Analysis Of Stress Concentration Research Articles

Lightweight Potential of Anisotropic Plate Lattice Metamaterials

Additive manufacturing enables the production of lattice structures, which have been proven to be a superior class of lightweight mechanical metamaterials whose specific stiffness can reach the theoretical limit of the upper Hashin–Shtrikman bound for isotropic cellular materials. To achieve isotropy, complex structures are required, which can be challenging in powder bed additive manufacturing, especially with regard to subsequent powder removal. The present study focuses on the Finite Element Method simulation of 2,5D anisotropic plate lattice metamaterials and the investigation of their lightweight potential. The intentional use of anisotropic structures allows the production of a cell architecture that is easily manufacturable via Laser Powder Bed Fusion (LPBF) while also enabling straightforward optimization for specific load cases. The work demonstrates that the considered anisotropic plate lattices exhibit high weight-specific stiffnesses, superior to those of honeycomb structures, and, simultaneously, a good de-powdering capability. A significant increase in stiffness and the associated surpassing of the upper Hashin–Shtrikman bound due to anisotropy is achievable by optimizing wall thicknesses depending on specific load cases. A stability analysis reveals that, in all lattice structures, plastic deformation is initiated before linear buckling occurs. An analysis of stress concentrations indicates that the introduction of radii at the plate intersections reduces stress peaks and simultaneously increases the weight-specific stiffnesses and thus the lightweight potential. Exemplary samples illustrate the feasibility of manufacturing the analyzed metamaterials within the LPBF process.

Analysis of dynamic stress concentration in three different types of poro-viscoelastic rock medium

Analysis of dynamic stress concentration in three different types of poro-viscoelastic rock medium

Stress and Couple Stress Concentration and Plastic Rotation Analysis of Local Micro-structure of Flat Plate

In classical elasticity, the analytical solution of the stress concentration coefficient at the edge of a circular plate hole is 3, but the experimental result is less than 3, and the fatigue theory still has no theoretical answer to the mechanism of fatigue. For the problem that the stress concentration coefficient is less than 3, the stress and couple stress concentration at the hole edge of a circular plate hole is calculated using generalized elasticity. On this basis, the strain-elastic and rotation-plastic theory is put forward, and an example of a flat wedge structure is used to demonstrate the plastic curvature of the contact boundary of different materials to explain the mechanism of fatigue. Through calculation, it is found that there is a stress concentration at the edge of the hole and a couple of stress concentrations, and the stress concentration coefficient decreases with the decrease of the hole diameter. For flat wedge structures, the plastic curvature is mainly concentrated on the contact surface of different materials, and the plastic curvature will increase obviously when the boundary changes. This paper provides a new idea for the development of fatigue theory.

Analysis of Stress Concentration in Functionally Graded Plates with Linearly Increasing Young’s Modulus

In this article, the strain and stress analyses of functionally graded plates with circular holes that are subject to a uniaxial far-field traction load are analytically considered. The Young’s modulus is assumed to vary linearly along the radial direction around the hole. The adoption of such a type of inhomogeneity variation can be justified as follows. Firstly, and among all the possible variations of stiffness, the linear one is indeed the simplest inhomogeneity distribution. Surprisingly however, according to our knowledge extent, the associated elastic fields were not yet addressed in the literature. Secondly, a linearly varying stiffness could reasonably imply a remarkable advantage from a technological point of view. In fact, unlike nonlinearly varying stiffness plates, manufacturing routes are only required to handle constant variations throughout the radial domain. After recalling the basic equations for plane stress elasticity, the displacement, strain, and stress fields around the hole were numerically tackled and discussed for different stiffness ratios. A comparison was also carried out with other Young’s modulus distributions that have been commonly employed in the literature.

