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Two different types of lead‐free solder joints Cu/(Sn3.0Ag0.5Cu)/Cu and Cu/Sn/(Sn3.0Ag0.5Cu)/Sn/Cu have been investigated. Joints are produced following the transient liquid phase like soldering process. The microstructure of different intermetallic compounds (IMCs) present at the joint interfaces, as well as their indentation hardness and elastic modulus, have been investigated and analyzed using scanning electron microscopy (SEM), X‐ray diffraction (XRD) spectroscopy, and nanoindentation. The exact position of different microcracks inside the interfaces has been identified by analyzing the elastic–plastic properties and interfacial toughness of these solder joints. The modulus and hardness of the Sn multilayer‐assisted solder joint interface are found to be 60.08%, and 90.18% higher than those of its non‐layered counterpart, respectively. The finite element analysis (FEA) has been done to estimate and compute stress distributions over the interfacial region. The dislocation mechanics involved in strengthening the joint strength are related to the nature of stress flow; as observed in FEA. It is reconfirmed that the high susceptibility to brittle failure of the non‐layered Cu‐SAC305 solder joints could be avoided by using a Sn interlayer in between the Cu substrates and the SAC305 solder paste. [ABSTRACT FROM AUTHOR]

Fatigue tests of nickel-based single-crystal superalloys with inclined film cooling holes (FCHs) at 1000°C were conducted to investigate the effects of crystal orientation and to quantify the fatigue performance of the high-temperature structures. Fractographic analysis and computations of stress concentrations revealed competitive failure mechanisms between mode I crack nucleation and fatigue crack growth in crystallographic plastic slip systems, whereas crack nucleation around inclined FCHs can be characterized by the known fatigue criteria derived for smooth specimens. A life prediction model based on the crystal slip mechanism and the theory of critical distance was introduced to predict the fatigue life of FCH structures and provided reasonable accuracy for different FCH specimens. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Utilizing lightweight composites in aerospace vehicles plays a pivotal role in sustainability by improving fuel efficiency and mitigating emissions. However, due to their low interlaminar strength, delaminations and microcracking degrade their strength and stiffness properties. Through-thickness stitching improves the interlaminar strength, thus increasing the delamination tolerance of composite structures. Therefore, in this study, the influence of repeated periodic stitching patterns, stitched at three different angles (0, 45, and 90°) w.r.t. the transverse direction, on the flexural properties of stitched composites is investigated. The strain distributions of these specimens were obtained using a single continuous optical fiber bonded to the tensile surface of the specimens. The results show that stitching at a 45° angle produced lower strains and higher flexural strength and bending modulus when compared to the stitched and unstitched laminates. An increase of 32.3 and 47.4% in the flexural strength and bending modulus were obtained, respectively, with reference to the unstitched laminates. The failure morphology of specimens was also analyzed using optical microscopy and revealed that the stitch seams arrested delaminations. However, due to the 45° angle, the damage progressed along a longer distance, thus resulting in an increased ultimate failure load. [ABSTRACT FROM AUTHOR]

This paper investigates the three-dimensional (3-D) dynamic stresses on a modern four-bladed hingeless coaxial rotor--inspired by the gross dimensions of the Sikorsky S-97 Raider at extreme flight speeds. The stresses are obtained using integrated 3-D (I3D) aeromechanical analysis--defined as the coupling of 3-D finite element-based structural dynamics with 3-D Reynolds-averaged Navier-Stokes-based fluid dynamics. The coupling was carried out with the University of Maryland/U.S. Army structural dynamic solver X3D and the U.S. Army CREATETM-AV Helios suite of fluid dynamic solvers. The new structural analysis is both enabled and driven by advanced high-performance computing, parallel and scalable solvers, high-order 3-D brick finite elements unified with multibody dynamics, integrated aeromechanics, and a special 3D-to-1D fluid-structure interface that refines the power of the delta-coupling procedure while retaining the advantages of existing computational fluid dynamics mesh motion schemes. The analysis is carried out at 220 knots (μ=0.5)--the cruise speed of the S-97 Raider without reduced tip speed--in order to study the stresses in extreme conditions. At such high speeds, the blade lift is dominated by the complex tip vortex roll-up, and the pitching moments and drag are dominated by the unsteady transonic shocks at the tip. Interesting 3-D dynamic stress patterns are revealed all across the blade that have remained invisible until now since they could neither be predicted nor measured in flight. The key conclusion is that such high-fidelity analysis is now indeed possible and, in fact, necessary to get deeper insights into the dynamics of coaxial rotors at extreme speeds. [ABSTRACT FROM AUTHOR]

