Effect of combined extrusion parameters on mechanical properties of basalt fiber-reinforced plastics based on polypropylene

Basalt fibers are efficient reinforcing fillers for polypropylene because they increase both the mechanical and the tribotechnical properties of composites. Basalt fibers can compete with traditional fillers (glass and asbestos fibers) of polypropylene with respect to technological, economic, and toxic properties. The effect of technological parameters of producing polypropylene-based basalt fiber-reinforced plastics (BFRPs) by combined extrusion on their mechanical properties has been investigated. The extrusion temperature was found to be the main parameter determining the mechanical properties of the BFRPs. With temperature growth from 180 to 240°C, the residual length of the basalt fibers in the composite, as well as the adhesive strength of the polymer-fiber system, increased, while the composite defectiveness decreased. The tensile strength and elastic modulus increased from 35 to 42 MPa and 3.2 to 4.2 GPa, respectively. At the same time, the growth in composite solidity led to its higher brittleness. Thus, a higher temperature of extrusion allows us to produce materials which can be subjected to tensile and bending loads, while the materials produced at a lower temperature of extrusion are impact stable. The effect of the gap size between the extruder body and moving disks on the mechanical properties of the BFRPs is less significant than that of temperature. An increase of the gap size from 2 to 8 mm improves the impregnation quality of the fibers, but the extruder productivity diminishes. The possibility of controling the properties of reinforced polypropylene by varying the technological parameters of combined extrusion is shown. The polypropylene-based BFRPs produced by the proposed method surpass the properties of glass and asbestos fiber-reinforced plastics.Submitted to the 10th International Conference on Mechanics of Composite Materials (Riga, April 20–23, 1998).Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 6, pp. 845–850, November–December, 1997.     

Wood-filled thermoplastic composites

Different physical properties of wood-filled thermoplastic materials produced by a special mixing and extrusion process are examined. The results show that the wood content and the kind of plastics are the main parameters that control the physical properties of composites. In general, wood-filled thermoplastic materials exhibit mechanical properties comparable to those of customary wood fiber products, i.e., medium density fiberboard (MDF); however, they show distinctly better behavior than the MDF and natural wood after exposure to moisture.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Universität Kassel, Institut für Werkstofftechnik, Kunstoff-und Recyclingtechnik, Mönchebergstraße 3, 34109 Kassel, Germany. Published in Mekhanika Kompozitnykh Materialov, Vol. 34, No. 6, pp. 795–802, November–December, 1998.     

旋转输液管动力稳定性理论分析北大核心CSCD

基于Lagrange原理和假设模态法建立了旋转输液管的动力学模型.通过降阶升维的方法求解系统的特征值问题,并分析了旋转输液管自由振动特性.得到了不同端部集中质量和转速下,系统特征值随流速升高的演变轨迹.揭示了临界流速随系统参数的变化规律.研究发现,内部流体的流动对旋转输液管动力学特性存在显著影响.在某些参数组合下,系统低阶模态能够形成不同形式的内共振关系.预示了旋转输液管模型蕴含丰富的动力学现象.     

Analysis of surface mechanical properties effects on the dynamic characteristics of a circular micro-diaphragm with a distributed mass

The influences of surface mechanical properties effects on the dynamic characteristics of a circular micro-diaphragm with a partially uniformly distributed mass are investigated. Surface mechanical properties effects on two sides are considered to be different as one side of the diaphragm contacts with biochemical media. A size-dependent analytical model is developed based on the thin plate theory and surface elasticity theory for the micro-diaphragm with a partially uniformly distributed mass. The Galerkin procedure is used to solve the governing equation. The size-dependence of the natural frequency and mass sensitivity of the micro-diaphragm with different surface mechanical properties effects is discussed. Results show that the influences of different surface mechanical properties effects on the natural frequency and mass sensitivity are more significant for thinner micro-diaphragms. The influences depend on the differences in the surface mechanical properties effects of the two surfaces.     

