Cutout Geometry Research Articles

Optimal design of tube flexure cut-out geometries for viscoelastic resilience and deployment performance

This paper presents a methodology for the design of deployable tube flexures made of ultra-thin carbon fiber composite. The proposed process aims to enhance viscoelastic resilience on recovery time after long-term stowage through the design of cut-out geometries. Viscoelasticity is modeled using an experimentally determined Prony series master curve. Bayesian optimization is employed to determine cut-out shapes based on the recovery time and Hashin failure criteria. Partial dependent plots are implemented to interpret the effect of cut-out formation on deployment performance. These reveal optimal profiles of cut-out shapes to achieve a desired operational performance. The efficiency of the proposed methodology is validated by experiment.

Machine learning-assisted fatigue performance optimization for cutout geometry of orthotropic steel bridge decks

Diaphragm cutout is a typical fatigue detail of orthotropic steel decks (OSDs). The cutout geometry could alter the structural responses and fatigue performance, significantly challenging the design process. This study proposes an efficient computational framework addressing fatigue performance optimization for the cutout geometry design. Sensitivity analysis is first carried out to identify the significant parameters, and the datasets are established according to the random sampling technique and the finite element (FE) model. Then, a comparison of prediction performance between the back-propagation neural networks (BPNNs) and radial basis function neural networks (RBFNNs) is employed to present the applicability of two types of artificial neural networks (ANNs) in the prediction of structural responses. Finally, the cutout geometry optimization is performed by integrating the prediction model and the multi-objective particle swarm optimization (MOPSO) algorithm. The validity and applicability of the framework are demonstrated with a real-world application. The optimization results show that the fatigue life is increased from 119.8 to 150.2 years for cutout detail 1 and from 37.4 to 70.2 years for cutout detail 2. The proposed framework can significantly reduce the computational burden and deliver an optimized scheme for the cutout design.

Considerations about the fatigue strength assessment of local cut-out in the double bottom floor

The aim of this paper is to obtain the effect on the fatigue strength assessment of the different geometrical variables involved in the design of the local cut-out, resulting from the intersection between the longitudinal stiffener and the double bottom floor of a bulkcarrier vessel; a common ship structural detail considered to be prone to fatigue failure. Based on finite element models, different combinations between cut-out geometries and longitudinal stiffeners, in terms of size and shape, are analysed to establish the structural behaviour, expressed in accordance with the location and value of hot spot and fatigue life. A novel and valuable scantling tool, known as fatigue sensitivity curves, is developed that determines fatigue life under loading conditions that differ from the design load and reduce fatigue strength. A series of experimental tests are carried out to investigate the fatigue crack growth and validate the numerical results, from the most effective combination of the local weight determination.

Design and optimization of automotive cardan shafts for industrial applications with enhanced performance and durability

A crucial part of a locomotive is the cardan shaft. A rear-wheel-drive vehicle's differential gear receives power from the engine through a spinning shaft known as a cardan shaft. The cardan shaft must turn at ever-changing angles between the gearbox and axle in order to function. High vibrations are experienced on it as a result of the constant rotation. This issue causes shafts to flex or distort. In this study, a cardan shaft's design and development are carried out. Although it is extensively beneficial in the locomotive industry, vibration is a significant issue with cardan shafts. Creo parametric software was used for developing the design, while Ansys was used to analyze it. Using Ansys software's modal analysis, verify the natural frequency. It is then contrasted with the different shaft cut-out geometries.

Effect of local cut-out on fatigue strength assessment in ship structures

The aim of the work is to evaluate different design alternatives to obtain criteria for the selection of the most effective design by fatigue strength assessment of the local cut-out as a result of the connection between the longitudinal or ordinary stiffener and the transverse web frame (longi-web) in the side hull structure (upper wing torsional box), very important area due to its high stress concentration, of a container vessel, one of the most important ships in terms of its influence on the world economy. Structural solutions and design guidelines are established, by means of numerical models validated by experimental tests, which allow alternative designs to be obtained that improve their fatigue behaviour. Standard cut-out geometries are studied under the presence of different variables (radius of curvature, longitudinal spacing, longitudinal stiffener cross-section, and flange arrangement) that are evaluated to determine their effect in the structural assessment (fatigue damage, stress concentration, and fracture mechanics) and the weight comparison between alternatives.

