Onur Çavuşoğlu

In this study, the effects of post-aging conditions on the mechanical properties, deformation behavior, and fracture characteristics of 6082-T6 aluminum alloy sheets were investigated, using tensile testing supported by DIC. Post-aging treatments were performed at 100 °C, 200 °C, 300 °C, and 400 °C, with holding times of 30, 60, and 90 min at each temperature. The following parameters were determined from the tensile tests: yield strength, tensile strength, strain-hardening exponent, uniform elongation, total elongation, and energy absorption capacity. Microstructural and fracture analyses were performed using optical microscopy and scanning electron microscopy, while x-ray diffraction was used to evaluate phase-related structural changes. Hardness variations were assessed by Vickers hardness testing. Fracture-surface dimple morphologies were quantitatively evaluated using average dimple diameter and standard deviation values to assess the temperature- and time-dependent variation in fracture behavior. The results showed that aging at 200 °C for 60 min provided a highly favorable strength–ductility balance and was identified as the most efficient processing condition in terms of the combined mechanical response, with a yield strength of approximately 289 MPa, tensile strength of about 400 MPa, uniform elongation of 15.9%, total elongation of 17.4%, hardness of 115.6 HV, and energy absorption of 61.36 MJ m ⁻³ . At 300 °C–400 °C, pronounced overaging occurred as precipitate coarsening reduced the effectiveness of precipitation strengthening, leading to significant degradation in mechanical performance. The strain-hardening response and energy absorption capacity were found to be strongly dependent on the aging condition. The results indicate a transition from relatively homogeneous deformation to strain-localized behavior as aging temperature increases, consistent with reduced deformation stability at elevated temperatures. Overall, these findings demonstrate that controlled post-aging can tailor the strength–ductility balance and fracture response of AA6082-T6 sheets.

Twinning-induced plasticity (TWIP) steels represent a significant development in automotive steel production, characterized by advanced strength and ductility properties. The present study empirically investigated the effects of process parameters on the cutting process and surface quality of TWIP980 steel sheet by abrasive water jet (AWJ) cutting. The cutting experiments were conducted on 1.4 mm thick sheet metal using four different traverse speeds (50, 100, 200, and 400 mm/min) and four different water jet pressures (1500, 2000, 2500, and 3000 bar). Two different abrasive flow rates (300 and 600 g/min) were also utilized. The cut surfaces were characterized in three dimensions with an optical profilometer. The parameters of surface roughness, kerf width, taper angle, and material removal rate (MRR) were determined. Furthermore, microhardness measurements were conducted on the cut surfaces. The optimal surface quality and geometrical accuracy were achieved by applying a combination of parameters, including 3000 bar of pressure, a traverse rate of 400 mm/min, and an abrasive flow rate of 600 g/min. Concurrently, an effective cutting performance with increased MRR and reduced taper angles was achieved under these conditions. The observed increase in microhardness with increasing pressure is attributable to a hardening effect resulting from local plastic deformation.

The use of aluminum alloys for lightweighting in the automotive industry is becoming widespread. In this study, Johnson–Cook plasticity and damage model parameters were determined to predict the plasticity and damage behavior of 6181A-T4 sheet material using finite element analysis software. Uniaxial tensile tests were performed at four different deformation rates (0.0083–0.333 s⁻¹) using tensile test specimens with four different triaxiality values (0.33, 0.36, 0.45, and 0.74). For a 3 mm thick 6181A-T4 aluminum alloy sheet, Johnson–Cook plasticity parameters were determined by the curve fitting method, and damage parameters were optimized using LS-OPT 7.0 software. Finite element analyses using Johnson–Cook plasticity and damage model parameters were compared with the experimental results, and it was observed that the finite element analyses produced very successful predictions. With the increase in strain rate, the yield strength increased, while the tensile strength showed limited change; uniform elongation, coefficient of hardening, and toughness showed a decreasing trend, and the fracture mode showed a transition from ductile to more brittle behavior. The coefficient of determination (R²) values between the Johnson–Cook model and the experimental data ranged from 0.8601 to 0.9837 depending on the strain-rate value.

The aging of commercial DP600 dual-phase steel under different pre-strain levels was conducted up to three times at 140 °C and 190 °C to investigate the effects of cyclic static strain aging (CSSA) on the material's mechanical properties. As the number of CSSA processes increased, the yield stress values exhibited a notable increase compared to those of the raw material. However, the yield strength demonstrated a tendency to decrease when the material was subjected to three cycles of strain aging at 140 °C. The yield stress values of dual-phase steels subjected to strain aging at 190 °C were higher than those of materials aged at 140 °C. As the CSSA temperature increased, the tensile stress values demonstrated a corresponding rise. However, the maximum tensile stress values of dual-phase steel demonstrated a decline with an increase in the number of CSSA repeats. Moreover, a reduction in Brinell hardness values was noted concurrently with an increase in ultimate tensile strength values. However, an inverse relationship was identified between the data points and the yield stress values. It was observed that the continuous yield property of dual-phase steel was lost following two and three CSSA processes at 190 °C.

The objective of this study was to examine the influence of martensite particle size on the formation of stress and strain in microstructures of dual-phase steels. In order to achieve this objective, the 3D representative volume element (RVE) method was utilized. Particle size distributions were obtained from the microstructures of DP600 and DP1000 dual-phase steels as they actually exist. Virtual dual-phase steel microstructures were generated according to the above distribution and subsequent validation analyses were performed. In the subsequent phase, microstructures of varying martensite particle sizes (1 µm, 1.98 µm, 3 µm for DP600 and 1.15 µm, 2 µm, 3 µm for DP1000) were formed, and the effects of particle size on deformation behavior under tensile loads were determined. The findings indicated that an increase in martensite particle size resulted in a reduction in tensile strength, accompanied by an increase in deformation amount.

In this study, the effects of punch edge radius and blanking clearance on product quality and blanking process in blanking of AISI 304 stainless steel sheet were investigated by using the fi-nite element analysis method. The blanking analyzes were performed at four different punch tip radii (0.01, 0.25, 0.5, 1 mm) and three different blanking clearance (1 %, 5%, 10%). As a result of the analysis, rollover, burr length increased, smooth sheared / fractured surface ratio and blanking force decreased with the increase in blanking clearance. Depending on the increase in the amount of punch tip radius, the blanking force, and burr length also increased, and the smooth sheared / fractured surface ratio decreased compared to the blanking process with flat punches.