UNIT 7
MECHANICAL ENGINEERING DESIGN
i) Introduction
Machine design is defined as the use of scientific principles, technical information, and imagination in the description of a machine or a mechanical system to perform specific functions with maximum economy and efficiency.
Ii) Design considerations
Design considerations are the characteristics that influence the design of the element or perhaps, the entire system. Normally, several such characteristics have to be considered in any design problem.
In a given design problem, the design engineer should identify the various design considerations and incorporate them in the design process in their order of importance.
For example, in the design of spring, the two most significant design considerations are strength and stiffness.
Some of the common design considerations are as follows:
1. Strength
2. Rigidity
3. Reliability
4. Safety
5. Cost
6. Weight
7. Ergonomics
8. Aesthetics
9. Manufacturing
10. Conformance to Standards
11. Assembly
12. Friction and Wear
13. Life
14. Vibrations
15. Thermal considerations
16. Lubrication
17. Maintenance
18. Flexibility
19. Size and Shape
20. Stiffness
21. Corrosion
22. Noise
The various design considerations, listed above, are discussed as follows:
1. Strength
The machine elements are subjected to any one or combination of loads like forces, bending moments, and torque
A machine element should have sufficient strength to avoid failure either due to yielding or due to fracture under the loads.
2. Rigidity
A machine element should have sufficient rigidity so that its linear as well as angular deflections, under the loading are within permissible limits.
3. Reliability
Reliability is defined as the probability that a component, system, or device will perform without failure for a specific time under the specified operating conditions.
A machine element should have reasonable good reliability so that it can perform its function satisfactorily over its life span.
4. Safety
A machine element should be designed such that it ensures the safety of users and machines.
5. Cost
The life cycle cost of the machine element consists of production cost, operating cost, maintenance cost, and disposal cost.
A machine element should have a minimum possible life cycle cost.
6. Weight
A machine element should have a minimum possible weight.
7. Ergonomics
Ergonomics is defined as the scientific study of the man-machine working environment relationship and the application of anatomical, physiological, and psychological principles to solve the problems arising from the relationship.
The objective of ergonomics is to make the machine fit for the user rather than to make the user adapt himself or herself to the machine. If the user is likely to communicate directly with the machine element, it should be designed with ergonomic considerations.
8. Aesthetics
Aesthetics deals with the appearance of the product. In the present day of buyer’s market, with several products available in the market are having most of the parameters identical, the appearance of the product is often a major factor in attracting the customer. This is particularly true for consumer durables like automobiles, domestic refrigerators, television, mobile, etc.
9. Manufacturing
In a design of machine element, the selection of manufacturing processes must be given due importance. The manufacturing processes should be selected such that the machine element can be produced with minimum manufacturing cost and as far as possible, with existing manufacturing facilities.
10. Conformance to Standards
A design of machine elements should conform to the national and/or international standards and codes.
11. Assembly
A machine element or a product should be designed such that it facilitates minimizing the assembly cost and time.
12. Friction and Wear
Friction and wear are major contributing factors for reducing the life of machine elements and increasing power loss. The friction can be reduced by improving the surface finish, adequately lubricating the surfaces, and replacing the sliding motion by rolling motion. The wear can be reduced by increasing the surface hardness.
13. Life
A machine element should be designed for an adequate life.
14. Vibrations
A machine element should be designed to keep the vibrations at a minimum level.
15. Thermal considerations
A machine element should be able to withstand the temperature to which it may be subjected. Besides, it should dissipate the heat generated, if any.
16. Lubrication
In the design of machine elements, due considerations must be given for the lubrication of the elements, if there is relative sliding or rolling motion between the elements.
17. Maintenance
A machine element should be such that it can be easily repaired or serviced.
18. Flexibility
A machine element should be flexible so that the modifications can be carried out with the minimum effort.
19. Size and Shape
As far as possible, standard sizes and shapes should be adopted for machine elements
20. Stiffness
Whenever stiffness is a functional requirement like in springs, the machine element should be designed with a precise value of required stiffness.
21. Corrosion
A machine element should be corrosion resistant. This can be achieved by a proper selection of material and adopting the surface coating.
22. Noise
The machine element should be designed such that the noise during operation is at a minimum.
Iii) Design process
Machine design is the process of selection of the materials, shapes, sizes, and arrangements of mechanical elements so that the resultant machine will perform the prescribed task.
The design of the machine element can be defined as the selection of material and the values for independent geometrical parameters so that the element satisfies its functional requirements and undesirable effects and is kept within the permissible limits.
