23-06-2014, 01:45 PM
[i]The Behaviour of Single Lap Joints under Bending Loading
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ABSTRACTS
The following is a list of the abstracts for papers which will be presented in
SECOND INTERNATIONAL SYMPOSIUM ON ADHESIVE JOINTS:
FORMATION CHARACTERISTICS AND TESTING. The listing is
alphabetical by presenting author. This list is updated continually to add
abstracts as they become available and make appropriate corrections. This list
may be conveniently searched by using the editor provided with most popular
browsers (e.g. Microsoft Explorer, Netscape, ... etc.)
The Behaviour of Single Lap Joints under Bending Loading
Although there has been a lot of work on the tensile loading of single lap joints
(SLJ) there exists only a small amount of work on joints loaded in bending. A
structural bonded joint will usually face a combination of tensile, compressive
and bending loads. The importance of the bending moment applied at the
edges of the overlap of a SLJ has long been addressed by Goland and
Reissner(1), Hart-Smith(2), and others. However, all these analyses concerned
the bending moment induced due to the eccentricity of the load path in the
SLJ configuration.
The behaviour of bonded SLJ under bending loading was investigated in the
current work. A single part toughened epoxy adhesive and hardened steel
adherends were used for the manufacture of the joints. The effect of adherend
thickness, adhesive thickness and overlap length was investigated both
experimentally and theoretically, using the finite element method and the
commercial code ABAQUS. Non-linear large displacement analyses were
carried out and the adhesive was modelled using a yield criterion that is
dependent on the hydrostatic stress component of stress.
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Experimentally it was found that there is a significant effect on the strength of
the joints from the adherend thickness while there is no effect in the strength
from the overlap length or the adhesive thickness. The joint strength increases
almost linearly as the adherend thickness increases while it remains almost
constant for joints with different overlap lengths or different adhesive
thicknesses.
Easy Removal of Pressure Sensitive Adhesives for Skin Applications
There are two essential requirements of medical pressure-sensitive adhesives:
that they should stick firmly to a difficult substrate (skin) and that they should
be easily and cleanly removed from that substrate when desired. These
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requirements would seem to be in conflict: ability to stick firmly is usually
characterised by peel testing, while removal of the dressings is by peeling,
where the force must be low to minimise the trauma to the skin.
A number of ways have been considered to resolve this conflict and these will
be discussed further in the paper. These may be divided into two broad
categories: those that make the best of existing pressure sensitive adhesives
technology, broadly taking a physical approach, and those that introduce novel
chemistry into the process. Physical approaches consider such details as the
dependence of peel force on peel angle, peel rate, backing materials and the
deformation of the skin during peeling. Careful selection of peel angle and
backing material can influence the peel force, though peel rate tends not to
have a very significant effect. In addition, the use of crosslinked adhesives, or
adhesive microspheres, can increase the ease of peeling of the dressing on
removal, but also reduce the ability of the dressing to adhere in the first place.
As an alternative to simply making the best of the physics of the peeling
process, various workers have devised chemical systems for making the
adhesive less strongly adhering at the time of removal. These systems usually
consist of introducing a 'switch' mechanism into a strongly-adhering adhesive
so that its adherence may be reduced significantly at the time of removal by
operation of the 'switch'. Means of activating the 'switch' include: heat
(warming or cooling), application of water via an absorbent backing and
exposure to visible light. These may produce physical or chemical changes in
the adhesive.
While these approaches bring benefits to patients, consideration of the science
behind them is leading to an enhanced understanding of the peeling process.
Stress Analysis and Strength Evaluation of Bonded shrink Fitted Joints
This paper deals with stress analysis and strength evaluation of bonded shrink
fitted joints under push-off force and torsion. The stress distributions in the
adhesive layer of bonded shrink fitted joints are analyzed by using the
axisymmetric theory of elasticity when an external push-off force and torsion
are applied to the upper end of shaft. The effect of the outer diameter and the
stiffness of rings on the interface stress distributions are clarified by the
numerical calculations. Using the interface stress distributions, joint strength
is predicted. In addition, joint strength was measured experimentally. It is
seen that a rupture of adhesive layer is initiated from the upper edge of the
interfaces when a torsion is applied to the upper end of shaft. In addition, it is
found that a rupture is initiated from the lower edge of the interface when the
push-off force is applied. The numerical results are in fairly good agreement
with the experimental results. It is found that the joint strength of bonded
shrink fitted joints is greater than that of shrink fitted joints and the
availability of the bonded shrink-fitted joints is demonstrated.
Prediction of the Strength of Plastically-Deforming Adhesive Joints
A general approach for analyzing the fracture of plastically-deforming adhesive
joints is presented. This approach couples the use of an embeddedprocess-
zone model to represent the behavior of the adhesive layer, and a
non-linear finite-element analysis to calculate the elastic-plastic deformation of
adherends. The procedures for determining the model parameters required to
analyze mode-I and mode-II loading are discussed. it is shown that once these
parameters have been determined, they can be combined with a mixed-mode
failure criterion to allow generate simulations of the fracture of different
geometries of joints. The excellent predictions that can be obtained with this
technique are demonstrated for mixed-mode geometries such as the
asymmetrical T-peel and the single lap-shear geometry. The numerical
calculations allow quantitative predictions of the loads and displacements (and
hence energy absorption) during deformation and fracture to be made. They
also result in accurate predictions of how the shape of the deformed joint
evolves during fracture.