IT

3. 1. What is the Destructive Test.
2. Types of Destructive Test.
3. Description of types

4. As the name suggests, destructive testing (DT)
includes methods where your material is broken down in
order to determine mechanical properties, such as strength,
toughness and hardness. In practice it means, for example,
finding out if the quality of a weld is good enough to
withstand extreme pressure or to verify the properties of a
material.

6. The types of Destructive are as follows;
a) Tensile Testing
b) Bend Testing
c) Impact Testing
d) Nick Break Testing
e) Hardness Testing

7. • Tensile testing, also known as tension testing, is a
fundamental materials science test in which a sample is
subjected to a controlled tension until failure.
• The results from the test are commonly used to select a
material for an application, for quality control, and to
predict how a material will react under other types
of forces.
• Properties that are directly measured via a tensile test
are ultimate tensile strength, maximum elongation and
reduction in area.
• For composite materials and textiles, biaxial tensile
testing is required.

9. • Bending tests are carried out to ensure that a metal has
sufficient ductility to stand bending without fracturing.
• A standard specimen is bent through a specified arc and
in the case of strip, the direction of grain flow is noted
and whether the bend is with or across the grain.
• Bend testing provides insight into the modulus of
elasticity and the bending strength or a material.
• Metallurgical offers three and four point bend setups
with interchangeable rollers for a variety of test
configurations.

11. • Test of the ability of a material to withstand impact,
used by engineers to predict its behaviour under actual
conditions.
• Many materials fail suddenly under impact, at flaws,
cracks, or notches.
• The most common impact tests use a swinging
pendulum to strike a notched bar; heights before and
after impact are used to compute the energy required
to fracture the bar.
It has two types.
 Charpy test.
 Izod test.

12.  Charpy test:-
In the Charpy test, the test piece is held
horizontally between two vertical bars, much like the lintel
over a door.
 Izod test:-
In the Izod test, the specimen stands erect, like
a fence post.

14.  In CNC m/c the control of all m/c functions is totally
transferred to a computerized control system.
 The control unit should be suited so that it is convenient
for the operator to operate the m/c from the central place.
The facilities which a control unit should offer are:
• Indicate the current status & position of various m/c tool
features & give feedback.
• Allow manual or semi-manual control of m/c tool elements.
• Enable m/c tool to be programmed.
The control unit part for allowing manual control &
programming of the m/c may be housed on the m/c structure
itself or separate control panel may be installed near the m/c.

15. In general, a work holding device for CNC applications should
have the following features:-
• It should restrict the linear & rotary motion of components.
• The component should not distort or deflect due to cutting forces
in the process.
• It should quick facilitate quick loading & unloading of
component.
• It should be fool proof.
• It should not interfere with the cutting tool.
• It should provide for easy removal of chips.
• It should be adaptable to automated loading/unloading of
components.

17. Automatic Tool Changer
(ATC)
 On the machining centers, ATC are provided to reduce the
idle time between change from operation another.
 The tool already fitted on the spindle is removed &
replaced in the tool magazine
The tool change cycle consist of two parts:
a. Tool selection cycle
b. Tool transfer cycle

18. AUTOMATIC TOOL CHANGER (ATC)

19.  Since the cutting time is much more in CNC m/c, the
volume of swarf generated is also more.
 Unless the swarf is quickly quality of the finished product.
Also the swarf can’t be allowed to accumulate at the m/c tool
because it may hamper the access to the m/c tool.
 In addition some auxiliary functions like automatic
component loading or automatic tool change may also be
affected by accumulation of swarf.
 To avoid these problem an efficient swarf control system
should be provided with the CNC m/c tools with some
mechanism to remove the swarf from the cutter & cutting
zone & for the disposal of swarf from the m/c tool area itself.