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Dimensional stability issues may occur in paper sheets when subjected to moisture content variations. Paper is in fact mainly composed of hydrophilic wood fibres that experience significant dimensional changes upon humidity variations. The hygro-expansive deformations at the single fibre level and their effects on the meso-structural fibrous network govern the hygro-mechanical response of paper at the macroscopic, sheet scale. The present contribution aims at offering a relation between theoretical predictions and experimental measurements of the hygro-expansive behaviour of paper. Experimental observations of the hygroscopic and mechanical response at the sheet level have been performed, providing the anisotropic hygro-elastic properties of the material in the in-plane principal directions. To understand the multi-scale nature of the phenomenon, a periodic two dimensional meso-structural model of the fibrous network has been developed. The effective material response is extracted via homogenization. The influence of several meso-scale parameters (hygro-mechanical properties and geometry of fibres, inter-fibre bonds and of the network) on the overall behaviour of the material can be studied; in particular, the in-plane fibre orientation distribution along a preferential direction affects strongly the anisotropy of the macro-scale response. The proposed model has been adopted to represent the effective material response, focusing on the hygro-elastic response only and thus neglecting possible irreversible effects occurring at the different scales. A comparison of the experimental data with the results obtained from the model as a function of the fibre orientation distribution reveals a good accuracy of the prediction, thereby showing its applicability to estimate paper’s hygro-expansive response. [ABSTRACT FROM PUBLISHER]

This document is a summary of a special issue of the International Journal of Mining, Reclamation & Environment focused on innovative mine backfill materials and structures. The issue includes fourteen research papers that discuss various aspects of backfill mining, such as stability, hydration characteristics, mechanical features, and curing effects. The papers cover topics such as predicting heavy metal occurrence forms in tailings, using steel slag in backfill materials, assessing the effects of backfill ingredients on mechanical features, and developing simulation models to predict fill strength. Other papers explore the impact of curing humidity on backfill deformation and mechanical characteristics, the spatial evolution of fracture toughness under external sulphate attack, the behavior of fibre-reinforced backfill specimens under different strain rates, and the ideal Poisson's ratio for grainy backfill products. The issue also includes papers on the stress features of backfill materials at different temperatures, inclinometer state analysis for field observation, the characterization of filling effects in coal mines, mixing features of waste rocks in backfill, and the use of microgrid fibres as a reinforcement in cemented rock fills. The author expresses appreciation to the authors, referees, and editors involved in the special issue and hopes that it will contribute to the advancement of advanced fill products and methods in mining. [Extracted from the article]

This paper focuses on the composite design with fibres loaded in the longitudinal direction as well as orientated at some certain angles. The study uses Bombyx Mori Moth Silk (BMM Silk) as fibres and vinyl ester as matrix material. The two sorts of composites having cross ply and angle ply laminate were considered for deformation study using the finite element analysis. According to the ASTM D 3039 testing standard, the tensile test was carried out to design and composite study of their occurred deformation. The rule of mixture was employed in order to evaluate the elastic constants of the prepared orthotropic composite laminate along the fibre direction and the evaluation of orthogonal stresses in transverse direction was carried out using the finite element procedure. The maximum orthogonal stress value of cross ply and angle ply was found to be 44.902 and 47.779 MPa, respectively. Also, the deformation occurred for both laminates was found to be of 0.083603 and 0.076428. This concludes that the deformation occurrence is more in case of angle ply and is less in cross ply laminates. [ABSTRACT FROM AUTHOR]

This work is a contribution to the characterization of the papermaking potential of wood pulps. Prevision of this potential developed during the drying process is the scope of this study. The VARIDIM© apparatus allows to measure shrinkage for different loads applied on the paper strip samples with constant air-drying conditions. The dried papers are then tested in an extensometer to determine mechanical properties. The main originality of this study lies in the possibility of classifying pulps by the maximum specific energy they are able to develop during drying shrinkage. [ABSTRACT FROM AUTHOR]

In this second part of the two-part paper, the layer thickness in the top-layer aluminium alloy and bottom-layer aluminium alloy samples were changed to see the effect if layer thickness has any influence on the deformation and springback behaviour. Four thickness were considered 0.2, 0.4, 0.6, and 0.8 mm for aluminium layer either as a top layer or the bottom layer. To match the bilayer thickness of 1 mm, the remaining thickness was given to the carbon fibre composite layer. Again the 10-process variation were simulated for each layer thickness of aluminium material and results were presented. As found in the first part of the paper the fixed roller and no roller process provides the highest springback in all considered cases. Three distinct regions in the springback profiles were observed with the top-layer or the bottom-layer aluminium material. If the aluminium material layer is towards the punch side and punch rollers are fixed and if the aluminium alloy material is towards the die side and die rollers are fixed the springback profiles are in between the highest and lowest springback cases. It was also noted that the springback increases with increase in the aluminium layer thickness. [ABSTRACT FROM AUTHOR]

The influence of underground humidity on the mechanical performance of cemented paste backfill (CPB) in metal mines is a problem that cannot be ignored. To this end, this paper conducted the curing experiments of CPB samples under different curing humidity (60%, 80% and 95%). Physical properties such as moisture content and dry density as well as mechanical properties such as uniaxial compressive strength, cohesion and internal friction angle of the CPB samples were monitored during fixed curing time (3, 7, 14 and 28 days). TGA/DTG, XRD and SEM were used to analyse the microstructure of CPB samples under different curing humidity at 3 and 28 days, and a BP neural network prediction model of CPB strength was established based on the obtained data. The results show that the curing humidity has a great influence on the physical and mechanical properties of the paste, and the amount of hydration products and the change of pore structure are the main reasons that affect the properties. In order to ensure the safety and economy of the CPB structure, the influence of environmental humidity on the paste should be considered in the filling design. [ABSTRACT FROM AUTHOR]

