Magnitude Of Strain Research Articles

Numerical Investigation of the Evolving Inelastic Deformation Path of a Solder Ball Joint under Various Loading Conditions

Solder joints of ball grid arrays (BGA) have been widely used to connect electronic components to printed circuit boards (PCBs) and are often subjected to mechanical stress. Several studies have been conducted on the mechanical reliability of solder joints. While these studies have been useful in the industry, detailed studies on how the inelastic deformation path of the solder ball joints evolves under specific loading conditions have not been sufficiently reported. This study aims to understand how the inelastic deformation path evolves when a solder joint is subjected to a constant external force by utilizing the theory of mechanics. It has also been found that the mechanical failure is strongly influenced by the evolution history of the deformation modes in materials. For this study, an elastoplastic constitutive model and a ductile fracture criterion were implemented into the vectorized user-defined material (VUMAT) subroutine of the ABAQUS program for finite element (FE) analysis. With the model, the evolution of the inelastic deformation path of a single solder ball under different loading conditions was numerically analyzed. Three loadings (shear, compression, and bending) were chosen as the basic loading conditions. In addition, combinations of the basic loadings resulted in three dual loadings and one complex loading. The simulation results showed that the shear and bending caused the fracture for both single and dual loadings, but when combined with compression, the fracture was suppressed. The results indicate that fracture is not solely determined by the magnitude of equivalent plastic strain but also by the evolution of inelastic deformation mode. This research offers an improved understanding of the significance of the inelastic deformation path and fracture.

Design and optimization of lightweight bending strain energy harvesters using irradiation cross-linked polypropylene ferroelectret

In this work, a concept for bending strain energy harvesting with lightweight ferroelectrets subject to metallic host structures is proposed. The energy harvester (EH) works with the ferroelectret irradiation cross-linked polypropylene (IXPP) and uses the piezoelectric δ 33-mode by transferring in-plane bending strain energy of a host structure to a compression of an IXPP stack. This is achieved with a simple and lightweight transmission made of structural steel. In this way, a high ratio of generated power per used EH mass can be achieved, being the main design goal of this paper. To demonstrate this, miniature EHs as unit cells for larger EH systems are investigated. The strain magnitude of the excitation in an aircraft wing of at 1.5 Hz from previous work is partly taken into account for calculations. In an analytical modeling approach, the energy conversion abilities of the presented concept is compared to concepts using lead zirconate titanate ceramics to stress the usefulness in cases where strain energy is the prominent source of vibration energy. Further, an optimization algorithm is presented for a static and a dynamic case without a host structure and for a dynamic case with an aluminum host structure. The optimized power output and power output per total EH mass for the three cases is calculated to and , 0.7 mW and 80 mW kg−1 as well as (at 1 N excitation magnitude) and (at 1 N excitation magnitude) respectively. Finally, experimental results for case three are presented to validate the model of the proposed and optimized EH topology up to 500 Hz. The results further show a good mechanical reproducibility of the measured transfer behavior and a fairly good reproducibility of the mechanical-electrical results due to deviations in material properties. A comparison of the model with the experimental results shows a good agreement. Therefore a linear ferroelectret model appears to be suitable to predict the system behavior in lower and higher frequency ranges as well as for high ferroelectret material strains. The optimized EH provides a comparably high ratio of power output per mass when added to a structure like an aircraft which is shown in a comparison to other research works. The performance in a real application can be further improved to 52 mW within a 1 m2 area using a clustering approach, discussed in the paper. Large deformations of lightweight structures like aircraft wings at low and high frequencies can thus be exploited to provide enough electrical power decentrally for low-power consumers.

