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This paper intends to study an effect of burnishing and annealing on static recrystallization. The result is expected to be used for a new technology to control only material surface microstructure in a steel plate. In this process, the stored strain energy by burnishing and the thermal energy by annealing lead to static recrystallization and grain growth in a material, which improve the microstructure of the material. In this paper, roller burnishing is employed to introduce the shear strain into the surface of the pure iron sheet. And effects of burnishing and annealing on static recrystallization in the finished surface layer are investigated utilizing Electron Back Scattering Diffraction (EBSD) analysis technique. The generation of shear deformation was confirmed by Kernel Average Misorientation (KAM) values at the surface layer. By conducting a series of the annealing and EBSD analyses, the static recrystallization process is observed. Since enough strain energy is accumulated by the burnishing in a specimen with large shear deformation zone, the static recrystallization occurs on the burnished surface preferentially after the annealing. [ABSTRACT FROM AUTHOR]

The standard assumption, some results and final conclusions of authors’ research on bridge testing are presented in the paper. The results concern more than two thousands bridge superstructures that have been already tested on site. The stiffness of the bridges as well as their behavior under load tests are described. The following values: superstructure displacement, strain and subsidence of supports have been analyzed by the static load tests. Moreover, the identification of dynamic amplification factor, natural frequency, mode shapes and damping have been analyzed by dynamic bridge testing. The paper focusses on the dynamic method of control the suspension system forces. Based on registration and analysis of free vibration of a suspender, the authors present quick, non-destructive and reliable test as the contemporary method to improve safety of arch and suspension bridge superstructures. [ABSTRACT FROM AUTHOR]

Assessment of soil dynamic parameters via wave propagation method utilizing results of theoretical and experimental analysis of elastic or visco–elastic waves. The theory underlying the problem of stress–wave propagation in half space medium is based on the assumption of an application of the impulse–seismic methods (ISM) or the phase velocity method. In this paper is only outlining the basic of the theoretical subject which is necessary for experimental applications. ISM experimental study of ground stress–wave propagation permits the ground to be modelled as a damped, viscoelastic half space. The viscoelastic model of soil simulation using the complex modulus conception , offers a very good approach to the actual soil behavior. The paper also presents the experimental ISM tests procedure in–situ and results obtained by correlation and spectral analysis. As an example, the finite element method (FEM) was in a case study also used for modelling the body and surface wave propagation processes in the ground modelled as an elastic medium. [ABSTRACT FROM AUTHOR]

The paper demonstrates an approach to calculating damping factors of flexible pavement courses according to the operational in-place testing. The mechanical and mathematical simulation of the dynamic strain-stress condition of the multilayer semi-infinite space allows studying quantitative and qualitative relationship of wave field attenuation factors and mechanical parameters of pavement design courses. The paper presents the effect of the damping factors of pavement courses on the energy volume transferred to the pavement structure due to a standard vehicle passage. [ABSTRACT FROM AUTHOR]

In this paper the authors have set off from a critical approach in order to evaluate the CO 2 emission in a lecture hall (amphitheater) with a high number of occupants – 62 -, in order to determine the moment when it is required for the ventilation systems to intervene in the provision of air exchanges necessary to assure the hygienic conditions. The notion of stress used in this context refers to the continuous and degrading action of the CO 2 emissions against the occupants, we named the CO 2 emission external agent, and the increase of CO 2 emission will lead to the decrease of the efficiency of occupants activity inside the amphitheatre. The CO 2 measurements were made in the amphitheatre on a group of students, and it helped to evaluate the phenomenon and the mathematical apparatus confirmed the application of the theory of reliability stress in the studied problem. We hope that this approach will contribute to the establishment of some practices referring to the control and management of the functioning of ventilation systems in buildings with a significant number of occupiers and will contribute to the design of a device to command and control the functioning of the ventilation installation in concordance with the CO 2 emissions on the basis of the theory presented in this paper. [ABSTRACT FROM AUTHOR]

The paper aims to assess the elastic-plastic behaviour of the honed pipes made of steel type E355 subjected to cyclic interior pressure using experimental methods and numerical analysis. In every industry domain, the pipes with thin or thick walls subjected to internal pressure are used. Regardless of the material they are used, the pipes are stressed on axial and circumferential directions, in time. Being subjected to variations of pressure or increasing of pressure over the allowable limit, the pipes can explode causing many damages. The pipes explosion subjected to internal pressure can be predicted knowing the elastic-plastic behavior of the pipe. Starting from theory of stresses in thin and thick pipes, the paper approaches the elastic - viscous and plastic behavior of the steel pipes subjected to periodical internal pressure by experimental. Besides identifying the rheological behavior of thin and thick pipes experimentally tested, the state of stresses and strains were analyzed by numerical method. The behavior of thick wall pipes differs from that of thin-walled pipes, both in terms of rheological and state of stresses and strains. The paper combines experiment and numerical methods for determining the probabilistic burst of the steel pipe. The samples (thin and thick wall pipes) were subjected to 20 loading cycles at 400 bar: the first 10 cycles of loading and unloading were produced for 60 second/cycle and than the other 10 cycles were produced for 120 second/cycle. The exterior diameter of tested pipes was measured both after 30 seconds of loading and after 30 seconds without pressure. These measurements were repeated for each cycle. [ABSTRACT FROM AUTHOR]

