The Peak Dynamic Loading of a Winch in Term of the Rope Flexibility

Abstract

The cable winch is modeled as a system with two degrees of freedom during a start-up and braking phase for two basic operating cases: raising a lifted load case and elastic bond tensed by a raised load force case. The theoretical calculations were verified with experimental studies. Consequently, it is possible to define the winch drive overloads factor. Moreover, the determination of the number of stress change cycles in the rope can be performed. This important is with regard on possibility of rise in the rope the fatigue cracks. In dynamic experiments, three typical cases of raising mechanisms were taking into account: lifting the load with raising it, lifting the load with tensed rope and braking the load while lowering.

Full text

The Peak Dynamic Loading of a Winch in Term
of the Rope Flexibility
Stanisław Michałowski
1,a
, Wiesław Cichocki
1,b
1
Cracow University of Technology, Institute of Machine Design, Cracow, Poland
a
pmmichal@cyf-kr.edu.pl,
b
pmcichoc@cyf-kr.edu.pl
Keywords: Crane lifting systems, Winch, Dynamic loading, Rope flexibility.
Abstract: The cable winch is modeled as a system with two degrees of freedom during a start-up
and braking phase for two basic operating cases: raising a lifted load case and elastic bond tensed
by a raised load force case. The theoretical calculations were verified with experimental studies.
Consequently, it is possible to define the winch drive overload’s factor. Moreover, the
determination of the number of stress change cycles in the rope can be performed. This important is
with regard on possibility of rise in the rope the fatigue cracks. In dynamic experiments, three
typical cases of raising mechanisms were taking into account: lifting the load with raising it, lifting
the load with tensed rope and braking the load while lowering.
1. Theoretical formulation of the problem
In crane lifting systems, there are generally used cable winches joined with other elements as:
motor, brake, reducer and drum on which a lifting load’s rope is wounded [7]. The rotating
elements demonstrate relatively low susceptibility. The rope on which transported load is hanging is
the element with higher susceptibility [6].
If the winch is fixed on a rigid construction, such a system can be easily modeled with two
degrees of freedom and with a single elastic bond without mass (a rope) [3]. Its physical model is
shown in Fig. 1 for dynamic analysis reasons [5], where: I – inertia momentum of all rotating
elements reduced to rotor, φ – rotor angle, M
w
– momentum reduced to rotor which is a difference
between motor momentum and winch motion resistance momentum with no load, D
b
– winch
drum’s diameter, m – lifted rope’s mass, y(t) – absolute displacement of the load, l – rope’s length,
E
l
– rope’s modulus of elasticity, F
l
– active cross-sectional area of the rope, i
k
– manifold times.
a) b)
I
(t)
m
c
y
(t)
1
2
3
Fig. 1. Tested system: a) physical model, b) theoretical model presented as a system
with two degrees of freedom
Key Engineering Materials Online: 2013-02-27
ISSN: 1662-9795, Vol. 542, pp 105-117
doi:10.4028/www.scientific.net/KEM.542.105
© 2013 Trans Tech Publications Ltd, Switzerland
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