Chain Grades and Basic Machines Quiz
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Questions and Answers

What happens when the effort and load are equal in a machine?

  • A state of equilibrium exists (correct)
  • The machine becomes inefficient
  • A state of motion occurs
  • A mechanical advantage is gained

How does increasing the number of cable lines affect a winch's capability?

  • It decreases the maximum tow weight
  • It allows the winch to pull more than its working load limit (correct)
  • It leads to faster towing speeds
  • It has no effect on the towing capability

What factor is not considered in the mechanical advantage example provided?

  • Number of cable lines
  • Load weight
  • Friction (correct)
  • Gear ratio

In a manual chain hoist, how does pulling down on one chain affect the other chain?

<p>It lifts the end of the other chain (C)</p> Signup and view all the answers

What is the potential multiplication factor of the force exerted on the hand chain of a manual chain hoist?

<p>30 times (C)</p> Signup and view all the answers

What does the Limit of Proportionality indicate in a tensile test?

<p>The point where stress and strain are proportional. (C)</p> Signup and view all the answers

Which term describes the condition where a material can return to its original dimensions after the load is removed?

<p>Elastic Limit (C)</p> Signup and view all the answers

What happens at the Yield Point during a tensile test?

<p>Permanent extension occurs without increasing the load. (D)</p> Signup and view all the answers

What is indicated by the Tensile Strength of a material?

<p>The maximum load a material can sustain. (B)</p> Signup and view all the answers

What does Plastic Deformation refer to?

<p>Permanent change in shape after the limit of proportionality is exceeded. (C)</p> Signup and view all the answers

At which point does necking begin in a tensile test?

<p>Ultimate Breaking Stress (A)</p> Signup and view all the answers

Which of the following descriptions best matches the term Ultimate Breaking Stress?

<p>The load at which a material can no longer withstand stress. (B)</p> Signup and view all the answers

Which statement about the relationship between tensile strength and ultimate breaking stress is true?

<p>Ultimate breaking stress occurs after tensile strength is reached. (C)</p> Signup and view all the answers

What does the formula for efficiency calculate in a machine?

<p>The relationship between Mechanical Advantage and Velocity Ratio (C)</p> Signup and view all the answers

Which type of polymer has been used for centuries?

<p>Shellac (A)</p> Signup and view all the answers

What is a common use of polymers in the lifting equipment industry?

<p>Producing roundslings and flat webbing slings (A)</p> Signup and view all the answers

Which of the following is NOT a synthetic polymer?

<p>Natural rubber (C)</p> Signup and view all the answers

What effect do additives like plasticisers and stabilisers have on polymers?

<p>Alter the properties of polymers (A)</p> Signup and view all the answers

What is the main constituent of wood and paper?

<p>Cellulose (D)</p> Signup and view all the answers

Which of the following materials is often associated with nylon to manufacture seals?

<p>Rubber (D)</p> Signup and view all the answers

What has contributed to the decline of fibre rope slings in favor of textile slings?

<p>Increased durability of newer materials (C)</p> Signup and view all the answers

What is the mechanical advantage when the load is 300kg and the effort is 50kg?

<p>6 (D)</p> Signup and view all the answers

What is the correct Velocity Ratio if the distance moved by effort is 75m and the distance moved by load is 3m?

<p>25 (B)</p> Signup and view all the answers

What does the term 'Efficiency' refer to in the context of machines?

<p>The ratio of useful output energy to input energy (A)</p> Signup and view all the answers

If a machine has a velocity ratio of 10, what does this imply?

<p>The effort moves 10 times farther than the load (B)</p> Signup and view all the answers

What happens to the effort required as the mechanical advantage increases?

<p>The effort decreases (C)</p> Signup and view all the answers

Which of the following statements about machines is incorrect?

<p>All input energy is converted to useful output (A)</p> Signup and view all the answers

Which calculation represents how efficient a machine is in transferring energy?

<p>Efficiency = Useful output energy ÷ Input energy (C)</p> Signup and view all the answers

If the distance moved by the effort is twice the distance moved by the load, what is the Velocity Ratio?

<p>2 (D)</p> Signup and view all the answers

What happens to a ductile material as stress is applied during a tensile test?

<p>It withstands elongation before yielding. (C)</p> Signup and view all the answers

Which type of stress is exemplified by a chain sling under load?

<p>Tension (A)</p> Signup and view all the answers

What effect does necking have on the stress in a test piece?

<p>It decreases the apparent stress recorded. (A)</p> Signup and view all the answers

Which statement correctly distinguishes a brittle material in a tensile test?

<p>It deforms and fractures at relatively high stress levels. (A)</p> Signup and view all the answers

What type of stress occurs with a shackle pin under load?

<p>Double shear (C)</p> Signup and view all the answers

In the context of loading conditions, how is compression defined?

<p>A pushing force applied to a material. (B)</p> Signup and view all the answers

Which of the following accurately describes the maximum tensile stress in a ductile material?

<p>It occurs after significant elongation. (B)</p> Signup and view all the answers

How does a ductile material's strength compare to that of a brittle material?

