افضل طريقة لتوليد الكهرباء في المنزل

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يوجد طرق كثيره لتوليد الكهرباء واليكم افضل طريقة لتوليد الكهرباء في المنزل واسرع الطرق ايضا مع ذكر مميزات كل طريقه لتوليد الكهرباء في المنزل توليد الكهرباء من الخلايا الشمسيه توليد الكهرباء من الخلايا الشمسيه فى المنزل يمكن توليد كهرباء فى المنزل عن طريق تركيب خلايا شمسيه اعلا المنزل او فى شرفه المنزل تتميز توليد الكهرباء من الخلايا الشمسيه بقله التكلفه وعدم الاحتياج الى وقود لكى يينتج

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UPSC | GATE Exam for Mechanical | Objective Question and Answers | Tamilnadu Teachers Recruitment Board

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Objective Question and Answers for UPSC / GATE Exams:

UPSC | GATE Exam for Mechanical | Objective Question and Answers | Tamilnadu Teachers Recruitment Board

The common soldering method used for soldering circuit components to their boards is known as:
  1. WAVE soldering
  2. Reflow soldering
  3. Furnace soldering
  4. Infrared soldering
Answer:

WAVE soldering

Hint:

Wave soldering is a large-scale soldering process by which electronic components are soldered to a printed circuit board (PCB) to form an electronic assembly. The name is derived from the use of waves of molten solder to attach metal components to the PCB.

Re-flow soldering is a process in which a solder paste (a sticky mixture of powdered solder and flux) is used to temporarily attach one or several electrical components to their contact pads, after which the entire assembly is subjected to controlled heat, which melts the solder, permanently connecting the joint.

Infrared Soldering by soldering individual joints with a hot air pencil.


The heat generated in metal cutting is dissipated in different proportions in to environment, tool, chip and work piece. The correct order of this proportion in descending magnitude is (no cutting fluid is used):
  1. Tool, work, chip, environment
  2. Work, tool, chip, environment
  3. Tool, chip, environment, work
  4. Chip, tool, work, environment
Answer:

Chip, tool, work, environment

Hint:

The maximum temperature in the cutting zone occurs not at the tool tip but at some distance further up the rake face. Material at a point (Chip) gets heated as it passes through the shear zone and finally leaves the chip. The point at built up edge, heating continues beyond the shear plane into the frictional heat region. So tool is the next highest absorbing medium. The point nearer to work their temperature rises merely due to conduction of heat into the work piece.


 

Flatness of slip gauges is checked with:
  1. Optical flat
  2. Electronic comparator
  3. Interferometer
  4. Linear measuring machine
Answer:

Electronic comparator

Hint:

For flatness measurement of surfaces the easiest and best way to test is with an optical flat. Normally Slip gauges and angular measuring instruments are used for accurate measurements of flatness in surface. Here the work piece and Optical flats are hold each other and a monochromatic lights are passed in between the gap. If the light bands visible then the surfaces are not in perfect contact.

In this question flatness of slip gauge are checked. So we need a high precisioned electronic comparator to check the flatness surface in slip gauges.

Interferometers are non contact type flatness measurement of surfaces such as thin, transparent wafers, substrates and windows.


The flatness of a machine bed can be measured using:
  1. Auto collimator
  2. Vernier calipers
  3. Height gauge
  4. Tool maker's microscope
Answer:

Height gauge

Hint:

Flatness is can be measured using a height gauge run across the surface of the part if only the reference feature is held parallel.

Autocollimator is an optical instrument which is used to measure small angles with very high sensitivity. Normally straightness measured with autocollimator.

Tool maker's microscope used for length, angle, Thread, and straightness measurements.


In a turbulent boundary layer over the entire length of a plate, the boundary layer thickness increase with its distances 'X' from the leading edge is:
  1. X1/2
  2. X1/5
  3. X2/5
  4. X4/5
Answer:

X4/5

Hint:

ρ α X (1 / 2)

When the fluid flows this cohesive force along with adhesion shows itself in the macroscopic scale as viscosity. As the flow proceeds downstream of the flat plate the viscosity is able to slow down more and more fluid layers above the flat plate. This is what is called momentum transfer. And hence the boundary layer thickness increases as the fluid moves downstream.


 

The continuity equation (du/dx)+ (dv/dy)=0 is valid for:
  1. Ideal fluid flow only
  2. In-compressible fluids, the flow may be steady (or) unsteady
  3. Steady flow, the flow may be compressible (or) in-compressible
  4. In-compressible fluids and steady flow
Answer:

In-compressible fluids, the flow may be steady (or) unsteady

Hint:

In-compressible flow means  du/dx+dv/dy=0, Some time du/dx = 0 and dv/dy = 0. So the flow may be steady or unsteady.

The post UPSC | GATE Exam for Mechanical | Objective Question and Answers | Tamilnadu Teachers Recruitment Board appeared first on Mechanical Engineering.



