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Materials
Properties of Materials- Chapter 1
| Question | Answer |
|---|---|
| Material Engineering | Understanding the behavior and performance of materials |
| Why we need this knowledge | For the design, construction & maintenance of civil structures |
| Advancements in Material Technology | Objectives • Better quality • More economical • Safer materials |
| Material Engineer | Involved in: • Selection • Specifications • QC/QA |
| Economic considerations | Cost of material include: • Direct cost (raw material & availability) • Manufacturing • Transportation • Placing • Maintenance Example: Bituminous mixtures |
| “Response to external load” depends on: | • Properties of materials • Magnitude, location, and type of load • Element geometry Example: Steel beam in a building |
| Types of material or element failure: | –Collapse failure –Functional failure Example: Structural beam or column in a building |
| Loading conditions: | • Static loading:“Remain in place (sustained or dead load) or removed slowly” Ex: Load of the structure, furniture, occupants, etc. • Dynamic loading: “cause vibration of structure” Ex: “Earthquakes”, Vehicles on roads or bridges”. |
| Elastic behavior | Deforms under load with perfect recovery after load removal of the load (Ideal condition) |
| Modulus of elasticity (E)= | Normal stress / Normal Strain |
| Poisson’s ratio = | Lateral strain/ Axial strain (Range: 0.0‐0.5) |
| Elastoplastic behavior | Types: Brittle material: No deformation (very little) prior to failure (Concrete). Ductile material: Appreciable plastic deformation prior to failure (Steel). |
| Toughness: | Amount of energy required to fracture a specimen or sample or the area under the stress strain curve. |
| Creep | Long term deformation caused by sustained loads (example: concrete). |
| Viscous flow | Short Term deformation caused by sustained load (example: asphalt mixtures) |
| Temperature | Generally, higher temperature increases toughness and visa versa (changes material from brittle to ductile) |
| Fracture mode of failure | Fails when loads exceeds the maximum stress (Ex: concrete column in building) |
| Fatigue mode of failure | Though stress are below maximum stress, it will fail as a result of repeated loads (Ex: highway pavement) |
| Excessive deformation(deflection) mode of failure | Makes people uncomfortable though the structure is sound |
| Factor of Safety (FS) | Stress at Failure/Allowable Stress |
| Density | Mass/Volume |
| Unit Weight | Weight/Volume |
| Specific Gravity | Mass of Material/Mass of water of equal volume at specified temp |
| Density and Unit Weight of Aggregates | Needs other terms to assess based on degree of compaction, voids, etc. |
| Thermal expansion | Rate of material expansion with temperature; expressed as coefficient of thermal expansion |
| Surface characteristics | Surface texture, abrasion resistance and wear, forms of surface deterioration |
| Corrosion form of surface deterioration | surface disintegration by dissolution (example: metals) |
| Degradation form of surface deterioration | loss of solvent (example: asphalt) |
| Wear form of surface deterioration | External abrasion action (example: rigid and flexible pavements/studded tires) |
| Aesthetic characteristics | Appearance of material, requires the collaboration between the architect and material engineer |
| Material Variability | Changing properties of certain material as a result of natural, production, environmental and human factor |
| Precision | Variability of repeated measurement under carefully controlled conditions |
| Accuracy | conformity of results to the true value or the absent of bias |
| Bias | Tendency of an estimate to deviate in one direction from the true value or systematic error between a test value and the true value |
| AMRL (American Materials Reference Laboratory) | a certification agency for engineering laboratory |
| Sampling | A true representation of a population (material) |
| Random Sampling | requires all elements of the population to have an equal chance to be chosen for selection |
| Representative Sampling | Taken from the population and representative of the entire lot |
| True sampling depends on: | •Number of samples •Nature of material •Rate of production •Production period •Production equipments |
| Control charts | A graphical presentation to verify a process's in control |
| Experimental Errors are caused by: | • Human errors • Machine errors |
Created by:
smh02
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