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A well‐known model of stress–strain behavior in continuous‐fiber ceramic composites was expanded, corrected, and coded in a popular programming language. Four versions of the code with differing output plot formats are included. They can be pasted into a program file and used without editing. One of them allows observing the changes in the stress–strain curve while varying nearly any of the input properties. The ability to observe or quickly plot and compare curves using different parameters can aid in understanding the roles of constituent and interface properties in composite behavior. It can also aid in inferring unmeasurable properties in actual composites. Comparisons of model output to experiment are presented and discussed.

PURPOSE The optimal abutment material and design for an angled implant-abutment connection in the esthetic zone is unclear. The purpose of this finite element analysis (FEA) study was to compare different abutment models by evaluating the stress values in the implant components and strain values on the simulated bone around an anterior maxillary implant with different angled abutment models and loading conditions. MATERIALS AND METHODS One O3.5×12-mm implant was placed in 3D FEA models representing the anterior left lateral segment of the maxilla. Three different contemporary implant models were created with 17- or 25-degree angled abutments (Ti base abutment, zirconia abutment, and titanium abutment) and 3D-modeled. The implant abutment model was an angled Ti base abutment (TIB), an angled zirconia abutment (ZIR), or an angled titanium abutment (TIT). Vertical and oblique loads of 100 N for the central incisors were applied as boundary conditions to the cingulum area and incisal area in a nonlinear FEA. RESULTS The TIB model resulted in reduced stress conditions. According to the von Mises stresses occurring on the screw, abutment, crown, and implant, especially under oblique loads, the TIB model was exposed to less stress than the ZIR or TIT models. Strain values in simulated cortical and trabecular bones were obtained lower in the TIB model. CONCLUSIONS When a standard implant was placed in the esthetic zone at an increased angle, the implants, abutments, and screws had more unfavorable stress levels; therefore, using a Ti-base abutment may reduce stress. The amount of contact surface of the implant with the simulated cortical bone is also an important factor affecting stress and strain. This article is protected by copyright. All rights reserved.

The stress and strain play an important role in strengthening of the precipitation-hardened Aluminum (Al) alloys. Despite the determination of relationship between the mechanical properties and the precipitation existing in the microstructure of these alloys, a quantitative analysis of the local stress and the strain fields at the hardening-precipitates level has been seldom reported. In this paper, the microstructure of a T8 temper AA2195 Al alloy is investigated using aberration corrected scanning transmission electron microscopy (AC-STEM). The strain fields in Al matrix in the vicinity of observed precipitates, namely T1 and β' , are determined using geometric phase analysis (GPA). Young's modulus (Ym ) mapping of the corresponding areas is determined from the valence electron energy loss spectroscopy (VEELS) measured bulk Plasmon energy (Ep ) of the alloys. The GPA-determined strains were then combined with VEELS-determined Ym under the linear theory of elasticity to give rise the local stresses in the alloy. The obtained results show that the local stresses in Al matrix having no precipitates were in the range of 138 ± 2 MPa. Whereas, in the vicinity of thin and thick T1 platelet shape precipitates, the stresses were found to be about 202 ± 3 MPa and 195 ±3 MPa, respectively. The stresses measured in the vicinity of β' spherical shape precipitates found out to be 140 ± 3 MPa which was near to the local stress value in Al matrix. Our findings suggest that the precipitate hardening in T8 temper AA2195 Al alloy predominantly stems from thin T1 precipitates.

Key responses of manufacturing processes are often represented by spatially or time-ordered data known as functional data. In practice, these are usually treated by extracting one or few representative scalar features from them to be used in the following analysis, with the risk of discarding relevant information available in the whole profile and of drawing only partial conclusions. To avoid that, new and more sophisticated methods can be retrieved from the functional data analysis (FDA) literature. In this work, that represents a contribution in the direction of integrating FDA methods into the manufacturing field, the use of function-on-function linear regression modelling is proposed. The approach is based on a finite-dimensional approximation of the regression coefficient function by means of two sets of basis functions, and two roughness penalties to control the degree of smoothness of the final estimator. The potential of the proposed method is demonstrated by applying it to a real-life case study in powder bed fusion additive manufacturing for metals to predict the mechanical properties of an additively manufactured artefact, given the particle size distribution of the powder used for its production.

