ANALYSIS OF INTER-LAMINAR STRESSES FOR COMPOSITE LAMINATED PLATE WITH INTERFACIAL DAMAGE

A constitutive model for composite laminated plates with the damage effect of the intra-layers and inter-laminar interface is presented. The model is based on the general six-degrees-of-freedom plate theory, the discontinuity of displacement on the interfaces are depicted by three shape functions, which are formulated according to solutions satisfying three equilibrium equations, By using the variation principle, the three-dimensional non-linear equilibrium differential equations of the laminated plates with two different damage models are derived. Then, considering a simply supported laminated plate with damage, an analytical solution is presented using finite difference method to obtain the inter-laminar stresses.

Nonlinear Static Finite Element Stress Analysis of Pipe-in-Pipe Risers

Owing to the complexity of the pipe-in-pipe (PIP) riser system in structure, load and restraint, many problems arise in the structural analysis of the system. This paper presents a new method for nonlinear static finite element stress analysis of the PIP riser system. The finite element (FE) model of the PIP riser system is built via software AutoPIPE 6.1. According to the specialties of a variety of components in the PIP riser system, different elements are used so as to model the system accurately. Allowing for the complication in modeling the effects of seabed restraint, a technique based on the bilinear spring concept is developed to calculate the soil properties. Then, based on a pipeline project, the entire procedure of stress analysis is discussed in detail, including creation of an FE model, processing of input data and analysis of results. A wide range of loading schemes is investigated to ascertain that the stresses remain within the acceptable range of the pipe material strength. Finally, the effects of the location of flanges, the thermal expansion of submarine pipelines and the seabed restraint on stress distribution in the riser and expansion loop are studied, which are valuable for pipeline designers.

STRESS ANALYSIS OF INJECTION MOLDED PARTS IN POST-FILLING STAGE

The linear isothermo-viscoelastic constitutive equation is established according to the principle of viscoelastic mechanics. Given the boundary conditions of the temperature field, the linear thermo-viscoelastic constitutive equation is established acording to the analysis of the thermorheologically simple. The stress analysis model is constructed on the base of some reasonable hypotheses which consider the restraint conditions of mold and the characteristics of injection molding in the post-filling stage. The mathematical model is calculated by the finite difference method. The results can help to predict the warpage of plastic products.

Stress analysis of functionally graded rotating discs: analytical and numerical solutions

This study deals with stress analysis of annular rotating discs made of functionally graded materials（FGMs）.Elasticity modulus and density of the discs are assumed to vary radially according to a power law function,but the material is of constant Poisson＇s ratio.A gradient parameter n is chosen between 0 and 1.0.When n = 0,the disc becomes a homogeneous isotropic material.Tangential and radial stress distributions and displacements on the disc are investigated for various gradient parameters n by means of the diverse elasticity modulus and density by using analytical and numerical solutions.Finally,a homogenous tangential stress distribution and the lowest radial stresses along the radius of a rotating disc are approximately obtained for the gradient parameter n = 1.0 compared with the homogeneous,isotropic case n = 0.This means that a disc made of FGMs has the capability of higher angular rotations compared with the homogeneous isotropic disc.

Multi-Scale Analysis of Fretting Fatigue in Heterogeneous Materials Using Computational Homogenization

This paper deals with modeling of the phenomenon of fretting fatigue in heterogeneous materials using the multi-scale computational homogenization technique and finite element analysis(FEA).The heterogeneous material for the specimens consists of a single hole model(25% void/cell,16% void/cell and 10% void/cell)and a four-hole model(25%void/cell).Using a representative volume element(RVE),we try to produce the equivalent homogenized properties and work on a homogeneous specimen for the study of fretting fatigue.Next,the fretting fatigue contact problem is performed for 3 new cases of models that consist of a homogeneous and a heterogeneous part(single hole cell)in the contact area.The aim is to analyze the normal and shear stresses of these models and compare them with the results of the corresponding heterogeneous models based on the Direct Numerical Simulation(DNS)method.Finally,by comparing the computational time and%deviations,we draw conclusions about the reliability and effectiveness of the proposed method.

