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

Workplace Safety: Personal Protective Equipment (PPE)

Hand Protection: Gloves and Their Risks

When handling a stock of spare parts, mechanical risks are primarily associated with the transport of parts, whether packed or unpacked. The main hazards include cuts from sharp edges or splinters from pallets.

Gloves for Mechanical Hazards

Gloves designed for mechanical hazards should offer good dexterity, tactile sensitivity, and cut protection. While some welding gloves provide thermal resistance, their primary function is often mechanical and thermal protection.

Gloves for Chemical Hazards

These types of gloves must meet specific minimum mechanical properties to bear the CE marking, ensuring they provide adequate protection against chemical exposure.... Continue reading "Workplace Hazard Control and Personal Protective Equipment" »

Introduction to Electronic Media Technology

Electronic media technology involves the use of microelectronics to create, retrieve, and report information.

Evolution of Computing

Early electronic components faced challenges: resistances impede the passage of current, while capacitors store electrical charge. Inductors are typically copper wires wound into a coil. Early vacuum tubes, metal cylinders covered by glass tubes, regulated the flow of electrons.

The evolution of computers can be summarized by generations:

• 1940s (1st Generation): Computers used vacuum tubes.
• 1950s (2nd Generation): Transistors and semiconductors appeared.
• Late 1950s - 1960s (3rd Generation): Integrated circuits were developed.
• 1969: ARPANET (connecting computers) was established.

Testing Properties of Materials

Conformation

Used to know the degree of suitability of materials to manufacture parts.

Features

Used to know the mechanical characteristics of metal.

Understanding the Mechanical Properties of Materials

Used to find out the mechanical properties of materials.

Defects

Used to verify that there are no defects in the parts.

Mechanical Properties

• Hardness
• Tensile strength
• Yield strength
• and so on

Types of Hardness Measurements

• Scratch
• Penetration
• Rebound

Penetration Methods

• Brinell: A steel ball is used as the indenter, and the measurement is the area that the steel ball leaves.
• Rockwell: A diamond-tipped conical tip is used for hard materials, and a spherical tip is used for soft materials. Hardness is found by measuring the depth

Critical Path Method (CPM) and Program Evaluation and Review Technique (PERT)

Activity Duration and Delays

If an activity's slack (MTIJ) equals zero, any delay in this activity will delay subsequent activities. However, activities can not delay the project if MTIJ is greater than zero.

Critical Path

The critical path is the longest path, which represents the minimum time necessary to complete the project. Activities on the critical path are called critical activities.

Activities with Uncertain Duration

When the duration of activities is not known with certainty, three estimates are used: optimistic (a_ij), realistic (m_ij), and pessimistic (b_ij). It is assumed that the duration of activities follows a beta distribution. Assuming t_ij are independent... Continue reading "Project Management & Optimization: CPM, PERT, Network Flow, & Integer Programming" »

Piston Verification: Ensuring Optimal Engine Performance

Checking Piston Sliding Zones

Inspect the sliding zones of the piston. There should be no signs of jamming or excessive friction.

Weight Difference Between Pistons

Use a balance to compare the weight of each piston. Differences up to 4 grams are allowed. Larger differences can cause crankshaft imbalance and vibrations.

Piston Diameter

Pistons are not perfectly cylindrical. Follow the manufacturer's instructions to measure the diameter at the specified zone, usually at a certain distance from the head, measured transversally at the same height as the bolt. The installation clearance between the piston and cylinder compensates for thermal expansion and is typically between 0.02 and 0.05 mm.

Bolt

Data Encapsulation and Abstraction

Data encapsulation hides data from users, making it accessible only through class methods. This promotes abstraction, allowing users to utilize functionalities without needing to understand their internal workings.

Method Classification

Methods can be categorized into three groups:

• Constructors/Destructors: Initialize and finalize objects.
• Modifiers: Change data member values.
• Inspectors: Return object state information without altering it.

Friend Functions

Friend functions bridge the gap between unrelated functions and classes, enabling external access to private data members when necessary.

Inline Functions

Inline functions replace function calls with their code, offering advantages like method and friend compatibility,... Continue reading "Data Encapsulation and Abstraction in Object-Oriented Programming" »

Transistors: Function and Types

The transistor is one of the most widely used electrical components, primarily made of semiconductor materials. Its main characteristic is its ability to amplify electric current.

Transistors typically have three terminals:

• Emitter (e)
• Collector (c)
• Base (b)

There are two main types of bipolar junction transistors (BJTs): NPN and PNP. Their fundamental function involves current amplification: a small current flowing through the base terminal controls a much larger current flowing between the collector and emitter terminals. The amplified current, along with the base current, typically flows out through the emitter (for NPN transistors) or into the emitter (for PNP transistors), with the collector handling the larger... Continue reading "Key Electronic Components: Function and Applications" »

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" »

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