Creasing is a process which indents a section of corrugated board along fold lines to facilitate a neat fold. The most common failure site in a box made out of corrugated board is at the folds, where the stiffness is reduced by the creasing operation. Crease depth is an important parameter to be controlled. If the crease is too shallow, the section will crack during folding due to excessive strain on the outer liner. On the other hand, if the crease is too deep, the board may crack during the creasing operation itself or it may fail during handling due to excessive reduction in local strength along the fold line. A review of the literature reveals that only a limited amount of research has been carried out on experimental creasing of corrugated boards and comparison with numerical analyses. However, modelling of paper for corrugated board has been successfully done using Hill's plasticity model. In this work, experimental investigations on creasing of corrugated paperboard are carried out. These are complemented by finite element simulations of the creasing process. The simulations are found to be in good agreement with the experimental results. The findings of the work done are helpful in understanding the mechanics of creasing more clearly and in arriving at an appropriate crease depth in order to reduce cracking of corrugated board during the creasing process. [ABSTRACT FROM AUTHOR]

To explore the mechanical properties and deformation mechanism of twin γ-TiAl alloy under load and impact, based on the special interface structure in polycrystals, twinning at room temperature is established in this paper simulation of nanoindentation response of twin γ-TiAl alloy. Through the load-displacement curve, the hardness and Young's modulus of the workpiece are obtained. By analysing the microstructure evolution behaviour under the action of the indenter, it is found that during the loading process, multiple dislocation rings are generated in the grain and slip to the lower part of the workpiece, resulting in the hardness decreasing with the increase of the indentation depth, which is consistent with the indentation size effect; The dislocation lock generated during the unloading process delayed the annihilation of the defect structure, but the dislocation and stacking fault structure disappeared completely and the stress concentrated at the defect residue; in the stress relaxation stage, the dislocation ring structure in the grain extends and annihilates away from the grain boundary, releasing a large amount of stress to reduce the indentation load, and then the defect structure around the indenter is stable to keep the load stable, with high stress at the defect. [ABSTRACT FROM AUTHOR]

Existing methods of vehicle crash velocity determination that are based on body deformation measurements take advantage of linear models. This method finds the linear dependence of equivalent energy speed (EES) which is the measure of kinetic energy loss due to vehicle collision, and Cs coefficient which is the average value of car body deformation. In this paper, authors managed to improve the accuracy of car velocity determination by taking the advantage of non-linear model, polynomial regression in order to calculate the bk coefficient and for the first time, a model where coefficient bk is dependent on two variables: Cs - average car body deformation and Lt - width of deformation field. The aim of this research paper is to demonstrate the new approach of surface approximation of bk coefficient in order to determine the vehicle EES. Authors also indicate the further direction of research. [ABSTRACT FROM AUTHOR]

Permanent deformation is one of the failure modes considered in the analysis and design of flexible pavements. ERAPave performance prediction (PP) which is a mechanistic empirical (ME) pavement design tool utilises two distinct models for the prediction of permanent deformation in the bound and unbound granular layers including subgrade. This paper aims to calibrate these models using pavement response and performance data from accelerated pavement testing (APT) structures. Material properties such as layer modulus were established through an optimisation that involves both falling weight deflectometer (FWD) and pavement response measurements. Based on the predicted performance results, a separate set of calibration was performed for permanent deformation development in moist and wet moisture conditions. The calibrated models have resulted in predictions that are in good agreement with observed performances. Furthermore, the model parameters successfully captured the initial densification behaviour and the associated sensitivity with axle load level. [ABSTRACT FROM AUTHOR]

In this contribution, to improve the deformation modelling based on data integration, the LS-VCE algorithm is proposed by obtaining a stochastic model of input multi-sensor data. So, one can achieve the accurate variance-covariance matrix of multi-sensor observations to participate in iterative least-squares. A practical application was made for the settlement observations from geotechnical settlement-meters and geodetic levelling (respectively known as internal and external sensors) to model the surface settlement variation of the Karkhe earth-dam. The determined variance component shows less contribution of the geotechnical settlements in the deformation modelling. An achievement of this paper is that the LS-VCE method improves the integration of the geotechnical with geodetic data by estimating an optimal stochastic model resulting in deformation model optimization. Validation results of estimated surface settlements on the check-points show an RMSE of about 3 cm and a relative-error of about 14%, which indicates the success of the modelling. [ABSTRACT FROM AUTHOR]

Reasonable evaluation and prediction of squeezing condition to avoid large deformation disaster in tunnels have been an important research issue. In order to accurately and rapidly predict the large deformation under complex geological conditions, this paper proposes a classification and prediction method for quick identification of large deformation in tunnel construction stage in a case study of Muzhailing Tunnel. Previous prediction methods of large deformation are usually based on the stages of geological survey and engineering design, and there are great difficulties in obtaining some prediction indexes in soft and fractured strata, such as uniaxial compressive strength. In this paper, the nonlinear deformation behaviors of surrounding rock were analyzed. The geo-stress condition, strata occurrence, rock strength, rock intactness and groundwater condition were chosen as evaluation indexes (including eight sub-indexes). The classification of large deformation was carried out based on the deformation statistics in Muzhailing Tunnel. And the fuzzy prediction was conducted and compared with other methods in engineering. The comparison results show that the new method has higher accuracy and applicability in predicting the large deformation of weak rock mass. This study provides a new approach for rapid identification and prediction of large deformation in tunnel construction stage. [ABSTRACT FROM AUTHOR]

The auxetic structure with negative Poisson's ratio has broad application prospects in many engineering fields. Although it is often simplified as a linear elastic problem in theoretical models, the generally used slender structure, such as the reentrant honeycombs, will inevitably undergo large deformation resulting in significant non-conservative load effects in the service conditions. Therefore, a numerical framework for modeling nonlinear deformation of the auxetic structures under follower loads with the complex variable element-free Galerkin method is developed in this paper. The application of the complex variable meshfree method is to deal with the numerical difficulties caused by mesh distortion that may occur in large deformation problems, and at the same time, it can improve the construction efficiency of meshfree shape functions through the complex variable moving least-squares approximation. The Galerkin weak form of the incremental total Lagrangian formula for large deformation problems with the enforced essential boundary conditions using the penalty method is derived and then discretized in the complex variable meshless implementation. Five numerical examples are presented with detailed convergence study to demonstrate the accuracy of the proposed approach in dealing with non-conservative large deformation of the slender auxetic structures. [ABSTRACT FROM AUTHOR]