The concept of machine design may be illustrated in the figure below.
Figure: Concept of Machine Design
For example, the process of design of a belt drive consists of:
- Selection of arrangement of mechanical elements like pulleys, belts, shaft, keys bearings, etc.
- Selection of shapes of these elements.
- Selection of materials of these mechanical elements.
- Selection of sizes of these mechanical elements.
Most of the problems in mechanical engineering design or specifically in machine design, do not have a unique right answer. There is a nearly endless number of workable designs, none of which could be called an incorrect answer. But of the correct answers, some are better than others.
Design Procedure:
Figure: Design Procedure
The general procedure that is followed in machine design is given in the above figure. It consists of the following steps:
1. Definition of Problem:
Define the design problem giving all input parameters, output parameters, and constraints.
2. Synthesis:
Once the problem is defined, the next step is synthesis. Synthesis is the process of selecting or creating the mechanism for the machine and the shapes of the mechanical elements to get the desired output with the given input.
3. Analysis of Forces:
Draw the free-body diagram of each element of the machines. Find out the forces (including moments and torque) acting on each element by force analysis.
4. Selection of Material:
Select the suitable material for each element. Four basic factors that are to be considered while selecting the materials are availability, cost, mechanical properties, and manufacturing considerations.
5. Determination of Mode of Failure:
Before finding out the dimensions of the elements, it is necessary to know the type of failure by which the element will fail when put into use.
6. Selection of Factor of Safety:
Based on the application, select the factor of safety. Knowing factor of safety and material strength, determine the permissible or design stress.
7. Determination of Dimensions:
Find the dimensions of each element of the machine by considering the forces acting on the element and the permissible stress.
8. Modification of Dimensions:
Modify the dimensions of the elements on the higher side, if required, based on the following considerations:
- Selection of standard parts available in the market.
- Convenience of assembly
- The convenience of Manufacturing.
9. Preparation of Drawings:
Prepare working drawing of each element or component with a minimum of two views showing the following details:
- a. Dimensions
- b. Dimensional Tolerances
- c. Surface Finish
- d. Geometrical Tolerances
- e. Special production requirement like heat treatment
Prepare assembly drawing giving part number, overall dimensions, and part list
The component drawing is supplied to the shop floor for manufacturing purposes, while the assembly drawing is supplied to the assembly shop.
10. Preparation of Design Report
Prepare a design report containing details about step 1 to step 8.
Iv) Type of stress and strain:
When a body is subjected to a system of external forces, it undergoes deformation. At the same time, by its strength, it offers resistance against this deformation. This internal resistance offered by the body to counteract the applied load is called stress.
The resistance per unit cross-sectional area is called stress. The deformation in-unit original dimension is termed as the stain.
Types of stresses and strains
Tensile stress
When an external force produces an elongation of the body in its direction, it is termed a tensile force.
P= External tensile load
R= Resistance induced in the material of the body
A=Cross sectional area
Tensile stress =Tensile load / Cross-sectional area of the body
Tensile strain
Tensile strain =Increase in length/ Original length
Compressive stress
When an external force causes shortening of the body in the direction of force, it is termed a compressive force. The stress developed in the body due to a compressive force is called compressive stress.
P= External compressive load
R=Resistance induced in the material of the body
A=Cross sectional area of the body
Compressive Stress = compressive load/ cross-sectional area of the body
Compressive strain
Compressive strain = decrease in length/ Original length
Shear stress
When a body is subjected to two equal and opposite forces acting tangentially across the resisting section, as a result of which the body tends to shear off across the section, then this tangential force is termed as shear force and the stress-induced is called shear stress.
Shear stress = Shear force/ Shear area
Shear strain
Shear strain =Transverse displacement/ Distance from the fixed base
Volumetric strain
The change in volume of an elastic body due to external force in-unit original volume is called the volumetric strain
Volumetric strain = dv/V
Lateral strain
When a material is subjected to uniaxial stress within the elastic limit, it deforms not only longitudinally but also laterally. Under tension, the lateral dimensions diminish, and under compression, they increase. The lateral deformation per unit original lateral dimension is called lateral strain.
v) Stress strain diagram
Stress-Strain Curve
The stress-strain relationship for materials is given by the material’s stress-strain curve. Under different loads, the stress and corresponding strain values are plotted. An example of a stress-strain curve is given below.
