Deformation Properties Of Materials Research Articles

The impact of material chemistry and morphology on attrition behavior of excipients during high shear blending

Particle breakage by attrition is unavoidable in some unit operations and can lead to uncontrolled behavior of materials during processing. The aim of this study is to clarify the impact of material properties on attrition behavior. For the first time, an integral study with varying morphologies and chemistries is performed to identify the key drivers that impact attrition during high shear blending. Based upon the observed changes in particle size distribution, it was concluded that dicalcium phosphate (DCP) was the most prone to attrition, followed by mannitol, lactose and microcrystalline cellulose (MCC). Granular particles were more sensitive to attrition than sieved and spherical particles. Changes in bulk density, flow function coefficient and tablet tensile strength were observed as the result of attrition. The magnitude and direction of change in these parameters was not only dependent on the amount of attrition, but also on the morphology and the material deformation properties.

Capturing the Temperature Dependence of Cleavage Fracture Toughness in the Ductile-to-Brittle Transition Regime in Ferritic Steels Using an Improved Engineering Local Approach

Abstract Ferritic steels, which are typically used for critical reactor components, including reactor pressure vessels (RPV), exhibit a temperature-dependent probability of cleavage fracture, termed ductile-to-brittle transition. The fracture process has been linked to the interaction between matrix plasticity and second-phase particles. Under high-enough loads, a competition exists between cleavage and ductile fracture, which results from particles rupturing to form microcracks or particles decohering to form microvoids, respectively. Currently, there is no sufficiently adequate model that can predict accurately the reduced probability of cleavage with increasing temperature and the associated increase of plastic deformation. In this work, failure probability has been estimated using a local approach to cleavage fracture incorporating the statistics of microcracks. It is shown that changes in the deformation material properties are not enough to capture the significant changes in fracture toughness. Instead, a correction to the fraction of particles converted to eligible for cleavage microcracks, with an exponential dependence on the plastic strains, is proposed. The proposed method is compared with previous corrections that incorporate the plastic strains, and its advantages are demonstrated. The method is developed for the RPV steel 22NiMoCr37 and using experimental data for a standard compact tension C(T) specimen. The proposed approach offers more accurate calculations of cleavage fracture toughness in the ductile-to-brittle transition regime using only a decoupled model, which is attractive for engineering practice.

A review on bending analysis of polymer-based flexible patch antenna for IoT and wireless applications

Flexible electronics have the potential to address the future demands for low power consumption, flexibility, low cost, scalability, and large manufacturing in a shorter amount of time. The low cost and bending capabilities of a flexible wearable wireless application have piqued the interest of academics. Wearable flexible antennas made of a variety of polymers such as Polydimethylsiloxane (PDMS), Polyimides (PI), Polyethylene Terephthalate (PET), Polytetrafluoroethylene (PTFE) and Kapton polyimide are currently in demand for research and development. Various prominent polymers are evaluated for their ability to bend in this detailed work. The widespread acceptance of Internet-of-Things (IoT) applications to support a wide range of technologies. That will enable a wide range of new applications to be enabled via wireless connectivity. Such applications need a comprehensive inspection of the bending and deformation properties of materials. The purpose of this paper is to compare traditional flexible materials with popular polymers materials. The article examines the physical, electrical, and mechanical properties of certain commonly used polymer substrates and delivers a complete analysis and review of them. The results show that bending various polymers has a significant impact on antenna performance metrics.

