Working document. P a
OET-010 Manufacturing Processes TAG Rubric MET
Objective
3. Distinguish between
different fabrication
processes such as
welding, fasteners,
and adhesives.
COURSE OUTLINE
SURVEY OF MANUFACTURING PROCESSES INSTRUCTOR: STEVE SYKES
Mon/Wed 2:30PM – 5:15PM OFFICE: 778-7946 (Room 434)
TEXT: MODERN MANUFACTURING PROCESSES
SME - DAVID L. GOETSCH Email:[email protected]
WEEK DATE LAB/ACTIVITY LECTURE/DEMONSTRATION ASSIGNMENTS
WEEKLY SCHEDULE OF TOPICS, ACTIVITIES, AND ASSIGNMENTS
1
2
3
4
5
6
7
8
*
9
10
11
12
13
14
15
16
1/12
1/19-21
1/26
2/02
2/09
2/16
2/23
3/02
3/09
3/16
3/23
3/30
4/06
4/13
4/20
4/27
5/04
Lecture
Lecture
Lecture
Exam 1,
Lecture
Lecture
Lab
Exam 2
Spring Break
Lecture
Lecture/Lab
Lecture
Exam 3, Lab
Lecture
Lecture/Lab
Lecture/Lab
Exam 4
Brief overview of course
Introduction of Manufacturing Processes
Manufacturing Safety
Engineering Materials, Metals, Physical Metallurgy
Heat Treatment
Welding/Related Processes
Welding Related Processes
Welding Symbols
Welding Lab
-------------------------------------------------
Pattern Making, Casting Processes
Sand Castings
Sand Castings (lab)
Field Trip
Metrology, Metal Cutting Theory
Turning Processes/
Milling Processes
Final’s Week
Manufacturing Research Presentation
Chap. 1,17
HO
Chap. 2
Chap. 7
Chap. 14
Chap. 14
Hand-out
----
Chap. 5
Handout
Handout
----
Chap. 9
Chap. 9
Chap. 10
Fillet Weld
Base Metal – metal to be welded
Bond Line – the junction of the weld metal and the base metal
Depth of Fusion – the distance that fusion extends into the base metal
Face of Weld – the exposed surface of a weld on the side from which the weld was made
Leg of Fillet Weld – the distance from the root of the joint to the toe of the fillet weld
Root of Weld – the shortest distance from the root of the fillet weld to its face
Throat of Fillet Weld – the point or points at which the bottom of the weld intersects the base metal surface or surfaces
Toe of a Weld – the junction between the face of a weld and the base metal
8
4
7 6 3
1
2
5
8
2
6
7
4
1
3
5
2
Groove Weld
Bevel Angle – the angle formed between the prepared edge of a member and a plane perpendicular to the surface
of a member
Groove Angle – the total included angle of the groove between parts to be joined by a groove weld
Groove Face – the surface of a member included in the groove
Root Face – that portion of the groove face adjacent to the root of the joint
Root Opening – the separation between the members to be joined at the root of the joint
1 2
4
3 5
5
3
2
1
4
3
Forces in Welding
Shielded Metal Arc Welding (SMAW)
an arc welding process which produces coalescence of metals by heating them with an arc between a coveredelectrode and the work. Shielding is obtained from decomposition of the electrode covering. Pressure is notused and filler metal is obtained from the electrode. (Stick )
5
Standard Location of Element of a Welding Symbol
6
Weld Fillet Gage
Checking Fillet Throat Size Checking Fillet Leg Size
Fasteners in Aviation
• Fastener Overview:
– Types of Fastener: • Permanent Fastening
– Welding
– Adhesive Bonding
– Riveting
• Temporary Fastening – Threaded
– Non-Threaded
Permanent Fastening
Welding
Adhesive Bonding
Riveting
9
Adhesive Bonding
10
• Adhesive bonded
composite test strips
Riveting
11
• Rivet joints on a
Cessna 152
Adhesives and Glues
Definition
• An adhesive is a compound that adheres or bonds two items together.
• The use of the terms adhesive and glue is confused.
– Historically natural compounds used as an adhesive were called glues
• Historically, glue only referred to protein colloids prepared from animal tissues.
– Synthetic compounds were called adhesives.
• Today the meaning of the term “adhesive” has been extended to any type of glue-like substances that is used to attach one material to another.
History of Adhesives
• The first adhesives were gums and other plant resins. – Vegetable gums:
• Guar gum
• Gum Arabic
• Archaeologists have found 6000-year-old ceramic vessels that had broken and been repaired using plant resin.
• Most early adhesives were animal glues made by rendering animal products. – Native Americans use of buffalo hooves
– Hide glue
– Bone glue
– Fish glue
– Rabbit skin glue
History--cont.
• Native Americans in what is now the eastern United States used a mixture of spruce gum and fat as adhesives and as caulk to waterproof seams in their birch bark canoes.
• During the times of Babylonia, tar-like glue was used for gluing statues.
• Egypt was one of the most prominent users of adhesives.
– The Egyptians used animal glues to adhere tombs, furniture, ivory, and papyrus.
• Mongols used adhesives to make their short bows.
• In Europe in the Middle Ages, egg whites were used to decorate parchments with gold leaves.
• In the 1700s, the first glue factory was founded in Holland, which manufactured hide glue.
• In the 1750s, the British introduced fish glue.
• As the modernization continued, new patents were issued by using rubber, bones, starch, fish, and casein.