The cranes are currently one of the most common devices for transporting loads and can be applied in many industry areas. This paper includes the numerical strength analysis only of the gantry crane beam. The mathematical model and numerical simulations of mechanical phenomena in the gantry crane beam are presented in this paper. The problem was solved by the finite element method. Analysis was made to the gantry crane beam, which cross-section was the I-beam or T-beam and it was loaded different loads. One takes into consideration in the numerical model the motion of the crane trolley along the beam. As a result of the computations carried out, the stresses and displacements of the structure of gantry crane were obtained. The influences of shape change of the crane beam on the Huber-Mises stress in the steel beam were estimated. It sought to that the maximum value of Huber-Mises stress induced in the gantry crane beam was less than the strength of material, because then the design is safe. [ABSTRACT FROM AUTHOR]

This paper presents the results of research on improving the efficiency of the mechanical agglomeration through optimising the distance to which the ram approaches the die face in the final position. The focus of this study is the influence of the compression length on the value of the ultimate stress in the process of mechanical agglomeration of crystallized carbon dioxide. The first part of the paper proposes a model describing the influence of the geometric parameters of the residual amount of material which must remain in the cylinder on the value of axial force during subsequent compression phase of the process. The research part of the paper presents the empirical research results to verify the proposed model. The results of the work will be used to determine the influence of the described geometrical parameters of the dry ice residue on the axial force value. The derived mathematical model will be used for defining the design requirements as the starting point for the design and building of dry ice compression and granulation machines. [ABSTRACT FROM AUTHOR]

The Particle Image Velocimetry is a powerful non-invasive technique to analyse displacements in experimental tests. Displacement increments elapsed between the capture of two digital images are commonly measured on points of a predefined grid fixed in the space. Therefore, tracking the movement of physical particles, which is interesting information especially in cases dealing with large displacements, is not possible when using this procedure. A post-processing code has been developed to get accumulated displacements, incremental and accumulated strains, as well as other variables such as velocity and acceleration, in points that represent a portion of the deformable object analysed. The procedure is of interest specially when dealing with large displacements. The method presented is especially useful to compare experimental measurements with MPM numerical results. The variables from the numerical model stored in material points can be directly compared with the experimental measurements obtained by means of the post-process code presented in the paper. The methodology is applied for the analysis of the failure of a dry granular slope performed in a 1 g scaled laboratory test which is numerically modelled with an MPM code (GeoPart). The aim of the paper is to show the capabilities of the new PIV interpretation procedure by comparing experimental and numerical results. The accuracy of the MPM model presented is not the main focus of the paper, but some limitations of the model are highlighted. [ABSTRACT FROM AUTHOR]

Stress oscillations and inaccuracies are commonly reported in the material point method (MPM). This paper investigates the causes and presents a method to reduce them. The oscillations are shown to result from, at least in part, two distinctly different causes, both originating from the shape function approximations used. The first is due to the components of the stiffness matrix (or other matrices) being derived by performing numerical integration using the material points, and the second is due to calculating the strain from the nodal displacements of the elements, interpolated to the material points, via the shape function spatial derivatives. In this paper, an improvement for the recovery of results from the nodes to the material points is presented, where an increase of the C n continuity along with an interpolation involving nodes from neighbouring elements is applied. [ABSTRACT FROM AUTHOR]

The paper presents a solution of the analysis concerning the behavior of the steel lattice girder under a cycle of dynamic impulse I=P·τ 0 . In this analysis I usethe theory of shakedown. I assume that this load causes anon elastic reaction which it contain dissipation of energy, so we have to continue the deformations and residue forces in the rods. At a certain intensity of these forces, the construction can reaction subsequent cycles of load without further dissipation of energy, i.e. in the field of secondary elastic. This condition is referred to as adapting the structure to the objective of cyclic loading. Lattice girder models the system of the masses gathered combined hinge of tension members and discrete compression members. Obtaining solutions requires a theory of moderately rods. Solution system dynamics are looking for using of the finite difference method with explicit time integration scheme. I look for shakedown load capacity by direct analysis of the dynamics of the girder in the area non elastic, by checking if there is a loss dissipation of energy in next cycles of loading. Thus determines the member of possible repetitions of the assumed impulse load exceeding which generates no longer increases dissipation of energy. In the analysis I take into account the possibility buckling compression members and consequently the non-elastic vibration in the longitudinal and transversal geometric nonlinearity range. The main issue is to determine after the next cycle of the load state of inelastic displacement nodes and residual internal in the rods. These amounts represent the initial condition to describe the load cycle. It is possible to use the approach presented in the paper, in order to assess the relevance of the type of accidental action. In such cases, it is assumed that low times of the impact of accidental action and assumed irreversible serviceability limit states with criterion limit deformation permanent structures or amplitude displacements and deformations. The intensity of the accidental action is greater than the shakedown load capacity. I use model of deformation of the material: perfectly elastic-plastic. The theory of shakedown is illustrated by the described examples. [ABSTRACT FROM AUTHOR]

By rapidly expanding from a compact, stowed bundle to a functional space enclosure, deployable structures can address temporary needs in a minimum amount of time. Using the intrinsic elastic behaviour of flexible elements — active bending — in the design of transformable or deployable structures leads to a wide range of kinetic concepts. This component transformation can decrease the complexity that often comes with rigid-body mechanisms. This paper presents one principle for deployable bending-active structures, based on the interaction between a deployable grid and a restraining membrane: deployable textile hybrid structures. A case study illustrates the design concept and the deployment and assembly processes that allow multiple structural transformations. The large interdependency of the form and material behaviour of bending-active structures, contrary to conventional form-active structures, requires a specific modelling approach. The approach presented in this paper allows feedback between the parametric input of starting geometry and material characteristics, and the output geometry and internal stress. Working with a high-strain fabric without cutting pattern, balancing the stresses and strains between the bending elements and tensile fabric becomes the prime focus. Although the preliminary results are acceptable in theory, a more detailed structural analysis and real-scale models should validate the assumptions of rapid assembly and the structural behaviour on a realistic and practical level. [ABSTRACT FROM AUTHOR]

