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15 Cards in this Set
- Front
- Back
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Failures are often caused by ____ of too great a ____ for the structure or material. |
Forces Magnitude |
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What are examples of external possibilities of forces on objects? |
Collisions Fires Human occupancy Unplanned uses Wear Weather Reasonable, foreseeable use/exposure |
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What are the two ways to consider safety factors? |
Designers method Text method |
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What is the designer’s method? |
Final Design = Require Design * Safety Factor (SF) This is the more familiar method. |
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What is the Text Method (observational)? |
Safety factor = Critical Load (that would cause failure) / Current Load |
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What is strain? |
The change in physical shape or deformation caused by stress. Failure usually occurs after some amount of strain. |
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What is stress? |
Force per unit area - internal to an object. Fluids have pressure, solids have stress. |
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True or false: you must try to consider all manners of failure to ensure that the correct materials are chosen. |
True |
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What are the different modes of failure? |
Static failures. Dynamic failures. Instability failure. Environmental-related failures. Creep. |
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What are static failures? |
Failures due to forces applied by structures that are not moving prior to failure. Shearing, tension, compression, bearing, bending, buckling. |
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What are dynamic failures? |
Failures due to forces applied due to movement. Fatiguing, impacting. |
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What is instability failure? |
Structure does not fail through breaking etc. It tips over, slides, rolls, etc. undesirably |
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What are examples of environmental-related failures? |
Rust. Fermentation. Exposure to sun/UV radiation. Temperature variations. |
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What is creep? |
Very slow, permanent deformation. Usually occurs within a range of temperature. |
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What kind of materials experience creep? |
Materials with high plasticity. i.e. old glass windows are thicker at the bottom due to creep (not exactly). i.e. spinning blades get thicker at the ends. |
