Principle Of Dissipation Research Articles

Experimental study on the improvement of bamboo properties using amide polymer repair material based on the principle of self-energy dissipation

Traditional bamboo and wood components have different holes due to their own and external factors, and the appropriate hole repair technology is the key to improve the component's energy dissipation capacity. In this paper, based on the principle of in-situ free radical polymerization and hollow glass microsphere (HGM) reinforced polymer, PAM hydrogel (PAMHG) with better deformation recovery ability and PAM/HGM amide polymer (AP) with better mechanical properties were prepared. Based on the principle of self-energy dissipation of components, AP is used to improve the deformation capacity of hollow bamboo. The ratio of PAMHG and AP was optimized by single factor test and orthogonal test. The performance of AP was verified by bending test, SEM, energy consumption analysis，durability test and statistical analysis of small diameter round bamboo. The size of the bamboo sample is 250 mm (L)×15 mm (D)×2.5 mm (t), in accordance with LY/T 3347–2023 " Testing methods for physical and mechanical properties of small diameter round bamboo " (China). The results showed that an appropriate amount of glycerol could effectively improve the volume stability of the hydrogel. HGM effectively improved the strength of the polymer, and when the mass ratio of HGM/PAM was 0.48, the maximum compressive strength was 0.8 MPa, which was 2.4 times higher than that of the undoped HGM, and at this time, the optimal polymer ratios were 25 g of AM, 1 g of MBA, 0.01 g of APS, 2 g of TEA, 2 g of Carbomer SF-1, a volume ratio of 1:1 of glycerol/deionized water that the dispersion medium was 70 ml, and HGM was 12 g. The average energy dissipation of grouted bamboo at ultimate load was 2.02 times that of the control group, and the highest bending strength and elastic modulus were 128.01 MPa and 11.24 GPa, which were 41.39 % and 39.75 % higher than that of the control group, respectively. The SEM results revealed that the AP partially prepolymerized solution could infiltrate into the cells and pores of the bamboo material to achieve filling, bonding, as well as reinforcing the bamboo tissue. In addition, the durability test shows that AP has good resistance to environmental pressure. The results of this paper can provide a reference for the restoration materials of bamboo and wood components.

Present Situation and Future Prospects of Motor Cooling System

Background: The motor cooling system is mainly used in aerospace, automotive, and marine fields, where the motor system is cooled to extend the service life and safety of the motor. The running power of motors rises too fast, which leads to the failure of heat dissipation as expected and shortens the service life of motors. Therefore, it is necessary to choose an appropriate cooling mode for motors to improve their cooling structure, reduce their temperature rise, and improve their reliability and service life. The internal motor cooling system can perform fixed-point heat dissipation, but the overall heat dissipation is poor. The external motor cooling system can perform overall heat dissipation but has high requirements on the structure. Over the years, the application and development of motor cooling systems have gained more and more attention. Objective: This paper discusses the structural characteristics, advantages, and development trends of the motor cooling system in order to reduce the temperature rise of the motor and improve its reliability and service life. This paper aims to provide an overview and systematic guidance for future designs of the motor cooling system. Methods: According to the structural characteristics of the motor cooling system and the requirements of the motor application field, the most typical internal cooling system and external cooling system in the motor cooling system are summarized. Results: By analyzing the causes and hazards of motor heating, the limited requirements of the motor system in use are summarized. The motor system is classified and compared based on the structure, heat dissipation principle, and use of the motor heat dissipation system. The characteristics of small volume and strong heat dissipation ability are also summarized. Based on the analysis of the internal and external cooling system, the problems of complex structure and poor cooling effect are summarized, and the future development trend and direction of the motor cooling system are discussed in detail. Conclusion: This paper divides the motor cooling system into an internal cooling system and an external cooling system according to the specifications and operating environment. This paper expounds on internal and external cooling systems' different principles, advantages, and disadvantages. This paper summarizes the cooling systems in recent years in order to facilitate their subsequent development and use. The main components of additional patents for future inventions are motor cooling systems, innovation in structure simplification, and cost performance optimization.