Abstract 12735: Investigating Cardiac Function After Anthracycline Exposure in Childhood Cancer Survivors With Modifiable Cardiovascular Risk Factors

Introduction: Anthracycline exposure can lead to cardiac dysfunction, which may possibly be worsened by secondary cardiovascular risk factors (CVRFs), such as hypertension, hyperlipidemia, obesity and diabetes. The prognostic impact of CVRFs in childhood cancer survivors is largely unknown. Now with advanced cardiac imaging, it is now possible to identify how CVRFs might influence subclinical cardiac function. Hypothesis: Anthracycline-exposed childhood cancer survivors with CVRFs will demonstrate echocardiogram-based subclinical cardiac dysfunction more frequently than those without. Methods: This is a single-center, retrospective study. Inclusion criteria are: < 18 years old, history of anthracycline-containing chemotherapy and 2 echocardiograms performed. Exclusion criteria are: congenital cardiac disease, subsequent cancer relapse and inadequate imaging quality. Echocardiographic images were analyzed for longitudinal left ventricular strain, left ventricular ejection fraction (LVEF) and myocardial performance index (MPI). Wilcoxon rank-sum test was used to compare measures of cardiac function between patients with at least one CVRF (at time of cancer diagnosis) and patients without. Results: There were 111 patients identified with 49.5% having dysfunction at some point in time. CVRFs were identified in 19 patients with the majority of those being obese (52.6%). At baseline, there was a statistically significant difference in mean strain between those with CVRFs vs those without (-19.4% vs -21.3%). At 1-6 months after chemotherapy completion, LVEF was significantly reduced in those with CVRFs vs those without (48.7% vs 59.7%) as well as mean strain (-15.8% vs -20.0%). At >5 years after chemotherapy, there was a decrease in strain magnitude in those with CVRFs vs those without (-17.7% vs -20.5%) along with abnormal mean MPI (0.57 vs 0.44). Conclusions: Anthracycline-exposed pediatric cancer survivors with CVRFs demonstrate reduced cardiac function at baseline and both at near-and long-term follow-up. Further investigation is warranted to investigate the significance of these reduced echocardiographic measures and CVRFs among childhood cancer survivors to mitigate cardiac morbidity as they age into adulthood.

Abstract 14417: Regional 4D Cardiac Magnetic Resonance Strain Associates With Late Gadolinium Enhancement in Duchenne Muscular Dystrophy Associated Cardiomyopathy

Introduction: Cardiomyopathy (CM) is the leading cause of death in Duchenne muscular dystrophy (DMD). Onset and clinical progression are varied. Cardiac magnetic resonance (CMR) late gadolinium enhancement (LGE) can detect fibrofatty replacement prior to decreased left ventricular ejection fraction (LVEF) but requires administration of gadolinium contrast agents. Non-contrast methods to characterize CM onset and progression could decrease scan time and exposure to gadolinium. Using a novel 4D (3D+time) regional strain analysis method, we hypothesized that the regional magnitude of surface area strain (E a ) would be significantly decreased in DMD patients with LGE and that E a would correlate with decreased LVEF . Methods: Short-axis cine CMR images for 43 pediatric DMD patients (13.6 ± 4.2 years) were compiled into 4D sequences for regional strain analysis (Fig. 1A). For all 4D sequences, epi- and endocardial borders were segmented across one cardiac cycle for kinematic analysis using a custom-built MATLAB graphical user interface (MathWorks, Natick, MA). Regional E a was measured by determining the relative change in the localized 4D endocardial surface mesh compared to end-diastole. Unpaired t-test and Spearman’s rho were used to determine statistical significance and correlation. Results: DMD patients had a range of CM severity: 13 with reduced LVEF of <55% (30% of total) and 28 with LGE (65% of total). Peak E a was significantly different between patients with and without LGE in the basal inferior ( p =0.022), basal inferolateral ( p <0.001), basal anterolateral ( p =0.002), mid inferolateral ( p =0.004), mid anterolateral ( p =0.018), and apical anterior ( p <0.032), regions (Fig.1B). Basal E a also correlated significantly with LVEF ( rho =-0.45, p< 0.001; Fig. 1C). Conclusion: Regional E a from 4D CMR in DMD was reduced in patients with LGE compared to those without LGE particularly in the basolateral regions. Peak basal E a correlated with a reduction in LVEF. LVEF.