Solving the problems of strength and destruction of materials and structural elements using a complex experimental-theoretical approach

The paper considers a complex experimental and theoretical approach to studying high-speed deformation of structural materials including a system of basic dynamic experiments aimed at determining the strength and deformation properties of materials under various types of stresses, a program for direct parametric identification of models of deformation and fracture, as well as a system of special verification experiments in the natural and numerical realizations, which makes it possible to assess the adequacy of the model obtained and its performance in conditions other than those in which it was received. To obtain a set of mechanical strength and deformation properties of materials under compression, tension or shear, a series of basic experiments was carried out on an installation that implements the Kolsky method using sets of split Hopkinson bar of various configurations. According to the results of these experiments, together with the data of static deformation, the parameters of the Johnson-Cook model of plasticity with various versions of the model factor responsible for the influence of the strain rate were identified. To test the adequacy of the model (verification), special test experiments have been developed that are simple enough, on the one hand, and allow an unambiguous interpretation of the results and numerical reproduction without simplifications, whilst, on the other hand, the stress state in these types of tests, as well as the history of changes in the loading parameters, differs from that in basic experiments. The chain of obtaining an adequate (verified) model of deformation and fracture used in software complexes for calculating the stress-strain state and the strength of critical structures under shock loading conditions is considered in the example of steel 3.

Limit states and safety factors under repeated loading

Verification of the structures operating possibility using numerical modeling beyond the elastic limit requires standardization of safety factors and calculation methods used to get them. In the framework of the discussion on the improvement of the strength standards of the aviation and nuclear industries for structures operating under low-cycle mechanical and reversible dilatation (temperature, hydrogen) external influences, the article discusses the limiting states; the deformation properties of materials necessary for their calculation; safety factors for loads and durability; calculation methods. The article divides limit states of structures under low-cycle actions into two groups: typical, corresponding to a qualitative change in the deformation type, and individual, determined by allowable displacements and cracks for a particular structure. The following types of deformation are considered: inelastic deformation only at the running-in stage (that changes to elastic after the auspicious residual stresses develop and cyclic hardening of the material); alternating flow (that continues with the number of cycles); progressive accumulation of strains and displacements; combined deformation (when both strain span and strain increment are non-zero in a stable cycle). The types of deformation differ in possible consequences for the structure and the initial data for the calculation: mechanical properties of the material required for modeling different types of deformation should be determined by fundamentally different tests. An analysis of individual limit states without taking into account differences in the types of deformation - and thus typical limit states - may be incorrect. The main focus of the article is on typical limit states. The limit states vary depending on the stage of operation at which inelastic cyclic deformation is allowed. Inelastic deformation expands allowable load range, the expansion due to the inelastic deformation at the running-in stage only is usually more significant than additional expansion due to the continuous inelastic deformation; besides, the inelastic deformation only at the running-in stage does not demand analysis of low-cycle fatigue and accumulated strains. Further expansion of the permissible load range, as well as solution of safety problems based on risk assessments, requires a more complete study of the deformation properties of materials at the pre-fracture stage, where cyclic softening predominates.

Prediction of mechanical properties for one-dimensional polymer structures

Subject of Research.The paper presents a technique for prediction of the mechanical properties of polymer materials. An equation is proposed for the highly elastic part of deformation in a differential-mode for one-dimensional polymer structures. The equation establishes that the preceding mechanical impact on deformation material properties is irrelevant. Method. A recursive method for solution of the proposed differential equation not integrable in quadratures was proposed. Tensile diagrams were experimentally obtained for fibers made of highly oriented polymers such as polyamide and polyethylene terephthalate in five loading conditions. The first load consisted in uniform loading of the fiber to rupture. In the other cases, the loading was carried out in three stages: with holding at control points, complete unloading and subsequent loading to rupture. Main Results. An equation for the highly elastic part of the deformation in a differential form is proposed and solved. Tensile diagrams are presented for one-dimensional polymer samples made of polyamide and polyethylene terephthalate up to the rupture values under various loading conditions. It is found that the preceding mechanical impacts do not affect significantly on the sample deformation properties. Samples made of polyamide and polyethylene terephthalate have practically no memory. Thus, the highly elastic part of the deformation relaxes into a stable state. Practical Relevance. The research shows that in an equilibrium state (regardless of the deformation method) each level of mechanical stress corresponds to a certain value of the equilibrium deformation; for a fixed deformation there is a fixed value of stress. The modeling results make it possible to predict the behavior of polymer materials under various operating conditions.

