Thursday, April 20, 2017

Mechanical Engineering - Interview Questions






GATE 2017 Mechanical Engineering Syallbus




Section 2: Applied Mechanics and Design

Engineering Mechanics: Free-body diagrams and equilibrium; trusses and frames;
virtual work; kinematics and dynamics of particles and of rigid bodies in plane
motion; impulse and momentum (linear and angular) and energy formulations,
collisions.

Mechanics of Materials: Stress and strain, elastic constants, Poisson's ratio; Mohr’s
circle for plane stress and plane strain; thin cylinders; shear force and bending
moment diagrams; bending and shear stresses; deflection of beams; torsion of
circular shafts; Euler’s theory of columns; energy methods; thermal stresses; strain
gauges and rosettes; testing of materials with universal testing machine; testing of
hardness and impact strength.

Theory of Machines: Displacement, velocity and acceleration analysis of plane
mechanisms; dynamic analysis of linkages; cams; gears and gear trains; flywheels
and governors; balancing of reciprocating and rotating masses; gyroscope.

Vibrations: Free and forced vibration of single degree of freedom systems, effect of
damping; vibration isolation; resonance; critical speeds of shafts.

Machine Design: Design for static and dynamic loading; failure theories; fatigue
strength and the S-N diagram; principles of the design of machine elements such as
bolted, riveted and welded joints; shafts, gears, rolling and sliding contact bearings,
brakes and clutches, springs.

Section 3: Fluid Mechanics and Thermal Sciences

Fluid Mechanics: Fluid properties; fluid statics, manometry, buoyancy, forces on
submerged bodies, stability of floating bodies; control-volume analysis of mass,
momentum and energy; fluid acceleration; differential equations of continuity and
momentum; Bernoulli’s equation; dimensional analysis; viscous flow of
incompressible fluids, boundary layer, elementary turbulent flow, flow through pipes,
head losses in pipes, bends and fittings.

Heat-Transfer: Modes of heat transfer; one dimensional heat conduction, resistance
concept and electrical analogy, heat transfer through fins; unsteady heat
conduction, lumped parameter system, Heisler's charts; thermal boundary layer,
dimensionless parameters in free and forced convective heat transfer, heat transfer
correlations for flow over flat plates and through pipes, effect of turbulence; heat
exchanger performance, LMTD and NTU methods; radiative heat transfer, StefanBoltzmann law, Wien's displacement law, black and grey surfaces, view factors,
radiation network analysis.

Thermodynamics:  Thermodynamic systems and processes; properties of pure
substances, behaviour of ideal and real gases; zeroth and first laws of
thermodynamics, calculation of work and heat in various processes; second law of
thermodynamics; thermodynamic property charts and tables, availability and
irreversibility; thermodynamic relations.

Applications: Power Engineering: Air and gas compressors; vapour and gas power
cycles, concepts of regeneration and reheat. I.C. Engines: Air-standard Otto, Diesel
and dual cycles. Refrigeration and air-conditioning: Vapour and gas refrigeration
and heat pump cycles; properties of moist air, psychrometric chart, basic
psychrometric processes. Turbomachinery: Impulse and reaction principles, velocity
diagrams, Pelton-wheel, Francis and Kaplan turbines.


Section 4: Materials, Manufacturing and Industrial Engineering

Engineering Materials:  Structure and properties of engineering materials, phase
diagrams, heat treatment, stress-strain diagrams for engineering materials.

Casting, Forming and Joining Processes: Different types of castings, design of
patterns, moulds and cores; solidification and cooling; riser and gating design.
Plastic deformation and yield criteria; fundamentals of hot and cold working
processes; load estimation for bulk (forging, rolling, extrusion, drawing) and sheet
(shearing, deep drawing, bending) metal forming processes; principles of powder
metallurgy. Principles of welding, brazing, soldering and adhesive bonding.

Machining and Machine Tool Operations: Mechanics of machining; basic machine
tools; single and multi-point cutting tools, tool geometry and materials, tool life and
wear; economics of machining; principles of non-traditional machining processes;
principles of work holding, design of jigs and fixtures.

