Notch Length Research Articles

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

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. 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. 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. 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". 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.

Z shape joints under uniaxial compression

In this paper, the effects of angle of Z shape non-persistent joint on the compressive behaviour of joint's bridge area under uniaxial compression load have been investigated. Furtheremore experimental test and Particle flow code in two dimension (PFC2D) have been used. concrete samples with dimension of 50 mmx50 mmx100 mm were prepared. Tensile strength of model material was 1 MPa. Within the specimen, three Z shape non-persistent notches were provided. The notch length was 1.5 cm. when two upper and lower notch have horizontal direction, the middle joint angle were 45o, 90o and 135o. When dips of two upper and lower notch was 90o, the middle joint angle were 45o, 90o and 135o degree. When dips of two upper and lower notch was 135 degree, the middle joint angle were 45o, 90o and 135o. Totally, 9 different configuration systems were prepared for Z shape non-persistent joints. Also, 37 models with different Z shape non-persistent notch angle were prepared in numerical model. The axial load with rate of 0.005 mm/s was applied to the model. Results indicated that the failure process was mostly governed by the Z shape non-persistent joint angle. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. In addition it was shown that the compresssive behaviour of discontinuities is depend on the number of the induced tensile cracks which are increased by increasing the middle joint angle. The middle joint has significant effect on the failure pattern. In fixed upper and lower joints angles, when the middle joint angle is 90o the failure stress has maximum value. On the other hand, it has minimum value when the middle joint angle was 135o. In fixed middle joint angle, the samples have minimum value when the upper and lower joints angles are 135o. At the end, the failure pattern and strength results of the experiential tests and the numerical simulations were similar.

Applicability of linear elastic fracture mechanics to compressive damage in carbon fiber reinforced epoxy matrix composites

The failure of carbon fiber reinforced epoxy matrix composites has been attributed to different mechanisms involving tensile, compressive and shear failure of the fibers or the matrix. This research serves to understand whether linear elastic fracture mechanics can explain the matrix behavior under compressive loading. Experiments and finite element analysis (FEA) are used to confirm that the matrix under compressive loads follows the relationships established by linear elastic fracture mechanics. The failure load is related to the corresponding notch length, and the observed relationship is compared to the relationship defined by linear elastic fracture mechanics.

CRACK PROPAGATION BEHAVIOR OF LATERALLY CONSTRAINED POLYMERS USED AS DIELECTRIC ELASTOMERS

ABSTRACT Dielectric elastomer-based transducers are rapidly gaining importance with the syntheses of new polymers that can potentially be used as dielectric materials. However, these materials are always prone to fracture in the presence of cracks and flaws. Failures originate from flaws (or notches), and a complete fracture may take place due to the propagation of cracks. The present work investigates the crack propagation behavior of two popular polymers, VHB 4910 and Ecoflex, that are widely used as dielectric elastomers. In this case, tensile loadings in laterally constrained boundary conditions are considered. The average crack propagation speed for Ecoflex is higher than that for VHB, implying that Ecoflex will fail earlier than that of VHB under similar conditions. Moreover, with increasing notch lengths at a fixed strain rate, the average crack propagation speed decreases appreciably but becomes constant for comparatively larger notches. The results also conclude that the average crack propagation speed and normalized crack tip diameter remain higher for VHB than for Ecoflex for larger normalized notch lengths. It is observed that the average crack propagation speed increases with strain rates, whereas the normalized crack tip diameter is independent of strain rates. Experimental results obtained here will provide a useful comparative insight to understand the failure behavior of two polymers widely used as dielectric elastomers.

