Real Working Conditions Research Articles

Development of a transient analytical method for multi-pipe earth-to-air heat exchangers with parallel configuration

A novel analytical model for calculating the thermal performance of multi-pipe earth-to-air heat exchangers is presented by considering soil thermal saturation as well as soil temperature fluctuations on the ground surface. The accuracy of the analytical model is validated using a three-dimensional numerical simulation. The proposed analytical model shows a great coincidence compared to the numerical simulation as well as already reported experimental data. Using this analytical approach, a three-pipe earth-to-air heat exchanger in realistic working conditions is simulated and the effect of the center-to-center distance of pipes on the outlet air temperature and averaged cooling capacity are also investigated. It is shown that while decreasing the distance between the pipes does not change the temperature of the outlet air in the initial working days, a reduction in the thermal performance is observed as the simulation proceeds. This can be attributed to the soil thermal saturation around the middle pipe. The average cooling capacity of the middle pipe reduces by 48%, 35%, 19%, 5%, 2%, and 1% with respect to a single-pipe earth-to-air heat exchanger system for the distance of 25, 50, 100, 200, 250 and 300 cm between the pipes, respectively. In addition, it is shown that increasing the air velocity through the pipes enhances the cooling capacity, especially for larger pipes distance. The cooling capacity of the earth-to-air heat exchanger is enhanced as a result of the increment in the soil thermal conductivity in such a way that the increment percentage is higher for smaller pipe distances. The appropraite distance between the pipes is also shown to be related to the soil thermal conductivity. It is shown that for soil with thermal conductivity of 0.5 and 2 W/m.K, the appropraite distance becomes 200 cm and 300 cm, respectively.

Blade reduced model considering local contact and analyzing blade vibration characteristics

A dynamic model of a tenoned rotating blade considering the pressure distribution characteristics of the contact interface is established and the degree of freedom of the model is reduced by the double coordination free-interface modal synthesis method in this paper. Firstly, the finite element model of the blade is established by ANSYS and the finite element matrix is extracted. Subsequently, multiple contact pairs were established on the contact surface of the tenon to capture the micro-slip characteristics of the contact interface. The normal pressure of the contact pair is obtained by the ANSYS blade-disk contact prediction and load equivalence to take the pressure distribution characteristics into account in the blade dynamics analysis. Then, non-uniform aerodynamic excitation is applied to the blade to simulate the load on the blade under real working conditions. Finally, the double coordination free-interface modal synthesis method is used to reduce the degree of freedom. Due to the coordination condition of the force and displacement of the substructure connection interface, the degree of freedom of the substructure interface is directly reduced. The final reduced degree of freedom is only the sum of the retained modes of the substructure, which greatly improves the computational efficiency. The dynamic equation is solved by the time integration method, and the effects of the tenon angle, rounded corner, and friction coefficient are discussed. The results show that the double coordination free-interface modal synthesis method can greatly reduce the degree of freedom of the tenon-connected blade model under the premise of ensuring accuracy while retaining the local contact characteristics of the contact interface. The structural parameters of the dovetail structure have a great influence on the vibration reduction characteristics of the blade. When designing the tenon structure, it is necessary to pay attention to these parameters.

Emerging Parameters Extraction Method of PV Modules Based on the Survival Strategies of Flying Foxes Optimization (FFO)