Finite volume simulation framework for die casting with uncertainty quantification

The present paper describes the development of a novel and comprehensive computational framework to simulate solidification problems in materials processing, specifically casting processes. Heat transfer, solidification and fluid flow due to natural convection are modeled. Empirical relations are used to estimate the microstructure parameters and mechanical properties. The fractional step algorithm is modified to deal with the numerical aspects of solidification by suitably altering the coefficients in the discretized equation to simulate selectively only in the liquid and mushy zones. This brings significant computational speed up as the simulation proceeds. Complex domains are represented by unstructured hexahedral elements. The algebraic multigrid method, blended with a Krylov subspace solver is used to accelerate convergence. State of the art uncertainty quantification technique is included in the framework to incorporate the effects of stochastic variations in the input parameters. Rigorous validation is presented using published experimental results of a solidification problem.     

Aging of polymer composite materials exposed to the conditions in outer space

A comprehensive investigation is made of glass, carbon, organic fiber-reinforced plastics, and epoxy-based hybrid composite materials employed in Salyut-type spacecraft which remained in space for up to 1501 1501 days. In particular, the properties, aging mechanism, and strain-strength variations in these materials due to exposure to the conditions in outer space were studied. After a series of tests were performed in space the standard strain and strength parameters as well as the mass, density, and thickness changes in the composite materials were estimated. Electron-microscopic and dynamic-mechanical analyses were performed, and the thermal expansion was estimated for a wide range of temperatures. The principal, dominant process occurring due to the continuous presence in outer space was found to be post-curing of the resin materials, which in turn affected the mechanical characteristics of the composite materials. After 456–1501 days in space the room-temperature strength of the composite materials (except for organic plastics) did not decrease, while at high temperatures it even increased. The post-curing and restructuring of some composite materials lowered their dynamic shear moduli in the glassy state of the resin. Due to consolidation of the surface layer of hybrid composite materials irradiated and subjected to thermal cycles, failure during bending varied from transverse fracture to delamination. The negative effect of the post-curing process was expressed as higher internal tension in the hybrid composite materials with different linear thermal expansion coefficients. The magnitude of this effect depended on the amplitude of the thermal cycles. The unprotected surface of the composites bombarded by atomic oxygen, microparticles, and space garbage were subjected to pickling and microerosion, the maximum effect occurring at the initial stage of exposure. Desorption of moisture and low-molecular products during the first 100–200 days of thermal cycling in the vacuum of near-earth orbit must be considered when estimating the total mass loss of composite materials. Data from microscopic, dynamic-mechanical, and other types of analyses revealed that the outer-space factors improved the supermolecular order of the resin volume, while the subsurface layer structure of the composite materials had loosened. Microcracks formed in the plastic's surface during 1501 days in outer space did not, in general, affect the mechanical parameters of the composite materials. Most of the observed effects of exposure to conditions in outer space were less pronounced for plastics protected by aluminum foil or other plastic coatings. The data obtained can be used for designing external elements of spacecraft by selecting materials with specified and predictable properties for long-term service.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 4, pp. 457–467, July–August, 1993.In conclusion we thank I. G. Zhigun and R. P. Shlits for assisting in determining the mechanical properties of PCM as well as the crew of the Salyut-6 and Salyut-7 space stations for setting up, monitoring, and delivering samples to earth.     

Investigation on the 2D Contact of Multilayer Functionally Graded Piezoelectric Material Coating Under Conducting Indenters北大核心CSCD

考虑了材料参数可按照任意函数形式变化的功能梯度压电材料(FGPM)涂层在不同形状导电压头作用下的接触问题,研究了梯度系数对功能梯度压电涂层接触力学行为的影响.建立了多层功能梯度压电材料涂层模型,运用了Fourier积分变换和传递矩阵将多层功能梯度压电材料涂层的接触问题转化为奇异积分方程.利用GaussChebyshev数值计算方法,得到了多层功能梯度压电材料涂层-基底结构在刚性导电平压头和圆柱形压头作用下的表面应力分布和电荷分布.利用数值解,分析了材料参数按照不同变化形式的FGPM涂层对最大压痕和电势的影响,还分析了功能梯度压电涂层内部的应力和电位移分布.研究结果表明,功能梯度压电材料参数的不同变化形式对结构的接触性能具有重要的影响.     

