General Principles of Design, Drawing & Importance of Safety Short Notes Part 4

By Sachin Singh|Updated : December 16th, 2019

Development of surfaces

A development is the unfold/unrolled flat / plane figure of a 3-D object. It is also called a pattern where the plane may show the true size of each area of the object. When the pattern is cut, it can be rolled or folded back into the original object as shown in figure 1.

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Figure 1. Typical development of the surface of a cuboid.

Types of development
There are three major types of development followed by industries. Examples are shown in figure 2.

  1. Parallel line development: In this parallel lines are used to construct the expanded pattern of each three-dimensional shape. The method divides the surface into a series of parallel lines to determine the shape of a pattern.
  2. Radial line development: In this, lines radiating from a central point to construct the expanded pattern of each three-dimensional shape is used. These shapes each form part of a cone and lines radiating from the vertex of the cone generate the expanded pattern of the curved surface as shown in the following explorations.
  3. Triangulation method: This is generally used for polyhedron, single curved surfaces, and warped surfaces.
  4. Approximate development: In this, the shapes obtained are only approximate.  After joining, the part is stretched or distorted to obtain the final shape.

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Figure 2. Typical examples of the various types of development.

A true development is one in which no stretching or distortion of the surfaces occurs and every surface of the development is the same size and shape as the corresponding surface on the 3-D object.  e.g. polyhedrons and single curved surfaces. 
As illustrated in figure 3, polyhedrons are composed entirely of plane surfaces that can be flattened true size onto a plane in a connected sequence, whereas single curved surfaces are composed of consecutive pairs of straight-line elements in the same plane which is obtained for a cone.

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Figure 3. shows the true development obtained for polyhedrons and single curved surface

An approximate development is one in which stretching or distortion occurs in the process of creating the development. The resulting flat surfaces are not the same size and shape as the corresponding surfaces on the 3-D object. Wrapped surfaces do not produce true developments, because pairs of consecutive straight-line elements do not form a plane. Also double-curved surfaces, such as a sphere do not produce true developments, because they do not contain any straight lines. An example of the approximate development of a sphere is shown in figure 4.

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Figure 4 showing an approximate development of a sphere.

Isometric Projections 

An isometric projection is a true representation of the isometric view of an object.  An isometric view of an object is created by rotating the object 45° about a vertical axis, then tilting the object (see figure 3,  in this case, a cube) forward until the body diagonal (AB) appears as a point in the front view.  The angle the cube is tilted forward is 35° 16’. The 3 axes that meet at A, B form equal angles of 120° and are called the isometric axes.   Each edge of the cube is parallel to one of the isometric axes.  Line parallel to one of the legs of the isometric axis is an isometric line.  Planes of the cube faces & all planes parallel to them are isometric planes.

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Figure 3. Rotation of the object with respect to the projection plane result in isometric projection.

The forward tilt of the cube causes the edges and planes of the cube to become shortened as it is projected onto the picture plane.   The lengths of the projected lines are equal to the cosine of 35° 16’, or 0.81647 times the true length. In other words, the projected lengths are approximately 80% of the true lengths. A drawing produced using a scale of 0.816 is called an isometric projection and is a true representation of the object. However, if the drawing is produced using full scale, it is called an isometric drawing, which is the same proportion as an isometric projection, but is larger by a factor of 1.23 to 1.  Figure 4. Illustrates the isometric projection and isometric drawing. Isometric drawings are almost always preferred over isometric projection for engineering drawings, because they are easier to produce. An isometric drawing is an axonometric pictorial drawing for which the angle between each axis equals 120° and the scale used is full scale.

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Figure 4 Shows the (a) isometric projection and (b) isometric drawing (or view) of a cuboid.

While drawing isometric projection, an Isometric scale is to be constructed for convenience and all the measurements are to be taken from this scale. As shown in figure 5, isometric scale is produced by positioning a regular scale at 45 ° to the horizontal and projecting lines vertically to a 30° line.

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Figure 5.  illustrates the construction of an isometric scale.

