This paper presents a validated finite element modeling approach for simulating shear cutting, needing a minimal amount of experimental characterization. Only one uniaxial tensile test and one force–displacement relationship from a punching experiment are needed for calibration, with maintained prediction accuracy compared to more experimentally demanding approaches. A key ingredient is the observation that the Lode angle parameter is close to zero in the fracture region, postulating that the fracture strain only depends on stress triaxiality, with one free calibration parameter. The true stress–strain behavior is provided from inverse modeling of the tensile test, whereas the fracture model is calibrated using the punching test. The model is verified for different materials by comparing force–displacement curves for punching experiments not used in the calibration. The prediction error for the intrusion is below 4%. A validation is made for two setups. The local residual stresses are measured using Focused Ion-Beam Digital Image Correlation (FIB-DIC). The simulated values are within the experimental bounds. Cut edge morphology and plastic strains obtained by nano-indentation mappings are compared to simulation results, showing a decent agreement. For trimming, the cut edge morphology prediction performance decreases at 17% cutting clearance while it is maintained over the whole range for punching. The predicted hardness values have a mean absolute percentage error below 7.5%. Finally, the effect of element size and remeshing is discussed and quantified. The minimal experimental characterization and simulation effort needed, enables an efficient optimization of the cutting process in the industry.

Shear cutting processes have a detrimental effect on fatigue of high strength metal components. The effect tends to increase with material grade, counteracting the task of reducing weight in chassis components using higher strength materials. Base material fatigue data are often available, but assessment of components with cut edges often require additional costly and time-consuming testing. This paper provides a methodology for estimation of fatigue life reduction by using residual stresses obtained from process simulations, and measured surface roughness in the cut edge. A stress relaxation criterion is applied to handle reduction of the initial local residual stresses. Two complex phase steels and one aluminum alloy are studied for validating the approach. Polished fatigue data is reduced to estimate S–N curves of trimmed and punched specimens at different load ratios. Good agreement between the model and test results are found for all cases. The needed data for the predictions are only a high cycle S–N relationship for polished material, uniaxial tensile properties, and the cut edge fracture surface residual stress and roughness without any parameter fitting, making it a convenient tool for estimating the reduction in fatigue life and for parameter studies.

Sheet metal punching is an important process in manufacturing of heavy-duty vehicle chassis components. The cut edges have a detrimental effect on high cycle fatigue life in uniaxial- and in-plane-bending but the reduction is less pronounced in out-of-plane bending. This paper aims to explain the reduced process sensitivity in out-of-plane bending fatigue, to quantify the high cycle fatigue life reduction at different load ratios, and to propose a methodology for fatigue life estimation. This could enhance the possibilities to identify critical load cases of chassis components, to judge whether fatigue life improving post-processes are necessary, and to locate critical initiation sites for fatigue. Fatigue testing of punched and polished specimens was conducted, and the punching process and four-point bending were simulated using FEM. The results were used to estimate crack initiation site, fatigue life reduction, and for validating the predictions. Fatigue life reduction is found to increase with increased load ratio, but to a smaller extent than expected. A contributing factor the reduced tensile residual stresses due to plasticity during the first load cycle. The reduced process sensitivity as compared to uniaxial fatigue could be explained by the separate locations of crack initiation and high tensile residual stresses in the cut edge. Specimen orientation seems to have a minor influence on the fatigue life. Only improving the outer surfaces, and not the central parts of the cut edge, could increase the high cycle fatigue life for pulsating and reversed loading.

Stamping and shot peening of chassis components such as wheels and cross beams introduce residual stresses that affect the fatigue life. The tensile residual stresses from stamping are often found in the most critical areas for fatigue. These areas are commonly subject to bending stress states while smooth material fatigue data for steel sheets more commonly is obtained by uniaxial testing. Both the sensitivity to residual stresses and change in load condition are material dependent posing a challenge in fatigue life estimation of formed and shot-peened specimens. This paper aims to provide a convenient tool for high cycle fatigue life estimations in these conditions solely dependent on uniaxial tensile properties without parameter fitting. The underlying causes for the material dependency is discussed and reflected in the methodology. Uniaxial fatigue testing and fatigue testing of formed specimens with and without subsequent shot peening are performed for validation.