Ring Compression Test


  Ring compression test has been widely used as a test to evaluate the friction condition in metal forming process.


THE PRINCIPLE OF RING TEST

For given conditions of temperature, strain, strain rate and initial specimen geometry of OD:ID:H the deformation of internal diameter of ring may be calculated as a unique function of interfacial friction coefficient.

Geometrical Change and Friction Condition


When a short ring specimen is plastically compressed  between two flat parallel platens (a), the internal diameter of the ring is increased if interface friction is low (b) and it is decreased if this friction is high (c) 

By measuring the change of the internal diameter, it is possible to evaluate friction condition, through the use of a friction calibration curve

For various forming conditions, the value of “m” vary as follows:



CASE A  : RING TEST SIMULATION FOR M=0.0
Material:AlZn5.6Mg2.5Cu1.6
Friction Shear Factor:m = 0.0
Dimensions:OD = 60mm, ID=30mm, Height = 20mm
Ring Temperature: 300 C
Die Temperature:250 C
% Reduction in height    : 50%( 10 mm)

Simulation Results
Final ID:42.0989 mm
% Decrease in ID:-40.3297 %
% Reduction in Height    :50%


CASE B : RING TEST SIMULATION FOR M=0.10
Material :AlZn5.6Mg2.5Cu1.6
Friction Shear Factor:m = 0.10
Dimensions:OD = 60mm, ID=30mm, Height = 20mm
Ring Temperature: 300 C
Die Temperature:250 C
% Reduction in height    : 50%( 10 mm)

Simulation Results
Final ID:34.5300 mm
% Decrease in ID:-15.1000 %
% Reduction in Height    :50%


CASE C : RING TEST SIMULATION FOR M=0.30
Material :AlZn5.6Mg2.5Cu1.6
Friction Shear Factor:m = 0.30
Dimensions:OD = 60mm, ID=30mm, Height = 20mm
Ring Temperature: 300 C
Die Temperature:250 C
% Reduction in height    : 50%( 10 mm)

Simulation Results
Final ID:25.8003 mm
% Decrease in ID:13.9990 %
% Reduction in Height    :50%


CASE D : SIMULATION FOR M=0.40
Material:AlZn5.6Mg2.5Cu1.6
Friction Shear Factor:m = 0.40
Dimensions:OD = 60mm, ID=30mm, Height = 20mm
Ring Temperature: 300 C
Die Temperature:250 C
% Reduction in height    : 50%( 10 mm)

Simulation Results
Final ID:22.6611 mm
% Decrease in ID:24.4630 %
% Reduction in Height    :50%


COMPARISION


A ring test simulation will be preformed for two different friction shear factors, one material, one press setup. The simulation is non-isothermal, therefore heat transfer at the interface is considered
The simulations show how temperature and shear friction factor affect metal flow and ring geometry. Compared to isothermal, non-isothermal deformation causes the level of friction to increase.