Failure assessment curve for austenitic stainless steel pipes of nuclear power plants

This paper presents a failure assessment curve (FAC), which predicts a conservative failure load of austenitic stainless steel pipes with a circumferential surface crack. Changes in material deformation properties due to cold working, neutron irradiation and thermal aging were taken into account. First, stress-strain curves for stainless steels were assumed for welded, irradiated, cold worked, thermal aged materials as well as undamaged materials using the Swift-type constitutive equation, whose material constants were estimated from the yield and ultimate strengths. Second, the FACs were analyzed for various material properties and crack and pipe geometries. It was shown that the FAC depended on the crack and pipe geometries, and the lower bound FAC were obtained. Finally, the universal FAC, applicable to stainless steel pipes regardless of crack geometries and material properties, was proposed.

Relating deformation parameters test research of mortar and limestone cooled to cryogenic temperatures

PurposeThe coefficient of thermal expansion (CTE) and modulus of elasticity (ME) values of mortar and stone from room temperature to cryogenic temperatures provide an experimental basis for the design of liquefied natural gas (LNG) storage tanks.Design/methodology/approachThe CTE and ME of mortar and limestone were measured by resistance strain gauge testing technology at cryogenic temperatures.FindingsThe test results showed that CTE values of mortar and stone decreased with the decrease of temperature and CTE values of mortar was greater than that of stone from 0 °C to −165 °C. The ME values of mortar increased significantly at cryogenic temperatures, and less change in stone.Originality/valueThe material at cryogenic temperatures may continue to work in the elastic phase due to the continuous increase of elastic modulus. Therefore, the study of material in the elastic stage may be more important than in the ultimate bearing capacity stage, and it is necessary to carry out further study surrounding the deformation properties of materials at cryogenic temperatures. The CTE and ME values of mortar and stone from room temperature to cryogenic temperatures provide an experimental basis for the design of LNG storage tanks.

Energy Absorption of Reinforced Concrete Constructions with Nonlinear Dynamic Deformation

A method is proposed for taking into account the specific features of the energy absorption of reinforced concrete constructions under dynamic loads under non-linear deformation conditions based on the application of the finite element method. Based on the consideration of the triaxial problem, the inconstancy of the energy absorption coefficient throughout the entire volume of the deformable body was revealed. It is shown that the hysteresis energy absorption depends on the level of the stress state and is determined by the deformation properties of materials. The solution of the problem is proposed to be obtained using an iterative process based on the method of integral estimates. Considering that the amount of energy absorbed by the structure depends on the level of the stress state, it becomes possible to control the process of energy absorption by changing the stress-strain state possible by varying the design, fixing conditions, changing reinforcement or any other constructive measures.

Strength evaluation of concrete elements with non-metallic reinforcement under short-term dynamic compression

The article presents a method for calculating the strength of concrete elements with non-metallic fiber, rod and external reinforcement. The algorithm and the calculation program are shown, which are based on the use of a nonlinear deformation model of the normal section of such elements, taking into account the real deformation properties of materials under static and short-term dynamic loading.

