ME - Mechanical Engineering
Online Magazine for Mechanical Engineers

Number of parts in a bicycle changes from one model to another. Parts of a bicycle are fitted by manufactures for the type of function needed. Below bicycle diagram shows the labeling of bicycle parts.

List of Bicycle parts:

  1. Top tube
  2. Down tube
  3. Seat tube
  4. Seat stay
  5. Chain stay
  6. Rear brakes
  7. Cogset
  8. Rear derailleur
  9. Front derailleur
  10. Chain
  11. Chain rings
  12. Pedal
  13. Crank arm
  14. Spokes
  15. Hub
  16. Rim
  17. Tire
  18. Valve
  19. Handlebar grip
  20. Head tube
  21. Shock absorber
  22. Front brakes
  23. Fork
  24. Saddle
  25. Seat
  26. Seat post
Saddle, seat, seat post is known saddle area of a bicycle. Top tube, down tube, seat tube, seat stay, chain stay together is called frame or body of a bicycle. Handlebar grip, head tube, shock absorber, front brakes, fork together are called front set of a cycle. Spokes, hub, rim, tire, valve are parts of a bicycle wheel.
Some bicycle have the extra features like carriage, bottle cage, front light, bell.
It is no doubt that earth moving equipment is expensive; thus, plenty of businesses within the construction industry choose to rent than buying one. Leasing is indeed a very practical option since it will relieve businesses of expensive ownership responsibilities. Be reminded though that it is also not easy for you to locate reliable businesses that lease earth moving equipment. Most businesses today wanted to avoid the hassle of finding a reputable business that lease such equipment by purchasing one.

Why Choose Japanese Manufactured Equipment:

Some of the leading machinery brands worldwide will include most Japanese manufactured products from Hitachi, Kobelco, Mitsubishi, Yanmar, Sumitomo, Kato, Furukawa, IHI, and Kubota. A lot of construction businesses all around the world choose to get earth moving machinery and heavy equipment directly from Japan because such equipment has higher depreciation rates than other countries.
Indeed, you have a vast selection to choose from. What is good about these products is that they have the quality that is second to none. Among the machineries that are of high demand these days are excavators. Oftentimes, businesses choose to buy excavators for sale in Japan since they are more affordable as opposed to other countries. Furthermore, the shipment is handled by Japan based exporters.
Another heavy equipment that is being bought directly from Japan will include bulldozers. Regardless of whether you want to buy used or new ones, you have different sizes to choose from. Also, you can also choose from top international to local brands like Komatsu, Mitsubishi, and Caterpillar. These heavy pieces of machinery are of high demand because it is commonly used for road construction.
Wheel loaders are often sought out by most foreign buyers for the construction industry. They usually buy these products in Japan because the selection is much easier. Also, they can always depend on the good quality of their purchase since such products undergo a thorough evaluation process. If you choose to purchase wheel loader, you actually have 2 options – you can make a direct purchase or perhaps buy it from auction. Buying it from auction is the most recommended way for you to obtain wheel loaders for your business since you can actually have big savings, most especially when there are very few interested buyers who are participating.
Indeed, Japan-made earth moving equipment is still on top. This is the main reason why most businesses in the construction industry want to invest in such. Quality and affordability is assured.
Mechanical Properties helps us to measure how materials behave under a load. Mechanical Properties of material are mentioned below.

Elastic Material:

A material which regains its original size and shape on removal stress is said to be elastic stress.

Plastic material:

A material which can undergo permanent deformation without rupture aid to be plastic material. This property of the material is known as plasticity. Plasticity is important when a material is to be mechanically formed by causing the material to flow.

Ductile Material:

A material which an undergo considerable deformation without rupture is said to be ductile material. The major portion of deformation is plastic.

Brittle material:

A material which ruptures with little or no plastic deformation is said to brittle materials.

Set of permanent set:

The deformation or strain remaining in a body after removal of stress is known as permanent set. This is due to elastic property of material.

Elastic limit:

The greatest stress that a material can take without permanent set on the removal of stress is known as elastic limit.

Proportionality limit:

The greatest stress that a material can take without deviation from straight line between stress and strain is known as proportionality limit.