Abstract 16832: Biomarker Enhanced Risk Prediction of Incident Heart Failure in Low-Risk Patients: The Atherosclerosis Risk in Communities (ARIC) Study

Background: Primary prevention strategies to reduce heart failure (HF) burden are urgently warranted. The Pooled Cohort equations to Prevent HF (PCP-HF) risk score is a validated risk tool that integrates readily available parameters obtained in primary care setting to estimate the 10-year risk for incident HF. Although PCP-HF performs well for high-risk individuals, the model’s predictive utility for low-risk individuals may potentially be enhanced by integration of biomarkers. Methods: In this study, the PCP-HF risk score was derived from data collected at visit 5 (2011-2013) of the ARIC cohort study and its 5-year predictive accuracy was investigated using surveillance data up to 2019. Participants with <10% PCP-HF risk probability of incident HF were classified as low-risk. Incremental improvement in predicting incident HF by including laboratory and imaging-based biomarkers in the low-risk population was analyzed by logistic regression, by calculating the area under the curve (AUC) from receiver operating characteristics. Results: Of 4980 study participants with 5 years of follow up, 47% had a low PCP-HF risk score (mean age 73 years, 71% women, 32% Black). Of these, 3% developed HF within 5 years. Compared to those with a high PCP-HF risk score, individuals with low PCP-HF risk score were younger, more often female and Black; had lower left ventricular (LV) mass index and left atrial volume index, higher magnitude of LV global longitudinal strain, and lower levels of NT-proBNP and hs-TnT. On further analysis, the model incorporating laboratory and imaging-based biomarkers exhibited greater predictive accuracy for incident HF compared to the original PCP-HF risk score in this low-risk population (AUC: 0.85 vs 0.62). Conclusion: The integration of laboratory and imaging-based biomarkers with the PCP-HF risk score enhances the predictive accuracy of risk modeling for incident HF, especially in individuals identified as low-risk by the 10-year risk prediction tool.

Feature-Tracking Strain Parameters Differ Between Highly Accelerated and Conventional Acquisitions: A Multisoftware Assessment.

Cardiac magnetic resonance imaging protocols have been adapted to fit the needs for faster, more efficient acquisitions, resulting in the development of highly accelerated, compressed sensing-based (CS) sequences. The aim of this study was to evaluate intersoftware and interacquisition differences for postprocessing software applied to both CS and conventional cine sequences. A total of 106 individuals (66 healthy volunteers, 40 patients with dilated cardiomyopathy, 51% female, 38±17y) underwent cardiac magnetic resonance at 3T with retrospectively gated conventional cine and CS sequences. Postprocessing was performed using 2 commercially available software solutions and 1 research prototype from 3 different developers. The agreement of clinical and feature-tracking strain parameters between software solutions and acquisition types was assessed by Bland-Altmann analyses and intraclass correlation coefficients. Differences between softwares and acquisitions were assessed using Kruskal-Wallis analysis of variances. In addition, receiver operating characteristic curve-derived cutoffs were used to evaluate whether sequence-specific cutoffs influence disease classification. There were significant intersoftware ( P <0.002 for all except LV end-diastolic volume per body surface area) and interacquisition differences ( P <0.02 for all except end-diastolic volume per body surface area from Neosoft, left ventricular mass per body surface area from cvi42 and TrufiStrain and global circumferential strain from Neosoft). However, the intraclass correlation coefficients between acquisitions were strong-to-excellent for all parameters (all ≥0.81). In comparing individual softwares to a pooled mean, Bland-Altmann analyses revealed smaller magnitudes of bias for cine acquisition than for CS acquisition. In addition, the application of conventional cutoffs to CS measurements did not result in the false reclassification of patients. Significantly lower magnitudes of strain and volumetric parameters were observed in retrospectively gated CS acquisitions, despite strong-to-excellent agreement amongst software solutions and acquisition types. It remains important to be aware of the acquisition type in the context of follow-up examinations, where different cutoffs might lead to misclassifications.

