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Lecture 1
| Question | Answer |
|---|---|
| What are the subcategories of metals? | Ferrous & non-ferrous metals. |
| What are the 4 main classifications/types of material properties that we study in this class? | Chemical, physical, mechanical, & manufacturing |
| What are chemical properties? | A material's characteristics that relate to the structure of material, its formation from the elements out of which it is made, & reactivity w/ chemicals, other materials & environments. |
| What are physical properties? | Characteristics of materials that pertain to the interaction of these materials w/ various forms of energy & w/ the human senses. |
| What are mechanical properties? | The characteristics of a material that are displayed when a force is applied to the material. They usually relate to the elastic/plastic behavior of the material. Usually used to indicate the suitability of a material for use in mechanical applications. |
| What are manufacturing properties? | Often associated w/ procurement & manufacturing considerations. |
| Can physical properties be measured without destroying/changing the material? | Yes. |
| Can mechanical properties be measured without destroying/changing the material? | No. |
| What do chemical properties of metals involve? | Composition, microstructure, phases, grain size, corrosion resistance, & inclusions. |
| What do physical properties of metals involve? | Melting point, magnetic, electrical, optical, acoustic, gravimetric, & color. |
| What do mechanical properties of metals involve? | Tensile/compressive properties, toughness, ductility, fatigue strength, hardness, creep resistance, & shear strength. |
| What do manufacturing properties of metals involve? | Available shapes, sizes, surface texture, & tolerances. |
| What are examples of chemical properties? | Oxidation & corrosion. |
| What are examples of physical properties? | Density, specific heat, thermal expansion, & conductivity, melting point, electrical & magnetic properties, optical, & Modulus of Elasticity. |
| What are examples of mechanical properties? | Strength, toughness, ductility, hardness, elasticity, fatigue, creep & Modulus of Elasticity. |
| Strength & toughness usually... | inversely correlated. |
| What are examples of manufacturing properties? | Castability, formability, machinability, & weldability. |
| What is composition? | Elements in weight percentage. |
| What is microstructure? | Arrangement of atoms creating micro components of the metal. |
| What are the types of microstructures? | FCC, BCC, BCT, & HCP. |
| What is grain size? | Dimension of 1 type of micro component. |
| What is corrosion resistance? | Chemical interaction w/ the environment. |
| What are inclusions? | Something in the metal that isn't metal |
| How are inclusions formed? | Usually from refining or welding. |
| What are examples of inclusions? | Hard spot, carbon node. |
| Shapes of metals effect... | All properties. |
| What is elastic behavior? | A metal will go back to its original position. |
| What is plastic behavior? | A metal will not go back to its original position. |
| What is a chemical property/example that every metal does? | Oxidation. |
| What does aluminum not do? | Corrode. |
| What is corrosion? | Material losing its mechanical properties due to the environment. |
| What is Modulus of Elasticity? | Material's resistance to deflection. A physical & mechanical property. |
| What is toughness? | Impact strength, resistance to impact. Material's ability to absorb energy before fracturing. |
| What is an example of toughness? | Playdough deforms but does not shatter. Ordinary low-cost, low-carbon steel has high toughness, but it is the weakest steel. |
| What is ductility? | Stretch, material keeps stretching but does not break. |
| What is strength? | How hard a material can be pulled before breaking or ability to accommodate stress. |
| What is creep? | The permanent elongation under a static load maintained for a period of time. Sag. |
| What is fatigue? | Material's resistance to loads. like static & cyclic loads, before breaking, like cyclic stresses. Growing of cracks in a material due to cyclic loading. Gradual failure of a material, caused by cracks growing a small amount due to each load cycle. |
| Carbon solubility related to FCC/BCC & lattice & interstitial site limits at? | 80-200pt Carbon |
| Steel is? | 2% carbon or less. |
| What is melting point? | Dependent upon chemistry. |
