Propagation Of Tension Research Articles

Dynamic propagation of tensile and shear fractures induced by impact load in rock based on the dual bilinear cohesive zone model

PurposeThe purpose of this study is to simulate the tensile and shear types of fractures using the mixed fracture criteria considering the energy evolution based on the dual bilinear cohesive zone model and investigate the dynamic propagation of tensile and shear fractures induced by an impact load in rock. The propagation of tension and shear at different scales induced by the impact load is also an important aspect of this study.Design/methodology/approachIn this study, based on the well-developed dual bilinear cohesive zone model and combined finite element-discrete element method, the dynamic propagation of tensile and shear fractures induced by the impact load in rock is investigated. Some key technologies, such as the governing partial differential equations, fracture criteria, numerical discretisation and detection and separation, are introduced to form the global algorithm and procedure. By comparing with the tensile and shear fractures induced by the impact load in rock disc in typical experiments, the effectiveness and reliability of the proposed method are well verified.FindingsThe dynamic propagation of tensile and shear fractures in the laboratory- and engineering-scale rock disc and rock strata are derived. The influence of mesh sensitivity, impact load velocities and load positions are investigated. The larger load velocities may induce larger fracture width and entire failure. When the impact load is applied near the left support constraint boundary, concentrated shear fractures appear around the loading region, as well as induced shear fracture band, which may induce local instability. The proposed method shows good applicability in studying the propagation of tensile and shear fractures under impact loads.Originality/valueThe proposed method can identify fracture propagation via the stress and energy evolution of rock masses under the impact load, which has potential to be extended into the investigation of the mixed fractures and disturbance of in-situ stresses during dynamic strata mining in deep energy development.

Cell protrusions and contractions generate long-range membrane tension propagation

Membrane tension is thought to be a long-range integrator of cell physiology. Membrane tension has been proposed to enable cell polarity during migration through front-back coordination and long-range protrusion competition. These roles necessitate effective tension transmission across the cell. However, conflicting observations have left the field divided as to whether cell membranes support or resist tension propagation. This discrepancy likely originates from the use of exogenous forces that may not accurately mimic endogenous forces. We overcome this complication by leveraging optogenetics to directly control localized actin-based protrusions or actomyosin contractions while simultaneously monitoring the propagation of membrane tension using dual-trap optical tweezers. Surprisingly, actin-driven protrusions and actomyosin contractions both elicit rapid global membrane tension propagation, whereas forces applied to cell membranes alone do not. We present a simple unifying mechanical model in which mechanical forces that engage the actin cortex drive rapid, robust membrane tension propagation through long-range membrane flows.

Do cell membranes support or resist tension propagation?

In cell migration, protrusions have been proposed to communicate with one another via long-range membrane tension propagation for the winner-take-all, thereby establishing the axis of cell movement. This coordination among protrusions necessitates rapid propagation of membrane tension across the cell. However, several prominent studies suggested otherwise, reporting that cell membranes resist tension propagation and challenging the role of membrane tension as a global integrator in cell physiology. The field hence remains largely divided over the debate of tension propagation, and one source of disagreement stems from differences in methodology. Experiments showing global tension propagation relied on endogenous mechanical perturbations from the cell, while others unable to detect propagation employed exogenous force applications to mimic endogenous counterparts.

Mechanical signaling at the cell membrane

Cell membranes are highly dynamic and experience constant mechanical perturbations. The ensuing change in membrane tension is a fundamental regulator of many membrane signaling and cellular transport processes. In most non-motile cells, local perturbations to membrane tension remain localized, leading to subcellular Ca2+ influx and vesicle fusion events. Exception to this rule can be found in the axon of neurons, where a rapid propagation of membrane tension coordinates the growth and branching of the axon across hundreds of microns.

Directed force propagation in semiflexible networks.

We consider the propagation of tension along specific filaments of a semiflexible filament network in response to the application of a point force using a combination of numerical simulations and analytic theory. We find the distribution of force within the network is highly heterogeneous, with a small number of fibers supporting a significant fraction of the applied load over distances of multiple mesh sizes surrounding the point of force application. We suggest that these structures may be thought of as tensile force chains, whose structure we explore via simulation. We develop self-consistent calculations of the point-force response function and introduce a transfer matrix approach to explore the decay of tension (into bending) energy and the branching of tensile force chains in the network.

