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The article analyses the effects of paper moisture content on energy absorbed during its tensile testing in the range of moisture equilibrium obtained during paper air conditioning at a temperature of 23 °C. To predict changes in breaking energy caused by changes in moisture content, two calculation methods were proposed. The methods were verified on the basis of laboratory tests and calculation results, and their practical usefulness was confirmed. [ABSTRACT FROM AUTHOR]

In this paper, an efficient computational framework for the full-wave design by optimization of complex microwave passive devices, such as antennas, filters, and multiplexers, is described. The framework consists of a computational engine, a 3D object modeler, and a graphical user interface. The computational engine, which is based on a finite element method with curvilinear higher-order tetrahedral elements, is coupled with built-in or external gradient-based optimization procedures. For speed, a model order reduction technique is used and the gradient computation is achieved by perturbation with geometry deformation, processed on the level of the individual mesh nodes. To maximize performance, the framework is targeted to multicore CPU architectures and its extended version can also use multiple GPUs. To illustrate the accuracy and high efficiency of the framework, we provide examples of simulations of a dielectric resonator antenna and full-wave design by optimization of two diplexers involving tens of unknowns, and show that the design can be completed within the duration of a few simulations using industry-standard FEM solvers. The accuracy of the design is confirmed by measurements. [ABSTRACT FROM AUTHOR]

The excavation of the pit causes displacement of the surrounding soil, and the excessive deformation causes damage to the existing support structure, which in turn affects the safety of the pit. Reasonable calculation of structural deformation and internal force is crucial for design and construction. Most of the existing theoretical methods simplify the diaphragm wall(DW) as an Euler-Bernoulli beam acting on the Winkler foundation, consider beam-soil interaction, and simplify the soil as isotropic and continuous. However, the shear effects due to the differential deformation of the structure, the unloading stresses acting on the structure due to foundation excavation, and the discontinuous nature of the multilayered soil are neglected. In this paper, an improved analysis method is proposed based on the elastic foundation beam theory. The DW is simplified as a Timoshenko beam and the foundation is simplified as a Vlasov two-parameter model, and a proposed model considering the shear effect of the DW and the interaction of adjacent springs is established, and the proposed method for the deformation and internal force of the DW is obtained by the finite-difference method. The correctness and applicability of the proposed method are verified by numerical simulation and field monitoring data. The effects of equivalent bending stiffness, equivalent shear stiffness, soil elastic modulus, and excavation depth on the deformation and internal force of the DW were further analyzed. The results show that the proposed method can accurately solve the deformation and internal force of the DW, and the maximum errors between the proposed method and the numerical simulation results are only 4.5 % and 1.3 %, respectively. The equivalent bending stiffness of the DW and the elastic modulus of the soil have more significant effects on the horizontal deformation and internal force. The excavation depth is more sensitive to the deformation of the DW, and there is an exponential decay trend between the two. When the equivalent shear and bending stiffnesses reach 6.8×107 kN·m2 and 2.9×107 kN/m, the effect on the horizontal deformation is no longer obvious. The proposed method in this paper can accurately calculate the internal force and deformation of the DW. [ABSTRACT FROM AUTHOR]

Presents a theory on frictional vibrations of paper-based friction material considering the interaction between its deformation and the consequent lubricant flow inside it. Vibration model; Derivation of stability criterion; Relation between negative damping components in critical state; Contribution of each parameter to stability.

The utilization of a supporting tool in Double-Sided Incremental Forming (DSIF) imposes a stabilizing compressive stress through the sheet’s thickness, increasing, thereby, the material’s formability and fatigue life. However, these favorable effects strongly depend on a steady tool-metal contact condition. This work presents a general DSIF control scheme, which augments the conventional position servo-loop with explicit force feedback control. The algorithm is examined for its robustness and effectiveness using complex geometries with varying curvatures and wall angles. The resulting parts have demonstrated enhanced material formability and geometric accuracy. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the rheological properties of long and short fiber bleached kraft pulp suspensions by using a new rotational viscometer. It is stated that the knowledge of pulp suspension rheology is important to obtain optimum design in the pulp and paper industry. Here, the authors state that the experimental rheograms were conformed to the Herschel-Bulkley model. They determine the rheological parameters on temperature, fiber length and pulp consistency to evaluate the influence of these factors to the process. The results revealed that the rheology of the pulp suspension is strongly affected by the pulp's consistency and the other factors mentioned above.

The article discusses that the mathematical expressions of plate instability could be applied to thin webs such as paper that have small but finite plate bending stiffness. It recalls the subject of plate instability and expand the theory to broaden the orthotropic properties of many webs. It examines the effects of web shear stiffness, web tension, and the traction between webs and rollers on troughs and wrinkles. It determines what levels of misalignment are acceptable in each span of a process machine for a given web material.

