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Load transfer and stress in a piled gravity retaining wall
Qun Chen, Li Wan, Changrong He, Zihui Lai, 2010, izvirni znanstveni članek

Opis: The piled retaining wall is a new type of railway retaining structure in China. In the current design, the retaining wall, the beam and the piles are assumed to be independent components. Both the mutual action of the retaining wall, the piles and beam, and the influence of the soil or rock foundation on the structure are not fully considered, so that there are some limitations in the current design method. In this paper, using field observations and a three-dimensional finite-element analysis, the lateral earth pressure on the wall back, the stress distributions and the forces of the reinforcements in the beam and the pile were studied. The simulation results were in good agreement with the field observation data. These results revealed that the tensile stresses were very small and that these stresses were positive in most zones in the beam and the pile. It can also be observed that the tensile stresses or forces in the beam and pile obtained in this study were much smaller than those obtained using the current design method. This clarified the fact that the current design method used for the beam and the pile was very conservative and that it should be optimized to consider the effect of the foundation on the whole structure and the interactions among the different components.
Ključne besede: piled gravity retaining wall, field observation, finite-element analysis, stress, load transfer mechanism
Objavljeno: 11.06.2018; Ogledov: 342; Prenosov: 42
.pdf Celotno besedilo (558,92 KB)
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A new method for determining extra time by considering ergonomic loads in the garment and metal working industries
Vekoslav Verhovnik, Andrej Polajnar, 1993, izvirni znanstveni članek

Opis: The changing labour conditions in the garment and metal-working industries have led to the necessity of determining new extra times to establish the time standard. In this paper, a method of measuring stress and strain imposed upon the operator in new working conditions by determining the additional production coefficient is presented. The method gives criteria and grades to assess stress at the workplace. Physical stress (dynamic and static), thermal and visual stress, discomfort caused by noise, aerosols, gases and vapours, and the stress due to monotony are assessed. The stresses are expressed by ecological, physiological and psychological indexes. The indexes are pondered. Ponderation includes the factor of the magnitude and the time of exposure to stress. Ponderation is expressed by the number of points, the total being an adequate presentation of the stresses. Stress and strain decrease the working performance of the operator. Therefore they must be included in the standard to compensate for the operator's lower working efficiency due to physical and psychological strain at the workplace, Short breaks and stops allowed during work enable the operator to perform work tasks without getting excessively tired. The necessary correction of the production time is made by applying the ergonomic coefficient Ker.
Ključne besede: job analysis, production planning, stress assessment, time study, working conditions, working environment
Objavljeno: 30.03.2017; Ogledov: 555; Prenosov: 73
.pdf Celotno besedilo (7,13 MB)
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Leak-before-break analysis of a pressurizer - estimation of the elastic-plastic semi-elliptical through-wall crack opening displacement
Nenad Gubeljak, Jožef Predan, Dražan Kozak, 2012, objavljeni znanstveni prispevek na konferenci

Opis: The work presents methods to estimate elastic-plastic semi-elliptical through-wall Crack Opening Displacement (COD) for the Leak-Before-Break analysis of a pressurizer. Usually proposed methods are based on GE/EPRI approach or on the reference stress and J-integral as stress intensity factor (SIF) along the crack tip. J-integral calculation provides the value of SIF ateach node of mesh along the crack tip, where values vary from the surface to middle section of material in respect to material properties. COD value is calculated through thickness along the centre of crack. The COD values are less sensitive to distance from crack tip and material properties. The engineering approach for the calculation of J-integral by using COD values and material full stress-strain data is given. COD values are proportional to surface length of semi-elliptical through wall crack of the pressurizer
Ključne besede: mehanika loma, semi-elliptical through-wall crack, crack opening displacement, GE/EPRI approach, leak-before-break analysis, reference stress approach
Objavljeno: 10.07.2015; Ogledov: 813; Prenosov: 29
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On new approach to rheological modeling of an electrostatic ash and water - quadratic law
Primož Ternik, 2002, objavljeni znanstveni prispevek na konferenci

Opis: In the paper a new rheological model for an electrostatic ash and water mixture is proposed. The fundamental equation of the rheological model was used to determine the relationship between the shear stress and the shear rate as well as the equation of a velocity profile for the flow through a straight pipe. Experimental results obtained from a capillary viscometer were used as the basis to determine the parameters for the proposed model by the non-linear regression analysis. With the Quadratic law a numerical analysis of a mixture flow through a capillary pipe with the finite volume method was performed. The derived equations for the velocity profile, shear stress and shear rate were validated through a comparison of numerically obtained and theoretical results. Finally, the compariosn between the Quadratic and the Power law is presented.
Ključne besede: fluid mechanics, non-Newtonian fluids, mixture of electrofilter ash and water, flow in pipes, capillary pipes, rheological model, velocity profile, shear stress, finite volume method, numerical analysis, quadratic law, power law, mehanika fluidov
Objavljeno: 01.06.2012; Ogledov: 1630; Prenosov: 26
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Modelling of surface crack growth under lubricated rolling-sliding contact loading
Boštjan Zafošnik, Zoran Ren, Jože Flašker, Gennady Mishuris, 2005, izvirni znanstveni članek

Opis: The paper describes modelling approach to computational simulation of surface crack growth subjected to lubricated rolling-sliding contact conditions. The model considers the size and orientation of the initial crack, normal and tangential loading due to rolling-sliding contact and the influence of fluid trapped inside the crack by a hydraulic pressure mechanism. The motion of the contact sliding load is simulated with different load cases. The strain energy density (SED) and maximum tangential stress (MTS) crack propagation criteria are modified to account for the influence of internal pressure along the crack surfaces due to trapped fluid. The developed model is used to simulate surface crack growth on a gear tooth flank, which has been also experimentally tested. It is shown that the crack growth path, determined with modified crack propagation criteria, is more accurately predicted than by using the criteria in its classical form.
Ključne besede: fracture mechanics, numerical methods, contact loading, finite element analysis, internal pressure, maximum tangential stress, strain energy density, surface crack growth
Objavljeno: 01.06.2012; Ogledov: 1876; Prenosov: 71
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Numerical analysis of constraint effect on ductile tearing in strength mismatched welded CCT specimens using micromechanical approach
Bashir Younise, Marko Rakin, Bojan Medjo, Nenad Gubeljak, Dražan Kozak, Aleksandar Sedmak, 2011, izvirni znanstveni članek

Opis: In this paper, constraint effect on ductile fracture initiation and propagation has been studied. Three-dimensional finite element analyses of mismatched welded joints made of high strength steel, have been performed for centre-cracked tensile (CCT) specimens. Different weld widths and material mismatching ratios have been considered. Ductile fracture parameter, crack tip opening displacement at crack growth initiation (CTODi), has been obtained for centre-cracked tensile (CCT) specimens using local approach to fracture and compared with experimental results of single edge bend specimens. Micromechanical complete Gurson model has been applied to investigate fracture behaviour of cracked welded joints. Crack tip constraint has been analysed through stress triaxiality in order to study transferability of fracture parameters from one geometry to another.
Ključne besede: constraint effect, ductile fracture, finite element analysis, material mismatching, stress triaxiality, transferability
Objavljeno: 01.06.2012; Ogledov: 1170; Prenosov: 81
.pdf Celotno besedilo (334,21 KB)
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