quality of material
o Nonconformity to
specifications
o Undesirable phases and
nonmetallic inclusions
Castings
o Porosity
o Inclusions
o Segregation
Forgings
o
Foldso
Fissures
o Unfavorable flow lines
Welds
o Improper fusion
o Cracks in heat affected zone
o Wrong filler material
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Muhammad Azeem Uddin | ME-4B | me131008
Machined parts
o Poor surface finish
o Grinding burns
Heat treatment
o Quench cracks
o Overheating
o Undertempering
Surface treatment
o
Improper cleaning
o
Improper plating
o Improper post treatment
Assembly
o Defective joining
o
Misorientation and
misalignment
o
Inadequate support
o Improper tightening
o
Improper balancing
o Damages by tools
o Assembly stresses
o Distortion
Improper inspection
Deviations from approved tolerances
Deviations from acceptance standards
Wrong techniques
Nonadherence to schedules of
inspection and calibration of inspection
tools Shortcuts to meet targets
Operation, service abnormalities, and abuses
Inadequate lubrication
Improper cleaning
Nonadherence to operating
instructions
o Overspeeding
o
Overloading
o Ill-trained operators
Unexpected service conditions Temperature and stress excursions
Vibrations
Changes in environment
Environmental effects
Various types of chemical corrosion
Stress corrosion
Corrosion fatigue
Erosion
Maintenance
Wrong replacement
Wrong tools Excessive concessions
Inadequate inspection
Ad hoc alterations
Inadequate condition monitoring and
preventive maintenance
Combination of the preceding
Combined action of some of the
preceding causes
Sabotage
Deliberate damage by antisocial acts
Mechanical damages
Explosive sabotage