Abstract
Accurate measurement of KIC values for gas pipeline steels is important for assessing pipe safety using failure
assessment diagrams. As direct measurement of KIC was impossible for the API X70 pipeline steel, multi-specimen fracture tests
were conducted to measure JIC using three-point bend geometry. The J values were calculated from load-displacement (F-δ)
plots, and the associated crack extensions were measured from the fracture surface of test specimens. Valid data points were
found for the constructed J-Δa plot resulting in JIC=356kN/m. More data points were added analytically to the J-Δa plot to
increase the number of data points without performing additional experiments for different J-Δa zones where test data was
unavailable. Consequently, displacement (δ) and crack-growth (Δa) from multi-specimen tests (with small displacements) were
used simultaneously, resulting in the variation of Δa-δ (crack growth law) and δ-Δa obtained for this steel. For new Δa values,
corresponding δ values were first calculated from δ-Δa. Then, corresponding J values for the obtained δ values were calculated
from the area under the F-δ record of a full-fractured specimen (with large displacement). Given Δa and J values for new data
points, the developed J-Δa plot with extra data points yielded a satisfactory estimation of JIC=345kN/m with only a -3.1% error.
This is promising and showed that the developed technique could ease the estimation of JIC significantly and reduce the time and
cost of expensive extra fracture toughness tests.
Key Words
API X70 steel; fracture toughness testing; gas transportation pipeline; indirect KIC estimation; multispecimen JIC test
Address
Mohammad Reza Movahedi:Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
Sayyed Hojjat Hashemi:Research Center on Pipeline and Related Studies, University of Birjand, Birjand, Iran
Abstract
Within the optimization field, addressing the intricate posed by fluidic pressure loads on functionally graded
structures with frequency-related designs is a kind of complex design challenges. This paper thus introduces an innovative
density-based topology optimization strategy for frequency-constraint functionally graded structures incorporating Darcy's law
and a drainage term. It ensures consistent treatment of design-dependent fluidic pressure loads to frequency-related structures
that dynamically adjust their direction and location throughout the design evolution. The porosity of each finite element, coupled
with its drainage term, is intricately linked to its density variable through a Heaviside function, ensuring a seamless transition
between solid and void phases. A design-specific pressure field is established by employing Darcy's law, and the associated
partial differential equation is solved using finite element analysis. Subsequently, this pressure field is utilized to ascertain
consistent nodal loads, enabling an efficient evaluation of load sensitivities through the adjoint-variable method. Moreover, this
novel approach incorporates load-dependent structures, frequency constraints, functionally graded material models, and
polygonal meshes, expanding its applicability and flexibility to a broader range of engineering scenarios. The proposed
methodology's effectiveness and robustness are demonstrated through numerical examples, including fluidic pressure-loaded
frequency-constraint structures undergoing small deformations, where compliance is minimized for structures optimized within
specified resource constraints.
Key Words
Dracy's law; frequency constraint; functionally graded material; polygonal topology optimization; pressure
loads
Address
Thanh T. Banh:Department of Architectural Engineering, Sejong University, Seoul 05006, Republic of Korea
Joowon Kang:Department of Architecture, Yeungnam University, Gyeongsan 38541, Korea
Soomi Shin:Research Institute of Industrial Technology, Pusan National University, Busan 46241, Korea
Lee Dongkyu:Department of Architectural Engineering, Sejong University, Seoul 05006, Republic of Korea
Abstract
In the present study, thermoelsatoplastic stresses and displacement for rotating hollow disks made of functionally
graded materials (FGMs) has been investigated. The linear elastic-fully plastic condition is considered. The material properties
except Poisson's ratio are assumed to vary in the radial direction as a power-law function. The heat conduction equation for the
one-dimensional problem in cylindrical coordinates is used to obtain temperature distribution in the disk. The plastic model is
based on the Tresca yield criterion and its associated flow rules under the assumption of perfectly plastic material behavior.
Exact solutions of field equations for elastic and plastic deformations are obtained. It is shown that the elastoplastic response of
the functionally graded (FG) disk is affected notably by the radial variation of material properties. It is also shown that,
depending on material properties and disk dimensions, different modes of plastic deformation may occur.
