Search Results (64)

This study presents a unique and comprehensive application of ANSYS Mechanical R19.2’s SMART crack growth feature, leveraging its capabilities to conduct an unprecedented parametric investigation into fatigue crack propagation behavior under a wide range of positive and negative stress ratios, and to provide detailed insights into the influence of hole positioning on crack trajectory. By uniquely employing an unstructured mesh method that significantly reduces computational overhead and automates mesh updates, this research overcomes traditional fracture simulation limitations. The investigation breaks new ground by comprehensively examining an unprecedented range of both positive (R = 0.1 to 0.5) and negative (R = −0.1 to −0.5) stress ratios, revealing previously unexplored relationships in fracture mechanics. Through rigorous and extensive numerical simulations on two distinct specimen configurations, i.e., a notched plate with a strategically positioned hole under fatigue loading and a cracked rectangular plate with dual holes under static loading, this work establishes groundbreaking correlations between stress parameters and fatigue behavior. The research reveals a novel inverse relationship between the equivalent stress intensity factor and stress ratio, alongside a previously uncharacterized inverse correlation between stress ratio and von Mises stress. Notably, a direct, accelerating relationship between stress ratio and fatigue life is demonstrated, where higher R-values non-linearly increase fatigue resistance by mitigating stress concentration, challenging conventional linear approximations. This investigation makes a substantial contribution to fracture mechanics by elucidating the fundamental role of hole positioning in controlling crack propagation paths. The research uniquely demonstrates that depending on precise hole location, cracks will either deviate toward the hole or maintain their original trajectory, a phenomenon attributed to the asymmetric stress distribution at the crack tip induced by the hole’s presence. These novel findings, validated against existing literature, represent a significant advancement in predictive modeling for fatigue life assessment, offering critical new insights for engineering design and maintenance strategies in high-stakes industries. Full article

Lamb waves offer a series of desirable features for Structural Health Monitoring (SHM) applications, such as the ability to detect small defects, allowing to detect damage at early stages of its evolution. On the downside, their propagation through media with multiple geometrical features results in complicated patterns, which complicate the task of damage detection, thus hindering the realization of their full potential. This is exacerbated by the fact that numerical models for Lamb waves, which could aid in both the prediction and interpretation of such patterns, are computationally expensive. The present paper provides a flexible surrogate to rapidly evaluate the sensor response in scenarios where Lamb waves propagate in plates that include multiple features or defects. To this end, an offline–online ray tracing approach is combined with Frequency Response Functions (FRFs) and transmissibility functions. Each ray is thereby represented either by a parametrized FRFs, if the origin of the ray lies in the actuator, or by a parametrized transmissibility function, if the origin of the ray lies in a feature. By exploiting the mechanical properties of propagating waves, it is possible to minimize the number of training simulations needed for the surrogate, thus avoiding the repeated evaluation of large models. The efficiency of the surrogate is demonstrated numerically, through an example, including different types of features, in particular through holes and notches, which result in both reflection and conversion of incident waves. For most sensor locations, the surrogate achieves an error between 1% and 4%, while providing a computational speedup of three to four orders of magnitude. Full article

This study investigates the effect of a non-zero fillet radius, ρ, on the fatigue behaviour of notched components under uniaxial loading. A new diagram is introduced, which discusses the relationship between the notch tip radius and the fatigue limit. It also identifies a critical radius, ρ**, precisely marking the transition from sharp to blunt notch behaviour. Additionally, its application to the “stop-hole” technique is considered, where both material properties and geometric characteristics are analysed, demonstrating that introducing a fillet radius can improve fatigue resistance. Full article

