Initiation and propagation of localized deformation in elasto-plastic strips under uniaxial tension

This paper deals with the evolution of inhomogeneous deformation in shape memory alloy strips and mild steel strips under uniaxial tension. New experiments on NiTi strips, which initially are in an austenitic phase, show that at a critical stress level martensite nucleates in sharp bands inclined at 55° to the axis of loading. Under prescribed end displacement martensite subsequently spreads either by steady-state propagation of inclined transition fronts or via a criss-cross pattern of finger-like features. Similar events have been reported in the literature regarding the evolution of Lüders bands in fine grained steel strips and wires. The similarity of macroscopic events, despite the different mechanisms of instability at the micro-level, prompted us to approximate the material behavior as a finitely deforming elasto-plastic solid with a trilinear up-down-up nominal stress-strain response. Two such stress-strain responses were used in finite element simulations of strip tension tests. In the first the true stress-strain response maintains its stability and in the second the intermediate branch has a negative slope. While both material models produced inhomogeneous deformations with features similar to those of the experiments, the larger initiation peak associated with the second gave results which closely resembled specific experiments. The numerical simulations confirmed that the evolution of events seen in experiments on SMAs and mild steels is strongly influenced by overall geometric (structural) effects. Furthermore, the success of this simple continuum constitutive model strongly suggests that continuum level events remain dominant players in such fine grained materials.     

Investigation of chatter marks on ground surfaces by means of optical methods

In order to characterise chatter marks, in this work, various ground samples are investigated by means of two different optical surface analysis techniques: by using a confocal white light microscope and an angle-resolved light scattering sensor, respectively. The latter is also applied to an industrial belt grinding process in both roughness- and waviness-modes of measuring. These in-process measurements are found in good agreement with those of visual counting. Data processing in terms of the Fourier transformation it is shown to equally well accesses the wavelength of chatter marks in both roughness- and waviness-modes. Therefore it is concluded that chatter marks occurring during the industrial belt grinding can be seen as a superposition of roughness changes and waviness.     

三种钢铁材料的光电光谱分析

介绍了铁基线材、高铬铸铁、高锰钢等3种钢铁的光电光谱定量测定方法。该方法是通过选用与分析材质同基体，主成分接近的标准样品绘制校准曲线，采用自编的计算机校正程序，找出试样的光谱分析值和化学分析值之间的关系模型，并将模型通过计算机程序拟合到控制样品中，当进行材质测定时，只需要在日常标准化操作后将拟合好的控制样品对校准曲线进行控样校正，就可以直接进行试样的测定。该测定方法实用，结果可靠，适用于无相同标准样品条件下的试样光谱定量分析。     

应用DV－5 2000型直读光谱仪分析钢中的酸溶和酸不溶铝

本文描述了用火花原子发射光谱分析的方法，应用美国Ｂａｉｒｄ公司ＤＶ－５２０００（ＨＲ－４００光源）直读光谱分析钢中的酸溶和酸不溶铝。实验中采取虚拟酸溶铝分析通道、二次积分的方法进行测定。本法快速简便，所得分析值与标准值吻合，结果令人满意。     

火焰原子吸收法测定钢铁中铅时阴离子表面活性剂的增感效应及其机理探讨

火焰原子吸收法测定钢铁中铅，采用0．2％十二烷基硫酸钠（SDS）和0．001mol／L硝酸介质，加入硫脲消除共存元素铋的干扰，铅的浓度在0—20μg／mL范围内服从比耳定律。方法检出限为0．10μg／mL，相对标准偏差为2．30％，回收率为97％—99％，样品测定结果令人满意。并对阴离子表面活性剂增感机理进行了探讨。     

Deformation analysis of ferrite/pearlite banded structure under uniaxial tension using digital image correlation

The ferrite/pearlite banded structure causes the anisotropic behavior of steel. In this paper, digital image correlation (DIC) was used to analyze the micro deformation of this microstructure under uniaxial tension. The reliability of DIC for this application was verified by a zero-deformation experiment. The results show that the performance of DIC can satisfy the requirements of the tensile deformation measurement. Then, two uniaxial tensile tests in different directions (longitudinal direction and transverse direction) were carried out and DIC was used to measure the micro deformation of the ferrite/pearlite banded structure. The measured results show that the ferrite bands undergo the main deformation in the transverse tension, which results in the relatively weaker tensile properties in the transverse direction than in the longitudinal direction. This work is useful to guide the modification of the bands morphology and extend the application scope of DIC.     

