Microstructure and forming mechanism of metals subjected to ultrasonic vibration plastic forming: A mini review

Compared with traditional plastic forming,ultrasonic vibration plastic forming has the advantages of reducing the forming force and improving the surface quality of the workpiece.This technology has a very broad application prospect in industrial manufactur-ing.Researchers have conducted extensive research on the ultrasonic vibration plastic forming of metals and laid a deep foundation for the development of this field.In this review,metals were classified according to their crystal structures.The effects of ultrasonic vibration on the microstructure of face-centered cubic,body-centered cubic,and hexagonal close-packed metals during plastic forming and the mech-anism underlying ultrasonic vibration forming were reviewed.The main challenges and future research direction of the ultrasonic vibra-tion plastic forming of metals were also discussed.

Contribution of mechanical forces to structural synaptic plasticity:insights from 3D cellular motility mechanisms

Cells,tissues,and organs are constantly subjected to the action of mechanical forces from the extracellular environment-and the nervous system is no exception.Cell-intrinsic properties such as membrane lipid composition,abundance of mechanosensors,and cytoskeletal dynamics make cells more or less likely to sense these forces.Intrinsic and extrinsic cues are integrated by cells and this combined information determines the rate and dynamics of membrane protrusion growth or retraction(Yamada and Sixt,2019).Cell protrusions are extensions of the plasma membrane that play crucial roles in diverse contexts such as cell migration and neuronal synapse formation.In the nervous system,neurons are highly dynamic cells that can change the size and number of their pre-and postsynaptic elements(called synaptic boutons and dendritic spines,respectively),in response to changes in the levels of synaptic activity through a process called plasticity.Synaptic plasticity is a hallmark of the nervous system and is present throughout our lives,being required for functions like memory formation or the learning of new motor skills(Minegishi et al.,2023;Pillai and Franze,2024).

Multi-Scale Design and Optimization of Composite Material Structure for Heavy-Duty Truck Protection Device

In this paper,to present a lightweight-developed front underrun protection device(FUPD)for heavy-duty trucks,plain weave carbon fiber reinforced plastic(CFRP)is used instead of the original high-strength steel.First,the mechanical and structural properties of plain carbon fiber composite anti-collision beams are comparatively analyzed from a multi-scale perspective.For studying the design capability of carbon fiber composite materials,we investigate the effects of TC-33 carbon fiber diameter(D),fiber yarn width(W)and height(H),and fiber yarn density(N)on the front underrun protective beam of carbon fiber compositematerials.Based on the investigation,a material-structure matching strategy suitable for the front underrun protective beam of heavy-duty trucks is proposed.Next,the composite material structure is optimized by applying size optimization and stack sequence optimization methods to obtain the higher performance carbon fiber composite front underrun protection beam of commercial vehicles.The results show that the fiber yarn height(H)has the greatest influence on the protective beam,and theH1matching scheme for the front underrun protective beamwith a carbon fiber composite structure exhibits superior performance.The proposed method achieves a weight reduction of 55.21% while still meeting regulatory requirements,which demonstrates its remarkable weight reduction effect.

Transition of plasticity and fracture mode of Zr-Al-Ni-Cu bulk metallic glasses with network structures

Effect of network structure on plasticity and fracture mode of Zr？Al？Ni？Cu bulk metallic glasses （BMGs） was investigated. The microstructures of transversal and longitudinal sections were exposed by chemical etching and observed by scanning electron microscopy （SEM）. The mechanical properties were examined by room-temperature uniaxial compression test. The results show that both plasticity and fracture mode are significantly affected by the network structure and the alteration occurs when the size of the network structure reaches up to a critical value. When the cell size （dc） of the network structure is ~3μm, Zr-based BMGs characterize in plasticity that decreases with increasingdc. The fracture mode gradually transforms from single 45° shear fracture to double 45° shear fracture and then cleavage fracture with increasingdc. In addition, the mechanisms of the transition of the plasticity and the fracture mode for these Zr-based BMGs are also discussed.

