{"id":100091,"date":"2026-02-15T20:17:47","date_gmt":"2026-02-15T20:17:47","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100091"},"modified":"2026-02-15T20:17:47","modified_gmt":"2026-02-15T20:17:47","slug":"fatigue-life-calculator","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/nb\/calculators\/fatigue-life-calculator\/","title":{"rendered":"Kalkulator for utmattelse og levetid | SN-kurve | Basquin-ligning | Gratis nettverkt\u00f8y"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Fatigue Life Calculator\",\"alternateName\":[\"S-N Curve Calculator\",\"Basquin Calculator\",\"Cycles to Failure Calculator\"],\"description\":\"Free fatigue life calculator using Basquin equation N = (\u03c3a\/a)^(1\/b). S-N curve approach.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/fatigue-life-calculator\/\",\"applicationCategory\":\"Engineering Calculator\",\"operatingSystem\":\"Any (Web Browser)\",\"offers\":{\"@type\":\"Offer\",\"price\":\"0\",\"priceCurrency\":\"EUR\"},\"creator\":{\"@type\":\"Organization\",\"name\":\"Vibromera\",\"url\":\"https:\/\/vibromera.eu\/\"},\"datePublished\":\"2024-01-01\",\"dateModified\":\"2025-02-14\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[\n{\"@type\":\"Question\",\"name\":\"What is an S-N curve?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"An S-N curve (W\u00f6hler curve) plots stress amplitude (S) versus number of cycles to failure (N) on a log-log scale. It characterizes a material's fatigue behavior and is used to predict fatigue life under cyclic loading.\"}},\n{\"@type\":\"Question\",\"name\":\"What is the Basquin equation?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The Basquin equation \u03c3a = a\u00b7N^b (or equivalently N = (\u03c3a\/a)^(1\/b)) describes the S-N curve in the high-cycle fatigue regime. Constants 'a' and 'b' are determined from material testing. Typical b values range from -0.05 to -0.12.\"}},\n{\"@type\":\"Question\",\"name\":\"What is the endurance limit?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The endurance limit (Se) is the stress amplitude below which a material can theoretically withstand infinite cycles without failure. Steel and titanium typically exhibit an endurance limit at ~10\u2076-10\u2077 cycles, roughly 40-50% of UTS. Aluminum and copper do not have a true endurance limit.\"}},\n{\"@type\":\"Question\",\"name\":\"What factors affect fatigue life?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Surface finish, stress concentration (notches, holes), mean stress, temperature, environment (corrosion), loading type (bending vs axial vs torsion), residual stresses, and material microstructure all significantly affect fatigue life.\"}},\n{\"@type\":\"Question\",\"name\":\"How accurate is the S-N approach?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The S-N approach is widely used for high-cycle fatigue (>10\u2074 cycles) and provides reasonable estimates. However, scatter in fatigue data is large \u2014 life predictions typically have a factor of 2-3 uncertainty. For critical applications, use probabilistic approaches and testing.\"}}\n]}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[\n{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vibromera.eu\/\"},\n{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Calculators\",\"item\":\"https:\/\/vibromera.eu\/calculators\/\"},\n{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Fatigue Life Calculator\",\"item\":\"https:\/\/vibromera.eu\/calculators\/fatigue-life-calculator\/\"}\n]}\n<\/script>\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.googleapis.com\">\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.gstatic.com\" crossorigin>\n\n<link 