ie 370 exam 2

shear stress

Stresses that act perpendicularly to each other (ex: scissors).

drawing

continuously reduces the diameter and increases the length of wires or tubes

cold isostatic pressing enhancing mechanical properties and dimensional integrity

applies uniform fluid pressure around a powder-filed mold, which compacts powder evenly. this reduces porosity and ensures consistent density improving strength, hardness, and precise dimensions

forming process impact on microstructure and mechanical properties of metals

refine metal grains and increase dislocation density leading to strain hardening which raises hardness and yield strength. Increases resistance to deformation though young’s modulus is unchanged, strengthen the material but can lead to brittleness in excess

hot working

shaping metal above its recrystallization temperature

advantages and disadvantages of hot working

advantages:

exceptional formability

reduced forming forces

grain refinement

homogenization of microstructure

welding and joining

disadvantages:

dimensional accuracy

surface oxidation

energy consumption

equipment requirements

forging

Involves shaping metal by compressive forced between dies.

forming process

Shaping solid materials by plastic deformation without melting.

bulk deformation processes

Involve a significant volume change of the work piece.

Includes: rolling, extrusion, forging, and drawing

rolling

Process that reduces the thickness and refines the grain structure of metal sheets or bar stocks by passing it between rollers.

flat rolling - creates sheet metal

shape rolling - produces specific shapes like angles

Very hot metal rolled at high pressures.

strain hardening effect

The more something strains, the harder it will become.

open-die forging

No closed die cavity. Allows for shape changes in multiple directions.

closed-die forging

Uses matched dies to form specific shapes.

isothermal forging

High-temperature forging to improve material properties and reduce forces.

extrusion

Forces a heated metal billet through a die to create continuous profiles.

direct extrusion

The ram pushes the billet directly through a die.

indirect extrusion

The container holds a billet, and the ram pushes against the container's bottom to extrude material.

hydrostatic extrusion

Fluid pressure transmits force to the billet, reducing friction and enabling complex shapes.

deep drawing

A sheet metal blank is drawn over a punch into a die cavity creating a deep cup shape.

tube and wire drawing

Process that continuously reduces the diameter and increases the length of wires or tubes using multiple dies. Can achieve high strength and precise tolerances.

Involves pulling (not pushing) and requires a mandrel. Friction at the edges causes metal to act plastically.

How do optical fibers work?

There is a glass core with a high index of refraction surrounded by glass cladding with a lower index of refraction.

Total internal refraction allows light to travel long distances through the fiber with minimal loss - light cannot enter the cladding because it is hitting at an angle higher than the critical angle.

How are optical fibers manufactured?

The primary manufacturing process used to create optical fibers is drawing.
Step 1: gas introduction and reaction into glass tube
step 2: core and cladding formation: high-refractive-index core on the inner core and lower-refractive-index cladding on the other side
step 3: fiber drawing- modified tube is heated and drawn at a constant temperature for uniformity forming solid, hole-free structure.
Efficient light transmission with minimal loss

straight bending

Creates linear bends in sheet metal using bending tools. Must account for springback.

contoured flanging

Bends sheet metal along a curved edge to create flanges.

forming process independent variables

- temperature

- strain rate

- tooling geometry

- lubrication

- product geometry

forming process dependent variables

- force of power requirements

- product properties

- exit temperature

- surface finish

- dimensional precision

- material flow details

What can be done to reduce the effects of springback when bending metal?

Extremely hot metal does not spring back.

What are important factors to consider when lubricating?

- easy to spread

- chemically compatible with work metal

- inexpensive

- environmentally friendly

spinning

shear spinning - Creates asymmetric cups/cones by pressing a sheet metal disk against a rolling tool.

tube spinning - Produces tubular parts using tubular blanks.

cold working

Shaping metal below its recrystallization temperature which is near net shape. Causes strength and hardness to increase but ductility to decrease. Usually involves spring back.

advantages/disadvantages of cold working

advantages:

- high dimensional accuracy (no thermal expansion)

- smooth surface finish

- energy efficient

disadvantages:

- limited formability

- high forces

- springback

- potential cracking

powder metallurgy

Process where fine powders are blended, pressed into a shape, and then heated to bond the surfaces.

Usually used for large quantities of small, intricate parts with high precision.

advantages of powder metallurgy

- shape complexity (internal features)

- tolerances/dimensional accuracy

- wide range of materials

- can tailor the porosity

- good for mass production of identical products

- cost-effective (minimal waste)

- improves strength and density

disadvantages of powder metallurgy

- high initial tooling cost

- only small parts

- variability in physical properties

- complicated process

stages of powder metallurgy in order

1. powder manufacturing

2. mixing/blending

3. compacting

4. sintering

melt atomization process

1. Metal is melted in a furnace.

2. High-velocity gas jets break the molten stream into droplets.

3. Droplets rapidly solidify due to large surface area exposed to cool gas.

4. Powder is collected and sorted.

advantages of melt atomization

- uniform spherical shape

- wide material range

- fine particle size

- purity and cleanliness

powder production methods

- melt atomization

- milling: grinds bulk materials using mills (for brittle materials)