PCR-DGGE Analysis of Bacterial Communities Structure in Babylonia areolata Culture Systems of The Subtidal Zone and The Pond Mulched Plastic Film and Sand in Bottom

To know the bacterial communities structure in Babylonia areolata culture systems and to research and optimize the management pattem of Babylonia areola-ta culture systems of the pond mulched plastic film and sand in bottom, the bacte- rial communities in Babylonia areolata culture systems of the sub-tidal zone and the pond mulched plastic film and sand in bottom were analyzed at molecular level by adopting the denaturing gradient gel electrophoresis （DGGE）. The results indicated that the dominant bacterial communities in Babylonia areolata culture systems of the sub-tidal zone and the pond mulched plastic film and sand in bottom, which were built on the basis of the seawater in East-island of Zhanjiang, included Proteobac- teda Chloroflexi, Cyanobacteria and Actinobacteria. The dominant bacterial groups in the above pond culture system were Garnmaproteobacteria, Alphaproteobacteria, Deltaprotecbacteda, Epsilonproteobacteda, Anaerolineae, Cyanobacteria and Acti- nobacteda. The dominant bacterial communities in the subtidal zone culture system were Gammaprotecbacteda, Alphaproteobacteria, Deltaproteobacteria, Anaerolineae and Cyanobacteda, and there were less Epsilonproteobacteria and Actinobacteria in the culture system. The higher diversity was detected in the above two culture sys- tems. The results of unweighted pair group method with arithmetic average （UPG- MA） showed that the bacterial communities of the sediment samples S1 and S2 in the above two culture systems were a cluster, the similarity of bacterial communities was 54.5%. The bacterial communities of seawater samples S3 and S4 in the above culture systems were in clusters, and the similarity of the bacterial communi- ties was 84.0%. The results showed that the microorganism ecological level in the Babylonia areolata culture systems of the pond mulched plastic film and sand in bottom could be similar to the sub-tidal zone culture systems through changing the pond seawater and monitoring the microbial population.

Brain structural plasticity in rats subjected to early binocular enucleation characterized by high resolution anatomical magnetic resonance imaging and diffusion tensor imaging

Visual deprivation leads to structural neuroplasticity in the blind subjects,including gray matter(GM)and white matter(WM)atrophy and alterations in structural connectivity.The rat model of binocular enucleation(BE)is a frequently used animal model for studying brain plasticity induced by early blindness.Yet few neuroimaging studies have been performed on this model to investigate whether or not the BE rats have image phenotypes similar to or comparable to,those observed in the early blind subjects.The current study aimed to assess brain structural plasticity in BE rats using anatomical magnetic resonance imaging(MRI)and diffusion tensor imaging(DTI).The results demonstrated that early BE at postnatal day 4(P4)caused almost complete degeneration of optic nerve(ON)and optic chiasma(OCH),atrophy in a number of visual and non-visual structures,including optic tract(OT),dorsal lateral geniculate nucleus(DLG)and corpus callosum(CC).The BE rats also exhibited impairments of WM microstructural integrity in the OT,and reduction of structural connectivity between the normal-appearing visual cortex(VC)and somatosensory/motor cortices at 4 months of age,likely as manifestations of deafferentationinduced maldevelopment.The structural neuroplasticity in BE rats observable to structural MRI parallels largely with what has been reported in blind subjects,suggesting that longitudinal neuroimaging studies on animal models of sensory deprivation can provide insights into how the brain changes its wiring and function during development/adaption in response to the lack of sensory stimuli.

Thermal Structure of Glass Fiber Reinforce Plastic Support Structure

The assembled form of thick-wall glass fiber reinforced plastics (GFRP) tube and 0Cr18Ni9 austenitic stainless steel pipes was designed as the radius thermal-insulating and load-supporting structure in cryogenic vessels. In order to study the thermal leakage and gap changes on the support structure, as well as radius temperature and stress distribution on GFRP tube, an experimental investigation has been taken. The results indicate that the support structure is proved to fit well as thermal-insulating and load-supporting part in cryo-genic vessels, furthermore has high security during cryogenic applications.

Structure realization method for collapse threshold of plastic deformation in train collision condition

To protect passengers, absorb enough kinetic energy and meet the special requirements for trains which are different from the other means of transportation, a method is presented to realize the plastic deformation threshold based on three main aspects of train connection structure, crashworthy vehicle structure, energy-absorbing component. In practical engineering, trains need enough strength and stiffness to transfer longitudinal force under the normal operation condition, and have to produce controllable large plastic dcfbrmation to absorb energy shortly under the collision condition. To realize the structural damage threshold of connecting structure in terminal end, two control methods are also proposed which can be divided as the parametric method based on ＇extrusion＇ and ＇cutting＇ theories; the method which can cut the connecting components between coupler-buffer devices and train bodies and separate them away when the damage thresholds of coupler-buffer devices are more than the pre-supposed damage thresholds. The damage thresholds can be realized based on changing the parameters of the number of shearing bolts, material parameters, etc. To realize the collision threshold of energy-absorbing components of trains, a control method is presented based on the ways of setting plastic deformation induced structure, local hole and pre-deformation structure. To realize the threshold of the controllable plastic structure of energy-absorbing vehicles, a control method is proposed for the multi-level longitudinal stiffness of train terminal structures.

