Material Design & Processing Communications最新文献

The economical and safe design of a concrete footing is considered in geotechnical engineering projects. The selection appropriate dimension of the concrete footing is a critical decision that needs to be made by professional engineering, and the accuracy of this decision plays a vital role in the economical and safe design of a geotechnical engineering project. In this study, the engineering judgment for the width design of concrete footing when different soil mixture configuration is rested beneath the concrete footing guided using linear regression and histogram models. The size of 1 (m), 1.3 (m), 1.6 (m), 1.9 (m), 2.2 (m), and 2.5 (m) is numerically selected to design width of concrete footing. The linear regression analysis applied to predict economical footing width with higher accuracy in considering all soil mixture designs. The results reveal the higher width of the concrete footing exhibit with higher accuracy. In this study, the proposed models guide the geotechnical engineers in the selection suitable width of concrete footing in a geotechnical engineering project. This study makes the bridge between the analytical method and the application of soil mixture in concrete footing design. The prediction width of concrete footing with high accuracy supports economically a structure and enhances the stability of the structure as well.

Seawalls are structures built parallel to the shoreline as a reinforcement of a part of the coastal profile. Seawalls are generally subjected to impact loads due to wave impact. In order to withstand the impact loads, the concrete seawalls should possess sufficient impact resistance. The use of crumb rubber particles as a replacement of aggregates improves the energy absorption capacity of the concrete structure. The use of rubcrete in concrete seawalls has not been tried in the past. So, this paper presents the feasibility study of using rubcrete in the concrete seawall by assessing the toughness of rubcrete seawalls. The impact strength of seawall was assessed for rubcrete seawalls by replacing 5%, 10%, and 15% of fine aggregate by crumb rubber. Numerical wave simulation was carried out in ANSYS Fluent, and the wave was coupled to the structure by one-way fluid–structure interaction. The results presented in the paper indicate that the addition of crumb rubber up to 15% shows enhanced toughness performance.

We investigate failure incidents of a solid oxide fuel cell (SOFC) system during start-up from ambient conditions as well as during operation around the design point, using numerical simulation with a view to performance and thermo-mechanical stresses. During start-up, which comprises heating and load ramping phases, the system's trajectory moves through a relatively large temperature range. The simulated failure scenarios include reversible operational discontinuities in terms of input parameters and irreversible hardware failures. Furthermore, we also present results for a complete power cut. A multiphysics modeling approach is used to couple thermal, electrochemical, chemical, and thermo-mechanical phenomena by means of time-dependent partial differential, algebraic, and integral equations. Simulations revealed that the system can smooth out thermal discontinuities that are within a few minutes, that is, within the range of its thermal inertia. However, during the initial phase of the start-up procedure, thermo-mechanical stresses are relatively high due to larger differences between the sintering (manufacturing) and operation temperature, which makes the system more susceptible to failure. This work demonstrates that a multiphysics approach with control- and reliability-relevant aspects leads to a realistic problem formulation and analysis for practical applications.

Al_0.1CoCrFeNi-high entropy alloy (HEA) /tungsten carbide (WC)metal matrix composite was successfully prepared by mechanical alloying and subsequent spark plasma sintering. The different volume fraction of WC was distributed evenly by varying the powder milling parameters from gentle milling (~1.37% WC) and intensive milling (~14.27% WC). Sintering of gently milled powder has resulted in the evolution of three-phased microstructure: α-fcc and Cr- rich σ-phase with some WC-phase distributed in the HEA matrix. On the other hand, the sintering of intensively milled powder has resulted in a two-phased microstructure: α-fcc phase with even and dense distribution of WC-phased particles without any Cr- rich σ-phase. The absence of σ-phase is attributed to a complete alloying of Cr in the HEA matrix. Microhardness analysis and compression test indicate that a ~ 13% difference in WC fraction has resulted in an enhancement in hardness (46%) and compressive strength (~ 500 MPa).

