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  1. 1 point
    Selection of material is an important aspect for manufacturing industries . The quality of product is highly depends upon its material properties. These properties are used to distinguish materials from each other. For Example: A harder material is used to make tools.A ductile material is used to draw wires. So the knowledge of mechanical properties of material is desirable for any mechanical student or for any person belongs to mechanical industries. This post brings top 18 mechanical properties. Mechanical properties of material: There are mainly two types of materials. First one is metal and other one is non metals. Metals are classified into two types : Ferrous metals and Non-ferrous metals. Ferrous metals mainly consist iron with comparatively small addition of other materials. It includes iron and its alloy such as cast iron, steel, HSS etc. Ferrous metals are widely used in mechanical industries for its various advantages. Nonferrous metals contain little or no iron. It includes aluminum, magnesium, copper, zinc etc. Most Mechanical properties are associated with metals. These are #1. Strength: The ability of material to withstand load without failure is known as strength. If a material can bear more load, it means it has more strength. Strength of any material mainly depends on type of loading and deformation before fracture. According to loading types, strength can be classified into three types. a. Tensile strength: b. Compressive strength: 3. Shear strength: According to the deformation before fracture, strength can be classified into three types. a. Elastic strength: b. Yield strength: c. Ultimate strength: #2. Homogeneity: If a material has same properties throughout its geometry, known as homogeneous material and the property is known as homogeneity. It is an ideal situation but practically no material is homogeneous. #3. Isotropy: A material which has same elastic properties along its all loading direction known as isotropic material. #4. Anisotropy: A material which exhibits different elastic properties in different loading direction known as an-isotropic material. #5. Elasticity: If a material regain its original dimension after removal of load, it is known as elastic material and the property by virtue of which it regains its original shape is known as elasticity. Every material possess some elasticity. It is measure as the ratio of stress to strain under elastic limit. #6. Plasticity: The ability of material to undergo some degree of permanent deformation without failure after removal of load is known as plasticity. This property is used for shaping material by metal working. It is mainly depends on temperature and elastic strength of material. #7. Ductility: Ductility is a property by virtue of which metal can be drawn into wires. It can also define as a property which permits permanent deformation before fracture under tensile loading. The amount of permanent deformation (measure in percentage elongation) decides either the material is ductile or not. Percentage elongation = (Final Gauge Length – Original Gauge Length )*100/ Original Gauge Length If the percentage elongation is greater than 5% in a gauge length 50 mm, the material is ductile and if it less than 5% it is not. #8. Brittleness: Brittleness is a property by virtue of which, a material will fail under loading without significant change in dimension. Glass and cast iron are well known brittle materials. #9. Stiffness: The ability of material to resist elastic deformation or deflection during loading, known as stiffness. A material which offers small change in dimension during loading is more stiffer. For example steel is stiffer than aluminum. #10. Hardness: The property of a material to resist penetration is known as hardness. It is an ability to resist scratching, abrasion or cutting. It is also define as an ability to resist fracture under point loading. #11. Toughness: Toughness is defined as an ability to withstand with plastic or elastic deformation without failure. It is defined as the amount of energy absorbed before actual fracture. #12. Malleability: A property by virtue of which a metal can flatten into thin sheets, known as malleability. It is also define as a property which permits plastic deformation under compression loading. #13. Machinability: A property by virtue of which a material can be cut easily. #14. Damping: The ability of metal to dissipate the energy of vibration or cyclic stress is called damping. Cast iron has good damping property, that’s why most of machines body made by cast iron. #15. Creep: The slow and progressive change in dimension of a material under influence of its safe working stress for long time is known as creep. Creep is mainly depend on time and temperature. The maximum amount of stress under which a material withstand during infinite time is known as creep strength. #16. Resilience: The amount of energy absorb under elastic limit during loading is called resilience. The maximum amount of the energy absorb under elastic limit is called proof resilience. #17. Fatigue Strength: The failure of a work piece under cyclic load or repeated load below its ultimate limit is known as fatigue. The maximum amount of cyclic load which a work piece can bear for infinite number of cycle is called fatigue strength. Fatigue strength is also depend on work piece shape, geometry, surface finish etc. #18. Embrittlement: The loss of ductility of a metal caused by physical or chemical changes, which make it brittle, is called embrittlement.
  2. 1 point

