Showing papers in "Journal of Strain Analysis for Engineering Design in 2022"

Ratcheting assessment of corroded elbow pipes subjected to internal pressure and cyclic bending moment

Abstract: The present study aimed to study ratcheting strains of corroded stainless steel 304LN elbow pipes subjected to internal pressure and cyclic bending moment. To this aim, spherical and cubical shapes...

Effect of magnetic field and voids on Rayleigh waves in a nonlocal thermoelastic half-space:

Abstract: This work is concerned with the propagation of surface waves is considered in an isotropic elastic homogeneous nonlocal generalized thermoelastic solid medium in the presence of a magnetic field an...

Design and experimental research of stress measurement system for ferromagnetic components based on ACSM method

Abstract: Stress is one of the important factors that cause fatigue and fracture of ferromagnetic components, and its accurate measurement is of great significance to ensure the safety and reliability of com...

Critical buckling load of composite laminates containing delamination using differential quadrature method and ABAQUS finite element

Abstract: Differential quadrature method (DQM) was used to compute the critical buckling load (CBL) of composite laminates containing complex delamination shapes. The composite laminate was initially flat; h...

Free vibration characteristics of viscoelastic nano-disks based on modified couple stress theory

Abstract: This paper investigates the vibrational behavior of a viscoelastic and size-dependent nano-disk based on the modified couple stress theory (MCST). The material characteristics in nano-scale are modeled according to Zener viscoelastic constitutive relation. In addition, displacement components are defined based on classical plate theory. Leaderman integral is also used to determine the viscous parts of the stress tensor. Hamilton’s principle is utilized to derive the governing equations of motion for specifying the strain, kinetic energy, and viscous work. The obtained equations are discretized with the help of the Galerkin method and decoupled through the diagonalization procedure. Laplace transformation is employed to solve the resulting equations in differential–integral form. The damping ratio, the imaginary part and real part of the Eigen frequency of the considered nano-disk are calculated to investigate the effects of influential parameters on the nano-disk vibrational behavior. These parameters include nonlocal parameter boundary conditions, geometric constant, power constant, and element relaxation coefficient. Results obtained on different mode shapes indicate that increasing the dimensionless element relaxation coefficient is followed by a decrease in the imaginary part of the Eigen frequency regarding the energy dissipation as well as a decrease in the real part of the Eigen frequency. Furthermore, increasing the h/l ratio is accompanied by variations in the imaginary part, real part, and damping ratio. According to the results, the effect of damping on vibrational behavior of the nano disk is more distinguished for smaller values of h/l.

Methods for measuring friction-independent flow stress curve to large strains using hyperbolic shaped compression specimen:

Abstract: The accurate measurement of flow stress curve to large strains using cylindrical compression specimen is always a great challenge due to the influence of friction. Recently, the present authors des...

Non-contact strain measurement to eliminate strain gages in vibration-based high cycle fatigue testing

Abstract: Digital Image Correlation (DIC) is a non-contacting, camera-based technique that calculates full-field displacements and strains by comparing digital images taken before and after an object is deformed. During a vibration-based fatigue test, DIC has an advantage over strain gages in that it is non-contacting and does not accumulate damage during the test. In this work, DIC was implemented to build strain-velocity calibration curves as an alternative to strain gages. First, a curve fit was applied to DIC displacements and strains along the free edge of the plate using an approximate solution for the mode shape of a cantilevered plate. In total, the curve fits were applied to three sets of DIC data: (i) the raw strains calculated with DIC; (ii) the in-plane U-displacements from which the raw DIC strains were computed; and (iii) the out-of-plane W-displacements observed in the direction of motion. Second, classical plate theory was used to calculate strains by taking derivatives of each of the applied curve fits. Third, the peak strains from each curve fit were used to build the strain-velocity calibration curves. Further, a Monte Carlo Method uncertainty analysis was performed to estimate the uncertainty of the curve fitted DIC and strain gage measurements. Of the three curve-fits, the DIC strains derived from the out-of-plane displacements provided the most precise measurements relative to a strain gage at all excitation levels used to build the calibration curves.

