{"id":1558,"date":"2023-02-17T07:45:37","date_gmt":"2023-02-17T15:45:37","guid":{"rendered":"https:\/\/www.fictiv.com\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness\/"},"modified":"2024-04-04T01:20:28","modified_gmt":"2024-04-04T08:20:28","slug":"engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness","status":"publish","type":"cpt_blog","link":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness","title":{"rendered":"Engineering Fundamentals Refresh: Strength vs. Stiffness vs. Hardness"},"content":{"rendered":"\n<p><em>This article was originally published in February 2017 by <\/em><a href=\"https:\/\/www.fictiv.com\/author\/humberto-villasenor-ochoa\">Humberto Villasenor<\/a><em>. The content has been updated.<\/em><\/p>\n\n\n\n<p>Understanding the differences between the mechanical properties of strength vs. stiffness vs. hardness is foundational in mechanical engineering, yet these properties are often confused. These properties are related, but they have important differences:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/www.fictiv.com\/articles\/how-to-design-for-stiffness-using-material-properties\">Stiffness<\/a> is an indicator of the tendency for an element to return to its original form after being subjected to a force.&nbsp;<\/li>\n\n\n\n<li><a href=\"http:\/\/xhttps\/\/www.engineersedge.com\/material_science\/strength.htm\">Strength<\/a> measures how much stress can be applied to an element before it deforms permanently or fractures. &nbsp;<\/li>\n\n\n\n<li>Hardness measures a material\u2019s resistance to surface deformation. For some metals, like <a href=\"https:\/\/www.fictiv.com\/materials\/cnc-steel\">steel<\/a>, hardness and tensile strength are roughly proportional (see ASTM A 370-68 Steel Tables).&nbsp;<\/li>\n<\/ul>\n\n\n\n<p>For this article, we\u2019ll review the fundamentals of each, identify common pitfalls differentiating mechanical strength vs. stiffness vs hardness, examine the technical differences between the three, and discuss their relevance in the selection of <a href=\"https:\/\/www.fictiv.com\/articles\/how-to-select-source-the-right-materials\">materials for product development<\/a>.&nbsp;<\/p>\n\n\n\n<p>It\u2019s especially easy to confuse strength vs stiffness. If a material is stiff, then it must be strong enough to support a large load, right? So, aren\u2019t strength and stiffness the same? No! A material can be strong and elastic or strong and stiff (See section \u201cAxial Loading on a Straight Member\u201d), but strength and stiffness are two separate qualities \u2014 there are many types of <a href=\"https:\/\/www.engineersedge.com\/material_science\/strength.htm\">material strength<\/a>, including tensile and yield strength.\u00a0<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Key Definitions&nbsp;<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Yield strength<\/strong> is used to describe materials that exhibit elastic behavior. It\u2019s the maximum tensile stress the material can handle before permanent deformation.&nbsp;<\/li>\n\n\n\n<li><strong>Ultimate strength<\/strong> refers to the maximum stress before failure occurs.&nbsp;<\/li>\n\n\n\n<li><strong>Fracture strength<\/strong> is the value corresponding to the stress at which total failure occurs.&nbsp;<\/li>\n\n\n\n<li><strong>Stiffness<\/strong> is how a component resists elastic deformation when a load is applied.&nbsp;<\/li>\n\n\n\n<li><strong>Hardness<\/strong> is resistance to localized surface deformation.&nbsp;<\/li>\n<\/ul>\n\n\n\n<p>Tensile strength can be calculated from hardness and is easy to determine because hardness tests \u2014 such as Rockwell \u2014 are simple to perform, inexpensive, and non-destructive because only a small penetration is performed on the specimen. For many metals, tensile strength increases as hardness increases.&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Young\u2019s Modulus<\/strong><\/h3>\n\n\n\n<p>Young\u2019s Modulus stress-strain curve is a great reference tool for understanding the relationship between stiffness and strength. Young\u2019s Modulus (aka elastic modulus, shear modulus, or bulk modulus) defines a material\u2019s ability to resist elastic deformation while under loading conditions and is the ratio of normal stress to normal strain. In basic terms, this tells us how easily a material can stretch and deform. \u00a0<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1010\" height=\"242\" data-src=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/Youngs-Modulus.png\" alt=\"\" class=\"wp-image-11377 lazyload\" data-srcset=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/Youngs-Modulus.png 1010w, https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/Youngs-Modulus-768x184.png 768w\" sizes=\"auto, (max-width: 1010px) 100vw, 1010px\" \/><\/figure>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"512\" height=\"366\" data-src=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/unnamed.png\" alt=\"Stress