Types of mechanical forces

 

A force exerted on a body can cause a change in either the shape or the motion of the body. The unit of force in SI system is the newton (N) and CGS system is dyne. No solid body is perfectly rigid and when forces are applied to it, changes in dimensions occur. Such changes are not always perceptible to the human eye since they are negligible. For example, the span of a bridge will sag under the weight of a vehicle and a spanner will bend slightly when tightening a nut. It is important for civil engineers and designers to appreciate the effects of forces on materials, together with their mechanical properties of materials.

There are three main types of mechanical forces that can act on a body. They are:

1.      Tensile force

2.      Compressive force and

3.      Shear force

1. Tensile force

Tensile force that tends to stretch a material, as shown in the figure 1 below.

Figure 1: Tensile force

For example,

1.      Rubber bands, when stretched, are in tension.

2.      The rope or cable of a crane carrying a load is in tension.

3.      When a nut is tightened, a bolt is under tension.

A tensile force will increases the length of the material on which it acts.

2. Compressive force

Compressive force that tends to squeeze or crush a material, as shown in the figure below.

For example,

A pillar supporting a bridge is in compression.

1. The sole of a shoe is in compression.
2. The jib of a crane is in compression.
3. A compressive force will decrease the length of the material on which it acts.

3. Shear force

Shear force that tends to slide one face of the material over an adjacent face.

For example,

1. A rivet holding two plates together is in shear if a tensile force is applied between the plates as shown in Figure
2. A guillotine cutting sheet metal, or garden shears, each provide a shear force.
3. A horizontal beam is subject to shear force.
4. Transmission joints on cars are subject to shear forces.

A shear force can cause a material to bend, slide or twist.

What is Cetane Number ???? Awesome information

 What is Cetane Number? How rating of fuels used in C. I. Engines (Compression Ignition Engines) is done using Cetane number and other parameters?

The knocking tendency is also found in compression ignition (C. I.) engines with an effect similar to that of S. I. engines, but it is due to a different phenomenon. The knock in C. I. engines is due to sudden ignition and abnormally rapid combustion of accumulated fuel in the combustion chamber. Such a situation occurs because of an ignition lag in the combustion of the fuel between the time of injection and the actual burning.

The property of ignition lag is generally measured in terms of cetane number. It is defined as the percentage, by volume, of cetane in a mixture of cetane and alpha-methyl-naphthalene that produces the same ignition lag as the fuel being tested, in the same engine and under the same operating conditions. For example, a fuel of cetane number 50 has the same ignition quality as a mixture of 50 percent cetane and 50 percent alpha-methyl-naphthalene.

The cetane which is a straight chain paraffin with good ignition quality is assigned a cetane number of 100 and alpha methyl-naphthalene which is a hydrocarbon with poor ignition quality, is assigned a zero cetane number.

Notes:                                                                             

1.    The knocking in C. I. engines may be controlled by decreasing ignition lag. The shorter the ignition lag, the lesser is the tendency to knock.

2.    The cetane number of diesel oil, generally available, is 40 to 55.

Eating Rice is health

 * Some  doctors have been deceived into believing that eating rice will lead to diabetes. *

* In fact, eating rice will cure diseases *

* What are the benefits of any rice!? *

1. * Black gourd rice *

Rice eaten by kings. Cancer does not come. Insulin secretion.

2. * Groom samba rice *:

Nerve, body strong. Masculinity may.

3. * Poongar rice *:

Is childbirth. Breastfeeding.

4. * Wild rice *:

Corrects diabetes, constipation, cancer.

5. * Conceived rice *:

By the way, things like constipation are okay.

6. * Chronological rice *:

After the Buddha had eaten. Brain, nerve, blood, kidney are OK.

7. * Bamboo rice *:

Arthritis and knee pain are okay.

8. * Sixtieth Curry Rice *:

The bone is right.

9. * Iluppaippusambar rice *:

Good for stroke. Foot pain is OK.

10. * Thangachamba rice *:

The tooth, the heart is strong.

11. * Black rice *:

Restores lost power. Cure deadly diseases.

12. * Garuda samba rice *:

Blood, body and mind are cleansed.