Pressure vessels are widely used in various aerospace and automotive applications. For some applications with limited space, spherical and ellipsoidal shapes are less attractive than toroids. Toroidal shapes can be defined as curved, endless hollow shapes that eliminate the need for end caps when used for pressure vessels. This study presents an analytical formulation using lamination parameters for the novel design of toroidal pressure vessels. The proposed design is based on stiffness tailoring by changing the fiber tow trajectories spatially through the structure to suppress the direct stress and strain gradients in the thickness direction, leading to reduced structural weight, defined as bend-free variable-angle-tow (VAT) toroidal pressure vessels. For a toroidal pressure vessel with a fixed geometry, the VAT distribution through the structure to suppress bending is obtained. Subsequently, the bending stresses and strain levels in the designed VAT toroidal pressure vessels are assessed numerically and compared with those of their isotropic and constant-stiffness composite counterparts. Results show that the designed VAT toroidal pressure vessel generates considerably lower degrees of bending than its corresponding isotropic and constant-stiffness composite counterparts. [ABSTRACT FROM AUTHOR]

The local interactions between the flame-front and turbulence control the dynamics, morphology, and propagation of a premixed turbulent flame. To investigate such complex dynamics of a flame-turbulence interaction, we present an experimental exposition of a premixed turbulent Bunsen flame. Several quantities have been evaluated to assess the flame-turbulence interaction. We first measured the statistics of the flowfield adjacent to the flame and compared it with the cold flow. This allowed us to evaluate the effect of the flame on the upstream turbulence. Subsequently, we performed statistical analyses of the local values of various stretch rates and quantified how their distribution changes with turbulence intensity and flame temperature. We also evaluated the pairwise relation among various stretch rates to assess their dependence on each other. Finally, we used flame particles to evaluate the Lagrangian evolution of stretch rates conditioned on flame-fronts. All the analyses presented in this work point out Karlovitz number as a key factor in determining the flame-turbulence interaction. Specifically, we observe a stronger influence of turbulent eddies on flames with increasing Karlovitz number, as evidenced by the reduced effect of flame on upstream flow, wider probability distribution functions of stretch rates, and increased persistence timescales for stretches. [ABSTRACT FROM AUTHOR]

Mechanical vibration-based de-icing technology using piezoelectric actuators has demonstrated the features of low-energy consumption and nonthermal concepts in combating icing. The research on these de-icing methods presents challenges as the guidelines for piezoelectric-actuator arrangement on structures are not well established during the design stage of a de-icing system. A piezoelectric-actuator array design framework is established to give a solution for the determination of its arrangement in actual applications. The concept of placing piezo actuators according to the structural vibration modes of the substrate is first obtained by theoretical analysis. Then the influence of the dimensions and position of the piezo actuator are researched on a scale based on the half wavelength of the vibration modes. The framework for the piezo-actuator array design, based on structural vibration modes, is developed within the constraints of those parameters influencing its behavior and control of the adhesive bonding-layer thickness. The detailed piezo-actuator array is determined based on the array-design framework and is also verified by experimental measurements and de-icing tests. We further demonstrate the usefulness of the designed piezo-actuator array and the corresponding array design frameworks through the occurrence of cracks and delamination of ice on the leading-edge structure under different icing cases in an ice wind tunnel. [ABSTRACT FROM AUTHOR]

Three-dimensional (3-D) solid finite element analysis (FEA) is used to model and study coaxial helicopter rotors. The 3-D FEA is coupled with a lifting line aerodynamic model with free wake to capture rotor-rotor interactions. Two open-access models are developed: one is the Metaltail (a hingeless coaxial rotorcraft), and the other is the coaxial rotor built from articulated UH-60A-like rotors. The former is the main focus of this work and is developed as an example case for the U.S. Army/DoD rotorcraft simulation software CREATETM-AV Helios, while the latter is merely for a regression test. The analysis is performed on a low-speed transition flight for which qualitative data are available for the Sikorsky S-97 Raider aircraft for comparison. Predictions of performance, airloads, vibratory loads, and 3-D stresses are discussed. In the absence of available geometry or property data of the S-97, this study is primarily meant to serve as a capability demonstration of 3-D rotor structural dynamic modeling for such rotors. [ABSTRACT FROM AUTHOR]

The work reports the proposed development of the laminated carbon fiber-reinforced polymer composites (CFRP), at a uniaxial angle as a primary bend clamp material assembly of the offshore gas lift pipelines. Generally, the clamps are utilized to repair the defect of the metallic pipelines due to their practical and mechanical strength. The existing bend clamp model poses challenges especially when applied to the J-tube bending side due to mechanical buckling and corrosion. This study evaluates the effect of laminated CFRP subjected to uniform uniaxial and in-plane compression on API 5 L X52. Several tests, including tensile, bend, and impact tests, are chosen to assess the effect of multiple and thick carbon layers to improve the clamp's mechanical properties. Scanning electronic microscope (SEM) intends to reveal the surface characterization of carbon fiber clamp. The result shows that laminated carbon fiber increases the durability and mechanical properties of the bend clamp for two weeks. The tensile test result shows that the uniaxial orientation has the highest tensile strength of about 2000N and is affected by the strong interfacial bond between the fiber and metal layers. The high impact energy of 2242 ± 0.001 J of the same orientation shows the stability of the clamp under unprecedented dynamic load and enhances the safety. The SEM result at uniaxial shows the resistance towards fracture has increased and was initiated from the air pocket in the composite.

