Mesh Size Research Articles

One-Way Fluid–Structure Interaction Simulation of the Added Damping of T(0,1) Modes of Two Partially Overlapped Identical Plates in Still Water

Abstract Structures with a partially overlapped status in water can be seen in some engineering applications, and the fluid-structure coupling vibration behavior of two partially overlapped identical plates has been studied previously through the experimental method. In this study, the added damping of the T(0,1) modes of two submerged partially overlapped plates is numerically investigated through the one-way fluid-structure interaction (FSI) method. The relevant numerical settings, like the mesh size, calculated periods, time-step size, and vibration amplitude, were tested first. Then, the numerical results were compared with experimental results, and good agreements were found. Finally, numerical results were analyzed. The vibration status of two plates in the joint abutting area or the overlapped area has an important influence on the added mass variation. When the added mass is higher, the phase difference between modal force and vibration displacement is also greater, which is the main reason for the higher added damping. The relationship between the phase difference and the frequency in water can be approximately fitted to a straight line, which can probably be used to predict the added damping variations caused by fluid boundary changes of submerged structures.

Influence of selected contaminations and melt filtration on the properties of ABS and ABS recyclate

AbstractPlastic recyclates can be contaminated with a variety of impurities due to their previous life, which cannot always be perfectly separated in recycling pretreatment steps. Hence melt filtration is an important step in reprocessing plastic recyclates to achieve material of sufficient purity, but it also leads to more stress on the material due to higher pressures and longer processing times. In our study, we investigated the influence of typical particulate impurities as may occur in recyclate on the mechanical and rheological properties of ABS. Even low amounts of contaminations lowered the key properties. Melt filtration of post‐consumer ABS recyclate with different mesh size melt screens showed little improvement of mechanical properties, but longer idle times and loss of material. Damage to the material caused by finer filtration could be shown by thermal measurements.Highlights Determination of properties of ABS contaminated with 0.5–2.0 wt.% of selected impurities (wood and rubber particles). Melt filtration of post‐consumer ABS recyclate with different melt screens. Investigation of process and properties of filtered ABS recyclate.

Fatigue crack growth simulation by extended finite element method: A review of case studies

AbstractNumerical simulation of fatigue crack growth (FCG) is presented, based on the application of the extended finite element method (XFEM). Couple of case studies are presented, as a review of recent experience of the Belgrade school of XFEM simulations, established at the Faculty of Mechanical Engineering. Case studies comprised Charpy specimen with initial crack at the notch tip, oil rig pipe with an axial surface crack, pressure vessels with a crack at the welded joint with connecting pipe, turbine shaft with a crack at the transition radius, optimization of a wing spar in respect to FCG, the effect of mesh size on fatigue life estimation of a stringer panel, fatigue life estimation of wing‐to‐fuselage connecting lug, geometry effect on fatigue life of orthopedic plates and fatigue life of hip implant. Based on these case studies, XFEM is discussed in respect to its accuracy and efficiency. It is concluded that XFEM is a versatile tool for simulation of FCG, providing an excellent option for precise and reliable fatigue life of a cracked component.

WEAR RESISTANT OF CACO3/FLY-ASH CERAMIC MATRIX COMPOSITE

This study aimed to investigate the potential of utilising fly ash, a harmful byproduct of coal waste, in the manufacturing of composite materials to reduce its environmental impact. Calcium carbonate (CaCO3) and fly ash were mixed with zinc stearate using the powder metallurgy method to create wear-resistant samples. The compaction load was adjusted to achieve optimal low-pressure compaction, with pressures of 22.75 MPa, 23.45 MPa, 24.14 MPa, and 24.83 MPa used for single punch pressing. After 10 minutes of holding time, sintering was conducted at 900 OC for 1 hour. The raw materials were tested using X-ray diffraction (XRD) and sieved based on the mesh size. The composite was characterised through various tests, including density testing, wear testing, and scanning electron microscopy (SEM) to observe the microstructure. The density value increased with the compaction load, with a maximum apparent density of 1.794 g/cm3 and the highest porosity percentage at a pressure of 22.75 Mpa of 31.155%. Furthermore, the specific wear value decreased as the compaction load increased, with the lowest specific abrasion value of 1.17 x 10-6 mm2/kg. Therefore, using fly ash to produce composite materials is a promising solution to reduce the negative impact of coal waste while producing wear-resistant materials.

