Edge Crack Research Articles

Effect of an Edge Crack on Static Deflection and Natural Frequency in a Composite Material Cantilever Beam

Effect of an Edge Crack on Static Deflection and Natural Frequency in a Composite Material Cantilever Beam

Effects of translaminar edge crack and fiber angle on fracture toughness and crack propagation behaviors of laminated carbon fiber composites

Abstract In this study, the translaminar fracture toughness of carbon fiber laminated composites with different layer sequences was investigated experimentally and numerically for different crack directions. In the numerical study, first of all, the critical stress intensity factor was determined by using the M-integral method. Three-dimensional model and M-integral analysis were achieved in the ANSYS finite element package program. The non-local stress fracture criterion was used to in order to find failure curves of the materials. Then, in order to find the crack propagation directions numerically, the solid model was transferred to the LS-DYNA program and progressive failure analysis was performed. Fracture toughness decreased by 9.92 % with the change of crack angle from 15° to 90°. As the fiber angle changed from 0° to 45°, it decreased by 9.17 %. The biggest error between the experimental and numerical study results was found at α = 45°, with a rate of 12.3 %.

EVALUATION OF THE LEVEL OF ROAD DAMAGE IN JELIDRO II-KUWUKAN-SAMBIKEREP ROADS USING THE PAVEMENT CONDITION INDEX (PCI) AND BINA MARGA METHOD

The road is a facility for land transportation that serves regional development. The deterioration of road quality can pose constraints on economic and social activities and endanger road users. Small damages can escalate if not promptly addressed, leading to losses. This reasearch aims to determine the type and level of damage on Jelidro II – Kuwukan - Sambikerep Roads STA 0+000 to STA 1+600. There are two methods for obtaining road condition values in this research, the methods are Pavement Condition Index method and the Bina Marga method. On the section of Jelidro II – Kuwukan - Sambikerep Roads, 8 types of damage were found, those are crocodile skin cracks, grade depression, edge cracks, potholes, patches, longitudinal cracks, slip cracks, and ravelling. The results of calculating the road condition value using the PCI method is 63,6 where the road is included in the good category. Calculations using the Bina Marga method get a priority order of 9. The two methods show that the road has the same type of treatment, that is a routine maintenance program with repair methods that can be carried out, namely surface layers such as asphalt resurfacing and patching holes. Keywords: Road Damage; PCI method; Bina Marga method.

ERNet: A Rapid Road Crack Detection Method Using Low-Altitude UAV Remote Sensing Images

The rapid and accurate detection of road cracks is of great significance for road health monitoring, but currently, this work is mainly completed through manual site surveys. Low-altitude UAV remote sensing can provide images with a centimeter-level or even subcentimeter-level ground resolution, which provides a new, efficient, and economical approach for rapid crack detection. Nevertheless, crack detection networks face challenges such as edge blurring and misidentification due to the heterogeneity of road cracks and the complexity of the background. To address these issues, we proposed a real-time edge reconstruction crack detection network (ERNet) that adopted multi-level information aggregation to reconstruct crack edges and improve the accuracy of segmentation between the target and the background. To capture global dependencies across spatial and channel levels, we proposed an efficient bilateral decomposed convolutional attention module (BDAM) that combined depth-separable convolution and dilated convolution to capture global dependencies across the spatial and channel levels. To enhance the accuracy of crack detection, we used a coordinate-based fusion module that integrated spatial, semantic, and edge reconstruction information. In addition, we proposed an automatic measurement of crack information for extracting the crack trunk and its corresponding length and width. The experimental results demonstrated that our network achieved the best balance between accuracy and inference speed compared to six established models.

Model for Calculating Stress Intensity Factors for an Inclined Crack at the Leading Edge of a Gas Turbine Engine Blade Under the Influence of Centrifugal Forces

