stuttgart seiltagung imw

8/9/2019 Stuttgart Seiltagung IMW

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OIPEEC Conference / 3rd

International Ropedays - Stuttgart - March 2009

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P. Dietz, A. Lohrengel, T. Schwarzer and M. Wchter ODN 08xxTechnical University of Clausthal, Fritz-Schting-Institute of Mechanical Engineering

Problems related to the design of multi layer drums for synthetic

and hybrid ropes

Summary

Rope drum and rope as parts of a hoisting system, must constantly be improvedand modified concerning rising standards. To fulfil the requirement of a further weightreduction of the system, high strength chemical-fibre (man-made fibre) ropes orcompound constructions, so called hybrids, shall be used in future when there is amultilayer winding of the drum. Their rope characteristics, that are different fromthose of common ropes, cause an entirely different drum load, which urgently

requires an adaptation of the existing calculation bases to the new rope types.This paper shall give a review on current projects on designing and dimensioningrope drums with a multi-layer winding with synthetic or hybrid ropes and gives anoutlook on further required steps to the adaptation of the calculation processes.

1 Introduction

The current valid and standardised dimensioningspecifications of hoists are based on theclassification of winding systems into time-based

and load-based collectives, for which geometry,loading and life time of the ropes are the leadingcriteria for dimensioning. In order to increase theperformance of the hoisting drum windingsystem while keeping the dimensions of thedrum constant, the safe working capacity of theropes was increased by the implementation ofnew rope-making techniques and innovative wirematerials. The different rope characteristics suchas bending stiffness and Poissons ratio led to adramatic increase in the load on the winding

drums and at the same time to new damagemechanisms. This has resulted in stronger andtherefore heavier dimensioning of the hoistingdrum elements.

At the Institute of Mechanical Engineering avariety of ropes were tested during different research projects. Their characteristicswere determined and the influence on the load conditions of the winding drum wasanalysed [1]. Furthermore a combined theory for the calculation of the load on thedrum cylinder and end plate as a total system was developed, which shows thecritical points in the transition area also a function of the stiffness of the drum cylinder

and the flanged wheels (flanges) [2]. Further research work was the inclusion ofpartly-ductile deformations which result in a clear calculated increase of bearingstrength and the development of a non-rotationally symmetric load model for the

Figure 1: Broken flange wheel.


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Innovative ropes and rope applications

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determination of the behaviour under load of multi-layer wound hoisting drums [3]. Onthe basis of those papers it was possible to develop the existing calculation methodtowards a weight reducing winding drum dimensioning. However, the potential forweight reduction for a given combination of drum and rope is almost exhausted at20%.

The usage of new rope materials like synthetics or compound materials as analternative to the pure wire rope is essential for a further optimisation of themass/performance ratio of future hoisting drum winding systems and therefore alsothe realisation of ultra-light weight constructions (with weight reductions of far morethan 20%) on the whole area of the conveyer technique. Todays commerciallyproduced high-tensile light weight fibres like Dyneema und Aramid [4], [5], [6] and [7]have the same tensile strength as steel wires while saving weight by a factor 6 to 8.Table 1 compares the characteristics of these fibres to steel wire.

Dyneema SK60 Aramid LM Steel wire

Density (g/cm3) 0.97 1.44 7.85

Tensile strength (N/mm2) 2700 2700 1770

Youngs modulus (N/mm2) 87000 58000 200000

Ultimate strain (%) 3.5 3.7 2.6

Table 1: Characteristics of fibres and steel wire [6].

The following calculation example clarifies the potential for weight reduction, whichbecomes usable by implementing synthetic ropes in cranes.

A lifting rope with a diameter of 23mm has a specific weight of ca. 3 kg/m. With alength of 800 m a common length for mobile cranes- the total weight is 2400 kg.Assuming, that a synthetic rope is at least five times lighter than the wire rope, therope weight is reduced by 1920 kg. In comparison the absolute weight reduction for afitting rope drum is 74 kg (with the assumption of a reduction by 20%).

For this reason synthetic ropes are predestined for the mobile service, since a hightraction force/weight ratio is required here. Furthermore the loads on the windingdrums decrease because of the lower self-weight of the rope as well as the smaller

bending stiffness compared to wire ropes. Light weight constructions will so bepossible. Moreover, the by far higher flexibility of synthetic ropes allows aminimisation of the dimensions of hoisting drum winding systems. A D/d ratio of 12/1up to 15/1 could be achieved by using synthetic ropes [8].