The paper gives a brief review of works describing bending torsion analysis of beams with corrugated web. The authors put forward a solution specifying V. Vlasov's famous thin-walled bars theory which is generally used to calculate stress-strain behaviour of beams with corrugated web bending torsion. The specification lies in the following: the researchers measure flexure-torsion characteristics of the cross-section while increasing pure torsion moment of the cross section by means of introducing equivalent flange thickness into calculations. To check the efficiency of the introduced method the authors calculated five beams with sinusoidal corrugation for two concentrated forces action. The paper introduces the results of these five methods of beam calculation including the one developed by the authors. The obtained results showed that the tension value in each case is almost the same (with maximum 7% difference in rates). The research also determines the scope limitations of the authors’ specified theory. [ABSTRACT FROM AUTHOR]

This paper reports the development of innovative tri-axial braided structures for strain and damage sensing of geotechnical structures. These innovative braided structures have been developed through braiding of polyester multi-filaments over an axial core composed of mixture of conductive (carbon) and non-conductive (glass) fibres. It was observed that the developed structures were capable of self-monitoring of strain and damage and tailoring the composition of core fibres resulted in excellent sensing of low strain in continuous manner with gauge factor as high as 23. It was further observed that the mechanical performance and surface roughness (which controls their adhesion with soils) could be easily tailored through adjustment of core and sheath component's parameters, respectively. Furthermore, a self-sensing epoxy matrix containing uniformly distributed short carbon fibres was developed in order to combine with the developed braided structures (through impregnation using a special technique) and to further enhance their self-sensing capability. The results discussed in this paper depict that these tailorable and innovative braided structures can be advantageously applied in geotechnical structures for sensing purposes. [ABSTRACT FROM AUTHOR]

Paper approaches the problem of considering the unsaturation of soils above water table in the slope stability analysis, condition for obtaining realistic results in both cases of rainfall infiltrating into the soil mass and drainage for improving soil stability. It presents in its first part a brief review methods related to unsaturated stress analysis applied for slope stability analysis, such as Unsaturated phi-b, Unsaturated Fredlund, Unsaturated Vanapalli, Unsaturated Khalili and Unsaturated Vilar model. These methods are estimating in different manners the shear strength depending on soil unsaturated conditions. These methods are applied in the second part of the paper in a case study, presenting a site affected by landslides located in Cluj-Napoca, Romania. For the slope stabilization a siphon drain system has been proposed and installed. An experimental program started and is ongoing on site, compromising site monitoring of suction using jet fill tensiometers and laboratory testing. Site measurement of suction in presence of drainage system was used for perform slope stability analysis using SVSlope software and the embedded methods for estimating the increase in soil shear strength when passing from saturated to unsaturated state. [ABSTRACT FROM AUTHOR]

Many of the world's railways run on ballasted track, which has for nearly 200 years provided a stable support for train operation. However, with trafficking the geometry of the track deteriorates, mainly as a result of the development of differential settlement of the track-bed (ballast and sub-base). When the geometry defects become too severe, maintenance is needed to realign the track to enable the continued safe running of trains. Maintenance is a major cost associated with ballasted railway track, which usually takes the form of tamping. However, tamping damages the ballast, resulting in a diminishing return period between maintenance interventions until eventually the track-bed requires full renewal. A major component of the differential settlement can be attributed to the ballast layer. However, differential settlement of lengths of track cannot easily be modelled or predicted either computationally or experimentally. Thus the total plastic (permanent) settlement is often used as a proxy for the potential for the development of differential settlement along a length of track in the field. Many empirical models have been developed to predict ballast settlement, usually as a function of the number of train axle passes and/or the cumulative load. However, these models may produce very different results, perhaps indicating that the input variables have not been adequately formulated. This paper describes some current empirical ballast settlement models, and evaluates them using experimental data generated using the Southampton Railway Testing Facility (SRTF). This apparatus represents a section of track consisting of a single sleeper bay 650 mm wide, confined by rigid sides that enforce plane strain conditions. The paper summarises the strengths and weaknesses of the existing models, and suggests variables that could be taken into account to improve them. [ABSTRACT FROM AUTHOR]

Treating soft clay with cement and fibre has become an effective ground improvement technique for transport infrastructure. Application of recycled fibres in deep soil mixing columns in soft soil sections of road and rail projects is being considered by designers and clients as an efficient technique. However, the combined effect of cement and fibre at failure requires further investigation. As the effective stresses increase to a sufficiently high stress, the effect of cementation is diminished due to the degradation of cementation bonds and the fibre exhibits failure due to either complete pull-out or breakage from the soil matrix. Thus, the failure envelope of the reinforced soil gradually merges with that of un-reinforced soil at higher stresses. In this paper, a constitutive model is proposed to simulate the behaviour of the cement treated-fibre reinforced soil based on the Critical State Soil Mechanic and the Modified Cam Clay model. In particular, the proposed model captures the beneficial effects of cementation and fibre reinforcement such as the improvement in strength and ductility while the cementation degradation and the failure mechanism of the fibre are also considered. In addition, a series of un-drained triaxial tests were conducted to verify the performance of the proposed model. This paper concludes that adding fibre into the cement treated soil clearly improves its residual strength, thus, a significant increase in ductility is observed and well simulated. In this study, by modifying the mean effective stress to include the cementation degradation and the fibre failure mechanism, the proposed model results in realistic prediction for the behaviour of soil treated with cement and fibre. [ABSTRACT FROM AUTHOR]

