Global Impact Dynamic Modeling and Verification of a Flexible Beam with Large Overall Motion

The theoretical modeling, numerical simulation, and experimental verification for the impact dynamics of a flexible beam with large overall motion are researched. Based on the rigid-flexible coupling dynamic theory of flexible multibody system, the rigid-flexible coupling dynamic equations of the beam are established. On the use of the continuous contact force method (CCFM) and the contact constraint method (CCM), the respective global impact dynamic equations of the system are derived to achieve dynamic transformation and solution in different stages including impact and unimpact status. The experimental study on the impact dynamics of the flexible beam is investigated, and the dynamic response in the impact process is obtained. The experimental results are compared with the results of the impact dynamic simulation and the finite element method (FEM) simulation. The system's dynamic behaviors in the impact process are analyzed, and the accuracy of the two impact dynamic theories is verified

Thermal Modeling and Prediction of The Lithium-ion Battery Based on Driving Behavior

Real-time monitoring of the battery thermal status is important to ensure the effectiveness of battery thermal management system (BTMS), which can effectively avoid thermal runaway. In the study of BTMS, driver behavior is one of the factors affecting the performance of the battery thermal status, and it is often neglected in battery temperature studies. Therefore, it is necessary to predict the dynamic heat generation of the battery in actual driving cycles. In this work, a thermal equivalent circuit model (TECM) and an artificial neural network (ANN) thermal model based on the driving data, which can predict the thermal behavior of the battery in real-world driving cycles, are proposed and established by MATLAB/Simulink tool. Driving behaviors analysis of different drivers are simulated by PI control as input, and battery temperature is used as output response. The results show that aggressive driving behavior leads to an increase in battery temperature of nearly 1.2 K per second, and the average prediction error of TECM model and ANN model is 0.13 K and 0.11 K, respectively. This indicates that both models can accurately estimate the real-time battery temperature. However, the computational speed of the ANN thermal model is only 0.2 s, which is more efficient for battery thermal management

Optimization of Nonlinear Lamb Wave Detection System Parameters in CFRP Laminates

Carbon fiber reinforced polymer (CFRP) laminates, as unique multifunctional materials, are widely applied in various aircraft, such as airliners, fighter planes, and space shuttles. To ensure aircraft safety during the production and application of CFRP laminates, it is necessary to improve the accuracy of nonlinear Lamb wave nondestructive testing to assess the damage in CFRP laminates caused by impact, high temperature, friction, corrosion, etc. In this study, the accuracy of nonlinear ultrasonic nondestructive testing was found to highly depend on the cycle number, output level and gain of the nonlinear ultrasonic detection system. Based on a single-factor experiment that considered the cycle number, output level, and gain of the amplifier as independent variables, a regression analysis was carried out on the fundamental wave amplitude value (A1) and second harmonic amplitude value (A2). Two response surface surrogate models were established to improve the accuracy of nonlinear Lamb wave nondestructive testing and to optimize the detection system parameters. The response surface models were verified via an analysis of variance (ANOVA), significance tests and an error statistical analysis. The results revealed the significant influence of these three factors on A1 and A2. Optimization of the response surface was achieved at eight cycles, an output level of 42 and a gain of 32 dB. Moreover, the nonlinear ultrasonic detection system achieved good operational stability, high accuracy and reliability under the above optimal parameter conditions. This approach provides scientific guidance for the accurate assessment of CFRP laminate damage

Research on Fatigue Life Prediction Method of Key Component of Turning Mechanism Based on Improved TCD

The main objective of this paper is to accurately obtain fatigue life prediction for the key components of a turning mechanism using the improved theory of critical distances (TCD). The irregularly shaped rotating arm is the central stressed part of the turning mechanism, which contains notches. It has been found that TCD achieves good results in predicting the fatigue strength or fatigue life of notched components with regular shape but is less commonly used for notched components with irregular shape. Therefore, TCD was improved and applied broadly to predict the fatigue life of an irregularly shaped rotating arm. Firstly, the notch depth and structure net width parameters were introduced into the low-order and low-accuracy classical TCD function to obtain a novel stress function with high computational efficiency and high accuracy, whereas the stress concentration factor was introduced to modify the length of critical distance. Secondly, the improved TCD was used to predict the fatigue strength of notched components with regular shape, and its accuracy was demonstrated by a fatigue experiment. Finally, the improved TCD was applied to predict the fatigue life of an irregularly shaped rotating arm. The deviation between prediction results and experimental results is less than 18%. The results demonstrate that the improved TCD can be applied effectively and accurately to predict the fatigue life of key components of turning mechanisms

Energy absorption characteristics of origami-inspired honeycomb sandwich structures under low-velocity impact loading

Lightweight origami structure has received increasing attention in the past years. This paper presents a new origami-inspired honeycomb sandwich plate, taking inspiration from two emerging sandwich structures reported in literatures. The purpose of this work was to investigate the influence of structural parameters on the impact response and demonstrate the outperformance of this novel sandwich structure. The low-velocity impact response of the origami-inspired honeycomb sandwich was investigated experimentally and numerically. And the numerical prediction closely matched the experimental results in terms of contact-force histories and permanent deformations of sandwich plates. The influence of structural parameters on the energy absorption characteristics has been analyzed by using the improved finite element model. Finally, the results of comparisons showed that origami-inspired honeycomb exceeded traditional honeycomb in energy absorption characteristics

An Ordinary State-Based Peridynamic Model of Unidirectional Carbon Fiber Reinforced Polymer Material in the Cutting Process

