What is the "Casting" Process !!! and how these are performed ???

Casting is a fabrication process whereby a totally molten metal is poured into a mold cavity having the desired shape; upon solidification, the metal assumes the shape of the mold but experiences some shrinkage. 

Casting techniques are employed when (1) the finished shape is so large or complicated that any other method would be impractical, (2) a particular alloy is so low in ductility that forming by either hot or cold working would be difficult, and (3) in comparison to other fabrication processes, casting is the most economical. 

Furthermore, the final step in the refining of even ductile metals may involve a casting process. A number of different casting techniques are commonly employed, including sand, die, investment, and continuous casting. Only a cursory treatment of each of these is offered.

                                                

                                                   

INVESTMENT CASTING

For investment (sometimes called lost-wax) casting, the pattern is made from a wax or plastic that has a low melting temperature. Around the pattern is poured a fluid slurry, which sets up to form a solid mold or investment; plaster of paris is usually used. The mold is then heated, such that the pattern melts and is burned out, leaving behind a mold cavity having the desired shape. This technique is employed when high dimensional accuracy, reproduction of fine detail, and an excellent finish are required—for example, in jewelry and dental crowns and inlays. Also, blades for gas turbines and jet engine impellers are investment cast.

 

CONTINUOUS CASTING

At the conclusion of extraction processes, many molten metals are solidified by casting into large ingot molds. The ingots are normally subjected to a primary hot rolling operation, the product of which is a flat sheet or slab; these are more convenient shapes as starting points for subsequent secondary metal-forming operations (i.e., forging, extrusion, drawing). These casting and rolling steps may be combined by a continuous casting (sometimes also termed ‘‘strand casting’’) process. Using this technique, the refined and molten metal is cast directly into a continuous strand which may have either a rectangular or circular cross section; solidification occurs in a water-cooled die having the desired cross-sectional geometry. The chemical composition and mechanical properties are more uniform throughout the cross sections for continuous castings than for ingot-cast products. Furthermore, continuous casting is highly automated and more efficient.

 In previous blog, we have discussed about the other casting processes..you can read the blog at here

 https://academyofengineers.blogspot.com/2020/06/what-is-casting-process-and-how-these.html

For more engineering topics or query : contact us

 

What is the "Casting" Process !!! and how these are performed ???

                                               

Casting is a fabrication process whereby a totally molten metal is poured into a mold cavity having the desired shape; upon solidification, the metal assumes the shape of the mold but experiences some shrinkage. Casting techniques are employed when (1) the finished shape is so large or complicated that any other method would be impractical, (2) a particular alloy is so low in ductility that forming by either hot or cold working would be difficult, and (3) in comparison to other fabrication processes, casting is the most economical. Furthermore, the final step in the refining of even ductile metals may involve a casting process. A number of different casting techniques are commonly employed, including sand, die, investment, and continuous casting. Only a cursory treatment of each of these is offered.

                                    

SAND CASTING

With sand casting, probably the most common method, ordinary sand is used as the mold material. A two-piece mold is formed by packing sand around a pattern that has the shape of the intended casting. Furthermore, a gating system is usually incorporated into the mold to expedite the flow of molten metal into the cavity and to minimize internal casting defects. Sand-cast parts include automotive cylinder blocks, fire hydrants, and large pipe fittings.

 

DIE CASTING

In die casting, the liquid metal is forced into a mold under pressure and at a relatively high velocity, and allowed to solidify with the pressure maintained. A two-piece permanent steel mold or die is employed; when clamped together, the two pieces form the desired shape. When complete solidification has been achieved, the die pieces are opened and the cast piece is ejected. Rapid casting rates are possible, making this an inexpensive method; furthermore, a single set of dies may be used for thousands of castings. However, this technique lends itself only to relatively small pieces and to alloys of zinc, aluminum, and magnesium, which have low melting temperatures.

In next blog, we have discussed about the other casting processes..

you may read the blog in detail

https://academyofengineers.blogspot.com/2020/06/what-is.html

For more engineering topics or query : contact us

 

 

 

The Classification of Engineering Materials

CLASSIFICATION OF MATERIALS

 

Solid materials have been conveniently grouped into three basic classifications - metals, ceramics, and polymers. This scheme is based primarily on chemical makeup and atomic structure, and most materials fall into one distinct grouping or another, although there are some intermediates. In addition, there are three other groups of important engineering materials—composites, semiconductors, and biomaterials.

