Single Bend Research Articles

From single to multi-stage forming process of copper thin sheet

In the electronics industry sector, different types of parts made out of copper alloys are used, such as metal supports (lead frames), on which the chips are assembled. These parts are produced using progressive dies, with several blanking and bending stages. There is a huge interest to numerically predict these multistage forming processes, to decrease design time and to anticipate production problems such as non-compliance with dimensional tolerances depending on the material used. This paper deals with the progressive forming of copper parts with single and multi-stage process coupled with experimental and numerical approaches for bending operations. The main contribution of this study is the design of a single stage bending tool for rectangular samples representative of multi-stage industrial processes, providing a relevant experimental database for numerical model validation. This device is based on the technology of progressive dies, though it allows the production of one part at a time. Instrumentation provides local load and displacement and an experimental database is built for Cu-ETP R290 copper strip. A multi-stage bending industrial process dedicated to the manufacturing of electrical contacts is also considered in this study. Numerical models of both single and multi-stage processes are developed, with a focus on the technological importance of a cam slider for the industrial process. The results show that the bending force is mainly influenced by the sample width. In addition, numerical models for the rectangular geometries capture some of the trends from the experiment such as the proportionality of the maximum force with the bent width. Overall, the models are able to predict springback within the process tolerance. Finally, comparison of one stage of the bending sequence with the single stage bending model showed that the single model approach gives similar results in terms of load and plastic deformation.

Nonlinear soliton spiral induces coupled multimode dynamics in multi-stable dissipative metamaterials

With the robust and self-trapped properties, recent advances about soliton dynamics in multi-stable mechanical metamaterials have led to many innovative techniques from signal processing to robotics. This work proposes a multi-stable mechanical metamaterial driven by nonlinear dissipative solitons, in which the coupling and decoupling of multiple locomotion modes can be achieved. Based on a cylinder network with asymmetric energy landscape, the uniform field model of Landau theory is developed. During the theoretical calculation, the analytical solutions of several dissipative solitons are derived, which allow multiple special behaviors of solitary waves, such as wave velocity gaps, directional propagation and spiral phase transition. By incorporating such effects into robotic designs, a variety of complex movements can be achieved by a single structure, including hopping, rolling, rotating, swinging, bending and translational components. In particular, as excitation positions change, the mechanical metamaterial can flexibly switch multiple locomotion modes without changing configurations, e.g., spinning and spin-less, straight and oblique as well as coupled multimode movements. This work wishes to provide some new inspirations for the applications of nonlinear elastic wave metamaterials and phase transition theory in robotics.

Experimental and numerical studies on the propagation paths of gear root cracks

Gear bending fatigue failure has a significant impact on the operational performance of advanced machinery, such as electric vehicles and wind turbines, potentially leading to failures and catastrophic consequences for transmission systems. Several methods are currently used to predict gear crack propagation; however, a comprehensive comparison of their accuracy and efficiency in predicting crack paths is lacking. In this study, the propagation path of root cracks in commonly used automotive gears was investigated using finite element (FE) analysis and experimental testing. Three mixed crack path prediction criteria were integrated to predict the gear root crack propagation using the commercial software ABAQUS by user-defined Python script. The impacts of gear crack parameters, including the gear initial crack length, on gear root crack propagation behaviour were analysed. The simulations were verified by the gear bending fatigue test using a single tooth bending test device. The results indicate that the simulation outcomes align with the experimental tests, demonstrating that all three criteria are effective in predicting gear root crack propagation behaviours.

Toughening Immiscible Polymer Blends: The Role of Interface-Crystallization-Induced Compatibilization Explored Through Nanoscale Visualization.