DESIGN OPTIMIZATION FOR TRUSS STRUCTURES UNDER ELASTO-PLASTIC LOADING CONDITION

In this paper, a method for the design optimization of elasto-plastic truss structures is proposed based on parametric variational principles （PVPs）. The optimization aims to find the minimum weight/volume solution under the constraints of allowable node displacements. The design optimization is a formulation of mathematical programming with equilibrium constraints （MPECs）. To overcome the numerical difficulties of the complementary constraints in optimization, an iteration process, comprising a quadratic programming （QP） and an updating process, is employed as the optimization method. Furthermore, the elasto-plastic buckling of truss mem- bers is considered as a constraint in design optimization. A combinational optimization strategy is proposed for the displacement constraints and the buckling constraint, which comprises the method mentioned above and an optimal criterion. Three numerical examples are presented to show the validity of the methods proposed.

Effect of alternate magnetic field on LY12 structure properties after thermal plastic forming

The powerful alternate magnetic field treatment is an effective not-heat treatment, which improves the coriaceous performance of the material. In order to reveal the effect rule of the powerful alternate magnetic field on the structure capability after thermal plastic forming, the experimental methods were adopted to compare the microcosmic structure of the LY12 aluminium alloy test pieces before and after the powerful alternate magnetic field treatment. The mechanism of the structure refining was analyzed theoretically. According to the effect rule of the alternate magnetic field on critical grain growth work and the magnetic vibration-constriction mechanism, the structure dynamics factors were analyzed. The results show that, after a certain powerful alternate magnetic field treatment, the mechanical capability of the LY12 aluminium alloy after thermal plastic forming can be reinforced, the structure intertwist deriving from the thermal plastic forming becomes even and the branch crystal is also smashed, consequently refines the structure. The powerful alternate magnetic field treatment can be regarded as an effective method to improve metal structure performance after heat plastic forming.

Quantitative structure-plasticity relationship in metallic glass:A machine learning study

The lack of the long-range order in the atomic structure challenges the identification of the structural defects,akin to dislocations in crystals,which are responsible for predicting plastic events and mechanical failure in metallic glasses(MGs).Although vast structural indicators have been proposed to identify the structural defects,quantitatively gauging the correlations between these proposed indicators based on the undeformed configuration and the plasticity of MGs upon external loads is still lacking.Here,we systematically analyze the ability of these indicators to predict plastic events in a representative MG model using machine learning method.Moreover,we evaluate the influences of coarse graining method and medium-range order on the predictive power.We demonstrate that indicators relevant to the low-frequency vibrational modes reveal the intrinsic structural characteristics of plastic rearrangements.Our work makes an important step towards quantitative assessments of given indicators,and thereby an effective identification of the structural defects in MGs.

RELIABILITY OF ELASTO-PLASTIC STRUCTURE USING FINITE ELEMENT METHOD

A solution of probabilistic FEM for elastic-plastic materials is presented based on the incremental theory of plasticity and a modified initial stress method. The formulations are deduced through a direct differentiation scheme. Partial differentiation of displacement, stress and the performance function can be iteratively performed with the computation of the mean values of displacement and stress. The presented method enjoys the efficiency of both the perturbation method and the finite difference method, but avoids the approximation during the partial differentiation calculation. In order to improve the efficiency, the adjoint vector method is introduced to calculate the differentiation of stress and displacement with respect to random variables. In addition, a time-saving computational method for reliability index of elastic-plastic materials is suggested based upon the advanced First Order Second Moment (FOSM) and by the usage of Taylor expansion for displacement. The suggested method is also applicable to 3-D cases.

SYNTHESIS OF PLASTIC PIGMENT WITH MULTIHOLLOW STRUCTURE

The polymer particle possessing hollow structure are playing an increasingly important role in industry. The latex particle with hollow structure as plastic pigment has a low density, strong spreading capacity and good glossiness. So it has been utilized for the manufacture of LWC in paper-making. In this paper, we prepared a kind of novel plastic pigment by the soapless seeded emulsion polymerization, this product with polyacrylate as core and with polystyrene as shell (PA/PS) had hollow structure after dryness. The preparation, characterization and properties of the latex were studied in detail by chemistry analysis and apparatus analysis such as TEM,FTIR,DLS.

Three-Dimensional Thermo-Elastic-Plastic Finite Element Method Modeling for Predicting Weld-Induced Residual Stresses and Distortions in Steel Stiffened-Plate Structures

The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced initial deflection and residual stress of plating in steel stiffened-plate structures. For this purpose, three-dimensional thermo-elastic-plastic finite element method computations are performed with varying plate thickness and weld bead length (leg length) in welded plate panels, the latter being associated with weld heat input. The finite element models are verified by a comparison with experimental database which was obtained by the authors in separate studies with full scale measurements. It is concluded that the nonlinear finite element method models developed in the present paper are very accurate in terms of predicting the weld-induced initial imperfections of steel stiffened plate structures. Details of the numerical computations together with test database are documented.

