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Frequency response function (FRF) identification is a key step in experimental modeling of many applications, including mechatronic systems. Applying these techniques to systems where measurement time is limited leads to a situation where the accuracy of the identified model is deteriorated by transient dynamics. This article aims to develop an identification procedure that mitigates these transient dynamics by employing local parametric modeling techniques. To improve the modeling accuracy, prior knowledge is suitably incorporated in the procedure while at the same time allowing for rational parameterizations that maintain a closed-form solution. The prior knowledge is exploited in a relevant local frequency range using a specific Möbius transformation. Preexisting methods, including the commonly used local polynomial method, are recovered as a special case. The presented framework leads to accurate identification results in a simulation study as well as on experimental measurement data.

It is a relevant objective in thermal physics and in building reciprocating internal combustion engines (RICE) to obtain new information about the thermal-mechanical characteristics of both stationary and pulsating gas-flows in a complex gas-dynamic system. The article discusses the physical features of the gas dynamics and heat transfer of flows along the length of a gas-dynamic system typical for RICE exhaust systems. Both an experimental set-up and experimental techniques are described. An indirect method for determining the local heat transfer coefficient of gas-flows in pipe-lines with a constant temperature hot-wire anemometer is proposed. The regularities of changes in the instantaneous values of the flow rate and the local heat transfer coefficient in time for stationary and pulsating gas-flows in different elements of the gas-dynamic system are obtained. The regularities of the change in the turbulence number of stationary and pulsating gas-flows along the length of reciprocating internal combustion engines gas-dynamic systems are established (it is shown that the turbulence number for a pulsating gas-flow is 1.3-2.1 times higher than for a stationary flow). The regularities of changes in the heat transfer coefficient along the length of the engine's gas-dynamic system for stationary and pulsating gas-flows were identified (it was established that the heat transfer coefficient for a stationary flow is 1.05-1.4 times higher than for a pulsating flow). Empirical equations are obtained to determine the turbulence number and heat transfer coefficient along the length of the gas-dynamic system. © 2022. All Rights Reserved. The work has been supported by the Russian Science Foundation (Grant No. 18-79-10003).

This present study centers sensitively on the determination of the effect of natural turkey feather fibers (TFFs) loading on fundamental features (thermal, mechanical, water-uptake, and micro-structural) of thermoplastic polyurethane (TPU). The composites with different TFFs contents (3, 6, 9, and 12 wt.%) were fabricated by the melt blending method using the twin screw extruder and micro-injection molder. The samples were characterized by means of differential scanning calorimeter (DSC), universal mechanical (tensile and hardness) tester, water-uptake, and scanning electron microscope (SEM) techniques. The thermal analysis depicted that the melting temperatures of the soft and hard segments as well as the crystallinity degree of TPU increased consistently with the increase of TFFs loading level thanks to the formation of better close-packed TPU chains in the matrices. As for the mechanical test results, when compared neat TPU, the tensile strengths were reinforced by 26.8% and 19.7%, and the modulus increased by 6.6% and 45.1% for the composite samples including 3% and 6% of TFFs, respectively. However, drastic diminishment were observed at further contents. Additionally, TFFs loadings brought about gradual increase in the water-uptake capacities of the composites due to the increasing of the number of voids and omnipresent flaws in TPU matrices. The taken SEM images also revealed that, at low contents, there existed the enrichment of interfacial adhesion between TFFs and TPU matrix, whereas the morphological appearance of the composites get worse at high contents accompanied by the formation of micro-structural defects.

Most industrial automation and control systems are remotely operated and monitored. We present the novel remote complex developed for educational purposes – to train engineering students in operating IACS intended for thermal mechanical equipment of power plants. Development of this remote training complex had multiple goals such as displaying all IACS components, operating real industrial equipment, simplicity, portability, and remote access. The typical structure of the automated process control system has been described. We have built a training stand in accordance with this structure, including all technology parts and connection of all sensors and equipment.

