{"id":5267,"date":"2026-04-24T11:49:45","date_gmt":"2026-04-24T09:49:45","guid":{"rendered":"https:\/\/www.traxx-group.com\/en\/?p=5267"},"modified":"2026-08-13T11:36:34","modified_gmt":"2026-08-13T09:36:34","slug":"bolt-load-after-temp-change","status":"publish","type":"post","link":"https:\/\/www.traxx-group.com\/en\/2026\/04\/24\/bolt-load-after-temp-change\/","title":{"rendered":"Bolt Load After Temp Change: Understanding Thermal Effects on Bolted Joints"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"5267\" class=\"elementor elementor-5267\" data-elementor-post-type=\"post\">\n\t\t\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-1ac9e70 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"1ac9e70\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-570a8dc\" data-id=\"570a8dc\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-beac1fe elementor-widget elementor-widget-table-of-contents\" data-id=\"beac1fe\" data-element_type=\"widget\" data-e-type=\"widget\" data-settings=\"{&quot;exclude_headings_by_selector&quot;:[],&quot;no_headings_message&quot;:&quot;Aucun titre n\\u2019a \\u00e9t\\u00e9 trouv\\u00e9 sur cette 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eicon-animation-spin eicon-loading\" aria-hidden=\"true\"><\/i>\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-53bd7c5e elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"53bd7c5e\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-22aa47eb\" data-id=\"22aa47eb\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-5713a140 elementor-widget elementor-widget-heading\" data-id=\"5713a140\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h1 class=\"elementor-heading-title elementor-size-default\">Bolt Load After Temp Change: Understanding Thermal Effects on Bolted Joints<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-75871157 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"75871157\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-bd48c1f\" data-id=\"bd48c1f\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-1496f198 elementor-widget elementor-widget-text-editor\" data-id=\"1496f198\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p data-start=\"455\" data-end=\"1098\">Bolted joints are critical elements in engineering applications, from aerospace and automotive to energy and railway sectors. The preload applied to a bolt ensures the structural integrity of the assembly. However, <strong>temperature changes can significantly affect bolt load.<\/strong> When a bolted assembly is heated or cooled, the bolt and clamped components expand or contract at different rates, depending on their material properties, dimensions, and thermal conductivity. This differential expansion can either increase or decrease the bolt preload, potentially leading to joint loosening, overloading, leakage, or even structural failure.<\/p><p data-start=\"455\" data-end=\"1098\">Consequences of bolt load after temp change :<\/p><p data-start=\"1100\" data-end=\"1534\">Temperature not only affects elastic elongation but can also trigger creep, relaxation, and changes in friction. These effects are particularly pronounced at high service temperatures (above ~250\u00b0C) and during transient thermal states, such as engine start-up, turbine ramp-up, or rapid heating\/cooling cycles. Engineers must understand and anticipate these <a href=\"https:\/\/www.engineersedge.com\/calculators\/bolt_preload_temperature_effects__16230.htm\">thermal impacts<\/a> to maintain safe and reliable bolted assemblies.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-151c8ee7 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"151c8ee7\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-4703e7f1\" data-id=\"4703e7f1\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-4b516c7d elementor-widget elementor-widget-heading\" data-id=\"4b516c7d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Physical mechanisms affecting bolt load after temp change<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-22d01767 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"22d01767\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-67817485\" data-id=\"67817485\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-1fd8ce36 elementor-widget elementor-widget-heading\" data-id=\"1fd8ce36\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Differential Thermal Expansion<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-38e2f42d elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"38e2f42d\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-77ed2d36\" data-id=\"77ed2d36\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-63bcb15e elementor-widget elementor-widget-text-editor\" data-id=\"63bcb15e\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p data-start=\"1931\" data-end=\"2219\">All materials expand or contract with temperature changes, but each material has its own coefficient of thermal expansion (<span class=\"katex\"><span class=\"katex-mathml\">\u03b1<\/span><\/span>). In bolted assemblies, when the bolt, nut, and clamped parts have different <span class=\"katex\"><span class=\"katex-mathml\">\u03b1<\/span><\/span>, temperature changes result in <strong data-start=\"2188\" data-end=\"2218\">variations in bolt preload<\/strong>.