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Met 121 Test 4
Test 4 study guide Missouri S&T Spring 2011
| Question | Answer |
|---|---|
| Assets of aluminum are | Lightweight, easy to fabricate, and good electrical and thermal conductivity |
| Limitations of aluminum are | poor wear resistance, low stiffness, poor in fatigue. |
| Aluminum and aluminum alloys are: | fabrication friendly |
| Wrought alloys are: | shaped as a solid. |
| Desirable attributes of wrought alloys are | low yield strength, high ductility, good strain hardening. |
| The designation system for wrought aluminum alloys involves a: | four-digit number |
| The suffix in the aluminum designation system designates the material: | condition (past processing history) |
| An aluminum alloy with a three-digit designation number is a: | cast aluminum alloy |
| Attractive properties for casting alloys include: | low melting point, good fluidity, high as-solidified strength |
| High strength aluminum alloys are | heat treatable |
| The best corrosion resistance is found in aluminum alloys that are: | non heat treatable |
| The most effective strengthening method for aluminum alloys is: | age hardening |
| (True/false) A high-strength aerospace aluminum alloy has strength equivalent to a quenched-and-tempered medium carbon steel. | false |
| (True/False) Casting alloys can be heat treated after casting for added strength. | True |
| In the color anodizing process, the material being colored is: | Al oxide |
| What are some assets of aluminum-lithium alloys | stronger, lighter, stiffer |
| Attributes of magnesium | Does not respond well to strengthening methods, strength to weight is good, it’s lighter than aluminum. |
| Limitations of magnesium alloys | poor wear resistance, poor elevated temp strength, poor fatigue resistance |
| (T/F) Magnesium can be cast to final shape provided the molten metal and hot solid is isolated from oxygen by some form of protective atmosphere and special mold materials are used. | True |
| Beryllium is unique among the engineering metals because of its extremely high: | Elastic Modulus |
| Titanium has a density that is: | Between steel and aluminum |
| (T/F) The corrosion resistance of titanium is due to an adherent oxide, much like Al. | True |
| Orthopedic implants and bone-repair screws and plates often use this material since it is strong, light weight and corrosion resistant to body fluids. | Titanium |
| Color anodizing is a surface finishing treatment that is somewhat unique to this metal | Al |
| This metal can be very difficult to fabricate. It is brittle at room temp (HCP). Machining chips can burn: and molten metal must be kept under protective atmosphere. | Mg |
| This metal is sometimes used for nuclear applications because it is relatively transparent to the movement of neutrons | Beryllium |
| This metal is lighter than Al, but stiffer than steel | Be |
| Because the YSstrongest/YSweakest ratio is only 3, design engineers must design to the material, rather than the material accommodating the design. | Mg |
| It is the only high temp lightweight metal, retaining useful strength to 900 F. | Ti |
| It is often used in place of aluminum when use involves elevated temp, or in place of steel for weight savings. | Ti |
| It has the lowest density of all of the engineering metals (i.e. is lightest) | Magnesium |
| People specifying the use of this metal are driven by a desire for light weight, and are willing to accept the numerous negative properties and characteristics. | Mg |
| Since this material is allotropic (BCC at elevated temp and HCP at room temp), it can be heat treated by both age hardening and phase transformation processes. | Ti |
| It offers the strength of a heat-treated medium-carbon steel at almost half the weight | Ti |
| Because of its FCC structure, it has the highest ductility of the lightweight metals | Al |
| Because this metal is considered to be toxic, processing often requires special precautions | Be |
| Its unusual designation system consists of two letters followed by two or three numbers, such as AZ61 or AM100. | Magnesium |
| Because of its FCC crystal structure, copper and copper alloys have: | excellent formability |
| Copper is the standard to which other materials are compared to rate: | conductivity |
| The good corrosion resistance of copper and nickel is: | An inherent property of the metal |
| When exposed to extremely low temps, copper and copper alloys: | do not embrittle |
| Copper and copper alloys are: | Heavier than steel |
| The primary uses of copper are related to its: | Conductivity and corrosion resistance |
| This material has “better corrosion resistance to more media than any other commercial alloy.” | Monel |
| This alloy is one of the most popular “low thermal expansion” alloys. | Invar |
| The electrical resistance heating wires for toasters are often made from this material: | Nickel-chromium |
| Copper (is, is not) considered to be an elevated temp material. | Is not. Ti, Ni, and Cobalt are |
| This is the only light-weight high-temp metal. | Titanium |
| Tungsten, Molybdenum, and Tantalum are____? | Refractory metals |
| Which properties are necessary for the coatings applied to refractory metals? | High melting point, matching thermal expansion, diffusion barrier to various gases |
| Nickel and cobalt form the basis of this group | Superalloys |
| Protective coatings are required in order for this material to function at extremely high temperatures (approaching 3000 F) | Refractory metals |
| All members of this group have the BCC structure and are heavier than steel | refractory metals |
| This metal has the best overall electrical and thermal conductivity, along with good formability and corrosion resistance | Copper |
| This metal has good strength and corrosion resistance at elevated temperatures coupled with good formability (due to its FCC structure) | Nickel |
| Because of the range of colors, alloys of this metal are often used in architectural and artistic applications | copper |
