MaterSciEng Lesson 3: Properties of Engineering Materials PDF

MATERSCIENG PROPERTIES OF ENGINEERING MATERIALS LESSON 3: Group 5 - ME301  CONTENT Strength MECHANICAL Elasticity PROPERTY Ductility Hardness  STRENGTH Strength of a material refers to it...

MATERSCIENG PROPERTIES OF ENGINEERING MATERIALS LESSON 3: Group 5 - ME301  CONTENT Strength MECHANICAL Elasticity PROPERTY Ductility Hardness  STRENGTH Strength of a material refers to its ability to resist an externally applied force without breaking or yielding. It is evaluated based on the amount of load a material can take before fracturing. Types of material strength include compressive strength, tensile strength, shear strength, and fatigue strength. TRIVIA AND FACTS Graphene: One of the strongest materials, it is about 200 times stronger than steel. Historical Use: Early civilizations relied on materials like wood and stone for their structural strength. Testing Methods: Machines like universal testing machines (UTMs) are used to measure material strength. Universal Testing Machine  ELASTICITY CAUSES Polymers (e.g., rubber): Elasticity arises as polymer chains stretch and return to their Elasticity is the ability of a material to return to its original original form when the force is removed. shape and size after being deformed or stretched by a force. When a material is deformed due to an applied force, it Metals: Elastic behavior occurs due to undergoes internal changes that cause stress. changes in atomic lattice structure that If the force is removed and the material returns to its original revert to their original form once the force state, it is said to exhibit elasticity. is removed. Materials with a high degree of elasticity are termed elastic materials. Most solid materials exhibit elastic behavior to some extent. The elastic limit is the maximum force and deformation a material can withstand while still returning to its original state. TRIVIA AND FACTS Rubber Bands: An everyday example of an elastic material, showcasing polymer chain behavior. Bridge Design: Elasticity is crucial in engineering suspension bridges to handle forces like wind and traffi c loads. Perfect Elasticity: No material is perfectly elastic; even highly elastic materials experience limits.  DUCTILITY A material property that refers to the ability of a material to undergo signifi cant plastic deformation before fracture, typically in the form of stretching or elongation. ductile material can stretch or elongate considerably without failing, which is diff erent from materials that may deform but break suddenly (brittle materials). APPLICATION Ductile materials, like those used in automobile crash zones, can deform in controlled ways during an impact, absorbing energy and protecting passengers. This is why materials like aluminum and mild steel are preferred in automotive body designs.  HARDNESS MOHS HARDNESS SCALE Hardness is a material's resistance to localized plastic A method to compare the diff erent kind of hardness deformation, such as indentation, scratching, cutting, or bending Hardness can be measured using a variety of techniques, including: Indentation: A very hard sphere is pushed into the material with a set force, and the width and depth of the resulting indent are measured. Scratch: The material is assessed for its resistance to scratching. Rebound hardness measurements: A technique for measuring hardness. TRIVIA AND FACTS Hardness is important because it infl uences: Ease of cutting, fi nishing, and polishing an objec0,t resistance to in-service scratching CHEMICAL PROPERTY CONTENT The chemical properties of a CORROSION RESISTANT material describe how it interacts with other substances and how its HYGROSCOPY chemical composition can change during chemical reactions. These PH properties are intrinsic and determine how the material REACTIVITY behaves under various conditions.  CORROSION RESISTANT The process by which a metal or alloy is gradually consumed by chemical reactions with water, gasses, or other substances in the air or water. Corrosion can occur through chemical or electrochemical reactions, and can be caused by various factor such as (oxygen and water, impurities, temperature and metal reactivity). The material's ability to resist chemical breakdown due to environmental factors like moisture, salt, or acids. MATERIALS Stainless steel resists corrosion, while regular steel does not.  HYGROSCOPY Hygroscopic materials absorb moisture from the air, often altering their physical or chemical properties, such as swelling or dissolving. HYGROSCOPIC SUBSTANCE Silica gel, Honey, Methanol, Concentrated sulfuric acid, Glycerine, Ethanol, Sodium chloride, Calcium  ACIDITY or BASICITY (pH) A measure of the concentration of hydrogen ions (H⁺) or hydroxide ions (OH⁻) in a substance. EXAMPLES Vinegar is acidic, while soap is basic. REACTION OF SODIUM WITH WATER REACTIVITY The tendency of a material to chemically react with other substances (e.g., water, acids, bases, oxygen). This property infl uences material degradation, such as corrosion in metals or oxidation in ceramics. Sodium reacts violently with water; iron reacts with oxygen to form PHYSICAL PROPERTY CONTENT DENSITY A physical property is a characteristic of a material CONDUCTIVITY that can be observed or measured without changing OPTICAL the material itself. It describes how the material behaves in diff erent CRYSTAL STRUCTURE conditions.  DENSITY Is the mass of a material per unit volume, typically expressed in units like grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³). It refl ects how tightly the material’s particles are packed together. For example, steel is denser than aluminum. Density is how heavy a material is for its size. It tells us how tightly packed the material’s particles are. CONDUCTIVITY The ability of a material to transfer energy, such as heat or electricity. Electrical conductivity measures how well a material allows the fl ow of electric current(e.g., copper is highly conductive), while thermal conductivity measures heat transfer effi ciency (e.g., diamond conducts heat well). Conductivity is how well a material can carry electricity or heat. Metals like copper are good conductors of electricity, while materials like rubber are not. CONDUCTIVE MATERIALS COPPER DIAMONDS ALUMINUM IRON  OPTICAL Optical properties describe how a material interacts with light, including its ability to transmit, refl ect, or absorb light. Optical properties describe how a material interacts with light, such as whether it lets light pass through (transparent), refl ects it (shiny), or absorbs it (opaque). MATERIAL Examples include transparency (e.g., glass), opacity, refractive index (bending of light), and color.  CRYSTAL STRUCTURE Crystal structure is the way the atoms or molecules in a material are arranged. It aff ects the material’s properties, like how hard or strong it is. For example, diamond has a diff erent crystal structure than graphite, making diamond much harder. FACTS Materials form crystal structures because atoms naturally arrange themselves in the most stable and lowest energy state. This helps the material stay strong and balanced. The type of structure depends on the atoms’ size, type of bonding, and conditions like temperature and pressure. TYPES OF CRYSTAL STRUCTURE 1. Simple Cubic (SC): Defi nition: Atoms are at the corners of a cube. 2. Face-Centered Cubic (FCC): Defi nition: Atoms are at the corners and the centers of each face of the cube. 3. Body-Centered Cubic (BCC): Defi nition: Atoms are at the corners and one atom in the center of the cube. 4. Hexagonal Close-Packed (HCP): Defi nition: Atoms are arranged CONCLUSION The properties of chemical, physical, and mechanical materials collectively determine their behavior, performance, and suitability for specific applications. While *chemical properties * define how materials interact with other substances, *physical properties* describe observable characteristics like density or conductivity, and *mechanical properties* relate to their ability to withstand forces, such as strength or elasticity. Together, these properties guide material selection in industries, ensuring functionality, durability, and safety.  ACTIVITY - IDENTIFICATION BY GROUPINGS 1. What is the ability of a material to resist an applied force? 2. What is the maximum force a material can withstand while returning to its original state? 3. What is the ability of a material to return to its original shape after deformation? 4. What type of materials can deform in controlled ways during impacts? 5. What describes how a material interacts with other substances? 6. What type of steel resists corrosion? 7. What type of materials absorb moisture from the air? 8. What is the English unit for density? 9. What is the ability to transfer heat or electricity in materials? 10. What affects a material's hardness and strength?