Soft Plates Research Articles

Nonlinear vibration behavior of a carry current ferromagnetic beam plate under magnetic fields and thermal loads

In order to study the magnetoelastic instability and natural frequency of a ferromagnetic plate under a magnetic field, different magnetic force models are considered. In the present study, considering more realistic assumptions, new equations for the study of the vibrational behavior of ferromagnetic beam plates carrying the electric current in the magnetic field are presented by employing the theory of Eringen and Maxwell relations. Conclusively, the effects of magnetic traction and thermal fields created by electric current and eddy currents are taken into account. The coupled nonlinear differential equations of the system are separated by the Galerkin method and solved numerically. The numerical results are compared with the results in the literature, and the effect of different parameters on the vibration characteristics of the soft ferromagnetic beam plate is investigated. The results show that the components of the force that are created by magnetic tractions, as well as the assumption of thermal couplings, can significantly change the vibrational behavior of the plates. Also, by increasing the intensity of the electric current and the magnetic field, the amplitude of the oscillations of the plate is increased and instability occurs for certain values of these parameters in the system.

An accurate zigzag theory for bending and buckling analysis of thick laminated sandwich plates with soft core

An accurate and computationally attractive zigzag theory is developed for bending and buckling analysis of thick laminated soft core sandwich plates. The kinematic assumptions of the proposed zigzag theory are obtained by superimposing a nonlinear zigzag function on the first-order shear deformation theory. In order to obtain the accurate transverse shear stresses, a preprocessing approach based on the three-dimensional equilibrium equations and the Reissner mixed variational theorem is used. It is significant that the second-order derivatives of in-plane displacement variables have been removed from the transverse shear stresses, such that the finite element implementation is greatly simplified. Thus, based on the proposed zigzag model, a computationally efficient four-node C0 quadrilateral plate element with linear interpolation function is proposed for bending and buckling analysis of soft core sandwich plates. The advantage of the present formulation is that no post-processing approach is needed to calculate the transverse shear stresses while maintaining the computational accuracy of a linear plate element. Moreover, the accurate transverse shear stresses can be involved in the strain energy which can actively improve the accuracy of critical loads. Performance of the proposed model is assessed by comparing with several benchmark solutions. Agreement between the present results and the reference solutions is very good, and the proposed model only includes the seven displacement variables which can demonstrate the accuracy and effectiveness of the proposed model.

Клінічне обґрунтування пристрою для попередження післяопераційної евентрації

Postoperative surgery is one of the most dangerous complications, especially in patients with malignant tumors of the abdominal cavity, where secondary immunodeficiency, cachexia, anemia, etc. occur. Today, there are many ways to prevent postoperative surgery in patients at high risk for this complication, but all of them, along with their advantages, have a number of disadvantages that greatly limit their use. Developing an effective, non-invasive device for preventing postoperative surgery may to some extent solve this problem. The purpose of the study is to substantiate the effectiveness of the device for the prevention of postoperative events, by studying the frequency of development of postoperative complications in patients with malignant tumors of the abdominal organs. Material and methods. We have proposed a device for the prevention of postoperative surgery, the use of which does not require additional surgical techniques during surgery, and also allows the use of the latter in the event of the incomplete (subcutaneous) event (patent No. 120209 from 25.10.2017). The device consists of 5 soft plates lined with soft cloth and connected to each other by the widest parts. The central plate is adjustable depending on the width of the back surface of the patient's torso. The two side plates at the free edges have 11 lacing loops. To substantiate the effectiveness of the use of this device, we investigated 107 operated patients with malignant tumors of the abdominal cavity. The comparison group consisted of 60 people who did not use the proposed device. The main group consisted of 47 patients who used the above device in the early postoperative period. Results of the study and their discussion. The results obtained indicate a significant predominance of the incidence of postoperative events in patients in the main group. It should be noted that there is no significant difference in the frequency of development of systemic and other local postoperative complications between the two study groups of patients, which indicates the representativeness of the sample since local postoperative complications lead to the development of eventration. Patients in the main group, starting from day 2 after surgery, had a markedly lower intra-abdominal pressure during the first 12 days of the early postoperative period. Conclusion. The use of the proposed device for the prevention of postoperative surgery allows a non-invasive way to prevent the development of the latter, as well as the occurrence of the incomplete event to prevent the development of full, without significantly affecting the level of intra-abdominal pressure, compared with conventional use of the bandage.

