Numerical Analysis of Edge Cracking in High-Silicon Steel during Cold Rolling with 3D Fracture Locus

In this study, a 3D fracture locus of high-silicon steel strip was constructed through a series of fracture tests with specimens of various shapes and corresponding finite element (FE) simulations of the fracture tests. A series of FE analyses coupled with the developed fracture locus was conducted, and the effect of the secondary roll-bending ratio (defined as L2/R2, where L2 and R2, respectively, denote the secondary work roll barrel length and the radius of the convex curvature of the work roll surface profile emulating positive roll bending) and the initial notch length on edge cracking in the strip during cold rolling was investigated. The results reveal that the 2D fracture locus that does not include the Lode angle parameter (varying between −0.81 and 0.72 during cold rolling) overestimates the edge cracking in the range of 13.1–22.2%. The effect of the initial notch length on the length of crack grown in the transverse direction of the strip during cold rolling is greatest when the ratio L2/R2 is 0.12.

Individual variation of tentorial notch morphometry in a series of neurocritical patients

ABSTRACT Background: Cadaveric studies on humans have shown anatomical variabilities in the morphometric characteristics of the tentorial notch. These anatomical variations could influence the worsening of neurocritical patients. Objectives: 1) To investigate the morphometric characteristics of the tentorial notch in neurocritical patients using computed tomography (CT); 2) To investigate the correlation between tentorial notch measurements by CT and by magnetic resonance imaging (MRI); and 3) To analyze the individual variability of the tentorial notch anatomy seen in neurocritical patients. Methods: Prospective series of neurocritical patients was examined. An imaging protocol for measurements was designed for CT and MRI. The level of the agreement of the measurements from CT and MR images was established. According to the measurements found, patients were divided into different types of tentorial notch. Results: We studied 34 neurocritical patients by CT and MRI. Measurements of the tentorial notch via CT and MRI showed significant agreement: concordance correlation coefficient of 0.96 for notch length and 0.85 for maximum width of tentorial notch. Classification of tentorial notch measurements according to the criteria established by Adler and Milhorat, we found the following: 15 patients (58%) corresponded to a "short" subtype; 7 (21%) to "small"; 3 (9%) to "narrow"; 2 (6%) to "wide"; 2 (6%) to “large”; 1 (3%) to “long”; and 4 (12%) to "typical". Conclusions: The anatomical variability of the tentorial notch could be detected in vivo by means of CT scan and MRI. Good agreement between the measurements made using these two imaging methods was found.

Failure Mechanism of Rock Specimens with a Notched Hole under Compression—A Numerical Study

Discontinuities are natural structures that exist in rocks and can affect the stability of rock structures. In this article, the influence of notch presence on the strength and failure evolution around a hole in compressed rock specimens is investigated numerically. Firstly, the uniaxial compressive test on a rock specimen with a circular hole is modeled, and the failure evolution in the specimen is simulated. In a separate model, notches are created at the surface of the hole. Results show that, when the notches are created in the model, a failure zone around the hole is transferred to a distance away from the surface of the hole. In addition, a parametric study is carried out to investigate the influence of the notch length and the confining pressure on the fracturing behavior of the specimen. Numerical results presented in this article indicate that the presence of notches at the surface of the hole and their dimensions can affect the fracturing mechanism of the specimen. In some cases, the failure at the boundary of the hole is prevented when the notches of certain dimensions are added to the hole. The insights gained from this numerical study may be helpful to control the failure around underground excavations.

Failure Mechanism of Rock Specimens with a Notched Hole Under Compression - A Numerical Study

Discontinuities are natural structures that exist in rocks and can affect the stability of rock structures. In this article, the influence of notch presence on the failure evolution around a hole in compressed rock specimens is investigated numerically. Firstly, the uniaxial compressive test on a rock specimen with a circular hole is modeled and the failure evolution in the specimen is simulated. In a separate model, notches are created at the surface of the hole. Results show that when the notches are created in the model, failure zone around the hole is transferred to a distance away from the surface of the hole. In addition, a parametric study is carried out to investigate the influence of the notch length and the confining pressure on the fracturing behavior of the specimen. Numerical results presented in this article indicate that the presence of notches at the surface of the hole and their dimensions can affect the fracturing mechanism of the specimen. In some cases, the failure at the boundary of the hole is prevented when the notches of certain dimensions are added to the hole. The insights gained from this numerical study may be helpful to control the failure around underground excavations.