Analysis of interlaminar stress and nonlinear dynamic response for composite laminated plates with interfacial damage

By considering the effect of interfacial damage and using the variation principle, three-dimensional nonlinear dynamic governing equations of the laminated plates with interfacial damage are derived based on the general sixdegrees-of-freedom plate theory towards the accurate stress analysis. The solutions of interlaminar stress and nonlinear dynamic response for a simply supported laminated plate with interfacial damage are obtained by using the finite difference method, and the results are validated by comparison with the solution of nonlinear finite element method. In numerical calculations, the effects of interfacial damage on the stress in the interface and the nonlinear dynamic response of laminated plates are discussed.

Stress and buckling analysis of a thick-walled micro sandwich panel with a flexible foam core and carbon nanotube reinforced composite (CNTRC) face sheets

In this paper,the stresses and buckling behaviors of a thick-walled mi-cro sandwich panel with a flexible foam core and carbon nanotube reinforced composite(CNTRC)face sheets are considered based on the high-order shear deformation theory(HSDT)and the modified couple stress theory(MCST).The governing equations of equi-librium are obtained based on the total potential energy principle.The effects of various parameters such as the aspect ratio,elastic foundation,temperature changes,and volume fraction of the canbon nanotubes(CNTs)on the critical buckling loads,normal stress,shear stress,and deflection of the thick-walled micro cylindrical sandwich panel consider-ing different distributions of CNTs are examined.The results are compared and validated with other studies,and showing an excellent compatibility.CNTs have become very use-ful and common candidates in sandwich structures,and they have been extensively used in many applications including nanotechnology,aerospace,and micro-structures.This paper also extends further applications of reinforced sandwich panels by providing the modified equations and formulae.

Alleviation for contact stresses in curvic attachments

This paper studied the contact stresses in curvic attachments.The principal purpose of this research is to employ a method of alleviating the fluctuating hoop stresses which can be considered to be a major contribution to fatigue failure in curvic attachments.This method entails novel precision geometry of the contacting flat on curvic which is a tactic to get appropriate arc heights in in-plane direction as well as vary radius in out-of-plane direction.The dimensional finite elements in both directions were analyzed.These analysis results indicated that significant reduction in fluctuating hoop stresses can be achieved by the proposed method,provided that the precision geometry is controlled sufficiently precisely.

Nonlinearity analysis of piezoelectric micromachined ultrasonic transducers based on couple stress theory

This paper studies the static deformation behavior of a piezoelectric micromachined ultrasonic transducer （PMUT） actuated by a strong external electric field. The transducer membrane consists of a piezoelectric layer, a passive layer and two electrode layers. The nonlinearities of the piezoelectric layer caused by electrostriction under a strong electric field are analyzed. Because the thickness of the transducer membrane is on the microscale, the size dependence of the deformation behavior is evaluated using the couple stress theory. The results show that the optimal ratio of the top electrode diameter and the membrane diameter is around 0.674. It is also found that this optimal value does not depend on any other parameters if the thicknesses of the two electrodes are negligible compared with those of the piezo- electric and passive layers. In addition, the nonlinearities of the piezoelectric layer will become stronger along with the increase of the electric field, which means that softening of the membrane stiffness occurs when a strong external electric field is applied. Meanwhile, the optimal thickness ratio for the passive layer and the piezoelectric layer is not equal to 1.0 which is usually adopted by previous researchers. Because there exists size dependence of membrane deforma-tion, the optimal value of this thickness ratio needs to be greater than 1.0 on the microscale.

TWO-DIMENSIONAL STRESS WAVE ANALYSIS IN INCOMPRESSIBLE ELASTIC SOLIDS

Two-dimensional stress wares in n general incompressible elastic solid are investigated. First, baxic equations for simple wares and shock waves are presented for a general strain energy junction. Then the characteristic ware speeds and the associated characteristic vectors are deduced. It is shown that there usually exist two simple waves and two shock wares. Finally, two examples are given for the case of plane strain deformation and antiplane strain deformation, respectively. It is proved that, in the case of plane strain deformation, the oblique reflection problem of a plane shock is not solvable in general.

PROBABILISTIC METHODOLOGY OF LOW CYCLE FATIGUE ANALYSIS

The cyclic stress-strain responses (CSSR), Neuber's rule (NR) and cyclic strain-life relation (CSLR) are treated as probabilistic curves in local stress and strain method of low cycle fatigue analysis. The randomness of loading and the theory of fatigue damage accumulation (TOFDA) are considered. The probabilistic analysis of local stress, local strain and fatigue life are constructed based on the first-order Taylor's series expansions. Through this method proposed fatigue reliability analysis can be accomplished.