Effect of fillers on compression loading performance of modified re-entrant honeycomb auxetic sandwich structures

Abstract: The auxetic sandwich panels for structures have been designed to provide impact protection. The aim of this work is to modify an auxetic (re-entrant) honeycomb cell to reduce the stress concentrations within the cell structure, and further enhancement of this design. The auxetic structure was filled to achieve a greater energy absorbance and enhance safety applications. Analytical and elastic three-dimensional finite element approaches were used to investigate the structural strength performance. The basic model (i.e. modified re-entrant strut cell design) consisted of the honeycomb auxetic polypropylene (PP) structure sandwiched between two steel plates (known as safety panels) which were placed under static compression loading. The cell geometry and size were then modified to reduce the stress concentration zones. The structure cells were filled with silly putty and polyvinyl chloride (PVC) foam. The effect of the filling the cells on the stress concentration and energy absorbance were analysed using elastic stress and deformation analysis methods. During the stress path analysis, it was found that an increase in Young’s modulus of the filling was directly proportional to a decrease in internal stresses. It was concluded that while filling the basic model with soft materials reduced the stress concentration, but it led to a reduction in the energy absorbance capability. Further on, the lower stress produced by the enhanced could be useful to prevent significant penetration of the protective panel. Compared to similar structures of steel, auxetic foam panels have the advantage of having only a fraction of the weight and being corrosion resistant at the same time as keeping impact strength. Graphical abstract

Optimization of design and fatigue simulations for an electric assisted bicycle frame using uniform design and grey relational analysis

Abstract: The electric assisted bicycle is the new transportation tool in the 21st century. The proposal of this article is to upgrade the fatigue safety factor for an electric assisted bicycle frame by integrating the uniform design, Kriging interpolation, entropy weighting method, grey relational analysis, and genetic algorithm. According to EN 15194 standard, the main objective function, the fatigue safety factor for an electric assisted bicycle frame is examined by ANSYS/Workbench software under three fatigue testing simulations. Five geometry parameters of an electric assisted bicycle frame are nominated to be the improved control factors. Since all control factors are continuous in the design space, the uniform design is certainly developed to construct a series of simulation experiments. For each model in the uniform design table, the fatigue finite element analysis is utilized to calculate the fatigue safety factor. Applying the multi-objective optimization procedure, the optimal design version of an electric bicycle frame has been obtained. For the fatigue safety factor, the revised design model has a maximum improvement of 19.59% when compared to the original design. Summery, the fatigue safety factor has been effectively elevated by executing the innovative multi-objective optimization procedure for an electric assisted bicycle frame system.

Nonlinear dynamics of flexible diaphragm coupling’s rotor system during maneuvering flight

Abstract: In this paper, the flexible multi-diaphragm coupling which is used as flexible power transmission shaft of the aeroengine accessory is taken as the research object, and the coupling stiffness matrix and axial nonlinear stiffness of the diaphragms are considered in the coupling rotor system. On this basis, in order to consider the influence of aircraft maneuvering load, in non-inertial system the bending-pendular-axial coupled differential equations of flexible diaphragm coupling were established by Lagrange method. The modal characteristics of the flexible diaphragm coupling were analyzed and compared with the finite element solutions, and the correctness of model is verified. Runge-Kutta method is used to solve and analyze the influence of different maneuvering flight conditions on the vibration characteristics of the flexible diaphragm coupling. The research indicates that the coupling between diaphragm’s axial and radial stiffness leads to the right shift of resonant region, the increase of resonance peak value, and the nonlinear characteristics of amplitude-frequency curve such as jump and multi-value. In the non-inertial system, only the installation distance a of the flexible diaphragm coupling along the wingspan leads to the increase of the axial deformation offset of the flexible diaphragm coupling in the rolling flight state. The increase of climbing or diving angular velocity makes the flexible diaphragm coupling’s vibration changes from single period to multi-period, bifurcation or chaos state; With the increase of diving angular velocity and rolling angular velocity, the axial critical speed gradually increases; Each flight condition not only affects the vibration characteristics, but also causes the axial, radial and angular deformation of the flexible diaphragm coupling to a certain extent. This study provided a theoretical basis and method for the design and analysis of diaphragm coupling.