<\/p><p data-start=\"2221\" data-end=\"2329\">The approximate change in preload <span class=\"katex\"><span class=\"katex-mathml\">\u0394F<\/span><\/span>\u00a0due to a temperature change <span class=\"katex\"><span class=\"katex-mathml\">\u0394T<\/span><\/span>\u00a0can be expressed as:<\/p><p><span class=\"katex-display\"><span class=\"katex\"><span class=\"katex-mathml\">\u0394F=E\u22c5A\u22c5(\u03b1 bolt\u2212\u03b1 part)\u22c5\u0394<\/span><span class=\"katex-html\" aria-hidden=\"true\"><span class=\"base\"><span class=\"mord mathnormal\">T<\/span><\/span><\/span><\/span><\/span><\/p><p data-start=\"2422\" data-end=\"2428\">Where:<\/p><ul data-start=\"2430\" data-end=\"2667\"><li data-start=\"2430\" data-end=\"2478\"><p data-start=\"2432\" data-end=\"2478\"><span class=\"katex\"><span class=\"katex-mathml\">E<\/span><\/span>\u00a0= Young&rsquo;s modulus of the bolt material<\/p><\/li><li data-start=\"2479\" data-end=\"2523\"><p data-start=\"2481\" data-end=\"2523\"><span class=\"katex\"><span class=\"katex-mathml\">A<\/span><\/span>\u00a0= cross-sectional area of the bolt<\/p><\/li><li data-start=\"2524\" data-end=\"2629\"><p data-start=\"2526\" data-end=\"2629\"><span class=\"katex\"><span class=\"katex-mathml\">\u03b1 bolt, <\/span><span class=\"katex-html\" aria-hidden=\"true\"><span class=\"base\"><span class=\"mord\"><span class=\"mord mathnormal\">\u03b1 <\/span><span class=\"msupsub\"><span class=\"vlist-t vlist-t2\"><span class=\"vlist-r\"><span class=\"vlist\"><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord text mtight\"><span class=\"mord mtight\">part<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span> = thermal expansion coefficients of bolt and clamped parts<\/p><\/li><li data-start=\"2630\" data-end=\"2667\"><p data-start=\"2632\" data-end=\"2667\"><span class=\"katex\"><span class=\"katex-mathml\">\u0394T<\/span><\/span>\u00a0= temperature change<\/p><\/li><\/ul><p data-start=\"2669\" data-end=\"2785\">A bolt with a smaller expansion coefficient than the clamped part will lose preload when heated, and vice versa.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-5b0a4314 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"5b0a4314\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-2461aba9\" data-id=\"2461aba9\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-1002f31 elementor-widget elementor-widget-heading\" data-id=\"1002f31\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Thermal Relaxation and Creep<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-127a2008 elementor-widget elementor-widget-text-editor\" data-id=\"127a2008\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p data-start=\"2830\" data-end=\"3125\">At service temperatures above 250\u00b0C, creep and relaxation phenomena occur in alloyed and construction steels. Even if bolts are preloaded elastically at the service temperature, a portion of the preload relaxes proportionally to the reduction in yield strength of the steel fastener.<\/p><p data-start=\"3127\" data-end=\"3205\">Creep deformation <span class=\"katex\"><span class=\"katex-mathml\">\u03f5<\/span><\/span>\u00a0can be modeled using the <strong data-start=\"3183\" data-end=\"3204\">Norton-Bailey law<\/strong>:<\/p><p><span class=\"katex-display\"><span class=\"katex\"><span class=\"katex-mathml\">\u03f5=A\u22c5\u03c3^n\u22c5(e^\u2212Q\/(RT))<\/span><\/span><\/span><\/p><p data-start=\"3261\" data-end=\"3267\">Where:<\/p><ul data-start=\"3269\" data-end=\"3436\"><li data-start=\"3269\" data-end=\"3300\"><p data-start=\"3271\" data-end=\"3300\"><span class=\"katex\"><span class=\"katex-mathml\">\u03f5<\/span><\/span>= creep strain<\/p><\/li><li data-start=\"3301\" data-end=\"3346\"><p data-start=\"3303\" data-end=\"3346\"><span class=\"katex\"><span class=\"katex-mathml\">A,n,Q<\/span><\/span>\u00a0= material-specific constants<\/p><\/li><li data-start=\"3347\" data-end=\"3378\"><p data-start=\"3349\" data-end=\"3378\"><span class=\"katex\"><span