The effects of extracellular matrix rigidity on 3-dimensional cultures of amnion membrane cells

IntroductionTo determine 3D growth of amnion membrane cells using soft substrate plates of various rigidities. MethodsAmnion epithelial (AEC) and mesenchymal cells (AMC) were cultured on 6-well soft substrate plates coated with matrigel and elastomer with rigidities of 0.5, 2, 8, 16, and 64 kPa (n = 3 each). Controls were cells in standard culture conditions. Cell morphology, spheroids' and sheets’ formations and viability (bright field microscopy and crystal violet staining), and cellular transitions (vimentin/cytokeratin-18 [CK-18] ratios) were analyzed. A Student t-test was used for statistical analyses. ResultsAECs in substrate rigidities between 2 and 8 kPa formed 3D features (spheroids and sheets) while retaining viability. Two kPa produced spheroids with epithelial characteristics (decrease in vimentin), and 8 kPa favored sheets. Transplantation and culture of AEC sheets with no matrix or elastomers, retained AECs’ viability and maintained their epithelial characteristics. Optimum AMC growth was also between 2 and 8 kP A, with predominance of vimentin; however, AMCs did not form 3D structures. Lower and higher rigidities transitioned AMCs into AECs (decrease in vimentin). DiscussionMatrix rigidities between 2 and 8 kPa produced 3D structures of AECs (spheroids and sheets), resembling amnion membranes’ morphology and exhibiting regenerative capacity in utero. Although AMCs grew in similar rigidities, a lack of 3D structures support their dispersed character in the membrane matrix. Extreme rigidities transitioned AMCs into AECs, suggesting that AMCs are transient cells (reservoirs) in the matrix required for remodeling. Compromises in matrix rigidity can cause membrane dysfunction and lead to adverse pregnancy outcomes.

Flexible manipulation of topologically protected waves in one-dimensional soft periodic plates

In this paper, we investigate the possibility of flexible manipulation of elastic waves propagating in soft periodic plates through topological state shifting. We design a soft 1D phononic crystal by connecting two different periodic plates made of hyperelastic materials. By choosing different geometrical parameters of the two plates, topologically protected state of elastic waves is observed at the interface between them. Since the hyperelastic material can undergo large elastic deformation, flexible and efficient shifting of topological state can be realized by applying appropriate pre-stretch on the structure. The interface state wave modes can be either activated or deactivated by an applied pre-stretch on the structures with different initial geometrical parameters. Due to the advantageous property that topologically protected wave modes are stable against any defects and disorders, it provides a robust way of manipulating waves propagation in real time. The system and the strategy proposed here have great potential in constructing various novel acoustic devices.

Histological Change in Soft Tissue Surrounding Titanium Plates after Jaw Surgery.

The aim of this study was to evaluate the microscopic structure of soft tissue covering titanium plates and screws used in jaw surgery (mandible fracture and orthognathic surgery), after a minimum period of 12 months from insertion, and to quantify the presence of any metallic particles. Periosteum covering the osteosynthesis plates was removed from 20 patients and examined by light microscopy in order to assess the cell morphological changes and the possibility of metal particles presence in the soft tissue. Local signs of tissue toxicity or inflammation were taken into consideration when evaluating the routine removal of titanium maxillofacial miniplates. No signs of screw loosening or acute inflammation were detected on the osteosynthesis site, but de-coloration of the periosteum was seen, and metallic particles were observed to have migrated into the soft tissues. Even if the titanium is well-tolerated by the human body in time, without severe local or general complications, our findings suggest that plate removal should be considered after bone healing has occurred.

Effect of Al, Ti and C additions on Widmanstätten microstructures and mechanical properties of cast Al0.6CoCrFeNi compositionally complex alloys

The cast microstructure of the Al0.6CoCrFeNi compositionally complex alloy was successfully refined with small additions of Al, Ti and C and its mechanical properties were optimized. In the as-cast state, this alloy has a Widmanstätten microstructure with coarse grains (∼110 μm) of a strong BCC/B2 matrix and soft FCC plates (∼65 vol.%) with large widths (∼1.3 μm). The addition of 0.25 at.% C to Al0.6CoCrFeNi stabilizes the FCC phase and favors the formation of a coarse dendritic microstructure making this alloy unsuitable for structural applications. In contrast, alloying of either 3 at.% Al, Ti, or 3% Ti and 0.25% C to Al0.6CoCrFeNi refined its Widmanstätten microstructure, i.e. the thickness of the FCC plates and/or the size of the prior BCC/B2 grains were significantly reduced. As a result of these microstructural changes, Al and Ti containing alloys show an outstanding strength (twice higher than that of Al0.6CoCrFeNi) and ductilities ≤5% at 20 °C. These properties are retained at 400 °C but at 700 °C, the strength and ductility of almost all alloys decrease. However, Ti containing alloys exhibit much larger ductilities (∼50%) at 700 °C due to their high density of grain boundaries which accommodate plastic deformation through grain boundary sliding.

