Steels: From Materials Science to Structural Engineering
Anodization, which is similar to electroplating, oxidizes the surface of the titanium strips by running a current through a solution in which the metal is suspended. Different combinations of time and voltage determine the thickness of the surface oxidation, which in turn determines the final color as light reflects off of it in different ways. How can we create planes that are so light and have so little drag that one day a flight from New York to Tokyo might take only 5 hours instead of 13?
How can we design medical implants that are biocompatible and don't wear out during a patient's lifetime? How can we make mountain bikes that are easier to carry over streams? How can we safely store nuclear waste for 10, years or more? From a Samurai sword to a steel I-beam to electrical wiring, metals are part of our past, present and future. Metals are the most common elements in the periodic table and are characterized by malleability, ductility, high electrical and thermal conductivity and a shiny surface that reflects light.
Metallic bonding where valence electrons are shared by the entire solid gives rise to the "free" electrons responsible for electrical and thermal conductivity. Most metals and alloys combinations of metals are also highly crystalline, which is the key to their ability deform plastically and to resist failure under repeated mechanical loading—good examples of this are the alloys used in aircraft that can compensate for deformation in high-speed flight, or skyscrapers designed to bend in the wind. When approaching the nanometer scale, in which electrons behave like waves and surface effects are important, metallic materials acquire intriguing properties.
For instance, silver nanoparticles are yellow and gold nanoparticles are burgundy. These new optical properties are interesting for sensing and communication technologies. With the cubes, signal can be identified with just ten thousand molecules. Without the nanocubes, ten billion molecules would be needed.
Take ideas from students and discuss each. Relatively low cost, minimal material requirements, minimal impact on the environment, low maintenance requirements and cost, safe, portable, and supports pedestrian modes of transport. Wire bridges have minimal impact on the surrounding environment, habitats and natural landscapes. They require little maintenance, have few if any accidents or fatalities, and are quite portable. The wire bridge also encourages pedestrian modes of transportation, which is better for personal health and maintaining a sustainable society.
- The Perfect 10 Diet: 10 Key Hormones That Hold the Secret to Losing Weight and Feeling Great-Fast!.
- Meta-Analysis for Public Management and Policy.
- There was a problem providing the content you requested?
- Metallurgical Materials Science and Alloy Design - RSS feeds MSE Journals!
- Hadrians Sozialpolitik (German Edition).
- Rig-Veda Book 9;
- Structural Engineering | List of High Impact Articles | PPts | Journals | Videos?
What might be some disadvantages of simple wire bridge in some situations? Not as suitable for heavy-load, high vehicle or railroad transport. In review, what are some of the materials engineers use for designing and building bridges in our towns and cities? Concrete for foundations and anchoring, steel for beams and cables, etc. Two basic materials are used to construct modern bridges: Other types of materials are not as commonly used as steel and concrete.
The following section describes in more detail steel, concrete and typical material properties and engineering terms used during the design of a bridge. Steel is a form of iron, which is created from iron ore, a rock that contains a high concentration of iron. All iron ores contain iron combined with oxygen.
To make iron from iron ore, the oxygen must be removed. One way to accomplish this is by using a bloomery or a blast furnace see the Additional Multimedia Support section for a link to a blast furnace animation. From pig iron, either "wrought iron" is created by eliminating most of the carbon, or steel is created by eliminating most of the impurities.
The many types of steel are called alloys. Concrete is simply a combination of two materials: Cement is a powder made of a variety of materials usually certain types of clay and limestone. When cement is mixed with water a chemical reaction called hydration occurs that causes the cement to harden.
Aggregate is a mixture of fine and coarse aggregates. The fine aggregate is typically sand; the coarse aggregate is typically gravel rock. When the cement, aggregate and water are mixed together a hardened mass called concrete results. View of fractured surfaces of a concrete core taken from a bridge deck and tested to failure by a huge tensile force. Department of Transportation, http: Structural engineers use material properties when designing bridge members.
The modulus of elasticity E or Young's modulus of a material is a constant associated with Hooke's Law. The modulus of elasticity indicates the stiffness of a material. Tensile strength is the amount of tensile stress that a material can resist before failing. Compressive strength is the amount of compressive stress that a material can resist before failing. A material that exhibits ductile properties can be subjected to large strains before it ruptures or fails.