vs Strain Curve\" class=\"wp-image-9362 lazyload\"\/><\/figure>\n\n\n\n<p>&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Stiffness&nbsp;<\/strong><\/h3>\n\n\n\n<p>Stiffness is a material\u2019s ability to return to its original form after being subjected to a force. Strength is how much stress can be applied to a material before it goes into plastic deformation or fractures. Stiffness and elastic modulus are related: as the elastic modulus goes up, the stiffness of a material also goes up. Since stiffness and strength are related to the elastic modulus of a material, you can look up the elastic modulus in a material properties reference handbook to determine the strength and\/or stiffness of a given material.&nbsp;<\/p>\n\n\n\n<p>The stiffness of a material can be quantified by the slope of the stress-strain curve, as illustrated in the graph below. There are many types of stiffness to consider, depending upon your application, including tension\/compression stiffness, axial force ratio, axial linear strain (EA), torsional stiffness, bending stiffness, beam stiffness, <a href=\"https:\/\/www.fictiv.com\/articles\/types-of-springs-and-their-applications-an-overview\">spring stiffness<\/a>, and shear stiffness. In general terms, the stiffness of a material is calculated by using the following equation:\u00a0<\/p>\n\n\n\n<style>\ndiv.qtn {\n  font-size: 16px;\n}\ndiv.q {\n  float: left;\n  height: 2em;\n  padding: 0.75em 0 0.75em 0;\n}\ndiv.frac {\n  float: left;\n  text-align: center;\n}\ndiv.numer {\n  border-bottom: 1px solid #76787a;\n}\n\n  <\/style>\n\n<div class=\"flex justify-center\">\n<div class=\"qtn\">\n<div class=\"q\"><i>stiffness<\/i> &nbsp; = &nbsp; <\/div>\n  <div class=\"frac\">\n    <div class=\"numer\"><i>Force<\/i><\/div>\n    <div class=\"denom\"><i>displacement<\/i><\/div>\n  <\/div>\n \n<\/div>\n<\/div>\n\n\n\n<p><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"512\" height=\"429\" data-src=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2022\/04\/unnamed-1.gif\" alt=\"stress-strain showing nonelastic region\" class=\"wp-image-9364 lazyload\"\/><\/figure>\n\n\n\n<p>The Young\u2019s modulus stress-strain curve shown above is a good way of graphically demonstrating stiffness. The ratio of stress to strain is the elastic modulus (stiffness), but the way a material responds to stress, and only the stress, defines the strength of the material.&nbsp;<\/p>\n\n\n\n<p><br><em><strong>Pro-Tip: <\/strong>Check out <a href=\"https:\/\/www.fictiv.com\/articles\/how-to-design-for-stiffness-using-a-geometric-approach\">How to Design for Part Stiffness Using a Geometric Approach<\/a> for a deeper dive into stiffness and how it\u2019s related to part geometry.&nbsp;<\/em><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Strength<\/h3>\n\n\n\n<p>Strength measures how much stress a material can handle before permanent deformation or fracture occurs. Both tensile strength and hardness are indicators of a metal\u2019s resistance to plastic deformation. Multiple types of strength are worth considering depending on your application, including ultimate tensile strength vs yield strength. Ultimate tensile strength is the maximum stress a material can withstand before it fails or breaks (which is the failure point in the graph above). Yield strength is the maximum stress a material can withstand before plastic deformation occurs (which is the yield point inthe  graph above). <em>Simple stress-strain curves illustrating stiff vs non-stiff behavior. Curves A and B correspond to stiffer materials, whereas curve C represents a non-stiff (ductile) material.<\/em> (<a href=\"https:\/\/www.plasticprop.com\/articles\/stress-strain-curve-material-properties-glance\">Image source)<\/a><\/p>\n\n\n\n<p><em>Pro-tip: If you want more information on how materials respond to stress and how to determine the strength of materials, check out <\/em><a href=\"https:\/\/courses.washington.edu\/me354a\/strength_theories.pdf\"><em>Strength Theory<\/em><\/a><em>.<\/em><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Hardness<\/h3>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"720\" height=\"480\" data-src=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-1.jpg\" alt=\"Hardness Tester\" class=\"wp-image-11380 lazyload\" data-srcset=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-1.jpg 720w, https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-1-600x400.jpg 600w\" sizes=\"auto, (max-width: 720px) 100vw, 720px\" \/><\/figure>\n\n\n\n<p>Hardness is a measure of a material\u2019s ability to withstand plastic deformation or a material\u2019s resistance to penetration by a pointed tool. This is a critical characteristic to consider in applications with two materials impacting each other \u2014 the harder one will scratch or cause plastic deformation on the other material. Hardness is dependent upon ductility, plasticity, strain, strength, toughness, viscosity, and viscoelasticity. It\u2019s an important measure when considering the wear resistance (abrasion or erosion resistance of a part) since harder materials typically have higher wear resistance. \u00a0<\/p>\n\n\n\n<p>Hardness testing is accomplished by lowering a probe with a hard (typically diamond) tip onto a material at a set force and measuring the amount of indentation that the probe (the indentor) produces (depth of plastic deformation). Hardness testers also operate by measuring the size of the impression left by the indentor.