mechanical engineering

Carbon steels

• Hard-drawn spring steel
  Low cost; general purpose; low stress; low fatigue life. Temperatures below 120°C. Tensile strength up to 1600 N mm -2.
• Piano (music) wire
  Tougher than harddrawn spring steel; high stress (tensile strength up to 2300 N inm- *); long fatigue life; used for 'small springs'. Temperatures below 120°C.
• Oil-tempered spring steel
  General purpose springs; stress not too high; unsuitable for shock or impact loads. Popular diameter range 3-15 mm.

Alloy steels

• Chrome-vanadium steel
  Best for shock and impact loaL,. Available in oiltempered and annealed condition. Used for internal combustion engine valve spriags. Temperatures up to 220 "C.
• Silicon-manganese steel
  High working stress; used for leaf springs; temperatures up to 220°C. Si1 icon-chromium steel Better than silicon-manganese; temperatures up to 220 "C.
• Stainless steels
  Cold drawn; tensile strength up to 1200Nmm-2. Temperatures from sub-zero to 290 "C, depending on type. Diameters up to 5mm.

Non-ferrous alloys

• Spring brass (70/30)
  Low strength, but cheap and easily formed. Good electrical conductivity.
• Phosphor bronze (5%Sn)
  High strength, resilience, corrosion resistance and fatigue strength. Good electrical conductivity. Tensile strength 770N mm-2. Wire diameters 0.15-7mm. Used for leaf and coil switch springs.
• Beryllium-copper (2 1/4%)
  Formed in soft condition and hardened. High tensile strength. Used for current-carrying brush springs and contacts. Tensile strength 1300Nmm-2.
• Inconel
  Nickel based alloy useful up to 370°C. Exceedingly good corrosion resistance. Diameters up to 7mm. Tensile strength up to 1300Nmm-2.

Moduli of spring materials

Grey iron
Grey iron is so called because of the colour of the fracture face. It contains 1.543% carbon and 0.3-5% silicon plus manganese, sulphur and phosphorus. It is brittle with low tensile strength, but is easy to cast.

Properties of some grey irons (BS 1452)

Spheroidal graphite (SG) iron

This is also called nodular iron because the graphite is in the form of small spheres or nodules. These result in higher ductility which can be improved further by heat treatment. Mechanical properties approach those of steel combined with good castability.

Properties of some SG irons (BS 2789)

Malleable irons

These have excellent machining qualities with strength similar to grey irons but better ductility as a result of closely controlled heat treatment. There are three types: white heart with superior casting properties; black heart with superior machining properties; and pearlitic which is superior to the other two but difficult to produce.

Properties of some maUeabie irons

* BHN : Brinell Hardness Number

Metals can be processed in a variety of ways. These can be classified roughly into casting, forming and machining. The following table gives characteristics of different processes for metals, although some may also apply to non-metallic materials such as plastics and composites.

General characteristics of metal processes :

Electrolytically refined copper (99.95% Pure) is used for components requiring high conductivity. Less Pure copper is used for chemical plant, domestic plumbing, etc. Copper is available in the form ofwire, sheet, strip, plate, round bar and tube. Copper is used in many alloys, including brasses, bronzes, aluminium bronze, cupronickel, nickel-silver and bryllium-copper.

Composition and mechanical properties of some copper alloys

Classification
Alloy steels differ from carbon steels in that they contain a high proportion of other alloying elements. The following are regarded as the minimum levels:

Alloy steels are classified according to increasing proportion of alloying elements and also phase change during heating and cooling as follows:
low alloy steels
medium alloy steels
high alloy steels
and according to the number of alloying elements as follows:
ternary - one element
quarternary - two elements
complex - more than two elements

General description

Low alloy steels

These generally have less than 1.8% nickel, less than 6% chromium, and less than 0.65% molybdenum. The tensile strength range is from 450-620 N mm-’ up to 85O-1000 N mm-2

Medium alloy steels

These have alloying elements ranging from 5-12%. They do not lend themselves to classification. They include: nickel steels used for structural work, axles, shafts, etc.; nickel-molybdenum steels capable of being case-hardened, which are used for cams, camshafts, rolling bearing races, etc.; and nickelchromemolybdenum steels of high strength which have good fatigue resistance.

High alloy steels

These have more than 12% alloying elements. A chromium content of 13-18% (stainless steel) gives good corrosion resistance; high wear resistance is obtained with austenitic steel containing over 11%  manganese. Some types have good heat resistance and high strength.