Objectives The aim of the present work was set to explore the role of root diameter, root length, and thickness of periodontal ligament (PDL) and its material properties (linear and non-linear elastic material models) on the stress and strain distribution, tooth displacement and centre of resistance (CR) location. Setting and sample population Both the bone and the tooth were considered as rigid bodies, and the PDL was modelled as a paraboloid with different geometric dimensions and material properties. Materials and methods To achieve this goal, a horizontal force of 1 N was applied in the CR location and the stress and strain distribution and tooth displacement were quantified. Locations of CR were estimated through iterative finite element procedure. Results It was predicted that the position of CR is in the range of 34%-39% of the root length, slightly higher than one-third of the root length reported in the literature. The geometrical dimensions of the PDL had no significant effect on the position of CR, especially in the non-linear material model of the PDL, while the initial displacement of the tooth was found to be highly dependent on the geometrical and mechanical properties of the PDL. Conclusion The simplified PDL modelling approach with non-linear material behaviour can be suggested for the estimation of initial tooth movement for individual clinical applications without the use of advanced 3D scans.

Atmospheric icing is a major cause of damage to electric power networks. During ice storms, “ice shedding off” cables and conductors can lead to major damage to power systems, mostly by mechanical failure. The brittleness of ice might be its most important and critical property possibly leading to hazardous events in urban regions, and involving equipment such as electrical power lines. To avoid or reduce the risks from this phenomenon, it is necessary to understand the mechanical behavior of ice, including ice strain, as well as its maximal strength and residual strength. The behavior of ice depends mainly on the applied stress and strain rate, as well as temperature, salinity, porosity, and particle size. As a fundamental subject on the deformation behavior of ice, the simple case of polycrystalline isotropic ice was chosen in this study. A methodology is developed to determine the stress‐strain curve for ice as a function of temperature and several uniaxial compression loading conditions. Mathematical relations are developed for several loading conditions and temperature. The results of this research allow to predict the maximal and residual strength of ice, as functions of strain rate and temperature.

Nickel based single crystal superalloys are predominantly used for turbine blades in aircraft engines and land based gas turbines. Understanding and predicting the fatigue failure of Ni based single crystal superalloys are critical to ensure the safety of these components during operation. In this paper, low cycle fatigue experiments were carried out to investigate cyclic deformation of a nickel based single cry stal superalloy MD2, recentlydeveloped by GE Power, with different crystallographic orientations. Specialty in situ scanning electron microscope (SEM) tests were also conducted to study the slip controlled initiation of short cracks under low cycle fatigu e. In particular, the stress strain responsefor both [001] and [111] orientations were used to calibrate a crystal plasticity model, which allowed us to simulate the activation of crystallographic slip systems and predict the initiation of short fatigue c rack. Using the accumulated shear strain as a criterion, the simulations confirmed that the slip system with the maximum accumulated shear strain appeared to control the crack initiation. The location and direction of slip traces and short cracks, captured by the crystal plasticity finite element simulations, agreed with the in situ2SEM observations. The modelling tool will be valuable for assessing the structural integritySEM observations. The modelling tool will be valuable for assessing the structural integrity of critical gas turbine blades.of critical gas turbine blades.

The mechanical deformation of sea ice has substantial influence over large-scale (e.g., > 10 km) ice properties, such as the ice thickness distribution, as well as small-scale (e.g., < 50 m) featur...