Metrology and Inspection: Limits, fits  and tolerances; linear and angular
measurements; comparators; gauge design; interferometry; form and finish
measurement; alignment and testing methods; tolerance analysis in manufacturing
and assembly.

Computer Integrated Manufacturing: Basic concepts of CAD/CAM and their
integration tools.

Production Planning and Control: Forecasting models, aggregate production
planning, scheduling, materials requirement planning.

Inventory Control: Deterministic models; safety stock inventory control systems.

Operations  Research:  Linear programming, simplex method, transportation,
assignment, network flow models, simple queuing models, PERT and CPM.

Interview Questions

Mechanical Engineering Materials


What are common engineering metals?

What are densities of   Iron, Aluminum, Magnesium, Titanium?

What are tensile strengths of Iron, Aluminum, Magnesium, Titanium?



Theory of Machines


What is a kinematic pair?
What is a lower pair? What is a higher pair?
What are various types of kinematic pairs?  Sliding pair, Turning pair, Rolling pair, Spherical pair, Screw or Helical pair

What is a kinematic chain?


When a number of links are connected in space such that the relative motion of any point on a link with respect to any other point on the other link follows a law, the chain is called a kinematic chain.

What is a mechanism?


When any one link in a kinematic chain is fixed, the kinematic chain becomes a mechansim.

What is a machine?


When the kinematic chain is considered as an agent for applying mechanical power, it should be referred to as a machine.

Inversions of Kinematic Chain with Four Lower Pairs (sliding or turning)

The slider crank chain (three turning pairs and one sliding pair)


First inversion: Slider crank
Second inversion: Oscillating cylinder engine, Crank and Slotted Lever mechanism,
Third inversion: Whitworth return motion
Fourth inversion: Hand-pump

The Double slider crank chain (two turning and two sliding pairs)

Pairs of the same kinds are adjacent.

First inversion: Elliptical trammel
Second inversion: Scotch Yoke
Third inversion: Oldham's Coupling

Four Bar Chain or Quadric Cycle Chain - Four turning pairs


1. Oscillatory motion (Crank and Lever Mechanism)
2. Complete rotation of  the crank and the follower - Quick return mechanism
3. Coupled wheels of a locomotive (Double crank)
4. Pantograph (Double lever mechanism)


Design of Machine Elements


Bolts and Screws


Screw pair: The screw thread is a form obtained by cutting a continuous helical groove on the cylindrical surface. The threaded portion engages with a corresponding threaded hole in the nut or machine part, the two elements form what is called a screw pair.

Standard screw thread forms

BSW
B.A.
Metric
Square
Acme
Buttress

Types of threaded fasteners (Bolts and Screws)
1. Through bolts or bolts 2. Tap bolt and cap screws  3. Studs   4. Machine screws

Keys


What is a key? Key joins a shaft to a machine part and the two rotate together. Ex. pulley and a shaft, flywheet and a shaft

What is a cotter?  It is a flat wedge shaped piece of  rectangular cross section  used to connect two shafts.

Shafts


What is a shaft?

Gears


Types: Spur gears, Bevel gears



Springs


What is a spring?
Types of springs: Helical springs, Leaf springs, Spiral springs, Torsion springs, Flat springs, Belleville springs



Strength of Materials


Types of stresses

Tensile, Compressive, Shear

Strain

Tensile, Compressive, Shear, Volumetric

Resiliance


Analysis of Rivet Joint

Lap joint, Butt joint

Design of a Riveted Joint

Diameter of the rivets, Pitch of the rivets, No. of rivets, Thickness of cover plates



Manufacturing Technology


Machining


Types of Machining


Outer surface  - Turning, Milling, Shaping, Planing, Grinding

Inner surface -  Drilling, Boring, Reaming

Screw thread cutting and Gear Cutting

Machine Tools 


Lathe, Milling, Shaping, Planer, Griding Machine, Milling Machine, Boring Machine

