Magnitude Of Tensile Stress Research Articles

Strain sensor on a chip for quantifying the magnitudes of tensile stress on cells

During cardiac development, mechanotransduction from the in vivo microenvironment modulates cardiomyocyte growth in terms of the number, area, and arrangement heterogeneity. However, the response of cells to different degrees of mechanical stimuli is unclear. Organ-on-a-chip, as a platform for investigating mechanical stress stimuli in cellular mimicry of the in vivo microenvironment, is limited by the lack of ability to accurately quantify externally induced stimuli. However, previous technology lacks the integration of external stimuli and feedback sensors in microfluidic platforms to obtain and apply precise amounts of external stimuli. Here, we designed a cell stretching platform with an in-situ sensor. The in-situ liquid metal sensors can accurately measure the mechanical stimulation caused by the deformation of the vacuum cavity exerted on cells. The platform was applied to human cardiomyocytes (AC16) under cyclic strain (5%, 10%, 15%, 20 and 25%), and we found that cyclic strain promoted cell growth induced the arrangement of cells on the membrane to gradually unify, and stabilized the cells at 15% amplitude, which was even more effective after 3 days of culture. The platform’s precise control and measurement of mechanical forces can be used to establish more accurate in vitro microenvironmental models for disease modeling and therapeutic research.

Gas Fracturing Simulation of Shale-Gas Reservoirs Considering Damage Effects and Fluid–Solid Coupling

With the increasing demand for energy and the depletion of traditional resources, the development of alternative energy sources has become a critical issue. Shale gas, as an abundant and widely distributed resource, has great potential as a substitute for conventional natural gas. However, due to the low permeability of shale-gas reservoirs, efficient extraction poses significant challenges. The application of hydraulic fracturing technology has been proven to effectively enhance rock permeability, but the influence of environmental factors on its efficiency remains unclear. In this study, we investigate the impact of gas fracturing on shale-gas extraction efficiency under varying environmental conditions using numerical simulations. Our simulations provide a comprehensive analysis of the physical changes that occur during the fracturing process, allowing us to evaluate the effects of gas fracturing on rock mechanics and permeability. We find that gas fracturing can effectively induce internal fractures within the rock, and the magnitude of tensile stress decreases gradually during the process. The boundary pressure of the rock mass is an important factor affecting the effectiveness of gas fracturing, as it exhibits an inverse relationship with the gas content present within the rock specimen. Furthermore, the VL constant demonstrates a direct correlation with gas content, while the permeability and PL constant exhibit an inverse relationship with it. Our simulation results provide insights into the optimization of gas fracturing technology under different geological parameter conditions, offering significant guidance for its practical applications.

Research on the Elastoplastic Theory and Evolution Law of Plastic Zone Contours of Horizontal Frozen Walls under Nonuniform Loads

The study of the changes in stress and deformation of frozen walls during excavation has always been a hot topic in underground freezing engineering, and the size of the plastic zone is an important basis for evaluating the stability of frozen walls. In response to the shortcomings in the current design of horizontal frozen walls, based on the internal excavation unloading conditions of the frozen wall in artificial ground freezing, an elastoplastic mechanical model for the interaction between a circular horizontal freezing wall and unfrozen soil mass is established under nonuniform loads to obtain the corresponding solutions for stress and displacement in the system. In this study, considering the shear stress of the plastic zone, the method for solving the traditional plastic zone contour equation is modified; consequently, the modified solution of the contour equation of the plastic zone for the frozen wall is obtained. Using this theoretical solution, the influence of the external load p0 and the lateral pressure coefficient λ on the contour line of plastic zone and tensile stress zone are analyzed by combining the project case, the calculation results show that: the λ=0.485 is the critical point where the inner edge of the frozen wall just happens to have tensile stress. When λ<0.485, the tensile stress zone is inevitable in the inner edge of the frozen wall vertical direction, and its range is only related to λ and increases with the decrease of λ. The p0 only affects the magnitude of tensile stress in the region, but does not affect its range. At this time, the frozen wall compression plastic zone contour evolves from crescent shaped to ear shaped with the increase of p0. When 0.485<λ<0.61, there will be no tensile stress zone, the frozen wall compression plastic zone contour also evolves from crescent shaped to ear shaped with the increase of p0. When λ>0.61, there will be also no tensile stress zone, with the increase of p0, the compression plastic zone contour evolves from the crescent shaped in the horizontal direction to the elliptical shaped, and there is no ear-shaped plastic zone in the whole evolution process. Based on our results, we show that our method can be used to provide a theoretical basis for the stability evaluation and parameter (thickness) design calculation of horizontal frozen walls under nonuniform loads.

