Chapter 2 - Sheet Metal Structures Flashcards
What are the two different types of sheet metal structures?
Monocoque and Semimonocoque
What are the five major stresses?
- Tension - primary stress that tries to pull a body apart
- Compression - another primary stress that tries to squeeze a part together
- Bending - Tries to pull one side of a body apart while at the same time squeezing the other side together
- Torsion - a twisting force
- Shear - opposing forces are applied on opposite sides of a body
Identify the Aluminum alloy series
1xxx
2xxx
3xxx
4xxx
5xxx
6xxx
7xxx
1xxx Aluminum - Pure aluminum 99% or higher
2xxx Copper
3xxx - **Maganese **
4xxx - Silicon
5xxx - Magnesium
6xxx - Magnesium and silicon
7xxx - zinc
Define annealing
Annealing is a process that softens a metal and decreases internal stresses by heating the metal to the annealing point and heald there until the metal becomes heat soaked. It is then cooled to 500 degrees F of a rate of about 50 degrees F per hour
Name what these aluminum alloys are commonly used for:
2117
2024
5052
7075
2117 - Mostly aircraft rivets
2024 - Majority used on structures
5052 - Gas tanks and fuel lines
7075 - When high strength is needed
What is alclading and why is it important?
Alclad consists of a pure aluminum coating rolled onto the surface of heat-treated aluminum alloy. The thickness of this coating is approximately 5% of the alloy’s thickness on each side. Alclading a surface greatly increases the corrosion resistance of an aluminum alloy.
Which alloys are heat treatable and non-heat treatable?
Non-heat treatable alloy
1100
3003
5052
Heat treatable alloy
2017
2117
2024
6061
7075
When appropriate, the metal hardness, or temper, is indicated by a letter designation seperated from the alloy designation by a dash. Name the following temper designations:
- O
- T3
- T6
O - Annealed
T3 - Soulution heat-treated and cold worked by the flattening or straightening operation
T6 - Solution heat-treated and artificially aged
Which two series of metals are heat-treatable?
7000 & 2000 series.
All others are non-heat treatable and must be hammered or cold worked to be treated.
Corrosion from two dissimalar metals is called what?
Glavanic corrosion
Artificial aging is another name for _______heat -treatment
Artificial aging is another name for precipitation heat -treatment
Name three disadvantages for using magnesium as a structural material.
cracks, corrodes, & burns easily
What is this tool and what should it and should NOT be used for?
Scribe
Should be used in sheet metal work only for marking the cut-off lines of a part. They should never be used for marking dimension lines for bending metal.
What is the purpose of a prick punch?
Once layout marks have been made with a soft pencil, permanent marks can be made in the location for holes with a sharp prick punch and a light tap with a small hammer.
What is the purpose of this tool?
Center punch
Enlarges a prick punch to begin for drilling
What is the purpose of this tool?
Pin Punch
Ideal for removing rivets
What is th epurpose of this tool?
Kett Saw
Easily removes damaged sections of sheet metal
What is the purpose of this tool?
Pneumatic-powered Kett Saw
performs straight line cuts
What is the purpose of this tool?
Name the advantages and disadvantages of this tool.
Nibbler
Advantage - makes detailed inside cuts
Disadvanteges - leaves rough edges after cutting
What are the two cuts of files and two ways to file?
Cuts
- Single cut - one row of teeth
- double-cut - two rows of teeth
Methods of filing
- Cross filing - the file is moved lengthwise across the work with the hands positioned at the edges
- Draw filing - the file is moved across the work
What is the purpose of this tool?
A squaring shear
Used to make straight cuts across the sheet metal
What are the types of machine brakes (forming tools)?
Press brakes
Cornice brakes
Bar folding machine
Box brake
All of these machines are used to make sharp bends rather than gentle curves
What are the three types of compound curve tools?
Stretch Press - uses a male die
Drop Hammer - Matching male and female dies are used
Hydropress - uses a male die
What are the advantage and disadvantage of using shrinkers and stretcher?
Shrinking and stretching tools are used to form contours in parts by expanding or compressing metal to make it form a curved surface.
What are cleco fasteners used for and what are it’s different colors?
Cleco fasteners are used to temperarily hold sheet metal parts together until they are riveted.
3/32 inch….(-3 diameter rivet) Silver
1/8………………(-4 diameter rivet) Copper
5/32…………..(-5 diameter rivet) Black
3/16……………(-6 diameter rivet) Brass
1/4…………………………………………………..Copper
What is the difference between the rivet codes for AN and MS20?
Decode the following: AN470 AD 4-4
AN - Airforce/Navy
MS20 - Military Standards 20 system
AN470 - head style
AD - Material
4-4 (diameter in 1/32 increments) (lenth in 1/16 increments)
Name the rivet head designs
AN426/MS20426 (standard flush rivet) AN470/MS20470
AN442 AN430
Name the rivets
Plain 1100 Aluminum (A)
Dimple 2117 Aluminum Alloy (AD)
Raised Cross 5056 (B) “ice box rivets”
Raised Dot 2017 (D) “ice box rivets”
Two raised dashes 2024 (DD) Raised ring 7050 (E)
How do you define strain?
The deformation of an object caused by stress
What is a stress-skin structure?
An aircraft without a truss frame providing a more streamline shape and reduced the weight. It is referred to having a monococoque design
What are the different types of fuselage designs?
Truss-type fuselage
Stressed-skin fuselage
- monocoque
- semi-monoque
The acculuted angle for cutting is at what degree?
118 degrees
What are two types of drill?
Pneumatic
variable speed
What is the rule of thumb when drilling into metals?
Soft metals - Higher speed, less pressure
Hard metals - Slower speed, harader pressure
What is dimpling and it’s two types?
When the top sheet of metal is too thin to counter-sink, the edges of the hole may be formed to accomodate the head of the rivet by using a set of dimple dies. The two types are:
Coin dimpling and Radius dimpling
Name the three parts of a drill
Tip - 59 degrees from the center line producing 118 degrees total
Shank - chucked into the drill motor
Body -
- flute - aids in carrying material out of the hole
- Land - provides a finishing dimention of the hole
What are the three main parts of a semmi-monocoque design?
stringer - horizontal lines
Former - vertical lines
Bilkhead - strongest part