Background/Objectives: The aim of the present study was to evaluate the relationship between the type of scapular notch (SN), the morphometry of the SN, and the area of the suprascapular nerve (SSN). In addition to determining whether scapular notches other than Type VI, according to the classification of Rengachary, can generate a predisposition to SSN entrapment neuropathy. Methods: One hundred and sixty-nine dry scapulae were examined, the scapular notches were classified, according to the classification of Rengachary, and for each SN, the superior transverse diameter (STD), longitudinal diameter (LD), and area of the SN were determined. The SSN was dissected in five shoulders and its area was calculated. The data were analyzed in the statistical software SPSS. Results: The values for the STD, LD, and area of the SN showed significant differences between the types of scapular notches (p < 0.0001). Along the same lines, a considerable positive correlation (r = 0.79; p < 0.0001) was established between the area of the SN and the STD. Similarly, a very strong positive correlation (r = 0.87; p < 0.0001) was established between the area of the SN and the LD. This indicated that, as the STD and the LD increase, the area of the SN increases. Conclusions: Although different studies have reported an association between SN Type VI and the compression of the SSN by the formation of a bony hole that reduces the area of the notch, we have found that SN Type IV presented a smaller area among the types of notches and a smaller area than the SSN, which exposes the SSN to be closer to or in contact with the superior transverse ligament of the scapula, potentially subjecting the nerve to greater pressure and potentially resulting in SSN entrapment. This is evidence that should be considered in the clinical diagnosis of patients with entrapment neuropathy, since the type of SN and the area of the SSN can be determined by ultrasound, which contributes to a more accurate preoperative evaluation and diagnosis. Full article

Placing empty holes between charging holes is widely used in blasting engineering to achieve directional fracture blasting. Studies have shown that the presence of a notch along the empty hole wall enhances stress concentration and supports improved control over crack propagation. The notch angle and length are the two main parameters influencing the impact of notch holes. Therefore, in this study, we used numerical simulations to investigate how varying notch angles and lengths influence the directional fracture blasting effect. The findings suggest that, among the different types of holes used in directional fracture rock blasting, notched empty holes have the most significant guiding effect, followed by empty holes, while the absence of empty holes yields the least effective results. In the directional fracture blasting of a notched empty hole, stress concentration occurs at the notch tip following the explosion. This alters the stress field distribution around the empty hole, which shifts from a compressive to a tangential tensile state. Additionally, this concentration of stress causes the explosion energy to be focused on that location, resulting in a directional fracture blasting effect. In blasting construction, selecting the appropriate notch hole parameters is necessary to achieve optimal effects and reduce damage to surrounding rocks. Based on the notch parameters assessed in this study, the optimal effect of directional fracture blasting is achieved when the notch angle is 30°. Full article

The stop-hole technique is a well-known strategy to extend the fatigue life of cracked components. The ability to estimate fatigue life after the hole is important for safety reasons. The objective here is to develop strategies for the accurate prediction of initiation and propagation life ahead of the stop-hole. Experimental work was developed in a Compact-Tension (CT) specimen made of 7050-T7451 aluminium alloy and with a 3 mm diameter hole. A total number of 625,000 load cycles were required to re-initiate the crack after the hole. Crack initiation life after the hole was estimated using the Theory of Critical Distances combined with the Smith–Watson–Topper parameter. A value of a₀ = 31.83 µm was obtained for El Haddad parameter, which was used to define the critical distance. The predicted life was found to be only 4% lower than the experimental value. The fatigue crack growth (FCG) rate was calculated using a node release strategy, assuming that cyclic plastic deformation is the main damage mechanism and that cumulative plastic strain is the crack driving parameter. A good agreement was found between the numerical predictions of da/dN and the experimental results. The main result, however, is the proposed methodology, which allows predicting the initiation and propagation lives in notched components. Full article

Pore and crack formation in parts produced by additive manufacturing (AM) processes, such as laser powder bed fusion, is one of the issues associated with AM technology. Surface and subsurface cracks and pores are induced during the printing process, undermining the printed part durability. In-situ detection of defects will enable the real-time or intermittent control of the process, resulting in higher product quality. In this paper, a new eddy current-based probe design is proposed to detect these defects in parts with various defects that mimic pores and cracks in additively manufactured parts. Electromagnetic finite element analyses were carried out to optimize the probe geometry, followed by fabricating a prototype. Artificial defects were seeded in stainless steel plates to assess the feasibility of detecting various flaws with different widths and lengths. The smallest defect detected had a 0.17 mm radius for blind holes and a 0.43 mm notch with a 5 mm length. All the defects were 0.5 mm from the surface, and the probe was placed on the back surface of the defects. The surface roughness of the tested samples was less than 2 µm. The results show promise for detecting defects, indicating a potential application in AM. Full article