Incorporation of the effect of strain rate in Mie-Gruneisen equation of state for polyethylene:

Abstract: Volume change versus pressure is expressed through an equation of state (EOS) such as the well-known Mie-Gruneisen equation. Equation of state is an essential requirement to be defined for numerica...

Influence of discontinuities on the fracture behaviour of CNT reinforced composites subjected to thermo-mechanical load using XIGA

Abstract: This paper is aimed to investigate the fracture behaviour of carbon nanotube (CNT) reinforced composite exposed to the thermo-mechanical environment in the presence of discontinuities using the extended isogeometric analysis (XIGA) method. The study focuses on finding the effects of discontinuities present in a finite plate with a pre-existing crack, on the stress intensity factors (SIFs). The mandatory equivalent mechanical and thermal properties are assessed with the help of various micromechanics models. Two types of CNTs are assumed to be reinforced in the epoxy-matrix: single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT). The CNT reinforced composite is examined for varying volume percentages of CNTs reinforcement. A comparative study is provided to see the influence of mechanical and coupled thermo-mechanical load on SIFs. Adiabatic crack is taken into account for the computational simulation for thermal loading condition. The interaction integral method is used for the extraction of SIFs. The findings of the test reveal that with the rise in the volume percentage of CNTs, the properties such as fracture energy and fracture toughness also rise. Moreover, the fracture of CNT reinforced composites is delayed with the increased content of CNT. The results establish the profound influence of holes on SIFs than the inclusions.

Experimental and numerical investigation of residual stress distribution in Al-6061 tubes under using tubular channel angular pressing process by new trapezoidal channel

Abstract: Tubular channel angular pressing (TCAP) method is an appropriate severe plastic deformation (SPD) techniques for the generation of ultra-fine grained (UFG) and nanostructured (NS) tubes. In forming methods, the measurement of residual stresses is very important due to their significant effects on the processed samples. Therefore, determining the residual stresses created by the TCAP method in metals is of great importance. In this research, the distribution of residual stresses in Al-6061 tubes under the TCAP process, was studied experimentally and numerically. For this purpose, first the TCAP process was applied on Al-6061 tubes and after that the residual stresses generated in the TCAPed tubes were measured. Sachs method was used experimentally to measure the residual stresses. Sachs method is one of the destructive, convenient and efficient methods for measuring the residual stresses of axisymmetric cylindrical samples. Residual stresses measured by Sachs method in the processed samples showed that the tensile and compressive residual stresses were created on the external and internal tube surfaces, respectively. In addition, a good agreement was existed between the results of the numerical simulation and experimental methods for measuring the residual stress distribution.

Optimal shaft-hub connections

Abstract: In all power transmitting machines the shaft-hub connection has a large impact on the overall machine size, if the strength can be increased we can reduce the size. The connection between shaft and hub is a machine element with many possible designs available and described in standards. The connection can be either permanent or changeable, the goal is in all cases to have as high a strength for the connection as possible. Focus is in the present paper on the connections with easy assembly and disassembly, that is, on positive connections (geometrically locked). The designs specified in standards are traditionally made with straight lines and circular arches. Alternatively the involute spline can be used. For this case the cutting tool shape is made with straight lines and circular arches. Present standard designs are not made with minimum stress concentrations as the main objective, other features as for example, easy manufacturing has the primary importance. In the present paper we show how the involute spline design can be significantly improved in relation to strength maximization by reducing the maximum stress. The maximum stress can in many cases be reduced by more than 54 % relative to standard design.

Computerized analysis of traveling wave vibration characteristics of aviation thin-walled spiral bevel gears

Abstract: Aviation thin-walled spiral bevel gears are prone to traveling wave vibration. This study proposes an efficient traveling wave vibration analysis method based on the contact finite element model of the spiral bevel gears. The excitation vibration modes under the typical working condition is obtained through comparison to the modal analysis and harmonic response analysis. The resonance modes and frequencies are determined by Campbell diagram. The effect of thin-walled structure parameters on the traveling wave vibration of aviation spiral bevel gears is investigated. The results show that the traveling wave vibration of the gear is easily excited by the forward traveling wave and backward traveling wave resonance of 2nd nodal diameter/1st nodal circle, forward traveling wave resonance of the 6th nodal diameter, backward traveling wave resonance of 7th nodal diameter. The increase of gear blank web thickness will decrease peak stresses. The increase of conical web thickness and angle will decrease the peak stresses of compound vibration. The adjacent modals will aggravate the vibration. The decrease of the modal frequency spacing will increase the peak stresses.

