scholarly journals NUMERICAL MODELING OF FIELD AND LABORATORY TESTS OF FILL-UP SOILS

2018 ◽  
Keyword(s):  
Numerical Modeling ◽  
Laboratory Tests

scholarly journals Advanced Complex Analysis of the Thermal Softening of Nitrided Layers in Tools during Hot Die Forging

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 355
Author(s):  
Jakub Krawczyk ◽  
Paweł Widomski ◽  
Marcin Kaszuba
Keyword(s):  
Numerical Modeling ◽  
Surface Layer ◽  
Laboratory Tests ◽  
Complex Analysis ◽  
Nitrided Layer ◽  
Hot Forging ◽  
Thermal Softening ◽  
Effect Of Temperature ◽  
Destructive Effect ◽  
Forging Process

This article is devoted to the issues of thermal softening of materials in the surface layer of forging tools. The research covers numerical modeling of the forging process, laboratory tests of tempering of nitrided layers, and the analysis of tempering of the surface layer of tools in the actual forging process. Numerical modeling was supported by measuring the temperature inside the tools with a thermocouple inserted into the tool to measure the temperature as close to the surface as possible. The modeling results confirmed the possibility of tempering the die material. The results of laboratory tests made it possible to determine the influence of temperature on tempering at different surface layer depths. Numerical analysis and measurement of surface layer microhardness of tools revealed the destructive effect of temperature during forging on the tempering of the nitrided layer and on the material layers located deeper below the nitrided layer. The results have shown that in the hot forging processes carried out in accordance with the adopted technology, the surface layer of working tools is overheated locally to a temperature above 600 °C and tempering occurs. Moreover, overheating effects are visible, because the surface layer is tempered to a depth of 0.3 mm. Finally, such tempering processes lead to a decrease in the die hardness, which causes accelerated wear because of the abrasion and plastic deformation. The nitriding does not protect against the tempering phenomenon, but only delays the material softening process, because tempering occurs in the nitrided layer and in the layers deeper under the nitrided layer. Below the nitrided layer, tempering occurs relatively quickly and a soft layer is formed with a hardness below 400 HV.

scholarly journals Adjustment of the Yielding System of Mechanical Rock Bolts for Room and Pillar Mining Method in Stratified Rock Mass

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2082 ◽  
Author(s):  
Krzysztof Skrzypkowski ◽  
Waldemar Korzeniowski ◽  
Krzysztof Zagórski ◽  
Anna Zagórska
Keyword(s):  
Numerical Modeling ◽  
Impact Energy ◽  
Laboratory Tests ◽  
Ore Deposits ◽  
Rock Bolt ◽  
Rock Bolts ◽  
Damage Area ◽  
Rock Bolt Support ◽  
The Impact ◽  
Bolt Support

The article presents a novel yielding mechanism, especially designed for the rock bolt support. Mechanical rock bolts with an expansion head and equipped with one, two, four and six dome bearing plates were tested in the laboratory conditions. Furthermore, in the Phase2D numerical program, five room and pillar widths were modeled. The main aim of numerical modeling was to determine the maximal range of the rock damage area and the total displacements in the expanded room. The models were made for a room and pillar method with a roof sag for copper ore deposits in the Legnica-Głogów Copper District in Poland. Additionally, in the article a load model of the rock bolt support as a result of a geomechanical seismic event is presented. Based on the results of laboratory tests (load–displacement characteristics), the strain energy of the bolt support equipped with the yielding device in the form of dome bearing plates was determined and compared with the impact energy caused by predicted falling rock layers. Based on the laboratory tests, numerical modeling and mathematical dynamic model of rock bolt support, the dependence of the drop height and the corresponding impact energy for the expanded room was determined.

scholarly journals Nowoczesne metody monitoringu geotechnicznego w polskich odkrywkowych kopalniach węgla brunatnego

2018 ◽  
Vol 27 (2) ◽  
pp. 152-166
Author(s):  
Zbigniew Bednarczyk
Keyword(s):  
Numerical Modeling ◽  
Laboratory Tests ◽  
Laser Scanning ◽  
Western Slope ◽  
The European Union ◽  
Line System ◽  
Lignite Mine ◽  
On Line ◽  
Scanning Lidar ◽  
New Research

The article presents research carried out within the framework of the European Union project Euracoal SLOPES. The project is conducted by the partners from six European countries and coordinated by the Geomechanics Center of Nottingham University. Geotechnical research performed in Poland, on the western slope of the Bełchatów Lignite Mine so-called Bełchatów Field included an advanced on-line system of inclinometer and piezometer monitoring of 100 m depth. It was supplemented by ground based laser scanning, LiDAR scanning with the usage of drone and laboratory tests. The results obtained were used for numerical modeling of the slope stability. This should allow for a better prediction of landslide risks and the testing of new research methods.

scholarly journals Advanced Complex Analysis of the Thermal Softening of Nitrided Layers in Tools During Hot Die Forging

2020 ◽  
Author(s):  
Jakub Krawczyk ◽  
Paweł Widomski ◽  
Marcin Kaszuba
Keyword(s):  
Numerical Modeling ◽  
Surface Layer ◽  
Laboratory Tests ◽  
Complex Analysis ◽  
Nitrided Layer ◽  
Thermal Softening ◽  
Effect Of Temperature ◽  
Destructive Effect ◽  
Forging Process ◽  
Influence Of Temperature On

This article is devoted to the issues of thermal softening of materials in the surface layer of forging tools. The research covers numerical modeling of the forging process, laboratory tests of tempering of nitrided layers and the analysis of tempering of the surface layer of tools in the actual forging process. Numerical modeling was supported by measuring the temperature inside the tools with a thermocouple inserted into the tool to measure the temperature as close to the surface as possible. The modeling results confirmed the possibility of tempering the die material. The results of laboratory tests made it possible to determine the influence of temperature on tempering at different surface layer depths. Numerical analysis and measurement of surface layer microhardness of tools revealed the destructive effect of temperature during forging on the tempering of the nitrided layer and on the material layers located deeper below the nitrided layer.