class=\"katex-mathml\">\u03c3<\/span><\/span>\u00a0= applied stress<\/p><\/li><li data-start=\"3379\" data-end=\"3403\"><p data-start=\"3381\" data-end=\"3403\"><span class=\"katex\"><span class=\"katex-mathml\">R<\/span><\/span>\u00a0= gas constant<\/p><\/li><li data-start=\"3404\" data-end=\"3436\"><p data-start=\"3406\" data-end=\"3436\"><span class=\"katex\"><span class=\"katex-mathml\">T<\/span><\/span>\u00a0= absolute temperature<\/p><\/li><\/ul><p data-start=\"3438\" data-end=\"3538\">This deformation gradually reduces bolt tension, potentially causing partial loosening of the joint<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-52ee9299 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"52ee9299\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-2074bfca\" data-id=\"2074bfca\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-83d6abf elementor-widget elementor-widget-heading\" data-id=\"83d6abf\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Friction Variation<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-72286378 elementor-widget elementor-widget-text-editor\" data-id=\"72286378\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p data-start=\"2713\" data-end=\"2743\">Temperature affects the <strong data-start=\"3597\" data-end=\"3621\">friction coefficient<\/strong> between the bolt, nut, and contact surfaces. Lower friction at high temperatures can unintentionally increase preload for a given torque, while higher friction may reduce torque transfer. Torque-based tightening alone is often unreliable under varying thermal conditions.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-91e3004 elementor-widget elementor-widget-heading\" data-id=\"91e3004\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Negative effects of bolt load after temp change<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5909074 elementor-widget elementor-widget-text-editor\" data-id=\"5909074\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p data-start=\"3941\" data-end=\"4259\">Temperature fluctuations cause bolts and parts to expand or contract at different rates, depending on temperature change speed, mass, part size, metal conductivity, and individual material expansion coefficients. These differences create <strong data-start=\"4183\" data-end=\"4205\">preload variations<\/strong>, often peaking during transient temperature states.<\/p><p data-start=\"4261\" data-end=\"4520\">Thermal cycling can also induce <strong data-start=\"4293\" data-end=\"4322\">thermally-induced fatigue<\/strong>, as not all regions expand uniformly. Boundaries between \u201chot\u201d and \u201ccold\u201d areas experience extra stress, potentially causing <strong data-start=\"4448\" data-end=\"4469\">localized fatigue<\/strong>. To minimize preload variations, engineers should:<\/p><ul data-start=\"4522\" data-end=\"4961\"><li data-start=\"4522\" data-end=\"4586\"><p data-start=\"4524\" data-end=\"4586\">Select materials with homogeneous expansion coefficients<\/p><\/li><li data-start=\"4587\" data-end=\"4647\"><p data-start=\"4589\" data-end=\"4647\">Account for preload loss due to creep and relaxation<\/p><\/li><li data-start=\"4648\" data-end=\"4845\"><p data-start=\"4650\" data-end=\"4845\">Follow modern design codes and joint-calculation guidelines, including evaluating mechanical property changes at service temperature, such as aging, precipitation, or heat treatment effects<\/p><\/li><li data-start=\"4846\" data-end=\"4961\"><p data-start=\"4848\" data-end=\"4961\">Ensure that thermal expansion differences do not induce excessive stress in the joint during service cycles<\/p><\/li><\/ul>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-36fc5f42 elementor-widget elementor-widget-image\" data-id=\"36fc5f42\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"768\" height=\"346\" src=\"https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/bolt-load-after-temp-change-engineering-768x346.jpg\" class=\"attachment-medium_large size-medium_large wp-image-5273\" alt=\"engineer measuring bolt load after temp change on a bolted joint\" srcset=\"https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/bolt-load-after-temp-change-engineering-768x346.jpg 768w, https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/bolt-load-after-temp-change-engineering-300x135.jpg 300w, https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/bolt-load-after-temp-change-engineering-1024x462.jpg 1024w, https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/bolt-load-after-temp-change-engineering.jpg 1344w\" sizes=\"(max-width: 768px) 100vw, 768px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-12923e9 