A Critique on “Measurement of the Hygric Resistance of Concrete Blocks with Perfect Contact Interface: Influence of the Contact Area”

Background: In March 2021, this journal published the article “Measurement of the hygric resistance of concrete blocks with perfect contact interface: influence of the contact area”. That article reports on a study on the impact of ‘perfect contact’ between concrete blocks on moisture absorption, with a focus on the impact of the sample cross-section. Objective: This critique aims at formulating several essential concerns on the hygric aspects of that article, thus expressing the discusser’s reservations on the reliability of the presented outcomes in particular and the published article in general. Methods: The data, as provided in the graphs of the critiqued article, are digitally extracted and further analysed by the discusser. Results: That analysis results in serious concerns with regard to 1) the magnitude of the quantified post-interface flows, 2) the distinguishability of the moisture absorption in the monolithic and perfect contact samples, 3) the robustness of the knee-point identification algorithm, 4) the dependability of the capillary absorption measurements, and 5) the consistency of the capillary absorption processing. These are finally translated into 8 concrete questions to be addressed by the authors of the critiqued article in order to placate these doubts and establish the reliability of their work. Conclusion: This critique formulates appreciable apprehension with respect to an earlier publication in the journal and invites its authors to respond to that via answering the 8 concrete questions. If not satisfactory, then the critiqued article’s findings cannot be considered reliable, and the journal should reconsider its prior publication.

Reflection-Refraction Coefficients and Energy Ratios in Couple Stress Micropolar Thermoviscous Elastic Solid

The reflection and refraction phenomenon of propagation of waves in couple stress micropolar thermoviscous elastic solid media with independent viscoelastic and micropolar properties have been studied. The structure of the model has been taken such that the plane interface is divides the given media into two half spaces in perfect contact. Here, we find that there are five waves, one of them is propagating independently while others are set of two coupled waves travelling with different speeds. Energy ratios, reflection and refraction coefficients relative to numerous reflected and refracted waves have been investigated when set of two coupled longitudinal waves and set of two coupled transverse waves strike at the interface through the solid medium. The inequality of energy ratios, refraction coefficients and reflection coefficients are evaluated numerically and presented graphically under three theories of thermoelasticity, namely, Green-Lindsay theory (GL), Lord-Shulman theory (LS), Coupled theory (CT) versus angular frequency and angle of incidence.

Measurement of the Hygric Resistance of Concrete Blocks with Perfect Contact Interface: Influence of the Contact Area

Introduction: Concrete sealing blocks are not only used in Brazil but worldwide. T he knowledge of the material properties in the presence of moisture becomes necessary to study the durability of buildings. Methods: An experimental study was carried out in order to analyse the effect of contact area on the capillary absorption coefficient of concrete samples used in sealing blocks, according to several standards: NBR 9779 (2012), EN 1015-18 (2002), ISO 15148 (2002) and ASTM C1794 (2015). Two types of specimens were analysed; monolithic samples and samples with a perfect contact interface. The monolithic samples were also subjected to axial and radial compression in order to enhance the capacity of masonry. Results: The experimental results for the samples with perfect contact interface indicate that the water absorption before the interface presents similar behaviour to the monolithic samples. However, it is possible to observe a reduction of the absorption rate when water reaches the interface due to the hygric resistance. In other words, the moisture transport is significantly retarded by the existence of an interface, i.e., the discontinuity of moisture content across the interface indicated that there was a difference in capillary pressure across the interface. Also, the interface contact area does not greatly influence the water-resistance values. Conclusion: Finally, the Hygric Resistance values (HR), in multilayer building components, with perfect contact interface are calculated using the “knee point” methodology.

DESIGN AND MODELING OF A TRIPLE-STEPPED BEAM WITH OUT-OF-PLANE MOTION FOR BISTABLE MICROSWITCH APPLICATIONS

Microswitches have been used for many different applications in building, automation, and security due to requiring little force. A novel design of a triple-stepped beam structure for a mechanical bistable microswitch is presented, and it was found that the bistability of the beam can be achieved by applying an electrostatic force which allows a high deflection with small electrode separation. A finite element method analysis has been used to design the bistable microswitch in a certain range of geometries based on the standard of Taiwan Semiconductor Manufacturing Company (TSMC). The simulation results show that the device requires a verylow input force to get to the bistable stages. The maximum force and the minimum force for switching between the bistable stages are 0.85 mN and 0.23 mN, respectively, which is suitable for electrostatic force at a microscale. The bistability is obtained with the second equilibrium at 75.17 µm that guarantees the perfect contact location between the beam and the conduction path (N+) located at 65.45 µm.

Bending by Concentrated Force of a Cantilever Strip Having a Through-thickness Crack Perpendicular to Its Axis

The article focuses on the bending problem for a cantilever beam with a straight through-thickness crack, perpendicular to its axis under bending by concentrated force. Depending on the crack location in relation to the axis, crack faces may be in three states: perfect contact, particular contact, or noncontact. Using the theory of functions of complex variable and complex potentials, the considered problem was reduced to a linear conjunction one. An analytical solution of the problem was obtained. In the case of particular contact, the length of the contact area and stress intensity factors were determined. The ultimate force that causes beam destruction was determined. Numerical analyses of the problem were also performed.

Study of Partially Transient Organic Epidermal Sensors

In this study, an all-organic, partially transient epidermal sensor with functional poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conjugated polymer printed onto a water-soluble polyethylene oxide (PEO) substrate is studied and presented. The sensor’s electronic properties were studied under static stress, dynamic load, and transient status. Electrode resistance remained approximately unchanged for up to 2% strain, and increased gradually within 6.5% strain under static stress. The electronic properties’ dependence on dynamic load showed a fast response time in the range of 0.05–3 Hz, and a reversible stretching threshold of 3% strain. A transiency study showed that the PEO substrate dissolved completely in water, while the PEDOT:PSS conjugated polymer electrode remained intact. The substrate-less, intrinsically soft PEDOT:PSS electrode formed perfect contact on human skin and stayed attached by Van der Waals force, and was demonstrated as a tattoolike epidermal sensor.

Water Absorption Curves versus Gamma-Ray Attenuation Profiles: A Comparative Analysis of Hygric Permeance Results

The knowledge of moisture transfer in multi-layered building materials and components using numerical simulations is fundamental to predict the behaviour of that building materials and components when in contact with moisture and to avoid some possible future pathology guarantying a correct performance.This paper describes a comparative analysis of experimental values of Hygric Permeance (HP) obtained by water absorption curves and gamma-ray attenuation profiles, for perfect contact interface.

Effect of the load level on the resistance of composite slabs with steel decking under fire conditions

The fire resistance of composite slabs with steel decking, in Europe, is usually defined using simple calculation models provided by the Eurocode EN 1994-1-2. For assessing the methodology of these simple calculation methods, a new advanced calculation method is presented, using the software ANSYS. The numerical model is first validated with experimental data reported on bibliography and then a parametric analysis is conducted to better understand the effect of the load level on the composite structure under fire. The validation of the simulations consisted of three different models: the first model considers perfect contact between the steel deck and the concrete topping, and the two following models consider the existence of an air gap between these materials, acting as a thermal resistance on the temperature field through the thickness of the slab. The numerical results show good approximation to the experimental results, mainly when using the non-perfect contact model, reaching 3.88% and 16.91% of difference with respect to the insulation and load-bearing criteria, respectively. Based on the validation models, a parametric study is presented, modifying the load level from 10% up to 75%. New simple calculation models are presented to define the fire resistance of composite slabs, considering the load level, and the debonding effect between the concrete and the steel deck.