Stress Distribution Maps Research Articles

Simulation and Experimental Study on Stress Relaxation Response of Polycrystalline γ-TiAl Alloy under Nanoindentation Based on Molecular Dynamics.

This study employed nano-indentation technology, molecular dynamics simulation, and experimental investigation to examine the stress relaxation behaviour of a polycrystalline γ-TiAl alloy. The simulation enabled the generation of a load-time curve, the visualisation of internal defect evolution, and the mapping of stress distribution across each grain during the stress relaxation stage. The findings indicate that the load remains stable following an initial decline, thereby elucidating the underlying mechanism of load change during stress relaxation. Furthermore, a nano-indentation test was conducted on the alloy, providing insight into the load variation and stress relaxation behaviour under different loading conditions. By comparing the simulation and experimental results, this study aims to guide the theoretical research and practical application of γ-TiAl alloys.

Residual stress distribution of silicon wafers machined by rotational grinding based on molecular dynamics

Wafer rotational grinding is widely used to thin silicon wafers and the grinding-induced residual stress distribution is desired to be known. However, it is difficult to obtain it directly by measurement since the variation of residual stress values of different locations tends to be submerged in the fluctuations of measured values. In this study, molecular dynamics was employed to obtain the residual stress states of ground monocrystalline silicon of different crystal directions. The actual cutting directions of the abrasive grains were obtained as the tangential directions of the abrasive grain's traces on the silicon wafer surface relative to the crystal coordinate system. It was found that the actual cutting direction of an abrasive grain along a single grinding trace would change from the center to the edge of the silicon wafer since the grinding traces are curved lines. The residual stress state at a specific point on the wafer surface was obtained by mapping the residual stress values obtained by molecular dynamics to the actual cutting direction. The residual stress distribution map was obtained successfully and any point of the ground silicon wafer could be known. The location of maximum residual stress was found to deviate from the [1 1 0] crystalline direction on the ground wafer due to the change in the actual cutting direction relative to it.

Exfoliation of an extruded Mg-4Li-1Ca alloy in presence of glucose and bovine serum albumin

Exfoliation corrosion (EFC) on extruded Mg-4Li-1Ca alloys as bone implant materials has not been reported. This study aimed to elucidate the degradation mechanism of a corrosion type-exfoliation occurred on an extruded Mg-4Li-1Ca alloy under the interaction of glucose (Glu) and bovine serum albumin (BSA) in Hank’s solution. The alloy microstructure, chemical composition, texture, stress distribution and Volta potential maps were characterized using metallographic microscopy, scanning electron microscopy and electron backscattered diffraction, and scanning Kelvin Probe. The alloy corrosion behavior was investigated via electrochemical testing and hydrogen evolution rate methods. X-ray diffraction, Fourier transform infrared spectrometry, X-ray photoelectron spectrometer, and fluorescence microscopy were used to analyze the corrosion products and the adsorption of the organic molecules. The experimental results indicated that the anodic second phase (Mg2Ca) were distributed in lamellar and rod-like patterns along the extrusion direction of the alloy, a lower Volta potential for Mg2Ca, texture and residual stresses also promote EFC. An increase in Glu concentration exacerbated the EFC, whereas BSA inhibited the EFC of the alloy. Higher Glu concentrations in BSA in turn inhibited EFC since Glu can complex with amino acids in proteins to form Glu-amino acid amides, which promoted protein adsorption and thereby forming a dense protective film on the alloy surface. The preferential dissolution of the Mg2Ca phase particles led to the complexation and adsorption of Glu and protein. This study enriches the understanding of the corrosion types in biomedical Mg-4Li-1Ca alloy and paving the way for enhancing the EFC resistance of the alloy.