Ti 2 AlNb intermetallic, as a relatively new high temperature-resistant structural material, belongs to typical difficult-to-machine material due to its excellent mechanical properties. This paper aims to investigate the dynamic deformation behavior in chip shear deformation zone and associated chip formation mechanism during the machining of Ti 2 AlNb intermetallic. A specialized cutting platform combined with a high speed imaging system is developed to realize in-situ detection of full field deformation and corresponding signal processing during the machining process. The high speed imaging system can capture in-situ material deformation images with a frequency of 100 kHz during cutting process while the digital image correlation method is adopted to characterize chip dynamic deformation signals quantitatively. A series of orthogonal cutting experiments for Ti 2 AlNb is conducted at different cutting depths and cutting speeds, based on which the influences of cutting parameters on chip morphologies and material removal process are studied. The distribution of material flowing velocity, as well as the strain rate fields within shear deformation zone in chip removal process of Ti 2 AlNb are analyzed. Finally, the formation mechanism of periodic built-up edge formed in the cutting speed range of 60–120 m·min−1 is elucidated. • Kinematic field of T i2 AlNb chip formation are in-situ detected and characterized. • Strain rate distribution during the formation of different types of chips is studied. • Chips morphology evolution of Ti 2 AlNb at varied cutting parameters is studied. • Formation mechanism of periodic built-up edges is analyzed with DIC method. [ABSTRACT FROM AUTHOR]

Stability of non-conservatively loaded elastic and inelastic bodies - a classic section of deformable solid mechanics that has been of interest for many years. In this paper, we study the motion stability of a free rod subjected to a constant tracking force on one of its ends. The problem is interesting in practical application, as it can be viewed as a simplified model of a rocket moving under the action of a jet force. The defining ratio of the rod material is the Kelvin-Voigt model. The solution to the problem is presented as a decomposition of the beam function. The number of terms of this expansion is substantiated. The critical load values in the presence and absence of viscosity are determined. It is established that the existence of a non-zero value of the internal viscosity coefficient in the Kelvin-Voigt model leads to a significant reduction in the critical load value compared to the elastic rod model. The given analytical results are confirmed by numerical calculations. [ABSTRACT FROM AUTHOR]

The present paper focuses on an elastic properties analysis of new and depreciated tires. The research was carried out using two different methods, field and numerical, respectively. The purpose of the study is to check whether there is a change in the elastic properties of a tire during its depreciation and to what extent the process affects the comfort of driving and riding. The experimental tests were conducted on a hydraulic test stand and by applying strength and deformation analysis the effect of its structure deformation was additionally considered. The investigation was performed on a vehicle-based tire test stand to find out stress-strain and tire deformation was with different vertical loading according to FEM. The numerical solution was reached by implementing SolidWorks - Simulation and Abaqus. The obtained results are graphically compared, and the average value of the elastic constant for a new and depreciated tire has been determined. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to developing a work roll prediction model that takes into account the impact both the mechanism and conditions on the work roll wear. This was accomplished by conducting an analytic calculation of work roll mechanism influence, constructing a work roll wear model, and combining the wear mechanism with actual wear data. The resulting model is applicable to both symmetric and asymmetric wear of the work roll. Experimental results showed that the relative error between measured and predicted values was less than 5%, with a maximum error of below 15%. This level of accuracy is sufficient for predicting roll wear and lays the foundation for improved strip shape control and roll design. Furthermore, this approach has the potential to generate significant economic benefits and has wide-ranging applications. [ABSTRACT FROM AUTHOR]

In this paper, triaxial loading and unloading tests under different conditions were carried out to explore the deformation and failure characteristics of hard rock marble, and the acoustic emission information of the test process was monitored synchronously to obtain the acoustic emission distribution characteristics. The test results show that: (1) when the confining pressure unloading rate is low, the rock yielding is more obvious, the damage peak is higher, and the Poisson effect is more obvious under loading and unloading, while when the unloading rate is high, it shows multi-stage damage; (2) there is a linear relationship between strain deviatoric stress flexibility and unloading rate, as the unloading rate accelerates, the circumferential and volumetric flexibility increases and the axial flexibility decreases; (3) the lower the unloading rate, the higher the confining pressure, and the main shear surface of the rock gathers a large number of tensile microcracks to form a shear zone, while the higher the unloading rate, the lower the confining pressure, and the main shear surface is thoroughly penetrated and ruptured; (4) acoustic emission can characterize the damage degree of marble in the process of loading and unloading, when the confining pressure is low, acoustic emission at the peak damage point appears sharp phenomenon, the overall damage increases with the accelerated rate of unloading, when the confining pressure is high, acoustic emission grows progressively, the overall damage decreases with the accelerated rate of unloading, the overall damage of the rock will appear " pre-peak to post-peak " hysteresis effect. [ABSTRACT FROM AUTHOR]

Gradient nanostructure was introduced to enhance the strength and ductility via deformation incompatibility accommodated by geometrical necessary dislocations for most metallic materials recently. However, few intensive researches were carried out to investigate the effect of gradient structure on the deformation twin evolution and resulting performance improvements. In the present paper, we produced gradient-structured AZ31 Mg alloy with fine-grain layers, parallel twin laminates and a coarse-grain core from two upmost surfaces to the center of plate. Surprisingly, this architected Mg alloy exhibited simultaneous enhancement of strength and ductility. Subsequent microstructural observations demonstrated that abundant twin-twin interactions resulting from higher strength and multi-axial stress state could make great contributions to the increase of work-hardening capability. This was further proved by the measurement of full-field strain evolution during the plastic deformation. Such a design strategy may provide a new path for producing advanced structure materials in which the deformation twinning works as one of the dominant plasticity mechanisms. [ABSTRACT FROM AUTHOR]