Abstract For shaped charge blasting projects in mining, civil engineering, and similar fields, it is proposed to modify the charge structure by combining slotted tubes and shaped charge liners to obtain a new type of charge structure. This aims to achieve directional rock breaking through the focused action of the shaped charge. The influence of different slotted pipe materials on the directional rock-breaking effect of concentrated energy using a new charge structure is explored through theoretical analysis combined with model test study, high-speed camera, stress–strain gauge, and other equipment. A comparison is made between slotted pipes made of aluminum, kraft paper, and PVC, with the cutting width of 2 mm. Based on the characteristics of the cracks formed after blasting, the new charge structure made of aluminum slotted pipe produces a penetrating crack that is almost consistent with the pre-cracking direction. Based on the corresponding characteristics of successively released blasting energy, the guiding and convergence effect of the new charge structure made of aluminum slotted pipe on the explosion energy is greater than that of the new charge structure made of the other two types of slotted pipe material. According to the strain data measured after blasting, the peak arrival time of the strain peak in the direction of the slotted pipe on one side of the shaped hood is shorter than that in the other two directions, and the peak strain is greater than that in the other two directions while having a better energy gathering effect. Based on the findings, the new charge structure with directional energy concentration has a damage reduction effect. Furthermore, the material of aluminum slotted pipe is found to be better than PVC slotted pipe, whereas the material of PVC slotted pipe is better than kraft paper slotted pipe in achieving directional rock breaking.

Based on the first-order shear deformation theory (FSDT), the large-amplitude vibration behavior of shallow spherical shells made of functionally graded materials (FGMs) due to the rapid decrease of temperature (cooling shock) is investigated. FGM is assumed to be a mixture of stainless steel and low-carbon steel whose properties are considered temperature dependent and are estimated based on the power-law model. According to FSDT and von Kármán assumptions, the governing equations of motion in conjunction with corresponding boundary conditions are obtained using Hamilton's principle. The temperature distribution is also achieved by means of the 1D Fourier transient heat conduction equation, considering two time-dependent thermal loading scenarios. The considered thermal boundary conditions allow that a temperature difference is created with a time delay for the structure under cooling shock. Also, the results of recent experiments are employed to estimate the temperature-dependent properties of structures. In the solution approach, the generalized differential quadrature method and the Newmark-beta integration scheme are utilized. Selected numerical results are presented to study the effects of thermal load rapidity time, geometry, magnitude of thermal load, and material gradient index on the thermally induced vibrations of spherical shells. Stresses generated in the shell due to the thermally induced vibrations are also investigated. [ABSTRACT FROM AUTHOR]

The accuracy of a wavelet depends on the choice of the mother wavelet adopted. The present work aims to predict the free vibration behavior of laminated sandwich plates using wavelet finite element (WFE). Different kinds of mother wavelets, namely, B-spline wavelet on the interval (BSWI), Gaussian, Haar, Daubechies 6 (db6), Biorthogonal 3.7 (bior3.7), Coiflet5 (coif5), Symlets (sym8), Morlet, Mexican hat (Mh), and Meyer mother wavelets, are employed in WFE for predicting the frequencies. Both symmetric and unsymmetric laminates are studied using the proposed approaches. A wide range of problems, including the influence of the geometric and material properties and end conditions on the free vibration behavior of the laminated sandwich plates, are solved. The effectiveness of the WFE over the conventional finite element method in terms of computational efficiency is discussed. In conclusion, BSWI-based WFE method (WFEM) is found to be the most accurate and computationally efficient in predicting the free vibration behavior of laminated sandwich plates. The accuracy of the WFEM depends widely on the type of mother wavelet adopted. [ABSTRACT FROM AUTHOR]

The article considers the problems in the numerical stress-strain analysis of heterogeneous models of rock samples and biological tissues. The information about the geometric structure of such models is usually obtained using computed tomography (CT). The construction of the unstructured hexahedral meshes (based on CT scan data) is used to reduce the problem dimension. Examples of estimating the effective properties of a core sample and modeling a human lower jaw are given in the article. [ABSTRACT FROM AUTHOR]

