1 / 14

Statics Activities

Statics Activities. Stress (s). Force per unit area ( s ) Typical engineering units p si (lb f /in 2 ) N/m 2 Stress = Force/Area Applied by external agents Area is X-section area Same definition as pressure. Stress (σ). applied to the material by external agents

oriel
Télécharger la présentation

Statics Activities

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Statics Activities

  2. Stress (s) • Force per unit area (s) • Typical engineering units • psi (lbf/in2) • N/m2 • Stress = Force/Area • Applied by external agents • Area is X-section area • Same definition as pressure

  3. Stress (σ) • applied to the material by external agents • force per unit area (same definition as pressure) • stress = force / area = F / A • unit: N/m2

  4. Types of Stress • tensile: object is pulled apart • compressive: object is pushed together • shear: equal and opposite forces applied across object’s faces

  5. Strain (ε) • material’s response to the stress • ratio of the change in length to the original length • strain = change in length / original length • strain = ΔL / Lo • units: dimensionless

  6. Stress • Example • Calculate the stress in a cylindrical rod if a 200N force is applied to one end. The radius of the cylinder is 4cm. A = p(0.04)2 = 0.0.05m2 s = 200N/0.005m2 = 40000N/m2 200 N A = pr2

  7. Shear stress • When stress develops in an area parallel to the force direction • Sometimes when a force affects surfaces, or materials with “grain” (i.e. wood, some crystals, shale rock), or specific geometries.

  8. Strain (e) • The ratio of change in length (DL) to original length (Lo) (dimensionless) • = DL/Lo • Brought about by a stress in a material • Can be temporary or permanent deformation

  9. Strain

  10. Elastic Modulus • Elastic modulus (E) (or Young’s modulus) • Indicator of relative strength of material E = s/e = (stress/strain)

  11. Modes of Failure • Materials can fail • Damaged (excessive strain- ductile failure) • Catastrophic (fracture)

  12. Ultimate Strength & Fracture • Ultimate Strength – A level of stress in a material that causes failure • Compression • Tension • Shear • Safety factors are applied to protect against reaching this level (2x,3x,4x, and higher).

More Related