The substantial growth in the development of coal seam gas (CSG) – also known as coal bed methane – fields in southern Queensland, Australia, over the past decade has been associated with various impacts on the environment and human activities. Of particular concern is the potential impact of CSG-induced subsidence on farming operations. Previous research in underground coal mining has shown that overlying competent formations can function as bridges over mined-out areas, effectively preventing subsurface deformation from fully or partially reaching the ground surface. Formation bridging can also occur in CSG producing areas. Modelling formation bridging is essential for understanding and predicting the historical and future impact of CSG production on the surface, respectively. This paper introduces a novel modelling methodology based on the elastic plate theory that helps in assessing the potential for formation bridging in overlying formations during CSG production. The applicability of this approach is demonstrated through a case study in the Surat Basin of southern Queensland. This study shows that excluding bridging for a particular formation rules it out for that formation when overlain by other formations or when it is thinner. Results of this study indicate that formation bridging in the study area may only occur during the very early phase of a CSG well's life cycle. Where the diffusivity of the coal seam is low, leading to a slower expansion of the influence area, there is also an increased likelihood of bridging taking place and persisting for an extended duration. Although the methodology introduced in this paper is mainly analytical, it offers an initial evaluation of the formation bridging probability across extensive basins where conducting detailed three-dimensional numerical modelling is challenging, if not impractical. This preliminary analysis may assist in deciding whether, and where, more comprehensive and detailed assessment of formation bridging is necessary. • A novel model based on the plate theory is presented for formation bridging. • Formations exhibit bridging effect if bending capacity exceeds coal compaction. • Formation bridging is more likely to occur early in the initial well life. [ABSTRACT FROM AUTHOR]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Considering the pile-slab subgrade project of the Hangzhou-Huang Shan Passenger Dedicated Line as the basis, this paper conducts a 1:10 largescale indoor model test for the horizontal bearing capacity of the pile-slab structure in steep mountainous areas to study the distribution of the pileslab structure stress, soil pressure and structural deformation and analyze the failure mode of the structure and slope. The research shows that when the subgrade with a double-row pile-slab structure is subjected to horizontal loading in the steep slope section, the steel bars of the pile body above the sliding surface are compressed, and the steel bars of the pile body below the sliding surface are under tension. With the increase in the horizontal load, the stress of the pile body steel bar remains basically unchanged or shows a steady increase and finally sharply increases. The deformation of the bearing plate is dominated by the horizontal displacement, and the horizontal displacement reaches 7.25 mm when the plate is broken. In addition, warping deformation of the inner high and outer low occurs. When the horizontal load reaches 157 kN, shallow damage and local collapse of the slope occur, and transverse and diagonal cracks occur at the top of the pile and near the sliding surface of the pile. During the test, the pile-slab structure always deforms more than the slope, and the overall stability of the structure is good. The test is suitable for sections where the remaining sliding force is less than 770 kN/m (equivalent to a slope length of 79.123 m). [ABSTRACT FROM AUTHOR]

In this paper we intend to reveal the architecture and structural styles in the outer unit of the Nankai accretionary prism, using a 672 km² seismic survey that was acquired by the Japanese Government in 2006 in order to infer the origins of some major tsunamigenic earthquakes. Understanding deformation mechanisms and the distribution and morphology of the thrust sheets and faults is essential for the oil and gas industry and for academic study as well, as scientists intend to prevent the impact of devastating hazards that appear often in active tectonic settings, such as subduction zones. [ABSTRACT FROM AUTHOR]

This paper aims to explore the effects of earthquakes on the properties of medium-height reinforced concrete houses in China. The results demonstrated a significant decrease in ultrasonic resonance frequency, indicating structural damage, with reductions of 26.5 %, 30.2 %, and 37 % observed for earthquakes of magnitudes 5.0, 5.3, and 5.7, respectively. Similarly, the dynamic modulus of elasticity exhibited a reduction of over 50 %. Measurements of carbonation depth revealed values of 34.65 mm, 38.97 mm, and 46.12 mm for earthquakes of magnitudes 5.0, 5.3, and 5.7, respectively. Accordingly, the percentage of mass loss amounted to 22.17 %, 36.87 %, and 49.78 %. Furthermore, experiments identified the least favourable outcomes during maximum seismic activity, with a recorded peak stress of 447.3 MPa at a deformation of 0.63 mm. These findings contribute to a better understanding of the impact of seismic events on reinforced concrete structures and the associated corrosion mechanisms. [ABSTRACT FROM AUTHOR]

