What is mechanical spring?

Spring is defined as an elastic machine element that deflects under the load action and returns to its original shape when the load is removed.

Functions of spring 

• To absorb shock and vibration
• To store energy
• To measure force
• Spring is used to apply force and control the motion

Types of Spring 

Spring is classified by its shape may be a wire helical coil. The most popular type of spring is the helical spring.

Helical spring is sometimes classified as spring close-coiled and spring open-coiled.

1. When the spring wire is coiled so close and its helix angle is very small, a helical spring is said to be close-coiled spring. Usually, a helix angle is less than 10 degrees.
2. A helical spring is said to be open-coiled spring, when the spring wire is coiled in such a way, that there is a large gap between the adjacent coil and its helix angle is large. Usually, a helix angle is more than 10 degrees. 

Two basic types of helical springs are following below :

1. Compression Spring
2. Extension Spring

Both this type of helical spring have the following advantages :

• They are easy to manufacture.
• They are cheaper than other types of spring.
• Their reliability is high.
• The deflation of spring is linearly propositional to the force acting on the spring. 

Due to the above advantages, the helical spring is popular and extensively used in a number of applications.

Helical Spring

Helical Torsion Spring 

The term torsion is somewhat misleading because the wire is subjected to bending stress.

The construction of this type of spring is similar to that of the compression or extension spring, expect the ends to be formed in such a way that the spring is loaded around the axis of a coil by a torque.

The helical torsion spring is used to transmit torque in the machine to a specific component. Helical torsion spring is used in door-hinges, brush-holders, starters for automobiles and door locks.

Helical torsion spring

Multi-leaf or Laminated Spring 

This spring is made up of a series of flat plates, usually in the semi-elliptical form. The flat plates are called leaves, the length of the leaves varies, the leaves are held together by means of U-bolts and a centre clip.

The longest leaf is called the master leaf and it bends at the both of two ends. The leaves of multi-leaf springs are subjected to bending stress. 

Multi-leaf spring is commonly used for vehicle, truck and rail wagon suspension.

Multileaf spring

Advantages and disadvantages of power screw

A power screw is a drive for converting rotary motion into a linear motion for power transmission in a machine. A power screw is also sometimes referred to as a translation screw. Instead of holding the parts together, it uses helical screw motion to transmit the power. Now in this article, you can check out the pros and cons of the power screw to understand more about it. 

Advantages of power screw:

• Large load-carrying capacity.
• Simple to design.
• Compact construction.
• Easy to manufacture.
• By applying small effort as 400 N, a load of 15 KN can be raised.
• Gives smooth and noiseless service without any maintenance.
• Self-locking property.
• Precise and accurate linear motion.

Disadvantages of power screw:

• Very poor efficiency is as low as 40%.
• It can be used for intermittent motion.
• High friction in threads causes rapid wear.

What is power screw

A power screw is a mechanical device used to convert rotary motion into linear motion and transmit power.

The power screw has three main parts such as screw, nut, and a part to hold either the screw or the nut. 

The power screw operates in two different ways depending on the holding arrangement. 

• In its bearing, the screw rotates, while the nut has axial motion.

The lathe's lead screw is an example of this category.

• The nut is kept stationary and screw moves in the axial direction 

Screw Jack and Machine Vice are examples of this category.

Applications of power screw : 

The main application of the power screw is the following below.

• To raise the load. Example - Screw-jack
• To obtain accurate motion in machining operations. Example - The lead screw of a lathe
• To clamp a workpiece. Example - Vice
•  To load a specimen. Example - Universal testing machine

Reference Books of Refrigeration and Airconditioning

1. Refrigeration and Air Conditioning by C. P. Arora FLIPKART
2. Basic Refrigeration and Air Conditioning by Ananthanarayanan FLIPKART
3. Refrigeration and Air Conditioning by G.F. Hundy, A.R.Trott, T.C. Welch FLIPKART
4. Refrigeration and Air Conditioning by Ameen Ahmadul FLIPKART
5. Refrigeration and Air Conditioning by W.F. Stoecker J.W. Jones FLIPKART 