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0.15s}.vc-related-link:hover{border-color:var(--vc-accent);color:var(--vc-accent);background:var(--vc-accent-light)}.vc-promo{margin-top:24px;padding:20px;background:linear-gradient(135deg,var(--vc-accent-light),var(--vc-surface));border:1px solid var(--vc-border);border-radius:var(--vc-radius-lg);display:flex;align-items:center;gap:16px}.vc-promo-text{flex:1;font-size:14px;color:var(--vc-ink-secondary)}.vc-promo-text strong{color:var(--vc-ink)}.vc-promo-link{padding:8px 20px;font-size:13px;font-weight:700;color:#fff;background:var(--vc-accent);border-radius:var(--vc-radius);text-decoration:none;white-space:nowrap;transition:background 0.15s}.vc-promo-link:hover{background:var(--vc-accent-hover)}.vc-footer{text-align:center;padding:32px 16px;font-size:13px;color:var(--vc-ink-muted)}.vc-footer a{color:var(--vc-accent);text-decoration:none}.vc-footer a:hover{text-decoration:underline}.vc-footer-links{margin-top:8px;font-size:12px}.vc-footer-links a{margin:0 8px}@media print{.vc-section-body{max-height:none!important}.vc-faq-a{max-height:none!important}.vc-results{max-height:none!important;padding:24px!important}.vc-copy-btn,.vc-section-chevron,.vc-faq-chevron,.vc-presets,.vc-promo{display:none!important}}\n.vc-viz{margin:20px 0;background:var(--vc-surface);border:1px solid var(--vc-border-light);border-radius:var(--vc-radius);padding:16px;overflow:hidden}.vc-viz svg{width:100%;height:auto;display:block}.vc-viz-title{font-family:var(--vc-mono);font-size:11px;font-weight:500;letter-spacing:0.1em;text-transform:uppercase;color:var(--vc-ink-muted);margin-bottom:12px}\n<\/style>\n\n<div class=\"vc-calculator\" id=\"vc-fatigue-life\">\n<header class=\"vc-header\">\n    <p class=\"vc-header-eyebrow\">Free Engineering Tool<\/p>\n    <h1 class=\"vc-header-title\">Fatigue Life Calculator<\/h1>\n    <p class=\"vc-header-subtitle\">Estimate cycles to failure using the S-N curve approach and Basquin equation. Enter stress amplitude, material constants, and endurance limit.<\/p>\n    <div class=\"vc-badges\"><span class=\"vc-badge\">S-N Curve<\/span><span class=\"vc-badge\">Basquin Equation<\/span><span class=\"vc-badge\">#170<\/span><\/div>\n<\/header>\n\n<div class=\"vc-card\">\n    <form class=\"vc-form\" id=\"vc-form\" autocomplete=\"off\">\n        <div class=\"vc-form-grid\">\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-Sa\">Stress Amplitude \u03c3_a <span class=\"vc-label-hint\">(MPa)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-Sa\" inputmode=\"decimal\" step=\"any\" min=\"0\" placeholder=\"e.g. 200\" value=\"200\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-Se\">Endurance Limit Se <span class=\"vc-label-hint\">(MPa)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-Se\" inputmode=\"decimal\" step=\"any\" min=\"0\" placeholder=\"e.g. 210\" value=\"210\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-UTS\">Ultimate Tensile Strength <span class=\"vc-label-hint\">(MPa)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-UTS\" inputmode=\"decimal\" step=\"any\" min=\"0\" placeholder=\"e.g. 500\" value=\"500\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-Ne\">Endurance Cycle Limit <span class=\"vc-label-hint\">(cycles)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-Ne\" inputmode=\"decimal\" step=\"any\" min=\"1\" placeholder=\"e.g. 1e6\" value=\"1000000\">\n            <\/div>\n        <\/div>\n        <div class=\"vc-presets\">\n            <div class=\"vc-presets-label\">Quick presets<\/div>\n            <button type=\"button\" class=\"vc-preset-btn\" data-Sa=\"180\" data-Se=\"210\" data-UTS=\"500\" data-Ne=\"1000000\">Steel