Experimental realization on stress distribution monitoring during 3D concrete printing

Stress distribution in 3D printed concrete (3DPC) plays a crucial role in monitoring filament deformation and buildability evaluation. However, real-time detection methods for assessing stress distribution are currently lacking. This study proposes a novel stress distribution monitoring system for 3DPC, which enables the visual display of the two-dimensional visual stress distribution of printed samples. By analyzing the stress distribution map provided by the system, an uneven distribution of stress and an increase of 95%-163% in cumulative stress were observed during the printing process. In addition, a 25% reduction in filament deformation by lateral constraints was also observed, where the accuracy of the monitoring system was further verified by studying the deformation of samples with varying filament amounts per layer and lateral constraint conditions, thereby offering new insights for predicting the buildability of 3DPC.

Stability of different fixation methods after reduction malarplasty under average and maximum masticatory forces: a finite element analysis

BackgroundAlthough titanium plates/screws are effective fixation methods (FM) after L-shaped osteotomy reduction malarplasty (LORM), the ideal FM remains controversial. This first finite element analysis (FEA) aimed to study the effect of various zygomatic body/zygomatic arch FM combinations and their placement vectors on the zygoma complex stability after virtual LORM under the effect of both average (150 N/mm2) and maximum (750 N/mm2) forces and three-dimensional (3D) mapping of stress and strain parameters distribution over the zygomatic bone, fixation methods, and total model.ResultsThe fixation methods about the short-arm of the L-shaped osteotomy showed lower stress, strain, and displacement values than those across the long-arm osteotomy site. Combined with any zygomatic arch fixation methods (ZAFm), the two bicortical screws group (2LS) on the zygomatic body osteotomy site resulted in smaller displacements and the lowest zygoma bone stress and displacement when combined with Mortice–Tenon structure (MT) as zygomatic arch fixation method. Applied forces caused statistically significant differences in zygomatic bone stress (P < 0.001 and P = 0.001) and displacement (P = 0.001 and P = 0.002).ConclusionAll FMs both on the zygomatic body and zygomatic arch provide adequate zygomatic complex stability after LORM. The 2LS group showed better resistance than rectangular plate (RP) and square plate (SP) with lower stress concentrations. The L-shaped plate with short-wing on the maxilla (LPwM) is more stable than having the short-wing on the zygoma bone (LPwZ). Future prospective clinical studies are required to validate the current findings.

Optimization of the biological valve appliance prosthetic heart valve

Highlights. With the use of numerical optimization algorithms, it is possible to qualitatively improve the performance (closing) of the leaflet apparatus of the heart valve prosthesis. Changing the length of the free edge of the lealflet of the prosthesis does not reduce the von Misess stress amplitude and does not change the nature of its distribution on the diagrams.Aim. Numerical study of the stress-strain state of a clinical heart valve prosthesis from the point of view of the impact of physiological loads and determination of ways to optimize the geometry of the biological leaflet apparatus.Methods. The object of study was a three-dimensional model of the UniLine (NeoCor, Russia) clinical prosthesis of the heart valve, size 23 mm, as well as four modifications focused on changing the length of the free edge. The study was carried out using the finite element method with imitation of the full cycle of operation of the leaflet apparatus under physiological conditions (pressure, heart rate). The parameters for the analysis were the qualitative and quantitative characteristics of the stress-strain state of the work of the five studied geometries.Results. It is shown that high stress areas are concentrated in two zones peripheral and free edges, regardless of the geometry. However, quantitatively, the von Mises stress amplitudes differed between the studied models. For example, the leaf shape, conventionally designated as “–10” degrees, demonstrated the smallest amplitude of this indicator relative to the original unmodified leaf model, thus reducing by a maximum of 18.8%. However, for the closed state, this model, on the contrary, showed an increase in the voltage index relative to the initial one by 8.3%. Other modification options showed similar trends.Conclusion. It is shown that despite the initial premise for optimizing the leaflet apparatus – reducing the length of the free edge and eliminating deformations of the closed state, the proposed geometry options did not significantly change the stress distribution map in the material, and also did not allow to significantly reduce the amplitudes of this parameter. Presumably, options for modifying the geometry and/or properties (rigidity, mobility) of another important component of the bioprosthesis, the support frame, which, in addition to the bearing function, provides damping of the hydrodynamic impact on the leaf due to some of its mobility, may become more promising.