For metallic materials, standard uniaxial tensile tests with round bar specimens or flat specimens only provide accurate equivalent stress–strain curve before diffuse necking. However, for numerical modelling of problems where very large strains occur, such as plastic forming and ductile damage and fracture, understanding the post‐necking strain hardening behaviour is necessary. Also, welding is a highly complex metallurgical process, and therefore, weldments are susceptible to material discontinuities, flaws, and residual stresses. It becomes even more important to characterize the equivalent stress–strain curve in large strains of each material zone in weldments properly for structural integrity assessment. The aim of this paper is to provide a state‐of‐the‐art review on quasi‐static standard tensile test for stress–strain curves measurement of metallic materials. Meanwhile, methods available in literature for characterization of the equivalent stress–strain curve in the post‐necking regime are introduced. Novel methods with axisymmetric notched round bar specimens for accurately capturing the equivalent stress–strain curve of each material zone in weldment are presented as well. Advantages and limitations of these methods are briefly discussed. © 2019 The Authors. Fatigue & Fracture of Engineering Materials & Structures published by John Wiley & Sons Ltd This is an open access article under the terms of the Creative Commons Attribution License

Three component mobility controlling vinylic rotaxane crosslinkers with two radically polymerizable vinyl groups (RC_Rs) were synthesized to prove that the mobility of the components of the RC_Rs plays a crucial role in determining the properties of rotaxane-crosslinked polymers (RCPs). RC_Rs (R=H, Me, or Et) were obtained from living ring-opening polymerization. RCP_Et was prepared using RC_Et, which exhibits the lowest component mobility. The low component mobility is reflected in inferior mechanical strength and stretching ability in tensile stress tests compared to components with good (R=Me) and high (R=H) mobility. However, RCP_Et exhibited significantly higher stress and strain values than the corresponding covalently crosslinked polymers (CCP_Rs). These results indicate that a suitable component mobility substantially enhances the mechanical strength of RCPs. This behavior could serve as a guiding principle for the molecular design of advanced RCs.

The objective of this study is to evaluate the stress distribution characteristics around three different dental implant designs during insertion into bone, using dynamic finite element stress analysis. Dental implant placement was simulated using finite element models. Three implants with different thread and body designs (Model 1: root form implant with three different thread shapes; Model 2: tapered implant with a double‐lead thread; and Model 3: conical tapered implant with a constant buttress thread) were assigned to insert into prepared bone cavity models until completely placed. Stress and strain distributions were descriptively analyzed. The von Mises stresses within the surrounding bone were measured. At the first 4‐mm depth of implant insertion, maximum stress within cortical bone for Model 3 (175 MPa) was less than the other models (180 MPa each). Stress values and concentration area were increasing whereas insertion depth increased. At full implant insertion depth, maximum stress level in Model 1 (35 MPa) within the cancellous bone was slightly greater than in Models 2 (30 MPa) and 3 (25 MPa), respectively. Generally, for all simulations, the highest stress value and the location of the stress concentration area were mostly in cortical bone. However, the stress distribution patterns during the insertion process were different between the models depending on the different designs geometry that contacted the surrounding bone. Different implant designs affect different stress generation patterns during implant insertion. A range of stress magnitude, generated in the surrounding bone, may influence bone healing around dental implants and final implant stability.

The properties of collapsible soil exhibit a lot of sensitivity toward the increase of water content, especially when the soil is close to the dry state. The inundation of collapsible soils induces a considerable drop in the void ratio (e) (ie, collapse potential, Cp, increase), which in return affects the dry unit weight (γd), friction angle (ϕ), and shear strength of the soil. The presented study employs large numbers of sandy and silty specimens of collapsible soils with different initial conditions (gathered from the literature) to develop a correlation that evaluates Cp of the soil (ie, settlement) due to inundation. The developed relationship accounts for the soil's initial properties such as the void ratio (e0), degree of saturation (Sr), and pressure applied to the inundated specimens. The presented model reflects the significant influence of Sr on Cp of inundated soil which considerably decreases by the increase of Sr. The determined properties of inundated collapsed soil, such as e and ϕ, are employed to construct the post‐inundation stress‐strain curve (ie, mobilized shear strength) of the soil based on the concepts of the conventional triaxial test. Comparisons between predicted and measured stress‐strain curves of inundated collapsible soils are presented for validation.