13. * Car Rice *:

Skin disease is OK.

14. * Umbrella Banana Rice *:

The bowel is cleansed.

15. * Kichili Samba Rice *:

High in iron and calcium.

16. * Blue samba rice *:

Anemia will go away.

17. * Cumin samba rice *:

Giving beauty. The resistance might.

18. * Pure Coriander Rice *:

The internal organs are strong.

19. * Pitted rice *:

Breastfeeding.

20. * Salem Sanna Rice *:

Strengthens muscle, nerve, and bone.

21. * Picini rice *:

Menstruation and pelvic pain are okay.

22. * Zucchini Rice *:

Pillow body may be leopard beauty.

23. * Walon Samba Rice *:

Is childbirth. Gather beauty for women and slim down in between. The hips are strong. Men may have sperm power.

24. * Watan Samba Rice *:

Quiet sleep will come

25. * Department *

Gives strength to the body. Increases strength. Strengthens the body.

26. * Until *

Reduce obesity. Prevent constipation. Reduce the amount of sugar

27. * Dye *

Relieves fever and dryness. Eliminates impotence. Controls stomach related diseases.

28. * Horsepower *

Muscles and bones become stronger.

39. * Hand stabbing *

Provides essential nutrients to the body. Prevents cancer. Prevents kidney stones. Helps to reduce body weight.

30. * Red wild rice *

Lowers cholesterol in the blood. Helps to control sugar levels.

31. * Red rice *

Minerals help greatly in the growth of hair, teeth, nails, muscles and bones.

32. * Dwarf rice *

Blood cleanses the body. Skin disease is cured.

Thanks.

Enthalpy

 Enthalpy is the measure of heat energy in the air due to sensible heat or latent heat. Sensible heat is the heat (energy) in the air due to the temperature of the air and the latent heat is the heat (energy) in the air due to the moisture of the air. The sum of the latent energy and the sensible energy is called the air enthalpy. Enthalpy is expressed in Btu per pound of dry air (Btu/lb of dry air) or kilojoules per kilogram (kJ/kg).

Enthalpy is useful in air heating and cooling applications. Air with same amount of energy may either be dry hot air (high sensible heat) or cool moist air (high latent heat)

The enthalpy scale is located above the saturation, upper boundary of the chart. Lines of constant enthalpy run diagonally downward from left to right across the chart; follow almost exactly the line of constant wet bulb temperature.

When a process takes place at constant pressure, the heat absorbed or released is equal to the Enthalpy change. Enthalpy is sometimes known as “heat content”, but “enthalpy” is an interesting and unusual word, so most people like to use it. Etymologically, the word “entropy” is derived from the Greek, meaning “turning” and “enthalpy” is derived from the Greek meaning “warming”. As for pronunciation, Entropy is usually stressed on its first syllable, while enthalpy is usually stressed on the second.

Enthalpy(H) is the sum of the internal energy(U) and the product of pressure(P) and volume(V).

Enthalpy H can be written as,

H = U + pV

Where, H = Enthalpy of the system

U = Internal energy of the system

p = Pressure of the system

V = Volume of the system

Enthalpy is not measured directly, however, the change in enthalpy (ΔH) is measured, which is the heat added or lost by the system. It is entirely dependent on the state functions T, p and U.

Enthalpy can also be written as

ΔH=ΔU+ΔPV

At constant temperature, for the process heat flow(q) is equal to the change in enthalpy, this is represented as

ΔH=q

Enthalpy Units

The Enthalpy is expressed as,

H = Energy/Mass

Any physical quantity can be represented by dimensions. The arbitrary magnitudes allocated to the dimensions are called units. There are two types of dimensions namely primary or fundamental and secondary or derived dimensions.

Primary dimensions are: mass, m; length, L; time, t; temperature, T

Secondary dimensions are the ones that can be derived from primary dimensions such as velocity(m/s2 ), pressure (Pa = kg/m.s2 ).

There are two unit systems currently available SI (International System) and USCS (United States Customary System) or English system. We, however, will use SI units exclusively in this course. The SI units are based on the decimal relationship between units.

