Jump to content
Mechanical Engineering Community

Leaderboard


Popular Content

Showing content with the highest reputation since 10/12/2018 in all areas

  1. 2 points
    1. It's not oil the best name is brake fluid as it consists a lot of material inside such as (silicone, glycol ether/borate ester, mineral oil) 2. One of the main things for BF, it must have a high boiling point to avoid vaporizing in the lines this is why we need to change the brake fluid from time to time as it has tendency to absorb water which will lower its boiling temperature leading to change part of the fluid into moisture and vapour inside the brake circuits and this will create vapour lock leading to being compressible and once it became compressible the brake foot force will not be transferred to the other brake parts (cylinders,brake pistons, ...) We have many types of BF each has its own dry/wet boiling temperature such as:- DOT3 (dry 205C/401F- wet 140C/284F) DOT4 (dry 230C/446F - wet 150C/311F) DOT5 (dry 260C/500F - wet 180C/365F) *Hygroscopic means (water absorbing)
  2. 1 point
    If a idler pulley is necessary, there are rules as to the diameter that should be used so as not the "break the back" of the belt, I assume you are talking v-belts. Then when tensioning the drive belts your need to apply about a 1% stretch to the cords in the belt, assumption is std belts with polyester cords. If you are thinking to firstly correctly tension the belts, then apply an idler, the whole drive could be over tensioned and damage the shaft and bearings. You have to tension the drive the same as you would with the idler in the system, Both Carlisle Belts and Gates have very good drive design programs for designing and provide tensioning information. This is not a simple procedure and the larger the drive the bigger the loads, also life and efficiency are very important.
  3. 1 point
    • Graded Mode
    • 10 minutes
    • 17 Questions
    • 15 Players
    Mechanical Engineering Quiz 8
  4. 1 point
    • Graded Mode
    • 15 minutes
    • 17 Questions
    • 52 Players
    Test your mechanical engineering concepts
  5. 1 point
    AKS15

    Mechanical Engineering Quiz 1

    How will the balance reading remain same in that "Bucket-Spring balance" question. Reading should increase perhaps.
  6. 1 point
    Why do we need to change brake oil the after a particular interval?
  7. 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.
  8. 1 point
    Thanks for writing here,welcome on https://mechanical-engg.com/ look forward for your active participation.
  9. 1 point
    Concept of heating is just simple with respect to welding. Majorly Pre or post heating in welding is to relieve stresses which are used to developed during welding. Pre heating: Power saving - by pre heating, heat gradient can be reduced and so to control heat generation, low heat input can be given and so process characteristics can be reduced accordingly Reduction in internal residual stresses - the stresses will are already inside the material can reduce the strength of the weld, to avoid that, pre treatment can be used Post heating: Post heating or annealing or normalizing is done mainly to reduce the thermal stresses developed during welding To relieve Hydrogen embrittlement in which Hydrogen has entrapped during welding from moisture or the filler material
  10. 1 point
    Eslam Ahmed

    Why pistons are usually dished at top ?

    To provide more turbulence and swirl. Thus, more homogeneous mixture gonna be obtained. This can lead to more heat transfer as well (as the surface area increases).
  11. 1 point
    the basic difference in air condition and refrigeration are: Air conditions is the controlled atmosphere in which you need to control temperature (may be lower or higher), humidity and air quality. where as in refrigeration need to maintain only lower temperature as required.
  12. 1 point
    DrD

    Machine Design Quiz 1

    To my mind, this quiz focused on mostly the wrong things. These are, for the most part, things that can easily be looked up in a design manual or a handbook. A much more interesting quiz would focus on the understanding and application of idea, the ability to correctly model systems, and the ability to understand and correctly interpret data. DrD
  13. 1 point
    In an open loop system input is independent of output. They are simple and fast process... In closed loop system input is dependent on output. They are complex and slow process... Closed loop system in general are provided with sensors that serve the purpose of controlling the input..
  14. 1 point
    This is wrong. A diesel engine utilizes the diesel cycle, whereas a petrol engine utilizes the otto cycle. The main difference between these two cycles, which are both non-ideal versions of the Carnot cycle, is their method of ignition. In the otto cycle, the combustion process is catalyzed by a spark. In the diesel cycle, the combustion process instantaneously begins when the air-fuel mixture temperature reaches the ignition temperature of the diesel fuel. A petrol engine cannot have a compression ratio as a large as a diesel engine. This is because it begins the combustion process pressure by sparking the petrol-air mixture to initiate ignition, rather than building up more pressure until ignition is initiated by reaching the ignition temperature of the petrol fuel. Thermal efficiency, which is a function of an engine's compression ratio, increases as the compression ratio increases. Though, when operating with the same compression ratio, a petrol engine is more efficient than a diesel engine, a diesel engine can have a higher efficiency than a petrol engine because it can utilize a much higher compression ratio that a petrol engine cannot possibly achieve. This is why, generally, diesel engines are more efficient than petrol engines.
  15. 1 point
  16. 1 point
    Priming is process of removing air from from suction pipe by filling water in suction.
  17. 1 point
    In my view nothing difference in efficiency. Based on the design configuration can be made to deliver same efficiency for same vehicle ?
  18. 1 point
    A diesel engine's compression ratio produces temperatures approx.. 210 deg C which is near the auto flash point of diesel fuel, this therefore causes combustion
  19. 0 points
    what is the difference between refrigeration and air conditioning? A major difference between refrigeration and air conditioning is the point of supply for the gases. Refrigeration systems have gas installed in a series of tubes. In old refrigerators, this gas was chloro-flouro-carbon, or CFC, but this has harmful effects on people, so refrigerators not contain HFC-134a. HFC-134a is the sole gas used as a coolant in refrigeration systems. Air conditioning systems use built-in chemicals, but also air from the room or rooms being heated. Gases built into air conditioning units cool air that circulates through the unit; the unit then redistributes the cooled air through the room. Air conditioners have circulation systems designed to project cool air away from the units while refrigeration units have circulation systems designed to retain coolant in a confined space. Refrigeration systems circulate cool liquids and gases through a series of tubes and vents. Cool air from within a refrigerator is sucked into a compressor that recycles the gas through the tubes. Air conditioners, while also employing tubes in the coolant system, have fans for the dispersal of air. Unlike refrigeration systems, which keep gases contained to a pre-determined space, air conditioning systems disperse cool air throughout areas of unknown volume. Refrigeration refers to processes that take thermal energy away from a place and gives off that energy to a place with a higher temperature. Naturally, thermal energy flows from a place with a higher temperature to a place with a lower temperature. Therefore, refrigeration runs against the natural heat flow and so it requires work to be done.Refrigerator is a name that we use for devices that are used to keep food at low temperatures. A refrigerator consists of a fluid called refrigerantwhich gets expanded and compressed in a cycle:
×