Molecular cloning, characterization and expression analysis of a catalase gene in Paphia textile

Catalase is an important antioxidant protein that can protect organisms against various forms of oxidative damage by eliminating hydrogen peroxide. In this study, the catalase c DNA of Paphia textile（Pt CAT） was cloned using RTPCR and rapid amplification of c DNA ends（RACE）. Pt CAT is 1 921 bp long and consists of a 5′-UTR of 50 bp, a 3′-UTR of 349 bp, and an ORF of 1 542 bp that encodes 513 amino acids with a molecular weight of 58.4 k D and an estimated isoelectric point of 8.2. Sequence alignment indicated that Pt CAT contained a highly conserved catalytic signature motif（^（61）FNRERIPERVVHAKGAG^（77））, a proximal heme-ligand signature sequence（^（352）RLFSYSDP^（359））, and three catalytic amino acid residues（H^（72）, N^（145）, and Y^（356））. Pt CAT also contains two putative N-glycosylation sites（^（34）NKT^（36） and ^（437）NFT^（439）） and a peroxisome-targeting signal（^（511）AQL^（513））. Furthermore, Pt CAT shares 53%–88% identity and 29%–89% similarity with other catalase amino acid sequences. Pt CAT m RNA was present in all tested organs, including the heart, digestive gland, adductor muscle, gonad, gill, and mantle, but its expression was highest in the digestive gland. High-temperature-induced stress produced two expression patterns of Pt CAT m RNA： first, an initial up-regulation followed by a down-regulation in the heart, digestive gland, and gonad and, second, consistent down-regulation in all other organs. These results demonstrate that Pt CAT is a typical member of the catalase family and might be involved in the responses to harmful environmental factors.

Static and Vibration Analysis of an Aluminium and Steel Bus Frame

The transport sector is increasing day by day to satisfy the global market requirement. The bus is still the main mode of intercity transportation in Canada. Despite, an essentially unchanged conception, the total weight of the bus has increased by over 25% during the last three decades. To solve this problem, industrialists have moved to the use of light metals in the transportation field. Therefore, use of lightweight materials, such as aluminum is essential to reduce the total weight of bus. In this study, the focus is on the bus frame as it represents 30% of the total weight and it is the most stressed part of the bus. Its life duration is more important compared to that of all other elements. Thus, a study of the static and vibratory behavior would be very decisive. In this article, two types of analysis are carried out. First is the modal analysis to determine the natural frequencies and the mode shapes using a developed dynamic model of the bus. Because if any of the excitation frequencies coincides with the natural frequencies of the bus frame, then resonance phenomenon occurs. This may lead to excessive deflection, high stress concentration, fatigue of the structure and vehicle discomfort. In this case, the results analysis shows that the natural frequencies are not affected by the change of material. The second type of analysis is the linear static stress analysis to consider the stress distribution and deformation frame pattern under static loads numerically. For the numerical method, the frame is designed using SolidWorks and the analysis is made using Ansys WorkBench. The maximum Von Mises stress obtained for the static loading is in the same order for the three chassis frames studied. But in the case of the aluminium frame, the weight of 764 kg was reduced.

Analysis of DNA Cytosine Methylation on Cotton under Salt Stress

DNA methylation,especially methylation of cytosine in eukaryotic organisms,has been implicated in gene regulation,genomic imprinting,the timing of DNA replication,and determination of chromatin structure.It was reported that 6.5% of the whole cytosine residues in the nuclear DNA in

Characterization and expression analysis of genes encoding Taxol biosynthetic enzymes in Taxus spp.

Taxol(Paclitaxel),an important anticancer drug,is derived at very low yields from Taxus(yew)species that grow very slowly.In the present study,thirteen genes that encode enzymes involved in Taxol biosynthesis in Taxus spp.were analyzed with bioinformatics methods,and their expression levels in different tissues and after cold and hormone treatments were also analyzed.The results indicated that many cis-elements related to abiotic stresses and hormones were found in the promoter sequences of the 8 genes involved in Taxol biosynthesis.Moreover,the 13 enzymes encoded by the target genes were located in different organelles and had many phosphorylation sites in the response proteins.The 13 genes were expressed highly either in roots or in stems,with lower transcripts in needles,and they were highly expressed after treatment with cold,gibberellin,methyl jasmonate or coronatine,consistent with predictions based on the bioinformatics analysis.These results suggest that the factors such as hormones and abiotic stresses stimulate taxane biosynthesis in yews,providing an important way to sustainably generate taxanes from yew trees or their cell cultures to improve Taxol yields.