Numerical Modeling and Experimental Validation of Bolted Lap Joints With 1D Hysteresis Finite Elements

2009 ◽  
Author(s):  
J. Abad ◽  
J. M. Franco ◽  
L. Lezaun ◽  
F. J. Martinez
Keyword(s):  
Numerical Modeling ◽  
3D Modeling ◽  
Laboratory Tests ◽  
Experimental Validation ◽  
3D Model ◽  
Lap Joints ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Lap Joint ◽  
3D Numerical Model

The work presented in this paper is part of a larger project for the modeling of dynamic behavior in bolted joints, and it is a further work on the adjustment of bolted joint 3D numerical model. This work shows the study and conclusions of the numerical modeling of a bolted lap joint by means of 1D hysteresis finite element and its validation with dynamical tests. The modeled joint is made up of two plates with a bolt, nut and washer. The behavior curve of the hysteresis element used was obtained by means of a 3D model of the joint, whose parameters and validation were carried out from the results of quasi-static laboratory tests. This procedure could be advantageously extended to any other lap joint given that its computational requirements are less than those required for a detailed 3D modeling.

scholarly journals Análise de um pavimento reforçado com geossintético a partir de resultados de ensaio em equipamento de grandes dimensões

TRANSPORTES ◽  
2011 ◽  
Vol 19 (3) ◽  
pp. 28
Author(s):  
Francis Massashi Kakuda ◽  
Alexandre Benetti Parreira ◽  
Glauco Tulio Pessa Fabbri
Keyword(s):  
Plastic Deformation ◽  
Numerical Modeling ◽  
Laboratory Tests ◽  
Resilient Modulus ◽  
Base Layer ◽  
Plastic Deformations ◽  
Elastic And Plastic Deformations ◽  
Back Calculation ◽  
Pavement Reinforcement ◽  
Elastic And Plastic Deformation

<p><strong>Resumo</strong>: O artigo analisa o beneficio do uso de uma geogrelha como reforço da camada de base de um pavimento. Seções do pavimento e subleito com dimensões próximas às reais submetidas a carregamentos cíclicos foram ensaiadas numa caixa metálica quadrada com lado de 1,5 m e altura de 1,2 m. Concluiu-se que a utilização da geogrelha proporciona a redução de deformações elásticas e permanentes, e que a eficiência do reforço posicionado na interface com o subleito é maior que a do reforço posicionado no horizonte médio da base. Foram ainda determinados os módulos de resiliência da base e do subleito a partir da retroanálise das bacias de deflexões obtidas nos ensaios. Finalmente, a análise numérica de um pavimento hipotético mostrou que a geogrelha pode proporcionar uma extensão expressiva na vida de fadiga do revestimento asfáltico.</p><p><strong>Palavras-chave</strong>: pavimentos reforçados com geosintéticos, geogrelha, ensaios de laboratório em verdadeira grandeza, deformações elásticas e plásticas sob carregamento cíclicos.</p><p><strong>Abstract</strong>: The article analyzes the benefits of the application of a geogrid as base layer pavement reinforcement. Cyclic loaded fullscale sections of pavement and subgrade were tested in a square metallic box with 1.5 m width and 1.2 m height. It was concluded that the geogrid reduces the elastic and plastic deformations and also that positioning the reinforcing at subgrade interface is more efficient than at base medium horizon. The base and subgrade resilient modulus were obtained by back calculation using the deflection basin results from the tests. Finally, a numerical modeling of a hypothetic pavement showed that the geogrid may conduct to an expressive increase of the bituminous surface life.</p><p><strong>Keywords</strong>: geosynthetic reforced pavement, geogrid, full-scale laboratory tests, elastic and plastic deformation under cyclic loadings.</p>

Critical limb ischaemia in diabetes: definition, assessment, prognosis

VASA ◽  
2001 ◽  
Vol 30 (Supplement 58) ◽  
pp. 21-27
Author(s):  
Luther
Keyword(s):  
Diabetic Foot ◽  
Laboratory Tests ◽  
Critical Limb Ischaemia ◽  
Limb Ischaemia ◽  
Clinical Use ◽  
Arterial Reconstruction ◽  
Arterial Circulation ◽  
Diabetic Foot Disease ◽  
Foot Disease ◽  
Fontaine Classification

In diabetic foot disease, critical limb ischaemia (CLI) cannot be precisely described using established definitions. For clinical use, the Fontaine classification complemented with any objective verification of a reduced arterial circulation is sufficient for decision making. For scientific purposes, objective measurement criteria should be reported. Assessment of CLI should rely on the physical examination of the limb arteries, complemented by laboratory tests like the shape of the PVR curve at ankle or toe levels, and arteriography. The prognosis of CLI in diabetic foot disease depends on the success of arterial reconstruction. The best prognosis for the patients is with a preserved limb. Reconstructive surgery is the best choice for the majority of patients.

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