Quantum thermodynamics of the spin-boson model using the principle of minimal dissipation

Quantum thermodynamics of the spin-boson model using the principle of minimal dissipation

Energy dissipation damage constitutive relation of CFRP passively confined coal sample

In view of the stability problem of coal pillars left over during coal resource mining, (Carbon Fiber Reinforced Polymer) CFRP sheet is applied in coal pillar reinforcement. Uniaxial compression tests of CFRP passively confined coal samples are carried out to explore the mechanical response mechanism of passively confined coal samples under different layers, and the energy dissipation damage constitutive relationship of CFRP passively confined coal samples is established based on the energy dissipation principle. The conclusions are: As CFRP layers increased, the local damage of coal samples before the peak evolved from a 'cliff-like jagged' to a 'capillary jagged', with post-peak instability marked by a shift to more 'cliff-like' characteristics. The tests revealed improvements in peak strength and elastic modulus, with a defined functional relationship between these properties and CFRP layers. The energy storage capacity of passively confined coal samples improved with CFRP layers, requiring less axial deformation to achieve equivalent energy levels. The energy dissipation rate showed an initial decrease followed by an increase, with a minimum inflection point, the elastic energy consumption ratio tends to decrease slowly and then rapidly during post-peak instability. A damage constitutive relationship and evolution equation were developed, highlighting that the CFRP sheet significantly inhibits damage, with diminishing effectiveness beyond two layers. The study concludes that three-layer CFRP sheets provide optimal confinement, offering a novel strategy for the reinforcement of coal pillars and the prevention and control of rock burst, without considering the actual coal pillar dimensions and shape. To sum up, the use of CFRP sheet to strengthen coal pillar has considerable potential research value in strengthening coal pillar and improving the recovery rate of coal resources.

Study on damping performance of non-ideal particle-tuned inerter damper

Aiming at the shortcomings of the current particle dampers and the needs of civil engineering vibration damping, while considering the damping in the non-ideal inertial vessel, a new type of non-ideal particle tuned inerter damper (NPTID) is proposed. Firstly, the construction and technical realization of NPTID are introduced, the mechanical model of NPTID is proposed based on the principle of energy dissipation by particle collision, and the motion control equations of the single-degree-of-freedom structure with an additional NPTID are established; then three natural seismic waves and one artificial seismic wave are selected as the external excitations, and the damping performance of the NPTID is analyzed; finally, the influence of key parameters on the control effect of the NPTID is investigated by parametric analysis. The results show that NPTID has good control effect, and can realize the reduction ratio of more than 43% by utilizing a 0.1% particle mass ratio.

Characterization of Sand and Dust Pollution Degradation Based on Sensitive Structure of Microelectromechanical System Flow Sensor.

The effect of sand and dust pollution on the sensitive structures of flow sensors in microelectromechanical systems (MEMS) is a hot issue in current MEMS reliability research. However, previous studies on sand and dust contamination have only searched for sensor accuracy degradation due to heat conduction in sand and dust cover and have yet to search for other failure-inducing factors. This paper aims to discover the other inducing factors for the accuracy failure of MEMS flow sensors under sand and dust pollution by using a combined model simulation and sample test method. The accuracy of a flow sensor is mainly reflected by the size of its thermistor, so in this study, the output value of the thermistor value was chosen as an electrical characterization parameter to verify the change in the sensor's accuracy side by side. The results show that after excluding the influence of heat conduction, when sand particles fall on the device, the mutual friction between the sand particles will produce an electrostatic current; through the principle of electrostatic dissipation into the thermistor, the principle of measurement leads to the resistance value becoming smaller, and when the sand dust is stationary for some time, the resistance value returns to the expected level. This finding provides theoretical guidance for finding failure-inducing factors in MEMS failure modes.

MEMS sensitive structure sand and dust friction contamination test and electrical variation characteristics

The impact of dust pollution on the sensitive components of Micro-Electro-Mechanical Systems (MEMS) has been a hot topic in current reliability research. However, previous studies have rarely focused on the fundamental analysis of the influence of dust pollutants on the sensitive components of MEMS, and these research results lack universality. This paper aims to present experimental results on the electrical characteristic changes of MEMS thermal sensitive resistors based on dust friction, providing a more detailed description and explanation. Through dust friction experiments, we investigated the effects of dust particle size and relative humidity on the electrical characteristics of MEMS devices. We chose the resistance value output as the electrical characteristic parameter, based on the performance exhibited during the dust friction experiments. We conducted a detailed analysis of the reasons for the changes in the electrical characteristic parameters. The research results showed that when dust particles settle on the device, the failure mode of the device manifests as resistance drift. The inducing factor is the electrostatic current generated by the friction between dust particles, which enters the sensitive components through the principle of electrostatic dissipation. The measurement principle leads to changes in the resistance value measurement, although the actual resistance value does not change. The magnitude of this electrostatic current is directly proportional to the size of the particles and inversely proportional to the relative humidity. This finding provides theoretical guidance for identifying failure-inducing factors in MEMS failure modes.

