Increase Of Notch Depth Research Articles

Effect of notch-to-depth ratio on flexural and fracture behaviors of UHPGC notched beams based on four-point bending test and acoustic emission

An ecological ultra-high-performance glass sand concrete (UHPGC) was prepared by partially replacing quartz sand in traditional ultra-high-performance concrete (UHPC) with glass sand recycled from waste glass. The four-point bending tests of UHPGC notched beams with different notch-depth ratios (0.2, 0.3, 0.4, and 0.5) were carried out, while acoustic emission (AE) monitoring was employed at the whole fracture process. Flexural toughness and residual flexural tensile strength were used to evaluate the flexural properties. Meanwhile, fracture energy and fracture toughness were used to evaluate the fracture properties. The results reveal that notch-depth ratio exhibits a significant effect on the flexural and fracture performances of UHPGC notched beams. The residual flexural tensile strength, flexural toughness, fracture energy and fracture toughness decrease with the increase of notch depth. Moreover, AE energy parameters can favorably characterize the differences of energy release in the fracture processes of UHPGC beams with different notch depths, and favorable correlations are observed between cumulative AE energy and fracture energy. Besides, AE wavelet entropy are constructed based on wavelet packet transform (WPT) of AE waveforms, and the evolution model of wavelet entropy is established. By comparing with the evolution process of AE energy information entropy, it is proved that the maximum point of wavelet entropy can be used as the key point to predict the peak load.

Stress distribution patterns during the gait cycle in patients with anterior femoral notching following total knee replacement

BackgroundAnterior femoral notching (AFN) is a severe complication of total knee replacement (TKR), which in a percentage of patients may lead to fractures after surgery. The purpose of this study was to investigate the stress distribution in patients with AFN and the safety depth of AFN during the gait cycle.MethodsWe performed a finite element (FE) analysis to analyse the mechanics around the femur during the gait cycle in patients with AFN. An adult volunteer was selected as the basis of the model. The TKR models were established in the 3D reconstruction software to simulate the AFN model during the TKR process, and the 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm AFN models were established, after which the prosthesis was assembled. Three key points of the gait cycle (0°, 22°, and 48°) were selected for the analysis.ResultsThe stress on each osteotomy surface was stable in the 0° phase. In the 22° phase, the maximum equivalent stress at 3 mm was observed. In the 48° phase, with the increase in notch depth, each osteotomy surface showed an overall increasing trend, the stress range was more extended, and the stress was more concentrated. Moreover, the maximum equivalent force value (158.3 MPa) exceeded the yield strength (115.1 MPa) of the femur when the depth of the notch was ≥ 3 mm.ConclusionsDuring the gait cycle, if there is an anterior femoral cortical notch ≥ 3 mm, the stress will be significantly increased, especially at 22° and 48°. The maximum equivalent stress exceeded the femoral yield strength and may increase the risk of periprosthetic fractures.

Fracture parameters of flyash and GGBS based Alkali activated concrete

In the world of concrete, Geopolymer concrete is an innovative and eco-friendly construction material which shall be produced by the chemical reaction of inorganic molecules to reduce CO2 emission and in engineering design safety is an essential parameter which needs to have greater attention when the failure consequences are severe. Cracking plays an important role in concrete structures by indicating major structural problems when subjected to loading. Fracture mechanics is a powerful tool for advanced study and the prime objective is to predict if a structure will fail or not by the presence of a crack. The study intends to assess the effect of the beam depth (75 mm, 150 mm and 300 mm) and molarities (6 M & 8 M) on the fracture parameters of geopolymer concrete beams. The geopolymer notched concrete beams were modelled using finite element analysis software (ANSYS 2021 R1) to study the fracture parameters of AAC. The fracture parameters like fracture energy, fracture toughness and stress intensity factor are investigated for the beams of varying sizes with varying notch depth ratios (ao/D = 0.15, 0.3, 0.45) defined as per RILEM specifications and analyzed under three-point bending test conditions using ANSYS. The results are obtained by developing the FEM model of beams using ANSYS. This study found that the fracture energy, fracture toughness and stress intensity factors values are increased with the increase in beam size & molarity and decreased with an increase of notch to depth ratio and it is also found that load-carrying capacity is decreased with the increase of notch depth to beam depth ratio.

