TENSILE TESTING-Lab 3

   Test specimens of  6061-T6 aluminum    1018 cold rolled steel PMMA (polymethymethacrylate) (cast acrylic) Polycarbonate (PC) ASTM E8/E8M testing standards Tensile test machine  INSTRON 5585H Series Floor Model Testing Systems

Universal Testing Equipments

    Universal testing machines first became widely used from 1900 to 1920.

Used to apply forces to specimens Vary from simple devices to complex systems that are controlled by computer Tensile Testing – loads are applied:   Mechanically with screw drives Hydraulically with pressurized oil/piston

Screw-Driven Machines

     Mechanical screw driven machine Rotation of large threaded screws moves the crosshead that applies a force to the specimen Before load cells, force was measured by weighing the system (see Dowling Figure 4.3) High accuracy High cost

Hydraulic Piston

    Preferred because of their higher load capacities, lower cost and accuracy (with the introduction of digital control loops) Applied by using the pressure oil pumped into hydraulic piston Before load cell force was measured by The pressure of the oil in the system.

Oil in the cylinder is controlled by means of coarse and fine – load and unload valves

Instron

    Established in 1946, Boston, MA Owners: Harold Hindman & George Burr – Both MIT graduates Decided to fulfill the need for machines used for testing new materials used in parachutes.

Designed first material testing machine based on strain gauge load cells and servo control  @1958 MTS Systems Corp used transistor technology and closed-loop concepts for the first time

Instron types (screw driven)

Single column Dual column Floor column

Instron 5585H Series Floor Model Testing

for tension, compression, bending and component testing 250kN (56,250 lbf) capacity 0.001-500 mm/min (0.00004 – 20 in/min) speed range 1256 mm x 575 mm (49.4 in x 22.6 in) test area Bluehill ® 2 Software compatibility

Testing Machine & specimen

load cell Load train Load frame crosshead LVDT universal joint grip specimen grip universal joint Load train Dogbone specimen grip fillet grip gage section Clip-on extensometer

Load Cell and Extensometer

      Both based on strain-gaged beam with mounted wheat stone bridge Load signals actually strain readings calibrated to appropriate loading levels UW ME Instron is capable of 250kN Clip-on axial and transverse extensometers Both send analog electronic signals to Instron control tower Bluehill (software) is used to retrieve the data

LVDT

   linear variable differential transformer a type of electrical transformer used for measuring linear displacement RVDT is the rotary variable differential transformer to measure angular displacement