Effect of Proximal Caries-driven Access on the Biomechanical Behavior of Endodontically Treated Maxillary Premolars

IntroductionThis study investigated the effects from the carious cavity and access from it on the fracture resistance of endodontically treated maxillary premolars using finite element analysis (FEA). MethodsA maxillary premolar was used to compare 3 types of access cavity related to having a proximal carious defect: caries-driven access (CDA), conservative access that has a mesial component (MCA), as well as traditional access with the same mesial component (MTA). Cyclic loading was simulated on the occlusal surface, and number of cycles until failure (NCF) was compared with the intact tooth model (IT). Mathematical analysis was done to evaluate the stress distribution patterns and calculated maximum von Mises (vM) and maximum principal stresses (MPS), with emphasis on pericervical region as a specific area of interest. ResultsMaximum vM registered on the IT was 6.14 MPa. CDA provided the highest NCF with 92.28% of the IT, followed by MCA (84.90%) and MTA (83.79%). The vM and MPS analysis showed that the stress values and patterns are affected more by the proximity of the occlusal load to the tooth/restoration interface. Concerning the pericervical region, maximum vM was registered for IT (4.11 MPa), followed by CDA (4.85 MPa) and then MCA (8.13 MPa) and MTA (8.61 MPa), whereas the MPS analysis revealed that CDA showed the highest magnitude of tensile stresses. ConclusionsA proximal CDA benefits the mechanical properties of maxillary premolars; however, its impact on the biological aspect should be assessed to provide a ruling for/against it.

Reductions in the Laser Welding Deformation of STS304 Cylindrical Structure Using the Pre-Stress Method

Welding deformation occurs due to non-uniform thermal expansion, thermal contraction, restraint, and phase transformation in a metal by a local welding heat source. This causes problems such as low buckling strength and the reduced workability of the production process. Correcting welding deformations in stainless steel using heat—such as by linear heating—causes metal sensitization, which should be avoided. Herein, welding deformation was reduced by applying tension stress instead of correcting the deformation by heating. A deformation-prevention jig was used to reduce welding deformation during the manufacturing of a cylinder made of STS304 by laser welding. The tensile stress was induced by pushing the cylinder shell outward using the deformation-prevention jig. A thermo-elastoplastic analysis was performed to investigate the effects of the magnitude of the tensile stress on welding deformation. Furthermore, the parametric results—which indicated a reduction in welding deformation—were verified through experiments. The thermo-elastoplastic analysis suggested that deformation did not occur when the magnitude of tensile stress was approximately 50% of the yield stress of the base metal. Moreover, the deformation was experimentally reduced by 11–20% when a tensile stress of 30 MPa was applied to the cylinder, compared with that in the absence of tensile stress.

The study of laser deep penetration processing on prefabricated cracks of high carbon steel

This paper describes the testing of laser deep penetration processing on controlled fragmentation of high carbon steel (50SiMnVB). The objective of this research is to make use of defects in deep penetration zones and optimize the quality of prefabricated cracks. The research shows that a deeper central crack appear in the deep penetration zone when the heat input is 60 J/mm, and the appeared crack is affected by martensite in microstructure, high microhardness and a high magnitude of tensile stress. Furthermore, the fracture mode of the deep penetration zones is mixed-mode (ductile and brittle fracture).

