Stress Mode Research Articles

Influence of spray angle in cold spray deposition of Ti-6Al-4V coatings on Al6061-T6 substrates

Cold spray (CS) has been deployed to deposit compact and well bonded Ti-6Al-4 V (Ti64) coatings. While the effects of gas pressure, gas temperature and powder feed rate have been well studied, the influence of spray angle during CS deposition of Ti64 powders is less understood. As actual components frequently have uneven or curved surfaces, it is critical to understand the impact of spray angle to design an efficient toolpath for repair or additive manufacturing of 3D freeform objects. In this work, off-normal spray angles were studied to elucidate their impact on the coating quality when depositing spherical Ti64 powders by CS on Al6061-T6 substrates using nitrogen as process gas. Evaluation of deposition efficiency and the coatings' surface roughness, cross-sectional microstructure, thickness and residual stress were performed to provide insight on the effects of spray angle. Finite Element Method (FEM) simulations were also performed in order to understand the dominant Ti64 deformation mode and development of residual stress in the coatings. Spray angle is identified to be an effective process parameter to control porosity, pore alignment and extent of surface compressive residual stress in the CS deposited materials. • Ti-6Al-4V powders were cold-sprayed onto Al6061-T6 substrates at 50, 60, 70 & 90°. • Decreasing spray angle led to increasing porosity & decreasing residual stress in Ti64. • Spray angle greater than 70° led to dense coating with low porosity • FEM simulation shows shear deformation induced compressive residual stress in Ti64. • Spray angle is an effective parameter to control cold-sprayed deposits' properties.

The Role of Oxidative Stress in the Pathogenesis of Vitiligo: A Culprit for Melanocyte Death.

Vitiligo is a common chronic acquired pigmentation disorder characterized by loss of pigmentation. Among various hypotheses proposed for the pathogenesis of vitiligo, oxidative stress-induced immune response that ultimately leads to melanocyte death remains most widely accepted. Oxidative stress which causes elevated levels of reactive oxygen species (ROS) can lead to dysfunction of molecules and organelles, triggering further immune response, and ultimately melanocyte death. In recent years, a variety of cell death modes have been studied, including apoptosis, autophagy and autophagic cell death, ferroptosis, and other novel modes of death, which will be discussed in this review in detail. Oxidative stress is also strongly linked to these modes of death. Under oxidative stress, ROS could induce autophagy by activating the Nrf2 antioxidant pathway of melanocytes. However, persistent stimulation of ROS might eventually lead to excessive activation of Nrf2 antioxidant pathway, which in turn will inactivate autophagy. Moreover, ferroptosis may be triggered by oxidative-related transcriptional production, including ARE, the positive feedback loop related to p62, and the reduced activity and expression of GPX4. Therefore, it is reasonable to infer that these modes of death are involved in the oxidative stress response, and that oxidative stress also acts as an initiator for various modes of death through some complex mechanisms. In this study, we aim to summarize the role of oxidative stress in vitiligo and discuss the corresponding mechanisms of interaction between various modes of cell death and oxidative stress. These findings may provide new ideas for exploring the pathogenesis and potential therapeutic targets of vitiligo.

Dynamic stress analysis of a metro bogie due to wheel out-of-roundness based on multibody dynamics algorithm