In vitro effect of horseshoe length on hoof wall deformation, expansion, and strain

Abstract Shoeing techniques have the potential to affect hoof growth, causing abnormal hoof conformations, which in turn put affected horses at risk for lameness and injury. Racehorses are often shod with shorter shoe branches which may predispose them to underrun heel hoof conformation. Horseshoe branch length was tested to determine the effect on hoof wall deformations, expansion, strain and fetlock extension during midstance limb loading. Our hypotheses were that shortening of the shoe branch length would increase fetlock extension, increase compressive strains at the heel, and change principal strain directions in a proximodorsal direction. Nine cadaveric forelimbs were loaded in vitro to simulate mid-stance from walk to canter loads. Analysis of variance was used to assess the effect of horseshoe (no shoe, short shoe, full shoe, and long shoe) on outcome variables. Hoof wall expansion and lateral hoof wall distortion did not differ among treatments. Principal compressive hoof wall strain magnitudes were greater than principal tensile strain magnitudes. As shoe length increased principal compressive strains decreased, except for the middle quarter location; shear strains increased for distal locations and decreased at the proximal heel location; and principal strain directions viewed on the lateral side of the right hoof rotated in a counterclockwise direction at middle and distal quarter locations. Results do not provide evidence that a shorter shoe increases fetlock extension. Additionally, as the shorter shoe had similar strain results to that of an unshod hoof, it is unclear if a shorter shoe could lead to the development of abnormal hoof conformations. Other factors that may play a role in changes of hoof conformation including surface type, amount of exercise and frequency of trimming as well as other planes within the xyz coordinate system for the fetlock and hoof should be investigated.

Effect of truck and train loading on permanent deformation and fatigue cracking behavior of asphalt concrete in flexible pavement highway and asphaltic overlayment track

Abstract This research investigated the largest magnitude of displacement and horizontal tensile strain in several critical locations within the asphalt concrete (AC) layer in both the flexible pavement highway (FPH) and asphaltic overlayment track (AOT) structure using the numerical modeling method. The role of the hauling loads, speed, and loading cycles of freight truck’s dumps and freight train’s wagons on the mechanical behavior of FPH and AOT in terms of the permanent deformation and fatigue cracking was examined. Furthermore, the performance of the FPH and AOT in terms of permanent deformation and fatigue cracking characteristics due to various magnitudes of hauling loads, speed, and loading cycles of freight truck’s dumps and freight train’s wagons was compared to determine the optimum infrastructure for the freight coal transportation, based on the hauling capacity as well as the magnitude of permanent deformation and the horizontal tensile strain of the AC layer. According to the findings of this study, it is suggested to choose the AOT structure with fourth or sixth loading systems to run the freight coal transportation with the highest magnitude of the hauling capacity of 360,000 tons, since it produces the minimum magnitude of the permanent deformation and fatigue cracking of the AC layer. Future research should be conducted to examine the potential and the characteristics of fatigue cracking due to the contact between the edge of the sleeper and the surface of the AC layer in AOT.

Dynamic finite element modelling of the macaque mandible during a complete mastication gape cycle.

Three-dimensional finite element models (FEMs) are powerful tools for studying the mechanical behaviour of the feeding system. Using validated, static FEMs we have previously shown that in rhesus macaques the largest food-related differences in strain magnitudes during unilateral postcanine chewing extend from the lingual symphysis to the endocondylar ridge of the balancing-side ramus. However, static FEMs only model a single time point during the gape cycle and probably do not fully capture the mechanical behaviour of the jaw during mastication. Bone strain patterns and moments applied to the mandible are known to vary during the gape cycle owing to variation in the activation peaks of the jaw-elevator muscles, suggesting that dynamic models are superior to static ones in studying feeding biomechanics. To test this hypothesis, we built dynamic FEMs of a complete gape cycle using muscle force data from in vivo experiments to elucidate the impact of relative timing of muscle force on mandible biomechanics. Results show that loading and strain regimes vary across the chewing cycle in subtly different ways for different foods, something which was not apparent in static FEMs. These results indicate that dynamic three-dimensional FEMs are more informative than static three-dimensional FEMs in capturing the mechanical behaviour of the jaw during feeding by reflecting the asymmetry in jaw-adductor muscle activations during a gape cycle. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

Human muscle-tendon unit mechanobiological responses to consecutive high strain cyclic loading.