Acoustic Emissions data recorded while marble specimens were subjected to various types of mechanical loading are analysed in the direction of detecting possible common characteristics that could be considered as fracture precursors. The tests carried out were either elementary (three-point bending and uniaxial tension) or structural ones (pure shear of marble blocks interconnected by means of metallic connectors). The data were analysed in terms of the Ib-value (improved b-value) and the F-function, paying special attention to the time interval just before fracture. The temporal variation of both the Ib-value and the F-function were plotted using logarithmic time scale, in terms of the time-to-failure parameter (t_f − t) (where t_f is the time instant of failure), since the specific way of presenting the data offers a deeper insight to what happens during the very last time interval before macroscopic fracture. The analysis indicated that both the Ib-value and the F-function provide clear indices designating entrance into the critical state, i.e., the state of impending fracture. In addition, it was concluded that a power law governs the behaviour of the Ib-value in the time interval before fracture and the exponent of this law seems to be somehow related to the loading scheme.

Railway sleepers are used for transferring loads from train wheels to the ballast. Damage to railway sleepers affects the integrity of the rail network. Prestressed concrete sleepers often get damaged during derailments. At the time of the derailment, a high-magnitude impact load acts for a short duration of time. Damage caused during derailment can be reduced by improving the energy absorption capacity of sleepers. The energy absorption capacity of sleepers can be enhanced by the use of rubber concrete (rubcrete). This paper presents the development of a failure prediction model using finite element analysis to simulate the impact behaviour of self-compacted rubcrete sleepers. This was validated by conducting limited experimental studies and was found to be in good agreement.

In situ process monitoring has frequently been cited as an critical requirement in certifying the performance of laser powder bed fusion (LPBF) components for use in high integrity applications. Despite much development in addressing this need, little attention has been been paid to monitoring the layer thickness during the process. In this paper, a laser displacement sensor has been integrated into the build chamber of an LPBF machine, and the height of the top surface layer of a component has been monitored during a build. This has permitted the deposited layer thickness to be measured throughout the build, and the effect on this of a change in processing conditions is characterised. The thermal contraction of the top layer in between successive laser scans has also been evaluated. This demonstrates the potential of utilising laser displacement sensory as a process monitoring tool in LPBF and provides insightful data for implementation in detailed process models.

Applied element method is a numerical tool for the analysis of structures. It is a rigid body method in which flexibility is introduced with the help of springs. It has few advantages such as lesser processing time and memory requirement than other numerical methods. In conventional numerical methods, node-to-node connection is necessary, and hence, transition elements are used to connect elements of different sizes. But in applied element method, node-to-node connection is not required, and hence, transition element is not used. As springs are used for connecting the elements, cracking can be modelled by removing the springs. Hence, failure analysis can be done more realistically using applied element method. The complete analysis up to collapse of the structure is also possible with applied element method. To illustrate this fact, applied element method is used to determine the stress concentration factor in this paper. Stress concentration factor in plate of finite width with circular and elliptical hole are determined with reasonable accuracy.

The self-healing mechanism of cementitious materials has been investigated by many researchers in the last two decades. In the journey of this quest, more and more advanced methods of analyzing the efficiency of healing have been employed. These methods are intended to clarify and quantify the healing mechanism. This paper presents five techniques, which are either common in the microstructure and nanostructure study or innovative in this field, which was used in order to identify the healing efficacy. Specifically, the application of scanning electron microscope (SEM) analysis, 3-D ultrasound tomography, nanoindentation, water absorption test (sorptivity), and software development in the Python programming environment for monitoring the crack closure have been used. The main objective of this study was to quantify several parameters, such as the geometry of the cracks, the properties of the healing products, as well as the healing depth. SEM analysis is a well-known technique that can contribute to identify the elements of the healing products and give the morphology of the surface. The methodology for nondestructive 3-D ultrasound tomography of healed specimens clarifies the ability of healing in depth. The nanoindentation technique enables localized contact response, which allows accurate estimates of the nanomechanical properties of the tested areas. The absorption method (sorptivity) is a representative method of recording cracks and open porosity. The software developed in a Python programming environment aimed at quantifying the surface crack closure and is an attempt to minimize the parameters that affect the inaccurate results, usually caused by the program's inability to detect only the crack. In addition, the results of each of the above methods are also presented, and their contribution to the study of healing is analyzed.

Ultrasonic pulse velocity (UPV) is a nondestructive technique used for the estimation of concrete properties. This paper investigates the use of UPV test in combination with compressive strength test in order to lower the uncertainty of the latter. For this purpose, 23 mixes were used. The uncertainty of converting UPV measuring results into compressive strength was estimated. A function for combining compressive strength test results with UPV measurements is introduced along with a corresponding uncertainty budget.