Deformation Of Elastic Material Research Articles

Geometric Design Methodology for Deployable Self-Locking Semicylindrical Structures

Due to their unique bistable characteristics, deployable self-locking structures are suitable for many engineering fields. Without changing the geometrical composition, such structures can be unfolded and locked solely by the elastic deformation of materials. However, their further applications are hampered by the lack of simple and systematic geometric design methodologies that consider arbitrary structural curvature profiles. This paper proposes such a methodology for double-layer semicylindrical grid structures to simplify their cumbersome geometric design. The proposed methodology takes joint sizes into account to ensure that the design results can be applied to actual projects without further adjustments. By introducing symmetry into the structural units (SUs) and selecting reasonable geometric parameters that describe the structural side elevation profile, a concise set of simultaneous nonlinear geometric constraint equations is established, the solution of which provides the geometric parameter values of the grid shape. On this basis, the remaining geometric parameter values, i.e., the geometric parameter values of the inner scissor-like elements (SLEs) of each SU, can be achieved from the equations derived from general SLEs. Design examples and the assembled physical grid structure indicate the feasibility and wide applicability of the proposed geometric design methodology.

Damage constitutive model of stratified cemented backfill based on coupling macroscopic and mesoscopic deformations

The mechanical properties and stress-strain relationship of cemented backfills with different stratified structure have a direct effect on the mining-filling cycle and the mining of adjacent pillars. To obtain the stress-strain evolution curves, the uniaxial compressive strength tests were performed on backfills with stratified numbers of 0, 1, 2 and 3. The deformation of stratified backfill under the compressive load is regarded as a compound of closed deformation of the macroscopic stratified structure and elastic deformation of material. The damage constitutive model of cemented backfills with different stratified structure are established by considering the influence of compacted section. Comparative analysis reveals that the calculated curve based on the established sectional damage constitutive model conforms well to the trial curve. The maximum closed strain of the structural plane has a more significant effect on the mechanical properties of backfill. In the Weibull distribution, with the increase of the parameter m, the peak strength of backfill gradually increases and then reaches to a certain value, and the stress-strain curve gradually becomes steeper, which shows that m is a reflection of the concentration level of micro-unit strength distribution in the backfill..

材料の弾性変形によるデバイリング形状変化の解析

材料の弾性変形によるデバイリング形状変化の解析

Wavelet method applied to specific adhesion of elastic solids via molecular bonds

We propose a wavelet method to analyze the stochastic-elastic problem of specific adhesion between two elastic solids via ligand-receptor bond clusters, which is governed by a nonlinear integro-differential equation with a singular Cauchy kernel to describe the mean-field coupling between deformation of elastic materials and stochastic behavior of the molecular bonds. To solve this problem, Galerkin method based on a wavelet approximation scheme is adopted, and special treatment which transforms the singular Cauchy kernel into a smooth one has been proposed to avoid the cumbersome calculation of singular integrals. Numerical results demonstrate that the method is fully capable of solving the specific adhesion problems with complex nonlinear and singular equations. Based on the proposed method, investigations are performed to reveal the relation between steady-state pulling force and mean surface separation under different stress concentration indexes, which is crucial for assembling the overall constitutive relations for multicellular tumor spheroids and polymer-matrix microcomposites.

Methodology and verification of calculations for contact stresses in a wheel–rail system

The distribution of contact stresses in the wheel–rail system is a decisive factor for the wear of elements and the safety of rail transport. Analytical calculations of stresses based on the Hertz theory can only be applied to elastic deformation of materials. High dynamic loads leading to plastic deformation (not considered in the Hertz theory) are a predominant cause of problems in the contact vicinity. These problems can be successfully resolved by applying the finite-elements method. Two- and three-dimensional test models were generated to estimate an error in numerical calculations in the MSC.MARC program. We compared the results of numerical calculations with analytical calculations. Based on the obtained results we defined the effect of parameters describing the finite-elements mesh on the calculation error for contact stresses, and adjusted mesh parameters appropriately to achieve as low as possible error in numerical calculations. We also defined the effect of material characteristics on the value of contact stresses on the wheel–rail interface.