A steel tube–reinforced concrete (ST-RC) column is composed of the inner concrete-filled steel tube (CFST) component and peripheral reinforced concrete (RC) component. In this study, the confinement interaction mechanism of axially loaded steel tube–reinforced concrete columns (ST-RC) was evaluated experimentally and analytically. Eleven column specimens were tested, including five ST-RC, three CFST, and three RC columns. The test results found that the confinement interaction between core CFST and outer RC components integrates both advantages while remarkably altering the section equilibrium and confinement mechanism compared with conventional confined concrete. Specifically, the following two aspects need to be considered. First, since the core CFST component is subjected to the secondary confinement provided by outer stirrups, the capacity of an ST-RC column is 1.07–1.21 times greater than that of the simple superposition of CFST and RC components (CFST+RC). Second, for the outer RC component, because the filled-in concrete is confined by the steel tube, the outer stirrups confinement cannot be effectively activated due to the weakened dilation of concrete. Such strain-lagging leads to a steeper falling branch of the load–axial strain curve of the ST-RC column under compression than that of CFST+RC. Finally, based on two modified constitutive models considering the confinement interaction mechanism in the ST-RC column, a well-defined analytical model for predicting the structural performance of axially loaded ST-RC columns was established. [ABSTRACT FROM AUTHOR]

The characterization of small-size engines requires dedicated rigs that are usually used for loading the power unit. Adding the possibility of motoring the engine is an important advantage that allows more detailed information on operating characteristics. It can be used for obtaining precious data that contribute to the development of more accurate numerical models and subsequent validation. Cost competitiveness is another essential aspect of small-size engines, given that development efforts need to be contained as much as possible. Within this context, the present work developed and tested a setup capable of cranking and motoring a small-size 50 cc spark ignition engine. Two configurations were considered for coupling an electric motor to the power unit: the first through a pulley-belt transmission and the second via a plastic clutch assembly. The main idea was to ensure the capability of motoring the engine up to a rotational velocity of 6000 rpm. Engine load was applied through a 1 kW electric generator connected directly to the crankshaft. The overall setup was designed in the two configurations and a stress–strain analysis was performed. The belt-driven option was found to be more favorable in terms of mechanical component requirements, showing a safety factor of around 4.0, while the plastic clutch assembly involved a more complex design phase and turned out to be more demanding, with a safety factor of around 2.9. [ABSTRACT FROM AUTHOR]

Vehicle load is the most frequent live load on cross-highway pipelines. Cross-highway pipelines will bear great stress under the rolling action of heavy vehicles, which leads to pipeline failure and damage. However, the current vehicle–road model and the pipeline–soil model are calculated independently of each other, which cannot accurately solve the stress response of buried pipelines in the process of a vehicle rolling in real time. This paper solves this problem. To study the real-time influence of vehicle load, vehicle speed, rolling position, and other dynamic factors on pipelines' stress, the ultimate bearing capacity of small-diameter gas pipelines under the action of a heavy vehicle rolling was quantified. This paper established the vehicle–pavement–pipeline model by combining Adams version 2020 and Abaqus version 2020, and the pipeline's dynamic stress response and ultimate bearing capacity under vehicle load were simulated numerically. According to the actual working conditions on-site, an experimental system for buried pipelines was established, and the test was verified with a 7-m-long pipeline. Simulated and experimental results were compared, and showed good agreement. The research results show that the stress on the pipeline is positively related to the vehicle load and diameter. However, with the increase in vehicle speed, the stress on the pipeline tends to decrease. When the burial depth of the pipeline reaches 1.5 m, the protective effect of soil on the pipeline is weakened. The study also found that the internal pressure has a certain protective effect which can reduce the impact of vehicle load on stress increment. This is a new discovery: the closer the rolling position is to the centerline of the pipeline, the greater is the peak stress. Finally, an evaluation method of the ultimate bearing capacity of buried pipelines and the overload warning index is proposed based on the von Mises stress, and vehicle overload warning curves were established. The vehicle overload warning curves can be used to determine whether the current vehicle load will be harmful to the pipeline, or to design the maximum vehicle load of a section in preliminary work. On-site application showed that the vehicle overload warning curves have high accuracy and can provide some guidance for the safe operation of the pipeline. [ABSTRACT FROM AUTHOR]