This paper established the temperature differential model of temperature-controlled materials, performed the numerical simulation of the relationship between mechanical properties and temperature of temperature-controlled materials, and discussed the stress-strain relationship of temperature-controlled materials at different temperatures. The final stimulation experiment showed that temperature-controlled materials have the advantages of large energy storage density, approximately constant temperature and compact structure during phase change. The results of this paper provide a certain reference for the further researches on the numerical simulation of forced bending deformation of temperature-controlled materials based on the differential equation model. [ABSTRACT FROM AUTHOR]

One of the nowadays challenges is the development of scientific sound models of knitwear deformations. The paper is devoted to developing an algorithm for constructing a frame model of rib 1x1 knits stretched in the course or wale direction. In the process of uniaxial stretching~ the shape of the sample depends on the tensile force's orientation. A frame model of a deformed knitted structure, and an algorithm of construction of a mesh frame, are developed during the study. The frame model makes it possible to find coordinates of intermeshing points of every stitch. Then yam characteristic points can be determined that, in turn, serve as input data for the construction of 3D model of rib 1x1 structure under uniaxial tensile deformations at the yarn level of detail. The study provides a graphical tool for formalization of geometric transformation that happen during 2D deformations of knitted structures, characterized by gradual change of the specimen's width crosswise to the loading direction. This model is intended to become a part of a general deformation model of knitted fabrics. [ABSTRACT FROM AUTHOR]

The structural deformation of a dam directly affects its lifespan and safety, making its accurate prediction crucial. Traditional prediction methods often overlook the nonlinearity and non-smoothness of deformation data. Moreover, the irregular intervals within the historical deformation data used for model training can reduce prediction accuracy. To address these issues, we propose a hybrid deep learning model that uses signal decomposition and reconstruction to enhance dam deformation prediction. This model employs a long short-term memory (LSTM) neural network optimized using a complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN). The self-attention mechanism in the LSTM model effectively captures the temporal features of dam deformation, alleviating the difficulties generated by the irregular intervals within the historical data used in model training. Furthermore, considering the lag effect of influencing factors on dam deformation and the differences among various measurement points, we propose a CEEMDAN-based feature selection method. Using 13 years worth of data from the Shuibuya Dam, we evaluate the accuracy and effectiveness of the CEEMDAN-Self-attention-LSTM model using indicators, such as MAE, RMSE, MAPE, and R 2 , and compared it with existing models. The experimental results show that this model reduces prediction error by more than 53.62%. • This paper proposes a dam deformation prediction model based on the CEEMDAN-Self-attention-LSTM model. • The CEEMDAN algorithm effectively reduces the complexity of dam deformation data. • The modelis able to better capture the cyclical changes between time steps. • A feature selection method based on CEEMDAN fully considers the lagging impact of environmental factors on dam deformation. • The predictive capability of this method is analyzed with a case study of the Shuibuya concretefaced rockfill dam. [ABSTRACT FROM AUTHOR]

The recognition of pipeline features contributes to its safe management by preventing severe consequences such as leakage resulting from bending deformation and denting under external pressure. However, extracting features of such a facility is complex and challenging when machine learning techniques are applied to feature recognition. Hence, this paper proposes a feature recognition technique for gas pipelines based on Gramian Time Frequency Enhancement Net (GTFE-Net), Bi-directional Long Short-Term Memory (BiLSTM) and attention mechanism (AM), namely GTFE-Net-BiLSTM-AM. Specifically, GTFE-Net is applied to enhance the time-frequency input bending strain signal, which is subsequently incorporated with the BiLSTM model to extract spatio-temporal features. The attention mechanism computes the corresponding weight of output features. The results show that the proposed method's recognition accuracy reaches 93.7%. The comparison study with the existing models validates the proposed method's superiority and shows that its accuracy is higher than that of the existing models (more than 0.9%) or their combined models (more than 1.1%). Overall, the proposed method contributes to the safety, reliability, and operation of natural gas pipelines. • An intelligent feature recognition method fo pipelines based on GTFE-Net-BiLSTM and attention mechanism is proposed. • GTFE-Net is used for time-frequency enhancement of the raw signal. • AM is used to calculate the weight of output features and improve the classification accuracy of the model. • A real-world IMU detection data is used for model training and validation. [ABSTRACT FROM AUTHOR]

This paper studies a longitudinal shape transformation model in which shapes are deformed in response to an internal growth potential that evolves according to an advection reaction diffusion process. This model extends prior works that considered a static growth potential, i.e., the initial growth potential is only advected by diffeomorphisms. We focus on the mathematical study of the corresponding system of coupled PDEs describing the joint dynamics of the diffeomorphic transformation together with the growth potential on the moving domain. Specifically, we prove the uniqueness and long time existence of solutions to this system with reasonable initial and boundary conditions as well as regularization on deformation fields. In addition, we provide a few simple simulations of this model in the case of isotropic elastic materials in 2D. [ABSTRACT FROM AUTHOR]

