mechanical properties

机械性能
  • 文章类型: Journal Article
    随着技术趋势的发展,使用废弃替代材料代替沙子材料的混凝土发现了良好结构性能的经济潜力。此外,易感裂纹,低强度重量比,和低抗压强度是收缩的原因。由于这个原因,该研究旨在通过引入椰子废短切纤维(wCF)来限制活荷载下的收缩并增加压缩和弯曲强度,废粉煤灰(wFA),和碳纳米管粉末(CNT)与常规波特兰糊混合。开发的混凝土由5重量%的wCF组成,10wt%wFA,和0、5、10和15重量%的CNT,并进行X射线衍射分析,堆积密度,压缩和弯曲强度,和吸水研究。X射线衍射图揭示了wCF,wFA,CNT,和基质成分。使用5wt%wCF开发的混凝土,10wt%wFA,和在28天内固化的15wt%CNT记录的最大压缩强度行为(47±1.8MPa),抗弯强度(4.9±0.19MPa),吸水率为(2.8±0.05%)。
    With the development of the technical trend, concrete using waste alternate material instead of sand material found economic potential for good structural behaviour. Besides, the susceptible crack, low strength-to-weight ratio, and low compressive strength are the reasons for shrinkage. Due to this reason, the investigation aims to limit the shrinkage under live load and increase the compression and flexural strength by the introduction of coconut waste chopped fiber (wCF), waste fly ash (wFA), and carbon nanotube powder (CNT) blended with conventional Portland paste. The developed concrete consists of 5 wt% wCF, 10 wt% wFA, and 0, 5, 10, and 15 wt% of CNT and is subjected to X-ray diffraction analysis, bulk density, compression and flexural strength, and water absorption studies. The X-ray diffraction pattern revealed the wCF, wFA, CNT, and matrix compositions. The concrete developed with 5 wt% wCF, 10 wt% wFA, and 15 wt% CNT cured within 28 days recorded maximum behaviour of compression strength (47 ± 1.8 MPa), flexural strength (4.9 ± 0.19 MPa), and water absorption of (2.8 ± 0.05 %).
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  • 文章类型: Journal Article
    本文重点研究了花岗岩微填料对静态力学性能的影响,阻尼行为,蚕丝-剑麻杂化复合材料的物理特性。复合材料结构是通过手动层工艺使用三层平织垫制成的,这些平织垫具有不同重量百分比(2、4和6wt%)的花岗岩微填料。分析了花岗岩-微填料对丝绸-剑麻的影响,并将结果与纯丝绸-剑麻(不含花岗岩-微填料)混合复合材料进行了比较。结果推断;开发的丝-剑麻混合复合材料的拉伸强度和弯曲强度值随着花岗岩-微填料含量的增加而增加,通过在丝剑麻上添加6wt%的花岗岩微填料,约5%和9%的值提高了。拉伸和弯曲断裂形态分析表明,具有两个(纵向和横向)方向的蚕丝-剑麻纤维毡的组合平织具有较高的机械性能,并且还观察到,花岗岩微填料分散在丝绸-剑麻纤维垫和树脂紧密堆积。通过添加6wt%的花岗岩微填料含量来获得改进的阻尼因子,比纯丝剑麻高出约75.8%。本文还对蚕丝-剑麻杂化复合材料的物理性能进行了分析和讨论。
    This paper focuses on the effect of granite-micro-filler on static mechanical properties, damping behavior, and physical characteristics of silk-sisal hybrid composite. The composites structures are fabricated by using three layers of plain weaves mat with varying weight percentages (2, 4, and 6 wt%) of granite-micro-filler by hand layer process. The effect of granite-micro-filler on silk-sisal is analyzed and results are compared with pure silk-sisal (without granite-Micro-filler) hybrid composite. The results infer that; the tensile strength and flexural strength value of the developed silk-sisal hybrid composites are increased with the increase in wt% of granite-micro-filler content than pure silk-sisal, approximately 5% and 9% improved value in order by adding 6 wt% granite-micro-filler on silk-sisal. The tensile and flexural fracture morphology analysis indicated that composed plain weave of silk-sisal fiber mat with two (longitudinal and transverse) directions possesses higher mechanical properties and also observed that, granite-micro-filler dispersed on silk-sisal fiber mat and resin with closely packed. The improved damping factor is obtained by adding 6 wt% of granite-micro-filler content, which is approximately 75.8% higher than pure silk-sisal. The physical properties of silk-sisal hybrid composite have also been analyzed and well discussed in this paper.