Stressed-deformed condition in composite in conditions of continuous pure life

Formulation of the problem . In the mechanics of deformable solids and in the support of materials, as well as in the mechanics of composite materials, the main simple types of stress-strain state are used such as: pure tensile, pure compression and pure shear. In the case of pure tension (compression), in addition to longitudinal deformations (deformations along the direction of uniaxial stress), transverse deformations arise (deformations are normal to the load axis). With a pure shear, normal deformations to the shear planes are not taken into account. However, as shown in Part 1 and Part 2 of inelastic clean shear studies [10], in homogeneous materials with different resistance of tension and compression there are deformations normal to the displacement planes. In composite materials, such studies have not been conducted. The solution of tasks of this type in the mechanics of a deformable solid and in the support of materials, as well as in the mechanics of composite materials is not provided. Goal. On the basis of the methods and conditions of the mechanics of deformable solids and the resistance of materials, as well as earlier studies on inelastic clean shear [10], to determine the effect of linear continuous reinforcement of a composite on its deformation properties under pure shear. Conclusions. The stiffness of a composite at displacement (with a matrix having different plastic properties under tension and compression) beyond the elasticity of the matrix increases with increasing stiffness of the reinforcing elements even if the reinforcing elements are not capable of accepting the shearing forces. In studies of a stress-strain state in equations and systems of equations of equilibrium of effort it is necessary to take into account the deformation properties of materials both in tension and compression.

Protection of cortex by overlying meninges tissue during dynamic indentation of the adolescent brain.

We present the first mechanical analysis of the protective capacity of the cranial meninges using in situ micro-indentation techniques. Force-relaxation tests are performed on in situ meninges and cortex tissue, under large strain dynamic micro-indentation. A quasi-linear viscoelastic model is used subsequently, providing time-dependent mechanical properties of these neural tissues under loading conditions comparable to what is experienced in TBI. The reported data highlights the large differences in mechanical properties between these two tissues. Finite element simulations of the indentation experiments are also performed to investigate the protective capacity of the meninges. These simulations show that the meninges protect the underlying brain tissue by reducing the overall magnitude of stress by 250% and up to 65% for strains.

Structural mechanisms of formation of adiabatic shear bands

The paper focuses on the experimental and theoretical study of plastic deformation instability and localization in materials subjected to dynamic loading and high-velocity perforation. We investigate the behavior of samples dynamically loaded during Hopkinson-Kolsky pressure bar tests in a regime close to simple shear conditions. Experiments were carried out using samples of a special shape and appropriate test rigging, which allowed us to realize a plane strain state. Also, the shear-compression specimens proposed in were investigated. The lateral surface of the samples was investigated in a real-time mode with the aid of a high-speed infra-red camera CEDIP Silver 450M. The temperature field distribution obtained at different time made it possible to trace the evolution of plastic strain localization. Use of a transmission electron microscope for studying the surface of samples showed that in the regions of strain localization there are parts taking the shape of bands and honeycomb structure in the deformed layer. The process of target perforation involving plug formation and ejection was investigated using a high-speed infra-red camera. A specially designed ballistic set-up for studying perforation was used to test samples in different impulse loading regimes followed by plastic flow instability and plug ejection. Changes in the velocity of the rear surface at different time of plug ejection were analyzed by Doppler interferometry techniques. The microstructure of tested samples was analyzed using an optical interferometer-profilometer and a scanning electron microscope. The subsequent processing of 3D deformation relief data enabled estimation of the distribution of plastic strain gradients at different time of plug formation and ejection. It has been found that in strain localization areas the subgrains are elongated taking the shape of bands and undergo fragmentation leading to the formation of super-microcrystalline structure, in which the size of grains is ~300nm. Rotational deformation modes give rise to the high angular disorientations of grains. The development of plastic shear instability regions has been simulated numerically. For this purpose, we use a recently developed theory, in which the influence of microshears on the deformation properties of materials has been studied by the methods of statistical physics and thermodynamics of irreversible processes. The results of theoretical and experimental studies suggest that one of the mechanisms of the plastic shear instability and localization of plastic strain at high-velocity perforation is related to structural and kinetic transitions in microshear ensembles.