The long-term settlement of railway tracks is a consequence of permanent deformations taking place in the track granular layers and subgrade. In the ballast layer, which experiences the highest stress amplitudes during train passages, these permanent deformations strongly depend on the loading conditions, which in turn depend on several factors as the train speed and axle loads, sleeper-ballast initial pressure, or track geometry quality. Moreover, under the action of moving loads from trains, further to a very significant increase of the vertical stress, the ballast layer experiences the rotation of the principal stresses, which is another aspect that significantly influences the long-term structural behaviour. This paper numerically analyses the stress changes in the ballast due to train passages, aiming at showing how these stresses may vary depending on the loading conditions. A numerical program of dynamic simulation is used that considers the nonlinear resilient nature of the ballast and the three-dimensional representation of the track-ballast-soil system using the FEM. The paper shows that dynamic effects due to trains travelling at very high speeds can significantly influence the stress path followed during loading and the principal stresses rotation inside the upper layers of the track. The paper also shows the importance of the consideration of the ballast nonlinear behaviour in the rotation of the principal stresses. [ABSTRACT FROM AUTHOR]

The small strain behaviour is a key indicator for assessing the performance of compacted fills. The initial compaction conditions i.e. water content and applied energy, govern compaction effectiveness and, thus, the structure and matric suction of compacted subgrade soil. This paper presents an experimental study of the small strain behaviour of a typical compacted subgrade soil, i.e. silty sand, prepared with different compaction conditions. Specimens were prepared for different compaction states to mimic the typical acceptance criteria of end-product specifications. The small strain modulus (G 0 ) was evaluated using Bender elements, while the post-compaction matric suction was measured using the filter paper method and a tensiometer. The experimental data indicates a strong modulus dependency on water content or suction across the compaction plane but suggests G 0 is better described as a function of the degree of saturation (S r ). The laboratory results are also examined in light of common end-product specifications, which show that it may be beneficial to compact the soil slightly dry of optimum moisture content from the modulus point of view. [ABSTRACT FROM AUTHOR]

The paper deals with computational modeling of radial tire for cars. The authors used FEA (Finite Element Analysis) utilizing program ANSYS. The authors are oriented not only to the strain-stress analyses of tire. In relation to the tire computational models, the composite structure parts (textile carcass, steel-cord belt and textile belt) cannot be implemented up to the level of reinforcing cords because of the time difficulty as well as the large number of the finite elements. The composite structure parts are partially replaced with some specified stiffness. The paper describes the different ways of replacement of structure represented by the steel-cord belt. These replacements are used for FEA of tire. [ABSTRACT FROM AUTHOR]

Experimental fatigue study has been conducted in this paper to investigate the effects of mean strain on the fatigue behavior of superelastic Nitinol in short life regime. Nitinol alloys are used in many applications such as aerospace and bioengineering in which these alloys may be subjected to cyclic loading with mean strains/stresses. For traditional metals, presence of tensile mean strain/stress can significantly reduce fatigue lives. For superelastic Nitinol alloys, however, a more complex behavior is observed under tensile mean strains and ironically some beneficial effects of tensile mean strains have been reported in the literature. This paper aims to experimentally study the effects of tensile mean strains on the fatigue resistance of superelastic Nitinol alloys. Fatigue tests were conducted at room temperature (∼24 °C) where the material shows superelastic response. Strain-controlled uniaxial fatigue tests with and without tensile mean strains were conducted on standard solid circular specimens. Cyclic deformation and fatigue of the material was studied. Results from this study demonstrates the detrimental effects of mean strain on the fatigue of superelastic Nitinol at least for comparatively large strain amplitudes. Scanning electron microscopy (SEM) was used to investigate the fracture surface and observe the crack initiation sites. Inclusions such as TiC particles located at or near the surface were found to serve as the main crack initiation sites. [ABSTRACT FROM AUTHOR]

The advantage of the new compressed natural gas (CNG) marine transportation technology is less investment in infrastructure and greater flexibility. It is highly competitive as compared to pipelines and liquefied natural gas (LNG) transport for distances of up to 2,500 – 3,000 nautical miles. Due to the high pressure inside CNG containers, its safety is the first important factor to be considered. Leak-before-break (LBB) is an important methodology of maintaining the integrity of pressure vessels. However, the Joule-Thomson (JT) cooling effect occurred during a leak may impact the validity of the LBB approach. In this paper, a looping model based on MATLAB software is developed starting with the gas at room temperature and 250 bar at the entrance of the crack. From this, the pressure and JT temperature drop is calculated initially, which in turn affects the gas properties, such as viscosity, density, thermal conductivity and heat transfer coefficients. Heat transfer and FEA analysis using a 3D model of the plate with a central through-thickness crack are carried out. Under the internal pressure of 250 bar, the temperature drop and the stress intensity factor in the vicinity of the crack is 59.7 °C and 120 MPa· m 1/2 , respectively. The stress intensify factor obtained is higher than the fracture toughness of the material at the same low temperature. However, the structure may not experience a catastrophic failure. The reasons for this phenomenon are discussed in the paper. [ABSTRACT FROM AUTHOR]

