Unit 1- (New).pdf

MARINE ENGINEERING, AUTOMATION & CONTROL SYSYTEMS- PAPER I Understanding Ship Systems: Deck officers need to have a basic understanding of ship machinery and systems. While they primarily focus on navigation, cargo handling, and safety, knowing how ship engines, generators, and other...

MARINE ENGINEERING, AUTOMATION & CONTROL SYSYTEMS- PAPER I Understanding Ship Systems: Deck officers need to have a basic understanding of ship machinery and systems. While they primarily focus on navigation, cargo handling, and safety, knowing how ship engines, generators, and other equipment work is essential. Marine engineering knowledge helps deck officers collaborate effectively with engine officers and understand the ship’s overall functioning. Emergency Situations: In emergencies, deck officers may need to operate machinery directly. Familiarity with marine engineering principles allows them to handle critical situations, such as fire-fighting, power loss, or machinery breakdowns. Quick decision-making during emergencies can prevent accidents and save lives. MARINE ENGINEERING, AUTOMATION & CONTROL SYSYTEMS- PAPER I Bridge-Machinery Coordination: Effective communication between the bridge (where deck officers operate) and the engine room (where engine officers work) is essential. Deck officers need to convey instructions accurately to engine officers, ensuring smooth coordination during maneuvers, speed changes, and machinery operations. Navigational Equipment: Modern ships rely on advanced navigational equipment, including GPS, radar, and electronic charts. Deck officers must understand these systems. Marine engineering concepts help deck officers troubleshoot navigation equipment issues and ensure accurate positioning. Safety and Pollution Prevention: Deck officers play a critical role in preventing accidents, collisions, and environmental pollution. Knowledge of marine engineering principles helps them maintain safety protocols, monitor machinery performance, and prevent oil spills or other environmental hazards. MARINE ENGINEERING, AUTOMATION & CONTROL SYSYTEMS- PAPER I Cargo Operations: Deck officers oversee cargo loading and unloading operations. Understanding the ship’s stability, ballast systems, and cargo handling equipment is vital. Marine engineering knowledge helps deck officers manage cargo safely and maintain stability during transit. Compliance with Regulations: International maritime regulations require deck officers to be familiar with ship systems and safety procedures. Marine engineering education ensures compliance with these regulations, enhancing overall ship safety. In summary, marine engineering knowledge complements the skills of deck officers, enabling them to operate ships efficiently, respond to emergencies, and maintain safety standards. MARINE ENGINEERING, AUTOMATION & CONTROL SYSYTEMS- PAPER I MARINE ENGINEERING, AUTOMATION & CONTROL SYSYTEMS- PAPER I MARINE ENGINEERING, AUTOMATION & CONTROL SYSYTEMS- PAPER I STRENGTH OF MATERIALS & MATERIAL SCIENCE  STRENGTH OF MATERIALS Strength of materials is the study of the behaviour of a structure (like a ship) and machinery members (like its engines) under the action of external loads. These loads create internal forces in the components which causes, or attempts to cause, deformation. All components are initially in a state of equilibrium meaning, the external force acting on it and the reaction at the points of support, are equal and the component maintains its shape and size. The internal force causing deformation is called stress and the deformation suffered by the equipment is called strain.  STRENGTH OF MATERIALS Stress and Strain What is Stress? Stress is defined as force per unit area within materials that arises from externally applied forces, uneven heating, or permanent deformation and that permits an accurate description and prediction of elastic, plastic, and fluid behaviour. Stress is given by the following formula: 𝐹 𝜎= 𝐴 where, σ is the stress applied, F is the force applied and A is the area of the force application. The unit of stress is N/m2.  STRENGTH OF MATERIALS Stress and Strain Types of Stress Stress applied to a material can be of two types as follows: Tensile Stress The external force per unit area of the material resulting in the stretch of the material is known as tensile stress. Compressive Stress Compressive stress is the force that is responsible for the deformation of the material, such that the volume of the material reduces.  STRENGTH OF MATERIALS Stress and Strain What is Strain? Strain is the amount of deformation experienced by the body in the direction of force applied, divided by the initial dimensions of the body. The following equation gives the relation for deformation in terms of the length of a solid: 𝜖= 𝛿𝑙 𝐿 where ε is the strain due to the stress applied, δl is the change in length and L is the original length of the material. The strain is a dimensionless quantity as it just defines the relative change in shape.  STRENGTH OF MATERIALS Stress and Strain Types of Strain Strain experienced by a body can be of two types depending on stress application as follows: Tensile Strain The deformation or elongation of a solid body due to applying a tensile force or stress is known as Tensile strain. In other words, tensile strain is produced when a body increases in length as applied forces try to stretch it. Compressive Strain Compressive strain is the deformation in a solid due to the application of compressive stress. In other words, compressive strain is produced when a body decreases in length when equal and opposite forces try to compress it.  