Precision Forming of Metals
The area of Precision Forming of Metals focuses on the most advanced aspects related to the physical and numerical modelling of net-shape and near net-shape operations in both bulk- and sheet-metal forming processes. The close collaboration with forming companies mainly working in the automotive, aerospace and energy sectors and with technology providers as well as the availability of pilot plants and state-of-the-art testing machines provide a sound scientific and industrial value to the innovative research approaches developed in this framework.
Current research lines focus on the
- development and calibration of numerical models of process chains based on bulk and sheet forming processes conducted under cold, warm and hot conditions, taking into account the thermal and mechanical behaviour of the forming dies and machines and the coupling with the post-forming operations;
- testing and modelling rheology, workability and damage, microstructure evolution during bulk and sheet forming conducted under cold, warm and hot conditions;
- testing and modelling boundary conditions (friction and heat transfer coefficients) at workpiece-die interfaces during bulk and sheet forming conducted under cold, warm and hot conditions;
- correlation between the process parameters and the technological and mechanical characteristics (e.g. machinability, hardness, fatigue strength) of the formed component during its service life;
- evaluation of the dynamic behaviour of forming presses and development of smart auxiliary devices (e.g. magneto-rheological dampers) to optimize the process performances.
Forging pilot plant
The screw press pilot plant allows physical simulation tests on forging processes, both at room and elevated temperatures. The screw press provide high precision in energy application and very close tolerance forgings. The machine allows analyzing the coefficient friction and wear mechanisms that are established in the classical massive deformation processes, replicating the most typical industrial process conditions.
Machine characteristics: Nominal force: 2300kN, Ram stroke: 320mm, Die weight: 4,5 kN, Total weight: 6900Kg.
The Instron Wolpert is designed for high-capacity tension, compression, bend/flex, and shear testing of real scale structural components made of diverse materials as metals, woods and concrete. The machine is provided by hydraulic wedges that can even clamp the dies allowing the simulation of real industrial hot and cold forging processes, behaving as an hydraulic forging press.
Machine characteristics: Load capacity: 1000KN,Test stroke: 610 mm, Maximum testing speed: 203 mm/min, Horizontal test opening: 870 mm.
The MTS hydraulic testing machine is used for material testing at room and at high temperatures, as well as dedicated set-up for tribological. The machine is equipped with an induction heating system to carry out the test at elevated temperatures. By using an environmental chamber the testing temperatures can be lowered down to -129°C using LO2.
Configurations: Extrusion test (direct and inverse extrusion), Double Cup Extrusion Test, Hole Expansion Test, Tensile test at room and high temperature, Compression test.
Machine characteristics: Nominal force: ±50 kN, Ram stroke: 0-150 mm, Ram speed: 0.01-150 mm/s, Testing temperature: -129°C – 950°C, Acquisition Frequency: 6000 Hz.
Rockwell hardness tester
The Wilson Rockwell 2000 hardness tester allows the measurement of materials hardness based on the Rockwell hardness test principle. The instrument is electronic controlled and can be programmed by means of a control panel in which the hardness scale and other test parameters can be set. The values of the material hardness are automatically calculated by the instrument control and plotted on the screen. High temperatures measurements are feasible thanks to a heating furnace that can heat up the specimens setting controlled heat cycles.
Machine characteristics: Minimum test temperature: ambient, Maximum test temperature: 725°C, Specimen dimensions: 200x200mm.
The universal UMT-3 tribometer, can be used for the determination of friction coefficient and wear behaviour. The machine is equipped with a specifically designed heating and cooling apparatus to replicate the thermo-mechanical cycles of the hot forming processes.
Machine characteristics: Normal load: 0-1000N, Speed: 0-300 rev/min, Temperature: 20-1000°C, Disk max diameter: 45mm (Hot) 90mm (Cold), Pin max diameter: 6mm.
Software for 3D deformation optical analysis
Aramis™ software allows evaluating the material behaviour under different testing conditions, no contact is required between the system and the samples and it is material independent. The system calculates the evolution of the deformation evaluating the position change and shape modification of the random points created on the sample surface. This system can be used for both tensile and Nakajima tests. In tensile tests, Aramis™ is employed to obtain the true stress strain curves, that describe the flow behaviour of the material, and to calculate the anisotropy parameters. During Nakajima test, Aramis™ allows obtaining the strain values to identify the Forming Limit Diagram (FLD).
