Strain Rate Ratio Research Articles

Combination of Different Sectional Elastography Techniques with Age to Optimize the Downgrading of Breast BI-RAIDS Class 4a Nodules.

This study aims to optimize the downgrading of BI-RADS class 4a nodules by combining various sectional elastography techniques with age. We performed conventional ultrasonography, strain elastography (SE), and shear wave elastography (SWE) on patients. Quantitative parameters recorded included age, cross-sectional and longitudinal area ratios (C-EI/B, L-EI/B), strain rate ratios (C-SR, L-SR), overall average elastic modulus values (C-Emean1, L-Emean1), five-point average elastic modulus values (C-Emean2, L-Emean2), and maximum elastic modulus values (C-Emax, L-Emax). Histopathological evaluations showed that out of 230 lesions, 45 were malignant, and 185 were benign. The sensitivity and specificity of conventional ultrasonography were 100% and 0%, respectively. In contrast, SE and SWE exhibited higher specificity but lower sensitivity. Crosssectional parameters (C-EI/B, C-SR, C-Emean1, C-Emean2, and C-Emax) outperformed their longitudinal counterparts, with C-SR and C-Emax showing the highest specificity (72.43% and 73.51%) and satisfactory sensitivity (80.00% and 88.89%). Combining age with C-SR and C-Emax significantly improved diagnostic efficiency, achieving a sensitivity of 97.78% and a specificity of 77.30%. Integrating age with C-SR and C-Emax effectively reduces unnecessary biopsies for most BI-RADS 4a benign lesions while maintaining a very low misdiagnosis rate.

A novel swiss-roll counterflow micro-combustor: Experimental investigation of methane-oxygen flame behavior over time

This study introduces a novel Swiss-roll micro-combustor design that employs a non-premixed counterflow flame for efficient and stable micro-combustion. This design addresses practical system challenges by (1) stabilizing the flame, (2) enhancing heat recovery and gas preheating, (3) aligning gas momentum with the exhaust, and (4) minimizing disruptive fluid motion within the channels. This research investigates the dynamic behavior and combustion characteristics of a methane-oxygen flame within the combustor across a range of equivalence ratios (1.50–3.38). A synergistic approach combining flame dynamics analysis, spectroscopy, and RGB image processing explores the interplay between flame temperature, strain rate, and equivalence ratio. The results demonstrate the effectiveness of the RGB method as a cost-efficient tool for predicting variations in C2∗ and CH∗ radicals and light-intensity radiations. While flame thickness and length exhibit complex dependencies on the fuel-to-oxygen ratio and wall temperature, specific radical emissions vary dynamically with the equivalence ratio. Notably, equivalence ratios of 1.94 and 2.26 exhibit minimal temporal variations in flame properties, suggesting optimal stability and predictability for practical applications. The investigated flame is classified as a “cool flame,” and efficiency declines with richer mixtures due to increased exhaust heat loss and incomplete combustion. This work paves the way for further micro-combustor design optimization and unlocks the potential of non-premixed counterflow flames in diverse micro-scale applications.

Ultrasound elastography predicts anticoagulation in lower extremity deep vein thrombosis.

To investigate predictors of anticoagulation efficacy in deep venous thrombosis (DVT) by ultrasound elastography (UE). The basic clinical, laboratory and ultrasound treatment data of fifty-eight patients with DVT were collected and analyzed. Then the results of ultrasound after 3-month anticoagulation treatment were compared among different groups. Multiple logistic regression analysis was used to identify independent risk factors that affected anticoagulation efficacy. The predictive efficacy of each independent risk factor was accessed by drawing operating characteristic (ROC) curves. According to the regression analysis, the elastic modulus (OR = 0.631, P = 0.001) and strain rate ratio (OR = 0.332, P = 0.006) were identified as independent risk factors for the effectiveness of anticoagulation therapy in patients with DVT. According to the ROC curves, elastic modulus and strain rate ratio could predict effective anticoagulation therapy for DVT, and the optimal threshold values were 22.10 kPa and 1.80 respectively. The corresponding AUC values were 0.879 and 0.854, with a sensitivity of 71.4% and 59.5%, a specificity of 93.7%, and a Youden index of 65.1% and 62.7%, respectively. The elastic modulus (≤22.10 kPa) or strain rate ratio (≤1.80) of the thrombus were independent predictors for the effectiveness of anticoagulation therapy.