Due to the complexity of the composite structure, analyzing the material failure process of carbon fiber reinforced polymers (CFRP) is fairly difficult, particularly for the machining process. Peridynamic theory, a new branch of solid mechanics, is a useful tool for dealing with discontinuities. This study presents an ordinary state-based peridynamic (OSB-PD) model for unidirectional CFRP material in the cutting process. In this model, angle tolerance is used to overcome the fiber angle limitation in a classical OSB-PD laminate method, and the short-range force approach is utilized to simulate the contact of the cutting tool and workpiece. The effectiveness of the supplied models is validated by tension and cutting tests. Finally, it can be indicated that the OSB-PD model is capable of predicting machined surface damage and cutting force, based on the comparison of simulation and experimental data

Towards Improving Rural Living Environment for Chinese Cold Region Based on Investigation of Thermal Environment and Space Usage Status

In recent years, many scholars worldwide have carried out research related to the relationship between the construction of rural dwellings and the indoor thermal environment in response to the issue of building sustainability. China’s rural revitalization has developed rapidly in recent years. Although previous research showed that the poor indoor thermal environment of vernacular dwellings has negative effects on residents’ thermal comfort and health, it is poorly studied in terms of residents’ space usage habits, their thermal comfort satisfaction, and their thermal sensation. Linyi, the largest and most populous city in Shandong, China, was selected as the research area to investigate the thermal environment and space usage by using in-depth questionnaire interviews and systematical measurements. The results show that there are seasonal differences in space usage in a typical vernacular dwelling. The field measurements show that the indoor temperature is 0–5 °C in winter if there is no heating and 26 °C in summer. By comprehensive comparison, it is found that there is a contradiction between residential space usage and the functional layout; residents choose to use rooms with worse thermal conditions in winter. The analysis of the questionnaires shows that residents have higher satisfaction with the indoor thermal environment in summer than in winter, and the thermal comfort range of residents is 23.3~30 °C in summer and 11.25~17.5 °C in winter. Additionally, the neutral thermal temperature of the indoor space is 26.7 °C in summer and 14.4 °C in winter. Although residents have better adaptability to the cold climate, the measurement data in winter are still beyond the comfort range. We suggest that these results can be used as a reference and data base for improving the living environment of rural vernacular dwellings in Chinese cold regions

Global transcriptomic analysis reveals candidate genes associated with different phosphorus acquisition strategies among soybean varieties

INTRODUCTION: Soybean adapts to phosphorus-deficient soils through three important phosphorus acquisition strategies, namely altered root conformation, exudation of carboxylic acids, and symbiosis with clumping mycorrhizal fungi. However, the trade-offs and regulatory mechanisms of these three phosphorus acquisition strategies in soybean have not been researched. METHODS: In this study, we investigated the responses of ten different soybean varieties to low soil phosphorus availability by determining biomass, phosphorus accumulation, root morphology, exudation, and mycorrhizal colonization rate. Furthermore, the molecular regulatory mechanisms underlying root phosphorus acquisition strategies were examined among varieties with different low-phosphorus tolerance using transcriptome sequencing and weighted gene co-expression network analysis. RESULTS AND DISCUSSION: The results showed that two types of phosphorus acquisition strategies—“outsourcing” and “do-it-yourself”—were employed by soybean varieties under low phosphorus availability. The “do-it-yourself” varieties, represented by QD11, Zh30, and Sd, obtained sufficient phosphorus by increasing their root surface area and secreting carboxylic acids. In contrast, the “outsourcing” varieties, represented by Zh301, Zh13, and Hc6, used increased symbiosis with mycorrhizae to obtain phosphorus owing to their large root diameters. Transcriptome analysis showed that the direction of acetyl-CoA metabolism could be the dividing line between the two strategies of soybean selection. ERF1 and WRKY1 may be involved in the regulation of phosphorus acquisition strategies for soybeans grown under low P environments. These findings will enhance our understanding of phosphorus acquisition strategies in soybeans. In addition, they will facilitate the development of breeding strategies that are more flexible to accommodate a variety of production scenarios in agriculture under low phosphorus environments. BACKGROUND: Association of gastric atrophy or cancer with levels of serum pepsinogens, gastrin-17 and anti-Helicobacter pylori IgG antibody have been extensively studied. However, the association of serum pepsinogen and gastrin-17 with H. pylori infection has not been studied in a large population

Towards Improving Rural Living Environment for Chinese Cold Region Based on Investigation of Thermal Environment and Space Usage Status

In recent years, many scholars worldwide have carried out research related to the relationship between the construction of rural dwellings and the indoor thermal environment in response to the issue of building sustainability. China’s rural revitalization has developed rapidly in recent years. Although previous research showed that the poor indoor thermal environment of vernacular dwellings has negative effects on residents’ thermal comfort and health, it is poorly studied in terms of residents’ space usage habits, their thermal comfort satisfaction, and their thermal sensation. Linyi, the largest and most populous city in Shandong, China, was selected as the research area to investigate the thermal environment and space usage by using in-depth questionnaire interviews and systematical measurements. The results show that there are seasonal differences in space usage in a typical vernacular dwelling. The field measurements show that the indoor temperature is 0–5 °C in winter if there is no heating and 26 °C in summer. By comprehensive comparison, it is found that there is a contradiction between residential space usage and the functional layout; residents choose to use rooms with worse thermal conditions in winter. The analysis of the questionnaires shows that residents have higher satisfaction with the indoor thermal environment in summer than in winter, and the thermal comfort range of residents is 23.3~30 °C in summer and 11.25~17.5 °C in winter. Additionally, the neutral thermal temperature of the indoor space is 26.7 °C in summer and 14.4 °C in winter. Although residents have better adaptability to the cold climate, the measurement data in winter are still beyond the comfort range. We suggest that these results can be used as a reference and data base for improving the living environment of rural vernacular dwellings in Chinese cold regions