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A Journal of Applied Mechanics and Mathematics by DrD, #21
© Machinery Dynamics Research, 2015
Rigid Body Rotordynamic
Instability, Part I
The rotating elements of machinery are usually balanced to avoid vibration which results in noise and fatigue damage. That said, perfect balance is not possible, and there are practical and economic limits to the effort that can be expended to balance machine components. Consequently, every rotating element has some degree of unbalance. This is usually slight, but it is always present.
As rotating elements increase in speed, the forces arising from unbalance increase as the square of the speed. At very low speeds, this usually causes no problem at all, but at higher speed, the increased deviation of the rotating element will eventually cause a collision or a rub. If this is allowed to persist for any length of time, it will often mean a wreck on the machine, with major damage to the rotor and the support structure. This is considered a loss of stability because the operating state deviates ever more and more with increasing speed. Interestingly, in many cases, if it is possible to get through the critical speed (the speed at which maximum deviation occurs), it is often possible to reach lower levels of deviation at higher speeds.
Because rotating elements are so very common in continuously operating machinery, the whole area of rotor dynamics has become extremely important and major efforts are made to understand the phenomena. The applications range from simple motor driven machinery to jet engines. Steam and gas turbines are included as well as all turbo pumps and compressors, so it is evident that this is a very broad topic. One of the most famous rotor dynamic stability problems involved the turbo pump on the space shuttle main engine. This problem was solved by my friend, Prof. Dara Childs. Here we consider only an elementary example as an introduction to a very broad and complex field.
For this short introductory article, consider the system shown in the upper part of Fig. 1, a rigid rotor enclosed in a rigid housing. The entire assembly is mounted to the wall at left with a spring and damper assembly. The center of mass of the rotor is off the axis by an amount ε. As drawn, ε appears quite large, but in actual practice it will be some tiny amount, typically less than one millimeter. The rotor remains centered in the housing at all times, and rotates at a constant angular speed Ω rad/sec. The horizontal displacement of the rotor axis is x(t), where x=0 is the stress free state of the spring.
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When something goes wrong in manufacturing after a long period with no issues we ask “who went on vacation.” Once that is out of the way we go to the drawings to get re-educated. Yep all the callouts are OK. But you continue to stare at the drawings looking for the problem source. The manufacturing engineer is contacted and he checks his shop paper. Machines have all been calibrated, correct cutter/abrasive is called out, and incoming inspection paperwork indicates material received is OK. The manufacturing engineer even sends you the paperwork he just read to you over the phone for you to also stare at. All looks ok on paper but we gaze at the paper wondering what we missed.
An important thing to remember at the start - the paperwork is the should-be not the reality of what is. In the case that follows the problem was a leaking oil seal. Customers of new vehicles were reporting leaks for a design that had been in production for years with no issue.
On rotating shafts with seals, the lead on the surface of the shaft (like the threads on a screw but tiny) produced during manufacturing is a critical item to control or prevent. For this case the shaft was plunge ground to avoid lead (tiny spiral grooves). That is what the drawing called for and that is what was being done. Fine grooves produced by grinding are not detectable by the eye so off to the lab the parts were sent. The profilometer did not pick up any lead. Puzzled at first someone recalled a method for detecting lead that sounds like black magic since the machines in the lab detected nothing. Drape a piece of thread over the shaft which is in the horizontal orientation. The thread is weighted on each end and the shaft rotated. If there is lead the string will move along the length of the shaft. Sure enough the string moved and the lead had a twist orientation that would pump oil out and cause a leak. But how can this be - the paperwork does not allow it and the machines is set up to prevent the creation of lead.
The operation was semi automated as I recall. The part was loaded by hand and the plunge grind was preprogrammed.
Anyone willing to venture a guess as to the cause? Check out this posting next week for the rest of the story.
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Today we have introduced the android app version 1 - the very basic app which will show you the latest discussion on your mobile phone.
You can download the same from
This is a very basic app to give a start .. we look forward for senior members , developers to associate to make it one of the best app for mechanical engineering profession
We request you to install the app on your phone and ask all your mechanical engineeirng friends to install the same..
Crystalline semiconductors such as silicon can catch photons and convert their energy into electron flows. New research shows that a little stretching could give one of silicon's lesser-known cousins its own place in the sun.Nature loves crystals. Salt, snowflakes and quartz are three examples of crystals – materials characterized by the lattice-like arrangement of their atoms and molecules.
Industry loves crystals, too. Electronics are based on a special family of crystals known as semiconductors, most famously silicon.
To make semiconductors useful, engineers must tweak their crystalline lattice in subtle ways to start and stop the flow of electrons.
Semiconductor engineers must know precisely how much energy it takes to move electrons in a crystal lattice.
This energy measure is the band gap. Semiconductor materials such as silicon, gallium arsenide and germanium each have a band gap unique to their crystalline lattice. This energy measure helps determine which material is best for which electronic task.
Now an interdisciplinary team at Stanford has made a semiconductor crystal with a variable band gap. Among other potential uses, this variable semiconductor could lead to solar cells that absorb more energy from the sun by being sensitive to a broader spectrum of light.
A colorized image, enlarged 100,000 times, shows an ultrathin layer of molybdenum disulfide stretched over the peaks and valleys of part of an electronic device. Just 3 atoms thick, this semiconductor material is stretched in ways to enhance its electronic potential to catch solar energy.
The material itself is not new. Molybdenum disulfide, or MoS2, is a rocky crystal, like quartz, that is refined for use as a catalyst and a lubricant.
