Comprehensively simulating the mixed-mode progressive delamination in composite laminates

Delamination, or interlaminar debonding, is a commonly observed failure mechanism in composite laminates. It is of great significance to comprehensively simulate the mixed-mode progressive delamination in composite structures because by doing this, people can save a lot of effort in evaluating the safe load which a composite structure can endure.^ The objective of this thesis is to develop a numerical approach to simulating double-cantilever beam (DCB) and mixed-mode bending (MMB) tests and also of specifying/validating various cohesive models. A finite element framework, which consists of properly selecting time integration scheme (explicit dynamic), viscosity, load rate and mass scaling, is developed to yield converged and accurate results.^ Two illustrative cohesive laws (linear and power-law) are programmed with a user- defined material subroutine for ABAQUS/Explicit, VUMAT, and implemented into the finite element framework. Parameters defined in cohesive laws are studied to evaluate their effects on the predicted load-displacement curves. ^ The finite element model, together with the predetermined model parameters, is found to be capable of producing converged and accurate results. The finite element framework, embedded with the illustrative cohesive laws, is found to be capable of handling various interfacial models.^ The present approach is concluded to be useful in simulating delamination with more sophisticated material models. Together with the method for determining model parameters, it can be used by computer codes other than ABAQUS

Acceleration compensation of a novel piezoelectric balance for the short duration impulse measurement: a time series analysis approach

A novel piezoelectric balance was developed to measure the six-component forces for the complex aircraft scaled model in the impulse combustion wind tunnel at a short duration airloads Mach number of 5. The piezoelectric balance using four triaxial piezoelectric load cells yields the high stiffness, sensitive and good dynamic response characteristics. The dynamic model-balance system was built to analyze the vibration characteristic. The time series analysis approach was developed on the basis of the system transfer function and the natural frequency, and the accelerated forces which induce the airloads overshooting oscillations had been obtained by the second order derivatives function. The experimental results have shown that the problem of overshooting oscillations effect of the impulse can be effectively solved by the acceleration compensation technology for the complex test model with the novel piezoelectric balance

Chinese herb medicine in augmented reality

Augmented reality becomes popular in education gradually, which provides a contextual and adaptive learning experience. Here, we develop a Chinese herb medicine AR platform based the 3dsMax and the Unity that allows users to visualize and interact with the herb model and learn the related information. The users use their mobile camera to scan the 2D herb picture to trigger the presentation of 3D AR model and corresponding text information on the screen in real-time. The system shows good performance and has high accuracy for the identification of herbal medicine after interference test and occlusion test. Users can interact with the herb AR model by rotating, scaling, and viewing transformation, which effectively enhances learners' interest in Chinese herb medicine

The mechanism of palmatine-mediated intestinal flora and host metabolism intervention in OA-OP comorbidity rats

BackgroundErXian decoction is a Chinese herbal compound that can prevent and control the course of osteoarthritis (OA) and osteoporosis (OP). OP and OA are two age-related diseases that often coexist in elderly individuals, and both are associated with dysregulation of the gut microbiome. In the initial study, Palmatine (PAL) was obtained by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and network pharmacological screening techniques, followed by 16S rRNA sequencing and serum metabolomics of intestinal contents, to explore the mechanism of PAL in the treatment of OA and OP.MethodsThe rats selected for this study were randomly divided into three groups: a sham group, an OA-OP group and a PAL group. The sham group was intragastrically administered normal saline solution, and the PLA group was treated with PAL for 56 days. Through microcomputed tomography (micro-CT), ELISA, 16S rRNA gene sequencing and non-targeted metabonomics research, we explored the potential mechanism of intestinal microbiota and serum metabolites in PAL treatment of OA-OP rats.ResultsPalmatine significantly repair bone microarchitecture of rat femur in OA-OP rats and improved cartilage damage. The analysis of intestinal microflora showed that PAL could also improve the intestinal microflora disorder of OA-OP rats. For example, the abundance of Firmicutes, Bacteroidota, Actinobacteria, Lactobacillus, unclassified_f_Lachnospiraceae, norank_f_Muribaculaceae, Lactobacillaceae, Lachnospiraceae and Muribaculaceae increased after PAL intervention. In addition, the results of metabolomics data analysis showed that PAL also change the metabolic status of OA-OP rats. After PAL intervention, metabolites such as 5-methoxytryptophol, 2-methoxy acetaminophen sulfate, beta-tyrosine, indole-3-carboxylic acid-O-sulfate and cyclodopa glucoside increased. Association analysis of metabolomics and gut microbiota (GM) showed that the communication of multiple flora and different metabolites played an important role in OP and OA.ConclusionPalmatine can improve cartilage degeneration and bone loss in OA-OP rats. The evidence we provided supports the idea that PAL improves OA-OP by altering GM and serum metabolites. In addition, the application of GM and serum metabolomics correlation analysis provides a new strategy for uncovering the mechanism of herbal treatment for bone diseases

