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Materials - Coggle Diagram

- - - - Ability to resis loading/ stress without being damaged
        
        Stress can be tensile, compression or shear in nature.
        This could result in deformation of the material, which can be elastic or plastic(permanent)
      - There are different test for different types of strengths like:
        
        Tensile test
        
        Testing something with known dimesion and geometry is being pullied in both direction with a constant speed and increasing force until it breaks
        
        :
        
        Typical stress-strain curve of an austentic stailess steel
    - - Modulus of elasticity represents the stiffness of a material.
        bend / deflection of structural beams is only dependent on the material’s modulus of elasticity, not the
        material’s strength
        
        In linear elastic region, strain (ε) is proportional to applied stress (σ). This is just Hookls law = σ = E x ε
        σ = Stress (MPa)
        E = Modulus of elasticity (GPa = 103 N/mm2)
        ε = Strain (-)
    - - This is the material's ability to deform before it breaks
        
        The ductility is what allows some the type of steel to take on more strain
        
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    - - Ability of a material to resist local plastic deformation. indentation (penetration), scratching, cutting or
        abrasion
        
        Tests
        
        BRINELL HARDNESS TEST METHOD
        
        applies a predetermined test load (F) to a carbide ball (diameter D), which is held for a predetermined time period and then removed
        The resulting impression is measured with specially designed Brinell microscope or optical system across at
        least two diameters
        
        Brinell hardness is calculated according to ratio of used force and surface area of indentation calotte
        
        Commonly used to test materials, which have a structure that is too coarse or that have too rough surface to be
        tested using some another test method
        
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        ROCKWELL HARDNESS TEST METHOD
        
        value is obtained by measuring the permanent depth of indentation produced by a force by using an indenter, a dimond cone or metal ball.
        
        The Rockwell method can be well used in routine inspections of hard materials. It's quick and accurate.
        
        55 HRC
        
        VICKERS HARDNESS TEST METHOD
        
        Pyramid-shaped diamond cone is pressed into material surface using a fixed force (load). The diagonals of indentation are measured and converted to a hardness value
        
        Optical measurement systems with automated measurement and conversion made by the test machine are
        available
        
        380 HV10/20, 380 is the value. HV is the vickerss is the hardness identification. 10 is the test load in kilogram force. 20 is the amount of time in seconds
    - - The ability of a material to absorb mechanical energy and resist fracturing when subjected to sudden impact or shock. There are factors that can impact this, such as temperature, Notches and sharp transitions on cross-sectional geometry and high strain rate
        
        Impact toughness test
        
        To determine the impact resistance or toughness of materials by recording the amount of energy absorbed during damage / fracture
        
        Test specimen is placed on the anvil where the both ends of test specimen are supported. Test involves damaging / fracturing of a notched impact test specimen with a swinging blow of pendulum hammer
        
        Test result
        
        General appearance of a fracture surface
        ▪ Ductile fracture is dull and fibrous
        ▪ Brittle fracture is bright and crystalline
        
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    - - Under static loading (short term), a material will fracture as ultimate tensile stress is exceeded
        Under dynamic (alternate) loading, a fracture can occur to material with stress value below yield strength
        
        Fatigue in other words is when metal is subjected to a repetitive or fluctuating load / stress
        
        This is normaly cause by negligable plastic deformation and normally happens with no warning.
        
        DIFFERENT NATURE OF FATIGUE LOADING
        
        Railway axels → train movement in curves → alternative forces
        → cyclic loading
        
        Boats / ships at sea → waves → alternative forces → cyclic
        loading
        
        Vehicles → road / terrain surface irregularities, pits, bumps, etc.
        → shake and jiggle → alternative forces → cyclic loading
      - Fatigue test
        
        Fatigue of structures is mainly dependent on geometrical factors → surface flaws / imperfections → crack initiation
        → crack growth → damage / fracture
        
        It better if the fatigue testing is done simulating the condition and shape used in the real world.
    - - Corrosion is the degradation of a metal resulting from chemical reactions between the material and surrounding
        environment
        
        Consquences can be: decline in surface quality, degeneration of the surface, dimensional changes, loss of strength properties, etc
        
        Corrosion types
    - - Different materials have different properties and chemical structure which affect what manufacturing processes they can go through. Some material are better for some amnufacturing processes than others
        
        MACHINEABILITY:
        WELDABILITY:
        FORMABILITY:
        MATERIAL COSTS:
        
        All of these things will affect what material you chose to use in your projects
    - - Wear is the damaging, gradual removal or deformation of a material at solid surfaces
        
