Stress Patterns Research Articles

Functional adaptation of the infant craniofacial system to mechanical loadings arising from masticatory forces.

The morphology and biomechanics of infant crania undergo significant changes between the pre- and post-weaning phases due to increasing loading of the masticatory system. The aims of this study were to characterize the changes in muscle forces, bite forces and the pattern of mechanical strain and stress arising from the aforementioned forces across crania in the first 48 months of life using imaging and finite element methods. A total of 51 head computed tomography scans of normal individuals were collected and analysed from a larger database of 217 individuals. The estimated mean muscle forces of temporalis, masseter and medial pterygoid increase from 30.9 to 87.0 N, 25.6 to 69.6 N and 23.1 to 58.9 N, respectively (0-48 months). Maximum bite force increases from 90.5 to 184.2 N (3-48 months). There is a change in the pattern of strain and stress from the calvaria to the face during postnatal development. Overall, this study highlights the changes in the mechanics of the craniofacial system during normal development. It further raises questions as to how and what level of changes in the mechanical forces during the development can alter the morphology of the craniofacial system.

Crack initiation life of aviation gear pair

Abstract The gear transmission system is an important part of the aero-engine. The most serious fault is tooth root fatigue fracture. This paper mainly discusses the time of fatigue crack initiation stage of aviation gear tooth root position. The crack initiation state can be evaluated by analyzing the root stress. The static contact analysis is solved by using the generated aviation gear pair model. The maximum stress in the bending direction of gear teeth is calculated. The changing pattern of tooth root stress with meshing position is described in detail. According to the multi-axial stress fatigue theory, the surface damage parameters and fatigue life of the gear tooth root position are calculated, and the location of the crack initiation is obtained. Fatigue cracks often appear at half of the gear tooth width and near the tooth root circle.

A Phono-stylistic Analysis of Utterance Stress in Steve Harvey's talk show

patterns of utterance stress in discourse direct attention to specific themes and reactions, controlling the flow and coherence of conversation. this study examines the utterance stress in Steve Harvey's selected episodes from a phono-stylistic perspective. this study is hoped to improve understanding of linguistic mechanism in talk show communication, highlighting the importance of phonetic features in transmitting meaning and increasing broadcast conversation participation. the researcher concentrates on the types of focus functions of utterance stress of some episodes available on YouTube. to conduct the analysis, the researcher adopts (Carr, 2013; Davenport& Hannahs 2005) to analyze utterance stress and Leech and Short (2007) to examine the stylistic features of the data selected. based on the adopted model, the study concludes: the study utilizes utterance stress, focus and content. while stylistic features include syntax, vocabulary, narrative viewpoint, politeness, impoliteness and cultural references.

Psychological Stress and Coping Pattern among Patients with Vitiligo

Psychological Stress and Coping Pattern among Patients with Vitiligo

Unveiling hemodynamic pulsatile flow dynamics in carotid artery stenosis: Insights from computational fluid dynamics

This paper presents a comprehensive model of hemodynamic pulsatile flow within the carotid artery, examining both normal conditions and those affected by stenosis. The primary focus lies in visualizing shear stress along the inner walls, aiming to elucidate how stenosis alters blood flow characteristics and subsequently impacts plaque deposition. Utilizing advanced computational fluid dynamics simulations, temporal variations in flow patterns, velocity profiles, and pressure gradients resulting from stenosis are captured, thereby elucidating the mechanical forces exerted on arterial walls. Moreover, this study analyzes the influence of hemodynamic parameters, such as Reynolds number, Womersley number, and arterial geometry, on flow disruption and stagnation points. Such insights are critical in understanding the mechanisms underlying plaque formation and progression. Critical thresholds of shear stress and flow patterns contributing to endothelial dysfunction and atherosclerotic lesion initiation are identified by comparing hemodynamic environments in healthy vs stenotic arteries. The results demonstrate significant differences in hemodynamic characteristics between stenosed and normal arteries, particularly near systolic peaks. Stenosed arteries exhibit notably higher velocities at arterial bifurcations during systole than normal arteries, indicative of altered flow dynamics. In addition, stenosis disrupts flow patterns, leading to vortex formation at locations beyond systolic peaks. Overall, findings from this research advance our understanding of cardiovascular disease pathogenesis and provide valuable insights into the hemodynamic effects of arterial stenosis.