In metro vehicle systems, the dynamic stress and vibration of the bogie frame have a significant impact on the safety and reliability of vehicles. This study presents a fracture failure analysis of the bogie frame for the metro vehicle. The analysis consists of a bogie frame dynamic stress test, a wheel out-of-roundness (OOR) measurement and a vibration transmissibility test of the vehicle which is also used for operational modal analysis of the bogie frame. The field test result shows that the bending of cross beam combined with torsion of side beams(49.5 Hz) which are aroused by the wheel OOR mainly contribute to the fatigue failure of the bogie frame. To investigate the effect of wheel OOR on the fatigue failure of the bogie frame, the multibody system (MBS) model of the metro vehicle was developed. The MBS model accounts for the flexibility of the bogie frame and the nonlinearity of wheel-rail contact. Furthermore, the modal stress recovery method was adopted to study the dynamic responses of the bogie frame. The measured wheel OOR data is used to validate the efficiency of the model and investigate the characteristics of dynamic stress in time histories as well as frequency spectra. Moreover, the dynamic stress of fracture site in the bogie frame with consideration of ideal polygonal wear in radial deviation including different orders and variable amplitudes was investigated. The phase shift of wheel OOR between different wheels proves to be influential in the bogie frame vibration and thus the characteristics of dynamic stress change accordingly. The recommended limit values of wheel OOR amplitude are shown based on numerical results.

Elastic-plastic Buckling Analysis of Q690 High Strength Steel Tubes Under Global Bending

In recent years, high-strength steel has been used extensively for infrastructures because of its many advantages, such as its ductility and strain-hardening properties, which are inferior to those of ordinary structural steel, and the small dimensions of the structural elements, which lead to greater freedom and elegance in design, resulting in lighter structures. In practice, imperfections such as residual stresses due to the welding process and pre-buckling mode imperfections are inevitable in cylindrical structures made of high-strength steel. A small imperfection amplitude can lead to a disproportionate reduction in buckling strength. Therefore, imperfection sensitivity should be considered when studying the buckling behaviour of the shell. The influence of the combined residual stress and pre-buckling mode imperfection on the buckling behaviour of Q690 high strength steel cylindrical shell under global bending has not yet been investigated and described for all dimensions. In this paper, the combined imperfections influences on the buckling behaviour of high-strength steel cylindrical shell in global bending in the elastic-plastic range are investigated. Using the ABAQUS fine elements software, perfect cylinders with a constant length to thickness ratio equal to 7 and a radius to thickness ratio in the range 10≤ r/t ≤700 were considered to perform the linear bifurcation analysis (LBA) and the geometric nonlinear analysis (GNA). The non-linear analysis with imperfections (GNIA) and the geometric and material non-linear analysis with imperfections (GMNIA) were then performed considering imperfection amplitudes between 0.01 and 2 to derive the critical buckling loads known as bifurcation point for the models with different aspect ratio. The influences of the combined imperfections show that moderately and very thin cylinders are very sensitive to the increase of the pre-buckling mode imperfection amplitude and their buckling strength is insensitive to plasticity. For thick cylinders, the effect of plasticity is more consistent, while the buckling strength is not significantly affected by the increase in pre-buckling mode imperfection amplitude. The main objective is to predict the buckling sensitivity of cylinders under the influence of combined residual stress and pre-buckling mode imperfection. The obtained results, comments and conclusions intend to allow for safer.