2 Problems with the usage of synthetic or hybrid ropes

The development of synthetic-based light weight ropes is still in the prototype state.For this reason there is only a small number of scientific results for synthetic ropes.

Basically until now, only research was done on the area of the maximum tensile forceand the number of bending over sheave fatigue cycles.


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The radial force Fridoes not occur immediately or suddenly as it is assumed with asteel cable, but increases to its maximum value over time. It depends on the rotation

of the drum by the angle i. The radial force can be expressed as in Equation (3).

t

r

(t)F(t)F

iLi

si

ri

= (3)

Since the pressure on the cylinder in position zjacts as a local force, it can virtuallybe distributed on the cylinder according to the Fourier series (Equation 4). Figure 3for example shows the pressure under the turn on position zj. The drum cylinder isdeformed by the radial force as shown in Figure 4.

( ) ++=

=1

0 sincos2

)(k

kkkzbkza

azp (4)

Figure 3:Pressure on the drum cylinder in the first layer on a rope diameter d s= 14 mm and atensile force Fs= 20 kN under the turn in the position zj, length of the drum cylinder L =500 mm; synthetic rope.

Pressure[N/mm

2]

Figure 4: Deformation of the rope cylinder under the pressure of the turn j; synthetic rope.

Deformation[mm]

Position zj[mm]

Position zj[mm]


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The rope is deformed by the radial force in the transverse direction. Depending on

the damping the radial force reaches its maximum after the time i/, at themaximum deformation. Figure 5 shows the deformation in the transverse direction asa function of the damping. A clear bow is noticeable at high damping in the slope ofthe deformation in transverse direction.

Figure 5: Rope deformation in transverse direction; synthetic rope.

The delay in the deformation caused by the damping induces an energy loss in the

rope. The loss during the winding of one turn over the angle iis shown in Figure 6.Here the impact of the damping according to the energy loss is clearly illustrated.

Figure 6: Energy loss in a synthetic rope.


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The winding of a rope on position zjtakes pressure off the turn in position zj-1- the so-called loss elimination effect [9]. For the synthetic rope the decay in the initial loaddepends on the damping and occurs just like the deformation in transverse directionwith a time delay. The time delay, combined with the physical characteristics of arope and respectively the drum cylinder (surface quality, coefficient of friction) will

affect the loss-elimination process (release process) of a synthetic rope in a differentway to that of the steel cable. Figure 7 shows the decay of the ropes initial loadwithin 8 ms as a function of the rope damping assuming the rope will not slip. Theslip behaviour of the rope will be determined by the surface characteristics of therope with respect to the drum and the construction specifications concerninggeometry of the groove, the turn distance and respectively the length of ascendancyand the parallel area.

Figure 7: Course of the rope load relieving on the position zj-1 in dependency of the damping,synthetic rope.

2.2 Numerical analysis of the impact of different rope characteristics on thecylinder load

In order to determine the impact of the different rope characteristics and thus thearising drum load when using a synthetic rope for multilayer winding, numericalanalysis was undertaken using a simplified FE-model. The model was broken downto a simple rope drum with a rope package that is assumed to be rectangular(idealised 5 rope layers).

A constant rope tensile force of FS = 20 kN was assumed in the model. Differentcombinations from transverse- and longitudinal Youngs modulus were assigned. Toinvestigate the impact of the drum stiffness in the model, the diameter ratio of the

cylinders diameter to the ropes diameter were varied with D/d = 24 and D/d = 17(while keeping the ropes diameter constant).


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Figure 8shows the graphs of the arising flanged wheel deformation for a diameterratio of D/d = 24 with different constant Youngs modulus in transverse direction ESQand changing Youngs modulus in longitudinal direction ESL.

Figure 8: Flanged wheel deformation over Youngs modulus in longitudinal direction ESL;D/d=24.