Nowadays, the world is encountering multiple challenges of energy security, economic recovery, and the effect of global warming. Investing in new fossil fuels only locks in uneconomic practices, sustains existing risks and increases the threats of climate change. In contrast, renewable energies, such as photovoltaic energy, constitute one of the most promising technologies in combating global increase in temperatures. Given its simplicity and low maintenance costs, photovoltaic energy is the most effective alternative to address the issues above. However, the standard test conditions (STCs) of PV modules are, in most cases, different from the real working conditions of a solar module. For instance, high levels of incident irradiation in an arid climate may cause the temperature of a module to rise by many degrees above the STC temperature of 25 °C, lowering the module’s performance. To effectively simulate and control PV systems for a given location, it has become paramount to develop a robust and accurate model that considers how PV modules behave. This study seeks to introduce an emerging metaheuristic optimization algorithm to estimate the unknown parameters of PV modules. The strategies deployed by flying foxes in the event of high temperatures have given birth to the development of a new metaheuristic algorithm called FFO. Contrary to previous methods, this new modeling procedure makes it possible to calculate all the parameters, regardless of temperature or irradiance. Four PV modules, having different technologies, were tested to evaluate the accuracy of the algorithm in question. The effectiveness of FFO is then contrasted with other well-known metaheuristics where single and double diode models are deployed. The results show that the FFO optimizer represents a substantial and compelling substitute for PV module extraction methods.

Stiffness Modeling and Deformation Analysis of Parallel Manipulators Based on the Principal Axes Decomposition of Compliance Matrices

Abstract This paper presents a general equivalent approach to solve the stiffness modeling or load-deformation problem of non-redundant parallel mechanisms. Based on the principal axes decomposition of structure compliance matrices, an equivalent six-degrees-of-freedom (6-DOFs) serial mechanism is established to approximate the load-deformation behavior of each flexible link in the mechanism. Hence, each limb of the parallel mechanism can be equivalent to a serial redundant rigid body mechanism with passive elastic joints, and the load-deformation problem can be transformed to the equilibrium configuration calculation of the equivalent mechanism. The main advantage of the proposed method is that the robotic kinematics and statics, rather than the elastic mechanics, can be directly adopted to solve the equilibrium configuration of the parallel mechanism under external load. Besides, a closed form solution of the corresponding deformation can be obtained, which can be solved by the gradient-based searching algorithm. Therefore, the final deformation will no longer be linear to the external load, which makes this method more accurate and more suitable for the deformation prediction and compensation in real industrial working conditions. In order to verify the effectiveness and correctness of this method, a 3PRRU parallel manipulator will be introduced as an example, to compare the load-deformation results with the finite element analysis (FEA) simulation and matrix calculation methods, so the nonlinearity feature can be shown in an intuitive manner.

Dynamic Galvanic Corrosion of Working Lithium Metal Anode Under Practical Conditions

AbstractThe practical deployment of lithium metal anodes in rechargeable batteries has been significantly restricted by poor electrochemical performance, which largely stemms from their high susceptibility to corrosion. Inan effort to complete the real picture of Li corrosion pathways, in this contribution, a dynamic galvanic corrosion mechanism under realistic working conditions is described, through which an extended solid electrolyte interphase (SEI) is progressively generated on the successively exposed copper substrate during the dynamic Li removal process. As determined by the titration gas chromatography method, the dynamic galvanic corrosion reaction is unveiled to induce an unfavorable extra Li loss and hence a reduced cell reversibility, especially at sluggish Li stripping rates. Systematic investigations reveal that three critical factors, including total step length of Li stripping, dynamic corrosion current (icorrosion) degradation speed, and SEI chemistry, are responsible form odulating the extent of dynamic galvanic corrosion in practical batteries. This work provides an important complement to current knowledge regarding the corrosion processes of working Li metal anodes, affording fresh insights into the design strategies toward high‐reversibility Li cycling.

Autonomous Unwrapping of General Pallets: A Novel Robot for Logistics Exploiting Contact-Based Planning