Investigations of strain rate, size, and crack length effects on the mechanical response of polycaprolactone electrospun membranes

The effects of strain rate, size (height × width), and pre-existing crack length on the mechanical response of polycaprolactone electrospun membranes were investigated by tension tests conducted at room temperature. In particular, tensile tests were performed with three different strain rates for strain rate effect tests, seven different geometries for elucidating the size effect, and three different initial notch lengths for crack growth experiments. The electrospun membranes were produced by the electrospinning technique using a polycaprolactone solution prepared in 1, 1, 1, 3, 3, 3-hexafluoro-2-propanol as the solvent. Scanning electron microscopy was utilized to show the continuous fiber structure without bead formation. The average fiber diameter was calculated as 1.113 ± 0.270 μm by using scanning electron microscopy images of the membranes. The chemical structure of polycaprolactone was analyzed by Fourier transform infrared spectroscopy, and the toxicity and cell viability of the electrospun membranes were shown by CellTiter 96® Aqueous One Solution Cell Proliferation Assay (MTS test). It was observed that the ultimate tensile strength and Young’s modulus decreased, and the elongation at failure value increased as the strain rate decreased from 10−1 to 10−3 s−1. Besides, positive strain rate sensitivity was observed on the mechanical response of electrospun polycaprolactone membranes. Moreover, the dependency of mechanical response on the size geometry has been well studied, and the optimum height and width combinations were specified. Also, crack growth was studied in terms of both macroscopic and microstructural deformation mechanisms and it is observed that individual fiber deformations and interactions are highly effective on the mechanical behavior and also propagation of the crack. Consequently, in this study, the size and strain rate effects and crack growth on the mechanical response of electrospun polycaprolactone membranes have been investigated extensively, and the results presented herein constitute an essential guideline for the usage of polycaprolactone electrospun membranes at different loading scenarios.

Tests of circular concrete-filled steel tubular stub columns with artificial notches representing local corrosions

Concrete-filled steel tubular (CFST) columns have been used in civil structures due to their affordability, high strength, superior ductility, and demonstrated fire resistance. However, there are remaining issues regarding the performances of the CFST columns with the locally corroded steel tubes, hindering the widespread acceptance of this type of members in practice. This paper focused on the circular CFST stub columns in which the steel tubes are locally corroded. To develop the critical data needed for understanding the behavior of such stub columns, a group of thirty specimens were designed, constructed and tested. Based on the recommendations from prior research, the local corrosions in the steel tubes of the specimens were represented by the artificial notches. The test parameters varied among the specimens included the notch orientations, lengths, depths, and widths. The test results revealed the influences of these parameters on different aspects of the responses of the stub columns with the corroded steel tubes. Computer models were also developed for the specimens and validated by the test results. Based on the test results and the results from parametric analyses using the validated computer models, a practical model to compute the peak resistance of a CFST stub column with the locally corroded steel tube was proposed and verified.

Size effect and other effects on mode I fracture toughness using two testing methods

Mode I fracture toughness (KIC) is an intrinsic material property that quantifies its resistance to tensile fracture propagation. The International Society for Rock Mechanics has endorsed four methods to determine the KIC of rock, namely, the short rod, chevron bend, cracked chevron notched Brazilian disc, and semi-circular bend (SCB) methods. In this study, we compare the results of the SCB technique with those of the recently proposed pseudo-compact tension (pCT) test, which has proven to be convenient for the assessment of KIC in both fragile and ductile rocks. We select the SCB as a benchmark method due to its popularity, simplicity, and straightforward testing configuration. We discuss the results of 146 tests performed with different lithologies (Arcera, Pinacas and Corvio sandstones, and Blanco Mera granite), different sample sizes (100, 50 and 38 mm diameter), and a range of notch lengths. We also assess test repeatability and intercomparability of the results obtained using the two techniques. Compared with the SCB test, the pCT test allows for improved control of the specimen behaviour after the peak load, which provides a greater wealth of fracture mechanics information. pCT specimens yield results with higher repeatability than SCB samples. Although we observe that KIC tends to decrease with an increase in the notch length ratio, this effect appears to be non-significant based on statistical assessments. Accordingly, the corresponding mean KIC values are comparable for medium- and large specimens. The influence of specimen size is more pronounced in the SCB tests, while the pCT tests show less dependence for harder lithologies. Therefore, to set up minimum specimen requirements for fracture toughness testing, in addition to geometrical constraints, some key lithology-dependent properties (strength, mineralogy, grain size, etc.) should also be considered. Further methodological considerations related to test execution are also discussed.