In response to a mechanical stimulus, tendons have a slower tissue renewal rate compared with muscles. This could, over time, lead to a higher mechanical demand (experienced strain) for the tendon, especially when a high strain magnitude exercise is repeated without sufficient recovery. The current study investigated the adaptive responses of the human triceps surae (TS) muscle-tendon unit (MTU) and extracellular matrix turnover-related biomarkers to repetitive high tendon strain cyclic loading. Eleven young adult males performed a progressive resistance exercise over 12 consecutive days, consisting of high Achilles tendon (AT) strain cyclic loading (90% MVC) with one leg once a day (LegT1) and the alternate leg three times a day (LegT3). Exercise-related changes in TS MTU mechanical properties and serum concentrations of extracellular matrix turnover-related biomarkers were analysed over the intervention period. Both legs demonstrated similar increases in maximal AT force (∼10%) over the 12day period of exercise. A ∼20% increase in maximal AT strain was found for LegT3 (P<0.05) after 8 consecutive exercise days, along with a corresponding decrease in AT stiffness. These effects were maintained even after a 48 h rest period. The AT mechanical properties for LegT1 were unaltered. Biomarker analysis revealed no sign of inflammation but there was altered collagen turnover and a delay in collagen type I synthesis. Accordingly, we suggest that tendon is vulnerable to frequent high magnitude cyclic mechanical loading as accumulation of micro-damage can potentially exceed the rate of biological repair, leading to increased maximal tendon strain.

Strain and Burden among Caregivers of Stroke Survivors in Punjab: A Cross-Sectional Study

Introduction: Caregivers may feel stressed and burdened while caring for a stroke survivor. However, very few studies have assessed the burden among caregivers of Indian stroke patients. Objectives: The present study was done to assess the magnitude and predictors of strain and burden among caregivers of stroke survivors discharged from a tertiary care hospital in Punjab, India. Method: This cross-sectional study included consecutive newly diagnosed stroke patients from January 2021 till April 2022 at a tertiary care teaching hospital in Amritsar, India. The level of strain and burden among the caregivers was assessed using the Caregiver’s strain index (CSI) and Zarit Caregiver Burden Scale (ZCBS) respectively. A minimum sample size of 110 stroke patients was calculated. Odds ratios were calculated for identifying predictors of strain and burden among caregivers using multivariate regression analysis. Results: Mean CSI for all caregivers was 6.67 ± 1.81. Using a cut-off of ≥ 7, authors found 40.2% of the caregivers to have great strain. Modified rankin scale (mRS) at the time of interview (AOR = 2.77, p value = 0.0063), presence of comorbidities in the patient (AOR = 3.07, p value = 0.023 and caregiver being female (AOR = 2.96, p value = 0.036) to be significantly associated with higher odds of having great strain. Using ZCBS, 18.1% had minimal burden, 53.5% had mild to moderate burden, 24.4% had moderate to severe burden and 3.9% had severe burden. mRS at the time of interview (AOR = 5.38, p value = 0.0048), presence of comorbidities in the patient (AOR = 7.63, p value = 0.0031), caregiver being female (AOR = 9.67, p value = 0.0072) and not being at all confident to care (AOR = 4.94, p value = 0.013) to be significantly associated with higher odds of having great burden, while rural residence (AOR = 0.55, p value = 0.0011) was associated with lower odds of high burden. Conclusion: High strain was observed among 40.1% of the care givers of Indian stroke survivors and 24.4% had moderate to severe burden. Thus, the strain and burden among caregivers of Indian stroke patients is very high.

Preservation of Circumferential and Radial Left Ventricular Function as a Mitigating Mechanism for Impaired Longitudinal Strain in Early Cardiac Amyloidosis

