Free Bending Research Articles

Mechanical Characterization of Ultra-Thin, Flexible Glass Substrates for RF Applications

Glass has been shown to be a capable core substrate material for high-frequency applications. In this article, we examine the capabilities of ultra-thin glass as a material that can be used for high-frequency flexible applications. The two stack-ups discussed in the work presented are 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> in total thickness with a core glass substrate (Schott AF32) of 30 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> thickness. One stack-up uses 15 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> JSR GT-N01 as a buildup dielectric on each side of the glass and the other uses 15 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> Taiyo Ink photo imageable dielectric (PID). Both stack-ups have been characterized to 110 GHz and have shown to have comparable performance to materials used in this frequency range. This work then focuses on the mechanical characterization of these stack-ups using free arc bending. The free arc bending tests show that both ultra-thin glass stack-ups are suitable for bending applications as the tested samples can bend to a panel separation below 33% of the sample’s total length. This article concludes that the ultra-thin glass stack-ups are suitable for high-frequency flexible applications because the electrical performance is comparable to other high-frequency rigid materials while exhibiting their flexible capabilities.

A series of multi-domain matched interface and boundary algorithms for dynamic and static responses of annular sectorial plates

A series of multi-domain matched interface and boundary (MDMIB) algorithms are proposed to analyze the free vibration and bending of annular sectorial thin plates. Through an in-depth understanding of the matched interface and boundary (MIB) method, six types of MDMIB algorithms are developed herein by using various domain decomposition techniques for handling bi-directional crossing interfaces due to non-homogeneous elastic foundations and discontinuous loads, which cannot be treated by the conventional MIB method. The rationale of the MDMIB method is to divide the entire computational domain into multiple subdomains that can be connected by using the interconnecting conditions between crossing interfaces and mesh lines. Annular sectorial plates, having non-uniform boundary conditions, partially supported elastic foundations, and patch loads, are all considered. Numerous examples are chosen to examine the computational performance of the MDMIB algorithms. For verification, the present results are checked against existing and finite element solutions. It is shown that the proposed MDMIB algorithms are highly effective to deal with the bi-directional interface problems.

Multiphysical Analytical Modeling and Design of A Magnetically Steerable Robotic Catheter for Treatment of Peripheral Artery Disease.

This article presents a unique multiphysical analytical modeling framework and solution algorithm to provide an effective tool for design of magnetically steerable robotic catheters (MSRCs) experiencing external interaction loads. Particularly, in this study, we are interested in design and fabrication of a MSRC with flexural patterns for treatment of peripheral artery disease (PAD). Aside from the parameters involved in the magnetic actuation system and the external interaction loads acting on the MSRC, the considered flexural patterns have a critical role on the deformation behavior and steerability of the proposed MSRC. Therefore, to optimally design such MSRC, we utilized the proposed multiphysical modeling approach and thoroughly evaluated the influence of involved parameters on the performance of the MSRC via two simulations studies. We also conducted experimental studies in a free bending condition and in the presence of different external interaction loads on two custom-designed MSRCs to thoroughly evaluate the efficacy of the proposed multiphysical model and solution algorithm. Our analysis demonstrates the accuracy of the proposed approach and necessity of utilizing such models to optimally design a MSRC before fabrication procedure.

Equilibrium Conformation of a Novel Cable-Driven Snake-Arm Robot under External Loads.

Based on the anti-parallelogram mechanism, an approximate cylindrical rolling joint is proposed to develop a novel cable-driven snake-arm robot with multiple degrees of freedom (DOF). Furthermore, the kinematics of the cable-driven snake-arm robot are established, and the mapping between actuator space and joint space is simplified by bending decoupling motion in the multiple segments. The workspace and bending configurations of the robot are obtained. The static model is established by the principle of minimum potential energy. Furthermore, the simplified cable constraints in the static model are proposed through Taylor expansion, which facilitates the equilibrium conformation analysis of the robot under different external forces. The cable-driven snake-arm robot prototype is developed to verify the feasibility of the robot design and the availability of the static model through the experiments of the free bending motion and the external load on the robot.