Effect of different buried depth on the disintegration characteristic of red-bed soft rock and the evolution model of disintegration breakage under cyclic drying-wetting

The disintegration of red-bed soft rock exhibits a strong correlation with various geological disasters. However, the investigation into the evolutionary mechanisms underlying disintegration breakage has not yet received extensive exploration. In order to comprehensively examine the disintegration characteristics of red-bed soft rock, the slake durability tests were conducted to red-bed soft rocks of varying burial depths. Subsequently, an investigation was carried out to examine the disintegration characteristics and the evolution of disintegration parameters, including the coefficient of uniformity (Cu), coefficient of curvature (Cc), disintegration rate (DRE), disintegration ratio (Dr), and fractal dimension (D), throughout the disintegration process. Finally, employing the energy dissipation theory, an energy dissipation model was developed to predicate the disintegration process of samples at various burial depths. The findings demonstrate a decrease in the abundance of large particles and a concurrent increase in the abundance of small particles as the number of drying-wetting cycles increases. Furthermore, as the number of drying-wetting cycles increases, a significant alteration is observed in the content of particles larger than 10 mm, whereas the content of particles smaller than 10 mm undergoes only minor changes. The disintegration parameters, including the curvature coefficient, non-uniformity coefficient, disintegration rate, and fractal dimension, exhibit a positive correlation with the number of drying-wetting cycles. Conversely, the disintegration index demonstrates a decreasing trend with the increasing number of cycles. Nevertheless, as the burial depth increases, a notable trend emerges in the disintegration process, characterized by a gradual increase in the content of large particles alongside a progressive decrease in the content of small particles. Concurrently, the curvature coefficient, non-uniformity coefficient, disintegration rate, and fractal dimension exhibit a gradual decline, while the durability index experiences a gradual increase. In addition, based on the principle of energy dissipation, it is revealed that the surface energy increment of red-bed soft rock increases with the increase of the number of drying-wetting cycles, but decreases with the increase of burial depth. Ultimately, by leveraging the outcomes of energy dissipation analyses, a theoretical model is constructed to elucidate the correlation between surface energy and both the number of drying-wetting cycles and burial depth. This model serves as a theoretical reference for predicting the disintegration behavior of samples, offering valuable insights for future research endeavors.

Interpretation of Second Law of Thermodynamics in Extended Procedures for the Exploitation of the Entropy Inequality: Korteweg Fluids and Strain-Gradient Elasticity as Examples.

In continuum physics the dissipation principle, first proposed by Coleman and Noll in 1963, regards second law of thermodynamics as a unilateral differential constraint on the constitutive equations. In 1996, Muschik and Ehrentraut provided a rigorous proof of such an approach under the assumption that, at an arbitrary instant, t0, in an arbitrary point, P0, of a continuous system, the entropy production is zero if, and only if, P0 is in thermodynamic equilibrium. In 2022, Cimmelli and Rogolino incorporated such an assumption in a more general formulation of the second law of thermodynamics. In this paper, we prove that the same conclusions hold if both the fundamental balance laws and their gradients are substituted into the entropy inequality. Such a methodology is applied to analyze the strain-gradient elasticity.

Energy evolution mechanism of structural surfaces in sandstones with different dips based on the energy principle.

A uniaxial compression test was conducted on sandstone specimens at various inclination angles to determine the energy evolution characteristics during deformation and damage. Based on the principle of minimum energy dissipation, an intrinsic model incorporating the damage threshold was developed to investigate the mechanical properties of sandstone at different inclination angles, and the energy damage evolution during deformation and damage. This study indicated that when the inclination angle of the structural surface remained below 40°, sandstone exhibited varying mechanical properties based on different inclination angles. The peak strain was positively correlated with the inclination angle, whereas the compressive strength and modulus of elasticity showed negative correlations. From an energy perspective, the deformation and damage of sandstone under external loading entail processes of energy input, accumulation, and dissipation. Moreover, higher inclination angles of the structural surface resulted in a smaller absorbed peak strain and a reduced proportion of dissipated energy relative to the energy input, thereby affecting the evolution of energy damage throughout the process. As the inclination angle of the structural surface increased, the absorbed total strain at the peak value decreased, whereas the proportion of the dissipated energy increased. Additionally, the damage threshold and critical value of the rock specimens increased with the inclination angle. The critical value, a composite index comprising the peak strain, compressive strength, and elastic modulus, also increased accordingly. These findings can offer a novel perspective for analyzing geological disasters triggered by fissure zones within underground rock formations.