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ANSYS Mechanical Workbench | ANSYS Designspace | FEA Software | Mechanical Engineering Software

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ANSYS Mechanical Workbench | ANSYS Design Space

Design Modeler (DM) is a component of ANSYS workbench. A cad like parametric modeler with analysis modeling goals:

  • 2D, 3D, Line and Surface modeling capability
  • Performs unique geometry modification capabilities for simulation such as
    • Feature simplification
    • Spot welds
    • Split surfaces
    • Surface Model Extraction
    • Planer Body Extraction
    • Beam Modeling
    • Enclosure Operation

The topmost tabs allow users to navigate between opened Workbench modules.

When exiting Workbench, the user will be prompted to save any files that have changed since the last save.

Simulation:

The basics of using simulation to perform analysis which include:

  • The simulation GUI and Operation
  • Introduction to Simulation Wizard
  • Basic Analysis Procedure

There are two ways of running simulation:

  1. Configured from within ANSYS Workbench
  2. Directly from CAD system

The components of the user interface are shown below:

Menus:

The menus provide much of the functionality present in simulation. The common used menu items are:

  • The title bar lists the currently active ANSYS license
  • "File > Save" to save the .dsdb Simulation database
  • "File > Clean" to delete mesh and results from database
  • "Edit > Select All" to select all current entities in the window
  • "Units"to change units on the fly
  • "Tools > Options" to customize settings and options
  • "Help > ANSYS Simulation Help" to invoke documentation

Tool Bars:

There are four sets of tool bars to provide users quick access to functionality also found in the menus. The Tool bars can be re-positioned anywhere on the top of the simulation window. The "Context" tool bar will change depending on what branch is active in the "Outline" tree. Tool tips appear if the cursor is placed over the tool bar button. A "Unit Conversion" tool bar is also available. Also "The Standard" Tool bar such as New, Open, Save, Bring Up Simulation Wizard, Solve Model, Capture Snapshot etc., is located on the Top of the window. The "Graphics" tool bar is used often on Select mode, Select Entities, Select Adjacent, Graphics manipulation, Fit all, Wire Frame, View ports etc.,

The left mouse button can be either in "selection" mode or "graphics manipulation" mode. The above tool bar buttons grouped as "Select entities" and " Graphics manipulation" controls the left mouse button behavior.

The selection of entities of the CAD geometry can be done either by individual selection or by box selection. This is controlled by the "Select Mode" icon.

The outline tree provides an easy way of organizing the model, materials, mesh, loads and results for the analysis. The outline tree is analogous to the "tree" found in many CAD software. However, instead of sketches and features, this tree contains analysis related items. The "Model" branch contains the input data required for the analysis whereas the "Engineering Data" branch holds generic material and convection data. The four main sections of the "Model" branch include "Geometry", "Contact", "Mesh', and "Environment".

The "Environment" branch contains the loads as well as the "solution" branch, which holds results for post processing.

Tree Outline:

The Tree outline shows icons for each branch, along with a status symbol. Example of the status symbols are below:

  • Check mark indicates branch is fully defined
  • Question mark indicates item has incomplete data
  • Lightning bolt indicates solving is required
  • Exclamation mark means problem exists
  • "X" means that item is suppressed
  • Transparent check mark means body or part is hidden
  • Green lightning bolt indicates item is currently being evaluated
  • Minus sign means that mapped face meshing failed

The user should become familiar with the basic status symbols shown here.

Details view:

The details view provides a means of inputting data. The contents will change, depending on branch selected.

White Field – current input data
  • Data in white text field can easily be changed by clicking on it, then entering data, as needed.
  • Some white fields require the user to select geometric entities on the screen and then click "Apply". Others require text data input from keyboard or selecting item from pull-down menu.
Gray (or Red) Field – informative data
  • It cannot be modified. These fields usually provide information or results data, such as the maximum stress or number of nodes generated by the mesher.
Yellow Field – incomplete input data
  • Data in yellow fields indicate that not enough information has been supplied. Users need to fill in data completely in order to solve model.

Graphics Window:

The Graphics Window shows the geometry an results. It can also provide worksheet listings, the HTML report and a Print Preview option.

Work sheet Tab:

Print preview Tab:

Job Status Tab:

The post ANSYS Mechanical Workbench | ANSYS Designspace | FEA Software | Mechanical Engineering Software appeared first on Mechanical Engineering.



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Types of Simulation Models | Different Types of Analysis | FEA Simulation

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FEA Simulation

In this article different types of analysis in simulation models are briefly explained. Some of the modules comprised are structural, thermal, CFX, and FE Modeler analysis types are explained here.

Originally FEA is developed for 2D type simulation and analysis (Plane stress). When 3D simulation and analysis introduced, which increases number of simultaneous algebraic equation to solve the problem. Here they introduced high order mesh elements for faster solving of the problem. Examples are triangular and quadrilateral mesh elements geometry, which define the coordinates of the nodes.

FEA Finite Element Analysis

FEA splits a particular component into several elements. Elements are reconnected at nodes, which glued the elements together. Normally for a entire component constructing a algebraic equations is very difficult. So the components are split into elements and the elements connected at nodes. For each elements solving the algebraic equation is very easy. When combined all the equations, we solve the problem for the entire components.

