Properties And Applications Of Different Metals Engineering Essay
(a) Steels, (b) Cast Iron, (c) Cu-alloy and (d) Ni-alloy are the subset of materials that follow conditions (E>100 and M>3) from modulus-density chart.
The equation indicates that the performance depends on the modulus of elasticity and relative cost. For increasing the performance, index M and the relative cost Cr should be lower and the young's modulus E should be higher.
(a) Cast Iron, (b) Wood product (c) Glass,
(d) Ceramics, (e) Mild Steel, and (f) Stainless Steel are the materials that allow these conditions. To reduce the buckling effect and be well constructed, the material should have higher value of young's modulus.
The following should be considered for construction material:
Properties of mild steel:
Mild steel contains a high amount of carbon as a major constituent. An alloy is a mixture of metals and non-metals, designed to have specific properties. To obtain mild steel, one should know the combination of alloys to make steel.
Properties of steel:
Steel, any alloy of iron, consisting of 0.2% to 2.1% of carbon, is a hardening agent. Along carbon, there are other metal elements that are a part of steel alloys. The other elements used in steel are chromium, manganese, tungsten and vanadium. All these elements along with carbon, act as hardening agents. The amount of carbon and other hardening agents, present in the alloy functions ductility, hardness and mild steel tensile strength.
Properties of cast iron:
Cast iron has the compressive strength which means the ability of a material to withstand forces which attempt to squeeze or compress it. The structure of Cast iron show resistance to deformation and provide a rigid frame. The problem of the structure breakdown becomes prominent if one part of the casting after the iron is poured into the molds, is very thin and another very thick.
Steel differs from wrought iron and cast iron by some percentage of carbon content. Steel contains more iron than wrought iron and less than that of cast iron. The reason is that steel is considered to occupy a position between these two metals. However, there is tremendous difference in the properties of steel, wrought and cast iron. Let's take a look at the physical properties of steel. From its component elements viz. iron and carbon, the physical properties of steel are totally different. The cooling down rapidly of steel from an extremely hot temperature after being put to water or oil is the main property of steel. The percentage composition of the constituent elements and the manufacturing process is necessary for the basis of its physical properties depends. In iron at a required temperature, some amount of carbon can be dissolved.
Properties of cement:
Nowadays cement is very costly. For construction purpose, cement is characterized as hydraulic or non-hydraulic. The chemical reaction that occurs independently of the mixture's water content is the hydration, due to which hydraulic cement hardens. It easily gets harden in underwater or even when constantly exposed to wet weather. When the anhydrous cement powder is mixed with water, produces hydrates that are not water-soluble, results to a chemical reaction. In order to retain the strength, non-hydraulic cements like gypsum plaster and lime must be kept dry.
Properties of wood and wood products:
Wood and wood products are substance obtained from trees which include wood pulp, wood flour, timber, lumber, veneer, pellets and chips. Wood products are cheaper than metals but due to the reason, that is lower value of modulus of rigidity, it is not used in heavy duty columns.
Properties of ceramic:
Like all materials, ceramic are known by the types of atoms present, the types of bonding between the atoms, and the way the atoms are packed together. In general, ceramics are considered as brittle, refractory, thermal insulators, electrical insulators, nonmagnetic, chemically stable, hard, wear-resistant, prone to thermal shock, and oxidation resistant.
Properties of glass:
According to the condition glass material very cheap, but modulus of rigidity is lower. Hence, it is a hard material but not enough tough to absorb a shock.
By the given condition Kci > 30 Mpa and from the chart 7, the mentioned materials can be considered:
(a) Cu-alloy (b) Steel-alloy (c) Ni-alloy and (d) Ti-alloy.
But according to the chart 15, only steel is suitable in the given criteria. For these materials the modulus of rigidity is given by:
Cu-alloy --- E = 200 Mpa.
Ni-alloy and Ti-alloy --- E = 400 Mpa.
Steel --- E = 800-1000 Mpa.
We can observe that steel has higher value of E; also, it is cheaper than other materials and is easily available.
For this application, the practical alternatives with steel can be Cast Iron, Al-alloy and fiber.
Stainless steel and its use:
Stainless steel is a group of iron-based metal containing at least 10% chromium (alloy metals). The chromium oxide "CrO" creates an invisible barrier ("passive film") to oxygen and moisture. Therefore the Chromium protects the iron against most corrosion or red-colored rust; thus the term "stainless" steel. The purpose of stainless steel is to provide hard steel material highly resistant to stain, rust and corrosion and resistance against adverse atmospheric conditions such as carbon dioxide, moisture, electrical fields, sulfur, salt, and chloride compounds; natural and artificially produced chemicals (e.g. ozone); extremes of weather conditions.
Fiber's property is similar as the above material. It is also light weight. So fiber products are used in many cars. But it is costly and hence is not beneficial for high speed cars.