Transient analysis of thermo-elastic waves in thick hollow cylinders using a stochastic hybrid numerical method,considering Gaussian mechanical properties

This article attempts to study the stochastic coupled thermo-elasticity of thick hollow cylinders subjected to thermal shock loading considering uncertainty in mechanical properties. The thermo-elastic governing equations based on Green–Naghdi theory (without energy dissipation) are stochastically solved using a hybrid numerical method (combined Galerkin finite element and Newmark finite difference methods). The mechanical properties are considered as random variables with Gaussian distribution, which are generated using Monte Carlo simulation method with various coefficients of variations (COVs). The effects of uncertainty in mechanical properties with various coefficients of variations on thermo-elastic wave propagation are studied in detail. Also, the maximum, mean and variance of temperature, displacement and stresses are illustrated across thickness of cylinder in various times.     

A transfer function technique to describe odor causing VOCs transport in a ventilated airspace with mixing/adsorption heterogeneity

A model describing odor causing volatile organic compounds (VOC-odor) transport in a ventilated airspace influenced by heterogeneity of adsorption surface of ambient aerosol and air mixing pattern is proposed and analyzed based on a transfer function modeling technique. In this study an advection–reaction impulse/step response function for VOC-odor is assumed. The system process presented by an ensemble transfer function is solved analytically in the Laplace domain. The analytical results are then numerically inverted using a modified fast Fourier transform algorithm. The model requires the specification of probability density function for residence time of airflow and for both equilibrium linear partitioning and first-order mass transfer rate parameters to quantify the specific air mixing pattern and transport processes. The model predicts the ensemble mean VOC-odor concentrations for a variety of adsorption kinetics and mixing pattern combinations as a function of the boundary impulse/step response inputs as well as residence time and adsorption rate statistics. The general behavior of output VOC-odor profiles is analyzed through the effects of mean adsorption rate coefficient, mean linear partitioning constant, mixing efficiency, mean residence time and coefficient of variations of both linear partitioning and rate coefficients. It indicates that when mixing/adsorption heterogeneity exists, simple complete mixing assumption and simple distribution of rate constant is inherently not sufficient to represent a more generally distributed mixing/adsorption process of VOC-odor transport in a ventilated airspace.     

Regulation of the mechanical properties of thermoplastic carbon fiber-reinforced plastics by changing their production conditions and surface treatment of the fibers

The effect of technological parameters of processing and surface treatment of carbon fibers on the mechanical properties of carbon fiber-reinforced plastics (CFRPs) was investigated. The copolymer of 1,3,5-trioxane with 1,3-dioxolane was used as the polymer matrix, and medium-modulus hydrated cellulose Ural LO-24 carbon fibers served as the reinforcing filler. The polymer matrix was mixed with the carbon fibers by the method of combined extrusion. The dependence of the mechanical properties of CFRPs on the technological parameters of screw-disk extrusion was studied. It was found that the properties of the composites were greatly affected by the size of the working disk gap, the disk rotation rate, and the temperature in the zone of normal stresses. The surface of the carbon fibers was activated with atmospheric oxygen in the temperature range of 450–600°C, with mass loss of the fibers no greater than 3–4%. A 30–40% increase in the mechanical properties of the CFRPs was achieved. A decrease in the melt index of the 1,3,5-trioxane copolymer with 1,3-dioxolane reinforced with oxidized carbon fibers was observed, which should be taken into account in processing the composites into products. Introduction of carbon fibers in the 1,3,5-trioxane copolymer with 1,3-dioxolane allows us to increase the wear resistance and decrease the friction coefficient, which makes it possibile to use these materials in the friction units of machines and mechanisms, such as plain bearings, gears, and flange packings.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 673–682, September–October, 1998.     

On the Mathematical Simulation of the Measuring of the Intraocular Pressure by Applanation Method after Refractive Surgery

Applanation tonometry estimates intraocular pressure (IOP) by quantifying the force needed to create a defined amount of deformation of the cornea (Goldmann tonometer) or by estimating the diameter of the circular contact area of the cornea and flat tonometer of defined load (Maklakov tonometer). The first simplest models of the applanation method for measurement of the IOP were based on approach, in which an eyeball is modelled as a thin-walled spherical liquid-filled soft shell with corneal biomechanical properties. It was usually supposed that these properties were the same for all patients. In this work numerical simulation have been carried out using finite element code ANSYS. The eye shell is modeled as two joint shells (cornea and sclera) with different mechanical properties. The results are obtained for numerous sets of parameters and were compared to clinical data. For statistics the measurements of IOP for both eyes of 120 patients before and one month after refractive surgery are used. All parameter of refractive surgery (depth, the width and the place of ablation - refractive surgery for myopia or hypermetropia) have effect on IOP reading obtained with both Goldmann and Maklakov tonometry. The results obtained by Goldmann tonometer are significantly more sensitive to all parameters of refractive surgery than those found with Maklakov tonometer with load 10 g. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Plastic Structural Analysis Under Stochastic Uncertainty