A declining increase of the deformation is clearly recognisable for an increasingYoungs modulus in longitudinal direction ESL for all Youngs moduli in transversedirection ESQ. By comparing the lowest and the highest calculated Youngs modulusin transverse direction ESQ over the Youngs modulus in longitudinal direction ESL,there is reached approximately a doubling in the deformation of the end plates. Thegraphs of the deformation of the flanged wheels are identical for the smaller diameter

ratio of D/d = 17. Deformations increase by factor 3 for all Youngs moduli intransverse direction ESQ. The same analysis was done for a constant Youngsmodulus in longitudinal direction ESL for a changing the modulus in transversedirection ESQ.

Figure 9 shows the calculated end plate deformations for the diameter ratio D/d = 24.There is a recognisable linear relationship in the calculation results between theflanged wheel deformation and the Youngs modulus in transverse direction ESQ. Thehighest deformation occurs for the lowest calculated Youngs modulus in thetransverse direction, as for the analysis with variable modulus in the longitudinaldirection.

Figure 10 shows the radial flexural stress as a function of the ropes Youngsmodulus in longitudinal direction ESL for the diameter ratio D/d = 24. The graph forthe radial bending stress for both diameter ratios shows similarities to the graphs ofthe flanged wheel deformations. The combination of the smallest Youngs modulus intransverse direction ESQwith the highest Youngs modulus in longitudinal directionESL produces the highest deformations and therefore the highest occurring stress,too. The flexural stress is about 1/3 higher than for the diameter D/d = 17.

The results of the numerical analysis show, that for a majority of combinations of theYoungs modulus in transverse and longitudinal direction, the flanged wheeldeformations and the radial bending stress are much higher than with the usage ofconventional wire ropes (cf. Figure 8 - Figure 10, value at ESQ= 1500 N/mm and ESL= 120000 N/mm). The Youngs moduli in transverse and longitudinal direction arenotably reduced in comparison to the conventional rope.

-0,15

-0,1

-0,05

0

0,05

0,1

0,15

0 20000 40000 60000 80000 100000 120000

Longitudinal modulus ESL[N/mm]

Deformation[mm]

ESQ = 400 ESQ = 600 ESQ = 800 ESQ = 1000 ESQ = 1500

0.15

0.1

0.05

0

-0.05

-0.1

-0.15


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The loads and deformations are mostly affected in a linear interrelationship by theYoungs modulus in the transverse direction. Furthermore the load increases for adecreased cylinder to rope diameter ratio (D/d).

Figure 9: Flanged wheel deformation over Youngs modulus in transverse direction ESQ;D/d=24

150

200

250

300

0 20000 40000 60000 80000 100000 120000

Longitudinal modulus ESL[N/mm]

Stress[N/

mm]

ESQ = 400 ESQ = 600 ESQ = 800 ESQ = 1000 ESQ = 1500

Figure 10: Radial bending stress at the flanged wheels over the Youngs modulus in longitudinal

direction ESL; D/d=24.

2.3 Experimental analysis of rope characteristics

The knowledge of the rope characteristics is very important for an exact dimensioningof a drum geometry as the ropes longitudinal and transversal modulus have a stronginfluence on the rope package stiffness and thus on the drums loading. This isespecially important in the case of multilayer winding. At the Institute of MechanicalEngineering two hybrid constructions were tested with regard to their ropecharacteristics during a research project (Figure 11). Several measurements with

different longitudinal and transversal stress rates as well as different numbers oflayers and layer arrangements were undertaken to determine the influence on therope characteristics.

-0,15

-0,1

-0,05

0

0,05

0,1

0,15

200 400 600 800 1000 1200 1400 1600

Transverse modulus ESQ[N/mm]

Deformation[mm]

ESL = 20000 ESL = 40000 ESL = 60000 ESL = 80000 ESL = 120000

0.15

0.1

0.05

0

-0.05

-0.1

-0.15


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Figure 11: Rope tensile force test stand for measurements of the rope characteristics.

The examined hybrid ropes are based on a widely used construction for hoistingropes as they combine good flexibility because of their 8 outer strands with a highwear resistance because of the compaction of those strands. In the following a fibrecore in the hybrid variants replaced the standard construction of the rope core (Figure12). The cross-sectional area of this core amounts about 25% of the total cross-sectional area.

The two examined variants have the same construction (based on a Turboplast) buta different fibre core material. The core materials are Aramid fibres with differentmechanical characteristics. Those fibres have a very high tensile strength combinedwith a low density and a low strain. Compared to a common steel wire thecharacteristic values of the used fibre types are shown in Table 2. The maindifference is the E-Modulus of the particular fibre.