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  • 文章类型: Journal Article
    氮化硅(Si3N4)是一种具有潜在应用的生物陶瓷材料。定制化和高可靠性是Si3N4生物陶瓷广泛应用的基础。本研究构建了一种新的微波加热结构,并成功制备了3D打印致密Si3N4材料,克服了大量3D打印有机成型剂对脱脂和烧结过程的不利影响,进一步提高Si3N4材料的综合性能。与对照材料相比,微波烧结的3D打印Si3N4材料具有最佳的机械性能:弯曲强度为928MPa,断裂韧性为9.61MPa·m1/2。同时,它具有最佳的生物相容性和抗菌性能,和细胞在材料表面表现出最好的活性。研究表明,材料优异的机械性能和生物活性主要与优质的脱脂,高洁净度烧结环境,以及微波环境下材料的高质量液相烧结。
    Silicon nitride (Si3N4) is a bioceramic material with potential applications. Customization and high reliability are the foundation for the widespread application of Si3N4 bioceramics. This study constructed a new microwave heating structure and successfully prepared 3D printed dense Si3N4 materials, overcoming the adverse effects of a large amount of 3D printed organic forming agents on degreasing and sintering processes, further improving the comprehensive performance of Si3N4 materials. Compared with control materials, the 3D printed Si3N4 materials by microwave sintering have the best mechanical performance: bending strength is 928 MPa, fracture toughness is 9.61 MPa·m1/2. Meanwhile, it has the best biocompatibility and antibacterial properties, and cells exhibit the best activity on the material surface. Research has shown that the excellent mechanical performance and biological activity of materials are mainly related to the high-quality degreasing, high cleanliness sintering environment, and high-quality liquid-phase sintering of materials in microwave environments.
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  • 文章类型: Journal Article
    铝合金由于其当前的工程应用而被广泛研究。由于其高强度和轻质,裂纹很容易在它们的表面引发,它们的整体功能和结构特性恶化,造成环境攻击。当前的研究强调了在铝-10锌合金中掺入1wt%二氧化硅纳米结构的显着影响。使用维氏硬度检查复合材料的特性,拉伸,和电化学测试(OCP,塔菲尔,和EIS)在各种人工老化温度(423、443和463K)下。二氧化硅纳米棒可以实现超细晶粒,硬度增加高达13.8%,在443K时将σUTS值增加高达79%,并将腐蚀率提高高达89.4%,超越Al-10Zn散装金属。我们证明,二氧化硅纳米棒有助于产生优异的纳米复合材料,不仅限制了负载下的失效事件,而且还耐腐蚀。我们的研究结果表明,二氧化硅纳米复合材料可以产生独特的功能,用于各种汽车,建筑,和航空航天应用。这种改进主要归因于纳米二氧化硅颗粒的大表面积,这改变了Al矩阵。微观结构,机械,电化学研究表明,结构细化的影响取决于纳米二氧化硅。
    Aluminum alloys have been widely studied because of their current engineering applications. Due to their high strength and lightweight, cracking can easily initiate on their surface, deteriorating their overall functional and structural properties and causing environmental attacks. The current study highlights the significant influence of incorporating 1 wt% silica nanostructure in aluminum-10 zinc alloys. The characteristics of the composites were examined using Vickers hardness, tensile, and electrochemical testing (OCP, Tafel, and EIS) at various artificial aging temperatures (423, 443, and 463 K). Silica nanorods may achieve ultrafine grains, increase hardness by up to 13.8%, increase σUTS values by up to 79% at 443 K, and improve corrosion rate by up to 89.4%, surpassing Al-10 Zn bulk metallics. We demonstrate that silica nanorods contribute to the creation of a superior nanocomposite that not only limits failure events under loading but also resists corrosion. Our findings suggest that silica nanocomposite can produce unique features for use in a variety of automotive, construction, and aerospace applications. This improvement can be attributed mainly to the large surface area of nano-silica particles, which alters the Al matrix. Microstructural, mechanical, and electrochemical studies revealed that the effects of structure refinement were dependent on nano-silica.