Rotating electroosmotic flows in soft parallel plate microchannels

We present a theoretical investigation of rotating electroosmotic flows (EOFs) in soft parallel plate microchannels. The soft microchannel, also called as the polyelectrolyte-grafted microchannel, is denoted as a rigid microchannel coated with a polyelectrolyte layer (PEL) on its surface. We compare the velocity in a soft microchannel with that in a rigid one for different rotating frequencies and find that the PEL has a trend to lower the velocities in both directions for a larger equivalent electrical double layer (EDL) thickness λFCL (λFCL = 0.3) and a smaller rotating frequency ω (ω < 5). However, for a larger rotating frequency ω (ω < 5), the main stream velocity u far away from the channel walls in a soft microchannel exceeds that in a rigid one. Inspired by the above results, we can control the EOF velocity in micro rotating systems by imparting PELs on the microchannel walls, which may be an interesting application in biomedical separation and chemical reaction.

Free Flap Outcomes of Microvascular Reconstruction after Repeated Segmental Mandibulectomy in Head and Neck Cancer Patients

This is the first study to investigate the impact of a second fibula flap or a soft tissue flap combined with bridging plate for a repeated segmental mandibulectomy reconstruction on flap outcomes in head and neck cancer patients. A retrospective comparative analysis (2007–2016) of 61 patients who underwent a second segmental mandibulectomy was performed. 20 patients underwent a fibula flap reconstruction whereas 41 had a soft tissue flap and plate reconstruction. No significant difference was seen in the operative time, total hospital stay, flap loss, re-exploration rates, plate exposure rate, or recipient site infection rate. On multivariate analysis, patients reconstructed with a soft tissue flap and bridging plate (odds ratio (OR) 3.997; 95% confidence interval (CI), 1.046–15.280, p = 0.043) and complications developed in previous surgery (OR 4.792; 95% CI, 1.120–20.493, p = 0.035) were shown to be independent predictors of a prolonged nasogastric tube dependence. The utilization of a soft tissue flap with plate is associated with comparative results of acute complication rate within 1 week, recipient site infection rate, and plate exposure rate to free fibula flaps alone. Free fibula flaps may result in a decreased risk for prolonged tube dependence compared to free soft tissue flap reconstructions.

Enhancement of the Critical Current of Bi-2223 Superconducting Coil by Using of Soft Ferromagnetic Material

The effects of soft ferromagnetic material placed nearby the high-Tc Bi-2223 coil is analyzed. Electro-magnetic simulation have been carried out to find the distributions of the magnetic field of the Bi-2223 coil. The used soft ferromagnetic material could change the distribution of the Bi-2223 coil’s magnetic field, and the transport capability of the Bi-2223 coil changes consequently. According to the simulation results, the thickness of the soft ferromagnetic material plate shows a notable effect on the coil, and the position and width of the plate could present negative effects. Experimental result of a Bi-2223 coil with B30P105 silicon steel plate is consistent with the simulation conclusions, and the critical current of the developed Bi-2223 coil could achieve an improvement of 15% by using of a piece of silicon steel plate with a thickness of 0.3 mm.

Duplication of uniqueness: electrotyping in nature printing and its application in contemporary art

The nature printing technique was designed for the electrotyping reproduction of leaves and other natural products. Authentic impressions could be performed by inserting leaves between two lead plates or pressing leaves into the lead plate by a press. The impression obtained in the soft lead plate could then be further reproduced by copper electroplating. Electrochemically deposited copper is hard-wearing and therefore very suitable for the production of printing plates. However, depending on the technical implementation and the choice of the materials used, decisive differences in the faithfulness of reproductions of original motifs may occur during the electrochemical deposition. A central topic in electroforming of printing plates is the choice of the conductive layer on the mould. In the present study, it has been shown that graphite powder represents a conductive phase on the siloxane mould superior to silver and copper powder. The grain size of the copper electrodeposit depended on the powder grain size. The copper plate deposited on graphite powder showed the lowest grain size (5–20 µm) and the highest homogeneity of the print background. Hand polishing of the printing plate resulted in a much better faithfulness of the motif details than that of the machine polished version. However, the background of the print derived from the machine polished plate was the most homogeneous. Electrochemical investigation showed that remnants of the silver powder could result in local elements that could enhance corrosion and thus impair the durability of the printing plates. This phenomenon was negligible with the conductive layers consisting of graphite and copper.