UTS=500, \u03c3a=180<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-Sa=\"250\" data-Se=\"300\" data-UTS=\"700\" data-Ne=\"1000000\">Alloy Steel \u03c3a=250<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-Sa=\"120\" data-Se=\"130\" data-UTS=\"310\" data-Ne=\"500000000\">Al 6061 \u03c3a=120<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-Sa=\"350\" data-Se=\"400\" data-UTS=\"1040\" data-Ne=\"1000000\">4340 Steel \u03c3a=350<\/button>\n        <\/div>\n    <\/form>\n    <div class=\"vc-results\" id=\"vc-results\">\n        <div class=\"vc-results-head\"><h2 class=\"vc-results-title\">Results<\/h2><button type=\"button\" class=\"vc-copy-btn\" id=\"vc-copy-btn\"><svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg> Copy<\/button><\/div>\n        <div class=\"vc-result-grid\">\n            <div class=\"vc-rcard vc-rcard-primary\"><div class=\"vc-rcard-label\">Cycles to Failure N<\/div><div class=\"vc-rcard-value\" id=\"vc-r-N\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Basquin Exponent b<\/div><div class=\"vc-rcard-value\" id=\"vc-r-b\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Basquin Coefficient a (\u03c3&#8217;f)<\/div><div class=\"vc-rcard-value\" id=\"vc-r-a\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Assessment<\/div><div class=\"vc-rcard-value\" id=\"vc-r-status\">\u2014<\/div><\/div>\n        <\/div>\n        <div class=\"vc-viz\" id=\"vc-viz\"><div class=\"vc-viz-title\">S\u2013N Curve (W\u00f6hler Diagram)<\/div><div id=\"vc-viz-svg\"><\/div><\/div>\n    <\/div>\n<\/div>\n\n<div class=\"vc-section vc-open\" id=\"vc-sec-theory\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"true\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\ud83d\udcd8<\/span><span class=\"vc-section-title\">Theory &amp; Formulas<\/span><\/span><svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button>\n    <div class=\"vc-section-body\"><div class=\"vc-section-inner vc-theory\">\n        <h3>Basquin Equation (High-Cycle Fatigue)<\/h3>\n        <div class=\"vc-formula-box\" id=\"vc-katex-1\"><\/div>\n        <div class=\"vc-formula-box\" id=\"vc-katex-2\"><\/div>\n        <p>The constants <strong>a<\/strong> (fatigue strength coefficient) and <strong>b<\/strong> (fatigue strength exponent) are derived from two known points on the S-N curve: (N=1000, \u03c3\u22480.9\u00b7UTS) and (Ne, Se).<\/p>\n        <div class=\"vc-warning-box\"><p style=\"margin:0;font-size:14px;color:var(--vc-ink-secondary);\"><strong>\u26a0\ufe0f Note:<\/strong> If \u03c3_a \u2264 Se, the component has infinite life (below endurance limit). This calculator uses the simplified Basquin approach and does not account for mean stress (Goodman\/Gerber) or surface finish corrections.<\/p><\/div>\n    <\/div><\/div>\n<\/div>\n\n<div class=\"vc-section\" id=\"vc-sec-related\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\ud83d\udd17<\/span><span class=\"vc-section-title\">Related Calculators<\/span><\/span><svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button>\n    <div class=\"vc-section-body\"><div class=\"vc-section-inner\"><div class=\"vc-related\">\n        <a class=\"vc-related-link\" href=\"\/calculators\/safety-factor-calculator\/\">Safety Factor<\/a>\n        <a class=\"vc-related-link\" href=\"\/calculators\/stress-calculator\/\">Stress Calculator<\/a>\n        <a class=\"vc-related-link\" href=\"\/calculators\/stress-concentration-factor\/\">Stress Concentration<\/a>\n    <\/div><\/div><\/div>\n<\/div>\n\n<div class=\"vc-section\" id=\"vc-sec-faq\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\u2753<\/span><span class=\"vc-section-title\">Frequently Asked Questions<\/span><\/span><svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button>\n    <div class=\"vc-section-body\"><div class=\"vc-section-inner\"><div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div><\/div><\/div>\n<\/div>\n\n<div class=\"vc-promo\"><div class=\"vc-promo-text\"><strong>Vibromera \u2014 Portable Balancing &amp; Vibration Analysis<\/strong><br>Professional field balancing instruments. Used in 50+ countries.