THREE-DIMENSIONAL ISODYNE STRESS ANALYSIS——PRESENT STATE, TRENDS, THEORETICAL PROBLEMS

The paper presents and discusses theoretical bases and methodology of development of two- and three-dimensional analytical and optical isodynes. Atten- tion is given to the theoretical admissibility of the major components of the physical and mathematical models which are taken as the theoretical basis of the isodynes, and of the related analytical and experimental procedures of stress analysis. Efficiency and reliability of the nondestructive isodyne stress analysis are discussed.

STRAIN-GRADIENT STRESS ANALYSIS IN SAINT-VENANT BENDING

Light beam deflections caused by stress or strain gradients are inves- tigated analytically and experimentally in homogeneous beam specimens which are subjected to a particular case of flexure with shear. This study is a generalization of the prior an alytical-experimental examination of strain-gradient light deflections produced in stressed plates, which had concentrated on the simplest case where in- formation of interest is collected along a line of symmetry of the stress field. Main purpose of the present investigation is to document the efficacy of the strain-gradient method in analysis of the general case of stress state. The most interesting stress state is that in a beam subjected to the Saint-Venant bending, where the transversal and the longitudinal axes of the beam are in pure shear. The obtained results are compared with the predictions of the developed analytical models and with the pre- dictions of Filon's stress function. The procedures of evaluating the photoelastic and material coefficients using strain-gradient techniques were tested positively.

General displacement arch-cantilever element method for stress analysis of arch dam

Based on the general displacement method and the basic hypothesis of the trial load method, a new advanced trial load method, the general displacement arch-cantilever element method, was proposed to derive the transformation relation of displacements and loads between the surface nodes and middle plane nodes. This method considers the nodes on upstream and downstream surfaces of the arch dam to be exit nodes （master nodes）, and the middle plane nodes to be slave nodes. According to the derived displacement and load transformation matrices, the equilibrium equation treating the displacement of middle plane nodes as a basic unknown variable is transformed into one that treats the displacement of upstream and downstream nodes as a basic unknown variable. Because the surface nodes have only three degrees of freedom （DOF）, this method can be directly coupled with the finite element method （FEM）, which is used for foundation simulation to analyze the stress of the arch dam with consideration of dam-foundation interaction. Moreover, using the FEM, the nodal load of the arch dam can be easily obtained. Case studies of a typical cylindrical arch dam and the Wudongde arch dam demonstrate the robustness and feasibility of the proposed method.

APPLICATION OF STOCHASTIC FINITE ELEMENT METHOD TO STRENGTH AND STABILITY ANALYSIS OF EARTH DAMS

This paper applies the stochastic finite element method to analyse the statistics of stresses in earth dams and assess the safety and reliability of the dams. Formulations of the stochastic finite element method are briefly reviewed and the procedure for assessing dam's strength and stability is described. As an example, a detailed analysis for an actual dam Nululin dam is performed. A practical method for studying built-dams based on the prototype observation data is described.

A Novel Deep Learning Based Healthcare Model for COVID-19 Pandemic Stress Analysis

Coronavirus(COVID-19)has impacted nearly every person across the globe either in terms of losses of life or as of lockdown.The current coronavirus(COVID-19)pandemic is a rare/special situation where people can express their feelings on Internet-based social networks.Social media is emerging as the biggest platform in recent years where people spend most of their time expressing themselves and their emotions.This research is based on gathering data from Twitter and analyzing the behavior of the people during the COVID-19 lockdown.The research is based on the logic expressed by people in this perspective and emotions for the suffering of COVID-19 and lockdown.In this research,we have used a Long Short-Term Memory(LSTM)network model with Convolutional Neural Network using Keras python deep-learning library to determine whether social media platform users are depressed in terms of positive,negative,or neutral emotional out bust based on their Twitter posts.The results showed that the model has 88.14%accuracy(representation of the correct prediction over the test dataset)after 10 epochs which most tweets showed had neutral polarity.The evaluation shows interesting results in positive(1),negative(–1),and neutral(0)emotions through different visualization.