To enhance the uplift capacity and facilitate the installation of multi-row perfobond connectors at shallow burial depths, this study puts forward a novel notched T-perfobond connector. The design incorporates an integrated flange at the bottom of the connector and a notch at the edge of the hole. Through pull-out model tests on four notched T-perfobond connectors, this research investigates their failure mechanisms and pull-out capacities. Utilizing the explicit dynamics method in ABAQUS, a finite-element model of the pull-out resistance test for notched T-perfobond connectors is established and verified against experimental data. Furthermore, a detailed parametric analysis involving 54 models is conducted, examining crucial parameters such as rib dimensions, hole geometry, flange size, notch width, bar diameter, and material properties. Based on the combined experimental and numerical results, this paper assesses the suitability of current formulas for calculating the pull-out capacity of perfobond connectors and proposes a refined calculation method specifically for notched T-perfobond connectors. All the findings reported in this paper can serve as a reference in the design and construction of composite structures. Full article

The detection of defects in aluminium alloys using eddy current testing (ECT) can be restricted by higher electrical conductivity. Considering the occurrence of discontinuities during the selective laser melting (SLM) process, checking the ability of the ECT method for the mentioned purpose could bring simple and fast material identification. The research described here is focused on the application of three ECT probes with different frequency ranges (0.3–100 kHz overall) for the identification of artificial defects in SLM aluminium alloy AlSi10Mg. Standard penetration depth for the mentioned frequency range and identification abilities of used probes expressed through lift-off diagrams precede the main part of the research. Experimental specimens were designed in four groups to check the signal sensitivity to variations in the size and depth of cavities. The signal behavior was evaluated according to notch-type and hole-type artificial defects’ presence on the surface of the material and spherical cavities in subsurface layers, filled and unfilled by unmolten powder. The maximal penetration depth of the identified defect, the smallest detectable notch-type and hole-type artificial defect, the main characteristics of signal curves based on defect properties and circumstances for distinguishing between the application of measurement regime were stated. These conclusions represent baselines for the creation of ECT methodology for the defectoscopy of evaluated material. Full article

This paper aims to investigate the response and fracture of EMT carbon steel round-hole tubes (EMT carbon steel RHTs) under cyclic bending loads. The study considers four different hole orientations (0°, 30°, 60°, and 90°) and five distinct hole diameters (2, 4, 6, 8, and 10 mm). The results reveal that hole orientation and diameter exert a minimal impact on the moment-curvature relationship, leading to the formation of stable loops. The ovalization-curvature graphs demonstrate a trend of asymmetry, serration, and growth with an increasing number of bending cycles. Additionally, larger hole orientations or smaller notch diameters result in reduced ovalization. Furthermore, the double logarithmic coordinates of the controlled curvature–number of cycles required to induce fracture reveal five parallel lines for different hole diameters when the hole orientation is fixed. Finally, in adopting the formulas for smooth tubes and for 6061-T6 aluminum alloy round-hole tubes (6061 aluminum alloy RHTs), this study adjusts the related material parameters. These modifications effectively describe the controlled curvature–number of cycles required to induce fracture for EMT carbon steel RHTs with different hole orientations and diameters under cyclic bending, demonstrating reasonable agreement with the experimental results. Full article

The static and fatigue analysis of plates made of 2D woven roving composites with holes is conducted. The parametrization of convex holes is proposed. The experimental results of the specimens without holes and with different shapes of notches are discussed. The experiments and the appropriate procedures are carried out with the aid of ASTM codes. The fatigue behavior is considered with the use of the low cycle fatigue method. The analysis is supplemented by numerical finite element modeling. The present work is an extension of the results discussed in the literature. The damage of plates with holes subjected to tension always occurs at the tip of the holes, i.e., (x = a, b = 0), both for static and fatigue failure. The originality and the novelty of this approach are described by the failure’s dependence on two parameters: n and the ratio of the a/b ratio characterizing the hole geometry. The fuzzy approach is employed to reduce the amount of experimental data. Full article