But in Nature Communications, Stanford mechanical engineer Xiaolin Zheng and physicist Hari Manoharan proved that MoS2 has some useful and unique electronic properties that derive from how this crystal forms its lattice.
Molybdenum disulfide is what scientists call a monolayer: A molybdenum atom links to two sulfurs in a triangular lattice that repeats sideways like a sheet of paper. The rock found in nature consists of many such monolayers stacked like a ream of paper. Each MoS2 monolayer has semiconductor potential.
"From a mechanical engineering standpoint, monolayer MoS2 is fascinating because its lattice can be greatly stretched without breaking," said Zheng, an associate professor.
By stretching the lattice, the Stanford researchers were able to shift the atoms in the monolayer. Those shifts changed the energy required to move electrons. Stretching the monolayer made MoS2 something new to science and potentially useful in electronics: an artificial crystal with a variable band gap.
"With a single, atomically thin semiconductor material we can get a wide range of band gaps," Manoharan said. "We think this will have broad ramifications in sensing, solar power and other electronics."
Scientists have been fascinated with monolayers since the Nobel Prize-winning discovery of graphene, a lattice made from a single layer of carbon atoms laid flat like a sheet of paper.
In 2012, nuclear and materials scientists at Massachusetts Institute of Technology devised a theory that involved the semiconductor potential of monolayer MoS2. With any semiconductor, engineers must tweak its lattice in some way to switch electron flows on and off. With silicon, the tweak involves introducing slight chemical impurities into the lattice.
In their simulation, the MIT researchers tweaked MoS2 by stretching its lattice. Using virtual pins, they poked a monolayer to create nanoscopic funnels, stretching the lattice and, theoretically, altering MoS2's band gap.
Band gap measures how much energy it takes to move an electron. The simulation suggested the funnel would strain the lattice the most at the point of the pin, creating a variety of band gaps from the bottom to the top of the monolayer.
The MIT researchers theorized that the funnel would be a great solar energy collector, capturing more sunlight across a wide swath of energy frequencies.
When Stanford postdoctoral scholar Hong Li joined the Department of Mechanical Engineering in 2013, he brought this idea to Zheng. She led the Stanford team that ended up proving all of this by literally standing the MIT theory on its head.
Instead of poking down with imaginary pins, the Stanford team stretched the MoS2 lattice by thrusting up from below. They did this – for real rather than in simulation – by creating an artificial landscape of hills and valleys underneath the monolayer.
They created this artificial landscape on a silicon chip, a material they chose not for its electronic properties, but because engineers know how to sculpt it in exquisite detail. They etched hills and valleys onto the silicon. Then they bathed their nanoscape with an industrial fluid and laid a monolayer of MoS2 on top.
Evaporation did the rest, pulling the semiconductor lattice down into the valleys and stretching it over the hills.
Alex Contryman, a PhD student in applied physics in Manoharan's lab, used scanning tunneling microscopy to determine the positions of the atoms in this artificial crystal. He also measured the variable band gap that resulted from straining the lattice this way.
The MIT theorists and specialists from Rice University and Texas A&M University contributed to the Nature Communications paper.
Team members believe this experiment sets the stage for further innovation on artificial crystals.
"One of the most exciting things about our process is that is scalable," Zheng said. "From an industrial standpoint, MoS2 is cheap to make."
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Atomic Number : 13
Density (20oC) : 2.70 g/cm3
Atomic Weight : 26.98
Melting point : 660o C
Boiling point : 2467o C
Aluminum finds use as a deoxidizer, grain refiner, nitride former and alloying agent in steels. Its ability to scavenge nitrogen led to its widespread use in drawing quality steels, especially for automotive applications. Since aluminum is so often added to high quality steels.
Metallic aluminum is the most common addition agent. It is sold in the form of notch bars, or stick, and as shot, cones, small ingots, chopped wire, “hockey pucks”, briquettes and other convenient forms such as coiled machine fed wire. These standard products are supplied in bulk or packaged in bags or drums. Purity for deoxidation grades is usually over 95%, the major tramp elements being zinc, tin, copper, magnesium, lead and manganese. Coiled aluminum wire is normally made to 99% minimum specification.
Ferroaluminum, a dense and highly efficient aluminum addition, contains 30-40% Al. It is supplied in lump form, 8 in. x 4 in., 5 in. x 2 in., 5 in. x D, and 2 in. x D, and nominal 12 lb. and 25 lb. pigs, packed in drums and pallet boxes.
Aluminum has a weak effect on hardenability (it is never added for this purpose) and, because of its grain refining properties, actually detracts from deep hardening. Heat treatable steels made to fine grain practice require slightly extra alloying to counteract this phenomenon. Aluminum is, however, a ferrite former and promotes graphitization during long-term holding at elevated temperatures. It also enhances creep, probably because of its grain refining property. Aluminum, therefore, should not be used in Cr-Mo or Cr-Mo-V steels specified for boiler or high temperature pressure vessel applications. Perversely, aluminum is otherwise beneficial to such materials since it reduces scaling through the formation of a more tightly adhering oxide film, particularly if chromium is present as well.
Beyond its important functions in deoxidation and grain size control, aluminum has several applications as an alloying agent. Nitriding steels, such as the Nitralloy family, contain up to 1.5% Al to produce a case with hardness as high as 1100 VHN (70 RC). The outer layer of this case must, however, be removed by grinding to prevent spalling in service. The oxidation (scaling) resistance imparted by aluminum is exploited in some stainless steels and various high temperature alloys. Precipitation hardening stainless steels (17/7 PH, 15/7 PH, etc.) make use of aluminum’s ability to form strength-inducing particles of intermetallic compounds. Aluminum is found in many superalloys for the same reason.