Analysis types available in Simulation are

Linear Stress:

Determines deflections, stresses, factor of safety etc., based on standard strength of materials concepts under static loading.

Modal:

Determines natural frequencies of a system (free Vibration), including the effects of loading on a pre-stressed structure.

Heat Transfer:

Steady state thermal analysis to solve for temperature field and heat flux. Temperature dependent conductivity and convection along with Thermal stress analysis.

Harmonic:

Determines structural response of system under sinusoidal excitation as a function of frequency.

Linear Buckling:

Determines failure load or safety factor for buckling and its buckling mode shapes.

Shape Optimization:

Indicates areas of possible volume reduction based on load paths through the part using topological optimization technology.

Nonlinear Structural:

Calculates deflections and stresses under static loading, accounting for large deflection effects, plasticity and contact non linearities.

Benefits of FEM

Many specializations under Mechanical Engineering's umbrella, such as aeronautical, bio mechanical, and automotive industries, are commonly using integrated FEM in product design and development. Several modern FEM packages include specific components such as thermal, electromagnetic, fluid, and structural working environments.

The benefits of FEM consist of "increased accuracy, enhanced design and better insight into critical design parameters, virtual prototyping, fewer hardware prototypes, a faster and less expensive design cycle, increased productivity and increased revenue".

The post Types of Simulation Models | Different Types of Analysis | FEA Simulation appeared first on Mechanical Engineering.



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Teachers Recruitment Board Tamilnadu Multiple Choice Questions for Mechanical Engineering

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No cutting fluid is used in the following operation:
  1. Planning and shaping
  2. Broaching
  3. Honing
  4. Thread rolling
Answer:

Planning and shaping

Hint:

In planning and shaping operation, cast iron work piece machined. Graphite in the cast iron acts as a lubricant in itself. But machining cast iron will get you fine powders everywhere that tend to sneak into your machines nooks and corners and get lodged there. The stuff later becomes very difficult to remove especially after mixing up with machine lube or oil.

 

Which one of the following is not a decision taken during the aggregate production planning stage?
  1. Scheduling of machines
  2. Amount of labour to be committed
  3. Rate at which production should happen
  4. Inventory to be carried forward
Answer:

Scheduling of machines

Hint:

The aggregate planning is particularly useful for organizations that experience seasonal or other fluctuations in demand or capacity. Planners must make decisions on output rates, employment levels and changes, inventory levels and changes, back orders, and subcontracting. So Aggregate production planning is a short term decision making process.

  • It is usually possible to
  • hire or lay off workers
  • increase or decrease number of shifts
  • increase / decrease number of working days in a week
  • decrease or increase working hours (overtime or under time)
  • subcontract work to other firms
  • build up or deplete inventory levels

 

Which of the following is incorrect regarding template in layout design?
  1. Templates are three dimensional representation of machines (or) equipments
  2. Templates are virtual picture of layout
  3. Templates are used for storage areas
  4. Templates shows the area occupied by machine
Answer:

Templates are three dimensional representation of machines (or) equipment's

Hint:

Two dimensional plan – Templates

Three dimensional plan – Miniature Models

 

Arrival rate of telephone calls to a telephone book is 9 minutes between two consecutive arrivals and length of the telephone call is assumed to be exponentially distributed with mean 3 minutes. The probability that a person will have to wait:
  1. 33
  2. 333
  3. 33
  4. 33
Answer:

0.333

Hint:

Here, N and Nq are the number of people in the system and in the queue respectively. Also W and Wq are the waiting time in the system and in the queue respectively. ρ is the ratio of arrival rate to service rate. Also the probabilities can be given as :

where, p0 is the probability of zero people in the system and pk is the probability of k people in the system.

Given:

Arrival rate λ = 1/9 minutes

Service rate μ = 1/3 minutes.

Probability that a person will have to wait

= (1/9)/(1/3) = 0.333

A dummy activity is used in PERT network to describe:
  1. Precedence relationship
  2. Necessary time delay
  3. Resource restriction
  4. Resource idleness
Answer:

Precedence relationship

Hint:

A CPM/PERT network consists of branches and node. The arrows in between the nodes indicated the precedence relationships between activities. A dummy activity inserted into the network to show a precedence relationship, but it does not represent any actual passage of time.

 

Slow cooling rate in solidification of casting results in:
  1. Fine dendrite with large arm spacing
  2. Coarse dendrite with large arm spacing
  3. Coarse dendrite with smaller arm spacing
  4. Fine dendrite with smaller arm spacing
Answer:

Coarse dendrite with large arm spacing

Hint:

Solidification mechanism is essential for preventing defects due to shrinkage. During solidification, cast forms develops cohesion and acquires structural characteristics. Since heat loss is more rapid near the mold walls than any other place, the first metal crystallizes called 'nuclei'. Slow cooling makes the dendrites to grow long whereas fast cooling causes short dendrite growth. So slow cooling results in larger grain structure and fast cooling results in small grain structure in the solidified metal.

The post Teachers Recruitment Board Tamilnadu Multiple Choice Questions for Mechanical Engineering appeared first on Mechanical Engineering.



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