<\/div><a class=\"vc-promo-link\" href=\"https:\/\/vibromera.eu\/\" target=\"_blank\" rel=\"noopener\">Learn More<\/a><\/div>\n<footer class=\"vc-footer\"><p>\u00a9 2024\u20132025 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a> \u2014 Engineering Calculators<\/p><p style=\"font-size:12px;margin-top:4px;\">Fatigue life S-N approach. Last updated: February 2025<\/p><div class=\"vc-footer-links\"><a href=\"\/calculators\/engineering-calculators\/\">All Calculators<\/a><a href=\"https:\/\/vibromera.eu\/contacts\/\">Contact<\/a><\/div><\/footer>\n<\/div>\n\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.js\"><\/script>\n<script>\n(function(){\n'use strict';\nvar SLUG='fatigue-life-calculator';\nfunction $(id){return document.getElementById(id)}\nfunction fmt(n,d){if(isNaN(n)||!isFinite(n))return'\u2014';var f=n.toFixed(d===undefined?2:d);return f.replace(\/(\\.\\d*?)0+$\/,'$1').replace(\/\\.$\/,'')}\nfunction fmtSci(n){if(isNaN(n)||!isFinite(n))return'\u2014';if(n>=1e9)return fmt(n\/1e9,2)+' \u00d7 10\u2079';if(n>=1e6)return fmt(n\/1e6,2)+' \u00d7 10\u2076';if(n>=1e3)return fmt(n\/1e3,1)+' \u00d7 10\u00b3';return fmt(n,0)}\n\nfunction drawSNCurve(Sa,Se,UTS,Ne,calcN){\n    var el=$('vc-viz-svg');if(!el)return;\n    var W=600,H=300,ml=65,mr=25,mt=25,mb=40,pw=W-ml-mr,ph=H-mt-mb;\n    var lMin=3,lMax=8,sup=['\\u00b3','\\u2074','\\u2075','\\u2076','\\u2077','\\u2078'];\n    function xP(l){return ml+(l-lMin)\/(lMax-lMin)*pw}\n    function yP(s){return mt+ph-s\/UTS*ph}\n    var o='<svg viewBox=\"0 0 600 300\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\">';\n    for(var g=lMin;g<=lMax;g++){var gx=xP(g);\n        o+='<line x1=\"'+gx+'\" y1=\"'+mt+'\" x2=\"'+gx+'\" y2=\"'+(mt+ph)+'\" stroke=\"#e8e4dd\" stroke-width=\"0.5\"\/>';\n        o+='<text x=\"'+gx+'\" y=\"'+(H-5)+'\" text-anchor=\"middle\" font-family=\"var(--vc-mono)\" font-size=\"10\" fill=\"#8a857e\">10'+sup[g-3]+'<\/text>';}\n    for(var i=0;i<=5;i++){var yv=UTS*i\/5,gy=yP(yv);\n        o+='<line x1=\"'+ml+'\" y1=\"'+gy+'\" x2=\"'+(ml+pw)+'\" y2=\"'+gy+'\" stroke=\"#e8e4dd\" stroke-width=\"0.5\"\/>';\n        o+='<text x=\"'+(ml-5)+'\" y=\"'+(gy+4)+'\" text-anchor=\"end\" font-family=\"var(--vc-mono)\" font-size=\"10\" fill=\"#8a857e\">'+Math.round(yv)+'<\/text>';}\n    var N1=1000,S1=.9*UTS,bv=Math.log(S1\/Se)\/Math.log(N1\/Ne),av=S1\/Math.pow(N1,bv),lNe=Math.log10(Ne),pts='';\n    for(var j=0;j<=80;j++){var lj=3+(Math.min(lNe,lMax)-3)*j\/80,Sj=av*Math.pow(Math.pow(10,lj),bv);\n        if(Sj>UTS)Sj=UTS;pts+=xP(lj).toFixed(1)+','+yP(Sj).toFixed(1)+' ';}\n    o+='<polyline points=\"'+pts+'\" fill=\"none\" stroke=\"var(--vc-accent)\" stroke-width=\"2.5\" stroke-linecap=\"round\"\/>';\n    if(lNe<lMax){\n        o+='<line x1=\"'+xP(lNe).toFixed(1)+'\" y1=\"'+yP(Se).toFixed(1)+'\" x2=\"'+xP(lMax)+'\" y2=\"'+yP(Se).toFixed(1)+'\" stroke=\"var(--vc-green)\" stroke-width=\"2\" stroke-dasharray=\"6,4\"\/>';\n        o+='<text x=\"'+(xP(lMax)-2)+'\" y=\"'+(yP(Se)-6)+'\" text-anchor=\"end\" font-family=\"var(--vc-mono)\" font-size=\"9\" fill=\"var(--vc-green)\">Se = '+Math.round(Se)+' MPa<\/text>';}\n    if(Sa<=Se){var ox=xP(7),oy=yP(Sa);\n        o+='<circle cx=\"'+ox+'\" cy=\"'+oy+'\" r=\"6\" fill=\"var(--vc-green)\" stroke=\"#fff\" stroke-width=\"2\"\/>';\n        