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Understanding Stress and Strain&nbsp;<\/strong><\/h2>\n\n\n\n<p>Stress is an internal force resulting from an applied load; it acts on the cross-section of a mechanical or structural component. Strain is the change in shape or size of a body (deformation) that occurs whenever a force is applied. There are two types of strain that correspond with the two types of stress: &nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Normal Strain<\/strong>: deformations that occur perpendicular to the cross-section; normal strain is caused by normal stress&nbsp;<\/li>\n\n\n\n<li><strong>Shear Strain<\/strong>: deformations that occur parallel to the cross-section; shear strain is caused by shear stress<\/li>\n<\/ul>\n\n\n\n<p><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"950\" height=\"731\" data-src=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image03.png\" alt=\"axial load, shear stresses, torsional stress, and bending stress\" class=\"wp-image-1553 lazyload\" data-srcset=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image03.png 950w, https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image03-300x231.png 300w, https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image03-768x591.png 768w\" sizes=\"auto, (max-width: 950px) 100vw, 950px\" \/><\/figure>\n\n\n\n<p><em>Top left: axial load causing tension or compression. Top right: shear stresses within a member. Bottom left: torsional stress about a circular cross-section. Bottom right: Bending stress caused by a moment.<\/em><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Examples: Strength vs. Stiffness&nbsp;<\/strong><\/h2>\n\n\n\n<p>To further understand the difference between strength and stiffness, let\u2019s go back to the basics of how we were or were probably initially taught about strength and stiffness. Utilize the following examples and downloadable calculator as thought exercises to deepen your understanding of the concepts of stiffness vs strength.&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Beam Deflection&nbsp;<\/strong><\/h3>\n\n\n\n<p>The image below is a finite element analysis (FEA) rendering of a beam subjected to a load. The beam\u2019s response to the loading is a deflection resulting from internal bending and shear stress. If the internal stresses exceed the yield strength of the beam\u2019s material, then you need a material with a higher Young\u2019s Modulus value \u2014 a material with higher stiffness (to resist deformation) and also higher yield strength (to prevent permanent deformation and possible fracture).<\/p>\n\n\n\n<p><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"950\" height=\"565\" data-src=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image05.gif\" alt=\"FEA analysis of beam deflection.\" class=\"wp-image-1555 lazyload\"\/><\/figure>\n\n\n\n<p><em>Finite Element Analysis of beam deflection.<\/em><\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\">Area Moment of Inertia Calculator<\/h3>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" data-src=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image.png\" alt=\"\" class=\"wp-image-11379 lazyload\"\/><\/figure>\n\n\n\n<p class=\"text-14\">If you\u2019re looking for a simple way to calculate the Area Moment of Inertia for a round tube, solid tube, or rectangular beam \u2014 or to calculate deflection and stiffness for a cantilever beam \u2014 you can use our <a href=\"https:\/\/www.fictiv.com\/tools\/area-moment-of-inertia-calculator\">Area Moment of Inertia Calculator<\/a>. This tool also allows you to play around with geometry to understand how the cross-sectional shape of a part impacts stiffness and deflection.