Experimental and compactional studies of interface toughening on GFRP by hierarchical distribution of halloysite nanotubes

The incorporation of nano-inclusions into the fiber-matrix interfacial regions to create hierarchical structured fiber reinforced polymers (FRPs) is a novel approach aimed at enhancing mechanical properties. However, the specific toughening mechanism facilitated by the hierarchical structure has not been extensively explored or discussed in detail. This study investigates the mechanical properties of glass fiber reinforced polymers (GFRPs) that have been hierarchically incorporated with natural halloysite nanotubes (HNTs) using experimental, computational, and numerical approaches. The hierarchical distribution of HNTs is achieved through electrophoretic deposition (EPD). The stiffening effect of HNTs incorporation is computed using the random-averaged micromechanical Mori-Tanaka model. Subsequently, stiffness and stress concentration analyses are carried out on mesoscale representative volume elements (RVEs) of GFRPs with periodic boundary condition (PBC) assignments in ABAQUS. Overall, the experimental results are consistent with the numerical and computational results in terms of trend and magnitude. The amorphous HNTs (AHNTs) with larger cross-sectional aspect ratios demonstrate significant enhancement of 45 % in transverse modulus. The in-plane stiffness and strength of GFRPs with hierarchical distribution are slightly inferior to those of GFRPs with random distribution. Nevertheless, the hierarchical distribution of nano-inclusions leads to a substantial improvement in interlaminar strength and toughness, with enhancements exceeding 70 % and 100 % respectively. This can be attributed to the reinforcement and toughening effects on the fiber-matrix interface brought about by the hierarchical distribution.

Analyzing Stress Concentration Factor in Finite Plate with Different Polygonal Discontinuities Under Uniaxial Compression Using FEM

A geometric, or theoretical, stress-concentration factor is the ratio of the actual maximum stress at the discontinuity to the nominal stress. Stress concentrations occur when there are irregularities in the geometry or material of a structural component that cause an interruption to the flow of stress. This arises from such details as holes, grooves, notches, and fillets. A detailed understanding of the stress concentration around the hole is essential for optimal design and resilience to mechanical failure. Therefore, in the design of structures, it is essential to study the effects of polygonal discontinuities in structures to achieve convenient and efficient designs. The current paper investigated the stress concentration factor around the polygonal holes in the finite structural steel plate, assuming a plane stress state and uniaxial compression loading. The present study provides a complete finite element analysis of stress concentrations in structural steel plates with polygonal cutouts (triangular, square, pentagonal, and hexagonal), in contrast to the side ratio of a polygonal hole, and the length, and height ratio of a square hole. The increasing order of stresses and SCF are square, triangular, pentagonal, and hexagonal. Due to the more edges of polygonal shapes parallel to the loading direction and minimum corners positioned in the direction of loading, a square-shaped hole produces 40% less SCF than a hexagonal-shaped hole.

Stress concentration in bone tissues and screw dental implants

Analysis of stress concentration in bone tissues and screw dental implants was per-formed on a model of screw join of the implant and surrounding bone tissues under the action of normal and tangential loads. The computations were performed by the bounda-ry element method for the plane strain state. It was assumed that those hollows in the spongy bone, which had formed in the bone after the implant insertion, are conformed to the screw thread on the implant. Bone tissues are considered as an isotropic and homo-geneous linear-elastic materials. It has been found that with the increasing in the spongy bone tissue elastic modulus, the maximum equivalent stresses in this bone tissue in-crease. Stresses in the cortical bone tissue decrease with the increasing in the spongy bone elastic modulus due to the decreasing in the load transferred to this bone part. Stresses in the spongy bone decrease with the increasing of the cortical bone layer elas-ticity modulus. The level of maximum stress in the cortical layer of the bone increases with the increasing of this bone tissue elastic modulus. The maximum of stresses in the cortical bone tissue are observed near the implant neck.

Mechanism validation after stress concentration analysis mathematical calculated with safety factor requirements using dedicated software with friction factor mate

It is feasible to use Computer Aided Design (CAD) and Finite Element Analysis (FEA) numerical simulation to validate the mathematical results obtained. Testing mechanisms in real world situations, prior to manufacturing, results in optimal designs and more reliable products. Simulation software tools evaluate the behavior of a system, improve the quality of data interpretation, and even increase product innovation. The present work shows the calculation of a simple mechanical system in two dimensions, involving the mechanical properties of the materials used, obtaining the maximum allowable load due to a required safety factor. The behavior of a mechanical element while in a stress concentration is shown along with the results obtained mathematically and with the dedicated software. Once the validity of the theoretical behavior (simulation) is known, the original design will be submitted showing the assembly with non-coincident meshing, the results obtained by the friction factor, the ISO clipping showing the volumes involved in a real situation, and the acquirement of the safety factor. The designer is shown a reliable method for decision making in the development of new equipment, modifications or even changes in the geometries and materials involved.