QUASISTATIC STRAIN RATES’ EFFECT TO THE PROPERTIES OF ADVANCED STEELS FOR AUTOMOTIVE INDUSTRY

The paper presents the findings of the strain rate effect, described in constitutive material models by strain rate sensitivity index m, to the strength and deformation material properties. These were evaluated from stress-strain diagrams recorded at tensile test using PC controlled testing machine TiraTEST 2300 according to STN EN ISO 6892-1. The high strength low alloyed steel H220PD, dual phase steel DP 600 and Trip steel RAK 40/70 were investigated at strain rates  = 0.0021, 0.083 and 0.125 s-1. The results indicate major influence of the strain rate to the strength properties while only minor influence have been found when evaluate the deformation properties. The results also shown single phase materials are more sensitive to the strain rate than dual phase materials.

Way of Optimization of Stress State of Elements of Concrete Structures

Inverse problems of the theory of elasticity for inhomogeneous bodies, as a rule, are used to identify the dependence of the mechanical properties of the material from the coordinates. It is known that in a thick-walled cylindrical or spherical shell under internal or external pressure the highest stresses are occurred close to the internal surface of the shell. The article presents several solutions of inverse problems, which are defined dependence of the elastic modulus of the radius, at which the equivalent stress in the shell is constant. Corresponding shells can be called equal stress shells. In most cases the change of the module of elasticity of a material leads to changes in its strength. It is shown that for some materials it is possible to create model of equal strength shell in which equivalent stress in each point is equal to material strength. In the article is also considered the way of modification material's deformation properties at which beams and rods, working under combined stress state (for example, the eccentric compression of columns, the strip foundation and so forth), are also will be equal stress.

Soil damping influence on seismic ground response: A parametric analysis for weak to moderate ground motion

Small-strain stiffness and damping ratio are the key parameters for modeling the dynamic behavior of soils, but they are often problematic and onerous to obtain under field conditions. This is particularly true for the attenuation characteristics. As an alternative to classical laboratory tests, that are costly and prone to inaccuracies due to scale and sampling issues, recent studies stress the opportunity of using in situ measurements, and particularly surface-wave methods. However, while these methods are often used to provide shear wave velocities, they are more rarely used to give in situ estimates of damping parameters. Similarly, it is uncommon to extract attenuation information from down-hole tests. In practice, the usual anti-earthquake design is confronted with a scarcity of laboratory test measurements and with the intricacies of obtaining reliable in situ attenuation measurements. Consequently, shaking simulations commonly use literature values of the damping coefficient. This choice is often motivated by the assumption that damping does not have a critical role in ground shaking evaluations, especially for weak-moderate motion cases. The purpose of this work is to provide, for these conditions, an analysis of when an accurate characterization of the damping coefficient is needed to produce reliable shaking predictions. We performed a stochastic analysis of synthetic seismic response for different realistic subsoil conditions using as input several real ground motion records. For completeness, we also compared linear-equivalent to fully non-linear shaking simulations, showing that, for the moderate-strain conditions we consider, the linear-equivalent approach is adequate. In our simulations we fixed the subsoil structures and material deformation properties while we adopted a Monte Carlo approach to explore the effects of randomly variable damping coefficient values. Our results show how an accurate knowledge of the attenuation coefficient is of minor importance in absence of strong impedance contrasts in the shallow subsurface.

Deformation of compound shells under action of internal shock wave loading

The compound shells under the action of internal shock wave loading are considered. The compound shell consists of a thin cylindrical shell and two thin parabolic shells at the edges. The boundary conditions in the shells joints satisfy the equality of displacements. The internal shock wave loading is modelled as the surplus pressure surface. This pressure is a function of the shell coordinates and time. The strain rate deformation of compound shell takes place in both the elastic and in plastic stages. In the elastic stage the equations of the structure motions are obtained by the assumed-modes method, which uses the kinetic and potential energies of the cylindrical and two parabolic shells. The dynamic behaviour of compound shells is treated. In local plastic zones the 3-D thermo-elastic-plastic model is used. The deformations are described by nonlinear model. The stress tensor elements are determined using dynamic deformation theory. The deformation properties of materials are influenced by the strain rate behaviour, the influence of temperature parameters, and the elastic-plastic properties of materials. The dynamic yield point of materials and Pisarenko-Lebedev's criterion of destruction are used. The modified adaptive finite differences method of numerical analysis is suggested for those simulations. The accuracy of the numerical simulation is verified on each temporal step of calculation and in the case of large deformation gradients.

