Flexural Bending Research Articles

A mechanics-based model for predicting flexible needle bending with large curvature in soft tissue

Percutaneous insertion is one of the most common minimally invasive procedures. Compared with traditional straight rigid needles, bevel-tipped flexible needle can generate curved trajectories to avoid obstacles and sensitive organs. However, the nonlinear large deflection problem challenges the bending prediction of the needle, which dramatically influences the surgical success rate. This paper analyzed the mechanism of needle-tissue interaction, and established a mechanics-based model of the needle bending during an insertion. And then, a discretization of the bending model was adopted to accurately predict the large bending of the needle in soft tissue. Insertion experiments were conducted to validate the bending prediction model. The results showed that the large needle bending was predicted with the mean/RMSE/maximumu error of 0.42 mm / 0.26 mm / 1.08 mm, which was clinically acceptable. This proved the rationality and accuracy of the proposed model.

Resonant response of a flexible semi-submersible floating structure: experimental analysis and second-order modelling

The dynamics and nonlinear wave forcing of a flexible floating structure are investigated experimentally and numerically. The floater was designed to match sub-harmonic rigid-body natural frequencies of typical floating wind turbine substructures, with the addition of a flexible bending mode. Experiments were carried out for three sea states with phase-shifted input signals to allow harmonic separation of the measured response. We find for the weakest sea states that sub-harmonic rigid-body motion is driven by even-harmonic difference frequency forcing, and by linear forcing for the strongest sea state. The flexible mode was tested in a soft, linearly forced layout, and a stiff layout, forced by second-, third- and fourth-harmonic frequency content, for increasing severity of the sea state. Further insight is gained by analysis of the amplitude scaling of the resonant response. A new simplified approach is proposed and compared with the recent method of Orszaghova et al. (J. Fluid Mech., vol. 929, 2021, A32). We find that resonant surge and pitch motions are dominated by even-harmonic potential-flow forcing and that odd-harmonic response is mainly potential-flow driven in surge and mainly drag driven in pitch. The measured responses are reproduced numerically with second-order forcing and quadratic drag loads, using a recent and computationally efficient calculation method, extended here for the heave, pitch and flexible motions. We are able to reproduce the response statistics and power spectra for the measurements, including the subharmonic pitch and heave modes and the flexible mode. Deeper analysis reveals that inaccuracies in the even-harmonic forcing content can be compensated by the odd-harmonic loads.

The Relationship Between Leg Explosive Power and Flexibility and Long Jump Ability in Squat Style

This research aims to determine the relationship between leg explosive power and flexibility and long jump ability in squatting style at UPT-SPF students at SD Inpres Panaikang II/1. This research is a descriptive study with one dependent variable, namely squatting long jump ability. The sample in this study consisted of 50 students. The instruments in this study used a long jump test without a start for leg explosive power, a forward bending flexibility test for flexibility data, and a squatting long jump ability test for squatting long jump ability data. Data analysis obtained the following results: (1) There is a relationship between leg explosive power and squatting long jump ability with correction results (r) = -0.451 (P < 0.05). (2) There is a relationship between flexibility and squatting long jump ability with a corrected value (r) = -0.425 (P < 0.05). (3) There is a joint relationship between leg explosive power and flexibility and squatting long jump ability with a corrected value of (R) = 0.496 (P < 0.05) and F value = 7.652 (P value = 0.000 < 0.05).

A Bilayer Method for Measuring Toughness and Strength of Dental Ceramics

The ever-increasing usage of ceramic materials in restorative dentistry necessitates a simple and effective method to evaluate flexural strength σF and fracture toughness KC. We propose a novel method to determine these quantities using a bilayer specimen composed of a brittle plate adhesively bonded onto a transparent polycarbonate substrate. When this bilayer structure is placed under spherical indentation, tunneling radial cracks initiate and propagate in the lower surface of the brittle layer. The failure analysis is based on previous theoretical relationships, which correlate σF with the indentation force P and layer thickness d, and KC with P and mean length of radial cracks. This work examines the accuracy and limitations of this approach using a wide range of contemporary dental ceramic materials. The effect of layer thickness, indenter radius, load level, and length and number of radial cracks are carefully examined. The accuracy of the predicted σF and KC is similar to those obtained with other concurrent test methods, such as biaxial flexure and 3-point bending (σF), and bending specimens with crack-initiation flaws (KC). The benefits of the present approach include treatment for small and thin plates, elimination of the need to introduce a precrack, and avoidance of dealing with local material nonlinearity effects for the KC measurements. Finally, the bilayer configuration resembles occlusal loading of a ceramic restoration (brittle layer) bonded to a posterior tooth (compliant substrate).