Endurance limit or fatigue limit:

The greatest stress, applied infinite number of times, that a material can take without causing failure is known as endurance limit or fatigue limit.

Ultimate strength:

The maximum stress material can take is known as ultimate strength. Ultimate strength is equal to maximum load divided by original area of cross section.

Modulus of resilience:

The energy stored per unit volume at the elastic limit is known as modulus of resilience.

Modulus of toughness:

The amount of work required per unit volume to cause failure, under static loading, is called modulus of toughness.

Modulus of rupture:

The ultimate strength in flexure or torsion is known as modulus of rupture.

Strain hardening:

The increase in strength after plastic zone due to rearrangement of molecules in the material.

Proof stress:

The stress which is just sufficient to cause a permanent set(elongation) equal to a specified percentage of the original gauge length.

Elastic strain:

Elastic strain is a dimensional change that occur in a material due to the application of loads and disappears completely on the removal of the loads.

Plastic strain:

It is a dimensional change that occurs in a material due to application of the loads and does not disappear after the removal of the loads.

Ductility and malleability:

The plastic response of material to tensile force is known as ductility and plastic response to compression force is known as malleability. The elongation and reduction of area of test piece tested to failure in tension are generally taken as measures of ductility of material.

Creep:

The long term deflection due to sustained (constant) loads.

Factor of safety:

Factor of safety is defined as follows
For Ductile materials,
F.O.S = yield stress / working stress
For Brittle materials,
F.O.S = ultimate stress / working stress

Margin of safety:

Margin of safety = Factor of safety - 1
Electro Chemical Machining (ECM) uses principle of electrolysis to remove metal from the work piece. Electrolysis is based on faradays laws of electrolysis which is stated as
weight of substance produced during electrolysis is proportional to current passing, length of time the process used and the equivalent weight of material which is deposited.
  • ECM process is just reverse of electroplating (anode loses metal to cathode). So in ECM work is made anode and tool is made cathode.
  • So work loses metal, but before depositing it on to tool, it is carried away by electrolyte.
  • In ECM tool is provided with a constant feed motion and electrolyte is pumped at a high pressure through the tool and the small gap between tool and workpiece.
  • The current used in this process is few thousands amperes and voltage used is 8-20 volts and gap is of the order of to 0.2mm.
  • MRR = 1600 mm3/min for each 1000 amperes. So, approximately 3 KWH is needed to remove 16*103 mm3 of metal, which is 30 times the energy required in convectional machining process.
  • Practically no tool wears in ECM.
  • MRR is independent of hardness of work.
Material removal rate in ECM process
Where,
F = faraday's constant = 96,500 Columns = 26.8 amp-hours
I = current flowing in amperes,
Z = Valances of metal dissolved,
A = atomic weight of material in grams,
MRR = Material removal rate in grams per second.

Current density = VK/y = ?. f/Z
Where,
y = gap between tool and work,
V = applied voltage,
K = conductivity of electrolyte(mho/mm),
? = density of work material kg/mm3,
f = tool feed rate (mm/sec).

Advantages:

  • Complex, concave curvature components can be produced easily by using convex and concave tools.
  • Tool wear is zero, same tool can be used for producing infinite number of components.
  • No direct contact between tool and work material so there are no forces, residual stresses.
  • The surface finish produced is excellent.

Limitations:

  • Out of all the unconventional machining methods Electro Chemical Machining requires high specific cutting energy.
  • Sharp corners not possible to produce.
  • Work material must be electrically conducting.
  • Generally preferable for producing contours only.

Applications:

Electro Chemical Machining technique removes material by atomic level dissolution of the same by electro chemical action. Thus the MRR is independent on the mechanical or physical properties of the work material. ECM can machine any electrically conductive work material irrespective of their hardness, strength or even thermal properties. Moreover as ECM leads to atomic level dissolution, the surface finish is excellent with almost stress free machined surface and without any thermal damage. Mainly ECM is used for producing complex shapes of compound like turbine blades.
ECM is used commonly for operations like
  • Die sinking
  • Profiling and contouring
  • Trepanning
  • Grinding
  • Drilling
  • Micro-machining 
Hello, Mechanical Engineering students, professionals
ME - Mechanical Engineering team wishes everyone a Happy New Year.
Happy new year wishes
Hope this new year brighten up your desired goals in your life
  • Freshers get the desired job.
  • Researchers get success in their projects.
  • All of us can get an opportunity to work in desired role.
  • All the profession working in a role get an promotion to work in high role job.
Happy new year wishes from ME - Mechanical Engineering team.
We wish you once again this new year to utilise opportunities and to get huge success for your career.
Any device which violates first law or second law of thermodynamics is called a perpetual motion machine (PMM). These devices operate under the principle of sustained or perpetual motion. That is, the machine will continuously perform same function repeatedly without stopping.
Perpetual Motion Machine