The effect of laser shock peening on surface integrity and high and very high cycle fatigue properties of 2024-T351 aluminum alloy

Laser shock peening (LSP) as an emerging surface peening technology that is widely used in aerospace manufacturing. The effect of laser shock peening on surface integrity and high cycle fatigue (HCF) and very high cycle fatigue (VHCF) properties of 2024-T351 aluminum alloy was investigated in this study. Accordingly, the surface roughness, surface topography, microstructural, microhardness and residual stress of specimens treated with two different LSP pulse energy levels (10 J and 20 J) were analyzed. Additionally, the HCF and VHCF test was performed by ultrasonic fatigue test system. The results showed that surface roughness Ra value and microhardness of LSP treated specimens increased by a maximum of 89.37% and 16.3% comparing to the untreated specimen, respectively. X-ray diffraction analysis also showed that subgrain sizes were refined to the nanoscale. Furthermore, high-level compressive residual stresses (the maximum value about −210 MPa with 700 μm thickness) were introduced to the surface layer of the specimens. The S-N curve results showed that LSP treatment reduced the fatigue life of specimens, and the higher the laser pulse energy, the more obvious the effect of reduction. The fatigue fracture of specimens was analyzed via scanning electron microscope and residual stress distribution map. It is observed that fatigue cracks are predominantly initiated at fractured secondary phase particle locations in a VHCF range for untreated specimens. However, for LSP specimens, surface and internal crack initiation mechanisms were both observed. Under low and intermediate stress levels, the tensile residual stresses (which coexists with the compressive residual stresses) initiated fatigue cracks from the interior of the specimens; under high-stress levels, fatigue cracks were initiated at the material surface.

Extended finite element simulation on Tensile, fracture toughness and fatigue crack growth behaviour of additively manufactured Ti6Al4V alloy

The mechanical properties such as tensile, fracture toughness, and fatigue properties of Additive Manufacturing (AM) fabricated Ti6Al4V alloy is critically crucial for structural applications. The in-house developed MATLAB-based extended finite elements method (XFEM) model has been utilized to analyse experimental results of fatigue, fracture, and tensile properties of AM fabricated Ti6Al4V alloy, to avoid expensive and destructive mechanical characterisation. The XFEM model was first used to validate the single edge cracked sample of laser powder bed fusion (LPBF) processed Ti6Al4V alloy for fatigue crack growth rate (FCGR). The XFEM simulation study was further extended to analyse fatigue life of center and double-side cracked specimens, as well as for evaluating fracture toughness KIC upon accounting potential crack initiation site. The model has also been developed to predict FCGR of edge cracked specimen under mixed-mode loading conditions. The critical stress intensity factor (SIF) and stress distribution map in the crack vicinity of the C(T) specimen were modelled through FEA Abaqus package to estimate the fracture toughness of Ti alloy. A similar XFEM approach was used to analyse the tensile properties of Ti alloy to predict its fracture behaviour through the center cracked specimen taken at the tensile gauge section. The strengthening mechanisms contributing to Ti alloy's static and dynamic properties are elucidated through microstructural characteristics of LPBF processed Ti6Al4V alloy reported in the literature.