In patients with cardiac amyloidosis (CA), left ventricular ejection fraction (LVEF) is frequently preserved, despite commonly reduced global longitudinal strain (GLS). We hypothesized that nonlongitudinal contraction may initially serve as a mitigating mechanism to maintain cardiac output and studied the relationship between global circumferential (GCS) and radial (GRS) strain with LVEF and extracellular volume (ECV), a marker of amyloid burden. Patients with CA who underwent cardiac magnetic resonance (CMR; n=140, 70.7±11.5years, 66% male) or echocardiography (n=67, 71±13years, 66% male) and normal controls (CMR, n=20; echocardiography, n=45) were retrospectively identified, and GCS, GLS, and GRS were quantified using feature-tracking CMR or speckle-tracking echocardiography and compared between CA patients with preserved and reduced LVEF (CAHFpEF, CAHFrEF) and controls. The prevalence of impaired strain (magnitudes <2.5th percentile of the controls) was compared between CAHFpEF and CAHFrEF and between ECV quartiles. While echocardiography-derived GLS was impaired in both CAHFpEF (-13.4%±3.1%, P<.003) and CAHFrEF (-9.1%±3.2%, P<.003), compared with controls (-20.8%±2.4%), GCS was more impaired in CAHFrEF compared with both controls (-15.6%±5.0% vs -32.3%±3.3%, P<.003) and CAHFpEF (-30.4%±5.7%, P<.003) and did not differ between CAHFpEF and controls (P=.24). The prevalence of abnormal CMR-derived GCS (P<.0001) and GRS (P<.0001) but not GLS (P=.054) varied significantly across ECV quartiles. Among CA patients with preserved LVEF, preserved GCS and GRS, despite near-universally impaired GLS, may be explained by an initial predominantly subendocardial involvement, where mostly longitudinal fibers are located. If confirmed in future studies, these findings may facilitate identification of patients with early stages of CA, when treatments may be most effective.

Effect of Cu Doping on Phase Transition, Thermal Strain, and Thermal Expansion Property in Polycrystalline Ni50Mn23−xCuxGa27 Alloys

The influence of Cu doping on phase transition, thermal strain, and thermal expansion property of polycrystalline Ni50Mn23−xCuxGa27(x = 1, 3, 5, 6 and 7) alloys is investigated. The results show that with increasing Cu concentration, martensitic transformation gradually gets close to Curie transition. A magnetostructural transition (MST) is observed in samples with x = 6 and 7. Such MST can enhance magnitude of transformation strain. Besides, Ni50Mn23−xCuxGa27 alloys possess an isotropic, recoverable, and thermally stable thermal strain. Excitedly, Cu doping can effectively tune the phase transition, thermal strain, and thermal expansion properties of Ni50Mn23−xCuxGa27 alloys. Adjustable coefficients of thermal expansion from positive to negative are obtained by Cu‐doped Ni50Mn23−xCuxGa27 alloys. The average linear expansion coefficient (α) between −140.44 and −207.70 ppm K−1 is observed in samples with x = 6 and 7 for a narrow temperature span of 11–14 K. When the temperature span is about 72 K (x = 6) and 73 K (x = 7), which is the largest temperature span observed in Ni–Mn–Ga‐based alloys recently, the α values decrease to about −36 ppm K−1. These findings are beneficial for manipulating the thermal expansion property of Ni–Mn–Ga–Cu alloys and their multifunctional applications.

Landslide susceptibility evaluation in Alpine environment: 1. 3D Finite Element modeling of the Ruinon (IT) case study

This manuscript is Part 1 of two companion papers that explore a multidisciplinary approach to predict velocity and stability of a large landslide located in the Central Italian Alps: the Ruinon landslide. The area is of high geological interest due to the presence of numerous shallow and deep gravitational instability processes that affect valley flanks, mainly driven by unfavorable morphological conditions and geomechanical properties of rock masses. In this manuscript, a 3D finite element model (FEM) was implemented in order to analyze the stress–strain distribution along the Ruinon rock-slope. Goals are to define the relation between morphological factors, mechanical parameters and the development of irreversible strains. The model was defined based on morphological features and mechanical properties detected along the slope, as well as on piezometric data from the landslide monitoring system. In a first step of the analysis, a static simulation was carried out under dry conditions. Then, a validation process was performed by comparing numerical outputs with geomorphological field observations. Finally, a parametric analysis was carried out where different piezometric level scenarios were evaluated in order to assess the influence of both mechanical parameters and pore pressure on the distribution of high sliding susceptibility areas. By overlaying satellite images with the model outputs, results were shown to accurately reproduce the extent of the slope areas subject to active gravitational instability. Parametric analyses showed a clear relationship between the input factors and the magnitude of strain, while the extension of areas subject to irreversible deformation did not change significantly. Stress distribution and stress–strain relations defined in this article are subsequently introduced in a thermo-hydro-mechanical (THM) numerical model presented in Part 2 of this work, where the evolution of the Ruinon landside is simulated.