Bending analysis of nanobeams based on the integral form of nonlocal elasticity using the numerical Rayleigh-Ritz technique

Abstract: The nonlocal theory is commonly applied for nanomaterials due to its capability in considering size influences. Available studies have shown that the differential version of this theory is not suitable for some problems such as bending of cantilever nanobeams, and the integral version must be used to avoid obtaining inconsistent results. Therefore, an attempt is made in this paper to propose an efficient variational formulation based on the integral nonlocal model for the analysis of nanobeams. The formulation is developed in a general form so that it can be used for arbitrary kernel functions. The nanobeams are modeled using the Bernoulli-Euler beam theory, and their bending behavior is analyzed. Derivation of governing equations is performed according to an energy-based approach. Also, a numerical approach based on the Rayleigh-Ritz method is developed for the solution of problem. Moreover, the results of integral and differential models are compared. It is revealed that by the proposed numerical solution, the paradox in the behavior of nanocantilever is resolved.

The vibration of viscothermoelastic static pre-stress nanobeam based on two-temperature dual-phase-lag heat conduction and subjected to ramp-type heat

Abstract: In this work, the two-temperature dual-phase-lag theorem has been used to present an analytical mathematical model for calculating the vibration in a viscothermoelastic nano-resonator. The governing equations have been derived when a simply supported nano-resonator is exposed to a ramp-type thermal load and static pre-stress. The governing equations have been solved by using a direct method and obtained the solution in the Laplace transform domain where the inversions of the Laplace transform have been calculated by using the Tzou approximation method. The increments of the dynamic and conductive temperatures, volumetric deformation, and stress regarding the resonator length for various cases of temperature type, static-pre-stress, and viscothermoelastic properties with different values of ramping heat parameter have been presented in figures and studied. The parameter of the two-temperature model, static pre-stress, ramp-type heat parameter, and viscothermoelastic parameter has a significant impact on all functions studied. The ramping time parameter may be utilized to change the thermal and mechanical properties of the nano-resonator.

Finite element analysis, prediction, and optimization of residual stresses in multi-pass arc welding with experimental evaluation

Abstract: Prediction and reduction of unwanted tensile Residual Stress of welded stainless-steel plates is presented in this paper. Validated finite element analysis and Artificial Neural Network (ANN) is employed to simulate and mathematically model the process, respectively. Taguchi design of experiments tool is utilized to generate input data for finite element analyses and also to choose the most accurate ANN structures. RSs are minimized using three methods: Taguchi suggestion, Comprehensive factorial search, and Particle Swarm Optimization, whose accuracy and response pace increases and decreases respectively in this order. Furthermore, adding and removing extra weld lines was proposed to reduce unwanted residual stresses by up to 50%. Finally, the shapes and amounts of results are experimentally verified using contour method and proposed novel application of roughness testing. Micro-grain structures of the welded samples were also investigated, and RSs were discussed considering metallography images.

Determination of the parameters of material models using dynamic indentation test and artificial neural network

Abstract: Stress-strain curves of materials normally change with strain rate and temperature and are normally defined by material models. In this study, a new technique was developed for determining the constants of material models. This technique was based on dynamic indentation test, numerical simulation using Ls-dyna code and artificial neural network. An indenter of tapered shape was shot against the materials as the target by a gas gun. The experiments were carried out for four strain rates and four temperatures. The target was made of pure copper. The penetration depth-time and load-time histories were captured by a LVDT and a piezoelectric load-cell, respectively and the load-penetration depth curve (P-h) was obtained. This curve is characterized by five parameters which are determined for each indentation test. On the other hand, the indentation test was simulated using Ls-dyna hydrocode. From the simulations, the P-h curves were obtained using Johnson-Cook (J-C) and Zerilli-Armstrong (Z-A) material models and the characterizing parameters of the numerical P-h curves were also identified. Finally, an artificial neural network (ANN) was trained by the numerical P-h curves parameters as the input and the constants of J-C and Z-A models as the output. The trained neural network was then tested by the experimental p-h curves parameters as the input and the constants of J-C and Z-A models as the output. Moreover, a number of dynamic compression tests were performed using the well-known Split Hopkinson Bar at the same strain rates and temperatures used for indentation tests and the stress-strain curves of material were obtained. A reasonable agreement was observed between the stress-strain curves predicted by neural network and the Split Hopkinson Bar. The proposed method does not need sophisticated instrumentation and in fact, the load-time and indentation depth-time histories are directly converted to stress-strain of material using an artificial neural network.

