{"id":15660,"date":"2025-05-07T17:02:18","date_gmt":"2025-05-07T15:02:18","guid":{"rendered":"https:\/\/www.servosis.com\/?p=15660"},"modified":"2025-05-07T17:02:18","modified_gmt":"2025-05-07T15:02:18","slug":"multiaxial-fatigue-tests","status":"publish","type":"post","link":"https:\/\/www.servosis.com\/en\/ensayos-de-fatiga-multiaxial\/","title":{"rendered":"Multiaxial fatigue testing: realistic simulation of complex loads"},"content":{"rendered":"<p>&nbsp;<\/p>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"wp-image-15663 aligncenter\" src=\"https:\/\/www.servosis.com\/wp-content\/uploads\/2025\/05\/Laboratorio-de-Ensayos-Mecanicos_Integridad-Estructural-y-Fatiga-1024x1024-1-300x300.jpg\" alt=\"Multiaxial Fatigue Tests\" width=\"451\" height=\"451\" srcset=\"https:\/\/www.servosis.com\/wp-content\/uploads\/2025\/05\/Laboratorio-de-Ensayos-Mecanicos_Integridad-Estructural-y-Fatiga-1024x1024-1-300x300.jpg 300w, https:\/\/www.servosis.com\/wp-content\/uploads\/2025\/05\/Laboratorio-de-Ensayos-Mecanicos_Integridad-Estructural-y-Fatiga-1024x1024-1-150x150.jpg 150w, https:\/\/www.servosis.com\/wp-content\/uploads\/2025\/05\/Laboratorio-de-Ensayos-Mecanicos_Integridad-Estructural-y-Fatiga-1024x1024-1-768x768.jpg 768w, https:\/\/www.servosis.com\/wp-content\/uploads\/2025\/05\/Laboratorio-de-Ensayos-Mecanicos_Integridad-Estructural-y-Fatiga-1024x1024-1-12x12.jpg 12w, https:\/\/www.servosis.com\/wp-content\/uploads\/2025\/05\/Laboratorio-de-Ensayos-Mecanicos_Integridad-Estructural-y-Fatiga-1024x1024-1-600x600.jpg 600w, https:\/\/www.servosis.com\/wp-content\/uploads\/2025\/05\/Laboratorio-de-Ensayos-Mecanicos_Integridad-Estructural-y-Fatiga-1024x1024-1-155x155.jpg 155w, https:\/\/www.servosis.com\/wp-content\/uploads\/2025\/05\/Laboratorio-de-Ensayos-Mecanicos_Integridad-Estructural-y-Fatiga-1024x1024-1.jpg 1024w\" sizes=\"(max-width: 451px) 100vw, 451px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"font-weight: 400;\">When we design a component for the real world, we know that loading conditions are rarely simple. A car frame, a hip prosthesis or the structure of a landing gear undergo combined tensile, compressive and torsional loads that are applied simultaneously and dynamically.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">To correctly predict their behavior, a classic uniaxial fatigue test is not enough: multiaxial fatigue tests come into play.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Today we will take a closer look at what they consist of, how they are performed, what challenges they pose and why they are essential for highly demanding industrial sectors.<\/span><\/p>\n<h2><b><br \/>\nWhat are multiaxial fatigue tests?<\/b><\/h2>\n<p><span style=\"font-weight: 400;\">Multiaxial fatigue tests are tests in which materials or components are subjected to multiple types of loads applied simultaneously:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Tension and torsion,<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Compression and torsion,<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Combined biaxial or triaxial forces.<\/span><span style=\"font-weight: 400;\">\n<p><\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">While traditional uniaxial tests only act a load in one direction (e.g. axial tension), multiaxial tests seek to more realistically replicate the stress states faced by the material in service.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In the laboratory, this involves applying combined loads on different axes, with amplitudes, phases and frequencies that can be controlled and modified to faithfully represent the component's operating environment.<\/span><span style=\"font-weight: 400;\"><\/p>\n<p><\/span><\/p>\n<h2><b><br \/>\nWhy perform multiaxial fatigue testing?<\/b><\/h2>\n<h3><b>Limitations of uniaxial tests<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">The <\/span><a href=\"https:\/\/www.servosis.com\/en\/s-n-curve-and-service-life-as-an-interpretation-of-all-fatigue-test-results\/\"><span style=\"font-weight: 400;\">fatigue tests<\/span><\/a><span style=\"font-weight: 400;\"> The conventional tests are relatively simple to perform and provide very useful information about the basic strength of a material. However, in most real-world applications, components experience multiaxial loading.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Some examples:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Automotive chassis: withstands vibration, bending and torsion in combination.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Aircraft fuselage: receives internal loads due to pressurization and external loads due to aerodynamics, simultaneously.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">A uniaxial test may underestimate or overestimate the actual strength, since it does not capture the interactions between different types of stresses.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">This can lead to premature failures or unnecessarily oversized designs.<\/span><\/p>\n<p>&nbsp;<\/p>\n<h3><b>Advantages of simulating realistic loading conditions<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">Performing multiaxial fatigue tests offers clear advantages:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Increased accuracy in estimating the useful life of critical components.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Detection of failure modes that would not manifest themselves in simple tests.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Optimization of designs to reduce weight and increase safety.<\/span><span style=\"font-weight: 400;\">\n<p><\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Regulatory compliance in sectors where realistic load simulation is mandatory (e.g. aeronautics or biomechanics).<\/span><span style=\"font-weight: 400;\">\n<p><\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Ultimately, it allows us to design and validate products more reliably.<\/span><span style=\"font-weight: 400;\"><\/p>\n<p><\/span><\/p>\n<h2><b><br \/>\nMethods and technologies for multiaxial fatigue tests<\/b><\/h2>\n<h3><b>Multiaxial testing machines: main features<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">To perform this type of testing, specialized machines capable of applying and controlling loads on more than one axis simultaneously are required.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Key features:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Servo-hydraulic or electromechanical multi-axis actuators: allow precise dynamic loads to be applied in multiple directions.