Post on 07-Apr-2018
transcript
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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