- chemical reduction: creates powders through chemical reactions (for refractory metals)

- electrodeposition: forms powder by depositing metal ions into a cathode

- rapidly solidifying

rapidly solidified powders

Created using specialized techniques to create microcrystalline fine grains) or amorphous (no long-range crystals) powder.

advantages of rapidly solidified powders

- enhanced strength/hardness

- wear/corrosion resistance

- enhanced magnetic properties

- lower sintering temperatures for shorter times

- near net shape

compaction sequence

1. cycle start

2. die positioning - may involve preheating

3. powder charging

4. lower punch movement - loose compaction

5. main compaction

6. dwell time (optional)

7. pressure release

8. upper punch withdrawal

9. part ejection

10. die cleaning and preparation

green strength

The strength of a compacted powder before sintering. Crucial for handling and shaping. Can be influenced by compacting pressure, particle interlocking, and lubricants.

characteristics of dry mixing

- simple and inexpensive

- wide range of material compatibility

- no wastewater generation

characteristics of wet mixing

- improved mixing efficiency

- reduced dust generation

- tailored functionalities

When should a single moving punch be used for compacting?

For soft things that can dissolve. Otherwise, multiple moving punches results in stronger, harder parts.

isostatic compaction

When powder is encapsulated in a flexible mold, which is them immersed in a pressurized gas or liquid.

sintering

The pressed-powder compacts are heating in a controlled atmosphere right below the melting point. Must occur in oxygen-free conditions

stages of sintering

1. burn off stage - removes lubricants and contaminants from the powder

2. high temperature stage - microstructure evolves and mechanical properties develop

3. cooling down - gradually decreasing the temperature to prevent defects

hot isostatic pressing

Combines powder compaction and sintering into a single step where high temperature and pressure are applied in a sealed chamber to enhance properties.

cold isostatic pressing

Compacts powders using uniform pressure from all directions, often using a fluid to transmit pressure uniformly.

What's an important consideration when designing parts for powder metallurgy?

Minimizing the amounts of sharp corners by replacing them with curves. Minimize the amount of punches required, which may involve machining after the fact.

machining

Using a sharp cutting tool to precisely remove material from a workpiece using shear deformation to form a chip.

turning (uses a lathe)

Machining process for creating cylindrical shapes using a rotating workpiece and a stationary, single-point cutting tool which scrapes off material.

chamfering

Creates angled edges at the intersection of two surfaces using turning with an angled tool.

threading

Creates helical groves for screw thready using turning with a pointed tool. This is the only method that can be used to make threads.

internal turning (boring)

Creates cylindrical cavities and features inside of the workpiece using specialized tools.

knurling

A type of turning that creates this specific texture.

cutting conditions for turning

cutting speed (v) - rotational speed of the workpiece

feed rate (f) - distance the tool moves per revolution

depth of cut (d) - amount of materials removed per pass

drilling

Machining process used to create cylindrical holes in workpieces using a rotating drill bit that penetrates the material.

boring

Requires there to already be a hole in the part.

countersinking/counterboring

countersinking - Creates a conical depression at the top of a hold for flat-head screws.

counterboring - Enlarges the top portion of a hole for countersunk fasteners.

cutting conditions in drilling

cutting speed (v) - the rotational speed of the drill bit

feed rate - the rate at which the drill bit penetrates the workpiece

thrust force - the force pushing the drill bit into the workpiece

milling

Utilizes rotating cutters to remove material from the workpiece surface.

cutting conditions for milling

cutting speed (v) - rotational speed of the cutter

feed rate (f) - the speed at which the workpiece moves relative to the cutter

depth of cut (d) - amount of materials removed per pass

CNC (computer numerical control)

A technology that replaces manual control with programmed instructions for automated operation and improved productivity.

broaching

Pushes a long, multi-toothed tool through a workpiece, creating precise internal profiles and shapes. Only one pass of the tool is necessary. Broaching can make non-round holes including squares and stars.

Requires there to already be a hole in the part.

planing

Similar to milling but using linear (non-rotating) tool motion for flat surfaces.

Best method to shear bubbles off of epoxy.

roughing vs finishing

roughing - the initial material removal which has a high depth and a low speed

finishing - final stage for achieving precise dimensions and smooth surfaces which has low depth and high speed

discontinuous chips

Short, individual segments with irregular shapes and sizes, typically associated with brittle materials.

Cause rough surface finish, tool jamming, and tool wear.

How can a discontinuous chip become a continuous one?

Scooping only a very thin amount of material at a time.

continuous chips

Long, unbroken spirals with uniform thickness and smooth surfaces, which are common in ductile materials due to plastic deformation.

Results in good surface finish and minimal tool wear.

continuous chip with built-up edge

Continuous chips with a deposit of material adhering to the face of the tool, which typically occurs with soft, ductile materials.