elementor-widget elementor-widget-heading\" data-id=\"12923e9\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Mathematical Model for bolt load after temperature change<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-1f560d9 elementor-widget elementor-widget-text-editor\" data-id=\"1f560d9\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p data-start=\"5033\" data-end=\"5180\">The <strong data-start=\"5037\" data-end=\"5056\">final bolt load<\/strong> <span class=\"katex\"><span class=\"katex-mathml\">F final<\/span><span class=\"katex-html\" aria-hidden=\"true\"><span class=\"base\"><span class=\"mord\"><span class=\"msupsub\"><span class=\"vlist-t vlist-t2\"><span class=\"vlist-r\"><span class=\"vlist-s\">\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span> after a temperature change can be estimated by combining thermal expansion, creep, and friction effects:<\/p><p><span class=\"katex-display\"><span class=\"katex\"><span class=\"katex-mathml\">F final=F0+E\u22c5A\u22c5(\u03b1bolt\u2212\u03b1part)\u22c5\u0394T\u2212\u0394Fcreep<\/span><span class=\"katex-html\" aria-hidden=\"true\"><span class=\"base\"><span class=\"mord\"><span class=\"msupsub\"><span class=\"vlist-t vlist-t2\"><span class=\"vlist-r\"><span class=\"vlist-s\">\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/p><ul data-start=\"5309\" data-end=\"5607\"><li data-start=\"5309\" data-end=\"5338\"><p data-start=\"5311\" data-end=\"5338\"><span class=\"katex\"><span class=\"katex-mathml\">F0<\/span><span class=\"katex-html\" aria-hidden=\"true\"><span class=\"base\"><span class=\"mord\"><span class=\"msupsub\"><span class=\"vlist-t vlist-t2\"><span class=\"vlist-r\"><span class=\"vlist-s\">\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span> = initial preload<\/p><\/li><li data-start=\"5339\" data-end=\"5378\"><p data-start=\"5341\" data-end=\"5378\"><span class=\"katex\"><span class=\"katex-mathml\">E<\/span><\/span>\u00a0= Young\u2019s modulus of the bolt<\/p><\/li><li data-start=\"5379\" data-end=\"5416\"><p data-start=\"5381\" data-end=\"5416\"><span class=\"katex\"><span class=\"katex-mathml\">A<\/span><\/span>\u00a0= bolt cross-sectional area<\/p><\/li><li data-start=\"5417\" data-end=\"5496\"><p data-start=\"5419\" data-end=\"5496\"><span class=\"katex\"><span class=\"katex-mathml\">\u03b1bolt,\u03b1part<\/span><span class=\"katex-html\" aria-hidden=\"true\"><span class=\"base\"><span class=\"mord\"><span class=\"msupsub\"><span class=\"vlist-t vlist-t2\"><span class=\"vlist-r\"><span class=\"vlist-s\">\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span> = thermal expansion coefficients<\/p><\/li><li data-start=\"5497\" data-end=\"5534\"><p data-start=\"5499\" data-end=\"5534\"><span class=\"katex\"><span class=\"katex-mathml\">\u0394T<\/span><\/span>= temperature change<\/p><\/li><li data-start=\"5535\" data-end=\"5607\"><p data-start=\"5537\" data-end=\"5607\"><span class=\"katex\"><span class=\"katex-mathml\">\u0394Fcreep<\/span><span class=\"katex-html\" aria-hidden=\"true\"><span class=\"base\"><span class=\"mord\"><span class=\"msupsub\"><span class=\"vlist-t vlist-t2\"><span class=\"vlist-r\"><span class=\"vlist-s\">\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span> = preload loss due to creep and relaxation<\/p><\/li><\/ul><p data-start=\"5609\" data-end=\"5632\"><span style=\"text-decoration: underline;\">Example Application<\/span><\/p><p data-start=\"5634\" data-end=\"5661\">Consider a steel bolt with:<\/p><ul data-start=\"5663\" data-end=\"5868\"><li data-start=\"5663\" data-end=\"5707\"><p data-start=\"5665\" data-end=\"5707\"><span class=\"katex\"><span class=\"katex-mathml\">F0=50 kN<\/span><\/span>\u00a0(initial preload)<\/p><\/li><li data-start=\"5708\" data-end=\"5739\"><p data-start=\"5710\" data-end=\"5739\"><span class=\"katex\"><span class=\"katex-mathml\">E=210\u2009000 MPa<\/span><\/span><\/p><\/li><li data-start=\"5740\" data-end=\"5768\"><p data-start=\"5742\" data-end=\"5768\"><span class=\"katex\"><span class=\"katex-mathml\">A=200\u2009mm\u00b2<\/span><\/span><\/p><\/li><li data-start=\"5769\" data-end=\"5818\"><p data-start=\"5771\" data-end=\"5818\"><span class=\"katex\"><span class=\"katex-mathml\">\u03b1bolt=12\u00d710<span class=\"katex-display\">^<\/span>\u22126 \/\u00b0C<\/span><\/span><\/p><\/li><li data-start=\"5819\" data-end=\"5868\"><p data-start=\"5821\" data-end=\"5868\"><span class=\"katex\"><span class=\"katex-mathml\">\u03b1part=18\u00d710<span class=\"katex-display\">^<\/span>\u22126\/\u00b0C<\/span><\/span><\/p><\/li><\/ul><p data-start=\"5870\" data-end=\"6063\">If the assembly experiences