A material that exhibits brittle properties shows little or no yielding before failure. Typical stress-strain diagram for steel and concrete. Engineers refer to stress-strain diagrams that graphically display all of these characteristics. In a stress-strain diagram for steel and concrete, the steel curve has a noticeable linear straight region; the slope of this linear region is the modulus of elasticity.
The end points of these curves represent failure.
Spotlight on Research
The concrete curve shows a steady increase in strain and stress before it ruptures. Concrete fails with little or no warning; thus, it is considered a brittle material. Just before steel breaks, it experiences a reduction in stress while strain increases. This is seen on the steel curve as the negative sloping section of the curve.
When steel fails, it presents some type of warning, typically in the form of large deflections; thus, steel is considered a ductile material.
The ability of a material to show little or no yielding before failure. A powder made of a variety of materials usually certain types of clay and limestone that when mixed with water hardens. Cement is an ingredient of concrete. The amount of compressive stress that a material can resist before failing. A combination of cement and aggregate into one solid mass.
- Montana Surrender.
- Spotlight on Research;
- Recommended pages.
- Taste and See: An invitation to read the Bible!
Gravel, sand, cement and water were mixed to create our concrete sidewalk. The ability of a material to be subjected to large strains before it ruptures or fails. A rock that contains a high concentration of iron. A constituent part of any structural or composite whole, such as a subordinate structural beam, column or wall. E Indicates the stiffness of a material. A concrete member with steel embedded inside it to resist tensile forces.
Refined iron that contains virtually no impurities. The elongation or contraction of a material per unit length of the material. Applied load divided by the material area it is acting on. The amount of tensile stress that a material can resist before failing. Think of bridges around your home, and along roadways, bike paths or walking paths that you use. What do the bridges look like? What types of materials were used to construct them? Many types of materials have been used to create modern bridges, including concrete, steel, wood, iron, plastic and stone.
Today, we learned that concrete and steel are the most commonly used materials in large modern bridges. What is an advantage to using steel? Steel has high strength in both compression and tension. Steel can be bent or shaped easily into different forms. Concrete can be shaped easily with the use of forms [much like molds]. Concrete is also extremely strong in compression. How about a disadvantage to steel? Concrete is very weak in tension.
Engineers consider all the advantages and disadvantages of materials when deciding which to incorporate into their bridge designs. What are other things that engineers must consider when selecting materials for construction of a bridge? The strength of the material is usually the most important factor engineers consider. They also think about the cost, availability, speed of construction, and suitability of that material for that particular bridge.
As a class, have students engage in open discussion. Remind students that in brainstorming, no idea or suggestion is "silly. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Have them raise their hands to respond. Write their ideas on the board. The worksheet includes a matching activity to reinforce vocabulary and definitions.
The three math problems include solving equations and are of increasing difficulty. Assign younger students only the first question. Add the next problem for older students.
Civil Engineering Research - Structural Engineering - University of Birmingham
Assign the third question as a math challenge to advanced students. Next time students ride in a car or bus, ask them to notice and record on paper the types of materials used in the bridges they cross. Lead a discussion of findings during the next class period. Many types of aggregates — such as sand, gravel, pebbles, glass, vermiculite and rubber - have been used to make concrete. One disadvantage to concrete is that it is weak when a tension force is applied to it and therefore has a very low tensile strength. Concrete has a tendency to crack, and special design precautions are often taken to control the cracking.
Reinforced concrete often has steel embedded in it. Why might there be so many types of aggregates? To achieve different purposes in different applications. Sometimes other materials are added to the concrete mix to give it specific characteristics not typical with plain concrete mixes, making the concrete less brittle, stronger, more durable, a better insulator, or less likely to suffer freeze-thaw damage. Incorporate synthetic fibers to improve elasticity, include bits of colored glass for more decorative applications, recycle glass and rubber waste material from recycling collection or old tires.
Assign internet research to learn more. Lead students in another TeachEngineering activity on the strength of materials, easily relatable to concrete: Engineering for the Three Little Pigs. Show students a blast furnace animation at the howstuffworks website: Watch a four-minute narrated film clip of the wind-induced collapse of the Tacoma Narrows Bridge in Washington in Called "Galloping Gertie," this suspension bridge collapsed four months after it was built. Farmington Hills, MI, Manual of Steel Construction: American Institute of Steel Construction, Accessed October 16, Good overview of concrete and cement http: Concrete in the Classroom: Source of some vocabulary definitions, with some adaptation http: EcoSystems — WireBridge Designs.
Cement and Concrete Basics.