Aluminum combines very readily with nitrogen, and this effect has important commercial uses. Aluminum killed deep drawing steels will be nonaging since AlN is extremely stable. Such steels will not exhibit stretcher strains (Lüder’s lines) or a yield point, even after prolonged holding after cold rolling. Aluminum is also added to nitriding steels for its ability to form an extremely hard case.
Aluminum is an important addition to some HSLA steels, and AlN was the first nitride used to control grain size in normalised and heat treated steels. Again, Al removes nitrogen from solution and provides grain refinement. Both of these effects promote high toughness, especially at low temperatures.
Mention should be made of the effect of aluminum on nonmetallic inclusions, since these will always be present in AK steel. Because aluminum is among the strongest deoxidizers known, it can combine with, and partially or totally reduce, any other oxides present in steel. The subject is quite complex and depends not only on aluminum, but also on oxygen, nitrogen, sulfur, manganese, silicon, and calcium contents. For ordinary steels, however, the pattern is generally as follows: unkilled steels will contain oxides of iron, manganese and silicon, to the extent they are present. Steels deoxidized with silicon and aluminum will contain complex inclusions containing silica, alumina and manganese and iron oxides. As aluminum is increased, it gradually replaces silicon in the inclusions, and the principal inclusions in aluminum killed steels will be alumina and iron-manganese aluminates. Calcium-aluminum deoxidized steels will contain calcium aluminates, the composition and properties of which will depend on oxygen content (see Calcium). The residual Al2O3 in a ladle aluminum deoxidized steel will usually be in the range of 0.015-0.020%. This alumina range will be present regardless of the amount of aluminum used for deoxidation. It is assumed that the remaining alumina of iron aluminate is slagged off.
Aluminum also has a profound effect on the structure of sulfide inclusions. The three basic types of sulfides present in steels have been designated as Type I (fine, randomly distributed spheroids, usually oxysulfides), Type II (intergranular chains which are most harmful to mechanical properties) and Type III (large, globular particles with complex, multiphase structures). Incomplete deoxidation with aluminum results in Type I inclusions; complete, but not excessive deoxidation produces Type II inclusions, while excessive aluminum addition leads to the formation of the Type III particles.
High aluminum contents also promote the generation of interdendritic alumina galaxies, which can impair machinability. Aluminum is added in some stainless grades to improve machinability.
Aluminum as alumina in calcium aluminate slags has found extensive use as slag conditioners at LMF stations. These are used to remove sulfur and inclusions, to lower costs of dolomitic lime, fluorspar, aluminum and calcium carbide additions, to protect the refractory lining, and to improve castability. Applications include both aluminum- and silicon-killed steels.
MRP and MRP2 are predecessors of ERP. An effective organization works with a unified database system. This post is intended to explain the need and benefits of such systems.
" MRP II is an integrated information system that synchronize all aspects of the business."
MRP II system co-ordinates:
by adopting a focal production plan and by using one unified database to plan and update activities in all the systems.
MRP can be divided into three parts which are composed of:
Product Planning functions which take place at the top management level
Operations planning handled by staff units
Operations control functions conducted by manufacturing line and staff supervisors
Checkpoints among the three divisions provide feedback regarding
adequacy of overall resources
completeness of resource commitments
quality of performance in carrying out the plans
Advantages of MRP II:
MRP information systems helped managers determine the quantity and timing of raw materials purchases. Information systems that would assist managers with other parts of the manufacturing process, MRP II, followed.
While MRP was primarily concerned with materials, MRP II was concerned with the integration of all aspects of the manufacturing process, including materials, finance and human relations.
MRP is concerned primarily with manufacturing materials while MRP II is concerned with the coordination of the entire manufacturing production, including materials, finance, and human relations.
While MRP allows for the coordination of raw materials purchasing, MRP II facilitates the development of a detailed production schedule that accounts for machine and labor capacity, scheduling the production runs according to the arrival of materials.
It involves developing a production plan from a business plan to specify monthly levels of production for each product line over the next five years. (Long term planning)
Production department is then expected to produce at the committed levels, sales dept to sell at these levels and finance department to assure adequate financial resources to built this product.
Production plan guides the master schedule and gives the weekly quantities of specific products to be built.
If capacity is not adequate, then the schedule or capacity is changed.
Once settled, this MPS is then used in MRP to create material requirement and priority schedules for production.
Then the CRP assures that capacity is available at scheduled time periods.
Execution and control activities ensures that master schedule is met.
Important terms and concepts:
The forecasting function seeks to predict demands in the future. Long-range forecasting is important to determining the capacity, tooling, and personnel requirements. Short-term forecasting converts a long-range forecast of part families to short-term forecasts of individual end items.
Resource planning is the process of determining capacity requirements over the long term. Decisions such as whether to build a new plant or to expand an existing one are part of the capacity planning function.
Aggregate planning is used to determine levels of production, staffing, inventory, overtime, and so on over the long term. For instance, the aggregate planning function will determine whether we build up inventories in anticipation of increased demand (from the forecasting function), "chase" the demand by varying capacity using overtime, or do some combination of both. Optimization techniques such as linear programming are often used to assist the aggregate planning process.
