{"id":2316,"date":"2019-02-28T16:49:29","date_gmt":"2019-02-28T14:49:29","guid":{"rendered":"https:\/\/fractory.co\/?p=2316"},"modified":"2024-01-26T17:22:26","modified_gmt":"2024-01-26T15:22:26","slug":"mechanical-properties-of-materials","status":"publish","type":"post","link":"https:\/\/fractory.com\/mechanical-properties-of-materials\/","title":{"rendered":"Mechanical Properties of Materials"},"content":{"rendered":"

We should probably start by admitting that the list of mechanical properties is pretty long. Some are more important and common than others, when describing a material. Therefore, we are looking at the topic from an engineer’s perspective. He needs to know the basics to differentiate types of metals<\/a> from one another to make an informed decision when designing something.<\/p>\n

Material Stress and Strain<\/h2>\n

First, we need to explain some of the physical concepts behind the mechanical properties. The main one is stress<\/strong>. Stress tells you how big of a force applies to an area. In mechanical engineering, it is mostly expressed in MPa’s or N\/mm2<\/sup>. Those two are interchangeable. The formula for stress is:<\/p>\n

\u03c3=F\/A, where F is force (N) and A is area (mm2<\/sup>).<\/p>\n

The second important concept is strain<\/strong>. Strain has no unit as it is a ratio of lengths. It is calculated as follows:<\/p>\n

\u03b5=(l-l0<\/sub>)\/l0<\/sub>, where l0<\/sub> is starting or initial length (mm) and l is stretched length (mm).<\/p>\n

Young’s Modulus<\/h2>\n

From those two concepts we get to our first mechanical properties – stiffness<\/strong> and elasticity<\/strong> as its opposite. It is an important factor for engineers when solving physics problems (material suitability for a certain application).<\/p>\n

\"Stiff
Stiff material does not compress nor elongate easily<\/figcaption><\/figure>\n

Stiffness is expressed as Young’s modulus, also known as the modulus of elasticity. As one of the primary mechanical properties of materials, it defines the relationship between stress and strain – the bigger its value, the stiffer the material.<\/p>\n

This means that the same load would deform two equally-sized parts differently if they have varying Young’s moduli. At the same time, a lesser value means that the material is more elastic.<\/p>\n

The formula for Young’s modulus:<\/p>\n

E=\u03c3\/\u03b5 (MPa)<\/p>\n

Yield Strength<\/h2>\n

Yield stress or yield strength is the value most often used in engineering calculations. It gives a material a stress value in MPa it can take before plastic deformation. This place is called the yield point. Before it, a material regains its former shape when lifting the load. After exceeding the yield point, the deformation is permanent.<\/p>\n

\"Stress-strain
Stress-strain curve<\/figcaption><\/figure>\n

There is a good reason for using yield stress as the most important factor in mechanical engineering. As can be seen from the stress-strain curve<\/a>, when stress goes beyond the yield point, the damage is not yet catastrophic. That leaves a “cushion” before a construction fails completely to the point of breaking.<\/p>\n

Tensile Strength<\/h2>\n

Ultimate tensile strength<\/a>, or just tensile strength, is the next step from yield strength. Also measured in MPa’s, this value indicates the maximum stress a material can withstand before fracturing.<\/p>\n

When choosing a suitable material to tolerate known forces, two materials with a similar yield strength may have different tensile strengths. Having higher tensile strength may help to avoid accidents if unforeseen forces are applied.<\/p>\n

Plasticity<\/h2>\n

Plasticity is a mechanical property of materials that shows the ability to deform under stress without breaking while retaining the deformed<\/em> shape after the load is lifted. Metals with higher plasticity are better for forming. This is evident in metal bending<\/a>.<\/p>\n

Two related mechanical properties of materials are ductility<\/strong> and malleability<\/strong>. Ductility has a pretty much similar description to plasticity – it is a material’s ability to undergo plastic deformation before breaking. It is expressed as a percent elongation or percent area reduction. Basically, ductility is a property you need when drawing thin metal wires, for example. A good example of such a ductile material is copper<\/a>. This makes the fabrication of wires possible.<\/p>\n

Malleability is, by definition, also similar. But it actually characterises a material’s suitability for compressive deformation. In essence, a metal with good malleability is fitting for producing metal plates or sheets by rolling or hammering.<\/p>\n

\n
\n Scale Your Manufacturing from Prototyping to Series<\/span>\n\n