Novel dual-direction electrostatic discharge device with lateral PNP transistor

With the shrinking of semiconductor technology and the increasing of integrated circuits, electrostatic discharge (ESD) as a common natural phenomenon has become one of the main reasons for the failure and reliability reduction of electronic products in integrated circuits. A novel dual-direction ESD device (PNP_DDSCR) with embedded lateral PNP transistor is proposed for diminishing ESD damage. The response process and current transportation of PNP_DDSCR under different ESD stress modes are investigated. Comparative analyses between conventional DDSCR and PNP_DDSCR are executed by TCAD simulation. On the stage of device triggering, the embedded lateral PNP transistor inner DDSCR system provides triggering current for device. The injection efficiency of parasitic transistor in the DDSCR system is improved, and the positive feedback system is promoted. Thus, the holding voltage of PNP_DDSCR is higher than that of conventional DDSCR. At the same time, an extra triggering path introduced by embedded lateral PNP transistor of PNP_DDSCR makes the total triggering path of device shorten. Therefore, the transient overshoot voltage of PNP_DDSCR is lower than that of DDSCR. For thermal performance, most of the heat first accumulates near the lateral PNP transistor , and then the peak point of heat turns to main SCR path with the conduction of PNP_DDSCR. The heat accumulation in PNP_DDSCR is shared by the path of embedded lateral PNP transistor. As a result, the average temperature in PNP_DDSCR is lower than that in DDSCR and the ability of PNP_DDSCR to dissipate heat is more perfect. Comparing with DDSCR, the conclusions are obtained. Under the condition of transmission line pulse (TLP) test simulation analyses, the triggering voltage is reduced by 31%, the holding voltage is increased by 16.8%, the ESD design window is optimized by 44.5%, and on-resistance is lower. When TLP stress is 2.67 A, the average temperature of PNP_DDSCR is much lower than that of traditional DDSCR in the whole conduction process. With the increase of pulse lasting time, average temperature difference between two devices becomes great further. According to the very fast TLP (VF-TLP) testing results, clamping capability of PNP_DDSCR under transient overshoot voltage is more stable under the condition of fast turn-on speed. When the VF-TLP stress is 0.1 A, the overshoot voltage of PNP_DDSCR device is the 37% of that of DDSCR device while the PNP_DDSCR maintains a relatively fast triggering speed. Thus, the ESD protection capability of PNP_DDSCR is superior.

Relationship with Hot Workability and Texture Evolution in an Al-Zn-Mg-Cu Alloy Under Hot Compressive Stress Mode

Relationship with Hot Workability and Texture Evolution in an Al-Zn-Mg-Cu Alloy Under Hot Compressive Stress Mode

A numerical analysis of friction stir welded joint using FEA

The present work deals with numerical analysis of welding by the FEM. Attempts have been made to determine temperature distribution, distortion, and residual stresses due to welding by finite element method in welded plate structures. General-purpose finite element software ANSYS was used. The FE analysis is split into two parts. To acquire the global temperature history generated during the welding process, a nonlinear transient thermal analysis is initially performed. The temperatures acquired from the thermal analysis are then used as loading to the stress mode in the stress analysis. Though the numerical model gives a more accurate result always there occurs a difference between the numerical result and the experimental result an error of 10.53% between the experimental and the simulated result was obtained.

Multi-objective Optimisation of Torsion Beam Structure of Driverless Vehicle Chassis for Improved Fatigue Resistance

The fatigue resistance of the torsion beam is the keyway to prolong the service life of the chassis of the driverless vehicle. The rigid-flexible coupling finite element model of the chassis is constructed using anti-fatigue algorithm. In this model, the stress time history of the torsion beam is obtained by modal stress recovery. The nominal stress method is used to analyze the fatigue life of the structure. It is known that the structure weight affects the fatigue life, so the algorithm aims at lightening the structure to realize the improved fatigue resistance of the torsional beam structure. The parametric model of torsion beam is constructed with mass and fatigue life as optimization objectives, first-order torsion mode frequency and torsion stiffness as constraints. Multi-objective particle swarm optimization (MPSO) based on the Kriging model is used to achieve improved fatigue life of the torsion beam. After optimization, the structural weight of the torsion beam is reduced by 19.20%, and the light-weight and anti-fatigue effect are better than the baseline design.

Graphene oxide incorporated flexible and free-standing PVDF/ZnO composite membrane for mechanical energy harvesting

Here we report the comparative study of mechanical energy harvesting properties of highly flexible, stretchable and free-standing poly (vinylidene fluoride) (PVDF) membranes loaded with various nanofillers like zinc oxide (ZnO), graphene oxide (GO) and ZnO/GO composites. Composite polymer membranes with dominating β-crystalline phase have been synthesized by effectively simpler and low-cost chemical synthesis method. The mechanical to electrical energy conversion is observed by measuring output voltage and current signal while repetitive mechanical stress is applied to the composite membranes in different modes like tapping, bending and stretching. Sufficient increment in open circuit voltage and short circuit current is observed in each mode of mechanical vibrations applied to both ZnO and GO loaded composite membranes compared to the pristine PVDF host matrix. The enhancement in output deliverable electrical power is attributed to the polar nature of ZnO and the formation of GO conduction network in composite membranes. The self-poled β-crystalline tri-phase PVDF/ZnO/GO composite membranes demonstrate the best energy harvesting performances among all the composites in each mode of mechanical stresses, making them suitable for flexible nanogenerators.