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  • 文章类型: Journal Article
    本文旨在探讨矿物掺合料与服役温度的综合作用,尤其是在寒冷的环境中,研究了磷酸镁修补砂浆(MPM)的性能。首先研究了粉煤灰掺量对MPM微观结构和性能的影响机理,然后研究了在-20°C下固化的粉煤灰改性MPM的性能演变规律,0°C,进一步揭示20°C和40°C。结果表明,粉煤灰的掺入对MPM的凝结时间和流动性没有显着影响。当MPM用10重量%和15重量%的粉煤灰改性时,其机械性能,粘合强度,耐水性,并有效提高了音量稳定性。粉煤灰降低了富含硬化MPM的鸟粪石的结晶度和连续性,它的颗粒嵌在鸟粪石和未反应的MgO之间。不同龄期固化的MPM-10抗压强度随固化温度的升高而增加,而弯曲强度,界面粘结强度,强度保持和线性收缩表现出相反的规律。当在0°C和-20°C下固化时,MPM-10仍然具有良好的早期强度,耐水性和界面粘结性能,这表明MPM-10具有在寒冷环境中对破裂部件进行紧急修复的能力。
    This article is aimed at discussing the combined effect of mineral admixture and servicing temperature, especially in cold environment, on the properties of magnesium phosphate repair mortar (MPM). The influence mechanism of fly ash content on the microstructure and performance of MPM were firstly investigated, and then the evolution rules in properties of fly ash modified MPM cured at - 20 °C, 0 °C, 20 °C and 40 °C were further revealed. The results show that the incorporation of fly ash has no significant effect on the setting time and fluidity of MPM. When MPM is modified with 10 wt% and 15 wt% fly ash, its mechanical properties, adhesive strength, water resistance, and volume stability are effectively improved. Fly ash reduces the crystallinity and continuity of struvite enriched in hardened MPM, and its particles are embedded among struvite and unreacted MgO. The compressive strength of MPM-10 cured for various ages increases with the elevating of curing temperature, while the flexural strength, interfacial bonding strength, strength retention and linear shrinkage exhibits the opposite laws. When cured at 0 °C and - 20 °C, MPM-10 still has good early strength, water resistance and interfacial bonding properties, which indicates that MPM-10 provides with an ability of emergency repair of cracked components served in cold environments.
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  • 文章类型: Journal Article
    随着我国煤炭开采逐渐向西部煤矿区转移,弱胶结泥岩巷道底板隆起已成为影响煤矿生产安全和效益的问题。此外,不同的开采速度会导致弱胶结泥岩巷道顶板和底板上的支撑应力波动。因此,全面了解弱胶结泥岩在不同加载速率下的力学特性,有利于改善此类巷道的底鼓问题,为进一步研究提供理论依据。在这种情况下,在各种加载速率(0.005、0.01、0.05和0.1mm/s)下,对弱胶结泥岩标本进行了一系列具有并发声发射监测的单轴力学测试。获得了应力-应变和声发射响应曲线,以有效地表征强度,变形,损坏,宏观不稳定,以及加载速率效应下泥岩的裂纹扩展特征。研究结果支持以下发现:(1)随着加载速率的增加,弱胶结泥岩的峰值强度和弹性模量显著增加,而峰值轴向应变和峰值径向变形显著减小。(2)随着加载速率的增加,引发弱胶结泥岩膨胀所需的应力逐渐增加,在膨胀开始时泥岩的应变与加载速率之间存在显着的幂律关系。(3)随着加载速率的增加,弱胶结泥岩的声发射振铃计数增加:弱胶结泥岩的破坏从小范围渐进破坏变为突然破坏,破坏模式从剪切破坏转变为拉伸-剪切复合材料破坏。(4)研究的泥岩损伤变量随着加载速率的增加而增加,遵循近似指数函数。研究结论可为深部巷道开采底鼓演化机理及控制提供理论依据。
    With the gradual shift of coal mining to the western coal mining region of China, floor heave in weakly cemented mudstone roadways has become an issue affecting the safety and efficiency of coal mine production. Additionally, different mining rates can lead to fluctuating support stresses on the roof and floor of weakly cemented mudstone roadways. Therefore, obtaining a comprehensive understanding of the mechanical properties of weakly cemented mudstone at different loading rates is conducive to improving the issue of floor heave in such roadways and provides a theoretical basis for further study. In this context, a series of uniaxial mechanical tests with concurrent acoustic emission monitoring were conducted on specimens of weakly