The internal flow characteristics of the check valve in the important service water system of a nuclear power plant are not understood, and the corresponding stress-strain analysis is lacking. At the same time, it is difficult to carry out experimental research. Therefore, the dynamic grid method was used to establish the fluid-solid coupling calculation model, and the simulation calculation was carried out, and the fluid-solid coupling characteristics of the swing check valve in the important service water system of nuclear power plant were studied. Firstly, based on the prototype of check valve of a nuclear power plant, the valve and water body model were established, and the final calculation model was determined after using the grid independence test. Then, the valve plate motion control rules were written using profile, the dynamic grid model was set up, and the interface and constraint conditions were set up by using ANSYS unidirectional fluid-structure coupling method to simulate the transient closing process of check valve. Finally, the velocity and pressure distribution of flow field and the stress and deformation changes of structure field with different opening degrees during valve closing were analyzed. The experimental results show that during the closing process, the maximum flow velocity of the flow field in the check valve occurring at the beginning of closing is 17.87 m/s and it gradually decreases to 0 m/s. The maximum equivalent force and maximum deformation of the check valve respectively appear at the connection between the shaft and the valve body and the lowest part of the valve plate, and the final maximum equivalent force and deformation are respectively 1.547 4×108 Pa and 4.74 mm, which increase as the open degree decrease. The calculation results obtain the flow field change characteristics and the stress and deformation response characteristics of the check valve closing condition, improve the reliability of equipment operation, which can provide a reference for the optimal design of the equipment. [ABSTRACT FROM AUTHOR]

Machine parts are exposed to stress accumulation due to geometric differences. Determining the stress accumulation locations is crucial to the design procedures. Studies on stress concentrations have been conducted in the past using a variety of theoretical and experimental methodologies, and distinct interpretations have been offered depending on the geometry of the machine part to be produced. The ability to complete activities with the least amount of effort and in the shortest amount of time has emerged as a result of the new computer technologies and software that have impacted many aspects of our everyday lives. One of these methods is the artificial neural networks (ANN) model, which is a branch of artificial intelligence. It is argued as a thesis in this study that fast and low-cost solutions can be found to problems in the field of solid mechanics by using the ANN model. For this purpose, a model has been developed to determine the SCF value with the ANN model of a plate with symmetrical V-shaped notch. The graphs obtained from previous experimental studies were converted to digital format and the Kt values obtained for the V-shaped notch problem with different parameters were converted into a data file. In this file, the SCF values to be obtained according to the strength upper limit safety factor value of the machine part, depending on the dimensional dimensions and material type required for the design, are calculated numerically in the form of an Excel file. An ANN-based code was created in MATLAB software and a new solution method was presented for parts containing a V-shaped notch. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Throughout the plastic deformation of sheet metal axisymmetric shape parts such as hemispherical products using the spinning process, the sheet metal experiences intensive stresses and strains. Therefore, producing sheet metal pieces using this technique requires substantial skills. The study and analysis of stresses, strains, and other parameters affecting the process by means of numerical strategies or experimental setups help to better understand the stress–strain state and how the material is deformed during the process. In this study, a 3D finite element model is developed using Abaqus/Explicit solver to systematically analyze the spinning of hemispherical sheet metal parts in both single and multi-pass spinning operations and were compared with the results obtained from the experiments to confirm their validity. During the process, stresses, strains, and wall thickness distribution of the samples were investigated and compared with relevant experimental outputs. Also, the geometrical condition of the final product and applied forces to the workpiece were examined. The results obtained from the two operations (single-pass and multi-pass) indicate adequate consistency between the results of the simulation models and the experiments. [ABSTRACT FROM AUTHOR]

This publication delves into geomechanical processes encountered during sequential longwall mining of coal seams, with a unique focus on reusing the conveyor track of the prior longwall as the ventilation pathway for the subsequent longwall. An in-depth geomechanical rationale is provided for the reuse of excavations within jointed rock formations. To ascertain the critical roles played by various support and protective elements at each distinct mining stage, a comprehensive analysis is performed using finite element techniques to delineate the three-dimensional stress-strain characteristics of the rock mass. Employing an innovative methodology integrating multifactorial analysis, contemporary structural identification algorithms, and a neuroheuristic approach for predictive mathematical modeling, an integral stability metric for reusable mining excavations is introduced. Specifically, this metric quantifies the relative preservation of the excavation's cross-sectional area following its connection to the second longwall. Furthermore, the study tackles the challenge of nonlinear optimization through the application of the generalized reduced gradient method (Frank-Wolfe), ultimately deriving the optimal combination of factors that maximizes the preservation of the crosssectional area for these reusable excavations. [ABSTRACT FROM AUTHOR]

Several methodologies have successfully described the runner blade shape as a set of discrete sections joining the hub and shroud, defined by 3D geometrical forms of considerable complexity. This task requires an appropriate parametric approach for its accurate reconstruction. Among them, piecewise Bernstein polynomials have been used to create parametrizations of twisted runner blades by extracting some cross-sectional hydrofoil profiles from reference CAD data to be approximated by such polynomials. Using the interpolating polynomial coefficients as parameters, more profiles are generated by Lagrangian techniques. The generated profiles are then stacked along the spanwise direction of the blade via transfinite interpolation to obtain a smooth and continuous representation of the reference blade. This versatile approach makes the description of a range of different blade shapes possible within the required accuracy and, furthermore, the design of new blade shapes. However, even though it is possible to redefine new blade shapes using the aforementioned parametrization, a remaining question is whether the parametrized blades are suitable as a replacement for the currently used ones. In order to assess the mechanical feasibility of the new shapes, several stages of analysis are required. In this paper, bearing in mind the standard hydraulic test conditions of the hydrofoil test case of the Norwegian Hydropower Center, we present a structural stress–strain analysis of the reparametrization of a Francis blade, thus showing its adequate computational performance in two model tests. [ABSTRACT FROM AUTHOR]