Effect of Ca/Si ratio on the properties of steel slag and deactivated ZSM-5 autoclaved aerated concrete

In this study, the feasibility of the complete replacement of lime by steel slag (SS) as a calcium material with deactivated ZSM-5 for the preparation of autoclaved aerated concrete (AAC) was investigated. The effects of the Ca/Si ratio on the foaming effect, bulk density and mechanical strength, mineral composition, pore structure and microstructure were studied. The results show that the increase of the Ca/Si ratio enhanced the early foaming effect. AAC with an optimum Ca/Si ratio of 0.92 had a compressive strength and bulk density of 3.1 MPa and 535 kg/m³, respectively, meeting the national standards (GB/T 11968-2020) of grade A2.5 and B05. The increase of the Ca/Si ratio significantly reduced the number of pores with a pore size greater than 60 μm. In addition, X-ray diffraction (XRD) and scanning electron microscopy (SEM) results show that an elevated Ca/Si ratio will change the shape and crystallinity of tobermorite.     

Enhanced Adsorption of Epoxy-Functional Nanoparticles onto Stainless Steel Significantly Reduces Friction in Tribological Studies

Epoxy-functional sterically-stabilized diblock copolymer nanoparticles (ca. 27 nm) are prepared via RAFT dispersion polymerization in mineral oil. Nanoparticle adsorption onto stainless steel is examined using a quartz crystal microbalance. Incorporating epoxy groups within the steric stabilizer chains results in a two-fold increase in the adsorbed amount, Γ, at 20 °C (7.6 mg m⁻²) compared to epoxy-core functional nanoparticles (3.7 mg m⁻²) or non-functional nanoparticles (3.8 mg m⁻²). A larger difference in Γ is observed at 40 °C; this suggests chemical adsorption of the nanoparticles rather than merely physical adsorption. A remarkable near five-fold increase in Γ is observed for ca. 50 nm epoxy-functional nanoparticles compared to non-functional nanoparticles (31.3 vs. 6.4 mg m⁻², respectively). Tribological studies confirm that chemical adsorption of the latter epoxy-functional nanoparticles leads to a significant reduction in friction between 60 °C and 120 °C.     

Characterization of plants and seaweeds based corrosion inhibitors against microbially influenced corrosion in a cooling tower water environment

This study compares the inhibitory activities of methanolic extraction of various plants including Artemisia pallens (MEAP), mangrove leaves like Rhizophora mangle (MERM), Avicennia marina (MEAM) and seaweeds such as Pandia povanica (MEPP), Sargassum tenerrimum (MEST) on the corrosion of mild steel (MS) coupons that were incubated on Pseudomonas stutzeri (P. stutzeri) SKR4 strain isolated from the cooling tower water (CTW). The activities of inhibitors are found using GCMS analysis and interactions between microbes and inhibitors were examined in the test for antibacterial activity, minimal inhibition concentration, biofilm formation assay. These all show an excellent inhibitory effect against P. stutzeri. The weight loss, impedance spectroscopy, and Tafel polarization tests used to validate the corrosion investigations show that the inhibitors MEAP-75, MERM-71, MEAM-69, MEPP-66 and MEST-63 % are effective at inhibiting corrosion at 25 ppm. According to Potentiodynamic polarization plots, these five inhibitors act as mixed-type inhibitors. The surface investigation of MS metals by FTIR, SEM, XRD to examine the biofilm surface and it revealed deep pitting corrosion in the bacterial system. In the conclusion, eco-friendly green inhibitors have controlled the biocorrosion in cooling tower water and are recommended for usage in industries as an alternative to environmentally hazardous inhibitors.     

Inexpensive and robust iron-based electrode substrates for water electrolysis and energy storage

The instability of iron under anodic conditions makes iron-based electrode substrates unsuitable for alkaline electrolyzers and rechargeable alkaline batteries. Therefore, significantly more expensive substrates such as nickel foam or sintered nickel are used. Nickel adds a significant cost to electrolysis and energy storage systems. We show that iron substrates can be stabilized using a unique protective thermal coating. These coatings can also yield some of the most electrocatalytically active electrodes in addition to showing no notable change in performance even after 1500 h of anodic polarization. Besides sintered iron, low-carbon steel mesh can be stabilized similarly. Low-carbon steel protected by a thin layer of lithium-doped cobalt spinel was found to be an excellent current collector for positive nickel hydroxide electrodes in alkaline batteries. Thus, surface-modified iron substrates, 40 times less expensive than nickel, are promising for lowering the material costs of alkaline water electrolyzers and rechargeable alkaline batteries.