Modelling and testing of Temperature-Dependent strength and toughness of asphalt concrete from −10 °C to + 23 °C using small notched beams

A closed-form fracture model with the consideration of the average aggregate size and crack-tip damage zone is used to analyse flexural strength of asphalt concrete using notched beams. Quasi-stable micro-crack formation and quasi-brittle fracture of these small samples with highly heterogeneous aggregate structures are formulated. While the apparent strength and fracture toughness of asphalt concrete based on Continuum Mechanics are size dependent, constant asymptotic “structural” tensile strength ft and “structural” fracture toughness KIC have been determined by this composite model from experimental results of notched beam specimens of any size with any notch length. Temperature (T) dependent ft and KIC measurements of asphalt concrete from −10 to + 23 °C, relevant to the real temperature environments, are then determined. The characteristic microstructure Cch in the model is the average aggregate size. The maximum failure load Pmax of asphalt concrete under three-point-bending (3-p-b) is linked directly to its constant “structural” tensile strength ft for a given temperature environment, independent of sample size and notch/crack length. In addition, although KIC is not valid for asphalt pavement with limited thickness, its influence is reflected through the “structural strength” criterion based on ft and Cch. This simple model can also be used as a design tool for asphalt concrete property optimization.

Biaxial Loading Effects on Strain Energy Release Rate and Crack-Tip Strain Field in Elastic Hydrogels

We characterized the strain energy release rate and local crack-tip strain field for elastic hydrogels under several types of biaxial loading: planar, unequal biaxial, and equibiaxial extensions. The strain energy release rate (G) in each type of biaxial strain is characterized via two different approaches. One evaluates G from the change in strain energy with respect to the notch length (Xc) using single-edge notched specimens with various Xc values. The other estimates G from the difference in strain energy density between the two regions far behind and ahead of the crack tip. The excellent agreement between the G values obtained by the two methods demonstrated their reliability. We also revealed the features of the local crack-tip strain field in biaxial loading, including crack-tip opening displacement, strain field area, strain magnitude resulting from crack opening, and strain singularity exponent for strain growth near the crack tip. Importantly, these properties are governed exclusively by G, independent of the biaxial loading type. The results provide an important basis for a comprehensive understanding of the fracture behavior of elastic soft materials under complicated deformations.

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.

Effect of different notch prefabrication methods and notch lengths on rock three-point bending test

Effect of different notch prefabrication methods and notch lengths on rock three-point bending test

Gross Morphological and Sex Wise Morphometrical Studies on Mandible of Adult Blue Bull (Boselaphus tragocamelus)

Background: The Blue bull (Boselaphus tragocamelus) is one of the biggest antelopes in Asia and is widely distributed in both the forests and adjoining villages with enough green grass.Methods: The present study was carried out on the mandible of six specimens of adult Blue bull (Boselaphus tragocamelus) of either sex. The biometrical parameters were measured by scale, graduated tape and digital Vernier’s caliper. The statistical analysis of the recorded data was done by independent samples t-Test with Systat Software Inc, USA and SPSS 16.0 version software.Result: The mandible of Blue bull consisted of two rami, i.e. horizontal and vertical rami. The two halves of this bone fused incompletely at the mandibular symphysis, situated at the midline. The average length of horizontal ramus of mandible was found to be 24.7±1.02 cm in female, which was significantly less (P less than 0.05) than that of males, where it was recorded as 35.4±1.97 cm. Similarly, the average thickness of vertical ramus at the base was found to be 0.53±0.001 cm in female, which was significantly less (P less than 0.05) than that of males, where it was recorded as 0.80±0.002 cm. The average cranio-caudal length of mandibular notch was found to be 1.32±0.01 cm in female, which was significantly less (P less than 0.05) than that of males, where it was recorded as 1.44±0.02 cm. Most of the biometrical observations on different parameters of mandible of Blue bull were having significantly (P less than 0.05) more values in males than females. Conclusion: Most of the biometrical observations on different parameters of mandible of Blue bull were having significantly (p less than 0.05) more values in males than females. The present gross and biometrical studies would be useful to the wild life professionals for determination of sex of this animal and solving vetero-legal cases related with this species.