The main part of scientific research is the results of the experiment, because they make it possible to establish the existing dependencies of the course of processes on a real object, confirm theoretical calculations and a mathematical model of an electrothermal-mechanical system. The work is devoted to the issue of experimental research of power supplies for measuring and recording equipment. According to the purpose, a technique was proposed by which experimental studies of the presence of pulses, noise and fluctuations in the output voltage of pulse and transformer power supplies were carried out. The influence of the deviation of the output voltage on the fluctuations of the voltage readings on the measuring and recording equipment has been investigated. Based on the results of experimental studies of power supplies, the proposed technique can be taken as a basis for selecting power supplies in accordance with the requirements for the required accuracy of reading indicators from the measuring equipment in accordance with their accuracy class, within the total error permissible for this type of experiment. A power source for measuring and recording equipment was selected for experimental studies of an electrothermal-mechanical system to intensify the process of methane formation in a biogas reactor in order to determine as accurately as possible the energy costs for biogas production, due to the fact that the process of producing biogas is long, therefore, a large error in determining energy costs affects an increase in actual energy costs in production in relation to the calculated and experimental data. The practical value of the work lies in the fact that the use of power supplies with a lower ripple of the output voltage in experiments will reduce the processing time of the obtained data arrays, increase the efficiency of the experiment and the accuracy of the revealed dependencies. The methodology presented in the work also makes it possible to more efficiently use financial resources for the purchase of devices in the preparation and conduct of scientific and experimental research. Keywords: power supply, voltage pulse, accuracy, scientific research, experiment, PeakTech

This study investigates the microstructure and local corrosion behavior of an Al–Mg–Si–Cu alloy, which has been subjected to cold-rolling with different deformation strain ratios (DSRs) and followed by artificial aging. Accelerated corrosion tests show that peak-aged samples with a small DSR (5–10%) are sensitive to inter-granular corrosion (IGC) along both the normal and rolling directions. When the DSR increases to medium strength (20–40%), IGC sensitivity decreases along both directions and corrosion propagates anisotropically. When the DSR is 60–80%, IGC sensitivity along the normal direction continues to decrease, but increases along the rolling direction, indicating pronounced corrosion anisotropy. Microstructural characterization reveals the decreased IGC sensitivity is mainly attributed to a reduction in element segregation at high-angle grain boundaries and the kinked and discontinuous grain boundary corrosion paths. The increased IGC sensitivity along the rolling direction could be related to the significantly flattened grains.

Traditionally, Ultralightweight Foam Concrete (ULFC) is primarily used to replace filling excavations, ditch restoration and underground channels, because of their high porosity, water absorption and low strength. Yet, ULFC is characterized by excellent thermal properties and could be an alternative for sustainable energy-efficient building material. This study investigates the properties of an ULFC strengthened with alkali-treated banana fibre. The low density ULFC of 600kg/m3 was fabricated and strengthened with alkali-treated banana fibre. Fibre volume fraction of 0.25%, 0.35%, 0.45% and 0.55% were compared to the unreinforced specimens, serving as the control specimen (no fibre addition). Mix proportioning of 1:1.5:0.45 of cement, sand, and water was respectively adopted throughout the mix. The alkali treated banana fibre strengthened ULFC was tested for compressive strength, sorptivity and thermal properties. Morphology of the treated fibre and ULFC composites was studied using SEM micrograph. The result depicts that ULFC exhibited the optimum compressive strength of 1.1604N/mm2 with the fibre volume fraction of 0.35%. Sorptivity or rate of water absorption was testified to upsurge, after 24 hours duration at fibre volume fraction of 0.55%, recording a 56.12% increment compared to the control specimen. The finding displays that at the highest-fibre volume fraction of 0.55%, thermal conductivity and diffusivity decrease by 13.17% and 28.16%, correspondingly, whiles the specific heat capacity increases to 37.17% all compared with unreinforced specimens. SEM images reveal that the presence of lumen and the nature of porous and fibrous alkali-treated banana fibre. Hence, it is endorsed that ULFC produced with alkali-treated banana fibre should be utilized as an infill material for composite system.