o+='<text x=\"'+(ox+10)+'\" y=\"'+(oy+4)+'\" font-family=\"var(--vc-font)\" font-size=\"11\" font-weight=\"600\" fill=\"var(--vc-green)\">\\u221e Infinite life<\/text>';}\n    else if(isFinite(calcN)&&calcN>0){var ln=Math.log10(calcN),ox2=xP(Math.max(lMin,Math.min(lMax,ln))),oy2=yP(Sa);\n        o+='<line x1=\"'+ox2.toFixed(1)+'\" y1=\"'+oy2.toFixed(1)+'\" x2=\"'+ox2.toFixed(1)+'\" y2=\"'+(mt+ph)+'\" stroke=\"var(--vc-accent)\" stroke-width=\"1\" stroke-dasharray=\"3,3\" opacity=\"0.5\"\/>';\n        o+='<line x1=\"'+ml+'\" y1=\"'+oy2.toFixed(1)+'\" x2=\"'+ox2.toFixed(1)+'\" y2=\"'+oy2.toFixed(1)+'\" stroke=\"var(--vc-accent)\" stroke-width=\"1\" stroke-dasharray=\"3,3\" opacity=\"0.5\"\/>';\n        o+='<circle cx=\"'+ox2.toFixed(1)+'\" cy=\"'+oy2.toFixed(1)+'\" r=\"6\" fill=\"var(--vc-accent)\" stroke=\"#fff\" stroke-width=\"2\"\/>';\n        if(ln>=lMin&&ln<=lMax){o+='<text x=\"'+(ox2+10)+'\" y=\"'+(oy2-8)+'\" font-family=\"var(--vc-font)\" font-size=\"10\" font-weight=\"600\" fill=\"var(--vc-accent)\">N = '+fmtSci(calcN)+'<\/text>';}}\n    o+='<line x1=\"'+ml+'\" y1=\"'+mt+'\" x2=\"'+ml+'\" y2=\"'+(mt+ph)+'\" stroke=\"var(--vc-ink)\" stroke-width=\"1.5\"\/>';\n    o+='<line x1=\"'+ml+'\" y1=\"'+(mt+ph)+'\" x2=\"'+(ml+pw)+'\" y2=\"'+(mt+ph)+'\" stroke=\"var(--vc-ink)\" stroke-width=\"1.5\"\/>';\n    o+='<text x=\"'+(ml+pw\/2)+'\" y=\"'+(H-1)+'\" text-anchor=\"middle\" font-family=\"var(--vc-font)\" font-size=\"10\" fill=\"var(--vc-ink-secondary)\">Cycles to failure N<\/text>';\n    o+='<text x=\"14\" y=\"'+(mt+ph\/2)+'\" text-anchor=\"middle\" font-family=\"var(--vc-font)\" font-size=\"10\" fill=\"var(--vc-ink-secondary)\" transform=\"rotate(-90,14,'+(mt+ph\/2)+')\">\\u03c3 Stress (MPa)<\/text>';\n    o+='<\/svg>';el.innerHTML=o;}\n\nfunction calculate(){\n    var Sa=parseFloat($('vc-Sa').value),Se=parseFloat($('vc-Se').value),UTS=parseFloat($('vc-UTS').value),Ne=parseFloat($('vc-Ne').value);\n    if(!Sa||Sa<=0||!Se||Se<=0||!UTS||UTS<=0||!Ne||Ne<=0){$('vc-results').classList.remove('vc-visible');return}\n\n    \/\/ If below endurance limit\n    if(Sa<=Se){\n        $('vc-r-N').innerHTML='\u221e <span class=\"vc-rcard-unit\">(infinite life)<\/span>';\n        $('vc-r-b').innerHTML='\u2014';\n        $('vc-r-a').innerHTML='\u2014';\n        $('vc-r-status').innerHTML='<span style=\"font-size:14px;color:var(--vc-green)\">\u2705 Below endurance limit \u2014 infinite life<\/span>';\n        drawSNCurve(Sa,Se,UTS,Ne,Infinity);$('vc-results').classList.add('vc-visible');return;\n    }\n\n    \/\/ Basquin: two points \u2014 (N1=1000, S1=0.9*UTS) and (Ne, Se)\n    var N1=1000, S1=0.9*UTS;\n    var b=Math.log(S1\/Se)\/Math.log(N1\/Ne);\n    var a=S1\/Math.pow(N1,b);\n\n    \/\/ N = (Sa\/a)^(1\/b)\n    var N=Math.pow(Sa\/a,1\/b);\n\n    var status;\n    if(N>1e7)status='<span style=\"font-size:14px;color:var(--vc-green)\">\u2705 High-cycle fatigue \u2014 long life<\/span>';\n    else if(N>1e5)status='<span style=\"font-size:14px;color:var(--vc-yellow)\">\u26a0\ufe0f Moderate fatigue life<\/span>';\n    else status='<span style=\"font-size:14px;color:var(--vc-red)\">\u274c Low fatigue life \u2014 review design<\/span>';\n\n    $('vc-r-N').innerHTML=fmtSci(N)+' <span class=\"vc-rcard-unit\">cycles<\/span>';\n    $('vc-r-b').innerHTML=fmt(b,4);\n    $('vc-r-a').innerHTML=fmt(a,1)+' <span class=\"vc-rcard-unit\">MPa<\/span>';\n    $('vc-r-status').innerHTML=status;\n    $('vc-results').classList.add('vc-visible');\n    drawSNCurve(Sa,Se,UTS,Ne,N);\n\n    saveHistory({Sa:Sa,Se:Se,UTS:UTS,N:N,_summary:'N='+fmtSci(N)+', \u03c3a='+Sa+' MPa'});\n}\n\ndocument.querySelectorAll('.vc-preset-btn').forEach(function(btn){btn.addEventListener('click',function(e){e.preventDefault();\n    