Results in jamming, poor surface finish, dimensional inaccuracy, and tool wear.

serrated chips

Continuous chips with sawtooth-like serrations along the edges, typically found in difficult-to-machine materials like ceramics and glass.

Results in poor surface finish and tool wear.

chip thickness ratio

The original chip thickness before cutting divided by the final chip thickness after cutting (R = to/tc).

R is typically less than 1 meaning that the chip thickness increases after cutting due to plastic deformation.

coefficient of friction

Frictional force divided by the normal force.

Must be measured when dry, because lube will reduce its value.

cutting temperature

Heat generated by friction and plastic deformation. 98% of energy gets converted into heat.

non-traditional machining

Processes that remove excess material by various techniques that do not use a sharp cutting tool.

They bypass material limitations due to direct mechanical contact between the workpiece and the cutting tool.

types of non-traditional processes

- mechanical

- electrical

- thermal

- chemical

ultrasonic machining (USM)

A piezoelectric transducer converts electrical energy into high-frequency vibrations transmitted through a slender tool immersed in an abrasive slurry. Workpiece is chipped away.

Only good method to cut a hole in glass.

advantages and disadvantages of USM

advantages:

- material versatility (for very hard/brittle materials)

- complex geometries

- minimal heat generation

- environmentally friendly

disadvantages:

- slow speed

- tool wear caused by abrasive action

waterjet cutting

Water is significantly pressurized and focused through a narrow nozzle which erodes the workpiece.

advantages and disadvantages of waterjet cutting

advantages:

- material versatility (anything waterproof)

- good surface finish

- complex geometries

- environmentally friendly (water is reused)

disadvantages:

- poor dimensional accuracy

- high water consumption

abrasive waterjet cutting

An abrasive feeder introduces fine-grained particles into the water stream increasing its cutting power.

advantages and disadvantages of abrasive waterjet cutting

advantages:

- increased power

- fast

- material compatibility (even more than regular waterjet cutting)

disadvantages:

- poor surface finish

- expensive

- added challenge of selecting the right abrasive material

electrochemical machining

Uses a negatively charged tool and electrolyte flow to dissolve a positively charged workpiece to replicate the shape of the tool. Electrolytes flow quickly to remove material.

This is the only way to make contact lenses or other smooth, spherical cavities.

advantages and disadvantages of electrochemical machining

advantages

- high precision (perfectly smooth)

- stress-free

- compatible with hard/brittle materials

- environmentally friendly

disadvantages:

- limited material compatibility (only conductive materials)

- maintenance

- tool wear

electrochemical deburring

Same concept as electrochemical machining but with the distinct purpose of removing burrs and sharp edges using a specifically shaped tool.

Used commonly for medical devices.

electrochemical grinding

An abrasive, electrolyte slurry flows between a shaped tool electrode and the workpiece causing dissolution and chipping.

advantages and disadvantages of electrochemical grinding

advantages:

- good surface finish

- minimal heat generation

- compatible with hard materials

- good for complex geometries

- fast/efficient

disadvantages:

- only used for metals

die sinking electric discharge machining

Uses a negatively charged tool that plunges into the workpiece submerged in a dielectric fluid, causing electrical discharges which erode the material.

advantages and disadvantages of die sinking electric discharge machining

advantages:

- complex geometries

- hard material compatibility

disadvantages:

- maintenance

- surface finish

- only compatible with conductive materials

wire electric discharge machining

Uses thin, electrically charge wire as the tool which travels through a submerged workpiece, guided by CNC. Electrical discharges melt and vaporize the workpiece.

advantages of wire electric discharge machining

advantages:

- ultra-precise

- complex geometries

- compatible with hard materials

- no direct contact

disadvantages:

- wire breakage

- slow

- poor surface finish

plasma arc machining

Utilizes a high-velocity jet of ionized gas to melt and remove material from the workpiece.

Can cut literally anything (conductive) very quickly, but the cut is messy and uneven.

advantage and disadvantages of plasma arc machining

advantages:

- fast

- minimal burrs

- non-contact

- mostly only cuts conductive materials but can do some nonconductive materials

disadvantages:

- heating may affect material properties

- poor surface finish

- safety

laser beam machinging

Utilizes a highly focused laser beam to deliver intense thermal energy onto the workpiece surface. Causes the material to melt/vaporize.

advantages and disadvantages of laser beam machining

advantages:

- precise

- material versatility

- environmentally friendly

- non-contact

disadvantages:

- high initial investment

- heating may affect material properties

how lasers work

Converts electrical energy into a highly coherent light beam that is monochromatic and with parallel light waves.

If a photon hits mirror 2 perpendicular, it will pass through.

inversion population

If the number of excited atoms is greater than the number of non-excited atoms, then the laser will be continuous.

electropolishing

Makes the workpiece the anode in an electrolytic bath which dissolves metal ions from the surface leaving a smoother finish.