MS&E Materials selection A+B

24 flashcards · Physics · by Kristóf Nagy

1. Mode of Loading

   Different ways a component experiences external forces, such as tension, compression, shear, bending, and torsion. Each mode requires consideration of specific geometric parameters and material properties in order to derive the corresponding PI.

2. Torsional Constant (J)

   Describes the relationship between torque and resulting angle change experienced by a shaft, providing insight into its resistance towards torsional deformations. Circular cross-sections have the highest torsional constant among common shapes.

3. Shape Factor (φ)

   Dimensionless quantity expressing the improvement achieved in structural efficiency after optimally redistributing material without changing overall area. Higher values indicate superior performance gains.

4. Radius of Gyration (k)

   Characterizes a shape's compactness by measuring the distance between the NA and furthest point on the cross-section. Smaller k values imply higher stiffness for same cross-sectional areas.

5. Neutral Axis (NA)

   An imaginary line within a cross-section experiencing zero bending stress while subjected to transverse loading. Its position depends on the cross-sectional shape and orientation relative to principal axes of inertia.

6. Principal Axes of Inertia

   Two mutually perpendicular axes passing through the centroid of a cross-section where maximum and minimum second moments of area occur. These provide insights regarding the distribution of material around the neutral axis.

7. Materials selection

   The process of choosing an appropriate material for a particular design application

8. Performance index

   A measure of how well a material meets the functional requirements of a design

9. Functional requirements

   The necessary characteristics that a material must possess in order to perform its intended function in a design

10. Free variables

    Variables that can be changed during the materials selection process in order to optimize the performance index

11. Structured database

    A type of database that stores data in a predefined format, allowing for efficient querying and comparison of materials

12. Unstructured database

    A type of database that stores data in a less formal manner, often consisting of text documents or other unstructured data formats

13. Constraint-based selection

    A method of materials selection that involves selecting materials that meet certain specified constraints

14. Section Modulus (Z)

    Measures the capacity of a beam to counteract bending stresses based on its cross-sectional shape. High Z values correspond to increased bending stiffness.

15. Polar Moment of Inertia (J)

    Represents a beam's ability to resist torsional deformation induced by twisting moments. Greater polar moments lead to better torsional rigidity.

16. Objective-based selection

    A method of materials selection that involves selecting materials that optimize a specific objective or performance metric

17. Second Moment of Area (I)

    A geometric measurement quantifying the resistance offered by a beam against bending stresses. Higher moments result in greater stiffness and lower deflection under load.

18. Design analysis

    The process of analyzing a design problem in order to determine the required functional requirements and identify potential materials candidates

19. Performance Index (PI)

    A measure used to compare different combinations of functional requirements, geometric parameters, and material properties in order to make an informed decision during the materials selection process. It can involve minimization or maximization depending on the objective.

20. Rod Buckling

    Understanding how rods fail due to instability caused by compressive loading. Calculation of critical force required for elastic buckling helps ensure safe designs.

21. Separable Performance Index

    When evaluating multiple functional requirements independently, each requirement receives a separate score computed through multiplication of individual scores obtained from function (f), geometrical parameter (g), and material property (m).

22. Functional Requirements

    The specific demands placed upon a component, such as stiffness, strength, fatigue limit, etc., which need to be met during its operation. These requirements help determine the appropriate PI for selecting suitable materials.

23. Geometric Parameters

    The physical characteristics of a component that influence its behavior under applied loads, including cross-sectional area, second moment of area, polar moment of inertia, etc. They play a role in determining the relevant shape factor associated with various modes of loading.

24. Material Properties

    Intrinsic qualities of materials that affect their performance, such as elastic modulus (Young's), yield strength, density, Poisson's ratio, coefficient of thermal expansion, electrical conductivity, etc. They contribute to calculating the PI values alongside functional requirements and geometric parameters.