Prompt-enhanced Hierarchical Transformer Elevating Cardiopulmonary Resuscitation Instruction via Temporal Action Segmentation

The vast majority of people who suffer unexpected cardiac arrest are performed cardiopulmonary resuscitation (CPR) by passersby in a desperate attempt to restore life, but endeavors turn out to be fruitless on account of disqualification. Fortunately, many pieces of research manifest that disciplined training will help to elevate the success rate of resuscitation, which constantly desires a seamless combination of novel techniques to yield further advancement. To this end, we collect a custom CPR video dataset in which trainees make efforts to behave resuscitation on mannequins independently in adherence to approved guidelines, thereby devising an auxiliary toolbox to assist supervision and rectification of intermediate potential issues via modern deep learning methodologies. Our research empirically views this problem as a temporal action segmentation (TAS) task in computer vision, which aims to segment an untrimmed video at a frame-wise level. Here, we propose a Prompt-enhanced hierarchical Transformer (PhiTrans) that integrates three indispensable modules, including a textual prompt-based Video Features Extractor (VFE), a transformer-based Action Segmentation Executor (ASE), and a regression-based Prediction Refinement Calibrator (PRC). The backbone of the model preferentially derives from applications in three approved public datasets (GTEA, 50Salads, and Breakfast) collected for TAS tasks, which accounts for the excavation of the segmentation pipeline on the CPR dataset. In general, we unprecedentedly probe into a feasible pipeline that genuinely elevates the CPR instruction qualification via action segmentation in conjunction with cutting-edge deep learning techniques. Associated experiments advocate our implementation with multiple metrics surpassing 91.0%.Comment: Transformer for Cardiopulmonary Resuscitatio

Failure Prediction for Composite Materials with Generalized Standard Models

Despite the advances of analytical and numerical methods for composite materials, it is still challenging to predict the onset and evolution of their different failure mechanisms. Because most failure mechanisms are irreversible processes in thermodynamics, it is beneficial to model them within a unified thermodynamic framework. Noting the advantages of so-called generalized standard models (GSMs) in this regard, the objective of this work is to formulate constitutive models for several main failure mechanisms: brittle fracture, interlaminar delamination, and fatigue behavior for both continuum damage and delamination, in a generalized standard manner. For brittle fracture, the numerical difficulties caused by damage and strain localization in traditional finite element analysis will be addressed and overcome. A nonlocal damage model utilizing an integral-type regularization technique will be derived based on a recently developed “local” continuum damage model. The objective is to make this model not only rigorously handle brittle fracture, but also incorporate common damage behavior such as damage anisotropy, distinct tensile and compressive damage behavior, and damage deactivation. A fully explicit integration scheme for the present model will be developed and implemented. For fatigue continuum damage, a viscodamage model, which can handle frequently observed brittle damage phenomena, is developed to produce stress-dependent fatigue damage evolution. The governing equation for damage evolution is derived using an incremental method. A class of closed-form incremental constitutive relations is derived. For interlaminar delamination, a cohesive zone model (CZM) will be proposed. Focus is placed on making the associated cohesive elements capable of displaying experimental critical energy release rate–mode mixture ratio relationships. To achieve this goal, each cohesive element is idealized as a deformable string exhibiting path dependent damage behavior. A damage model having a path dependence function will be developed, which will be constructed such that each cohesive element can exhibit designated, possibly sophisticated mixed-mode behavior. The rate form of the cohesive law will be subsequently derived. Finally, a CZM for interlaminar fatigue, capable of handling brittle damage behavior, is developed to produce realistic interlaminar crack propagation under high-cycle fatigue. An implicit integration scheme, which can handle complex separation paths and mixed-mode delamination, is developed. Many numerical examples will be utilized to clearly demonstrate the capabilities of the proposed nonlocal damage model, continuum fatigue damage model, and CZMs for quasi-static and fatigue delamination