Reference Books of Theory of Machine

1. Theory of Machines by Thomas Bevan FLIPKART
2. Theory of Machines by R.S. Khurmy, J.K. Gupta FLIPKART 
3. Theory of Machines by S S Raran FLIPKART

Reference Books of Thermodynamics

1. Engineering Thermodynamics by Nag P. K FLIPKART
2. Engineering Thermodynamics by M. Achuthan FLIPKART 
3. Thermodynamics: An engineering approach by Yunus A. Cengel, Michael A. Boles FLIPKART 
4. Fundamentals of Engineering Thermodynamics by M. J. Moran and H. N. Shapiro FLIPKART
5. Principle of Engineering Thermodynamics by Moran, Shapiro, Boettner, Bailey FLIPKART
6. Fundamentals of Thermodynamics by Sonntag R. E, Borgnakke C., and Van Wylen G. J FLIPKART
7. Applied Thermodynamics by Eastop FLIPKART

Reference Books of Fluid Mechanics

1. Fluid Mechanics by Fox FLIPKART
2. A Textbook of Fluid Mechanics and Hydraulic Machines by R.K.Bansal FLIPKART
3. Fluid Mechanics by V.L. Streeter FLIPKART
4. Fundamentals of Fluid Mechanics by A.L. Prasuhn FLIPKART
5. Introduction of Fluid Mechanics and Fluid Machines by Biswas FLIPKART 
6. Fluid Mechanics and Hydraulic Machines by K Subramanya FLIPKART 

Reference books of Strength of Material

1. Strength of Materials by Bhavikatti FLIPKART 
2. Mechanics of Structures by Junarkar S.B. FLIPKART
3. Strength of Materials Vol. I by S.P. Timonshenko FLIPKART
4. Strength of Materials Vol.II by S.P. Timonshenko FLIPKART
5. Strength of Material by S. Ramamrutham FLIPKART 
6. Strength of Material by R.S. Khurmi N Khurmi FLIPKART 
7. Engineering Mechanics of Solids by Egor. P.Popov FLIPKART
8. Advanced Mechanics of Solids by Srinath L.N FLIPKART

Reference Books of Solid Mechanics

1. An Introduction to Mechanics of Solids by S.H. Crandall, N.C. Dahl and S.J.Lardner FLIPKART
2. Theory of Elasticity by Timoshenko S.P. and Goodier J.N. FLIPKART
3. Solid Mechanics by S.M.A. Kazimi FLIPKART
4. Introduction to Mechanics of Solids by E.P. Popov FLIPKART
5. Mechanics of Solids by Arbind Kumar Singh FLIPKART

Reference Books of Engineering Graphics and Drawaing

1. Engineering Drawing and Graphics by K. Venugopal FLIPKART
2. Engineering Drawing by N.D. Bhatt and V.M. Panchal FLIPKART
3. Engineering Graphics by B. Bhattacharyya FLIPKART

What is factor of safety

In machine design, while designing the component, it is necessary to provide sufficient reserve strength in case of an accident so this is achieved by taking a suitable factor of safety.

fs = Failure stress / Allowable stress

fs = Failure load / Working load

The magnitude of the factor of safety depends upon the following factors:

• Effect of failure 
• Types of load
• A degree of accuracy in force analysis
• Material of component
• Reliability of component
• Cost of component
• Testing of the machine element
• Service conditions
• Quality of manufacture

Points mention below the following condition where a higher factor of safety is chosen :

• Magnitude and nature of external forces acting on the machine component cannot be precisely estimated.
• The material of the machine component has a non-homogeneous structure.
• The component of the machine is subject to the force of impact in service.
• There is a possibility of residual stresses in a machine component.
• The machine part is subjected to a high temperature during operation.
• In applications such as aircraft components, higher reliability is required.
• There is a possibility if abnormal variation in external load on some occasions.
• The machine part's manufacturing quality is poor.
• There is stress concentration in a machine component.

A higher factor of safety increases the component's reliability.