        Consquences can be: Loss of mass, dimensional changes, degredation of the surface
        
        Types:
        
        ABRASIVE WEARING: when a hard and rough surface slides across a softer surface, along with hard particles that
        penetrate into softer material and remove material (debris) with grinding and breaking of softer material
        
        ADHESIVE WEARING: caused by relative motion, “direct contact” and plastic deformation that create wear debris and
        material transfer from one surface to another
        
        EROSIVE WEARING:Erosive wear is caused by the impact of solid or liquid particles against the wearing surface. Impacting particles gradually remove material from the surface through repeated deformations and cutting actions
- - - - Vast variety of steel alloys and various forms (e.g., sheets, beams, pipes, etc.) offer different properties (e.g.,
        strength, ductility, hardness, etc.) to be selected for wide range of applications
        
        STEELS – CLASSIFICATION OF GRADES: Steel grades are classified by many ways. Depending on classification, an individual steel grade can be considered to have multipleclassification at the same time for example:
        
        By alloying element content levels. Non-alloyed, (low-, medium-, high-) alloyed steels
        
        By carbon content (C-%) level
        Low carbon, medium carbon, high carbon
        
        By microstructure. Austenitic, ferritic, bainitic, martensitic, etc
        
        DESIGNATION SYSTEMS For the purposes of designation, steel names are classified into two main categories.
        Category 1: Steels designated according to their application and mechanical or physical properties
        Category 2: Steels designated according to their chemical composition
        
        S to B, Suffixed by specified minimum yield strength (Rp0.2) in MPa for the smallest thickness range
        Y, Suffixed by nominal tensile strength (Rm) in MPa
        Example: Very common S355 → structural steel with yield strength of 355 MPa
        
        C45 (non alloy steel) → Carbon, C content: 45/100 = 0.45%.
        The format that the example shows above is only for Non alloy steels with manganese (Mn) content (% by mass) < 1%
        
        Non alloy steels with an average manganese (Mn) content ≥ 1%, alloy steels (except high-speed steels)
        where the content, by weight, of every average alloying element is < 5%
        Carbon content = 100 × specified average carbon percentage
        Alloying elements → chemical symbols indicating alloying
        elements that characterize the steel
        
        Elements are followed by numbers, separated by hyphens, representing respectively the average percentage content of the elements multiplied by the following factors
        Example: 34CrNiMo6-4, Carbon, C content: 34/100 = 0.34%, Chromium, Cr content: 6/4 = 1.5%, Nickel, Ni content: 4/4 = 1%, Molybdenum, Mo content: → not notified → minor alloying content
        
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        Stainless steels and other alloy steels (except high-speed steels) where the average content by weight of at least one alloying element is ≥ 5%.
        Letter X
        Carbon content = 100 × specified average carbon percentage
        Alloying elements → chemical symbols indicating alloying elements that characterize the steel
        Elements are followed by numbers, separated by hyphens, representing respectively the average percentage content of the elements rounded to the nearest integer
        
        Example: X3CrNiMo18-10-3 (austenitic stainless steel) →
        Carbon, C content: 3/100 = 0.03%
        Chromium, Cr content: = 18%
        Nickel, Ni content: = 10%
        Molybdenum, Mo content: = 3%
        
        Example: HS2-9-1-8 (high-speed steel) → W = 2%, Mo = 9%, V = 1%, Co = 8%
        
        High-speed steels
        Letters HS = high-speed and PM = powder metallurgy (where necessary)
        Numbers, separated by hyphens, indicating percentage content of alloying elements in the following
        order:
        Tungsten (W)
        Molybdenum (Mo)
        vanadium (V)
        Cobalt (Co)
        
        DESIGNATION PRINCIPLES FOR STEEL NAMES
        
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        By application / mechanical / physical properties. Structural steels, engineering steels, case-hardened steels, tool steels, etc
        
        Structural Steels
        Designation according to the application (S = structural + nominal yield strength), trend of steel evolution:
        ever-growing yield strength levels
        Limited carbon content - “low” (approx. C ~ 0.12…0.20%)
        
        Good weldability in general, Good formability in general. Low level of impurities, e.g., sulfur (S) and phosphor (P). Applications: welded structures and assemblies / general use, etc. Building frames, bridges, stairways, handrails, machines’ and transportation vehicles’ frames, etc
        
        Engineering steels:
        Designation according to the application (E = engineering + nominal yield strength). Carbon content not so strictly limited compared to structural steels
        
        Impurity levels, e.g., sulfur (S) “unrestricted” → improvement of machinability. Good machinability in general, poor weldability in general.
        