Indication of feeding ground inside the Manta Ray's cleaning station by investigation of the zooplankton community composition in Raja Ampat Islands, Indonesia

Abstract. Widiastuti, Borumei D. 2024. Indication of feeding ground inside the Manta Ray's cleaning station by investigation of the zooplankton community composition in Raja Ampat Islands, Indonesia. Biodiversitas 25: 1239-1245. Raja Ampat Islands, Indonesia, hosts reef manta ray (Mobula alfredi) and oceanic manta ray (Mobula birostris). Studies reported that these areas have functioned as manta ray cleaning and nursery sites. However, food availability is also the main attraction for manta ray aggregation. Thus, this study investigated the zooplankton community composition and abundance in the Manta Sandy Spot, a manta's cleaning station, to indicate its other role as the manta ray's feeding ground. Three sampling sites were located around the cleaning station bordered by mooring. A plankton net collected samples with a 100 µm mesh size, a mouth diameter of 30 cm, and a 1 m length horizontally towed from a boat for 5-10 min at a speed of ~2 knots. Manta ray's behavior was observed by snorkeling in the surface waters. Results demonstrated that the zooplankton was only composed of Copepod, consisting of three orders: Calanoida, Cyclopoida, and Harpacticoida. Among these orders, Calanoids dominated the zooplankton composition (93%). These genera were further grouped according to their body sizes, whereas three genera in Calanoids (Eucalanus, Calanus, and Undinula) were categorized as large-bodied zooplankton. The presence of the large-bodied zooplankton in the water samples, Calanoids, and Cyclopoids, which have been reported as the manta rays' preferred prey, indicates the area's role as the manta ray's feeding ground. This finding is supported by studies that found these zooplankton in the water where manta rays' feeding activity occurred and were absent in areas with no feeding activity. More indications were demonstrated by the manta ray's behavior, which followed the feeding activity criteria.

A multimesh finite element method for integral nonlocal elasticity using mesh-decoupling technique

This study presents a generalized multimesh nonlocal finite element method (M2-FEM) that addresses several long-standing challenges in the numerical simulation of Eringen’s integral elasticity theories, often used to model nonlocal effects. The major challenges in the numerical simulation of integral boundary value problems are primarily rooted in the coupling of the spatial discretization of the global (parent) and integral (child) domains, which severely restricts both the applicability and the computational efficiency of existing algorithms by imposing an implicit trade-off between the accuracy of the child domain and the resources required by the overall parent domain. One of the defining contributions of this study consists in the development of a mesh-decoupling technique that generates isolated sets of meshes such that the parent and child domains can be discretized and approximated independently. This mesh-decoupling has multi-fold advantages on the simulation of integral theories such that, when compared to existing state-of-the-art techniques, the proposed algorithm achieves a greater ability to adopt generalized integral kernel functions, the ability to handle non-regular (non-rectangular) domains via unstructured meshing, and simultaneously better numerical accuracy and efficiency (hence allowing greater flexibility in both mesh size and computational cost trade-off decisions). Both benchmark studies and several case studies are conducted to assess the effectiveness of M2-FEM. Simulation results confirm that M2-FEM can accurately simulate integral nonlocal problems and demonstrate its multi-fold computational advantages over existing mesh-coupling-based nonlocal finite element methods. Overall, the proposed M2-FEM algorithm is very general and it can be applied to a variety of integral theories, even beyond nonlocal elasticity.