In this work, we research the combined influence of residual thermal stress, interface debonding and oxidation, and temperature on first matrix cracking stress of fiber reinforced ceramic-matrix composites (FRCMCs). Based on the shear-lag theory, the axial stress distribution of matrix and fiber considering interface oxidation and residual thermal stress is given, and we propose a criterion for interface debonding. Then, a thermal-mechanical-oxidation coupled first matrix cracking stress model is proposed for FRCMCs, according to energy balance approach. Reasonable agreement is obtained between the model predictions and available experimental results of SiCf/RBSN and SiCf/SiC composites. Moreover, the effects of some key material parameters and oxidation time on first matrix cracking stress are analyzed quantitatively by the model. This research offers a quantitative tool for evaluating and predicting the matrix cracking behavior of FRCMCs under thermal-mechanical-oxidation coupled environment.

Biobased poly(1,3-propylene 2,5-furandicarboxylate) (PPF) and carbon nanotubes (CNTs) nanocomposites were prepared by a solution and coagulation method at low CNTs loadings of 0.5 to 2 wt% in this research. The morphology, thermal stability, dynamic mechanical property, and crystallization behavior of PPF-CNTs nanocomposites were investigated in detail. CNTs dispersed well in PPF matrix. The incorporation of CNTs slightly increased the thermal stability while remarkably improved the storage modulus of PPF in the nanocomposites. CNTs not only promoted the melt crystallization behavior at a constant cooling rate but also increased the isothermal crystallization rate at the same crystallization temperature as the nucleating agent. The crystallization mechanism of PPF was not modified by CNTs.

In this work, an experimental design was applied in the injection molding process of polycaprolactone (PCL), aiming to evaluate the mechanical properties (impact strength, tensile strength and Shore D Hardness), thermal (differential scanning calorimetry (DSC)) and thermomechanical (heat deflection temperature (HDT)), in PCL injected specimens. A type 2n planning was applied, with n = 3 and central point, having the input factors: processing temperature profile, mold temperature and injection flow. The results showed that the DSC curves presented a complex mechanism during crystallization, suggesting that depending on the processing conditions a high degree of crystallinity can be obtained. When using a higher processing temperature and a higher injection flow, there is an increase in the mass of the PCL parts. The impact strength is more expressive when a higher injection flow and a lower processing temperature are applied, reaching values around 260 J/m. The mold temperature impairs the elongation at the break of the PCL, while the elastic modulus was governed by the degree of crystallinity. A deleterious effect on HDT was observed with increased injection flow, suggesting that this parameter negatively affects thermomechanical resistance. The use of experimental design in the processing of PCL is important, since it is possible to optimize properties with the ideal conditions of injection molding.

In past two decades, numerous 3D printing applications of acrylonitrile butadiene styrene (ABS) based mechanically blended composites for secondary (2°) recycling has been reported. But hitherto li...

PurposeIn this paper, a three-dimensional size-dependent constitutive model of SMP Timoshenko micro-beam is developed to describe the micromechanical properties.Design/methodology/approachAccording to the Hamilton's principle, the equilibrium equations and boundary conditions of the model are established and according to the modified couple stress theory, the model is available to capturing the size effect because of the material length scale parameter. Based on the model, the simply supported beam was taken for example to be solved and simulated.FindingsResults show that the size effect of SMP micro-beam is more obvious when the dimensionless beam height is similar or the larger of the value of loading time. The rigidity and strength of the SMP beam decrease with the increasing of the dimensionless beam height or the loading time. The viscous property of SMP micro-beam plays a more important role with the larger dimensionless beam height. And the smaller the dimensionless beam height is, the more obvious the shape memory effect of the SMP micro-beam is.Originality/valueThis work implies prediction of size-dependent thermo-mechanical behaviors of the SMP micro-beam and will provide a theoretical basis for design SMP microstructures in the field of micro/nanomechanics.

The real-time thermal–mechanical–frictional coupling characteristics of bearings are critical to the accuracy, reliability, and life of entire machines. To obtain the real-time dynamic characteristics of ball bearings, a novel model to calculate point contact dynamic friction in mixed lubrication was firstly presented in this work. The model of time-varying thermal contact resistance under fit between the ring and the ball, between the ring and the housing, and between the ring and the shaft was established using the fractal theory and the heat transfer theory. Furthermore, an inverse thermal network method with time-varying thermal contact resistance was presented. Using these models, the real-time thermal–mechanical–frictional coupling characteristics of ball bearings were obtained. The effectiveness of the presented models was verified by experiment and comparison.