This study explores the novel approach of interface-crystallization-induced compatibilization (ICIC) via stereocomplexation as a promising method to improve the interfacial strength in thermodynamically immiscible polymers. Herein, two distinct reactive interfacial compatibilizers, poly(styrene-co-glycidyl methacrylate)-graft-poly(l-lactic acid) (SAL) and poly(styrene-co-glycidyl methacrylate)-graft-poly(d-lactic acid) (SAD) are synthesized via reactive melt blending in an integrated grafting and blending process. This approach is demonstrated to enhance the interfacial strength of immiscible polyvinylidene fluoride/poly l-lactic acid (PVDF/PLLA) 50/50 blends via ICIC. IR nanoimaging indicates a cocontinuous morphology in the blends. The blend compatibilized with SAD exhibits a higher storage modulus, as unveiled by small amplitude oscillatory shear (SAOS) in the melt state at a temperature below the melting temperature of the stereocomplex (SC) crystals and by DMTA measurements in the solid state. This increase is attributed to the formation of a 200-300 nm thick rigid interfacial SC crystalline layer that is directly visible using AFM imaging and chemically characterized via IR nanospectroscopy. This ICIC also results in a significant toughening of the blend, with the elongation at break increasing more than 20-fold. Moreover, the fracture toughness factor obtained from single edge-notch bending (SENB) tests is doubled with ICIC as compared to the uncompatibilized blend, indicating the strong crack-resistance capability as a result of ICIC. This improvement is also evident in SEM images, where thinner and longer fibrillation is observed on the fractured surface in the presence of ICIC.

An experimental and numerical study on chloride transport in concrete under single bending load and coastal soft soil environment

This paper presents an experimental and numerical simulation study on the corrosion of chloride ions in concrete components, using a single pre-applied bending load to represent an additional bending moment caused by an external one-off disturbance. Besides, a novel correlation testing method, the Pearson-Mutual Information (PMI) method, is proposed based on Pearson correlation coefficients and mutual information theory. The findings indicate that a significant effect on chloride ion transport is only observed when the ratio of the applied bending load to the ultimate bending load (λ) exceeds 0.3. There is a distinctly positive and nonlinear relationship between λ and free chloride concentration (CCl), the apparent chloride diffusion coefficient (Da), as well as apparent surface chloride concentration (Cs). The bivariate time-varying model developed in this study demonstrates high fitting accuracy, with simulation results that closely correspond to actual measured data, achieving a coefficient of determination (R²) of 0.98 or higher. Furthermore, a sensitivity analysis of the model input parameters indicates that Cs is more sensitive than Da, and λ is identified as the key parameter. The impacts of the interfacial transition zone (ITZ) and its diffusion coefficient (Ditz) were found to be minimal on the output of the model.

Moment Gradient Factor Verification for Selected Monosymmetric Beams under Linear Moment Gradients

The reuse of doubly symmetric beams by converting them into monosymmetric section beams offers some promising outcomes and has potential for mitigating carbon footprint of structures. However, due to their complexity monosymmetric sections must be used in a configuration that allows the monosymmetry effects to act beneficially. Although the South African design standard for hot-rolled steel does not provide any guidance on the design of monosymmetric beams, the Southern African steel construction handbook provides a formula for determining the critical elastic buckling moment for monosymmetric beams. This guidance implies that the moment gradient factor used for doubly symmetric sections can be used on monosymmetric sections as well. The aim of the study was to verify the validity of this approach of extending the moment gradient factor used for doubly symmetric beams to monosymmetric beams for two specific types of monosymmetric sections. It was found that although this approach appears to be justified for monosymmetric members in single curvature bending it may produce unconservative values of the critical buckling load in double curvature bending between restraint points. The level of un-conservatism also varies for different spans of the same member. This makes it difficult to specify a single moment modification factor value for these cases. The sensitivity in terms of load reduction observed for double curvature bending case was different for the two members examined with this attributed to differences in how the shear centre moves relative to the centroid. It is recommended that the critical buckling load for monosymmetric sections be determined on a case specific basis for members in double curvature from linear moment gradients. Under single curvature bending the moment gradient factor for doubly symmetric members appears to give acceptable predictions of the critical load.

