Testing in Ice Mikko Suominen Content of the lecture - PowerPoint PPT Presentation

MEC-E4004 - Model Scale Testing in Ice Mikko Suominen

Content of the lecture • Introduction • The course • Aim, time table, practicalities • Sea Ice • Occurence • Conditions • Properties • Wrap up, the next lecture 30.10.2017 2

Introduction • Mikko Suominen • M.Sc in Marine Technology 2011 • Doctoral Student / Ice Tank manager Uncertainty and variation in the measured ice- • induced loads on the ship hull • Expected defense in Jan/Feb 2018 • Other hobbies wrestling, triathlon • Introduction round • Your motivation to be on this course? 30.10.2017 3

The aim of the course • To introduce students to principles of ice model scale testing • Give hands on experience about conducting model scale testing • After the course, the student • has a general understanding about sea ice existence and properties • understands the principles of conducting model scale testing in ice can conduct and report model scale tests in ice • has experience on peer-review and presentation • 30.10.2017 4

Content of the course • 3 lectures • Model scale tests in ice • Seminar (presentation) • Peer-review • Final reporting • Grading 25% seminar, 25% peer-review • • 50% final reporting 30.10.2017 5

Time table Mon, Oct 30, 14-16 – 1st lecture Mon, Nov 6, 14-16 – 2nd lecture, Tue Nov 7, 8-15 – Testing in AAT Mon, Nov 13, 14-16 – 3rd lecture Mon, Nov 20, 14-16 – No lecture Mon, Nov 24, 23:59 – DL to send the report for peer review Mon, Dec 4, 14-16 – Seminar and return of the reviewed report Mon, Dec 8, 23:59 – DL for the final report For meetings: address Tietotie 1 C email mikko.suominen@aalto.fi 30.10.2017 6

Questions? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 30.10.2017 7

The aim and learning outcomes of the lecture • To introduce students to sea ice • After the lecture students know • where and what kind of sea ice conditions exists • the basics of the sea ice growth and structure • Has general knowledga about the mechanical properties of sea ice Discussion • What do you know about ice? 30.10.2017 8

Sea ice Occurrence – Arctic http://www.polarview.org/ 30.10.2017 9

Sea ice Occurrence – Antarctic http://www.polarview.org/ 30.10.2017 10

Sea ice Occurrence – other areas Baltic Sea Sea of Okhotsk Great Lakes Caspian Sea Bohai Sea 30.10.2017 11

Sea ice Conditions – growth • The main parameter for the ice thickness growth is the cumulative sum of freezing temperatures of air • Zubov (1938, 1945) based on empirical data 𝐼 2 + 𝛽 1 𝐼 = 𝛽 2 𝐺𝐺𝐸 • H = ice thickness, α 1 and α 2 = empirical factors, FFD = freezing degree-days FFD accounts the degrees below the freezing point of the water • • Salinity in Oceans 35 ‰ and freezing point at -4 o C, in the Baltic Sea 3- 6 ‰ at surface and freezing point -0.3 o C • For the Baltic Sea α 1 =50 and α 2 = 8 (Frederking et al., 2005) • Theoretically, the growth of ice thickness can be understood (Maykut, 1986, based on heat balance : ” heat input = flux out” based on Anderson, 1961) 30.10.2017 12

Sea ice Conditions – growth • Growth of the multiyear ice (Maykut and Untersteiner, 1971) 30.10.2017 13

Sea ice Conditions – growth & conditions • Ice Growth Process • Calm sea: • Frazil ice  Grease ice  Nilas  (possible Rafting  ) Ice sheet video • Rough Sea • Frazile ice  Pancake ice  (possible Rafting or Ridging  ) Ice Sheet 30.10.2017 14

Sea ice Conditions - Ridges (Polojärvi, 2013) 30.10.2017 15

Sea ice Conditions – Ice Channel • Especially on the fast ice area ice channels are formed when ships use the same route (Sandkvist, 1978) 30.10.2017 16

Sea ice Conditions - structure • The top layer randomly oriented crystals • The best oriented c-axia starts to dominate the growth • Transitiom from random to columnar • Columnar ice is not isotropic (Perey and Pounder, 1958) 30.10.2017 17