In order not to get bridges collapsed instantaneously, this paper introduces the degradation laws of mechanical performance of corroded steel by making use of different electrochemical detections (by electrochemical detection, the features of corroded steel could be obtained quickly) and finite element analysis. Then according to the laws, this paper sets up “time-varying model” for the situation that carrying capacity changes because part of the bridge suffers corrosion. By the “time-varying model”, a scientific deduction on the remained service life can be made. In this way, a relatively accurate forecast on the durability of bridges being used can be achieved. First, by a orthogonal test where the simulated corrosion is sped up, a relationship between electrochemical signal and corrosion ratio was established; second, by finite element analysis, a relation model between the steel corrosion and steel deformation obtained by electrochemical detection. By linking “potential signals -corrosion degree - deformation degree” and detecting the crystal microstructure of corrosion section, macroscopic deformation and microstructure of the materials were correlated. Then, under a complicated stress, this paper introduces the emergency response system and evolution mechanism of the corroded steel. By setting up a time-varying model involving “electrochemical signals - corrosion degree- deformation degree”, a fast diagnosis system based on electrochemical signal is formed. Depending on such a diagnosis system, a forecast system to predict the durability of the bridges being used can be made, which is similar to the medical judgment that someone's lifetime or age can be predicted by the bone age. Then pursuant to the forecast, we can prevent crises before they emerge. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental studies which were carried out to investigate residual properties of heat-treated concrete mixes made with recycled aggregates by adding fly ash. Mixes made with natural aggregates were used as control mixes. Concrete cylinders made of both types of mixes were employed in the experimental programme. The cylinders were heat treated at temperature varying from 100°C to 1000°C in increments of 100°C and were tested in compression and tension to determine their respective residual strengths. The residual strengths of both types of mixes followed a similar pattern of reduction at higher temperature exposure. The residual compressive stress and elastic modulus became nearly 15% at 900°C and 700°C, respectively. A slightly higher mass loss was observed in RAC mixes due to the use of recycled aggregates which contained more free water and sustained larger thermal deformation on heating at high temperatures. [ABSTRACT FROM AUTHOR]

This paper explains a preliminary study on the effect of oxidizing environment on the sagging deformation of Pressurized heavy water reactor coolant channel at extreme temperature. The coolant channel consists of two concentric tubes- calandria tube (outer tube) and pressure tube (inner tube). It is difficult to perform experiments with full-length coolant channels in the laboratory. Hence, a scaled-down concept is developed for scaling the coolant channels with a 1:3 scale. The various aspects of the geometric scaling of tubes are elaborated in this paper. The calculations for hydrogen generation are also presented analytically using existing and widely used correlations. The zirconium alloy of the calandria tube has reacted violently with steam, and the temperature escalation beyond 750°C produces significant chemical heat flux. The calandria tube has completely decayed during the experiment, and the channel is disassembled and fragmented into segments. Few segments are equal to one weight simulator length. Since the calandria tube cannot resist the deformation of the pressure tube due to loss in its structural strength, the pressure tube has undergone enormous unrestricted sagging before the channel failure. A maximum of 320 mm sag is reported at the mid-length of the channel. The scanning micrograph of the channel surface shows spalled oxide layers containing 45.89 weight percentage oxygen. [ABSTRACT FROM AUTHOR]

In this paper, a porous material–bi-directional corrugated honeycomb aluminum (Bi-DCHA) was manufactured, and quasi-static compression experiments were performed in axial (Y/Z-direction) and radial (X-direction) directions. It was concluded that the mechanical properties in the Y/Z directions were better than those in X-direction. Further, to verify the effect of expanded polypropylene (EPP) on the properties of Bi-DCHA, three different density EPP were used to fill them, and the property of Y/Z-direction was performed. As a result, compared with Bi-DCHA unfilled with EPP, the performance of Bi-DCHA filled with EPP improved, and is better than the sum of EPP and Bi-DCHA unfilled with EPP. Observing the stress-strain curves of the four groups of samples, we can find that the initial peak stress (σP) of the Bi-DCHA filled with EPP is lower than Bi-DCHA; the stress in the plateau zone (σpl) increases with the increase of the EPP density. Observing the deformation process of the specimen, it was found that after filling the EPP, the deformation process of the specimen changed from global buckling/tilt mode to local compact plastic deformation mode. The energy absorption effect of Bi-DCHA filled with EPP is stronger than that of unfilled specimen. [ABSTRACT FROM AUTHOR]

Obtaining the load distribution and radial deformations of planetary roller screw mechanism (PRSM) for the load carrying capacity design under complex loading conditions (multi-directional loads) is beneficial to decelerate fatigue and wear of threads. However, the combined effects of axial load, radial load and turning torque (overturning moment) were ignored in previous studies due to the complicated structure of PRSM. This paper presents a multi-roller beam-bar-spring (MR-BBS) model that incorporate radial load, turning torque and thread modification. The proposed model extended the theoretic method for calculating bending behavior of screw and rollers, which can more precisely describe the locus of the threads and roller axis. The load distribution of threads and load sharing among rollers of a PRSM under different external loads and cycling process are analyzed. The results show that the load distribution is more sensitive to turning torque of screw but relatively insensitive to the radial load. Moreover, the load distribution moderately changes with the variation of modification factor. Based on thread modification, the variable lead PRSM is proposed so that the uniformity of load sharing with complex load can be optimized. A multi-roller beam-bar-spring (MR-BBS) model is developed that incorporate axial load, radial load, turning torque and thread modification. The load distribution of threads and load sharing among rollers of a PRSM under different external loads and cycling process are analyzed. The load distribution is more sensitive to turning torque of screw but relatively insensitive to the radial load. The variable lead PRSM is proposed so that the uniformity of load sharing with complex load can be optimized. [ABSTRACT FROM AUTHOR]