Detection and characterisation of defects in composite materials using microwave non-destructive testing methods

This paper proposes a technique for detecting impact-induced surface and subsurface fractures in Glass Fibre Reinforced Composites (GFRPs) and hybrid composite materials. Various categories of composite samples, namely Unidirectional GFRP, Bidirectional GFRP, Woven mat GFRP and Carbon-flax hybrid composites are fabricated by the hand-layup process, and cracks are induced in the samples by three-point flexural bending test using a Universal Testing Machine. Near-field microwave Non-Destructive Testing (NDT) is employed in detecting the above cracks by recording the S11 parameter from the microwave transceiver probe throughout the sample. For image rendering the resulting outputs are passed as a 2-dimensional array to the image-rendering algorithms, namely Iterative Curve-Based Interpolation (ICBI), Improved New Edge-Directed Interpolation (INEDI) and the Lanczos algorithm. The most suitable algorithm to identify the clear picture and size of crack is identified, and the effectiveness of Microwave NDT for these composites is analysed.

Enhancement of Control Stability Using Double Pulleys for Coupled Tendon-Driven Long-Reach Manipulator “Super Dragon”

The exploration and inspection of narrow spaces in nuclear facilities require the use of long-reach manipulators. Coupled tendon-driven manipulators can realize lightweight and slender arms by positioning actuators, such as motors, at the base. Currently, we are developing a coupled tendon-driven super long-reach articulated arm, which we name “Super Dragon.” Super Dragon is a robot arm with a total length of 10 m, a maximum arm diameter of 0.2 m, and 10 joints. In this paper, we focused on the elasticity and elongation of ropes. The joint actuation of Super Dragon utilizes synthetic fiber ropes characterized by their high strength and flexible bending. However, when these ropes are used over long lengths, wire elongation occurs, thus causing the joint angles to exhibit unintended and unstable behavior. Therefore, we focused on a specific posture and employ a double pulley as a mechanical solution to suppress unstable behavior. We introduced stability criteria and performed parametric searches to obtain the appropriate double pulley radii. Subsequently, we identified the position and radius of the introduced double pulley that can be analytically stabilized. By installing a double pulley in the actual machine and conducting experiments, we successfully suppressed the unstable behavior.

Greatly Improved the Tunable Amplitude of Ferromagnetism Based on Interface Effect of Flexible Pt/YIG Heterojunctions.

Flexible quantum spin electronic devices based on ferromagnetic insulators have attracted wide attention due to their outstanding advantages of low-power dissipation and noncontact sensing. However, ferromagnetic insulators, such as monocrystalline yttrium iron garnet (Y3Fe5O12, YIG), hve weak stress effects with a small magnetostrictive coefficient (λ110, 10 ppm), making it difficult to achieve a large magnetic tunable amplitude. In this paper, large-scale (with a diameter of 40 mm), flexible Pt/YIG heterojunctions were obtained by double-cavity magnetron sputtering technology, indicating typical soft magnetism and good bending fatigue characteristics. Here, the 3 nm thickness of the Pt layer triggers an obvious magnetic proximity effect, in which the in-plane ferromagnetic resonance field is decreased by 70 Oe compared to flexible Cu/YIG heterojunctions. Meanwhile, it shows a wide tunable amplitude of 110 Oe under the flexible bending stresses, which is induced by the sensitive interface effect of Pt (3 nm)/YIG heterojunctions. The saturation magnetization of Pt/YIG heterojunctions is negatively correlated with Pt thickness rather than the relative stability of Cu/YIG heterojunctions, depending on the magnetic proximity effect. It brings greater application possibilities for flexible stress-sensitive magnetic oxides in spin logic electronic devices.