Factors to be considered during machine design

In machine design, there are so many factors to consider when designing the machine because the small amount of machine error leads to a high amount of loss so it is better to take care of some factor when designing the machine.

The list of these factors is given below :

• Cost
• High output and efficiency
• Strength
• Stiffness or rigidity
• Wear resistance
• Lubrication
• Operational safety
• Ease of assembly
• Ease and simplicity of disassembly
• Ease and simplicity of servicing and control
• Lightweight and minimum dimensions
• Reliability
• Durability
• Economy of performance
• Accessibility
• Processability
• Compliance with state standards
• The economy of repairs and maintenance
• Use of standard parts
• Use of easily available materials
• The appearance of the machine
• Number of machines to be built

Types of thermodynamic process

Introduction of thermodynamic process : 

Before going to study the thermodynamic process and types of thermodynamic processes, let us understand the meaning of the thermodynamic state of the system. The system has a certain temperature, pressure, volume, etc. characteristics. The present values of the system property are called the thermodynamic state of the system. 

Thermodynamic process :

When the system undergoes a change from one thermodynamic state to final state due change in properties such as temperature, pressure, and volume etc the system is said to have undergone the thermodynamic process. Types of the thermodynamic process described below. 

In simple word, a thermodynamic process occurred when the system changes from initial state to the final state.

• Process - Adiabatic 

Properties held constant - Heat energy 

• Process - Isenthalpic 

Properties held constant - Enthalpy

• Process - Isentropic 

Properties held constant - Entropy, Heat energy, Equilibrium 

• Process - Isobaric 

Properties held constant - Pressure 

• Process - Isochoric 

Properties held constant - Volume 

• Process - Isothermal   

Properties held constant - Temperature

• Process - Isotropic 

Properties held constant - Direction 

• Process - Polytropic 

Properties held constant - PVⁿ = C

• Process - Reversible 

Properties held constant - Entropy, Equilibrium 

Adiabatic process:  

An adiabatic process occurs when no heat can flow between a thermodynamic system and its surroundings. 

In this process Q = 0.

Example - Vertical flow of air in the atmosphere, Air expands and cools as it rises, and contracts and grows warmer as it descends. 

Isenthalpic process : 

An isenthalpic process is also called isoenthalpic process. It is a thermodynamic process in which enthalpy is constant. 

In this process H = 0. 

Example - Throttling process, consider the lifting of a relief valve or safety valve on a pressure vessel.

Isentropic process :

An isentropic process is an idealized thermodynamic process in which both adiabatic and reversible. 

It is a process in which entropy remains constant. 

In this process ΔS  = 0.

Example - Some isentropic thermodynamics device such as pumps, gas compressors, turbines, nozzles, diffusers.

Isothermal process :  

An isothermal process is a change of a system, in which the temperature of the system stays constant but heat may flow in or out of the system during an isothermal process. 

In this process ΔT = 0.

Example - Condensation, All the reactions going on in the refrigerator as a constant temperature is maintained in it, Melting of ice at zero degrees, and heat pump. 

Isochoric process :  

An isochoric process as the name suggests iso means same and choric means volume also called constant-volume process or isovolumetric process or isometric process. 

It is a thermodynamic process during which the volume of the closed system is kept constant.

In this process ΔV = 0.

Example - Heating of a gas in a closed cylinder.

Isobaric process : 

An isobaric is a thermodynamic process where the pressure of the system stays constant. 

In this process  ΔP  = 0.

Example: Heating of water in an open vessel and the expansion of a gas in a cylinder with a freely moving piston.

Isotropic process : 

The isotropic process is one that the permittivity ε and permeability μ of the medium is uniform in all directions of the medium. 

Example - Glass and metals are examples of isotropic materials. 

Reversible processes :  

A reversible process is a process whose direction can be reversed by including infinitesimal changes to some property of the system via its surroundings. In thermodynamics, throughout the entire process, the system is in thermodynamic equilibrium with its surroundings.

Example - Frictionless relative motion, and expansion and compression of spring.

Polytropic Process :

A polytropic is a thermodynamic process that obeys the relation where p is the pressure, V is volume, n is the polytropic index and C is a constant. The equation of this process describes multiple expansion and compression processes which include heat transfer. 

