Динамическая потеря устойчивости стержня при сжатии (простейшая модель) — различия между версиями

  1 	var integrator = VerletIntegrator;
  2   	var t = 0;
  3   	var dt = 0.002;
  4   	var step = 0;
  5   	var timeValue = document.getElementById('timeValue');
  6   	var stepFromBoard = 7;
  7         var displacementData = {'x': [], 'y': []};
  8     var forceData = {'x': [], 'y': []};
  9   	var displacementPlotCanvas = document.getElementById('displacementPlot');
 10   	var forcePlotCanvas = document.getElementById('forcePlot');
 11     var textColor = 'rgb(51, 51, 51)';  
 12   	var weight = undefined;
 13 	var springs = new Array();
 14 	var leftAttachment = undefined;
 15 	var rightAttachment = undefined;
 16 	var middleAttachment = createVerletElement([300, 200],null,Infinity,'isoscales triangle',[16, 10, '-y'],'Turquoise');
 17 	applyInitionalConditions();
 18 	draw();
 19 	function applyInitionalConditions(){
 20 		var displacement = +document.getElementById('displacement').value;
 21 		var velocity = +document.getElementById('velocity').value;
 22 		var stiffness1 = +document.getElementById('stiffness1').value;
 23 		var stiffness2 = +document.getElementById('stiffness2').value;
 24 		var mass = +document.getElementById('mass').value;
 25       	weight = createVerletElement([300, 200 - displacement],null,mass,'square',[20],'BlueViolet');
 26 		leftAttachment = createVerletElement([14, 200],[14 - velocity * dt, 200],Infinity,'isoscales triangle',[16, 10, '-y'],'Turquoise');
 27 		rightAttachment = createVerletElement([586, 200],[586 + velocity * dt, 200],Infinity,'isoscales triangle',[16, 10, '-y'],'Turquoise');
 28       	springs = new Array();
 29 		springs.push(createSpringElement(leftAttachment, weight, null, stiffness1, [12, 12], 'Tomato'));
 30 		springs.push(createSpringElement(rightAttachment, weight, null, stiffness1, [12, 12], 'Tomato'));
 31 		springs.push(createSpringElement(middleAttachment, weight, 0, stiffness2, [3, 8], 'Silver'));
 32     }
 33     function applyPhysics(){
 34 		if(t > 5.12 && keepPlaying){
 35           	keepPlaying = false;
 36             document.getElementById('play').className = 'inactive';
 37             return;
 38       	}
 39       	var deltaX, deltaY, deltalength, diff;
 40 		var force = {'x': 0, 'y': 0};
 41       	var springForceX = 0;
 42       	for(var i = 0; i < springs.length; ++i){
 43           	deltaX = springs[i].end.position.x - springs[i].start.position.x;
 44             deltaY = springs[i].end.position.y - springs[i].start.position.y;
 45             deltalength = Math.sqrt(Math.pow(deltaX, 2) + Math.pow(deltaY, 2));
 46           	if(deltalength){
 47 				diff =  1 - springs[i].freeLength / deltalength;
 48             }else{diff = 0;}
 49             force.y -= springs[i].stiffness * deltaY * diff;
 50           	if(0 == i){
 51               	springForceX = -springs[i].stiffness * deltaX * diff;
 52           	}
 53       	}
 54       	integrator(weight, force, dt);
 55 		integrator(leftAttachment, null, dt);
 56       	integrator(rightAttachment, null, dt);
 57       	
 58       	if(!(step % 5)){
 59 			displacementData.x.push(t);
 60 			displacementData.y.push(200 - weight.position.y);
 61 			forceData.x.push(t);
 62 			forceData.y.push(springForceX);
 63           	plotFromData(displacementPlotCanvas, displacementData, 'y(t)', 'rgb(56, 195, 237)', undefined, textColor);
 64           	plotFromData(forcePlotCanvas, forceData, 'Fx(t)', 'rgb(195, 237, 56)', undefined, textColor);
 65       	} 
 66 		timeValue.textContent = t.toFixed(2);
 67 		++step;
 68     }
 69   	function draw(){
 70 		ctx.clearRect(0, 0, canvas.width, canvas.height);
 71 		for(var i = 0; i < springs.length; ++i){
 72 			springs[i].draw();
 73 		}
 74 		leftAttachment.draw();
 75 		rightAttachment.draw();
 76 		middleAttachment.draw();
 77 		weight.draw();
 78   	}
 79   
 80   	/* Events */
 81   	document.getElementById('play').onclick = function(){
 82       	document.getElementById('conditions').className = 'hide';
 83       	document.getElementById('stand').className = '';
 84     	animate(5);
 85     }
 86 	document.getElementById('displacement').onchange = function(){
 87 		document.getElementById('displacementValue').textContent = (+this.value).toFixed(1);
 88 		applyInitionalConditions();
 89       	draw();
 90   	}
 91 	document.getElementById('velocity').onchange = function(){
 92 		document.getElementById('velocityValue').textContent = (+this.value).toFixed(1);
 93 		applyInitionalConditions();
 94       	draw();
 95   	}
 96 	document.getElementById('stiffness1').onchange = function(){
 97 		document.getElementById('stiffness1Value').textContent = (+this.value).toFixed(1);
 98 		applyInitionalConditions();
 99       	draw();
100   	}
101 	document.getElementById('stiffness2').onchange = function(){
102 		document.getElementById('stiffness2Value').textContent = (+this.value).toFixed(1);
103 		applyInitionalConditions();
104       	draw();
105   	}
106 	document.getElementById('mass').onchange = function(){
107 		document.getElementById('massValue').textContent = (+this.value).toFixed(1);
108 		applyInitionalConditions();
109       	draw();
110   	}
111     function drawSpringElement(){
112         drawSpring(
113           			this.start.position.x,
114           			this.end.position.x,
115           			this.start.position.y,
116           			this.end.position.y,
117           			this.sizes[0],
118           			this.sizes[1],
119           			this.color
120         			);
121     }
122     function drawSpring(xStart, xEnd, yStart, yEnd, n, h, color){
123       	ctx.beginPath();
124         ctx.lineWidth = 2;
125         ctx.strokeStyle = color;
126         var L = xEnd - xStart;
127         var Ly = yEnd - yStart;
128         for (var i = 0; i < n; ++i){
129             var x_st = xStart + L / n * i;
130             var y_st = yStart + Ly / n * i;
131             var x_end = xStart + L / n * (i + 1);
132             var y_end = yStart + Ly / n * (i + 1);
133             var l = x_end - x_st;
134             var ly = y_end - y_st;
135             ctx.beginPath();
136             ctx.bezierCurveTo(x_st, y_st, x_st + l / 4, y_st + ly / 4 +  h, x_st + l / 2, y_st + ly / 2);
137             ctx.bezierCurveTo(x_st + l / 2, y_st + ly / 2, x_st + 3 * l / 4, y_st + 3 * ly / 4 - h, x_st + l, y_st + ly);
138             ctx.stroke();
139         }
140       	ctx.closePath();
141     }