Few investigations have considered comprehensive deformation constraints when calculating thermal stress of concrete slab. In this paper, the comprehensive and refined non-linear deformation constraints model of concrete slab is firstly proposed by setting non-linear spring elements at bottom and side of the slab and the capacity of shear load transfer across joints is considered as well. The results show that thermal stresses calculated by refined non-linear deformation constraints model are in good consistent with experimental results. The foundation reaction modulus has little effect on thermal stresses, but has a significant effect on gap between slab and its foundation. The stiffer base results in higher curling stresses at bottom of slab, and the types of base have an important effect on frictional resistance in horizontal direction at bottom of slab. The larger shear stiffness of joints will increase thermal stresses and shear force along joints but decrease deflections of slab. [ABSTRACT FROM AUTHOR]

In this paper, we presented an extended family of Miura-ori structures with programmable multi-step deformation via arraying and mirroring. We found that there is a competitive relationship between thickness gradient and structural gradient for these origami structures. Furthermore, we demonstrate that the multi-step deformation can be designed by altering the geometrical parametric and the order of these origami structures and the number of deformation stages will change with the change of the thickness gradient. Therefore, the current study can be used to construct novel origami metamaterials for engineering applications, such as energy absorbers for both light and heavy impacts. [ABSTRACT FROM AUTHOR]

With the increase of demands for anti-collision performance in many fields, the negative Poisson's ratio structure has attracted the attention of researchers due to its light weight and high shear stiffness. Therefore, a new negative Poisson's ratio (NPR) structure named three-beam star honeycomb (TBSH) is proposed based on the classical star honeycomb (CSH). The stress equation of TBSH is derived by energy method, and its deformation characteristics and mechanical properties are studied. The results show that the structural deformation modes are different under different impact velocities, and TBSH has more obvious NPR effect. In addition, the influence of geometrical parameters on energy absorption of structures is also investigated. Finally, the thickness gradient is introduced into this structure, and the thickness gradient is optimized by multi-island genetic algorithm (MIGA). After optimization, the specific energy absorption (SEA) of the structure is significantly improved, while the initial peak stress (IPS) is decreased. The new structure proposed in this paper is expected to provide a novel design thinking and optimization idea for superstructure design. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of gas cutting during removal of constraint jig plates on deformation after submerged arc welding, the authors have conducted the experiments on a series of processes using a constraint jig plates in a test specimen modeling the deck of a steel bridge. In this paper, an Idealized explicit FEM developed by the authors is applied to investigate in detail the factors that cause springback deformation during the gas cutting of the constraint jig plates. A series of welding and cutting processes using a constraint jig plates were modeled, and then a three-dimensional thermo-elastic-plastic analysis was performed using the Idealized explicit FEM. As a result, it is confirmed that the experimental and analytical results were in good agreement, and the validity of the analysis method was demonstrated. In addition, it is found that the inherent deformation during gas cutting had a significant influence on the springback deformation by the numerical analysis. Then, we proposed a simplified mechanical model to estimate the deformation during gas cutting. As a result, it was found that the proposed mechanical model showed quantitatively good agreement with the springback deformation. [ABSTRACT FROM AUTHOR]

In this paper, a new type of laser beam (co-axial ring beam + core beam) is introduced to weld SUS301 stainless steel with thickness of 0.6 mm, mainly expounds the influence of ring laser on welding deformation and mechanical properties. The ring laser power (RLP), core laser power (CLP) and welding speed (WS) are identified by the response surface method. The maximum deformation after welding, dimensions of the top and bottom of the weld, and the hardness are considered to be the process response. In the process of welding parameter optimization, the multiple regression model of process parameters and response is established by using Box–Behnken parameter optimization design method. Through the significance evaluation, it is found that the accuracy of the regression model is better. Then, the welding process parameters that meet the welding performance and minimum deformation are confirmed by the response surface optimization method. The optimal process parameters are verified by experiments. [ABSTRACT FROM AUTHOR]

Bimetal laminated composite has gained more and more attention as it owns excellent physical, chemical and mechanical properties of both the component metals. Rolling is a common method to prepare such hybrid materials. However, since there is generally significant material property difference between the two metal plates and the quality of the rolled products is restrained by many processing parameters, defects such as low bonding strength, high residual stress, serious warpage and edge cracks are difficult to avoid in the laminated composite. A novel preparation method denominated as Lattice Severe Deformation Rolling (LSDR) is proposed in the present paper that applying a specially designed cross-corrugated roll on the difficult-to-deform metal plate for the first-pass rolling. The plates undergo local severe shearing strains twice through the whole rolling process, which is beneficial for refining the grains and improving the mechanical properties of the laminated composite. Commercial AZ31B magnesium alloy plate and 5052 aluminum alloy plate are selected to perform the confirmatory experiment. The results indicate that AZ31B Mg/5052 Al laminated composite can be produced with high bonding strength, slight warpage and edge cracks. LSDR is considered as a promising method for high-quality bimetal laminated composite preparation. [ABSTRACT FROM AUTHOR]

This paper reports the latest attempt to model the creep deformation and rupture for high Cr (91) alloy under low stress range. While accurately predicting the creep deformation and damage and the ultimate rupture is paramount important, both for the academic research and industrial applications, the current situation is unsatisfactory, particularly for the lower stress range. This paper systematically investigates the formulation as well as tentatively underlines the scientific reasons, to improve and accurately predict the creep deformation, creep damage and the ultimate rupture of P91 in the stress range of 80–125 MPa. This paper contributes to the knowledge on how to accurately model the creep deformation and damage for P91. Furthermore, it contributes to the methodology through the development of a generic model. [ABSTRACT FROM AUTHOR]