PVⁿ = C

From this relationship, we can arrive at relationships for several other types of a thermodynamic process.

• When n = 0 the process is isobaric
• When n = 1 the process is isothermal
• When n = k the process is isentropic
• When n = ∞ the process is isochoric

Example - Expansion of the combustion gasses in the cylinder of a water-cooled reciprocating engine.

Properties of a system in thermodynamics

Introduction of various properties :

Thermodynamic property is a point function and defines the state of a system. It is independent of the path followed. 

Generally, a thermodynamic property is two types one is macroscopic and another one is microscopic property.

The word microscopic means something like so small that it can only be seen with the use of microscope while macroscopic means either to something that can be seen with the naked eye or large in scale. 

If a system contains a large number of chemical species such as atoms, ions, and molecules, called macroscopic system and the properties which are associated with this system are called macroscopic properties.

Examples: pressure, volume, temperature, composition, density, viscosity, surface tension, refractive index, colour etc.

Extensive properties: 

Extensive properties depend upon the quantity of matter which is contained in the system. 

Extensive property is dependent on mass.

Examples: mass, volume, heat capacity, internal energy, enthalpy, entropy, Gibb's free energy. 

Intensive properties:  

Intensive properties depend upon the amount of the substance which is present in the system.

The intensive property is not dependent on mass.

Examples: temperature, refractive index, density, surface tension, specific heat, freezing point, and boiling point.

What is Entropy?

Definition of Entropy :

Entropy is a thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work and interpreted as the molecular disorder in the system. 

In other words, entropy is the measure of a system's thermal energy per unit temperature that is unavailable for doing useful work. OR Entropy is also the measure of the number of possible arrangements the atoms in a system can have. 

SI unit for entropy is J / K ( joules/degree Kelvin ).

Example: 

Spraying perfume in the corner of the room and we all know what happens next. The perfume will not just stay in the corner of the room but the perfume molecule eventually fills up the room. The perfume went an ordered state to a state of the disorder so the system gets disorder so is called the higher entropy.

Avogadro's Law | Principle | Formula

Principle of Avogadro's law: 

Avogadro's law is a mole of a substance has a mass numerically equal to the molecular weight of the substance.

1 gm mole of oxygen has a mass of 32 gm.

Avogadro's law state that the volume of a gm mol of all gases at the pressure of 760 mm Hg and the temperature of 0^o C is the same and is equal to 22.4 liters.

For a certain gas, we can say that if m is its mass in kg, and M is its molecular weight, then the number of kg moles of gas n would be given by

n = m kg / M kg/kg mol

n = m / M kg moles

The Moler weight is given by  V / n  m³ / kg mol

V represents the total volume of the gas in m³       

Available Energy | Availability | Irreversibility | Definition | Formula

What is Available Energy?

Energy sources can be divided into two groups:

• High-grade energy
• Low-grade energy

Under the second law of thermodynamics, the complete conversion of low-grade energy, heat, into high-grade energy, shaft-work is impossible, that part of low-grade energy which is available for conversation is called as available energy.

The maximum work output in a cycle obtained from a certain heat input is called available energy.

What is Availability?

Whenever useful work is obtained during a process in which the system undergoes a change of state, the process must be terminated when the pressure and temperature of the system have become equal to the pressure and temperature of the surrounding.

The availability of the given system is defined as the maximum useful work that is obtained in a process in which the system comes to equilibrium with its surroundings.

Availability is, therefore, a composite property depending on the state of both the system and surroundings.

What is Irreversibility?

The actual work done by a system is always less than the idealized reversible work, and irreversibility is called the difference between these two. 

I = W_max - W

This is also sometimes referred to as degradation or dissipation.

What is anodizing | Types | Why anodizing | Anodizing Sequence

Anodizing is an electrochemical process that converts the metal surface into a decorative, resistance to corrosion, durable, anodic oxide finish. Mostly the aluminum is ideally suited for anodizing but also some other nonferrous metals, such as magnesium and titanium also can be anodized. 