a temperature increase of <span class=\"katex\"><span class=\"katex-mathml\">\u0394T=100\u00b0C<\/span><\/span>\u00a0and a creep-induced preload loss of <span class=\"katex\"><span class=\"katex-mathml\">\u0394Fcreep=2\u2009kN<\/span><\/span>, the final bolt load can be estimated as:<\/p><p><span class=\"katex-display\"><span class=\"katex\"><span class=\"katex-mathml\">\u0394Fthermal=210\u2009000\u22c5200\u00d710\u22126\u22c5(\u22126\u00d710\u22126)\u22c5100=\u221225.2kN<\/span><\/span><\/span>\u00a0<\/p><p><span class=\"katex-display\"><span class=\"katex\"><span class=\"katex-mathml\">Ffinal=50\u221225.2\u22122=22.8\u2009kN<\/span><\/span><\/span><\/p><p data-start=\"6243\" data-end=\"6464\">Interpretation: The bolt loses more than half of its initial preload due to <strong data-start=\"6323\" data-end=\"6366\">thermal expansion differences and creep<\/strong>, highlighting the importance of proper material selection, joint design, and preload measurement.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-7b29f9b2 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"7b29f9b2\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-46cf3ab4\" data-id=\"46cf3ab4\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-b027f89 elementor-widget elementor-widget-heading\" data-id=\"b027f89\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Sector Applications<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-cd44c92 elementor-widget elementor-widget-text-editor\" data-id=\"cd44c92\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p data-start=\"6498\" data-end=\"6640\">Aerospace: Engines and airframe components experience extreme thermal changes. Preload loss can compromise critical assembly safety.<\/p><p data-start=\"6642\" data-end=\"6793\">Energy: Thermal cycles in power plants or nuclear facilities increase the risk of leakages or structural failures if bolts relax excessively.<\/p><p data-start=\"6795\" data-end=\"6939\">Automotive: Engines undergo rapid heating and cooling cycles. Accurate bolt preload prevents gasket failures or component deformation.<\/p><p data-start=\"6941\" data-end=\"7101\">Railway: Rails and mechanical components are exposed to environmental and braking-induced thermal variations. Preload loss affects stability and safety.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-bf7c464 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"bf7c464\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-1cf3f57\" data-id=\"1cf3f57\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-fe909ab elementor-widget elementor-widget-heading\" data-id=\"fe909ab\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Measuring and Compensating Bolt Preload with Temperature Variations: TRAXX M2<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-ca0ace5 elementor-widget elementor-widget-text-editor\" data-id=\"ca0ace5\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p data-start=\"7193\" data-end=\"7417\">The <strong data-start=\"7197\" data-end=\"7209\">TRAXX M2<\/strong> ultrasonic bolt tension meter directly measures <strong data-start=\"7258\" data-end=\"7277\">bolt elongation<\/strong> and calculates preload independent of torque. One of its key advantages is handling <a href=\"https:\/\/www.engineersedge.com\/calculators\/bolt_preload_temperature_effects__16230.htm\">temperature variations<\/a>, which are critical because:<\/p><ul data-start=\"7419\" data-end=\"7640\"><li data-start=\"7419\" data-end=\"7541\"><p data-start=\"7421\" data-end=\"7541\">Temperature changes alter both the mechanical length of the bolt and the ultrasonic wave propagation velocity.<\/p><\/li><li data-start=\"7542\" data-end=\"7640\"><p data-start=\"7544\" data-end=\"7640\">Even small variations of a few degrees can introduce 10\u201320% errors in tension measurement.<\/p><\/li><\/ul><p data-start=\"7642\" data-end=\"7686\"><span style=\"text-decoration: underline;\">How TRAXX M2 Compensates for Temperature :\u00a0<\/span><\/p><ol data-start=\"7688\" data-end=\"8496\"><li data-start=\"7688\" data-end=\"7835\"><p data-start=\"7691\" data-end=\"7835\">Preliminary Temperature Calibration: The system determines the variation of ultrasonic length per \u00b0C (ns\/\u00b0C) as a function of temperature.<\/p><\/li><li data-start=\"7836\" data-end=\"7990\"><p data-start=\"7839\" data-end=\"7990\">Linear Relationship: The calibration reveals a nearly linear relationship, defining the temperature coefficient (<span class=\"katex\"><span class=\"katex-mathml\">\u03b2<\/span><\/span>) for the assembly.