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Questions and Answers
What is the primary purpose of using an inclined plane?
What is the primary purpose of using an inclined plane?
Which of the following is NOT a simple machine?
Which of the following is NOT a simple machine?
What is the term used to describe the force required to lift an object using a simple machine?
What is the term used to describe the force required to lift an object using a simple machine?
How do compound machines provide an advantage over simple machines?
How do compound machines provide an advantage over simple machines?
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What is the relationship between weight and force in the context of lifting machines?
What is the relationship between weight and force in the context of lifting machines?
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Which simple machine is primarily used to change the direction of force?
Which simple machine is primarily used to change the direction of force?
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What is the name of the point where a lever pivots?
What is the name of the point where a lever pivots?
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What is the primary purpose of a wedge?
What is the primary purpose of a wedge?
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At what point does the material begin to exhibit plastic deformation?
At what point does the material begin to exhibit plastic deformation?
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What is the point where the stress-strain graph is no longer a straight line?
What is the point where the stress-strain graph is no longer a straight line?
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Which point indicates the maximum load the material can withstand before failure?
Which point indicates the maximum load the material can withstand before failure?
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What happens to the cross-sectional area of the material after exceeding the tensile strength?
What happens to the cross-sectional area of the material after exceeding the tensile strength?
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Up to which point can the test piece return to its original dimensions if the load is removed?
Up to which point can the test piece return to its original dimensions if the load is removed?
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What phenomenon occurs at the point where the load suddenly drops despite the material extending?
What phenomenon occurs at the point where the load suddenly drops despite the material extending?
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What is the term used to describe the situation where the limit of proportionality and the elastic limit are practically the same for mild steel?
What is the term used to describe the situation where the limit of proportionality and the elastic limit are practically the same for mild steel?
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What is the typical occurrence at the point of the 'ultimate breaking stress'?
What is the typical occurrence at the point of the 'ultimate breaking stress'?
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If a 1-ton WLL winch is used with 6 lines of cable, what is the maximum tow weight?
If a 1-ton WLL winch is used with 6 lines of cable, what is the maximum tow weight?
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What is the primary reason why the force exerted on the hand chain of a manual hoist is multiplied by the gearbox?
What is the primary reason why the force exerted on the hand chain of a manual hoist is multiplied by the gearbox?
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If a manual chain hoist has a gear ratio of 25, and the operator exerts a force of 40N on the hand chain, what is the force applied to the load?
If a manual chain hoist has a gear ratio of 25, and the operator exerts a force of 40N on the hand chain, what is the force applied to the load?
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In a simple winch system with a single line of cable, the mechanical advantage is:
In a simple winch system with a single line of cable, the mechanical advantage is:
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What happens to the mechanical advantage of a simple winch as the number of lines of cable increases?
What happens to the mechanical advantage of a simple winch as the number of lines of cable increases?
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What is the main constituent of wood and paper?
What is the main constituent of wood and paper?
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Which of the following is NOT a natural polymer?
Which of the following is NOT a natural polymer?
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What is the benefit of using polymers in lifting equipment?
What is the benefit of using polymers in lifting equipment?
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What is the function of additives such as plasticisers and stabilisers in polymers?
What is the function of additives such as plasticisers and stabilisers in polymers?
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Which of the following is NOT a common use of polymers in the lifting equipment industry?
Which of the following is NOT a common use of polymers in the lifting equipment industry?
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What is the traditional form of textile sling?
What is the traditional form of textile sling?
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What is the formula for calculating the efficiency of a machine?
What is the formula for calculating the efficiency of a machine?
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A device that wastes very little of its input energy is considered to be:
A device that wastes very little of its input energy is considered to be:
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What are two heat treatments that are often used to alter the properties of materials?
What are two heat treatments that are often used to alter the properties of materials?
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Which property describes a material's ability to deform under stress without fracturing?
Which property describes a material's ability to deform under stress without fracturing?
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Which of these statements is TRUE regarding stress in lifting equipment?
Which of these statements is TRUE regarding stress in lifting equipment?
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What is the term used to describe the change in shape of a material under load?
What is the term used to describe the change in shape of a material under load?
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What is the main purpose of the tensile test?
What is the main purpose of the tensile test?
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Which of the following is NOT a key mechanical property revealed by the tensile test?
Which of the following is NOT a key mechanical property revealed by the tensile test?
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How is the tensile test relevant to lifting equipment examiners?
How is the tensile test relevant to lifting equipment examiners?
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Imagine a lifting hook made of steel. Which property of steel is MOST important in determining how much weight the hook can safely lift?
Imagine a lifting hook made of steel. Which property of steel is MOST important in determining how much weight the hook can safely lift?
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What is the primary purpose of a tensile test when assessing lifting equipment materials?
What is the primary purpose of a tensile test when assessing lifting equipment materials?
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Which of the following is NOT a typical property revealed by a tensile test?
Which of the following is NOT a typical property revealed by a tensile test?
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What is the common term for the plotted graph generated from a tensile test?
What is the common term for the plotted graph generated from a tensile test?
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What is the significance of the 'Limit of Proportionality' point on the stress/strain curve?
What is the significance of the 'Limit of Proportionality' point on the stress/strain curve?
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What is the defining characteristic of the 'Elastic Limit' point on the stress/strain curve?