Flame characteristics and NO emission behaviors of methane/ammonia counterflow premixed flames with opposed N2 or air stream

Behaviors of methane/ammonia counterflow premixed flames and NO emission are numerically and experimentally investigated with opposed N2 or air stream by varying strain rate (ag) and equivalence ratio (ϕ). The premixed stream is 80% methane and 20% ammonia by volume mixed with air considering the utilization of ammonia by blending hydrocarbon fuels. The opposed stream is either N2 or air considering the potential application in gas turbines having single- or two-stage combustion. The simulations are conducted by increasing ag up to flame extinction for a specified ϕ and an experiment is conducted to evaluate various kinetic mechanisms. The extinction strain rate increases monotonically with ϕ with opposed air stream (AS), while increases and then decreases with opposed nitrogen stream (NS). The extinction mechanisms are explained by adopting the concepts of the local equilibrium temperature and heat loss ratio. For lean and rich mixtures with NS and lean mixtures with AS, the extinction occurs due to comparable effects of incomplete reaction and heat loss from the flame to the downstream burnt region. While for rich mixtures with AS, the extinction is attributed mainly to incomplete reaction. The contribution of thermal NO as compared with prompt NO in NO production is weak for all cases with NS and AS. The emission index (EINO) for lean and rich mixtures with NS and for lean mixtures with AS decreases monotonically with the increase of strain rate for all ϕ. Increasing equivalence ratio at a specified ag decreases NO production for lean and rich mixtures with NS and lean mixtures with AS. While for rich mixtures with AS, the EINO increases monotonically with ag. From the reaction pathway analysis, for lean mixtures, the effect of increasing ag on the reduction of NO production is attributed by weakening NH-related reaction paths, while NH2-related reaction paths change little. When ϕ increases for a specified ag with NS, NO production is reduced by weakening NH2-related reaction paths and strengthening NH-related reaction paths. For rich mixtures with AS, increasing ag increases NO production by strengthening NH2-related reaction paths.

Unsteady MHD flow analysis of hybrid nanofluid over a shrinking surface with porous media and heat generation: Computational study on entropy generation and Bejan number

The use of hybrid nanofluids in real-world situations is essential for enhancing the efficiency of heat transmission, especially in cooling semiconductor technology and industrial processes. The entropy generation on unsteady Al2O3-Cu/H2O hybrid nanofluid flow over a three-dimensional shrinking sheet is addressed numerically in this study, taking into account the effects of magnetohydrodynamic (MHD), nonlinear thermal radiation, porous media, heat generation, viscous dissipation, joule heating, and convective conditions. Using well-known non-similarity transformations, the model is carefully converted from partial differential equations (PDEs) to ordinary differential equations (ODEs). Afterwards, the behaviors of critical physical characteristics are uncovered across different parameter configurations by a numerical solution using the finite difference technique in bvp4c MATLAB. The velocity profiles of hybrid nanofluid grow proportionately with increases in the values of ϕ2,M,A,K and λ parameters. As Rd,θw,Ec,Bi,H and ϕ2 increase, the temperature of the hybrid nanofluid rises, but as M and A increase, the temperature falls. The local skin friction in both the x and y- directions is increased by enhancing the unsteadiness A, nanoparticle volume fraction ϕ2, magnetic M, porous media K, and the ratio of strain rate λ parameter on the shrinking surface. The local Nusselt number is improved by cumulative the unsteadiness A, nanoparticle volume fraction ϕ2, magnetic M, and Biot number Bi parameter in the direction of a shrinking surface, while the Nusselt number decreases when Eckert number Ec, thermal radiation Rd, heat production H, and temperature ratio θw are improved. An upsurge in the magnetic parameter leads to the development of entropy generation. Increasing levels of the magnetic parameters led to a reduction in the Bejan number. At a nanoparticle volume fraction of 1 % and a nonlinearity radiation scenario, where the unsteadiness values are 0.5, the Nusselt number for hybrid nanofluid shows an estimated improvement of 10.55 % compared to regular nanofluid.