 

A brief explanation of the material types and representative characteristics can be given as ---

 

METALS

Metallic materials are normally combinations of metallic elements. They have large numbers of non-localized electrons; that is, these electrons are not bound to particular atoms. Many properties of metals are directly attributable to these electrons. Metals are extremely good conductors of electricity and heat and are not transparent to visible light; a polished metal surface has a lustrous appearance. Furthermore, metals are quite strong, yet deformable, which accounts for their extensive use in structural applications.

 

CERAMICS

Ceramics are compounds between metallic and nonmetallic elements; they are most frequently oxides, nitrides, and carbides. The wide range of materials that falls within this classification includes ceramics that are composed of clay minerals, cement, and glass. These materials are typically insulative to the passage of electricity and heat, and are more resistant to high temperatures and harsh environments than metals and polymers. With regard to mechanical behavior, ceramics are hard but very brittle.

 

POLYMERS

Polymers include the familiar plastic and rubber materials. Many of them are organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic elements; furthermore, they have very large molecular structures. These materials typically have low densities and may be extremely flexible.

                                

COMPOSITES

A number of composite materials have been engineered that consist of more than one material type. Fiberglass is a familiar example, in which glass fibers are embedded within a polymeric material. A composite is designed to display a combination of the best characteristics of each of the component materials. Fiberglass acquires strength from the glass and flexibility from the polymer. Many of the recent material developments have involved composite materials.

 

 SEMICONDUCTORS

Semiconductors have electrical properties that are intermediate between the electrical conductors and insulators. Furthermore, the electrical characteristics of these materials are extremely sensitive to the presence of minute concentrations of impurity atoms, which concentrations may be controlled over very small spatial regions. The semiconductors have made possible the advent of integrated circuitry that has totally revolutionized the electronics and computer industries (not to mention our lives) over the past two decades.

 

BIOMATERIALS

Biomaterials are employed in components implanted into the human body forreplacement of diseased or damaged body parts. These materials must not produce toxic substances and must be compatible with body tissues (i.e., must not cause adverse biological reactions).

 

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What are the assumptions of "quantum free electron theory" ?

 In 1929, Somerfield stated to apply quantum mechanics to explain conductivity phenomenon in metal. He has improved the Drude - Lorentz theory by quantizing the free electron energy and retained the classical concept of free motion of electron at a random.

 ASSUMPTIONS:-

·         The electrons are free to move within the metal like gaseous molecules. They are confined to the metal due to surface potential.

·         The velocity distribution of the free electrons is described by Fermi-Dirac Statistics because electrons are spin half particles.

·         The free electrons would go into the different energy levels by following Pauli’s exclusion Principle which states that no two electrons have same set of Quantum numbers.

·         The motion of electrons is associated with a complex wave called matter wave, according to De-Broglie hypothesis.

·         The electrons cannot have all energies but will have discrete energies according to the equation, E = n² h² / 8ma².

 

Drawbacks:

Conductivity: According to Quantum free electron theory, the conductivity of a metal is

σ = μne, here ‘μ’ is the mobility of electrons, ‘n’ is the free electron concentration and ‘e’ is the electron charge.

According to the above equation, polyvalent metals like Aluminum (Al) should be more conductive than monovalent metals like copper (Cu). But experimentally it is not so.

 Hall coefficient: According to the free electron theory, the hall coefficients for all metals is negative where as there are certain metals like Be, Cd, Zn for which the Hall coefficient is + ve. Free electron theory could not explain why certain substances behave as insulators and some other substances as semiconductors; in spite of they have free electrons in them.

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How a Stepper Motor works ???

See,

Basically the stepper motor is an electromechanical device which converts electrical power into mechanical power. Also it is a brushless, synchronous electric motor that can divide a full rotation into an expansive number of steps. The motor’s position can be controlled accurately without any feedback mechanism, as long as the motor is carefully sized to the application. Stepper motors are similar to switched reluctance motors.

 

The stepper motor uses the theory of operation for magnets to make the motor shaft turn a precise distance when a pulse of electricity is provided. The stator has eight poles, and the rotor has six poles. The rotor will require 24 pulses of electricity to move the 24 steps to make one complete revolution. Another way to say this is that the rotor will move precisely 15° for each pulse of electricity that the motor receives.