A plastic Stillinger-Weber potential-based discretized virtual internal bond approach for modeling soft rock fracture and its application in tunnel failure

Soft rocks present some undesirable behaviors, such as low strength, high plasticity and softening. These traits pose challenges in the design and construction of soft rock tunnels. To address these issues and model plastic fracture behaviors of soft rocks, we proposed a plastic Stillinger-Weber (PSW) potential and integrated it into the discretized virtual internal bond (DVIB) model. The PSW-DVIB model combines the strengths of the plastic DVIB and the SW-DVIB models. It not only effectively reproduces the plastic fracture behavior but also accurately reflects the Poisson’s ratio. Moreover, due to the inclusion of fracture energy in the PSW potential, the simulation results are basically mesh size independent. The PSW-DVIB model is then utilized to investigate the failure behaviors of soft rock tunnels. The effects of the coefficient of lateral pressure, in-situ stress, Poisson’s ratio and tunnel shape on tunnel failure are investigated. The simulated results indicate that the coefficient of lateral pressure has significant influence on the failure zone distribution of the surrounding rock. With the coefficient of lateral pressure increasing, the failure degree of surrounding rock decreases firstly and then increases. The optimum coefficients of lateral pressure for the stability of circular, arched and square tunnels are about 1.00, 0.75 and 0.75, respectively. When the in-situ stress or Poisson’s ratio is larger, the influence of the coefficient of lateral pressure on tunnel failure is more obvious. The influence of the coefficient of lateral pressure on square tunnels are more significant than the arched tunnels, and then the circular tunnels. These findings provide valuable insights for the design and construction of soft rock tunnels.

Influence of panel density on the characteristics of novel multifunctional particleboard

ABSTRACT A novel approach to produce a multifunctional particleboard (PB) with lower density and high electrical conductivity is presented. To this end, woven carbon nets with a perforated structure were inserted into the panel structure during mat formation. PB with different densities of 600, 650, 700, and 750 kg/m3 were produced without and with carbon nets having a mesh size of 225 mm2. The physical and mechanical properties of the PB were evaluated according to the EN310, EN319 and EN317 standards, respectively, and the electrical properties were measured using the developed “four-probe method”. It was found that, increasing the panel density from 600 to 750 kg/m3 led to a significant improvement in flexural strength and internal bond strength but had a negative effect on the thickness swelling of the PB. The results also showed that by incorporating carbon nets into the panel structure, the insulated PB was transformed into an electrically conductive panel suitable for furniture applications. The electrical resistance of the panels was significantly reduced by increasing the panel density to 750 kg/m3. The carbon nets also significantly improved the flexural properties of the composites and had some negative effects on the internal bond strength. The piece of furniture produced also confirmed the suitability of the multifunctional PB for illuminating the LED lamps and integrating the cell phone charging technology into the panels.

Dynamic behaviors of concrete gravity dam against combined blast wave and bubble pulsation of underwater explosion

Underwater explosion process mainly includes the preceding blast wave and the succeeding bubble pulsation, while the effect of bubble pulsation on hydraulic structures is always neglected. This paper aims to numerically study the dynamic behaviors of prototype concrete gravity dam against underwater explosion, considering the combined effects of blast wave and bubble pulsation. Firstly, a finite element analysis (FEA) approach for predicting the underwater explosion loadings, as well as the damage evolution and dynamic responses of dam against underwater explosions was proposed, in which the hydrostatic pressure of reservoir and the dead load of dam were considered. Based on Cole's formula and the existing underwater explosion tests, the reliability of FEA approach, including the mesh sizes, material models and the corresponding parameters, as well as the mapping, Fluid-Structure Interaction and contact algorithms, was comprehensively validated. Secondly, to realize the simulation of the prototype gravity dam impeded by the validated small Lagrange mesh size, a mesh transition strategy was proposed based on the equivalence of dam damage modes and total eroded element mass. Finally, the dynamic behaviors of a typical 120 m-height concrete gravity dam against underwater explosion, i.e., 1 t of TNT equivalence detonated at a depth of 35 m and standoff distances of 4–16 m, were examined. The dimensionless distance λR, i.e., the ratio of the standoff distance to the maximum bubble radius, was introduced to quantitatively evaluate the underwater explosion loadings and dynamic behaviors of the dam. It indicates that, the blast wave firstly leads to the local compressive damage on the upstream surface, as well as the tensile damage on the downstream folded slope and dam heel. The succeeding free vibration and bubble pulsation will further aggravate the damage degree, resulting in the cracking of dam neck and heel. Especially for the scenarios when λR ≤ 1.22, the overall sliding of dam is highly prone to occur.