The gas turbine is used in a wide range of applications. Common uses include power generation plants and military and commercial aircraft. In Jet Engine applications, the power output of the turbine is used to provide thrust for the aircraft.

• The working substance is air and treated as an ideal gas throughout the cycle
• The combustion process is modeled as a constant pressure heat addition
• The exhaust is modeled as a constant pressure heat rejection process
  

• (1-2) Isentropic Compression
• (2-3) Reversible Constant Pressure Heat Addition
• (3-4) Isentropic Expansion
• (4-1) Reversible Constant Pressure Heat Rejection
  

The pv and Ts diagrams are shown below.

Carbon steels

Their use is restricted to the cutting of soft metals and wood. Performance is poor above 250°C.

High-speed Steels

These are used extensively, particularly for multi-point tools. They have been replaced to a large extent by carbides for single-point tools. Their main application
is for form tools and complex shapes, e.g. for gearcutting and broaching. They are also used for twist drills, reamers, etc.

Carbides

These consist of powdered carbides of tungsten, titanium, tantalum, niobium, etc., with powdered cobalt as binder. They are produced by pressing the powder
in dies and sintering at high temperature. They are then ground to the final shape. They are generally used as tips and can operate up to 1oo0"C.

Laminated carbide

These consist of a hard thin layer of titanium carbide bonded to a tungsten carbide body. The surface has very high strength at high temperature, whilst the body has high thermal conductivity and thus efficient removal of heat.

Diamonds

These are the hardest of all cutting materials with low thermal expansion and good conductivity. They are twice as good as carbides under compression. A good finish can be obtained with non-ferrous metals and final polishing can be eliminated. Diamonds are particularly good for cutting aluminium and magnesium alloys, copper, brass and zinc. They have a long life.

Pipe cross-sectional area, empty pipe weight, pipe filled with water weight, inside and outside pipe surface area for a unit length pipe can be calculated with the equations below.
pipe diameter cross sectional area
Cross Sectional Area
Cross-sectional Area of a Steel Pipe can be calculated as
A = 0.785 di 2
where
A = cross-sectional area of pipe (Square Inches)
di = inside diameter (inches)

Weight of Empty Steel Pipes
Weight of empty steel pipes can be calculated as
wp = 10.6802 t (do - t)
where
wp =weight of steel pipe (Pounds per Foot Pipe)
t = pipe wall thickness (Inches)
do = outside diameter (inches)

Weight of Water in Pipes filled with Water
Weight of water in pipes filled with water can be calculated as
ww = 0.3405 di 2
where
ww = weight of steel pipe filled with water (Pounds per Foot Pipe)
di = inside diameter (inches)

Outside Surface Area of Pipes
Outside surface area of steel pipes can be calculated as
Ao = 0.2618 do
where
Ao = outside area of pipe - per foot (Square Feet)
do = outside diameter (inches)

Inside Surface Area of Pipes
Inside surface area of steel pipes can be calculated as
Ai = 0.2618 di
where
Ai = inside area of pipe - per foot (Square Feet)
di = inside diameter (inches)

Area of the Metal
Area of the metal can be calculated as
Am = 0.785 (do 2 - di 2)
where
Am = area of the metal (Square inches)
di = inside diameter (inches)
do = outside diameter (inches)

The American National Standards Institute - ANSI - is a private, non-profit organization that administers and coordinates the U.S. voluntary standardization and conformity assessment system.

ANSI provides a forum for development of American national standards from organizations as

• ASME - American Society of Mechanical Engineers
• NFPA - National Fire Protection Association and more,
  

• ISO - International Organization for Standardization,
• DIN - Deutsches Institut für Normung eV,
• IEC - International Electro technical Commission and others.
  

• ASME - American Society of Mechanical Engineers and
• IEEE - Institute of Electrical and Electronics Engineers.
  

In gas welding the heat to melt the metal parts being welded is produced by the combination of oxygen and an inflammable gas such as acetylene, propane, butane, etc. Acetylene is the most commonly used gas; propane and butane are cheaper but less efficient.

Oxyacetylene welding
A flame temperature of about 3250 "C melts the metals which fuse together to form a strong joint. Extra metal may be supplied from a filler rod and a flux may be used to prevent oxidation. The gas is supplied from high pressure bottles fitted with special regulators which reduce the pressure to 0.134.5 bar. Gauges indicate the pressures before and after the regulators. A torch mixes the gases which issue from a copper nozzle designed to suit the weld size. The process produces harmful radiation and goggles must be worn. The process is suitable for steel plate up to 25mm thick, but is mostly used for plate about 2 mm thick.

