Hole In Plate Research Articles

Finite element analysis of stress concentration singularities in orthotropic/isotropic hole plates on an aircraft wing

The cutouts in the ribs of aircraft wings create stress concentrations. Stress concentrations in an elastic body are very important in structural design and are mainly caused by two mechanisms: the concentration of force acting on a body and geometric discontinuities in the object, such as holes or sudden changes in the geometry of the object's surface. To obtain equivalent stresses and strains for a wing rib without a cutout and with a circular cutout, we considered a perforated plate as the test piece. We studied the stress concentration factor (SCF), around a circular central hole in isotropic and orthotropic rectangular plates subjected to tensile loading using the finite element model, and validated it by comparing the constitutive analytical equations of Heywood and Howland for orthotropic and infinite isotropic plates and with the Matlab program. Next, we analyzed the overall and net stress concentration factor around the hole as a function of different variables: the plate diameter-width ratio (d/W), the effect of the fiber orientation angle (θ°),and the effect of the length/width ratio (L/W). Abaqus was used as design software to extract stress concentration factors for materials such as Al 2024-T3, Glass/Epoxy, and Carbon/Epoxy. These results were then compared with the analytical formula using Matlab as the programming software, the statistics showed that there was good agreement between the stress concentration factor around the hole using Abaqus and the Matlab program formula. It can be concluded that the application of Matlab software for SCF estimation is faster than Abaqus software.

Effects of Using Seed Tube on Seed Distribution Uniformity in Single Seed Planters

In single-seed sowing of small seeds, in addition to seed size and shape, critical problems can be experienced due to the electrostatic force that occurs during seeds adhering to the plate holes. To find a solution to these problems, the effect of using seed tubes in single-seed planters was the subject of the study. For this purpose, the study, designed with two different seed drop heights (115 mm and 200 mm) and without and with seed tube, was carried out at three different forward speeds (0.5 m s-1, 1.0 m s-1, and 1.5 m s-1). According to the analysis results applied to the data, it was determined that the seed distribution uniformity was negatively affected by the increase in seed drop height and progress speed, and the planting quality deteriorated. While it was expected that the use of seed tubes in single-seed planters would have a positive effect on the uniformity of seed distribution intra-rows and inter-rows, it was found that on the contrary, the uniformity of seed distribution deteriorated and there was a high degree of variation. The best values for seed distribution uniformity were obtained with a forward speed of 0.5 m s-1, a seed drop height of 115 mm, and no seed tube.

Damage evaluation in plain-woven CFRP plate with circular hole under cyclic tensile loading using electrical impedance tomography

Understanding and predicting damage progression within thin plain-woven carbon fiber-reinforced polymer (CFRP) components is an essential issue for scheduling maintenance intervals and structural inspections and typically requires extensive test series. However, uncertainties always remain and result in conservative design and unnecessary downtimes due to the repeated inspections of a healthy structure. Structural health monitoring (SHM) can be used to reduce these uncertainties, as it allows one to evaluate the condition of a mechanical structure during operation. Numerous SHM methods have been developed, which achieve different levels of damage identification but are often investigated at small coupons with nonrealistic structural damages and loading conditions on both structure and sensor. The present research investigates electrical impedance tomography (EIT) featuring an elastoresistive thin-film sensor to evaluate damage that propagates from a circular hole in a large plate under cyclic tensile–tensile multiblock loading. Applied fatigue loads were increased multiple times up to a total number of two million cycles. During the loading, damage initiated at the hole and continuously propagated into the plate. Repeated EIT evaluations of the applied sensor and validating evaluations by means of digital image correlation clearly revealed the robustness of the hardware and the potential of the SHM method for damage evaluation of plain-woven CFRP components.