It is a relevant objective in thermal physics and piston engine construction to develop technical solutions for controlling the gas dynamics and heat exchange of gas flows in the intake system of turbocharged engines in order to improve performance. The article presents other authors’ data on the improvement of processes in the gas exchange systems of piston engines. It also provides a description of experimental set-ups, instruments, measurement tools and research methods for establishing the thermal-mechanical characteristics of pulsating flows in the intake system of a turbocharged engine. The instantaneous values of the gas flow rate and the local heat transfer coefficient were determined using the measured results by applying a constant temperature hot-wire anemometer (H-WA). The article describes technical solutions for influencing the gas dynamics and heat exchange of gas flows by stabilising and turbulising the flow. The regularities of changes in the instantaneous values of the flow velocity, pressure and the local heat transfer coefficient in time for a pulsating gas flow with different intake system configurations are obtained. It is shown that the installation of a levelling grid in the compressor outlet channel leads to the stabilisation of the flow and the suppression of heat transfer in the engine intake system by an average of 15% compared to the base system. It was found that the presence of a channel with grooves in the intake system leads to flow turbulisation and the intensification of heat transfer in the intake system by an average of 25%.

A transparent organic crystalline material guanidinium nitrate (GuN) was fruitfully harvested. Structure of GuN was verified by SXRD and its monoclinic system with Cm space group. Optical nature of GuN was confirmed by T%, n, ∆n and optical limiting. Strength nature of the GuN was tested by optical and mechanical hardness. The energy gap, global reactivity descriptors, linear and non-linear optical parameters were calculated at B3LYP/6-31G (d,p) level. Second- and third-order effective non-linearity was deliberated experimentally.

New PVC/ABS and CoCl2 composites with various concentrations of cobalt chloride (?10 wt. %) were synthesized by solution casting techniques and investigated by spectro-chemical, morphological and thermal mode of characterization. The FT-IR, XRD and SEM analyses proved the smooth distribution and uniformity of the constituents of the composite materials. Thermal behavior showed that the addition of CoCl2 to the PVC/ABS blends enhanced the thermal stability and improved mechanical properties of composites due to crosslinking between PVC/ABS blend and CoCl2. Thus based on their remarkable morphology, thermomechanical stability and promising bioactivities, the synthesized composites could be applied for high performance polymeric materials in the field of biomedics and electronics.

This article presents a study of the structure of a Ti–Ni alloy and the sequence of phase transformations depending on the conditions and chemical composition. The dependencies of the manifestation of thermal mechanical characteristics for obtaining the necessary structural properties of parts from a shape-memory and/or an ultraelastic alloy are presented.

In this work, a series of high-density polyethylene (HDPE)/asphaltene composites were fabricated via the melt blending method. The composites were characterized, and the degradability, thermal, and mechanical stabilities of the products were analyzed. TGA results showed that HDPE/asphaltene composites had better thermal properties, e.g. higher degradation temperatures than asphaltene-free pristine HDPE. The high intermolecular interactions between the asphaltene and HDPE resulted in the degradation mechanism break, delaying the decomposition of composites and increasing their thermal stabilities. The results of DSC analysis indicated that the presence of asphaltene induces higher crystallinity and melting temperature in the composite matrix. According to the XRD results, the crystalline size was increased by increasing the asphaltene loading level due to the nucleating effect of asphaltene and the proper interactions developed between the asphaltene particles and HDPE chains. The proper dispersion of asphaltene in the composite matrix was confirmed by SEM images. The obtained results from the hardness analysis indicated higher mechanical stability for the composites, proportional to the content of the incorporated asphaltene to the composite. The results showed that asphaltene can be considered as an appropriate choice to improve the HDPE properties.