In recent years, robotics has been largely applied to improve the efficiency of logistic processes. Pallets cover a crucial role in the logistic flow, since they represent the main way to store and ship items. When put onto pallets, the items are wrapped with plastic films to protect them and prevent them from falling. Despite being the first and necessary operation for handling the stacked goods, unwrapping—the task of removing the plastic films wrapped around the goods—has not yet been satisfactorily automated. We propose the first robotic solution for autonomous unwrapping of generally shaped pallets, including both homogeneous and heterogeneous pallets. Force and torque measurements are exploited to retrieve information on the collisions between the end-effector and the wrapped items or the plastic film. Based on the contact information, we design a novel reactive planning strategy that makes the unwrapping task effective and robust on pallets with uncertain position or shape. We present the results of an extensive experimental campaign to validate the proposed method. Note to Practitioners—This work is motivated by the fact that unwrapping machines are not yet common on the market. The few commercial examples are usually bulky machines that lack the flexibility to adapt to different and irregularly shaped pallets. Thus, the crucial operation of removing the plastic film around palletized goods is still mainly performed by hand. Blade handling, ladders, and electrostatic shocks are sources of potential injury. We propose a flexible, autonomous unwrapping robot suitable for both cuboid and irregularly shaped pallets. The robot is composed of a robotic arm, a custom cutting end-effector, a vision module, and a suitable planning and control unit. The reduced dimensions allow it to be mounted on a mobile base. The robot has been successfully tested on different pallet configurations. However, extensive testing in real-world scenarios should be carried out to assess both reliability and time efficiency in more realistic working conditions. Moreover, real pallets can reach considerable heights. Thus, a prismatic joint should be integrated to address such cases. Finally, unwrapping in the presence of typical plastic straps and different types of film, e.g., the shrink one, is to be evaluated.

Components and Psychological Characteristics of Soft Skills

The development of soft skills is in the focus of attention of the world's largest companies and organizations, in particular, the Organization for Economic Development and Cooperation (OECD), the World Economic Forum (WEF). This is due to the fact that geopolitical and technological trends determine the skills that future specialists need to meet the requirements of the labor market. In the conditions of technological development of a dynamically developing modern society, radical changes in world education, expressed in the formation of a single educational space, the needs of the subjects of education have strengthened the requirements for higher education. As part of this process, new educational standards, a new system for assessing the quality of education are being introduced, modules of educational programs integrated with production are being developed. This, in turn, contributes to the search for the closest and optimal ways to form soft skills of graduates of higher educational institutions to real working conditions. Interdisciplinary direction plays a crucial role in almost all professional fields. The problem of the development of soft skills since the middle of the last century has been dealt with at various times by many scientists who consider and study the concept of soft skills in various aspects. This article, presented in this regard, substantiates the relevance of the formation of soft skills in future specialists. The definitions of the concepts of skill, soft skill, which have been studied and formulated in the fundamental research works of research scientists, are given. Classifications of scientists from far and near abroad by components of soft skills and their psychological component are systematized in the form of tables. As a result of the theoretical analysis, the authors identified the main components of soft skills, such as emotional intelligence, communication skills, critical thinking skills and leadership. The psychological features of the components of soft skills and their relationship are determined. The most important factors of the information and communication technologies (ICT) market are defined as technological development, continuous expansion of the ICT space, the need for a high level of soft skills. The importance of the formation of soft skills among graduates of higher educational institutions is shown.

Systematic Review of Smart Classroom for Hard Skills Training in Augmented and Virtual Reality Environments

Advances in augmented and virtual reality (AVR) technology have allowed for the development of AVR interactive learning environments (AVR-ILEs) with increasing fidelity. When paired with a suitably capable computer tutor agent, such environments can permit adaptive and self-directed learning of procedural skills in some cases. We undertook a comprehensive review of published smart classroom (SC) solutions to facilitate hard skills training in AVR-ILEs. We established the learning context and implemented support for hard skills training for each of the seven solutions that qualified for the final analysis. Typically, AVR-ILEs mimic realistic work conditions or equipment. The aim of this study is to solutions featuring a smart classroom for hard skills training in an AVR-ILEs have been described. In the study, it is also aimed to types of AVR-ILEs from a smart classroom (SC) have been implemented to support hard skills training. This systematic review is based on the reporting criteria of PRISMA 2020 and the scope of the study consists of 9 academic studies including the keyword "smart classroom" and the keywords "augmented reality" or "virtual reality" in academic studies scanned in Scopus, IEEE Xplore, Eric, ScienceDirect and ACM Digital Library. In this study, the distribution of the studies used in the Smart Classroom for Hard Skills Training in Augmented and Virtual Reality Environments (SCHST-AVRE) by solution, domain, country, concept description, country, reviewed papers, learning objective(s), learning tasks, and the context of the technology used is included. In order to contribute to the research on the AVR-ILEs, it has been tried to determine the opportunities and risks that teaching in the SCHST-AVRE can offer to the field of education. In addition, it is thought that this study will shed a light on future studies.