Stability analysis of plates using cut Bogner-Fox-Schmit elements

In this paper, the classical C1-continuous Bogner-Fox-Schmit (BFS) elements are employed to study the buckling behavior of rectangular plates with multiple cutouts. BFS elements are constructed by taking the tensor product of cubic Hermitian polynomials, and thus, arguably constitute one of the simplest approaches to deriving plate/shell elements. The simplicity, however, comes at the cost of requiring regular/structured discretizations, which significantly restricts their use for applications featuring complex geometrical details. To circumvent this shortcoming, a combination of a fictitious domain approach, in particular the finite cell method (FCM), with BFS elements is proposed. Consequently, a typically geometry-conforming discretization is replaced by a structured Cartesian background mesh in conjunction with a more involved numerical integration of the system matrices. This opens the path to analyzing geometrically more complex structures such as plates with one ore more cutouts. Here, the main focus is on the stability (buckling) analysis of such plates. By means of two numerical examples featuring only one circular cutout, it is shown that the critical load can be obtained with high accuracy using the proposed approach. In this context, the attained numerical results are compared with high-fidelity solutions computed using isogeometric analysis (IGA). Moreover, the position of a circular cutout is optimized to maximize the critical buckling load, before the last example demonstrates the applicability of Cut BFS elements to more complex cutout geometries.

Effect of Window and Hole Pattern Cut-Outs on Design Optimization of 3D Printed Braces.

BackgroundThere are many different Thoracic Lumbar Sacral Orthosis style brace designs available in the market for the correction of scoliosis deformity. Hole cut out patterns, are commonly used in brace designs. These cut-outs may be subdivided into two groups: hole patterns and windows. Hole patterns are an array of holes which are implemented to lighten the weight of a brace and allow for the skin to breathe. Windows provide space for spinal derotation and/or breathing. From an examination of the literature, it appears that a systematic analysis of the effect of these cut-outs on the structural integrity and functionality of the brace has not been undertaken. Furthermore, there is a lack of understanding on the effect of spacing, size and geometry of the cut-outs on the mechanical behavior of the brace.Method of ApproachIn this study, Finite Element Analysis is employed to examine the mechanical response of the brace to these cut-outs. Geometry for the Thoracic Lumbar Sacral Orthosis was obtained by scanning an existing brace using an optical scan and converted into a Computer Aided Design model. A systematic approach was undertaken where cut-out geometry, spacing and size was varied. The deformation and stress in the thickness of the brace was ascertained from the Finite Element Analysis. An appropriate factor of safety for the structural analysis was determined using a standardized approach and used to quantify the structural integrity of the brace due to the cut-out. Various geometries were analyzed for the hole patterns including circle, triangle, diamond, and hexagon. For the window, the geometries considered were circle, trapezoidal and the “bib” geometry.ResultsIt was found that linear hole patterns where the holes are aligned do not provide a desirable structural factor safety. Furthermore, among all the possible geometries, the hexagonal cut-out was the best structurally while reducing the weight of the brace the most. The optimal spacing was found to be 12 mm, and the optimal hole surface area was found to be 78.54 mm2. For the windows in the abdominal area, the “bib” shape provided the best structural integrity and generated the lowest amount of deformation. An increase in the size of this window had a small effect on the stress but an almost negligible effect on the deformation.ConclusionsA hexagonal hole pattern should be used with a spacing of 12 mm and each hole should have a surface area of 78.54 mm2. Windows in the abdominal area should be of “bib” shape. The size of the window cut-outs does not affect the brace stress and deformation significantly. Thus, the size of these windows should be based on the functional aspects of the brace, i.e., the minimum required size needed to permit the patient to breathe comfortably as in the case of the abdominal window or to allow for proper derotation, as in the case of the derotation window.

Thermomechanical loading and cut-out effect on static and dynamic responses of multilayered structure with TD properties

The influences of cut-out on the static and dynamic deflection of the multilayered composites under thermomechanical are predicted numerically. In this regard, a mathematical model is prepared using the third-order kinematics associated with the isoparametric finite element steps. Moreover, the solution accuracy of the derived model has been tested frequently by solving a series of examples (obtained from MATLAB code) similar to the published one. In addition, the model verification is extended further by comparing the numerical results with the in-house experimental data recorded under the static and dynamic loading conditions. The equivalent single-layer theoretical model (prepared for the cut-out abided laminated structure) exactness is maintained by considering the variation of in-plane displacement as cubic. In contrast, the state space variable along with the thickness is constant. Additionally, the experimental comparisons are made considering the influences of different cut-out geometry, temperature increment, and loading intensities. The effects of cut-out and the laminated structural geometrical parameters that affect the final design consideration due to the thermomechanical loading as well as the temperature-dependent properties are computed using the derived model, and the outcomes are discussed in detail.