        Relatively high carbon (C) and sulfur (S) content levels → restricted weldability (brittleness, cold and
        hot cracking issues). Applications: basic machine components, etc. Axles, pins, pivots, etc. (C-Mn steels)
        
        Case-hardened steels:
        Case hardening = Treatment consisting of carburizing followed by quench hardening. The steels that are in general intended for the fabrication of case-hardened machine parts. Manufactured from the case hardening non-alloyed or alloyed steels
        
        Quenching produces hard and wear resistant material surface with high hardness (~ 60…65 HRC),
        whereas inner core of material stays soft and ductile
        
        Alloying element ranges, approx.
        ▪ C ~ 0.2%
        ▪ Mn ~ 1%
        ▪ Cr ~ 0.4…1.8%
        ▪ Mo ~ 0.1…0.5%
        ▪ Ni ~ 0.4…1.7%
  - - - Easier to make castings compared to steels
        Molten metal is more fluidity compared to steels (higher Si content)
        Easier to cast precise structures with relatively thin wall thicknesses
        
        However, steels contain
        less than 2%, and usually less than 1% carbon, whereas all cast irons contain more than 2% carbon
        
        CLASSIFICATION OF GRADES: Shape of graphite microstructure affects remarkably the properties of cast irons, Shape, quantity and distribution of graphite precipitates within the base matrix
        
        Most common shapes of graphite kernel and resulting designations according to graphite microstructure
        morphology are:
        Lamellar, Spheroidal, Vermicular
        
        SFS-EN 1560
        Sequence of symbols: Letters GJ
        L = Lamellar (grey cast iron)
        S = Spheroidal
        V = Vermicular
        Suffixed by ultimate tensile strength in MPa
        GJS-500 → spheroidal cast iron, ultimate tensile strength 500 MPa
        
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  - - - THE EFFECT OF CHROMIUM CONTENT:
        
        CLASSIFICATION: Classification by predominant metallurgical phase or phases present.
        Austenitic (Face-Centered Cubic = FCC crystal structure)
        Ferritic (Body-Centered Cubic = BCC crystal structure)
        Duplex, i.e., austenitic-ferritic (FCC + BCC crystal structure)
        Martensitic (Body-Centered Tetragonal = BCT crystal structure)
        
        OVERVIEW OF CORROSION RESISTANCE OF
        DIFFERENT GRADES:
        
        Austenitic: C 0.02-0.05%, Cr 17-19% (25), Ni 7-14% (24), Mo 2.0-6.5%, Mn <2%, Si <1%, Nb, Ti
        Ferritic: C 0.03-0.08%, Cr 12-18% (29), Mn <1%, Si <1%, Mo 1-4%
        Duplex (austenitic-ferritic): C 0.03%, Cr 18-26%, Ni 4-8%, Mo 3.0-4.5%, N 0.2%
        Martensitic: C 0.15-0.70%, Cr 12-17%, Mo 0.2-1.0%, Ni, Mn <1%, Si <1%
        
        AUSTENITIC STAINLESS STEELS: Most of austenitic stainless steel alloys are based on 18Cr / 8Ni system
        E.g., designation X5CrNi18-10 (i.e., EN 1.4301 /
        AISI 304)
        Corrosion resistance can be further improved with
        molybdenium alloying
        E.g., Mo ≈ 2-3% → X3CrNiMo17-13-3 (i.e., EN
        1.4436 / AISI 316)
        Increasing Cr, Ni, Mo, N (0.1-0.2%) alloying improves
        both corrosion resistance and strength
        
        Less alloyed basic grades (types 304 / 316) are prone to stress-corrosion cracking in highly oxidizing acids such as nitric acid
        Tensile stresses + warm / hot (> 60°C) chloride
        environment
        
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- - - - Because wood is aliving materia, setting a wood on strict standards, norms and dimensions is more difficult compared to other materials, which is why treatments are done to stabalise its properties
        
        wood is Hygroscopic material, Anisotropic material and Heterogeneous structure.
        