Behavior of geometrically-similar Basalt FRP bars-reinforced concrete beams under dynamic torsional loads

A numerical model utilizing 3D mesoscale simulation methods was developed to investigate the influence of strain rate on the torsional performance of geometrically similar Basalt Fiber Reinforced Polymer bars-reinforced concrete (BFRP-RC) beams, as well as the corresponding size effects. The model incorporates concrete heterogeneity, material strain rate effects, and the dynamic bond-slip relationship between BFRP bars and concrete. The torsional performance of BFRP-RC beams with different structural sizes and stirrup ratios was analyzed under different strain rates. The study yielded the following findings: (1) The damage degree of BFRP-RC beams increases with the rising strain rate. (2) Increasing strain rate and stirrup ratio enhances the beams’ torsional strength and ductility while attenuating the size effect, albeit not eliminating it. (3) The impact of increasing strain rate on beam strength, ductility, and size effect outweighs that of increasing stirrup ratio. Finally, based on the Bažant size effect law (SEL) combined with the simulation results, a new size effect law was proposed that can quantitatively consider the effect of strain rate and stirrup ratio on the torsional strength of BFRP-RC beams.

The value of elastography strain rate ratio in benign and malignant BI-RADS-US 3-4 breast masses.

In the realm of breast diagnostics, Breast Imaging Reporting and Data System (BI-RADS) serves as a systematic framework, guiding a methodical exploration into the nuanced narratives of masses. The current study aims to investigate the value of strain rate ratio (SR) of elastography for benign and malignant breast masses categorized by BI-RADS for Ultrasonography (BI-RADS-US) category 3-4. Ultrasonographic data of 1099 breast masses that underwent both elastography and pathological examination were retrospectively analyzed by non-parametric test, consistency analysis and receiver operating characteristic (ROC) curve sequentially. ROC curve was used to evaluate the diagnostic effect of SR method in different BI-RADS categories of breast lesions. The maximum Youden index obtained from the ROC curve was 0.845. At a cut-off value of 3.57, the SR values' diagnostic sensitivity, specificity, accuracy, positive predictive value and negative predictive value for distinguishing benign and malignant breast lesions were 85.7 %, 98.8 %, 93.6 %, 97.9 % and 91.45 %, respectively. Consistency analysis showed that the consistency between SR value and pathological diagnosis was 93.6 % (κ = 0.864). In addition, the SR values between benign and malignant lesions of BI-RADS 3 and 4 were statistically different (P < 0.001). ROC analysis indicated that the diagnostic area under curve (AUC) for SR value in BI-RADS 3, 4a, 4b and 4c lesions were 0.985, 0.866, 0.793 and 0.916, respectively. In addition, the study observed 58 cases of missed diagnosis and 20 cases of misdiagnosis in evaluating benign and malignant breast lesions. The elastic SR ratio method has a good diagnostic value for the evaluation of breast masses, particularly for lesions with a score of 3-4. The elastic SR ratio method is instrumental in enhancing the accuracy of diagnosis.

Quantitative evaluation of endobronchial ultrasound elastography in the diagnosis of benign and malignant mediastinal and hilar lymph nodes

ObjectiveTo compare the diagnostic value of different quantitative methods of endobronchial ultrasound elastography in benign and malignant mediastinal and hilar lymph nodes. MethodsThis retrospective study included patients who underwent endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) for mediastinal and hilar lymph node enlargement in our hospital between January 2019 and August 2022. We compared different quantitative elastography parameters [red area ratio (RAR, lymph node red area/lymph node area), green area ratio (GAR, lymph node green area/lymph node area), blue area ratio (SAR, lymph node blue area/lymph node area), mixed area ratio (MAR, lymph node green area/lymph node area), blue-green lymph node area/lymph node area), strain rate ratio (SR), strain rate in the target lymph node (LPA), ratio of blue area to total lymph node area outside the center of the target lymph node (PAR), and average grey value (MGV)], in order to find the best quantitative evaluation method. ResultsA total of 244 patients (346 lymph nodes) were included in this study. All quantitative elastography parameters were statistically significant for the differentiation of benign and malignant lesions except the average grey value of the target lymph nodes. The area under the receiver operating characteristic curve of SAR was 0.872 (95% confidence interval: 0.83−0.91), the cutoff value was 0.409, and the sensitivity, specificity, positive and negative predictive values were 85.4%, 78.0%, 80.4%, and 83.4%, respectively. ConclusionCompared with other types of quantitative analysis, SAR has a higher predictive significance for benign and malignant lymph nodes.