Optimal design of tube flexure cut-out geometries for deployment performance

A design methodology is proposed for deployable tube flexures made of ultra-thin carbon fiber composite. The methodology is developed to achieve desired stowage and deployment performance in the absence of material failure. The cut-out shape in the tube flexure is determined by means of a Bayesian optimization technique. The objective function is defined based on both desired moment characteristics and Hashin failure criteria. Multiple cut-out parameterization schemes are presented. Bayesian optimization is shown to be effective and significant performance improvements are achieved thought use of spline-based optimization in comparison to more conventional forms. The efficiency of the approach is validated via experiment.

The Impact of the Cut-Out Shape on the Dynamic Behavior of Composite Thin Circular Plates

This study measures the impact of the cut-out shape on the fundamental frequency and the harmonic response of thin composite circular plates under fixed boundary conditions. For this purpose, the Finite Element Method has been employed using the SHELL181 element of ANSYS Workbench 18.2 software. Nine different circular plates having central equilateral triangle, square, regular pentagon, regular hexagon, regular heptagon, regular octagon, regular nonagon, regular decagon, and circular cut-outs have been designed to understand the changes in the vibrational behavior of a structure as the cut-out geometry approximates to circular. Additionally, a solid circular plate has been modelled for comparison purposes. To investigate the effect of the cut-out shape more deeply, all structures have been designed as cross-ply and angle-ply composites. The free vibration analysis has been performed to obtain the fundamental frequency of each structure. The harmonic response analysis problem has been solved by employing the Mode Superposition Method and considering a constant damping ratio. The results of the study have been interpreted by considering the displacement response, stress, and phase shifts at a certain frequency range. The results indicate that the shape of the cut-out considerably affects the fundamental frequency and harmonic response of the circular structure regardless of its fiber orientation.

Effect of Cutout on the Stability and Failure of Laminated Composite Cylindrical Panels Subjected to In-Plane Pulse Loads

In this investigation, the nonlinear dynamic buckling analysis and the failure analysis of laminated composite cylindrical (LCC) panel with different shapes of cutouts under the action of rectangular in-plane pulse loads are performed in the finite element framework. Cross-ply laminates which are balanced symmetric are considered in the investigation. The first ply failure load (FPFL) of the panel is evaluated and checked whether it occurs before the nonlinear dynamic buckling phenomenon considering Tsai–Wu failure criterion. Convergence and validation studies are undertaken, and the results are compared with those from the existing literature. The effects of loading duration, cutout area and cutout geometry on the panel are investigated in detail and results are reported. The results indicate that for the panel with cutout, its dynamic buckling load (DBL), in certain cases, compared to the static buckling load (SBL), can be lower even if the loading duration is half of its first natural period. Additionally, the vibration and the static buckling analyses of the panels are carried out as and when required.

Effect of cutout geometry on the failure strength of symmetric laminates under uniform heat flux

The present work aims to investigate the thermal stress distribution in an infinite symmetrical laminated composite plate with a polygonal cutout to determine the laminate failure strength based on the first ply failure according to Hashin–Rotem and Tsai–Wu criteria. Lekhnitskii’s solution technique has been used to obtain the required potential functions. The extension of the technique used for the circular and elliptical cutouts into polygonal cutouts was performed using conformal mapping function in accordance with the procedure of complex variables. The main parameters such as cutout orientation, bluntness factor, the aspect ratio of the cutout, as well as stacking sequences in composite plates with symmetrical laminates made of glass/epoxy material containing triangular, square, pentagonal, and hexagonal cutouts have been examined. According to the research findings, it is possible to improve the failure strength of perforated plates by appropriate selection of cutout shapes along with the optimum values of the effective parameters. The unexpected result was that circular geometry was not always the best choice for the cutout because the selection of appropriate values for the parameters under consideration for a laminate with non-circular cutout leads to higher failure strength compared to the same plate with circular cutout.