Experimental response of a fusible PVC pipe with service connections to axial pullout

This paper investigates the axial pullout response of a fusible polyvinyl chloride (FPVC) main pipe with two service connections. A large-scale pullout experiment in dense sand was conducted to investigate the behaviour of service lines to axial pullout of the main pipe and the impact of service connections on the main pipe’s axial pullout resistance, axial force distribution, and moment distribution. The study assesses the response of both crosslinked polyethylene (PEX) and copper service lines as well as the role of goosenecks. Distributed fibre optic sensors (DFOS) have provided insight into the strain distributions along the main pipe and service lines. The experimental results have shown that service connections significantly increase the axial pullout resistance of the main pipe when compared to a previous test on an identical pipe without service connections. The movement of the service connections was found to reduce the earth pressure in a region behind the service connection. Hinging of the service saddles was observed to result in single curvature bending of the service lines. DFOS data along the main pipe has been used to approximate the individual load-displacement responses of the PEX and copper service connections.

Characteristics of thalweg profile and cross-sectional geometry along alluvial river bends

ABSTRACT River bends have always drawn attention for their complicated hydraulic, geometric and migration nature. Laboratory as well as field experiments have been carried out to study the geometric behaviour of channel bends. This study aims to analyse the nature of the thalweg profile, longitudinal and transverse slope and distribution of depth in the cross-sectional geometry of both single and consecutive double bends of the channel. In the single bend, the thalweg approaches to the outer bank and becomes closest after the apex of the bend whereas in the successive bends of a double bend, the thalweg is closest before the apex of the bend. These results indicate that the thalweg of a bend depends on the previous consecutive bend. The longitudinal slopes vary periodically along the river bend creating the deepest pool before the apex of the bend. The centre line transverse slope varies periodically; however, the outer transverse slope with respect to the thalweg is maximum where the thalweg is closest to the outer bank. The thalweg and outer quarter line to centre line depth ratio is higher before the apex and reduces after the apex of the bend. The inner quarter line to centre line depth ratio varies periodically with a relatively smaller amplitude.

Modelling and analysis of long floating hose string at different working states during the pumping ashore process

ABSTRACT During the pumping ashore process, a long floating hose string connects with the shoreline and the other end either free-floating or linking a Trailing Suction Hopper Dredger (TSHD), which suffered both motions of the TSHD and itself under the wind, wave and currents. It is necessary to evaluate the dynamics of the floating hose string to ensure its reliability because their deformation in waves matter the inside slurry flow transportation and may suffer unexpected damaged during the operation and even cause the project delay. Although the composite structure of the dredging hoses can refer to the floating hoses in offshore oil transportation, the bending stiffness, long-distance behaviour and coupling with the motions of the ship and the hose string bring new challenges for modelling and solving. In order to solve the problems, in this study, a numerical model of kilometres-long floating hose string with mechanical properties of the composite hose materials is established with single hose segment bending test data, macro model with lumped mass theory, dynamics of the hose string and coupling analysis with the ship motions. The dynamic performance of kilometres-long floating hoses during the free-floating state and connected TSHD for pumping state with different angles of wind, current, and wave are investigated. The analyses indicate that axial tensions and bending moments of the first 100 m and last 200 m of floating hose string should be noticed, and the amplitude of the tensions remain low and relatively stable when the 60° incoming wave to the ship, which is a better choice in practical operation. Finally, the effects of different sea conditions and lengths of hose string are carried out. The nonlinear geometry and forces of different lengths’ floating hoses during the pumping ashore process were obtained for practical operation reference. Results can help to evaluate long-distance floating hose motions under different sea conditions and provide practical operation suggestions for the working process.

Galerkin boundary method for static analysis of single thin mitered bend

The problem of a single unreinforced thin-walled mitered bend under static loading (inner pressure or bending in-plane moment) is examined. Despite its age and long history, few practically efficient developments have been made for this problem. The essence of current solution consists in consideration of the stress-strain state of a straight thin cylindrical shell and projecting its inner forces onto the miter plane. All parameters of the shell are expanded into Fourier series with respect to circumferential coordinate. Analytical expressions for eigenfunctions of the shell are found using the decoupling procedure. Then, boundary conditions are satisfied by the Galerkin boundary method. Comparison with known theoretical and FEA results shows great efficiency of proposed approach.

