AE 210 Final Exam Review
There is a choice of tooth forms in selecting a blade for the vertical band machine. For a cutting, what form tooth should be used?
Hook
Rivets are used primarily for which of the following joint types?
Lap
Relative to the dimension of the casting, the pattern that determines the geometry of the casting in expendable mold processes is usually made oversized, the same size, and undersized.
Oversized
What is a cutting fluid?
any liquid or gas applied directly to the machining operation to improve cutting performance
Why most popular fuel among OFW group is Acetylene (C2H2)?
b/c it is capable of higher temperatures than any other, up to 3480/6300 F
Which two of the following processes a permanent joint?
expansion fits and welding
screw
externally threaded fastener generally assembled into a blind threaded hole
What are the 2 major groups of metals?
ferrous and nonferrous
What are 3 dangers present in machine shop?
grinding dust, chemical hazards, hazardous fumes
How does carburizing work?
heating a part of low carbon steel in a carbon- rich environment so that C is diffused into a surface.
Annealing
heating and soaking a metal at a suitable temperature for a certain time, and slowly cooling.
Ferrous metals of engineering importance are alloys of ------and ------. These alloys divided into major groups:--------and -------.
iron, carbon, steel, cast iron
Rule
is a linear measuring instrument whose graduations represent real units of lengths and their subdivision
What is Gas Metal Arc Welding?
is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal(s),
bolt
is an externally threaded fastener inserted through hoes in a assembly
bolt
is an externally threaded fastener inserted through holes in a assembly
scale
is graduated into imaginary units either smaller or larger than the real units they represent.
Preferred mode: Gradual wear
is preferred b/c it leads to longest possible use of the tool.
sheet metal working
is usually between rollers to make them even
Essential factors for a successful solid-state weld are ?
must be very clean and must be close together so atomic bonding cannot occur
Bulk Deformation
shape change before deformation in metal parts whose initially starts out in a bulk rather than a sheet of metal.
For therule, use a coarse-tooth blade on------- material, for sufficient chip clearance
softer
What damaging effects will be caused by high temperature at work?
surface burns and cracks metallurgical damage immediately softening of work surface if heat treated residual stresses in work surface
Manufactering
the application of physical and chemical processes to alter the geometry, properties, and/or appearance of a given and starting material to make parts or products. (also includes assembly of multiple parts to make products)
Polymers can be divided into three type. The type that can be subjected to heating and cooling cycles without significant degradation---------, and type that exhibit elastic extensibility when relatively low mechanical stress is ------------.
thermoplastic,elastomers
Which way should the adjustable wrench be turned?
towards the moveable jaw
electric arc welding
uses an electric arc to provide heat. Metal is welded by heat generated by an electric arc.
In oxyacetylene welding, the maximum temperature reached the tip of the inner cone...
while the outer envelope expands and shields work surface from the atmosphere
In oxyacetylene welding, the maximum temperature reached at the tip of the inner cone...
while the outer envelope spreads out and shields work surface from the atmosphere
What is Shielded Metal Arc Welding/ stick welding?
a filler metal rod coated with chemical that provide flux and shielding
additive manufactering
a process of joining materials to make 3D model data, usually layer upon layer, as opposed to subtractive manufactering and formative manufactering methodologist
Arc welding
a technique in which metals are welded using heat generated by an electric arc.
For a CNC machine tool to accomplish its task, it must be programmed. So programming is the process of...
-developing a sequence of events to be done -a set of cutting tools to be used -a set of machine control functions to be used
What are the Solid State Welding (SSW) advantages over fusion welding possesses?
- If no melting, then no heat affected zone, so -the metal around joint retains original properties
Some SSW processes can be used to
- bond dissimilar metals, without concerns about relative melting points, thermal expansions, and other problems arise in FW
Name the types of joint operations
- butt joint -corner joint -lap joint -tee joint -edge joint
Please list the 4 basic types of the chip in machining
- discontinuous chip -continuous chip -continuous chip w/ Built-up Edge -Serrated chip
A machine tool is a power-driven machine that performs a machining operations. What are the 3 main functions for a machine tool?