The calculator is based on the piping formulas and equations below:

Moment of Inertia
Moment of inertia can be expressed as
I = 0.0491 (do4 - di4)
where
I = moment of inertia (in4)
do = outside diameter (in)
di = inside diameter (in)

Section Modulus
Section modulus can be expressed as
Z = 0.0982 (do4 - di4) / do
where
Z = section modulus (in3)

Transverse Metal Area
Transverse metal area can be expressed as
Am = π (do2 - di2) / 4
where
Am = transverse metal area (in2)

External Pipe Surface
External pipe or tube surface per ft of length can be expressed as
Ao = π do / 12
where
Ao = external pipe surface area (ft2 per ft pipe)

Internal Pipe Surface
Internal pipe or tube surface per ft of length can be expressed as
Ai = π di / 12
where
Ai = internal pipe surface area (ft2 per ft pipe)

Transverse Internal Area
Transverse internal area can be expressed as
Aa = 0.7854 di2
where
Aa = transverse internal area (in2)

Circumference External
External circumference can be expressed as
Ce = π do
where
Ce = external circumference (in)

Circumference Internal
Internal circumference can be expressed as
Ci = π di
where
Ci = internal circumference (in)

The heat of fusion is generated by an electric arc struck between two electrodes, one of which is the workpiece and the other a ‘welding rod’. The welding rod is made of a metal similar to the workpiece and is coated with a solid flux which melts and prevents oxidation of the weld. The rod is used to fill the welded joint. Power is obtained from an a.c. or d.c. ‘welding set’ providing a regulated low-voltage high-current supply to an ‘electrode holder’ and ‘earthing clamp’. The work is done on a steel ‘welding table’ to which the work is clamped and to which the earthing clamp is attached to complete the circuit.

Antimony
A brittle lustrous white metal used mainly as an alloying element for casting and bearing alloys and in solders.

Beryllium
A white metal similar in appearance to aluminium. Brittle at room temperature. Has many applications in the nuclear field and for electronic tubes. With copper and nickel it produces alloys with high strength and electrical conductivity. Beryllium iron has good corrosion and heat resistance.

Cadmium
A fairly expensive soft white metal like tin. Used for plating and electrical storage batteries. It has good resistance to water and saline atmospheres and is useful as plating for electrical parts since it takes solder readily.

Chromium
A steel-grey soft but brittle metal. Small traces of carbide give it extreme hardness. It is used extensively in alloys and for electroplating and is also used for electrical resistance wire and in magnet alloys.

Lead
A heavy, soft, ductile metal of low strength but with good corrosion resistance. It is used for chemical equipment, roofing, cable sheathing and radiation shielding. It is also used in alloys for solder and bearings.

Lead-tin alloys
These are used as ‘soft solders’, often with a little antimony for strength. Tinman’s solder Approximately 2 parts of tin to 1 part of lead. Used for electrical jointing and tinplate can sealing. Plumber’s solder Approximately 2 parts of lead to 1 part of tin. Used for wiping lead pipe joints. Type metal Contains about 25% tin, with lead and some antimony. Has negligible shrinkage. Bearing metal Lead based ‘white metal’ contains lead, tin, antimony and copper, etc.

Magnesium
A very light metal, only one-quarter the weight of steel and two-thirds that of aluminium, but not easily cold worked. Usually alloyed with up to 10% aluminium and often small amounts of manganese, zinc and zirconium. Used for aircraft and internal combustion engine parts, nuclear fuel cans and sand and die castings. Magnesium and its alloys corrode less in normal temperatures than does steel.

Manganese
A silvery white hard brittle metal present in most steels. It is used in manganese bronze and high nickel alloys and to improve corrosion resistance in magnesium alloys.

Nickel
Nickel has high corrosion resistance. It is used for chemical plant, coating steel plate and electroplating as a base for chromium. Nickel is used for many steel, iron and non-ferrous alloys. Nickel-base alloys Monel Used for steam turbine blades and chemical plant. Composition: 68%Ni, 3o%cu, 2%0Fe. Inconel Good at elevated temperatures, e.g. for cooker heater sheaths. Composition:  8O%Ni, 14%Cr, 6%Fe.
Nimonic A series of alloys based on 70-80%Ni, with small amounts of Ti, Co, Fe, A1 and C. Has high resistance to creep and is used for gas turbine discs and blades, and combustion chambers. Strong up to 900 “C.