Perpetual motion machine can be of two types:

PMM-1: Perpetual motion machines of first class does work without intake of energy, thus violate the first law of thermodynamics.
PMM-2: Perpetual motion machines of second class is an engine without any heat rejection or a refrigerator without work input, thus violate second law of thermodynamics.
Despite of numerous attempts, no perpetual motion machines is known to have worked in nature.

Some GIFs that make us believe perpetual motion machines a reality
Perpetual motion machine gif
Perpetual motion machine image
Perpetual motion machine example
If construction of perpetual motion machine is possible in nature then we could generate free energy, no need to worry about fuel and pollution problems.
The air-standard diesel cycle is shown on p-V and T-s diagrams respectively. This is the ideal cycle for the diesel engine, which is also called the compression ignition engine.
Diesel cycle consists of two reversible adiabatic, one reversible isobar and one reversible isochoric process.
P-vand T-s diagram for the air-standard diesel cycle
Pressure-volume and Temperature-entropy diagram for the air-standard Diesel cycle
Basic processes in diesel cycle
1-2; Reversible adiabatic compression
2-3: Constant pressure heat addition
3-4: Reversible adiabatic expansion
4-1: Constant volume heat rejection

Thermal efficiency of diesel cycle

Diesel cycle Thermal efficiency Thermal efficiency formula for diesel cycle
Where, Compression ratio = rk = v1/v2 ,
Expansion ratio = re = v4/v3 ,
Cut off ratio = rcv3/v2 .

The normal range of compression ratio for diesel cycle is 16 to 20 whereas for spark-ignition engines it is 6 to 10. due to high compression ratios used in diesel engines the efficiency of a diesel engine is more than that of a gasoline engine.

LEARN NEW ADVANCE MECHANICAL-AUTOMOBILE  TECHNOLOGY: Learn how can a Camera be used to Reverse Engineer, Analysis 3D scanning (as 3D Scanner) and help create a 3D Printed model of same with 3D Printers.

Atkinson cycle is an ideal cycle for Otto engine exhausting to a gas turbine. In this cycle the isentropic expansion 3-4 of an Otto cycle (1-2-3-4) is further allowed to the lowest cycle pressure so as to increase the work output. With this modification the cycle is known as Atkinson cycle. The cycle is shown on p-V and T-s diagrams.
P-vand T-s diagram for the air-standard Atkinson cycle
Pressure-volume and Temperature-entropy diagram for the air-standard Atkinson cycle

Thermal Efficiency of Atkinson cycle

thermal efficiency Atkinson Cycle efficiency Atkinson Cycle
Where, Compression ratio = rk = v1/ v2,
the expansion ratio = re = v4/v3
Electroslag welding (ESW) and its applications are similar to electrogas welding. The main difference is that the arc is started between the electrode tip and the bottom of the part to be welded. Flux is added, which then melts by the heat of the arc. After the molten slag reaches the tip of the electrode, the arc is extinguished. Heat is produced continuously by the electrical resistance of the molten slag. Because the arc is extinguished, Electroslag welding is not strictly an arc-welding process. Single or multiple solid as well as flux-cored electrodes may be used.
Equipment used for electroslag-Welding operations
Equipment used for electroslag-Welding operations
Electroslag welding is capable of welding plates with thicknesses ranging from 50 mm to more than 900 mm and welding is done in one pass. The current required is about 600 A at 40 to 50 Volts although higher currents are used for thick plates. The travel speed of the weld is in the range from 12 to 36 mm/min. Weld quality is high. This process is used for large structural-steel sections, such as heavy machinery, bridges, ships and nuclear-reactor vessels.