Numerical Investigation of Partially Premixed Flames Under Transcritical Conditions

Understanding the characteristics of partially premixed flames (PPFs) under transcritical conditions is of critical importance for the development of fuel-rich staged rocket engines. While substantial progress has been achieved for transcritical non-premixed flames (NPFs), comparatively little effort has been made to investigate transcritical PPFs. To this end, a series of transcritical counterflow gaseous hydrogen/liquid oxygen (GH2/LOX) PPFs is simulated to investigate the thermodynamic structure of PPF and to examine the effects of molecular diffusion modeling, strain rate, and the equivalence ratio at the fuel-rich side on PPFs in physical space and mixture fraction space, as well as reduced temperature/reduced pressure space. The comparisons between the NPF and PPF demonstrate that the PPF exhibits a bimodal structure in physical space: a premixed reaction zone at the fuel inlet side and a non-premixed reaction zone at the oxidizer side. In mixture fraction space, the C-shaped structure of PPF is observed owing to the differential diffusion of species. It is found that the choice of molecular diffusion model has a significant impact on PPF structure. The presence of a loop at subcritical pressures in a reduced temperature/reduced pressure space is caused by the differential diffusion of species and the formation of [Formula: see text] in the non-premixed reaction zone. Furthermore, the results indicate that the premixed reaction zones in the PPFs are very sensitive to the change in strain rate and/or equivalence ratio of the premixed mixture at the fuel inlet side. For a given equivalence ratio, increasing strain rate can suppress the differential diffusion effect and the C-shaped structure, while it has a negligible impact on the non-premixed reaction and hence on loop formation.

Application Value of Ultrasound Elastography Combined With Contrast-Enhanced Ultrasound (CEUS) Quantitative Analysis in Differentiation of Nodular Fibrocystic Changes of the Breast From Invasive Ductal Carcinoma.

This study aimed to compare the value of ultrasound elastography combined with contrast-enhanced ultrasound (CEUS) quantitative analysis in the differentiation of nodular fibrocystic breast change (FBC) from breast invasive ductal carcinoma (BIDC). We selected 50 patients each with nodular FBC and BIDC, who were admitted to the Affiliated Hospital of Zunyi Medical University from January 2018 to December 2021. Their ultrasonic elastic images and CEUS videos were collected, their ultrasound elastography scores and the ratio of strain rate (SR) of the lesions were determined, and the exported DICOM format videos of CEUS were quantitatively analyzed using VueBox software to obtain quantitative perfusion parameters. The differences between the ultrasound elastography score and SR while comparing nodular FBC and BIDC cases were statistically significant (p < .05). The sensitivity, specificity, and accuracy of ultrasound elastography scores in the differential diagnoses of nodular FBC and BIDC were 74%, 88%, and 81%, respectively. Additionally, the sensitivity, specificity, and accuracy of SR in the differential diagnosis of nodular FBC and BIDC were 94%, 78%, and 86%, respectively. Statistically significant differences were observed in the CEUS quantitative perfusion parameters PE, AUC (WiAUC, WoAUC, WiWoAUC), and WiPI in both nodular FBC and BIDC according to the VueBox software (p < .05). The sensitivity, specificity, and accuracy of CEUS quantitative analysis in the differential diagnoses of nodular FBC and BIDC were 66%, 82%, and 74%, respectively. Using the pathological findings as the gold standard, ROC curves were established, and the area under the curve (AUC) of the CEUS quantitative analysis, elasticity score, SR, and ultrasound elastography combined with CEUS quantitative analysis were 0.731, 0.838, and 0.892, as well as 0.945, respectively. Ultrasound elasticity scoring, SR and CEUS quantitative analysis have certain application value for differentiating nodular FBC cases from BIDC; however, ultrasound elasticity imaging combined with CEUS quantitative analysis can help in improving the differential diagnostic efficacy of nodular FBC cases from BIDC.

