ANALYSIS OF SHAPES JAW IN CLASPING PROCESS
J. Juraszek, J. Nowak
A) Technical University of Bielsko – Biała, Department of Mechanical Engineering
43 – 300 Bielsko – Biała, Willowa 2, Poland
B) OBR Bosmal, 43-300 Bielsko-Biała, Sarni Stok
Abstract
This is one of the basing problems of clasping. A comparison of effectiveness of rope
clamps forming on hexagon, octagon, decagon, based upon an assessment of intensity
of residual stress in the layer of material of compressing socket adjacent to line was
made in the paper. It has shown some models of clasp joint by FEM. Described model
enables strain analysis foundationing elasto-plastic material linear hardening provided
Huber - Mises yield conditions and Prandtl - Reuss stress strain relations. The analysis
of clamp forming process for different socket shape made it possible to use the
differences in distribution of residual stress to increase the load carrying ability due to
purposeful rotation of subsequent clamps.
1. INTRODUCTION
The new thing is the determination of the influence of clasp number on the load
capacity of the joint (this is a non-linear relationship and the formulation of the reasons
of this non-linearity), and influence of shapes jaw. The influence of the one clasp upon
another has been taken account. The joints repeatedly clasped are used in order to
obtain a better load capacity. The previous works have shown that the: increase of
clasp width causes the increase of loading capacity of nearly linear character while the
increase of pressing force also causes the increase of loading capacity of the joint but it
is limited to by the maximum pressure of the press and by the resistance of the rope.
When we want to increase the load capacity of the joint using jaws with the same width it
is necessary change the shape of jaws. Many different rope clamps are used worldwide.
Clamps on hexagon are very popular in their midst but other also can be used e.g.
clamps on octagon or decagon. All types of clamps fulfil a purpose i.e. they transfer load
from a line to elements connected but information about an influence of an applied
compressing method along with a clamp shape on effectiveness of the applied method
is difficult to find.
A comparison of effectiveness of rope clamps forming on hexagon, octagon and
decagon based upon an assessment of intensity of residual stresses in the layer of
material of compressing socket adjacent to a line was made in the paper. Several
experiments have been carried out with one hexagonal clasp for the joints with eighteen
clasps.
2. MODEL
Model consist with two part:
-concrete socket with holes which sizes are identical and as real one
-wire, material parameters that is modulus of elasticity, modulus o strain hardening
were founded by tension testing machine according PN-90/H 04310.
Using the pre-processor of the finite element method package ANSYS, the model of
the system: line – compressing socket – clamp was prepared. The fixed arrangement of
the system: line – compressing socket was assumed whereas changes of clamp
geometry were only considered, what results in three variants of the system with clamps:
hexagon, octagon or decagon shape. The experimental determinate material properties
were assigned to every element. Non-linear bilinear σ−ε characteristics were applied.
Constrains and loads were added to this model. Constrains and loads for the first of
analysed variants, i.e. for the system with hexagon clamp, are presented in Fig.2. In
case of remaining two variants, boundary conditions have the same form because only
the geometry of the contact surface between clamp and socket is different.
3. ANALYSIS OF CLASPING PROCESSES
Comparisons of results received were made upon a fragment of an internal part of
the compressing socket. Differences between values of stress intensities in the four first
layers of the socket for every of three ‘line - socket - clamp’ variants were considered
and analysed. For an assessment of changes of values of stress intensity in particular
layers of socket material, tendency line described by second order polynomial was
introduced. Results of forming process of clamps are presented in Figures
Based upon the results obtaining during loading process of the considered system the
following conclusions can be drawn:
• the highest values of stress intensity in every analysed layer are for hexagon
shape clamp and the lowest for decagon clamp fig.2.;
• the highest values of stress intensity after unloading are for decagon shape
clamp and the lowest for octagon clamp fig.1.;
• an increase of stress intensity values was stated taking into account direction
from the surface of division of clamps to the vertical symmetry plane alongside of
every layer;
• performing the analysis of the course of tendency lines for
Comparison of stress for subsequent clamps /after loading/
2000
1800
1600
stress intensity
1400
1200
octagon
hexagon
decagon
1000
800
600
400
200
0
1
2
3
type of jaw
Fig.1. Stress intensity after unloading.
900
800
700
600
500
stress
decagon
hexagon
octagon
400
300
200
100
0
1
2
type jaw
Fig.2. Stress intensity after loading.
3
MN
SINT
(AVG)
DMX =.004235
SMN =.311E+08
SMX =.748E+09
.311E+08
.111E+09
.190E+09
.270E+09
.350E+09
.429E+09
.509E+09
.588E+09
.668E+09
.748E+09
MX
Y
Z
X
Fig.3. The stress intensity of forming process of hexagon clamp.
SINT
(AVG)
DMX =.00282
SMN =.109E+08
SMX =.636E+09
.109E+08
.804E+08
.150E+09
.219E+09
.289E+09
.358E+09
.428E+09
.497E+09
.567E+09
.636E+09
MN
MX
Y
Z
X
Fig.4. The stress intensity of forming process of octagon clamp.
particular clamps in subsequent material layers - the statements made in the
previous conclusions can be confirmed;
Based upon the presented charts, the following issues come out:
the highest values of residual stress intensity occur for decagon clamp;
local extreme values of residual stresses are consistent with places where contact
between socket and wires takes place;
amplitude of changes of residual stress intensity alongside every layer reaches the
highest value for decagon clamp the lowest values of residual stress intensity occur for
octagon clamp;
the most uniform distribution of residual stresses is achieved in case of hexagon clamp.
SINT
(AVG)
DMX =.0095
SMN =.864E+08
SMX =.249E+10
.864E+08
.353E+09
.620E+09
.887E+09
.115E+10
.142E+10
.169E+10
.195E+10
.222E+10
.249E+10
MX
Y
Z
X
MN
Fig.5. Effect of forming process of hexagon clamp – stress intensity after loading
SINT
(AVG)
DMX =.0074
SMN =.150E+09
SMX =.209E+10
.150E+09
.366E+09
.581E+09
.797E+09
.101E+10
.123E+10
.144E+10
.166E+10
.187E+10
.209E+10
MX
Y
Z
X
MN
Fig.6. Effect of forming process of decagon clamp – stress intensity after loading
4. CONCLUSIONS
The results obtained in this paper can be used in the direct engineering practice for
design new joints or modernising the existing ones.
Increase of clasping pressure allows to increase the residual pressure and this way to increase joint hosting capacity lowest decrease of stresses between loading and
unloading processes occurs for decagon clamp.
The analysis of clamp forming process for different socket shapes made it possible
to use the differences in distribution of stresses after unloading to increase the loadcarrying ability due to purposeful rotation of subsequent clamps.
It has been shown in the paper that there is the possibility to use the method of FEM
for analysing the clasping process taking into account the appropriate cress stiffness of
the rope.
5. REFERENCES
[1] Meguid S., Shagal G., Stranart J., Daly J.: “Three-dimensional dynamic finite
element analysis of shot-penning induced residual stresses”. Finite Elements in Analysis
and Design, Vol.31, nr3, January 1999.
[2] Kleiber M.: “Metoda elementów skończonych w nieliniowej mechanice kontinuum”,
PWN Warszawa 1984.
[3] Hinton D, Owen E.: Finite Element in Plasticity. Swansea 1980.