| What is magnetic? | Ferrous based materials primarily. |
| What are examples of magnetic materials? | Iron, nickel, & cobalt. |
| Magnetic involves... | Retention & strength of magnetic field, & HB hystersis curves (strength & flux density). |
| What is electrical? | conductivity & resistivity (galvanic series). |
| What is optical? | Reflectivity. |
| What is acoustic? | Speed of sound through metal (used for ultrasonic inspection). |
| What is gravimetric? | Weight or mass. Density & specific gravity are related. |
| What is color? | Metals often used for decorative purposes. Can be determined without destroying a material. |
| What is thermal conductivity? | The steady-state heat that will be transmitted by a material of given thickness & temperature difference per unit area. |
| What is thermal expansion? | A physical property that applies to all materials. This is important when dissimilar materials will be fastened & heated, & when materials are locally heated. |
| What is Elastic Modulus/Modulus of Elasticity? | Used to measure the relative stiffness of material. |
| What is Poisson's Ratio? | Lateral strain in a loaded shape compared with the length strain. |
| What is Shear Modulus G? | When Hook's Law does not apply. G = E / 2 * (1 + Poisson's Ratio). Rule: 3/8E. |
| What is 3/8E? | |
| What are examples of strength? | Tensile, yield, compression, flexural, shear, creep, & stress rupture. |
| What are examples of formability? | % elongation & reduction in area, & bend radius. |
| What are examples of stiffness? | Modulus of elasticity, flexural modulus, & shear modulus. |
| What are examples of toughness? | Impact strength, notch sensitivity, & critical stress intensity factor. |
| How do you test the impact strength of a metal? | Charpy test. |
| What are examples of durability? | Hardness, wear resistance, & fatigue strength. |
| What is durability? | How hard something is. |
| What are the 5 types of stress? | Tensile, compression, bending, torsion, & shear. |
| What does stress/strain involve? | Modulus of Elasticity/Young's Modulus, Hook's Law, Poisson's Ratio, & Shear Modulus-G |
| What is Hook's Law? | Elastic vs. Plastic |
| What is tension? | Stretching |
| What is compression? | Squishing |
| What is shear? | Pushing 1 end of an object. |
| What is bending? | Straight forward concept: Pushing or applying forces in different areas of an object. |
| What is torsion? | Twisting. |
| What is linear elastic behavior? | The specimen elongates in proportion to the load. |
| What is engineering stress? | The ratio of the applied load F to the original cross-sectional area A_0. |
| What is the formula for stress? | σ = F / A_0. where F is the applied force & A is the cross-sectional area, & σ is the stress. |
| What is the formula for strain? | ε = (l - l_0) / l_0 |
| What is the formula for Modulus of Elasticity? | E = σ / ε = (F / A_0) / (l - l_0) / l_0 |
| What is the Modulus of Elasticity of steel? | 30E6 psi |
| What is the Modulus of Elasticity of aluminum? | 10E6 psi |
| What is the Modulus of Elasticity of polystyrene? | 0.5E6 psi |
| What is the formula for Hooke's Law? | σ_t = E * ε _t, where E is the Modulus of Elasticity . |
| Label the stress/strain curve. | X-axis: strain Y-axis: stress Slope: Modulus of Elasticity Involves the elastic & plastic range, elastic limit, engineering yield strength, ultimate tensile strength, break point, & necking. |
| What is tensile testing? | Stretching a piece of material to determine mechanical properties. |
| Elastic limit is also the..? | True yield point. |
| Engineering yield strength has an offset of..? | 0.2% |
| What is yield strength? | Design stresses must be lower than the yield strength to ensure that a part does not fail by plastic deformation. Shear strength maybe estimated from the yield strength. |
| What are the material properties obtained from tensile testing? | Modulus of elasticity, yield strength, ultimate tensile strength, ultimate tensile strength/yield strength ratio, percent elongation & reduction in area, & the general shape of the curve. Also be used to determine compressive, shear, & flexural strength. |
| What is ultimate tensile strength? | The ultimate tensile stress is the max stress observed in a tensile test. Necking begins when this value is reached. |
| What is the ultimate tensile strength/yield strength ratio? | The ratio of the ultimate tensile strength to the yield strength provides an indication of the degree of work hardening that has occurred. |