Failure analysis of curved interface in pultruded fiber-reinforced polymer laminations using phase-field approach

Pultruded fiber-reinforced polymer (FRP) composites frequently encounter fabric misalignment perpendicular to the pultrusion direction, resulting in the formation of a curved interface. For predicting delamination in pultruded fabric with curved interfaces, the phase field model is employed in the commercial software ABAQUS® through the UMAT and HETVAL subroutines. In this study, the Mode-I, Mode-II, and mixed-Mode delamination behavior are successfully simulated to validate the efficiency of the proposed phase field method. A parametric study is conducted to investigate the impact of mesh size and phase field length on the simulation results. The recommended mesh size and interface length of the phase-field model are given. Finally, the validated phase-field model is used to predict the delamination behavior exposed to Mode-I, Mode-II, and mixed-Mode loading for the curved interface. The results indicate that specimens with a curved interface exhibit greater bearing capacity compared to those with a planar interface.

Master S-N Curve Fatigue Life Prediction of a Railroad Car Bogie Based on Mesh Insensitive Structural Stress Method

Fatigue life prediction of a welded structure is a complex phenomenon due to the nature of fatigue and the welding process. Additionally, Finite Element Method (FEM) results are extremely sensitive to the size of elements. Therefore, it is difficult to adopt a method to estimate the fatigue life, especially for welded structures. Besides, mesh size independence is a critical issue to perform fatigue life prediction methods that eliminates the need for excessive element numbers in the mesh. This paper investigates the Master S-N Curve Approach (MCA) using the output parameters of the mesh insensitive Structural Stress Method (SSM). MCA based on SSM employs structural stresses recovered from nodal forces and nodal moments. To recover these inputs, FEM model should be established properly. Thus, boundary conditions and applied loads were prepared for the model according to the BS EN 13749:2021. The submodeling technique in ANSYS software was used to analyze the bogie structure. To justify the mesh independence for the model, different mesh sizes were tested. In a specific range for shell bodies, SSM was shown to provide sufficient mesh independence feature. Furthermore, MCA was compared with Hot Spot Stress Method and Nominal Stress Method based on their fatigue life estimations.

The Côte d’Argent, France: Quantification of Plastic Pollution in Beach Sediments

Pollution with anthropogenic waste, particularly persistent plastic, has now reached every remote corner of the world. The French Atlantic coast, given its extensive coastline, is particularly affected. To gain an overview of current plastic pollution, this study examined a stretch of 250 km along the Silver Coast of France. Sampling was conducted at a total of 14 beach sections, each with five sampling sites in a transect. At each collection site, a square of 0.25 m2 was marked. The top 5 cm of beach sediment was collected and sieved on-site using an analysis sieve (mesh size 1 mm), resulting in a total of approximately 0.8 m3 of sediment, corresponding to a total weight of 1300 kg of examined beach sediment. A total of 1972 plastic particles were extracted and analysed using infrared spectroscopy, corresponding to 1.5 particles kg−1 of beach sediment. Pellets (885 particles), polyethylene as the polymer type (1349 particles), and particles in the size range of microplastics (943 particles) were most frequently found. The significant pollution by pellets suggests that the spread of plastic waste is not primarily attributable to tourism (in February/March 2023). The substantial accumulation of meso- and macro-waste (with 863 and 166 particles) also indicates that research focusing on microplastics should be expanded to include these size categories, as microplastics can develop from them over time.

ANALYSIS OF PRODUCTION FACTORS FOR GILLNET FISHING GEAR AT THE TECHNICAL IMPLEMENTATION UNIT (UPT) OF THE FISHERY PORT OF RIAU PROVINCE

Dumai City relies entirely on marine waters for its fisheries production, with gillnets being a predominant fishing gear among local fishermen. Gillnets, characterized by their rectangular shape with varying mesh sizes, utilize floats and weights. This study aimed to identify the factors influencing gillnet catches in Dumai City. Results from simultaneous testing revealed that all production factors significantly impact catch quantities. Through multiple linear regression analysis, it was determined which factors exerted positive and negative effects. The regression equation, Y = 0.108 – 0.183 X1 – 0.411 X2 – 0.345 X3 + 0.173 X4 + 0.116 X5 + 0.451 X6 + 0.181 X7 – 0.106 X8 + 0.223 X9, elucidated these relationships. The cumulative effect of production factors on catches amounted to 64.20%. This study provides valuable insights into optimizing gillnet fishing practices in Dumai City's marine environment.