Experimental Study on the Vibration Reduction Performance of the Spindle Rotor of a Rubbing Machine Based on Aluminium Foam Material

Larger vibration and noise often exist in agricultural machinery due to the harsh working environment and high power. The rubbing machine is one of the indispensable pieces of equipment in the agriculture and livestock industry, and it is affected by the vibration of large constraints on its promotion and use. To reduce the vibration of the rubbing machine, the vibration characteristics of the spindle rotor were first analysed by modal simulation, thus determining the larger contributions to the spindle rotor vibration. Second, aluminium foam material was installed in the large deformation part of the spindle rotor. Its vibration reduction and energy absorption characteristics were used to optimise the vibration reduction design by increasing the damping. Third, a steel ball impact test was conducted to analyse the vibration characteristics of the optimised spindle rotor. The results show that the maximum impact accelerations were reduced by 28.4% and 64.75% in the axial and radial directions, respectively, and the impact energies were reduced by 67.3% and 90.65% in the axial and radial directions within 2 s of impact collision, respectively, indicating that the optimised spindle rotor damping increased significantly. In addition, the vibration reduction effect of the optimised rubbing machine was verified by a bench test. By measuring the change degree of the static component of the spindle rotor vibration, the axial, radial, and vertical vibrations of the spindle rotor were improved by 5.78%, 10.32%, and 23.96%, respectively. Therefore, optimising the spindle rotor with aluminium foam material can reduce the vibration generated during the impact of the material on the spindle rotor. The rubbing machine’s vibration, damping, and energy absorption were also realised in real working conditions.

Detailed investigation of supersonic film cooling performance in a convergent divergent nozzle

Abstract This paper numerically studied supersonic film cooling performance in a convergent divergent nozzle, for the purpose of exploring and extending the knowledge of high-efficient cooling techniques for exhaust nozzles in real working conditions. The work was conducted with a steady state RANS approach with the SST turbulence model. The boundary conditions were chosen to mimic a real engine condition. The slot height and the inlet pressure ratio were varied to investigate the effect of the geometrical condition and flow condition. The flow field was analyzed in detail to study the phenomena of the supersonic secondary flow injected into the transonic flow. Besides the cooling effectiveness, the thrust coefficient and the discharge coefficient for the cooling cases were discussed together with the baseline case, to evaluate the influence of the supersonic coolant injection on the nozzle performance. The work can be a basis for the design of cooling schemes in an aero-engine exhaust nozzle.

Screening of technologies for limiting the occurrence of disinfection by-products in urban water systems

Providing safe tap water while limiting the occurrence of disinfection by-products (DBPs) is probably one of the most challenging aspects of environmental chemical engineering within the urban water cycle. In the present work, an investigation about this challenge for the real water conditions of a full-scale drinking water treatment plant has been carried out. Five different and well-known technologies (four different aeration procedures, coagulation, hydrogen peroxide dosage, ion exchange and ultrafiltration) were studied in a real surface water matrix from an engineering point of view. A preliminary estimation of operation costs was also included. The study was focused primarily on trihalomethanes (THMs) and bromate, the DBPs currently regulated by the Spanish legislation, under the real treatment conditions of a drinking water treatment plant that distributes water to 100,000 inhabitants from a surface water reservoir. Based on the results, agitation aeration exhibited the greatest performance to remove THMs directly (86.46 % of removal). Ion exchange resin showed the best potential to inhibit their formation by 100 % bromide removal. Moreover, hydrogen peroxide dosage showed outstanding results in tests performed at full-scale for preventing the formation of bromate in the ozonation stage by 60 %. This was also the cheapest technology according to the dosage cost analysis performed, with 0.01 €·m−3. Thus, this investigation about the elimination of DBPs can be used as a reference to select the optimal treatment technology for limiting their occurrence under real working conditions for full-scale drinking water treatment plants.