Metaheuristic Optimization of Laminated Composite Plates with Cut-Outs

The stacking sequence optimization of laminated composite plates while maximizing the structural performance or minimizing the weight is a subject investigated extensively in the literature. Meanwhile, research on the optimization of laminates with cut-outs has been relatively limited. Cut-outs being an indispensable feature of structural components, this paper concentrates on the stacking sequence optimization of composite laminates in the presence of circular cut-outs. The buckling load of a laminate is used as a metric to quantify the structural performance. Here the laminates are modeled as carbon fiber-reinforced composites using the finite element analysis software, ABAQUS. For the optimization, the widely used harmony search algorithm is applied. In terms of design variables, ply thickness, and fiber orientation angles of the plies are used as continuously changing variables. In addition to the stacking sequence, another geometric variable to consider is the aspect ratio (ratio of the length of the longer sides to the length of the shorter sides of the plate) of the rectangular laminates. The optimization is carried out for three different aspect ratios. It is shown that, by using dispersed stacking sequences instead of the commonly used 0°/±45°/±90° fiber angle stacks, significantly higher buckling loads can be achieved. Furthermore, changing the cut-out geometry is found to have a significant effect on the structural performance.

Hot-spot stress models of cutout detail on orthotropic steel bridge decks

Stress distributions along the critical section of the floorbeam cutout detail of two different cutout geometries were studied based on bridge field tests. Stress concentration at cutout detail was significant and highly dependent on cutout geometry, hence nominal stress could not be applied. The existing HSS models failed to exclude significantly nonlinear stress at original cutout detail due to their first reference points too close to free edge of cutout, and hence they significantly underestimated fatigue life. A new HSS model, with two reference points located respectively 1.0 t and 1.5 t away from the free edge of cutout, was suggested and validated for the two types of cutout geometry. Because the retrofit cutout geometry increases stress at the area 0.5 t away from the free edge, the fatigue life using various HSS models is significantly low compared to the bridge design life. It is concluded that the suggested HSS model and FAT100 may be applicable to fatigue evaluation of cutout detail with different cutout geometry.

Size-dependent nonlinear bending behavior of porous FGM quasi-3D microplates with a central cutout based on nonlocal strain gradient isogeometric finite element modelling

With the aid of the non-uniform rational B-spline (NURBS)-based isogeometric technique, for the first time, the size-dependent geometrically nonlinear bending characteristics of microplates made of porous functionally graded materials (FGMs) having a central cutout with different shapes are studied. The nonlocal strain gradient continuum elasticity within the framework a hybrid higher-order quasi-3D plate theory is adopted to describe the kinematic relations via only four unknowns. To capture the effective material properties, a porosity-dependent rule of mixture is employed. The nonlocal strain gradient nonlinear load–deflection responses are obtained corresponding to various geometrical and material parameters as well as different boundary conditions. It is revealed that the significance of both the nonlocal and strain gradient reduces. This prediction is the same for all values of the material property gradient index as well as the porosity index. Also, it is demonstrated that a central cutout leads to change the trend of load–deflection response, and this change occurs at a specific value for the applied distributed load which depends on several parameters such as the cutout geometry and boundary conditions. In addition, it is displayed that corresponding to different maximum deflections, the significance of the strain gradient size effect in the absence of nonlocality on the nonlinear flexural stiffness of a porous FGM microplate is more than that of the nonlocal size effect in the absence of the strain gradient size dependency.

Design methodology in transverse webs of the torsional box structure in an ultra large container ship

Container ships has a transverse section in the form of an open profile, making it very sensitive to torsion phenomena. To minimize this effect, a structure known as a torsion box exists, which is subject to high stresses influenced by the fatigue phenomenon and the existence of cut-outs, for the passage of the longitudinal stiffeners, acting as stress concentrators. The aim of this study is to propose a two-stage design methodology to aid designers in satisfying the structural requirements and contribute with to a better understanding of the considered structure. The transverse webs of a torsional box structure are examined by comparing different cut-out geometries from numerical models with different regular load conditions to obtain the variables of the fatigue safety factor through linear regression models. The most appropriate geometry of the torsion box is established in terms of minimum weight, from nonlinear multivariable optimization models.