Sea ice Conditions - structure 30.10.2017 18

Sea ice Properties • The properties depend on temperature, structure, orientation, brine volume, porosity, strain rate, and scale. • Single values should not be given. • Sea ice is a natural material, all properties have statistical nature. • Many properties appear to depend on the measurement procedure • Many sea ice properties depend on the ice conditions and season also • Ice can not be described by purely brittle, plastic or viscous material – not isotropic material • Compressive and flexural strength, and Young’s modulus the most interesting for structures and model scale testing 30.10.2017 19

Sea ice Properties – Compressive strength • Ice failure under compression a complex process • Various failure modes – partly speed dependent (Riska, 1994) (after Frederking, 1977) 30.10.2017 20

Sea ice Properties – Compressive strength • Different test set-ups to measure compressive strength (Timco & Weeks, 2010) 30.10.2017 21

Sea ice Properties – Compressive strength • Pressure area curve applied for design purposes (Sanderson, 1988) 30.10.2017 22

Sea ice Properties – Compressive strength • Pressure area curve applied for design purposes (Masterson et al., 2007) (Taylor et al., 2010) 30.10.2017 23

Sea ice F Properties – Flexural strength • Two approaches to measure: c antilever beam test and simple beam test • In situ cantilever beams are typically used • High scatter in the results e.g. due the stress concentration at the root • In simple beam test, the beam is loaded from 3 or 4 points • Four point bending the most reliable • Both tests assume the ice in the homogeneous and perfectly elastic •  Flexural strength ~ Tensile strength Not true for ice • • Flexural strength an index value • However significant for many reasons (Kujala, 1994) 30.10.2017 24

Sea ice Properties – Flexural strength • Measured flexural strength values Flexural strength [kPa] (Timco & Weeks, 2010) (Kujala, 1994) 30.10.2017 25

Sea ice Properties – Young’s modulus • Measured values vary from 1.7 to 5.7 GPa when measured by flexural waves and from 1.7 to 9.1 GPa when determined by body-wave velocities • The flexural wave velocity is controlled by the overall properties of an ice sheet • The body-wave velocity is controlled by the high velocity channel in the commonly colder, less saline and stronger upper section of the ice •  The difference is reasonable • Note! mechanical measurement (in situ cantilever beam etc.) of the Modulus is not truly elastic • Ice is not truly elastic Called Effective Modulus or the Strain Modulus. • (Timco & Weeks, 2010) (Langleben and Pounder,1963) 30.10.2017 26

Wrap-up • What is the difference between the open water hull form with respect to ice going vessel? Why? • Could a good open water vessel be good in ice conditions? 30.10.2017 27

The next time • Focus on • Ship performance in ice • How properties and conditions are scale • Practicalities of conducting model scale tests 30.10.2017 28

Thank you! 30.10.2017 29

References Anderson, D., 1961. Growth rate of sea ice. J Glaciol 3(30):1170 – 72. Frederking R., Kouts T., Riska, K., 2005. In: Kujala, P., Suominen, M., Jalonen, R. (Eds.). Increasing the Safety of Icebound Shipping – Final Scientific Report: Vol 1 and 2. Helsinki University of Technology, Ship Laboratory, Report M- 302, Espoo, Finland, 2007, Deliverable D 4-1. August, 2005. Frederking, R.M.W., 1977. Plane-strain compressive strength of columnar-grained and granular snow-ice. Journal of Glaciology 18, 505 – 516. Kujala, P., 1994. On the Statistics of Ice Loads on Ship Hull in the Baltic. Doctoral Thesis, Helsinki University of Technology, Ship Laboratory, Acta Polytechnica Scandinavica Mechanical Engineering Series No. 116, 98 p. Langleben, M., Pounder, E., 1963. Elastic parameters of sea ice. In: Kingery, W.D. (Ed.), Ice and Snow. MIT Press, USA, pp. 69 – 78. Masterson, D.,Frederking, R., Wright, B., Karna, T., Maddock, W., 2007. A REVISED ICE PRESSURE-AREA CURVE, POAC-07, Dalian, China, June 27-30, 2007. Maykut, G., 1986. The surface heat and mass balance. In The geophysics of sea ice, ed. N. Untersteiner, 395 – 463. New York: Plenum Press. Maykut, G., Untersteiner, N., 1971. Some results from a time dependent thermodynamic model of sea ice. JGR 76(6):1550 – 75. Polojärvi, P., 2013. Sea ice ridge keel punch through experiments: model experoiments and numerical modeling with discrete and combined finite-discrete ekement methods. Doctoral Thesis, Aalto University. 30.10.2017 30