The thermal, mechanical, rheological, and surface characteristics of some xanthan/poly(vinyl alcohol)/red grape pomace composite cryogels prepared by the freeze/thawing approach were investigated. The results were discussed in comparison with those obtained for individual xanthan or poly(vinyl alcohol) cryogel networks synthesized under the same conditions. The mechanical strength of the cryogels was enhanced by increasing the number of freeze/thawing cycles, and by the addition of a natural polyphenol (i.e. red grape pomace). The thermal stability of the poly(vinyl alcohol) in the blend significantly decreased upon the addition of 50% xanthan, while the presence of a single neat melting profile indicated good component miscibility for the chosen ratios. The water sorption capacity depended on the amount of polyphenol incorporated, thus the hydrophilicity of the cryogel films decreased with the increase of polyphenol content.

The polyurethane (PU) has been showing a dramatic increase in applications related to material science and technology. However, the mechanical, physical and thermal properties could be further improved by loading PU with zirconia (Zr) to create renewable materials known as polyurethane–zirconia (PUZ) composites. In this study, PU matrix was treated with wt.% Zr at 0.5, 1.0, 1.5 and 2.0. In this study, the thermo-mechanical properties and the morphology were investigated of PU and PUZ nano-samples. The images of the scanning electron microscope (SEM) were the prime tool in investigating PU and PUZ surfaces and fractured surfaces showing vanishing the cracks and formation of agglomeration on the sample PUZ-1.5%. In addition, the tensile strength, Young’s modulus and maximum loading were improved by 36.7, 31.8 and 39.1%, respectively, at Zr loading of 1.5 wt.%. The flexural stress and the load were improved by 94.3% and 93.6%, respectively, when Zr loading was 1.5 wt.%. The impact without and with a notch was improved by 110.7% and 62.6%, respectively, at Zr loading of 1.5 wt.%. The the morphologies of the PU surface and Zr surface supported by SEM images. Regarding the storage modulus ability of PU and PUZ composites, Zr loading has negatively influenced E. The E functioning temperature was observed to move from 142 to 183°C. Another effect was determined by adding a small amount of Zr. This small amount was enough to shift the crystallization temperature (${T}_c$) and the melting temperature (${T}_m$) of PU from 125 to 129°C and from 150 to 144°C, respectively.

A simple and efficient strategy was discussed for the synthesis of polydimethylsiloxane nanocomposites, based on the in situ sonochemical polymerization of hexamethylcyclotrisiloxane between the nanosheets of Maghnite; Maghnite is a treated Algerian mineral clay that can act as a catalyst and as an inorganic reinforcement at the same time. Three types of Maghnite were prepared: raw, sodium and organophilic Maghnite. The nanocomposites synthesis was carried out on the type of Maghnite that showed the greatest interlayer spacing, by varying its content weight. The structure of obtained materials was identified by FTIR-ATR and 1H MAS NMR spectroscopies. Moreover, the dispersion state of Maghnite particles was examined by XRD, TEM and SEM. TGA has been used to study the thermal properties. The evaluation of the mechanical properties evolution was by measuring the Young’s modulus and yield strength. The nitrogen adsorption capacity was calculated at 77 K. Exfoliated composites (5% loading) have shown better enhancement results concerning morphological, thermal, mechanical properties and adsorption capacity.

As increased in demand for using memory devices in automotive applications, board level reliability (BLR) has been the one of the critical issue for using FBGA type packages in automotive. The required specification of BLR is listed in various standards (AEC-Q100, Q104 etc) and it is varied by automotive application customers. Most of customers are targeting grade from 1 to 3, however, requirement to memory package is grade 1 (−40°C~125°C). Currently low power (LP) memory device is widely adopted in automotive applications due to its wide bandwidth and high density capability. From package reliability point of view, it is challenge to satisfy the required BLR for target package by 1) dimension optimization, 2) selection of material, 3) mount condition, and 4) work around method. In this paper, the best combination to achieve the highest BLR life time was investigated compared with current mobile application LP4 package. Large pad size with large ball, high content of Ag in solder ball and Ni/Au pad finish were the best combination to result in the longest life time. Various density of LP4 package BLR were also estimated by mechanical simulation based from actual thermal cycling test on the highest Si volume LP4 package.