        Hygroscopic material = ability to absorb and release moisture depending on the relative humidity of the surrounding air
        
        Anisotropic material = properties of wood differ in longitudinal (grain), radial and tangential direction
        
        Heterogeneous structure = many properties, e.g., density and color, vary from the surface to core and from base to the top, as well as with orientation of wood cells
        
        Structure
        
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        Mechanical properties Of the internal (i.e., structural) factors, mechanical properties are most strongly
        influenced by
        
        Wood density (growth rate)
        
        Direction of cellular structure and its possible variations
        
        The main external factors affecting the mechanical properties of wood are: humidty, temperrature, direction of stress in relation of the cellular structure, Loading rate, long-term stress, variations in stress and conditions
        
        When a part of wood is loaded above the proportional limit, the
        deformation no longer follows Hooke's law. If the load is increased, the stress is in the deformation range until the
        breaking limit (ultimate strength, σmax) is reached
        
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        Fracture behavior: caused by external stress depends on the type of the stress and its orientation in relation to the cellular structure of wood
        
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        Due to anisotropy, mechanical properties are different in radial,
        tangential and longitudinal (grain) directions, for example:
        
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- - - - The polymers may be composed of carbon, hydrogen, oxygen and /or silicon
        Most polymers contain carbon and hydrogen (polypropylene,
        polyethylene and polystyrene)
        
        Monomers are generated in the oil refining process as a by-product
        
        NOMENCLATURE OF PLASTICS
        
        The simplest and most commonly used naming system is based on the English name of the starting polymer monomer. If there is only one starting monomer, the name of the polymer is obtained by adding the prefix poly to the name of the monomer, e.g. ethylene → polyethylene
        
        The symbols are usually formed from the initials of the English name of the polymer
        e.g. polypropylene (PP) means both polypropylene polymer and polypropylene
        plastic
        
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        In copolymers, the slash separates the symbols of the different polymers.
        The designation of the copolymer shows all its structural polymers, with the polymer with the highest molar or mass percentage being the first to be declared, e.g. S / B styrene / butadiene
        
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        Polyamides are separated by indicating the number of carbon atoms PA6 (six carbon atoms monomer) and PA610 (two monomers, six carbon atoms and ten carbon atoms)
        
        Thermoplastics: are meltable and moulded repeatedly. They are environmentally friendly compared to thermosetting
        plastics. PP, LDPE and HDPE are often used thermoplastics in composites and are cheaper to thermoset plastics
        
        Thermoplastics can be joined together by heat, for example
        by welding or heat sealing.
        Thermoplastics contain linear or straight or branched polymer
        chains. The forces connecting the long molecular chains transversely to each other are weak and are called secondary bonds
        
        Thermoplastics include, for example, polyethylenes, polypropylenes and polyamides.
        Thermoplastic raw materials used in the manufacture of plastic
        products may be in the form of granules, flakes or powder
        
        Thermosetting plastics: are not re-shapable after curing. Harder but at the same time more brittle than thermoplastics. Composites use e.g. epoxy and phenol formaldehyde resins and are also more expenseive that thermoplastics. In liquid form the are hazardous
        
        In the curing reaction, the polymer chains of the resin crosslink, i.e., are interconnected by covalent bonds to form a network-like structure. Due to networking, the polymer chains lose their ability to slidepast each other. The structure stiffens, the polymer does not melt or flow under the influence of heat, so it cannot be re-shaped
        
        ELASTIC: A polymer is called an elastic (elastomer) when it has a large structure.
        
        Elastomers are divided into rubbers and thermoplastic elastomers. Thermoplastic elastomers behave like thermoplastics, making them easy to process and recycle. Rubber recycling is much more difficult
        
        Additives: are used in plastics for a very wide variety of
        reasons. They can be used, for example, Speed up and simplify the manufacturing of the products, Alter or extend the properties of the polymer, Dye, Stabilize against environmental impact (increase product life, lower the price of the product
        
        The composites usually contain one or more additives,The most commonly used are thermal stabilizers and dyes. In addition to these, various lubricants, flame retardants, antistatic agents, fillers and reinforcing agents as well as electrically conductive substances and plasticizers are used
        
        Mainstream plastics (basic plastics, mass-produced plastics) have a very wide range
        of applications
        
        Their strength and heat resistance are not very good, but correspondingly the price is low. Main plastics include polyolefins (PE, PP), PVC and styrene plastics. The consumption of these plastics covers 80% of the total plastic consumption
        
        Engineering plastics have better strength and heat resistance compared to bulk
        plastics
        
        The price is higher. These plastics are used reinforced or alloyed. Applications include a variety of technical applications on a large scale. Typical engineering plastics include polyamides (PA), polyester (PET and PBT) and polycarbonate (PC). The price range is 2 - 10 € / kg
        
        Specialty plastics have been developed for certain
        special purposes.
        
        Customized and in many cases superior properties over other materials (strength / weight ratio, chemical resistance, possibility to make integrated products) increase the price. Typical are polyimides (PI), polysulfides (PSU) and polyether
        ketones (PEEK)
        
        The price is 10 - 100 € / kg, but it can rise to more than 2 000 € / kg