Elucidation of Spatial Positioning of Ribosomes around Chromosome in Escherichia coli Cytoplasm via a Data-Informed Polymer-Based Model.

The spatial arrangement of ribosomes and chromosome in Escherichia coli's cytoplasm challenges conventional wisdom. Contrary to the notion of ribosomes acting as inert crowders to the chromosome in the cytoplasm, here we propose a nuanced view by integrating a wide array of experimental data sets into a polymer-based computer model. A set of data-informed computer simulations determines that a delicate balance of attractive and repulsive interactions between ribosomes and the chromosome is required in order to reproduce experimentally obtained linear densities and brings forth the view that ribosomes are not mere inert crowders in the cytoplasm. The model finds that the ribosomes represent themselves as a poor solvent for the chromosome with a 50 nm mesh size, consistent with previous experimental analysis. Our multidimensional analysis of ribosome distribution, both free (30S and 50S) and bound (70S polysome), uncovers a relatively less pronounced segregation pattern than previously thought. Notably, we identify a ribosome-rich central region within the innermost core of the nucleoid. Moreover, our exploration of the chromosome mesh size and the conformation of bound ribosomes suggests that these ribosomes maintain elongated shapes, enabling them to navigate through the chromosome mesh and access the central core. This dynamic localization challenges the static segregation model and underscores the pivotal role of ribosome-chromosome interactions in cellular media.

Cyclic behavior of existing RC bridge piers strengthened by exterior ECC and BFRP/ECC composite jacketing at pier base

Engineered cementitious composites (ECC) are a class of high-performance fiber-reinforced cementitious composites. This study proposes using ECC and BFRP grid-reinforced ECC (BFRP/ECC) as external jackets at the base of existing RC bridge piers to enhance seismic performance. Seven 1/5-scale RC bridge piers were tested under reversed cyclic loading, including one unmodified pier as reference and six reinforced piers with varying jacket thickness, height, interface, and BFRP grid mesh size. The test results demonstrate that both ECC and BFRP/ECC composite jacketing effectively enhance ductility. The hysteretic response of the reinforced piers with different interfacial properties, however, varied significantly. The piers with interfacial shear keys exhibited enhanced flexural strength, ductility, and energy dissipation capacity but sustained severe damage as jacketing thickness and height increased. Conversely, the piers with smooth interfaces showed insignificant improvements in flexural strength but significant enhancement in ductility with marginal damage. This behavior can be attributed to the fact that the exterior jacketing in specimens with interfacial shear keys was under bi-axial tension-compression stress state due to flexural compression and lateral expansion of the plastic hinge, while the jacket in specimens with smooth interfaces acted solely as lateral confinement.

Effect of Surface Structure on the Sensitivity of Fluorescence-Enhanced Si Photodiodes for Ultraviolet C Light Measurement

This study aims to significantly enhance the sensitivity of a fluorescence-enhanced Si photodiode (FE-PD) to ultraviolet C-ray (UVC) light by optimizing the three-dimensional surface shape of the phosphor attached to the Si-PD, thereby increasing the UVC detection sensitivity. In the sensitivity-enhanced FE-PD, the surface of the red fluorescent acrylic resin phosphor affixed to the Si-PD was carved with a stripe and grid at varying depths, and triangular roofs and square pyramids at various angles. The effects of roughening the phosphor surfaces with diamond abrasives of varying mesh sizes—ranging from #180 to #3000—were comparatively evaluated against those with flat, mirror-like surfaces. As observed, the UVC light sensitivity of the FE-PD using a surface-carved triangular roofs and square pyramids at angle of 70° exhibited significant improvements compared to the Si-PD with both non-modified and mirror-polished phosphors. Thus, the FE-PD with a surface-modified phosphor is a promising candidate for UVC light sensor.