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fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><polyline points=\"20 6 9 17 4 12\"\/><\/svg> Copied!';setTimeout(function(){b.classList.remove('vc-copied');b.innerHTML='<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg> Copy';},2000)})}\n});\n\ndocument.querySelectorAll('.vc-section-toggle').forEach(function(btn){btn.addEventListener('click',function(){var s=this.closest('.vc-section');s.classList.toggle('vc-open');this.setAttribute('aria-expanded',s.classList.contains('vc-open'))})});\n\nvar faqData=[\n    {q:'What is an S-N curve?',a:'<p>An S-N (W\u00f6hler) curve plots stress amplitude vs cycles to failure on log-log scale. It characterizes a material\\'s fatigue behavior.<\/p>'},\n    {q:'What is the Basquin equation?',a:'<p>\u03c3a = a\u00b7N^b describes the S-N curve in high-cycle fatigue. Constants a and b are from material testing. Typical b: -0.05 to -0.12.<\/p>'},\n    {q:'What is the endurance limit?',a:'<p>The stress amplitude below which infinite life is expected. Steel: ~40-50% of UTS at 10\u2076 cycles. Aluminum has no true endurance limit.<\/p>'},\n    {q:'What factors affect fatigue life?',a:'<p>Surface finish, stress concentration, mean stress, temperature, corrosion, loading type, residual stress, and microstructure.<\/p>'},\n    {q:'How accurate is the S-N approach?',a:'<p>Reasonable for high-cycle fatigue (>10\u2074 cycles). Scatter is large \u2014 factor of 2-3 uncertainty. Use probabilistic methods for critical applications.<\/p>'}\n];\nvar fl=$('vc-faq-list');faqData.forEach(function(f){fl.innerHTML+='<div class=\"vc-faq-item\"><button type=\"button\" class=\"vc-faq-q\"><span>'+f.q+'<\/span><svg class=\"vc-faq-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button><div class=\"vc-faq-a\"><div class=\"vc-faq-a-inner\">'+f.a+'<\/div><\/div><\/div>'});\nfl.addEventListener('click',function(e){var b=e.target.closest('.vc-faq-q');if(!b)return;b.closest('.vc-faq-item').classList.toggle('vc-open')});\n\nfunction saveHistory(entry){var key='vc_history_'+SLUG;var arr=[];try{arr=JSON.parse(localStorage.getItem(key))||[]}catch(e){}entry._ts=new Date().toISOString();arr.unshift(entry);if(arr.length>10)arr=arr.slice(0,10);try{localStorage.setItem(key,JSON.stringify(arr))}catch(e){}}\n\nfunction renderFormulas(){try{\n    katex.render('\\\\sigma_a = a \\\\cdot N^b',$('vc-katex-1'),{displayMode:true,throwOnError:false});\n    katex.render('N = \\\\left(\\\\frac{\\\\sigma_a}{a}\\\\right)^{1\/b}',$('vc-katex-2'),{displayMode:true,throwOnError:false});\n}catch(e){}}\n\nfunction init(){renderFormulas();calculate()}\nif(document.readyState==='loading'){document.addEventListener('DOMContentLoaded',init)}else{init()}\n})();\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>Gratis kalkulator for utmattingslevetid p\u00e5 nett ved bruk av SN-kurve og Basquin-ligning. Skriv inn spenningsamplitude, utholdenhetsgrense, UTS og Basquin-konstanter for \u00e5 beregne sykluser til brudd.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100091","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100091","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":1,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100091\/revisions"}],"predecessor-version":[{"id":100424,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100091\/revisions\/100424"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/media?parent=100091"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/categories?post=100091"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/tags?post=100091"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}