Design and Implementation of a Versatile Flexible 3D Wire Bending Machine with Accuracy Algorithm

Design and Implementation of a Versatile Flexible 3D Wire Bending Machine with Accuracy Algorithm

Adaptive pneumatic soft gripper with embedded flexible bending sensor

Purpose The purpose of this paper is to introduce a variable distance pneumatic gripper with embedded flexible sensors, which can effectively grasp fragile and flexible objects. Design/methodology/approach Based on the motion principle of the three-jaw chuck and the pneumatic “fast pneumatic network” (FPN), a variable distance pneumatic holder embedded with a flexible sensor is designed. A structural design plan and preparation process of a soft driver is proposed, using carbon nanotubes as filler in a polyurethane (PU) sponge. A flexible bending sensor based on carbon nanotube materials was produced. A static model of the soft driver cavity was established, and a bending simulation was performed. Based on the designed variable distance soft pneumatic gripper, a real-time monitoring and control system was developed. Combined with the developed pneumatic control system, gripping experiments on objects of different shapes and easily deformable and fragile objects were conducted. Findings In this paper, a variable-distance pneumatic gripper embedded with a flexible sensor was designed, and a control system for real-time monitoring and multi-terminal input was developed. Combined with the developed pneumatic control system, a measure was carried out to measure the relationship between the bending angle, output force and air pressure of the soft driver. Flexible bending sensor performance test. The gripper diameter and gripping weight were tested, and the maximum gripping diameter was determined to be 182 mm, the maximum gripping weight was approximately 900 g and the average measurement error of the bending sensor was 5.91%. Objects of different shapes and easily deformable and fragile objects were tested. Originality/value Based on the motion principle of the three-jaw chuck and the pneumatic FPN, a variable distance pneumatic gripper with embedded flexible sensors is proposed by using the method of layered and step-by-step preparation. The authors studied the gripper structure design, simulation analysis, prototype preparation, control system construction and experimental testing. The results show that the designed flexible pneumatic gripper with variable distance can grasp common objects.

Linear composite curvature MITC3+ flat shell elements

This paper introduces a novel linear composite curvature MITC3+ flat shell element, named κMITC3+, that combines the advantages of the MITC3+ theory for flexural (bending and shear) behavior and the Allman-like triangular element (which ensures a true rotation of drilling degrees of freedom and eliminates a spurious energy mode) for membrane behavior. To enhance the bending behavior of the MITC3+ approach, we propose an assumed composite curvature field that is constructed using a polynomial projection technique derived from the orthogonality condition of the compatibility equation in the Hu-Washizu principle. Since two additional internal cross-section rotations are interpolated by cubic bubble functions, a linear polynomial function of the admissible space is chosen that provides a significant enhancement of bending behavior. The κMITC3+ element successfully passes all critical tests and exhibits superior performance compared to the original MITC3+ element and the recent CS-MITC18+ element.

Substantial enhancement of optoelectronics and piezoelectric properties of novel hollow ZnO nanorods towards efficient flexible touch and bending sensor

The novel solid and hollow ZnO nanorods were prepared by chemical synthesis approach. The hollow ZnO NRs show a large optical band gap as compared to the solid ZnO NRs which is attributed to quantum confinement effect. The unique emission spectra of hollow ZnO NRs show an exceptional ability for visible emission as compared to solid ZnO NRs owing to unique hollow structure, which enhanced multiple scattering. The piezoelectric potential of hollow nanorod shows about 3.75 times higher peizopotential than the solid nanorods with length (a = 200 nm) and height (h = 1000 nm). The piezoelectric potential was found to be increased with the height of nanorod with a fixed length. Interestingly, the piezoelectric potential increases with decreasing wall thickness in hollow nanorod. The hollow ZnO NRs-based touch sensor shows five times higher piezoelectric response as compared to the solid ZnO NRs. These results provide valuable information for future studies aimed at improving the piezoelectric properties of hollow nanostructures for potential applications in energy harvesting and sensing.

Unusual flexibility of transparent poly(methylsilsesquioxane) aerogels by surfactant-induced mesoscopic fiber-like assembly

High-performance thermal insulators represented by aerogels are regarded as one of the most promising materials for energy savings. However, significantly low mechanical strength has been a barrier for aerogels to be utilized in various social domains such as houses, buildings, and industrial plants. Here, we report a synthetic strategy to realize highly transparent aerogels with unusually high bending flexibility based on poly(methylsilsesquioxane) (PMSQ) network. We have constructed mesoscopic fine fiber-like structures of various sizes in PMSQ gels by the combination of phase separation suppression by tetramethylammonium hydroxide (TMAOH) and mesoscopic fiber-like assembly by nonionic poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-b-PPO-b-PEO) type surfactant. The optimized mesoscale structures of PMSQ gels have realized highly transparent and resilient monolithic aerogels with much high bendability compared to those reported in previous works. This work will provide a way to highly insulating materials with glasslike transparency and high mechanical flexibility.

