Knee anterior cruciate ligament bio stiffness measuring instrument

Aiming at the lack of timely and effective evaluation of knee anterior cruciate ligament (ACL) reconstruction, a knee ACL force and displacement measuring instrument was developed. Test experiments were carried out using a laboratory-made test platform and a robotic arm. Firstly, the importance of anterior cruciate ligament reconstruction surgery is introduced. The necessity of this kind of measuring instrument is proposed. The reliability of the lower stiffness measuring instrument under different measurement conditions in space is verified by the mechanical model of the previous ACL in-situ measurement. Then the design structure and measurement system of the instrument are introduced in detail. Finally, using the laboratory-made test platform and the UR5 robot arm and stiffness measuring instrument for the displacement and force test accuracy experiments, and the pig bone anterior cruciate ligament test and postoperative evaluation experiments, prove that the measuring instrument can be used for ACL Assessment of reconstructive surgery

Rapid validation of water wave metamaterials in a desktop-scale wave measurement system

Metamaterials have a unique ability to manipulate wave phenomena beyond their natural capabilities, and they have shown great promise in electromagnetic and acoustic wave control. However, their exploration in hydrodynamics remains limited. This article introduces a novel desktop-scale wave measurement system, specifically designed for the rapid prototyping and validation of water wave metamaterials. By utilizing 3D printing, the system accelerates the transition from theoretical designs to practical testing, offering a versatile and user-friendly platform. This is further enhanced by a synchronized stereo-camera setup and advanced data processing algorithms, enabling precise measurement and reconstruction of water wave behavior. Our experimental results demonstrate the system’s effectiveness in capturing intricate interactions between engineered structures and water waves. This significantly advances rapid prototyping for water wave metamaterial research, underscoring the system’s potential to catalyze further innovation in this emerging field

Experimental and computational analysis of elastomer membranes used in oscillating water column WECs

The study investigates the structural characterisation of flexible membranes used in oscillating water column (OWC) wave energy converters (WECs). Four commonly utilised elastomers – natural rubber, nitrile rubber, silicone, and latex – were subjected to a novel hyperelastic model selection process. A custom bulge test setup enabled the selection of second-order Mooney-Rivlin (SOMR) and Yeoh models for relevant accuracy (RMSE<0.018MPa), stability and numerical validation. A 1:20 scale OWC model with latex was tested in a water tank to examine the effects of waves with a frequency range of 0.25–1.4 Hz and up to 0.24m amplitude. Water tank experiments demonstrated smooth frequency responses for OWC with membrane, beneficial for consistent power generation. A dry test rig was designed and built to replicate OWC inflation conditions and apply cyclic loadings up to 1.5 Hz, overcoming pressure limitations of the water tank, exploring wider material options, and validating numerical simulation. An optical motion capture system, Qualisys, supported the validation process by providing precise data on membrane deformation during experiments. Furthermore, finite element analysis (FEA) was utilised to conduct stress analysis and parametric studies, assessing the suitability of these materials for flexible OWC application

Numerical analysis of flexible tube wave energy converter using CFD-FEA method

To better understand the performance of flexible tube wave energy converters (WECs) in ocean waves, a coupled numerical analysis tool based on computational fluid dynamics and a finite element method is employed to perform numerical simulations for the well-known Anaconda WEC under given different regular wave conditions. The nonlinear behaviour of Natural Rubber is considered by using YEOH hyper-elastic model. Fluid-structure interaction responses of the Anaconda WEC are compared considering the impact of incident wave speed on the performance of the device. The free surface around the WEC, internal pressure and velocity in the flexible tube, structure deformation and stress distribution are fully explored. The results show that the proposed numerical analysis tool in this work is able to predict the complex fluid-structure interactions of flexible tube WEC in waves, including wave nonlinearity and inhomogeneous distribution of stress at cross-section. The typical resonant responses are also captured when the incident wave speed matches the bulge wave speed. The internal pressure amplitude, capture width, structural deformation and hoop stress all increase at resonance. Moreover, the deformed shape of the flexible tube is found to depend on the ratio of wavelength to tube length

Numerical analysis of structured sheet material in flexible oscillating water column wave energy converter

To improve the power output and reduce the stress levels for Flexible Wave Energy Converters (FlexWECs), a structured material using a sheet of natural rubber with a specific pattern called NR937 is developed in this research. Mechanical characterisation tests are conducted to determine the material properties, and the YEOH hyper-elastic model is employed to capture the nonlinear behaviour of this material. Fluid-structure interaction simulations are performed for a FlexWEC using a CFD-FEA tool. The responses of the Poly-A-OWC model equipped with both the innovative NR937 material and a conventional sheet of Natural Rubber (NR) are compared, and the deformation of flexible membrane, stress distribution, flow field, and power output are all fully explored. The results indicate that at resonance, the deformation amplitude of the flexible membrane using NR937 is increased by 1.3 times compared to that using NR, while the maximum stress increases by only 12%. Additionally, the peak power output of the Oscillating Water Column (OWC) Wave Energy Converter (WEC) utilizing NR937 is approximately 2.6 times higher than that of the WEC using NR. This suggests that structured sheet materials possess potential for improving the performance of FlexWECs, including increasing power output, reducing stress levels in flexible membrane and extending the service life