Cutting resistance of soft materials: Effects of blade inclination and friction

In cutting soft elastic materials, friction is often the most relevant term of the total applied force, and techniques to minimise the required effort involve the restraint of frictional dissipation. It is well known from practical experience that cutting is made much easier if performed with a combination of slicing and pushing. A slice-push effect, known to reduce the cutting force, can be introduced by skewing the blade with respect to the travelling direction of the blade itself. The observed drop of the required force is connected to the competing dissipative contributions, with frictional dissipation being reduced at larger inclination angles. This study reports the results of several cutting tests on soft elastomeric plates, in which we have recorded the experimental force-displacement curves during the insertion of sharp stainless-steel blades. An energy-based model is employed to discern the different contributions to the measured force in the various stages of the cutting process, with particular focus on the steady state initiated after full penetration of the blade. The effects of the inclination angle of the blade are discussed with respect to the steady state force obtained from the experiments.

Численное решение задачи об изгибе шарнирно закрепленной трехслойной пластины с трансверсально-мягким заполнителем

Численное решение задачи об изгибе шарнирно закрепленной трехслойной пластины с трансверсально-мягким заполнителем

Stress analysis in transverse loading of soft core sandwich plates with various boundary conditions

In this paper, the transverse loading of sandwich plate is formulated to study the three-dimensional stress field in the sandwich plates for various edge conditions. The formulation is based on the weak formulation approach. A complete three-dimensional displacement field is considered and the weak formulation approach is employed to obtain the governing equations of the plate using the three dimensional equilibrium equations of elasticity. An analytical solution is presented for governing equations when two opposite edges of plate are simply supported. A one-step stress recovery scheme is used to compute the out-of-plane stresses in the sandwich plates. A comparison is made with the predictions of exact elasticity solutions in the open literature and very good agreements are achieved. The distribution of stresses is investigated for various boundary conditions and the log-linear procedure is employed to study the order of stress singularity at free and clamped edge of the plate. It is seen that the present approach accurately predicts the distribution of out-of-plane stresses and local concentration of stresses in the vicinity of free and clamped edges of sandwich structures.

195. Electronic Brachytherapy in clinical practice: Implementation and comparison against conventional techniques and electron montecarlo algorithm

Purpose Electronic Brachytherapy (EBX), a technique that utilizes miniaturized X-Rays source, is gaining ground in radiotherapy treatment in presence of small superficial lesions. This work focuses on acceptance test, commissioning, clinical implementation and dosimetric features of the novel EBX system Esteya® (Elekta AB, Stockholm, Sweden). Methods Flatness and symmetry of X-ray beams have been evaluated according IEC60976 using a high definition 2D array equipped of liquid filled ionization chambers (SRS 1000, PTW, Germany). Half Value Layer (HVL), PDD and absolute dose have been measured for each applicator with a soft X-ray parallel plate chamber (T34013 PTW, Germany) and solid water according to IAEA TRS 398 [1] . Dose distributions have been compared with the ones calculated for conventional electron treatments. Calculations have been carried out in a virtual water phantom by electron montecarlo (eMc) algorithm implemented in a commercial TPS (Monaco v. 5.11, Elekta) for each applicator. Results Flatness, symmetry and penumbra showed excellent performance even if compared with eMC plans. Build up absence and PDDs slopes allow good homogeneity for coverage in superficial targets. Conclusions Shielding requirements, patient compliance and global management of Electronic brachytherapy sources are well known advantages [2] . This study demonstrated that EBX could be a valid alternative to electron treatment in case of small skin lesions also from a dosimetric point of view.

Tunable bandgaps in soft phononic plates with spring-mass-like resonators

Controlling band gaps of phononic crystals in real time through external stimuli (e.g. mechanical loadings, electric fields, and magnetic fields) shows potential applications in adaptive acoustic devices. It has been indicated that alteration of structural geometry or effective material properties due to external mechanical loadings will effectively change the bandgaps. In this regard, inducing significant post-buckling deformations in phononic crystals becomes an effective way to tune the band gaps. Few studies however have been reported to tune the band gaps through small deformations under which the geometry of phononic crystals is almost unchanged. In this work, a phononic crystal plate made of soft material with resonant units is proposed. Each resonant unit consists of a mass which is connected to the perforated plate by thin beams. Finite element method is employed to study the deformation and the dispersion behavior of such structure when subject to external mechanical loadings. Obvious complete band gaps are found to even exist in the intact structure without any mechanical loading. The evolution of band gaps under stretching is systematically revealed. Results show that remarkable tunability of bandgaps with small pre-stretch or extension is realized when strong resonance appears for some particular modes. The resonance frequency is mainly affected by the mass of the resonator and the stiffness of the connecting beams. In the proposed structure, the stiffness of the connecting beams can be substantially increased under a small pre-stretch. As a result, the resonance frequencies of resonant modes are increased, giving rise to a remarkable modification of the band gaps, while the geometry of the structure is nearly unchanged.