Study on the mechanism of crack formation and the behavior of crack propagation of directional tension blasting in deep and high stress coal mine

Roadway safety is related to the high productivity and efficiency of coal mining, roof cutting and pressure releasing technology is one of the effective measures for roadway stability control. Under deep mining conditions,the stress condition around the blasthole is complex, and the expansion of directional crack will be affected by high ground stress. In this paper, Based on the engineering background of the roof Cutting and Pressure Relief Technology of Non-pillar Automatic Roadway Formation in guotun coal mine, the crack propagation mechanism and propagation evolution of deep rock under directional tension blasting were investigated. Based on the stress model of blasthole under the deep condition, the mechanical conditions of crack propagation under the action of directional detonation wave and high surrounding rock binding force are obtained theoretically; The mechanical model of directional blasting under the condition of stress constraint is established by using LS-DYNA numerical calculation software, the evolution characteristics of effective stress and the law of crack growth are analyzed; Finally, through the drilling peep and other technical means, the field measurement of the presplitting effect is carried out, which verifies the previous research results and puts forward the appropriate roof presplitting scheme. The results show that when the deep roof strata of Guotun coal mine adopt four hole continuous blasting and per blasthole charge of 2800g, the roof strata can form a continuous seam, and the Roof presplitting effect is the best.

Propagation of Membrane Tension in Neuronal Axons

Propagation of Membrane Tension in Neuronal Axons

Cell Membranes Resist Flow

The fluid-mosaic model posits a liquid-like plasma membrane, which can flow in response to tension gradients. It is widely assumed that membrane flow transmits local changes in membrane tension across the cell in milliseconds, mediating long-range signaling. Here, we show that propagation of membrane tension occurs quickly in cell-attached blebs but is largely suppressed in intact cells. The failure of tension to propagate in cells is explained by a fluid dynamical model that incorporates the flow resistance from cytoskeleton-bound transmembrane proteins. Perturbations to tension propagate diffusively, with a diffusion coefficient Dσ ∼0.024μm2/s in HeLa cells. In primary endothelial cells, local increases in membrane tension lead only to local activation of mechanosensitive ion channels and to local vesicle fusion. Thus, membrane tension is not a mediator of long-range intracellular signaling, but local variations in tension mediate distinct processes in sub-cellular domains.

Root type matters: measurement of water uptake by seminal, crown, and lateral roots in maize.

The ability of plants to take up water from the soil depends on both the root architecture and the distribution and evolution of the hydraulic conductivities among root types and along the root length. The mature maize (Zea mays L.) root system is composed of primary, seminal, and crown roots together with their respective laterals. Our understanding of root water uptake of maize is largely based on measurements of primary and seminal roots. Crown roots might have a different ability to extract water from the soil, but their hydraulic function remains unknown. The aim of this study was to measure the location of water uptake in mature maize and investigate differences between seminal, crown, and lateral roots. Neutron radiography and injections of deuterated water were used to visualize the root architecture and water transport in 5-week-old maize root systems. Water was mainly taken up by crown roots. Seminal roots and their laterals, which were the main location of water uptake in younger plants, made a minor contribution to water uptake. In contrast to younger seminal roots, crown roots were also able to take up water from their most distal segments. The greater uptake of crown roots compared with seminal roots is explained by their higher axial conductivity in the proximal parts and by the fact that they are connected to the shoot above the seminal roots, which favors the propagation of xylem tension along the crown roots. The deeper water uptake of crown roots is explained by their shorter and fewer laterals, which decreases the dissipation of water potential along the roots.

Dynamics of Tissue-Induced Alignment of Fibrous Extracellular Matrix

Aligned fibers of extracellular matrix (ECM) affect the direction, efficiency, and persistence of migrating cells. To uncover the mechanisms by which multicellular tissues align their surrounding ECM before migration, we used an engineered three-dimensional culture model to investigate the dynamics of ECM alignment around tissues of defined geometry. Analysis of ECM alignment over time revealed that tissues rapidly reorganize their surrounding matrix, with a characteristic time that depends on the type of cell and the initial tissue geometry. We found that matrix metalloproteinase activity is not required for matrix alignment before cell migration. Instead, alignment is driven by Rho-mediated cytoskeletal contractility and accelerated by propagation of tension through intercellular adhesions. Our data suggest that multicellular tissues align their surrounding matrix by pulling collectively to exert strain, which is primarily a physical process. Consistently, the pattern of matrix alignment depends on tissue geometry and the resulting distribution of mechanical strain, with asymmetric tissues generating a higher degree of matrix alignment along their longest axes. The rapid ability of multicellular tissues to physically remodel their matrix enables their constituent cells to migrate efficiently along aligned fibers and to quickly change their direction according to other microenvironmental cues, which is important for both normal and disease processes.

DEVELOPMENT OF RISK ASSESSMENT SYSTEM OF CHILD'S FEMUR AND FOREARM FRACTURE DUE TO AIR-FILLED PLAY EQUIPMENT AND RECOMMENDATION REGARDING ITS SAFE USE

BackgroundRecently, the number of injuries due to play equipment consisting of an air-inflated membrane has been rapidly increasing. For example, a child fractures his femur when he is jumping on...

Propagation of tension along a polymer chain

We study the propagation of tension caused by an external force along a long polymeric molecule in two different settings, namely along a free polymer in three-dimensional (3D) space being pulled from one end, and along a prestretched circular polymer, confined in a narrow circular tube. We show that in both cases, the tension propagation is governed by a diffusion equation, and in particular, the tension front propagates as t(1/2) along the contour of the chain. The results are confirmed numerically, and by molecular dynamics simulations in the case of the 3D polymer. We also compare our results with the previously suggested ones for the translocation setting, and discuss why tension propagation is slower in that case.