Relation between edge stress, bending strength, surface stress and fracture pattern of thermally toughened glass

Thermally toughened safety glass must meet safety requirements in the building industry. Here, destructive tests are defined in the product standards, which must be carried out on small, standardized format (360 mm × 1100 mm) glass elements to determine the fracture pattern and bending strength. This is costly and not in the interests of sustainability. As part of the quality control of optical anisotropy effects in thermally toughened glass, isochromatic scans that can provide information on the edge stress are acquired. The evaluation of the isochromatics and retardations at the edge with deduction of the edge stress and transfer to bending strength and fracture pattern could provide essential findings for assuring the safety requirements of thermally toughened glass. In this experimental investigation, the surface and edge stress were measured on standardized format thermally toughened safety glass, with different edge processing and glass thicknesses from three different suppliers. Afterwards, the fracture pattern is controlled, or the bending strength is analyzed in a destructive four-point bending test. Conclusively, the results from the photoelastic and destructive tests are compared to determine whether the photoelastic measurement methods used to measure surface and edge stress can be employed as quality control.

Изотермическое прессование в конической матрице релаксирующего материала

The relations for calculating the deformation mode and force conditions of isothermal extrusion of blanks made of high-strength metallic alloys are proposed. Under isothermal deformation, the material is hardened and softened, which is associated with the manifestation of the viscous properties of the material (creep). In this regard, the state of viscoplasticity is taken on. The deformation state is accompanied by stress relaxation, which is greater the lower the speed (longer duration) of the operation. Based on the mechanics of deformation, the dependence of moulding conditions (deformation, force, damage to the work material) is expressed by analytical relations. The power balance of activity of forces results in a pressure estimation for isothermal exposure. In this case, a discontinuous field of path velocities is used, which consists of a block of deformations and rigid blocks. The blocks are separated by slip surfaces. Deformations occur in the deformation block and on slip surfaces. Since pressing leads to the occurrence of micro-damages, the damage rate of the coating material was estimated. In this case, the criteria of fracture kinetics are used: energy and deformation equations. The damage rate of the material depends on the speed and degree of deformation, or solely on the degree of deformation. For a number of materials, reducing the speed helps to reduce damage and, consequently, the possibility of increasing the degree of shaping of the primary blank. The relations for stiffness analysis of the stress pattern are given, on which the damage also depends. Calculations of the pressure and damage of the material under compaction for blanks made of titanium and high-strength aluminum alloys have been performed. It is shown that at low operation speeds on the appropriate hydraulic forging equipment, the exposure pressure decreases significantly. The aluminum alloy damaging is also reduced, and for titanium it depends only on the degree of forming.

Evaluating stress and displacement in the craniomandibular complex using Twin Block appliances at varied angles: A finite element study

ObjectivesThe objective of this investigation was to assess the stress and displacement pattern of the craniomandibular complex by employing finite element methodology to simulate diverse angulations of inclined planes that are incorporated in the Twin Block appliance. MethodsA 3D finite element representation was established by use of Cone Beam Computed Tomography (CBCT) scans. This comprehensive structure included craniofacial skeletal components, the articular disc, a posterior disc elastic layer, dental elements, periodontal ligaments, and a Twin Block appliance. This investigation is the first to incorporated inclined planes featuring three distinct angulations (45, 60, and 70°) as the study models. Mechanical impacts were evaluated within the glenoid fossa, tooth, condylar, and articular disc regions. ResultsIn all simulations, the stress generated by the Twin Block appliance was distributed across teeth and periodontal ligament, facilitating the anterior movement of mandibular teeth and the posterior displacement of maxillary teeth. Within the temporomandibular joint region, compressive forces on the superior and posterior facets of the condyle diminished, coinciding with the stress configuration that fosters condylar and mandibular growth. Stress dispersion homogenized in the condylar anterior facet and articular disc, with considerable tensile stress in the glenoid fossa's posterior aspect conforming to stress distribution that promote fossa reconfiguration. The 70° inclined plane exerts the highest force on the tissues. The condyle's maximum and minimum principal stresses are 0.36 MPa and −0.15 MPa, respectively, while those of the glenoid fossa are 0.54 MPa and −0.23 MPa. ConclusionThree angled appliances serve the purpose of advancing the mandible. A 45° inclined plane relative to the occlusal plane exerts balanced anteroposterior and vertical forces on the mandibular arch. Steeper angles yield greater horizontal forces, which may enhance forward growth and efficient repositioning.

