scholarly journals Features of the Surface and Subsurface Waves Application for Ultrasonic Evaluation of Physicomechanical Properties of Solids. Part 2. Strenghtned Inhomogeneous Surface Layer

2019 ◽  
Vol 10 (1) ◽  
pp. 69-79
Author(s):  
A. R. Baev ◽  
A. L Mayorov ◽  
N. V. Levkovich ◽  
M. V. Asadchaya
Keyword(s):  
Experimental Data ◽  
Surface Layer ◽  
Spatial Distribution ◽  
Surface Wave ◽  
High Frequency ◽  
Hardened Layer ◽  
Gray Iron ◽  
Physicomechanical Properties ◽  
Inhomogeneous Surface ◽  
Ultrasonic Evaluation

The propagation of a pulsed signal of a surface wave over an object with a non-uniform surface layer, obtained, for example, as a result of surface hardening, with structural damage, is accompanied by the dispersion of the velocity of the wave carrying important information about the parameters of such a layer. The aim of the work is to study the relationship between the acoustic parameters of a pulsed acoustic signal of a surface and subsurface waves and the surface layer of steel specimens hardened by high-frequency hardening, and gray iron-chill. Features of the surface and subsurface waves application for ultrasonic evaluation of physicomechanical properties of solids. Strenghtned inhomogeneous surface layer.A brief analysis of the known works on determining the depth of hardened surface layers by various methods, including high-frequency hardening, cementation, etc., is carried out. Based on the Oulder integral expression. The dependence connecting the wave velocity, its frequency, the depth of the hardened layer and the spatial distribution of hardness represented as a step with a changing slope of its side surface simulating the transition zone of the hardened layer are calculated.Using the pulse method and low-aperture transducers with a frequency of 1−3.8 MHz, the dependences of the surface wave velocity on the cutting height of a layer hardened by HDTV hardening are obtained. A comparison of experimental data and calculations of the theoretical model showed a good qualitative correspondence between them, demonstrate a high «sensitivity» of the method in relation to the nature of the change in hardness over the depth of the hardened layer. It is shown that the proposed approach is promising for solving the inverse problem of restoring the spatial distribution of hardness based on experimental data.The goniometric method was approbated to determine the dependence between amplitude-angle characteristics and depth of the surface steel layers hardened by high-frequency hardening and depth of hardened gray iron specimens layer – with chill. It is shown that the optimal angle corresponding maximum of excited surface wave amplitude in steel specimens is decreasing up to 24–26'vs. hardened depth layer. But when the tested specimens from cast iron this angle decreasing is nearly of 6°. Recommendations on the use of research results in practice are given.

scholarly journals Topographic Position, Land Use and Soil Management Effects on Soil Organic Carbon (Vineyard Region of Niš, Serbia)

Agronomy ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1438
Author(s):  
Snežana Jakšić ◽  
Jordana Ninkov ◽  
Stanko Milić ◽  
Jovica Vasin ◽  
Milorad Živanov ◽  
...  
Keyword(s):  
Land Use ◽  
Surface Layer ◽  
Spatial Distribution ◽  
Soil Erosion ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Compaction ◽  
Soil Management ◽  
Forest Land ◽  
Topographic Position

Spatial distribution of soil organic carbon (SOC) is the result of a combination of various factors related to both the natural environment and anthropogenic activities. The aim of this study was to examine (i) the state of SOC in topsoil and subsoil of vineyards compared to the nearest forest, (ii) the influence of soil management on SOC, (iii) the variation in SOC content with topographic position, (iv) the intensity of soil erosion in order to estimate the leaching of SOC from upper to lower topographic positions, and (v) the significance of SOC for the reduction of soil’s susceptibility to compaction. The study area was the vineyard region of Niš, which represents a medium-sized vineyard region in Serbia. About 32% of the total land area is affected, to some degree, by soil erosion. However, according to the mean annual soil loss rate, the total area is classified as having tolerable erosion risk. Land use was shown to be an important factor that controls SOC content. The vineyards contained less SOC than forest land. The SOC content was affected by topographic position. The interactive effect of topographic position and land use on SOC was significant. The SOC of forest land was significantly higher at the upper position than at the middle and lower positions. Spatial distribution of organic carbon in vineyards was not influenced by altitude, but occurred as a consequence of different soil management practices. The deep tillage at 60–80 cm, along with application of organic amendments, showed the potential to preserve SOC in the subsoil and prevent carbon loss from the surface layer. Penetrometric resistance values indicated optimum soil compaction in the surface layer of the soil, while low permeability was observed in deeper layers. Increases in SOC content reduce soil compaction and thus the risk of erosion and landslides. Knowledge of soil carbon distribution as a function of topographic position, land use and soil management is important for sustainable production and climate change mitigation.

