Quiz 1 Flashcards
True or False: Failure only occurs when a component breaks.
False. Failure occurs whenever the component is unable to function nominally.
What is failure?
Inability of a component to function as intended.
Why is the study of failure important?
Helps to learn from mistakes to prevent future failures and for mitigation.
What is the main cause of failure in aircraft components?
Fatigue
What is the main cause of failure in the general engineering industry?
Corrosion
What are the four main categories/modes of failure?
Deformation, fracture, wear, and corrosion
What is deformation?
Any change to the shape of the material
What is fracture?
Any cracks or breaks due to stress
What is corrosion?
Deformation due to the material due to chemical reactions with the environment
What is wear?
Undesired removal of material from contacting surfaces by mechanical action (i.e. gears)
Define failure mode
Specific manner in which a failure occurs as a result of the failure mechanism
What are the primary causes of equipment failure?
Design deficiencies, material defects, manufacturing/installation defects, and service life anomalies
What does root cause analysis refer to?
Understanding of the underlying cause of failure so corrective action can be taken
What are the energy forms?
Chemical, Optical, Mechanical, Electrical, Thermal, Magnetic, Acoustic, and Nuclear (COMET MAN)
Which has the larger depth of field, SEM or OM?
SEM
Which microscope (SEM, TEM, or OM) has the highest resolution?
TEM; resolution up to 2 Angstrom
What do SEM, TEM, and OM stand for?
Scanning Electron Microscopy, Transmission Electron Microscopy, and Optical Microscope
Which microscope (SEM, TEM, or OM) has the highest magnification?
TEM; goes up to 1,000,000x magnification
Which technique (SEM, TEM, or OM) is most useful for fractography?
SEM
What is fractography?
Study of the fracture surface of a material
Which microscope (SEM, TEM, or OM) requires the easiest sample preparation?
SEM
How would you prepare an OM sample?
Sectioning, Mounting, Grinding, Polishing, Etching
Which microscope (SEM, TEM, or OM) has the most difficult sample preparation?
TEM
Which tests can be performed to determine the mechanical properties of a sample?
Mechanical (compression and tension) and hardness tests
Which tests can be performed to determine the chemical composition of metals?
Energy Dispersive Xray (EDX) using SEM and spectroscopy
Which tests can be used to classify polymeric materials?
Fourier Transform Infrared spectroscopy (FTIR)
Which tests might be helpful in determining manufacturing imperfections?
X-ray CT, ultrasonic C-scan, and SEM
What are the steps in failure analysis?
0: Think
1: Collect Data
2: Preserve Fracture Surface
3: Preliminary Visual Exam
4: Non-Destructive Testing (NDT)
5: Chemical Analysis
6: Mechanical Testing
7: Macroscopic Exam
8: Microscopic Exam
9: Metallography
10: Failure Mechanisms
11: Calculations/FEA
12: Test in Service Conditions
13: Reporting
True or False: The order of the failure analysis steps are not very important as long as all the steps are completed.
False
Why do structures fail?
Negligence during design, construction, or operation and new application of the design
What is failure analysis?
The systematic process of investigating and understanding the reasons behind the failure of a component, system, or material
What is failure prevention?
Involves strategies and practices designed to avoid or minimize the occurrence of failures in systems, components, or materials
What are types of distortion?
Yielding during service, creep, and buckling
What is the most common type of corrosion?
Uniform corrosion due to rust on iron or steel
What are types of fracture?
Monotonic and fatigue
What is included in a case study?
Summary of events, documentation and analysis, discussion of ramifications, and recommendations
What should be considered during failure analysis?
Physical evidence, use of engineering and scientific principles, and analytical tools
What are the categories of root cause analysis?
Physical Roots (i.e. equipment), Human Roots (i.e. human factors), and Latent Roots (i.e. procedural/systemic cause)
What is a physical root?
Technical explanation of why a part failed
What is a human root?
Human errors that led to the physical cause – whether acts of omission or commission
What is a latent root?
Deficiency in management procedures or systems that allowed human errors to go unchecked
What is metallography?
The study of structure and composition of metals using microscopy
What is a microstructure?
Arrangement of phases and defects within a material
What is a crystal structure?
Arrangement of atoms within a unit cell
What are types of non-destructive testing?
X-ray (radiography), ultrasound, dye penetrant, magnetic particle inspection (MPI), and studying cracks and porosity