Determination of the strength of the support sections of concrete beams with BFRP under the action of shear forces

In a few foreign codes (ACI, Eurocode 2, JSCE, CSA, CNR), the principles for calculating flexible concrete elements with (BFRP) are preserved the same as for calculating concrete structures with steel reinforcement. Experimental studies have not confirmed these principles, which indicates the relevance of research. Two calculation models are proposed for determining the strength near the support sections of concrete beams with BFRP. The first model considers the calculation of beams with average (a/d=2) and large (a/d=3) shear spans along the main inclined crack, taking into account the experimentally established length of its projection lcrf1, the coefficients ϕख़2, ϕख़3 and ϕख़4 the magnitude of tensile stresses in the transverse fittings. The second computational model provides for the calculation of these beams with small shear spans (a/d<1) along a compressed inclined strip using the experimentally established coefficient kf,. The use of the presented design models provides good convergence (coefficient of variation ν=8%) of the calculated and experimental values of strength near the support sections of concrete beams with BFRP.

BUBBLE DYNAMICS-BASED MODELING OF THE CAVITATION DYNAMICS IN LUBRICATED CONTACTS

Cavitation is a common phenomenon in fluid machinery and lubricated contacts. In lubricated contacts, there is a presumption that the short-term tensile stresses at the onset of bubble formation have an influence on material wear. To investigate the duration and magnitude of tensile stresses in lubricating films using numerical simulation, a suitable simulation model must be developed. The chosen simulation approach with bubble dynamics is based on the coupling of the Reynolds equation and Rayleigh-Plesset equation (introduced about 20 years ago by Someya).Following the basic approach from the author’s earlier papers on the negative squeeze motion with bubble dynamics for the simulation of mixed lubrication of rough surfaces, the paper at hand shows modifications to the Rayleigh-Plesset equation that are required to get the time scale for the dynamic processes right. This additional term is called the dilatational viscosity term, and it significantly influences the behavior of the numerical model.

Influence of Polymeric Restorative Materials on the Stress Distribution in Posterior Fixed Partial Dentures: 3D Finite Element Analysis.

Background: This study evaluated the effect of interim restorative materials (acrylic resin (AR), resin composite (RC) or polyetheretherketone (PEEK) for dental computer-aided design/computer-aided manufacturing (CAD/CAM)) on the stress distribution of a posterior three-unit fixed partial denture. Methods: The abutment teeth (first molar and first premolar) were modeled using the BioCAD protocol containing 1.5 mm of axial reduction and converging axial walls. A static structural analysis was performed in the computer-aided engineering software, and the Maximum Principal Stress criterion was used to analyze the prosthesis and the cement layers of both abutment teeth. The materials were considered isotropic, linearly elastic, homogeneous and with bonded contacts. An axial load (600 N) was applied to the occlusal surface of the second premolar. Results: Regardless of the restorative material, the region of the prosthetic connectors showed the highest tensile stress magnitude. The highest stress peak was observed with the use of RC (129 MPa) compared to PEEK and AR. For the cement layers, RC showed the lowest values in the occlusal region (7 MPa) and the highest values for the cervical margin (14 MPa) compared to PEEK (21 and 12 MPa) and AR (21 and 13 MPa). Conclusions: Different interim restorative materials for posterior fixed partial dentures present different biomechanical behavior. The use of resin composite can attenuate the stress magnitude on the cement layer, and the use of acrylic resin can attenuate the stress magnitude on the connector region.