Key Words
Functionally Graded Material (FGM); rotating disk; thermoelastoplastic
Address
Nadia Alavi, Mohammad Zamani Nejad and Anahita Nikeghbalyan:Department of Mechanical Engineering, Yasouj University, P. O. Box: 75914-353, Yasouj, Iran
Amin Hadi:Cellular and Molecular Research Center, Yasuj University of Medical Sciences, Yasuj, Iran
Abstract
The present research investigates the combination resonance behaviors of porous FG shallow shells reinforced with
oblique stiffeners and subjected to a two-term excitation. The oblique stiffeners considered in this research reinforce the shell
internally and externally. To model the stiffeners, Lekhnitskii's smeared stiffeners technique is utilized. According to the firstorder shear deformation theory (FSDT) and stress functions, a nonlinear model of the oblique stiffened shallow shell is
established. With regard to the FSDT and von-Kármán nonlinear geometric assumptions, the stress-strain relationships for the
present shell system are developed. Also, in order to discretize the nonlinear governing equations, the Galerkin method is
implemented. To obtain the required relations for investigating the combination resonance theoretically, the method of multiple
scales is applied. For verifying the results of the present research, generated results are compared with previous research.
Additionally, a comparison with the P-T method is conducted to increase the validity of the generated results, as this method has
illustrated advantages over other numerical methods in terms of accuracy and reliability. In this method, the piecewise constant
argument is used jointly with the Taylor series expansion, which is why it is named the P-T method. The effects of stiffeners
with different angles, and the effects of material parameters on the combination resonance behaviors of the present system are
addressed. With the findings of this research, researchers and engineers in this field may use them as benchmarks for their design
and research of porous FG shallow shells.
Address
Kamran Foroutan and Liming Dai:1)Sino-Canada Research Centre of Computation and Mathematics, Qinghai Normal University, Xining, Qinghai, China
2)Industrial Systems Engineering, University of Regina, Regina, SK, S4S 0A2, Canada
Haixing Zhao:Sino-Canada Research Centre of Computation and Mathematics, Qinghai Normal University, Xining, Qinghai, China
Abstract
The main objective of the present paper is to investigate the nonlinear vibration of buckled beams fixed at both ends
and made of Aluminium allay (Al-alloy) reinforced with randomly dispersed Single Walled Carbon Nanotube (SWNT). The
Mori-Tanak (M-T) micromechanical approach is selected to predict the homogenized material properties of the beams. The
differential equation of motion governing the nonlinear behavior of the Euler-Bernoulli homogeneous beam is solved using an
analytical method. The influences of diverse parameters including axial load, vibration amplitude, SWNT volume fraction,
SWNT aspect ratio and beam slenderness ratio on the nonlinear frequency are studied.
Key Words
aluminium alloy; analytical solution; nonlinear dynamics; SWNT
Address
Abdellatif Selmi:1)Department of Civil Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, Alkharj 11942, Saudi Arabia
2)Ecole Nationale d'Ingenieurs de Tunis (ENIT), Civil Engineering Laboratory. B.P. 37, Le belvedere 1002, Tunis, Tunsia
Samy Antit:Ecole Nationale d'Ingenieurs de Tunis (ENIT), Civil Engineering Laboratory. B.P. 37, Le belvedere 1002, Tunis, Tunsia
Abstract
Artificial neural networks (ANN) have been the focus of several studies when it comes to evaluating the pile's
bearing capacity. Nonetheless, the principal drawbacks of employing this method are the sluggish rate of convergence and the
constraints of ANN in locating global minima. The current work aimed to build four ANN-based prediction models enhanced
with methods from the black hole algorithm (BHA), league championship algorithm (LCA), shuffled complex evolution (SCE),
and symbiotic organisms search (SOS) to estimate the carrying capacity of piles in cold climates. To provide the crucial dataset
required to build the model, fifty-eight concrete pile experiments were conducted. The pile geometrical properties, internal
friction angle Φ shaft, internal friction angle Φ tip, pile length, pile area, and vertical effective stress were established as the
network inputs, and the BHA, LCA, SCE, and SOS-based ANN models were set up to provide the pile bearing capacity as the
output. Following a sensitivity analysis to determine the optimal BHA, LCA, SCE, and SOS parameters and a train and test
procedure to determine the optimal network architecture or the number of hidden nodes, the best prediction approach was
selected. The outcomes show a good agreement between the measured bearing capabilities and the pile bearing capacities
forecasted by SCE-MLP. The testing dataset's respective mean square error and coefficient of determination, which are 0.91846
and 391.1539, indicate that using the SCE-MLP approach as a practical, efficient, and highly reliable technique to forecast the
pile's bearing capacity is advantageous.