<p>It is often weaker than the brittle material. (B)</p> Signup and view all the answers

What is the primary distinction between normalised and hardened tempered chains?

<p>Normalised chains can be used at a factor of safety of 5:1. (A), Hardened tempered chains cannot be in a normalised condition. (B)</p> Signup and view all the answers

What was the critical change made during the European standards programme in the late 1980s?

<p>Using number grades for medium tolerance chain and letter grades for fine tolerance chain. (C)</p> Signup and view all the answers

Which grade is used to identify hardened and tempered chains after the factor of safety was reduced to 4:1?

<p>Grade M (D)</p> Signup and view all the answers

What term was previously used for chains specifically designated for hoists?

<p>Calibrated (D)</p> Signup and view all the answers

Which of the following options best describes simple machines?

<p>They include devices like levers and wheels that can multiply applied force. (D)</p> Signup and view all the answers

How are the grades for components other than chain defined?

<p>By compatibility with the same grade of chain. (C)</p> Signup and view all the answers

What is a characteristic of compound machines compared to simple machines?

<p>They consist of multiple simple machines that work together. (B)</p> Signup and view all the answers

What does the 'M(4)', 'S(6)', and 'T(8)' designation indicate?

<p>Heat treatment and safety factor of chains. (B)</p> Signup and view all the answers

Flashcards

Mechanical Advantage (MA)

The relationship between the force applied to a machine and the load it moves.

Equilibrium in a Machine

The state where the force and effort applied to a machine are equal.

Winch and Cable Lines

Increasing cable lines on a winch multiplies the maximum tow weight.

Chain Hoist Operation

Pulling down on one chain loop turns a pulley, lifting the other end, increasing the mechanical work.

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Gear Ratio in a Chain Hoist

The gear ratio in a hand-operated chain hoist can multiply the force exerted on the chain by up to 30 times.

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Simple Machines

Basic machines with one or few components.

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Compound Machines

Machines combining simple machines.

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Lever

A simple machine that uses a pivot point (fulcrum).

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Wheel and Axle

A simple machine using a wheel and a rod.

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Chain Grades (M, S, T)

Chain classifications based on heat treatment and tolerance.

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Medium Tolerance

Chain accuracy standard.

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Fine Tolerance

Chain accuracy standard; more precise than medium.

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Chain Heat Treatment

Process to strengthen chain by modifying material properties

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Mechanical Advantage

The ratio of load to effort in a machine, representing how much easier it makes a task.

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Efficiency of a Machine

The ratio of the useful work output to the total work input, expressed as a percentage. It quantifies how effectively a machine converts energy into useful work.

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Calculate Mechanical Advantage

Divide the load by the effort to determine the mechanical advantage.

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Velocity Ratio (VR)

The ratio of the distance moved by the effort to the distance moved by the load in a machine.

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Velocity Ratio

The ratio of the distance moved by the effort to the distance moved by the load in a machine.

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Polymers

Large molecules made up of repeating units of smaller molecules (monomers).

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Calculate Velocity Ratio

Divide the distance moved by the effort by the distance moved by the load.

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Efficiency of a Machine

The percentage of the input energy that is converted into useful output energy.

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Natural Polymers

Polymers derived from natural sources, such as plants or animals.

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Synthetic Polymers

Man-made polymers created through chemical processes.

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Why is Efficiency Important?

A machine's efficiency determines how much useful work is done for the energy input. Higher efficiency means less wasted energy.

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Factors Affecting Efficiency

Friction, heat, and wear can reduce a machine's efficiency.

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Additives in Polymers

Substances added to polymers to modify their properties, such as flexibility, strength, or resistance to heat.

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Polymers in Lifting Equipment

Polymers are commonly used in lifting equipment for components such as slings, ropes, gears, and seals due to their lightweight, durable, and flexible nature.

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Goal of Machine Design

To maximize efficiency by minimizing energy loss due to friction and other factors.

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Stress in a Test Piece

The force applied per unit area of a material, measured in Pascals (Pa) or pounds per square inch (psi).

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Necking

The process where a material under tensile stress starts to thin down in a specific area due to localized deformation.

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Ductile Material

A material that can undergo significant plastic deformation before fracturing. It can stretch and bend without breaking.

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Brittle Material

A material that breaks or fractures with little to no deformation.

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Tensile Test

A test used to measure a material's strength under a pulling force.

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Types of Stress

The different ways in which a force can be applied to a material, classified by how the force acts.

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Single Shear

Force applied to a material across a single area, causing it to cut or break.

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Double Shear

Force applied across two areas of a material, distributing the force over a wider zone.

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Limit of Proportionality

The point on a stress-strain curve where the relationship between stress and strain becomes non-linear. Beyond this point, the material starts to deform permanently.

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Elastic Limit

The maximum stress a material can withstand before undergoing permanent deformation. If the load is removed within this limit, the material will return to its original shape.

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Yield Point

The point on a stress-strain curve where the material begins to deform permanently without any increase in load. Sometimes there is a slight drop in load, creating an upper and lower yield point.