Structural Performance of Additively Manufactured Composite Lattice Structures: Strain Rate, Cell Geometry, and Weight Ratio Effects

The proliferation of ordered cellular structures in industrial and technological applications is justified by their superior mechanical performance, including tunable energy absorption strategies and potential multifunctionality. This research evaluates the mechanical response of composite lattice structures fabricated using vat photopolymerization additive manufacturing process and printable particulate composite materials. Several generations of modified printable resins are prepared by hybridizing flexible resin with varying glass microballoons reinforcement weight percentages. Multifaceted characterization regiments highlight the process–property–performance interrelationship by submitting printed composite structures to quasi‐static and impact‐loading scenarios combined with digital stills and high‐speed photography, respectively. Image analyses of optical and scanning electron micrographs quantify the dimensional accuracy of the composite lattice structures with cylindrical and hexagonal cellular geometries. The mechanical characterization uncovers the effect of cell geometry and reinforcement on the global structural behavior, eliciting differences in load‐bearing capacity, local strain developments, and structural densification. Exploratory digital image correlation supports the global structural deformations, revealing their relationship with the developed local strain state within the unit cells. The outcomes of this research elucidate the effect of strain rate, unit cell geometry, and reinforcing ratios on the structural performance of composite lattice structures at the macro‐ and microstructure levels.

Comparison of anisotropic yield functions and calibrations for accurate thickness prediction in hole expansion test

The hole expansion test is an appropriate evaluation method for assessing the formability of automotive parts, where fracture prediction using simulated localized thickness is crucial. However, the accurate thickness prediction in the hole expansion test remains challenging. In this study, the selection of yield functions and calibration strategies were investigated to accurately predict the thickness of advanced high-strength steel subjected to the hole expansion test. An accurate description of the material anisotropy is important for thickness prediction because of the generation of various multiaxial stress states. To describe plastic anisotropy, a series of uniaxial tension, bulge, and in-plane biaxial tension tests were conducted on DP980 steel. Because conventional biaxial tension tests for DP980 steel showed a small strain range owing to its low ductility, a new laser-welding-reinforced biaxial tension test was developed to investigate the anisotropy of the plane strain at large strains. Differences in the ratio of the plastic strain rates were observed between the conventional and new tests. Finally, a hole expansion test and corresponding finite element simulations were conducted with different yield functions and calibrations for the Yld2000-2d yield function. The thickness strain profiles along the hole circumference and 3 mm inward were measured and predicted using simulations. In conclusion, both the yield stress and the ratio of plastic strain rates in the plane strain state were equally important for accurate thickness prediction during the DP980 hole expansion test. Furthermore, the crack location was inconsistent with the thinnest region in the experiment, which might be because of the shear fracture anisotropy encountered in DP980 steel.

Suppression of NOx emissions by intensive strain in lean premixed hydrogen flamelets

NOx formation in premixed, highly-strained, pure hydrogen-air flamelets is investigated at lean conditions. Detailed-chemistry, one-dimensional and two-dimensional simulations are performed on a reactants-to-products configuration with varying applied strain rate. The results highlight for the first time for lean pure-hydrogen flamelets that NOx emissions are suppressed as strain rate is increased. The most substantial decrease is observed across the thermal NOx formation pathway. Here the suppression of NOx is triggered by a redistribution across the flamelet of the radicals involved in the pathway reactions. A comparison with methane flamelets is further performed to understand to what extent the observed trends with strain can be specifically linked to hydrogen burning features. Similar NOx suppression trends with strain are also observed for increased pressure and different equivalence ratios, although with different rates of decrease. A correlation is proposed based on the observed results and further theoretical considerations, to predict NOx emissions according to applied strain rate and equivalence ratio.

