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use a primer for better wetting
of the metal surface by the
adhesive as well.
The joint construction should be
related to the adhesion process
and its requirements for large
bonding areas. Peeling and
cleaving forces on adhesive
joints must be avoided and
bending forces should be
reduced to a minimum.
The adhesive can be applied
manually (e.g. with the use of
cartridges) or for larger areas
with automated machines. The
bonding should take place in a
dry and well ventilated and
dust-free workshop.
The work must be done in strict
compliance with the manufacturer
´s rules. The production parameters
such as resin/hardener ratio,
duration and pressure component
fit up during adhesive curing, curing
temperature, etc. must be controlled
properly.
1.5. Creep and ageing
The durability of adhesive joints
depends on factors such as proper
pre-treatment, chemical composition
of the adhesive and
service conditions like stresses,
temperature, humidity and exposure
to ultraviolet radiation (polymers
are sensitive to this kind of
radiation and tend to lose their
mechanical properties).
The ageing of bonded joints can
be caused by creep under stress
(creep can be defined as timedependent
increase in the
length of visco-elastic substances
subject to a constant
tensile load).
Adhesive joints should therefore
be inspected regularly to prevent
damages and to enable
repair prior to a possible failure.
Prototype floor section made
of bonded sheets and extruded
stiffeners
Patented by Alcan
132
ALUMINIUM IN COMMERCIAL VEHICULES CHAPTER IX OTHER JOINING TECHNIQUES 132 | 133
Bolting creates a joint which can
be opened and closed as many
times as necessary. It is besides
welding the most conventional
method for joining metals. In
contradiction to welding, different
metals can be joined. In
commercial vehicles this is most
likely the connection between
steel and aluminium (e.g. the
connection between chassis and
tank or tipper body). Special
precautions should be taken to
avoid galvanic corrosion, please
refer to Chapter XI.
The choice of the fastening
geometry will depend on the
result of the calculation of the
applied stresses. In the combination
of steel screws with aluminium
plates, the risk of galvanic
corrosion must be considered:
insulating gaskets should be
placed around the contact area
between both metals.
2. Screwing and bolt fastening
Riveting is today a widespread
joining method in different sectors
of industry, including commercial
vehicle construction. As
it is a very safe and easy-toapply
technique, riveting has
become a very common method
for joining assemblies e.g. in the
construction of the bodies of
refrigerated trailers.
Machine riveting has a lot of
advantages:
• High-speed: Machine riveting
allows fast operations with the use
of pneumatic or hydraulic tools
• Ease of control: the clamping
force is always guaranteed by
the system as it is less than the
force needed to snap the rivet
• Optical appearance: Machine
riveting can be combined with a
plastic capping of the rivet
• It does not require skilled
operators
• Mixed joints are possible: different
metals, plastics, sandwich
or honeycomb panels
Rivets can be divided into
2 main subcategories: self piercing
rivets and conventional rivets
which require holes that
must be drilled prior to riveting.
Conventional can be sorted into
two families:
• Lockbolts which visually look
like they create the same type of
connection as a conventional
bolt, but unlike conventional
nuts and bolts; they will not
work loose, even during
extreme vibration. They can only
be used when both sides of the
joint are accessible. Lockbolts
consist of a pin which is inserted
in the hole and a collar which is
placed on the pin from the
opposite end. The tool is placed
over the fastener pintail and
activated, the pin head pulls
against the material, the tool
anvil then push’s the collar
against the joint, at this stage
the initial clamp is generated.
The tool then swages the collar
into the pin. The pintail then
breaks and the installation is
complete (Figure IX.2).
3. Riveting
133
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