Problems from limit load or shakedown analysis are based on the convex, linear or linearized yield/strength condition and the linear equilibrium equation for the generic stress vector. Having to take into account, in practice, stochastic variations of the model parameters (e.g., yield stresses, plastic capacities) and external loadings, the basic stochastic plastic analysis problem must be replaced by an appropriate deterministic substitute problem. Instead of calculating approximatively the probability of failure based on a certain choice of failure modes, here, a direct approach is presented based on the costs for missing carrying capacity and the failure costs (e.g., costs for damage, repair, compensation for weakness within the structure, etc.). Based on the basic mechanical survival conditions, the failure costs may be represented by the minimum value of a convex and often linear program. Several mathematical properties of this program are shown. Minimizing then the total expected costs subject to the remaining (simple) deterministic constraints, a stochastic optimization problem is obtained which may be represented by a “Stochastic Convex Program (SCP) with recourse”. Working with linearized yield/strength conditions, a “Stochastic Linear Program (SLP) with complete fixed recourse” is obtained. In case of a discretely distributed probability distribution or after the discretization of a more general probability distribution of the random structural parameters and loadings as well as certain random cost factors one has a linear program (LP) with a so-called “dual decomposition data” structure. For stochastic programs of this type many theoretical results and efficient numerical solution procedures (LP-solver) are available. The mathematical properties of theses substitute problems are considered. Furthermore approximate analytical formulas for the limit load factor are given.     

Modeling the moisture dependent material behavior of adhesive bonds close to the glass transition temperature

In the presented work, a viscoelastic cross-linked polyurethane is investigated. Environmental influences lead to an inhomogeneous spatial distribution of the mechanical properties in polymer adhesives. Diffusive transport mechanisms transfer water from the environment into the polymer. Further effects like temperature, also have an influence on the mechanical behavior of adhesives. The model respects these influences and takes the incompressibility of the material into account. Viscoelastic behavior can be observed, especially close to the glass transition temperature [3]. Additional to these general effects on polymers, adhesive bonds show a dependency of the mechanical behavior on the thickness of the layer. For numerical investigations, all necessary balance and constitutive equations are implemented in the open-source C++ finite element code deal.II [1, 2]. With the help of this implementation and by comparing experimental results and results gained from simulations, material parameters of the used polymer can be identified. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The use of the adjoint variables in the development of improvement criteria for chemical reactors

The adjoint variables of optimization theory are used in order to investigate the effects of global and local mixing. Global mixing may be caused by bypass, recycle, or general feed bypass. Local mixing is studied by replacing a small part of the reactor with a perfectly mixed cell of equal volume. As an example, a complex reaction system with competing side reactions of different orders is studied in detail.This work was supported by the National Science Foundation, Systems Grant No. GU-1153.     

Antifrictional properties of compositions in the polyamide - copper system

Conclusion 1. The antifrictional properties of metallopolymer compositions made up by a thermal method in an air atmosphere (method A) and in a hydrogen atmosphere (method B), and also made up by mechanical mixing of P610 polyamide powders and PM grade copper (method C) have been investigated.2. It has been shown that the metallopolymer obtained by the thermal method in a hydrogen medium, at a degree of filling of 30% or more by wt., has less wear of the composition as compared with compositions made up by method C which are similar in degree of filling.3. Compositions made up by method A have a loosened structure and are comparable in wear resistance with the unfilled polymer.4. The coefficient of friction of the metallopolymer obtained in a hydrogen medium is less at the selected slippage regime than the coefficient of friction of the pure polyamide by a factor of 1.5, and is 20% less than that of the metal-filled composition made up by mechanical mixing in accordance with method C.5. It has been shown that the temperature on the friction surface of the metallopolymer made up by method B is less than that of the pure polyamide or the metal-filled composition made up by method C, by 40°C and by 20°C, respectively.Lenin Young Communist League. Riga Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 6, pp. 1043–1048, November–December, 1978.     