FARKLI RADİUS BAŞI TİPLERİNİN MORFOMETRİK KARŞILAŞTIRILMASI

The aim of this study is to determine morphometric measurements difference of radial head (RH) types. 49 dry radial bones were included in the study. After determining the types of radius, morphometric measurements were made with digital calliper. The parameters were determined as the length of radius, height of the radius, transverse diameter of RH, anterior-posterior diameter of RH, radial tuberosity transverse diameter and height, length and transverse diameter of ulnar notch. As the result of RH classification, it has been determined that; 20 bones had irregular, 15 bones had oval and 14 bones had round type. In order to on all group average; radius length of RH, the height of RH, transverse diameter of RH, anteroposterior diameter of RH were calculated as 207.99±21.97 mm, 9.45±1.68 mm, 19.94±3.15 mm, 20.20±3.09 mm respectively. In order to on all group aver-age; transverse diameter of radial tuberosity, height of radial tuberosity, the height of ulnar notch, transverse diameter of ulnar notch were 12.07±1.3 mm, 25.36±2.78 mm, 13.86±1.56 mm, 5.27±0.8 mm respectively. Ac-cording to the results of One Way Anova analysis, no statistically significant difference was found between RH types (p>0.05). No statistically significant difference was found between RH types in all parameters.

Karbon/epoksi ve E-cam/epoksi ile Onarılmış Çentikli Alüminyum 5754-H111 Charpy Darbe Tepkisi

I this study, aluminum sheets with three different notch depths were repaired with carbon/epoxy and e-glass/epoxy composites and than were investigated experimentally for their response to Charpy impact. [90/45/-45] oriented triaxial fabrics were used in patch reinforcement materials. Composite laminates were performed in [90/45/-45/45/-45/90] orientation by placing these three axial fabrics on top each other. Hand lay-up technique was used in the creation of laminated composites. The reinforcement fabrics wetted by hand lay-up were cured by hot molding at 100 °C and 7 bar pressure. Water jet was used for sizing both aluminum and repair elements. The sized aluminum and repair elements were glued to each other as one-side with a double component methyl methacrylate adhesive. In the experimental stage, some mechanical properties of the composites were determined first. Afterwords, of the aluminum plates as repaired and unrepaired in three different notch lengths (3mm, 5mm, 7mm), energy absorption was determined by conducting Charpy notch impact tests. In addition Scanning Electron Microscope (SEM) analysis of composite patches were performed..

Shear Mechanism of Non-Persistent Notches Using Punch Shear Test

Experimental and discrete element methods were used to investigate the effect of non-persistent notch angle on the shear behavior of joint’s bridge area. A punch-through shear test was used to model the gypsum cracks under shear loading. Gypsum samples with dimension of 150 × 150 × 50 mm were prepared in the laboratory. Within the specimen model and near the one edge, two notches were provided. Six different configuration systems were prepared for notches. In these configurations, the length of notches was taken as 2 cm. Assuming a plane strain condition, special rectangular models were prepared with dimensions of 100 × 100 mm. Similar to those for joints configuration systems in the experimental tests, i.e. six models with different rock bridge lengths and rock bridge joint angle were prepared. The axial load was applied to the punch through the central portion of the model. This testing showed that the failure process was mostly governed by the notch angle. The shear strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. The failure pattern and failure strength are similar in both methods, i.e. the experimental testing and the numerical simulation methods.