The effect of elastic deformation on the minor hysteresis loops of low carbon steel

The effect of elastic tensile deformations on the magnetic permeability of a structural low-carbon steel 20K (0.23 % C, 0.20 % Si, 0.46 % Mn) at various magnetic states was experimentally studied. To obtain these parameters, the measurements of minor hysteresis loops, which begin in the demagnetized state and in the remanent magnetization state, were carried out. The maximum tensile stress equal to 250 MPa that corresponds to 90 % of the conditional yield strength of studied steel. Stress dependences of the initial and reversible magnetic permeabilities as well as differential magnetic permeability along the descending branch of the minor hysteresis loop, which starts in the remanent magnetization state, are non-monotonic. They have extremums at σ = 50–70 MPa. However, stress dependences of the sums of those parameters are monotonic. The relative changes reach 25 % at tensile stresses of 250 MPa which make the promise of using the sums of magnetic permeabilities as parameters for assessing the magnitude of tensile stresses.

Discrete element simulation of the ultrasonic-assisted scratching process of Al2O3 ceramic under compressive pre-stress

The ultrasonic-assisted scratching process (USP) of Al2O3 ceramic under a compressive pre-stress was simulated using the discrete element method. Using the cluster method, the bond-particle model (BPM) was generated, and the normal scratching process (NSP) and USP were simulated. The simulation results indicated that cracks first occurred beneath the cutter tip and subsequently transformed from lateral to median cracks. Additionally, when the compressive stress was exerted, the crack initiation was restricted, but the USP led to larger median-crack depths when the number of cracks decreased. Meanwhile, during both scratching processes, the tangential forces exhibited a dynamic nature, and their fluctuations were affected by the initiation of the cracks. Combined with the experimental result, the USP exhibited a steadier fluctuation than the NSP did. An analysis of the stress cloud image of the endpoint on the scratching groove indicated that the maximum-stress region was immediately beneath the cutter tip, and the stress in this region was compressive. Additionally, a tensile stress remained along the scratched groove, and the tensile-stress magnitude in the USP was larger than that in the NSP, indicating that crack initiation is related to tensile stress. Finally, the scratch experiment was carried out. The result obtained was similar to the simulation result.

Effects of dilution on the hardness and residual stresses in multipass steel weldments

A thermal-metallurgical-mechanical model was developed to study the effects of dilution in each weld pass for multipass gas tungsten arc and submerged arc welding in low alloy steel (i.e. SA508) plates. Hardness distributions and residual stresses were measured on the transverse sections perpendicular to the welding direction of the manufactured weldments. The predicted hardness and residual stresses were compared with the measurement data and shown to be reasonably accurate. The results showed that dilution can significantly affect both the hardness and the residual stress field in the weld metal. It was found that, for the base and filler materials used, increased dilution led to greater weld-metal hardness and reduced the magnitude of tensile stress or promoted compressive stress in the as-deposited and reheated weld metals. This mechanical behaviour is associated with the tendency for diluted weld metal to experience delayed austenite decomposition, owing to the high hardenability of SA508 steel relative to the filler materials used. Although dilution is irrelevant for the hardness of the base material and its transformation products adjacent to the weld metal, it affected the full-field residual stresses via the equilibrium interaction between the stresses in the base and weld metals.

Use of Magnetic Anisotropy Method for Assessing Residual Stresses in Metal Structures

A series of experiments on measuring of difference between the main mechanical stresses (DPMS) was carried out using a mechanical stress scanner based on the magnetoanisotropic method. The magnitude of the DPMS is fixed when a magnetic field is induced on a carbon steel plate under uniaxial tension. A direct proportional relationship is shown between the magnitude of the DPMS signal recorded by the scanner and the magnitude of tensile stresses in the plate in the region of elastic deformation of steel. Measurement of the DPMS signal in the central part of similar plates previously subjected to elastic-plastic bending showed that positive values of the signal are fixed in the surface layers of the metal on the inside of the plate, which corresponds to tensile residual stresses, while the negative ones concentrate at the external surface, which corresponds to compressive stresses. A transverse incision on a curved plate from the inside leads to a decrease in the value of the signal of the DPMS, which indicates a decrease in the level of residual stresses in the metal. The values of the DPMS signal in the central part of the curved plate, recalculated using the established calibration dependence on the value of the residual stresses, were compared with the values of the stresses established by calculation, based on the Henki’s theorem on the unloading of an elastic-plastic body. A satisfactory convergence was obtained between the experimental and calculated data.