EXPERIMENTAL STUDY ON ELASTIC－PLASTIC CONTROLLING DESIGN FOR BOX STEEL STRUCTURES

The principle of increasing structural loading abillity by the using of elastic-plastic con- trolling design, which can make steel reach a highcr yield slrength through controlling undue strains produced in loaded box steel structures and no damager to the static mechanical properties of the used materials, is dealt with under the guarantee of strength, rigidity, and stability. A new idea of elastic--plastic controlling design, which is mainly based on the elastic-plastic theory and experi- mental results and is different from the current design which is mainly based handbooks and design- er' s experience, is established. That is: the loading time and its effect on loaded structures are con- sidered, and the potential strength in used matcrials is fully utilized through the controlling of struc- tural strains in design. By the using of this design method, the weight and cost of box structures will be reduced in large amount.

基于Pro/EMechanica Structure的塑料产品装配结构设计

以手机的装配结构设计为例,在分析其零部件的结构特点及卡扣连接、压力装配等装配关系后,借助Pro/E Mechanica Structure模块分析手机在装配中,手机前盖、后盖等塑料零部件在静载荷作用下可能出现的变形,进而改进并优化结构,并且对改进前后结构受静载荷作用的应力值进行比较,结果满足使用的力学性能要求。因此通过基于Pro/E Mechanica Structure的塑料产品装配设计,可以降低成本、加快完成塑料产品的开发。

EFFECT OF EQUAL-CHANNEL ANGULAR PRESSING ON STRUCTURE OF Al ALLOY 2024

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Lim kinase,a bi-functional effector in injury-induced structural plasticity of synapses

The structural plasticity of synaptic terminals contributes to normal nervous system function but also to neural degeneration, in the form of terminal retraction, and regeneration, due to process growth. Synaptic morphological change is mediated through the actin cytoskeleton, which is enriched in axonal and dendritic terminals. Whereas the three RhoGTPases, RhoA, Cdc42 and Rac, function as upstream signaling nodes sensitive to extracellular stimuli, LIMK-cofilin activity serves as a common downstream effector to up-regulate actin turnover, which is necessary for both polymerization and depolymerization. The dual effects of LIMK activity make LIMK a potential target of therapeutic intervention for iniury-induced synaptic plasticity, as LIMK inhibition can stabilize actin cytoskeleton and preserve existing structure. This therapeutic benefit of LIMK inhibition has been demonstrated in animal models of injury-induced axon retraction and neuritic sprouting by rod photoreceptors. A better understanding of the regulation of LIMK-cofilin activity and the interaction with the microtubular cytoskeleton may open new ways to promote synaptic regeneration that can benefit neuronal degenerative disease.

Numerical Analyses of Bearing Capacity of Deep-Embedded Large-Diameter Cylindrical Structure on Soft Ground Against Lateral Loads

Presented in this paper is a three-dimensional plastic limit analysis method of bearing capacity of the deeply-embedded large-diameter cylindrical structure in the cross-anisotmpic soft ground. The most likely failure mechanism is assumed to be of a composite rupture surface which is composed of an individual wedge in the passive zone or two wedges in both active and passive zones near the mudline, depending on the separation or bonding state at the interface between the cylindrical structure and neighboring soils in the active wedge, and a truncated spherical slip surface at the base of the cylinder when the structure tends to overturn around a point located on the symmetry axis of the structure. The cylindrical structure and soil interaction system under consideration is also numerically analyzed by the finite element method by virtue of the general-purpose FEM software ABAQUS, in which the soil is assumed to obey tie Hill＇s criterion of yield. Both the failure mechanism assumed and the plastic limit analysis predictions are validated by numerical computations based on FEM. For the K0-consolidated ground of clays typically with anisotropic undrained strength property, it is indicated through a parametric study that limit analysis without consideration of anisotropy of soil overestimates the lateral ultimate bearing capacity of a deeply-embedded cylindrical structure in soft ground in a certain condition.

Temperature control and cracking prevention in coastal thin-wall concrete structures

A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the temperature and stress field of the Cao＇e Sluice during the construction period. From the calculated results, we can find that the temperaiure and stress of concrete cooled with plastic pipes are much lower than those of concrete without pipes. Moreover, plastic pipes could not be corroded by seawater. That is to say, a good effect of temperature control and cracking prevention can be achieved, which provides a useful reference for other similar nearshore concrete projects.