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i.e.  isometric length = 82% (approximately)

Isometric axes can be positioned in a number of ways to create different views of the same object. Figure 6(a)  is a regular isometric, in which the viewpoint is looking down on the top of the object. In a regular isometric, the axes at 30° to the horizontal are drawn upward from the horizontal. In the reversed axis isometric, as shown in figure 6(b),  the viewpoint is looking up on the bottom of the object, and the 30° axes are drawn downward from the horizontal.  Figure 6(c)&(d) show the long axis isometric, where the viewpoint is looking from the right or from the left of the object, and one axis is drawn at 60 ° to the horizontal. While drawing the Isometric view, first the viewpoint will have to be decided for obtaining the maximum technical information.

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Perspective projections

When an object is viewed from different directions and at different distances, the appearance of the object will be different. Such view is called perspective view.  Perspective projections mimic what the human eyes see. Perspective views are not important for a manufacturing unit.  They are used to communicate information to non-technical persons. Hence it is very important for commercial purposes. In perspective projection, all lines of sight start at a single point.  Distance from the observer to the object is finite and the object is viewed from a single point – projectors are not parallel.

Two commonly used Perspective Projection methods are

  • Visual Ray method
  • Vanishing Point method

Common types of perspective Projection

  • Parallel Perspective or 1-point perspective: Here one face of the object is kept parallel to the PPP. The edges perpendicular to this face appears to be converging to a VP.
  • Angular Perspective or 2-point perspective: One edge of the object is kept parallel to the PPP. Each edges perpendicular to them converges to one of the two VPs.
  • Oblique Perspective or 3-point Perspective: Neither an edge nor a face of the object is kept parallel to PPP. Ach edges is seen to be converging to one of the three VPs.

Safety in Engineering

Safety in engineering refers to the identification and control of causal factors in engineering in order to provide value to organizations. There are many goals of engineering safety and some of these are as follows: —

  • Reduce accidents
  • Control or eliminate hazards
  • Develop new methods for construction
  • Maximize public confidence

Important Terms:

  • Unsafe condition: Any condition that will result in an accident.
  • Accident: It is an unplanned and undesired event.
  • Hazard: These are the physiological and behavioral factors which if not controlled effectively, result in harmful occurrences.
  • Safety assessment: This is a qualitative/quantitative determination of safety.
  • Unsafe act: This is an act that is not safe for an individual/employee.
  • Accident report: This is a document that records the findings of an accident investigation incorporating accident cause/causes and the recommended measures.
  • Injury: This is a wound or other specific/certain damage.
  • Safety plan: The series of procedures followed to satisfy all safety-related requirements.

Types of Hazards-

  • Material Handling Hazards- Manual material handling can involve lifting, carrying, lowering, pushing, and pulling.
  • Machine Hazards- Any machine can be a hazard, especially those with moving parts that can get tangled in a worker’s clothes or come in contact with worker’s body.
  • Energy Hazards- Workers can be seriously injured by the sudden movement of machine components, electrical shock or other releases of energy when they are adjusting or maintaining equipment.
  • Work Practice Hazards- Failure to have or to follow safe work practices is a significant cause of injuries.
  • Confined Space Hazards- Confined spaces are workspaces where hazardous gases, vapours, dusts or fumes may build up or where an oxygen-deficient atmosphere may be created. Examples include: storage tanks, vaults, pits, vats, silos, pipelines, ducts and tunnels.
  • Physical Hazards- Physical hazards are forms of energy that can harm the body if exposed.
  • Chemical Hazards- Chemical hazards can take the form of solids, liquids, vapours, gases, dusts, fumes or mists.
  • Biological Hazards- Biological hazards are living things or substances produced by living things that can cause illness in humans.
  • Ergonomic or Work Design Hazards- Ergonomic hazards arise from the design and organization of work. They can harm the body by placing strain on the musculoskeletal system and overloading the muscles, tendons, joints, ligaments, nerves and blood vessels.

SAFETY MANAGEMENT

Safety Policy includes:

  • Safety Promotion: Although safety can to some extent be engineered into equipment and processes, it is still necessary to motivate employees to perform their’ work safely.
  • Safety Committee: A safety committee is most useful mechanism for facilitating the necessary co-operative effort that is essential to success in accident prevention. It should consist of representatives from top management, supervision from the workers. It should act as an advisory body and meet regularly.
  • SAFETY FUNCTIONARIES

There are a number of specialized safety functionaries known by different designations such as safety-officers, safety advisers, safety directors, who are mainly appointed to administer the organization’s safety policies and programs.