The elongation of the bolt hole is an important parameter for assessing the failure of bolted joints. However, direct experimental measurement using strain gauges and extensometers is difficult. This article shows that digital image correlation (DIC) can overcome the difficulties and provide important indications of the failure mechanisms of bolted joints. Hole elongation was measured using DIC in the following carbon/epoxy composite configurations: standard open-hole tensile (OHT) and filled-hole tensile (FHT), single-lap shear only-bolted (OB), and single-lap shear hybrid-bolted/bonded (HBB) joints. For each configuration, the hole-elongation changes were tracked for cross-ply (CP) and quasi-isotropic (QI) stacking sequences with two thicknesses. In the tensile load direction for OHT and FHT cases, CP showed a greater hole elongation than QI. However, the opposite trend was observed in the transverse direction. In OB joints, bypass loads contributed more to the hole elongation than bearing action. In HBB joints, it has been observed that the adhesive significantly reduces hole elongation, particularly for CP configurations. Moreover, it was found that in HBB joints, hole elongation was independent of laminate lay-up, while it was very determinative in OB joints. Full article

Owing to the substantial benefits in environmental protection and resource saving, recycled aggregate concrete (RAC) is increasingly used in civil engineering; among the different types, RAC-filled steel tubes are an efficient structural form utilizing the advantages of concrete and steel tubes. This paper proposed a novel full-bolted beam-to-concrete-filled steel tube (CFST) joint and investigated the anchoring behavior of the steel plates embedded in RAC-filled steel tubes, which represents the behavior of the tensile zone in this joint, to demonstrate the feasibility of utilizing RAC in composite structures. The specimen consisted of a CFST and a connecting plate embedded in the CFST. In total, 18 specimens were tested to study the effects of concrete type (i.e., recycled aggregate concrete and natural aggregate concrete), anchoring type (i.e., plate with holes, notches, and rebars), and plate thickness on the pullout behavior, such as anchorage strength, load–displacement response, and ductility. Based on experimental results, the aggregate type of the concrete does not affect the pullout behavior obviously but the influence of anchoring type is significant. Among the three anchoring methods, the plate with rebars exhibits the best performance in terms of anchorage strength and ductility, and is recommended for the beam-to-CFST joint. In addition, plate thickness obviously affects the behavior of plates with holes and notches, the bearing area of which is proportional to the thickness, whereas the pullout behavior of the plates with rebars is independent of thickness. Finally, design formulas are proposed to estimate the anchorage strength of the connecting plates, and their reasonability is validated using the experimental results. Full article

The scaling of the strength of composite parts with part size is referred to as the size effect. In the presence of notches, stress concentration affects a portion of material that increases with the notch size. Furthermore, in woven composites, the notch and tow size can be comparable, thus demanding a mesoscale approach to properly capture the stress intensification. In this paper, a probabilistic mesoscale method to model the size effect in notched woven composites is presented. First, the stress distribution is estimated with a finite element model, calibrated on experimental Digital Image Correlation data. The FE model simulates the mesoscale heterogeneity of the woven reinforced material and replicates the local stress intensification at the tow level. Then, a three-parameter Weibull-based statistical model is introduced to model the probability of failure from the calculated stress distribution and the volume of the part. An equivalent stress is used to capture the relevant fiber and matrix failure modes and the maximum value within the specimen volume is the random variable of the model. The method is applied to open-hole tension tests of a woven twill carbon fiber–epoxy composite. Two specimen widths and three width-to-diameter ratios, from 3 to 12, are considered. Specimen width produced an observable size effect, whereas the variation of hole size in the range considered did not. The statistical model is found to accurately describe the experimental observations, efficiently replicating an inverse size effect, regardless of hole size, while wider specimens lead to a lower probability of failure. Full article

Specimens made of various materials with different geometric features were investigated to predict the failure loads using the recently proposed criterion comprised of both stress and stress gradient conditions. The notch types were cracks and holes, and the materials were brittle, ductile, isotropic, orthotropic, or fibrous composites. The predicted failure stresses or loads were compared to experimental results, and both experimental and theoretically predicted results agreed well for all the different cases. This suggests that the stress and stress-gradient-based failure criterion is both versatile and accurate in predicting the failure of various materials and geometric features. Full article