Ultra-high-strength steels (UHSS) combined with tailor-stamping technologies are increasingly being adopted in automotive body production due to crashworthiness improvements and part weight reduction, which meet safety and energy saving demands. Recently, USIBOR®2000 (37MnB5) steel has been added to the family of UHSS. This new material allows higher performance with respect to its predecessor USIBOR®1500 (22MnB5). In this work, the two steels are compared for the manufacturing of an automotive B-Pillar by press-hardening with a tailored tool tempering approach. A Finite Element (FE) model has been developed for the numerical simulation of thermomechanical cycles of the press-hardening process. The FE-simulations have been performed with the aim of obtaining soft zones in the part, by varying the quenching time and the temperature of heated tools. The effects of these parameters on the mechanical properties of the part have been experimentally evaluated thanks to hardness and tensile tests performed on specimens subjected to the numerical thermo-mechanical cycles using the Geeble-3180 physical simulator. The results show that for both UHSS, an increase in quenching time leads to a decrease in hardness up to a threshold value, which is lower for the USIBOR®1500. Moreover, higher mechanical resistance and lower elongation at break values are derived for the USIBOR®2000 steel than for USIBOR®1500 steel.

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The study focuses on the analysis of the softening effects of the work-hardened aluminum alloy sheets EN AW 5754 H32 1.5 mm thick, through the physical simulation of thermal cycles induced in the material by laser heat treatments (LHTs). A numerical-experimental approach was implemented to define the laser thermal cycles and to subsequently reproduce them on the GleebleTM 3180 physical simulator. The obtained softening was measured by microhardness and metallographic analysis tests. For the definition of laser thermal cycles, preliminary tests with a 2.5 kW CO2 laser source have been realized, and a three-dimensional transient finite element thermal models were developed and calibrated with the experimental results. The investigated laser heat treatment parameters explored thermal cycles with different shape, interaction time, and peak temperature. Physical simulation tests were performed using laser thermal cycles that showed the maximum softening of the aluminum alloy. A three-dimensional transient finite element thermoelectric model was developed to design the shape of the Gleeble specimens, which satisfy the heating and cooling rate required by laser thermal cycles. Results obtained show that it is possible to physically simulate the investigated laser thermal cycles, reducing the cross section of the shaped part of the specimen. Softening effects depend on the thermal cycle shape. Greater softening is observed by increasing the interaction time and the peak temperature, but beyond a peak temperature threshold value, negligible effects are detected.

The main goals of the transport industry are lightweight and the increase in safety for passengers. Consequently, the choice of materials is very important. The materials adopted in recent years are lightweight alloys, such as aluminum and magnesium alloys, carbon fiber-reinforced polymers, and advanced highstrength steel (AHSS). In the automotive industry, five classes of AHSS are distinguished: dual-phase steel (DP), complex phase steel (CP), transformationinduced plasticity steel (TRIP), martensitic steel (MART), and press-hardened steel (PHS). [1,2] DP steels are ferritic-martensitic phase steels, which exhibit a strength between 450 and 1400 MPa depending on the amount of martensite. [3] Complex phase steels contain bainitic, martensitic, and ferritic phases and show higher formability than DP ones. [1] TRIP steels are characterized by a certain amount of retained austenite phase, which transforms into the martensite phase during the deformation. This effect helps the distribution of the strain and increases elongation, justifying the greater formability of TRIP steels compared to CP and DP steels. [1,4] Martensitic steels have high strength levels but show very low formability. Finally, the press-hardened steels are typically carbonmanganese-boron alloyed steels, [5] which are generally adopted in the press hardening (PH) process where the unformed blank is heated in a furnace up to the complete austenitization temperature, formed in the hot condition and finally quenched in the die. These steels are typically delivered in ferritic-pearlitic conditions and have, at the end of the PH process, almost doubled resistance levels due to the transformation into the martensitic phase due to the quenching phase. Among the PHS, the most common one is the 22MnB5; [5] however, other steel grades with higher carbon content are recently proposed to be used in the PH process. [6][7][8] PHS combined with the PH process allow to satisfy at the same time the requirements related to safety and those related to vehicle weight reduction, [9] therefore they are increasingly adopted in anti-intrusion applications of automotive structures (bumpers, doors, bodies-in-white).Current innovation trends are aimed at opportunities these AHSS offer in terms of tailored mechanical properties. [10][11][12][13][14] Currently, the stamped part designing with customized performances includes forming technologies that use tailor rolled blanks, tailor welded blanks, patchwork blanks, tailor tool tempering, tailor heating, and tailor cooling process. [15] A great deal of research has been carried out around the tool tempering approach in recent years. [12,13,16] With this approach, the tailored properties are achieved by exploiting different cooling conditions during the