Purpose To relate the principal stress, strain, and total deformation in the premaxilla region beneath a complete denture to the pattern of premaxilla bone resorption when opposed by a conventional complete denture (CD) or by a two-implant-retained overdenture (IOD) using finite element analysis (FEA). Materials and methods Three-dimensional solid models of the maxilla, mucosa, and denture of a selected edentulous patient were created using Mimics and CATIA software. The FEA model was created and duplicated in ANSYS 16.0 to perform two simulations for the IOD and the CD models. The values of maximum stress and strain and total deformation were obtained and compared to the outcomes of premaxilla resorption from a parallel clinical study. Results The maximum principal stress in the premaxilla in the IOD model ranged from 0.019 to 0.336 MPa, while it ranged from 0.011 to 0.193 MPa in the CD model. The maximum principal strain in the IOD model was 1.75 times greater than that in the CD model. Total deformation was 1.8 times higher in the IOD model. Greater bone resorption was observed in regions of higher stress, which were on the occlusal and buccal sides of the premaxilla residual ridge. Conclusion Stress, strain, and total deformation values present in the premaxilla area beneath a CD were approximately two times greater in a comparison between an opposing mandibular two-IOD and an opposing mandibular CD. The results were consistent with a parallel clinical study in which the rate of premaxilla bone resorption was almost three times greater in the IOD group.

Publisher's version (útgefin grein), Knowledge about the plastic behavior of reinforcement steel bars in reinforced concrete (RC) structures is important, especially for seismic design. This paper presents the results of experimental tests where the main aim was to map the plastic deformations of long ribbed reinforcement bars, both in the axial and lateral directions, in order to provide useful information about the behavior of reinforcement bars inside concrete. The study showed that the digital image correlation (DIC) technique is very suitable for this kind of tests. The uniaxial stress–strain curves for side‐by‐side and different gauge lengths (1d, 3d, 5d, 10d) were identical all the way to the max stress, but after that the segment including the neck dominated the strain development. The Poisson's ratio increased rapidly during the yielding phase to 0.44–0.49 and was constant all the way to rupture. The location of the neck could be predicted at the end of the yielding phase., This work was supported by a doctoral grant from the Eimskip University Fund of the University of Iceland, by the University of Iceland Research Fund, and by the Ludvigs Storr Trust Fund.

We present a method for evaluating the 3D refractive indices and 3D true stress and/or 3D true strain profiles of "isotactic polypropylene iPP" fibers during necking deformation. Observing the changes in geometrical shape during the deformation process is necessary to understand the mechanical performance of iPP fibers. 3D geometric shape profile and actual stress and strain profiles were measured for iPP fibers during the propagation of neck deformation. These measurements were performed with the aid of an in-situ opto- mechanical device to dynamically characterize different properties of fibers at different strain rates. A software image analysis program was used to calculate the 3D opto-mechanical properties of iPP fibers. The obtained results show that the used dynamic stretching device can be easily used to monitor the deformation process with high accuracy. The effective stress and strain can be determined from the filaments profile. For illustration microinterferograms are given.

A formulation is proposed for true stress–true strain relationships in the plastic regime that exhibit sigmoidal shapes, such as those of certain metastable austenitic stainless steels (MASS). It contains two terms, broadly accounting for contributions to hardening from conventional plasticity and from mechanical stimulation of martensite formation. It is a continuous function, designed to cover the plastic strain range from zero up to several tens of percent. It is shown that it is suitable for capture of a range of curve shapes of this type—experimental data from tensile testing of a MASS alloy over a range of temperature, with good fidelity. The formulation incorporates six independent parameters, although there may be scope for limiting the range of values that they can have, facilitating convergence operations. Information is presented about how convergence is obtained. The equation is thus expected to be suitable for use in finite element method (FEM) models for simulation of plastic deformation in various scenarios, including indentation. Future work will involve exploration of the details of this.