cemented mudstone under various loading rates (0.005, 0.01, 0.05, and 0.1 mm/s). The stress‒strain and acoustic emission response curves were obtained to effectively characterize the strength, deformation, damage, macroscale instability, and crack propagation characteristics of the mudstone under the influence of loading rate effects. The research results support the following findings: (1) With increasing loading rate, the peak strength and elastic modulus of weakly cemented mudstone significantly increase, while the peak axial strain and peak radial deformation significantly decrease. (2) With increasing loading rate, the stress required to trigger the expansion of weakly cemented mudstone gradually increases, and a significant power-law relationship arises between the strain of the mudstone at the start of expansion and the loading rate. (3) With increasing loading rate, the acoustic emission ringing count of weakly cemented mudstone increases: The failure of weakly cemented mudstone changes from small-range progressive failure to sudden failure, and the failure mode transitions from shear failure to tensile‒shear composite failure. (4) The studied mudstone damage variables increase with increasing loading rate, following an approximate exponential function. The conclusions obtained in this work can provide a theoretical basis for the evolution mechanism and control of floor heave in deep roadway mining.
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  • 文章类型: Journal Article
    尽管运行特定假体(RSP)的机械性能会影响运行性能,制造商并不总是报告它们。本研究旨在回顾有关RSP机械和结构特性及其与运行性能的关系的现有文献。
    使用与RSP的机械性能和运行性能相关的关键字进行了全面搜索。搜索词包括刚度和滞后,以及性能结果,包括代谢成本和运行速度。非同行评审和非英文出版物被排除在外。
    评论中包含了20篇文章。16项研究使用材料试验机测量RSP材料性能,四篇文章使用了其他技术,包括2D/3D视频捕获和部队平台。测量技术和结果报告都不一致,这限制了得出广泛结论的能力。此外,尽管测量了材料特性的数值数据,但一些研究没有报告它们。相对较少的文章同时测量了材料特性和运行性能并评估了相关性。
    几篇文章将假体特性与运行性能联系起来。然而,机械性能的测量和报告不一致,随着运动员假肢系统的多因素性质,限制得出关于材料和结构特性与运动员表现之间关系的广泛结论的能力。目前的证据可能是有用的临床医生寻求方法来优化RSP刚度在个案的基础上;然而,对不同RSP的属性及其在性能中的作用进行更一致和系统的比较将使临床医师受益.
    UNASSIGNED: Although mechanical properties of running specific prostheses (RSPs) can affect running performance, manufacturers do not consistently report them. This study aimed to review existing literature on RSP mechanical and structural properties and their relationship with running performance.
    UNASSIGNED: A comprehensive search was conducted using keywords related to mechanical properties of RSPs and running performance. Search terms included stiffness and hysteresis, as well as performance outcomes including metabolic cost and running speed. Non-peer-reviewed and non-English publications were excluded.
    UNASSIGNED: Twenty articles were included in the review. Sixteen studies used a material testing machine to measure RSP material properties, and four articles used other techniques including 2D/3D video capture and force platforms. Both measurement techniques and reporting of outcomes were inconsistent, which limits the ability to draw broad conclusions. Additionally, several studies did not report the numerical data for material properties despite measuring them. Relatively few articles measured both material properties and running performance and assessed correlations.