A convolutional neural network was used to enhance the localization of strain and stress for a generalized method of cells model of a metallic microstructure. Enhanced shear strains, measured in terms of the linear regression coefficients as a function of ground truth strains, were improved from inaccurate and uncorrelated (slope=0.003, r²=0.000) to accurate and well correlated (slope=0.961, r²=0.946) relative to ground truth (slope=1.0, r²=1.0). Kernel sizes of 2 or 3 were effective in the convolutional neural network (padding = "same"). graphical processing unit (GPU)-parallelized enhancement costs were low after training (range 0.41-3.45%) compared to the baseline generalized method of cells, and are significantly faster than finite element. The accuracy of enhanced localized shear strains and stress is expected to yield benefits for damage progression models, especially in the context of hierarchical multiscale methods where the generalized method of cells is applied at the intermediate scale. [ABSTRACT FROM AUTHOR]

The characterization of small-size engines requires dedicated rigs that are usually used for loading the power unit. Adding the possibility of motoring the engine is an important advantage that allows more detailed information on operating characteristics. It can be used for obtaining precious data that contribute to the development of more accurate numerical models and subsequent validation. Cost competitiveness is another essential aspect of small-size engines, given that development efforts need to be contained as much as possible. Within this context, the present work developed and tested a setup capable of cranking and motoring a small-size 50 cc spark ignition engine. Two configurations were considered for coupling an electric motor to the power unit: the first through a pulley-belt transmission and the second via a plastic clutch assembly. The main idea was to ensure the capability of motoring the engine up to a rotational velocity of 6000 rpm. Engine load was applied through a 1 kW electric generator connected directly to the crankshaft. The overall setup was designed in the two configurations and a stress–strain analysis was performed. The belt-driven option was found to be more favorable in terms of mechanical component requirements, showing a safety factor of around 4.0, while the plastic clutch assembly involved a more complex design phase and turned out to be more demanding, with a safety factor of around 2.9.

Spinning membrane structures are of benefit to space applications because they can be deployed without such mass resources as booms. On the other hand, the lack of supporting structures can lead to undesirable deformations that are dominated by a complex partial differential equation. In this paper, an analytical description for transverse vibrations of spinning membranes is presented. It is shown that the eigenfunctions can be written using the Zernike polynomials; in the presented framework, however, a more practical representation that focuses on the physical characteristics of the vibrations is developed. Furthermore, response to external forces, or controls, is formulated by introducing an extended form of an impulse response function (IRF) that includes spatial information in addition to time information. The deformation under arbitrary forces can be calculated through a convolution integral with the extended IRF. Moreover, the Fourier transform of the IRF gives the frequency response function, which can be useful in designing a vibration control system. To verify the validity of the developed model, the analytical solution is compared to the numerical solution in the finite element analysis. Results demonstrate that both solutions agree in the modal analysis, frequency response analysis, and transient response analysis. [ABSTRACT FROM AUTHOR]

This research involves stress-strain analysis in poly(methyl methacrylate) (PMMA) octagonal shape compressed by hydraulic system. The observation of uniaxially stressed samples was carried out using reflection photoelasticity technique. The results of fringe order number and principal stress angle were used to determine stress and strain distribution in the samples by shear difference method. It was found that high stress-strain region was close to the contact point where compressive force was applied but it was zero at the edge of the samples. The area of high strain region increased as the magnitude of force was increased but it decreased as the dimension of octagonal shape was increased. [ABSTRACT FROM AUTHOR]

Several methodologies have successfully described the runner blade shape as a set of discrete sections joining the hub and shroud, defined by 3D geometrical forms of considerable complexity. This task requires an appropriate parametric approach for its accurate reconstruction. Among them, piecewise Bernstein polynomials have been used to create parametrizations of twisted runner blades by extracting some cross-sectional hydrofoil profiles from reference CAD data to be approximated by such polynomials. Using the interpolating polynomial coefficients as parameters, more profiles are generated by Lagrangian techniques. The generated profiles are then stacked along the spanwise direction of the blade via transfinite interpolation to obtain a smooth and continuous representation of the reference blade. This versatile approach makes the description of a range of different blade shapes possible within the required accuracy and, furthermore, the design of new blade shapes. However, even though it is possible to redefine new blade shapes using the aforementioned parametrization, a remaining question is whether the parametrized blades are suitable as a replacement for the currently used ones. In order to assess the mechanical feasibility of the new shapes, several stages of analysis are required. In this paper, bearing in mind the standard hydraulic test conditions of the hydrofoil test case of the Norwegian Hydropower Center, we present a structural stress–strain analysis of the reparametrization of a Francis blade, thus showing its adequate computational performance in two model tests.