Free vibration and bending of one-dimensional quasicrystal layered composite beams by using the state space and differential quadrature approach

Free vibration and bending of one-dimensional quasicrystal layered composite beams by using the state space and differential quadrature approach

Free in-plane bending vibration of flexible L-shaped nanostructures based on the nonlocal beam theory

Free in-plane bending vibration of flexible L-shaped nanostructures based on the nonlocal beam theory

Six-axis free bending and twisting analysis of spiral square tube

Six-axis free bending and twisting (6FBT) technology enables the integral forming of square tube components with complex shapes. However, the process analysis method and the deformation behavior of square tube spiral components in the bending and twisting process have not been investigated. In this paper, an analytical model of the bending die trajectory suitable for one-time forming of square tube spiral components is proposed and verified by FE simulations and experiments. In this model, the bending direction of the component axis is changed continuously by adding an additional cross section torsion angle in the bending process of the square tube, and then the spiral member is formed. This paper further reveals the laws of stress, strain, wall thickness distribution and cross section distortion of 304 stainless steel square tube spiral components in the 6FBT process. The results show that during the forming process, the equivalent stress on the edge of the square tube is greater than that on the surface, the wall thickness reduction on each cross section only occurs on the outside of the bent, and the section distortion between the inside and outside of the bent is larger than that between the inside and outside of the twist.

Mechanical Modeling of Tube Bending Considering Elastoplastic Evolution of Tube Cross-Section.

Aluminum alloy tubes are widely used in various industries because of their excellent performance. Up to now, when the tube is bent, the elastoplastic deformation evolution mechanism of the cross-section has not been clear, and no direct analytical proof has been found. In this paper, based on the bilinear material model assumption, a new mechanical model of tube plane bending deformation is constructed. The analytical model can describe in detail the evolution mechanism of elastic–plastic deformation on the cross-section of the tube after bending deformation, the position of the elastic–plastic boundary, the position of the radius of the strain neutral layer, and the relationship between the bending moment over the section and the bending radius. According to this model, the deformation law of the tube cross-section during bending is elucidated. The results are as follows: (1) the deformation evolution of the cross-section of the bending deformed tube calculated by the analytical model is in good agreement with the finite element model (FEM) of pure bending. (2) By comparing the results of the analytical model with FEM results, and the processing test of the self-designed four-axis free bending forming tube bender, the bending moments are in good agreement. (3) Compared with the bending moments calculated by several other analytical models of tube bending, this model has a relatively small deviation value.

Bending Behavior of a Frictional Single-Layered Spiral Strand Subjected to Multi-Axial Loads: Numerical and Experimental Investigation

Bending deformation gives rise to interwire slippage for spiral strands subjected to multi-axial loads, and further induces wear or fatigue phenomena in practice. The interwire friction would resist bending deformation and lead to uneven tension distribution of individual constituent wires but little research has quantified these effects. To figure out this issue, a beam finite element (FE) is established, into which a penalty stiffness algorithm and a Coulomb friction model are incorporated. A series of free bending simulations are developed for parametric study on deflection near the terminations and tension distribution of individual wire for strands with different levels of length and friction coefficient as well as external loads. Based on the simulation results, it is found that strand length has little influence on bending deformation and tension distribution if the strand length exceeds six times the pitch length. A deflection formula extended from the classical Euler beam model well predicts the sag deflections and the relative error with respect to experimental measurements is less than 10%. Furthermore, additional axial tension induced by the friction is clearly characterized and an approximate expression is proposed to estimate tension distribution for outer layer wires. Its predictions are encouraging for longer strands.

NURBS-based refined plate theory for metal foam plates with porosities

In this article, the free vibration, bending, and transient analyses of the porous metal foam plate via an isogeometric analysis (IGA) are investigated. Three types of porosity distributions across the thickness of the metal foam plate including uniform, symmetric and asymmetric are inspected. The refined higher-order shear deformation theory is utilized to reduce one variable as comparing to the higher-order shear deformation theory. The present theory without using shear correction factors overcomes the shear locking phenomenon. The governing equations of the porous metal foam plate are obtained by using the Hamilton’s principle and then solved by isogeometric analysis to determine natural frequencies, deflections and dynamic responses. The effects of different parameters including porosity distributions, porosity coefficient, length–thickness ratios and boundary conditions on the frequencies, deflections and dynamic responses of the metal foam plate are studied. The numerical results show that an increase of the porous coefficient leads to a decline of frequencies and a rise of displacements of the plate. Key findings can be given for manufacturing metal foam structures.