A Data-Driven LiFePO4 Battery Capacity Estimation Method Based on Cloud Charging Data from Electric Vehicles

The accuracy of capacity estimation is of great importance to the safe, efficient, and reliable operation of battery systems. In recent years, data-driven methods have emerged as promising alternatives to capacity estimation due to higher estimation accuracy. Despite significant progress, data-driven methods are mainly developed by experimental data under well-controlled charge–discharge processes, which are seldom available for practical battery health monitoring under realistic conditions due to uncertainties in environmental and operational conditions. In this paper, a novel method to estimate the capacity of large-format LiFePO4 batteries based on real data from electric vehicles is proposed. A comprehensive dataset consisting of 85 vehicles that has been running for around one year under diverse nominal conditions derived from a cloud platform is generated. A classification and aggregation capacity prediction method is developed, combining a battery aging experiment with big data analysis on cloud data. Based on degradation mechanisms, IC curve features are extracted, and a linear regression model is established to realize high-precision estimation for slow-charging data with constant-current charging. The selected features are highly correlated with capacity (Pearson correlation coefficient < 0.85 for all vehicles), and the MSE of the capacity estimation results is less than 1 Ah. On the basis of protocol analysis and mechanism studies, a feature set including internal resistance, temperature, and statistical characteristics of the voltage curve is constructed, and a neural network (NN) model is established for multi-stage variable-current fast-charging data. Finally, the above two models are integrated to achieve capacity prediction under complex and changeable realistic working conditions, and the relative error of the capacity estimation method is less than 0.8%. An aging experiment using the battery, which is the same as those equipped in the vehicles in the dataset, is carried out to verify the methods. To the best of the authors’ knowledge, our study is the first to verify a capacity estimation model derived from field data using an aging experiment of the same type of battery.

Pilot Scale Evaluation of Wild Saccharomyces cerevisiae Strains in Aglianico

In winemaking, the influence of Saccharomyces cerevisiae strains on the aromatic components of wine is well recognized on a laboratory scale, but few studies deal with the comparison of numerous strains on a pilot scale fermentation. In this scenario, the present work aimed to validate the fermentative behavior of seven wild S. cerevisiae strains on pilot-scale fermentations to evaluate their impact on the aromatic profiles of the resulting wines. The strains, isolated from grapes of different Italian regional varieties, were tested in pilot-scale fermentation trials performed in the cellar in 1 hL of Aglianico grape must. Then, wines were analyzed for their microbiological cell loads, main chemical parameters of enological interest (ethanol, total sugars, fructose, glucose, total and volatile acidity, malic and lactic acids) and volatile aroma profiles by GC/MS/SPME. Seventy-six volatile compounds belonging to six different classes (esters, alcohols, terpenes, aldehydes, acids, and ketones) were identified. The seven strains showed different trends and significant differences, and for each class of compounds, high-producing and low-producing strains were found. Since the present work was performed at a pilot-scale level, mimicking as much as possible real working conditions, the results obtained can be considered as a validation of the screened S. cerevisiae strains and a strategy to discriminate in real closed conditions strains able to impart desired wine sensory features.