Childhood Apraxia of Speech: A Descriptive and Prescriptive Model of Assessment and Diagnosis.

Childhood apraxia of speech (CAS) represents a significant diagnostic and therapeutic challenge within the field of clinical neuropsychology, characterized by its nuanced presentation and multifactorial nature. The aim of this study was to distil and synthesize the broad spectrum of research into a coherent model for the assessment and diagnosis of CAS. Through a mixed-method design, the quantitative phase analyzed 290 studies, unveiling 10 clusters: developmental apraxia, tabby talk, intellectual disabilities, underlying speech processes, breakpoint localization, speech characteristics, functional characteristics, clinical practice, and treatment outcome. The qualitative phase conducted a thematic analysis on the most cited and recent literature, identifying 10 categories: neurobiological markers, speech motor control, perceptual speech features, auditory processing, prosody and stress patterns, parent- and self-report measures, intervention response, motor learning and generalization, comorbidity analysis, and cultural and linguistic considerations. Integrating these findings, a descriptive and prescriptive model was developed, encapsulating the complexities of CAS and providing a structured approach for clinicians. This model advances the understanding of CAS and supports the development of targeted interventions. This study concludes with a call for evidence-based personalized treatment plans that account for the diverse neurobiological and cultural backgrounds of children with CAS. Its implications for practice include the integration of cutting-edge assessment tools that embrace the heterogeneity of CAS presentations, ensuring that interventions are as unique as the children they aim to support.

An integrated three-dimensional aeromechanical analysis for the prediction of stresses on modern coaxial rotors

This paper presents the first application of an Integrated Three-Dimensional aeromechanical analysis—defined as the coupled solution of three-dimensional finite element-based structural dynamics with a three-dimensional Reynolds-Averaged Navier-Stokes-based fluid dynamics—to predict the stresses on a modern coaxial rotor. The coupling was carried out with the University of Maryland’s structural dynamic solver X3D and the U.S. Army’s CREATETM–AV Helios suite of fluid dynamic solvers. A modern four-bladed hingeless coaxial rotor model—inspired by the gross dimensions of the Sikorsky S-97 Raider but generic and open source otherwise—is developed as a demonstration test case. The new structural solver is driven by parallel and scalable solvers and advanced high performance computing. It is enabled by high-order three-dimensional brick finite elements unified with multibody dynamics, integrated aerodynamics, and a special 3D-to-1D fluid-structure interfaces refines the power of delta-coupling procedure while retaining the advantages of existing CFD mesh motion schemes. The analysis predicts the three-dimensional stresses on the rotor blades and hub, together with the deformations, airloads, and wake, in an integrated manner. Two flight conditions are studied: a low-speed flight at 37 knots and a high-speed flight at 150 knots. Interesting three-dimensional unsteady stress patterns are revealed all across the blade but particularly inboard of 50% rotor radius—patterns that change from flight to flight and have remained invisible until now—since they could neither be predicted nor measured in flight. The maximum axial stresses exhibited 3/rev variation at low speed, and 2/rev variation at high speed flight. The lower rotor carried higher oscillatory stress burden at low speed, whereas both the rotors shared the same stress burden at high speed flight. The key conclusion is that such analysis is now indeed possible, and the stress patterns they reveal provide deeper insights into the dynamics of advanced rotors, and these might provide a path toward mitigating them in the future.

The 3D stress field of Nordland, northern Norway – insights from numerical modelling

Abstract The Nordland area in northern Norway is the seismically most active area on mainland Fennoscandia. It exhibits patterns of coastal extension, which contrasts with the first-order regional stress pattern that reflects compression aligned with the North Atlantic ridge push. The regional stress field has been considered to emanate from the interaction of ridge push and glacial isostatic adjustment; while the local stress pattern can be additionally influenced by gravitational, topographic stresses, as well as the flexural effects of erosion and sediment deposition. We employ finite element numerical models at a crustal scale to study the 3D stress field, using existing geometric constraints from previous geophysical studies. Internal body forces, induced by variations in density, topography or Moho depth, already yield significant deviatoric stresses. In the models tested, these can strongly influence the near-surface stress regime, in particular for the continental margin setting we are investigating. In addition, redistribution of rock mass, which occurred mainly under Pleistocene glaciation, can modify the stress field significantly on a semi-regional scale. We consider this process to be the main driver for the coastal extension, in particular in areas where erosion has been high.