Key Words
artificial neural network; bearing capacity; metaheuristic algorithms; pile
Address
Zhou Jingting:School of Civil Engineering, Southwest Jiatong University, Chengdu, China
Hossein Moayedi:1)Institute of Research and Development, Duy Tan University, Da Nang, Vietnam
2)School of Engineering & Technology, Duy Tan University, Da Nang, Vietnam
Marieh Fatahizadeh:ICUBE, UMR 7357, CNRS, INSA de Strasbourg, Strasbourg, France
Narges Varamini:Department of Civil and Environmental Engineering, Shiraz University, Iran
Abstract
This paper aims to develop Machine Learning (ML) algorithms to predict the buckling resistance of cold-formed
steel (CFS) channels with restrained flanges, widely used in typical CFS sheathed wall panels, and provide practical design tools
for engineers. The effects of cross-sectional restraints were first evaluated on the elastic buckling behaviour of CFS channels
subjected to pure axial compressive load or bending moment. Feedforward multi-layer Artificial Neural Networks (ANNs) were
then trained on different datasets comprising CFS channels with various dimensions and properties, plate thicknesses, and
restraining conditions on one or two flanges, while the elastic distortional buckling resistance of the elements were determined
according to the Finite Strip Method (FSM). To develop less biased networks and ensure that every observation from the original
dataset has the chance of appearing in the training and test set, a K-fold cross-validation technique was implemented. In addition,
the hyperparameters of the ANNs were tuned using a grid search technique to provide ANNs with optimum performances. The
results demonstrated that the trained ANNs were able to predict the elastic distortional buckling resistance of CFS flangerestrained elements with an average accuracy of 99% in terms of coefficient of determination. The developed models were then
used to propose a simple ANN-based design formula for the prediction of the elastic distortional buckling stress of CFS flangerestrained elements. Finally, the proposed formula was further evaluated on a separate set of unseen data to ensure its accuracy
for practical applications.
Abstract
In this research, for the first time the instability boundaries for a spinning shaft reinforced with graphene
nanoplatelets undergone the principle parametric resonance are determined and examined taking into account the gyroscopic
effect. In this respect, the extracted equations of motion in our previous research (Ref. Asadi et al. (2023)) are implemented and
efficiently upgraded. In the upgraded discretized equations the effect of the Rayleigh's damping and the varying spinning speed
is included that leads to a different dynamical discretized governing equations. The previous research was about the free
vibration analysis of spinning graphene-based shafts examined by an eigen-value problem analysis; while, in the current
research an advanced mechanical analysis is addressed in details for the first time that is the dynamics instability of the
aforementioned shaft subjected to the principal parametric resonance. The spinning speed of the shaft is considered to be varied
harmonically as a function of time. Rayleigh's damping effect is applied to the governing equations in order to regard the energy
loss of the system. Resorting to Bolotin
Address
Neda Asadi:Faculty of Engineering, Shahrekord University, Shahrekord, Iran
Hadi Arvin and Yaghoub Tadi Beni:1)Faculty of Engineering, Shahrekord University, Shahrekord, Iran
2)Nanotechnology Research Institute, Shahrekord University, Shahrekord, Iran
Krzysztof Kamil Zur:Faculty of Mechanical Engineering, Bialystok University of Technology, Bialystok 15-351, Poland