Failure behavior of electromagnetic driven nailing riveted joint for Al/steel structures subjected to fatigue loading

Electromagnetic high-speed nailing (E-HSN) has wide application prospect due to the advantage of high flexibility, unilateral operation and excellent performance. In this paper, the fatigue behavior of E-HSN joints with the aluminum alloy 5052 (Al)/high-strength steel DP590 (HSS) structure was systematically studied. The fatigue tests were conducted and Basquin equation was used to fit the fatigue data. Fatigue fracture were observed. The results showed that the joint had two typical fatigue failure modes. The cyclic stress of 253 MPa was the critical point of two failure modes. The rivet shank fractured under a higher cyclic stress (mode 1, over or equal to the critical point) and rivet head fractured under a lower cyclic stress (mode 2, below the critical point). Moreover, the fracture appearance was analyzed to reveal the failure mode and mechanism of the joints. The quasi-cleavage fracture in the fatigue fracture mode 1 was characterized by ductile and brittle mixed fracture. For the fatigue fracture mode 2, cleavage cracks appeared cleavage fan shape due to the large-angle grain boundary. Finally, based on the damage evolution model, the fatigue life prediction values of E-HSN joints were obtained. The predicted results were basically distributed within 2 times error band, which showed good accuracy and consistency.

Improving carbohydrate accumulation in Chlamydomonas debaryana induced by sulfur starvation using response surface methodology.

Most methods that promote carbohydrate production negatively affect cell growth and microalgal biomass production. This study explores, in a two-stage cultivation strategy, in Chlamydomonas debaryana the optimization of certain culture conditions for high carbohydrate production without loss of biomass. In the first stage, the interaction between sodium bicarbonate supplementation, aeration, and different growth periods was optimized using the response surface methodology (RMS). The 3-factor Box-Behnken design (BBD) was applied, and a second-order polynomial regression analysis was used to analyze the experimental data. The results showed that 0.45g L-1 of sodium bicarbonate combined with a good aerated agitation (0.6 L min-1) and a cultivation period of 18days are optimal to produce 5.02g L-1 of biomass containing 43% of carbohydrates.Under these optimized growth conditions, accumulation of carbohydrates was studied using different modes of nutritional stress. The results indicated that carbohydrate content was improved and the maximum accumulation (about 60% of the dry weight) was recorded under sulfur starvation with only a 14% reduction in biomass as compared to control. This study showed promising results as to biomass production and carbohydrate yield by the microalgae C. debaryana in view of production of third-generation biofuels.

Comparison of diabetes to other prognostic predictors among patients referred for cardiac stress testing: A contemporary analysis from the REFINE SPECT Registry

BackgroundDiabetes mellitus (DM) is increasingly prevalent among contemporary populations referred for cardiac stress testing, but its potency as a predictor for major adverse cardiovascular events (MACE) vs other clinical variables is not well delineated. Methods and ResultsFrom 19,658 patients who underwent SPECT-MPI, we identified 3122 patients with DM without known coronary artery disease (CAD) (DM+/CAD−) and 3564 without DM with known CAD (DM−/CAD+). Propensity score matching was used to control for the differences in characteristics between DM+/CAD− and DM−/CAD+ groups. There was comparable MACE in the matched DM+/CAD− and DM−/CAD+ groups (HR 1.15, 95% CI 0.97-1.37). By Chi-square analysis, type of stress (exercise or pharmacologic), total perfusion deficit (TPD), and left ventricular function were the most potent predictors of MACE, followed by CAD and DM status. The combined consideration of mode of stress, TPD, and DM provided synergistic stratification, an 8.87-fold (HR 8.87, 95% CI 7.27-10.82) increase in MACE among pharmacologically stressed patients with DM and TPD > 10% (vs non-ischemic, exercised stressed patients without DM). ConclusionsPropensity-matched patients with DM and no known CAD have similar MACE risk compared to patients with known CAD and no DM. DM is synergistic with mode of stress testing and TPD in predicting the risk of cardiac stress test patients.