The study is devoted to the issue of the destruction of a body with an inclined crack during rotation. A mathematical model for calculating stress intensity factors in a rectangular plate with an inclined crack under the influence of centrifugal tensile forces during rotation around an axis lying in the plane of the plate is constructed in the article. Based on the equations of the theory of elasticity and the principles of brittle fracture mechanics, relationships were obtained that relate the stress intensity factors of type I and II, the rotation speed and geometry of the plate, as well as the parameters of the crack: length, angle of inclination to the axis of rotation, distance from the axis of rotation to the crack. The complexity of the study is because the plate in question with an inclined crack is under the action of mass forces. Therefore, the values of the effective stresses are not the same along the crack edge. Accordingly, stress intensity factors will depend on the location of the crack relative to the axis of rotation. The influence of the crack location and plate rotation speed on the change in stress intensity factor values is analyzed based on the results obtained. As the distance from the axis of rotation to the crack increases, the values of the stress intensity factors decrease. As the plate rotation frequency increases, the stress intensity coefficients increase according to a parabolic law. The results of the study can be used to assess the limit state of the rotating blades of a gas turbine engine in the presence of an inclined crack. The mathematical model can find practical application for assessing the critical speed regime of blade rotation in the presence of cracks of various lengths and angles of inclination to the rotation axis.

Vison Transformer-Based Automatic Crack Detection on Dam Surface

Dam is an essential structure in hydraulic engineering, and its surface cracks pose significant threats to its integrity, impermeability, and durability. Automated crack detection methods based on computer vision offer substantial advantages over manual approaches with regard to efficiency, objectivity and precision. However, current methods face challenges such as misidentification, discontinuity, and loss of details when analyzing real-world dam crack images. These images often exhibit characteristics such as low contrast, complex backgrounds, and diverse crack morphologies. To address the above challenges, this paper presents a pure Vision Transformer (ViT)-based dam crack segmentation network (DCST-net). The DCST-net utilizes an improved Swin Transformer (SwinT) block as the fundamental block for enhancing the long-range dependencies within a SegNet-like encoder–decoder structure. Additionally, we employ a weighted attention block to facilitate side fusion between the symmetric pair of encoder and decoder in each stage to sharpen the edge of crack. To demonstrate the superior performance of our proposed method, six semantic segmentation models have been trained and tested on both a self-built dam crack dataset and two publicly available datasets. Comparison results indicate that our proposed model outperforms the mainstream methods in terms of visualization and most evaluation metrics, highlighting its potential for practical application in dam safety inspection and maintenance.

Nonlocal modelling of piezoelectric solid with cracks based on peridynamic differential operator

The paper establishes a nonlocal model for piezoelectric solids using the Peridynamic differential operator. The method transforms the displacement-electric potential equation, constitutive equation, and boundary conditions of piezoelectric solids from a local differential form to a nonlocal integral form. The solution for the displacement and electric potential distributions in piezoelectric solids is obtained using variational principles and the Lagrange multiplier method. The correctness and effectiveness of the model are validated through a comparison of the deformation analysis of piezoelectric solid square plates with analytical solutions. Analysis of piezoelectric solid square plates with edge cracks proves the applicability of this model for solving discontinuous problems. Furthermore, the paper explores the suitability of the model in analysing problems involving multiple cracks in piezoelectric solid plates, highlighting its capability to address defective piezoelectric solid problems. This model provides a new perspective for solving problems involving defects under electro-mechanical coupling conditions.

Validation of pneumatic crack detection in hole expansion test

According to the standard ISO 16630, the hole expansion test (HET) has to be stopped at the instant when the first through-thickness crack appears at the edge of the hole. The detection of the crack is challenging, since the maximum opening width should not exceed 0.1 mm at the inner diameter according to the newest version of the standard from 2017. A pneumatic crack detection has been introduced in which a pressure drop is used to identify the through-thickness crack. In the present paper, this method for stopping the hole expansion test is validated. It was tested for steels with different edge crack sensitivities and compared to stopping with force drop method. Therefore, the curves of pressure and force have been analysed. The influence of hole insertion method (shear cutting or abrasive water jet cutting) as well as specific hole expansion parameters (punch speed, air pressure) have been investigated. Besides the expanded diameters to evaluate the edge crack sensitivity, the opening width of the edge cracks were analysed to determine the suitability of the crack detection methods for different hole expansion ratios (HER).