Stress-Strain Curve
Explaining Stress-Strain Graph
The stress-strain graph has different points or regions as follows:
- Proportional limit
- Elastic limit
- Yield point
- Ultimate stress point
- Fracture or breaking point
(i) Proportional Limit
It is the region in the stress-strain curve that obeys Hooke’s Law. In this limit, the ratio of stress with strain gives us a proportionality constant known as young’s modulus. The point OA in the graph is called the proportional limit.
(ii) Elastic Limit
It is the point in the graph up to which the material returns to its original position when the load acting on it is completely removed. Beyond this limit, the material doesn’t return to its original position and a plastic deformation starts to appear in it.
(iii) Yield Point
The yield point is defined as the point at which the material starts to deform plastically. After the yield point is passed, permanent plastic deformation occurs. There are two yield points (i) upper yield point (ii) lower yield point.
(iv) Ultimate Stress Point
It is a point that represents the maximum stress that a material can endure before failure. Beyond this point, failure occurs.
(v) Fracture or Breaking Point
It is the point in the stress-strain curve at which the failure of the material takes place.
Hooke’s Law
In the 19th-century, while studying springs and elasticity, English scientist Robert Hooke noticed that many materials exhibited a similar property when the stress-strain relationship was studied. There was a linear region where the force required to stretch the material was proportional to the extension of the material. This is known as Hooke’s Law.
Hooke’s Law states that the strain of the material is proportional to the applied stress within the elastic limit of that material.
Mathematically, Hooke’s law is commonly expressed as:
F = –k.x
Where,
- F is the force
- x is the extension length
- k is the constant of proportionality known as spring constant in N/m
Vi) Modes of failure
There are more than twenty different recognizable ways the material can fail, including the most common forms: fracture, fatigue, wear, and corrosion.[1] Each of these and other common failure modes are described briefly in the following sections or will be featured in the next two issues of materializing.
Brittle Fracture
A brittle fracture occurs when mechanical loads exceed a material’s ultimate tensile strength causing it to fracture into two or There are more than twenty different recognizable ways the material can fail, including the most common forms: fracture, fatigue, wear, and corrosion. Each of these and other common failure modes are described briefly in the following sections or will be featured in the next two issues of Material EASE.
i) Brittle Fracture
A brittle fracture occurs when mechanical loads exceed a material’s ultimate tensile strength causing it to fracture into two or more parts without undergoing any significant plastic deformation or strain failure. Material characteristics and defects such as notches, voids, inclusions, cracks, and residual stresses are the typical initiation points for the formation of a crack leading to brittle fracture Once the crack is initiated the material will undergo catastrophic failure fairly quickly under a sustained load. There is little energy absorbed (compared to ductile fracture) during the brittle fracture process. This failure mode commonly occurs in brittle materials such as ceramics and hard metals. Eliminating or minimizing surface and internal material defects is an important method in improving a material’s resistance to brittle fracture. Many of these defects originate during material fabrication or processing steps. Therefore, it is important to give these early stages in the life cycle proper attention to reduce the material’s susceptibility to brittle fracture.
Fabricating a part with a smooth surface is also important in preventing brittle fracture. For instance, sharp textures and notches on the surface of the material can initiate brittle fracture. Careful handling of the material after it’s produced will also help to prevent unnecessary mechanical damage such as scratches and gouges, which can ultimately lead to brittle fracture. Finally, an appropriate materials selection process to choose a suitable material for the intended application is important in ensuring that it will be capable of handling the applied mechanical loads. Ductile Failure Ductile materials that are subjected to tensile or shear stress will elastically or plastically strain to accommodate the load and absorb the energy. Yielding occurs when the material’s yield strength is exceeded and can no longer return to its original shape and size. This is followed by ductile fracture which occurs when the deformation processes can no longer sustain the applied load. Both of these failure modes are described in more detail below.
Creep
Creep is a time-dependent process where a material under applied stress exhibits a dimensional change. The process is also temperature-dependent since the creep or dimensional change that occurs under applied stress increases considerably as temperature increases. A material experiences creep failure when the dimensional change renders the material useless in performing its intended function. Sufficient strain or creep can result in fracture, known as stress rupture, which is discussed briefly in a subsequent section. Figure 5 shows the time-dependent nature of creep failure
Yielding
Yielding failure (also known as gross plastic deformation) occurs when a material subject to mechanical loading exhibits sufficient plastic deformation such that it can no longer perform its intended function. This mode of failure results in deflected, stretched, or otherwise misshapen components, and is typical in ductile materials such as metals and polymers. Ceramics and very hard metals are inherently brittle materials and therefore yielding is not a significant concern. An example of this type of failure is often observed in ductile materials subjected to tensile stress. These malleable materials tend to absorb the applied load by undergoing plastic deformation, which causes an elongation of the material. Yield strength is a measurement of a material’s resistance to yielding failure, and it denotes the stress at which the material begins to exhibit a disproportionate increase in strain within creasing stress. Figure 2 shows a picture of several misshapen helicopter components that experienced yielding failure.