Study of dynamic mechanical behavior of 1060-H112 aluminum alloy: Experimental and numerical simulation

Abstract: 1060-H112 aluminum alloy with high ductility is widely used in industrial engineering. The study of its dynamic mechanical behavior has theoretical and engineering application value. In this paper, quasi-static tensile tests from room temperature to 250°C and high strain rate compression tests were conducted using a universal material testing machine and a Hopkinson compression bar. By using a hybrid test-numerical simulation method, a modified Johnson-Cook (MJC) strength model and Cockcroft-Latham (C-L) fracture criterion parameters were calibrated. Subsequently, Taylor impact tests were performed on 1060-H112 aluminum alloy specimens with a diameter of 12.66 mm and a length of 50.64 mm in the range of 176.3–483.03 m/s. Upsetting and tensile tearing were observed in the tests. A 12.68 mm diameter blunt nosed projectile impact test on 2 mm 1060-H112 aluminum alloy plate was also conducted with a light gas gun system, and the speed related parameters and failure modes were obtained. Finally, a three-dimensional model corresponding to the test was established in ABAQUS/Explicit finite element simulation software, and the failure modes of the Taylor rod and the velocity parameters and failure modes of the target impact test were predicted. The results show that the MJC strength model and the C-L fracture criterion can predict the experimental results of the two tests accurately. It shows that the MJC strength model and C-L fracture criterion have high accuracy, and they will play an important role in the application of 1060-H112 aluminum alloy in industrial engineering.

Flat and rounded contacts: Modelling the effect of a moment with application to fretting fatigue tests

Abstract: The problem of elastic indentation by a punch having the form of a flat front face but with edge rounding, and subject to both a normal load and moment, indenting an elastically similar half-plane is considered. Contact pressure in the neighbourhood of the edges shows a local peak, and the object of the paper is to show how different combinations of normal load and moment can give rise to the same near edge behaviour and peak pressure. The result found is very simple, and of direct practical application in fretting fatigue studies, both analytical and experimental.

A mesh refinement scheme for fourth order bi-harmonic equation of mixed boundary-value elastic problems

Abstract: Fourth order bi-harmonic equation is extensively used for stress-strain analysis of mixed boundary-value elastic problems. However, currently existing uniform mesh scheme based on finite difference method (FDM) needs vast amount of computational resources and efforts for an acceptable solution. Therefore, in this study, a mesh refinement (MR) scheme based on FDM is developed to solve fourth order bi-harmonic equation effectively. The developed MR scheme allows high resolution computation in sub-domains of interest and relatively low resolution in other regions which overcomes the memory exhausting problems associating with the traditional uniform mesh based FDM. In this paper, sub-domain that needs high resolution (mesh refinement) are identified based on gradient of stress and displacement vectors. A very high gradient in any region signifies the need of fine mesh because coarse grained meshes are not adequate to capture the sharply changing stresses or displacements. Once the sub-domains of interest are identified, the mesh refinement is done by splitting course meshes into smaller meshes. Several new stencils are created to satisfy the fourth order by harmonic equation and associated boundary conditions over the various sizes of meshes. The developed MR scheme has been applied to solve several classical mixed boundary-value elastic problems to show its applicability. In addition, the validity, effectiveness, and superiority of the MR scheme have been established by comparing of obtained solutions with uniform mesh results, finite element method (FEM) results, and the well-known analytical results. Our results show that the developed MR scheme can provide a more reliable and accurate result than the conventional uniform mesh scheme with a reduced number of equations, thus, saves a huge amount of computational memory.