Stabilization of flavin mononucleotide by capturing its “tail” with porous organic polymers for long-term photocatalytic degradation of micropollutants

Flavin mononucleotide (FMN) produces photo-induced reactive oxygen species (ROS), making it a bio-based and sustainable photosensitizer for micropollutant degradation. However, the rapid self-degradation of FMN under light poses challenges in practical applications. We propose for the first time to use porous organic polymer (POP) structures as particles and in situ grown on nanofibrous membranes to capture the ribityl side chain (“tail”) of FMN by electrostatic-driven guest-host interaction. By restraining the free bending mode of FMN in POP, its self-degradation is highly inhibited, showing a prolonged half-life (102.7 and 79.7 times to that in solution and in β-cyclodextrin, respectively) without any impact on the ROS production even after 16 h of UVA irradiation. As a proof-of-concept, the photocatalytic degradation efficiency of FMN-POP complexes can be achieved at 58–93% against micropollutants under UVA. The stabilization of FMN by the “tail” capture in the POP allows its photocatalytic degradation function to be continuously online.

A Stepwise Guide to Freehand Bending of Orbital Floor Mesh.

Summary:Orbital fractures can often result in enophthalmos or diplopia. Orbital reconstruction with titanium meshes is the current treatment modality. Adapting the titanium orbital floor mesh is often challenging due to the complex anatomy of the orbital floor. Here, a stepwise free hand bending technique of a titanium orbital floor mesh is described. The bending can be done preoperatively, and mesh fit can be checked against a dry anatomical skull before sterilization. The methodical approach to free hand bending of titanium orbital floor mesh minimizes the intraoperative adjustments and permits quick orbital reconstruction. Trainees and less-experienced surgeons can benefit from the methodical approach to free hand bending of titanium orbital floor mesh.

Investigation on the influence of weld position on the deformation behavior of welded tube during free bending process

The plastic deformation behavior of welded tube is affected by the non-uniform distribution of the mechanical properties of welded tube during the free bending process. To explore the influence of weld position on the forming quality and axis dimensional accuracy of welded tube, the free bending experiment and numerical simulation of welded tube were conducted in this paper. First, the principle of free bending was theoretically deduced and the stress distribution of bent tube was analyzed. Then, the hardness test and uniaxial tensile test were conducted to obtain the mechanical properties of weld zone and parent zone of welded tube. The material strength in the weld zone of welded tube is significantly higher than that in the parent zone. Finally, the free bending experiment and numerical simulation with different weld positions were carried out, and the influence of weld position on the bending radius, cross-sectional distortion, and wall thickness of bent tube was discussed. All these findings advance the insight into the free bending deformation behavior of welded tube and help to improve the forming quality of welded tubes and facilitate the application of free bending technology in welded tube.

Data-Driven Kinematic Model of PneuNets Bending Actuators for Soft Grasping Tasks

The paper proposes a novel data-driven approximation kinematic (DAK) model to estimate the shape and opening level of a PneuNets soft gripper in relation to the applied pressure signal. The model offers suitable capabilities for implementing in real-time applications involving soft grasping planning and size recognition of fragile objects with different sizes and shapes. The proposed DAK model estimates the free bending behavior of a PneuNets actuator (soft gripper finger) based on a set of approximation functions derived from experimental data and an equivalent serial mechanism that mimics the shape of the actuator. The model was tested for a commercial PneuNets actuator with decreasing chamber height, produced by SoftGripping Co. (Hamburg, Germany). The model validation is accomplished through a set of experiments, where the shape and elementary displacements were measured using a digital image processing technique. The experimental data and the estimated data from the DAK model were compared and analyzed, respectively. The proposed approach has applicability in sensorless/self-sensing bending control algorithms of PneuNets actuators and in soft grasping applications where the robotic system must estimate the opening level of the gripper in order to be able to accomplish its task.

Influence of Preheating and Postweld Heat Treatment on the Structure and Strength of the Wire Frame Welded Joint Made of Spring Steel C62D

This article investigates the automatic welding of Ø4.5 mm high carbon steel wire frame. Using spring steel wire frame in car seat fabrication reduces its weight and helps to maintain rigidity. The thermal effect during the welding process can unacceptably deteriorate the mechanical properties of the material. It is proposed to use preheating and heat treatment to obtain a joint with required mechanical properties. To reduce of effect on entire product rigidity the thermal treatment was carried out locally in the zone of joining. Heating was carried out using a gas flame. Metallographic and microhardness measurements were used for the structural study. Mechanical properties were evaluated by static tension and free bending test. The recording of thermal cycles during the welding and heat treatment was carried out using chromel-alumel and tungsten-rhenium thermocouples.