Study on Temporal and Spatial Characteristics of Overlying Strata in the Deep Coal Mining Process

This study adopts the stress relief method to test the in situ stress in the field to obtain the in situ stress distribution characteristics of no. 2 + 3# coal seam. A three-dimensional model was established with the no. S3012 working face as the engineering background, and the measured in situ stress values were applied to the three-dimensional model, and the spatial-temporal evolution characteristics of coal and rock mass around the stope during coal seam mining were studied. The specific conclusions are as follows: the three-dimensional stress distribution map in front of, behind, and on both sides of the working face in the process of coal mining are obtained. As the working face goes on, the maximum value of the supporting stress formed in front of, behind, and on both sides of the working face shifts to the corner, presenting a “hump-like” distribution. The stress concentration coefficient of front, back, and both sides of stope increases linearly with the increase of the mining size. Under the same mining size, the stress concentration coefficient in front of stope is the smallest, and the stress concentration coefficient on both sides is the largest. The three-dimensional displacement field distribution nephogram of overlying strata in the process of coal mining is obtained. With the continuous advance of the working face, the roof strata of coal seam undergo the continuous dynamic subsidence process, and the roof subsidence increases continuously, showing the shape of “bowl” with sharp bottom. In the process of working face mining, the roof displacement of coal seam showed an “O” shape evolution characteristic. The three-dimensional distribution cloud map of the plastic zone of coal and rock mass in the process of the working face mining was obtained, and the failure volume of the plastic zone gradually increases with the continuous progress of the working face.

Finite element analysis of stress in the gallery of gravity dam on inclined bedrock based on ANSYS model

Taking a variety of galleries in a concrete gravity dam body as the research object, it analyzes the changing law of stress concentration phenomenon around the galleries in the dam body affected by the holes of the galleries. Use the large-scale finite element application software ANSYS to model the dam and the bedrock within a limited range, change the position of the gallery to obtain different solid models, and obtain the stress distribution map around the gallery after loading calculations. The results show that when the distance between the gallery and the upstream dam surface changes from 3.0 to 9.0m, the maximum principal stress of the gallery section gradually decreases and tends to remain unchanged; there is obvious stress concentration at the gallery and the dam heel. When the drainage gallery is arranged in the vertical direction, the change of the distance affects the stress distribution and state of the gallery. When the distance is changed from 15 to 25m, the stress changes from 0.106e7 to 0.088e7Pa, and tends to be stable, and the mutual influence gradually decreases. This provides guidance and suggestions for the design of the gravity dam gallery on the inclined bedrock.

First-Motion Focal Mechanism Solutions for 2015–2019 M ≥ 4.0 Italian Earthquakes

A list of 100 focal mechanism solutions that occurred in Italy between 2015 and 2019 has been compiled for earthquakes with magnitude M ≥ 4.0. We define earthquake parameters for additional 22 seismic events with 3.0 ≤ M &amp;lt; 4.0 for two specific key zones: Muccia, at the northern termination of the Amatrice–Visso–Norcia 2016–2018 central Italy seismic sequence, and Montecilfone (southern Italy) struck in 2018 by a deep, strike-slip Mw 5.1 earthquake apparently anomalous for the southern Apennines extensional belt. First-motion focal mechanism solutions are a good proxy for the initial rupture and they provide important additional information on the source mechanism. The catalog compiled in the present paper provides earthquake parameters for individual events of interest to contribute, as a valuable source of information, for further studies as seismotectonic investigations and stress distribution maps. We calculated the focal mechanisms using as a reference the phase pickings reported in the Italian Seismic Bulletin (BSI). We visually checked the reference picks to accurately revise manual first-motion polarities, or include new onsets when they are not present in the BSI dataset, for the selected earthquakes within the whole Italian region, with a separate focus on the Amatrice–Visso–Norcia seismic sequence area from August 24, 2016 to August 24, 2018. For the Montecilfone area, we combined the information on the geometry and kinematics of the source of the 2018 Mw 5.1 event obtained in this study with available subsurface and structural data on the Outer Apulia Carbonate Platform to improve understanding of this intriguing strike-slip sequence. Our analysis suggests that the Montecilfone earthquake ruptured a W–E trending strike-slip dextral fault. This structure is confined within the Apulia crystalline crust and it might represent the western prolongation of the Mattinata Fault–Apricena Fault active and seismogenic structures. The calculated focal mechanisms of the entire catalog are of good quality complementing important details on source mechanics from moment tensors and confirming the relevance of systematically including manually revised and more accurate polarity data within the BSI database.