    Version 1.1.0

    36,446 downloads

    A COMPLETE INSTRUCTOR AND STUDENT SUPPLEMENT PACKAGE - Continued These ppts are set of instructor and student supplements. . A FOCUS ON DIAGNOSIS AND PROBLEM SOLVING The primary focus of these ppts is to satisfy the need for problem diagnosis. Time and again, the author has heard that technicians need more training in diagnostic procedures and skill development. To meet this need and to help illustrate how real problems are solved, diagnostic stories are included throughout. Each new topic covers the parts involved as well as their purpose, function, and operation, and how to test and diagnose each system.
  3. 1 point
    Many years ago, I was involved as an expert in a legal dispute. My company was suing the US Army in a contract dispute. I got a very bad taste for lawyers as a result. An Army facility had designed a mechanical system and put out drawings for the system as the basis for suppliers to bid on building the system. There were five major suppliers bidding to build these devices for the Army, and the bidding was extremely competitive. Being higher by half a cent ($0.005) per unit would mean losing the bid. My employer had the misfortune to win the bidding, and we were building this rather complicated mechanical system (around 200 parts) for about $15 per unit with many 1000s to be built. Each week's production would be declared to be a "lot," typically around 20,000 units. The inspectors would draw a random sample for testing, and if all tests were passed, the lot was accepted and the company was paid for the material. If any tests were failed (and there were about a dozen different tests), the lot was rejected and the company received no payment. Dimensional tolerances were extremely critical, and the company had taken then into account in the bidding. In suing the Army, my employer was alleging that the tolerances had been deliberately set loose for the bidding while the Army knew that closer tolerances were required in order to consistently meet all the specifications and pass the tests. The Army denied this. My job for 18 months was to demonstrate mathematically that there were dimensional combinations within the allowed tolerances that would fail some of the tests, and therefore that the Army had misled the bidders in the original contract negotiations. I did this quite fully, showing that some combinations would work while others would not, even though all were within the specifications on the drawings. I was completely disgusted by the attitudes of the lawyers on both sides. The had ZERO interest in the truth; they only care about winning the argument. They were only interested in information that supported their side of the case. If a part of my study did not support my employer's case, our attorneys ordered me to destroy that paper work and to deny that I had ever done it if asked. I refused to do that; the truth is the truth. Most of my encounters with lawyers since that time has supported my early evaluation; they are evil men (and women) intent only on winning. Truth means nothing to a lawyer! DrD
  4. 1 point
    Knocking (also knock, detonation, spark knock, pinging or pinking) in start interior burning motors happens when burning of a portion of the air/fuel blend in the chamber does not result from spread of the fire front touched off by the start plug, however at least one pockets of air/fuel blend detonate outside the envelope of the ordinary ignition front. The fuel-air charge is intended to be lighted by the start plug just, and at an exact point in the cylinder's stroke. Knock happens when the pinnacle of the burning procedure never again happens at the ideal minute for the four-stroke cycle. The stun wave makes the trademark metallic "pinging" sound, and barrel weight increments drastically. Impacts of motor knocking reach from immaterial to totally ruinous.
  5. 1 point

    10,107 downloads

    Presentation on Design of- Clutch Brake Belts Chain Gears
  6. 1 point
    When fuel is injected into combustion chamber, the droplets of fuel takes heat from surrounding air and vaporizes. Then it's temperature goes on increasing till it reaches to auto ignition temperature and then combustion starts. This whole process requires some time (fraction of second) and it is known as IGNITION DELAY OR DELAY PERIOD. Ideally, as injrction starts, ignition should take place simultaneously. That is , ignition delay should be as small as possible. Suppose auto ignition temperature of fuel is more then there will be more ignition delay period. This means that after injection start, the fuel will droplets will accumulate in combustion chamber. And after auto ignition temperature reaches, this accumulated fuel burns promptly. In fact it explodes. This is cause of knocking in CI Engine. There are several factors which affects knocking such as A/F ratio, compression ratio, auto ignition temperature, engine speed, inlet temperature, intake pressure etc. It is very difficult to differentiate between normal engine running and knocking in case of CI Engine.
  7. 1 point
    The variation in the sound of every bike is due to the design of the path of flow of exhaust gases with suitable emission control techniques.


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