| This group has the highest operating temps of the engineering metals | Refractory Metals |
| Metals from this group can be used at elevated temps up to 2000 F | superalloys |
| Ceramic materials have _________ atomic bonding. | Ionic or Covalent |
| The crystal structures of ceramic materials are often quite complex because: | Atoms of different sizes are in the same structure, charge neutrality must be maintained throughout ionic structures, and covalent structures often have a limited number of nearest neighbors. |
| The equilibrium structure in ceramic materials (lowest energy) is: | Crystalline |
| If we cool faster than the critical cooling rate that separates glass and crystalline ceramics, we are likely to produce a: | glass |
| While crystalline ceramic materials contain dislocations, they do not exhibit plastic deformation because: | dislocation movement is difficult and fracture occurs at a lower stress |
| Full theoretical density is difficult to achieve in processed ceramics because: | Voids remain between the particles after sintering |
| According to the principles of fracture mechanics, brittle materials will fail when: | The combination of load (stress) and flaw size reaches a critical value. |
| The fracture resistance of a ceramic material is best improved by: | Decreasing the flaw size |
| While it is unlikely that we will be able to change the ______ of ceramic materials, it may be possible to impart significant amounts of _____. | Brittleness, toughness |
| Tempered glass has enhanced fracture resistance because it incorporates: | Compressive residual stresses on the surface induced by quenching. |
| Cermets gain their enhanced toughness through: | A metal matrix |
| Transformation toughening involves: | A metastable phase that changes structure and expands when a crack comes near. |
| In this toughening mechanism, ceramic materials are alloyed to eliminate any phase changes over the entire range of expected operating temperatures. | Stabilization |
| For elevated temperature creep resistance, a crystalline ceramic should have ____ crystals. | Large |
| Crystalline ceramic products are usually fabricated by: | Pressing and sintering(firing) solid particles |
| Ceramic materials excel when: | Physical properties dominate the selection process. |
| Ceramics used in products like sandpaper, grinding wheels, and cutting tools are called: | Abrasives |
| Ceramic materials that are used for applications like the containment of molten metals are: | Refractories |
| The white “Corelle” dinnerware and Corningware baking pans are examples of: | Glass Ceramics |
| Good corrosion resistance and elevated temperature strength are an asset of what group of ceramic materials? | Advanced ceramics |
| The wide variation in mechanical properties for nominally “identical” ceramic components (same material and same processing) can be attributed to: | Variation in the size, shape and location of flaws. |
| While a ceramic engine block would allow higher operating temps, and eliminate the need for cooling, a major barrier is likely to be: | The material will still be brittle. |
| List four attractive properties of polymeric materials. | Ease of fabrication, can have integral color, good corrosion resistance, and light weight. |
| The bonding mechanism between the atoms along the spine of linear polymers is: | Covalent |
| Increasing the amount of initiator or activator in an addition polymerization reaction will ____ the length of the chains and ____ the strength of the resulting polymer. | Decrease, Decrease |
| The functionality of polymer reactants that form linear or chain-type polymers is: | Two |
| The functionality of polymer reactants that form 3-dimensional network polymers is: | three or more |
| The “degree of polymerization” refers to the: | Average number of mers per molecule |
| Two different types of monomers or reactants are required for this type of polymerization that involves the production of a small by-product molecule. | Condensation polymerization |
| The recyclable plastics are of what type of polymer? | Thermoplastic polymers |
| The highest rigidity is found in this type of polymer | Thermosetting |
| Heating softens, cooling hardens, and the cycle can be repeated with this type of polymer. | Thermoplastic |
| High strength polymers would most likely be of this type. | Thermosetting |
| This type of polymer is the most easily recycled. | Thermoplastic |
| Extremely large elastic deformations are possible with this class of polymers | Elastomeric |
| Extremely large plastic deformations are possible with this class of polymers | Thermoplastic |
| An adhesive example of this class of polymers would be two-part epoxy | Thermosetting |
| An adhesive example of this class of polymers would be hot-melt glue | Thermoplastic |
| An adhesive example of this class of polymers would be flexible silicone bathtub caulk | Elastomeric |
| Will increasing the length of the average change increase or decrease the strength of a thermoplastic polymer? | Increase |
| Will replacing hydrogen side atoms with chlorine increase or decrease the strength of a thermoplastic polymer? | Increase |
| Will plastically deforming or “cold working” increase or decrease the strength of a thermoplastic polymer? | Increase |
| Will inducing extensive branching of the chains increase or decrease the strength of a thermoplastic polymer? | Decrease |
| Will inducing “crystallization” during cooling increase or decrease the strength of a thermoplastic polymer? | Increase |
| (True/False) The strength of a “high-strength” polymer is equivalent to that of an engineering metal. | False |
| (True/False) The rigidity of a rigid polymer is similar to that of an engineering metal. | False |
| (True/False) Adhesive bonding is an attractive means of joining dissimilar materials. | True |
| (True/False) Adhesive joints often compensate for their lower strength by increasing the area of the bond. | True |