Adhesive/Glue Terms
• Pot time – The amount of time that can elapse between when the adhesive is exposed/mixed until the
reaction develops to the point that the adhesive will not produce a good joint. – Movement of the joint during this time should not reduce the strength of the joint. – Varies with the type of adhesive and the environment.
• Set time – Starts with the assembly of the joint. – Any stress applied to the joint during this time will reduce the strength of the joint. – For some adhesives it is the amount of time pressure should be held on the joint.
• Cure time – The amount of time before the adhesive reaches maximum strength. – Varies with the type of adhesive an the environment
Advantages and
Disadvantages of
Adhesive Bonding
Advantages
No stress concentrations due to
piercing of the adherend
Improved fatigue resistance
Lighter weight structures
Ability to join and seal simultaneously
Ability to join shock-sensitive
substrates
Can be less expensive than
mechanical fasteners
Process can be easily automated
Disadvantages
Strength is dependent upon the
condition of the adherend surface
Limited non destructive quality control
methods
Can be more expensive
Bond quality is dependent upon many
variables
No single universal adhesive for all
applications
Limited disassembly and repair
Categories of Adhesives
• Structural – Natural – Synthetic adhesives
– Thermoplastic adhesives
– Thermosetting
• Pressure sensitive
Structural adhesives harden by one
of four (4) methods:
1. Evaporation of a solvent or water
(white glue),
2. Reaction with radiation (dental
adhesives),
3. Chemical reaction (two part
epoxy)
4. Cooling (hot melt)
• Pressure sensitive adhesives (PSA’s) form a bond simply by the
application of light pressure to marry the adhesive with the adherend.
• Pressure sensitive adhesives are designed with a balance between flow
and resistance to flow.
• PSA’s are designed for either permanent or removable applications
Natural Adhesives
Type Notes
Fish Improved temperature resistance, resistance to water compared to above
Animal Made from collagen, (Skin/bone) with sugar and glycerol added for flexibility.
Supplied as powder/bead which is dissolved in water
Casein Made from milk precipitated with acid. Supplied a powder for mixing with water.
Improved properties compared to all above glues
Vegetable Based on starch, dextrine.
Supplied as a powder for mixing with water.
Low strength.
Low resistance to water/high temps
Generally set by solvent evaporation.
They are generally of low strength and are susceptible to moisture and mold.
Their use is restricted to the joining of low strength materials.
http://www.roymech.co.uk/Useful_Tables/Adhesives/Nat_Adhesives.html
Synthetic Adhesives Elastomers
Based on natural and synthetic rubbers set by solvent evaporation or heat curing.
They have relatively low shear strength and suffer from creep and are therefore used for unstressed joints.
They are useful for flexible bonds with plastics and rubbers.
Natural Rubber Rubber solution with bonding be evaporation of solvent.
Not suitable for loaded structures or adverse environments.
Good for water but low resistance to oils and solvents
Polychloroprene (Neoprene)
Polyurethene Two component adhesives which can be formulated for applications.
Resistant to acids, oils some solvents and alkalis.
Susceptible to moisture.
Load bearing duties viable.
Flexible bonds suitable for shock and vibratory loading.
High strength joints
Silicone Rubber Set at room temperatures.
Has a high temperature service temperature of up to 300o C.
Low shear strength. Very good sealing /space filling adhesive - widely used
for glazing
http://www.roymech.co.uk/Useful_Tables/Adhesives/Adhesives.html#Types
Thermoplastic Adhesives
• Fusible
• Soluble
• Poor heat and creep resistant.
• They are normally used for low/medium loads.
• They have good resistance to oils but poor resistance to water.
Polyvinyl Acetate
(PVA)
Supplied as an emulsion in water, for porous materials, especially wood
Shear strength is good
Resistant to oil
Poor resistance to water
Low heat tolerance ( White glue)
Cyanoacrylates Harden quickly in seconds based on catalytic action of surface moisture.
Good for rubber.
Care needed when used with metals in moist warm conditions. "Superglue"
Thermo Setting Adhesives
Type Info
Resorcinol
resins
Good water resistance.
Used for exterior plywood.
Polyesters
(unsaturated)
Usually made to harden by chemical action rather than by the
evaporation of solvents and thus cure with little shrinkage.
Polyamides High performance adhesives requiring higher curing temperatures
and bonding pressures (up to 0.7 MPa ).
High cost adhesive.
Epoxy resins Epoxy (mostly 2-part) adhesives have good strength and chemical
resistance, do not produce volatiles during curing, and have low
shrinkage.
Form extremely strong and durable bonds with most materials in
well-designed joints.
Single part adhesives require heat for setting or long setting times.
Set as a result of the build up of molecular chains to produce a rigid cross linked structure.
Using Adhesives
• Apply adhesive – Uniform layer
– Some suggest using a notched applicator.
– Insure joint has sufficient adhesive to form a squeeze line when the joint is clamped.
• No squeeze line = insufficient adhesive (starved joint)
• Excessive adhesive squeezing out = wasted adhesive
• Select the best
adhesive for the
materials being used
and the
environment.
– Follow manufacturers
instructions.
• Prepare joint
– Clean
– Close fitting
– Dampen
Using Adhesives--cont.
• Force surfaces together – Use correct amount of pressure
• Insufficient pressure will result in a poor joint
• Excessive pressure may reduce joint strength
– Clamps
– Nails or other fasteners
Adhesive Failure
• Adhesives can fail at several different points.
• Common failures are: – Cohesive – Adhesive (Interfacial) – Mixed fracture – Alternating crack path