Dietary and Lifestyle Characteristics and Metabolic Disorders in Reproductive-Age Women: Explorative Study in Peshawar Pakistan

Background: In rural areas, women significantly contribute to both household and agricultural activities. Their involvement in diverse tasks impacts their health, emphasizing the need to study how their lifestyle, dietary habits, and stress levels relate to metabolic health. Objective: This cross-sectional study aims to examine the relationship between lifestyle, dietary diversity, psychological stress, and metabolic indicators among rural women of reproductive age. Methods: Data were collected from 300 women aged 20 to 40, free from chronic conditions, using standardized subjective and objective measures. These included assessments of nutritional status, psychosocial factors, dietary habits, physical activity, sleep duration, body composition, blood pressure, and fasting glucose levels. Dietary patterns were analyzed using Principal Component and Factor Analysis via SPSS. Results: The average age of the participants was 27 years. Mean weight was 61.7 ± 14.2 kg and mean height 156.3 ± 5.7 cm. About 31% were overweight and 13% underweight. The average Perceived Stress Score was 14.9, with 47.5% experiencing low stress and 8.5% high stress. Dietary diversity was low for 42.5% of the women. Sedentary lifestyles correlated strongly with adverse metabolic indicators. Principal dietary patterns identified were savory cereals, dairy-based vegetables, and high-fat red meat. High-fat red meat consumption showed strong correlations with increased BMI and visceral body fat. Conclusion: Lifestyle factors, psychological stress, and dietary patterns, especially high consumption of red meat and fat, significantly influence metabolic health among rural women.

Biomechanical mechanisms of anterior cruciate ligament injury in the jerk dip phase of clean and jerk: A case study of an injury event captured on-site

BackgroundWeightlifting exposes athletes to significant loads, potentially placing the knee joint in an abnormal mechanical environment and leading to anterior cruciate ligament (ACL) injuries. Once an ACL injury occurs, it can affect athletes’ competitive ability to varying degrees and even prematurely end their career. Understanding the biomechanical mechanisms of ACL injuries in weightlifters helps in comprehensively understanding the stress patterns and degrees on ACL during human movement, and identifying potential injury-causing factors, thereby enabling the implementation of appropriate preventive measures to reduce the occurrence of injuries. This study aimed to explore the biomechanical mechanisms of ACL injuries during the jerk dip phase of clean and jerk in weightlifters, providing a theoretical basis for the prevention of ACL injuries in weightlifting sports. MethodsThis study utilized the German SIMI Motion 10.2 movement analysis system and the AnyBody simulation system to analyze the kinematic and dynamic parameters of a 109 kg + class weightlifter (height: 191 cm, age: 22 years, weight: 148 kg, athletic level: elite) performing a 205 kg clean and jerk (non-injured) and a 210 kg clean and jerk (ACL injury occurred). The differences in kinematic and dynamic indicators of lower limb joints under injured and non-injured jerk dip conditions were investigated. ResultsKnee joint torque during non-injured clean and jerk was consistently positive (i.e., external rotation) but turned from positive to negative (i.e., from external rotation to internal rotation) during injured clean and jerk and reached a maximum internal rotation torque of 21.34 Nm at the moment of injury. At every moment, the muscle activation and simulated muscle force of the quadriceps and gastrocnemius during the injured clean and jerk were higher than those during the non-injured clean and jerk. By contrast, the muscle activation and simulated muscle force of the semitendinosus, semimembranosus, biceps femoris, and soleus during non-injured clean and jerk were higher than those during injured clean and jerk. The knee joint internal rotation angle during injured clean and jerk first increased and then declined, reaching a peak at 46.93° at the moment of injury, whereas it gradually increased during non-injured clean and jerk. The proximal tibia on the left side during the injured clean and jerk moved forward faster by 0.76 m/s compared with that during the non-injured clean and jerk. ConclusionsThe small muscle activation and simulated muscle force of the hamstring and soleus could not resist timely and effectively the large muscle activation and simulated muscle force of the quadriceps (especially the medial quad) and gastrocnemius. As such, the force applied to the ACL could exceed its ultimate load-bearing capacity. Kinematic indicators in the athlete's injured lift demonstrated certain disparities from those in their non-injured lift. Knee internal rotation and tibial anterior translation during the jerk dip phase of weightlifting might be the kinematic characteristics of ACL injuries.

