|
Torque Testing
Torque Testing Overview
There are different torque testing
measurement device and systems
torque testing systems and
equipments in the market for the
broad range of functional torque
testing and measuring applications.
Applications include automotive
steering, drivetrain component
testing and assembly, seat testing,
bearing preload testing and
torque-to-turn testing.
Before torque testing: What
is Torque?
A torque (¦Ó) in physics, also called
a moment (of force), is a
pseudo-vector that measures the
tendency of a force to rotate an
object about some axis (center). The
magnitude of a torque is defined as
the product of a force and the
length of the lever arm (radius).
Just as a force is a push or a pull,
a torque can be thought of as a
twist.
The SI unit for torque is the newton
meter (N m). In U.S. customary
units, it is measured in foot pounds
(ft•lbf) (also known as 'pound
feet'). The symbol for torque is ¦Ó,
the Greek letter tau.
Before torque testing:
Torque Explanation
The force applied to a lever
multiplied by its distance from the
lever's fulcrum, the length of the
lever arm, is its torque. A force of
three newtons applied two meters
from the fulcrum, for example,
exerts the same torque as one newton
applied six meters from the fulcrum.
This assumes the force is in a
direction at right angles to the
straight lever. The direction of the
torque can be determined by using
the right hand grip rule: curl the
fingers of your right hand the
direction of rotation and stick your
thumb out so it is aligned with the
axis of rotation. Your thumb points
in the direction of the torque
vector.
Mathematically, the torque on a
particle (which has the position r
in some reference frame) can be
defined as the cross product:
where r is the particle's position
vector relative to the fulcrum, F is
the force acting on the particle.
The torque on a body determines the
rate of change of its angular
momentum,
where L is the angular momentum
vector, t stands for time.
As can be seen from either of these
relationships, torque is a vector,
which points along the axis of the
rotation it would tend to cause.
Before torque testing:
Machine torque
Torque is part of the basic
specification of an engine: the
power output of an engine is
expressed as its torque multiplied
by its rotational speed of the axis.
Internal-combustion engines produce
useful torque only over a limited
range of rotational speeds
(typically from around 1,000¨C6,000
rpm for a small car). The varying
torque output over that range can be
measured with a dynamometer, and
shown as a torque curve. The peak of
that torque curve usually occurs
somewhat below the overall power
peak. The torque peak cannot, by
definition, appear at higher rpm
than the power peak.
Understanding the relationship
between torque, power and engine
speed is vital in automotive
engineering, concerned as it is with
transmitting power from the engine
through the drive train to the
wheels. Power is typically a
function of torque and engine speed.
The gearing of the drive train must
be chosen appropriately to make the
most of the motor's torque
characteristics.
Steam engines and electric motors
tend to produce maximum torque close
to zero rpm, with the torque
diminishing as rotational speed
rises (due to increasing friction
and other constraints). Therefore,
these types of engines usually have
quite different types of drivetrains
from internal combustion engines.
Torque is also the easiest way to
explain mechanical advantage in just
about every simple machine.
Reference download link:
Torque Transducer + Torque Meter
http://www.powerlinkpt.com/downloads/13.pdf
|