A modified fuzzy clustering framework for catalyst activity monitoring in the selective catalytic reduction system

AbstractThe catalyst activity monitoring in the selective catalytic reduction (SCR) system is of great importance for safety and economic operation in the power plant. To address the problem, a framework based on clustering considering time delay has been proposed. A compound parameter, , is put forward in this paper as a strategy to remove the influences from gas volume (power output), inlet NOx concentration, and outlet NOx concentration to the ammonia amount. A modified entropy‐based fuzzy clustering (EFC) method is proposed by a threshold varying model and then tested for its efficiency by four datasets from the University of California, Irvine (UCI) machine learning repository. With the maximum mutual information entropy coefficient (MIC) method for detecting time delay and the modified EFC method, process data from three working levels are handled for automatically obtained clustering centres. The proposed activity value, , is then calculated based on 1440 process data before and after the catalyst replacement shown in boxplot figures. The results of the framework are analyzed to be in accordance with the real working conditions, with values and fluctuation ranges starting to fall near first from the 721st sample in the 24th box.

Inhomogeneous airflow and heat transfer characteristics of buoyancy-driven airflow in aircraft cockpits

ABSTRACT In-flight airflow and temperature distributions are key parameters for the thermal design of aircraft cockpit. In real working conditions, the effect of gravitational acceleration on flow and heat transfer characteristics is crucial but has long been ignored in the cockpit study. Gravitational acceleration also induces buoyant force and inhomogeneous thermal transport, which gives rise to thermal challenges of aircraft cockpit. To address this challenge, an SST k-ω turbulence model was well validated with 94% prediction accuracy to evaluate the inhomogeneous characteristics. The results indicated that the buoyancy-driven temperature distribution became progressively more inhomogeneous as gravitational acceleration increased. It was also found that the nonlinear variations in temperature were observed in the vertical direction from 0 to 1.5 m. Besides, a dimensionless parameter Gr* (∝107) was used to quantitatively assess the buoyant force. The results showed that the buoyancy force was considerably similar at 2.0 g and 4.0 g, and largely different from the trend at 1.0 g. Indeed, a common characteristic of these three conditions is the presence of a large inhomogeneity coefficient R in the top region of the cockpit. Therefore, an important limitation when designing the thermal structure of cockpit is the inhomogeneous feature of which the follow-up study needs to be carried out.

Features of the Internal Force Factors Distribution in Reinforced Concrete Piles of Complex Cross Section under the Influence of a Transverse Load

Bar reinforced concrete structures, which include piles, in real working conditions perceive a whole range of internal force factors. Axial tension-compression forces, bending moments and shear forces are the most commonly perceived internal force factors. Of particular interest is the effect on the cross section of the shear force. If a complex curly shape is replaced by elementary form, then the calculation is not difficult. However, when calculating the composite cross section, there is no unambiguous solution. In accordance with the adopted regulatory documentation, it is necessary to accept only a main part, while discarding the surrounding areas. It is important to study the configuration of the shape of a complex section for the perception of a shear force. The purpose of the work was to refine the account of the entire complex section using numerical simulation by the finite element method, analytical calculations and small-scale experiments. Determination of further practical application of the obtained results on real structures was also the goal of the study. The parameters of the distribution of shear force between the main rib and flanges were obtained by numerical analysis and small-scale experiments. Numerical models of rectangular and tee cross sections beams have been developed. Analytical dependences were studied and full-scale tests of reinforced concrete beams of various sections were carried out. It has been established that when taking into account the work of the entire cross-section, the bearing capacity of concrete for the action of a shear force is 20% greater than when calculating only the main section without taking into account the shelves.

Research on Interdependence between Specific Rock Cutting Energy and Specific Drilling Energy

A method based on extensive laboratory and field measurements was developed to determine the dependence of specific rock cutting energy (SEc) on specific drilling energy (SEd) for machines with different operating and design characteristics and similar breaking mechanics. Laboratory measurements were performed on a linear rock cutting device and a laboratory drill, using a measurement system to measure electrical power and cutting forces using force/torque transducers. Field power consumption measurements were performed on a chainsaw cutting machine and a hydraulic rotary drill under real working conditions in the dimension stone quarries. The analysis of the measured results confirmed the strong dependence of the specific rock cutting energy on the specific drilling energy and confirmed that laboratory devices can be used to simulate actual rock cutting and drilling process. In addition, the results are applicable in the dimension stone exploration and exploitation phase in order to assess and reduce energy consumption by optimizing the operating parameters of the chain cutter and/or the hydraulic rotary drill.