Freeform parameterizations to reproduce structure deformation are increasingly important topics in laser-scanner-based deformation analyses. High-accuracy assurance of free-form surface approximation is extremely critical for reliable deformation analysis. One main challenge in this field is the model selection. Improper model complexity could result in under-fitting the real object shape or overfitting data noises, and thus a failure of deformation analysis. A multi-sensor system could integrate advantages of different sensors and improve the quality of mission completed. This paper combines terrestrial laser scanning (TLS) and laser tracker (LT) technologies, to enhance high-accuracy surface modeling in deformation analysis. A surface-based B-spline approximation and a multi-sensor system are investigated, the latter of which focuses mainly on the combination of TLS and LT technologies. The innovation of this paper is that the surface-based B-spline approximation is validated and optimized with LT corner cube reflectors. Hypothesis testing is adopted to select the best parameter setting by judging most consistency of TLS and LT in various epochs. In the B-spline surface modeling, both instrumental and numerical uncertainties are considered. We use the instrumental uncertainty model based on intensity value, as well as numerical uncertainty based on adjustment theories. A sampling strategy is proposed to avoid data gaps and obtain even distributed data points. [ABSTRACT FROM AUTHOR]

The elastoplastic behavior of the contact interface, powerfully influencing the contact stress distribution, is investigated to reinforce the uniformity of the contact stress distribution in this paper. Since the contact interface elastoplastic behavior has predominant and direct effects on contact deformation, whereas different contact deformation distributions can result in completely different contact stress distributions, it is theoretically feasible to enhance the uniformity of the contact stress distribution by optimizing the contact interface elastoplastic behavior. To realize this aim, a heuristic-based elastoplastic behavior optimization algorithm is developed, in which the elastoplastic behavior of the contact interface is optimized by changing the yield strength of the materials around contact interface. The uniformity of the contact stress is represented by its variance, and is defined as the objective function. Bilinear material model and von Mises yield criterion are adopted. Two contact cases are presented to evaluate the effectiveness of the proposed elastoplastic behavior optimization algorithm in terms of improving the uniformity of the contact stress. Some new phenomena during the elastoplastic behavior optimization are also observed and explained. [ABSTRACT FROM AUTHOR]

Large extrusion container (EC) is the key part of an extrusion machine, and generally it depends on shrink fitting of multi-layers to boost its strength. Because of the harsh condition of high temperature and pressure, the shrinkage between every 2 layers of EC would be consumed due to creep deformation. However, shrinkage loss would generate insufficient support to each outer layer and result in axial endplay or crack of EC, which brings both safety issues and economic losses. Since the repair and replacement of EC due to its failure are significantly time-consuming as well as expensive, assessment of EC's lifetime related with shrinkage loss resulting from creep deformation is of great meaning and importance. However, research of this field is very limited. In this paper, based on the proposed damage-coupled constitutive model incorporating creep behavior, the relationship between shrinkage and creep deformation and the influence of shrinkage loss on EC's serving lifetime have been investigated. Furthermore, shrinkage loss under different contact presses and extrusion speeds has been discussed. Results can be used to guide the shrinkage design of EC's shrink-fitting in design stage and modify the manufacturing dimension of replacement layer after certain failure occurrence, thus prolong the serving lifetime of EC to the utmost. [ABSTRACT FROM AUTHOR]

Support structure plays an important role on sustaining overhang areas, resistingshape deformation and reducing thermal stress in many additive manufacturing (AM) processes. However, design of support structures in the preparation stage and removing of those structures in the post-processing stage are still time-consuming and costly. To reduce support structure volume, post-processing time and improve the printing quality, this paper proposes a novel enhanced bio-inspired generative design method, integrating parametric L-system rules and lattice structure configuration, to generate lightweight, easy-to-remove and heat-diffusion-friendly biomimetic support structures. A complex dental component with freeform geometries and discontinuous support areas is selected as a case study to compare with existing popular support design methods. The comparison results show the proposed method exhibits a good support performance for complex dental overhang areas. Hence it has potential to be adopted for other AM processes where support structures are required. [ABSTRACT FROM AUTHOR]

Inspired by the vast amounts of investigations carried out on three-dimensional (3D) printed structures and their recent accelerated developments, the present review paper comprehensively describes the current trends as well as promising findings of 3D printed energy absorbing structures (EAS) for crashworthiness application. Particular attention is paid to the mechanical behaviour and crushing performance of 3D printed EAS. The main 3D printing technological processes, their material feedstocks choices and unique structural designs, investigated recently, are discussed in detail. Deformation modes obtained by 3D printed EAS under different loading conditions are identified. Additionally, salient suggestions with future realisation of complex 3D printed EAS are provided. This review will serve as a springboard to propel the technological advancement of additively manufactured EAS incorporated into moving vehicles and utilised as protective devices. Hence, setting the goals to encourage novel research that guarantees the efficient protection of lives and valuables during mild and catastrophic impacts. [ABSTRACT FROM AUTHOR]

The large-scale and rapid land subsidence that occurs in mining areas often leads to problems, such as densely spaced interference fringes and the temporal decorrelation of interferometric synthetic aperture radar (InSAR) interferograms. To solve these problems, sub-band InSAR is applied to monitor the large-scale deformation that occurs in mining areas. First of all, four different bandwidth images with three sub-band bandwidth parameters are used to extract simulated mining-induced subsidence with seven different deformation magnitudes. The results of the simulation experiment suggest the following conclusions. In monitoring subsidence with different deformation magnitudes using images with different bandwidths, an optimal monitoring value exists; wider image bandwidths lead to smaller optimal monitoring values and higher monitoring accuracies. Therefore, an appropriate sub-band bandwidth should be selected that depends upon the image bandwidth and the subsidence level to achieve optimal monitoring. The optimal sub-band bandwidth for monitoring subsidence of different magnitudes in mining areas is determined through simulation experiments, and these conclusions can provide a technical basis for selecting the appropriate sub-band bandwidth for the monitoring of subsidence in mining areas. Although sub-band InSAR can reduce the number of interference fringes and the difficulty of unwrapping, the simultaneous introduction of large amounts of noise leads to reduced monitoring precision, and the application of the probability integral method in the prediction of mine subsidence is more mature. Therefore, the combined use of sub-band InSAR and the probability integral fusion method to monitor mining-induced deformation is proposed in this paper. The probability integral method is used to perform noise peeling on the interferometric phases of the sub-bands to improve the monitoring accuracy of sub-band interferometry. Then, according to the results of the simulation experiment, the fusion method with the appropriate sub-band bandwidth parameters is applied to monitor the surface deformation associated with working face 52,304 from 2 December 2012 to 13 December 2012. Finally, the monitoring results are compared with the results of monitoring using conventional differential interferometric synthetic aperture radar (D-InSAR) and global positioning system (GPS) field survey data. The results show that the reliability and accuracy of the fusion method are much better than those of conventional D-InSAR in monitoring the large-scale deformation that occurs at the edges of subsidence basins. [ABSTRACT FROM AUTHOR]