This paper is based on a ductile failure simulation under dynamic loading conditions using finite element (FE) analyses. This paper proposed to implement fracture simulation based on the energy based numerical ductile fracture model. The energy based numerical ductile fracture model is determined to be incremental damage in terms of stress triaxiality ( σ m / σ e ) and fracture strain energy ( W f ) for dimple fracture from tensile test result with FE analyses technique. Since dynamic loading effect is especially important to assess crack-like defect components, this work propose the integrated model which combines quasi-static with dynamic loading effect. In order to validate energy based numerical ductile fracture model in dynamic loading conditions, this paper compares FE results with test results. The tensile properties for SA 508 Gr. 1a carbon steel were examined over a wide range of strain rates. Five different strain rate tensile test results are fitted by Johnson-Cook model. Also, two types of notch tensile tests were examined under four different strain rates. The energy based numerical ductile fracture model criterion was calibrated by FE analyses with strain rate dependent tensile and notch test results. The calibrated damage model predicts CT test result. Simulated results agree well with experimental data. [ABSTRACT FROM AUTHOR]

Elbows are highly stressed components and are critical to the integrity of the pipework systems and important to the safety of plants. In this paper, a local collapse solution for elbow end welds has been developed and subsequently used in defect assessments. A creep-fatigue crack growth assessment of the elbow end weld has been carried out assuming a defect initiated in the weld under the loading conditions of internal pressure, system moment, high temperature and welding residual stress. For the elbow end weld, the limiting defect calculation has been conducted using R6 procedures and the creep-fatigue crack growth assessments have been performed using R5. Furthermore, appropriate combinations of creep deformation and creep crack growth used for the R5 assessment are detailed in the paper. A surface breaking circumferential semi-elliptical defect postulated on the external surface has been assessed. After presenting the detailed assessment result, conclusions are drawn. [ABSTRACT FROM AUTHOR]

Shanghai Nuclear Engineering Research and Design Institute (SNERDI) had been involved in ASME Section III environment assistant fatigue (EAF) task group (TG) and undertaken the calculation and verification work of first round sample problem, which was intended to test the engineering application of environmentally assisted fatigue (EAF) using the F en correction factor method of Code Case N-792 Rev.0 and the proposed Code Case for evaluation of strain rate in EAF evaluations. This paper will present the sample problem of a light water reactor (LWR) primary loop stainless steel nozzle under some thermal transients and the calculation procedure of detailed integral methods according to Code Case N-792. Moreover, the method of strain rate calculation was particularly studied and discussed which is essential to the F en value. The F en correction factor results and the comparison with other participants is presented in this paper. [ABSTRACT FROM AUTHOR]

In a 3-part series of papers, of which this paper is Part II, we investigate the applicability of the fully quadratic hexa-27 element (see Part I) to four problems of interest to the pressure vessels and piping community: (1) The solid-element-based analysis of a welded pipe elbow with a longitudinal surface crack in one of its weldments. (2) The solid-element-based analysis of the elastic bending of a simple cantilever beam, of which the exact solution is known. (3) The tetra-04 element-based analysis of the deformation of a wrench. (4) The shell-element-based analysis of a barrel vault. In this paper, we develop a two-step method first to estimate the uncertainty of a converging series of finite-element-mesh-density-parametric solutions using a 4-parameter logistic function, and then to extrapolate the results of a specific quantity (e.g., a stress component) to an extremely fine mesh density approaching the infinite degrees of freedom. The estimated parameter of the upper bound of the logistic function serves as the “best” estimate of the chosen quantity such as a specific stress component. Using a super-parametric approach, as described in Part III of this series, we show that the hexa-27 element is superior to tetra-04, hexa-08, and hexa-20. [ABSTRACT FROM AUTHOR]

Heavy wall reactors and large diameter pressure vessels usually face unique challenges in their erection onto their foundations at the jobsite. Today, 800 ton to 1,500 ton reactors and or large diameter vessels with diameters ranging up to 15 meters are common in the refining industry. These pressure vessels are usually fabricated in shops dispersed globally and require unique heavy duty equipment for their safe handling, transportation and erection. The challenge is to find a safe, efficient and cost effective solution based upon the limitations of the equipment, job site and the lift equipment available for erection. Equipment for the handling heavy reactors and large diameter pressure equipment is usually scarce, expensive. Planning well in advance of the lift date is required. Careful consideration must be given to the choice and design of attachment to the pressure vessels used for the lift to ensure that the vessel and lifting components are not overstressed during the lifting process. This paper identifies the types of evaluations that must be performed to determine the stresses in the vessel and lifting attachments during the lifting. The paper also discusses different types of lifting lugs that may be attached to each end of the vessel either by bolting or welding and discusses the pros and cons of each. The paper also provides an example of a finite element analysis (FEA) of a top nozzle, a FEA of a pair of lifting trunions and a FEA of welded on lifting lugs for buried pipe. The intent of the paper is to outline the effects on the vessel due to different types of lifting configurations in combination with the lifting parameters. This paper is not intended to provide guidance on how to design lifting lugs. [ABSTRACT FROM AUTHOR]

This paper presents a procedure to predict fracture toughness of steel material using small punch test (or notched small punch test) and finite element (FE) damage analysis. Tensile property can be determined from setting the constitutive equations and can be validated by comparing the small punch (SP) test data with FE results applying the determined tensile property. FE damage analysis used in this paper is based on the strain-based fracture model. Material constants in the model are normally determined from analyzing notched bar tensile tests. To determine these material constants from SP test instead of notched bar tensile tests, simplified model (with only one material constant) can be introduced and used in the simulations. SP test and notched small punch (NSP) test are simulated via FE damage analyses using the tensile property and simplified strain-based fracture model. NSP simulation results are sensitive to element size. However, SP simulation results are not sensitive to element size. Compact tension (C(T)) test is also simulated and it can be found that the proper element size for C(T) simulation is four times of that for NSP simulation to predict cracking initiation toughness. [ABSTRACT FROM AUTHOR]

