Failure Analysis

Question 1

What three trends can be tracked by using a fluid testing schedule?

Answer 1

Wear rates of internal components
Rate of fluid and additive detioration
External contamination (Ingressed)

Question 2

What is the main concern during the break in period?

Answer 2

During the break in period, extremely small particles will be broken away and suspended within the oil, but not trapped within the filter. Smaller than 15 microns.

Question 3

At what point does predictive maintenance become failure maintenance?

Answer 3

Once the inspections begin to show more wear particles and you are in the high risk period.

Question 4

What three items are investigated during oil analysis?

Answer 4

Deteroiration of the oil and additives
Amount of particles in the oil
Presence of foreign particles

Question 5

How many ounces is a typical oil sample?

Answer 5

4 oz

Question 6

What 3 main sections are on an oil sample lab report?

Answer 6

Metals
Physical properties
Other properties

Question 7

What is Viscosity of a fluid?

How is a change in viscosity caused?

Answer 7

Viscosity is a measure of a fluids resistance to flow
Contamination by other products
High temps
Extended service intervals

Question 8

How does water get into a system, and what does it cause?

Answer 8

Water is ingested as contamination, or created as condensation.
Components can rust, oils can become acidic, and can act as a catalyst causing creation of metallic substances.

Question 9

What do solids in the oil indicate, and how is it caused?

Answer 9

Solids indicate varnish, sludge and soot created by the combustion process.
These are caused by high operating temperatures, or outside contamination.

Question 10

If your oil analysis indicates increased tin content, what could this be coming from?

Answer 10

Tin wear is caused by wearing of sacrificial overlays during break in periods.

Question 11

If Aluminum is highlighted on the oil sample report, what could be the cause?

Answer 11

Pistons, superchargers, turbochargers, bearings, engine blocks and gearbox housings.

Question 12

Your lab report comes back with large amounts of Silicon in the oil, what caused this?

Answer 12

Dirt ingested in the sample is most likely

Question 13

If lab results indicate excessive Chromium in your oil, what could be the cause?

Answer 13

Hard surfacing is being removed
Piston Rings wearing
Gearbox bearings and shaftsd

Question 14

If there is Nickel found in your oil sample report, what does this indicate?

Answer 14

Frictionless roller bearings, shafts or gears are wearing.

Question 15

What are three sources of coolant contamination?

Answer 15

Wearing components
Corrosion
Environmental Sources ingressed

Question 16

When performing an exhaust gas analysis, what are three items being measured? How are they formed?

Answer 16

Hydrocarbons from low combustion temperatures
Carbon Monoxide from restricted supply air
Nitrogen from high combustion temperatures

Question 17

What is Failure Analysis by definition

Answer 17

A Systematic process to reduce costs and limit risks/liability

Question 18

What is the term for the grainy texture of a broken metal part?

Answer 18

Lattice Structure

Question 19

What determines a parts Overall Strength and Ductility?

Answer 19

The amount of carbon in the steel, and heat treating processes.

Question 20

What is the carbon content of low carbon steel?

Answer 20

0.02-0.25%

Question 21

What is the carbon content of medium carbon steel?

Answer 21

0.25-0.50%

Question 22

What is the carbon content of high carbon steel?

Answer 22

0.5-2%

Question 23

What are the three types of metal fractures?

Answer 23

Fatigue Fracture,
Brittle Fracture
Ductile Fracture

Question 24

How do you determine a failure to be a fatigue fracture?

Answer 24

There will be a clear initiation site, with beach marks indicating prolonged fracturing of the material. Ending with a clear snapping point called the shear lip.

Question 25

How do you determine a failure to be a brittle fracture?

Answer 25

There will be a clear and rough break, typically due to a one time shock load.

Question 26

How do you determine a failure to be a ductile fracture?

Answer 26

The ductile fracture will have plastic deformation, where the part was clearly stretched or stressed past its original shape, ending with a clear snapped off area.

Question 27

What are three ways that wear can be classified?

Answer 27

Type of stress
Movement of the part
Damage to the wear surface

Question 28

What is adhesive wear?

Answer 28

Without proper lubrication, two metal parts will begin to contact, causing a bonding and breaking action. This creates ridges causing further surface wear and heat.

Question 29

What is abrasive wear?

Answer 29

Abrasive wear is the scraping stress caused by particles caught between two surfaces in motion.

Question 30

What does surface fatigue wear look like?

Answer 30

On rolling surfaces such as cam lobes or bearing races, where the load is applied and released it causes surface wear in its normal use.

Question 31

An apprentice is installing a new wheel bearing, it in an interference fit on the spindle and they strike it with a hammer unevenly, what has happened?

Answer 31

True Brinelling: shows up as indentations on the bearing race all the way around, due to improper installation.
This can also be seen with improper preload causing the rollers to impact the race in normal operation.

Question 32

While inspecting the Steering Shaft U joints for reassembly, you notice that the ends have impact marks on only 50% of the surface, what caused this?

Answer 32

False brinelling: the wear or removal of material on a bearing surface in one spot, due to improper lubrication. Typically the wear site will have a reddish tinge due to oxidation of the lubricant.

Question 33

How might you determine that parts have corrosive wear?

Answer 33

Chemical or electrochemical reaction between surfaces, shown by rusting, scaling and pitting.

Question 34

If you see a cylinder liner with pitting around the water jacket, what is this a sign of?

Answer 34

Erosive wear caused by cavitation.

Question 35

What are the two main reasons for component failure?

Answer 35

improper installation

poor maintenance procedures

Question 36

At what temperature are Nitrogen oxides formed in the exhaust gas?

Answer 36

2500 fahrenheit