In recent decades, the automotive industry has had a constant evolution with consequent enhancement of products quality. In industrial applications, quality may be defined as conformance to product specifications and repeatability of manufacturing process. Moreover, in the modern era of Industry 4.0, research on technological innovation has made the real-time control of manufacturing process possible. Moving from the above context, a method is proposed to perform real-time control of a deep-drawing process, using the stamping of the upper front cross member of a car chassis as industrial case study. In particular, it is proposed to calibrate the force acting on the blank holder, defining a regulation curve that considers the material yield stress and the friction coefficient as the main noise variables of the process. Firstly, deep-drawing process was modeled by using commercial Finite Element (FE) software AutoForm. By means of AutoForm Sigma tool, the stability and capability of deep-drawing process were analyzed. Numerical results were then exploited to create metamodels, by using the kriging technique, which shows the relationships between the process parameters and appropriate quality indices. Multi-objective optimization with a desirability function was carried out to identify the optimal values of input parameters for deep-drawing process. Finally, the desired regulation curve was obtained by maximizing total desirability. The resulting regulation curve can be exploited as a useful tool for real-time control of the force acting on the blank holder.

The applicability of active thermography as a non-destructive method to distinguish heat treated from not-treated boron steel has been investigated. While the usual hardness semi-destructive tests influence the inspected surface, laser thermography is capable of verifying the effectiveness of heat treatment in boron steel in a non-destructive way without any surface modification. The procedure has been verified on two plates of boron steels with different structures (100% ferritic–pearlitic and 100% martensitic).

The automotive industry is interested in manufacturing components with tailored mechanical properties. To this end, advanced heating treatments can be exploited to obtain the so-called Tailored Heat-Treated Blanks (THTB). However, mechanical properties are strongly affected by the process parameters of heating treatments, which require a preliminary design. Physical simulation can be a decisive tool in this phase to obtain useful information at the laboratory scale, even when heat treatments such as those carried out with laser technologies impose high heating and cooling rates on the material. This work uses physical simulation to investigate the changes in strength and ductility caused by laser heat treatment (LHT) on aluminum alloys hardened by aging; the methodology was implemented on the EN AW 6082 T6 alloy. First, a finite-element (FE) transient thermal model was developed to simulate LHT by varying the process parameters (laser power/peak temperature and treatment speed). Second, the resulting thermal cycles were physically simulated by means of the Gleeble 3180 system. Third, the strength and the ductility of physically simulated specimens were evaluated through micro-hardness and tensile tests; to study aging effects, investigations were performed both (i) right after Gleeble tests (samples in the supersaturated solid state, i.e., as-physically simulated (APS) state) and (ii) after one week from Gleeble tests (aged specimens—T4 state). The obtained results show that there are peak temperatures that guarantee maximum softening levels for each investigated state (T4 and APS). The optimal peak temperature ranges are in agreement with the data in the literature, demonstrating that the proposed methodology is suitable for the study of softening phenomena on aging-hardened aluminum alloys.

Recently, metals have been processed with fused filament fabrication (FFF) printers, in the form of mixture of metal powder and a polymeric binder. This new area of additive manufacturing is called metal-fused filament fabrication (metal FFF), and it is characterized by several advantages: low cost of manufacturing for small batches, ease of use, lower cost of energy and lower risks compared to the main metal additive manufacturing technologies. Being a novel technique, it is of great importance to understand the mechanical behaviour of the fabricated parts to reach the potential applications. In this work, the mechanical response of parts printed by metal FFF was analysed by means of digital image correlation (DIC) technique. This latter allowed to better highlight the anisotropic mechanical behaviour of the FFF parts when varying some 3D printing parameters, such as building orientation and number of wall layers and enabled a complete characterization of material useful for numerical calculation and finite element analysis. With this aim, 316L stainless steel filament and a consumer 3D printer were used for the fabrication of tensile test specimens. Three different building orientations and three different numbers of wall layers were evaluated. Results obtained from the tensile tests conducted with the DIC system highlighted the anisotropy of the strain behaviour when varying building orientation and printing strategy. More in details, flatwise and sideways configurations returned higher values of tensile strength, elongation at break and Poisson’s ratio compared to upright one, while the increase of number of wall layers, in some cases, caused a decrease of the mechanical properties.