High-strength concrete (HSC) is increasingly used in columns of building all over the world. Although it offers superior properties, it is relatively a brittle material. This study intends to improve the ductility of HSC using modified pretensioning confinement technique. It investigates the effects of the technique on the performance of the column and develops equations to predict the stress–strain. The basis of the technique is to apply a pretensioning force to relatively low-cost steel straps wrapped around the specimens. A modified end clip which is able to be self-regulated is used to secure the strap ends. The parameters studied include various spacing between straps and number of layers of straps. The confined specimens were tested in compression until failure under monotonic loading conditions, focusing particularly on the mode of failure, loads at peak and ultimate conditions and longitudinal and lateral strains in both concrete and straps. It was observed that the pretensioning technique using steel straps enhanced the ductility as well as the strength of the concrete as the confining ratio increases. Moreover, the layers of straps had also delayed the onset of volumetric expansion and therefore, the concrete failure. Based on the regression analysis, new equations of strength and strain for the confined HSC column have been developed to predict its stress–strain behavior.

In this paper, several multiaxial fatigue damage parameters taking into account non-proportional additional hardening are reviewed. According to the way non-proportional additional hardening is considered in the model, the damage parameters are classified into two categories: (i) equivalent damage parameters and (ii) direct damage parameters. The equivalent damage parameters usually define a non-proportional coefficient to consider non-proportional additional cyclic hardening, and make a combination of this non-proportional coefficient with stress and/or strain quantities to calculate the equivalent damage parameters. In contrast, the direct damage parameters are directly estimated from the stress and strain quantities of interest. The accuracy of four multiaxial fatigue damage parameters in predicting fatigue lifetime is checked against about 150 groups of experimental data for 10 different metallic materials under multiaxial fatigue loading. The results revealed that both Itoh’s model, one of equivalent damage parameters, and Suemel’s model, which belong to direct damage parameters, could provide a better correlation with the experimental results than others assessed in this paper. So, direct damage parameters are not better than the equivalent damage parameters in predicting fatigue lifetime.

This study investigates the progressive damage behavior of three-dimensional (3D) braided composites using a new analytical constitutive model. The composite microstructure is represented by yarns and an out-of-yarn matrix. The progressive damage behavior of yarns is modeled by a 3D Linde failure criterion, and that of the out-of-yarn matrix is modeled by an extended Drucker–Prager criterion. A bridging model is used to establish stress and strain relations between fiber and polymer matrix. Thus, the constitutive model of 3D braided composites is developed in the form of a system of analytical equations, and a numerical solution for the equation set is provided in this study. The elastic modulus, the strength constants, and the stress–strain behavior of 3D braided composites under tension and shear are computed by the model, and the results are consistent with the finite element results and the experimental data. The nonlinear damage behavior of 3D braided composites under unidirectional tension, compression, and shear is analyzed. The composite materials show repeated stiffness degradations during damage evolution because of successive failures of different compositions. Damage behavior depends significantly on the stress states and braiding structures of the composites. Braiding angle and fiber volume fraction mainly influence the mechanical properties of the composites, but barely affect the failure modes and tendencies of stress–strain curves. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

The hysteresis loops, stress and strain behavior, lifetime behavior and fracture characteristic of 4Cr5MoSiV1 hot work die steel at a wide range of mechanical strain amplitudes (from 0.5% to 1.3%) during the in-phase (IP) and out-of-phase (OP) thermomechanical fatigue (TMF) tests cycling from 400 °C to 700 °C under full reverse strain-controlled condition were investigated. Stress-mechanical strain hysteresis loops of 4Cr5MoSiV1 steel are asymmetric, and stress reduction appears at high-temperature half cycles owing to a decrease in strength with increasing temperature. 4Cr5MoSiV1 steel always exhibits continuous cyclic softening for both types of TMF tests, and the cyclic softening rate is larger in OP loading condition. OP TMF life of 4Cr5MoSiV1 steel is approximately 60% of IP TMF life at the same mechanical strain amplitude and maximum temperature. Lifetime determined and predicted in both types of TMF tests is adequately described by the Ostergren model. Fracture surfaces under IP TMF loading display the striation and tear ridge, showing quasi-cleavage characteristics, and the cracks are less but longer. However, fracture surfaces under OP TMF loading mainly display the striation and dimple characteristics, and the cracks are more and shorter.