Subject of this paper is to analyze the effect of prestressing on the plastic behavior of reinforced concrete frame. One-story frame with span of 15m was designed as reinforced concrete structure as well as prestressed concrete structure. For each frame nonlinear model was constructed and nonlinear time-history analysis was conducted using seven ground motions records selected according to EN 1998-1. Results of nonlinear analysis for both frames were analyzed and compared and conclusions regard the effect of prestressing on plastic behavior of reinforced frame are presented in this paper. [ABSTRACT FROM AUTHOR]

Foundation structures, their testing and modelling is a wide area to research. A lot of different elements are tested or modeled in the world. Analysis of interaction between the foundation structures and the subsoil has been developed for many years. For the determination of stress in foundation structure is needed to determine the influence of the stiffness respectively pliability of subsoil to structural internal forces, and vice versa, how the stiffness of the foundation structure affects the resulting subsidence. This paper deals with experimental tests of square reinforced concrete foundation slabs on the subsoil which are carried out at the Faculty of Civil Engineering in Ostrava. Those slabs are loaded with concentric load and are mounted with string strain gauges to measure stress-strain characteristics. Pressure sensors are also mounted under slab to monitor contact stress in the subsoil. Total deformation of the concrete foundation slabs are measured too using potentiometric sensors. The tests results are compared with bending moments and deformations analysis according to subsoil models given in Eurocodes using FEM analysis. In this paper are described performed experimental test and presented as currently results from the test as results from the computing analysis on the slabs and their comparison. [ABSTRACT FROM AUTHOR]

The paper presents calculations of monolith slab and beam floor with pre-stressed wire rope reinforcement. The numerical modeling of the slab is performed with PC “Lira-SAPR 2013”. The paper describes finite elements used in calculations, the conditions of the slab reinforcement, concrete and wire rope reinforcement connections. The calculation results are shown as stress isofields in concrete and steel elements of the slab. The paper also estimates pre-stressed wire rope reinforcement efficiency when used in slab and beam floor. The authors compare stress and strain condition of typical monolith slab and beam floor with reinforcement bars and slab and beam floor with wire rope reinforcement while changing intermediate slab thickness. The results are presented as a finite element model of monolith slab and beam floor with pre-stressed wire rope reinforcement and with untensioned reinforcement. [ABSTRACT FROM AUTHOR]

The article is devoted to the problems of making cargo passages through low-head waterpower developments (those built in XX century in Central Russia). The paper presents an analysis of layout and structural properties of these passages which go through phreatic and concrete dams and through river-run power plants. The paper stresses the importance of these cargo passages for transport connection both at the time when hydraulic engineering structures were being built and nowadays. The research also points out the problems in cargo passages operation and explains why these problems occur. Motor highways through the biggest hydroelectric power stations of the Volga are taken as an example. The author offers some efficient technical solutions for making cargo passages through lowland rivers more effective. [ABSTRACT FROM AUTHOR]

The paper presents a methodology for calculating stress and strain state in beams with corrugated web. The methodology has been developed by the authors and is simpler than the existing method of calculation. While calculating, the authors offer to change the corrugated web for a plane orthotropic plate with the reduced modulus of elasticity showing the same non-rigid characteristics as the corrugated web. The given mathematical notation calculates the reduced modulus of elasticity of a plane orthotropic plate simulating the performance of the corrugated web. The calculation in the paper is made for a beam with corrugated web used as a cross-beam plane gate in hydraulic engineering structures. The calculation results got by the authors while using their methodology are compared with those obtained by the finite-element method (FEM). [ABSTRACT FROM AUTHOR]

This paper focuses on problems associated with aircraft sustainment related issues and illustrates how cracks that grow from small naturally occurring material discontinuities in operational aircraft behave. The example discussed in this paper, which is associated with crack growth under a representative maritime aircraft load spectrum, when taken in conjunction with previous studies into cracks growing under combat aircraft load spectra illustrates how for cracks that grow from naturally occurring material discontinuities under such operational load spectra there is generally little crack closure so that the crack growth history from its initial equivalent pre-crack size (EPS) through to final failure can be easily and accurately computed. [ABSTRACT FROM AUTHOR]

This paper presents a discussion on multi-axial fatigue criteria for random stresses which are formulated as spectral methods in the frequency-domain. Spectral solutions to the multi-axial problem can be viewed as a natural step forward from uni-axial spectral methods. The paper attempts to identify and critically analyze some underlying principles that join together different multi-axial spectral methods. General remarks on advantages and drawbacks of multi-axial spectral methods from the literature are pointed out and commented on. [ABSTRACT FROM AUTHOR]

Small computer software for analysis of stress concentration factors was developed at Faculty of Mechanical Engineering Sarajevo. Software name is AlfaK. Developing process of the software was presented in previous papers of same authors, in this paper testing of the software was done using numerical analysis. To test accuracy of AlfaK software, analysis of stress concentration factors was done numerically using CATIA V5 commercial software for characteristic geometrical changes in form. Obtained data from numerical analysis are used for comparison with results from AlfaK, and on that way, accuracy of AlfaK software is investigated. [ABSTRACT FROM AUTHOR]

Considering the title of this paper–“Application of Photostress method in stress analysis of structural elements under consideration of centrifugal force effect”–it can be assumed that PhotoStress method can be applied in experimental mechanics when analysing stresses and deformations of bodies in motion. The purpose of this paper is to introduce and identify photoelastic phenomena, specify dynamic stress analysis based on PhotoStress method and experimental analysis of deformation and stress fields of the rotating sample by means of PhotoStress method. The verification of solution accuracy is done through final comparison with a simulation programme. [ABSTRACT FROM AUTHOR]

