Machine Dynamics and Design Process

Machine Dynamics

• Dynamics studies the forces and torques that cause motion in machine parts.
• Kinetics analyzes the inertia forces generated due to mass and motion of the parts.
• Statics studies forces and their effects when parts are at rest.
• Kinematics analyzes the relative motion of different machine parts without considering the forces involved.

Machine Design Process:

• It typically starts with defining the functional requirements for the machine.
• Kinematics and dynamic analysis are integral parts of the design process.
• They provide crucial inputs and outputs for various design steps, like sizing, sealing, lubrication, material selection, manufacturing, maintenance, safety, and assembly.

Kinematics Terminology

• Kinematics focuses on the geometry of motion, studying the how, not the why, of machine part movement.
• Kinematic Analysis determines the displacement, velocity, and acceleration of a mechanism's parts.
• Linkage is a chain of connected rigid parts in a mechanism.
• Frame is the reference point for motion of all other parts.
• Links are the individual elements of a mechanism connecting to other elements.
• Simple Link has two joints connecting it to other links.
• Complex Link has more than two joints.
• Rigid Link does not deform during motion.
• Flexible Link deforms partly during motion transmission.
• Fluid Link uses a fluid medium for motion transmission.

Machine vs. Mechanism vs. Structure

• Machine is a complete product designed to alter, transmit, and direct forces, achieving a specific goal.
• Mechanism is a specific functional unit within a machine tasked with transferring motion and forces. It modifies and transforms motion and is considered the "heart" of the machine.
• Structure is an assemblage of rigid bodies that are stationary relative to one another, designed to carry loads and maintain form.

Classification of Kinematic Pairs

• Kinematic pairs describe the connections between moving parts.
• Lower Order/Full Joints allow relative motion between connected links in one degree of freedom.
• Higher Order/Half Joints allow more degrees of freedom within the connection, for example, cam joints.

Mobility

• Mobility (M) is the number of independent movements a mechanism can have - it's the degrees of freedom (DOF).
• Coincident Joints occur when three links meet on a single pin, requiring modelling as two separate pins.
• Idle Degrees of Freedom are redundant movements in a link that do not impact other links.
• A Locked Mechanism has zero or negative degrees of freedom, meaning it is unable to move.

Vectors

• Parallel Vectors share the same direction.
• Equal Vectors have the same magnitude and direction.
• Anti-parallel Vectors have opposite directions.
• Negative Vectors are anti-parallel and have the same magnitude.
• Collinear Vectors lie on the same line.
• Co-initial Vectors share the same starting point.
• Co-terminus Vectors share the same endpoint.
• Coplanar Vectors lie on the same plane.
• Non-coplanar Vectors are distributed in space.

Vector Types by Effect

• Polar Vectors have straight line effect. Examples include Displacement, Velocity, Acceleration, and Force.
• Axial Vectors have rotational effect. Examples include Angular momentum, Angular velocity, and Angular acceleration.

Position vs. Displacement

• Position is the location of a point on a mechanism.
• Displacement is the result of motion:
  • Linear Displacement is the straight-line distance between two positions.
  • Angular Displacement is the distance between two positions of a rotating link.

Position Analysis

• Graphical Analysis visually determines the position of a point on a mechanism.
• Analytical Analysis uses mathematical equations to determine the position of a point on a mechanism.

Special Conditions

• Limiting Positions represent the extreme configurations of a mechanism, where a follower link reaches its most forward or backward points.

Explore the fundamental concepts of machine dynamics, including kinetics, statics, and kinematics. This quiz delves into the machine design process and the crucial role that dynamic analysis plays in defining and meeting functional requirements. Test your understanding of the terminology and principles that guide the movement of machine parts.