Evidence for Magnetized Basin Ejecta on the Moon From Observations and Modeling of Demagnetized Craters

AbstractThe formation of lunar crustal magnetic anomalies is not well understood, and most anomalies are not associated with any obvious geologic features. To investigate further, we studied lunar craters from 100 to 400 km in diameter (totaling 305 craters) that may have demagnetized the crust. We find that the four craters Chaplygin, Keeler, Gauss, and Fermi are highly likely to have demagnetized the crust, based on our statistical methods. We modeled the magnetic source of these craters as a simple hole in a thin magnetized plate, representing the destruction of a surficial magnetized layer (Hypothesis 1). Alternatively, we also simulated the impact demagnetization of deeper‐seated magnetism in the crust by shock and temperature (Hypothesis 2). Some interior magnetization remains unexplained under both hypotheses, but the destruction of a pre‐existing surficial layer of magnetized material is consistent with the location of the peak in each crater's magnetic field. We also find three of the craters are inversely correlated with remotely sensed iron, further supporting our interpretation that the craters demagnetized a surficial layer. The four craters are located on magnetized ejecta deposits from the South Pole‐Aitken, Orientale, and Crisium basins. Hence, these four craters further support the hypothesis that large provinces of magnetized material on the Moon arise from hot impact ejecta that cooled in a dynamo field.

Hydro-acoustic numerical methodology to compute noise generated by perforated plates in duct systems

The paper presents an innovative numerical methodology to determine hydro-acoustic behavior of perforated plates. One of the main objectives is to have a methodology that ensures a good prediction of radiated noise in ducts with a limited computational cost. The initial assessment is carried out considering the entire perforated plate. The acoustic source is determined by applying Lightill Analogy to the CFD results from LES for the whole perforated plate. An acoustic simulation is then performed to determine the dynamic pressure in the duct on either side of the perforated plate. An experimental set-up is built in order to obtain the noise generated by the perforated plate. It also allows to assess the validity of the established method. A good correlation is observed in terms of dynamic pressure upstream and downstream the perforated plate. An optimization of the method is then carried out to reduce the computational time by determining the acoustic source generated by a unit hole. This source is then applied in the acoustic simulation to each hole of the perforated plate. Comparison with measurements is also satisfactory for this simplified method.

Calibrated the direct current potential drop method for fatigue crack propagation testing of nickel-based superalloy with film cooling hole

Turbine blades in aviation engines commonly feature a nickel-based superalloy structure integrated with film cooling holes to enhance inlet gas temperature. However, the presence of these film cooling holes often results in frequent occurrences of fracture failures nearby. The direct current potential drop (DCPD) method, renowned for its exceptional crack sensitivity, is frequently utilized for crack length monitoring. This study establishes a FEM model of the film cooling hole plate specimen to determine the optimal probe point location. Subsequently, a mapping relationship is derived to calibrate Johnson’s formula, accounting for the unequal crack lengths at the edges of film cooling holes. It is confirmed that the crack length measured by the DCPD method represents the cumulative crack lengths on both sides of the hole. Fatigue crack propagation experiments are then conducted, with crack length monitored using a microscope. The results affirm the successful application of the calibrated formula to the film cooling hole plate specimen, exhibiting an average error within 0.1 mm.

Expansion of a hole in a thin plate considering arbitrary smooth pressure-independent yield criterion and work-hardening law

A solution for arbitrary smooth pressure-independent yield criterion and work-hardening law is obtained for the expansion of a hole in an initially uniform infinite plate under plane stress conditions. It is then specialized to widely used yield criteria and work-hardening laws. It is shown that both yield criterion and work-hardening law affect the qualitative behavior of the solution, especially near the hole's surface. In particular, local thickening or thinning may occur there. It is due to the fact that the thickness and yield stress contribute to sustaining the pressure applied to the hole's surface. Therefore, the higher hardening rate requires a smaller thickness. A criterion for the solution's validity applies, and a procedure for using this criterion is developed. Numerical examples illustrate the solution for von Mises and Hosford's yield criteria and Swift's and Voce's hardening laws.

BPNN-based prediction for the shapes of a petal hole induced by hydrodynamic ram

The attitude angles of a projectile moving through a liquid are important factors that influence the dynamic failure of liquid-filled structures induced by hydrodynamic ram (HRAM). In this study, the effect of the attitude angles of a cylindrical projectile on the shapes of the petal hole in the rear plate of a kerosene-filled tank was investigated through ballistic impact experiments using three-dimensional digital image correlation, finite element simulations, and a back propagation neural network (BPNN). The inclination angle λ characterizing the shapes of the petal hole was related to the projection shapes of the projectile when impacting on the rear plate. The formation of petal-hole shapes was also accompanied by the formation of plastic hinge lines in the rear plate. Additionally, a method combining a BPNN and physical equations that accurately predict the drag coefficient and motion of a projectile moving through a liquid was proposed. A function describing the shapes of the petal hole was provided in the 2D space of the two initial attitude angles. The results provide offer insights into trajectory stability during liquid entry and aid in predicting the dynamic failure mode of a liquid-filled tank induced by HRAM.

