Mechanical principles
Fundamental Concepts
- Mechanical engineering principles focus on the science and mathematics of object motion.
- Understanding these principles means mastering the forces and accelerations acting on objects.
- Important in this realm are newton's laws of motion, which describe how objects behave when acted upon by external forces.
Forces
- Forces are pushes or pulls on an object, resulting in acceleration.
- They can be represented as vectors, giving them both magnitude and direction.
- Equilibrium Forces: If the net force on an object is zero, it's said to be in equilibrium, this can either be a state of rest or uniform motion.
- Convincing free-body diagrams can be used to understand and calculate the forces acting on an object.
Stress and Strains
- An external force applied to an object can produce an internal force within the object, known as stress.
- Stress is equal to the force applied divided by the area it is applied over.
- Strain is the elongation or compression (change in length) per unit length of an object when a stress is applied.
- The ratio of stress to strain is known as the modulus of elasticity or Young's modulus and is a characteristic property of materials.
Physics of Solids
- Different materials respond to stress and strain in different ways, and this is described by their mechanical properties.
- The behaviour of a solid material when subjected to stress is known as mechanical behaviour.
- Some common stress-strain mechanical behaviours include elasticity, plasticity, and fracture.
Momentum and Energy
- Momentum is the product of an object's mass and velocity. It is also a vector quantity.
- The principle of conservation of momentum states that for any system closed to all external forces, the total momentum is constant.
- Work is the energy transfer due to a force acting over a distance.
- Kinetic Energy is the energy of an object due to its motion, while potential energy is due to its position or state.
- The principle of conservation of energy states that the total energy of an isolated system remains constant.
Material Selection
- Each engineering material has unique properties that make it suitable for particular applications.
- Some factors influencing material selection include cost, availability, and mechanical properties.
- Advanced materials such as composites mix properties of different materials to produce something greater than the sum of its parts.
- Material testing, such as tensile testing, hardness testing and impact testing, provides valuable information about a material’s mechanical and physical properties.
By understanding and applying these mechanical principles, we can predict how systems will react under specific conditions for greater safety, reliability, and efficiency. Whether designing a bridge, a car, or a computer part, these principles provide the groundwork for successful engineering.