Residual stress on the surface and subsurface has a great influence on the distortion and fatigue life. Rapid and accurate prediction of residual stress is important for the optimization of the machining process in intelligent manufacturing. A novel analytical model is proposed based on the equivalent stress method in this paper. The nonlinear flow characteristics of the work-piece material in the tool-work-piece contact surface and thermal-mechanical coupling effect are fully considered. A new cutting force prediction model was established and the relative errors are within 12%, which verifies the accuracy and the effectiveness of the model for further application to residual stress prediction. The thermal-mechanical conditions of the primary shear plane and machined surface are revealed based on the equivalent stress method. Then, internal stress of work-piece is caused by mechanical load and thermal load obtained on account of linear elasticity theory and heat-elastic-plastic mechanics theory. The predicted residual stress profiles have a high degree of consistency with measurement results of orthogonal turning of 20Cr2Ni4A alloy steel. Prediction accuracy of surface residual stresses was 11.3%, 12.2%, and 12.7% for the condition of v = 24 m/min, ap = 0.1 mm; v = 36 m/min, ap = 0.2 mm; v = 48 m/min, ap = 0.3 mm respectively. The predicted results of the maximum compressive stresses and DMCS are also acceptable. Ultimately, the residual stress profiles obtained from proposed model were reliable. The proposed model has high computational efficiency and provides a new idea for the analytical prediction of residual stress. And the proposed model can be used for further residual stress analysis and prediction of 3D cutting process.

Novel mixed matrix membranes with various Cloisite®15A in polyimide (PI) matrix were developed for gas separation. The synthesized membranes were characterized by the FE-SEM, XRD, DTG and TEM. Acco...

Two types of thermosetting polyimide (PI) resin were prepared using a polymerization monomeric reactant method, and high performance PI fabric/PI resin composites were fabricated through a wet infiltration and thermoforming process. The properties of a PI fabric, PI resin, and PI/PI composites were comprehensively analyzed. The experimental results indicate that a resin end-capped with phenylacetylene achieves a better processability and heat resistance. The two composites exhibit excellent thermal, mechanical, and dielectric properties. They achieve a glass transition temperature of higher than 320°C and a 5% weight loss temperature of over 600°C under an air atmosphere. During mechanical testing, an interlaminar shear strength exceeding 35 MPa was achieved, whereas the maximum flexural strength was found to be greater than 400 MPa. Moreover, their dielectric constant at 1 MHz was below 3.4, with a dielectric loss of no more than 0.01.

After thermally curing p-tert-butylcalix[8]arene glycidyl ether with benzoxazine, the thermal, mechanical, and dielectric properties of the copolymer products were evaluated. Incorporation of p-ter...

In this study, well-dispersed nanocomposite films with triacetate cellulose (TAC) as a matrix and reinforced with lemon peel-cellulose nanofibers (lemon peel-CNF) were developed. The nanofibers in aqueous solution were solvent-exchanged to methanol by a series of centrifuging and re-dispersing steps. Afterward, using the solution casting method, the mixture of recycled TAC (rTAC) film and nanofibers prepared by stirring combined with ball milling technique to achieve full dispersed solution was coated onto glass to obtain a thin film. The dispersion effect of CNF in TAC was observed by transmission electron microscopy. The optical, mechanical, and thermal properties of the nanocomposite films were characterized experimentally. The results showed that with varying CNF content (1–7 wt%), the haze was slightly increased while the transmittance was not affected compared with that of rTAC film (92.7%). The addition of CNF increased the tensile strength by 60%, tensile strain by 150%, and yield strength by 50%. Creep compliance improved for all nanocomposites compared with rTAC film. CNF led to a significant reduction in the thermal expansion properties of rTAC film.

Tetrahexcarbon (TH-carbon) was recently predicted to be a stable two-dimensional semiconductor with an intrinsic direct band gap, making it promising for practical applications in optoelectronic de...

This paper mainly investigated the revolution of residual stresses and dimension stability in high-precision components during thermal-mechanical processes. Especially, originate of residual stress and its influences on dimension stability, from each step of the design and manufacture processes to thermal-mechanical processes, as well as their complicated interactions were elucidated in detail. Finally, the recent progress of modern analytical and computational techniques were discussed to provide possibilities to quantitative predict and control residual stresses and dimensional stabilities in high-precision components.