&nbsp;<\/p>\n\n\n\n<p><a href=\"#modal-10\" data-mce-download-modal-open=\"modal-10\">Download Free Calculator<\/a><\/p>\n\n\n\n<div class=\"modal micromodal-slide z-50 relative\" id=\"modal-10\" aria-hidden=\"true\">\n    <div class=\"modal__overlay fixed inset-0 flex justify-center items-center bg-black bg-opacity-75\" tabindex=\"-1\" data-mce-download-modal-close=\"modal-10\">\n        <div class=\"modal__container max-w-lg max-h-screen\" role=\"dialog\" aria-modal=\"true\" aria-labelledby=\"modal-10-title\">\n            <main class=\"modal__content w-full\">\n                <div class=\"h-full embed-responsive aspect-ratio-16\/9 relative h-0 flex justify-center\">\n                    <div class=\"w-full px-4\">\n                        <div class=\"bg-white h-full p-4\">\n                            <div class=\"download-form-wrapper\">\n                            \n                                <input type=\"text\" style=\"display: none\">\n                                <div>\n                                    <div class=\"mb-2\">\n                                        <p class=\"uppercase font-museo-700 text-grey-400 text-14\">DOWNLOAD FREE CALCULATOR<\/p>\n                                    <\/div>\n                                    <div class=\"mb-2\">\n                                        <form class=\"mktoForm underline\" data-form-type=\"resource\" data-formId=\"39\"><\/form>\n                                    <\/div>\n                                    <div class=\"text-center\">\n\n                                        <div class=\"gdpr-text\">\n                                            <p class=\"text-10 text-grey-400\">By signing up, you agree to our \n                                                <a class=\"text-teal-light\" href=\"\/terms\">Terms of Use<\/a> and <a class=\"text-teal-light\" href=\"\/privacy\">Privacy Policy<\/a>. \n                                                We may use the info you submit to contact you and use data from third parties to personalize your experience.<br>\n                                            <\/p>\n                                        <\/div>            \n                                    <\/div>\n                                <\/div>\n                            <\/div>\n\n                            <div class=\"download-form-success hidden\">\n                                <p class=\"text-24\">Thank you for downloading!<\/p>\n                            <\/div>\n                        <\/div>\n                    <\/div>\n                <\/div>\n            <\/main>\n        <\/div>\n    <\/div>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Axial Loading on a Straight Member &#8211; Stiffness<\/strong><\/h3>\n\n\n\n<p>To further understand stiffness, let\u2019s consider a metal bar in tension, subjected to an axial load (bending moment). The internal stresses cause a deformation of 1% of the metal\u2019s original length when it breaks at 100 lbf.&nbsp;<\/p>\n\n\n\n<p>Next, consider a rubber-like rod-shaped polymer that\u2019s subjected to the same force but deforms 5% of its original length and breaks at 100 lbf. Both materials are equally strong, but the metal is stiffer than the polymer, which means that it deflects less for the same given loading condition. This thought exercise is a great way to show that as stiffness increases, the amount of deformation for a given load decreases.\u00a0<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"950\" height=\"821\" data-src=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image06.jpg\" alt=\"tensile strength test\" class=\"wp-image-1556 lazyload\" data-srcset=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image06.jpg 950w, https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image06-300x259.jpg 300w, https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image06-768x664.jpg 768w\" sizes=\"auto, (max-width: 950px) 100vw, 950px\" \/><\/figure>\n\n\n\n<p><em>Tensile strength test.<\/em><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Thermal Stress&nbsp;<\/strong><\/h2>\n\n\n\n<p>Thermal stress also affects the deformation response of a component that is already subject to some force \u2014 thermal stress affects the strength of materials. Consider a case of a bar with a force applied to it that is also exposed to a temperature differential, causing a temperature gradient within the member &#8211; and therefore thermal stress; the thermal stress induces additional strain to the strain already imposed by forces acting on it. For example, metals expand when heated and contract when cooled, which stresses the material, and when coupled with any externally applied stress from loading, the metal will fail more rapidly. Here is the method for calculating thermal stress:\u00a0 \u00a0<\/p>\n\n\n\n<p class=\"has-text-align-center\">\ud835\udf0e=\ud835\udc38\ud835\udefc\u0394\ud835\udc47&nbsp;<\/p>\n\n\n\n<p class=\"has-text-align-center\">\ud835\udf0e=E\ud835\udefc\u0394T&nbsp;<\/p>\n\n\n\n<p class=\"has-text-align-center\">\ud835\udf0e = thermal stress&nbsp;<\/p>\n\n\n\n<p class=\"has-text-align-center\">Where \u03b1 = coefficient of thermal expansion&nbsp;<\/p>\n\n\n\n<p class=\"has-text-align-center\">\u0394T = difference in initial temperature and final temperature&nbsp;<\/p>\n\n\n\n<p class=\"has-text-align-center\">E = Young\u2019s Modulus&nbsp;<\/p>\n\n\n\n<p>The equation above shows how thermal stress is dependent on Young\u2019s Modulus, or the stiffness of a material. Computing thermal stress provides insight into what values of stiffness and strength are appropriate for your design (assuming the temperature difference is not large enough that it will change the microscopic properties of the material).