Rough-cut capacity planning (RCCP) is used to provide a quick capacity check of a few critical resources to ensure the feasibility of the master production schedule. Although more detailed than aggregate planning, RCCP is less detailed than capacity requirements planning (CRP), which is another tool for performing capacity checks after the MRP processing.
Capacity requirements planning (CRP) provides a more detailed capacity check.
Long range planning involves three functions: resource planning, aggregate planning, and forecasting. Intermediate includes production planning functions. The plans generated in the long- and intermediate-term planning functions are implemented in the short-term control.
You would want MRP 2 if you want the following:
1) You want the right materials landing on the right dock with the right quantities at the right time.
2) You want your receiving, storing, assembling and shipping of product to accurately flow.
3) You want to efficiently handle the movement of materials between multiple warehouses and destinations.
4) You want to be able manage high-volume vs low-volume materials differently.
5) You want to accurately fulfill orders in increased volume
Eg: Company is in the industrial goods wholesale distribution business.
Company has larger warehouses in China and in the India.
Company has 10 commercial outlets in the India and in Canada.
Each Outlet stocks high-volume products
Each warehouse aggregates product from around the world.
Company takes customer orders over the web, via customer service and walk-in outlet traffic.
Each warehouse fulfills orders from all sources.
The MRP would help operations and accounting manage material coordination around the world to ensure (1) efficiency and (2) profitability. It accomplishes these goals by providing insight into predictive purchasing, insight into material availability, and accountability of order execution.
Another important concept is material costing. MRP helps provide insight into accurate material costing (product costs, freight, duties, taxes, handling, etc...). Accurate material costing provides insight into product and customer profitability.
Benefits of MRP II in engineering, finance and costing
Better control of inventories
Productive relationship with suppliers
Improved design control
Better quality and quality control
Reduced working capital for inventory
Improved cash flow through quicker deliveries
Accurate inventory records
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Cr : Improves corrosion resistance and abrasion resistance
Cu : Improves corrosion resistance
Ni : Improves fracture toughness and machinability
Co& Mo : Melting point and servicing temperature
W & V : High temperature strength and hardness
S : Machinability
Mn : Hardenability
Ti : Hardenability and wear resistance
Al : Toughness,acts as deoxidant
Si : Hardenability and formability
Mg : Machinability
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Differences between Welding, Soldering and Brazing
Welding, Soldering and Brazing are the metal joining process. Each type of joining process has its own significance. Type of joining process to be used for joining two parts depends on many factors. In this article I have covered the differences between the joining processes welding, soldering and brazing.
1 Welding joints are strongest joints used to bear the load. Strength of the welded portion of joint is usually more than the strength of base metal. Soldering joints are weakest joints out of three. Not meant to bear the load. Use to make electrical contacts generally. Brazing are weaker than welding joints but stronger than soldering joints. This can be used to bear the load up to some extent. 2 Temperature required is 3800 degree Centigrade in Welding joints. Temperature requirement is up to 450 degree Centigrade in Soldering joints. Temperature may go to 600 degree Centigrade in Brazing joints. 3 Work piece to be joined need to be heated till their melting point. Heating of the work pieces is not required Work pieces are heated but below their melting point. 4 Mechanical properties of base metal may change at the joint due to heating and cooling. No change in mechanical properties after joining. May change in mechanical properties of joint but it is almost negligible. 5 Heat cost is involved and high skill level is required. Cost involved and skill requirements are very low. Cost involved and sill required are in between others two. 6 Heat treatment is generally required to eliminate undesirable effects of welding. No heat treatment is required. No heat treatment is required after brazing. 7 No preheating of workpiece is required before welding as it is carried out at high temperature. Preheating of workpieces before soldering is good for making good quality joint. Preheating is desirable to make strong joint as brazing is carried out at relatively low temperature.
Did you know that approximately 75% of the total manufacturing costs are already committed at the Conceptual Design phase?
Committed Manufacturing Costs by product design stage
This means that product design optimisation during the conceptual design phase can optimise on 75% of the committed product manufacturing costs. If you start optimising after the end of the conceptual design phase then you can only optimise on the remaining 25% of the committed product manufacturing costs. Therefore the most effective and beneficial optimisation approach starts as early as possible within the product design process.
Being able to predict product maximum variation using minimum and maximum worse case values within the conceptual design phase, and to identify and fine tune the main contributors, will dramatically decrease the expected product costs as well as increase the overall product quality. Knowing the main contributors to the maximum product variation will also help you to use larger tolerances for low impact contributors which will decrease the product costs even further.
Applying optimisation at the Product Conceptual Design Phase most likely will result in the following benefits for you:
- Acceleration of product’s time-to-market
- Reduction of associated costs for design changes
- Increase of product quality and robustness
- Analysis and correction of potential failures and associated risks as early as possible
- Identify and assess risks during conceptual product design
All the best,
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Fatigue failures occur when a structural member is subjected to fluctuating stresses or strain due to the action of repeated loading of varying or constant magnitude for a period (time). Failure of the member will occur at a stress below it tensile strength. The mechanics of the failure will depend on whether the material is considered brittle (sudden fracture) or ductile (gradual fracture).
Engineers undertake fatigue life calculations to design against fatigue failure, although absolute fatigue life is near impossible the fatique life calculated by available methods allows for very good prediction of fatique life that enables successful engineering design.
