1.3 Methods for Investigating and Testing Materials Flashcards
Describe the simple workshop test for toughness
Place material in vice and hit with hammer
Describe the simple workshop test for hardness
Use a dot punch to produce an indent in the sample material. The smaller the indent, the harder the material
Describe the simple workshop test for tensile strength
Clamp each end of the material and place weights on one end. less deflection under load means the material has more tensile strength
State the simple workshop test for malleability and ductility
Place sample in vice and bend to 90°. Cracks on the outside indicate a lack of ductility. Cracks on the inside indicate a lack of malleability
State the simple workshop test for corrosion
Place the material sample outside in an area exposed to weather and leave for a set amount of time
States the simple workshop test for electrical conductivity
Place multimeter probes at each end of the sample. Measure the resistance on the multimeter. The higher the resistance, the lower the conductivity.
State the simple workshop test for thermal conductivity
Light a Bunsen burner under the other end of material. Record the time it takes for the temperature to read the set point at the other end of the sample. The shorter the time it takes, the higher the thermal conductivity of the material
State the industrial test for tensile strength
A tensometer machine is used
The standard test piece is held in a clamp at each end
One clamp is fixed and moves on a worm drive gear mechanism
The test piece is stretched, the load and distance traveled is plotted, giving information on the elastic limit, yield point, maximum load & final breaking point after ‘necking’
State and describe the name of the industrial test used to test toughness
The Izod impact test
A notched piece is held vertically to the vice of the machine
A pendulum is released from a set position and swings to strike the piece
The energy absorbed by the test piece is calculated from the height the pendulum swings after it hits the test piece
The material for absorbs the most impact is the toughest and it gives the least pendulum swing
Brittle materials absorb less energy and the pendulum swings further
State the three industrial tests for hardness
The Rockwell test,
The Brinell test
Vickers pyramid test
State a general description of industrial hardness tests
All hardness tests involve a load being applied to the material with the resultant indentation determining its hardness. The smaller the indentation the harder the material
Describe the Rockwell test
A pre-load is applied to the material using a diamond indenter
Diamond is used because it will not deform under load
Preload is the datum position
And additional load his van applied to the test material and held for a predetermined length of time (dwell time)
The load is released and the distance between the preload and applied load is measured
Describe the Brinell test
A hardened standard-sized steel ball is forced into the material’s surface using a preset load and the diameter of the indent in the surface is measured
Describe the Vickers Pyramid test
Used for very hard materials
Uses a diamond Square based pyramid to indent the surface of the material
A microscope is then used to measure the size of the indent
Give two facts about non-destructive testing (NDT)
1) It is used for products rather than materials
2) The product is not destroyed during testing.
