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