The Glucocorticoid Receptor-Dependent Stress Response in Human Erythropoiesis Is BCL11A-Dependent

Extrapolations from data in mouse models and from human erythroid cells expanded ex vivo with the glucocorticoid receptor (GR) agonist Dexamethasone (Dex), suggest that GR plays an important role in the regulation of stress erythropoiesis 1. However, the mechanistic details of stress erythropoiesis are still poorly understood.By exploring the effects of Dex on erythroid expansion of CD34+ cells from a large number of healthy adult donors (n=25), we documented that Dex expands a population of immature erythroid cells which express high levels of BCL11A. In addition, in these cells BCL11A is mostly in the nuclei, compared to cells grown without Dex. These results suggest that GR regulates the transcriptional activity of BCL11A.To validate the role of BCL11A in the Dex response, we made observations in cells from patients with BCL11A deficiencies 2. We found that BCL11A-deficient CD34+ cells generate lower numbers of maturing erythroid cells compared to controls with Dex addition, suggesting that they respond poorly to Dex (Fig 1). Of note, RNAseq analyses indicate that erythroid cells expanded from the patients express levels of BCL11A lower than that of their parent cells while the levels of expression of other genes known to mediate the response to Dex of erythroid cells (ZFP36L2, CDKNIC and PPARA 3-5) expressed by these cells is normal.Further we extended our observations to Cushing's patients with highier cortisol levels, before(V1) and after their treatment(V2) using concurrent age and weight matched healthy controls (MC). There is no significant difference in frequency of CD34+ cells among V1, V2 and MC (range 0.3-2% in all cases). CD34 pos cells from all groups express similar levels of cKIT, IL-3Rβ, CXCR4 and CALR. However, a greater proportion of CD34+ cells from V1 express CD36 and CD110 (the thrombospondin and thrombopoietin receptor) and CD133 (the hematopoietic stem cell marker prominin) than those from V2 and MC (60-80% vs 10-20%), suggesting that the circulating progenitor cells from active Cushing's patients are a unique population likely generated in response to their high cortisol levels given that the phenotype of CD34+ cells from the blood of V2 patients is similar to that found in MC. The phenotype of CD34+ cells from Cushing's patients in vivo is similar to that of CD34+ cells generated in vitro after 2-4 days of culture with Dex 3,6,7. V1 progenitor cells generate similarly large number of immature erythroid cells in culture with and without Dex. By contrast with normal cells, these active cells also express lower levels of the cytoplasm-restricted form of GRα (GRS203) and greater levels of GILZ and BCL11A than normal or V2 cells.In conclusion, the data presented here indicate that GR activation switches the erythroid differentiation program from the steady-state to the stress mode and that activation of BCL11A is part of the response of erythroid cells to Dex.References1) Varricchio et al Am J Blood Res. 2014;4:53; 2) Funnell et al Blood 2015; 126:89; 3) Ashley et al JCI 2020;130:2097; 4) Zhang L et al Nature 2013;499:92; 5) Lee et al Nature 2015;522:474; 6) Heideveld et al Haematologica 2015; 100:1396; 7) Xiang et al Blood 2015;125:1803. [Display omitted] DisclosuresMigliaccio: Dompe farmaceutici Spa R&D: Other: received funding for reserach .