STRENGTH OF MATERIALS Stress and Strain Stress-Strain Curve. The material’s stress-strain curve gives its stress- strain relationship. In a stress-strain curve, the stress and its corresponding strain values are plotted.  STRENGTH OF MATERIALS Stress and Strain The different regions in the stress-strain diagram are: Proportional Limit It is the region in the stress-strain curve that obeys Hooke’s Law. In this limit, the stress-strain ratio gives us a proportionality constant known as Young’s modulus. The point OA in the graph represents the proportional limit. Elastic Limit It is the point in the graph up to which the material returns to its original position when the load acting on it is completely removed. Beyond this limit, the material doesn’t return to its original position, and a plastic deformation starts to appear in it.  STRENGTH OF MATERIALS Stress and Strain Yield Point The yield point is defined as the point at which the material starts to deform plastically. After the yield point is passed, permanent plastic deformation occurs. There are two yield points (i) upper yield point (ii) lower yield point. Ultimate Stress Point It is a point that represents the maximum stress that a material can endure before failure. Beyond this point, failure occurs. Fracture or Breaking Point It is the point in the stress-strain curve at which the failure of the material takes place.  STRENGTH OF MATERIALS Stress: When a load acts on a member it gets distributed among the internal forces in the material causing cohesion, these are called stresses. Stresses which are perpendicular to the plane on which they act are called direct stresses and can either be tensile or compressive. Strain is a measure of the deformation produced in a member by the load. Direct stress produces a change in length in the direction of the stress. Tensile strains are considered positive while compressive strains are negative.  STRENGTH OF MATERIALS Stress and Strain Stress and strain take different forms in different situations. Generally, for small deformations, the stress and strain are proportional to each other, and this is known as Hooke’s Law. Hooke’s law states that the strain of the material is proportional to the applied stress within the elastic limit of that material. When the elastic materials are stretched, the atoms and molecules deform until stress is applied, and when the stress is removed, they return to their initial state. Mathematically, Hooke’s law is expressed as: F = –kx In the equation, F is the force, x is the extension in length, k is the constant of proportionality known as the spring constant in N/m. STRENGTH OF MATERIALS Types of Stresses and Strains STRENGTH OF MATERIALS Types of Stresses and Strains  STRENGTH OF MATERIALS Types of Stresses and Strains The cylinder will experience a force downward on the lower surface of the cylinder and an equal and opposite force on the upper surface of the cylinder. The cylinder has an original length of Io and surface area of Ao. As the Cylinder is pulled with the force F the cylinder will lengthen and the resulting length will be l. Stress, σ, is defined as the force divided by the initial surface area, σ=F/Ao. This pulling stress is called tensile stress. Strain is what results from this stress. Strain, ε, is defined as the change in length divided by the original length, ε=ΔI/Io.  STRENGTH OF MATERIALS Types of Stresses and Strains Examples of Tensile Stresses A rubber band being pulled apart. Two people on opposite ends of a rope, pulling the rope away from each other. Developed in the cable of a construction crane when an object is suspended. Developed in the cables of a suspension bridge as cars and other vehicles pass over the bridge decking.  STRENGTH OF MATERIALS Types of Stresses and Strains The term “tensile stress” describes the state in which an applied force tends to elongate the material along the axis of the applied force. It can be numerically represented as the ratio of the magnitude of the applied force to the cross-sectional area on which the force is applied: Stress = F/A The Unit of Measurement of tensile stress, as well as those for all other types of stress, Pascals (Pa) - Newton/m2 Pounds per square inch (psi).  STRENGTH OF MATERIALS Types of Stresses and Strains How Does Tensile Stress Work? When a force is applied to a material that tends to pull the material's atoms apart, the material resists, because the bonds between atoms are so strong. The total stretching force is spread across all the atoms on a cross-sectional plane, all of which are resisting the applied force. The stretching force per unit of cross-sectional area is what we call "tensile stress. The level of tensile stress at which plastic deformation begins to occur varies depending on the material’s chemical composition, microstructural details, and environmental conditions (such as temperature). These factors largely control a material’s mechanical properties. Stress concentrations due to part geometry can also impact the deformation mechanics of a material. STRENGTH OF MATERIALS Types of Stresses and Strains  STRENGTH OF MATERIALS Types of Stresses and Strains Benefits of Tensile Stress Testing Determine Tensile Strength: Some materials are preferred over others for a particular application due to their higher tensile strengths. Tensile strength describes the stress at which a material will rupture while yield strength is the stress value at which plastic deformation occurs. High tensile strength means that the material is strong and can be used in structural applications where applied forces tend to elongate or stretch materials. Measure Ductility: Ductility can be determined from tensile strength by calculating the slope of the linear portion of a stress-strain curve. High ductility means materials can experience significant deformation before failure. This is highly desirable in numerous applications such as the cables in suspension bridges, structural beams, and more. Evaluate Fatigue Resistance: Fatigue resistance is a material’s ability to withstand cyclic or repeated loading. Materials with higher tensile strength and ductility have higher fatigue resistance. Fatigue resistance is desirable in applications with oscillating loads such as bridge crossmembers and aircraft components.  