Ductile Fracture
A failure mode that is somewhat opposite to brittle fracture is a ductile fracture. The ductile fracture occurs when a material experiences substantial plastic deformation or strain while being stressed beyond its yield strength and is consequently torn into two pieces. An extensive amount of energy is absorbed during the deformation process. Similar to brittle fracture, however, cracks are typically nucleated at material defects, such as voids and inclusions. As ductile materials experience plastic deformation, existing voids coalesce to form the crack tip. The actual crack propagation process in the ductile fracture is generally a slow process with the crack growing at a very moderate rate as voids coalesce at the fracture surface. An obvious but important consideration is that this type of failure is common in ductile materials, typically metals and polymers.
Buckling
Buckling occurs when a material subjected to compressive or torsional stresses can no longer support the load, and it consequently fails by bulging, bending, bowing, or forming a kink or other unnatural characteristic. Bars, tubes, and columns are shapes that are commonly susceptible to failure by buckling. Besides, I-beams and other more complex geometries may experience buckling under compressive or torsional loads. Strength and hardness properties do not indicate a material’s susceptibility to buckling. Buckling is dependent on the shape and respective dimensions of the material as well as the modulus of elasticity, which is dependent on temperature. Therefore, buckling is more likely to occur at higher temperatures where the modulus of elasticity is lower since materials tend to soften when they are heated.
Elastic Distortion
A material can fail without being permanently changed when it is elastically deformed to such an extent that it fails to perform its intended function. Elastic deformation occurs when a material is subjected to a load that does not exceed its yield strength. This non-permanent distortion can cause the material, for example, to obstruct another component in a system failure. Elastic distortion can be induced by a load and affected by a change in temperature. For example, a material’s elastic modulus is temperature-dependent, and if an unanticipated temperature change occurs the material may undergo elastic deformation at a smaller load than it would at the normal operating temperature. The selection of a material with a sufficiently high modulus to withstand loads without experiencing elastic deformation can prevent this type of failure from occurring.
Creep Buckling
Creep buckling is a failure mode that occurs when the creep process renders a material unable to support loads it could other-wise handle and as a result the material buckles.
Stress Rupture
Stress rupture, also known as creep fracture, is a mechanism that is closely related to creep except that the material eventually fractures under the applied load. Creep is the time- and temperature-dependent elongation of a material that is subjected to stress. When this stress overcomes the material’s ability to strain, it will rupture. Cracking that proceeds the rupture of the material can be either Trans granular or intergranular.
Thermal Relaxation
Thermal relaxation is a process related to the temperature-dependent creep failure mode. Failure by thermal relaxation commonly occurs in fastener materials or other materials that are pre-stressed such that they could support a greater load than their non-pre stressed counterpart. As the material undergoes creep at high temperatures their residual stresses are relieved which may render the material unable to support the given load.
Fatigue
Fatigue is an extremely common failure mode and deserves considerable attention because it can inflict damage on a material at a stress level that is far less than the material’s design limit. Fatigue has been attributed with playing a role in approximately90% of all material structural failures.[6]A material that fractures into two or more pieces after being subjected to cyclic stress (fluctuating load) over a while is considered to have failed by fatigue. The maximum value of the cyclic stress (stress amplitude) for fatigue failure is less than the material’s ultimate tensile strength. It is often the case that the maximum value of the cyclic stress is so low that if it were applied at a constant level the material would be able to easily support the load without incurring any damage. Cyclic loads cause the initiation and growth of a crack, and ultimately when the crack is significant enough such that the material can no longer support the load, the material fractures. The fatigue failure mechanism involves three stages: crack initiation, crack propagation, and material rupture. Similar to both ductile and brittle fracture, fatigue cracks are often initiated by material in homogeneities, such as notches, grooves, surface discontinuities, flaws, and other material defects. These in homogeneities or initiation points act as stress raisers where the applied stress concentrates until it exceeds the local strength of the material and produces a crack. The best way to prevent fatigue failure is to keep fatigue cracks from initiating, which can be accomplished by removing or minimizing crack initiators, or by minimizing the stress amplitude. Once fatigue cracks have been initiated they will seek out the easiest or weakest path to propagate through the material.