There are three main method used to calculate fatique life. These methods are stress life method, strain life method and crack propagation method. An engineer must determine which method is best for the particular physical problem pose to the design at hand because each method has assumptions which must truly represent the physics of the project problem. In addition, design philosophies need to be taken into account, when choosing fatigue life calculation methods
Stress life method or S-N method is used when the cycle of the stress acting on the structure is high (HCL) > 10^3 cycles and the fatique life is required in the elastic range of the material.
Fatigue life can vary greatly for small changes in stress or strain levels therefore fatigue life calculation requires close attention to be paid to the stress and strain calculation process and the stress and strain magnitude obtained.
Depending on the problem and material for which fatigue life is required, physical test or finite element analysis may be performed to determine the stress and strain level of the material. FEA is a mature technology and offers many benefit to engineering process hence it is commonly used alone or combined with testing (note that testing can be an expensive venture). Testing is sometimes used to validate FEA analysis result while FEA is used to reduce testing cost. When there is reason to believe that either the FEA is correct by analytical method or from historical test result, testing should be ignored.
After testing or FEA has been undertaken, the fatigue life is predicted base on S-N curve of the material in the stress – life approach.
Note that fatigue failure is affected by stress concentration, corrosion, temperature, overload, metallurgical structure, residual stress and combined stress.
KINETIC ENERGY RECOVERY SYSTEM
A kinetic energy recovery system (often known simply as KERS) is an automotive system for recovering a moving vehicle's kinetic energy under braking. The recovered energy is stored in a reservoir (for example a flywheel or high voltage batteries) for later use under acceleration. Formula One has stated that they support responsible solutions to the world's environmental challenges, and the FIA allowed the use of 60 kW (82 PS; 80 bhp) KERS in the regulations for the 2009 Formula One seasonTeams began testing systems in 2008: energy can either be stored as mechanical energy (as in a flywheel) or as electrical energy (as in a battery or supercapacitor). Kimi Räikkönen took the lead of the 2009 Belgian Grand Prix with a KERS-aided overtake and subsequently won the race. With the introduction of KERS in the 2009 season, only four teams used it at some point in the season: Ferrari, Renault, BMW and McLaren. Eventually, during the season, Renault and BMW stopped using the system. Vodafone McLaren Mercedes became the first team to win a F1 GP using a KERS equipped car when Lewis Hamilton won the Hungarian Grand Prix on July 26, 2009. Their second KERS equipped car finished fifth. At the following race, Lewis Hamilton became the first driver to take pole position with a KERS car, his team mate, Heikki Kovalainen qualifying second. This was also the first instance of an all KERS front row. On August 30, 2009, Kimi Räikkönen won the Belgian Grand Prix with his KERS equipped Ferrari. It was the first time that KERS contributed directly to a race victory, with second placed Giancarlo Fisichella claiming "Actually, I was quicker than Kimi. He only took me because of KERS at the beginning"
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Free vibrations :
• Free vibration takes place when a system oscillates under the action of forces inherent in the system itself due to initial disturbance, and when the externally applied forces are absent.
• The system under free vibration will vibrate at one or more of its natural frequencies, which areproperties of the dynamical system, established by its mass and stiffness distribution.
Forced vibrations :
- The vibration that takes place under the excitation of external forces is called forced vibration.
- If excitation is harmonic, the system is forced to vibrate at excitation frequency . If the frequency of excitation coincide with one of the natural frequencies of the system, a condition of resonance is encountered and dangerously large oscillations may result, which results in failure of major structures, i.e., bridges, buildings, or airplane wings etc.
- Thus calculation of natural frequencies is of major importance in the study of vibrations.
- Because of friction & other resistances vibrating systems are subjected to damping to some degree due to dissipation of energy.
- Damping has very little effect on natural frequency of the system, and hence the calculations for natural frequencies are generally made on the basis of no damping.
- Damping is of great importance in limiting the amplitude of oscillation at resonance.
The Design and Working
The design included two parts.
1) The Hovercraft
2)The Drum seeder
A hovercraft is a vehicle that hovers just above the ground, or over snow or water, by a cushion of air. Also known as air cushion vehicle, it is a craft capable of travelling over land, water or ice and other surfaces both at speed, and when stationary. It operates by creating a cushion of high pressure air between the hull of the vessel and the surface below. Typically this cushion is contained between a flexible skirt. Hovercrafts are hybrid vessels operated by a pilot as an aircraft rather than a captain as a marine vessel. They typically hover at heights between 200mm and 600mm above any surface and can operate at speeds above 37km per hour. They can clean gradient up to
20 degree. Locations which are not easily accessible by landed vehicles due to natural phenomena are best suited for hovercrafts.
The hovercraft floats above the ground surface on a cushion of air supplied by the lift fan. The air cushion makes the hovercraft essentially frictionless. Air is blown into the skirt through a hole by the blower .The skirt inflates and the increasing air pressure acts on the base of the hull thereby pushing up (lifting) the unit. Small holes made underneath the skirt prevent it from bursting and provide the cushion of air needed. A little effort on the hovercraft propels it in the direction of the push.
As soon as the assembly floats, a blower incorporated in the thrust engine blows air backwards which provides an equal reaction that causes the vehicle to move forward. Little power is needed as the air cushion has drastically reduced friction. Steering effect is achieved by mounting rudders in the airflow from the blower or propeller. A change in direction of the rudders changes the direction of air flow thereby resulting in a change in direction of the vehicle. This is achieved by connecting wire cables and pulleys to a handle. When the handle is pushed it changes the direction of the rudders.