Finite element analysis of stress concentration in thin plates and cylindrical shells with a circular hole surrounded by an inclusion of a functionally graded material

Finite element analysis of stress concentration in thin plates and cylindrical shells with a circular hole surrounded by an inclusion of a functionally graded material

Stochastic FE analysis of stress concentrations in curved glulam beams due to the uncertainty of material direction

When curved glulam beams are subjected to bending, tension perpendicular to grain is introduced. In this work, Monte-Carlo analysis is conducted to study the influence of the annual-ring orientation of individual board on stress concentration in the radial direction. A virtual cutting program is developed which simulates the sawing processes of boards and yields a database of sawn boards, each with a characterized material direction with respect to the pith location. Lamellas are randomly selected from the database to construct curved glulam beams in FE models for Monte-Carlo simulation. Parameters including lumber diameter distribution, taper function, orthotropic elastic properties are considered for four common wood genera in Europe: spruce, pine, larch, and beech.Statistical analysis shows that when the annual-ring effect is considered, the average radial stress in the middle height area of the glulam beams can reach up 1.56 times (even higher on the middle width and height area) compared to the common practice, where wood is usually simplified as transverse isotropic material. Such stress concentration, which can trigger early damage of the structure, indicates an underestimation of stress perpendicular to grain in common practice. Moreover, parameter studies show that the stress redistribution depends not only on the mechanical properties of wood species but also on the width of the board layer.

Analysis of Strong Stress Concentrations of Key Joints for Super-Spanned Steel Truss Bridges

Analysis of Strong Stress Concentrations of Key Joints for Super-Spanned Steel Truss Bridges

Analysis and Improvement of Stress Concentration in Composite Structure Tank Roof

Analysis and Improvement of Stress Concentration in Composite Structure Tank Roof

Fatigue Behavior of M20 Torque Shear High-Strength Bolts under Constant-Amplitude Loading

Torque-shear high strength bolts were developed and widely used recently, and such high-tensile bolts may fracture in practical engineering due to the frequent complex loads, resulting in economic losses and even casualties. However, the fatigue performance of M20 torque shear high-strength bolts under constant-amplitude loading has not been investigated yet, and there are no specific design provisions for determining the constant-amplitude fatigue performance of such bolts. Hence, a total of 10 constant-amplitude fatigue tests were conducted using an MTS fatigue testing machine. For comparison, five different stress amplitudes were investigated. The fatigue performance, stress concentration and fracture analysis were analyzed. The scanning electron microscope images of fatigue failure were obtained to analyze the fatigue fracture characteristics of high-tensile bolts. A finite element model was established to analyze the stress distribution and the hot-spot stress of the bolts. The results suggested that the allowable nominal stress amplitude of M20 torque-shear type high-strength bolts was 96.371 MPa, while the allowable hot-spot stress amplitude was 283.296 MPa. Finally, the test results were compared against the existing design provisions. Upon comparison, the existing design formulas in GB 50017(2017), ANSI/AISC 360-16 (2010) and Eurocode 3 (2003) were found to be generally conservative. The S-N curve of torque-shear high strength bolts under constant-amplitude loading was proposed using the hot-spot stress amplitudes.

Isogeometric analysis of stress concentrations and failure strength in composite plates with circular holes using RHT-splines

This paper studies the stress concentration factors (SCFs) to predict the first ply failure (FPF) of cross and angle-ply laminate composite plates with single circular holes. The rational splines over hierarchical T-meshes (RHT-splines) were chosen as a surface design methodology for Isogeometric Analysis (IGA) due to their ability to exactly represent the geometry, efficient and simple local refinement algorithm, and reduction of the superfluous control points of the NURBS surface. The Bézier extraction concept was used as an element structure for IGA that allows mapping the Bernstein polynomials basis functions on Bezier elements to be performed on RHT-splines geometries. Several failure criteria and composite materials are employed in numerical examples for different fiber orientation angles through Matlab® implementation. The results obtained by the IGA based on RHT-splines showed very good conformity with those obtained by the analytic approach and finite element method (FEM) published in the literature, which demonstrates the robustness and accuracy of the IGA using RHT-splines and provides an effective and realistic way to determine SCF and failure strength. The Matlab® program for the analytical approach and failure theories is made an open-source and can be downloaded from (Github Website).