The work reports the proposed development of the laminated carbon fiber-reinforced polymer composites (CFRP), at a uniaxial angle as a primary bend clamp material assembly of the offshore gas lift pipelines. Generally, the clamps are utilized to repair the defect of the metallic pipelines due to their practical and mechanical strength. The existing bend clamp model poses challenges especially when applied to the J-tube bending side due to mechanical buckling and corrosion. This study evaluates the effect of laminated CFRP subjected to uniform uniaxial and in-plane compression on API 5 L X52. Several tests, including tensile, bend, and impact tests, are chosen to assess the effect of multiple and thick carbon layers to improve the clamp's mechanical properties. Scanning electronic microscope (SEM) intends to reveal the surface characterization of carbon fiber clamp. The result shows that laminated carbon fiber increases the durability and mechanical properties of the bend clamp for two weeks. The tensile test result shows that the uniaxial orientation has the highest tensile strength of about 2000N and is affected by the strong interfacial bond between the fiber and metal layers. The high impact energy of 2242 ± 0.001 J of the same orientation shows the stability of the clamp under unprecedented dynamic load and enhances the safety. The SEM result at uniaxial shows the resistance towards fracture has increased and was initiated from the air pocket in the composite., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Shell structures with a mid surface of helicoid shape find application in many technical fields, mostly in civil and mechanical engineering. There is a variety of helicoid shells, but the most well-known and used are two types of ruled helicoids: right and oblique. The article is devoted to analytical and numeric-analytical methodologies for shallow right and oblique helicoids. The general approach is based on Kirchhoff–Love linear theory of thin elastic shells. Analytical results can be used for preliminary design and calculations aimed at the understanding of construction physics and regularities of stress-strain state behavior. Two methodologies of stress-strain analysis are presented: the analytical method for shallow right helicoid, and the numeric-analytic method for oblique helicoid (including any special or degenerated case). The numerical results are verified. The results and approach outlined could be of interest to designers and scientists, who want to understand the generalities of thin ruled helicoid shell behavior.

The basic definitions and a history of the development of biomimetics as a discipline that considers nature-inspired design are presented in this paper. The discussion and the results of the application of principles of nature-inspired design in machine elements design are given. The fact that transition zones that Nature chose and designed on trees in many cases survived for more than a hundred years, resisting on the various and variable external loads and other external conditions, is considered. Presented case study used the nature-inspired transition shapes in the research of innovative design and geometric optimization of transition zones of high-loaded shafts. The comparative Finite Element Analysis is performed for a particular transition zone with traditional engineering design, as well as with nature-inspired design. The conclusions about the increase of load capacity that is obtained with innovative biomimetics design are discussed. [ABSTRACT FROM AUTHOR]

This study investigated the effects of Pb 2 O 3 nanoparticles on the thermal, mechanical, and shielding properties of epoxy resin, liquid silicone rubber, and polyvinyl chloride composites which have been proposed as efficient substitutes for traditional lead-based materials for shielding gamma and X-ray radiations. The Pb 2 O 3 nanoparticles were synthesized using a low-cost electrochemical method, characterized by XRD and SEM analysis, and uniformly dispersed in the polymer matrix by casting technique. The mechanical and thermal properties of the samples were investigated by stress-strain and TGA analysis, and the effectiveness of Pb 2 O 3 in improving the radiation shielding capabilities of the polymers was investigated by analyzing parameters such as the mass attenuation coefficients and the half-value layer factor for gamma rays. The results showed that the addition of Pb 2 O 3 nanoparticles had no adverse effect on the thermal stability of polyvinyl chloride (PVC) composites; at the same time, it decreased the thermal stability and increased the weight loss of Epoxy Resin (ER) and Liquid Silicon Rubber (LSR) composites. The nanocomposites had higher tensile strength and modulus of elasticity than the original polymer, and their shielding properties improved with increasing nanofiller content. This study provides insights into modifying the properties of composites using fillers and polymers to improve their properties for various applications. [Display omitted] • Different epoxy resin, silicone, and PVC-based Pb 2 O 3 nano composites (namely 10, 20, 30, and 40 wt%) were produced. • Low-priced electrochemical synthesis method was used to synthesize Pb 2 O 3 nano particles. • Thermal, mechanical, and shielding properties of constructed nano composites were experimentally assessed. • Findings: PVC thermal stability unaffected by Pb2O3 nanoparticles. ER and LSR composites' stability reduced; weight loss increased. • Nanocomposites surpassed original polymer in strength, elasticity, and shielding with increased nanofiller content. [ABSTRACT FROM AUTHOR]