Tools - Single point, Multi point   -  Turning, Milling cutters, Shaping tool, Planing tool, Griding wheel, Drills, Reamers, Boring tool, Broach, Tap, Knurling tool

Tools materials:  1. Carbon steels, 2. Medium alloy steels, 3. High speed steels, 4. Cemented carbides 5. Stellites  6. Ceramics  7. Diamond  8. PCBN - Polycrystalline Boron Nitride  9. Abrasives

Coolants  1. Oils  2. Water emulsions  3, Gaseous coolants  4. Dry machining


Operations done on various machine tools


Lathe:  1. Turning,  2. Taper turning, 3. Thread cutting, 4. Chamfering,  5. Knurling  6. Facing  7. Grooving  8. Forming  9. Filing 10. Polishing  11. Reaming  12. Drilling  13. Boring

Milling Machine Operations:  1. Plain milling  2. Side milling, 3. Straddle milling,  4. Gang milling  5. Profile milling,  6.  Form milling,  7. thread milling,  8. Cam milling  9. Helical milling  10. gear cutting  11, Saw milling

Drilling Machine Operations:  1. Drilling  2. Reaming  3. Boring  4. Counter boring  5. Countersinking  6.  Spot facing  7.  Tapping  8.  Grinding  9. Lapping


Updated 23 April 2017,  4 April 2015

Magnesium - Use in Automobiles



Update on 23 April 2017




Magnesium alloys are widely used in automotive applications, 3C (computer, communication,
and consumer electronics), tools, and to some extent in aerospace and aeronautics. Their main
advantage is low density. Aluminum alloys with a density of ~2.8 g/cm are 50% heavier compared
with magnesium alloys having a density of ~1.8 g/cm . The low density of magnesium alloys has a
significant economic savings effect and this is especially true in the aerospace and aeronautic industries. Here, the use of magnesium casting alloys for pumps, housings, accessories, and hardware for the handling of liquefied gases is of interest. Magnesium wrought alloys in sheets or extrusions may be used for tanks of liquefied gases, extruded ribs, and connectors. Most of the magnesium alloys have been developed and used with High Pressure Die Casting (HPDC). They contain a minimum of 4 wt. % Al to improve their castability and several other alloying elements to improve their corrosion properties, strength, and creep resistance. There are only a few
magnesium alloys for wrought applications in the market. AZ31 is the most widely investigated
alloy, but AZ80 and ZE10 are also used.

Source: Influence of Cryogenic Temperatures on the Microstructure and Mechanical Properties of
Magnesium Alloys: A Review by Hajo Dieringa


Research Alliance for Magnesium in Automotive Applications


The researchers at Birmingham City University have signed a deal with Meridian — a leading manufacturer of magnesium components in the auto industry — to promote the use of magnesium as an alternative to aluminum and steel. The research alliance will explore new methods to make its production more economic for Meridian as well as its clients. The alliance has set sustainability and weight savings as top objectives in achieving fuel efficiency.

Benefits of using magnesum

It is abundant on the earth. Magnesium has unique 100 percent recyclable property. Magnesium is 75 percent lighter than steel and 33 percent lighter than aluminum.


Meridian, produces 5,000 net metric tons of die-cast products a year in the UK plant and serves number automobile manufactures  including Jaguar, BMW, Ford, Land Rover, Honda, and Volvo.
But the current manufacturing methods had been costly  and the small volume players are not able to utlize magnesium components because of it. The partnership will aim to reduce manufacturing costs and overcome this barrier for low volume manufacturers and this would help to increase use of magnesium in aviation sector also. Another core area of investigation will be the reduction of waste, as the current production process of magnesium creates product and waste in almost equal quantity.



A section of players in the auto industry, despite being convinced about the high utility of magnesium in instrument panels, are wary of the high costs in sourcing the material.
Previously, the United States, Canada, Australia, and the Middle East were top magnesium producers,. Now, China is the new bulk supplier.



A 2015 report by Lucintel reported that in the automotive industry,  interior, powertrain, chassis, and exterior are the major application area of magnesium alloys material in a vehicle.