High-Cycle Fatigue
High-cycle fatigue is defined as fatigue where the material is subjected to a relatively large number of cycles before failure occurs. Generally, for the fatigue mechanism to be considered high-cycle fatigue the number of cycles required to produce failure is greater than 10,000. The deformation exhibited by a material subjected to high-cycle fatigue is typically elastic.
Low-Cycle Fatigue
A fatigue failure that occurs after a relatively small number of cycles is considered to be low-cycle fatigue. Typically, when a material fails due to fatigue after less than 10,000 cycles, it is considered to be low-cycle fatigue. The mechanisms of crack.
Thermal Fatigue
Simple temperature fluctuations or repeated heating and cooling can impose stresses on a material leading to fatigue damage and potential failure. Materials generally exhibit a dimensional change or strain to some extent in response to temperature changes. This response can be significant in some materials, especially metals, and can induce thermal stresses on the material if it is mechanically confined in some way. When a material is exposed to conditions of fluctuating temperatures it can cause cyclic fatigue loading, which can result in crack growth and possibly fracture. This process is referred to as thermal fatigue
Vii) Factor of safety
The factor of safety (FOS) is the ability of a system's structural capacity to be viable beyond its expected or actual loads. A FOS may be expressed as a ratio that compares absolute strength to the actual applied load, or it may be expressed as a constant value that a structure must meet or exceed according to law, specification, contract, or standard.
Design and engineering standards usually specify the allowable stress, or ultimate strength of a given material divided by the factor of safety, rather than use an arbitrary safety factor because these factors can be misleading and have been known to imply greater safety than is the case. For example, a safety factor of 2 does not mean that a structure can carry twice as much load as it was designed for.
The safety factor depends on the materials and use of an item. Different industries have varying ideas on what FoS should be required. Although there is some ambiguity regarding safety factors, there are some general guidelines across multiple verticals. If the consequences of failure are significant, such as loss of life, personal harm, or property loss, a higher FoS is likely to be required by design or by law. When a structure’s ability to carry load must be determined to a reasonable accuracy but comprehensive testing is impractical (such as with bridges and buildings), safety factors need to be calculated using detailed analysis.
Cost is also a consideration. As the FoS increases, the cost of the product also increases, so it may be necessary to determine how much extra it might cost per part to achieve a certain FoS and whether that is a viable business model. Striking a balance between cost reduction and safety is essential.
Viii) Engineering material properties
1. Classification of Engineering Materials
2. Properties of Engineering Materials
PHYSICAL PROPERTIES
- Specific Gravity-defined as the weight of a given volume of a material as compared to the weight of a given volume of water it is measured at a temperature of 60 degree F(15.5 degrees C)
- Specific Heat-heat required to raise the temperature of the unit weight of the material by one degree.
- Fusibility & Fluidity-the property of a material where it tends to melt and flows when the heat is applied.
- Weld ability-ability of uniting two pieces of metal by applying pressure or heat or both.
- Elasticity-property due to which a metal regains its original dimension on the removal of load.
- Plasticity-beyond elastic limit the material is unable to regain its original shape and retains its moulded shape. This property is called plasticity.
- Porosity-materials in their plastic or molten state contain some dissolved gasses which are evaporated once they are set forming holes and pores. This property is known as porosity.
MECHANICAL PROPERTIES
- Strength-ability of a material to resist the application of load without rupture.
- Hardness-ability of a material to resist penetration or scratching.
- Hardenability-ability of a material to be hardened by heat treatment.
- Toughness-property of a material where it can absorb energy before actual fracture.
- Brittleness-ability of a material to fracture on receiving shock or blow
- Malleability-ability of a material to be hammered into thin sheets.
- Ductility-ability of a material to be drawn into wires.
- Creep & Slip-ability of a material to flow like a viscous liquid under the application of stress and temperature is called creep .the phenomenon where deformation stops even if the load is acting.
- Resilience-property of a material to absorb energy within the elastic range. This is required for springing action.
THERMAL PROPERTIES
- Conductivity-ability of a material to conduct heat from a hot end to a cold end. Silver and copper are good conductors of heat.
ELECTRICAL PROPERTIES-
- Conductivity-ability of a material to conduct electricity from one end to another.
MAGNETIC PROPERTIES
- The ability of a material to act as a magnet and attract materials like iron, steel, nickel, etc.