As discussed above,The hovercraft works on air cushion.In the present prototype, air cushion is provided through an electric blower (16000 rpm) blower which pumps air into the skirt thereby inflating the bag skirt. The air pressure thus raises the craft up above the ground. The vehicle has two engines; the rear and the front. A stator fan is attached to the front or lift engine which directs air into the skirt to provide air pressure needed to lift the craft. The propeller attached to the rear or thrust engine develops the thrust needed to propel the craft. The propeller is enclosed by the thrust duct which makes it possible to direct the air. The duct is bell-shaped such that it
increases the velocity of air escaping the duct. The polyester skirt is PVC coated which gives it more strength to sustain the air pressure. It is made air tight. The hull is a platform which sustains the entire weight of the craft. A hole is made on the hull through which air enters the skirt.
After successfully fabricating the hovercraft and testing it on level grounds the next step was to incorporate a drum seeder into the system.A drum seeder is a manual sowing device consisting of a cylindrical drum attached to a central shaft having wheels attached to both sides of the shaft. It was developed with a ease the way of manual labour of sowing using traditional methods but had several demerits compared to what was trying to achieve.In this design ,the idea is to obtain the sowing with the help of rotating drums which have the required slots in the right spacing on its surface, so that the seeds will fall to the field under the force of gravity.
For seeding by a drum seeder, the seeds are soaked in water for 24 hours followed by incubation in gunny bags and straw for 24-48 hours depending upon the weather temperature. The germination length of seeds should not be more than 1-2 mm to avoid any mechanical injury of pregerminated seeds and also to ensure free flow of seeds in the drum seeder. The pregerminated free flowing clean paddy seeds are filled upto 50 percent depth in each seed box by opening the hinge cover. Then the covers are closed
The machine is pulled by one farmer on well leveled puddled field after draining the standing water because standing water more than one cm depth disturbs the seeds sown in straight lines. The pregerminated paddy seeds are sown with the help of drum seeder in well leveled puddled field after draining the standing water. If there is more water than 1 cm then seed will float. Therefore, if there is more standing water in the fields it is better to leave the fields for 1-2 days for settling of puddled soil. Covering the seeds below wet soil surface is not desirable as anaerobic condition gives less germination percent. The posture required is a standing posture throughout the
seeding of pregerminated paddy seeds carried out in the fields.
Ares where improvements can be made from existing device:
- The seeder has to be pulled at uniform speed though the muddy paddy field to get the correct spacing, which is impossible.
- The seeder tends to sink in the mud when fully loaded with seeds. And pulling it through the muddy field requires a lot of energy.
- Footprints of the operator (seeder) were left on the field, in which seeds could end up and result in decay.
- The transplanting device was heavy and will sink in the muddy field
- The process of transplanting was unnecessary and time consuming
In the paddy fields of Kuttanad, which is one of the only two places in the world where agriculture is done below sea level, the soil condition is very soft and the sinkage is very high. The farmers who do the broadcasting sowing now, when they step into the field, they sink into the mud till their knee. Moving through this soft soil is very difficult even for a single farmer, thus pulling or pushing a device through the field is even hectic and hard task. This is the reason why we thought of using a hovercraft to carry the farming mechanism over the field, so that the hovercraft can hover over the ground easily and a remote control to control the farming mechanism means that the
farmer does not even have to step into the field. He can just stay at the side of the field, on the boundary and control the hovercraft and the farming mechanism through the remote.
The benefit of this hovercraft idea is that now, the work done by the farmer is tremendously reduced, all he has to do is control the craft through the remote and make sure that the device is moving in straight lines, and just ensuring that the farming happens in the required manner. This means that the energy expended by the farmer is greatly reduced and thereby the area that can be covered by the farmer in a single day is far more than that can be covered in the conventional method. This is because the farmer needs to take no or very few breaks as he is not required to do any work than controlling the device.
Testing and Results
Testing was conducted by filling the seed container with half its capacity. The device was made to move a distance of 5 meters on a level floor to simulate the seeding process. The device has to move precisely straight so that the correct spacing is achieved between seeds. During testing, the device tend to move side ward (towards left). This was due to the slight inclination of the thrust fan duct, which was inclined. This inclination was removed and tested again, which gave positive results. When the seed drum was rotated by the synchronous motor, which get activated by the forward motion of the hovercraft, seeds were discharged on to the ground with approximately the required spacing. A uniform motion was achieved, and the sowing was able to be done in straight line of 10 meters in less than 2 minutes.,with right spacing in between.
A comparison of time saved; Traditional method Vs HVSD
Conducted a survey that covered the target area. Accordingly the process of traditional farming followed here includes two steps. Firstly the process of broadcasting or sowing of pregerminated seeds which by experience will take about 24 manhours of work to cover one hectare of the field.The second step ; transplantation is done after 18- 20 days ., which takes about 320 manhours/hectare. So the complete process takes about 344 manhours/hectare. On the contrary,the final prototype is estimated to take a meagre 40 manhours/hectare to complete the same task more effectively under ideal conditions.To add, the people of the area has 24x7 access to stable power supply of 240 V.
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Is there any process to make helical gear by horizontal milling machine by use of involute gear cutter. I know for this process there are not such finishing but I want to do maximum possible machining by involute gear cutter. What is the setup required of dividing head spindle and any other for tapering tooth space?