MODELING THE PROCESS OF OPERATION OF HIGH-SPEED EQUIPMENT AND THE INFLUENCE OF THERMAL PARAMETERS ON WORKING BODIES

Introduction. The article is devoted to the study of heat transfer processes occurring in space and time. Therefore, the study of thermal conductivity is reduced to the study of space-time temperature changes. Distinguish between stationary and non-stationary temperature fields. A non-stationary temperature field is a field whose temperature changes not only in space, but also over time. A stationary temperature field is a field whose temperature at any point does not change over time. Materials and methods. To solve problems associated with finding the temperature field, it is necessary to have a differential equation of thermal conductivity, which gives the relationship between temperature, time and coordinates of the elementary volume. The differential heat conduction equation describes the transfer of heat inside the body. In order to find the temperature field inside the body at any moment of time, that is, to solve the differential equation, it is necessary to know the geometric shape of the body and the boundary conditions. Boundary conditions consist of initial and boundary conditions. Research results. As a result of modeling the process of upsetting during stage-by-stage deformation, including 30 steps at each impact (total of 3 impacts) using the QForm-2D software package, maps of stress and strain distribution over the volume of the workpiece were obtained. Discussion and conclusions. The main process parameters influencing the nature of the technological force are the accumulated deformation and the resistance of the material to plastic deformation. From the analysis of the obtained pictures of the distribution of deformation over the cross section of the sample after upsetting, that under the accepted conditions it is uneven. The greatest accumulated deformation is observed in the center and in the peripheral layers on the contact surface, and in other areas its value is less than 0.1. The same unevenness is shown by the stress distribution pattern. This is explained by the fact that with an increase in the degree of deformation, the rate of heat release decreases in the same zones where the maximum accumulated deformation is concentrated.

Treatment option for knee Osteoarthrosis: Influence of PU-spacers on pressure distribution in 3D-printed knee models

Aims and Objectives:What is the effect of polycarbonate-urethane (PU) interpositional knee spacers on load distribution in 3D printed knee models and can this be a potential treatment for knee osteoarthrosis (KOA)?KOA accounts for 83% of the total OA burden associated with tremendous physical and mental limitations in patients’ lives, but also with an enormous impact on health care systems worldwide [1]. An interpositional mimicked knee spacer could serve as an additional treatment in patients with medial KOA and postpone more invasive treatment options. To date, existing spacers failing to reveal satisfactory results, primarily due to dislocation and methodological issues [2, 3]. This study aimed to examine whether and to what extent a set of differently shaped PU-spacers can reduce stress in the medial knee compartment.Materials and Methods:A knee simulator was utilized to investigate the knee joint loading via pneumatic actuators with and without the insertion of four different spacer types into the medial compartment of six 3D printed knee models (material: PLA). The knee models corresponded to six cadaveric right limbs, which were segmented from CT-scans to create CAD models using a reverse engineering approach (Figure 1).Figure 1: Depiction of the performed work sections. The loading conditions were performed by applying simulated muscle forces (quadriceps: 700 N, hamstrings: 250) induced by pneumatic actuators. Joint contact stress and stress distribution were determined using Tekscan Pressure Mapping Sensors 4000 (50 Hz, Tekscan Inc., South Boston, USA). Thirty cycles of flexion-extension motion were recorded between 180-90° with each spacer-type in the each printed knee model.Results:All spacer types showed reduced mean stress values by 71-75% compared to the no-spacer test condition (Figure 2a, b). This result was associated with a redistribution of the acting force to a larger area (+145-295%) induced by the corresponding spacer-type.Figure 2: a) Time series representing the mean stress curve progressions for all test conditions b) Exemplary peak stress distribution map for no-spacer and spacer M1f125 condition. The mentioned relationship exhibits the major functional principal of the mimicked knee spacer, namely to reduce knee joint loads, hence providing pain relief in the osteoarthritic knee.Conclusion:The results of the current study demonstrate that a knee spacer could theoretically complement the common treatment options for KOA, avoiding loss of bone, preserving the natural bone stock, reducing pain, and extending the time to one of the other treatment methods without compromising the patient’s future knee replacement. However, several major aspects must be considered in future studies including, e.g. spacer geometry, testing in cadaveric knees, higher acting forces and limb kinematics.