Multi-component electro-hydro-thermodynamic model with phase-field method. I. Dielectric

We derive a multi-component electro-hydro-thermodynamic (EHTD) model for both leaky and perfect dielectric materials via the principle of energy dissipation. Differing from previous electro-hydrodynamic (EHD) models focusing on fluid mechanics, the electrochemical potential expression is revised and the electric field related term is added to the mass and momentum conservation equations. Resulting from this new correction, we obtain a generalized electro-hydro-thermodynamic stress tensor including the effect of Kortweg and Maxwell stresses. We observe the magnificent impact of the electric field on the thermodynamic equilibrium of the system in two aspects: (i) phase diagram modified by the electric field; (ii) electric field induced surface tension decrease/increase. In addition, the proposed model is validated and shows well conformity with previous analytical solutions in literature. As exemplary applications, we perform phase-field simulations to study the ternary droplet coalescence and spinodal decomposition and observe several typical morphological transformations, such as satellite drop formation and Quincke rotation.

Glassy-like Transients in Semiconductor Nanomaterials.

Glassy behavior is manifested by three time-dependent characteristics of a dynamic physical property. Such behaviors have been found in the electrical conductivity transients of various disordered systems, but the mechanisms that yield the glassy behavior are still under intensive debate. The focus of the present work is on the effect of the quantum confinement (QC) and the Coulomb blockade (CB) effects on the experimentally observed glassy-like behavior in semiconductor nanomaterials. Correspondingly, we studied the transient electrical currents in semiconductor systems that contain CdSe or Si nanosize crystallites, as a function of that size and the ambient temperature. In particular, in contrast to the more commonly studied post-excitation behavior in electronic glassy systems, we have also examined the current transients during the excitation. This has enabled us to show that the glassy behavior is a result of the nanosize nature of the studied systems and thus to conclude that the observed characteristics are sensitive to the above effects. Following this and the temperature dependence of the transients, we derived a more detailed macroscopic and microscopic understanding of the corresponding transport mechanisms and their glassy manifestations. We concluded that the observed electrical transients must be explained not only by the commonly suggested principle of the minimization of energy upon the approach to equilibrium, as in the mechanical (say, viscose) glass, but also by the principle of minimal energy dissipation by the electrical current which determines the percolation network of the electrical conductivity. We further suggest that the deep reason for the glassy-like behavior that is observed in the electrical transients of the nanomaterials studied is the close similarity between the localization range of electrons due to the Coulomb blockade and the caging range of the uncharged atomic-size particles in the classical mechanical glass. These considerations are expected to be useful for the understanding and planning of semiconductor nanodevices such as corresponding quantum dot memories and quantum well MOSFETs.

Research on anti-swing control strategies for three-dimensional overhead cranes with non-stationary enhanced swing angle suppression

In this paper, a non-stationary enhanced swing angle suppression control strategy is proposed to address the issue of excessive swinging angles during the transportation process of a three-dimensional overhead crane. Firstly, in response to the substantial non-stationary initial swing angle resulting from the abrupt increase in driving force during the startup of the overhead crane, we have devised a time-varying damping resistance model. This model is specifically designed to curtail the rapid force surge, subsequently diminishing the swing angle of the payload. Secondly, during the transport phase of the overhead crane, we have established an augmented coupling signal between the displacement tracking error and the payload swing angle tracking error. Drawing upon the principles of energy dissipation, we have devised a nonlinear sway controller. Next, the closed-loop stability of the control system is validated through the use of Lyapunov’s method and the LaSalle invariance principle. Finally, the proposed control strategy’s effectiveness has been substantiated through simulation analysis and physical experiments. This approach not only proves capable of effectively suppressing excessive payload swing angles during the transportation process of the overhead crane but also facilitates the rapid and precise positioning of the payload. This significantly enhances the efficiency of the overhead crane’s transport operations.