There has been a mistake in the work presented in the paper ‘Solving conformal wheel-rail rolling contact problems’ [Vollebregt E, Segal A. Solving conformal wheel-rail rolling contact problems. Veh Syst Dyn. 2014;52(suppl. 1):455-468] on conformal contact analysis. This concerns the reference results for the Hertzian/planar test-case. The ‘effective lateral radius’ was computed twice higher than it should be. This makes the Hertzian ellipse appear wider and shorter than in the corrected results. Furthermore, the effect of contact angle on the effective curvature was omitted in both the Hertzian and conformal test cases. Finally, it has been argued that there could be an error in our formulas for the creep calculation. In that case, however, the formulation proves to be right if interpreted properly, and is easier to understand than that of the earlier references. This paper presents the corrections and their effects on the results. The normal problem appears to be affected the most: the size and shape of the contact area, total force and maximum pressure. The corrections reduce the influence of conformality compared to the planar contact approach, in correspondence with findings of Blanco-Lorenzo et al. [On the influence of conformity on wheel-rail rolling contact mechanics. Tribol Int. 2016;103:647-667]. The tangential problem is affected also, through the traction bound . There the same conclusions hold as before, when looking at other, closer conformal contact situations. [ABSTRACT FROM AUTHOR]

Magnetoelasticity theories describe the behavior of solids in response to the application of a magnetic field. This paper presents a new thermodynamically consistent constitutive theory for simulating nonlinear responses of solids for which the strain energy density depends on the deformation gradient through the Biot strain tensor and specializes the theory for application to the problem of finite deformation of a circular cylindrical tube. The derived theory appears to be attractive for applications as it provides a relatively simple mathematical expression for modeling nonlinear magneto-mechanical responses of solids. For the considered problem, it is obtained that a higher modified pressure is required to maintain a specified azimuthal stretch when a magnetic field is applied. Finally, and among other things, it is observed that the influence of the magnetic field can either decline or progressively enhance with increasing azimuthal stretch. [ABSTRACT FROM AUTHOR]

In the case of a fast drainage process, water movements result in a rapid change in capillary pressure and shrinkage of a porous material. Until now the models used to predict the deformation of most porous media are based on the quasi-static behaviour laws, and dynamic effects are completely neglected. In this paper, a fully coupled model with dynamic capillarity effect considered is proposed for unsaturated water-air flow within deforming porous media. Then, this model is validated with respect to documented experiment on investigation of dynamic capillarity effect in unsaturated sand. The Finite Element Method (FEM) and backward Euler method are used for the discrete approximation of the partial differential equations in space and time, respectively. Numerical results provided by dynamic model have high agreement with recorded experiment data. Moreover, numerical results also reveal that dynamic effects on capillary pressure could cause unexpected deformation (shrinkage) for porous media. All investigations suggest that dynamic effects on capillary pressure should be taken into account to predict unsaturated water-air flow and shrinkage for porous media. [ABSTRACT FROM AUTHOR]

This paper presents a new approach for calibration of Mechanistic-Empirical Pavement Design Guide (MEPDG) permanent deformation models using the Hamburg Wheel Rut Tester (HWRT) Data. The approach was applied on two Ontario mixes tested in HWRT to calibrate and validate the asphalt concrete (AC) rut models. Data from one Long-Term Pavement Performance (LTPP) programme test section in Ontario were also used for verification, calibration and validation of the AC and unbound pavement layer rut models. The section had two construction (CN) life spans, one before milling and overlay (CN1) and one after (CN2). The study used two finite element models and an Excel VBA sheet to run the verification, calibration and validation of the MEPDG rut models. Proposed calibration coefficients resulted in significant reduction in bias, sum of squared errors (SSE) and standard error of estimate (SEE) for rutting by at least 91% for the two HWRT mixes and by at least 67% for CN1 and CN2, when compared with the global and Ontario local calibration coefficients. The results support the conclusion that the approach of using laboratory wheel tracking device data for calibrating the MEPDG rut models is promising. [ABSTRACT FROM AUTHOR]

Thin-walled tubes are widely used as energy absorption devices because of their excellent crashworthiness. In this paper, a novel tubular configuration with a double-layer sinusoidal corrugated section, namely, a double-layer sinusoidal tube (D-LSCT), is proposed to improve the energy absorption capacities. Quasi-static compression experiments and finite element simulations were used to analyse the axial crushing behaviour and energy absorption performance of the D-LSCTs. The results revealed that the geometric parameters had a significant effect on the crashworthiness of the D-LSCTs and that the D-LSCTs had four deformation modes: ordered progression extensional mode (OPEM), ordered progression inextensional mode (OPIM), inextensional mode (IM) and mushroom mode (MM). OPEM and OPIM were more ideal modes, while the IM and MM were unideal modes. To further improve the deformation stability, D-LSCTs were transformed into a three-layer structure by superimposing a regular polygon tube. Experiments and simulations showed that the improved structural design can indeed stabilise deformation and improve the crashworthiness performance. [ABSTRACT FROM AUTHOR]