Anodizing is a surface treatment process to improve surface roughness, toughness, and surface quality.

The Anodizing process changes the microscopic texture of the surface and the crystal structure of the metal near the surface. The anodic film is made by passing an electrical current through an acid electrolyte bath in which the aluminum is immersed and combined with the metal. The thickness and surface characteristics of the coating are strictly controlled to meet the specification of the end product. 

The process is called anodizing because in this process forms the anode on an electrode by the electrical circuit.

Types of anodizing

• Chromic acid anodizing, low voltage process, chrome-free process. 
• Conventional room temperature sulphuric acid anodizing. 
• Hard coat anodizing, done in sulphuric acid at temperatures close to the freezing point of water. 

Why anodizing?

• A very thin coating. 
• Extremely durable, hard, abrasion resistance, and long-lasting. Coating lasts indefinitely.
• Some types of anodizing have colors that are fade-resistant in sunlight nearly indefinitely. 
• Excellent corrosion protection. 
• Environmentally friendly surface finish.
• Good electrical insulator. 
• Inexpensive competitive with powder coating and paints. 
• It can be readily recycled. 

Typical Anodizing Sequence

The anodizing process is not completed in a single anodizing tank but includes pretreatment steps before anodizing and post-treatment after it. A typical and perhaps the most common sequence would be:

• Clean
• Rinse
• Etch
• Rinse
• Desmut
• Rinse
• Anodize
• Rinse
• Neutralize
• Rinse
• Dye
• Rinse
• Seal
• Rinse

In this sequence, the cleaning tank would be a non-etch alkali cleaner to remove soils by using ultrasonic agitation in the cleaning tanks.

Most commonly, the etch process would be caustic soda, but it could be an acid etch like ammonium bi-fluoride. Etching dissolves aluminium so that it can be minimized or skipped for some alloys, leaving the other alloying materials behind. 

Aluminum for mirrors or reflectors is brightly dipped in a very strong nitric-phosphoric bath to give a mirror finish.

Definitely, bright dipping is not just another tank. It is one of the real nasties in surface finishing and before attempting to specify it or use it, you should see installations that do bright dipping to understand ventilation and secondary containment issues. 

The desmut step attempts to dissolve on the surface of the parts of the grey-black alloying ingredients like silicon, copper, zinc, and magnesium. This step is sometimes referred to as de-oxidizing, a misnomer widely accepted. In the desmut step, the constituents will depend on the alloying ingredients that need to be removed. 

Trying to neutralize sulfuric acid through a dip of sodium bicarbonate or a dip in dilute nitric acid is fairly common. 

Dyes are usually heated and can be organic dyes relatively similar to fabric dyes, or they can be inorganic metallic salts, often applied with the help of A.C, especially for architectural work. Electricity, giving the name two-step anodizing. The processes can also be combined by applying an inorganic dye and then overdyeing with an organic dye.  

Sealing is the step of swelling at the top of the honeycomb-like anodizing pores to lock in the dye and lock dirt out. Sealing is an independent science, with older approaches such as steam or D.I. boiling. Water used as well as newer processes of mid-temperature such as nickel acetate and low-temperature seals such as nickel fluoride. 

For military work, chromic acid sealing may still be specified for best corrosion resistance and color matching.

The D.I is often the last step in the process of water rinse to minimize problems with staining.

Conclusion

This is a brief overview of the chemistry of the anodizing process. The process can encounter many difficulties in an industry if care is not taken to ensure that concentration and temperature solutions are controlled. After each stage, thorough rinsing of the work is performed to ensure that it enters the next process in the correct condition. It also ensures that solution contamination is kept to a minimum from one stage to the previous stage. Another aspect not covered by this industry is that of quality control. Even in small plants, chemists are employed to constantly check and monitor the conditions of the solutions and make recommendations/adjustments. Furthermore, the thickness of the film, its density, and the color quality is frequently checked.

Explore more information:

1. What is Hardening
2. What is Annealing
3. What is Carburizing
4. What is Normalizing
5. What is Stress Relieving
6. What is Tempering