    UNASSIGNED: Several articles connected prosthesis properties to running performance. However, inconsistent measurement and reporting of mechanical properties, along with the multifactorial nature of the athlete-prosthesis system, limit the ability to draw broad conclusions regarding the relationship between material and structural properties and athlete performance. Current evidence may be useful for clinicians seeking ways to optimize RSP stiffness in a case-by-case basis; however, clinicians would benefit from more consistent and systematic comparisons of the attributes of different RSPs and their role in performance.
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  • 文章类型: Journal Article
    本研究介绍了一种新的方法,利用机器学习技术来预测工程水泥基复合材料(ECCs)的关键力学性能,从典型到异常高强度水平。这些属性,包括抗压强度,抗弯强度,抗拉强度,和拉伸应变能力,不仅可以预测,而且可以精确估计。调查包括对来自相关研究的1532个数据集的细致汇编和检查。四种机器学习算法,线性回归(LR),K个最近邻(KNN),随机森林(RF),和极端梯度增强(XGB),建立ECC力学性能预测模型,确定最优模型。最佳模型用于使用SHapley加法扩张(SHAP)来仔细检查特征重要性并进行深入的参数分析。随后,针对ECC力学性能设计了综合控制策略。此策略可以为ECC设计提供可操作的指导,装备土木工程和材料科学的工程师和专业人士,在整个设计工作中做出明智的决定。结果表明,RF模型对抗压强度和抗折强度的预测精度最高。测试组上的R2值为0.92和0.91。XGB模型在预测抗拉强度和拉伸应变能力方面表现出色,测试集上的R2值为0.87和0.80,分别。拉伸应变能力的预测精度最低。同时,拉伸应变能力的MAE仅为0.84%,小于以前研究中测试结果的变异性(1.77%)。抗压强度和抗拉强度对水灰比(W)和减水剂(WR)的变化表现出很高的敏感性。相比之下,弯曲强度仅对W的变化表现出很高的敏感性。相反,拉伸应变能力对输入特征的敏感性是中等和一致的。ECC的机械属性来自多个正负特征的综合作用。值得注意的是,在所有特征中,WR对抗压强度的影响最大,而聚乙烯(PE)纤维成为影响弯曲强度的主要驱动力,抗拉强度,和拉伸应变能力。
    The present study introduces a novel approach utilizing machine learning techniques to predict the crucial mechanical properties of engineered cementitious composites (ECCs), spanning from typical to exceptionally high strength levels. These properties, including compressive strength, flexural strength, tensile strength, and tensile strain capacity, can not only be predicted but also precisely estimated. The investigation encompassed a meticulous compilation and examination of 1532 datasets sourced from pertinent research. Four machine learning algorithms, linear regression (LR), K nearest neighbors (KNN), random forest (RF), and extreme gradient boosting (XGB), were used to establish the prediction model of ECC mechanical properties and determine the optimal model. The optimal model was utilized to employ SHapley Additive exPlanations (SHAP) for scrutinizing feature importance and conducting an in-depth parametric analysis. Subsequently, a comprehensive control strategy was devised for ECC mechanical properties. This strategy can provide actionable guidance for ECC design, equipping engineers and professionals in civil engineering and material science to make informed decisions throughout their design endeavors. The results show that the RF model demonstrated the highest prediction accuracy for compressive strength and flexural strength, with R2 values of 0.92 and 0.91 on the test set. The XGB model outperformed in predicting tensile strength and tensile strain capacity, with R2 values of 0.87 and 0.80 on the test set, respectively. The prediction of tensile strain capacity was the least accurate. Meanwhile, the MAE of the tensile strain capacity was a mere 0.84%, smaller than the variability (1.77%) of the test results in previous research. Compressive strength and tensile strength demonstrated high sensitivity to variations in both water-cement ratio (W) and water reducer (WR). In contrast, flexural strength exhibited high sensitivity solely to changes in W. Conversely, the sensitivity of tensile strain capacity to input features was moderate and consistent. The mechanical attributes of ECC emerged from the combined effects of multiple positive and negative features. Notably, WR exerted the most significant influence on compressive strength among all features, whereas polyethylene (PE) fiber emerged as the primary driver affecting flexural strength, tensile strength, and tensile strain capacity.