&nbsp;<a href=\"https:\/\/www.fictiv.com\/articles\/heat-exchanger-material-selection\">Learn more about using thermal properties for material selection in this article, Heat Exchanger Material Selection.&nbsp;<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Retrieving Mechanical Property Data&nbsp;<\/strong><\/h2>\n\n\n\n<p>If you\u2019re looking for the mechanical (or thermal or electrical) property data of a given material, you can get it from the American Society for Testing Materials (ASTM) or by consulting the material manufacturer\u2019s website. Typically, the data values available range from material stiffness and mechanical strength to hardness and tensile strength. <a href=\"http:\/\/www.matweb.com\/\">MatWeb<\/a> is a particularly useful resource with accurate data that can be obtained quickly.\u00a0<\/p>\n\n\n\n<p><strong>Pro-Tip: <\/strong>If you are new to reading material data sheets to obtain mechanical property data,<a href=\"https:\/\/www.fictiv.com\/articles\/how-to-read-material-data-sheets\"> check out this resource, How to Read Material Data Sheets.&nbsp;<\/a><\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Best Practices Designing for Strength, Stiffness, and Hardness&nbsp;<\/strong><\/h3>\n\n\n\n<p>Here are three best practices to keep in mind throughout the design process:\u00a0<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Identify Critical Components First<\/strong><\/li>\n<\/ol>\n\n\n\n<p>In the early stages of your design, such as when constructing the CAD model <a href=\"https:\/\/www.fictiv.com\/articles\/cad-design-terms\">(learn more about CAD design terms in this article)<\/a>, determine which components will be critical to your design \u2014 aka, which ones will be subjected to impact loadings, uniform loadings, concentrated loads, constant loads, etc. Doing so gives you an idea of the stiffness or strength you need for those components. It\u2019s also a good idea to develop graphical representations of complex dynamical systems using bond graph or block-diagram modeling and utilize software to model sophisticated systems.\u00a0<\/p>\n\n\n\n<p><strong>2. Determine Applied Forces to Each Component and Calculate Stress&nbsp;<\/strong><\/p>\n\n\n\n<p>Next, calculate the expected stresses on mechanical components to determine where problems may arise or where forces are large. Measure how the design responds to various inputs using instrumentation techniques and perform data analysis to predict your model\u2019s behavior. Consider creep and fatigue variables in subsystems and those associated with the environment to which your system will be exposed. For a refresher on calculating stresses that designed components are subjected to, I recommend consulting this <a href=\"https:\/\/www.amazon.com\/Shigleys-Mechanical-Engineering-Design-McGraw-Hill\/dp\/0073398209\">mechanical engineering design book<\/a>.&nbsp;<\/p>\n\n\n\n<p><strong>3. Best Practices for Material Selection&nbsp;<\/strong><\/p>\n\n\n\n<p>As previously discussed, each material type has its own set of mechanical, thermal, and electrical properties. Different materials are optimal for different applications. For example, ceramics are usually brittle, meaning that there\u2019s hardly any deformation before fracture. So, cracks may spread rapidly with little accompanying plastic deformation. In contrast, metals exhibit two modes in response to an applied stress: ductility or brittleness. Ductile materials are accompanied by plastic deformation before fracture, while brittle materials are not.<\/p>\n\n\n\n<p>If you are looking for a resource on selecting the best material for <a href=\"https:\/\/www.fictiv.com\/cnc-machining-service\">CNC machining<\/a> in the face of <a href=\"https:\/\/www.fictiv.com\/quality-assurance\">competing requirements<\/a>, check out this resource, <a href=\"https:\/\/www.fictiv.com\/articles\/your-guide-to-picking-the-best-cnc-materials-for-machining\">Your Guide to Picking the Best CNC Materials for Machining<\/a>.\u00a0<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"950\" height=\"850\" data-src=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image07.png\" alt=\"Ductile vs. Brittle\" class=\"wp-image-1557 lazyload\" data-srcset=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image07.png 950w, https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image07-300x268.png 300w, https:\/\/www.fictiv.com\/wp-content\/uploads\/2017\/02\/strength-vs.