Topology Optimization and Design for Additive Manufactured Supporting Structure of Vehicle Rudder

The object investigated in this work is a design method for the supporting structure of vehicle rudders, which are the crucial components in flight control system. As a practical application of topology optimization for additive manufacture, the design process was presented in this article. To obtain the optimal material distribution, topology optimization based on SIMP method was applied, with compliance minimization as the optimization objective. A numerical optimization model was built and calculated in Inspire, and the result in an equivalent load scheme of 30 percent point load and 70 percent uniform pressure was adopted to be the initial geometry for the subsequent design. Concentrating on realizing the optimized geometry, this design took a series of technical constrains for additive manufacture and mass requirements into consideration. Notably, the FEM simulation for the supporting structure is necessary, which consist of stress analysis and mode analysis. And the technical feasibility was verified in its practical manufacturing process. Finally, by the experiment about dynamic characteristic, it is verified that the lightweight rudder designed in this work can satisfy all the requirements for flight control.

Experimental and numerical analysis on rectangular concrete-filled steel tubular columns with T-shaped stiffeners

Rectangular concrete-filled steel tubular (RCFST) columns are widely used in mega frame-core tube-outrigger truss super high-rise buildings, yet the local buckling of the steel tube may cause a large amount of waste on the steel material. In order to resolve this problem, this paper investigates the axial compression behavior of giant RCFST columns with T-shaped stiffeners by means of experimental and numerical analysis. Firstly, axial compression tests on 12 RCFST columns are conducted. The experimental results indicate that T-shaped stiffeners can improve the ultimate bearing capacity of RCFST columns, and the effect is more significant with the increase of the width-to-thickness ratio of the steel tube. However, T-shaped stiffeners have little effect on improving the ductility of axial compression members. Secondly, finite element (FE) models are established using ABAQUS and are verified against the experimental results. Subsequently, detailed parametric analysis and theoretical derivation are conducted based on the validated FE models. The results reveal the variation law of critical buckling stress and failure mode with respect to stiffness ratio. Finally, the design equations and procedures of T-shaped stiffeners in RCFST columns are obtained, by which the cross-section size of T-shaped stiffeners can be optimized, leading to a more economical design.

Correlation analysis of stress and family function and coping modes in pregnant women with pregnancy-induced hypertension syndrome.

Pregnancy-induced hypertension is a common complication in obstetrics and an important cause of maternal death. We explored the correlations among stress, family function and coping mode in women with pregnancy-induced hypertension syndrome. A total of 58 pregnant women with pregnancy-induced hypertension syndrome were included in the study. The perceived stress scale (PSS), family assessment device (FAD), and medical coping modes questionnaire (MCMQ) were used to assess stress level, family function, and coping mode, respectively. The PSS score was 28 (interquartile range: 20-43). The total FAD score was 128.1±27.1. The subscale scores were problem-solving, affective responsiveness, communication, roles, behavior control, affective involvement, and general function, in order of decreasing score. Significant correlations were noted between PSS score and total FAD score, affective responsiveness, problem-solving, communication, roles, affective involvement, and behavior control (all P<0.05). PSS score was significantly correlated with "Escape" (P=0.016) and "Yield" (P<0.001) in the MCMQ. Single-factor analysis showed that education level, average household income, and FAD total score were significantly different in those with a low or high PSS score. Logistic regression indicated the FAD total score as an independent factor for the PSS score. Women with pregnancy-induced hypertension syndrome with a high PSS score tended to adopt the "Escape" and "Yield" coping modes. Family function integrity is essential for reducing PSS scores.

Sensitivity of an infinite-strip-shaped polyvinylidene fluoride film in an underwater plane sound field

The sensitivity of an infinite-strip-shaped polyvinylidene fluoride (PVDF) film in an underwater plane sound field is analyzed in this paper. The high-frequency sensitivity is characterized by the resonances of the symmetrical in-plane stress modes with traction-free boundary conditions at the ends of the film and by the anti-resonances due to the superposition of the stress components. The low-frequency sensitivity exhibits a simple hydrostatic response. The directional property of the in-plane stress component, generated by the incident sound across the thickness, has two contributions. The first is from the aperture and dipolar functions of the incident sound pressure over the PVDF surfaces and at the two ends of the film. The second is from an amplitude modulation by an angle-dependent gain. The directional property of the in-plane stress component by the sound pressure at the two ends of the film is only controlled by the dipolar function, and that of the stress component in the thickness direction is only determined by the aperture function. The illustration of the frequency and directional features of the PVDF film may advance understanding of the mechanisms involved in generating the voltage output of PVDF by an incident sound field.