| (True/False) Adhesive bonding is an attractive means of joining materials that will be used at elevated temperatures | False |
| (True/False) Adhesives can provide an electrical and thermal insulating barrier in a joint. | True |
| What type of composite are two or more distinct layers present | Laminar |
| “Aspect ratio” characterizes one of the components in this type of composite | Fiber-reinforced |
| What type of composite is anisotropic behavior always expected in | Laminar |
| The primary purpose of this type of composite is to retain strength to higher operating temperatures—SAP and TD-nickel are common examples. | Dispersion-Strengthened Particulate |
| This type of composite is often used when the objective is improved wear or corrosion resistance | Laminar |
| Small amounts of tiny oxide particles are dispersed throughout a matrix in this type of composite | Dispersion-strengthened particulate |
| Examples of this type of composite are U.S. sandwich coinage, honeycomb, and corregated cardboard | Laminar |
| Examples of this type of composite are grinding wheels, concrete, and cemented carbides | True Particulate |
| Examples of this type of composite include graphite-epoxy golf-club shafts and steel-belted radial automobile tires | Fiber-reinforced |
| This type of composite is most likely to exhibit isotropic properties | Particulate |
| A significant difference in thermal expansion is essential to the performance of: | Bimetallics |
| Alclad is a laminar composite consisting of: | A corrosion-resistant aluminum skin over a high-strength aluminum core |
| In fiber-reinforced composites, the role of fibers is to: | Carry load and impart stiffness |
| We generally want the matrix material in a fiber or particulate composite material to be: | Strong, tough and ductile |
| 3 attractive properties of fiber reinforced composites are: | Light Weight, Good Fatigue Life, and High Strength and Stiffness |
| 3 limitations to the use of fiber composites are: | Difficulty of inspection, limited repairability, and limited joining options |
| “Specific strength” is defined as the ratio of yield strength to ____. | Density |
| “Aspect ratio” is the ratio of: | Fiber length to diameter |
| The strength of a composite typically increases when the aspect ratio is: | Increased |
| The strength of a fiber-reinforced composite would be expected to increase if we: | Increase the volume fraction of fibers, reduce the diameter of the fibers, and/or align the fibers in the direction of maximum stress |
| Attractive properties of Kevlar fibers include: | High strength, light weight, and a negative coefficient of thermal expansion. |
| In polymer-matrix fiber-reinforced composites the polymer matrix: | Can be either thermoplastic or thermosetting |
| Weak bonding between the fiber and matrix is actually an asset in the performance of ___ matrix fiber-reinforced composites. | Ceramic |
| The rule of mixtures estimates a composite property by computing a weighted average based on the ____ of the various components. | Volume fraction |
| A rule of mixtures calculation will give an accurate prediction of: | Density |
| Over 90% of all corrosion is _______ in nature. | Electrochemical (Galvanic) |
| In a galvanic corrosion cell, corrosion occurs at the _____ where electrons are ______. | Anode, created. |
| What is a composition cell? | 2 DISSIMILAR metals are in contact to complete a galvanic cell. One of the metals become anode and corrodes and other becomes cathode and is protected. |
| Cast iron to copper water pipe, and steel nails in aluminum siding are an example of _____ cells. | Composition |
| Differences in the form of chemistry yield a ______ cell. | Composition |
| Environmental differences yield ______ cells. | Concentration |
| Loading differences yield ______ cells. | Stress |
| What happens in concentration cell? | Concentration differences in the electrolyte induce galvanic action. Ex: Oxygen concentration cell: Where concentration of oxygen in electrolyte is lowest, the metal adjoining the electrolyte becomes the anode and corrodes. |
| Soil line corrosion, crevice corrosion, and moss on pipeline are examples of ______ cells. | Concentration |
| Explain stress cells | If you have stress that varies from location to location in a metal. The highest stress location acts as anode and corrodes. |
| Nails corroding at heads and tips with unattacked shanks are examples of corrosion caused by _______ cells. | stress |
| Three good ways to reduce corosion are. | Break the electrical contact, use a sacrificial anode, and use various coatings. |
| Cobalt is considered to be a _______. | Superalloy |
| If we wish to increase the strength of a chain-type polymer, we can ____ the amount of activator or catalyst to ___ the average length of the chain molecules. | Decrease, Increase |
| In order to produce a network or framework polymer, we must have reacting mers with a functionality of ____. | Three or more |
| If we progressively increase the degree of cross-linking in a polymer, we would expect the material to become ____ and _____ ductile. | Stronger, less |
| When producing a laminar material, such as corrugated cardboard or honeycomb, our objective is often to impart: | Enhanced strength and stiffness |
| In a fiber-reinforced composite, we usually expect ductility and toughness to be imparted by the: | Matrix |
| What does the rule of mixtures do? | Predicts properties as a weighted average of th properties of the components. |
| When two materials from galvanic series come into contact the one _____ in the series is expected to experience acceleration of corrosion. | Higher in the series. |
| Age hardened aluminum has been characteried as having poorer corrosion resistance than the weaker, single-phase, non-heat-treatable alloys. This is because the heat-treatable alloys are a form of ______ corrosion cell. | Composition |
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