Dual-Function Wearable Hydrogel Optical Fiber for Monitoring Posture and Sweat pH.

In recent years, wearable devices have been widely used for human health monitoring. Such monitoring predominantly relies on the principles of optics and electronics. However, electronic detection is susceptible to electromagnetic interference, and traditional optical fiber detection is limited in functionality and unable to simultaneously detect both physical and chemical signals. Hence, a wearable, embedded asymmetric color-blocked optical fiber sensor based on a hydrogel has been developed. Its sensing principle is grounded in the total internal reflection within the optical fiber. The method for posture sensing involves changes in the light path due to fiber bending with color blocks providing wavelength-selective modulation by absorption changes. Sweat pH sensing is facilitated by variations in fluorescence intensity triggered by sweat-induced conformational changes in Rhodamine B. With just one fiber, it achieves both physical and chemical signal detection. Fabricated using a molding technique, this fiber boasts excellent biocompatibility and can accurately discern single and multiple bending points, with a recognition range of 0-90° for a single segment, a detection limit of 0.02 mm-1 and a sweat pH sensing linear regression R2 of 0.993, alongside great light propagation properties (-0.6 dB·cm-1). With its extensive capabilities, it holds promise for applications in medical monitoring.

Investigation on the Torsional–Flexural Instability Phenomena during the Bending Process of Hairpin Windings: Experimental Tests and FE Model Validation

Modern electric motors developed for the automotive industry have an ever higher power density with a relatively compact size. Among the various existing solutions to improve torque and power density, a reduction in the dimensions of the end-windings has been explored, aiming to decrease volume, weight, and losses. However, more compact end-windings often lead to complex shapes of the conductors, especially when preformed hairpin windings are considered. The rectangular cross-section of hairpin conductors makes them prone to deviating out of the bending plane during the forming process. This phenomenon, known as torsional–flexural instability, is influenced by the specific aspect ratio of the cross-section dimensions and the bending direction. This study focuses on understanding this instability phenomenon, aiming to identify a potential threshold of the cross-section aspect ratio. The instability makes it difficult to predict the final geometry, potentially compromising the compliance with the geometric tolerances. A finite element model is developed to analyse a single planar bend in a hairpin conductor. Various cross-section dimensions with different aspect ratios are simulated identifying those that experience instability. Moreover, an experimental campaign is conducted to confirm the occurrence of instability by testing the same single planar bending. The experimental data obtained are used to validate the finite element model for the tested dimensions. The aim is to provide designers with a useful tool to select hairpin geometries that are more suitable for the folding process, contributing to successful assembly and improving the overall design process of preformed hairpin conductors.

Single-Material Solvent-Driven Polydimethylsiloxane Sponge Bending Actuators.

Soft robots mimic the agility of living organisms without rigid joints and muscles. Continuum bending (CB) is one type of motion living organisms can display. CB can be achieved using pneumatic, electroactive, or thermal actuators prepared by casting an active layer on a passive layer. The corresponding input actuates only the active layer in the assembly resulting in the bending of the structure. These two different layers must be laminated well during manufacturing. However, the formed bilayer can still delaminate later, and the detachment hampers the actuator's reversible, long-time use. An approach to creating a single material bending actuator was previously reported, for which spatial gradient swelling was used. This authentic approach allows a single material to be manufactured as a bending actuator, allowing easy access to such actuators without lamination. In this study, we show spatial porosity differences in the sponges of polydimethylsiloxane (PDMS) (a common material in soft robotics) can be used to create the required anisotropy for bending. The spongy polymers are manufactured through table sugar templates and actuated by (organic) solvent absorption/desorption. This enables some versatility in the mechanical properties, shape, actuation force, and actuation speed. The one-material system's straightforward production and seamless nature are advantageous for reversible and repetitive bending. This simple method can further be developed in hydrogels and polymers for soft robotics and functional materials.