Does gait influence biomechanics in a distal femoral osteotomy? An early post operative fracture after DFO above a Tomofix® plate in a multiple sclerosis and low-density bone affected patient: choose a longer plate—a case report

BackgroundDistal femur osteotomies are a well known and valuable treatment option to manage valgus malalignment with unicompartmental arthritis. Early postoperative complications are well known, and risk factors, such as pulmonary diseases, smoke, high dependent functional status, and body mass index, have been studied, but no study is available about osteotomies when gait is abnormal because of neurodegenerative conditions or when mineral density is below the normal rate.Case presentationWe report the case of a 44 year-old female Mediterranean patient who underwent a biplanar distal femur opening wedge osteotomy surgery following a lateral meniscus total removal, which led to the subsequent development of lateral compartment osteoarthritis and pain, despite general comorbidities, such as multiple sclerosis. Additionally, 2 months later a supracondylar femur fracture above the previously applied Tomofix® plate was reported. Fracture was treated by applying a LCP condylar 16 hole (336 mm) plate, a structural fibular graft, and strut fibular graft on the opposite side.ConclusionThe overall aim of this case report is to provide a lesson to surgeons who want to perform a realignment surgery of the lower limb in patients with abnormal gait. Not only mechanical axes are to be considered, but also bone density, patient’s gait, and load force distribution along the bone stock. Emerging literature on three-dimensional cutting guides fails to account for these factors, thus promoting a standardized approach to surgery across all patients. The present case highlights a patient with low bone density and abnormal force distribution resulting from a pathologic neurodegenerative gait. In such cases, treatment decisions must carefully consider the biomechanical vulnerabilities of the native bone and the distribution of vector forces. These conditions must lead the choice toward a longer plate if an osteotomy is indicated, because surgery is more likely to fail.

Experimental study on low-cycle fatigue performance of high-strength bolted shear connections

In strong earthquakes, low-cycle fatigue fractures may occur in the bolted connections of steel braced frames. Ensuring a high low-cycle fatigue life for high-strength bolted connections is of paramount significance in enhancing the overall safety and collapse resistance of steel structures. Despite substantial research on plate fatigue failure within bolted connections, there remains a research gap regarding low-cycle fatigue failure of high-strength bolts in these connections. This study aims to address the aforementioned shortcomings by conducting 34 sets of low-cycle fatigue tests on high-strength bolted connections. The test specimens all experienced low-cycle shear fatigue fracture at the threaded or unthreaded portion of the bolt shank as the dominant failure mode. Residual deformations were observed in the holes of connection plates. Based on the test data, ultimate shear capacity of a single shear connection is around 0.61Fy (tensile yield bearing capacity of bolt) when the shear force passes through the unthreaded portion and drops to 0.54Fy for the shear force at the thread. The untreated Q355 (minimum yield strength of 355 MPa) steel surface has an average anti-slip coefficient of around 0.37, while milling reduces it to approximately 0.30. The influence patterns of loading amplitude, bolt material, minimum plate thickness, bolt diameter, shear force position and connection type on low-cycle fatigue life are given by range analysis. Among them, variance analysis shows that loading amplitude and bolt material are the primary influencing factors. The correlation coefficient between loading amplitude and low-cycle fatigue life is −0.92, indicating a strong negative correlation. The degradation amount and rate of anti-slip capacity and shear capacity of bolted connections are also investigated. To propose reliable life prediction method, three models were used to establish the relationship between dimensionless shear deformation and low-cycle fatigue life of 10.9-grade high-strength bolted connections. It is not appropriate to use the fatigue categories defined in current standards to predict the low-cycle shear fatigue life of high-strength bolted connections.

