Ductile fracture modeling of metallic materials: a short review

Since the end of the last century a lot of research on ductile damaging and fracture process has been carried out. The interest and the attention on the topic are due to several aspects. The margin to reduce the costs of production or maintenance can be still improved by a better knowledge of the ductile failure, leading to the necessity to overcome traditional approaches. New materials or technologies introduced in the industrial market require new strategies and approaches to model the metal behavior. In particular, the increase of the computational power together with the use of finite elements (FE), extended finite elements (X-FE), discrete elements (DE) methods need the formulation of constitutive models capable of describing accurately the physical phenomenon of the damaging process. Therefore, the recent development of novel constitutive models and damage criteria. This work offers an overview on the current state of the art in non-linear deformation and damaging process reviewing the main constitutive models and their numerical applications

Ductile damage evolution law for proportional and non-proportional loading conditions

The characterization of ductile damage evolution, and its description, have been the object of extensive research in the continuum damage mechanic field. Many different models have been developed since the pioneering works carried out a few decades ago. In detail, the stress triaxiality and the Lode angle parameters have been identified as the two main variables that affect the material ductility. The literature offers a great number of investigations under monotonic loading conditions, however, a proper characterization of the damage evolution under cyclic loading or non-proportional loading is still missing. In this paper, an unconventional coupled elastoplastic and damage constitutive model with a Mohr-Coulomb failure criterion is presented. The novelty of this study is represented by the modification of the ductile damage law in order to consider the damage evolution under non-proportional loading conditions. Therefore, the idea is to investigate the structural response of a steel bridge column subjected to a cyclic non-proportional loading, showing how, a different approach in the description of the ductile damage evolution, is necessary for a realistic description of the pier behavior

Ductile damage evolution law for proportional and non-proportional loading conditions

The characterization of ductile damage evolution, and its description, have been the object of extensive research in the continuum damage mechanic field. Many different models have been developed since the pioneering works carried out a few decades ago. In detail, the stress triaxiality and the Lode angle parameters have been identified as the two main variables that affect the material ductility. The literature offers a great number of investigations under monotonic loading conditions, however, a proper characterization of the damage evolution under cyclic loading or nonproportional loading is still missing. In this paper, an unconventional coupled elastoplastic and damage constitutive model with a Mohr-Coulomb failure criterion is presented. The novelty of this study is represented by the modification of the ductile damage law in order to consider the damage evolution under non-proportional loading conditions. Therefore, the idea is to investigate the structural response of a steel bridge column subjected to a cyclic non-proportional loading, showing how, a different approach in the description of the ductile damage evolution, is necessary for a realistic description of the pier behaviou

Correlation between frontal lobe oxy-hemoglobin and severity of depression assessed using near-infrared spectroscopy

AbstractIntroductionThe search for objective biomarkers of psychiatric disorders has a long history. Despite this, no universally accepted instruments or methods to detect biomarkers have been developed. One potential exception is near-infrared spectroscopy, although interpreting the measures of blood flow recorded with this technique remains controversial. In this study, we aimed to investigate the relationship between recorded blood flow and depression severity assessed using the Hamilton depression scale in patients with various psychiatric disorders.MethodsEnrolled patients (n=43) had DSM-IV diagnoses of major depressive disorder (n=25), bipolar disorder I (n=5), schizophrenia (n=3), dysthymic disorder (n=3), psychotic disorder (n=3), panic disorder (n=2), and Obsessive Compulsive Disorder (n=2). The verbal fluency task was administered during blood flow recording from the frontal and temporal lobes.ResultsWe found that severity of depression was negatively correlated with the integral value of blood flow in the frontal lobe, irrespective of psychiatric diagnosis (F=5.94, p=0.02).DiscussionOur results support blood flow in the frontal lobe as a potential biomarker of depression severity across various psychiatric disorders.LimitationLimited sample size, no replication in the second set

Femtosecond laser peening of 2024 aluminum alloy without a sacrificial overlay under atmospheric conditions

The authors have successfully performed femtosecond laser peening on a 2024 aluminum alloy without any sacrificial overlays. Laser pulses were directly irradiated to the surface of specimens in the air without water film as a plasma confinement medium during the peening treatment. The fatigue life was improved as much as 38 times in comparison with base material at a stress amplitude of 195 MPa. The fatigue strength of the peened specimen after 2 × 106 cycles was 58 MPa larger than that of the base material. The femtosecond laser peening process has a great potential to be applied in various fields where conventional peening methods cannot be used, as this process can be performed under ambient conditions without the use of a plasma confinement medium such as water or transparent materials.Sano T., Eimura T., Kashiwabara R., et al. Femtosecond laser peening of 2024 aluminum alloy without a sacrificial overlay under atmospheric conditions. Journal of Laser Applications, 29, 1, 012005. https://doi.org/10.2351/1.4967013