Origami is an old art of paper folding. From mechanical point of view origami can be defined as a folded structure. In the present paper a comparative study of four origami inspired folded plate structures is presented. Longitudinal, facet, egg-box and Miura-ori origami modules are used for the analysis. The models are based on six-parameter shell theory with the use of the finite element method. Convergence analysis of each module is presented. Numerical study of roof folded plates in oriented to the comparison of maximal displacements and stresses in the structures. Some parametric analysis is also presented. [ABSTRACT FROM AUTHOR]

This paper focuses on a technique for predicting surface cracks in hot free forging. These surface cracks occur at the side on which strains concentrate when a round bar is compressed by hot free forging. A final product has hardly any surface cracks because they are removed by gas scarfing. These conventional manufacturing processes have an industrial problem of low productivity with a waste of time. The suppression of the surface cracks is required. The mechanism and criteria for the surface cracks are not clear. In this paper, the mechanism of surface cracking was estimated, compared with the actual forging process. The mechanical property was evaluated by a high temperature tensile test. Various numerical simulations which changed the damage parameter ( C value) were carried out. The critical value ( C 1 ) is calculated by shape comparison between the tensile test and the numerical simulation. It is possible to predict the surface cracking in the hot forging process by using this parameter. [ABSTRACT FROM AUTHOR]

The present paper aims to develop a simple method based on inverse analysis that allows us to determine the laws of plastic flow coefficients and the friction coefficient between the material and punch. Selecting from different types of tests, we have chosen the Hecker test, because this test requires a single form of punch, the hemispherical one. In this test, the friction between the punch and the blank-sheet is caused by the blank-sheet strains and not by the movement it makes (as in deep drawing case). Besides the friction coefficient, other parameters like hardening and strength coefficients (n and k), influence the distribution of stresses and strains in the material. Using the Hecker test, we determined the curves force vs. displacement and major strain vs. displacement for three points located at different heights on the dome. Obtained from the test, these curves will stay on the basis of multi-criteria optimization analysis performed with LS-Dyna and Ls-Opt. The force vs. displacement curve was obtained using a hydraulic transducer and the major strains vs. displacement curves were obtained using the optical system Aramis which provides full information on the three-dimensional coordinates, displacements, strain variations, etc. On the other hand, using the Ls-Dyna software we will simulate the Hecker test and we will get the same types of curves (force vs. displacement and principal strains vs. displacement). Inverse analysis will consist in minimizing the “distance” between the curves obtained by simulation and experimentally obtained curves. We must to mention that this paper contains a big hypothesis: the identification is valid only for the chosen mesh and modelling of friction. [ABSTRACT FROM AUTHOR]

Forming limit diagrams are a useful tool to anticipate the formability of sheets for various sheet metal forming processes. The objective of this paper is to propose a method for calculating forming limit diagrams for conductive and nonconductive printed layers on sheet metal surfaces. These printed layers can be used to manufacture printed electronics like strain gages or temperature sensors. In this paper the forming limits of these printed layers are determined in notched tensile tests by evaluating the crack pattern on the surface of the printed specimens. The crack pattern is digitized with a reflected light microscope. Additionally, the major and minor strains of the printed specimens are measured with an optical deformation analysis system. The forming limit diagrams for the investigated printed layers are subsequently calculated by synchronizing the crack pattern with the measured major and minor strains on the specimens’ surfaces. The results achieved by this method are tested for reproducibility. [ABSTRACT FROM AUTHOR]

Fiber Bragg gratings (FBG's) have been used as communication devices and sensors in applications. To extent the FBG's ability for the uniform distributed disturbances, this study computed reflection spectra of an apodized FBG subjected to strain gradients ranging from 0 to 1 strain/m. Based on the coupled-mode theory, in this paper reflection spectra and their corresponding areas were calculated. For apodization functions, the raised-Gaussian and raised-cosine were considered in this study. In parameter study, two parameters of an FBG: the grating length and the effective index change were taken as variables to understand their effects on its reflection spectra. Results show that the larger effective index change increases the range of linear relationship between strain gradients and spectra areas; and the larger grating length increases the slope of the linear relationship. In applications, as a filter, at larger strain gradients those spectra from apodized FBG display almost linear segment over the wavelength ranges 1 or even up to 40 nm, depending on the grating length. Equivalent to the strain gradients, results obtained in this paper also can be applied for the temperature gradients, if the ratio between wavelength shifts from one micro-strain and from one degree Celsius, for example, is suitable assigned. [ABSTRACT FROM AUTHOR]

Abstract: Fatigue crack growth (FCG) could be encountered in many mechanical components, which can be made from either thin or thick steel plates (or shells) and, therefore, be subjected to a plane-stress or a plane-strain condition, respectively. The loads applied in a solid body containing a narrow notch or a sharp crack will induce a yield zone near its tip with a dimension that will depend on the mechanical properties of the material, as well as on the thickness of the body, the crack length and the magnitude of the loads applied. Crack propagation can then occur under mode I, II, III or mixed-mode for general loading. The paper presents JI, JII and JIII integral functions, which were correlated with the elastic stress intensity factors KI, KII and KIII, for thin and thick CT specimens. The evaluation of J-Integral values was carried out for different crack lengths, along the crack front, and using the Finite Element Method (FEM), with collapsed nodes and midside nodes dislocated to ¼ of the edge's length, in order to simulate the crack tip singularity. Interaction between in-plane, in-plane sliding and out-of-plane modes are also discussed in the paper. In addition, FCG rates under mode I, mode III and a mixed-mode (mode I+III) were experimentally determined, at room temperature, for a high-strength Cr-Mn austenitic stainless steel. [Copyright &y& Elsevier]