Development of the Design of Plate with Variable Diameters of Holes and Its Impact on Meat-Grinding Quality and Efficiency

Meat-grinder plates are critical for efficiently processing meat, significantly influencing the grinding process. This study aimed to develop a meat-grinder plate with variable diameter holes and assess its impact on ground meat quality and processing efficiency. Various meat types (beef, horse meat, mutton, chicken, and pork) were processed using both plate designs: a control plate with a constant hole diameter of 12 mm and a developed plate with featured holes increasing in diameter from periphery to center (8 mm–12 mm–16 mm). The results demonstrate that the developed plate significantly improves the WBC of minced meat, with notable increases in beef (58.3% vs. 57.7%), horse meat (61.8% vs. 56.2%), chicken (51.0% vs. 49.1%), and pork (46.1% vs. 43.6%), indicating a more homogeneous particle size distribution. Yield stress, a critical factor influencing the rheological properties of minced meat, also showed substantial improvements, particularly in poultry (18.9% increase) and pork (31.3% increase). The variable hole design produced a higher proportion of intermediate-sized particles, contributing to a more cohesive texture and potentially enhancing the binding properties of processed meat products. Theoretical calculations based on the Hagen–Poiseuille equation and empirical data confirmed that the new plate design increases the grinder’s productivity by 50%, with average throughput rising from 150 kg/h to 225 kg/h. Additionally, the developed plate reduced power consumption by up to 7.3%, particularly in horse meat processing, highlighting its cost effectiveness for industrial applications. These findings suggest that the variable diameter hole plate design offers substantial improvements in ground meat quality and processing efficiency, with potential implications for industrial meat-processing operations.

A novel hybrid boundary element for polygonal holes with rounded corners in two-dimensional anisotropic elastic solids

A novel hybrid boundary element is developed for polygonal holes in finite anisotropic elastic plates based on two different special fundamental solutions for holes. Since these special fundamental solutions satisfy traction-free condition along the hole's boundary, there is no mesh required on the boundary of polygonal holes. Various types of polygonal holes with rounded corners, such as triangles, rhombuses, ovals, pentagons, are considered by adding proper perturbation to an elliptical hole. The developed hybrid element is a mixture of two special boundary elements: one is based on the special fundamental solution derived through nonconformal mapping and the other is based on the solution derived through perturbation technique with conformal mapping. The special boundary element methods are combined through submodeling technique. First, the global model is solved using the perturbation solution. Then, using the displacements obtained from global model, an auxiliary submodel is set up and the results are evaluated with the nonconformal solution. The present method is compared and validated with conventional boundary element method and finite element method. The effect of hole curvature, material anisotropy, and loading condition on the stress distribution around the hole is presented.

Comment on “Explicit solutions in Cartesian coordinates for an elliptic hole in an infinite elastic plate” by M. Oore and S. Oore

Comment on “Explicit solutions in Cartesian coordinates for an elliptic hole in an infinite elastic plate” by M. Oore and S. Oore

Investigation of process parameters for modeling of ceramic composite SiSiC IN dry EDM (DEDM) cutting

The manufacturing industry is currently grappling with issues related to energy dissipation and product quality, both of which significantly impact productivity. In addressing this pertinent concern, this study endeavours to identify the key indicators that contribute a crucial role in machining process. The Dry EDM (DEDM) emerges as a novel technology, wherein environmentally friendly gases serve as an alternative dielectric medium instead of liquid EDM approaches. In conventional EDM process, hydrocarbon oils release toxic emissions while the gases used in Dry EDM process don’t produce harmful emissions and hence make the DEDM process sustainable.An investigation has been carried out to observe the influence of different gases like O2, N2 and Air on Siliconized Silicon-Carbide plate (SiSiC) of ø50mm*2 mm under Dry Electrical Discharge Machining. Effect of different tools is also observed using varying shapes of electrodes like plane Cu electrode of ø6 mm diameter with 60 mm length and tubular shape with outer diameter ø6mm and inner diameter ø5.1 mm with a length of 60 mm. The three gases are one by one supplied through a nozzle in the presence of plane Cu electrode to make the holes in SiSiC plate. The same process is executed with tubular Cu electrode. Modified Taguchi Orthogonal Array is applied to analyze the effect of control factors such as gap voltage, discharge current and pulse on-time through a series of experiments. Effect of different shape of tools and different gases is observed for the material removal rate (MRR) and surface roughness (SR) of specimen.In this paper, a latest DEDM process of swirl assisted flushing is proposed which provides a new technique to solve the problems of low MRR and poor surface integrity. Swirl assisted flushing works on Decay Law and also microscopic investigation justifies its validity. It is concluded by this research that current and Pulse on time are more contributing factors about 53.3 % and 27 % respectively. Furthermore, it is noted that DEDM increases MRR 19.5 % and lowers Ra approximately 2/3 than traditional machining. The MRR of O2 is about 3.1 times more than Air and N2 comes at least position while N2 creates better quality of surface due to formation of an inert nitride layer. Empirical relations are established for SR and MRR using Minitab 18 Software to develop a robust model. Confirmation test is performed to check the validity of developed mathematical model. The Novelty of this research is also extended by introducing a new method SAF. The results are finally evaluated by ANOVA.