Numerical analysis of stress and distortion in bulk deposited structures of Inconel 625 alloy: Influence of deposition strategies

This study explores the numerical analysis of effective stress and distortion (dimensional variations) in bulk deposited structures of Inconel 625 alloy with seven different deposition strategies using wire arc additive manufacturing (WAAM) process. Due to the challenges in detecting in-situ stress changes during bulk deposition, numerical analysis is employed to approximate stress distribution. The goal is to investigate stress and distortion (dimensional variations) in the build direction (BD), longitudinal and transverse directions, and understand their impact on anisotropy and asymmetry. The findings reveal distinct patterns in effective stress, with initial decrease in bottom, followed by a gradual increase at the middle and rapid increase thereafter, regardless of deposition strategies. Parallel and contour deposition strategies exhibit lower effective stress compared to spiral strategies. Distortion (dimensional variations) along the BD increases with height, and parallel strategies result in higher distortion. The parallel strategies show increasing distortion from one edge to the other, while spiral and contour strategies lead to high distortion at the center. The parallel and contour deposition strategies exhibit higher compressive stress at the bottom and middle compared to the spiral strategies. Anisotropy analysis indicates higher stress anisotropy in parallel and contour patterns, but lower distortion anisotropy compared to spiral patterns. Empirical equations are developed to understand the relationship between stress, distortion (dimensional variations) and hardness. The study suggests that higher effective stress can adversely affect material yielding behavior. This study undertakes a comparison between FEA and analytical model which reveals a close alignment in the residual stress distributions in the build direction.

Directed biomechanical compressive forces enhance fusion efficiency in model placental trophoblast cultures.

The syncytiotrophoblast is a multinucleated structure that arises from fusion of mononucleated cytotrophoblasts, to sheath the placental villi and regulate transport across the maternal-fetal interface. Here, we ask whether the dynamic mechanical forces that must arise during villous development might influence fusion, and explore this question using in vitro choriocarcinoma trophoblast models. We demonstrate that mechanical stress patterns arise around sites of localized fusion in cell monolayers, in patterns that match computational predictions of villous morphogenesis. We then externally apply these mechanical stress patterns to cell monolayers and demonstrate that equibiaxial compressive stresses (but not uniaxial or equibiaxial tensile stresses) enhance expression of the syndecan-1 and loss of E-cadherin as markers of fusion. These findings suggest that the mechanical stresses that contribute towards sculpting the placental villi may also impact fusion in the developing tissue. We then extend this concept towards 3D cultures and demonstrate that fusion can be enhanced by applying low isometric compressive stresses to spheroid models, even in the absence of an inducing agent. These results indicate that mechanical stimulation is a potent activator of cellular fusion, suggesting novel avenues to improve experimental reproductive modelling, placental tissue engineering, and understanding disorders of pregnancy development.

A comparative analysis of the puncturing abilities of cephalopod beak rostra using engineering tools

Cephalopods, a diverse class of carnivorous marine predators, exhibit a wide range of feeding behaviours and foraging strategies related to their lifestyle, habitat and morphological adaptations. Their beaks play a crucial role in capturing and processing prey. This study investigates the link between the shape of the rostrum of cephalopod beaks and their function through a mix of experimental and computational approaches. Fourteen upper beak rostrum models from a range of cephalopod species, representing their morphological and ecological diversity, were 3D-printed, and subjected to uniaxial puncture tests. Force and displacement were recorded to estimate puncture ability. Finite Element Analysis (FEA) was used to explore the form–function relationship under loading conditions mimicking biting and pulling, analysing stress patterns across different rostrum morphologies. The results show that rostrum size significantly influenced puncture performance, with smaller rostra requiring less force and displacement for puncturing. However, larger rostra exhibited higher structural stiffness, suggesting increased vulnerability to stress during biting. Morphology-driven tests demonstrated species-specific differences in puncture abilities, with rostrum sharpness playing a crucial role. FEA results further indicated that longer and sharper rostra were more susceptible to stress, potentially impacting their overall structural integrity. The findings highlight the trade-off between rostrum size and sharpness in cephalopod beaks, with implications for prey selection and feeding efficiency. The study contributes to understanding the morpho-functional aspects of cephalopod beaks and their role in prey capture and consumption, shedding light on the evolutionary pressures shaping these remarkable marine predators.