- hold part work -positions tool relative to work -provides power at speed, feed, and depths that have been set
Many SSW processes
- produce welded joints that bond the entire contact interface between two parts rather than at distinct spots
What are Machinability Criteria in Production?
- tool life -forces and power -surface finish -ease of chip disposal
What are the 3 modes of tool failure? Which one is the preferred mode and why?
-Fracture failure: cutting force becomes excessive and/or dynamic, leading to brittle fracture -temperature failure: cutting temp. is too high for a tool material -gradual wear: gradual wearing of the cutting tool
What are the Arc Welding Design Guidelines?
-Maintain dimension control and minimize distortion -should be able to perform flat welding, since it's the fastest and convenient welding position
The Mechanical Properties have effect on the Machinability. Please discuss the effects of hardness, stress ductility
-hardness: high hardness means abrasive wear increases so tool life is reduced -Strength: high strength means cutting forces, specific energy, and cutting temp ductility: high> tearing of metal to form chip, causing chip disposal problems and poor finish
coolants for machinery
-has a water base -Most effective at high cutting speeds where heat generation and high temperatures are problems -most effective of tool materials that are most susceptible to temperature failures
What are the advantages of CNC machining
-high precision positioning of workpieces and cutting tools -the ability to program different jobs
usually oil based fluids
-most effective a lower cutting speeds -decreases temp. in the operation
Why is dressing the wheel important?
-re sharpening the wheel: accomplished by rotating disk, abrasive stick, or another grinding wheel held a wheel being dressed as it rotates Functions: breaks off dulled grits to expose new sharp grains remove chips clogged in the wheel
What are the 2 systems of positioning dimensions used in CNC programming?
-the incremental positioning system -the absolute positioning system
Why machined features, such as sharp corners, edges,and points, should be avoided?
-they are difficult to machine -they tend to break during machining they create burrs and dangerous to handle
Machining Parameters that determine surface geometry. What are the 3 major geometric factors?
-type of machining operations -tool, geometry especially nose radius -feed -surface geometry that results from only these factors is the "ideal" or "theoretical" surface roughness
Why is machining important?
-variety of work materials can be machined, most frequently used to cut metals -variety of part shapes and special geometric features, possible, screw threads -accurate round holes -very straight edge & surfaces, good dimensional accuracy and surface finishes
What is the range of carbon percentages that defines an iron-carbon alloy as steel?
0.02% to 2.11%
The dividing line between warm working and cold working is usually taken to be which of the following temperatures relative to the melting point of the given metal Tm= the melting temperature on an temperature scale?
0.3TM
Why abrasive processes are important
1. Can be used on all types of materials 2. Some can produce extremely fine surface finishes, to 0.025m(1-in) 3. Some can hold dimensions to extremely close tolerances
What is fundamental difference between a fusion weld and solid-state weld?
1. Fusion welding: two parts are joined in some cases. Filler metal is added. 2. Solid-state welding: two pieces are joined under a pressure providing an intimate contact between them. No filler metal is added.
What are the 3 major causes of wheel wear in the grinding process?
1. Grain fracture- when a portion of the grain breaks off, but the rest of the grain remains bonded in the wheel 2. Attritions wear- dulling of individuals grains, resulting in flat spots and rounded edges 3. Bond wear- the individual grains are pulled out the bonding material
What are the 3 processing steps in precipitation hardening?
1. Solution treatment- alloy is heated to a temperature T's above solvus line into the alpha phase region and held for a period sufficient to dissolve the beta phase. 2. Quenching- to room temperature to create a supersaturated solid solution. 3. Precipitation Treatment-alloy is heated to a temperature Tp, below Ts, to cause precipitation of fine particles of the beta phase
What are the 4 zones in the cross section of a typical fusion welded joint?