Vulnerable window of yield strength for swelling-driven fracture of phase-transforming battery materials

Despite numerous experimental and theoretical investigations of the mechanical behavior of high-capacity Si and Ge Li-ion battery anodes, our basic understanding of swelling-driven fracture in these materials remains limited. Existing theoretical studies have provided insights into elasto-plastic deformations caused by large volume change phase transformations, but have not modeled fracture explicitly beyond Griffith’s criterion. Here, we use a multi-physics phase-field approach to model self-consistently anisotropic phase transformation, elasto-plastic deformation, and crack initiation and propagation during lithiation of Si nanopillars. Our computational results reveal that fracture occurs within a “vulnerable window” inside the two-dimensional parameter space of yield strength and fracture energy and highlight the importance of taking into account the surface localization of plastic deformation to accurately predict the magnitude of tensile stresses at the onset of fracture. They further demonstrate how the increased robustness of hollow nanopillars can be understood as a direct effect of anode geometry on the size of this vulnerable window. Those insights provide an improved theoretical basis for designing next-generation mechanically stable phase-transforming battery materials undergoing large volume changes.

Moment Redistribution in Segmental Cantilever Bridges: Simplified Approach

Moment redistribution due to creep of concrete in cast-in-place segmental cantilever bridges can be accounted for with sophisticated software. Although this approach to design frequently is preferred, experienced engineers often do a final check based on hand calculations that have stood the test of time. This paper deals with the latter approach. Principles governing moment redistribution due to creep were revised, and results from this investigation were used to develop a novel graphical aid suitable for hand calculations in an attempt to estimate the magnitude of tensile stresses due to moment redistribution because of creep. It was found that tension stresses due to creep are not likely to exceed 2 MPa (290 psi) because the post-tensioning provided by top cables balance approximately 70%–85% of the bending moments due to concrete weight. An example for routine designs was provided.

Rolling contact fatigue assessment of repair rail welds

A repair welding procedure is numerically simulated. To validate the numerical model, analyses of the temperature evolution in a repaired rail are compared to existing full-scale test results. Thermomechanical simulations are carried out to evaluate the residual stress formation during welding and how the residual stress field is influenced by subsequent wheel passages during operations. The risk of rolling contact fatigue (RCF) is analysed and results discussed. It is found that tensile stress magnitudes resulting from welding decrease substantially during rolling contact loading. The influence of the residual stresses on RCF is found to be minor on the surface and somewhat more severe in a layer at the bottom of the repair weld. In addition to residual stresses, there is also a risk that welding introduces material defects and alters material properties. The influence of these factors on the risk of RCF is discussed.

Contact problem for a composite material with nacre inspired microstructure

Bi-material composites with nacre inspired brick and mortar microstructures, characterized by stiff elements of one phase with high aspect ratio separated by thin layers of the second one, are considered. Such microstructure is proved to provide an efficient solution for the problem of a crack arrest. However, contrary to the case of a homogeneous material, an external pressure, applied to a part of the composite boundary, can cause significant tensile stresses which increase the danger of crack nucleation. Investigation of the influence of microstructure parameters on the magnitude of tensile stresses is performed by means of the classical Flamant-like problem of an orthotropic half-plane subjected to a normal external distributed loading. Adequate analysis of this problem represents a serious computational task due to the geometry of the considered layout and the high contrast between the composite constituents. This difficulty is presently circumvented by deriving a micro-to-macro analysis in the framework of which an analytical solution of the auxiliary elasticity problem, followed by the discrete Fourier transform and the higher-order theory are employed. As a result, full scale continuum modeling of both composite constituents without employing any simplifying assumptions is presented. In the framework of the present proposed modeling, the influence of stiff elements aspect ratio on the overall stress distribution is demonstrated.