STRENGTH OF MATERIALS Types of Stresses and Strains Examples of Tensile stress in ships: Structural parts of a ship that are subjected to bending will have a tensile stress induced in one direction. Hogging and Sagging that occurs when a ship is underway in heavy seas causing bending. Reciprocating machinery Wires and ropes used for lifting loads Braces used in engines and boilers. All bolts and fasteners used in machinery spaces.  STRENGTH OF MATERIALS Types of Stresses and Strains If instead of pulling on the material, it is pushed or compressed the cylinder will experience compressive stress.  STRENGTH OF MATERIALS Types of Stresses and Strains What Causes Compressive Stress? Compressive stress is caused by atomic dislocations. The dimensions of a material tend to grow in the directions perpendicular to the direction at which the compressive force is applied. When a compressive force is applied, atoms dislocate around a slip plane or an imaginary plane through the material’s microstructure. The atoms above the slip plane compress while the atoms below the slip plane go into tension. This phenomenon is what causes the “widening” effect when materials are in compression. STRENGTH OF MATERIALS Types of Stresses and Strains  STRENGTH OF MATERIALS Types of Stresses and Strains Examples of Compression stress in ships: Structural parts of a ship that are subjected to bending will have a compression stress induced in one direction. Hogging and Sagging that occurs when a ship is underway in heavy seas causing bending. Heavy engine components have a compressive stress on their foundations. Heavy machinery bolted to decks and tanktops.  STRENGTH OF MATERIALS Types of Stresses and Strains Stress - Compression Compression stresses develop within a material when forces compress or crush the material. A column that supports an overhead beam is in compression, and the internal stresses that develop within the column are compressive stresses.  STRENGTH OF MATERIALS Types of Stresses and Strains Shear forces act in one direction at the top of a structure and the opposite direction at the bottom, causing shearing deformation. Example, when you cut a piece of material, shear force is involved. It’s depicted in shear diagrams for different sections along a structural member as a pair of vector forces of equal magnitude but opposite directions.  STRENGTH OF MATERIALS Cutting with Scissors: When you use scissors to cut paper, fabric, or other materials, shear forces are at play. The blades apply opposing forces along the cutting edge, causing the material to separate. Bolts and Nuts: When tightening a bolt with a wrench, shear forces act on the threads. The force applied to the bolt head creates a shear force that prevents the nut from rotating. Rivets in Aircraft Wings: In aircraft construction, rivets hold structural components together. Shear forces occur at the rivet joints, ensuring the wing panels remain connected during flight. Slicing Food: When you slice a tomato or bread with a knife, shear forces cut through the material. The blade applies opposing forces, resulting in a clean cut. Earthquake-Resistant Buildings: Buildings designed to withstand earthquakes have shear walls or diagonal braces. These elements absorb lateral forces during seismic events, preventing the building from collapsing.  STRENGTH OF MATERIALS Types of Stresses and Strains Examples of Shearing force in ships: When a ship is being loaded with cargo the ship experiences a shearing force at the point where the load acts. A ship’s tanktops are specially strengthened to withstand this effect. The pitching motion of a ship induces a shearing force on areas where heavy weights are resting. The ship’s keel is one of the principal parts subjected to this force.  STRENGTH OF MATERIALS Types of Stresses and Strains What Is Torsional Stress? Torsional stress is a form of shear stress experienced by a body when a twisting force is applied. Example. A car's engine/gearbox will attempt to turn the car’s axle, while the wheels on the other end of the axle will resist the turning. This will cause torsional stress about the center point of the axle.  STRENGTH OF MATERIALS Properties of Metals The following are the mechanical properties used as measurements of how metals behave under load: Strength, Hardness, Toughness, Elasticity, Plasticity, Brittleness, Ductility And Malleability These properties are described in terms of the types of force or stress that the metal must withstand and how these are resisted.  