Influence of the kneading water content in the behaviour of single-coat mortars

The effect of water content in the kneading process of mortars for application as single-coat renders was evaluated in terms of several properties. These properties refer to the mortar product in the fresh and hardened state. Characteristics under evaluation in function of kneading water are, for fresh mortar, the apparent density and entrained air while, for hardened products, apparent density, shrinkage, mechanical properties, abrasion wear and permeability amongst others. If some of these characteristics are obtained by standard tests, others, like abrasion wear, had to be adapted and are described here.Both for fresh and hardened products characteristics, kneading water amount significantly changes them and it was possible to establish the proper content of water to be used in order to get a well-behaved single-coat mortar.     

Influence of Experimental Setup and Plastic Deformation on the Shaft-Loaded Blister Test

In the shaft-loaded blister test (SLBT), plastic deformation often occurs at the contact area between the shaft tip and adhesive layer, leading to a larger displacement (blister height) than if the film was loaded elastically. As a consequence, incorporating the displacement variable into the analysis can result in misleading values of the applied strain energy-release rate, G. In this work, the influence of plastic yielding at the contact area on G of a thin film was investigated as a function of some common SLBT experimental variables, namely, substrate hole diameter, film thickness, and shaft-tip diameter. Test specimens consisted of plies of pressure-sensitive adhesive tape adhered to a rigid glass substrate. G was calculated from the following Equations: (1) load-based, (2) hybrid, (3) displacement-based, and (4) combination. Decreasing the film thickness, increasing the hole diameter, or decreasing the shaft-tip diameter lead to more plastic yielding at the contact area as well as to an increase in blister height. The increased blister height resulting from plastic deformation leads to disagreement among the values of G calculated from the different Equations when the displacement variable was included in the calculation. However, the load-based equation, which does not include the displacement, was determined to be independent of plastic yielding and the “correct” equation for calculating G. In addition, the film tensile rigidity (Eh) was calculated using an experimental compliance calibration. The effects of film thickness on the mechanical behavior of the film (bending plate vs. stretching membrane) as well as methods to determine the displacement resulting from plastic deformation are also discussed.     

Enhanced bending strength and microwave dielectric properties of Li2MgTi3O8 ceramics by adding Si3N4 reinforcing phase

In the 5G era, the dielectric materials used in microwave electronic components must have not only have good microwave dielectric characteristics but also excellent structural characteristics. Li₂MgTi₃O₈ (LMT) ceramics have excellent microwave dielectric properties; however, their low bending strength limits their further applications in the 5G era. In this work, the dielectric properties and bending strength of LMT ceramics were optimized by the addition of Si₃N₄ reinforcing phase using a solid-phase method, and the effects of Si₃N₄ addition on the sintering properties, microscopic structure, crystalline phase, dielectric properties and bending strength of ceramics were investigated. The X-ray diffraction pattern indicates that all ceramics exhibit spinel structure. Combined with the phenomenon of grain reduction in the SEM graph, it indicates that the addition of Si₃N₄ can inhibit the grain growth and achieve the purpose of fine-grain strengthening. The dispersion enhancement of second phase particles is also one of the reasons for the increase of bending strength. LMT ceramics doped with 0.5 wt% Si₃N₄ exhibited the maximum bending strength after sintering at 1050 °C for 4 h, which was 76.97% higher than that of pure LMT ceramics. In addition, the ceramics exhibited outstanding dielectric properties: a dielectric constant of 23.20, quality factor of 49344 GHz, and temperature coefficient of ?5.90 ppm/°C. The high bending strength and good microwave dielectric properties indicate that Si₃N₄-added LMT ceramics can be effectively applied in the 5G era.     

工艺参数对SAC-MDF水泥力学性能的影响

以硫铝酸盐水泥(SAC)为基材，聚合物选用取聚乙烯醇(PVA)，并掺加硅烷偶联剂(KH)制备出抗弯强度达165MPa以上，抗压强度超过267MPa的高强SAC-MDF水泥材料，并优化出一套这种材料适宜制备的工艺参数。极少量的硅烷偶联剂能显著提高SAC-MDF水泥的抗弯强度和韧性，增加幅度分别达49．76％和14．55％。     

磨加工及残余应力对氮化硅陶瓷强度的影响

利用X-射线衍射方法测量了经不同磨削的氮化硅陶瓷表面残余应力及其对抗弯强度的影响。结果表明，磨削工艺所引入的残余应力是拉应力，对陶瓷抗弯强度有显著降低。     

多晶氧化铝纤维对莫来石—氧化锆陶瓷材料的增强研究

以电熔莫来石、半稳定氧化锆和α-氧化铝微粉为主要原料,制备莫来石—氧化锆陶瓷材料。在材料中分别外加了（V%）0、5%、10%、15%和20%的多晶氧化铝纤维,并将试样在1500℃保温3h烧成,制备出氧化铝纤维增韧的莫来石—氧化锆复相陶瓷。研究了氧化铝纤维对试样的加热线收缩率、常温耐压强度、常温抗折强度和热震稳定性的影响。结果表明：加入适量的多晶氧化铝纤维能够显著降低莫来石—氧化锆复相陶瓷的加热线收缩率,大幅度提高其常温抗折强度和热震稳定性,而常温耐压强度只有轻微下降。     

Derivation of a crack opening deflection relationship for fibre reinforced concrete panels using a stochastic model: Application for predicting the flexural behaviour of round panels using stress crack opening diagrams

This study is aimed at proposing a simple analytical model to investigate the post-cracking behaviour of FRC panels, using an arbitrary tension softening, stress crack opening diagram, as the input. A new relationship that links the crack opening to the panel deflection is proposed. Due to the stochastic nature of material properties, the random fibre distribution, and other uncertainties that are involved in concrete mix, this relationship is developed from the analysis of beams having the same thickness using the Monte Carlo simulation (MCS) technique. The softening diagrams obtained from direct tensile tests are used as the input for the calculation, in a deterministic way, of the mean load displacement response of round panels. A good agreement is found between the model predictions and the experimental results.     

烧结法微晶玻璃装饰板材的力学性能研究

本文研究了烧结法微晶玻璃装饰板材的密度、抗折强度等力学性能,讨论了成分、结构对密度、抗折强度的影响.     

壁厚补偿原理在R/D<2弯管制作工艺中的应用

介绍了壁厚补偿原理在R/D值较小情况下弯管制作中的应用。该方法克服了常规工艺在此情况下容易出现的问题 ,使弯管加工的各项指标均优于国家标准     

Injection molding,debinding and sintering of ZrO2 ceramic modified by silane couping agent

In this paper, Injection molding, debinding and sintering of ZrO₂ ceramic modified by silane coupling agent (A151) were studied by measuring the melt index of feedstocks, the soluble removal ratio of green parts, the bending strength of green and sintered parts, the surface and fractural morphologies of sintered parts. The results showed that the melt index of ZrO₂ feedstocks, the weight removal ratio of soluble binders, and the bending strength of green parts increased after adding A151. When the density of sintered parts was between 5.97–6.03 g/cm³, it was not the main factor influencing the bending strength. However, the bending strengths of sintered parts decreased due to microcrack formation when thermal debinding process was too fast or slow. The interesting phenomenon of the abnormal grain growth with transgranular fracture in the sintered parts obviously occurred above 1550 ℃, which made the effect of sintering temperature on the strength become complex.