Longitudinal response of confined semiflexible polymers

The longitudinal response of single semiflexible polymers to sudden changes in externally applied forces is known to be controlled by the propagation and relaxation of backbone tension. Under many experimental circumstances, realized, for example, in nanofluidic devices or in polymeric networks or solutions, these polymers are effectively confined in a channel- or tubelike geometry. By means of heuristic scaling laws and rigorous analytical theory, we analyze the tension dynamics of confined semiflexible polymers for various generic experimental setups. It turns out that in contrast to the well-known linear response, the influence of confinement on the nonlinear dynamics can largely be described as that of an effective prestress. We also study the free relaxation of an initially confined chain, finding a surprising superlinear ~t(9/8) growth law for the change in end-to-end distance at short times.

Electric fields in polymers during dynamic deformation

The transverse vibrations of a beam and the propagation of tension, compression, and shear deformation waves along the axis of a rod are studied by recording the electric field that appears under these conditions near the rod. Experiments are performed on samples made of various plastic materials in order to compare the effect of the properties of a material on the electric response during dynamic deformation, all other things being equal. Dynamic Young’s moduli are determined during bending vibrations and the propagation of longitudinal waves. It is shown that the location and type of antenna should be taken into account to adequately interpret a recorded signal and a dynamic mechanical process.

Tension dynamics and viscoelasticity of extensible wormlike chains

The dynamic response of prestressed semiflexible biopolymers is characterized by the propagation and relaxation of tension, which arises due to the near inextensibility of a stiff backbone. It is coupled to the dynamics of contour length stored in thermal undulations but also to the local relaxation of elongational strain. We present a systematic theory of tension dynamics for stiff yet extensible wormlike chains. Our results show that even moderate prestress gives rise to distinct Rouse-like extensibility signatures in the high-frequency viscoelastic response.

Beyond Parameter Estimation: Extending Biomechanical Modeling by the Explicit Exploration of Model Topology

Selecting a model topology that realistically predicts biomechanical function remains an unsolved problem. Today's dominant modeling approach is to replicate experimental input/output data by performing parameter estimation on an assumed topology. In contrast, we propose that modeling some complex biomechanical systems requires the explicit and simultaneous exploration of model topology (i.e., the type, number, and organization of physics-based functional building blocks) and parameter values. In this paper, we use the example of modeling the notoriously complex tendon networks of the fingers to present three critical advances towards the goal of implementing this extended modeling paradigm. First, we describe a novel computational environment to perform quasi-static simulations of arbitrary topologies of elastic structures undergoing large deformations. Second, we use this form of simulation to show that the assumed topology for the tendon network of a finger plays an important role in the propagation of tension to the finger joints. Third, we demonstrate the use of a novel inference algorithm that simultaneously explores the topology and parameter values for hidden synthetic tendon networks. We conclude by discussing critical issues of observability, separability, and uniqueness of topological features inferred from input/output data, and outline the challenges that need to be overcome to apply this novel modeling paradigm to extract causal models in real anatomical systems.

Propagation and Relaxation of Tension in Stiff Polymers

We present a unified theory for the longitudinal dynamic response of a stiff polymer in solution to various external perturbations (mechanical excitations, hydrodynamic flows, electrical fields, temperature quenches, etc.) that can be represented as sudden changes of ambient/boundary conditions. The theory relies on a comprehensive analysis of the nonequilibrium propagation and relaxation of backbone stresses in a wormlike chain. We recover and substantially extend previous results based on heuristic arguments. New experimental implications are pointed out.

Pulling-Speed-Dependent Force-Extension Profiles for Semiflexible Chains

We present theory and simulations to describe nonequilibrium stretching of semiflexible chains that serve as models of DNA molecules. Using a self-consistent dynamical variational approach, we calculate the force-extension curves for worm-like chains as a function of the pulling speed, v 0. Due to nonequilibrium effects the stretching force, which increases with v 0, shows nonmonotonic variations as the persistence length increases. To complement the theoretical calculations we also present Langevin simulation results for extensible worm-like chain models for the dynamics of stretching. The theoretical force-extension predictions compare well with the simulation results. The simulations show that, at high enough pulling speeds, the propagation of tension along the chain conformations transverse to the applied force occurs by the Brochard-Wyart’s stem-flower mechanism. The predicted nonequilibrium effects can only be observed in double-stranded DNA at large (∼100 μm/s) pulling speeds.

Pulling on a Filament

We propose a simple scaling argument to describe the propagation of tension along a filament suddenly pulled by one of its ends, a problem recently considered by Seifert, Wintz and Nelson (Phys. Rev. Lett. 77 (1996) 5389-5392).