What is the defining characteristic of the 'Elastic Limit' point on the stress/strain curve?
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What is the most accurate description of 'Ultimate Breaking Stress'?
What is the most accurate description of 'Ultimate Breaking Stress'?
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Why is it essential for lifting equipment examiners to understand material properties determined from tensile tests?
Why is it essential for lifting equipment examiners to understand material properties determined from tensile tests?
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What is the primary reason for preparing standard size specimens for tensile testing?
What is the primary reason for preparing standard size specimens for tensile testing?
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Study Notes
Chain Grades
- Original BS grade 40 used at a safety factor of 5:1, either normalized or hardened and tempered.
- Mark 04 for normalized, 40 for hardened and tempered.
- Later, the safety factor was reduced to 4:1, necessitating hardened and tempered chain, with grade M used for distinction.
- All three grades have the same breaking strength, but heat treatment and ratings vary.
- Letters and numbers became interchangeable (M4, S6, T8).
- Number grades for medium-tolerance chain in slings, letter grades for fine-tolerance chain in hoists.
- Medium and fine tolerance terms introduced.
- All machine-made chain is calibrated; the difference is in accuracy.
- European separation of number and letter grades adopted in ISO.
- Hand-operated hoists use through-hardened chain (grades T, DAT, DT.)
- Power operation uses surface hardening for wear (grades TH and VH).
- Chain grades for components other than chain are defined by compatibility, not always strict stress levels.
- Manufacturers determine component dimensions, influencing stress levels.
Basic Machines
- A machine is a mechanism applying force at one point to transmit force to another for a specific purpose (gaining mechanical advantage).
- Machines are categorized into simple and compound machines.
Simple Machines
- Lever: a pivot point that multiplies applied force.
- Wheel and axle: a rod and wheel that multiplies force.
- Pulley: a wheel with a rope that changes force direction.
- Inclined plane: a flat surface angled ends for reduced force.
- Wedge: a triangular shape used to separate, hold, or lift objects.
- Screw: a cylindrical shaft with grooves that moves objects through rotational force.
Compound Machines
- A collection of simple machines.
- More complex work than individual simple machines.
- Provides a greater advantage than simple machines.
- Examples include mobile cranes (jib/mast, pulleys, screws (limit switch), wheel-axles (drive train wheels)).
Weight and Force
- Weight and force are equal, similar units.
- Lifting machines use a small effort to lift a larger load.
- The force required for lifting is called effort, and the force being lifted is called load.
- Formula: Work = Force x Distance
- Moment of force/turning moment (TM): turning effect of a force applied to a lever at a distance from a pivot point.
- Formula: Turning Moment = Force x Distance
Mechanical Advantage (MA)
-Equal effort and load is a state of equilibrium (no movement).
- An increasing amount of effort will move the load.
- Calculated as Load/Effort ratio.
- Example: Using winches—the more lines of cable between the winch and the vehicle, the heavier the load that can be pulled and towed as well.
Velocity Ratio (VR)
- Relationship between distances moved by effort and load.
- The effort needs to move a greater distance to move the load a shorter distance.
- Calculated as: Distance moved by effort/Distance moved by load.
Efficiency (EFF)
- Machines designed to waste little energy to transfer useful energy.
- Indicator of energy transfer effectiveness.
- Formula: Efficiency = MA/VR x 100%
Polymers and Natural Fibres
- Natural Polymers: Examples include shellac, wool, silk, natural rubber. Cellulose (wood and paper).
- Synthetic Polymers: Examples include synthetic rubber, resin, nylon, PVC, polypropylene, polyamide, polyester, high-modulus polyethylene.
Heat Treatment
- Metals heated and cooled to change microstructure, creating desirable physical/mechanical properties to suit a specific application.
- Processes can increase or decrease strength, complete/surface harden, toughen, relieve stresses, or refine grain structure.
- Three stages: heating, soaking, cooling.
- Methods include hardening and tempering.
- Properties that can be changed include toughness, brittleness, ductility, hardness.
Stress and Strain
- Forces act on lifting equipment under loaded conditions; strength is a related important property.
- Relating force to cross-sectional area to cause stress.
- Calculate stress by force divided by area
- When a load (force) is applied, a material will change shape (strain).
- Example: stretching an elastic band.
Tensile Test
- Fundamental mechanical test.
- Provides information and quantifies material properties.
- Important for understanding material specifications for lifting equipment.
- Specimen of determined size (round, square, or rectangular).
- Load applied until fracture; load/elongation curves are plotted.
- Determine elastic limit, yield point, ultimate tensile strength, and elongation/reduction in cross-sectional area.
- Local necking: a reduction in cross-sectional area under tensile load exceeding the maximum tensile strength.
Shear, Tension, and Compression
- Single shear: forces acting across a material (e.g., lifting lug).
- Double shear: forces acting across a material in two areas (e.g., a shackle pin).
- Compression: a pushing force (e.g., a jack body).
- Tension: a pulling force (e.g., a chain sling).
- Torsion: a twisting force (e.g., a rotating gearbox shaft).
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Description
This quiz explores the different grades of chains, their specifications, and safety factors used in various applications. You'll learn about normalized and hardened chains, the introduction of medium and fine tolerance terms, and the impact of ISO standards on chain grading. Test your knowledge on the distinctions between number and letter grades assigned to these vital components.