The river health of Alista River based on macroinvertebrates communities at Selorejo Village Dau Subdistrict Malang Regency

The Alista River is one of the rivers in the upstream Brantas watershed which has relatively natural conditions, but currently there are agricultural activities on the riverbank. The aim of this study was to analyze the health status in Alista River based on the macroinvertebrate communities. This study uses a survey method. Sampling was carried out at 5 stations based on different land use. Sampling of macroinvertebrates used the kicking technique with a hand net with a mesh size of 500 μm in a 10 meter long riffle area. Data analysis used the value of BMWP index (Biological Monitoring Working Party) and the ASPT (Average Score Per Taxon). The results of the identification of macroinvertebrates found were 38 families for instance Glossossomatidae, Lepidosmatidae, and Richardsonianidae. The families belong to 10 orders and 3 classes. The lowest family is 11 families at station 5 (citrus and bamboo gardens). The highest families are 29 families at station 3 (citrus gardens and forests). The results show BMWP-ASPT score ranged from 6.3–4.3 indicating excellent to moderately poor health status. Stations with excellent categories, namely stations 1,2,3,4. Station land use 1,2,3 secondary forest before tourism was discovered including Glossosomatidae. Station 4′s land use is in the form of a tourism location and Lumbriculidae has been found. Stations in the moderately poor category, namely station 5 which is located after tourism sites (citrus gardens and settlements) were found Richardsonianidae.

In-situ synthesis of CdS and Ag2S quantum dots in poly(diallyldimethylammonium chloride) gels

In this study, we proposed a hybridization method for polymer and quantum dots (QDs) by directly forming QDs in polymer gel; this method was completely different from conventional methods such as mixing and encapsulation. QDs were fabricated by reacting metal ions in solution with sulfide ions adsorbed in a gel made from poly(diallyldimethylammonium chloride) (PDADMAC), a cationic polymer. CdS and Ag2S QDs were successfully fabricated in PDADMAC gel for in situ synthesis, and visible light (534 nm) and NIR (1070 nm) emissions were observed in PDADMAC gel containing CdS and Ag2S QDs, respectively. We also discussed the formation mechanism of QDs in the gel considering the mesh size of polymer networks in PDADMAC gel.

Antioxidant and antibacterial activity of sappan wood (Caesalpinia sappan L.) kombucha

Sappan wood (Caesalpinia sappan Linn) is well known for its antioxidants, anti-inflammatories, and antibacterials. Unfortunately, this plant has not been used properly. In this study, sappan wood is processed into a kombucha drink through fermentation. Kombucha fermentation gives sappan wood drink a distinct and pleasant flavor while improving quality. The study aimed to increase the functional value of kombucha using sappan wood as raw material. Kombucha was prepared with sappan wood powder (16 mesh size) at various concentrations (0.4, 0.8, 1.2, 1.6, and 2% (w/v)) and 10% (w/v) sugar concentration. The effect of various sappan wood concentrations as a substrate for kombucha demonstrated a significant (p<0.05) reduction in pH and improvement in total phenol content, IC50 value of antioxidant activity, and antibacterial activity against E. coli. The best sappan wood kombucha treatment was obtained at a concentration of 1.2% with pH of 3.85, total phenol of 874.44 mg GAE/mL, total sugar of 6.62%, IC50 value of 85.43 ppm, antibacterial activity against E. coli of 8.57 mm, and antibacterial activity against S. aureus of 7.99 mm.

Comparative analysis of nondimensionalization approaches for solving the 2‐D differentially heated cavity problem

AbstractThis work reports a numerical study on the effect of three nondimensionalization approaches that are commonly used to solve the classic problem of the 2‐D differentially heated cavity. The governing equations were discretized using orthogonal collocation with Legendre polynomials, and the resulting algebraic system was solved via Newton–Raphson method with LU factorization. The simulations were performed for Rayleigh numbers between 103 and 108, considering the Prandtl number equal to 0.71 and a geometric aspect ratio equal to 1, analyzing the convergence and the computation time on the flow lines, isotherms and the Nusselt number. The mesh size that provides independent results was 51 × 51. Approach II was the most suitable for the nondimensionalization of the differentially heated cavity problem.