Weak Solutions of Mullins–Sekerka Flow as a Hilbert Space Gradient Flow

We propose a novel weak solution theory for the Mullins–Sekerka equation in dimensions d=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d=2$$\\end{document} and 3, primarily motivated from a gradient flow perspective. Previous existence results on weak solutions due to Luckhaus and Sturzenhecker (Calc. Var. PDE 3, 1995) or Röger (SIAM J. Math. Anal. 37, 2005) left open the inclusion of both a sharp energy dissipation principle and a weak formulation of the contact angle at the intersection of the interface and the domain boundary. To incorporate these, we introduce a functional framework encoding a weak solution concept for Mullins–Sekerka flow essentially relying only on (i) a single sharp energy dissipation inequality in the spirit of De Giorgi, and (ii) a weak formulation for an arbitrary fixed contact angle through a distributional representation of the first variation of the underlying capillary energy. Both ingredients are intrinsic to the interface of the evolving phase indicator and an explicit distributional PDE formulation with potentials can be derived from them. The existence of weak solutions is established via subsequential limit points of the naturally associated minimizing movements scheme. Smooth solutions are consistent with the classical Mullins–Sekerka flow, and even further, we expect our solution concept to be amenable, at least in principle, to the recently developed relative entropy approach for curvature driven interface evolution.

Optimized design of an enthesis-mimicking suture anchor-tendon hybrid graft for mechanically robust bone-tendon repair

Repair of functionally graded biological interfaces requires joining dissimilar materials such as hard bone to soft tendon/ligament, with re-injuries/re-tears expected to be minimized by incorporating biomimicking, stress-reducing features within grafts. At bone-tendon interfaces (entheses), stress can be reduced via angled insertion, geometric flaring, mechanical gradation, and interdigitation of tissues. Here, we incorporated enthesis attributes into 3D in silico and physical models of a unique suture anchor-tendon hybrid graft (SATHG) and investigated their effects on stress reduction via finite element analyses (FEA) studies. Over 20 different simulations altering SATHG angulation, flaring, mechanical gradation, and interdigitation identified an optimal design, which included 90° angulation, 25° flaring, and a compliant (ascending then descending) mechanical gradient in SATHG's bone-to-tendon-like transitional region. This design reduced peak stress concentration factor (SCF) by 43.6 % relative to an ascending-only mechanical gradient typically used in hard-to-soft tissue engineering. To verify FEA results, SATHG models were fabricated using a photocrosslinkable bone-tendon-like polyurethane (QHM polymer) for ex vivo tensile assessment. Tensile testing showed that ultimate load (132.9 N), displacement-at-failure (1.78 mm), stiffness (135.4 N/mm), and total work-to-failure (422.1 × 10−3 J) were highest in the optimized design. Furthermore, to assess envisioned usage, SATHG pull-out testing and 6-week in vivo implantation into large, 0.5-cm segmental supraspinatus tendon defects was performed. SATHG pull-out testing showed secure bone attachment while histological assessment such as hematoxylin and eosin (H&E) together with Safranin-O staining showed biocompatibility including enthesis regeneration. This work demonstrates that engineering biomaterials with FEA-optimized, enthesis-like attributes shows potential for enhancing hard-to-soft tissue repair. Statement of significanceSuccessful repair of hard-to-soft tissue injuries is challenging due to high stress concentrations within bone-tendon/ligament grafts that mechanically compromise repair strength. While stress-reducing gradient biomaterials have been reported, little-to-no attention has focused on other bone-tendon/ligament interface (enthesis) features. To this end, a unique bone-tendon graft (SATHG) was developed by combining two common orthopaedic devices along with biomimetic incorporation of four enthesis-like features to reduce stress and encourage widespread clinician adoption. Notably, utilizing designs based on natural stress dissipation principles such as anchor insertion angle, geometric flaring, and mechanical gradation reduced stress by 43.6 % in silico, which was confirmed ex vivo, while in vivo studies showed SATHG's ability to support native enthesis regeneration. Thus, SATHG shows promise for hard-to-soft tissue repairs.

Thermodynamics of Life as a Speculative Model for Planetary Technology

Originating from nineteenth century physics, the concept of entropy—a measure of disorder, randomness, and/or the dissipation of useful energy—underlay a cosmology where order and complexity were seen as highly improbable phenomena in a universe tending toward chaos and disorganisation. Nearly a century later, theoretical frameworks were developed for understanding the production of entropy as an enabling feature of self-organized complexity in the natural world. These ideas would contribute to establishing connections between the origins, development, and evolution of life and the principles of a thermodynamic universe. For some, they also supplied the conceptual foundations for theorizing about a universal natural tendency driving the development of increasingly complex and ordered systems which amplify processes of entropy production and energy dissipation and dispersal. In this paper I chart a path through the aforementioned ideas and present their relevance in framing a relationship between our technological civilization and the Earth system. I then speculate about the prospect of a technosphere whose constitution and activity are aligned with thermodynamic principles of dissipation and entropy-production, drawing on theoretical biology and recent developments in bioengineering to envision a paradigm where technology becomes living matter itself.