 

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Let’s talk about MEMORY !!!!

Let’s talk about MEMORY !!!!

 

Memory Hierarchy

A memory unit is the collection of storage units or devices together. The memory unit stores the binary information in the form of bits. Generally, memory/storage is classified into 2 categories:

●       Volatile Memory: This loses its data, when power is switched off.

●       Non-Volatile Memory: This is a permanent storage and does not lose any data when power is switched off.

 The total memory capacity of a computer can be visualized by hierarchy of components. The memory hierarchy system consists of all storage devices contained in a computer system from the slow Auxiliary Memory to fast Main Memory and to smaller Cache memory.

 

 

Auxillary memory access time is generally 1000 times that of the main memory, hence it is at the bottom of the hierarchy.

 

 The main memory occupies the central position because it is equipped to communicate directly with the CPU and with auxiliary memory devices through Input/output processor (I/O).

 When the program not residing in main memory is needed by the CPU, they are brought in from auxiliary memory.

 Programs not currently needed in main memory are transferred into auxiliary memory to provide space in main memory for other programs that are currently in use.

 The cache memory is used to store program data which is currently being executed in the CPU. Approximate access time ratio between cache memory and main memory is about 1 to 7~10

 

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What is exactly Heisenberg’s uncertainty principle?

Let's start discuss on it---

According to Classical mechanics, a moving particle at any instant has fixed position in space and definite momentum which can be determined simultaneously with any desired accuracy. This assumption is true for objects of appreciable size, but fails in particles of atomic dimensions.

 

·         Since a moving atomic particle has to be regarded as a de-Broglie wave group, there is a limit to measure particle properties.

·         If the group is considered to be narrow, it is easier to locate its position, but the uncertainty in calculating its velocity and momentum increases.

·         If the group is wide, its momentum is estimated easily, but there is great uncertainty about the exact location of the particle.

 

Heisenberg a German scientist in 1927, gave uncertainty principle which states that “The determination of exact position and momentum of a moving particle simultaneously is impossible’’.

In general, if △x represents the error in measurement of position of particle along x-axis, and △p represents error in measurement of momentum, then

                                                                              △x. △p = h

Or limitation to find the position and momentum of a particle is

                                                                           (△x).(△p) ≥ h/4π

i.e. Heisenberg uncertainty principle states that both the position and momentum  cannot be measured simultaneously with perfect accuracy.

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Let's discuss today about the “DEVELOPMENT OF MICROSTRUCTURES IN IRON–CARBON ALLOYS”

Today we talk about the “DEVELOPMENT OF MICROSTRUCTURES IN IRON–CARBON ALLOYS”.

Phase changes that occur upon passing from the ϒ region into the ∝ + Fe₃C phase field are relatively complex. 

Consider, for example, an alloy of eutectoid composition (0.76 wt% C) as it is cooled from a temperature within the ϒ phase region, say, 800˚C, that is, beginning at point a and moving down the vertical line xx’. Initially, the alloy is composed entirely of the austenite phase having a composition of 0.76 wt% C and corresponding microstructure. As the alloy is cooled, there will occur no changes until the eutectoid temperature (727˚C) is reached.

 

The microstructure for this eutectoid steel that is slowly cooled through the eutectoid temperature consists of alternating layers or lamellae of the two phases (∝ and Fe₃C) that form simultaneously during the transformation. In this case, the relative layer thickness is approximately 8 to 1. This microstructure point b, is called pearlite because it has the appearance of mother of pearl when viewed under the microscope at low magnifications.

 

 

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Do you know the meaning of "Dispersion" in Optics ???

In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency. Media having this common property may be termed dispersive media. Sometimes the term chromatic dispersion is used for specificity.

Although the term is used in the field of optics to describe light and other electromagnetic waves and for telecommunication signals along transmission lines or optical fiber.

                                                         

In optics, one important and familiar consequence of dispersion is the change in the angle of refraction of different colors of light,  as seen in the spectrum produced by a dispersive prism and in chromatic aberration of lenses.

In some applications such as telecommunications, the absolute phase of a wave is often not important but only the propagation of wave packets or "pulses"; in that case one is interested only in variations of group velocity with frequency, so-called group-velocity dispersion.

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Do you know about Laser Holography ???