-stiffness-image07-768x687.png 768w\" sizes=\"auto, (max-width: 950px) 100vw, 950px\" \/><\/figure>\n\n\n\n<p><em>Figure 7. Ductile vs. Brittle<\/em><\/p>\n\n\n\n<p>The fracture process for ductile metals normally occurs in several stages (ductility and brittleness in polymers depend on temperature). For raw materials, determine which manufacturing processes will provide you with the desired material properties. Testing of materials should conform to ASTM standards, so consult engineering handbooks to obtain reliable material data.\u00a0<\/p>\n\n\n\n<p>In addition, <a href=\"https:\/\/www.fictiv.com\/cnc-machining-service\">materials<\/a> should be selected based on the environmental conditions the components will be exposed to. The chemical composition of a material determines its ability to withstand environmental conditions such as water, salt solutions or even chemical corrosion. Stainless steel, aluminum, and titanium are good material choices when environmental resistance is necessary. Bear in mind that a material\u2019s hardness plays a role in determining whether or not it can withstand abrasive environments such as desert conditions. As a rule, your material should have a higher hardness than the abrasive materials it may come into contact with to prevent material loss. &nbsp;<\/p>\n\n\n\n<p>&nbsp;4. Verify Designs Before Prototyping&nbsp;<\/p>\n\n\n\n<p>Design optimization and verification should be performed prior to prototyping a design, and <a href=\"https:\/\/www.fictiv.com\/articles\/list-of-cad-software-programs\">CAD software<\/a> can assess and optimize the geometry of your design. FEA analysis and numerical analysis are a good idea, and when feasible, double-check your analysis with hand calculations before prototyping begins to save time and money. Also, consult with other engineers for review.\u00a0<\/p>\n\n\n\n<p>It\u2019s also critical to consider <a href=\"https:\/\/www.fictiv.com\/masterclass\/dfm-for-cnc-masterclass\">design for manufacturability (DFM)<\/a> when optimizing a design prior to production. Even the most intelligent designs will fail if they don\u2019t account for the limitations of manufacturing methods. That\u2019s why <a href=\"https:\/\/www.fictiv.com\/\">Fictiv offers instant DFM feedback<\/a> for every design that\u2019s uploaded to our platform.&nbsp;<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Main Takeaways&nbsp;<\/strong><\/h2>\n\n\n\n<p>The proper understanding and implementation of stiffness, strength, and other mechanical properties in your design process is critical for building high-quality products. A clear understanding of a product\u2019s intended use is key for choosing appropriate materials that are cost-effective, safe, and have the required structural integrity to achieve the desired performance. Here are a few things to keep in mind when making your material selections:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Mechanical strength measures how much stress can be applied to an element before it deforms permanently or fractures.&nbsp;<\/li>\n\n\n\n<li>Stiffness in mechanical engineering is an indicator of the tendency for an element to return to its original form after being subjected to a force. If you are looking for a simple way to calculate the stiffness of a cantilever beam, check out our <a href=\"https:\/\/www.fictiv.com\/tools\/area-moment-of-inertia-calculator\">Area Moment of Inertia Calculator<\/a>.<\/li>\n\n\n\n<li>Hardness measures a material\u2019s resistance to surface deformation.&nbsp;<\/li>\n\n\n\n<li>Young\u2019s Modulus quantifies the amount that a material is able to resist elastic deformation under loading conditions. A stiff material has a high Young\u2019s Modulus and is able to hold its shape minimally when subjected to elastic loads. \u00a0<\/li>\n\n\n\n<li>Ultimate Tensile Strength, referred to as Tensile Strength, is the maximum tensile load a material can withstand prior to fracturing.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Sourcing Simplified<\/strong><\/h2>\n\n\n\n<p>Navigating the complexities of sourcing materials with the ideal strength, stiffness, and hardness for your project can be daunting. Fictiv simplifies this process, acting as your one-stop shop for custom mechanical parts. Whether you&#8217;re exploring <a href=\"https:\/\/www.fictiv.com\/cnc-machining-service\">CNC machining<\/a>, <a href=\"https:\/\/www.fictiv.com\/injection-molding-service\">injection molding<\/a>, <a href=\"https:\/\/www.fictiv.com\/3d-printing-service\">3D printing<\/a>, or <a href=\"https:\/\/www.fictiv.com\">other processes<\/a>, our engineering experts are here to assist you in selecting the perfect material for your application. We guide you seamlessly through the manufacturing stages, ensuring outstanding results.<\/p>\n\n\n\n<p>Experience the ease of our platform by <a href=\"https:\/\/app.fictiv.com\/signup\">creating an account<\/a> and uploading your design.