Microstructure and texture transformation of wedge-shaped rolled 3%Y2O3p/ZGK200 composites

The microstructure and texture transformation of 3%Y2O3p/ZGK200 composites after wedge-shaped rolling were investigated. The 3%Y2O3p/ZGK200 composites could be wedge-shaped rolled for 50 % reduction without obvious edge cracks. Basal <a> slip, prismatic <a> slip and pyramidal <c+a> slip detected by in-grain misorientation axes (IGMA) combined with Schmid factor (SF) analysis were abundantly activated during the whole rolling process. Different from the activation of all kinds of dislocation slips, many {10 1‾ 2} extension twins and few {101‾ 1}-{101‾ 2} secondary twins were activated with a reduction of 10 %. With increasing reduction from 30 % to 50 %, {101‾ 1}-{101‾ 2} secondary twins and {101‾ 1} compression twins started to play more important roles. Finally, the rolled deformed grains were elongated along rolling direction (RD) with abundant twins. During the whole rolling process, few recrystallized grains were found in the composites due to the effect of Gd addition. The {101‾ 2} extension twins whose c-axis oriented along normal direction (ND) should be attributed to the formation of basal texture, which was kept unchanged during the whole rolling process.

Experimental and Numerical Studies on the Vibration of Hybrid Composite with an Edge Crack

The hybrid composite plate is increasingly used in marine, robotic arm, and other applications. Edge crack is the greatest common fault in the structural systems during its working time. In this research, the successful fabrications of a hybrid composite of epoxy-based composites reinforced with bamboo and glass fibers have been done to examine the vibration characteristics under free vibration. First-order shear deformation theory is used to study the fundamental natural frequencies of asymmetrically hybrid composite beam with edge cracks for cantilever beam boundary conditions. Both numerical (FEM) using ABAQUS software and experimental investigations are done for the vibration analysis of unidirectional bamboo/glass fiber epoxy hybrid composite (BGHC) beam with edge cracks using fracture mechanics theory. It is observed that implications edge crack with different crack depth and various fiber weight ratio parameters have a major effect on vibration analysis. Also, it is clear that the natural frequencies of the hybrid composite are significantly affected due to the fiber weight ratio and crack depth of the hybrid composite materials. So, crack lengths are playing a vital role in the dynamic or vibration characteristics of the hybrid composite materials. The results of natural frequencies have been shown that they are decreased with an increase in crack depth and an increase in the bamboo fiber weight. Thus, BGHC-2 made from 30% bamboo and 10% glass fiber can be a viable candidate for applications that will produce good vibration properties. Generally, the first-third natural frequency of the hybrid composite beam decreases within the increase of bamboo fiber and decreases in glass fiber. The composite materials having 60% of epoxy with 20% bamboo and 20% glass fiber, and 60% of epoxy with 10% glass and 30% bamboo fibers, are observed with a gradual decrease in the values of natural frequencies with respect to increasing in crack depth. A fine agreement was accomplished between the simulation and experimental results. Therefore, the present approach can be used to identify cracks for mechanical health monitoring by linking the variation in natural frequencies of the hybrid composite beams.

Research on the Crushing of Reinforced Concrete Two-Way Slabs by Pulse Power Discharge Technology

The application of pulse power discharge (PPD) technology in the crushing and dismantling of concrete structures has characteristics related to both green and environmental protection, as well as safety and reliability, with broad application prospects in the construction and municipal engineering fields in dense urban areas. Nevertheless, the research into using this technology to break reinforced concrete (RC) slabs is very limited, while the influence of key parameters on the crushing effect of reinforced concrete slabs is not clear. To solve this problem, a finite element model of an RC slab was established by ABAQUS. The effect of a shock wave generated by PPD on the surrounding concrete was simulated by an explosion-load equivalent, and the development process of concrete crack was simulated by a cohesive force model. Based on the results of the model analysis, the effects of reinforcement spacing, as well as diameter and concrete strength on the crushing effect of RC slabs were investigated. The results show that the increase in reinforcement diameter and the decrease in reinforcement spacing have a significant effect on limiting the development of cracks. According to the development of cracks, they can be divided into three types: edge cracks, cracks between central holes, and cracks between edge holes. The influence of reinforcement spacing and diameter on the first two crack widths is the most obvious. The increase in concrete strength also reduces the width of cracks. Based on the analysis results, the calculation expressions of the crushing effect of the PPD technique on RC slabs were established, which provides theoretical support for the popularization and application of this technique.