Non-linear mean-field modelling of UD composite laminates accounting for average asymmetric plasticity of the matrix, debonding and progressive failure

As an effective and accurate method for modelling composite materials, mean-field homogenization is still not well studied in modelling non-linear and damage behaviours of UD composites. Investigated micro FE-simulations show that the matrix of UD composites exhibits different average plastic behaviour, named as average asymmetric matrix plasticity (AAMP), when the composite behaves different under shear, longitudinal and transverse loadings. In this study, a non-linear mean-field debonding model (NMFDM) combining a mean-field model and a fibre–matrix interface debonding model, is developed to simulate UD composites under consideration of AAMP, fibre–matrix interface damage and progressive failure. AAMP is considered by using so-called stress mode factor, which is expressed in terms of basic invariants of the matrix deviatoric stress tensor and is used as an indicator for detection of differences in the loading mode. The material behaviour of UD composites with imperfect interface is assumed identical as for perfect interface and stiffness reduced fibres. Progressive failure criteria are established with consideration of fibre breakage and matrix crack for different fibre orientations. As a representative example for the NMFDM, a C30/E201 UD composite is studied. To verify the model, experiments are conducted on polymers, carbon fibres and UD CFRPs. Finally, the model is applied to simulate a perforated CFRP laminate, which shows excellent prediction ability on deformation, debonding and progressive failure.

Embedding artificial neural networks into twin cohesive zone models for composites fatigue delamination prediction under various stress ratios and mode mixities

This paper presents for the first time a novel numerical technique for modelling fatigue delamination growth in fibre reinforced composites, which is based on coupling two twin cohesive zone models with a single-hidden-layer artificial neural network. The simulation approach proposed here can describe composites fatigue delamination under negative & positive stress ratios and the full range of mode mixities. In the modelling strategy, each segment of a composites interface is described by two twin cohesive elements, which jointly provide local fracture mechanics parameters into a feedforward single-hidden-layer neural network, without the need to know the global load R ratio. In turn, the neural network algorithm feeds the fatigue crack propagation rate da/dN back into the twin cohesive elements, which follow a static and fatigue cohesive law in a synchronous fashion. The novel modelling methodology has been implemented in an explicit finite element scheme. The modelling strategy is first verified and validated by several benchmark cases, involving mode I Double Cantilever Beam tests, mode II End Loaded Split tests with and without reversal, as well as Mixed-Mode Bending tests. A relevant application of the modelling technique is demonstrated considering a tapered laminate, which experiences non-proportional loading due to the presence of combined static tension and cyclic bending.

Effects of forces on chromatin.

Chromatin is a unique structure of DNA and histone proteins in the cell nucleus and the site of dynamic regulation of gene expression. Soluble factors are known to affect the chromatin structure and function via activating or inhibiting specific transcription factors. Forces on chromatin come from exogenous stresses on the cell surface and/or endogenous stresses, which are regulated by substrate mechanics, geometry, and topology. Forces on chromatin involve direct (via adhesion molecules, cytoskeleton, and the linker of nucleoskeleton and cytoskeleton complexes) and indirect (via diffusion and/or translocation processes) signaling pathways to modulate levels of chromatin folding and deformation to regulate transcription, which is controlled by histone modifications and depends on magnitude, direction, rate/frequency, duration, and modes of stresses. The rapid force transmission pathway activates multiple genes simultaneously, and the force may act like a “supertranscription factor.” The indirect mechanotransduction pathways and the rapid force transmission pathway together exert sustained impacts on the chromatin, the nucleus, and cell functions.