Fracture Parameters and Cracking Propagation of Cold Recycled Mixture Considering Material Heterogeneity Based on Extended Finite Element Method

Cold recycled mixture (CRM) has been widely used around the world mainly because of its good ability to resist reflection cracking. In this study, mixed-mode cracking tests were carried out by the designed rotary test device to evaluate the cracking resistance of CRM. Through the finite element method, the heterogeneous model of CRM based on its meso-structure was established. The cracking process of CRM was simulated using the extended finite element method, and the influence of different notch lengths on its anti-cracking performance was studied. The results show that the mixed-mode fracture test method can effectively evaluate the cracking resistance of CRM by the proposed fracture parameters. The virtual tests under three of five kinds of mixed-cracking modes have good simulation to capture the cracking behavior of CRM. The effect of notch length on the initial crack angle and the crack propagation process of the CRM is mainly related to the distribution characteristics of its meso-structure. With the increase of the proportion of Mode II cracking, the crack development path gradually deviates, and the failure elements gradually increase. At any mixed-mode level, there is an obvious linear relationship between the peak load, fracture energy, and the notch length.

Designing a Compact Microstrip Antenna Using the Machine Learning Approach

This paper presents how machine learning techniques may be applied in the process of designing a compact dual-band H-shaped rectangular microstrip antenna (RMSA) operating in 0.75–2.20 GHz and 3.0–3.44 GHz frequency ranges. In the design process, the same dimensions of upper and lower notches are incorporated, with the centered position right in the middle. Notch length and width are verified for investigating the antenna. An artificial neural network (ANN) model is developed from the simulated dataset, and is used for shape prediction. The same dataset is used to create a mathematical model as well. The predicted outcome is compared and it is determined that the model relying on ANN offers better results

The Effect of Notches on the Failure of Two-Dimensional Nonwoven Fiber Networks

The tearing response of sheets of nonwoven fiber material is investigated. It addresses the question on how notch length and notch geometry is related to the tearing strength and tearing processes. The system considered consists of elastic-brittle fibers connected by strong interfiber bonds. Fiber fracture is the only failure mechanism. For a random fiber orientation case, deformation of the unnotched specimen occurs by long-range fiber chains connecting the load inducing boundaries, and failure is by tearing the cross section. The strength of the notched random fiber sheets is well described by a net section criterion, independent of the notch geometry. For a fiber orientation with symmetry relative to the loading direction, tensile loading is transferred by formation of the X-shaped fiber chains centered in the specimen. The subsequent failure occurs along the fiber chain by shear. Thus, the tearing strength is independent of the notch depth in double-edge notched and single-edge notched specimens, when the presence of shallow notch does not disrupt the force chains in the model. As the notch disturbs the fiber chains, alternative shear failure path forms near the notch tip, leading to a dependence of failure strength on the notch geometry. Then, the failure strength of notched nonwoven networks is described by a shear strength and a notch geometry term.

Guidelines and Limitations of the Compact Compression Specimen

Damage initiation and propagation material models for carbon fiber composites can be categorized according to the loading applied to constituent components. An example of such categorization is fiber tension, fiber compression, matrix tension, and matrix compression material models. Of these, matrix compression has been by far the least studied based on amount of published literature. Recent work at Oregon State University (OSU) has begun to address this lack of study. OSU researchers have published several papers culminating in the specification of an effective test specimen for isolating matrix compression damage initiation and propagation in carbon fiber laminates. While providing compelling results indicating the effectiveness and usefulness of this test specimen, little or no information has been provided regarding its manufacture, usable notch lengths, and optimum loading rate during testing. Experience at OSU has shown that this information is critical and not trivial to obtain. The purpose of this paper is to provide specific guidelines and “lessons learned” needed for other researchers to efficiently and effectively use this specimen in a comprehensive study. Test specimens are manufactured in the OSU Composites Materials Manufacturing Laboratory using typical commercial pre-peg carbon fiber following the specified layup and curing procedures. Once the material was cured the carbon fiber plate was then water-jet cut into the desired geometry and notch length. Usable notch length and optimum loading rate was determined by testing a series of specimens. All testing was conducted at an OSU lab using a universal testing machine with Digital Image Correlation (DIC) data collected. Specimens were preloaded and matrix compression initiation and propagation data collected until tensile failure occurred on the back edge of the specimen. Testing showed that shorter notch lengths result in inconsistent data and longer in effective initiation but limited propagation due to reduced ligament length. Testing suggested that a speed less than 5 mm/min gave the best results as faster displacement rates caused less crack propagation to occur, while increasing the likelihood of the specimen to fail in tension along its back edge. Through the use of these guidelines, researchers are able to manufacture and use an effective test specimen for the investigation of matrix compression damage initiation and propagation.