Fibre typeTensile strength

[MPa]Breaking strain

[%]E-Modulus

[GPa]Density[g/cm]

Standard Module (SM)

3250

3.7

75

1.44

High Module (HM) 3100 2.7 105 1.45

Wire 1770 2.6 200 7.85

Table 2: Comparison of fibre and wire characteristics [6].

As comparison for the determined characteristic values two common constructionsfor hoisting ropes are used: the PDD 1315 CZ and the PC EUROLIFT. These are fullsteel wire ropes with a different rope construction. All ropes have a nominal diameter

of 23 mm and a minimum breaking load Fmindepending on the particular constructionbetween 410 kN and 490 kN.


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The presented analysis refers in the first place to the determination of the ropestransversal modulus ESQ as the ropes longitudinal modulus ESL is determined andstated by the rope manufacturer when specifying the breaking load. In Figure 13 theparticular transversal modulus depending on the longitudinal stress rate kL with aconstant transversal stress rate kQ= 0.07 is illustrated.

In the diagram an increase of the transversal modulus with an increase of thelongitudinal stress rate with respect to the tensile force is shown for all examinedropes. The hybrid construction with the fibre core (SM) has the lowest transversal

modulus in all measurements. The transversal modulus of the rope with the HM fibrecore is at all measurement points 1.5 times higher than the standard variant. Of greatsignificance is the fact that the determined transversal moduli of the hybrid

Figure 12: Cross section of the tested hybrid wire, left the core, right the complete rope

0

400

800

1200

1600

2000

0,0 0,1 0,2 0,3 0,4

Longitudinal stress rate KL

ESQ

[N/mm]

Turboplast SM Turboplast HM

PC Eurolift PDD 1315 CZ

Figure 13: ESQ as a function of kL; kQ = 0.07; 1. Layer.


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construction are close to those of the PC Eurolift construction (kQ= 0.07), which is afull steel wire rope construction. The PDD 1315 CZ has a much higher transversalstiffness than the Eurolift.

Increasing the transversal stress rate to kQ= 0.1 leads to an almost identical patternas in the previous statement. Because of the higher longitudinal pre-stressing and

thus a compaction of the ropes cross-sectional area, the determined transversalmoduli are 25 to 35% higher than with a transversal stress rate of kQ= 0.07.

In Figure 14 the particular transversal modulus depending on the number of layerswith a constant transversal stress rate of kQ= 0.07 is illustrated.

In general, a declining decrease of the stiffness with a constant increase of thenumber of layers can be detected at the layer-related demonstration of thetransversal modulus. It will lead to a constant value with higher number of layers. Thedifferences concerning the transversal stiffness especially in the first layer diminishwith an increase in the number of layers, thus there is just a small variation from thethird layer on.

In this case the determined transversal moduli with kQ= 0.1 are almost identical tothose before. The transversal stiffnesses of the two hybrid constructions are alsoalmost identical in higher ranges of layers of the examined transversal stress rates.The higher longitudinal pre-stressing leads to a higher transversal modulus in the firsttwo layers (analogy to the examination of one layer).

The determined values for both rope constructions are in the usual range for thoserope cross-sectional areas and constructions [1], [2].

3 Conclusion and outlookThe article shows that synthetic or hybrid ropes as running ropes can push thelight weight constructions on the area of hoisting devices, last but not least due to

0

400

800

1200

1600

2000

0 1 2 3 4 5

Layer number

ESQ

[N/m

m]

Turboplast SM Turboplast HM

PC Eurolift PDD 1315 CZ

Figure 14: ESQin dependence of the layer number; kL00.2; kQ= 0.07


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their weight advantage in comparison to wire ropes with the same load capacity.There are only a few scientific researches done on that application; the problem of amultilayer winding was not investigated yet. This lack of information prevents a wideindustrial use of those ropes as running ropes.

The numerical and analytical analyses resulted that the load behaviour of the rope

drums changes when used with synthetic ropes. A reduction in the Youngs modulusin transverse direction results in an increase of the load in the drum flanges on theone hand, while on the other hand the load on the drum cylinder is reduced.Furthermore an energy loss, which is converted to heat, is induced in the system bythe damping in the synthetic ropes. All those effects must be considered in theexisting dimensioning models, which finally allow a stress related, weight optimiseddrum design for the usage of synthetic or hybrid ropes.