This paper presents aspects of the technological construction of parts assembled by cold welding. During pressing, effects of the material transport mechanisms occur in the form of deformations of the parts to be joined. Thus, on shaft-type parts and bushing-type parts, assembly attempts were made, the result being the obtaining of parts that underwent shape changes during pressing. Additional devices for placing and guiding parts on the press have been designed and used to prevent these deformations. The obtained results were much improved, the deformations being able to be controlled and directed to the desired areas. [ABSTRACT FROM AUTHOR]

Copyright of Mechanics & Advanced Technologies is the property of National Technical University of Ukraine KPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments. [ABSTRACT FROM AUTHOR]

This paper applies stacking sequence optimization for maximizing the buckling load of rotationally restrained laminated composite rectangular plates with different boundary conditions resting on an elastic Pasternak foundation subjected to uniaxial and biaxial in-plane static loads. The Mindlin Plate Theory (MPT), which considers the firstorder shear deformation effect, was used to extract the characteristic equations of the plates under in-plane loading, including plate-foundation interaction. The buckling problem of laminated plates was analyzed by the Rayleigh-Ritz method. The aim of optimization was to maximize the buckling load and post-buckling load capacities using Genetic Algorithm (GA) method, and the design variable was the ply orientation. The results showed that the optimal orientation, of the laminated square plate under biaxial in-plane loading in various conditions was 45°, approximately. The existence of a foundation, clamped boundary conditions, and high aspect ratio led to increase in the optimal orientation. [ABSTRACT FROM AUTHOR]

This paper aims to study the impact analysis of a composite sandwich panel with a exible foam core subjected to low-velocity impact loading using a finite element model in ABAQUS/CAE software. Impact damage remains a major concern for all structural components; creating internal damage and reducing the structural strength of a structure. Very few multiple-mass impact studies have been done on the composite sandwich panel. In the present work, the formulation is based on the first-order shear deformation theory which is used to develop the model. Impacts were done over the top of the face sheet with different velocities and impact masses. The numerical model is verified by that of the experimental literature. Good agreements in terms of contact-force histories and deformation of the sandwich panel are found. Once results are validated for a single impact, furthermore, the study has been extended to multi-mass impact analysis with varying velocities of the impactor. Comparisons of various parameters such as contact force, deformation, and von Mises stress results are reported. Also, comparisons of impact responses shown for a cylindrical sandwich panel with a exible core were studied and reported. [ABSTRACT FROM AUTHOR]

Wellbore instability due to natural fractures is a significant issue impeding drilling operations in shale formations. However, most of the existing literature on wellbore stability analysis focuses on the coupled effects of fluid flow and deformation, and the impact of three-dimensional natural fracture characteristics on wellbore instability is not yet closely examined. This paper carried out a series of experiments to analyze the shale sample's fracture characteristics and shear strength. A fully coupled 3D hydro-mechanical model was then developed using the distinct element method (DEM) to investigate the wellbore instability. Finally, a comprehensive parametric study was performed to analyze the effects of characteristics of fractures (e.g., distribution density, fracture roughness and associated shear strength, dip angle, and seepage time) on wellbore stability under different in-situ stress states. The results show that the shear strength of shale increases with the increase in normal pressure (4 MPa, 6 MPa, and 8 MPa); the shear strength increases by 64.9% when the roughness is 0.325 mm (the largest increase among the three roughness cases). The maximum displacement around the wellbore is 1.3–1.5 times greater under the presence of weak planes than under no weak planes. Fracture roughness poses an important impact on wellbore stability because larger fracture roughness is associated with higher fracture shear strength. As the dip angle of the weak plane increases, the number of yield zones (shear failure) and maximum wellbore displacement increases and then decreases, and the peak occurs at the dip angle of 45°. The seepage time of drilling fluid is positively correlated with the number of yield zones around the wellbore, and the damage rate of drilling fluid to wellbore stability gradually decreases with the seepage time. • Direct shear experiments were carried out to investigate the shear strength of the shale under different normal stresses. • A 3D hydro-mechanical model for wellbore instability in fractured formations was developed. • Displacement around the wellbore is 1.3–1.5 times greater under the presence of weak planes than under no weak planes. • Displacement around the wellbore reaches the maximum when the dip angle of the weak plane is 45°. [ABSTRACT FROM AUTHOR]

Based on the unique monoclinic characteristics of the plastic deformation of the tetra-missing rib honeycomb, the symmetrical design of the whole and subunits of the tetra-missing rib honeycomb was carried out in this paper, and two new types of tetra-missing rib honeycomb with symmetrical structural characteristics were obtained. First, quasi-static compression was performed on three structures, including a conventional tetra-missing rib honeycomb, and the experimental results showed that both symmetrical designs could effectively improve the plastic deformation of the conventional tetra-missing rib honeycomb. At the same time, round holes were introduced into the three honeycomb structures, and the mechanical properties and deformation modes of the three structures under quasi-static loads were explored. The results of two sets of experiments were compared, and it was found that the introduction of round holes could improve the structural stiffness of the honeycomb. Second, Abaqus/Explicit was used to construct a finite element numerical model in the later stage, and the accuracy of the model was verified. The number of honeycomb cells was determined for the three honeycomb structures, and finally, the dynamic Poisson's ratio of the honeycomb structure in plastic deformation was determined, and the negative Poisson's ratio (NPR) effect of the three honeycombs was compared. [ABSTRACT FROM AUTHOR]