<\/span><span style=\"font-weight: 400;\"><br \/>\n<\/span><span style=\"font-weight: 400;\">Multichannel controllers: each actuator is operated independently or in coordination, controlling amplitude, phase and frequency.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Advanced data acquisition systems: allow all relevant variables to be recorded in real time for detailed analysis.<\/span><span style=\"font-weight: 400;\">\n<p><\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">At Servosis, we adapt our equipment to allow customized multiaxial test configurations according to each customer's needs.<\/span><\/p>\n<h3><b><br \/>\nLoading modes and trajectory types<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">In multiaxial fatigue testing, loads can be applied in different ways:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Proportional loads: the stresses applied in each direction maintain a constant relationship (e.g. tension and torsion in phase).<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Non-proportional loads: loads vary in magnitude and direction, simulating more complex and realistic conditions.<\/span><span style=\"font-weight: 400;\">\n<p><\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Some common load paths include:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Elliptical: typical in components subjected to bending and torsion.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Circular: in balanced biaxial loads.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Random: when seeking to replicate highly dynamic and unpredictable environments.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Each mode affects component life differently.<\/span><span style=\"font-weight: 400;\"><\/p>\n<p><\/span><\/p>\n<h2><b>Critical variables to control<\/b><\/h2>\n<p><span style=\"font-weight: 400;\">During the trial, monitoring is essential:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Ratio between principal stresses (\u03c31\/\u03c32).<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Angle of application of loads with respect to the material.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Temporal sequence of loads (if simultaneous or alternating).<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Misconfiguration can generate unrepresentative results or, worse, misinterpret fatigue behavior.<\/span><\/p>\n<p>&nbsp;<\/p>\n<h2><b>Technical challenges in multiaxial fatigue tests<\/b><\/h2>\n<p><span style=\"font-weight: 400;\">Although multiaxial fatigue testing is very valuable, it also presents technical challenges:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Accurate specimen preparation: specimens must withstand multiple loads simultaneously without introducing errors due to misalignment.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Load alignment: essential to avoid artificial stress concentrations that alter results.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Complexity in the analysis of results: there are no unique S-N curves for multiaxial loads.<\/span><span style=\"font-weight: 400;\">\n<p><\/span><\/li>\n<\/ul>\n<h2><b><br \/>\nPractical applications of multiaxial fatigue tests<\/b><\/h2>\n<p><span style=\"font-weight: 400;\">Multiaxial fatigue testing is becoming the standard in industries where safety and reliability are critical:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Automotive: verification of frames, drive shafts and suspension systems subjected to multiple dynamic forces.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Aeronautics: validation of structural components such as airframes or landing gears, which undergo combined stresses during flight and landing.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Biomechanics: testing of orthopedic prostheses and medical devices working under simultaneous compression, torsion and bending in the human body.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Railway: analysis of bogies, wheels and railway suspension systems undergoing vertical, lateral and torsional loads.<\/span><span style=\"font-weight: 400;\">\n<p><\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Each industry has its own regulations and validation requirements, where the ability to simulate multi-axial loads becomes critical.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Today more than ever, the demands of safety, efficiency and reliability require that our designs be tested in conditions that reflect their actual use. Multiaxial fatigue testing represents this evolution: more demanding tests, but also much more representative.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">At Servosis, we understand the complexity of these tests and work together with our customers to design multiaxial testing systems adapted to each specific application. Because testing well is designing better.<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><a href=\"https:\/\/www.servosis.com\/en\/contact-2\/\">We are here to help you.\u00a0<\/a><\/span><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>","protected":false},"excerpt":{"rendered":"<p>&nbsp; &nbsp; Cuando dise\u00f1amos un componente para el mundo real, sabemos que las condiciones de carga rara vez son simples. Un bastidor de coche, una pr\u00f3tesis de cadera o la estructura de un tren de aterrizaje sufren cargas combinadas de tensi\u00f3n, compresi\u00f3n y torsi\u00f3n que se aplican simult\u00e1neamente y de forma din\u00e1mica.\u00a0 Para predecir correctamente [&hellip;]<\/p>\n","protected":false},"author":8,"featured_media":15663,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"om_disable_all_campaigns":false,"inline_featured_image":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[18],"tags":[],"class_list":["post-15660","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-noticias"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/posts\/15660","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/comments?post=15660"}],"version-history":[{"count":0,"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/posts\/15660\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/media\/15663"}],"wp:attachment":[{"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/media?parent=15660"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/categories?post=15660"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.servosis.com\/en\/wp-json\/wp\/v2\/tags?post=15660"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}