Analytical methods presented to analyze the buried steel pipelines at strike-slip fault crossing use the Euler-Bernoulli beam theory. The cross-section of a buried pipe that is completely surrounded by soil cannot rotate freely and would not be remained perpendicular to the bending line after deformation. So it would be better to take into consideration a rotation between the cross-section and the bending line. The developed model improves the existing methodologies by using the Timoshenko beam theory and considering the shear deformations as a refinement to the existing methodologies. The proposed model results are compared with the results of an existing analytical model and it is found that the maximum bending and axial strains decrease with taking into consideration the shear deformations. Furthermore, it is shown that the difference between the results of models increases with an increase in the burial depth.

In this article, a method is proposed for calculating the reinforcement of concrete ceiling slabs with carbon composite materials based on the finite element model in the computer program SCAD Office PC. This method allows the most complete and accurate representation to be obtained of the structure stress-strain state before and after reinforcement with composite materials. Therefore, it allows high-quality designing and reduces the cost conducting calculations and tests on a large scale. The design values are taken from the initial data, and include conclusions based on the results of analysis of the technical state of the structuresand drawings from the calculation section of the CS (reinforced concrete structures).

This article presents a numerical analysis of laser-welded flange pipe joints. The presented results concern the welding of low carbon S235JR and stainless 316L steels using a CO2 laser in lap and fillet joint configurations. The estimation of welding parameters was achieved using Simufact Welding software and numerical simulation, where output power, feed rate, efficiency and intensity distribution (Gaussian parameter) were analysed. In accordance with the established model, a thermo-mechanical simulation was performed. The calculated joint geometries show good agreement with experiments; therefore, the obtained results were used to study selected joint properties of both joint types. Stress-strain distribution was estimated on the basis of thermo-mechanical analysis. Weld bead geometry obtained from numerical simulation was compared with the results from trial joints. The numerical model established for both joint configurations shows good agreement with experimental results and were assumed to be accurate. The results of the performed analysis shown some advantages of the use of this configuration of lap joints in flange pipe joints.

The mechanical aspects of deformation-induced surface roughening inherent in microstructural inhomogeneity are studied numerically using single inclusion models. Three-dimensional finite-element calculations of uniaxial tension are performed for a set of single inclusion models where a cubic-shaped inclusion is embedded into a homogeneous matrix. The inclusion-to-surface distance, tilt angle about the axis of tension, and the ratio between the matrix and inclusion elastic-plastic properties are varied in different combinations to study the effects which these parameters have on the development of out-of-plane surface displacements under uniaxial tension. It has been shown that all stress and strain tensor components in the vicinity of inclusions take on non-zero values, including those directed across the load axis. Thus, the free surface becomes rough under the action of internal forces originated from the inhomogeneous stress-strain fields. Some illustrative examples of surface roughening under uniaxial tension are shown for multiple ellipsoidal inclusions periodically arranged in a subsurface layer of an elastic-plastic material.

The natural aggregates are depleting in developing countries due to the excessive usage in road and building construction. In the present study, the engineering properties of abundantly available lateritic soil stabilized with Ground Granulated Blast Furnace Slag (GGBS) and alkali solutions like Sodium hydroxide and Sodium silicate was evaluated. The suitability of stabilized soil as a base course in flexible pavements was investigated. The lateritic soil was treated with 15, 20, 25 and 30% of GGBS and alkali solutions consisting of 5% of Sodium oxide with Silica Modulus (Ms) of 0.5, 1.0 and 1.5 at a constant water binder ratio of 0.25. The improved unconfined compressive strength, flexural strength, and fatigue life were observed from the soil treated with 30% of GGBS and alkali solution having Ms 1.0 air-cured for 28 days at ambient temperature. The improvement is due to the formation of Calcium Silicate Hydrates and Calcium Alumino Silicate Hydrates from an exothermic reaction between Calcium ions and the dissolved silicates and aluminates present in GGBS and alkali solutions. The samples treated with 25, 30% of GGBS and alkali solution having 1.0 Ms cured for 28 days found to be durable in Wetting-Drying and Freezing-Thawing tests. The compact and densified crystal orientation of the treated soil samples was observed from the microstructure images obtained from the Scanning Electron Microscope technique. The design of low and high volume roads was suggested with stabilized soil and strains developed at different locations on the proposed pavement were analyzed using pavement analysis software. [ABSTRACT FROM AUTHOR]