Aluminum is a soft and lightweight metal. It has a dull silvery appearance, because of a thin layer of oxidation that forms quickly when it is exposed to air. The use of aluminum exceeds that of any other metal except iron. Pure aluminum easily forms alloys with many elements such as copper, zinc, magnesium, manganese and silicon. Alloys make it much stronger.
Iron is a lustrous, ductile, malleable, silver-gray metal (group VIII of the periodic table). It is known to exist in four distinct crystalline forms. Iron rusts in dump air, but not in dry air. It dissolves readily in dilute acids. Iron is chemically active and forms two major series of chemical compounds, the bivalent iron (II), or ferrous, compounds and the trivalent iron (III), or ferric, compounds. Iron is the most used of all the metals, including 95 % of all the metal tonnage produced worldwide. Thanks to the combination of low cost and high strength it is indispensable. Its applications go from food containers to family cars, from screwdrivers to washing machines, from cargo ships to paper staples.
Hence, Cast Iron is the most suitable material for car body.
As steel body is removed, the material used in car body different from steel can be cast iron.
Cast iron has high percentage of carbon which gives toughness to the body.
Mostly, car body is made from Steel or Al-alloy. It is strong, paintable, and relatively easy to mould to the right shape. This doesn't mean it is the best material - many cars use Fiberglass, some use carbon fiber.
The material for heat exchanger to extract heat from geo-thermally heated saline water at 120 C should be:
Material (ranked by M1)
High Conductivity Coppers - have the best performance index but relatively poor corrosion resistance.
Brasses - Again, relatively poor corrosion resistance
Wrought Stainless Steel - A good choice, but steel is more dense than copper
Aluminum Bronzes - An economical and practical choice
From chart 1, the modulus E: Cu-alloy -> E = 150 Gpa, Steel -> E = 200 Gpa
The fracture toughness is given by: Cu -> Kic = 100 - 150 Gpa, Steel -> Kic = 200 Gpa
But for the heat exchanger the heat should be distributed from hot fluid to cold fluid so the material should not be dense. If material is dense then the heat will not be given up to cold fluid properly. Hence, Cu alloy is used here.
Here, C- clamp for electronic components has temperature of 450C.
Considering the following:
x - thickness, t - time
Î» - thermal conductivity,
Ï - density, and - Special heat capacity.
We have the relation, and
Again, clamp has low thermal inertia and it reaches temperatures quickly. So the material has higher value of (diffusivity). For getting higher value of it should have less dense material and low special heat capacity.
From above three materials can be considered:
Al alloy -> = 0.902 S (J/9C)
Cu alloy -> = 0.385 S (J/9C)
Cast Iron -> = 0.450 S (J/9C)
Al alloy is not suitable according to the criteria because of higher and low melting point.
Cast iron and Al alloy have higher value than Cu alloy. Hence, the most suitable material is Cu alloy.
Where, = Peak Stress
M = Moment
F = Force, and
I = Moment of Inertia
From equation, =>
Substituting value of x from above we get:
But, M = FL,
So, the force depends on b, length, stress and moment of inertia. The material should have less length and high stress. Cast iron is suitable material for following these conditions.
The materials used for leaf spring is mentioned below:
All these materials are used in hardened and tempered state. The physical properties of some of these materials are as follows:
50 Cr 1 ultimate tensile strength 1680-2200Mpa
Tensile yield strength 1540-1750Mpa
Brinell hardness number 461-601Mpa
50 Cr 1 v 23 ultimate tensile strength 1900-2200Mpa
Tensile yield strength 1680-1890Mpa
Brinell hardness number 534-601Mpa
55 Si 2 Mn 90 ultimate tensile strength 1820-2060Mpa
Tensile yield strength 1680-1920Mpa
Brinell hardness number 534-601Mpa
We have, B = width and T = thickness
Also consider deflection and stiffness.
The deflection depends on force, modulus, and moment of inertia.
The max value of deflection is proportional to double power of length so the length should be less, otherwise it will fail under some load.
The thickness must be considerably high.
Moment of inertia also depends on the B and T.
The spring should of carbon steel.
Carbon steel properties:
composition per weight C = 0.37-0.44%, Mn = 0.60-0.90%, P = 0.04%, S = 0.05%
Density (Ã-1000 kg/m3)=7.845 at T = 25 c
Poisson's Ratio = 0.27-0.30 at T = 25 c
Elastic Modulus (GPa) = 190-210 at T = 25 c
Tensile Strength (Mpa) = 518.8
Yield Strength (Mpa) = 353.4
Elongation (%) = 30.2
Reduction in Area (%) = 57.2
Hardness (HB) = 149 at T = 25 c
Impact Strength (J) = 44.3
General material and characteristic of trucks:
Use a general Young's modulus of steel is 200 kN/mm2. You will have a good approximation. The different alloys do not have huge variations (195-210 kN/mm2). The variation is more in other mechanical properties. As a rule of thumb the modulus will go up with higher melt temperature of the alloy.