Effect of prior processing on the decomposition of the β phase in Ti–Nb alloys during intermediate heat treatments

Metastable β-Ti alloys exhibit multiple decomposition pathways during isothermal ageing. Ages at intermediate temperatures below the α/β transus result in the formation of α or isothermal ω. The effect of prior processing on these pathways remains largely unexplored within the literature. Therefore, the role of processing on a Ti–Nb alloy was investigated in cold rolled and solutioned conditions. The solutioned sample showed evidence of recrystallisation, with shear bands remnant from the prior cold rolling that exhibited a greater degree of texture than the surrounding material. During isothermal ageing ωiso was observed outside of these bands whilst α phase precipitated within the bands and throughout the cold rolled sample. This shows that the remnant strain from the rolling process facilitated α nucleation over ωiso due to accommodation of the α/β interface. Additionally, it was seen that the magnitude of internal strains had a marked effect on the α morphology observed.

A framework for predicting residual mechanical response fields for laser powder bed fusion at the polycrystalline length scale

A framework is developed to directly model the effect of processing parameters utilized during laser powder bed fusion additive manufacturing (LPBF AM) on material thermomechanical response during solidification in order to predict residual stress and strain development at the microstructure-resolved polycrystalline length scale. Specifically, a workflow is established where the processing parameters serve as input to a cellular automata finite element (CAFE) model that simulates the microstructure solidification evolution via a thermally driven empirical solidification law. The CAFE’s output microstructures serve as representative volume elements which are input to a Multiphysics finite element solver, which solves the thermally driven mechanical response during solidification based on the crystal plasticity finite element formulation. A model validation study is presented, which demonstrates that the modeling framework accurately predicts various features of intragrain misorientation when compared to electron backscatter diffraction data of an LBPF 316L thin wall part built using a GE/Concept Laser M2 SLM system. Following model validation, four variations of processing parameters are chosen to investigate the influence of scan strategy and laser scan velocity on the manufacturing of an LPBF 316L thin wall. Also included is an analogous simulation that treats the microstructure as isotropic and homogeneous, which allows for quantifying the contribution of microstructural heterogeneity on residual stress and strain distribution and magnitudes. Correlations between processing parameters, temperature fields, texture and grain morphology, and the resulting as-built mechanical response are determined and discussed. The current research has the potential to provide valuable insights and guidance for designing AM build conditions to optimize residual mechanical response together with grain structures and textures.

Variability in tibia-fibular geometry is associated with increased tibial strain from running loads.

Variation in tibial geometry may alter strain magnitude and distribution during locomotion. We investigated the effect of tibia-fibula geometric variations on tibial strain with running loads applied at various speeds. Participant-specific three-dimensional models of the tibia-fibula were created using lower limb computed tomography scans from 30 cadavers. Finite-element models were developed in FEBio, and running loads from 3, 4 and 5 m s-1 were applied to extract effective strain from the tibial shaft. Linear regression models evaluated the relationship between geometric characteristics and effective strain along the tibial shaft. We found a statistically significant positive relationship between: (i) increased thickness of the midshaft to upper tibia with increased condyle prominence and effective strain at points along the distal anterolateral and proximal posterior regions of the tibial shaft; and (ii) increased midshaft cortical thickness and effective strain at points along the medial aspect of the distal tibial shaft. It is possible that increased thickness in the more proximal region of the tibia causes strain to redistribute to areas that are more susceptible to the applied loads. A thickness imbalance between the upper and distal portions of the tibial shaft could have a negative impact on tibial stress injury risk.