Copyright of Industria Textila is the property of Institutul National de Cercetare-Dezvoltare pentru Textile si Pielarie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The 3rd Edition of API 579-1/ASME FFS-1 2016 Fitness-For-Service includes a new Part 14 dedicated to fatigue assessment. An important section in this part covers the fatigue assessment of welded joints. In this paper, an overview of the fatigue methods for welded joints is provided and extensions are recommended. First, an overview is given of the classical fatigue method used in the ASME B&PV Code based on smooth bar fatigue curves in conjunction with a fatigue strength reduction factor. In addition, the mesh insensitive structural stress method is outlined using an equivalent stress parameter based on fracture mechanics considerations in conjunction with a master S-N curve based on the analysis of over 2000 high and low cycle S-N test data. The resulting master S-N curve approach is applicable to high cycle fatigue and low cycle fatigue if a Neuber correction is introduced. In this paper, a new structural strain method is presented to extend the early structural stress based master S-N curve method to the low cycle fatigue regime in which plastic deformations can be significant while an elastic core is present. With this new method, some of the inconsistencies of the pseudo-elastic structural stress procedure can be eliminated, such as its use of Neuber’s rule in approximating structural strain beyond yield. The earlier mesh-insensitive structural stress based master S-N curve method can now be viewed as an application of the structural strain method in the high cycle regime, in which structural strains are linearly related to traction-based structural stresses according to Hooke’s law. Thus, both low cycle and high cycle fatigue behavior can now be treated in a unified manner. In the low-cycle regime, the structural strain method characterizes fatigue damage directly in terms of structural strains that satisfy a linear through-thickness deformation gradient assumption, material nonlinear behavior, and equilibrium conditions. A PVRC Joint Industry Project is currently sponsoring work on the structural strain method that will lead to its incorporation in the next edition of API 579-1/ASME FFS-1. [ABSTRACT FROM AUTHOR]

In this paper, a new discrete element method (DEM) containing particle flow code (PFC) is presented as an efficient-to-implement alternative to the existing finite element method (FEM) for simulating internal forces and deformations of a hot-rolled H-section steel beam subject to static loading. Unlike FEM, which is efficient to solve continuous problems, the PFC method can solve discontinuous problems, such as collapse procedure of structures, and the collapse procedure of the structure can be monitored at different times in a more time-saving way. First of all, a linear constitutive model in FEM was built to compare with the linear parallel bond model built in PFC, a hot-rolled H-section steel beam considering geometrically non-linearity subject to static loading was simulated and the simulation results were compared with theoretical solution and FEM results. Both internal forces and deformations before yielding were compared and good agreements were achieved. Secondly, with the object-oriented programming technique and the redeveloped interface of PFC, a user-defined parallel bond model was developed to consider material nonlinearity and compared with the bilinear constitutive model built in FEM. Both internal forces and deformations before and after yielding were compared and good agreements were observed. Thus, the DEM model adopted in this paper can be efficiently used to simulate the behavior of the H-section steel beam. In the future, the developed parallel bond model can be used to simulate the performance of H-section steel beam subject to vertical impact loading and three-dimensional steel framed structure subject to horizontal collision. [ABSTRACT FROM AUTHOR]

Reliable deformation measurement is required for proper quantification of fire performance of concrete structures. Predictive capability of models for many critical properties, including Young’s moduli, stress-strain relationships and load-induced thermal strains, is first and foremost dependent on such reliable deformation capturing. This paper first presents a state-of-the-art review of existing methods for capturing deformation of concrete structures at elevated temperatures. Key merits, limitations and challenges associated with each measuring technique are discussed. It is shown that existing testing facilities and measuring instruments generally do not allow reliable direct measurement of deformation and strain of high-temperature concrete. As a result, the deformation has typically been captured either indirectly or outside the heated zones, inevitably introducing additional uncertainty and errors that are difficult to be adequately quantified. On the basis of that review, the paper details a new test set-up for reliable non-contact full-field deformation capturing of concrete structures at high temperatures using 3D Digital Image Correlation technique. Key features of the new setup that enable to successfully address major challenges of thermal boundary condition, thermal stability of speckle pattern, contrast of image and hot air movement are presented; together with evidences giving confidence to the reliability of such set-up. With its combined advantages of reliable full-field deformation capturing and thermal boundary conditions on test specimens, the new set-up allows to generate required reliable data on performance of concrete at elevated temperatures, thereby facilitating the development of effective rational fire design and analysis of concrete structures. [ABSTRACT FROM AUTHOR]