Ductility is obtained by selecting a raw material that has inherent characteristics for ductility. Also, the combination of annealing and rolling used will affect this process. The size and arrangement of the carbide particles and the ferrite areas in the steel create the ductility. Production must be designed to bring about the carbide structure at the final size for the ductility required. High ductility simplifies the manufacture of the spring or form and also makes impossible parts possible to make.
Harden ability is really set in the original melting of the steel. This is done by varying the de-oxidation process which results in shallow hardening fine-grained steels or deep hardening coarse-grained steels.
According to the CES chart the following materials are selected:
(a) Aluminum alloy (b) Wrought Iron (c) Copper alloy (d) Ceramics
Aluminum alloys are alloys in which aluminum (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About 85% of aluminum is used for wrought products, for example rolled plate, foils and extrusions. Cast aluminum alloys yield cost effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminum alloy system is Al-Si, where the high levels of silicon (4.0% to 13%) contribute to give good casting characteristics. Aluminum alloys are widely used in engineering structures and components where light weight or corrosion resistance is required.
(b) Wrought Iron:
Wrought iron is an iron alloy with very low carbon content, in comparison to steel, and has fibrous inclusions, known as slag. This is what gives it a "grain" resembling wood, which is visible when it is etched or bent to the point of failure. Wrought iron is tough, malleable, ductile and easily welded. Historically, it was known as "commercially pure iron" however it no longer qualifies because current standards for commercially pure iron require a carbon content of less than 0.008 %wt.
(c) Copper Alloys:
Copper alloys are metal alloys that have copper as their principal component. They have high resistance against corrosion. The best known traditional types are bronze; where tin is a significant addition, and brass, using zinc instead. Both these are imprecise terms, and today the term copper alloy tends to be substituted, especially by museums. Copper is somewhat costly than steels.
Ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (e.g., a glass). Because most common ceramics are crystalline, the definition of ceramic is often restricted to inorganic crystalline materials, as opposed to the non-crystalline glasses. The earliest ceramics were pottery objects made from clay, either by itself or mixed with other materials, hardened in fire. Later ceramics were glazed and fired to create a colored, smooth surface. Ceramics now include domestic, industrial and building products and art objects.
We obtain following materials from the charts 1 and 7 as per given conditions:
(a)Aluminum (b) Balsa (c) ABS fins (c) Titanium
(d) Magnesium (e) Polystyrene
For the development and application of new aluminum alloys with properties and strength-to-weight ratios that make possible the design of future aircraft with improved payload and design safety margins. Airframe designers need lightweight materials that are strong, durable, damage-tolerant, and economical to fabricate. Aluminum alloy products have filled this need since the 1920s. Despite the advances in polymer matrix composites, manufacturers of airframes for passenger jetliners look to aluminum-base materials for the bulk of their needs.
The best solution by far, is to use a poly/ABS fin with the inner portion of the fin cut out and replaced with balsa, thus getting the durability of a manmade material where it is needed and the lightness and stiffness of balsa. This is all extra work on initial construction but, it seems to be worth it due to less time spent repairing the rocket over its service life.
(c) ABS fins:
Fins may make with 2.5 mm ABS cored with 1/8" balsa for model rocket. It is not that tricky cutting out the core with a dermal multi-purpose bit, but the fins were around 16 sq. in.--a decent size palette to work with, as your fin size decreases this method would get trickier. The resultant fin was noticeably lighter and stiffer than its pure ABS sibling. It saves approximately 28% of the total weight of EACH fin.--Definitely worth the extra effort in fin construction.
Values for the pure element are found under the name Titanium, Ti. Grades 1, 2, 3, 4, 7, 11, and 12 and considered 'unalloyed' titanium and have similar mechanical properties. Grades 1 through 4 allow increasing levels of impurities. Grades 7 and 11 have 0.2% palladium added to improve titanium's already excellent corrosion resistance. Grade 12 features 0.8% Ni and 0.3% Mo to improve the corrosion resistance at a lower cost than Pd. Titanium alloys generally feature higher strength than unalloyed titanium.
The density of the magnesium is about 2/3 of that of aluminum and a quarter of that of steel. Magnesium is the lightest among metallic materials which are being used practically. Although magnesium alloy has a higher density than plastics, its tensile strength and Young's modulus per unit weight are higher than plastics. This enables to make a lighter part by using magnesium alloy than plastics. The thermal conductivity of magnesium alloy is much higher than that of plastics. Magnesium casings of electronic appliances can dissipate heat, which is generated in the electronic circuit, much more effectively than plastic casings.
Polystyrene is actually an aromatic polymer that is made from the monomer styrene. It is a long hydrocarbon chain that has a phenyl group attached to every carbon atom. Styrene is an aromatic monomer, commercially manufactured from petroleum. Polystyrene is a vinyl polymer, manufactured from the styrene monomer by free radical vinyl polymerization.
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