Complex Deformation Behavior of GPa Grade Advanced High-strength Automotive Steel

To explore the complex deformation behavior of advanced high-strength automotive steel, the biaxial tensile test was carried out by using the thinned cruciform specimen. The stress in the central deformation area of the thinned specimen was analyzed by the simulation to verify the effectiveness of the specimen. The biaxial tensile test of metal sheets and the calculation method of yield trajectory were studied. The yield trajectories of DP980 and QP980 under different loading paths were obtained by using the strain-rate ratio control. The research results provide important technical support for improving the forming simulation accuracy of advanced high-strength steel DP980 and QP980.

Spatio-temporal variations of seismic coupling along a transform fault: the western North Anatolian Fault Zone

SUMMARY The Main Marmara Fault (MMF) forms a major segment of the North Anatolian Fault Zone (NAFZ) in northwestern Türkiye. The MMF represents a seismic gap with currently high seismic hazard and associated risk for the Istanbul metropolitan area. Here we estimate the seismic coupling defined as the ratio of the seismic strain rate to the tectonic strain rate, for the MMF and adjacent NAFZ segments. This ratio indicates the fraction of total strain accumulated with time that is released seismically. We compare the results of seismic strain rates and coupling estimated from earthquakes included in historical and instrumental catalogues, which allows us to identify fault segments that represent a considerable seismic threat during the current seismic cycle. We find that along the main fault traces hosting the large events, seismic strain rates from the historical catalogue are of the same order as the tectonic strain rates. In contrast, coupling estimates based on seismic data from the instrumental catalogue covering also off-fault areas, are up to 100 times smaller, highlighting that most of the seismic energy is released in large earthquakes with recurrence times longer than the time covered by the instrumental catalogue. Within the Sea of Marmara, a significant portion (48%) of shear strain from the instrumental catalogue is currently being accommodated by seismic deformation. Significant variations of the seismic coupling are observed before and after the 1999 M &amp;gt; 7 Izmit earthquake, highlighting the different contribution of aseismic slip over different portions of the seismic cycle. A comparison of the temporal evolution of the 1999 Izmit and Düzce post-seismic deformation with seismic strain rates shows that the largest seismic strain rates coincide with the largest post-seismic deformation.

Comparative analysis of ultrasonic elastosonography and contrast-enhanced ultrasonography in the diagnosis of benign and malignant intraocular tumors.

To compare the diagnostic value of ultrasonic elastosonography (UE) and contrast-enhanced ultrasonography (CEUS) for benign and malignant intraocular tumors. This retrospective study enrolled patients with intraocular tumors at Beijing Tongren Hospital, Capital Medical University (August 2016 to January 2020). The strain rate ratio (strain rate of tumor tissue divided by strain rate of surrounding normal tissue) was measured by UE. CEUS was performed using SonoVue® contrast agent. The performance of each method at differentiating benign from malignant intraocular tumors was evaluated by receiver operating characteristic curve analysis. The analysis included 147 eyes in 145 patients (45.6 ± 13.4years-old; 66 males): 117 patients (119 eyes) with malignant tumors and 28 patients (28 eyes) with benign tumors. At an optimal cutoff of 22.67 for the strain rate ratio, UE distinguished benign from malignant tumors with a sensitivity of 86.6% and a specificity of 96.4%. CEUS showed that 117 eyes with malignant tumors had a fast-in, fast-out time-intensity curve, and only two eyes with malignant tumors had a fast-in, slow-out curve, while all 28 eyes with benign tumors had a fast-in, slow-out curve. CEUS differentiated benign from malignant tumors with a sensitivity of 98.3% and a specificity of 100%. The diagnostic results differed significantly between the two methods (P = 0.004, McNemar test). The diagnostic performances of the two tests were moderately consistent (κ = 0.657, P < 0.001). Both CEUS and UE have good diagnostic value in the differentiation of benign intraocular tumors from malignant intraocular tumors.