Analysis of Two Surfaces under Viscoelastic Contact

This paper presents the analysis of the contact surfaces between a rigid cylinder and a soft plate for viscoelastic material. The contact pressure and deformation of the plate in contact region were determined using finite element technique. Moreover, the characteristics of two surfaces of cylindrical roller and plate under elastohydrodynamic lubrication with nonNewtonian fluid were examined using finite difference technique with full adaptive multigrid method . In this study the simulation of viscoelastic material in contact was under taken to determine the effects of material behaviors on the deformation of plate compared to the elastic materials. The results indicated that the deformation shapes were nonlinearly dependent with the applied loads. Furthermore, the deformation of elastic material would reach a certain value in a period of time whereas the deformation of viscoelastic material was increased inconsistently with time. The film pressure and film thickness profiles in the contact regime were investigated at various loads. The minimum film thickness occurs near the trailing edge of contact region and becomes very small under heavy loads.

Influence of Blank-Holder Force on Springback of Cap-Shape Parts Bending

Springback is the prominent problem in bending forming of sheet metal, which is difficult to control accurately, especially for the complex shaped bending parts. The change of blank-holder force will cause significant changes of bending springback amount. The theoretical analytical model of cap-shape parts bending, which takes into account of the harden ability, anisotropy and elastic deformation of material, is proposed in this paper based on the plane deformation assumption and the bending theory of sheet metal, the cap-shape parts bending of wide sheet is analyzed theoretically, the approximate calculation relational expression is derived between the blank-holder force and springback angle, and the influence of blank-holder force on springback is discussed. In the same conditions, the springback result deduced from theoretical formula is basically consistent with numerical simulation and experiment result.

Influence of Friction on Springback of Quadrangle Parts Bending

Springback is the prominent problem in bending forming of sheet metal, which is difficult to control accurately, especially for the complex shaped bending parts. The change of friction conditions will cause significant changes of bending springback amount. The theoretical analytical model of quadrangle parts bending, which takes into account of the harden ability, anisotropy and elastic deformation of material, is proposed in this paper based on the plane deformation assumption and the bending theory of sheet metal, the quadrangle parts bending of wide sheet is analyzed theoretically, the approximate calculation relational expression is derived between friction coefficient and springback angle, and the influence of friction on springback is discussed. In the same conditions, the springback result deduced from theoretical formula is basically consistent with numerical simulation and experiment result.

Elastic Deformation of Materials under Distributed Shear Loading

In this work, the deformation of material under localised tangential loading has been investigated. An analytical expression to predict deformation and strain patterns under tangential loading over a rectangular patch on a surface is validated against experiential tests using surface displacement measurement and finite element modelling. The predicted force- displacement data and displacement/strain patterns show close agreement with experimental results a rubber test material and FE results. The ranges of specimen geometries that minimise the boundary effects have been determined.

A new pressure regulation device using high pressure isolation valves

A new high pressure equipment has been developed in the context of the French High Pressure Network. It includes a new concept of high pressure isolation valves and a new device of pressure regulation. The main feature of the valves is the absence of the stuffing box and a working mode based on the elastic deformation of materials. The regulation device uses these high-performance valves and proposes a compact system allowing the programming of pressure cycles up to 2000 bar with a high reliability and flexibility. The setup is regularly used for in situ experiments in high pressure and high temperature cells at ESRF.

A new pressure regulation device using high pressure isolation valves

A new high pressure equipment has been developed in the context of the French High Pressure Network. It includes a new concept of high pressure isolation valves and a new device of pressure regulation. The main feature of the valves is the absence of the stuffing box and a working mode based on the elastic deformation of materials. The regulation device uses these high-performance valves and proposes a compact system allowing the programming of pressure cycles up to 2000 bar with a high reliability and flexibility. The setup is regularly used for in situ experiments in high pressure and high temperature cells at ESRF.

