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This paper seeks to analyse 3D growing concrete structures taking into account the phenomenon of body accretion, necessary for the simulation of the construction sequence, and carbon dioxide attack.

A typical 3D segmental bridge made of precast concrete is studied through a fully coupled thermo‐hygro‐mechanical F.E. model. The durability of the bridge is evaluated and carbonation effects are considered. Creep, relaxation and shrinkage effects are included according to the theory developed in the 1970s by Bažant for concretes and geomaterials; the fluid phases are considered as a unique mixture which interacts with a solid phase. The porous material is modelled using n Maxwell elements in parallel (Maxwell‐chain model).

First, calibration analyses are developed to check the VISCO3D model capabilities for predicting carbonation phenomena within concrete and the full 3D structure is modelled to further assess the durability of the bridge under severe conditions of CO₂ attack.

The adopted numerical model accounts for the strong coupling mechanisms of CO₂ diffusion in the gas phase, moisture and heat transfer, CaCO₃ formation and the availability of Ca(OH)₂ in the pore solution due to its transport by water movement. Additionally, the phenomenon of a sequential construction is studied and numerically reproduced by a sequence of “births” for the 3D finite elements discretizing the bridge. The fully coupled model is here extended to 3D problems for accreting bodies (as segmental bridges) in order to gather the effects of multi‐dimensional attacks of carbon dioxide for such structures.

The purpose of this paper is to present the effect of the aging at 200°C on creep and hardening behavior of hardenable 6101 aluminum alloy manufactured by an industrial wiredrawing process used for construction of self-supporting overhead aerial power line conductors.

The creep tests were carried out under applied constant stress 100 MPa and constant temperature 150°C. Hardness measurements were also used to investigate the mechanical behavior of the aged alloy. Micrographs of the fractured wires by creep tests were performed by scanning electron microscope. Electrical resistivity of the aged alloy was measured at different time of the aging treatment.

The authors have found the relationship between the precipitation sequence, the mechanical properties and the electrical resistivity of aged 6101 aluminum alloy.

The optimum properties were also deduced.

This paper aims to develop a numerical, micromechanical model to predict the evolution of autogenous shrinkage of hydrating cement paste at early age (up to 7 days). Autogeneous shrinkage can be important in high-performance concrete characterized by low water to cement (w/c) ratios. The occurrence of this phenomenon during the first few days of hardening may result in early-age cracking in concrete structures. A good prediction of autogeneous shrinkage is necessary to achieve better understanding of the mechanisms and the deployment of effective measures to prevent early-age cracking.

Three-dimensional digital microstructures from the hydration modelling platform μic of cement paste were used to simulate macroscopic autogenous shrinkage based on the mechanism of capillary tension. Elastic and creep properties of the digital microstructures were calculated by means of finite element (FE) method homogenization. Autogenous shrinkage was then estimated as the average hydrostatic strain resulting from the capillary stress that was globally applied on the simulated digital microstructures. For this estimation, two approaches of homogenization technique, i.e. analytical poro-elasticity and numerical creep-superposition were used.

The comparisons of between the simulated and experimentally measured deformations indicate that the creep-superposition approach is more reasonable to estimate shrinkage at different water to cement ratios. It was found that better estimations could be obtained at low degrees of hydration, by assuming a loosely packed calcium silicate hydrates (C-S-H) growing in the microstructures. The simulation results show how numerical models can be used to upscale from microscopic characteristics of phases to macroscopic composite properties such as elasticity, creep and shrinkage.

While the good predictions of some cement paste properties from the microstructure at early age were obtained, the current models have several limitations that are needed to overcome in the future. Firstly, the limitation of pore-structure representation is not only from lack understanding of C-S-H structure but also from the computational complexity. Secondly, the models do not consider early-age expansion that usually happens in practice and appears to be superimposed on an underlying shrinkage as observed in experiments. Thirdly, the simplified assumptions for mechanical simulation do not accurately reflect the solid–liquid interactions in the real partially saturated system, for example, the globally applying capillary stress on the boundary of the microstructure to find the effective deformation, neglecting water flow and the pore pressure. Last but not least, the models, due to the computational complexities, use many simplifications such as FE approximation, mechanical phase properties and creep statistical data.

This study holistically tackles the phenomenon of autogeneous shrinkage through microstructural modelling. In a first such attempt, the authors have used the same microstructural model to simulate the microstructural development, elastic properties, creep and autogeneous shrinkage. The task of putting these models together was not simple. The authors have successfully handled several problems at each step in an elegant manner. For example, although several earlier studies have pointed out that discrete models are unable to capture the late setting times of cements due to mesh effects, this study offers the most effective solution yet on the problem. It is also the first time that creep and shrinkage have been modelled on a young evolving microstructure that is subjected to a time variable load.

While the implementation of lead‐free solder technology has been the focus of much recent research, the challenge of joint structural integrity should not be overlooked. The paper summarises the significant variability in the mechanical properties of solders, both in terms of the prevailing testing conditions and between the alloys themselves. Using conventional routes to life prediction for an elementary creep situation, it demonstrates the critical importance of understanding the failure processes and utilising materials data that are appropriate.

IN 1946, a short conference on creep in metals was held at the initiative of the National Physical Laboratory. The aircraft gas turbine was then relatively new. It had been developed during the war as a small fighter engine with outstanding power/weight ratio and short life. Since then it has been applied successfully to commercial aircraft and to ship propulsion and its use in power generation is being actively explored. These applications require in general larger engines, longer lives (up to 100,000 hours in many cases), and high thermal efficiency.

For a solution of a problem in practical engineering to be of any value it must be capable of concrete numerical computation at the design stage; and, moreover, it must be such that definite results can be arrived at in a reasonable time. It is seldom necessary for the solution to be exact, since the data and conditions of engineering problems are rarely precise. But what is expected of a solution to a practical problem is that it should give a fairly good approximation to the values observed experimentally or known from experience.