Effect of rolling reduction on microstructure, mechanical properties and fracture features of hot isostatically pressed 30CrMnSiNi2A low alloy ultrahigh strength steel

As a powder metallurgy (PM) defect, existence of prior particle boundaries (PPBs) often makes mechanical properties visibly deteriorated. Hot rolling has been found to be an effective method of destroying PPBs. In present study, five different rolling reductions are applied to explore the effects of rolling reduction on evolution of PPBs in PM 30CrMnSiNi2A steels. Microstructure, mechanical properties and fracture modes of five samples are systematically analyzed and compared. Increase of rolling reduction not only makes Al-rich PPBs refined but also makes continuous PPBs structure gradually transform to dispersed oxides and short chain fragments, which can be attributed to deformation of powder particles. Change on distribution of PPBs leads to the variation of fracture modes. A strength-ductility-toughness balance is achieved when the rolling reduction scales up to 60 %. Although increase of rolling reduction causes grain refinement, work hardening and improvement of PPBs, it promotes formation of edge cracks. Occurrence of edge cracks is strongly associated with PPBs inclusions and makes ductility and toughness deteriorated.

Analysis of failure characteristics of screen plates of ring hammer crusher used in coal handling applications

The screen plate, a critical component within a ring hammer crusher (also known as a ring granulator or rolling ring crusher), plays a vital role in the secondary crushing of coal. Functioning both as a platform for coal crushing and as a sieve to achieve the desired coal size, it is essential to understand and examine its failure characteristics to enhance its mechanical and wear resistance properties in coal handling applications. This study thoroughly explored the failure modes, mechanisms, and underlying causes of screen plate failures. Microscopic techniques such as optical microscopy (OM), scanning electron microscopy (SEM), Vickers microhardness test and spectrochemical analysis were utilised to identify the failure mechanism. Failure modes identified from the macroscopic analysis were discharged hole widening, hole wall break-off, plate edge crack, plate fracture, one-sided edge slimming, and general surface wear of the screen plate. The fractographic and wear track analysis identified the principal failure mechanisms of three-body abrasive wear, two-body sliding abrasion wear, shear-induced fatigue fracture and brittle shear fracture. The root causes of the failures are the rotor’s direct impact, defects in the parent material, the presence of hard materials in the coal and the use of unsuitable steel grade in the screen plate manufacturing. The service life of the screen plate can be improved through proper material selection, uniform crusher feeding, surface modification of the surface of the “as purchase” screen plate with appropriate wear-resistant materials, and adherence to good maintenance practices.

Galerkin finite block method with Lagrange multipliers method for cracked solids in functionally graded materials

This paper presents the application of the Galerkin Finite Block Method (GFBM) to address cracked solids associated with Functionally Graded Materials (FGMs), leveraging the foundational principles of the Galerkin method. The equilibrium equations pertinent to FGMs are articulated in their weak form. Employing Chebyshev polynomials as shape functions, the GFBM integrates mapping techniques to accommodate irregular finite or semi-infinite physical domains. Boundary and continuity conditions are enforced through the Lagrange Multiplier Method. The domain integrals are calculated through either analytical or numerical integration. The proposed method can easily solve the edge crack or diagonal crack problem by using the crack opening displacement method. The accuracy and convergence of the proposed method are illustrated through a selection of numerical examples. The obtained numerical solutions are verified with analytical solutions and the results from the Finite Element Method.

Analysis of Pavement Conditions and Handling of Road Damage at the Surface Layer

The Cukul - Buni Kasih road section at the Garut Regency Boundary in Pangalengan District, West Bandung Regency, West Java Province, is pivotal in facilitating economic growth and regional development. Spanning 3.493 km with a width of 3.12 m, this study aims to assess its condition and identify road damage types. Key indices, including SDI (Surface Distress Index), RCI (Road Condition Index), IRI (International Roughness Index), and PCI (Pavement Condition Index), were employed to evaluate road health. Visual analysis revealed an average SDI value of 112, indicating minor damage. The RCI method yielded an average value of 5, denoting slightly damaged conditions. IRI assessment resulted in an average value of 9, reflecting slight damage. The PCI method yielded an average of 46, signifying poor (bad) conditions. Predominant damage types include potholes, alongside alligator cracking, patching, edge cracking, weathering/raveling, and rutting. In summary, the Cukul – Buni Kasih road section (Garut Regency Boundary) is predominantly damaged, necessitating urgent attention. The assessment utilizing SDI, RCI, IRI, and PCI methods provides valuable insights for planning and executing necessary road maintenance measures.

