Notes, summaries, assignments, exams, and problems for Technology

Casting Processes

Casting: The process used to produce useful parts or objects from molten metal. It consists of pouring molten metal into a container (mold) shaped like the part or object being constructed, allowing it to harden as it cools.

Molds (e.g., sand, plaster, cavity wax, plastic) are filled with molten metal to produce parts similar to the mold shape.

Mold Types

• Green sand
• Dry layer
• Dry sand
• Metal
• Clay
• Furans
• CO2 process
• Special types

Foundry Core Characteristics

Cores must possess the following characteristics:

• Permeable
• Heat resistant
• Easy to collapse (after casting)
• Dry strength
• Friability
• Minimum tendency to generate gas

Pattern Types

Disposable Patterns

These are destroyed during the process of preparing the piece. They do not require special tolerances,... Continue reading "Metal Casting, Pressing & Machining Processes" »

Features: Mechanical resistance, a larger amount of carbon, increased hardness and strength. The most resistant are the beam, shaft, and power transmission systems. Softer elements are used for cold applications and should be addressed. In alloy steels, other factors can yield the best resultant mechanical or chemical properties. Stainless steel incorporates chrome, offering high resistance to corrosion.

Non-ferrous Alloys

• Bronze: An alloy of copper with tin. It is resistant to copper and does not corrode, possessing mechanical properties similar to steel.
• Brass: Formed with copper and zinc. This alloy offers higher hardness and ductility than pure copper.
• Duralumin: Aluminum alloys with other metals. The most common are copper, magnesium, manganese,

Advantages of Plastic in Automotive Construction

• Weight reduction
• Impact recovery and resistance
• Resistant to oxidation
• Easily moldable

How Plastics Are Formed

Plastics are formed by large polymer molecules, also known as macromolecules.

Four Steps in Plastic Manufacturing

1. Obtaining raw materials
2. Synthesis of polymers
3. Adding molding and additives
4. Finishing

Polycondensation vs. Polyaddition

In polycondensation, monomers unite in a chain formation, while in polyaddition, formed chains bind to each other, similar to the general polymerization process.

Polymer Structures

Polymers can have various structures:

• Linear: Long chains of monomers linked by primary bonds.
• Branched: Secondary chains attached to the main chain.
• Reticulated (Crosslinked): One or more polymer

4x4, AWD, and Transfer Case Systems

Limited Slip Differential

A limited-slip differential incorporates a mechanism to mitigate the standard differential's effect during situations where one wheel loses traction. This system engages automatically without driver intervention, unlike manual lockers.

Track-Lok

The Track-Lok system is a regular differential without locking. If one wheel rotates, the opposite wheel will generate the same torque. Part of the torque transmission from the crown gear is passed through a clutch. The clutch sets contain multiple clutch discs with radial grooves on plates made of fiber material.

Track-Lok clutches are engaged by two concurrent forces. The first is the preset force exerted by Belleville spring washers within... Continue reading "4x4, AWD, and Transfer Case Systems in Vehicles" »

Classifying Intermittent Injection Systems

Sequential: Fuel injectors provide fuel in a synchronized manner when the valve is open.

Semisecuencial: Fuel injectors trigger in couples every turn of the motor.

Simultaneous: Fuel injectors provide fuel at all times.

Accumulator Functions in NMEC Fuel Injection System

The accumulator keeps fuel pressure in the circuit after the engine stops, and it dampens the noise produced by the fuel pump.

Difference between Injection and Sequential Semisecuencial

The sequential injection fuel injectors provide fuel in a synchronized manner when the intake valve is open. The injection nozzles are driven by semisecuencial couples every turn of the motor.

No Combined Injections System

The combined injection systems are... Continue reading "Fuel Injection Systems: Operation and Functionality" »

What is Computer Security?

Security is the set of actions, tools, and devices whose purpose is to provide a computer system with integrity, confidentiality, and availability.

• Integrity: Prevents the modification of information by any user who has not been previously authorized.
• Confidentiality: Prevents data visualization by users who have no privileges on the system.
• Availability: Ensures that authorized users have access to the system and its resources when needed.

What Must We Protect Against?

We must protect against ourselves, accidents, breakdowns, malicious intruders, and malware.

Active Security

Active security is designed to prevent damage to computer systems:

1. Appropriate passwords
2. Data encryption
3. Computer security software

Passive Security

Passive

Character Devices and Block Devices

Character devices read and write data as a byte stream. Examples of character devices are printers and keyboards that allow the handling of a single byte at a time.

Block devices read and write information in fragments ("blocks") to the block device at a time. Examples include hard drives, floppy disks, and CD/ROM drives.

Locate Command

The locate command writes the names of files and directories that match a given pattern. It is the fastest of the two commands because it depends on a database (updated daily by default) instead of looking in real-time. It finds files that have been deleted since the last update of the database.

bzip2 Command

The bzip2 command tends to generate more compact compressed files but... Continue reading "Character & Block Devices, bzip2, Inodes, Links, Find & Mount" »

Hydraulic Systems

Storage

Fluid storage tanks are constructed of steel plates and brackets to contain fluid, sediment, and contaminants, and to dissipate generated heat. These tanks are typically coated with water-resistant paint. The bottom of the tank should be sloped with a drain plug for vacuum cleaning. Lids, vents, and air filters prevent the entry of impurities. Baffles within the tank prevent turbulent flow, allowing sediment to settle, separating air from the fluid, preventing foaming, and dissipating heat. Tank capacity should be 2-3 times the pump supply group capacity. Tanks should also have a sight glass, suction line, return line, and drainage.

Filtration

Filtration is the mechanical or physical process of separating materials using... Continue reading "Hydraulic Systems: Components, Functionality, and Maintenance" »

Force

Force is an action capable of producing or modifying the state of motion or deformation. It can be observed through the effects produced by contact or distance between two bodies. Forces are represented by arrows indicating direction and sense. They are measured using a dynamometer, with the unit being Newton.

Mechanical Properties

Mechanical properties determine the behavior of materials when subjected to forces.

Resistance

The ability of a material to resist forces without distorting or breaking.

• Tenacity and Fragility: Tenacity is the property of a material to withstand forces and shocks without breaking, while fragility is the opposite.
• Elasticity: The property of a material to recover its original shape after being deformed by a force.
• Plasticity:

Composite Materials

Selection Criteria of the Method to Use

1. Specified technology
2. Production parameters

Cost per Piece

• Preparation and setup time
• Tooling needs, equipment, and human resources
• Production rates
• Material cost
• Size range

Ranking Methods

Contact Molding

Molded fiber-matrix (of the piece). Starting material:

1. In situ dry fiber impregnated with resin. Wet process.
2. Fiber resin impregnated with cure retardant.

Prepregs: Mat and mixed. 70% fiber, guidance! Cut pollution, not very expensive, 10 layers, vacuum autoclave, existing alternatives.

Variants

(Increase production rates when structural requirements are not high):

1. Projection Method: Mix by air pressure. Reduces production time by 30%.

2. Centrifuge Method: The projection of the mixing is done inside a