The quality of weld in Electro Slag welding depends on

  • The ratio of width of the weld pool and its maximum depth known as Form Factor.
  • Weld current and voltage.
  • Slag depth.
  • Number of electrodes and their spacing etc.
Eddy Parsons cars of the year for 2014.
Quickest away from the lights is regular autoexpress.co.uk reader and car fan Eddy Parsons, aged 11, from Hertfordshire. He’s compiled a brilliant list of his must have cars, plus a few special awards including family car, executive car, most annoying and innovative car of the year.

City Car

Citroen C - Funky styling and good value for money
Citroen C - city car of year 2014

Supermini

the Mini Hatch - remains at the top with classic looks and modern tech - the Cooper is outstanding.
the Mini Hatch

Small family car

Audi A3 - belies its age with stylish looks and a luxurious cabin.
Audi A3

Family car

Volkswagen Passat - stylish, classy and comes with a heap of tech.
Volkswagen Passat

Executive car

Mercedes C Class - beats 3 Series thanks to better styling, better value for money and better interior.
Mercedes C Class

Small SUV

Citroen C4 Cactus
Citroen C4 Cactus

Large SUV

Range Rover Sport
Range Rover Sport

Luxury Car

Mercedes S Class - it's forward thinking, luxurious, fast and has got loads of room.
Mercedes S Class

Electric car

BMW i3 - stylish and stunning - a car you had want even if you didn't know it was electric.
BMW i3

Supercar

BMW i8 - futuristic and brilliant, with a fantastic powertrain.
BMW i8

Most annoying car

G-Wiz 
G-Wiz

Most innovative car

Volvo XC90 - Packed with safety features and includes more advanced technology.
Volvo XC90
  • Electron Beam Machining (EBM) is a thermal process. Here a steam of high speed electrons impinges on the work surface so that the kinetic energy of electrons is transferred to work producing intense heating.
  • Depending upon the intensity of heating the work piece can melt and vaporize.
  • The process of heating by electron beam is used for annealing, welding or metal removal.
  • During EBM process very high velocities can be obtained by using enough voltage of 1,50,000 V can produce velocity of 228,478 km/sec and it is focused on 10 - 200 μM diameter. Power density can go up to 6500 billion W/sq.mm. Such a power density can vaporize any substance immediately.
  • Complex contours can be easily machined by maneuvering the electron beam using magnetic deflection coils.
  • To avoid a collision of the accelerating electrons with the air molecules, the process has to be conducted in vacuum. So EBM is not suitable for large work pieces.
  • Process is accomplished with vacuum so no possibility of contamination.
  • No effects on work piece because about 25-50μm away from machining spot remains at room temperature and so no effects of high temperature on work.
electron beam machining process
Schematic illustration of the electron beam machining process

MRR in EBM:

Q = area of slot or hole * speed of cutting = A*V
Where power for 'Q' MRR is P = C.Q
Where,
C = Specific power consumption
Thermal velocity acquired by an electron of the work material due to EB is
Electron Beam thermal velocity
Where, Kb = Boltzmann constant
M = mass of one atom of work.
T = rise in temperature

Advantages:

  • Very small size holes can be produced.
  • Surface finish produced is good.
  • Highly reactive metals like Al and Mg can be machined very easily.

Limitations:

  • Material removal rate is very low compared to other convectional machining processes.
  • Maintaining perfect vacuum is very difficult.
  • The machining process can't be seen by operator.
  • Workpiece material should be electrically conducting.

Applications:

  • Used for producing very small size holes like holes in diesel injection nozzles, Air brakes etc.
  • Used only for circular holes.
  • Water Jets alone (without abrasives) can be used for cutting. Thin jets of high pressure and high velocity have been used to cut materials such wood, coal, textiles, rocks, concrete, asbestos.
  • The mechanism of material removal rate is by erosion. When high pressure water jet emerges of a nozzle, it attains a large kinetic energy.
  • High velocity jet strikes the work piece, its kinetic energy is converted into pressure energy including high stresses in the work material.
  • When the induced stress exceeds the ultimate shear stress of the material, rupture takes place.
Water Jet Machining
Schematic illustration of water jet machining

Characteristics of Water Jet Machining (WJM):

  • The pressures normally used in WJM are 1500 to 4000 MPa.
  • Nozzle is made by sintered diamond and exit nozzle is about 0.05 to 0.35 mm.
  • No moving parts in the system, so less operating and maintenance costs and safe process.
  • No thermal damage to work and intricate shapes can be cut.
  • The process is convenient for cutting soft and rubber like materials because teeth will get clogged in conventional methods.