Influence of air DBD plasma treatment on the shear and flexural strength of adhesively bonded glass fiber reinforced epoxy composite joints

In this study, air dielectric barrier discharge (DBD) plasma treatment was applied at various voltages and treatment durations to improve the bonding strength of glass fiber reinforced epoxy composites (GF/EP). In addition, single lap shear and three-point bending strengths of adhesively bonded joints were compared between untreated and surface-treated (sanding, peel ply, and plasma) samples. Surface properties of GF/EP composites were examined using contact angle, surface free energy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and Atomic Force Microscopy (AFM). Then, mechanical tests (single lap shear and three point bending) were performed and the damage modes were determined. Surface analyses revealed that wettability and polar functional groups increased on the GF/EP surface after plasma treatment. From the mechanical test results, it was observed that the plasma treatment applied to GF/EP composites increased both single lap shear and flexural strength compared to untreated, sanding and peel ply surface treatments. After both single lap shear and 3-point bending tests, adhesive, and light fiber tear failure modes were observed.

One‐Step Photo‐Patterning Process for Multi‐Modal and Transformative Structural Coloration: Toward Anti‐Counterfeiting Applications

AbstractThe selective interactions of light with matter enable the existence of colors in nature. Through the precise modification of material properties, photonic crystals, plasmonic nanoparticles, and dielectric metasurfaces can produce bright and vivid structural colors. However, this approach is rendered inadequate by its complex fabrication processes, limited working area, and lack of inherent material‐property tuning. Here, a novel one‐step fabrication process based on ultraviolet‐curable chitosan (UVCC) for generating structural multicolor patterns in polydimethylsiloxane in a single bending event is presented. UV exposure through a grayscale photomask controls the polymerization of the UVCC, enabling manipulation of its thickness, thereby allowing the production of size‐, wavelength‐, and amplitude‐controllable wrinkles under compressive stress. This enables the exhibition of selective structural coloration in response to incoming incident light. Upon the release of applied stresses, the wrinkles disappear, and the bilayer device becomes transparent again. Notably, repeating the process allows for dynamic covert–overt switching of the structural colors. This firm control over the active‐layer thickness, simple device structure, cost‐effectiveness, facile fabrication process, and vibrant‐color tuning ability make this one‐step photopatterning approach more competitive for structural‐color applications. Finally, the authenticity of a cosmetic cream is evaluated to demonstrate the anti‐counterfeiting effect of the UVCC circumference wrinkles.

Single Curvature Bending of Structural Stitched Textile Reinforcements Part I: Experimental Work

Aerospace structural components made from polymer matrix composites (PMCs) offer numerous advantages. Their high stiffness and high strength combined with low densities enable lower fuel consumption coupled with higher payloads. As a result, PMCs provide an important economic advantage over typical metallic airframes. Textile reinforcements for PMCs are made by assembling reinforcement fibres, typically carbon. Then, the textile reinforcements are typically cut into smaller pieces, stacked, draped and assembled into a dry assembly called a preform, the shape of which generally approaches that of the PMC part to be made. This manufacturing process is labour intensive and expensive.Novel thick, net-shape, drapable, high fibre volume fraction (vf) textile reinforcements used toward manufacturing aerospace PMCs are being developed at the University of Ottawa. The technology enables the manufacturing of flat, drapable multilayered near net-shape preforms. The bending and in-plane shear behaviours of such novel thick reinforcement textiles was investigated to understand and define the behaviour of such thick fabric reinforcements when formed into required shapes. A bending apparatus was developed for investigating the bending behaviour of these novel thick reinforcement fabrics.