Easy method to measure the packaging-induced stress of a semiconductor laser diode by lasing wavelength shifting.

In this paper, the packaging-induced stresses are theoretically calculated by modeling multilayered structures for different packaging structures. We report a method to measure the packaging-induced stress of a laser diode array (LDA) by comparing the emission wavelength of the single emitter located in the middle of a laser bar before and after packaging. The wavelength is tested under a low duty cycle (50μs/10Hz, DC 0.05%) to eliminate the thermal effect to wavelength shifting. Experimental calculation results for the packaging-induced stress of LDAs are in good agreement with the theoretical calculations and simulation results. For a GaAs laser bar, we find the packaging stresses are compression stresses, which make the emission wavelength blue-shift in terms of 1.09×10-2 nm/MPa. We propose a mapping of packaging-induced stress distribution in laser bars on a microscopic scale by considering the emission spectra of each emitter in a laser bar. Compared to single-emitter resolved photo-current or micro-photoluminescence measurements, as proposed by other authors, we offer a much easier tool to test and map the distribution of packaging-induced stress in laser bars.

Design and analysis of the flange-bolted joint with respect to required tightness and strength

Abstract The paper presents the method of design and strength analysis of the flange-gasketed-bolted joint. In the first part, analytical calculations were carried out. Their purpose was to determine the assembly torque of nuts to achieve the desired tightness. The flanged joint designated as DN100 PN40 with two different gaskets was taken into consideration. The analytical calculations were performed in accordance with the algorithm included in PN EN 1591-1. In the further step, the numerical calculations were carried out to support the analytical results. The outcome of these calculations were maps of the contact stress distribution on the gasket surface, estimation of safety factors of individual joint elements as well as determination of the flange rotation. Data from the numerical calculations were compared with the analytical results, which confirmed their satisfactory compliance. In the last stage, the experimental tests of the joint were carried out. The main results of the test were the measured values of the leakage level, tightening force of the bolt and estimated safety factors. An indirect result of the experimental measurements were maps of the stress distribution on the contact surface of the gasket, which were determined by means of the measuring film. Ultimately, based on the experimental results, it was found that the proposed analytical method of calculation and simulation of the joint by means of the finite element method was a very good tool for the design of the joint at the required tightness level.

Computational approach to evaluating the strength of eggs: Implications for laying in organic egg production

With the aim of characterising the different stress patterns in several egg types and evaluating the resistivity of the eggshell while impacting in free fall, experimental tests and computational simulations have been performed on eggs of the species Gallus gallus (domestic hen), Struthio camelus (ostrich), and Testudo sp. (tortoise). The different types of failure were determined for each taxa and stress distribution maps were recorded and correlated between experimental results and simulations using finite element analysis (FEA). For domestic hens, the numerical results obtained in both tests have highly correlation with the results obtained in previous works; for ostrich ( S. camelus ) and tortoise ( Testudo sp.) eggshells, this new data represented a useful tool to understand in further works the failure mechanisms of the eggshells. More interestingly, the present study provides the first empirical and mathematic results that allow confident safety intervals to be established that relate to the laying process in the poultry industry. • Understand the mechanical of eggshells are crucial for egg production. • Eggshell resistivity is evaluated using both empirical and computational tests. • Newly classification of failure helps to understand failure mechanisms. • For first time, ostrich and turtle eggshell mechanics are provided. • Results set relationships between impact velocity, substrate, and type of failure.