1. fusion zone 2. weld interference 3. heat affected zone (HAZ) 4. Unaffected base metal zone
Disadvantages of Plasma Air Welding
1. high equipment cost 2. Larger torch size than other Aw processes 3. tends to restrict access in some joints
What are the disadvantages of welding compared to other assembly operations?
1. performed manually 2. most welding processes are dangerous 3. does not allow for convenient disassembly 4. the defects can reduced the strength of the joint
What the advantages of welding compared to other assembly operations??
1. provides a permanent joint 2. the welded joint can be stronger than the parent materials. 3. usually the most economical way to join components in terms of material usage and fabrication costs 4. not restricted to the factory environment
Cutting temperatures are important in machining, because high temperature can result in?
1. reduce tool life 2.produce hot chips that pose safety hazards to the machine operator 3. can cause inaccuracies in part dimensions due to thermal expansions of work material
Reasons why metals are annealed
1. reduces hardness and brittleness 2. soften metals for machining or forming 3. obtain desirable mechanical properties 4.recrystallize cold worked metals 5. relieve residual stresses induced by shaping
Each machining operation produces a characteristic part geometry due to two factors:
1. relative motions between tool and work part -generating: part geometry determined by feeding trajectory of cutting tool 2. shape of the cutting tool -forming: part geometry is created by the shape of the cutting tool
What are the purposes of heat treatment in manufactering?
1. to soften a metal prior to forming 2. to relieve strain hardening that occurs during forming. 3.to strengthen and harden the metal near the end of the manufactering sequence.
What the 4-quenching media used in the quenching of steel to produce martensite?
1.Brine: salt water, usually agitated (fastest cooling rate) 2. Still fresh water 3.Still oil 4. Air (slowest cooling rate)
The cutting tools can be classified into 2 categories, single- point tools and multiple cutting edge tools.What is the main difference between them?
1.one dominant cutting edge: -point is usually rounded to form a nose radius -turning uses single point tools 2. More than one cutting edge -motion relative to work achieved by rotating -Drilling and milling use rotating multiple cuttign edge tool
peripheral milling
Cutter axis parallel to surface being machined Cutting edges on outside periphery of cutter
Face Milling
Cutter axis perpendicular to surface being milled Cutting edges on both the end and outside periphery of the cutter
What is unit melting energy in welding, and what are the factors in depends on?
Definition:Heat to raise temperature of solid metal to a melting point-Depends on the metal's volumetric specific heat Heat to transform metal from solid to liquid phase at melting point- Depends on metal's heat fusion
Why plasma air welding can be achieved a higher temperature (28,000 C) (50,000 F) than arc welding processes
Due to the constriction of the arc it produces a plasma jet of small diameter and very high density
What is Friction Stir Welding (FSW) and what makes it distinguished from Friction Welding (FRW)
FSW the metal is not melted, but it uses a third body tool to join the metals together. In FRW, it generates heat by mechanical friction between workpieces.
A metal alloy is composed of two or more elements, all of which are metallic.
False
The volume of the riser must always be greater than the volume of the casting in order to avoid premature solidification
False
Which one of the following is property-enhanced operation?
Heat treatment
In the grinding process, how to achieve the best surface finish?
Small grain sizes higher wheel speeds denser wheel structure means more grits per wheel area smaller grit size & dense wheel structure high wheel speeds & low work speeds small depths of cut & large wheel diameters
The part produced in a sheet metal operation is called which?
Stamping
Define a groove weld
The groove weld refers to beads that are deposited in a groove between two members to be joined. -usually requires part edge to be shaped into a groove to facilitate weld penetration (Mostly associated with butt joints)
Better mechanical properties are generally associated with wrought metals compared with cast metals.
True
Hot working involves metal forming processes carried out above the recrystallization temperature.
True
Most mechanical assembly methods involve the use discrete fasteners that are added to the parts during the assembly
True