<\/p><\/li><li data-start=\"7991\" data-end=\"8148\"><p data-start=\"7994\" data-end=\"8148\">Temperature Probe Integration: During measurement, the system reads the bolt temperature and automatically applies the corresponding correction.<\/p><\/li><li data-start=\"8149\" data-end=\"8346\"><p data-start=\"8152\" data-end=\"8346\">Length Reset to Initial Temperature: The measured ultrasonic length is adjusted to the temperature of the initial reference measurement, effectively eliminating temperature-induced errors.<\/p><\/li><li data-start=\"8347\" data-end=\"8496\"><p data-start=\"8350\" data-end=\"8496\">Tension Calculation: The corrected length is used to compute the preload, ensuring <strong data-start=\"8437\" data-end=\"8460\">accuracy within \u00b13%<\/strong> despite temperature fluctuations.<\/p><\/li><\/ol><p data-start=\"8498\" data-end=\"8630\">This approach allows engineers to monitor<strong data-start=\"8532\" data-end=\"8578\"> bolt load after temp change<\/strong> reliably, even in challenging thermal environments.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5dfd5ad elementor-widget elementor-widget-image\" data-id=\"5dfd5ad\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"623\" height=\"411\" src=\"https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/bolt-load-after-temp-change-on-gas-turbine.jpg\" class=\"attachment-medium_large size-medium_large wp-image-5283\" alt=\"\" srcset=\"https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/bolt-load-after-temp-change-on-gas-turbine.jpg 623w, https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/bolt-load-after-temp-change-on-gas-turbine-300x198.jpg 300w\" sizes=\"(max-width: 623px) 100vw, 623px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-f18cb2b elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"f18cb2b\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-77a5db9\" data-id=\"77a5db9\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-2d6dd75 elementor-widget elementor-widget-heading\" data-id=\"2d6dd75\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Conclusion on bolt load after temp change<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-0c0006a elementor-widget elementor-widget-text-editor\" data-id=\"0c0006a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p data-start=\"7193\" data-end=\"7417\">Temperature variations have a major impact on bolt preload due to differential expansion, creep, relaxation, friction changes, and transient thermal effects. Mathematical modeling combined with advanced measurement solutions, like the TRAXX M2, allows engineers to accurately monitor and compensate<strong> bolt load after temp change<\/strong>, <a href=\"https:\/\/www.traxx-group.com\/en\/assembly-monitoring\/\">ensuring joint integrity<\/a>, safety, and long-term performance across aerospace, automotive, energy, and railway applications.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-1e8753e elementor-widget elementor-widget-image\" data-id=\"1e8753e\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"300\" height=\"200\" src=\"https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/Temperature-Effect-on-Bolt-Tension-300x200.png\" class=\"attachment-medium size-medium wp-image-5305\" alt=\"diagram of Temperature Effect on Bolt load\" srcset=\"https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/Temperature-Effect-on-Bolt-Tension-300x200.png 300w, https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/Temperature-Effect-on-Bolt-Tension-1024x683.png 1024w, https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/Temperature-Effect-on-Bolt-Tension-768x512.png 768w, https:\/\/www.traxx-group.com\/en\/wp-content\/uploads\/2025\/10\/Temperature-Effect-on-Bolt-Tension.png 1536w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>This article explores the mechanisms affecting bolt load after temp change, presents mathematical models and real-world examples, highlights negative effects on bolted joints, and discusses modern measurement solutions including the TRAXX M2 ultrasonic bolt tension meter.<\/p>\n","protected":false},"author":2,"featured_media":5271,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[8],"tags":[],"class_list":["post-5267","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.3 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Bolt Load after temp change : Thermal effects on bolted joints<\/title>\n<meta name=\"description\" content=\"This article explores the mechanisms affecting bolt load after temp change, presents mathematical models, and discusses solutions such as ultrasonic bolt load measurement.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" 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