Performance evaluation of absorption thermal energy storage/transmission using ionic liquid absorbents

Efficient thermal energy storage and transmission are considered as two of the most significant challenges for decarbonisation in thermal energy utilization. The liquid-gas absorption thermal energy storage/transmission system is promising approach to tackle these challenges, owing to the long-term stability, flexibility in heat/cooling output, and liquid medium. At present, the shortcomings of conventional absorption working fluids have triggered considerable interest in searching for novel working pairs, such as ionic liquids (ILs). However, it is still unknown whether ILs can work effectively in thermal energy transmission with long distance. In this study, the absorption thermal energy storage/transmission systems using IL absorbents are theoretically investigated. modeling frameworks for working pairs screening and performance evaluation are proposed. Results show that the IL-based working pairs present better or comparable performance than conventional working pairs (including H2O/Salts and NH3/Salts). Among the investigated IL-based working pairs, H2O/[EMIM][EtSO4] presents highest COP (around 0.62) and exergy efficiency (around 0.32), and is relatively close to H2O/LiBr. As for energy storage density, H2O/[EMIM][Ac] performs better than H2O/LiBr, presenting 137.4 kWh/m3 with a desorption temperature of 115 °C. The present work provides a straightforward screening of IL absorbents for thermal energy storage and transmission purposes

Piezoelectric Sensor of Control Surface Hinge Moment

Based on the theory of piezoelectricity, a new sensor of control surface hinge moment with high linearity which uses piezoelectric quartz crystal as sensitive element is studied. It realizes the measurement of force by measuring the charge which is generated by piezoelectric quartz crystal that is integrated inside of sensor. In order to simulate the interaction between airfoil and airflow under the steady state, ANSYS is used to analyze the stress of airfoil in the air. ANSYS is also used to analyze potential distribution and electric field intensity distribution of piezoelectric quartz crystal which is under the action of force and moment, respectively. The measuring principle and design process of sensor are given in this paper, and the linearity and repeatability of sensor are obtained on the basis of experimental research and data analysis. The new sensor offers a new thinking for lucubrating and accurate measurement of hinge moment sensor

Research on the Structure and Signal Transmission of Rotary Piezoelectric Dynamometer

Cutting force real-time monitoring has become an increasing prominent role in high precision mechanical parts processing. A new type of cutting force dynamometer which is able to be mounted on the spindle of machine tool is proposed in this paper. At first, it is proved theoretically that the charge quantity can be obtained through measuring the induced charge quantity generated by electrostatic induction. Then the feasibility of this method is verified by an experiment. X0°-cut wafer and Y0°-cut wafer of α piezoelectric quartz are analyzed by ANSYS software separately and the distribution regularity of the polarized charge when piezoelectric quartz wafer surface is subjected to force or torque is obtained. On the basis of the above analysis, a kind of piezoelectric three-component dynamometer is designed. It can measure cutting depth resistance, feed resistance and torque with only two X0°-cut quartz wafers and two Y0°-cut quartz wafers

Research on the Dynamic Error and Acceleration Compensation for the Piezoelectric Sensor

Piezoelectric force sensors are used in more and more industries and areas for the monitoring of the production process or testing products' performance. In some high-precision testing fields, the dynamic measurement performances of the test system itself have to be examined. Based on the dynamic response mathematical model of test system itself, this paper studies the dynamic measuring acceleration error compensation method. Firstly, according to the motion differential equation of the test system, the dynamic response transfer function is built and the root cause of the test system dynamic testing error is studied. Then the modal parameters of the system are obtained using the experimental modal analysis method and a deterministic response transfer function is established. The acceleration impact item is separated out by the method of separation of variables and weight coefficient method. Combining numerical differentiation, the expression used to calculate the acceleration is achieved. Finally, acceleration compensation experiment is done