| What is the percent elongation? | Indication of material ductility & toughness. |
| What is the percent reduction in area? | Indication of material ductility & toughness. |
| What is the general shape of the curve? | Area under the curve provides a relative indication of material toughness. Interstitial activity in the material maybe observed. Relative levels of work hardening are assessed. |
| What is hardness of a metal? | Resistance to permanent indentation, scratch/wear. A general indication of the strength of material & of its resistance to scratching & wear. |
| What is the indenter for a Brinell hardness test? | 10 mm steel (HBS)/tungsten carbide (HBW) ball. |
| What are the loads for a Brinell hardness test? | 500 kg, 1500 kg, & 3000 kg |
| What is the formula of the hardness number for a Brinell hardness test? | HB = (2 * P) / (pi * D) * (D - sqrt(D**2 - d**2)) |
| What is the formula of the hardness number for a Vickers hardness test? | HV = (1.854 * P) / L**2 |
| What are the loads for a Vickers hardness test? | 1-120 kg |
| What is the indenter for a Vickers hardness test? | Diamond pyramid |
| What is the indenter for a Knoop hardness test? | Diamond pyramid |
| What are the loads for a Knoop hardness test? | 25 g-5kg |
| What is the formula of the hardness number for a Knoop hardness test? | HK = (14.2 * P) / L**2 |
| What is the indenter of a Rockwell A C D test? | Diamond cone |
| What is the indenter of a Rockwell B F G test? | 1/16 in diameter steel ball |
| What is the indenter of a Rockwell E test? | 1/8 in diameter steel ball |
| What is the load for a Rockwell A hardness test? | 60 kg |
| What is the load for a Rockwell C hardness test? | 150 kg |
| What is the load for a Rockwell D hardness test? | 100 kg |
| What is the load for a Rockwell B hardness test? | 100 kg |
| What is the load for a Rockwell F hardness test? | 60 kg |
| What is the load for a Rockwell G hardness test? | 150 kg |
| What is the load for a Rockwell E hardness test? | 100 kg |
| What is the formula of the hardness number for a Rockwell HRA, HRC, & HRD hardness test? | 100 - 500*t |
| What is the formula of the hardness number for a Rockwell HRB, HRF, HRE & HRG hardness test? | 130 - 500*t |
| How do you perform the Rockwell hardness test? | Apply minor load, apply major load, remove major load, measure difference in indentation depth. |
| What is the superficial minor load? | 3 kg |
| What is the regular minor load? | 10 kg |
| What are the superficial major loads? | 15 kg, 30 kg, & 45 kg |
| What are the regular major loads? | 60 kg, 100 kg, & 150 kg |
| How do you perform the Brinell hardness test? | Use scope to read diameter - 2 readings that are averaged, compare a chart for the Brinell hardness number. |
| How do you perform the microhardness test? | Use a microscope to select the indentation area, use a dimensional measurement to determine the hardness, then cross reference to a chart to produce a hardness number. |
| What does 50-60 HRC mean? | A hardness value of 50 to 60 using the Rockwell C scale. |
| What does 85 HR15T max mean? | A max hardness value of 85 using the Rockwell Superficial 15T scale. |
| What does 185-240 HV_100 mean? | A hardness value of 185-240 using the Vickers hardness tester & a test load of 100 kg-force, use HK for Knopp. |
| What does 200 HB min mean? | A min hardness value of 200 using the Brinell hardness tester. |
| What is the application of the Knoop & Vickers hardness test? | Microhardness of soft steels to ceramics. |
| What is the application of the Brinell hardness test? | Soft steels & metals to 40 HRC |
| What is the application of the Rockwell B hardness test? | Soft steels & nonferrous metals |
| What is the application of the Rockwell T hardness test? | Thin soft metals |
| What is the application of the Rockwell N hardness test? | Hard thin sheet metals |
| What is the application of the Rockwell A hardness test? | Cemented carbides |
| What is the application of the Rockwell R hardness test? | Polymers |
| What is the application of the Rockwell C hardness test? | Hardened metals (thick) |
| What is impact toughness? | The energy dissipated in breaking the specimen. |
| What is the impact test useful for? | Determines the ductile-brittle transition temperature or toughness of materials. |
| Materials w/ high impact resistance has..? | High strength, ductility, & toughness. |
| What is notch sensitivity? | Sensitivity to surface defects. It lowers impact toughness. |
| What are mechanical failures? | Creep & fatigue |