The post-critical behaviour of compressed plate with non-standard play orientation

Thin-walled carbon/epoxy composite plate elements with a central cut-out under compressive loading are investigated. The work focused on the original concept of this element, for use as elastic or load-bearing element and whether possibility to shape their structural rigidity by changing the cut-out geometry or the laminate’s lay-up. The lowest buckling mode exhibits a small postcritical rigidity and is reached at low loads. The calculations carried out earlier show that plates with forced higher form of buckling are characterized by stable, progressive paths of post-critical equilibrium, enabling their use as elastic elements. The aim of the study, partially revealed in this abstract, requires a thorough analysis of the effect of the B matrix form on the coupled composite behaviour. Coupling stiffness matrices of unsymmetrical laminates have been thoroughly described by, among others, York, Altenbach. The commercial ABAQUS program using the finite element method was used to develop the discrete model and perform numerical calculations. Experiment was performed on a universal testing machine. The obtained results are of significant practical importance in the design of structures with elastic elements, allowing to achieve the required maintenance characteristics of the device.

Using a variable value of the fictitious radius to estimate fatigue life of notched elements

AbstractThe article discusses the problem related to estimating fatigue life of elements containing stress concentrators. The algorithm for estimating fatigue life presented in this work uses a fictitious ray based on the Neuber method. The proposed algorithm takes into account the variability of microstructural length, which depends on the number of failure cycles. The function thus obtained can be used to select the appropriate value for this length, which simplifies the calculation procedure needed to estimate fatigue life. In addition, this work includes an analysis of the impact of variable cutout geometry on the value of the support coefficient. As a result, it was possible to extend the application of this concept to lower fatigue life values and to structural elements with different notch geometries. The method was verified by performing experiments using elements made of three steel grades. A good correlation between calculation and experimental results was obtained.

Fatigue behavior of orthotropic bridge decks with two types of cutout geometry based on field monitoring and FEM analysis

This paper provides comparative results on stress behavior and fatigue performance of two types of cutout geometry on orthotropic bridge decks based on simultaneous field monitoring and finite-element method (FEM) analysis. The two types of cutout are incorporated in two closely spaced diaphragms with distance of 6 m and at the same transverse location on a real bridge, allowing simultaneous stress measurement under random traffic flows. The research was conducted on the Pingsheng Bridge in Southern China, a self-anchored suspension bridge with a main span of 350 m and a steel box girder with orthotropic steel bridge decks (OSBD). Results of the study reveal that the two types of cutout geometry present high stress response and severe stress concentration at the floorbeam (FB) cutout, and that the excessively large stress at the original FB cutout contributes greatly to the early cracks of this detail. Compared to the original cutout geometry, the new cutout geometry with large radius increases the stress level at the FB cutout, resulting in a further low fatigue life at this detail. Meanwhile, the new cutout geometry also deteriorates the fatigue resistance at the rib-to-floorbeam (RF) weld connection, particularly at the detail of rib wall at cutout, where the stress level is significantly increased and its fatigue life becomes substantially lower than the design life of 100 years. In addition, the new cutout geometry only slightly improves the out-of-plane distortion under direct wheel loading, and the in-plane stress still dominates the total stress at the FB cutout. Since the new cutout geometry weakens the FB web, the total stress at FB cutout will increase due to the increased in-plane stress. The research also finds that if the free edge of cutout did not satisfy the fabrication requirement per the AASHTO LRFD, category B is suggested for fatigue evaluation at the FB cutout, which is confirmed by the observed fatigue life of the original FB cutout on the real bridge. It is concluded that the new cutout geometry lowers the fatigue resistance both at the FB cutout and at the RF weld connection, hence it will no longer be recommended to retrofit the present bridge in the future.

Effects of embedded perforation geometry on the free vibration of tow-steered variable stiffness composite laminated panels

The free vibration characteristics of the variable stiffness composite laminated plates containing embedded cutout of desired shapes is investigated. The circular, elliptical and quadrilateral perforation geometries are taken into account. In order to provide a strongly flexible calculation tool, an isogeometric analysis formulation based on the non-uniform rational B-splines (NURBS) along with the Nitsche technique is developed based on the first order shear deformation plate theory. The effects of change in the mechanical properties of tow steered laminates throughout the geometry due to fibers following prescribed curvilinear paths are taken into account in the integration procedures. The accuracy and reliability of the calculations is shown through some representative comparisons. The effects of change in the cutout geometry, location and orientation in conjunction with the curvilinear fiber placement are studied.