This study aims to investigate the micro mechanism of macro rheological characteristics for composite modified asphalt.Grey relational analysis (GRA) was used to analyze the correlation between macro rheological indexes and micro infrared spectroscopy indexes.

First, a dynamic shear rheometer and a bending beam rheometer were used to obtain the evaluation indexes of high- and low-temperature rheological characteristics for asphalt (virgin, SBS/styrene butadiene rubber [SBR], SBS/rubber and SBR/rubber) respectively, and its variation rules were analyzed. Subsequently, the infrared spectroscopy test was used to obtain the micro rheological characteristics of asphalt, which were qualitatively and quantitatively analyzed, and its variation rules were analyzed. Finally, with the help of GRA, the macro-micro evaluation indexes were correlated, and the improvement efficiency of composite modifiers on asphalt was explored from rheological characteristics.

It was found that the deformation resistance and aging resistance of SBS/rubber composite modified asphalt are relatively good, and the modification effect of composite modifier and virgin asphalt is realized through physical combination, and the rheological characteristics change with the accumulation of functional groups. The correlation between macro rutting factor and micro functional group index is high, and the relationship between macro Burgers model parameters and micro functional group index is also close.

Results reveal the basic principle of inherent-improved synergistic effect for composite modifiers on asphalt and provide a theoretical basis for improving the composite modified asphalt.

Knowledge of the behavior of concrete at mesoscale level requires, as a fundamental aspect, to characterize aggregates and specifically, their thermal properties if fire hazards (e.g. spalling) are accounted for. The assessment of aggregates performance (and, correspondingly, concrete materials made of aggregates, cement paste and ITZ – interfacial transition zone) is crucial for defining a realistic structural response as well as damage scenarios.

It is here assumed that concrete creep is associated to cement paste only and that creep obeys to the B3 model proposed by Bažant and Baweja since it shows good compatibility with experimental results and it is properly justified theoretically.

First, the three‐dimensionality of the geometric description of concrete at the meso‐level can be appreciated; then, creep of cement paste and ITZ allows to incorporate in the model the complex reality of creep, which is not only a matter of fluid flow and pressure dissipation but also the result of chemical‐physical reactions; again, the description of concrete as a composite material, in connection with porous media analysis, allows for understanding the hygro‐thermal and mechanical response of concrete, e.g. hygral barriers due to the presence of aggregates can be seen only at this modelling level. Finally, from the mechanical viewpoint, the remarkable damage peak effect arising from the inclusion of ITZ, if compared with the less pronounced peak when ITZ is disregarded from the analysis, is reported.

The fully coupled 3D F.E. code NEWCON3D has been adopted to perform fully coupled thermo‐hygro‐mechanical meso‐scale analyses of concrete characterized by aggregates of various types and various thermal properties. The 3D approach allows for differentiating each constituent (cement paste, aggregate and ITZ), even from the point of view of their rheologic behaviour. Additionally, model B3 has been upgraded by the calculation of the effective humidity state when evaluating drying creep, instead than using approximate expressions. Damage maps allows for defining an appropriate concrete mixture to withstand spalling and to characterize the coupled behaviour of ITZ as well.

The purpose of this paper is to develop a new alloying method for solders by using a metal organic modified flux in solder pastes.

This paper presents the impact of six metal organic compounds (Co, Fe, Al; stearate, oxalate, citrate) on the melting and solidification behaviour in comparison to the revealed microstructure.

It could be shown that Co and Al influence the supercooling whereas Fe exhibits no effect. Co reduces the supercooling of the cast of about 10 K and affects the nucleation. Al retards the solidification up to 185°C. Doping of the solder by flux containing metal organic compounds is successful and the alloying elements Co and Fe are found in the microstructure.

This paper provides a starting‐point for the new alloying method – so far only fluxes for solder pastes have been investigated.

The reactive alloying method enables the use of new alloying elements for solder pastes in unmodified soldering processes.

The purpose of this paper is to investigate the morphology evolution and the composition transformation of Au-Sn intermetallic compounds (IMCs) of the new Au/Sn-5Sb-1Cu-0.1Ni-0.1Ag/(Au)Ni solder joint during the high temperature aging.

Sn-5Sb-1Cu-0.1Ni-0.1Ag solder balls (500 µm in diameter), heat sink with structure of 7.4 µm Au layer on 5 µm Ni-plated Cu alloy and Si chip with 5.16 µm plated Au were used to fabricate micro-solder joints. The joints were performed in a furnace at 150°C for 150, 250 and 350 h aging. The samples were polished and deep etched before analyzed by metallographic microscope and scanning electron microscopy, respectively. Energy dispersive x-ray spectroscopy was used to identify the composition of the IMCs.

ß-(Au,Ni,Cu)₁₀Sn phase is formed during the soldering process. The IMCs evolution has two periods during the aging. The first is the ξ-(Au,Ni,Cu)₅Sn, ξ-(Au,Cu)₅Sn and δ-AuSn were formed and grew to form a full-compound joint after about 150 h aging. The second is the conversion of the full-compound joint. The IMCs converted to ξ′ phase when the aging time extends to 250 h, and transformed to ε-(Au,Ni,Cu)Sn₂ and η-(Au,Ni,Cu)Sn₄ after 350 h aging. The thicker gold layer and thinner solder joint can promote the growth of the IMCs. ß-(Au,Ni,Cu)₁₀Sn emerged in Au/SnSb-CuNiAg/(Au)Ni in this research, which is not usually found.

The results in this study have a significant meaning for the application of the new Sn-5Sb-1Cu-0.1Ni-0.1Ag in harsh conditions.