In metal forming processes, friction between tool and workpiece is an important parameter influencing the material flow, surface quality and tool life. Theoretical models of friction in metal forming are based on analysis of the real contact area in tool-workpiece interfaces. Several research groups have studied and modelled the asperity flattening of workpiece material against tool surface in dry contact or in contact interfaces with only thin layers of lubrication with the aim to improve understanding of friction in metal forming. This paper aims at giving a review of the most important contributions during the last 80 years covering experimental techniques, upper bound solutions, slip-line analyses and numerical simulations. Each of the contributions shed light on the importance of the real contact area and the influencing parameters including the material properties, surface conditions, normal pressure, sliding length and speed, temperature changes, friction on the flattened plateaus and deformation of the underlying material. The review illustrates the development in the understanding of asperity flattening and the methods of analysis. Finally, the present paper discusses the necessary future work in order to advance further in modelling of real contact area in relation to implementation of frictional conditions existing finite element codes for simulation of metal forming processes. [ABSTRACT FROM AUTHOR]

This paper is devoted to the development of technological process of production of magnesium alloy tubes by laser dieless drawing process. The purpose of the paper is the development and verification of the FEM code for simulation of LDD process and the study of main regularities of this process for magnesium alloy tubes. The problems of forecasting the geometric dimensions of the tube and the possibility of the crack of the material were considered.. The developed FEM code takes into account the three-dimensional deformation of the material, thermal processes, laser heating, the mechanical properties of the material and process parameters. Calibration of the model included the definition of the absorption coefficient, which determines the efficiency of laser heating. For this purpose the experimental analysis of the temperature distribution during the process was made. In laboratory conditions the experiment of laser dieless drawing of tube from AZ31 alloy was performed with the initial outside diameter of 5 mm and a wall thickness of 1 mm. In the experiment the tube surface was covered with a graphite paint to increase the absorption coefficient. The value of absorption coefficient was determined by the inverse analysis and was equal to 0.12. The calculated results were used for producing tube in laboratory. As a result, a good correspondence of geometrical dimensions of the final tube with the calculated values was achieved. [ABSTRACT FROM AUTHOR]

Stamping is one of the most widely used sheet metal forming processes. Esthetics and durability of the deformed products are limited by defects in the form of strain localization, grooves or cracks. Forming limits, e. g. in form of forming limit curve (FLC), help to avoid above-mentioned defects in the sheet metal during forming. Besides the common steel sheets for deep drawing processes, e.g. DC04, components can also be made of metal with specified strength and chemical resistance properties. One of such materials is titanium sheet. In this paper, FLC for GR1 titanium sheet will be presented. It was obtained by means of a new author’s method named as ALSAD (Analysis of Laser Speckle Activity Differences). So far, applied methods of FLC determination have been mainly based on the measurement of the strain distribution in the area of the created groove, deformation gradient and deformation speed. For this reason, detection of strain localization has been dependent on the strain measurement method. The ALSAD, based on laser speckle phenomenon allows detection of defects initiation on the sample surface independently of the strain distribution measurement and it allows, for example, to relate a moment of defect initiation directly to the sample height or forces occurring in the process. In this paper strain values for strain localization, grooves and cracks for GR1 titanium sheet will be shown. Obtained results show good formability of this material, which was verified by means of 3D digital microscope. Such results allow tracing precisely the formation of the defects starting from strain localization up to the crack appearance, which would be helpful for advanced numerical simulations. [ABSTRACT FROM AUTHOR]

Due to the special characteristics of metal forming processes (i.e., large deformations, complex nonlinear, etc.), finite element method (FEM) often encounters the mesh distortion problem in simulating large and severe deformation metal forming processes. Once meshes become severely distorted, the whole simulation process cannot be continued unless the remeshing is used. Nevertheless, remeshing usually leads to not only the deterioration of computational precision but also the increase of time-consuming. To solve the problem, a meshless method known as natural element method (NEM) is introduced to analyze metal forming processes in the paper. The shape function of NEM is constructed by employing the natural neighbor interpolation method, and it has the high accuracy of the approximation. In addition, because the shape function possesses the Kronecker δ property like the FEM, the essential boundary conditions can be imposed directly. Therefore, the paper combines NEM with rigid/visco-plastic flow theory and applies it to simulate metal forming processes. Furthermore, a numerical analysis procedure is developed. A numerical example of metal forming processes is analyzed. The validity of the numerical simulation program is evaluated by comparing simulation results with those obtained by rigid/visco-plastic finite element method. [ABSTRACT FROM AUTHOR]