MAJOR CAUSES OF ENGINE BREAKDOWN OR SUDDEN STOPPING.

 MAJOR CAUSES OF ENGINE BREAKDOWN OR SUDDEN STOPPING.

1) Overheated engine 

2) Chocked catalytic converter 

3) Electrical issues in the Ignition System.

4) Inadequate Transmission Fluid leading to increased friction in the gearbox.

5) Loose engine Bolts. 

CAUSES OF ENGINE BREAKDOWN.

- Engine overheating.

As the fuel burns the Chemical Energy is changed to Heat Energy. The engine further changes the Heat Energy to Mechanical Energy which propels the car.

If this Heat in the Engine bay goes beyond the normal range, the pistons and the engine start expanding. Engine expansion compresses the cylinder decreaing their diameter and hence icreasing the friction between the the piston and the Cylinder Walls as the piston moves up and down.

Eventually if the temperature keeps rising the piston is tightly held by the cylinder walls and its unable to move again and this  leads to a sudden engine stop.

CAUSES OF ENGINE OVERHEATING.

1) Defective Radiator Cap.

2) Leakage in the cooling system 

3) Condensed Engine coolant 

4) Blockage to coolant circulation delivery galleries.

5) Low Engine Oil level.

6) Broken or Defective Water Pump. 

Follow For More Educative Lectures.

Thank You.

Super alloy and its amazing components

 Composition: OF super alloy

These alloys are referred to as iron-base, cobalt-base or nickel-base super alloys. They contain nickel, chromium, cobalt and molybdenum as major alloying elements; Most super alloys have a maximum service temperature of about 1000°C for non-load bearing components.

Iron base super alloys generally contain composition of 32% to 67% iron, from 15% to 22% chromium and from 9% to 38% nickel.

Cobalt-base super alloys generally contain composition of 35% to 65% cobalt, 19% to 30% chromium and up to 35% nickel. Cobalt (Co) is white-colored metal that resembles nickel. These super alloys are not as strong as nickel-base super alloys in this they retain their strength at higher temperatures.

Nickel-base super alloys are the most common of the super alloys and they are available in a variety of compositions. The composition of nickel is from 38% to 76%; they also contain up to 27% chromium and 20% cobalt. Common alloys in this group are the Hastelloy, Inconel, Nimonic, Rene, Udimet, Astroloy and Waspaloy series.

 

What Mechanical Engineers Do

 What Mechanical Engineers Do

Mechanical engineers research, design, build, configure and test mechanical and thermal sensors and devices, including tools, machinery and equipment.

Duties of Mechanical Engineers

Mechanical engineers usually do the following:

Analyze issues to see how mechanical and heating devices can help a machine solve a particular problem

Designing or redesigning mechanical and heating devices or accessories using analytics and computer aided design

Investigate equipment failures or difficulties to detect operation malfunction and suggest solutions

Design Create and test prototypes of the devices they design

Results Examine the test results and modify the design or layout as needed

Oversee the manufacturing process for the device

Mechanical engineering is one of the broadest fields of engineering. Mechanical engineers design and oversee many products, from medical devices to new batteries.

Mechanical engineers design electric generators, internal combustion engines and generating engines such as steam and gas turbines, and electric machines such as air conditioning and air conditioning systems.

Mechanical engineers design other machines within buildings, such as elevators and escalators. They also design material-handling systems such as conveyor systems and automatic transmission stations.

Like other engineers, mechanical engineers use computers extensively. Mechanical engineers are usually responsible for integrating sensors, controllers and machinery. Computer technology enables mechanical engineers to create and analyze designs, run simulations and test how a machine may work, interact with connected systems, and create specifications for parts.

Examples of the following types of mechanical engineers:

Auto research engineers seek to improve the performance of cars. These engineers are working to improve the traditional features of cars such as suspension, and they are also working on aerodynamics and new potential fuels.

Engineers work to create and maintain ecosystems where temperature and humidity must be kept within certain limits. They make similar systems for planes, trains, cars, schools and even computer rooms.

Robot engineers design, build, and maintain robots. These engineers plan how robots use sensors to detect objects based on light or smell, and design how these sensors fit into the design of the robots.