Implementation of microcontroller board on a sustainable and degradable PLA/flax composite substrate: a case study

In this paper, we present a novel polylactic-acid/flax-composite substrate and the implementation of a demonstrator: a microcontroller board based on commercial design. The substrate is developed for printed circuit board (PCB) applications. The pre-preg is biodegradable, reinforced, and flame-retarded. The novel material was developed to counter the increasing amount of e-waste and to improve the sustainability of the microelectronics sector. The motivation was to present a working circuit in commercial complexity that can be implemented on a rigid substrate made of natural, bio-based materials with a structure very similar to the widely used Flame Retardant Class 4 (FR4) substrate at an early technological readiness level (2–3). The circuit design is based on the Arduino Nano open-source microcontroller board design so that the demonstration could be programmable and easy to fit into education, IoT applications, and embedded designs. During the work, the design was optimized at the level of layout. The copper-clad pre-preg was then prepared and processed with subtractive printed wiring technology and through hole plating. The traditional surface mounting methodology was applied for assembly. The resulting yield of PCB production was around 50%. Signal analysis was successful with analogue data acquisition (voltage) and low-frequency (4 kHz) tests, indistinguishable from sample FR4 boards. Eventually, the samples were subjected to highly accelerated stress test (HAST). HAST tests revealed limitations compared to traditional FR4 printed circuit materials. After six cycles, the weight loss was around 30% in the case of PLA/Flax, and as three-point bending tests showed, the possible ultimate strength (25 MPa at a flexural state) was reduced by 80%. Finally, the sustainability aspect was assessed, where we found that ∼95 vol% and ∼90 wt% of the traditional substrate can be substituted, significantly easing the load of waste on the environment.

Cancelling the effect of sharp notches or cracks with graded elastic modulus materials

Recent technologies permit to build materials which have elastic spatially varying modulus which can also imitate solutions adopted in Nature to optimize some structures. It has been shown that for example the stress concentration due to a hole in an infinite plate can be cancelled with a radially varying modulus making it similar to load-bearing bones which seem to resist structural failures even in the presence of blood vessel holes (foramina). Here, we attempt to study the classical problem of a sharp wedge (which includes the important case of a crack) looking for stresses varying as power law of the distance from the notch tip, σ∼rα, with a modulus varying as E∼rβ. In the inhomogeneous case the order of singularity of the LEFM case decreases if β>0, as confirmed by FEM investigations. Hence, we can remove stress singularities, which suggests an interesting alternative to the “rounding” of the notch. More in general, since for many materials it has been found that both strength and modulus are power laws of the density, using the so called strength-modulus exponent ratio we can obtain optimal design by keeping the asymptotic stress constantly equal to the strength. The present investigation paves the way for a new optimization strategy in the problems which eliminates size-scale effects due to singular stress fields, with potentially very wide applications.

Temperature-Stress Coupling Fatigue Behavior of Film-Cooling Holes in Complex Temperature Fields.

