Image:Damped spring.gif

Illustration of en:Damping

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Source	self-made with en:Matlab. Converted to gif animation with the en:ImageMagick convert tool (see the specific command later in the code).
Date	02:42, 24 June 2007 (UTC)
Author	Oleg Alexandrov
Permission (Reusing this image)	see below
Other versions	Harmonic version

I, the copyright holder of this work, hereby release it into the public domain. This applies worldwide. In case this is not legally possible: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law. Afrikaans | Alemannisch | Aragonés | العربية | Asturianu | Български | Català | Česky | Cymraeg | Dansk | Deutsch | Eʋegbe | Ελληνικά | English | Español | Esperanto | Euskara | Estremeñu | فارسی | Français | Galego | 한국어 | हिन्दी | Hrvatski | Ido | Bahasa Indonesia | Íslenska | Italiano | עברית | Kurdî / كوردی | Latina | Lietuvių | Latviešu | Magyar | Македонски | Bahasa Melayu | Nederlands | ‪Norsk (bokmål)‬ | ‪Norsk (nynorsk)‬ | 日本語 | Polski | Português | Ripoarisch | Română | Русский | Shqip | Slovenčina | Slovenščina | Српски / Srpski | Svenska | ไทย | Tagalog | Türkçe | Українська | Tiếng Việt | Walon | ‪中文(简体)‬ | ‪中文(繁體)‬ | zh-yue-hant | +/-

[edit] Source code

% Illustration of a damped spring

function main()

% colors
   black =    [0, 0, 0];
   white    = 0.99*[1, 1, 1];
   cobalt   = [0        71      171]/256;
   pblue    = [0        49      83]/256;
   tene     = [205      87      0]/256;
   wall_color   = pblue;
   spring_color = cobalt;
   mass_color    = tene;
   a=0.65; bmass_color   = a*mass_color+(1-a)*black;
   % linewidth and fontsize
   lw=2;
   fs=20;

   ww = 0.5;  % wall width
   ms = 0.25; % the size of the mass        
   sw=0.1;    % spring width
   curls = 8;

   A = 0.45; % the amplitude of spring oscillations
   B = -1; % the y coordinate of the base state (the origin is higher, at the wall)

   %  Each of the small lines has length l
   l = 0.05;

   N = 15;  % times per oscillation 
   No = 4; % number of oscillations
   damping = 0.1; % controls the damping
   for i = 1:(N*No+5)

      % set up the plotting window
      figure(1); clf; hold on; axis equal; axis off;

   
      t = 2*pi*(i-1)/(N-0)+pi/2; % current time
      H= A*exp(-damping*t)*sin(t) +  B;      % position of the mass

      % plot the spring from Start to End
      Start = [0, 0]; End = [0, H];
      [X, Y]=do_plot_spring(Start, End, curls, sw);
      plot(X, Y, 'linewidth', lw, 'color', spring_color); 

      % Here we cheat. We modify the point B so that the mass is attached exactly at the end of the
      % spring. This should not be necessary. I am too lazy to to the exact calculation.
      K = length(X); End(1) = X(K); End(2) = Y(K);
            
      % plot the wall from which the spring is hanging
      plot_wall(-ww/2, ww/2, l, lw, wall_color);

      % plot the mass at the end of the spring
      X=[-ms/2 ms/2 ms/2 -ms/2 -ms/2 ms/2]+End(1); Y=[0 0 -ms -ms 0 0]+End(2);
      H=fill(X, Y, mass_color, 'EdgeColor', bmass_color, 'linewidth', lw);

          
          % the bounding box
          Sx = -0.4*ww;  Sy = B-A*exp(-damping*3*pi/2)-ms+0.05; 
          Lx = 0.4*ww+l; Ly=l;
          axis([Sx, Lx, Sy, Ly]);
          plot(Sx, Sy, '*', 'color', white); % a hack to avoid a saveas to eps bug
          
      saveas(gcf, sprintf('Spring_frame%d.eps', 1000+i), 'psc2') %save the current frame
      disp(sprintf('Spring_frame%d', 1000+i)); %show the frame number we are at
      
      pause(0.1);
      
   end

% The following command was used to create the animated figure.    
% convert -antialias -loop 10000  -delay 7 -compress LZW Spring_frame10* Damped_spring.gif
   

function [X, Y]=do_plot_spring(A, B, curls, sw);
%  plot a 3D spring, then project it onto 2D. theta controls the angle of projection.
%  The string starts at A and ends at B

   % will rotate by theta when projecting from 1D to 2D
   theta=pi/6;
   Npoints = 500;
   
   % spring length
   D = sqrt((A(1)-B(1))^2+(A(2)-B(2))^2);
   
   X=linspace(0, 1, Npoints);

   XX = linspace(-pi/2, 2*pi*curls+pi/2, Npoints);
   Y=-sw*cos(XX);
   Z=sw*sin(XX);
   
%  b gives the length of the small straight segments at the ends
%  of the spring (to which the wall and the mass are attached)
   b= 0.05; 

% stretch the spring in X to make it of length D - 2*b
   N = length(X);
   X = (D-2*b)*(X-X(1))/(X(N)-X(1));
   
% shift by b to the rigth and add the two small segments of length b
   X=[0, X+b X(N)+2*b]; Y=[Y(1) Y Y(N)]; Z=[Z(1) Z Z(N)]; 

   % project the 3D spring to 2D
   M=[cos(theta) sin(theta); -sin(theta) cos(theta)];
   N=length(X);
   for i=1:N;
      V=M*[X(i), Z(i)]';
      X(i)=V(1); Z(i)=V(2);
   end

%  shift the spring to start from 0
   X = X-X(1);
   
% now that we have the horisontal spring (X, Y) of length D,
% rotate and translate it to go from A to B
   Theta = atan2(B(2)-A(2), B(1)-A(1));
   M=[cos(Theta) -sin(Theta); sin(Theta) cos(Theta)];

   N=length(X);
   for i=1:N;
      V=M*[X(i), Y(i)]'+A';
      X(i)=V(1); Y(i)=V(2);
   end

function plot_wall(S, E, l, lw, wall_color)

%  Plot a wall from S to E.
   no=20; spacing=(E-S)/(no-1);
   
   plot([S, E], [0, 0], 'linewidth', 1.8*lw, 'color', wall_color);

   V=l*(0:0.1:1);

   for i=0:(no-1)
      plot(S+ i*spacing + V, V, 'color', wall_color)
   end

Les pages ci-dessous contiennent cette image :

• Amortissement physique
• Tension transitoire de rétablissement