Novel methods to probe and evaluate the mechanical properties of High entropy alloy are gaining popularity to accelerate the development of new material for structural application and for establishing the physics-based mechanical property models. Nanoindentation techniques are predominantly suitable for evaluating the properties of materials in which deformation volumes can be cautiously controlled, and indentation can be applied to probe the properties of specific phases or features present within the microstructure. The current investigation is based on the plastic deformation response of Eutectic High Entropy Alloy, AlCoCrFeNi2.1, using experimental and computational approaches. In this paper, the plastic deformation of eutectic high entropy alloy AlCoCrFeNi2.1 is investigated using nanoindentation over a broad range of strain rates at room temperature to probe the mechanical properties of Eutectic High Entropy Alloy, AlCoCrFeNi2.1 and also to understand its elasto-plastic behaviour of BCC and FCC phase present in the alloy. In order to capture the deformation mechanism of material under the tip of the nano-indenter as well as to predict the load variation with depth, molecular dynamic simulation is performed. A characteristic load-depth curve has also been generated from the developed model, which is in good agreement with the experimental one. These findings will lead to understanding the phase-specific contribution to bulk mechanical response of multicomponent alloys and aid in designing structural materials with high fracture toughness. [ABSTRACT FROM AUTHOR]

Slender systems in which the length dominates over the other dimensions are an integral part of offshore systems. Modelling of such systems takes into account bending, sometimes torsional, and more rarely longitudinal deformations. The paper presents a new formulation of the segment method, in which the elongation of a slender link is considered; it is also possible to restrict analysis to one selected deformation while neglecting the others, which results in a very high computational efficiency. The models take into account the impact of the environment and the flows inside risers. Validation is carried out by comparing the simulation results with those presented by other researchers. The method is then applied in the solution of dynamic optimisation problems concerning the re-entry process, which includes disconnecting the riser from the wellhead and moving the platform with the riser. Due to consideration of sea currents, this task is a spatial problem. [ABSTRACT FROM AUTHOR]

Ascribed to its wide sensing range, high sensitivity, and low stiffness to match target objects with complex 3D shapes, the stretchable strain sensor has shown its promising applications in various fields, ranging from healthcare, bodynet, and intelligent traffic system, to the robotic system. This paper presents a low-cost and straightforward fabrication technology for the stretchable strain fiber with the combined attributes of a wide sensing range, exceptional linearity, and high durability. The hybrid composite consisting of carbon black and silicone is utilized as the functional material to respond to the external mechanical deformation due to the piezoresistive effect. To address the remarkable hysteresis of the CB-silicone composites, the latex tubes with excellent mechanical robustness and a considerable accessible tensile strain are introduced as the outer supporting components. After injecting the conductive CB-silicone composite into these tubes, the stretchable strain fibers are successfully prepared. Notably, the stretchable strain sensor exhibits linearity (R2 = 0.9854) in a wide sensing range (0–400%) and remarkable durability even after the 2500 cycles under 100% tension. Additionally, the potential of this stretchable strain fiber as the wearable strain sensor and the real-time feedback is demonstrated by detecting the body motion and the expansion devices. [ABSTRACT FROM AUTHOR]

The seakeeping behavior of a ship in waves is different from its behavior in calm water. The resistance and seakeeping performance of a ship must be considered in the early-stage design. Therefore, this paper proposes a hull form optimization framework aiming to achieve the minimum total resistance in waves using a computational fluid dynamics (CFD) technique. A sinusoidal wave is adopted to establish the numerical wave tank and the overset mesh technique is used to facilitate the motions of the ships in question. The total resistance of the hull in waves is regarded as the objective function which is calculated using the Reynolds averaged Navier–Stokes (RANS) method. The arbitrary shape deformation (ASD) technique is used to change the geometry. Under displacement and design variables, a hybrid algorithm is developed to evaluate the objective function combining the optimal Latin hypercube design (Opt LHD) and the non-linear programming by quadratic Lagrangian (NLPQL) algorithm. Finally, two examples of hull form optimization are presented and discussed for David Taylor Model Basin (DTMB) model 5512 and WIGLEY III cases. The results show the effectiveness of the optimization framework developed in the present study, which can lay the foundation for further optimization of full-scale ships. [ABSTRACT FROM AUTHOR]

The deformation of suction caisson foundations in response to complex cyclic loadings is an essential consideration in their design. Under cyclic loadings, pore pressure and unrecoverable deformation in the foundations accumulate depending on the properties of both the foundation soil and the loads. In this paper, a finite element method (FEM) is developed based on a thermodynamics-based constitutive model. This paper first presents the formulation and calibration of the model. Then, the FEM numerical model is introduced. Finally, predictions are made for field trials of suction caissons in clay subjected to quasi-static cyclic loadings. The rotation angle and the settlement of suction caissons are well predicted. The pore pressure development and stiffness degradation in the foundation are also captured by the model. Furthermore, the effect of the ratio of skirt length to the diameter on the rotation of suction caisson foundations subjected to cyclic loads is studied numerically. [ABSTRACT FROM PUBLISHER]

Monopile foundations installed at an offshore site must withstand severe marine environments during their service life. Consequently, their long-term behaviors require careful estimation to ensure adequate safety. This paper details a program involving 1-g model tests on the monotonic and cyclic lateral behavior of a monopile installed in overconsolidated marine clay. Using a self-manufactured loading device, attempts were made to simulate the possible response of the monopile during the serviceability limit state. Experimental results indicate that the deformational response of the monopile, which behaves as shakedown when applied to higher load levels, heavily depends on the load level. However, despite the dominant influence of the load level, the variation in loading frequency could extend the accumulation process of the pile-head deformation sustained from the first hundred to over 1000 loading cycles. In addition, the cyclic regimes of the foundation secant stiffness are affected by the loading frequencies, exhibiting either pure softening or combined softening/stiffening. The feasibility of the available design criteria and empirical models to estimate deformation accumulation is also evaluated based on the proposed test results, indicating that reassessment of the available design methodology is needed to promote applications of the monopile foundation. [ABSTRACT FROM AUTHOR]

