What is Materials Joining

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What is Materials Joining?

• Materials joining refers to an extensive group of
  manufacturing processes
• Welding
• Adhesive bonding
• Brazing and Soldering
• These processes join a wide range of materials
• Metals
• Ceramics
• Polymers
• Composites
• Electronic materials

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Why Materials Joining?

• Materials joining contributes over 50 billion to
  the U.S. economy annually and is associated with
  over 50 percent of the gross national product,
  according to the American Welding Society

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Things to consider when fabricating parts

• Material Properties
• Design of Part
• Process Selection
• Inspection of Finished Part
• Codes and Standards for Production

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Materials properties

• Strength
• Weight
• Elastic Modulus
• Fatigue Properties
• Impact Properties
• Thermal/Electrical Properties
• Corrosion Properties

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Materials properties

• Strength
• Weight
• Elastic Modulus
• Fatigue Properties
• Impact Properties
• Thermal/Electrical Properties
• Corrosion Properties

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H2O
O
CO2
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Things to consider when fabricating parts

• Material Properties
• Design of Part
• Process Selection
• Inspection of Finished Part
• Codes and Standards for Production

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Joint Types
Joint Design

• Butt joint
• Continuity of section
• T joint
• Flanges or stiffeners
• Lap joint
• No joint preparation
• Corner joint
• Edge joint
• Two or more parallel, or nearly parallel members

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Weld Types
Joint Design

• Fillet weld
• Approximately triangular
• No joint preparation required
• Most common weld in structural work
• Square Weld
• Penetration difficult with single double used to
  ensure strength
• Sometimes root is opened and a backing bar is used

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Weld Types
Joint Design

• Bevel groove
• Single bevel is widely used
• Double preferred if metal thickness 3/4
• V-groove
• Both members beveled
• Butt joints for plate thickness greater than 1/4
  inch
• Double welds reduce distortion and require 1/2
  the weld metal for a given plate thickness

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Weld Types
Joint Design

• J-groove
• Single well suited for butted corner and T joints
• Machined or carbon arc gouged preparation
• U-groove
• Rounded base allows larger electrodes for
  narrower groove angles
• Machined or carbon arc gouged preparation

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Things to consider when fabricating parts

• Material Properties
• Design of Part
• Process Selection
• Inspection of Finished Part
• Codes and Standards for Production

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Gas Tungsten Arc Welding
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Electron Beam Welding (EBW)
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Laser Beam Welding (LBW)
High Energy Density Processes

• Single pass weld penetration up to 3/4 in steel
• Materials need not be conductive
• No filler metal required
• Low heat input produces low distortion
• Does not require a vacuum

Plasma keyhole
Keyhole welding
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Joining Plastics
Welding of Plastics

• Polymer - a single building block (mer) is
  repeated to form a long chain molecule
• Thermoplastic polymers soften when heated, harden
  when cooled
• 2-liter bottles, leisure suits
• Thermosetting polymers dont soften when heated
• Car tires, caulking compound

(Poly)ethylene
add H2O2
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Why Adhesive Bonding?
Adhesive Bonding

• Dissimilar materials
• Plastic to metal
• Materials that can be damaged by mechanical
  attachments
• Shock absorption or mechanical dampening
• Laminate structures
• Skin to honeycomb structure

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Hot Plate, Hot Gas, Infrared

• Advantages
• Provide strong joints
• Reliable
• Used on difficult to join plastics
• Limitations
• Slow
• Limited temperature range

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Hot Plate, Infrared Welding
Welding of Plastics

• Advantages
• Provide strong joints
• Reliable
• Used on difficult to join plastics
• Limitations
• Slow
• Limited temperature range

Hot plate welding
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Hot Gas Welding
Welding of Plastics

• Thermoplastics (hotmelts)
• Adhesive is heated until it softens, then hardens
  on cooling
• Hot gas softens filler and base material
• Filler is pulled or fed into the joint

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Vibration Welding
Welding of Plastics

• Advantages
• Speed
• Used on many materials
• Limitations
• Size
• Requires fixturing
• Equipment costly

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Ultrasonic Welding
Welding of Plastics

• Advantages
• Fast
• Can spot or seam weld
• Limitations
• Equipment complex, many variables
• Only use on small parts
• Cannot weld all plastics

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Things to consider when fabricating parts

• Material Properties
• Design of Part
• Process Selection
• Inspection of Finished Part
• Codes and Standards for Production

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Factors that Influence Process Selection

• Material joining needs
• Capabilities of available processes
• Cost
• Environment
• Required welding speed
• Skill level
• Part Fit-up

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YOUR LABORATORY EXPERIMENT
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Things to consider when fabricating parts

• Material Properties
• Design of Part
• Process Selection
• Inspection of Finished Part
• Codes and Standards for Production

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