This research investigates the complex temperature distribution and fatigue behavior of single film-cooling holes manufactured by lasers with different pulse widths in a real flow field. The aerodynamic and heat transfer characteristics of film-cooling holes manufactured using lasers with different pulse widths were analyzed through laser drilling experiments, conjugate heat transfer simulations, and crystal plasticity finite element methods. The study investigated the relationship between changes in the geometric accuracy of the film-cooling holes and the corresponding flow and temperature fields during the film-cooling process. Additionally, the effects of temperature and structural variations on the stress around the holes in a flat plate composed of the second-generation nickel-based single-crystal superalloy DD6 in real flow and temperature fields were studied. The coupling effect of the temperature and stress fields around the holes on the fatigue behavior of the film-cooling holes was examined, and the fatigue damage mechanism of film-cooling holes in complex temperature fields was analyzed. It was found that changes in the blowing ratio do not affect the temperature and stress distributions around the holes but only alter the temperature peak. An increase in the temperature peak results in a decrease in the stress peak. Additionally, the fatigue damage of single film-cooling holes is determined by both the structural defects of the holes and the changes in material behavior due to the temperature around the holes, with the structural influence being more significant.

Explicit solutions in Cartesian coordinates for an elliptic hole in an infinite elastic plate

An explicit analytical solution for an elliptical hole in an infinite elastic plate is derived for uniaxial load from the earliest work on this configuration. This is used along with the biaxial loading case and more recent solutions, available in curvilinear coordinates, to transform the stress fields into Cartesian coordinates along the x and y axes, reducing the curvilinear solutions to simplified short-form expressions of x and y. The present closed-form results are the functions of polynomials of the second and third order of x or y along the x or y axes, respectively, and have the most concise form to the best of the authors’ knowledge. The displacements for plain stress condition are calculated directly from the present stress field expressions, as functions of second-order polynomials of x or y and demonstrate overall consistency. Application of the present stress field and displacements results to special cases, such as a circular hole, a crack, and an elliptical hole in a pressurized cylindrical shell, are shown to agree with published solutions where available.

Modification of Dean's Method for Determining Impedance with an Inhomogeneous Sound Field in a Resonator

A modification of Dean’s method is proposed for determining the impedance in the case of a nonuniform sound field on the front and bottom surfaces of a resonator. Instead of acoustic pressures in Dean’s formula, the modification uses the coefficients of eigenfunctions, which correspond to a uniform acoustic pressure distribution on the front and bottom surfaces of the resonator. The eigenproblem is solved by the finite element method; the coefficients of the eigenfunctions are found by the least squares method. At the current stage of research, the full-scale experiment has been replaced by numerical simulation in a linear formulation of sound propagation in an impedance tube with normal wave incidence with a honeycomb resonator attached to it. The inhomogeneity of the pressure field over the cross section of the resonator is created from the different positions of holes in the resonator face plate. The study is done for a different number of acoustic pressure measurement points at the bottom of the resonator. Calculations show that the proposed method is efficient and provides good agreement with the straight method for determining impedance. However, the possibilities of using modification of Dean’s method in full-scale measurements are limited, because accurate resonator impedance determination requires a large number of measurement points.

Effect of Excessive Clamping Force on Bolted CFRP Composite Plates

Friction-type bolted joints are widely used in both the civil and aerospace industries. Uncontrolled excessive bolt clamping force can cause damage to the laminated fiber-reinforced polymeric (FRP) composite through the thickness and damage the joint before applying the service loads. The effect of the friction coefficient (between 0 and 0.3), bolt clearance, joint type, and other parameters on failure modes and the maximum bolt clamping force of the carbon FRP lapped joint is studied. A three-dimensional finite element (FE) model consisting of a bolt, a washer, a laminate FRP composite plate, and steel plates was developed for the simulation of the double- (3DD) and single (3DS)-lapped bolted joint. The FE model was validated by using experimental results and was able to predict the experimental results by a difference of between 2.2 and 6.7%. The joint capacity of the clamping force was found to be greatly increased by adopting the double lap technique, which involves placing an FRP composite plate between two steel plates. Also, it was recommended to use an internal washer diameter less than or equal to the FRP composite plate hole diameter since a larger washer clearance can produce higher contact pressure and reduce the resistance by 22%. In addition, reducing the bolt head diameter can lead to a 65% reduction in the 3DS joint clamping strength.