FEATool Multiphysics
v1.17.0
Finite Element Analysis Toolbox
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EX_SPANNER STL geometry import and stress calculation of a spanner.
[ FEA, OUT ] = EX_SPANNER( VARARGIN ) Example to import a STL CAD geometry and calculate displacements on a fixed spanner. The load force may be distributed in the tangential load direction with the force fraction parameter FRAC.
Accepts the following property/value pairs.
Input Value/{Default} Description ----------------------------------------------------------------------------------- E scalar {190e3} Modulus of elasticity [N/mm^2] nu scalar {0.29} Poissons ratio force scalar {1000} Load force [N] frac scalar {0} Fraction of stress against pulling direction sfun string {sflag1} Shape function for displacements iplot scalar 0/{1} Plot solution (=1) . Output Value/(Size) Description ----------------------------------------------------------------------------------- fea struct Problem definition struct out struct Output struct
cOptDef = { 'E', 190e3; 'nu', 0.29; 'force', 1000; 'frac', 0; 'sfun', 'sflag1'; 'iplot', 1; 'fid', 1 }; [got,opt] = parseopt(cOptDef,varargin{:}); % Define scaling factor m to mm. USE_METERS = true; s = double( ~USE_METERS + USE_METERS*1e-3 ); % Import (and scale) grid. fea.sdim = {'x','y','z'}; fea.geom = impexp_stl( 'spanner1.stl', 'import', [], 'solid', 2, 'extend', 0 ); fea.grid = gridgen( fea, 'hmax', 5, 'gridgen', 'robust', 'fid', opt.fid ); fea.grid.p = fea.grid.p*s; % Add linear elasticity physics mode and define material parameters. fea = addphys( fea, @linearelasticity ); fea.phys.el.sfun = { opt.sfun opt.sfun opt.sfun }; fea.phys.el.eqn.coef{1,end} = { opt.nu }; fea.phys.el.eqn.coef{2,end} = { opt.E/s^2 }; % Set all boundaries to no load per default. n_bdr = max(fea.grid.b(3,:)); bc_sel = cell(3,n_bdr); [bc_sel{:}] = deal(0); % Fix all displacements on mandible boundaries. i_fix = [13 14]; i_force = [3 1]; faxis = [1 3]; [bc_sel{:,i_fix}] = deal(1); fea.phys.el.bdr.coef{5} = bc_sel; % Apply force for x > 140 mm. force = opt.force/(6*s*80*s); fea.phys.el.bdr.coef{7}{faxis(1),i_force(1)} = ['-',num2str((1-opt.frac)*force),'*(y>140*',num2str(s),')']; fea.phys.el.bdr.coef{7}{faxis(2),i_force(2)} = [num2str(opt.frac*force),'*(y>140*',num2str(s),')']; % Parse and solve problem. fea = parsephys(fea); fea = parseprob(fea); fea.sol.u = solvestat( fea, 'fid', opt.fid, 'icub', 1+str2num(strrep(opt.sfun,'sflag','')) ); % Postprocessing. if( opt.iplot>0 ) subplot(1,2,1) postplot( fea, 'surfexpr', ['sqrt(u^2+v^2+w^2)/',num2str(s)] ) view([30 20]) title('Total displacement (mm)') subplot(1,2,2) DSCALE = 5; dp = zeros(size(fea.grid.p)); for i=1:3 dp(i,:) = DSCALE*evalexpr( fea.dvar{i}, fea.grid.p, fea ); end fea_disp.grid = fea.grid; fea_disp.grid.p = fea_disp.grid.p + dp; plotgrid( fea_disp ) title(['Displacement plot']) view([30 20]) end % Error checking. u = fea.sol.u(unique(fea.eqn.dofm{1}(:)))/s; v = fea.sol.u(unique(fea.eqn.ndof(1)+fea.eqn.dofm{2}(:)))/s; w = fea.sol.u(unique(sum(fea.eqn.ndof(1:2))+fea.eqn.dofm{3}(:)))/s; out.disp = sqrt( u.^2 + v.^2 + w.^2 ); out.pass = nan; if( ~(got.frac || got.E || got.nu || got.force) ) out.pass = abs( max(out.disp) - 2.5 )/2.5 < 0.1; end if( nargout==0 ) clear fea out else fea.grid.p = fea.grid.p/s; end