For more details see:  http://www.techtimes.com/articles/192905/20170117/is-magnesium-the-next-big-thing-material-touted-as-viable-alternative-for-luxury-car-makers-aerospace-industry.htm#sthash.zavgv8OV.dpuf

Fiat Chrysler Automobiles NV is using a magnesium skeleton covered by a thin steel shell in its 2017 Pacifica minivan liftgate. The part now weighs 22 pounds less. The part is made by die casting.  It also allowed the auto maker to create pockets within the door itself for the installation of speakers and taillamps. The move eliminated the need for about a half-dozen brackets, reducing costs.

https://www.wsj.com/articles/how-auto-companies-are-making-their-cars-lighter-1465351441

http://www.gfau.com/com/en/products-and-solutions/passenger-car.html  - Some components made with magnesium details are available.

23 March 2014


Magnesium is now the center of attention for the United States Automotive Materials Partnership (USAMP). This USCAR initiative investigates ways to develop a family car that can attain 2.9 L/100 km (80 mpg). The $10 million project involves the U. S. government, automakers, suppliers, universities, and national laboratories.
http://www.meridian-mag.com/magnesium-auto-parts/



Racing cars used magnesium parts in the 1920's.  Extensively use occurred  in commercial vehicles in 1936 when the Volkswagen Beetle was introduced. The car contained around 20kg of magnesium in the powertrain and during its peak production in 1971, consumption of magnesium reached 42,000 tonnes per annum.

Magnesium in Automotive

But now magnesium is being as a strategic lightweight material in the automotive industry and it  is the driving force behind the growth of use of magnesium in industry. Technological advances in magnesium alloys made in the mid 1980's and the continuous drive to minimise weight and fuel consumption of cars, today, there is more use of magnesium in  the automotive industry.

Further growth is forecast over the next 10 years. In Europe, the increase in using magnesium as a structural lightweight material is being led by the Volkswagen Group of companies, with the material also being used by other leading manufacturers including DaimlerChrysler (Mercedes Benz), BMW, Ford and Jaguar. Presently, around 14 kgs of magnesium are used in the VW Passat, Audi A4 & A6. All those vehicles use magnesium transmission casings cast in AZ91D, offering a 20%-25% weight saving over aluminium. Other applications include instrument panels, intake manifolds, cylinder head covers, inner boot lid sections and steering components which utilise the more ductile AM50A & AM60B alloys. In North America, The GM full sized Savana & Express vans use up to 26kg of magnesium alloy.

The motorsport industry worldwide has recognised the advantages to be gained from using the sand cast high performance alloys originally developed for the aerospace industry and is using them now.. Their lightweight and high strength to weight ratio provide many teams with a competitive advantage. Elektron®21 is becoming more widely used in motorsport applications, for example replacing Elektron®RZ5  (ZE41) gearboxes.  Elektron®WE43 and Elektron®WE54 alloys in cast and wrought form are being used increasingly in motor racing engines, often due to the very high operating stresses and temperatures.

More information on electron range of magnesium alloys and uses
http://www.magnesium-elektron.com/markets-applications.asp?ID=7

Interesting paper of 2004
Automotive Applications of Magnesium and Its Alloys
http://www.igcar.gov.in/transiim/2004/vol57-4overview2.pdf
The paper predicted that from the present 25 Kg per vehicle, the use can go even up to 180 kg per vehicle assuming the vehicle weight at 1200 Kgs.



Magnesium - Chemistry from IIT JEE Blog


Updated on 23 April 2017, 23 March 2014

Wednesday, April 20, 2016

3D Printing Books Information




3D Printing with Biomaterials: Towards a Sustainable and
https://books.google.co.in/books?isbn=1614994862
A.J.M. van Wijk, ‎I. van Wijk - 2015 - ‎Preview - ‎More editions
It notifies me that a new door panel from bio-plastic, reinforced with natural fibers, was printed overnight and replaced by the ... 3D printing – or Additive Manufacturing – is a group of manufacturing techniques defined as the process of joining ...