Nonlocal dual-phase-lag thermoviscoelastic response of a polymer microbeam incorporating modified couple stress and fractional viscoelastic theories

Abstract: Ultra-slow relaxation process of polymers has the memory-dependent feature, integer-order thermoviscoelastic models may fail to describe the dynamic behaviors of viscoelastic structures accurately. Additionally, it is noticed that the small-scale effect of elastic deformation and heat conduction in a non-isothermal temperature environment is becoming significant due to the development of micro-devices. To better capture the memory-dependent effect and the small-scale effect of viscoelastic micro-structures in heat transfer environment, as a first attempt, present work focuses on developing a refined fractional Kelvin-Voigt thermoviscoelastic model by incorporating the nonlocal dual-phase-lag (NDPL) heat conduction model and the modified coupled stress theory (MCST). Then, the model is applied to investigating the transient response of a polymer microbeam subjected to a harmonic thermal loading. The governing equations involving the modified parameters are formulated and then solved by Laplace transform method. Some parametric results are demonstrated to display the impacts of the nonlocal thermal parameter, the material length-scale parameter and the fractional-order parameter on the considered physical quantities. The results show that the small-scale effect and the memory-dependent effects strongly depend on the polymer micro-structure characteristics in thermal environment.

3-D analytical solution of non-homogeneous transversely isotropic thick closed cylindrical shells

Abstract: This paper presents an effective analytical method based on displacement potential functions (DPF) for solving 3D static problem of thick and multilayer transversely isotropic cylindrical shells with simply supported end boundary conditions. By using the DPF method, the three-dimensional elasticity equations are simplified and decoupled into two linear partial differential equations of fourth and second order as governing differential equations. The governing equations are solved by the separation of variable method in terms of fields that exactly satisfy end boundary conditions and the continuity of a closed cylinder in the hoop direction. The analysis covers a straightforward solution process for handling problems on multilayered cylindrical shells of transversely isotropic material, adopting all boundary and continuity conditions. Extensive sets of general radial loads located on the inner and outer faces of the cylindrical shell may be stated and examined with in a systematic manner. Comparisons are performed to other existing analytical results for one and multilayered cylindrical shells, and show excellent agreement for different materials, thicknesses and aspect ratios of the shell. In addition, various more involved problems are studied and solved analytically for single and three-layered shells of transversely isotropic material with different sets of radial loading functions at the outer and inner shell surfaces. The results of the present study can be used as benchmark solutions for other studies.

Hole-drilling method eccentricity error correction using a convolutional neural network

Abstract: Hole eccentricity is an important error source when residual stress is measured via the hole-drilling method. The conventional ways to correct eccentricity error for hole-drilling residual stress measurement rely on complicated mathematical processes and are difficult to use. To overcome this shortcoming, this paper proposes a method that uses a convolutional neural network to correct for the hole-drilling method eccentricity error. First, the hole-drilling method measurement process in uniform biaxial stress field is simulated via the finite element method. The influence of the eccentric distance, eccentric angle, and stress ratio on the strain measurement error is discussed. Then, a convolutional neural network is trained using simulated data and the hole-drilling method strain measurement error is predicted for arbitrary eccentricity conditions. Finally, the residual stress is corrected by introducing the strain error into its equation. The simulated residual stresses of ten eccentric measurement points in predefined stress fields are corrected using this procedure to conducted numerical tests. The maximum error of simulated stresses decreased from 30.46% to −4.67% after correction. Therefore, the hole eccentricity has a significant influence on the residual stress measurement accuracy of hole-drilling method. The proposed correction method can effectively eliminate this error.

Analysis of low velocity impact properties of basalt fiber composites considering strain rate effect

Abstract: This study focuses on the strain rate effect on the mechanical properties and damage evolution of basalt fiber reinforced composites subjected to low-velocity impact. A constitutive model is developed to accurately analyze the failure behavior of BFRP laminates. The strain-rate-dependent (SRD) model puts emphasis on a modified stress-strain relationship described by dynamic increase factor (DIF) to update mechanical properties timely during the impact loading and the damage evolution simulation is performed with the finite element code of ABAQUS software. The results shown in the LVI simulation confirmed the validity of the SRD model in comparison with the conclusions of experiments. Furthermore, detailed comparisons are discussed between the strain rate dependent (SRD) model and the strain rate independent (SRI) model under various simulations of different impact energy, thickness, and ply angles of laminates.

