http://ercnsm.osu.edu/sites/ercnsm.osu.edu/files/uploads/S_press/650.pdf

Mechanical servo press technology for metal forming

The paper deals with the testing and modelling of metals response when subjected to sheet forming operations. The focus is both on the modelling of hardening behaviour and yield criteria and on the description of the sheet metal formability limits. Within this scope, the paper provides a critical review of the models available today for predicting the material behaviour at both industrial and scientific level, and the tests needed to identify the models’ material parameters. The most recent advances in the field are also presented and discussed with particular emphasis on the challenges the sheet metal forming community is now facing.

Testing and modelling of material behaviour and formability in sheet metal forming

An experimental study on the comparative assessment of hydraulic bulge test analysis methods

In order to fully characterize the plasticity and fracture of magnesium AZ31B-H24 sheets, a set of mechanical experiments (105 in total) were performed under different loading conditions, including monotonic uniaxial tension, notch tension, in-plane uniaxial compression, wide compression (or called biaxial compression), plane strain compression, through-thickness compression, in-plane shear, punch test, and uniaxial compression–tension reverse loading. Both the plastic strain histories and stress responses were obtained under the above loading conditions, which give a comprehensive picture of mechanical behaviors of this material. An orthotropic yield criterion involving two linear anisotropic transformation tensors, CPB06ex2, in conjunction with its associated flow rule, and a modified semi-analytical Sachs isotropic hardening model was fully calibrated to describe both the anisotropy in plastic flow and tension–compression asymmetry in stress–strain behaviors. An all-strain based modified-Mohr–Coulomb fracture model, transformed from a stress triaxiality based model, was applied to describe the calibrated fracture locus. Applying a linear transformation to the plastic strain tensor, a non-conjugated anisotropic equivalent strain was proposed to characterize anisotropic fracture behaviors. Good correlations were achieved between experimental results and model predictions in terms of material yield strengths, strain hardening curves, plastic flow directions and ductile fracture strains.

Experimental study on the mechanical properties of AZ31B-H24 magnesium alloy sheets under various loading conditions

Experimental studies of deep drawing of AZ31B magnesium alloy sheet under various thermal conditions

Elevated temperature hydraulic bulge tests for Mg AZ31-O alloy sheets were conducted using a submerged tool, designed to minimize the temperature variation in the sheet. Experiments were conducted between room temperature and 225 °C, at various approximate true strain rates. Bulge profiles at different bulge heights were measured using a CMM and the best radius values were calculated through least-square fit using several measured points. Residual plots were made to demonstrate the amount of deviation from a sphere with increasing bulge height. Measured and calculated bulge radius and thickness values were compared with the available analytical models. Amount of error that occurs in flow stress calculation by deploying the well-known membrane theory was investigated.

Determination of the flow stress of magnesium AZ31-O sheet at elevated temperatures using the hydraulic bulge test

An Experimental Study on Nonisothermal Deep Drawing Process Using Aluminum and Magnesium Alloys

Experimental and viscoplastic finite element analysis (FEA) of thermo-mechanical plastic deformation in nonisothermal warm deep drawing is studied using SS304. A nonisothermal deep drawing tool is used in a servo-motor-controlled press. Drawability window of SS304 under elevated temperatures (25–225 °C) and low to high strain rates (drawing speeds of 2.5, 25, and 50 mm/s) were determined. A viscoplastic thermal material model is adopted for nonwork softening material behaviors, as seen in low-temperature forming of SS304, and found to be easily applicable and quite satisfactory. Tensile and equi-biaxial bulge tests were conducted for more accurate flow stress data to be used in FEA. Measured punch load–stroke and cup’s curvilinear thickness (rolling/transverse) curves were successfully compared with predictions from the nonisothermal FE model of the warm deep drawing.

Nonisothermal warm deep drawing of SS304: FE modeling and experiments using servo press

The effect of extrusion method and lubrication on formability of aluminum tubes in hydroforming is experimentally investigated. First, the formability differences between seamless and porthole aluminum 6063 and 6260 alloy tubes, at T1 and T6 heat treatment conditions, are studied using free bulging. Second, the performances of a wide range of lubricants are ranked using zone-dependent friction tests, e.g., guiding zone and expansion zone, which emulate the two different interface mechanics existing in a THF operation. Results showed that seamless tubes, under any condition, give 5 % more expansion compared to porthole. Also, if a tube has T6 condition, seamless shows clear formability advantage over porthole. However, porthole is found to be quite satisfactory for tubes at T1 condition since they achieved more than %10 expansion. “Zone-dependent” (expansion zone and guiding zone) lubrication tests are conducted using wet and dry lubricants. Results showed that while a dry lubricant performed best in the expansion zone, a wet lubricant performed best in the guiding zone.

Serhat Kaya

Papers

Determination of the flow stress of magnesium AZ31-O sheet at elevated temperatures using the hydraulic bulge test

An Experimental Study on Nonisothermal Deep Drawing Process Using Aluminum and Magnesium Alloys

Nonisothermal warm deep drawing of SS304: FE modeling and experiments using servo press

Evaluating porthole and seamless aluminum tubes and lubricants for hydroforming

Improving the formability limts of lightweight metal alloy sheet using advanced processes -finite element modeling and experimental validation-