Platinum
A soft ductile white metal with exceptional resistance to corrosion and chemical attack. Platinum and its alloys are widely used for electrical contacts, electrodes and resistance wire.

Silver
A ductile malleable metal with exceptional thermal and electrical conductivity. It resists most chemicals but tarnishes in a sulphurous atmosphere. It is used for electrical contacts, plating, bearing linings and as an alloying element.

Tin
A low-melting-point metal with silvery appearance and high corrosion resistance. It is used for tinplate, bearing alloys and solder.

Titanium
An expensive metal with low density, high strength and excellent corrosion resistance. It is used in the aircraft industry, generally alloyed with up to 10% aluminium with some manganese, vanadium and tin. Titanium is very heat resistant.

Tungsten
A heavy refractory steel-grey metal which can only be produced in shapes by powder metallurgy (m.p.3410 “C). It is used as an alloying element in tool and die steels and in tungsten carbide tool tips. It is also used in permanent magnets.

Zinc
Pure zinc has a melting point of only 400 “C so is good for die casting, usually with 1-2%0Cu and 4%A1 to increase strength. Used for carburettors, fuel pumps, door handles, toys, etc., and also for galvanizing sheet steel, nails and wire, and in bronze.

Aluminium

This acts as a deoxidizer to increase resistance to oxidation and scaling. It aids nitriding, restricts grain growth, and may reduce strength unless in small quantities. The range used is 0-2%.

Chromium

A range of O M % , improves wear, oxidation, scaling resistance, strength and hardenability. It also increases high-temperature strength, but with some loss of ductility. Chromium combines with carbon to form a wear-resistant microstructure. Above 12% the steel is stainless, up to 30% it is used in martensitic and ferritic stainless steel with nickel.

Cobalt

Cobalt provides air hardening and resistance to scaling. It improves the cutting properties of tool steel with 8-10%. With chromium, cobalt gives certain high alloy steels high-temperature scaling resistance.

Copper

The typical range is 0.24.5%. It has limited application for improving corrosion resistance and yield strength of low alloy steels and promotes a tenacious oxide film.

Lead

Up to 0.25% is used. It increases machineability in plain carbon steels rather than in alloy steels.

Manganese

The range used is 0.3-2%. It reduces sulphur brittleness, is pearlitic up to 2%, and a hardening agent up to 1 Yo. From 1-2% it improves strength and toughness and is non-magnetic above 5%.

Molybdenum

The range used is 0.3-5%. It is a carbide forming element which promotes grain refinement and increases high-temperature strength, creep resistance, and hardenability. Molybdenum reduces temper brittleness in nickel-chromium steels.

Nickel

The range used is 0.3-5%. It improves strength, toughness and hardenability, without affecting ductility. A high proportion of it improves corrosion resistance. For parts subject to fatigue 5% is used, and above 27% the steel is non-magnetic. Nickel romotes an austenitic structure.

Silicon

The usual range is 0.2-3%. It has little effect below 3%. At 3% it improves strength and hardenability but reduces ductility. Silicon acts as a deoxidizer.

Sulphur

Up to 0.5% sulphur forms sulphides which improve machineability but reduces ductility and weldability.

Titanium

This is a strong carbide forming element. In proportions of O.2-O.75% it is used in maraging steels to make them age-hardening and to give high strength. It stabilizes austenitic stainless steel.

Tungsten

This forms hard stable carbides and promotes grain refining with great hardness and toughness at high temperatures. It is a main alloying element in high speed tool steels. It is also used for permanent-magnet steels

This is a carbide forming element and deoxidizer used with nickel and/or chromium to increase strength. It improves hardenability and grain refinement and combines with carbon to form wear-resistant microconstituents. As a deoxidizer it is useful for casting
steels, improving strength and hardness and eliminating blowholes, etc. Vanadium is used in high-speed and pearlitic chromium steels.

Vanadium

This is a carbide forming element and deoxidizer used with nickel and/or chromium to increase strength. It improves hardenability and grain refinement and combines with carbon to form wear-resistant microconstituents. As a deoxidizer it is useful for casting
steels, improving strength and hardness and eliminating blowholes, etc. Vanadium is used in high-speed and pearlitic chromium steels.

A pump does not completely convert the kinetic to pressure energy. Some of the energy is always lost internal and external in the pump.