Topological study about deformation behavior and energy absorption performances of 3D chiral structures under dynamic impacts

Abstract: The dynamic deformation behavior and energy absorption characteristics of the 3D chiral structures were analyzed by the explicit dynamics analysis module of ANSYS/LS-DYNA. The 3D chiral structure arrayed with different micro-cell parameters cells are established. The respective influences of impact velocities, rotation angles, number and diameter of beams on the deformation behaviors, the dynamic plateau stresses, the absorbed energy, and crush stress efficiency (CSE) are explored in detail. It is shown that the 3D chiral structure exhibits torsional effect and has better energy absorption properties under low-speed impact. At high speed impact, the 3D chiral structure is affected by the impact reinforcement. This leads to a segmentation characteristic between plateau stress and impact velocity for 3D chiral structures. For the given impact velocity, the dynamic plateau stresses are related to the number and diameter of beam by a power law and a quadratic curves, respectively. The results of this study provide scientific guidance and technical support for the optimization and effective design of 3D chiral structures.

An dynamical evaluation of size-dependent weakened nano-beam based on the nonlocal strain gradient theory

Abstract: This paper examines the free lateral vibration of a cracked nano-beam based on Euler-Bernoulli beam theory and nonlocal strain gradient theory (NSGT). Due to the importance and application of nanostructures, their mechanical and mechanical properties are essential. The governing equations and boundary conditions related to using the Hamilton principle have been extracted. The beam separation with the nano-beams division into two parts attached to the Torsion spring is modeled. The model calls the excess strain energy due to crack and increases the discontinuity in the deflection slope. This study investigated the effects of crack propagation, crack intensity, material length scale parameter, and various nonlocal parameters. A comparison of previous studies has been published, where a good agreement is observed. The results show that the parameters mentioned above play an important role in dynamical behavior.

Research on the stability analysis of milling of thin-walled parts based on the dynamic characteristics

Abstract: Chatter in thin-walled parts is easy to occur in the process of machining, so the analysis of the stability of thin-walled parts has always been a research hotspot. In this paper, considering the influence of cutter eccentricity on milling force first, the coefficients of milling force were able to be identified by combining the milling force model with genetic algorithm. The results show that this method can obtain the milling force coefficients only by one experiment, and the accuracy is higher. Then the tool point Frequency Response Function (FRF) for a given combination can be calculated by using the Receptance coupling substructure analysis (RCSA) method that uses Timoshenko beam theory. Finally, the milling system can be divided into three types by aspect ratio. That is, when aspect ratio is less than 0.03, the system is considered to be a rigid tool-flexible workpiece system, but aspect ratio is between 0.03 and 0.2, the system is considered to be a flexible tool-flexible system, then aspect ratio is greater than 0.2, the system is considered to be a flexible cutter-rigid workpiece system.

A computationally efficient C0 continuous finite element model for thermo-mechanical analysis of cross-ply and angle-ply composite plates in non-polynomial axiomatic framework

Abstract: In the present article, the thermo-mechanical bending response of multi-layered composite plates is investigated in the framework of inverse-hyperbolic shear deformation theory using a generalized finite element model. The mathematical development is carried out under the assumptions of linear structural kinematics for the materials following generalized Hooke’s law. Energy-based finite element formulation and the principle of minimum potential energy are employed to develop the finite element governing equations. A computationally efficient C0 continuous finite element formulation is developed to examine the response of laminated composites subjected to constant, linear, and non-linear temperature change. Numerical analyses are carried out for composite laminates considering various lamination sequences (cross-ply as well as angle-ply), boundary conditions, loading conditions, span-thickness ratio, etc. The present results are compared with the existing analytical and numerical results and their agreement is observed. The effect of fiber orientation angle on bending response is analyzed to enable the optimal design of laminated composite structures under thermo-mechanical loading.