Pressure sensor yarns with a sheath-core structure using multi-fiber polymer

Textiles are expected to be used as a platform for soft and flexible electronic devices that closely fit the human body and curved surfaces, which are strongly demanded in our highly networked society. This study presents pressure-sensing double-ply yarns in which two independent conductive yarns are insulated using covering yarns of multi-fiber polymer to form a sheath-core structure. When force is applied to the double-ply yarn, the electric resistance between the two conductive yarns decreases significantly due to the deformations caused by the elasticity of the multi-fiber covering, and the applied force can be detected from the resistance change. The proposed sensor yarn has a distinctive characteristic of being sensitive to compressive and tensile strains but extremely insensitive to free bending without tension. We fabricated fabrics embedded with the sensor yarns and demonstrated that they can sense external forces as well as the sensor yarns, although sensitivity is decreased. These yarns and fabrics can be implemented in soft electronic devices such as wearable devices and biological sensors that must be fitted to human bodies or curved surfaces. This work contributes to the development of smart textiles that can be applied to flexible, wearable electronics.

Поперечный изгиб заготовки прямоугольного сечения при больших пластических деформациях

The technological operation of bending is widely used in the manufacture of various parts — both rod parts, for example, springs of various types, and shell parts, for example, shells and bottoms of petrochemical apparatuses, ship hulls, automobiles, etc. The maximum plastic strains that arise in this case vary over a wide range and can reach quite large values, significantly exceeding the elastic strains. Regardless of the maximum deformation levels, residual stresses occur in the product, affecting its performance. The study of free three-point bending of a workpiece with a rectangular cross section was carried out at different ratios of the radius of the punch contacting cylindrical surface to the height of the workpiece as well as at different ratios of the width to the height of the workpiece. The workpiece material is low-carbon steel with a real (not approximated) deformation diagram. Stress state, cross-sectional shape change and residual stresses are numerically investigated using the finite element method.

Design and evaluation of in-plane silicon microneedles fabricated with post-CMOS compatible processes

In this paper, a comprehensive study was carried out on in-plane silicon (Si) microneedles, a useful tool for transdermal drug delivery and sample collection. Microneedles with eleven designs were investigated by post-complementary metal-oxide-semiconductor (CMOS) compatible microfabrication processes and characterized via pricking tests by insertion in chicken breast flesh. Mechanical strength of all designs were also evaluated by theoretical calculation and finite element modeling (FEM) for bending and buckling analysis. To efficiently improve the sharpness and insertion, the wedge-shaped needle tips with thickness determined by Si wafer thickness were sharpened by a wet chemical etching process. Insertion forces recorded from pricking tests and bending and buckling from theoretical calculation and FEM analysis before and after etching were compared. The results showed that the insertion force, free bending force and the maximum buckling force were all reduced and the maximum bending stress were improved after tip sharpening. Furthermore, the buckling safety factor of all eleven designs was great than 1 and the maximum bending stress was less than the fracture strength of Si, indicating that our in-plane Si microneedles are robust enough for insertion into human skin.

A parametric analysis of free vibration and bending behavior of sandwich beam containing an open-cell metal foam core

A parametric analysis of free vibration and bending behavior of sandwich beam containing an open-cell metal foam core

Force and Microstructure Variation of SLM Prepared AlMgSc Samples during Three-Point Bending.

Lightweight parts manufactured by metal selective laser melting (SLM) are widely applied in machinery industries because of their high specific strength, good energy absorption effect, and complex shape that are difficult to form by mechanical machining. These samples often serve in three-dimensional stress states. However, previous publications mainly focused on the unidirectional tensile/compressive properties of the samples. In this paper, AlMgSc samples with different geometric parameters were prepared by the SLM process, and the variation of force and microstructure during three-point bending were systematically investigated. The results demonstrate that the deformation resistance of these samples has good continuity without mutation in bending, even for brittle materials; the bending force-displacement curves exhibit representative variation stages during the entire bending process; the equivalent bending strength deduced from free bending formula is not applicable when compactability is less than 67%. The variations of grain orientation and size of the three representative bending layers also show regularity.