Hazard Analysis & Method:

  1. Failure modes and effect analysis (FMEA): FMEA is a powerful design tool to analyses engineering systems from their reliability aspect. More specifically, the method is used to conduct analysis of each potential failure mode in a system to examine the effects of such failure modes on the system.
  2. Failure mode effects and criticality analysis (FMECA): FMECA was developed by the National Aeronautics and Astronautics administration (NASA) for assuring the specified reliability of space systems, and in the 1970s the U.S. department of defense developed a military standard entitled procedures for performing a failure mode, effects, and critically analysis. Basically, FMECA is an extension of FMEA. When FMEA is extended to group each potential failure effect with respect to its severity (this includes documenting catastrophic and critical failures) the technique is called FMECA.
  3. Fault tree analysis (FTA): This method was developed in the early 1960s to perform reliability analysis of the Minuteman Launch Control System. FTA is widely used in industry to perform reliability analysis of engineering systems during design and development.
  4. Preliminary Hazard Analysis (PHA): This method is basically used during the conceptual design phase and is relatively an unstructured approach because of the unavailability of definitive information such as drawings and functional flow diagram.
  5. Control Charts: It developed by water A. Shewhart in 1924 fro application in quality control. Today, are used in various areas including safety analysis. A control chart may simply be described as a graphical method used to determine whether a process is in a state of statistical control or out of control.

Occupational Safety and Health

Occupational safety and health (OSH), also commonly referred to as occupational health and safety (OHS), occupational health, or workplace health and safety (WHS), is a multidisciplinary field concerned with the safety, health, and welfare of people at work. These terms also refer to the goals of this field, so their use in the sense of this article was originally an abbreviation of occupational safety and health program/department etc.

The goals of occupational safety and health programs include to foster a safe and healthy work environment. OSH may also protect co-workers, family members, employers, customers, and many others who might be affected by the workplace environment. In the United States, the term occupational health and safety is referred to as occupational health and occupational and non-occupational safety and includes safety for activities outside of work.

In common-law jurisdictions, employers have a common law duty to take reasonable care of the safety of their employees. Statute law may in addition impose other general duties, introduce specific duties, and create government bodies with powers to regulate workplace safety issues: details of this vary from jurisdiction to jurisdiction.

Role
Role refers to the employee’s primary responsibilities in the organization. A lot of research has been done in the area of role strain, role ambiguity and role conflict primarily in industrial organizations. Role Ambiguity refers to the lack of available information necessary to conduct the role. Effective communication on role boundaries, working procedures and practice, expected time frame and outcome can contribute to role clarity(Kenyon, 2008).

Stress at the Workplace
Stress is experienced when the environmental demands exceed the individual’s ability to deal with it. The individual’s perception and assessment of the situation determines their response. Research in the area of job stress has revealed outcomes such as decreased job satisfaction (Fox et al, 1993), poor mental health (Mausner-Dorsch & Eaton, 2000) and compromised immune function (Meijman et al,
1995). People, however adapt to stressors and develop coping strategies and personal resources.

Career Growth
Most people aspire to having positions with increased responsibility and challenges at their workplace. A higher position is also associated with greater control and autonomy and increased financial reward and
valued social position. The lack of opportunities for career growth is a primary source of job dissatisfaction. Organizations and employers that encourage skill acquisition and career growth at all
levels will have better morale and productivity than organizations that are rigid (Kenyon, 2008).

Unemployment
Work contributes to psychological well-being through the opportunity to utilize skills, financial rewards, interpersonal contact, time structure, status and identity.
Unemployment thus is a state that has many ramifications such as loss of purpose and meaning in life, identity, financial resources, relationships, status and time structure. These effects result in lowered self esteem and a higher incidence of depression (Evans & Haworth, 1991).

Antisocial Behavior in the Workplace
Antisocial behavior refers to incidents such as assaults, fights, harassment, aggression and other negative behaviors. This behavior comes at a cost both for employers as well as employees. For the
employer it results in lost productivity due to absenteeism and high turnover. For employees it results in reduced job satisfaction and well being (Kenyon, 2008).

National Safety Council: The main objective of the Council which is an independent and self supporting national. level institution, has been to generate, develop and maintain a movement of safety awareness at the national level To achieve this objective, the Council conducts a variety of educational, training and promotional activities.

Next - Basics of Project Management Part 1

ESE 2019 Prelims Paper I - Revision Plan

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