Mechanical behavior of a novel lattice structure with two-step deformation

Lattice structures are increasingly attracting attention due to their excellent mechanical properties and broad application prospects. However, most developed lattices feature single-step deformation or single plateau stress, which confine its multi-task applications. Herein, a novel body-centered cubic (NBCC) with two-step deformation based on body-centered cubic (BCC) and bionic fractal design is introduced. NBCC exhibits bi-plateau stress in the stress–strain curves. The underlying mechanism is caused by the bending and buckling deformation of the struts. The mechanical behaviors of NBCC are investigated by finite element simulation which verified by experiment. Compared with traditional BCC, NBCC has improved modulus of elasticity by 88 %, yield strength by 21.2 %, and specific energy absorption by 108 % when ρ′ and α are 0.07 and 0.5, respectively. Moreover, the elastic modulus as well as yield strength increase with geometrical ratio α. The specific energy absorption tends to maximum at the geometric ratio α = 0.6 ∼ 0.7. From the Ashby map, the proposed NBCC lattice possesses high energy absorption, exceeding most of the existing architected materials at the same density. Furthermore, the results show that NBCC has better isotropy of elastic modulus and tends to be more isotropic material compared to BCC. Finally, theoretical model of two-step plateau stress is established based on hinge dissipation principle. This work opens up new insights into the use of element replacement design to create multi-step pathways that can be applied to design engineering structures with multiple tasks and application for impact protection.

Estimating the interfacial permeability for flow into a poroelastic medium.

Boundary conditions between a porous solid and a fluid has been a long-standing problem in modeling porous media. For deformable poroelastic materials such as hydrogels, the question is further complicated by the elastic stress from the solid network. Recently, an interfacial permeability condition has been developed from the principle of positive energy dissipation on the hydrogel-fluid interface. Although this boundary condition has been used in flow computations and yielded reasonable predictions, it contains an interfacial permeability η as a phenomenological parameter. In this work, we use pore-scale models of flow into a periodic array of solid cylinders or parallel holes to determine η as a function of the pore size and porosity. This provides a means to evaluate the interfacial permeability for a wide range of poroelastic materials, including hydrogels, foams and biological tissues, to enable realistic flow simulations.

Study on Failure Energy per Unit Area of Concrete Specimens Based on Minimum Energy Dissipation Theory.

In order to study the strength change of concrete specimens under different loading conditions, based on the principle of minimum energy dissipation, the damage energy per unit area of concrete was studied. By using finite element numerical simulation software for concrete specimens with different failure modes of tension, pressure, bending and torsion, a double-broken line damage constitutive model is adopted. The failure forms of concrete specimens under different loading conditions, as well as the failure area and failure energy of each specimen during loading, are simulated and analyzed. The failure energy per unit area under different failure modes was quantitively calculated, the relationship between the failure area and failure energy consumption under different failure modes was analyzed. The results show that, under different failure modes, the failure area of concrete specimens is different, the energy consumed during failure is different, and the strength is different. However, no matter how the failure mode changes during the failure process, the failure energy W per unit area remains constant and fluctuates in the range of 2.0~6.0 mJ/cm2, which is related to the physical properties of concrete itself.

Real-Time Temperature Prediction of Power Devices Using an Improved Thermal Equivalent Circuit Model and Application in Power Electronics.

As a core component of photovoltaic power generation systems, insulated gate bipolar transistor (IGBT) modules continually suffer from severe temperature swings due to complex operation conditions and various environmental conditions, resulting in fatigue failure. The junction temperature prediction guarantees that the IGBT module operates within the safety threshold. The thermal equivalent circuit model is a common approach to predicting junction temperature. However, the model parameters are easily affected by the solder aging. An accurate temperature prediction by the model is impossible during service. This paper proposes an improved thermal equivalent circuit model that can remove the effect of solder aging. Firstly, the solder aging process is monitored in real-time based on the case temperatures. Secondly, the model parameters are corrected by the thermal impedance from chip to baseplate based on the linear thermal characteristic. The simulation and experimental results show that the proposed model can reduce the temperature prediction error by more than 90% under the same aging condition. The proposed method only depends on the case temperatures to correct the model parameters, which is more economical. In addition, the experimental and simulation analysis in this work can help students of power electronics courses have an in-depth knowledge of power devices' mechanical structure, heat dissipation principles, temperature distribution, junction temperature monitoring, and so on.