Efficient and Stable Flexible Organic Solar Cells via the Enhanced Optical‐Thermal Radiative Transfer

AbstractHeating is a knotty factor contributing to device degradation of flexible organic solar cells (FOSCs), and thermal regulation plays a crucial role in the realization of long operational lifetime. Herein, a passive cooling strategy for stable FOSCs is proposed by boosting the optical‐thermal radiative transfer to reduce the insufficient thermal dissipation and the elevated temperature caused by irradiation‐induced heating, while retaining their flexibility and portability. A spectrally selective coupling structure consisting of subwavelength hemisphere pattern and distributed Bragg reflector is integrated into FOSCs to collectively enhance out‐coupling of infrared radiation and limit near‐infrared absorption‐induced heat generation, leading to a reduced heat power intensity of 292.5 W cm−2 and the decreased working temperature by 9.6 °C under outdoor sunlight irradiation. The D18:Y6:PC71BM‐based FOSCs achieve a power conversion efficiency of over 17% with a prolonged T80 lifetime as long as one year under real outdoor working conditions. These results represent a new opportunity for enhancing the operational stability of FOSCs.

Thermal stress calculation of wax-based warm mix asphalt considering thermorheologically complex behavior

The warm mix asphalts which reduce the environmental pollution always show thermorheologically complex behavior under the realistic working conditions (the long-term loading at the low temperature) in the cold region. However, many scholars ignore the thermorheologically complex behavior when calculating thermal stresses. In this paper, the new thermal stresses calculation method considering thermorheological complexity of four wax-based warm mix additives (Fischer-Tropsch (F-T) based wax, fatty acid amides (FAA) based wax, polyethylene (PE)-based wax, and linear aliphatic hydrocarbon (LAH)-based wax) modified asphalt binders were proposed, which was the process of incremental iterative (Named as ‘the incremental method’). The results show that the warm mix asphalt exhibits the thermorheologically complex behavior under long-term loading condition at the low temperature through the tail of the master curve of stiffness modulus, and the thermal stresses considering thermorheologically complex characteristics calculated by the incremental method are greater than that calculated by the traditional Monismith method. Therefore, the incremental method should be used to calculate the thermal stress of asphalt binders under the long-term loading condition instead of the Monismith method, otherwise the cracking risk of the asphalt binder will be underestimated. The wax-based warm mix additives with longer chain molecules and cold storage time can increase the thermorheological complexity more evidently, and the thermal stresses of asphalts with thermorheologically complex characteristics are more sensitive to cooling rate. All in all, the proposed incremental method will provide a supplement to the calculation method of the thermal stresses in the asphalt binder.

Simulated Study of the Machinability of the Nomex Honeycomb Structure

The Nomex honeycomb core has been widely used in many industrial fields, especially the aircraft and aerospace industries, due to its high strength and stiffness to heaviness ratio. Machining of the Nomex honeycomb structure is usually associated with tearing of the walls, deformations of the cells and the appearance of burrs. Therefore, milling of the Nomex honeycomb structure represents an industrial hurdle challenge for scientists and researchers about the quality of the machined surface and the integrity of the cutting tool. In response to this problem, we have developed a three-dimensional numerical model of finite elements based on the real conditions of experimental work by means of the analysis software Abaqus. Based on the developed numerical model, an experimental validation was performed by comparing the quality of the surface and the adhesive wear of the cutting tool determined from the numerical simulation and that established by the experiment. In addition, the effect of geometric parameters in terms of wedge angle and cutting tool diameter on material accumulation, chip size, generated surface and cutting forces was analyzed. The results of the quantitative analysis prove that the choice of cutting conditions and cutting tool geometry in terms of favorable rake angle and tool diameter improves the surface quality of the generated part and optimizes the integrity of the cutting tool.