Idiot's Guides: 3D Printing
https://books.google.co.in/books?isbn=1615647457
Cameron Coward - 2015 - ‎Preview - ‎More editions
Are you free to use whatever software you like, or are you stuck with a particular program made by the manufacturer? Depending on your needs and expectations, those could be major factors in your decision on which 3D printer to purchase.

An Introduction to 3D Printing:
https://books.google.co.in/books?isbn=1622878973
Victoria Zukas, ‎Jonas A Zukas - 2015 - ‎Preview - ‎More editions
This book is aimed at an audience consisting of two kinds of readers.


3D Printing with Delta Printers
https://books.google.co.in/books?isbn=1484211731
Charles Bell - 2015 - ‎Preview - ‎More editions
The book also covers tips for building your own delta printer as well as examples of common enhancements. This book will enable you to build, configure, and enhance your delta printer.

Make: 3D Printing Projects: Toys, Bots, Tools, and ...
https://books.google.co.in/books?isbn=1457187205
Brook Drumm, ‎James Floyd Kelly, ‎Rick Winscot - 2015 - ‎Preview - ‎More editions
Written by the founder of Printrbot, his staff, and veteran DIY authors, this book of projects exemplifies the broad range of highly personalized, limit-pushing project possibilities of 3D printing when combined with affordable electronic ...




A Focus on SLM and SLS Methods in 3D Printing
Emerald Group Publishing Limited
Emerald Group Publishing, 06-Nov-2015 - Business & Economics - 216 pages


A Focus on SLM and SLS Methods in 3D Printing is an indispensable collection of articles for anyone involved in additive manufacturing - from academics and researchers through to engineers and managers within the manufacturing industry. The collection features examples of innovative research involving selective laser melting and selective laser sintering techniques applied across a range of contexts.
https://books.google.co.in/books?id=tMndCgAAQBAJ



Fabricated: The New World of 3D Printing
https://books.google.co.in/books?isbn=1118416945
Hod Lipson, ‎Melba Kurman - 2013 - ‎Preview - ‎More editions

Beginning Google Sketchup for 3D Printing
https://books.google.co.in/books?isbn=1430233613
Sandeep Singh - 2010 - ‎Preview - ‎More editions
What you’ll learn 3D design for beginners Using Sketchup Using the online 3D printing pipeline Animating Sketchup 3D models Becoming familiar with rapid prototyping technology Navigating new 3D and personal fabrication technologies ...

Printing in Plastic: Build Your Own 3D Printer
https://books.google.co.in/books?isbn=1430234431
James Floyd Kelly, ‎Patrick Hood-Daniel - 2011 - ‎Preview - ‎More editions
Leads you through building a personal fabrication machine capable of creating small parts and objects from plastic Provides example projects to get you started on the road to designing and fabricating your own parts Provides an excellent ...

3D Printing: The Next Industrial Revolution
https://books.google.co.in/books?isbn=148418176X
Christopher Barnatt - 2013 - ‎No preview
The book is written for a wide audience, including 3D printing enthusiasts, entrepreneurs, designers, investors, students, and indeed anybody who wants to be more informed about the next round of radical technological change.

Mastering 3D Printing
https://books.google.co.in/books?isbn=148420025X
Joan Horvath - 2014 - ‎Preview - ‎More editions
Mastering 3D Printing shows you how to get the most out of your printer, including how to design models, choose materials, work with different printers, and integrate 3D printing with traditional prototyping to make techniques like sand ...

3D Printing For Dummies
https://books.google.co.in/books?isbn=1118660773
Kalani Kirk Hausman, ‎Richard Horne - 2014 - ‎Preview - ‎More editions
Bring your designs to life with this For Dummies guide Straight from science fiction to your living room! 3D printing is here, and this friendly guide cuts through the technical jargon to show you how 3D printing works, what it can (and can ...

Practical 3D Printers: The Science and Art of 3D Printing
https://books.google.co.in/books?isbn=1430243929
Brian Evans - 2012 - ‎Preview - ‎More editions
What you’ll learn The various types of 3D printers, what they have in common, and what sets each one apart The printer toolchain, including controllers and printer interfaces The art of calibrating your printer How to find and create 3D ...

