Materials Technology Chapter 1

Fracture toughness measures a material's resistance to brittle fracture when a crack is present.

The three modes are KIC (opening mode), KIIC (pure shear), and KIIIC (tearing mode).

As temperature increases, some material properties may change, leading to additional strain under static loading.

<p>The Larson-Muller parameter is defined as $LMP = \frac{(18.3 + \log t)}{T/100}$.</p> Signup and view all the answers

<p>Aluminum structures typically have low fracture toughness, making visual inspection for cracks essential to prevent catastrophic failures.</p> Signup and view all the answers

<p>The opening mode (KIC) is characterized by normal stresses acting perpendicular to the crack surface.</p> Signup and view all the answers

<p>Aluminum's properties can degrade significantly at high temperatures, resulting in extremely poor performance.</p> Signup and view all the answers

<p>Some plastics possess good toughness but can have poor fracture toughness, making them susceptible to fractures from minor cracks.</p> Signup and view all the answers

<p>The amount of material used and its recyclability are significant factors.</p> Signup and view all the answers

<p>Brittle materials require a high safety coefficient, while ductile materials require a low safety coefficient.</p> Signup and view all the answers

<p>75-80% of engineering materials are typically metals.</p> Signup and view all the answers

<p>Qualitative properties are non-numerically quantifiable, while quantitative properties are numerically measurable for direct comparison.</p> Signup and view all the answers

<p>Homogeneity refers to materials having the same properties at every point, which is vital for predictable performance.</p> Signup and view all the answers

<p>Isotropic materials have uniform properties in all directions, while anisotropic materials exhibit different behaviors depending on the direction.</p> Signup and view all the answers

<p>Tensile strength and hardness are two examples of quantitative properties.</p> Signup and view all the answers

<p>Manufacturing processes can impact the homogeneity and isotropy of materials, influencing their overall behavior.</p> Signup and view all the answers

<p>Preloaded joints help avoid shear stresses when force is applied, ensuring the integrity of the material joint.</p> Signup and view all the answers

<p>Ultimate shear and yield point shear can be approximated using specific formulas related to the material's properties.</p> Signup and view all the answers

<p>Torsion strength refers to the material's resistance to twisting forces and is crucial for components like keys in locks.</p> Signup and view all the answers

<p>Resilience measures a material's capacity to store elastic energy, represented by the area below the elastic line on stress-strain diagrams.</p> Signup and view all the answers

<p>A clear elastic limit is not present in torsion strength due to variations in distance of the stresses experienced by the material.</p> Signup and view all the answers

<p>When the external surface of a material reaches its elastic limit, the material achieves torsion strength and subsequently may break.</p> Signup and view all the answers

<p>If torsion strength information is unavailable, tensile formulas should be applied instead.</p> Signup and view all the answers

<p>The area below the elastic line represents the elastic potential energy stored in the material, which is critical for evaluating resilience.</p> Signup and view all the answers

<p>The primary creep phase is characterized by a fast onset where the creep rate starts to appear with a loose slope on the curve.</p> Signup and view all the answers

<p>Secondary creep occurs at a constant creep rate that reflects a linear relationship, compared to the accelerating rate seen in primary creep.</p> Signup and view all the answers

<p>During tertiary creep, the extension rate accelerates significantly, leading to the total failure of the material.</p> Signup and view all the answers

<p>Creep behavior is influenced by temperature, with higher temperatures leading to more pronounced creep rates and shortened secondary creep periods.</p> Signup and view all the answers

<p>Viscoelasticity allows for recovery of initial geometry after the load is removed, while viscoplasticity results in permanent deformation until breaking occurs.</p> Signup and view all the answers

<p>The Larson-Miller parameter measures the equivalence of time at temperature for assessing stress rupture in steel under thermally activated creep.</p> Signup and view all the answers

<p>Under constant stress, variations in temperature will alter the creep rate, with higher temperatures typically resulting in faster creep rates.</p> Signup and view all the answers

<p>Creep leads to necking, which is a localized decrease in cross-section, resulting from the continuous deformation under stress.</p> Signup and view all the answers

<p>Toughness measures a material's ability to absorb energy without deformation, which is crucial for car structure pieces to prevent damage from small impacts.</p> Signup and view all the answers

<p>They are rare and almost impossible to find in nature, usually appearing when materials are mixed to form composite materials.</p> Signup and view all the answers

<p>Toughness can be computed as the product of elastic limit and ultimate strain.</p> Signup and view all the answers

<p>Elasticity allows a material to recover its initial shape after the removal of external loads.</p> Signup and view all the answers

<p>At lower temperatures, materials tend to behave brittly, while at higher temperatures, materials are more ductile and tougher.</p> Signup and view all the answers

<p>Plasticity enables a material to undergo permanent deformation without additional stress, often rendering it unusable after exceeding a limit.</p> Signup and view all the answers

<p>Ductile fracture occurs later than brittle fracture, indicating that ductile materials have higher toughness and can absorb more energy.</p> Signup and view all the answers

<p>Hardness is related to a material's resistance to scratching and plastic deformation, which often correlates with its ultimate strength.</p> Signup and view all the answers

<p>Pure elastic materials, like gels, are mostly used for specific applications such as impact absorption, rather than general engineering purposes.</p> Signup and view all the answers

<p>They allow parts of the car to absorb energy without failing immediately, reducing damage to occupants.</p> Signup and view all the answers

<p>The Charpy V-notch pendulum hammer test is commonly used to measure toughness by comparing energy differences before and after impact.</p> Signup and view all the answers

<p>Ductility refers to a material's ability to sustain significant strain before breaking, while fragility indicates its tendency to break suddenly under stress.</p> Signup and view all the answers

<p>High toughness in vehicle materials enables them to absorb impacts efficiently, thereby minimizing deformation and enhancing passenger safety.</p> Signup and view all the answers

<p>Hardness measurements indicate a material's resistance to surface wear and can inform material selection for components that experience friction.</p> Signup and view all the answers

<p>The material would undergo permanent deformation under load and would not return to its original shape, likely becoming ineffective for its intended purpose.</p> Signup and view all the answers

<p>In automotive design, using materials that are both elastic and plastic can enhance safety by absorbing impact energy during collisions.</p> Signup and view all the answers