Exploration on the enhanced mechanism of copper surface tribology by WS2 from MD simulation

This study employs molecular dynamics (MD) simulations with Stillinger-Weber (SW) and Embedded Atom Method (EAM) potentials to investigate the tribological behavior of WS2 coatings on a copper substrate against spherical alumina indenter. Various loads, rotational speeds, and temperatures are explored to analyze their effects on tribological properties. The investigation reveals compelling insights: load-dependent frictional behavior, elucidation of non-linear stress patterns with rotational speeds, and the discernment of temperature-induced alterations in friction coefficient. Furthermore, through detailed analysis utilizing Radial Distribution Function (RDF) methodology, molecular rearrangement dynamics are unveiled, enriching our understanding of the WS2-copper interplay. This research contributes to understanding the intricate dynamics of WS2 coatings and copper interactions, crucial for optimizing tribological performance in practical applications.

Effects of thermal cycling on residual stress in alloy parts via selective laser melting

Contradictory interpretation of the parameter dependence of residual stress in alloy parts formed through selective laser melting (SLM) were found in existing research, which is thought to be clarified in the present article. Parametrical simulations and experiments were designed and conducted firstly to concentrate on the dominant significance of the typical thermal cycling in SLM. It has been proved both by the XRD, EBSD and TEM experiments that correlation between residual stress and energy density depends on the peculiar characteristic of thermal cycling. Furthermore, the microscopic characterization accompanied with simulations of computational fluid dynamics, computational thermo-elastic-plastic mechanics and molecular dynamics reveals the effects of typical thermal cycling on the patterns of residual stress.

Effect of regionalized structures on rock fracture process

The structure of rocks plays a crucial role in their failure process. However, it is ignored that the interactions between rock internal structure and the effect of its own evolution on the rock fracture process. To investigate the effect between the evolution law of rock regionalized structures and their interaction relationships during failure. We conducted an experiment using visual acoustic imaging monitoring to study rock failure, introducing a new concept of characteristics of rock structure—regionalized structures. The findings reveal three main types of regionalized structures in rocks: skeleton regions, variable regions, and damage regions. These structures combine to form four categories of complex rock structures: block-type support skeletons, point column-type support skeletons, suspension-type weak support skeletons, and no skeletons. During the failure process, we found that these regionalized structures worked together synergistically to control rock failure. Although the evolutionary relationships among the structures show some similarities, the final fracture states vary significantly. Stress and strain distribution patterns clearly demonstrate that variations in the force capacities and roles of the regionalized structures influence the synergistic evolutionary relationships, ultimately impacting the mode of rock failure. This work provides new insights for further research on rock failure mechanisms and can significantly contribute to preventing rock engineering disasters related to regionalized structures.

Prosody outweighs statistics in 6-month-old German-learning infants' speech segmentation.

It is well established that infants use various cues to find words within fluent speech from about 7 to 8months of age. Research suggests that two main mechanisms support infants' speech segmentation: prosodic cues like the word stress patterns, and distributional cues like transitional probabilities (TPs). We tested 6-month-old German-learning infants' use of prosodic and statistical cues for speech segmentation in three experiments. In Experiment 1, infants were familiarized with an artificial language string where TPs signaled either word boundaries or iambic words-a stress pattern that is disfavored in German. Experiment 2 was a control and only the test phase was presented. In Experiment 3, prosodic cues were absent in the string and only TPs signaled word boundaries. All experiments included the same conditions at test: disyllabic words with high TPs in the string, words with low TPs and words with non-co-occurring syllables. Results showed that infants relied more strongly on prosodic cues than on TPs for word segmentation. Notably, no segmentation evidence emerged when prosodic cues were absent in the string. This finding underlines early impacts of language-specific structural properties on segmentation mechanisms.