| What causes creep? | Higher temperature or not, depending on the material in question. |
| What are examples of material creep? | High-temperature applications like gas turbine blades. Old glass windows where the bottom is much thicker than the top. Ice flow in a glacier. Warping of plastic dishes in the dishwasher. |
| What is the transition temperature of creep? | The temperature at which creep starts & the max temperature at which the material remains structurally reliable. |
| What causes cyclic stresses? | Fluctuating mechanical loads or by thermal stresses. |
| Why do parts fail in terms of fatigue? | Because of fatigue failure at a lower stress level than it does under static loading. |
| What is the bending test? | Mainly used for brittle materials. Modulus of rupture, flexural strength, or transverse rupture strength is the stress at fracture in bending. |
| Strength & toughness are mechanical properties, while density & thermal expansion are physical properties. | True |
| How are solids formed? | When definite bonds exist between component atoms or molecules. |
| What does amorphous mean? | Without form |
| What materials are amorphous? | Glass & plastic |
| What materials have a crystalline structure? | Metals & inorganic compounds. |
| What are unit cells? | Repeating structures arranged by atoms in a crystalline structure. |
| What is a lattice? | A larger 3-D array formed by multiple cells. |
| How are grains formed? | Many crystals grow in a melt at the same time where they meet. |
| What are grain boundaries? | Junctions of the crystallites. |
| What is a BCC? | Body-centered cubic |
| What is a FCC? | Face-centered cubic |
| How are chemical properties measured? | In a chemical laboratory & cannot be determined by visual observation. |
| How can color be determined? | By looking at the substance or with an instrument. |
| How can density be determined? | By weighing & measuring the volume of an object, & it does not have to be changed or destroyed to be measured. |
| What are the applications of mechanical properties? | Parts that carry a load, absorb a shock, resist wear, etc. |
| Surface roughness is a..? | Dimensional property |
| Flammability is an important chemical property in metals & ceramics. | False. It's not important in metals & ceramics, but is important in plastics. |
| What are thermal properties? | Specific heat, thermal expansion & conductivity & use temperature. This is a physical property. Its important any time a part is to be used at some temperature other than the temperature at which is was fabricated or perform some heat transfer. |
| What is specific heat? | The amount of heat energy required to raise a given mass of material (1 g) a given temperature change (1 degree C) (BTU/1b degree F for English). All materials have this. Determines the cost of a material. |
| Where does thermal expansion take place? | On the volume of the material. |
| What are the units for thermal expansion? | in/in-degree F or cm/cm-degree C |
| Thermal expansion applies to all structures & all products, & it is an engineering issue that must be dealt with. It must always be considered in an engineering design. | True |
| What are applications of thermal conductivity? | Heat-sealing heads, heat exchanges, heat sinks, heating platens, die casting, & plastic-molding cavities. |
| What are the units for thermal conductivity? | BTU/hr/ft/degree F for English or W/mK for metric |
| What are applications of electrical properties? | Electrical conductor or insulator. |
| What are magnetic properties? | Whether a material will be attracted by a magnetic field. Permeability, retentivity, hysteresis loss, coercivity, intrinsic induction, etc. |
| What is another name for magnetic? | Ferromagnetism. |
| What is ferromagnetism? | The result of a set of circumstances associated with the magnetic moments of electrons & the configuration of atoms in a material. |
| What are applications of gravimetric? | Costs of various materials & porosity. |
| How are colors produced? | by absorptions of portions of the spectrum of electromagnetic radiation that is visible light. |
| What are the units of stress? | lb/in**2 or Pa in English, Newtons/m**2 in SI |
| What are the units of strain? | in/in or m/m, therefore unitless. |
| How can the Modulus of Elasticity be measured? | In a tension or compression test. |
| What does the Modulus of Elasticity not change? | heat treatment, manufacturing technique, shape, etc. |
| What is the Modulus of Elasticity of copper? | 18E6 psi |