Two-target pursuit-evasion differential games in the plane

Two-target versions of the game of two cars and the homicidal chauffeur game are introduced. This enables us to consider pursuitevasion withouta priori role assignment. A generic example of the two-target homicidal chauffeur game is considered in detail; in particular, a map of the game and its corresponding winning strategies are found using Lyapunov methods of analysis. The effects of altering game parameters, such as the speed and maneuverability ratios, and the weapon system parameters are then presented. It is found that certain winning strategies include a swerve-type maneuver and that, for certain sets of parameters, regions of stagnation and different modes of draw occur.This work was partially supported by a grant from Control Data.     

Heat-Kernel Approach to UV/IR Mixing on Isospectral Deformation Manifolds

We work out the general features of perturbative field theory on noncommutative manifolds defined by isospectral deformation. These (in general curved) ‘quantum spaces’, generalizing Moyal planes and noncommutative tori, are constructed using Rieffel’s theory of deformation quantization by actions of Our framework, incorporating background field methods and tools of QFT in curved spaces, allows to deal both with compact and non-compact spaces, as well as with periodic and non-periodic deformations, essentially in the same way. We compute the quantum effective action up to one loop for a scalar theory, showing the different UV/IR mixing phenomena for different kinds of isospectral deformations. The presence and behavior of the non-planar parts of the Green functions is understood simply in terms of off-diagonal heat kernel contributions. For periodic deformations, a Diophantine condition on the noncommutivity parameters is found to play a role in the analytical nature of the non-planar part of the one-loop reduced effective action. Existence of fixed points for the action may give rise to a new kind of UV/IR mixing. Communicated by Vincent Rivasseau submitted 22/12/04, accepted 22/03/05     

Change in the properties of impact polystyrene during multiple processing

It has been shown experimentally that the multiple extrusion of grade UP-1E impact polystyrene (5–7 cycles) has almost no effect on most of the physicomechanical properties, the content of volatiles and helium or the residual monomer content. Multiple processing of the same polystyrene by injection molding (10 cycles) causes partial degradation of the material and the destruction of its crosslinked fraction, which results in increased fluidity, reduced molecular weight, and a partial improvement in mechanical properties (approximately up to the fifth or sixth cycle).Mekhanika Polimerov, Vol. 3, No. 1, pp. 156–160, 1967     

A variant of the theory of thick multilayer cylindrical shells

Equations are derived which describe the stress field in thick orthotropic cylindrical shells of a material whose mechanical properties vary across the thickness. An iterative computation procedure is set up which takes into account transverse strains and where the initial approximation corresponds to the hypothesis of straight normals. The convergence of this method is estimated for the case of a thick orthotropic cylinder under axisymmetric strain, and the results are compared with the exact solution.     

A model of weak viscoelastic nematodynamics

The paper develops a continuum theory of weak viscoelastic nematodynamics of Maxwell type. It can describe the molecular elasticity effects in mono-domain flows of liquid crystalline polymers as well as the viscoelastic effects in suspensions of uniaxially symmetric particles in polymer fluids. Along with viscoelastic and nematic kinematics, the theory employs a general form of weakly elastic thermodynamic potential and the Leslie–Ericksen–Parodi type constitutive equations for viscous nematic liquids, while ignoring inertia effects and the Frank (orientation) elasticity in liquid crystal polymers. In general case, even the simplest Maxwell model has many basic parameters. Nevertheless, recently discovered algebraic properties of nematic operations reveal a general structure of the theory and present it in a simple form. It is shown that the evolution equation for director is also viscoelastic. An example of magnetization exemplifies the action of non-symmetric stresses. When the magnetic field is absent, the theory is reduced to the symmetric, fluid mechanical case with relaxation properties for both the stress and director. Our recent analyses of elastic and viscous soft deformation modes are also extended to the viscoelastic case. The occurrence of possible soft modes minimizes both the free energy and dissipation, and also significantly decreases the number of material parameters. In symmetric linear case, the theory is explicitly presented in terms of anisotropic linear memory functionals. Several analytical results demonstrate a rich behavior predicted by the developed model for steady and unsteady flows in simple shearing and simple elongation.