A nondestructive raman spectra stress 2D analysis for the pressure sensor sensitive silicon membrane

The residual stresses introduced by the bonding process has become a key effect for the MEMS product yield improvements. Many in-situ stress measurements have to destruct the devices. Raman spectroscopy is a nondestructive inelastic scattering measuring. Interpreting the silicon Raman frequency shifting can describe the stress location and intensity quantitatively in the lattice. The confocal microscopic observation can realize micrometer scale resolution. However, the limited visual field cannot provide the device stress distribution overview. In the meantime, the microscope loading platform displacement (only 100 μm) will introduce severe random errors (4 ± 1 μm) in the overlapping movements. Since the local stress intensity could be converted into a RGB gray pixel. Through the image mosaic algorithms, the measured local residual stress distribution maps (750 μm × 160 μm) could be stitched to an enlarged stress distribution map (750 μm × 340 μm). This methodology could not only expand the stress inspection overview(60 ± 2%), but also examine and eliminate the displacement random errors. The analysis results showed that the residual stresses were about 70 ± 5% of the simulation value. The uniform difference between the measured and simulated values indicated a trustable stress analysis.

Structural analysis of deep soil loosening machine MAS-65

Deep soil loosening machine MAS 65 is destined to work soil at depths exceeding 45 cm, thus the machine’s frame is subjected to loads which could affect its structural integrity. Within this paper a static structural analysis was performed on the machine’s 3D model using finite element method and strain and stress distribution maps were created. Using the Von Mises stress map there were identified several critical points which could fail during normal exploitation conditions and which should be monitored by strain gages during field tests in order to prevent structural failure.

Strength Analysis of a Ducted Axial Fan Blade

This paper presents a numerical strength analysis of a ducted axial fan blade. Ducted axial fans are a large group of fluid-flow machines. The analysis was designed to determine the causes of cyclic failures of a ventilation unit. The paper presents a reverse engineering approach to the mapping of the fan blade’s geometrical features. The geometrical features were mapped by triangulation from the scanning images produced by a 3D optical scanner. These were followed by simplifying assumptions on which the numerical calculations were based. The numerical calculations were carried out at the operating rotational speeds of the ducted axial fan’s rotor. The course of the numerical calculations is described, and their results are also presented herein. The results are represented on colour maps of stress distribution for selected structural elements of the fan blade. The stress distribution at a blade cross-section was compared to CT scans of the fractures of failed rotor blade airfoils. Final conclusions were developed which show that the design engineering process of fans should feature optimisation of the fan’s efficiency, including the strength and performance parameters, which should include the service life of the fan.

Multiphysics Characterization of a Novel SiC Power Module

This paper proposes a novel power module concept specially designed for highly reliable silicon carbide (SiC) power devices for medium- and high-power applications. The concept consists of two clamped structures: 1) a press-pack power stage accommodating SiC power switch dies and 2) perpendicularly clamped press-pack heatsinks, in which the heatsinks are in contact with electrically insulated case plates of the power stage. The concept enables bondless package with symmetric double-sided cooling of the dies and allows for an order of magnitude higher clamping force on the heatsinks than what can be applied on the dies. The concept has been evaluated in a first demonstrator (half-bridge configuration with 10 paralleled SiC dies in each position). The experimental methodologies, setups, and procedures have been presented. The commutation loop inductance is approximately 9 nH at 78 kHz. The junction-to-case thermal resistance is approximately 0.028 K/W. Furthermore, a simplified 3-D finite-element thermomechanical model representing the center unit of the demonstrator has been established for the purpose of future optimization. The accuracy of the simulated temperatures is within 4% compared to the measurements. Finally, a 3-D thermomechanical stress distribution map has been obtained for the simplified model of the demonstrator.