engineering graphics and design eng

8/6/2019 Engineering Graphics and Design Eng

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Engineering drawing can be a universal

language to communicate your ideas.

The engineering design process usessketching and CAD to communicate and

record ideas.

Engineering Graphics


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Geometric Elements

A point

A line

A curvePlanes

Closed 2-D elements

SurfacesSolids


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A Point

Specifies an exactlocation in space

Dimensionless

No heightNo width

No depth


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A Line

Has length and direction but no width

All points are collinear

May be infinite

At least one point must be specifiedDirection may be specified with a second point or

with an angle

May be finite

Defined by two end pointsDefined by one end point, a length, and direction


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A Curve

The locus of points along a curve are notcollinear

The direction is constantly changing

Single curved linesall points on the curve lie on a single plane

A regular curveThe distance from a fixed point to any point on

the curve is a constantExamples: arc and circle


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Planes

A two dimensional slice of space

No thickness (2-D)

Any orientation defined by:3 points

2 parallel lines

a line and a point

2 intersecting lines

Appears as a line when the direction

of view is parallel to the plane


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Closed 2-D Elements (planar)

BB

AA

Triangles

Three sides

Equilateral triangle (all sides equal, 60 deg.

angles) Isosceles triangle (two sides equal)

Right triangle (one angle is 90 degrees)

A^2+B^2=C^2 (Pythagorean theorem)

SinU=A/C

CosU!B/C CC

UU


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Closed 2-D Elements (planar) Parallelograms

4 sides

Opposite sides are parallel

Ex. square, rectangle, and rhombus

Regular polygons

All sides have equal length

3 sides: equilateral triangle

4 sides: square 5 sides: pentagon

Circumscribed or inscribed


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Closed 2-D Elements (planar) Circles

Radius (R)

Diameter (D)

Angle (1 rev = 360o 0 0)

Circumference (2*3.14159*R)

Tangent

Chord

A line perpendicular to themidpoint of a chord passes through

the center of the circle

Concentric circles

DD

RR

UU


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Surfaces

Does not have thickness

Two dimensional at every point

No mass

No volume

May be planar

May be used to define the boundary of a 3-

D object


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Solids

Three dimensional

They have a volume

There are two main types of solids,

"Polyhedra", and "Non-Polyhedra"


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A polyhedron is a solid with flat faces (from Greek poly- meaning

"many" and -edron meaning "face").

Each flat surface (or "face") is a polygon.

So, to be a polyhedron there should be no curved surfaces.

Polyhedron

Platonic Solids

Prisms

Pyramids


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Tetrahedron4 Faces

4 Vertices

6 Edges

Platonic Solids

Octahedron

8 Faces

6 Vertices

12 Edges

Dodecahedron

12 Faces

20 Vertices30 Edges

Icosahedron

20 Faces

12 Vertices

30 Edges


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Two equal parallel faces

Sides are parallelograms

Prisms

Square Prism

Cube

Cross-Section

Cross-Section

Cross-Section

Cross-Section

Triangular Prism

Pentagonal Prism

A prism has the same cross section all along its length


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A pyramid is made by connecting a base to an apex.

Pyramid

Common intersection

point (vertex)

There are many types of Pyramids, and they are

named after the shape of their base.

Triangular Pyramid

Base

Square Pyramid

Pentagonal Pyramid

Base

Base


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Non-Polyhedra

Cones

Cylinders

Spheres

Torus

Some solids have curved surfaces, or a mix of curved and

flat surfaces (so they aren't polyhedra).

Examples:Torus Facts

Notice these interesting

things:It can be made by

revolving a small circle

along a line made by

another circle.

It has no edges or

vertices

It is not a polyhedron


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THANK YOU

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