The performed experimental examinations for measuring rope characteristics haveshown that using the hybrid constructions with different fibre material leads to areduced transversal modulus because of the fibre core. Furthermore one can get into

the range of normal wire rope constructions by varying the fibre material. Because ofthis alteration in the rope characteristics there is also a changing of the drumsloading behaviour.

Currently on the Institute of Mechanical Engineering experimental measurements ona 5 layer winding (Figure 15) are carried out for a hybrid wire rope in order to validatethe theoretical models. Figure 16 shows the 32 applied strain gauges with the cablinginside the test drum to measure the axial and tangential elongations.

Figure 16: Applied strain gauges at the test drum

Figure 15: Hybrid construction on test stand


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Figures 17 and 18 show examples of the tangential stress and axial stress variationover the time during the test run for a 23 mm steel rope. In both an increasing stresspattern over the test time is visible in every layer. At higher layer numbers theincrease of the stress under constant tensile force reduces due to different relaxationeffects [2]. The results of this measurement are the basis for the running comparison

with the hybrid wire rope.

Figure 17: Characteristics of the measured tangential stress.

Figure 18: Characteristics of the measured axial stress.

-350

-300

-250

-200

-150

-100

-50

0

50

00:00 01:26 02:53 04:19 05:46 07:12 08:38 10:05 11:31 12:58 14:24 15:50 17:17 18:43

time [mm:ss]

stress

[N/mm

2]

1st layer

2nd layer

3rd layer

4th layer5th layer

-50

-40

-30

-20-10

0

10

20

30

40

50

60

70

80

90

100

00:00 01:26 02:53 04:19 05:46 07:12 08:38 10:05 11:31 12:58 14:24 15:50 17:17 18:43

time [mm:ss]

stress[N/mm

2]

1st layer 2nd layer 3rd layer

4th layer 5th layer


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4 References

[1] Henschel, J. Dimensionierung von Windentrommeln,Dissertation TU Clausthal,Verlag und Vertriebsgesellschaft mbH, Dsseldorf, 2000.

[2] Mupende, I. Beanspruchungs- und Verformungsverhalten des Systems

Trommelmantel Bordscheiben bei mehrlagig bewickelten Seiltrommelnunter elastischem und plastischem Werkstoffverhalten, Dissertation, TUClausthal, Curvillier Verlag Gttingen, 2001.

[3] Otto, St. Ein nicht-rotationssymmetrisches Belastungsmodell fr die Ermittlungdes Beanspruchungsverhaltens mehrlagig bewickelter Seiltrommeln, Diss.TU Clausthal 2003.

[4] Jacobs, M. and Dingenen, J. Zugkrftig. Leichtfasern fr Hochleistungsseile,Draht Welt Heft 3, 1991.

[5] Rebel, G., Verreet, R. and Ridge, I.M.L. Lightweight ropes for liftingapplications, in I.M.L. Ridge ed. Proceedings of the OIPEEC Conference

Trends for Ropes: design, application, operation, Athens, Greece 27th- 28thMarch 2006, pp 33-54, ISBN: 978-0-9552500-0-2.

[6] Ridge, I.M.L., OHear, N., Verreet, R., Grabandt, O. and Das, C.A. High strengthfibre cored steel wire rope for deep hoisting applications,in I.M.L. Ridge, ed.,Proceedings of the OIPEEC Conference How to get the most out of yourropes Johannesburg, South Africa, September 2007, ODN 0820, 225-240,ISBN: 978-0-9552500-1-9.

[7] O'Hear, N., Grabandt, O., Hobbs, R.E. Synthetic fibre ropes for mine winding,in: I.M.L. Ridge, ed, Proceedings of the OIPEEC Conference Trends forRopes: design, application, operation, Athens, Greece 27th - 28th March2006, pp 17-32, ISBN: 978-0-9552500-0-2.

[8] Foster, G. New fibre rope technologies drive increased applications, Seatechnology Heft 7, 1989.

[9] Dietz, P. Ein Verfahren zur Berechnung ein- und mehrlagig bewickelterSeiltrommeln;Dissertation, TH Darmstadt, Darmstadt, 1971.

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