| What does the Modulus of Elasticity & Poisson's ratio have in common? | Both called elastic constants of materials. They apply when deflections (strains) are such that the material will recover its original shape after a load is removed. |
| Room temperature tensile strength of 1133 steel is..? | 55-57 MPa |
| Shear strength of 1133 steel is..? | 22-23 MPa |
| Compressive strength of 1133 steel is..? | 59-61 MPa |
| What is the formula for percent elongation? | (l_f - l_i )/ l_i |
| What is the formula for percent reduction in area? | (A_i - A_f) / A_i |
| What is work/strain hardening? | When a metal is plastically deformed, interactions with dislocations in the material's structure can cause the material to become stronger & harder. |
| What is resilience? | A material's ability to absorb elastic energy. |
| What is an example of resilience? | Spring used for shock absorption |
| What is the formula for resilience? | (1/2) * σ**2_el * ε_el = σ**2_el / (2 *E), where σ_el is the stress limit, ε_el is the strain at the elastic limit, & E is the modulus of elasticity. |
| What is an application of resilience? | When large absorption is required, suitable materials have a higher elastic limit (yield point) & a low elastic modulus. |
| How is toughness calculated? | Calculate the total area under the stress-strain curve up to the point of fracture. |
| What is shear strength? | The stress at which a shear-loaded member will fail. |
| Shear stresses are __ related to the shear strains through an elastic constant called __. | Proportionally, Shear modulus. |
| What are shear stresses? | Stresses from torsion loads |
| What is the shear modulus? | Important for calculating the stiffness/rigidity of a torsion bar or another component loaded in shear. |
| The hardness of materials often is equated with..? | Wear resistance & durability. |
| What is the Mohs hardness test? | Scratching the surface w/ different types of minerals. |
| Hardness numbers measured on 1 test can always be converted to comparable hardness numbers measured on another scale. | False. They cannot be converted. |
| What are the units of absolute hardness? | kg/mm**2 |
| How is absolute hardness measured? | With a microhardness machine. |
| Toughness does not correlate with strength. | True. |
| What are the units for toughness? | ft-lb, J, etc |
| How is strength measured? | By tensile, compression, shear, or other test that slowly pulls /pushes on a specimen until it breaks. |
| How is toughness measured? | As the area under the load-deformation curve w/ units of force & distance. By an impact test that or a test that evaluates the ease of propagating a crack in a material, producing a fracture toughness parameter. |
| What is impact strength tests? | Measure a material's ability to withstand shock loading. |
| What is impact strength? | The energy required to fracture a given volume of material. |
| What are the units of impact strength? | ft-lb (English) & J or J/cm**3 (metric) |
| Ceramics & brittle metals like gray cast iron have..? | Negligible toughness |
| How is impact strength affected? | By temperature |
| FCCs strengthen at slightly..? | Lower temperatures |
| What are examples of FCCs? | Austenitic stainless steel, copper, & aluminum |
| What is the tensile test not very well used for? | How well a material will withstand dynamic loads/loading at elevated temperatures. |
| How is fatigue strength/endurance limit obtained? | By repeatedly loading a specimen at given stress levels until it fails. |
| How are stress levels calculated? | By strain gages. |
| Cyclic loading..? | Reduces the allowable stress that a material can withstand. |
| What does creep rate? | The resistance of a material to plastic deformation under sustained load. |
| How is creep strength of metals expressed? | The stress necessary to produce 0.1% strain in 1000 h. |
| What is stress rupture? | Shows the stress at which a part will fail under sustained load at elevated temperature. |
| What is fracture mechanics? | Based on analysis of the state of stress at the tip of a crack in a material. |
| What is critical stress intensity factor? | A measure of a material's fracture resistance. The higher the critical stress intensity factor, the more resistant that material is to mechanical resistance. |
| % of carbon determines? | How strong a& hard the steel is |
| During a tensile test, necking begins when the ultimate tensile strength is reached? | True |
| Interstitial sites are locations in between atoms making up the crystal structure. | True |
Created by:
Texi Rae