Tensile stress distribution in maxillary central incisors restored with cast-made and prefabricated dental posts.

Abstract: Aim: To analyze and compare the tensile stress distribution in endodontically treated teeth restored with cast-made (Ni-Cr and gold) and prefabricated (titanium and glass fibre) dental posts. Methodology: Four three-dimensional finite element (FE) models of a maxillary central incisor restored with Ni-Cr cast-made (Model Ni-Cr), gold cast-made (Model GO), prefabricated titanium (Model TI) and prefabricated glass fibre (Model FP) posts were constructed. An oblique loading of 100N was applied to each three-dimensional model. Tensile stress distribution within the root dentine and at the post and surrounding structure interfaces were analysed. Results: In all the FE models studied, a higher magnitude of tensile stresses was observed on the palatal aspect of the cervical dentin as compared to the labial aspect and progressively decreases from the outer to the inner part of the root. The gold cast-made and glass fibre post models showed significantly less tensile stress concentration in the post-core component than the other experimental models. The maximum tensile stress was seen on the palatal aspect of the Ni-Cr compared to other posts. The higher magnitude interfacial tensile stress concentration was observed in a pulpless tooth restored with a Ni-Cr cast-made post, followed by titanium and gold cast-made posts, respectively. However, the minimum interfacial tensile stress was noticed in a pulpless tooth restored with a glass fibre post. Conclusion: Glass fibre posts tend to transfer tensile stress more homogenously within the tooth and at interfaces than the other types of investigated posts.

The effect of dynamic aging on the cyclic stability of Cu73Al16Mn11 shape memory alloy

This study focuses on the effect of dynamic aging on the thermo-mechanical cyclic stability of Cu73Al16Mn11 (at%) shape memory alloy (SMA) during constant stress (isobaric) and stress-free heating-cooling experiments. Isobaric heating-cooling experiments under various tensile stress magnitudes revealed almost no residual strain up to 60MPa. Subsequently, the cyclic stability of the samples was further investigated via thermal cycles under 60MPa with increasing upper cycle temperature (UCT) values. The increase in UCT led to the ordering of the parent phase and formation of the bainite and α phases. In addition to the effect of UCT on the formation of bainite, stress had an accelerating effect on the bainitic transformation. The martensitic transformation temperatures increased due to ordering when UCTs were set to 120°C and 145°C and then started to decrease due to the formation of the bainite and α phases when the UCTs were set to 175°C and 205°C. Consequently, it was determined that the cyclic stability of Cu-Al-Mn SMAs for high temperature applications strongly depends on the UCT.

Computed Tomography–Based 3-Dimensional Finite Element Analyses of Various Types of Plates Placed for a Virtually Reduced Unilateral Condylar Fracture of the Mandible of a Patient

This study was performed to evaluate stresses in various types of plates placed for a virtually reduced unilateral condylar fracture of the mandible using computed tomography-based 3-dimensional finite element (FE) models of a patient to select the optimal plate system. A computed tomography-based FE model of the mandible of a patient with a unilateral condylar fracture was constructed. The fracture was virtually reduced and fixed with 1 straight titanium plate; 2 straight titanium plates; 2 straight poly-L-lactic acid plates; and 4-hole (box), 5-hole (strut), and 7-hole (lambda) condylar plates. Stresses developing in these plates were analyzed by applying 478.1N of bite force at the first molar of the contralateral side of the mandible. The magnitudes of tensile stress were within the tensile strength in all types of plates. However, the magnitudes of compressive stress in 1 straight titanium plate and 2 straight poly-L-lactic acid plates were beyond the compressive strength. The tensile and compressive stresses of the 5-hole (strut) plate were the smallest among the 3 types of condylar plates. Fixation by 2 straight titanium plates or any type of condylar plate was biomechanically indicated for the condylar fracture of this patient. Among these plates, the 5-hole (strut) plate was considered optimal. FE analysis is useful in selecting the optimal fixation method in the individual patient.