Numerical study of two-dimensional problems of nonsymmetric elasticity

We consider the algorithm of the finite element method for solving two-dimensional problems of nonsymmetric elasticity. We discuss the possibilities of the algorithm and its efficiency by comparing the numerical results with the well-known analytic solutions. We present the results obtained by solving the problem of tension of a plate weakened by a series of holes and the problem of tension for a plate with a central crack. The numerical results thus obtained are considered as an addition to the analytic solutions in the context of experimental justification of couple-stress effects arising under deformation of elastic materials and in the context of solving the identification problem for mechanical constants in nonsymmetric elasticity.

Rapid prototyping of active microfluidic components based on magnetically modified elastomeric materials

Replica molding of elastomeric materials has proven to be an extremely useful new technology for the formation of complex microfluidic systems. Recent demonstrations of convenient methods for production of such systems by simple, rapid methods that do not require expensive fabrication facilities have enabled the extensive use of microsystems in research and development into a host of new application fields. This report describes a simple new method for fabricating active elastomeric components in microfluidic systems that is based on deformation of elastic materials that have been impregnated or coated with magnetic materials. Computer controlled miniature electromagnets are used to activate switching valves within microfluidics systems. Similar fabrication techniques can be easily extended to construct complex, and potentially completely integrated, microfluidic systems containing active valves, pumps, injectors, mixers, and flow controllers. Preliminary results indicate fabrication of channels approximately 200 μm in width, with valves approximately 5 mm in size (including both valve chamber and valve actuator). The fabrication cycle time is on the order of one day using readily available benchtop equipment, and the valves seal hermetically against a 1.5 kPa back pressure.

圧電素子を利用した力センサの静特性の改善

This paper deals with a piezoelectric force sensor with static sensitivity and the improvement of the static characteristics. It is difficult for an electric-charge type force sensor to have static sensitivity because of the leak of the charge. On the other hand, the piezoelectric element has electrical resonance characteristics, and the resonance frequency is slightly shifted by the impedance change due to the applied stress. The voltage induced to the sensor element corresponds to the given load when it is oscillated with the fixed frequency near the resonance and with the alternating current of constant amplitude. It has been confirmed that the output stability is maintained and the drift is made negligible when the oscillation frequency is strictly fixed and that the hysteresis between the load and the sensor output is removed when the amplitude of current is kept constant by the feedback control. The force is applied directly on the sensor without converting the force into the deformation of elastic material. Then, the sensor can be made thin and it will be expected to be used in the wider application fields.

Formulation and Analysis of EHL Problems for Soft Materials

This paper presents a qualitative and numerical analysis of the new formulation of a steady problem for lubricated rollers made of elastic materials with low Young’s modulus. The feature that makes this formulation different from the classic one is that the linear velocities of the surfaces take into account tangential deformations of elastic materials. Therefore, in Reynolds equation, the surface linear velocities are represented by functions of the location in the contact region instead of constants. The new formulation predicts the formation of a significant depression (dimple) in the contact surfaces of soft materials as opposed to flat surfaces in the classic EHL theory. The paper also describes the dependence of dimple sizes on problem parameters. [S0742-4787(00)02003-8]

Elastic Deformation of Materials with Ellipsoidal Inclusion and Polycrystals

The elastic deformation of inhomogeneous materials, especially materials with spherical or ellipsoidal inclusion and polycrystals is investigated, by expressing them with several models. Constraint ratio proposed previously is used to express deformation behaviour of materials, which is obtained from the strain distribution calculated numerically based on the models. At first, inclusion imbedded in matrix is studied by finite element model of inclusion as well as by Eshelby's analysis. The value of constraint ratio is nearly equal to 0.5 when the inclusion is spherical. The result is closely related to that of the self-consistent model of polycrystals. The value of constraint ratio in spheroidal inclusion increases when it is oblate in the stress direction, while it decreases when it is prolate. Next, the influence of irregularity of grain size in polycrystals on deformation behaviour is discussed. The overall deformation behaviour of the polycrystals is correlated with constraint ratio in each grain. The deformation mode of ply crystals changes into that under constant strain when the irregularity increases.

Elastic Deformation of Materials with Ellipsoidal Inclusion and Polycrystals

Elastic Deformation of Materials with Ellipsoidal Inclusion and Polycrystals