Mechanical and fracture behaviors of compacted gold mine tailings by semi-circular bending tests and digital image correlation

The storage and handling of mine tailings (MTs) pose significant economic and environmental problems and finding suitable recycling or re-use alternatives for MTs is an on-going process. One of those alternatives is creating MTs-based adobes or compacted MTs, which then can be used in construction materials and ground stabilization applications Therefore, the fully understanding of the mechanical and fracture behaviors for the compacted MTs are significant for the applications. However, no study on such behaviors of the compacted MTs was documented in the literature. In this study, the investigations of the mechanical and fracture behaviors of the compacted MTs were carried out experimentally by using semi-circular bending tests (SCB) and digital image correlation (DIC). The SCB tests were conducted by using three-point bending instruments. Mode I fracture behaviors were therefore obtained by manually setting different notch depths with various loading span distances. The influences of notch depths and span distances on the Mode I fracture toughness, KI, were obtained by testing the notched SCB specimens. Additionally, the influences of notch depths and span distances on the fracture process zone (FPZ) and fracture energy were evaluated. Results showed that the measured Mode I fracture toughness was not evidently influenced by the notch depths and span distances. The fracture energy decreased with the increase of notch depth and span distance. Finally, the maximum major principal strains were found to increase with the increase of notch depths.

Influences of Casing Wear on Mechanical Behavior of Packer Element

Packer element is made of hyperelastic rubber, and its mechanic performance determines the packer’s sealing effect. In oil field, casing wear is often found and in some special circumstance the packer has to set at worn casing section. In order to study the effect of casing wear on element mechanical behavior, contact pressure between element and casing with crescent-shaped wear notch is calculated by use of commercial ANSYS software. The influences of notch depth and diameter of drill pipe joint on contact pressure are discussed in detail. The results show that the contact pressure has a saddle-shaped distribution along axial direction similar to that without wear. But minimum contact pressure decreases rapidly when the notch depth increases. And a larger diameter of drill pipe joint can give rise to lower contact pressure near the notch.

Fatigue damage evolution and finite element simulation of the samples under different notch morphology

Based on the theory of continuous damage mechanics and the principle of irreversible thermodynamics, the damage evolution model of low cycle fatigue is investigated. By programming the damage evolution model as UMAT subroutine in ABAQUS, the fatigue damage and crack initiation life of notch materials under specific loads are simulated, and the crack initiation location is determined. Furthermore, the effects of root radius, depth and opening angle on crack initiation life are investigated. The results show that the crack initiation occurs easily in the notch root where the damage is the most serious and the plastic strain accumulates fastest under cyclic loading. With the increase of notch depth and root radius, the crack initiation life decreases. For V-notched specimens, when the notch depth remains unchanged, the crack initiation life will decrease with the increase of the opening angle.

Flange-notched wood I-joists reinforced with OSB collars: Experimental investigation and sensitivity analysis

A total of 220 four-point quasi-static bending tests were performed on 3.66 m and 6.10 m long wood I-joists. In addition to control specimens, two different notch sizes (100 × 100 mm and 100 × 150 mm) at three different locations (305, 455 and 610 mm from the support) and two Oriented Strand Board (OSB) collar reinforcements were considered to evaluate their impact on failure mode, stiffness, and load-carrying capacity. While the joist from the control series without notch failed in flexure, the notched I-joists failed mostly in combined flexure-shear failure. It was found that the reduction in capacity and stiffness increases with the increase in notch depth and notch distance from support. Reinforcing the I-joists with OSB collars at the notch prevented brittle shear failure and improved capacity compared to the unreinforced I-joists. Regression models were proposed to estimate the capacity of unreinforced and reinforced I-joists with flange notches. By conducting a sensitivity analysis, it was found that the I-joist aspect ratio, notch depth, notch location and reinforcement type have a significant impact on the capacity of reinforced I-joists.

RETRACTED: On study of effect of varying tempering temperature and notch geometry on fracture surface morphology of P911 (9Cr-1Mo-1W-V-Nb) steel

Abstract Before putting in service, the creep strength enhanced ferritic (CSEF) steels are subjected to varying tempering treatment to produce a vast array of mechanical properties and to achieve the optimum combination of microstructure and mechanical properties by controlling normalizing and tempering temperature/time. In the present investigation, P911 steel was subjected to a fixed normalizing temperature of 1040 °C for 1 h and then, subjected to varying tempering temperature (720 °C–800 °C) for 2 h of tempering time. The effect of notch geometry on the tensile properties with respect to the varying tempering temperature was also investigated. The microstructural characterization was studied using optical microscope and field-emission scanning electron microscope (FESEM). A decrease in grain size, hardness and strength were noticed with increase in tempering temperature initially but after 740 °C, the grain size and strength were found to be increased continuously. The area fraction of precipitates was found to be varied inversely with the grain size. For a particular tempering temperature, an increase in notch depth resulted in increase in strength and decrease in ductility. The best combination of hardness, ductility and strength were achieved after normalized at 1040 °C for 1 h and tempered at 760 °C for 2 h.