Adaptive multi-point flexible-bending technology for improving the quality of profile using discrete dies driven by snake-shaped motion mechanism

Based on the application of snake-spine-like structures, this paper proposes a roller-type multi-point flexible 3D profile bending process with snake-spine-like structures (Flexible stretch-bending with roller dies - driven by snake-like mechanism, FSBRD-S), and establishes a finite element model. Taking the L-shaped cross-section profile as the research object, different working modes and contact modes are defined to study their impact on crease defects during the vertical bending step, and the new structure is designed to improve the forming quality of the products' surface. The research results show that changing the contact mode leads to a change in the relative angle between the die and the billet. In the process of larger angle vertical bending, the FSBRD-S process can effectively reduce the crease defects generated by the traditional FSBRD process, especially in the area near the clamp. Furthermore, this article proposes the FSBRD-S shape-adjusting technology, which allows for adjustments to the FSBRD-S process based on actual needs, to obtain products with different surface qualities.

‘Double Puzzle’ at the Shumagin seismic gap, Alaska Peninsula: intraslab strike-slip faulting loaded by lateral variations in megathrust fault friction

SUMMARY Along the Aleutian megathrust, the Shumagin seismic gap (162° W–158.5° W) had not hosted a large megathrust earthquake during the observational period 1946–2020. Geodetic evidence suggests a prominent trench-parallel transition from strong to weak kinematic coupling in this segment, indicating varying frictional properties of the megathrust. In 2020 July and October, the occurrence of two large, but dissimilar earthquakes in this seismic gap (the Mw 7.8 Simeonof Island thrust event on 2020 July 22 followed by the Mw 7.6 Sand Point intraslab strike-slip event on 2020 October 19) presented a unique opportunity to examine the interaction between stresses on the megathrust and within the downgoing slab. We use geodetic and geophysical evidence to derive a more accurate kinematic coupling model of the megathrust in this area and show that the Mw 7.6 Sand Point earthquake within the downgoing Pacific slab, likely occurred as a result of both trench-perpendicular interseismic shear stress caused by variable kinematic coupling of the megathrust and coseismic stress changes resulting from the Simeonof Island event. Furthermore, we show that the location of the strike-slip event coincides with along-strike change in the megathrust gravitational anomaly and flexural bending of the downgoing plate, suggesting a long-term interaction between megathrust frictional properties and the structure of the plate interface and downgoing slab.

Moisture diffusion analysis and their effects on the mechanical properties of organic particle filled natural fiber reinforced hybrid polymer composites

This investigation explores the water intake characteristics of hybrid composite samples composed of Wood Dust as organic filler (WD), Prosopis Juliflora as fiber (PJF), and epoxy as matrix. The specimens underwent immersion in both distilled and seawater environments for a duration of 240 hours. The composite samples, with compositions of 10WD + 30PJF + 60 PF, 20WD + 20PJF + 60 PF, and 30WD + 10PJF + 60 PF, were subjected to moisture content measurements at different intervals. Mechanical properties were tested following ASTM standards for both dry and wet conditions. Results indicate that seawater immersion leads to higher moisture absorption compared to distilled (condensed) water, with the fiber (PJF)-rich composite (30PJF +10WD + 60 PF) exhibiting the greatest water absorption. The water absorption pattern exhibited by the hybrid composite of WD/PJF/PF does not adhere to a Fickian behavior. Tensile, flexural, and impact properties were evaluated, with the (10WD + 30PJF + 60 PF) specimen showcasing superior performance in dry conditions, boasting a tensile character of 51 MPa, flexural (bending) strength of 60 MPa, and impact value of 1.4 KJ/m2. However, its strength diminishes upon exposure to distilled water and seawater. SEM analysis of fractured surfaces from seawater-exposed specimens provides additional insights. In conclusion, this study sheds light on the influence of immersion on moisture absorption and mechanical properties, emphasizing the prevalence of non-Fickian behavior and the varying performance of different compositions, with the (10WD + 30PJF + 60 PF) composition demonstrating remarkable strength under dry conditions.