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Tensile Strength

The maximum stress a material can withstand before it begins to fracture. This point corresponds to the point of maximum load on a stress-strain curve.

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Ultimate Breaking Stress

The stress at the point of failure, where the material breaks completely. It's often lower than the tensile strength due to the reduction in cross-sectional area during necking.

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Plastic Deformation

The permanent deformation of a material that occurs when the load exceeds the elastic limit. Unlike elastic deformation, it's a permanent change.

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What is the difference between the Limit of Proportionality and the Elastic Limit?

The limit of proportionality is the point where the stress-strain relationship becomes non-linear. The elastic limit is the point where the material starts to deform permanently. In some materials, these points may be very close, but they can also differ.

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Study Notes

Chain Grades

  • Early BS grade 40 chain came in normalized or hardened/tempered conditions, marked as 04 or 40 respectively.
  • Later, a 4:1 safety factor led to the use of grade M.
  • All grades now use interchangeable letter/number designations (e.g., M4, S6, T8).
  • Number grades denote medium tolerance chains for slings, while letter grades denote fine tolerance chains for hoists.
  • All machine-made chain is calibrated, but the distinction lies in accuracy standards.
  • European standards adopted the number/letter grade separation.
  • Hand-operated hoist chains are through-hardened, while power-operated chains are surface-hardened (grades T, DAT, and DT) to improve wear.
  • ISO also uses TH and VH for through-hardened grades (T and V) for hand-operated hoists.
  • Non-chain components are graded by compatibility with the same chain grade, not strictly by stress levels.

Basic Machines

  • A machine is a mechanism using applied force at one point to transmit force to another, gaining a mechanical advantage for a specific purpose.
  • Simple machines include: levers, wheel/axle, pulleys, inclined planes, wedges, and screws.
  • Compound machines combine simple machines for more complex work (e.g., a mobile crane - using levers, pulleys, screws, drive train wheels).
  • Lifting equipment is constructed using multiple combined basic machines for targeted tasks.

Weight and Force

  • Weight and force are often treated as equivalent, though not strictly so, with identical unit measurements.
  • A lifting machine uses a smaller effort to lift a larger load.
  • Simple machines increase the work done with a given effort or decrease the effort required to do a certain amount of work.
  • Work is calculated by multiplying force by distance.
  • A turning moment, or moment of force, results when a force (effort) is applied at a distance (d) from a turning point, calculated as F x d

Mechanical Advantage (MA)

  • Mechanical advantage occurs when the force pushing an object is not equal to the force needed to move the object.
  • The mechanical advantage is simply the ratio to find out how much each amount of force gets multiplied.
  • Increasing cable lines between a winch and a vehicle allows for greater load capacity exceeding the winch's working load limit for the single line.

Velocity Ratio (VR)

  • Machines move loads by applying small forces over larger distances; the velocity ratio is the ratio of these distances.
  • The formula for Velocity Ratio is: Distance moved by effort / Distance moved by load

Efficiency (EFF)

  • Machines' purpose is to use as little energy as possible for input while producing useful output.
  • Efficiency is the measure of converting input energy into useful energy stores
  • Higher efficiency means less energy loss, with an efficient machine wasting very little input energy.
  • Efficiency is calculated as (Mechanical Advantage ÷ Velocity Ratio) x 100%.

Polymers and Natural Fibres

  • Polymers are divided into natural (like shellac, wool, silk, natural rubber, and cellulose) and synthetic (like synthetic rubber, resin, nylon, PVC, polypropylene, polyamide, polyester, HMPE, etc) types.
  • Natural fibrous materials, including rope slings, ropes using hemp, manila and sisal are common materials for lifting equipment.
  • These materials offer a wide array of properties such as lightweight, easy handling, durability, and are commonly used (within lifting equipment applications such as slings, ropes, gears, bushes and sheaves).

Heat Treatment

  • Heat treatment alters metal microstructure and characteristics for specific applications by manipulating temperatures and cooling rates.
  • Processes like hardening increase strength, softening decreases strength, and tempering toughens.
  • Annealing refines grain structure and relieves stresses.
  • Each process involves heating, soaking, and cooling phases.

Stress and Strain

  • Stress (force / area) and strain (change in shape) are important mechanical properties of lifting equipment.
  • Stress impacts a material's ability to withstand a force before it inevitably breaks.
  • Strain describes how the object deforms under force (for example, stretching an elastic band).
  • Tensile tests, or tension tests, are an important method to assess materials (such as metals).
  • The results of performing tensile tests allow for calculation of properties such as elastic limit, yield points, ultimate tensile stress, and elongation behavior, all of which help determine material suitability for load-bearing applications.

Shear, Tension, and Compression

  • Single/double shear force acts across a material in one/two areas.
  • Compression force is a push.
  • Tension force is a pull.
  • Torsion is a twisting force.

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Description

Test your knowledge on the different grades of chains and their specifications in hoists and slings, along with the fundamentals of basic machines. This quiz covers topics like safety factors, grade designations, and effectiveness of various chain types. Challenge your understanding of these mechanical components and their applications!

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