Analysis of stress and strain concentrations around an elliptical hole via finite element and response surface methodology

Analysis of stress and strain concentrations around an elliptical hole via finite element and response surface methodology

Stochastic Fe Analysis of Stress Concentrations in Curved Glulam Beams Due to the Uncertainty of Material Direction

Stochastic Fe Analysis of Stress Concentrations in Curved Glulam Beams Due to the Uncertainty of Material Direction

3D FEM analysis of stress concentrations in a rectangular thick plate with PZT inclusions under bending

3D FEM analysis of stress concentrations in a rectangular thick plate with PZT inclusions under bending

Analysis of stress and strain concentration around a centralized elliptical hole in a monodomain liquid crystal elastomer sheet

Liquid crystal elastomers (LCEs) are a kind of soft materials which couple the high elastic deformability with the unique properties of liquid crystals. Such combination endows notched LCEs unusual stress and strain concentration behaviors, which is preliminary discussed by us in the case of a large sheet with a centralized circular hole. Here we extend our study from circular holes to more generalized, elliptical holes. We investigate the stress and strain fields around a centralized elliptical hole in a LCE sheet subjected to uniaxial stretches by finite element methods. The effects of the shape factor, defined as the ratio of the minor-to-major axis of the ellipse, are mainly concerned. Compared with common elastomers like neoHookean, LCEs get higher stress and strain concentration factors (SCFs), and the location of maximal strain deviates slightly from that of maximal stress. With the decrease of the shape factor (a sharper ellipse) the SCFs of LCEs rise much severer than those of neoHookean, and the deviation is diminishing. In addition, as the stretch increases, the region near the root is getting close to an approximately uniaxial stress state, and the high strain region will extend non-monotonously along the hole edge, which differs from a monotonous extension of the high stress region. All the unusual behaviors of LCEs above are attributed to the spontaneous strain induced by director rotation. Attempts to correlate stress and strain concentration behaviors to the spontaneous strain are made in this article.

Stress concentration analysis of functionally graded material coated elliptical inclusion under uniaxial tension

The present work aims to numerically analyze the stress concentration around the central elliptical inclusion coated by functionally graded material (FGM) using Extended Finite Element Method (XFEM). The inclusion was considered in a finite panel subjected to unity far field uniaxial tensile stress. Young's modulus was assumed to be vary with power law function along the normal direction to the inclusion boundary. A MATLAB code was prepared to solve the inclusion problems with XFEM. The stress concentration was analyzed for different geometrical (panel size, inclusion size, ellipse aspect ratio) and coating parameters (FGM function and coating thickness). The results of the study reveal that the FGM coating significantly lowered the Stress Concentration Factor (SCF). The power law index 0.25 was noted as the optimal value to reduce SCF for considered range of other parameters. Higher coating thickness was found better to reduce SCF significantly. The aspect ratio of ellipse was noticed as less significant for FGM coated inclusions; however, it is quite substantial for uncoated inclusions.

Numerical analysis of stress concentration around bridge bank seat in Geosynthetic Reinforced Soil – Integrated Bridge Systems (GRS-IBS)

Geosynthetic Reinforced Soil – Integrated Bridge Systems involve directly supporting the bridge abutment bank seat on the top of a reinforced soil structure without piles or bridge bearings. Analysis, using Plaxis 2D, found that the arrangement of geogrid in the upper part of the reinforced soil abutment, the distance of the abutment bank seat from the wall face and the direction of horizontal load application were important considerations in controlling the deformational response of the abutment. Placing the bank seat further away from the wall face reduced wall displacement, peak vertical stress and settlement under the bank seat and peak strain in the geogrid. Adding secondary reinforcement in the top of the wall reduced wall deformations, peak vertical stress and settlement under the bank seat. The secondary reinforcement redistributed the tension in the geogrid immediately under the bank seat. Longer secondary reinforcement was more efficient at controlling displacement, while shorter secondary reinforcement reduced the peak vertical stress under the bank seat. The line of maximum tension, which was largely independent of horizontal load direction, originated close to the bottom-rear corner of the bank seat and was log spiral in shape, terminating at the toe of the wall.