Main characteristics: acquisition rate 1-29 fps, strain measuring range (%) 0.005 up to >2000, strain measuring accuracy (%) up to 0.005, specimen temperature -100 up to 1500°C.
Cold and Hot Nakajima test equipment.
Nakajima set-up consists of an hemispherical punch used to bulge the sheet metal specimen clamped between a die and a blank-holder. Cartridge heaters are inserted in both the hemispherical punch and the blank-holder to keep the temperature of the blank during the experiments constant. An induction heating head is used to heat up the blank to the target temperature. Used for characterisation of forming limit diagram (FLD), Cold and Hot (isothermal or non-isothermal) Nakajima test.
Machine characteristics: Internal die radius: 15mm, Specimen thickness: 0.5mm – 1.75mm, Specimen dimension: 200mmx200mm – 30mmx200mm, Nominal punch force: 200 kN, Punch diameter: 100mm, Punch speed: 5-100 mm/s, Testing specimen temperature: 20°C – 950°C.
Cold and Hot torsion test equipment.
Torsion test is a very versatile material-characterization test, which is used both for cold and hot conditions to assess a material rheological behavior for large deformations which are typical of most industrial processes, but which cannot be reached by standard compression tests. Moreover it can be used to assess the material formability in a shear-type stress state, which cannot be attained by standard tensile tests. The experimental apparatus is provided with an induction heating system to heat up the specimen to the target temperature.
Machine characteristics: Max rotation speed: 3000 rpm, Max torque: 240 Nm, Testing temperature range: 20°C-1200°C.
Thermal and mechanical testing system
The Gleeble 3800 is a fully integrated digital closed loop control thermal and mechanical testing system. The direct resistance heating system of the Gleeble 3800 can heat specimens or can hold steady-state equilibrium temperatures. High thermal conductivity grips hold the specimen, making the Gleeble 3800 capable of high cooling rates. The system is a complete, fully integrated hydraulic servo system capable of exerting both compression that tension.
Machine characteristics: Heating and cooling rate up to 2000 °C/s, Compression force up to 20 0 kN, Tensile force up to 100 kN, Displacement rate up to 2000 mm/s.
The induction heating is largely used to heat electrically-conductive materials because it assures a fast, efficient, free flames, aimed and contactless heating process. The generator supplies AC to a coil (the inductor) that generates an electromagnetic filed; positioning the sample in this field, the eddy currents that pass through the material produce an increase of temperature. The heated areas depend on the shape of inductors: different geometrical structures are available to heat tubes, cylindrical specimens and sheets metal. Two generators can be used: Felmi and ATE; they differ in their frequency, high frequency and lower frequency, respectively.
Main characteristics: Felmi’s frequency 50 up to 300 kHz; ATE’s frequency 50 up to 120 kHz.
Finite element software for deformation processes
FORGE® NxT is the software solution for the simulation of hot and cold-forming processes. It enables the simulation of many hot-forming processes such as closed-die forging , open-die forging , rolling , reducer rolling , cross wedge rolling , thread rolling , shape rolling, ring rolling , rotary forging, flow forming, hydroforming , incremental forging, orbital forging , friction welding , extrusion, fastening , wire drawing, deep drawing, shearing, sheet metal forming , piercing, glass forming , blanking cutting , superplastic forming , trimming and some additional non-conventional processes. Cold-forming operations can also be handled. It is suited to quote new components, validate forging sequences, address shop floor issues, improve forging yield and design innovative and high-technology forged products.
Scanning Electron Microscopy (SEM)
The Scanning Electron Microscopy (SEM) allows the determination the chemical composition and structure of the materials, through high energy electron beam in a vacuum. The beam-specimen interaction generates various signals that are acquired by appropriate detectors and subsequently processed to form an image. Magnification range from 6 up to 100'000x.
Accessories: Energy Dispersive X-Ray Analysis (EDS), Environmental Scanning Electron Microscope (ESEM), Electron Backscatter Diffraction (EBSD), heating chamber, up to 1500°C, for analyses at high temperature.