Temperature Effects on Ice Adhesion Strength for Wind Turbine MaterialsRajkiran Gouni and David H. Matthiesen, Case Western Reserve University, Cleveland, Ohio

Presented at the AWEA WINDPOWER 2011 Conference & Exhibition May 22-25, 2011 Anaheim, CA

Introduction

References

Wind turbines operating in off-shore environments are challenged with icing conditions in cold temperature regions.

The lack of a standardized method to measure adhesive strength of ice to materials

Experimental conditions to compare various results.

Figure 1. Wind turbine operating in cold climate [3]

Icing on wind turbines is a major concern for

operation of these machines in cold weather

conditions. The concern is for both the static

structural materials, such as foundations and

towers, as well as the dynamic lifting materials,

such as blades. One mitigation strategy is to

cover these components with coatings that

reduce the wetting of water. The question then

becomes, ‘How do these coatings affect the

bonding strength of ice that does build up?’ A

measurement technique was designed and

measurements are reported on the shear

strength of ice with these coating materials

1) Icing on Wing Turbines Affects, Iopara Inc., Wind Turbine and Aeronautics Consulting.

2) H.H.G Jellinek, “Adhesive properties of ice”, Journal of Colloid Science, Vol. 14. pp. 268-280, 1959.

3) Mohammad R. Kasaai and Masoud Farzaneh, “A critical review of evaluation methods of ice adhesion strength on the surface of materials”, Proceedings of 23rd .

4) International Conference on Offshore Mechanics and Arctic Engineering, June 2-25, 2004.

5) M F Hassan, H P Lee and S P Lim, “The variation of ice adhesion strength with substrate surface roughness”, Measurement Science and Technology, Vol. 21, 075701, 2010.

6) L.E. Raraty and D. Tabor, “The adhesion and strength properties of ice”, Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 245, No. 1241, pp. 184- 201, June 3, 1958.

7) Nathan Mulherin and Robert B. Haehnel, “Measuring the adhesion strength of ice”, Cold Regions Research & Engineering Laboratory, U.S Army Corps of Engineers.

This work was sponsored by DOE grant DE-EE0000275 to The Great Lakes Energy Institute and Case Western Reserve University acknowledges the contribution of the State of Ohio, Department of Development and the Third Frontier Commission, which provided funding in support of TECH 10-011 The Ohio Wind Energy Research and Commercialization (WERC) Center project.

Abstract

Specimen PreparationDouble lap shear test was the technique

developed to conduct experiments on adhesion strength of ice to materials. ASTM Standard D 3528-96 Modification of adhesive dimensions

accordingly for ice

Figure 2. Schematic of specimen geometry.

Experimental ConditionsTemperature -10 oC, -15 oC and -20 oC.Material surfaces:

304 Stainless SteelEpoxy Polyamide Primer CoatPolyurethane Top Coat

Measured surface roughness of each materialDistilled water used to prepare iceConstant loading rate and interfacial area

Testing ConditionsMTS testing machine with INSTRON

temperature controlling chamberLoading rate of 0.0016 mm/s, Interfacial area = 34 x 15 = 510 mm2

Load cell --> 889 NRecorded temperature, time, loadCalculated Stress vs. Strain

(a) (b) (c)Figure 3. (a) Specimen preparation mould, (b) Experimental set-up and (c) Loaded specimen after failure

a

b cFigure 4. (a) Adhesive fracture, (b) Adhesive fracture,

(c) Cohesive fracture (only observed in stainless steel at -20oC).

Experimental Procedures

Experimental Results

Temperature(oC)

Stainless(MPa)

Polyamide(MPa)

Polyurethane(MPa)

-10 0.77±0.04 0.34±0.09 0.29±0.14

-15 1.15±0.13 0.57±0.11 0.37±0.06

-20 1.42±0.16 0.59±0.13 0.47±0.09

Experimental Results

Conclusions

1. A new standardized experimental method was successfully developed.

2. The double lap shear test has a high degree of repeatability and gives freedom to change the test conditions.

3. The adhesive strength of ice to stainless steel was studied and found that, with decreasing temperature from -10 oC to -20oC, the force of adhesion increased from 0.77 MPa to 1.42 MPa.

4. At -20 oC, a change in fracture behavior from adhesive break to combination of adhesive and cohesive break was observed for ice/stainless steel interface.

5. Unlike stainless steel, the fracture of coating materials at all the three temperatures was found to be adhesive in nature.

6. At all three temperatures it was found that the adhesion strength of ice to the polyurethane top coat was always less than the epoxy polyamide primer coat or the stainless steel.

Objectives

To develop an experimental technique (based on ASTM standard) to investigate the ice adhesion strength to surfaces

To investigate the effect of temperature on adhesive strength of ice

To study the effect of material surfaces on ice adhesion strength

To understand the fracture behavior of ice, adhered to surfaces

1.6 mm

1.6 mm

34 mm

81.5 mm

0.8 mm

-10 oC

-15 oC

Micro cracks in the sub surface of ice

-20 oC

Cohesive break in combination with adhesive

Figure 5. Adhesive Strength as a function of temperature for the wind turbine materials tested.

Table 1. Adhesive Strength for the wind turbine materials tested.