IMPACT TEST

IMPACT TEST:

               Impact tests are designed to measure the resistance to failure of a material to a suddenly applied force. The test measures the impact energy, or the energy absorbed prior to fracture. The most common methods of measuring impact energy are the:

Charpy Test
Izod Test

Impact Energy:

                Impact energy is a measure of the work done to fracture a test specimen.
 
                           
                 
                                   Impact testing machine                       reading scale &pointer

                     When the striker impacts the specimen, the specimen will absorb energy until it yields. At this point, the specimen will begin to undergo plastic deformation at the notch. The test specimen continues to absorb energy and work hardens at the plastic zone at the notch. When the specimen can absorb no more energy, fracture occurs.

                    Impact is a very important phenomenon in governing the life of a structure. For example, in the case of an aircraft, impact can take place by a bird hitting a plane while it is cruising, or during takeoff and landing the aircraft may be struck by debris present on the runway, and as well as other causes. An arm held at a specific height (constant potential energy) is released. The arm hits the sample and breaks it. From the energy absorbed by the sample, its impact strength is determined.

The Izod Test:

Izod impact strength testing is an ASTM standard method of determining impact strength. A notched sample is generally used to determine impact strength. 

The Izod impact test differs from the Charpy impact test in that the sample is held in a cantilevered beam configuration as opposed to a three-point bending configuration. In Izod test, the specimen is held on one end and is free on the other end. This way it forms a cantilever beam. This test can also be used to determine the notch sensitivity.

Izod & Charpy Test Specimens:

             Izod test specimens normally measure 75x10x10mm and have a notch machined across one of the larger faces. The notches may be:
V-notch – A V-shaped notch, 2mm deep, with 45° angle and 0.25mm radius along the base
               
                         
           
                                                   Charpy test specimen                                                                                            
              The Izod test involves striking a suitable test piece with a striker, mounted at the end of a pendulum. The test piece is fixed in place at one end and the striker sticks the test piece immediately behind a machined notch.




DESCRIPTION OF MACHINE:

                       The pendulum impact testing machine consists of the robust frame the pendulum the specimen support and the measuring dial the pendulum shaft is fitted in anti friction bearing. The pendulum is clamped to pendulum shaft the pendulum consists of the pendulum pipe and the pendulum hammer of U taped design into this the striker is mounted for conducting Izod impact test. 
The range within which the pendulum is swinging is partially protested by the guard. A latch is provided which keeps the pendulum is elevated position. A lever is provided for operating the latch and releasing the pendulum .There is a dial attached concentrically with the pendulum shaft. The scale is designed such that the impart energy absorbed in breaking the specimen can be read directly in joules    
                 

PROCEDURE:

Measure the dimensions of specimen, rise the pendulum and keep it  in position and adjust the pointer  on 168 N-m reading on the dial indicates the energy stored in the pendulum. 
Clamp the specimen in the specimen support with the help of clamping screw and setting gauge and next step is cone is to be taken that the notch on the specimen should take the pendulum stricken
Operate the lever so that the pendulum is released and the specimen breaks 
Wait till the pendulum reverses its swing and carefully swinging pendulum by operating the pendulum brake
Note down the in part energy 
Remove the broken specimen by losing the damp screw.

Comments

Post a Comment

Popular posts from this blog

Pro/ENGINEER Functionality

Image
    Pro/ENGINEER Functionality The basic functionality of Pro/ENGINEER is broken into four major areas: •          Part Modeling and Design •          Assembly Modeling and Design •          Design Documentation (Drawing Generation) •          General Functionality                                 Part Design and Modeling Defining Geometry - Feature-Based Design • Create sketched features including protrusions, cuts, and slots made by either extruding, revolving, or sweeping along a 2D sketched trajectory, or blending between parallel sections  • Create pick and place features, such as holes, shafts, chamfers, rounds, shells, regular drafts, flanges, ribs, etc.  • Sketch c...
Read more

PATTERNS

PATTERNS:              From the design, provided by an engineer or designer, a skilled pattern maker builds a pattern of the object to be produced, using wood, metal, or plastic; other materials to be used can be polystyrene or even sand strickled into shape. The metal to be cast will contract during solidification, and this may be non-uniform due to uneven cooling. Therefore, the pattern must be slightly larger than the finished product, a difference known as contraction allowance. Pattern-makers are able to produce suitable patterns using ‘contraction rules’. Different scaled rules are used for different metals because different metals/alloys contract at different rates. Patterns also have core prints; these create registers within the moulds, into which are placed sand cores. Sand cores are used to create undercut profiles and holes which cannot be moulded.                  Paths for the entrance of...
Read more

Mechanical behavior of Al-Sic-Zn-Cu Metal Matrix Composite

                     Aluminum is the world‘s most abundant metal and is the third most common element, comprising 8% of the earth’s crust. The versatility of aluminum makes it the most widely used metal after steel. After iron, aluminum is now the second most widely used metal in the world. This is because aluminum has a unique combination of attractive properties. Low weight, high strength, superior malleability, easy machining, excellent corrosion resistance and good thermal and electrical conductivity are amongst aluminum’s most important properties. Aluminum is also very easy to recycle. A unique combination of properties makes aluminum and its alloys one of the most versatile engineering and construction material available today. A metal matrix composite (MMC) is composite material with at least two constituent parts, one being a metal. MMCs are made by dispersing a reinforcing material into a metal matrix. The matrix is the ...
Read more