Shear forming is an incremental cold forming process. It transforms 2D plates into 3D structures commonly consisting of conical geometry. Roller(s) push the blank onto a cone-shaped mandrel, resulting in a decrease of the initial thickness. The shear forming process has diverse advantages, such as improved material utilisation, enhanced product characteristics, good surface finish, consistent geometric control and reduced production costs. Shear forming has potential applications in a wide range of conical geometries used within advanced aerospace structures, which are currently manufactured from bulk forgings with high associated machining costs. Research findings related to shear forming have been published over the past two decades, however, important remaining questions have still to be answered, with this paper addressing one such gap associated with the material deformation mechanism. Several studies have demonstrated the impact of key process variables on the final geometry and surface roughness, such as the feeds, roller nose radius and mandrel/roller offset. Although the material outputs are essential, as they link directly with the mechanical properties of the final components, the microstructure and texture of the material after shear forming have rarely been studied. Achieving a greater understanding in this area could reduce the reliance upon mechanical testing to validate the process and ease the exploitation route of the technology into advanced aerospace applications. Firstly, this paper presents the principle of shear forming and its related terminology. Then, a brief overview of the shear forming process including its history and origin is given. The areas of focus are a selection of the main variables encountered within this process which could impact the final properties. The generation of local stresses due to deviations from the sine law, the angle variations, and forces required during the forming operation are also considered. This is explored in the context of forming 304L stainless steel plates. This paper is written based upon experiments which observed a 52% thickness reduction using one roller. Scanning Electron Microscopy (SEM), Electron BackScatter Diffraction (EBSD) and hardness testing were utilised to characterise the shear formed material. The initial heterogeneous microstructure with relatively equiaxed grains evolved into a microstructure with elongated grains along with shear bands. A texture analysis revealed a simple shear mechanism of deformation, and theoretical and experimental shears were found to match. Identifying the mechanism of deformation was the first step to a better understanding of the effect imparted by the shear forming process on the material. Further studies will look at the impact of the key process variables on both the microstructure and texture as well as heat treatment optimisation. [ABSTRACT FROM AUTHOR]

Incremental bulk deformation processes have traditionally been difficult to simulate. This paper will argue that, despite advances in computation and software, they remain difficult to model. The main reason for this is the shortage of ideas on what is the real objective of FE modelling for such processes. Even a very detailed model and data obtained in simulation does not give answers to the main question - how to optimise the process parameters? High computational time and volume of information only aggravate the situation. All modern mathematical techniques of dimensionality reduction (such as POD/PGD) lose their power when the priorities and acceptable compromises of modelling are not clear. This paper tries to use a large volume of available experimental and modelling experience to illustrate this problem and look for possible break-through directions. [ABSTRACT FROM AUTHOR]

The paper considers the questions of experimental research of deformation of elastic elements regarding the foil gas dynamic bearings. This research is required to check the adequacy of developed theoretical basics and the applicability to the real operation of a high-speed rotor. The paper presents the description of a test rig, the choice of the controlled and measured parameters, the experimental set up of the systems of control and measurement; and identifies the range of controlled parameters deviation. The paper also features schemes and photos of original measurement system, which include a mechanical part and the data acquisition system. The data acquisition system is based on an ADC by National Instruments and inductive proximity sensors. The software developed in LabVIEW is used as an instrument of experimental data registration. The test results have been compared to the numerical results of the mathematical modeling. [ABSTRACT FROM AUTHOR]

At mesoscale, dynamic alternating milling forces and relative stiffness of thin wall are the main factors affecting the deformation of thin-walled structures. To improve the machining accuracy and effectively control the thin wall deformation, this paper investigates the control strategies of dynamic milling forces and deformation mechanism in milling of different thin-walled structures. The instantaneous deformation of thin wall in high temperature casting wax supported milling is analyzed. A deformation control method of thin wall based on the dynamic stability of micro milling forces is proposed in high-speed milling process. Three representative milling experiments on microchannel cold plate with cantilevered boundary, single impeller blade with mixed boundaries, and cantilevered structure shaped like variable curvature wavy line are presented. The milling deformation mechanisms of these three thin-walled structures with different target thickness are further investigated in free milling and casting wax supported milling. Compared with free milling, the milling forces and thickness dimension of thin wall machined under different control strategies are analyzed. By monitoring the milling forces in milling of different micro-walled structures, the small difference and fluctuation of milling forces at different positions, together with the reduced thickness errors verify the effectiveness of the control strategies, using high temperature precision casting wax as auxiliary support in reducing the thin wall deflection. Additionally, the optimal milling control strategy of thin wall is determined. [ABSTRACT FROM AUTHOR]

In the present paper, we study some almost paracomplex structures on the tangent bundle with vertical rescaled Berger deformation metric and search conditions for these structures to be anti-paraKäahler, quasi-anti-paraKäahler. [ABSTRACT FROM AUTHOR]

As the characterization of superplastic materials requires elevated temperatures and strain rate control, standard bulge testing procedure with optical measuring systems is not feasible for the determination of biaxial stress–strain curves. Standard superplastic bulge forming tests performed at constant pressure can be used for the identification of material constants or formability evaluation, but they are not applicable for accurate characterization of deformation behavior providing stress–strain curves at constant strain rates. The present paper is aimed to provide a technique for the direct characterization of stress–strain behavior of superplastic materials in conditions of biaxial tension. This technique is based on bulge forming testing with a closed-loop pressure control procedure allowing one to maintain the value of the effective stress at the dome pole at the predefined constant level. Thus, the variation of strain rate is reduced compared to the constant pressure testing. The results are evaluated using a double-step numerical procedure which provides the way to calculate the stress–strain curves, corresponding to constant referenced strain rates. The developed technique was used to characterize superplastic aluminum alloy Alnovi-U in conditions of biaxial tension at 500 °C. [ABSTRACT FROM AUTHOR]