Numerical and experimental study of thickness effect on deflection of glass plate in elastic deformation machining method

Elastic deformation machining is a fabrication method that uses the elastic deformation properties of materials to make a desired surface form. Coupled with plane lapping machining process, the fabrication method is suitable for machining large aspheric surfaces. In this method, the workpiece is deformed under load and the bottom side of the workpiece is lapped to a flat surface. When the load is released, the bottom surface of the workpiece will be shaped into an aspheric shape. However, the thickness of workpiece is changed in the lapping process while the load remains unchanged. Therefore, the form accuracy of workpiece will increase with desired form surface. The effect of vacuum pressure on deflection of glass plate which changed thickness in lapping process is predicted in this study based on the numerical finite element analysis (FEA) results to determine vacuum pressure values which correspond with changed thickness of workpiece in the experimental process. The study indicates that, the effect of changed thickness on profile accuracy of workpiece in the elastic deformation machining is significant. The form accuracy of workpiece is improved from 62 μm to 1.6 μm which vacuum pressure is reduced from 50 kPa to 42 kPa in the experimental process.

Non‐linear deformation properties of materials with stochastically distributed anisotropic inclusions

AbstractIn the present contribution, the problem of non‐linear deformation of materials with stochastically distributed anisotropic inclusions is considered on the basis of the methods of mechanics of stochastically non‐homogeneous media. The homogenization model of materials of stochastic structure with physically non‐linear components is developed for the case of a matrix which is strengthened by unidirectional ellipsoidal inclusions. It is assumed that the matrix is isotropic, deforms non‐linearly; inclusions are linear‐elastic and have transversally‐isotropic symmetry of physical and mechanical properties. Stochastic differential equations of physically non‐linear elasticity theory form the underlying equations. Transformation of these equations into integral equations by using the Green's function and application of the method of conditional moments allow us to reduce the problem to a system of non‐linear algebraic equations. This system of non‐linear algebraic equations is solved by the Newton‐Raphson method. On the analytical as well as the numerical basis, the algorithm for determination of the non‐linear effective characteristics of such a material is introduced. The non‐linear behavior of such a material is caused by the non‐linear matrix deformations. On the basis of the numerical solution, the dependences of homogenized Poisson's coefficients on macro‐strains and the non‐linear stress‐strain diagrams for a material with randomly distributed unidirectional ellipsoidal pores are predicted and discussed for different volume fractions of pores. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Effect of Water Absorption on the Creep Behavior for Polymer Composite Materials

In this investigation, a low cost, mechanically operated creep testing machine capable of determining the deformation property of material is developed for providing an economical means of performing standard creep experiments. Creep tests are performed to study the nonlinear viscoelastic behavior of epoxy resin and {unidirectional (θ=0o) and woven fabric (θ=0o, 90o)) E-glass/epoxy composite materials under various environmental effects at room temperature and different values of applied stresses. Tested specimens are immersed in three different solutions {acidic water (HCL), PH=5), (distilled water (H2O), PH=7}, and {Alkaline water (NaOH), PH=10}. The experimental creep data can be fitted with general power time function. This function is modified where the effect of gained moisture content, applied stress and aged time on the creep strain are suggested as variables in the creep strain equation. Results show that the creep strain increased with increasing the (pH) level and increased more with increasing the values of the applied stress. Also, the results show that the alkaline water “NaOH solution” is more effective than other solutions on the composite viscoelastic behavior. The concluded degradation rates are 36%, 57% and 62.633% for epoxy, woven fabric composite (Mat) (θ= 0o,90o), and unidirectional composite (θ= 0o), respectively. The developed equation gives an appropriate criterion for describing long time creep strain.