Fixture errors are one of the error sources in machining operations. The fixture errors consist of positioning inaccuracies and errors due to workpiece and fixture deformations. Fixture locators’ height error causes incorrect positioning of the workpiece in the fixture and inaccuracy in machined surfaces which can be much more than the locators’ height error. For machining precise workpieces, it is necessary to eliminate these errors. This paper presents a method for modelling and compensating the fixture locators’ height error effect on workpiece machined surfaces. In this method, the planes of workpiece actual coordinate system (ACS) are mathematically modelled in the workpiece theoretical coordinate system (TCS). Using the model, required homogenous transformation matrix for coinciding ACS with TCS and modifying machining toolpath for compensating the errors is generated. The presented model is used to develop a post-processing fixture locator error compensation module, which can modify CNC machining codes to eliminate the effect of fixture locators’ height error on the workpiece machined surfaces. For verifying the presented method, machining simulations and cutting experiments have been performed in this work. The results show that the method can eliminate the effect of fixture locators’ height error on the workpiece machined surfaces considerably. [ABSTRACT FROM PUBLISHER]

In this paper, we focus on the super Kupershmidt operators (also called super O -operators or relative Rota-Baxter operators) of a Malcev superalgebra. We first consider the relationship between Nijenhuis operators and super Kupershimidt operators. Then we discuss Kupershmidt-(dual-)Nijenhuis structures on a Malcev superalgebra. Moreover, we study the deformations of Nijenhuis elements and obtain a deformation theory of super Kupershmidt operators on a Malcev superalgebra. Communicated by Alberto Elduque [ABSTRACT FROM AUTHOR]

Surface residual stress is made on the aero-engine blades by shot peening to improve the fatigue life of the blades. As the service time increases, the surface residual stress is decreasing due to thermomechanical relaxation and the centrifugal load caused by high-speed rotation. Therefore, the surface residual stress detection is of great importance for predicting the remaining life of aero-engine blades. Up to now, efficient and non-contact detection of surface residual stress is still a challenge. In this paper, an active thermal deformation excitation (ATDE) method for surface residual stress is proposed. According to the thermal deformation theory, the thermal deformation of the material is positively correlated with the surface residual stress, and by measuring the thermal deformation the surface residual stress can be detected and evaluated. The theoretical deformation model was established, and simulation models with different surface residual stresses were constructed. A detection system was proposed to detect the blade deformation with different surface residual stresses. Results show that there was a linear relationship between the blade deformation and the surface residual stress from −636 Mpa to −1403 Mpa. [ABSTRACT FROM AUTHOR]

The increasing number of studies on the behaviour of stent placement in recent decades provides a clear understanding of peripheral artery disease (PAD). The severe mechanical loads (axial tension and compression, bending, radial compression and torsion) deformation of the femoropopliteal artery (FPA) is responsible for the highest failure rate of permanent nickel-titanium (Nitinol) stents. Therefore, the purpose of this article is to review research papers that examined the deformation of the natural load environment of FPA, the properties of Nitinol and mechanical considerations. In conclusion, a better understanding of mechanical behaviour for FPA Nitinol stents contributes to increased mechanical performance and fatigue-life. [ABSTRACT FROM AUTHOR]

Norms and guidelines on passive safety currently provide insufficient guidance on restoration, customisation or post-accident repair of vehicles. Vehicle rollover is usually considered to be one of the most complex cases. The analysis has shown very complex loads acting on the vehicle roof structure. Practice of vehicle post-accident servicing and design shows that the joint between roof structure and A-pillar is subjected to the most extreme damages. The paper pursues the aim of identifying rollover damages on roof structural elements and the influence of weld layout resulting from repair of vehicle roof A-pillar on the strength of safety frame during vehicle rollover. The methodology of strength test on vehicle roof support structure is presented in the body of the paper. Results generated during application of static compressive load to the vehicle roof structure are discussed in detail in the paper section dealing with the results. [ABSTRACT FROM AUTHOR]

Subsea pipelines during the operation condition are often subjected to high compressive longitudinal force and internal pressure. Besides, an irregular seabed profile causes the bending moment load on the pipeline which rests on the seabed. In this paper, pipeline deformations and pipe combined stresses over depressions in the operation condition are assessed by using an analytical method. The MATLAB software is employed for these analyses. Based on different loads and span lengths, some zones are defined for pipe combined stresses. Also, the buckling critical load for pipeline over depressions is provided in this paper. Adjusting pipelay tension during installation on irregular seabeds could be a practical method for avoiding damages such as global buckling and bursting. This approach is then extended to the situation in which the pipe touches the sea floor at the middle of depressions. Subsequently, stresses can decrease and pipe can adopt the seabed profile, so span lengths can reduce. [ABSTRACT FROM PUBLISHER]

This paper introduces a novel modelling method for variation propagation calculation of 3-D assemblies taking into account geometric variation and part deformation, which are neglected in most models in tolerance analysis. Initially, numerical studies are carried out in order to illustrate the characteristics of strain distribution in components and contact forces on the mating surfaces of a 3-D assembly. According to these characteristics, a linear equivalent model using springs to represent the elastic mating surfaces with geometric variation was presented. Then, the equilibrium criterions corresponding to actual contact situations and iterative searching algorithm of the equilibrium status of contacting were developed. The proposed modelling and calculation method were finally applied to the assembly of two machined parts, on which finite-element analyses and experimental tests were conducted to validate the effectiveness and accuracy. This linear contact model also shows an important advantage on modelling and calculating efficiency, which enable the practical application to variation propagation calculation in both tolerance design and assembly process. [ABSTRACT FROM PUBLISHER]

The use of index parameters to evaluate the performance of asphalt mixtures has become an important process for making informed pavement material decisions. These index parameters are indicators of asphalt mixture performance and thus are widely used in the asphalt paving industry. This paper presents a new rutting index parameter to assess the rutting resistance of asphalt mixtures using the stress sweep rutting test and the permanent deformation shift model. The proposed parameter, referred to as the Rutting Strain Index (RSI), is novel in that it integrates material testing and structural simulations. To develop the RSI index parameter, more than 70 mixtures from different geographical locations that exhibit a wide variety of performance were evaluated. The results show that the RSI is able to capture the effects of mix design factors, such as RAP content, binder content, and volumetric properties. Furthermore, a set of RSI threshold values are proposed for different allowable traffic levels in terms of rutting. The RSI can be employed by agencies as a tool for performance engineered mix design and quality assurance purposes whereby agencies will be able to accept or reject a mixture based on RSI thresholds. [ABSTRACT FROM AUTHOR]