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Five stroke engine gives an option of a much more fuel efficient engine
Engine capacity 700cc (turbocharged)
Peak power 130 bhp @ 7000 rpm
Peak torque 166 Nm @ 5000 rpm
Fuel consumption of only 226 g/kWh
for more info visit www.blogger.com/blogger.g?blogID=1816197738566227847#editor/target=post;postID=7749471607111123754;onPublishedMenu=allposts;onClosedMenu=allposts;postNum=0;src=postname
Atypical InFlow Thermodynamic
Technology Proposal Submission
Novel Fueled Motor Engine Type
Gearturbine Imagens Gallery at Behance:
*State of the art Innovative concept Top system Higher efficient percent.*Power by bar, for Air-Planes, Sea-Boats, Land-Transport & Dynamic Power-Plant Generation.
-Have similar system of the Aeolipile Heron Steam device from Alexandria 10-70 AD. -New Form-Function Motor-Engine Device. Next Step, Epic Design Change, Broken-Seal Revelation. -Desirable Power-Plant Innovation.
YouTube; * Atypical New • GEARTURBINE / Retrodynamic = DextroRPM VS LevoInFlow + Ying Yang Thrust Way Type - Non Waste Looses
-This innovative concept consists of hull and core where are held all 8 Steps of the work-flow which make the concept functional. The core has several gears and turbines which are responsible for these 8 steps (5 of them are dedicated to the turbo stages). The first step is fuel compression, followed by 2 cold turbo levels. The fourth step is where the fuel starts burning – combustion stage, which creates thrust for the next, 5th step – thrust step, which provides power to the planetary gears and turbines and moves the system. This step is followed by two hot turbo steps and the circle is enclosed by the final 8th step – bigger turbine. All this motion in a retrodynamic circumstance effect, wich is plus higher RPM speed by self motion. The Reaction at front of the action.
*8-X/Y Thermodynamic CYCLE - Way Steps:
1)1-Compression / bigger
2)2-Turbo 1 cold
3)2-Turbo 2 cold
4)2-Combustion - circular motion flames / opposites
5)2-Thrust - single turbo & planetary gears / ying yang
6)2-Turbo 2 hot
7)2-Turbo 1 hot
8)1-Turbine / bigger
-With Retrodynamic Dextrogiro vs Levogiro Phenomenon Effect. / Rotor-RPM VS InFlow / front to front; "Collision-Interaction Type" - inflow vs blades-gear-move. Technical unique dynamic innovative motion mode. [Retrodynamic Reaction = When the inflow have more velocity the rotor have more RPM Acceleration, with high (XY Position) Momentum] Which the internal flow (and rotor) duplicate its speed, when activated being in a rotor (and inflow) with [inverse] opposite Turns. The Reaction at front of the action. A very strong Novel torque power concept.
-Non waste parasitic looses for; friction, cooling, lubrication & combustion.
-Shape-Mass + Rotary-Motion = Inertia-Dynamic / Form-Function Wide [Flat] Cylindrical shape + positive dynamic rotary mass = continue Inertia positive tendency motion. Kinetic Rotating Mass. Tendency of matter to continue to move. Like a Free-Wheel.
-Combustion 2Two continue circular [Rockets] flames. [ying yang] opposite one to the other. – With 2TWO very long distance INFLOW [inside propulsion] CONDUITS. -4 TURBOS Rotary Total Thrust-Power Regeneration Power System. -Mechanical direct 2two [small] Planetary Gears at polar position. -Like the Ying Yang Symbol/Concept.
-The Mechanical Gear Power Thrust Point Wide out the Rotor circumference were have much more lever [HIGH Torque] POWER THRUST. -No blade erosion by sand & very low heat target signature profile. -3 points of power thrust; 1-flow way, 2-gear, 3-turbine. *Patent; Dic. 1991 IMPI Mexico #197187 All Rights Reserved. Carlos Barrera.
·2-Imploturbocompressor; One Moving Part System Excellence Design - The InFlow Interaction comes from Macro-Flow and goes to Micro-Flow by Implossion - Only One Compression Step; Inflow, Compression and outflow at one simple circular dynamic motion Concept.
Imploturbocompressor Imagens Gallery at Behance:
*·“Excellence in Design" because is only one moving part. Only one unique compression step. Inflow and out flow at the same one system, This invention by its nature a logic and simple conception in the dynamics flow mechanics area. The invention is a wing made of one piece in a rotating motion, contained in a pair cavity system connected by implocavity, and interacting dynamically with a flow, that passes internally "Imploded" through its simple mechanism. This flow can be gas (air) or liquid (water). And have two different applications, in two different form-function; this one can be received (using the dynamic flow passage, as a receiver). Or it can be generated (with a power plant, generating a propulsion).
An example cut be, as a Bike needs a chain to work from motor to wheel. And for the Imploturbocompressor application, cut be as; in a circumstance at the engine, as an A-activate flow, and with a a tube flow conduit going to the wheel as a B-receiving-flow the work use.
To see a Imploturbocompressor animation, is posible on a simple way, just to check the Hurricane Satellite view, and is the same implo inflow way nature.
And when the flow that is received and that is intended to be used at best, must no necessarily by a exhausting or rejection gas, but must be a dynamic passing gas or liquid flow with the only intention to count it or to measure it. This could be possible at the passing and interacting period when it passes inside its simple mechanism. This can be in any point of the work flow trajectory.
In case the flow that is received is a water falling by gravity, and a dynamo is placed on the rotary bar, the Imploturbocompressor can profit an be obtained by generating? electricity such as obtained by the pelton well, like I say before. The "Imploturbocompressor", is a good option to pump water, or a gas flow, and all kinds of pipes lines dynamic moves.