Actually in conventional photography a negative is made first and using it a positive print is produced later. The positive print is only a two-dimensional record of light intensity received from a three-dimensional object. It contains information about the square of the amplitude of the light wave is not recorded and is lost.

According to this technique both the phase and intensity attributes of the wave are recorded and when viewed the photograph shows a three-dimensional image of the object. This technique is named holography.

Holography is a two-state process. In the first stage a hologram is recorded in the form of interference pattern. In the second stage the hologram acts as a diffraction grating for the reconstruction beam and the image of the project is reconstructed from the hologram.

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Do you know about CAPP ???

What is Computer Aided Process Planning (CAPP)?

A set of inter related work activities that are characterized by a set of specific inputs and value added tasks that produce a set of specific output is called ‘process’ and ‘process planning’ refers to a set of instructions that are used to make a component or a part so that the design specifications are met. 

     The manual experience based process planning method is most widely used. The biggest problem with this approach is that it is time consuming and the plans developed over a period of time may not be consistent.

                               

Computer aided process planning (CAPP) is able to handle comfortably the complex task of viewing the total operation as an integrated system. In CAPP, all the individual operations and steps involved in making each part or component are coordinated with each other and are performed efficiently and reliably. CAPP is a powerful tool for efficiently planning and scheduling manufacturing operations.

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New trends that can help shape the future of Engineering

Digital adoption is a massive opportunity for companies that leverage the right technologies

 

Cloud Computing

The majority of companies have or will be using some aspect of Cloud computing. The future of Cloud computing will straddle both private and public clouds, adding new challenges to the role of IT.

                                                       

Artificial intelligence (AI)

AI enables producers to make sense of the overwhelming data that their factories, operations and consumers generate, and to transform that data into meaningful decisions.

 

Applying AI to the connectivity of Internet of Things (IoT), producers are able to orchestrate and streamline business processes from desktops to machines, across department walls and tiers of suppliers.

 

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Which stream do I select in Engineering ???

Many students are choosing to focus their education and career goals in one of the fields of engineering and with a good reason: employment opportunities for many types of engineers are expected to grow significantly over the next decade.

We will discuss some of the hot trending engineering sectors in this blog.

ENVIRONMENTAL ENGINEERING

Environmental engineers are generally tasked with applying engineering ideas and principles, as well as those related to soil science in order to develop solutions to issues posed by the environment. Types of projects on which an environmental engineering might work include those aimed at improving waste disposal, water treatment, recycling, public health and even air pollution.

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BIOMEDICAL ENGINEERING

Biomedical engineering is a growing field that exists at the intersection of medicine and engineering. The students who choose to tackle this demanding career will have the opportunity to save many and advance life saving and quality of life improving techniques throughout the span of their working and researching lives.

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COMPUTER SCIENCE

Computer science is highly mathematical and more theoretical than Software engineering. There are lots of folds and certainly CS majors will do their fair share of coding and analyzing.

For any other queries or doubts; you may directly contact us…

For furthermore engineering field in details, we will explore in the next blog.

Thanks for your patience for reading this blog.

Which stream do I select in Engineering ???

Many students are choosing to focus their education and career goals in one of the fields of engineering and with a good reason: employment opportunities for many types of engineers are expected to grow significantly over the next decade.

We will discuss some of the hot trending engineering sectors in this blog.

PETROLEUM ENGINEERING

While a growing number of industries are looking to cleaner forms of energy, there still is an overall dependence on fossil fuels and the work of petroleum engineers. Petroleum engineers are responsible for designing and developing ways to extract oil and gas from deposits beneath the ground. Furthermore, some petroleum engineers focus on discovering new ways to extract oil and gas from older wells already in existence.

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INDUSTRIAL ENGINEERING

The work of an industrial engineer is generally focused on the concept of efficiency in production. An industrial engineer may be tasked with developing efficient systems that integrate workers, machines, information, materials and energy in the creation of a product or the provision of a specific service.

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COMPUTER HARDWARE ENGINEERING

Computer hardware engineers generally research, design, develop and test computer systems, as well as components such as processors, memory devices, networks, circuit boards, and routers. Many perform detailed research to help advance the field of computer systems.

For any other queries or doubts; you may directly contact us…

For furthermore engineering field, We will explore in the next blog.

Thanks for your patience for reading this blog.