Limitations of Water Jet Machining:

  • Initial setup cost for Water Jet Machining process is very high and hard materials cannot be cut.
  • Cutting of hard materials have been over come by introducing abrasives in water in WJM also called Abrasive Water Jet Machining (AWJM).
In AWJM abrasives below 0.45 micron size is mixed with water and compressed to 420 MPa with this machine a 25 mm thick Al has been cut for 100 mm/min.
On zinc-nickel steel of 25mm thick the rate of cutting is 35.5 mm/min, but on the same work EDM can cut 2.5 mm/min.
Gas Tungsten-arc Welding (GTAW) formerly known as TIG (Tungsten Inert Gas) welding, the filler metal is supplied from a filler wire as shown in figure below. The tungsten electrode is not used during this welding operation, a constant and stable arc gap is maintained at a constant current level. The filler metals are similar to the metals to be welded and flux is not used. The shielding gas used in this welding process is usually argon or helium (or a mixture of these both gases). Welding with gas tungsten-arc welding may be done without using filler metals. for example, in the welding of close-fit joints.
Gas Tungsten-arc welding
gas tungsten-arc welding process
Depending on the type of metals to be welded, the power supply is either DC at 200A or AC at 500A (see below image). In general, AC is preferred for welding metals aluminium and magnesium, because the cleaning action of AC removes oxides and improves weld quality. Thorium or zirconium can be used in the tungsten electrodes to improve their electron emission characteristics. The power supply ranges from 8 to 20 kW. Contamination of the tungsten electrode by the molten metal can be a major problem, particularly in critical applications, because it can cause discontinuities in the weld. Contact of the electrode with the molten-metal pool should be avoided.
Equipment for gas tungsten-arc welding
Equipment for gas tungsten-arc welding operations
The gas tungsten-arc welding process is used for a wide variety of applications and metals, particularly aluminium, magnesium, titanium and the refractory metals. It is highly suitable for thin metals. The cost of the inert gas makes this process more expensive than Shielded Metal-arc Welding but provides welds of very high quality and surface finish. The equipment used for gas tungsten-arc welding process is portable.

Applications:

  • Originally developed for welding Aluminium and Magnesium.
  • The other metals are Stainless steel, High carbon steel, Copper, Monel(Ni + Cu+ Fe + Mg)), Inconel (Cu + Cr + Fe), Brass, Bronze, Silver, Molybdenum etc.
  • This process is used for joining various combinations of dissimilar metals like brazing and braze welding.
  • Pipe work required for high pressure steam lines, chemical and petroleum industries.
  • Welding of air craft frame, jet engine casing, rocket motor casing.
  • Accuracy welding of parts in atomic energy.
  • Expansions bellows, transistors cases, instrument diagrams etc.

Advantages:

  • Gas Tungsten-arc welds are stronger and more ductile.
  • No danger corrosion due to no flux is used.
  • No post weld cleaning because of no slag.
  • Wide variety of joints can be made because no flux is used.
  • There is very little or no smoke, fumes or sparks at all. This helps in making a neat and sounder weld.
  • As the shielding gas is transparent, operator can clearly observe the weld.
  • Fusion welds can be made in merely all commercial metals.

Limitations:

  • Because of usage of inert gas, coolant and coolant pump etc the cost of Tungsten Inert Gas welding is very high.
  • Maximum thickness of plate which can be joined by this welding process directly is up to 5mm.
  • For welding of above 5mm thickness plate additional filler rod must be used.
  • Even though tungsten electrode is not melting but at high temperature the atoms of tungsten may get diffused from the tip of electrodes and entering into the weld pool which will increase the brittleness of weld bead.
To overcome this Limitations of GTAW process, the next welding process developed is Gas Metal-arc Welding.