Internal losses

• hydraulic losses - disk friction in the impeller, loss due to rapid change in direction an velocities through the pump
• volumetric losses - internal recirculation at wear rings and bushes
  

• mechanical losses - friction in seals and bearings

• Best Efficiency Point - BEP

Typical properties of alloy steels

A = ausformed, MA = martempered, CR =cold rolled, P = poor, F = fair, G = good, PH = preheat required, PR = protection required, HT = at high temperature, HTR = when heat treated, FHTR=final heat treatment required.

Temperature (sometimes called thermodynamic temperature) is a measure of the average kinetic energy of a systems particles. Temperature is the degree of "hotness" ( or "coldness"), a measure of the heat intensity.

When two objects of different temperature are in contact, the warmer object becomes colder while the colder object becomes warmer. It means that heat flows from the warmer object to the colder one.

Degree Celsius (oC) and Degree Fahrenheit (oF)
Thermometer helps us determine how cold or how hot a substance is. Temperatures in science (and in most of the world) are measured and reported in degrees Celsius (oC). In the US, it is common to report temperature in degrees Fahrenheit (oF). On both the Celsius and Fahrenheit scales the temperature at which ice melts (water freezes) and the temperature at which water boils, are used as reference points.

• On the Celsius scale, the freezing point of water is defined as 0 oC, and the boiling point of water is defined as 100 oC.
• On the Fahrenheit scale, the water freezes at 32 oF and the water boils at 212 oF.
  

Density
Density is defined as an objects mass per unit volume. Mass is a property.

• Mass and Weight - the Difference! - What is weight and what is mass? An explanation of the difference between weight and mass.

• Unit converter for other units

• Densities and material properties for common materials

Type and composition	Condition	Tensile MN/m2	Product	Use
Pure copper 99.95%Cu	O	220	Sheet, strip wire	High conductivity electrical applications
	H	350
98.85%cu	O	220	All wrought forms	Chemical plant. Deep drawn, spun articles
	H	360
99.25%cu +0.5%As	O	220	All wrought forms	Retains strength at high temperatures. Heat exchangers, steam pipes
	H	360
Brasses 9O%Cu, 10%Zn-gilding metal	O	280	Sheet, strip and wire	Imitation jewellery, decorative work
	H	510
7o%cU, 30%Zn-Cartridge brass	O	325	Sheet, strip	High ductility for deep drawing
	H	700
65%Cu, 35%Zn- standard brass	O	340	Sheet, strip and extrusions	General cold working alloy
	H	700
60%Cu, 40%Zn- Muntz metal	M	375	Hot rolled plate and extrusions	Condenser and heat exchanger plates
59%Cu, 35%Zn, 2%Mn, 2%A1, 2%Fe	M	600	Cast and hot worked forms	Ships screws, rudders
58%Cu, 39%Zn, 3%Pb free cutting	M	440	Extrusions	High speed machine parts
Bronzes 95.5%Cu, 3%Sn, 1.5Zn	O	325	Strip	Coinage
	H	725
5.5%Sn, O.l%Zn, Cu	O	360	Sheet, strip and wire	Springs, steam turbine blades
	H	700
10%Sn, 0.03-0.25P, Cu- phosphor bronze	M	280	Castings	Bushes, bearings and springs
10%Sn, O.S%P, Cu	M	280	Castings	General-purpose castings and bearings
10%Sn, 2%Zn, Cu-Admiralty gunmetal	M	300	Castings	Pressure-tight castings, pump,valve bodies
Aluminium bronze 95?'ocU, 5%AI	O	400	Strip and tubing	Imitation jewellery, condenser tubes
	H	770
10Y0A1, 2.5%Fe, 2-5%Ni, Cu	M	700	Hot worked and cast products	High-strength castings and forgings
Cupronickel 75%cu, 25%Ni	O	360	Strip	British 'silver' coinage
	H	600
70%Cu, 30%Ni	O	375	Sheet and tubing	Condenser tubes, good corrosion resistance
	H	650
29%cu, 68%Ni, 1.25%Fe,1.25%Mn	O	550	All forms	Chemical plant, good corrosion resistance
	H	725
Nickel-silver 55%Cu, 27%Zn, l8%Ni	O	375	Sheet and strip	Decorative use and cutlery
	H	650
Ber y llium-copper 1.75-2.5%Be, 0.5% co, c u	WP	1300	Sheet, strip, wire, forgings	Non-spark tools, springs

0 =annealed, M =as manufactured, H =fully work hardened, WP=solution heat treated and precipitation hardened.