Theory of Flexural Shear, Bending and Torsion for a Thin-Walled Beam of Open Section

Theory of Flexural Shear, Bending and Torsion for a Thin-Walled Beam of Open Section

Analysis of Flexible Screen Bending Strain Measurement Based on Digital Image Correlation (Invited)

Analysis of Flexible Screen Bending Strain Measurement Based on Digital Image Correlation (Invited)

Bending fatigue performance due to different roughing-finishing sequences and post-processing of components produced by Wire EDM

The relationships between machining conditions, boundary layer and mechanical component functionality are known qualitatively for selected Wire Electrical Discharge Machining (Wire EDM/WEDM) applications and continuous further developments of this manufacturing technology minimize the thermal influences significantly. Nevertheless, the use of WEDM processes has so far been severely limited in safety-critical applications, especially in the field of turbomachinery construction and aerospace. For example, the removal of the generated surface layers is often still mandatory, although cutting processes can also leave a distinct thermo-mechanically influenced rim zone on the component. This conservative approach currently unnecessarily reduces the manufacturing potential of WEDM processes considerably and calls for an objective comparison of component function. In this paper, therefore, the flexural bending fatigue strengths of differently wire-eroded surfaces based on roughing-finishing sequences and optional post-processing treatment are compared with industrially established reference process chains.

Self-Healing, Laminated, and Low Resistance NH3 Sensor Based on 6,6',6″-(Nitrilotris(benzene-4,1-diyl))tris(5-phenylpyrazine-2,3-dicarbonitrile) Sensing Material Operating at Room Temperature.

With the rapid development of the concept of the Internet of Things (IoT), gas sensors with the function of simulating the human sense of smell became irreplaceable as a key element. Among them, ammonia (NH3) sensors played an important role in respiration tests, environmental monitoring, safety, and other fields. However, the fabrication of the high-performance device with high stability and resistance to mechanical damages was still a challenge. In this work, polyurethane (PU) with excellent self-healing ability was applied as the substrate, and the sensor was designed from new sensitive material design and device structure optimization, through applying the organic molecule with groups which could absorb NH3 and the laminated structure to shorten the electronic transmission path to achieve a low resistance state and favorable sensing properties. Accordingly, a room temperature flexible NH3 sensor based on 6,6',6″-(nitrilotris(benzene-4,1-diyl))tris(5-phenylpyrazine-2,3-dicarbonitrile) (TPA-3DCNPZ) was successfully developed. The device could self-heal by means of a thermal evaporation assisted method. It exhibited a detection limit of 1 ppm at 98% relative humidity (RH), as well as great stability, selectivity, bending flexibility, and self-healing properties. The improved NH3 sensing performance under high RH was further investigated by complex impedance plots (CIPs) and density functional theory (DFT), attributing to the enhanced adsorption of NH3. The TPA-3DCNPZ based NH3 sensors proved to have great potential for application on simulated exhaled breath to determine the severity of kidney diseases and the progress of treatment. This work also provided new ideas for the construction of high-performance room temperature NH3 sensors.

Dynamic micromechanical measurement of the flexural modulus of micrometre-sized diameter single natural fibres using a vibrating microcantilever technique

Abstract The dynamic response of a structure is a manifestation of its inherent characteristics, including material density, mechanical modulus, thermo- and viscoelastic properties, and geometric properties. Together, these factors influence how the material behaves in dynamic scenarios, dictating its damping properties and behaviour under varying forces. In this study we present a novel approach to accurately determine the flexural (bending) modulus of microscopic diameter natural fibres (flax) using microcantilever vibration analysis. Traditionally, the characterisation of the mechanical properties of fibres has relied on macroscopic methods such as tensile testing, which often results in high scatter in measurement data; furthermore, tensile testing does not accurately represent microscale or dynamic conditions and can be complex in terms of sample preparation and loading. To address this, we have developed a microscale technique involving the fabrication of microcantilevers using flat polypropylene support chips, inspired by microelectromechanical systems approaches. Our method provides a refined method for accurately characterising the mechanical modulus of flax fibres, with reduced data dispersion compared to traditional macroscopic testing. Furthermore, by reducing the influence of inherent fibre defects and maintaining homogeneity along the length of the fibre, our micro-scale technique provides reliable modulus determination. This work opens avenues for improved understanding and application of natural and man-made fibres, such as glass and optical fibres, in a variety of fields.