Abstract
The majority of offshore wind turbines in Europe are supported by monopile type foundation structures. Monopiles are made of large thickness steel plates which are longitudinally welded to fabricate “cans” and these cans are subsequently welded around the circumference to manufacture a monopile. Monopile structures can have diameters of 4-10m, with wall thicknesses of 40-150mm. To achieve the cylindrical shape in individual cans, large thickness steel plates are typically cold formed via the three-roll bending process. During forming of these plates, the material is subjected to plastic pre-strain, which subsequently influences the fracture and fatigue properties of monopile structures. In this study, a finite element model has been developed to predict the pre-straining levels in monopiles of different dimensions. To determine the influence of numerous manufacturing practices, a sensitivity analysis of different factors has been conducted. These include fabrication dependent variables such as the influence of friction coefficient and bending force, and geometry dependent factors such as plate thickness, length, and distance between rollers. From the numerical results, a range of expected material pre-strain levels have been identified and presented in this paper.
Highlights
The plate can be split into three regions by their contact points: the formed region, the deformation region, and undeformed region
Numerical investigations regarding the effects of the three-roll bending manufacturing process on the plastic strain levels in offshore wind monopiles have been conducted
The maximum plastic strain range obtained from of finite element cases from load levels, friction coefficients, and distance between rollers considered was from -1.6% to 1.6% for S355 steel
Summary
Renewable energy is predicted to be one of the fastest growing maritime sectors. Currently, wind energy already mKeReeyteswno1er1wd%s:abHoliegfhtehPnereesrEsguUyre’isTsupprobriewndeeiBrctldaededem;tCoarnebdeepa;onFnidneitioesfEpltrehemedeinfcattsMetdeesthtthogda;rto3bDwyiMnthogdeemly;aeSraiimrtiu2ml0aet3io0sne,.cittsorisn.sCtaullrerdenctalyp,awciitnydweinllerrgeaycahlruepadtyo m23e%etso1f1E%uroofpeth’se EtoUta’ls eploewcterircidteymdaenmdaanndd (iEsuprroepdeicatnedWthinadt bEyntehregyyeAasrs2o0c3ia0t,ioitns, i2n0st1a7ll)e. dFcoarptahciistytowbilel rteeacchhniucpalltyo 2fe3a%sibolef,Eituriospcer’uscitaoltaflorelnecetwricoitfyfshdoermeacnodnc(EeputrsopaenadndWesiignndsEtnoebrgeydAevsesloocpieadtioinn, o2r0d1e7r)t.oFuotriltihzeisthtoe bdeeetpeecrh,nliacraglelyr feexapsaibnslee,s iat nids cwruincdialpofoternntieawl oofffasrheoarsescuocnhcaespttsheanMd eddeistiegrnrasnteoanb,eAdtelavnetliocpeadndinNoorrdtherSteoauwtialitzeersth(Ee udreoeppeearn, lWarginedr eExnpearngsyeAs sasnodciwatiinodn,p2o0t1e3n)ti.al of areas such as the Mediterranean, Atlantic and North Sea waters Known as three-roll forming (called the pyramid type) or plate bending, is the process of giving a curvature to a sheet/bar/shaped section by bending it between two or three adjustable cylindrical rolls Common applications of this procedure are in making cylinders for pressure tanks, boilers, corrugate pipe, structural sections for submarines, aircraft and nuclear reactors (Altan, et al, 1983). This process is known as a continuous manufacturing process, meaning that local deformation is moving over the entire plate, and at any instant only a small region is being formed. Numerical investigations regarding the effects of the three-roll bending manufacturing process on the plastic strain levels in offshore wind monopiles have been conducted. The results of this work will be accounted for in engineering critical assessments
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