Spiral to flat fracture transition for notched rods under torsional loading

The transition of the fracture surface in notched and unnotched PMMA rods under torsional loading is investigated experimentally. The experiments show that for crack initiation from a notch, resulting in dynamic fracture propagation, as the notch depth increases, the surface transitions from a spiral fracture to a nominally flat, but faceted surface. The facets coarsen and merge as the crack grows toward the center of the rod. The resulting fracture surfaces as well as the multiple internal micro-cracks are visualized using micro CT scanning.

Finite Element Analysis on the Response of Local Sharp-Notched Circular Tubes under Cyclic Bending

In this study, the finite element software ANSYS was used to analyze the mechanical behavior of local sharp-notched circular tubes under cyclic bending. The local sharp-notched depths include: 0.2, 0.4, 0.6, 0.8 and 1.0 mm, and the local sharp-notched directions include: 0, 30, 60 and 90 degrees. According to the experimental result, the notch depth has no influence on the moment-curvature relationship. But the notch depth increases, the unsymmetrical phenomenon of the ovalization-curvature relationship becomes more obvious and the speed of ovalization accelerates. In addition, the ovalization-curvature relationship becomes symmetrical when the direction angle increases. The ANSYS analysis was compared with the experimental finding. Although some differences between the experimental and simulated results, but both trends were very similar.

On Reduction of Stress Concentration around the Pin Hole in Turbine Discs

The stress concentration phenomenon around holes in rotated components is discussed. Firstly, finite element analysis of a simplified model of turbine disc flange is carried out, and then a method is developed by designing an intended-cut notch on the model to reduce the stress around the pin hole. Furthermore, two characteristic parameters which determine the configuration of the notch, namely notch depth and arc length parameter, are investigated by changing the notch dimensions. The results show that this method can reduce the stress around the hole significantly, notch depth and arc length have an important impact on the stress concentration factor (SCF), the SCF decreases with the increase of notch depth, and increasing the arc length within a critical scope results in the decrease of the SCF.

Time-Domain Hybrid Global-Local Prediction of Guided Waves Interaction with Damage

This paper presents a hybrid finite element and analytical method to predict the 1-D guided wave propagation interaction with damage for nondestructive evaluation (NDE) and structural health monitoring (SHM) application. The finite element mesh is used to describe the region around the damage (defects or flaws). In contrast to other hybrid models developed elsewhere, the interaction between Lamb waves and defects is computed in the time domain using the explicit solver of the commercial finite element method (FEM) software ABAQUS. Analytical methods can perform efficient modeling of wave propagation but are limited to simple geometries. Realistic structures with complicated geometries are usually modeled with the FEM. However, to obtain an accurate wave propagation solution at ultrasonic frequencies is computationally intensive and may become prohibitive for realistic structures. In response to today's complex cases not covered by the simulation tools available, we aim to develop an efficient and accessible tool for SHM applications. This tool will be based on a hybrid coupling between analytical solutions and time domain numerical codes. Lamb wave interaction with a notch is investigated by using this method, and the results obtained are with respect to transmission, reflection and mode conversion. Because of the symmetric mode shape, S0 is more sensitive to the shallow notch than A0. By making use of the fact that the reflection increases with increase in notch depth and mode conversion are maximized when the notch is around half through the thickness of the plate, the reflection and conversion coefficients can be used to characterize the depth of the notch.

Estimation of fracture properties for high strength and ultra high strength concrete beams and size effect

This article presents the details of estimation of fracture parameters for high strength concrete (HSC, HSC1) and ultra high strength concrete (UHSC). Brief details about characterization of ingredients of HSC, HSC1 and UHSC have been provided. Experiments have been carried out on beams made up of HSC, HSC1 and UHSC considering various sizes and notch depths. Fracture characteristics such as size independent fracture energy ( Gf), size of fracture process zone ( Cf), fracture toughness ( KIC) and crack tip opening displacement (CTODc) have been estimated based on the experimental observations. From the studies, it is observed that (i) UHSC has high fracture energy and ductility inspite of having a very low value of Cf; (ii) relatively much more homogeneous than other concretes, because of absence of coarse aggregates and well-graded smaller size particles; (iii) the critical SIF ( KIC) values are increasing with increase of beam depth and decreasing with increase of notch depth. Generally, it can be noted that there is significant increase in fracture toughness and CTODc. They are about 7 times in HSC1 and about 10 times in UHSC compared to those in HSC; (iv) for notch-to-depth ratio 0.1, Bazant’s size effect model slightly overestimates the maximum failure loads compared to experimental observations and Karihaloo’s model slightly underestimates the maximum failure loads. For the notch-to-depth ratio ranging from 0.2 to 0.4 for the case of UHSC, it can be observed that, both the size effect models predict more or less similar maximum failure loads compared to corresponding experimental values.