<\/p>\n\n\n\n<p><strong>For further learning, check out these Fictiv resources:&nbsp;<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/www.fictiv.com\/tools\/press-fit-calculator\">Tool: Press Fit Calculator<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.fictiv.com\/articles\/how-to-design-for-stiffness-using-material-properties\">Article: How to Design for Stiffness Using Material Properties<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.fictiv.com\/articles\/how-to-design-for-stiffness-using-a-geometric-approach\">Article: How to Design for Part Stiffness Using a Geometric Approach<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.fictiv.com\/articles\/design-methods-to-improve-torsional-rigidity\">Article: Design Methods to Improve Torsional Rigidity<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.fictiv.com\/webinars\/how-to-manufacture-complex-designs\">Webinar: How to Manufacture Complex Designs<\/a><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>This article was originally published in February 2017 by Humberto Villasenor. The content has been updated. Understanding the differences between the mechanical properties of strength vs. stiffness vs. hardness is foundational in mechanical engineering, yet these properties are often confused. These properties are related, but they have important differences:&nbsp; For this article, we\u2019ll review the [&hellip;]<\/p>\n","protected":false},"author":147,"featured_media":11379,"parent":0,"menu_order":0,"template":"","fictiv_role":[29],"fictiv_topic":[28],"fictiv_industry":[],"fictiv_manufacturing_process":[],"coauthors":[168,104],"class_list":["post-1558","cpt_blog","type-cpt_blog","status-publish","has-post-thumbnail","hentry","fictiv_topic-mechanical-design"],"aioseo_notices":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v24.2 (Yoast SEO v24.2) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Engineering Fundamentals Refresh: Strength vs. Stiffness vs. Hardness | Fictiv<\/title>\n<meta name=\"description\" content=\"Learn about common pitfalls and technical differences among mechanical strength, stiffness and hardness and their relevance to selecting\u00a0materials\u00a0for product development. Read now!\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Engineering Fundamentals Refresh: Strength vs. Stiffness vs. Hardness\" \/>\n<meta property=\"og:description\" content=\"Learn about common pitfalls and technical differences among mechanical strength, stiffness and hardness and their relevance to selecting\u00a0materials\u00a0for product development. Read now!\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness\" \/>\n<meta property=\"og:site_name\" content=\"Fictiv\" \/>\n<meta property=\"article:modified_time\" content=\"2024-04-04T08:20:28+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-png.webp\" \/>\n\t<meta property=\"og:image:width\" content=\"690\" \/>\n\t<meta property=\"og:image:height\" content=\"240\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"10 minutes\" \/>\n\t<meta name=\"twitter:label2\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data2\" content=\"Tessa Axsom, Humberto Villasenor\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness\",\"url\":\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness\",\"name\":\"Engineering Fundamentals Refresh: Strength vs. Stiffness vs. Hardness | Fictiv\",\"isPartOf\":{\"@id\":\"https:\/\/www.fictiv.com\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#primaryimage\"},\"image\":{\"@id\":\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-png.webp\",\"datePublished\":\"2023-02-17T15:45:37+00:00\",\"dateModified\":\"2024-04-04T08:20:28+00:00\",\"description\":\"Learn about common pitfalls and technical differences among mechanical strength, stiffness and hardness and their relevance to selecting\u00a0materials\u00a0for product development. Read now!\",\"breadcrumb\":{\"@id\":\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#primaryimage\",\"url\":\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-png.webp\",\"contentUrl\":\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-png.webp\",\"width\":690,\"height\":240},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.fictiv.com\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Articles\",\"item\":\"https:\/\/www.fictiv.com\/articles\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Engineering Fundamentals Refresh: Strength vs. Stiffness vs. Hardness\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.fictiv.com\/#website\",\"url\":\"https:\/\/www.fictiv.com\/\",\"name\":\"Fictiv\",\"description\":\"On-Demand Manufacturing, CNC Machining &amp; 3D Printing\",\"publisher\":{\"@id\":\"https:\/\/www.fictiv.com\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.fictiv.com\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Organization\",\"@id\":\"https:\/\/www.fictiv.com\/#organization\",\"name\":\"Fictiv\",\"url\":\"https:\/\/www.fictiv.com\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.fictiv.com\/#\/schema\/logo\/image\/\",\"url\":\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2020\/09\/Fictiv-Logo-Green-1.png\",\"contentUrl\":\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2020\/09\/Fictiv-Logo-Green-1.png\",\"width\":1284,\"height\":678,\"caption\":\"Fictiv\"},\"image\":{\"@id\":\"https:\/\/www.fictiv.com\/#\/schema\/logo\/image\/\"}}]}<\/script>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"Engineering