EM-Wave Diffraction by a Finite Plate with Dirichlet Conditions in the Ionosphere of Cold Plasma

In the current communication, the problem of plane wave diffraction by a conductible plate of finite length in the presence of cold plasma is investigated. The boundary-value problem corresponding to this model is formulated by Fourier transform which then leads to the Wiener−Hopf equation. The resulting equation has been solved by the Wiener−Hopf procedure in a standard way. The separated field (diffracted field) is analyzed in an anisotropic medium using asymptotic expansion and modified stationary phase method. The problem can be made simple by assuming e2→0, where e2 is the element of permittivity tensor. This happens, if the operating frequency is assumed to be very large as compared to ωc (cyclotron frequency) while it is of same order of ωp (the plasma frequency). The case e1 =1, e2→0 leads to the results for soft plate of finite length in an isotropic medium. Graphical study is performed to investigate the behavior of separated field for various physical parameters for isotropic and anisotropic media.

Aramid fabric/nano-size dual phase shear thickening fluid composites response to ballistic impact

The dual phase STF is a combination of nanosilica and calcium carbonate dispersed in polyethylene glycol and ethanol. Its assimilation into aramid fibers has been accomplished through a combination of ultrasonic dispersion and airbrush. This technique led to an increase of the inter-yarn friction and the projectile’s deformation. It also led to an increase on damaged layers, but at same time, the trauma cavity volume was reduced. From the ballistic tests performed, the 25% w/w nanosilica and 75% w/w calcium carbonate (STF4) combination obtained the best result. The work done by the soft ballistic plate into the body’s tissue was reduced by 40% with the same ballistic protection of traditional bullet proof vests. A 19 layers of aramid fibers impregnated with STF4 proved to have the same ballistic performance of a traditional 32 layers of aramid fibers bullet proof vest.

Wrinkles in soft dielectric plates

We show that a smooth giant voltage actuation of soft dielectric plates is not easily obtained in practice. In principle one can exploit, through pre-deformation, the snap-through behavior of their loading curve to deliver a large stretch prior to electric breakdown. However, we demonstrate here that even in this favorable scenario, the soft dielectric is likely to first encounter the plate wrinkling phenomenon, as modeled by the onset of small-amplitude sinusoidal perturbations on its faces. We provide an explicit treatment of this incremental boundary value problem. We also derive closed-form expressions for the two limit cases of very thin membranes (with vanishing thickness) and of thick plates (with thickness comparable to or greater than the wavelength of the perturbation). We treat explicitly examples of ideal dielectric free energy functions (where the mechanical part is of the neo-Hookean, Mooney–Rivlin or Gent form) and of dielectrics exhibiting polarization saturation. In addition to the expected buckling mode coming from the purely elastic case, we discover a second mode occurring at large voltages in extension. We find that plates always wrinkle anti-symmetrically, before the symmetric modes can be reached. Finally, we make the link with the classical results of the Hessian electro-mechanical instability criterion and of Euler buckling for an elastic column.

Non-invasive Raman identification of crystalline and glassy phases in a 1781 Sèvres Royal Factory soft paste porcelain plate

A Raman study of a Sèvres soft paste (frit) porcelain plate allowed the identification of both the crystalline and amorphous phases. Cristobalite and pseudowollastonite gave main Raman signatures in the body where also tridymite, amorphous alkali silicate glass and lead arsenate apatite were detected. Na0.4K0.1Ca0.5Pb4(AsO4)3 lacunar apatite is identified as opacifier in blue and green overglaze enamel. Pb-Sb-reach pyrochlore (Naples Yellow) pigment was found in yellow and green overglaze enamels. The orange hue is obtained by superposing a hematite bearing red paint stroke over the yellow. These results are compared to those previously obtained by detailed OM, SEM, XRD and XRF analyses. Some of the phases identified by XRD (quartz, tridymite) are hardly detected by Raman and vice versa cristobalite was not found by XRD, most probably due to its low amount.