Study on Notch Sensitivity of Fracture Properties of Concrete Containing Nano‐SiO2 Particles and Fly Ash

The fracture parameters and fracture relational curves of the concrete containing nano‐SiO2 and fly ash with different relative notch depth of the notched beam specimens were measured by means of three‐point bending method. The results indicate that the relative notch depth of the notched specimens has great effect on ac, , , GF, CMODc, and the fracture relational curves of the concrete containing nano‐SiO2 and fly ash. There is a tendency of increase in ac and CMODc with the increase of relative notch depth, while , , and GF are decreasing gradually with the increase of relative notch depth of the notched beam specimens. Besides, when the relative notch depth increases from 0.2 to 0.5, the nonlinear stage of the curve becomes shorter and shorter, and the descent stage of the curve becomes sharper and sharper. The fracture parameters of ac, , , GF, and CMODc and the fracture curves are sensitive to the relative notch depth, while CTODc may be not sensitive to the relative notch depth of the specimens of the concrete containing nano‐SiO2 and fly ash.

Fatigue Crack Growth Study and Remaining Life Assessment of High Strength and Ultra High Strength Concrete Beams

This paper presents the details of crack growth study and remaining life assessment of concrete specimens made up of high strength concrete (HSC, HSC1) and ultra high strength concrete (UHSC). Flexural fatigue tests have been conducted on HSC, HSC1 and UHSC beams under constant amplitude loading with a stress ratio of 0.2. It is observed from the studies that (i) the failure patterns of HSC1 and UHSC beams indicate their ductility as the member was intact till the crack propagated up to 90% of the beam depth and (ii) the remaining life decreases with increase of notch depth (iii) the failure of the specimen is influenced by the frequency of loading. A ``Net K'' model has been proposed by using non-linear fracture mechanics principles for crack growth analysis and remaining life prediction. SIF (K) has been computed by using the principle of superposition. SIP due to the cohesive forces applied on the effective crack face inside the process zone has been obtained through Green's function approach by applying bi-linear tension softening relationship to consider the cohesive the stresses acting ahead of the crack tip. Remaining life values have been have been predicted and compared with the corresponding experimental values and observed that they are in good agreement with each other.

Performance deterioration of the governing stage nozzle caused by solid particle erosion in the steam turbine

In the steam turbine, solid particle erosion on a nozzle cascade is known to damage the profile and surface smoothness of the cascade, which increases the flow loss of steam. The present study aims to make clear the relations between nozzle loss and surface degradation, aerodynamic parameters, as well as the shape, location, and size of the erosion notch. A series of numerical simulations were conducted to model the aerodynamic performance of various existing eroded nozzles. The results indicate that the nozzle loss caused by the surface degradation shows an approximate linear decrease with an increase in notch depth. The nozzle loss caused by the erosion notch increases with either a decrease in the exit Mach number or an increase of the notch area. For the same erosion-induced weight loss of the nozzle, the asymmetric notch and local notch cause more nozzle loss than the symmetric notch and quasi-global notch. This means that the performance deterioration can be reduced to a minimum value if the erosion is uniform along the span-wise of the nozzle. In addition, a combined experimental and numerical investigation is conducted to explore the erosion damage process of the nozzle. The result suggests that the eroded nozzle should be replaced by a new nozzle before the notch begins to propagate.

Mandibular antegonial notch depth distribution and its relationship with craniofacial morphology in different skeletal patterns

Background: Antegonial notch is a small concavity at the inferior surface of the mandible. The purpose of this study is to identify the distribution of mandibular antegonial notch depth and its relationship with craniofacial morphology in different skeletal patterns. Materials and method: The sample included 191 pretreatment digital lateral cephalometric radiographs (93 males, 98 females) collected from the Orthodontic Department in the College of Dentistry, University of Baghdad. The sample was divided into three groups according to the skeletal classes, and then each group divided according to depth of mandibular antegonial notch into: shallow, medium, and deep groups. Sixteen angular and thirteen linear measurements were used. Results: Cl I had the highest percentage of medium antegonial notch. Cl II had the highest percentage of deep notch, while Cl III had the highest percentage of shallow notch. Males had significantly deeper notch than females in Cl I and Cl II. Significant difference found between males skeletal Cl II and Cl III. The craniofacial measurements showed significant changes with the increase in antegonial notch depth variably in different classes. Conclusions: Angular measurements of cranial base more concerned with mandibular morphology than linear measurements. The increase in vertical growth pattern and backward rotation of the mandible in association with the increase in notch depth appeared particularly in skeletal Cl II.