Suffusion in gap-graded granular soils subjected to strain-controlled cyclic loading with coupled CFD-DEM method

The suffusion mechanism of gap-graded soils subjected to cyclic loading, which is common in foundations of transportation engineering and marine structures, has not been fully understood. This paper employs the coupled computational fluid dynamics and discrete element method (CFD-DEM) to investigate the effect of cyclic loading on suffusion. The cyclic loading is simulated in a strain-controlled way, by which, samples with different frequencies (i.e., 0.5 Hz, 1 Hz, and 2 Hz) and strain amplitudes (i.e., 0.5 %, 1 %, 2 %) undergo erosion of 20 s duration with a constant hydraulic gradient and confining pressure. The influence of cyclic loading on suffusion is examined from both the macroscopic and microscopic perspective through the capture of erosion mass, void ratio variation, particle velocity field, fines trajectory, and force chain. Results indicate that the higher the cyclic frequency and strain magnitude, the more severe the loss of the fines. The vibratory compaction of dynamic loading could lead to the clogging of the sample, decreasing the hydraulic conductivity. In addition, the different micromechanisms of fines erosion during loading and unloading is presented.

A Study on the Influence of Double Tunnel Excavations on the Settlement Deformation of Flood Control Dikes

This article combines numerical simulation and field monitoring methods to study the stability of the overlying Liuyang River embankment in the tunnel crossing between Huaqiao Station and Rice Museum Station of Changsha Metro’s Line 6. Using AutoCAD, 3Dmine, and COMSOL Multiphysics, a calculation model of the entire subway tunnel section crossing the flood control embankment under the coupling of fluids and solids was established. The process of tunnel-crossing the embankment and the variation in spatial displacement and plastic strain in different geological layers were analyzed from the perspective of time evolution and spatial distribution. The research results show that during the process of crossing the embankment, the deformation of the east bank is greater than that of the west bank, and crossing the west bank is the relatively riskier stage of the entire project. Moreover, during the process of crossing the embankment, the overlying soil layer will produce a plastic strain zone, and only a small amount of plastic strain is generated in the surrounding sandstone layer of the tunnel walls. In terms of the magnitude of plastic strain, the plastic strain area produced by the leading tunnel’s surrounding rocks is larger than that of the following tunnel. As the excavation progresses, a funnel-shaped settlement displacement gradually forms during the passage of the leading tunnel, and this settlement funnel gradually expands during the passage of the following tunnel, with the maximum settlement point transitioning from directly above the leading tunnel to the middle position between the two tunnels. Using the jitter filter algorithm and the adjacent average method to process the field monitoring data, the results show that the monitored deformation results well match the simulated settlement results.

Association of insulin use with LV remodeling and clinical outcomes in diabetic patients with heart failure and reduced ejection fraction: assessed by cardiac MRI

BackgroundInsulin is commonly used in type 2 diabetes mellitus (T2DM) to achieve glycemic control. However, recent evidence showed that insulin use is associated with poor outcomes in the context of heart failure (HF). Since heart failure with reduced ejection fraction (HFrEF) accounts for approximately 50% of cases in the general HF population, we aimed to evaluate the effect of insulin treatment on left ventricular (LV) remodeling and contractility abnormalities in a HFrEF cohort and assess whether insulin was a predictor of adverse outcomes in this entity.MethodsA total of 377 HFrEF patients who underwent cardiac MRI were included and divided according to diabetes status and the need for insulin treatment. LV structural and functional indices, as well as systolic strains, were measured. The determinants of impaired myocardial strains were assessed using linear regression analysis. The associated endpoints were determined using a multivariable Cox proportional hazards model.ResultsT2DM patients on insulin displayed a higher indexed LV end-diastolic volume and LV mass than those with T2DM not on insulin or those without T2DM, despite similar LV ejection fractions, accompanied by a higher three-dimensional spherical index (P < 0.01). Worse longitudinal and circumferential peak systolic strain was shown to occur in T2DM patients on insulin (P < 0.01). Insulin treatment was independently associated with impaired magnitudes of systolic strain. The median follow-up duration was 32.4 months (IQR, 15.6–43.2 months). Insulin treatment remained consistently associated with poor outcomes after adjustment for established confounders, with an adjusted hazard ratio of 3.11; (95% CI, 1.45–6.87; P = 0.009) in the overall cohort and 2.16 (95% CI, 1.08–4.59; P = 0.030) in the diabetes cohort.ConclusionsInsulin may further lead to adverse LV remodeling and contractile dysfunction in the context of HFrEF with T2DM. Considerable care should be taken when treating HFrEF patients with insulin.