STRENGTH OF MATERIALS Properties of Metals Hardness The resistance of a material to force penetration or bending is hardness. Hardness is the ability of a material to resist scratching, abrasion, cutting, or penetration. Toughness It is the property of a material that enables it to withstand shock or impact. Toughness is the opposite condition of brittleness. The toughness may be considering the combination of strength and plasticity. Brittleness The brittleness of a property of a material enables it to withstand permanent deformation. They will break rather than bend under shock or impact. Generally, brittle metals have high compressive strength but low tensile strength.  STRENGTH OF MATERIALS Properties of Metals Stiffness It is a mechanical property. The stiffness is the resistance of a material to elastic deformation or deflection. In stiffness, a material that suffers light deformation under load has a high degree of stiffness. The stiffness of a structure is important in many engineering applications, so the modulus of elasticity is often one of the primary properties when selecting a material. Ductility The ductility is a property of a material that enables it to be drawn out into a thin wire. Mild steel, copper, and aluminum are good examples of a ductile material.  STRENGTH OF MATERIALS Properties of Metals Malleability Malleability is a property of a material that permits it to be hammered or rolled into sheets of other sizes and shapes. Aluminum, copper, tin, lead e#1tc are examples of malleable metals. Cohesion It is a mechanical property. Cohesion is a property of a solid body by which it resists being broken into a fragment. Impact Strength The impact strength is the ability of a metal to resist suddenly applied loads. #  STRENGTH OF MATERIALS Properties of Metals Fatigue The fatigue is the long effect of repeated straining action which causes the strain or break of the material. It is the term ‘fatigue’ used to describe the fatigue of material under repeatedly applied forces. Creep The creep is a slow and progressive deformation of a material with time at a constant force. The simplest type of creep deformation is viscous flow. Some metals generally exhibit creep at high temperatures, whereas plastic, rubber, and similar amorphous materials are very temperature-sensitive to creep. The force for a specified rate of strain at constant temperature is called creep strength STRENGTH OF MATERIALS Classification of Materials STRENGTH OF MATERIALS Properties of Material  STRENGTH OF MATERIALS Fatigue Failure Fatigue is the weakening of a material caused by cyclic loading that results in progressive, brittle and localized structural damage. Once a crack has initiated, each loading cycle will grow the crack a small amount, even when repeated alternating or cyclic stresses are of an intensity considerably below the normal strength. The stresses could be due to vibration or thermal cycling. Fatigue damage is caused by: simultaneous action of cyclic stress, tensile stress (whether directly applied or residual), plastic strain. If any one of these three is not present, a fatigue crack will not initiate and propagate. The majority of engineering failures are caused by fatigue.  STRENGTH OF MATERIALS Fatigue Failure High Cycle Fatigue vs Low Cycle Fatigue Fatigue has been separated into regions of high cycle fatigue and low cycle fatigue. The chief difference between high cycle and low cycle fatigue is the number of cycles to failure. Transition between LCF and HCF is determined by the stress level, i.e. transition between plastic and elastic deformations. High cycle fatigue require more than 104 cycles to failure where stress is low and primarily elastic. Low cycle fatigue is characterized by repeated plastic deformation (i.e. in each cycle) and therefore, the number of cycles to failure is low. In the plastic region large changes in strain can be produced by small changes in stress. Experiments have shown that low cycle fatigue is also crack growth. Fatigue failures, both for high and low cycle, all follow the same basic steps process of crack initiation, stage I crack growth, stage II crack growth, and finally ultimate failure. STRENGTH OF MATERIALS Fatigue Failure  STRENGTH OF MATERIALS Properties of Metals Ductility Malleability Malleability is the property of metal Ductility is the property of metal associated with the ability to be associated with the ability to be stretched hammered into a thin sheet without into wire without breaking. breaking The external force or stress is tensile The external force or stress is stress compressive stress The ductile materials show high The malleable materials do not malleability necessarily exhibit good ductility The nature of ductility is stretching The nature of malleability is compressive Examples are copper, nickel, gold etc.. Examples are gold, silver aluminium etc.  MATERIAL SCIENCE Property Definition Strength The ability to resist an applied force Tensile Strength Maximum pulling force a material can withstand before failure Yield Strength Stress at which the material reaches plasticity Ultimate Tensile Strength Stress at which a material breaks Compressive Strength Resistance of a material under a pushing force Ductility Amount a material can be stretched while being deformed Malleability Ability of a material to be deformed without breaking Hardness The ability of a material to be deformed without breaking Toughness The ability of a material to resist wear and abrasion Brittleness Potential for a material to shatter on impact Stiffness The ability of a material to withstand an impact without breaking Elasticity The ability of a material to resist bending Plasticity Material’s ability to permanently deform after stretching STRENGTH OF MATERIALS Properties of Metals