Ultrasonic Evaluation of Compressive Residual Stress of Surface Treated Metals

2005 ◽  
Vol 490-491 ◽  
pp. 184-189 ◽  
Author(s):  
Farid Belahcene ◽  
Xiaolai Zhou ◽  
Jian Lu
Keyword(s):  
Experimental Data ◽  
Residual Stresses ◽  
Nondestructive Evaluation ◽  
Subsurface Layer ◽  
Surface Mechanical Attrition Treatment ◽  
Shallow Subsurface ◽  
Ultrasonic Evaluation ◽  
Mechanical Attrition ◽  
Machine Parts ◽  
Compressive Residual Stresses

Shot peening is an effective method of improving fatigue performance of machine parts in the industry by producing a thin surface layer of compressive residual stresses that prevents crack initiation and retards crack growth during service. Nondestructive evaluation of the prevailing compressive residual stresses in the shallow subsurface layer is realized by the critically refracted longitudinal (Lcr) waves. This paper presents experimental data obtained on SMAT (surface mechanical attrition treatment) steel alloy S355 sample. Comparative travel-time shows that there are statistically significant differences in treated and untreated specimen. With knowledge of the acoustoelastic constants which are obtained by a test calibration, the experimental data indicates that compressive residual stresses are distributed near subsurface (hundreds of micron). These stress results show that the Lcr technique is efficient for evaluation of residual stresses after the surface treatment.

Promising Methods for Activating Rubber Crumbs

2017 ◽  
Vol 44 (3) ◽  
pp. 31-34 ◽  
Author(s):  
V.F. Kablov ◽  
A.V. Perfil'ev ◽  
V.P. Shabanova
Keyword(s):  
Surface Layer ◽  
Microwave Energy ◽  
Physicomechanical Properties ◽  
Surface Activation ◽  
Rubber Composites

Methods for activating the surface of rubber crumbs using different physicochemical effects are examined. The properties of industry-produced activated rubber crumbs and the prospects of their use in different polymer compounds are analysed. The influence of the degree and depth of devulcanisation of the surface layer of rubber crumbs on the rheological and physicomechanical properties of rubber composites is shown. Promising directions of modern research in the area of surface activation of rubber crumbs are described. It is shown that the application of microwave energy to activate rubber crumbs directly before the manufacture of articles from them makes it possible to obtain products with improved properties.

Effect of Additional Shear Strain Layer on Microstructure and Tensile Strength of Fine Wire

2007 ◽  
Vol 340-341 ◽  
pp. 525-530 ◽  
Author(s):  
Satoshi Kajino ◽  
Motoo Asakawa
Keyword(s):  
Tensile Strength ◽  
Surface Layer ◽  
Tensile Test ◽  
Shear Strain ◽  
Crystal Orientation ◽  
Hardened Layer ◽  
High Tensile Strength ◽  
Center Layer ◽  
Fine Wire ◽  
Strain Layer

The mechanical and electrical applications of fine wires (D = 0.1 mm) has become more widely spread. In general, it is well known that fine drawn wires have high tensile strength while maintaining ductility. It has been determined that a hardened layer of around 0.04 mm in depth, referred to as the “additional shear strain layer,” is generated beneath the surface layer of the wire, and this additional shear strain layer affected the tensile strength of the fine wire. As an origin of this phenomenon, it was ascertained that the microstructure of surface layer was finer than that of center layer. The purpose of this paper is to investigate the effect of die angle on the microstructure and the tensile strength of the additional shear strain layer. The tensile test was performed as the surface layer was thinned by electro-polishing, and the crystal orientation and the crystal grain were measured via EBSD. As a result, it was ascertained that die angle affected the tensile strength and crystal grain refinement of the additional shear stray layer.

Recent advances in high-frequency surface-wave methods

2015 ◽  
Author(s):  
Jianghai Xia ◽  
Lingli Gao ◽  
Yudi Pan ◽  
Chao Shen
Keyword(s):  
Surface Wave ◽  
High Frequency ◽  
Recent Advances ◽  
Wave Methods

Modern and Holocene microbial mats and associated microbially induced sedimentary structures (MISS) on the southeastern coast of Tunisia (Mediterranean Sea)

2020 ◽  
pp. 1-21
Author(s):  
Rached Lakhdar ◽  
Mohamed Soussi ◽  
Rachida Talbi
Keyword(s):  
Spatial Distribution ◽  
High Frequency ◽  
Depositional Environment ◽  
Microbial Mats ◽  
Coastal Environment ◽  
Tidal Dynamics ◽  
Very High Frequency ◽  
Intertidal Zones ◽  
Sedimentary Structures ◽  
Very High

Abstract On the southeastern Tunisian coastline, very diverse living microbial mats colonize the lower supratidal and intertidal zones, and locally may extend into the upper infratidal zone. The interaction between the benthic cyanobacteria and their siliciclastic substratum leads to the development of several types of microbially induced sedimentary structures (MISS). The mapping of the microbial mats has allowed the identification of the types of MISS that characterize the different segments of the coastal environment. The modern microbial mats have been compared with those recorded at the top of the Holocene deposits, which are composed of biodegraded microbial black mats alternating with white laminae made of clastic and evaporitic sediments, indicative of very high frequency cycles of flood and drought. A hypothetic profile showing their occurrences along the different areas bordering the coastline is proposed as a guide for the reconstruction of the ancient depositional environment. The roles of tidal dynamics, storms, and climate in controlling their genesis and spatial distribution, are discussed and highlighted. The modern MISS of southeastern Tunisia are compared with their equivalents that are well documented through the different geological eras.

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