Abstract: This paper deduced the cavity geometry of the plate under the action of one-way and two-way squeeze equipment which is hyperbolic for two-way squeezed, hyperbolic and arc for one-way squeezed. This paper points out the different stress characteristics and applicable conditions of bearing plate for the two kinds of squeezed branch pile, and provides references for the development of the squeezed branch pile. [Copyright &y& Elsevier]

Abstract: Effect of contact load and surface roughness on friction behavior in plane strain extrusion is one of the biggest phenomena in improving the sliding performance of cold forward extrusion. Wear resistance that commonly occurs on the plane requires an appropriate method to obtain the finest product surfaces. This paper highlighted is the correlation between contact load and surface roughness on the friction behavior and wear resistance of the sliding plane in the extrusion process. The analysis described in this paper involved the experiments to assess the contact load in the extrusion and the surface roughness. The experiments were set up by using pure aluminium A1100 as billet extruded between dies made of hot work tool steel (SKD11). Extrusion ratio of the process is three (3) and the billets were pressed by a hydraulic press machine. The contact load for each experiment was taken at a 20mm length of the extrusion, and the average surface roughness of the aluminium was plotted on a graph. Three types of lubricants were used in this study: Refined Bleached Deodorized (RBD) palm stearin and two types of paraffinic mineral oil, 95 and 460. These two types of paraffinic mineral oil differed in viscosity. These three types of lubricants were run with four different quantities: 0.1mg, 1mg, 5mg, and 20mg. The results showed that an increased amount of lubricant reduced the surface roughness. The correlation between contact load and surface roughness showed significant differences for each lubricant while at 5mg of RBD palm stearin and paraffinic mineral oil 460, the results showed the same contact load but different surface roughness. [Copyright &y& Elsevier]

Abstract: The paper presents conclusions of the experimental verification of highway composite steel-concrete bridge behavior. After performing the standard proof-load test, the more detailed verification of stress and deformation state of two-girder continuous bridge structure was accomplished. The location of strain and deflection measurements and testing procedures are described. The comparison of the experimentally obtained values with the values calculated using suitable computational model is also presented in the paper. [Copyright &y& Elsevier]

Abstract: The paper analyses the problem of elliptic reinforced concrete shells calculation, while only taking into account membrane efforts. Normal and shear forces of such shells are usually determined using stress function. This paper discusses the estimation of the coefficients of the chosen stress function. [Copyright &y& Elsevier]

Abstract: The Finite Element Method (FEM) and other numerical methods are very effectively implemented in linear and nonlinear analysis of structures. Recently, a new displacement based Applied Element Method (AEM) has been developed, which is applicable for static linear and non linear analysis of framed and continuum structures. In AEM structural member is divided into virtual elements connected through normal and shear springs representing stresses and strains of certain portion of structure. FEM assumes the material as continuous and is able to indicate highly stressed region of structure but it is difficult to model separation of element unless crack location is known. The main advantage of applied element method is that it can track the structural collapse behaviour passing through all stages of the application of loads. In this paper, basic introduction to applied element method is presented. The differences between FEM and AEM are discussed. The application of AEM is illustrated through static analysis of portal frame. The portal frame is divided into different number of square elements. The elements are connected through varying number of normal and shear springs. The effect of size of elements and number of springs for connecting elements on analysis results is presented in the paper. The analysis results are also compared with that of FEM. [Copyright &y& Elsevier]

The behavior of cementitious materials under severe loading is of particular interest, for research on ballistic impact, penetration and near distance explosions, where very high pressures are developed. Therefore it is important to investigate the behavior of such materials in the exceptionally high hydrostatic pressures range. One of the key characteristics of this behavior is the equation of state (EOS) that is the relationship between hydrostatic pressure and density (or bulk strain). However it has not been adequately investigated, and therefore the mechanisms of cementitious materials deformation and damage that are developed within that range of high pressures is at least partly obscure and far from being clearly understood. This is partly because the controlled application of extreme pressures requires special equipment and expensive experimental setups and testing is associated with a wide variety of technical problems. This paper aims at presentation of the development of an experimental setup to perform confined compression tests of mortar and concrete specimens at high pressures up to 1GPa. It presents the experimental study of different cement paste and mortar specimens and their comparison with previous results, obtained under high pressures up to 300 MPa. This allows the investigations of size effect for unsaturated samples, as well as the effect of the sand volumetric content on the loading branch of the equation of state. The experimental study shows a good repeatability for the cement paste specimens and for mortar specimens with fine sand. It also shows that decrease of water/cement ratio in the cement paste mix as well as increase of the sand volumetric contain in mortar results in monotonic increase of the secant bulk modulus of the loading branch of EOS. The comparison of the mean loading branch of the experimental EOS for unsaturated specimens having 30 mm diameter (70 mm height) and 70 mm diameter (150 mm height) clearly indicates that there is practically no size effect for all tested mixture compositions. While for the cement paste there is no difference up to 270 MPa (highest pressure level in the test in the small apparatus), the addition of sand yields an increase of the difference, which, anyway, remains small. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on different tube forming processes by plastic deformation, including expansion, reduction and inversion of tube ends, using circle grid analysis in order to obtain strain-loading paths in different regions of the principal strain space. The experimental work was carried out on commercial AA6063-T6 tubes and includes independent material characterization by means of tensile, stack compression and instability tests. Finite element modelling of the tube forming processes by means of an in-house computer program gives support to the presentation and allows assessing the overall accuracy, validity and reliability of using circle grid analysis to investigate formability and failure in tube forming. [ABSTRACT FROM AUTHOR]