Or only receive the air-liquid flow, in order to measure its passage with a counter placed on the bar, because when this flow passes through the simple mechanism of a rotating wing made of only one piece it interacts within the implocavities system. And this flow can be air wind, with the difference of can have an horizontal work position, and that particle technical circumstances make an easy way for urban building work new use application, and have wind flow from all the sides 180 grades view. The aforementioned information about this invention refers to technical applications, such as a dynamic flow receiver. (whether being gas or liquid).
With the appropriate power plant and the appropriate dimensioning and number of RPM this invention is also feasible to generate an atmospheric air propulsion and the auto-propulsion of an aircraft. Being an effective and very simple system that implodes and compresses the atmospheric air permits the creation of a new concept of propulsion for aircrafts, due to its simple mechanism and innovative nature. At the place of the aircraft were the system appears and the manner how the propulsion direction can be oriented with a vectorial flow (no lobster tail) with I call "yo-yo system" (middle cut (at the shell) to move, one side loose), guided and balanced is feasible to create a new concept of TOVL-vertical take-off landing, Because the exhaust propulsion can going out radial in all the 360 vectorial positions, going out direct all the time in all the vectors direction. With his rotor cover for an better furtive fly, like going down of a bridge for example.
Likewise, with the due form and dimensioning, and considering the liquid density and the due revolutions for this element there could be generated a propulsion (water) in order to move an aquatic ship, whether on surface or under water. Also can be a good option to pump liquid combustion for a rocket propulsion.
Making a metaphoric comparison with the intention to expose it more clearly for a better comprehension of this innovative technical detail, it would be similar to the trajectory and motion of a dynamic flow compared with a rope (extended) that passes through the system would have now a knot (without obstructing the flow), so the complete way of the flow at the imploturbocompresor system have three direct ways and between make two different turns; direct way (entrance) - turn - direct way (implocavity) - turn - direct way (exit), all this in a 1 simple circular move system concept.
Its prudent to mention that the curves and the inclinations of the blades of a rotating wing made of this invention, is conferred by its shape and function a structural rigidity allowing it to conduct and alter appropriately the dynamic flow passing through its system.8364
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In today’s world, organizations must keep pace with ever increasing changes. The complexity of the business requires numerous functions in order to be competitive. A brief description of common business functional responsibilities include the following:Human ResourcesThe human resources (HR) department is responsible for an analysis of the needs and training of the workforce, employee turnover analysis, absenteeism analysis, and attitude surveys. In addition, the HR department may recruit, select, and hire people for the organization.EngineeringAs a support service, production engineering is the problem solving arm of the company. The engineering department should be proactive (always searching) in their problem solving activities. The planning of new equipment or processes is a must for this department.Sales and MarketingIt is up to sales and marketing to develop effective plans to identify customers and markets for the company’s current products and services, and to identify wants and needs for new products. They should work with engineering in order to pass along customer ideas or desires. The development of a marketing plan helps guide the production plan.FinanceThe financial department, in many plants, includes the accounting department. The accounting function compiles monthly statements and the proﬁt or loss statements for the company. A standard cost system should be in place so that data can be collected and based against it. Budget forecasts, capital project requests, and external funding can also be coordinated by the finance department.Product LiabilityIn the manufacture of certain products, there are numerous legal ramiﬁcations. The theories based upon breach of warranty have a statutory basis in the Uniform Commercial Code. Product safety requirements and labeling laws not only protect the consumer, but also should reduce the liability risk to the company.ManufacturingThe manufacturing activity is associated with companies manufacturing a product or products. Manufacturing takes designs from engineering, schedules from planning and assembles, and tests the company products. For a service organization, this function is replaced by the personnel performing the service.Safety and HealthThe safety and health department aids the company in complying with local, state, federal, and industry regulations. The best known safety agencies include OSHA, state safety agencies, NFPA, etc. These agencies impact the establishment of a safety program, safety committee, and special safety task forces for the company.Legal and RegulatoryA legal department (or attorneys on retainer) may be necessary to handle legal matters, especially in the very litigious society of today. A review of purchase agreements, land contracts, leases, right-of-ways, tax abatements, economic impact grants, etc. are examples.Research and Development (R&D)Research and development activities are critical for the future of the company. The customer is satisfied for a certain time span with the existing product or service, but eventually the customer will want a new and improved product. lnteraction with the marketing function and customer is needed to generate new ideas and products.Click here to read more
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why pressure cooker cooks fast?
The pressure of steam increases water temperature, when temperature of water is higher than its boiling point (100oC), it can help to cook faster.
pressure inside pressure cooker is directly proportional to water temperature
P ∝ T , as P increases T increases.
Average pressure inside a household pressure cooker can be 15 pounds per square inch.
Average Temperature inside will be 121oC (250oF).
1 pound per square inch = 0.0689475729 bar
15 pounds per square inch = 1.03421 bar
How a pressure cooker works?
By steam + Pressure.
normal boiling point of water =100oC = 373k
In pressure cooker,
1. The water is filled less than 2-3rd of the container's capacity.
2. Subjected to heat.
3. Steam is produced.
4. Enough pressure shuts safety spring loaded valve.
5. Pressure increases and acts on ingredients inside.
6. Pressure acts uniformly.
7. Temperature of water raises above 110-120oC
8. Increase in Temperature = Decrease in Cooking Time.
9. When pressure is high, weight is lifted.
10. Steam is sent out.
11. Food is cooked in less time.
1679, the pressure cooker was created by Denis Papin, French Physicist and Mathematician.
1680, He made safety valve.
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