Influence of layering sequence on performance of jute/wool epoxy hybrid composites: a comparative study with automotive plastic

Natural fibres such as Jute and Wool are increasingly being used in fibre reinforced polymer composites, hence progressively supplanting synthetic fibres. Combining these two unique natural fibers would improve the performance of composites used in secondary structural applications. This study is intended to investigate the effects of Jute and Wool fiber arrangement on mechanical properties in an epoxy matrix. In order to achieve this, hand layup was employed to fabricate composite laminates consisting of four layered fabric layers stacked in sequences, as Jute/Wool/Wool/Jute (JW1), Wool/Jute/Jute/Wool (JW2), Jute/Wool/Jute/Wool (JW3), and Jute/Jute/Wool/Wool (JW4). Effect of these stacking sequences on the properties of Natural Fibre Hybrid Composites (NFHCs) was evaluated by conducting a series of standardized tests such as Flexural, Interlaminar Shear Strength (ILSS), Impact and Single End Notch Bend (SENB) tests, as per ASTM standards. On the other hand an automobile interior thermoplastic material was evaluated for different mechanical properties and compared with hybrid Jute-Wool composite. Experimental results showed that the JW1 composite, exhibited superior mechanical properties because it has tailored with a Wool fabric at the core and Jute fabric on its outer surface. Hence, JW1 had a remarkable tensile strength of 40 MPa, a maximum flexural strength of 99 MPa and extremely high interlaminar shear strength (ILSS) of 3.09 MPa. In addition to this, JW1 also had high fracture toughness, measuring around 72 M P a m 1 /2, and impressive impact strength of 85 J/m2. Furthermore, scanning electron microscope (SEM) photo images confirmed that the presence of strong bonding between the fibres and matrix in JW1 composite exhibited and overall improvement of mechanical performance by 82% when compared with other combinations (JW2, JW3, and JW4) including automotive plastics.

CSR-induced Projected Emittance Growth Study For The Beam Switchyard At The European XFEL

Minimizing projected emittance of high brightness electron beam is important for efficient overlap between electron beam and radiation pulse in an FEL facility. Coherent synchrotron radiation (CSR) emission in a single bending section in the beam transport system usually introduces different slice energy modulation hence different slice transverse kicks in the designed dispersion-free lattice, causing projected emittance growth. Here we present theoretical and simulation study of CSR effect on the projected emittance growth in the beam switchyard arc before SASE2 undulator beamline at the European XFEL. We analyze arc optics impact on CSR effect and discuss possible schemes for emittance degradation compensation.

Dynamic modeling and stress reduction optimization of parallel pipelines based on pipe-solid element coupling

In aero-engine, spatially parallel pipelines are prone to damage under the harmonic excitation produced by rotors, thus there is an urgent need for vibration reduction research. This paper presents a finite element modeling method for parallel pipelines based on pipe-solid element coupling and performs clamp layout optimization with the objective of reducing the stress response. The modeling idea can be described as follows: the regions of the pipeline with higher stress, such as single and dual clamps and bend sections, are modeled using solid elements, while other regions are modeled using pipe elements, and the different parts are coupled together to complete the overall modeling. An optimization model is created with clamp positions as design variables and the objective function is set as reducing stress response under the resonance condition of the fundamental frequency excitation. The procedure for solving the optimization model is provided based on genetic algorithms. A case study is conducted on a parallel pipeline system with one dual clamp and four single clamps. The rationality of the created spatial parallel pipeline model based on pipe-solid element coupling is demonstrated through a constructed pipeline test system. The model is shown to provide sufficient accuracy while having higher computational efficiency compared with a full 3D solid element model. Furthermore, the stress reduction optimization is performed, and a clamp layout that minimizes the maximum resonant stress of the parallel pipeline system is obtained.

Nonlinear finite element analysis of partially encased composite columns under non-uniform moments

This paper presents a numerical investigation to evaluate the behavior of partially encased composite (PEC) columns with compact sections of three different heights submitted to non-uniform moment distribution. A 3D finite element model developed using the software ABAQUS was calibrated based on results from previous experimental research. The influence of concrete constitutive model parameters, column slenderness, load eccentricities, and moment distribution along height was investigated. The parametric study showed that constant moment distribution (case 1) is the most critical compared to linear moment variation (cases 2 and 3). This pattern is a direct consequence of the larger displacements at the mid-height section that causes higher second-order moments in the case 1 column. Long columns activated more confinement when a single curvature bending moment was applied at a minor axis. An increase in slenderness decreased the load capacity for non-uniform bending moments through the major axis.