Finite element modeling of acoustic field induced by laser line source near surface defect

A numerical model of acoustic field induced by laser line source near the surface defect is established by finite element method (FEM), where a surface notch of rectangular shape has been introduced to represent the fatigue defect for the convenience of modeling. After calculating numerically the transient displacement distributions, which are generated by the laser irradiation, the ultrasonic wave modes on the surface and in the body of the plate material are presented in details. The longitudinal, transverse and surface acoustic waves (SAWs) excited by laser pulses near surface notch are compared under the situations that the notch depths are different. As the notch depth increases, the directivity of the bulk waves generation changes greatly. The amplitude of the reflected SAW rises observably at the same time, which is observed experimentally when the laser source is shifted near the surface notch in scanning laser line source (SLLS) measurement. Another effect induced by the surface notch is the time lag of the transmitted SAW pulse with respect to the original incident pulse. These phenomena can be explained from the results. The conclusions can be used to surface notch depth evaluation.

Vibration of Plates with Constrained V-Notches or Cracks

This paper reports the first known free vibration solutions for thin circular plates with V-notches having various edge conditions. The classical Ritz method is employed with 2 sets of admissible functions assumed for the transverse vibratory displacements. These sets include: 1) mathematically complete algebraic-trigonometric polynomials which guarantee convergence to exact frequencies as sufficient terms are retained; and 2) corner functions to account for the bending moment singularities at the sharp re-entrant corner of the V-notch. Extensive convergence studies summarized herein confirm that the corner functions substantially enhance the convergence and accuracy of nondimensional frequencies for circular plates having a free circumferential edge and various combinations edge conditions of the V-notch. Accurate (5 significant figures) frequencies are presented for clamped-free, clamped-hinged, and hinged-free notches for the spectra of notch angles, causing a re-entrant vertex corner of the radial edges. For very small notch angles, a clamped-free, clamped-hinged, or hinged-free radial crack ensues. One general observation is that, for the range of notch angles considered, there is a substantial increase in the first 6 frequencies as the notch depth increases. The frequency increase with increasing notch depth is more pronounced in the higher modes than the lower ones, and is quite substantial for segmental plates with notch angles equal to 180 deg. A large reduction in frequencies is also observed as the notch angle decreases at a constant notch depth. A new database of accurate frequencies and mode shapes for sectorial, semicircular and segmental plates is presented with which future solutions drawn from alternative numerical procedures and finite element and boundary element techniques may be compared. Normalized contours of the transverse vibratory displacement are shown for plates with various notch depths and notch angles of 5, 30, 60, 90, and 180 deg.

Influence of nanometre‐sized notch and water on the fracture behaviour of single crystal silicon microelements

The influence of a notch and a water environment on the quasi‐static and fatigue fracture behaviour was investigated in single crystal silicon microelements. The tests were conducted in smooth and notched microcantilever beam samples. Smooth specimens were prepared by micromachining (photo‐etching) of (110) silicon wafers. For some specimens, a nanometre‐sized notch was machined 100 μm away from the sample root by using a focused ion beam system. A machining condition was optimized, and the V‐shaped notch was successfully introduced. The radius of curvature of the notch, measured by an atomic force microscope (AFM), decreased with an increase in notch depth, and ranged from about 20 to 100 nm. Single‐crystal Si microelements deformed elastically until final failure, which was of a brittle nature. The maximum fracture strength of a smooth microcantilever specimen reached about 7.7 GPa, which was higher than that obtained in millimetre‐sized single crystal Si samples. However, the fracture strength decreased with an increase in notch depth, even though the notch depth was of the order of a nanometre. This means that a nanometre deep notch, which is often regarded as surface roughness in ordinary‐sized mechanical components, caused a decrease in the fracture strength of Si microelements. The fracture initiated at the notch, and then the {111} crack propagated in the direction normal to the sample surface. Fatigue tests were also conducted in laboratory air and in pure water at a stress cycle frequency of 0.1 Hz and a stress ratio of 0.1. In laboratory air, no fatigue damage was observed even though the surface was nanoscopically examined by an AFM. However, when the fatigue tests were conducted in pure water, the fatigue lives in water were decreased. Crack formation on the {111} plane was promoted by a synergistic effect of the dynamic loading and the water environment. Atomic force microscopy was capable of imaging the nanoscopic cracks, which caused failure in water.