ON THE FEATURES OF REFLECTION OF SHEAR ELASTIC WAVE PULSES FROM A VERTICAL CRACK

A computer simulation of the characteristics of pulse signals of shear waves reflected from the edge of a vertical crack coming to the surface of the control object and a bottom crack using radiated pulses of various lengths with narrow, medium width and wide spectra was carried out. Within the limits of changing the calculation parameters, a feature of pulse reflection is established – the ratio of the maxima of the envelope pulses when reflected from a crack coming to the surface of the OK and the bottom crack is approximately 3.40 (10.6 dB), which coincides with the corresponding ratio of the maxima of the spectra. Based on the results of calculations of pulse shapes with frequency spectrum of different widths when waves are reflected from a vertical crack, the recommendation is justified not to use long pulses with narrow spectra with reduced beam resolution in the time of flight diffraction method.

A Review of Sheet Metal Forming Evaluation of Advanced High-Strength Steels (AHSS)

This paper presents a review on the formability evaluation of AHSS, enhancing necking-based failure criteria limitations. Complementary fracture/damage constitutive modeling approaches specifically tailored to formability evaluation, validated through numerical and experimental methods, are also subjects of research. AHSS are widely processed through sheet metal forming processes. Although an excellent choice when lightweight, high-strength, and ductility are critical factors, their multi-phase microstructure accentuates forming challenges. To accurately model forming behavior, necking-based failure criteria as well as direct fracture models require improvements. As a necking-based failure model, the conventional forming limit diagram/curve (FLD/FLC) presents limitations in estimating direct fracture (surface cracks, edge cracks, shear cracks), as well as deformation histories under non-linear strain paths. Thus, significant research efforts are being made towards the development of advanced fracture constitutive models capable of predicting fracture scenarios without necking, which are more frequently observed in the realm of AHSS. Scientific community research is divided into several directions aiming at improving the forming and fracture behavior accuracy of parts subjected to sheet metal forming operations. In this review paper, a comprehensive overview of ductile fracture modeling is presented. Firstly, the limitations of FLD/FLC in modeling fracture behavior in sheet metal forming operations are studied, followed by recent trends in constitutive material modeling. Afterwards, advancements in material characterization methods to cover a broad range of stress states are discussed. Finally, damage and fracture models predicting failure in AHSS are investigated. This review paper supplies relevant information on the current issues the sheet metal forming community is challenged with due to the trend towards AHSS employment in the automotive industry.

Mitigation of Edge Cracks by Controlling the Manganese-to-Sulfur Ratio (Mn/S) in Low Carbon Boron Steel

Mitigation of Edge Cracks by Controlling the Manganese-to-Sulfur Ratio (Mn/S) in Low Carbon Boron Steel

Elastomers Fail from the Edge

The performance of soft devices is limited by the fracture resistance of elastomers. Thus, understanding how fracture resistance changes with material and sample geometry is an important challenge. A key observation is that thicker elastomers can be significantly tougher than thinner ones. We show that this surprising toughness enhancement in thick samples emerges from the 3D geometry of the fracture process. In contrast to the classical picture of a 2D crack, failure is driven by the growth of two separate “edge” cracks that nucleate early on at a sample’s sides. As loading is increased, these cracks propagate in towards the sample midplane. When they merge, samples reach their ultimate failure strength. In thicker samples, edge cracks need to propagate farther before meeting, resulting in increased sample toughness. We demonstrate that edge-crack growth is controlled by the elastomer’s strain-stiffening properties. Our results have direct implications for how to effectively toughen elastomers by controlling their geometry and large-strain mechanical properties. Published by the American Physical Society 2024

Role of multi-variant deformation-induced HCP plates in cryogenic mechanical properties of an FCC high entropy alloy

We investigated the temperature-dependent mechanical properties and deformation mechanisms of the Fe49.5Mn30Co10Cr10C0.2Ti0.1V0.1Mo0.1 alloy from room temperature to cryogenic temperatures. As the deformation temperature decreased, both the strength and strain-hardening rate increased, while ductility tended to decrease. The higher strength of the material deformed at 123 K, compared to that deformed at 223 K, can be attributed to the larger number of multivariant HCP plates and higher hetero deformation induced (HDI) strengthening in the former. Multivariant deformation-induced HCP plates were the primary deformation mechanisms at all deformation temperatures, and cryogenic deformation activated intersecting shear, defined as the primary HCP plate being sheared by the secondary HCP plate. This mechanism contributed to stress relaxation and enhanced deformation accommodation. The reduced ductility observed in the material deformed at 123 K may be attributed to coarse edge and grain boundary cracks, which were more pronounced when the TRIP effect was enhanced.