Makers: The New Industrial Revolution
https://books.google.co.in/books?isbn=1448136806
Chris Anderson - 2012 - ‎Preview - ‎More editions
Chris Anderson, bestselling author of The Long Tail, explains how this is happening: how such technologies as 3D printing and electronics assembly are becoming available to everybody, and how people are building successful businesses as a ...

LEO the Maker Prince: Journeys in 3D Printing
https://books.google.co.in/books?isbn=1457183102
Carla Diana - 2013 - ‎Preview - ‎More editions
Readers can come along for the journey, too: all of the objects in the book are printable one way or another.

Additive Manufacturing Technologies: 3D Printing, Rapid ...
https://books.google.co.in/books?isbn=1493921134
Ian Gibson, ‎David Rosen, ‎Brent Stucker - 2014 - ‎Preview - ‎More editions
This book covers in detail the various aspects of joining materials to form parts.

Tuesday, April 12, 2016

Industrial Revolution 4.0 - New Machines - New Processes - New Skills



First:  Mechanization, Water Power, Steam Power

Second: Mass Production, Assembly Line, Electricity

Third: Automation, Computerisation, CNC

Fourth: Cyber Physical Systems, Machine to Machine connections, Analytics based Machine Control


https://en.wikipedia.org/wiki/Industry_4.0

http://www.mckinsey.com/business-functions/operations/our-insights/manufacturings-next-act

http://prd.accenture.com/microsites/digital-industry/index.html

Tuesday, April 5, 2016

Patents of Selective Laser Printing





http://www.google.co.in/patents/US5155324
Carl Deckard,

http://www.google.co.in/patents/US5718951

http://www.google.co.in/patents/US5718951

http://www.google.co.in/patents/US5746844

http://www.google.co.in/patents/US5787965

Apparatus for creating a free-form three-dimensional article using a layer-by-layer deposition of a molten metal and deposition of a powdered metal as a support material
US 5960853 A

http://www.google.com/patents/US20020015654
Suman Das, Joseph Beaman

https://www.google.nl/patents/US6676892

http://www.google.is/patents/US8826938

https://www.google.nl/patents/WO1992008566A1


http://news.thomasnet.com/imt/2013/09/04/selective-laser-sintering-patent-expiration-will-not-be-a-game-changer






https://books.google.co.in/books?id=goh9CAAAQBAJ


http://www.me.utexas.edu/news/news/selective-laser-sintering-birth-of-an-industry

http://www.google.ch/patents/US20070141375

http://hackaday.com/2013/09/11/3d-printering-key-patents/

http://3dprintingindustry.com/2014/08/14/first-low-cost-sls-3d-printers-hit-scene/

http://www.google.co.ve/patents/US8329092

https://www.google.com.ar/patents/EP2412007A1?cl=en

http://www.google.ch/patents/US20040056022

http://www.google.co.in/patents/US20050287031

https://www.google.nl/patents/US4938816

http://patents.justia.com/patent/20090208361

http://patents.justia.com/patent/20110286874

https://www.google.nl/patents/US20120067501

https://www.google.nl/patents/US7514649

http://www.google.co.in/patents/US8828116

https://www.google.nl/patents/WO2014207751A3

https://www.google.nl/patents/EP1296776A1

https://www.google.nl/patents/EP1236526B1

https://www.google.nl/patents/EP2899012A1

https://www.google.be/patents/WO2014176536A1











3D Printing of Titanium





https://3dprint.com/111142/3d-printing-with-titanium/


http://3d-printing-titanium.com/


http://3dprintingindustry.com/2015/03/10/3d-printing-titanium-the-bin-of-broken-dreams-part-1/


http://www.3ders.org/articles/20151209-praxair-to-market-ames-laboratorys-titanium-powder-for-metal-3d-printing.html

http://titanium3dprinting.com/

https://en.wikipedia.org/wiki/Direct_metal_laser_sintering

http://zenithtecnica.com/