The Tentorial Notch: Morphometric Analysis and its Clinical Relevance to Neurosurgery

Introduction: The tentorial aperture is a complex space that varies considerably in size and shape. Although this space is defined by the free edges of the tentorium cerebelli, it has remained anatomically elusive. Modern neuroimaging methods routinely provide images of the tentorial notch but the literature so far available is remarkably devoid of extensive observations on the different types of tentorial notches. Dimensions of tentorial notch may determine the clinical sequelae and prognosis of many neurological conditions. Aim: To analyse the anatomical variations of tentorial notch, elucidating its clinical relevance in neurosurgery. Materials and Methods: A descriptive cross-sectional study was performed from August 2010-January2012. The midbrain was sectioned in an axial plane following the contour of the tentorial edge during medico-legal autopsies in 40 adult human cadavers, age ranging from 20 to 65 years. The parameters measured were: 1) Anterior Notch Width (ANW), the width of tentorial notch through the posterior aspect of the dorsum sellae; 2) Maximum Notch Width (MNW), the maximum width of the tentorial notch in axial plane; 3) Notch Length (NL), the distance between posterosuperior edge of the dorsum sellae in the mid-plane and the apex of notch; 4) Interpedunculoclival (IC) distance, the distance from the interpeduncular fossa to the posterosuperior edge of the dorsum sellae; 5) Apicotectal (AT) distance, the distance between the tectum of midbrain in the mid-plane and the apex of tentorial notch. The data obtained was analysed using Statistical Package for the Social Sciences (SPSS) version 21.0. Results: The quartile groups defined by MNW (mean 29.77±2.26 mm) were labeled as narrow, midrange and wide. Quartile groups defined by NL (mean 57.98±4.52 mm) were labeled as short, midrange and long. By combining these six groups into matrix formation, tentorial notches were classified into eight types. Applying quartile distribution technique to IC (mean 21.21±3.72 mm), brainstem positions within the tentorial notch were labeled as prefixed, midposition and postfixed. Conclusion: Variations in the dimensions of tentorial aperture may be implicated in the different clinical presentations related to transtentorial herniation, concussion and acceleration-deceleration injuries. The results of the present study provide a baseline data about tentorial notch which may facilitate neurosurgical decision making.

Morphometric Study of Suprascapular Notch and Its Variations in Dried Human Scapulae

The study was undertaken to see the variation of the suprascapular notch. The notch is present on the superior border of the scapula near the root of coracoid process. It is roofed by the superior transverse ligament and is converted into foramen for the passage of suprascapular nerve. The study was carried out on 121 scapulae in the department of Anatomy RMC Loni, Ahmednagar. The parameters included in the study were presence of notch, shape of notch, transvers length of notch, edge of notch, ossification of transverse ligament and other finding were also noted. The parameters were measured by Vernier calliper and appropriate statistical tests were applied.
 The supra-scapular notch was present in 82.64% of scapulae. U Deep shaped notch was most common shape followed by J shallow shaped notch. Round edge at the depth of the notch was more common.
 The knowledge of suprascapular notch variations is of great importance for surgeons performing suprascapular nerve decompression especially by means of endoscopic techniques. Our anatomical study helps the clinicians before planning a surgery.

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

Fracture Properties and Process Zone Length of High Strength Concrete Using Size Effect Method.(Dept.C)

This paper gives a report on a fracture mechanics study of legal strength concrete with compressive strength up 80 MPa.. 6 mixes were selected, designed to achieve a slump above 100 mm and strength up to 80 MPa.. The investigation used tiered levels of silica fume(0, 10%, 20% by weight of cement) and two coarse aggregate proportions of local aggregate (0.48, 0.65 by volume) In each case, compressive strength, splitting tensile strength, flexural strength fracture energy Gr and Fracture process zone Cr were determined. A test method for determining fracture energy Gr and process zone length Cr, defined by the size effect wide is generalized theory, has been proposed. It allows the use of specimenc of the different size and shape but with same notch length. This paper proposes test und data analysis procedures. The results obtained by the Size effect law (SEL) apparently follow the trend of fracture energy increasing as the compressive strength of the concrete increases. On the other hand, process zone length or decrease considerably with increase in strength. The Bazant's size effect taw gives a very good account of the size dependency of flexural strength for both normal and high strength concrete. As observed in the size effect curve, the fracture behavior of the HSC seems to be more brittle than that of the normal strength concrete. Linear classic fracture mechanics (LEFM) is applicable to HSC in the normal size range than nonlinear fracture mechanics.