Fundamentals Refresh: Strength vs. Stiffness vs. Hardness | Fictiv","description":"Learn about common pitfalls and technical differences among mechanical strength, stiffness and hardness and their relevance to selecting\u00a0materials\u00a0for product development. Read now!","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness","og_locale":"en_US","og_type":"article","og_title":"Engineering Fundamentals Refresh: Strength vs. Stiffness vs. Hardness","og_description":"Learn about common pitfalls and technical differences among mechanical strength, stiffness and hardness and their relevance to selecting\u00a0materials\u00a0for product development. Read now!","og_url":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness","og_site_name":"Fictiv","article_modified_time":"2024-04-04T08:20:28+00:00","og_image":[{"width":690,"height":240,"url":"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-png.webp","type":"image\/png"}],"twitter_card":"summary_large_image","twitter_misc":{"Est. reading time":"10 minutes","Written by":"Tessa Axsom, Humberto Villasenor"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness","url":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness","name":"Engineering Fundamentals Refresh: Strength vs. Stiffness vs. Hardness | Fictiv","isPartOf":{"@id":"https:\/\/www.fictiv.com\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#primaryimage"},"image":{"@id":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#primaryimage"},"thumbnailUrl":"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-png.webp","datePublished":"2023-02-17T15:45:37+00:00","dateModified":"2024-04-04T08:20:28+00:00","description":"Learn about common pitfalls and technical differences among mechanical strength, stiffness and hardness and their relevance to selecting\u00a0materials\u00a0for product development. Read now!","breadcrumb":{"@id":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#primaryimage","url":"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-png.webp","contentUrl":"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/02\/image-png.webp","width":690,"height":240},{"@type":"BreadcrumbList","@id":"https:\/\/www.fictiv.com\/articles\/engineering-fundamentals-refresh-strength-vs-stiffness-vs-hardness#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.fictiv.com\/"},{"@type":"ListItem","position":2,"name":"Articles","item":"https:\/\/www.fictiv.com\/articles"},{"@type":"ListItem","position":3,"name":"Engineering Fundamentals Refresh: Strength vs. Stiffness vs. Hardness"}]},{"@type":"WebSite","@id":"https:\/\/www.fictiv.com\/#website","url":"https:\/\/www.fictiv.com\/","name":"Fictiv","description":"On-Demand Manufacturing, CNC Machining &amp; 3D Printing","publisher":{"@id":"https:\/\/www.fictiv.com\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.fictiv.com\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/www.fictiv.com\/#organization","name":"Fictiv","url":"https:\/\/www.fictiv.com\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.fictiv.com\/#\/schema\/logo\/image\/","url":"https:\/\/www.fictiv.com\/wp-content\/uploads\/2020\/09\/Fictiv-Logo-Green-1.png","contentUrl":"https:\/\/www.fictiv.com\/wp-content\/uploads\/2020\/09\/Fictiv-Logo-Green-1.png","width":1284,"height":678,"caption":"Fictiv"},"image":{"@id":"https:\/\/www.fictiv.com\/#\/schema\/logo\/image\/"}}]}},"_links":{"self":[{"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/articles\/1558","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/articles"}],"about":[{"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/types\/cpt_blog"}],"author":[{"embeddable":true,"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/users\/147"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/media\/11379"}],"wp:attachment":[{"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/media?parent=1558"}],"wp:term":[{"taxonomy":"fictiv_role","embeddable":true,"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/fictiv_role?post=1558"},{"taxonomy":"fictiv_topic","embeddable":true,"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/fictiv_topic?post=1558"},{"taxonomy":"fictiv_industry","embeddable":true,"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/fictiv_industry?post=1558"},{"taxonomy":"fictiv_manufacturing_process","embeddable":true,"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/fictiv_manufacturing_process?post=1558"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.fictiv.com\/wp-json\/wp\/v2\/coauthors?post=1558"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}