A Data-Driven Model to Predict Constitutive and Failure Behavior of Elastomers Considering the Strain Rate, Temperature, and Filler Ratio

Abstract This new machine-learned (ML) constitutive model for elastomers has been developed to capture the dependence of elastomer behavior on loading conditions such as strain rate and temperature, as well as compound morphology factors such as filler percentage and crosslink density. It is based on our recent new generation of machine-learning algorithms known as conditional neural networks (CondNNs) Ghaderi et al. (2020, “A Physics-Informed Assembly of Feed-Forward Neural Network Engines to Predict Inelasticity in Cross-Linked Polymers,” Polymers, 12(11), p. 2628), and uses data-infused knowledge-driven machine-learned surrogate functions to describe the quasi-static response of polymer batches in cross-linked elastomers. The model reduces the 3D stress-strain mapping space into a 1D space, and this order reduction significantly reduces the training cost by minimizing the search space. It is capable of considering the effects of loading conditions such as strain rate, temperature, and filler percentage in different deformation states, as well as enjoying a high training speed and accuracy even in complicated loading scenarios. It can be used for advanced implementations in finite element programs due to its computing efficiency, simplicity, correctness, and interpretability. It is applicable to a variety of soft materials, including soft robotics, soft digital materials (DMs), hydrogels, and adhesives. This model has a distinct advantage over existing phenomenological models as it can capture strain rate and temperature dependency in a much more comprehensive way.

Enhancement in the fatigue resistances of triply periodic surfaces-based scaffolds

To improve the endurance limits of triply periodic minimal surface (TPMS)-based scaffolds, the post-treatment process combing hot isostatic pressing (HIP) and electropolishing (ELP) was proposed and conducted in TPMS-based scaffolds with various structures. Thus, the fatigue properties were enhanced from three aspects: changing the topological structures of TPMSs, improving surface qualities and eliminating internal defects. The stretching-dominated scaffold-new diamond (AD) and the bending-dominated scaffold-network-based gyroid (IG) were selected and their relative densities were set to 20%. These scaffolds were fabricated by electron beam melting using Ti6Al4V powders. HIP and ELP were conducted in the manufactured scaffolds. Then, compression–compression fatigue tests were performed and fatigue parameters such as fatigue life, accumulated strain rate, fatigue strength and fatigue ratio were obtained. The experimental techniques of scanning electron microscopy, microcomputer tomography, optical microscopic, X-ray diffraction and electron backscattered diffraction were carried out to characterise the surface qualities, internal defects and microstructures. The effects of topological structure and surface quality on the stress distribution on TPMS-based scaffolds under compressive loading were investigated by finite element analysis. Results show that topological structures, surface qualities and internal defects all affect the fatigue properties of TPMS-based scaffolds. Under cyclic compressive loading, the fatigue ratios of IG and AD without undergoing post-treatment are 0.11 and 0.59, respectively, while they rise to 0.26 and 0.69 after HIP and ELP. Compared with surface qualities and internal defects, topological structures influence the fatigue properties of TPMS-based scaffolds more prominently. The fatigue properties of TPMS-based scaffolds can be enhanced by the post-treatment process combing HIP and ELP, and greater improvement will be obtained for bending-dominated structures than stretching-dominated structures. Thus, manipulating the topological structures and increasing the buckling components of TPMS-based scaffolds is an effective way to obtain porous scaffolds with excellent fatigue properties under cyclic compressive loading. HIP and ELP can also be adopted to further improve their fatigue lives. The novelty of this study lies in improving the fatigue properties of TPMS-based scaffolds from the three aspects, which are changing the topology structure, improving the surface quality and reducing the internal defects, and the mechanisms of improving the fatigue properties of TPMS-based scaffolds are systematically discussed.

Validation of axial and transverse force–displacement responses and principal strain rate ratios in the critical zone as a precursor to anisotropic damage prediction in metal sheets

Validation of axial and transverse force–displacement responses and principal strain rate ratios in the critical zone as a precursor to anisotropic damage prediction in metal sheets

Parameters of contact lines of rolls

The article defines the parameters of the contact lines of the rolls. Calculation formulas are found for determining such parameters as the ratio of strain rates in roll pairs when the deformation of the semi-finished leather product and the coating of are given by rheological models. It was revealed that the forms of contact lines in roll pairs do not depend on the methods of specifying the deformation of the leather material and the coating of the rolls.