Aesthetic considerations, Ergonomics consideration Pattern involves the division of area. The pattern helps to create interest in plain surfaces. Patterns can be random or made up of elements that are repeated. Patterns can be used to create rhythm and movement.
Colour
Colour has no form but can complement form. Used badly colour can completely ruin a design. Alternatively, Aesthetic considerations, Ergonomics considerations used well colour can make a good design great! Colours can be mixed. Mixing primary colours at the centre of the colour wheel produces secondary colours. These secondary colours can be further mixed to create tertiary colours. Colours close to each other on the colour wheel produce harmony e.g. Red and orange. Colours opposite each other on the colour wheel create contrast e.g. Red and green.
Colour has three properties:-
Intensity - brightness e.g. Bright red or dull red.
Temperature - warm colours e.g. Red and orange cold colours e.g. Blue and green.
Tone - the lightness or darkness of a colour. Small quantities of white or black can be added to basic colours to create light and dark shades of a colour.
Texture and Finish
The surface of an object is the part that is most seen. Texture and finish are used to enhance their appearance and improve function e.g. Textured hand grips.
Style
The style of an object is created by combining tone, colour, texture, form, etc. Many designers have a recognizable style that they apply to their work.
Style is constantly changing, what is popular today may not be popular in a year or two. The designer has the responsibility of making sure that the style of his or her design will appeal to those who will buy it. Art Nouveau, Victorian and Gothic is well-known style. Each style has its particular look. Whilst designers have argued for years over the importance of style and function, it is probably true to say that the best designs have a good balance of the two. When you come to design a product you should try to take account of aesthetics – but remember a design that looks great but doesn't work or is difficult to use is not good!
Ii) Ergonomics consideration
Ergonomics is a design factor that is of critical importance. By using ergonomics the designer is taking into consideration the usage of the design. It begins by looking closely at how the product will be used, decide on the characteristics of the user and the product and the relationship between them.
Consider the factors which will ensure the health, safety, convenience, and comfort of the user. Compare your design ideas, i.e. carry out tests to see if the product is designed well from the ergonomic point of view.
When designing products for people you must take into account their physical size, weight, reach, and movement. To do this you will need data relating to human dimensions.
Ergonomics is the process of designing or arranging workplaces, products, and systems so that they fit the people who use them. Most people have heard of ergonomics and think it is something to do with seating or with the design of car controls and instruments – and it is… but it is so much more. Ergonomics applies to the design of anything that involves people – workspaces, sports and leisure, health and safety.
Ergonomics (or ‘human factors’ as it is referred to in North America) is a branch of science that aims to learn about human abilities and limitations, and then apply this learning to improve people’s interaction with products, systems, and environments.
Ergonomics aims to improve workspaces and environments to minimize the risk of injury or harm. So as technologies change, so too does the need to ensure that the tools we access for work, rest, and play are designed for our body’s requirements.
Why is Ergonomics important?
In the workplace: According to Safe Work Australia, the total economic cost of work-related injuries and illnesses is estimated to be 60 billion dollars. Recent research has shown that lower back pain is the world’s most common work-related disability – affecting employees from offices, building sites and in the highest risk category, agriculture.
Ergonomics aims to create safe, comfortable, and productive workspaces by bringing human abilities and limitations into the design of a workspace, including the individual’s body size, strength, skill, speed, sensory abilities (vision, hearing), and even attitudes.
In the greater population: The number of people in Australia aged 75 and over is forecast to double over the next 50 years. With this, equipment, services, and systems will need to be designed to accommodate the increasing needs of the ageing population, applying to public transport, building facilities, and living spaces.
How does ergonomics work?
Ergonomics is a relatively new branch of science that celebrated its 50th anniversary in 1999 but relies on research carried out in many other older, established scientific areas, such as engineering, physiology, and psychology.
To achieve best practice design, Ergonomists use the data and techniques of several disciplines:
- Anthropometry: body sizes, shapes; populations and variations
- Biomechanics: muscles, levers, forces, strength
- Environmental physics: noise, light, heat, cold, radiation, vibration body systems: hearing, vision, sensations
- Applied psychology: skill, learning, errors, differences
- Social psychology: groups, communication, learning, behaviours.
References:
1. Engineering Thermodynamics, P K Nag, The Tata McGraw-Hill Companies
2. Mechanical Engineering Design, Joseph E Shigley, Charles R Mischke, The Tata McGraw-Hill Companies
3. Production Technology Vol. I & II, O.P. Khanna, Dhanpat Ray Publications