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  • 文章类型: Journal Article
    本文研究了不同储存条件对三种类型的农业生物质颗粒的选定理化性质的影响:向日葵壳,麦草和大麻,和木质颗粒。测试是在气候室中进行的,可以模拟真实的储存条件,即具有高空气湿度和可变(±)环境空气温度的条件。结果表明,与木质生物质相比,农业生物质颗粒的降解能力更高。与在高湿度(90%RH)下相比,粒料在变化的±温度下降解的程度较小。水分完全饱和后,农产品颗粒的耐久性平均下降9%,而在向日葵果壳颗粒和木质颗粒的冷冻和除霜后,耐久性降低了2%,和11%的大麻草丸。相比之下,在环境(30°C和90%RH)中,农产品颗粒的下降强度指数下降了20%,在不同的温度条件下下降了15%。没有注意到干物质中所有颗粒的能量参数的变化。另一方面,颗粒在不同环境条件下储存时,水分含量的增加会导致热值降低。
    This article examines the effects of different storage conditions on selected physicochemical properties of three types of agro-biomass pellets: sunflower husks, wheat straw and hemp hurds, and wood pellets. The tests were carried out in a climatic chamber, which allows simulation of real storage conditions, i.e. conditions with high air humidity and variable (±) ambient air temperatures. The results showed higher degradability of agro-biomass pellets compared to woody biomass. The pellets degraded to a less extent at varying  ± temperatures than at high humidity (90% RH). After complete moisture saturation, durability decreases for agro-pellets by an average of 9%, while after freezing and defreezing for sunflower husk pellets and woody pellets durability decreases by 2%, and for hemp hurd pellets by 11%. In contrast, strength-by-dropping index for agro-pellets decreased by 20% after being in the environment (30 °C and 90%RH) and 15% under varying temperature conditions. No change in the energy parameters of all pellets in the dry matter was noted. On the other hand, an increase in the moisture content of pellets when they are stored under different environmental conditions results in a decrease in calorific value.
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  • 文章类型: Journal Article
    脂蛋白(LPs)是胶束样结构,其大小与细胞外囊泡(EV)相似,因此通常是共同分离的,正如电动汽车社区内深入讨论的那样。来自人血浆的LP特别令人感兴趣,因为它们负责胆固醇酯和其他脂肪在动脉中的沉积,引起病变,最终是动脉粥样硬化。血浆脂蛋白可以根据它们的大小来划分,密度和组成为乳糜微粒(CM),极低密度脂蛋白(VLDL),低密度脂蛋白(LDL)和高密度脂蛋白(HDL)。这里,我们使用原子力显微镜对LP进行机械表征。我们表明,用于EV分析的纳米压痕方法也可以用来表征LP,揭示某些粒子之间的特定差异。将LP相互比较,与CM和VLDL相比,LDL表现出更高的弯曲模量,这可能与胆固醇和载脂蛋白的差异有关。此外,CM通常在压痕后在表面上塌陷,HDL在表面粘附后表现出非常低的高度,这两者都是EV样品中存在LP的指示。我们的分析为LP的机械特性提供了新的系统见解。
    Lipoproteins (LPs) are micelle-like structures with a similar size to extracellular vesicles (EVs) and are therefore often co-isolated, as intensively discussed within the EV community. LPs from human blood plasma are of particular interest as they are responsible for the deposition of cholesterol ester and other fats in the artery, causing lesions, and eventually atherosclerosis. Plasma lipoproteins can be divided according to their size, density and composition into chylomicrons (CM), very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL) and high-density lipoproteins (HDL). Here, we use atomic force microscopy for mechanical characterization of LPs. We show that the nanoindentation approach used for EV analysis can also be used to characterize LPs, revealing specific differences between some of the particles. Comparing LPs with each other, LDL exhibit a higher bending modulus as compared to CM and VLDL, which is likely related to differences in cholesterol and apolipoproteins. Furthermore, CM typically collapse on the surface after indentation and HDL exhibit a very low height after surface adhesion both being indications for the presence of LPs in an EV sample. Our analysis provides new systematic insights into the mechanical characteristics of LPs.
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