Mooney-Rivlin Constitutive Model Research Articles

Fatigue characteristics of rubber isolation layers used in high speed railway ballastless tracks: A theoretical and experimental study

In order to enhance operational conditions for high-speed trains on long-span bridges, the utilization of rubber under-ballast mats were taken as a novel isolation layer in ballastless tracks. Due to the increased train axle load, it is imperative to conduct investigation into the fatigue properties of the rubber isolation layer, so as to ensure the smoothness of the railways. In this work, a series of fatigue tests were performed on the rubber isolation layer to obtain the influence of stress amplitude and loading cycles on its fatigue performance. The results demonstrate a pronounced non-linear load–displacement relationship of the rubber isolation layer with increasing load, while the fatigue endurance significantly decreases with escalating the stress amplitude. Moreover, considering the hyperelastic properties of rubber material, the Mooney-Rivlin constitutive model was employed in finite element simulations. Subsequently, the stress distributions of the rubber isolation layer were analyzed, and the fatigue life was evaluated based on Luo stress method. The rubber isolation layer exhibits localized damage that does not affect the overall performance after 32 years of normal service condition. Therefore, the fatigue performance of the rubber isolation layer remains reliability, providing assurance for the application in ballastless tracks on high-speed railway long-span bridges.

Studying the nonlinear response of incompressible hyperelastic thin circular cylindrical shells with geometric imperfections

This study presents a comprehensive analysis of hyperelastic thin cylindrical shells exhibiting initial geometrical imperfections. The nonlinear equations of motion are derived using an improved formulation of Donnell’s nonlinear shallow-shell theory and Lagrange’s equations, incorporating the small strain hypothesis. Mooney–Rivlin constitutive model is employed to capture the hyperelastic behavior of the material. The coupled nonlinear equations of motion are analytically solved using Multiple-Scale method, which effectively accounts for the inherent nonlinearity of the system. To ensure the model’s accuracy, the linear model is verified by comparing the results with those obtained through hybrid finite element method. Subsequently, the model with only geometrical nonlinearity is evaluated against other research works existing in the open literature to ensure its reliability and precision. Finally, the results of the model, considering both geometrical and physical nonlinearity, are verified against the results obtained from Abaqus software. The main objective of this research is to provide a detailed understanding of the response of hyperelastic thin cylindrical shells in the presence of initial geometric imperfections. In this order, the impact of three distinct geometric imperfections – axisymmetric, asymmetric, and a combination of driven and companion modes – on the natural frequency is examined. The behavior of each of these geometric imperfections is investigated by varying their respective coefficients. The numerical results indicate that geometric imperfections enhance the natural frequency, and employing different models for imperfections leads to a variation in this trend. In the amplitude response of hyperelastic cylindrical shells, two peaks coexist, reflecting the softening and hardening responses of the system. Distinct initial geometric imperfections influence these two peaks.

Functionally graded Gelatine/PVA-based composite hydrogel for repairing the soft tissues of diarthrodial joints

Functionally graded materials are innovative materials in which the composition of the microstructural elements varies gradually in different directions, instigating changes in properties that can be exploited for enrichment in the performance of the hydrogels based on the application. The present study involves the development of functionally graded hydrogel (FGH) for the soft tissues of the diarthrodial joints. FGH is prepared from gelatine, guar gum, polyvinyl alcohol, and copper nanoparticles. The compressive behavior of the FGH composite hydrogels was evaluated under the compressive loads. The mean compressive strength of the FGH was found to be 378 kPa. The rate-dependent hyperplastic mechanical behavior of FGH was modeled under compressive conditions by combining the block represents the influence of the strain rate effect in the J-C model with the Mooney-Rivlin constitutive model. The hybrid model's predictability was satisfactory, with a mean absolute error of 10.88 kPa. Furthermore, swelling and biocompatibility properties of hydrogel were assessed. The developed FGH exhibited adequate mechanical and biocompatibility properties and was a promising material for repairing and regenerating soft tissues in the diarthrodial joints.

Research on Design and Optimization of Large Metal Bipolar Plate Sealing for Proton Exchange Membrane Fuel Cells

The sealing system, as the most important load-bearing component, is a critical part of the stack assembly in a proton exchange membrane fuel cell (PEMFC). Currently, flat or single-peak sealing gaskets are commonly used for large metal bipolar plate sealing, which can easily cause problems such as significant internal stress and distortion displacement. In order to solve this problem, an innovative double-peak sealing gasket structure is proposed. Based on the Mooney–Rivlin constitutive model, the impact of the sealing material hardness, friction coefficient, and compression ratio on the sealing performance are investigated. Meanwhile, the double-peak seal is fabricated and assembled into a single fuel cell for testing. The results show that the sealing performance of a double-peak sealing gasket with extended wings has been optimized, and the maximum contact pressure on the upper and lower contact surfaces is 1.2 MPa and 0.67 MPa, respectively, which is greater than the given air pressure of 0.1 MPa. And the sealing effect is optimal with a 45 Shore A hardness rubber, a friction coefficient of 0.05, and an initial compression ratio of 35%. The simulation and experimental sealing performance of the sealing gasket under different compression ratios remain similar.

Modelling of laminated glass PVB walls of buildings exposed to vehicle impact with different speeds

This paper presents an analytical model, developed for laminated glass subjected to a low-velocity impact. It has the ability to capture glass cracks as well as large non-linear deformations. It is based mathematically on the first-order deformation concept, which considers the effect of membrane and transverse shear as well as bending. This theory uses damage mechanics to capture the glass cracking. For this purpose, several experiments have been carried out based on PVB laminated glass. The history of acceleration, transverse central displacement and velocity estimated over time is in a favourable relationship with the experimental information. In terms of laminated glass, non-dimensional coefficients have been suggested that regulate both the first peak contact force and the maximum transverse displacement. Laminated glass consists of several layers of soda-lime glass sheets bound together by intermediate layers of polyvinyl butyral (or PVB). Cracking of the glass layer is the main cause of laminated glass damage under both low and high-speed impacts. The main objective of the present article is to conduct experimental studies and numerical analyses of the glass ply cracking mechanism as part of the development of new strength parameters for PVB laminated glass. The non-linear characteristics of PVB are described using the Mooney-Rivlin constitutive model. The present article proves that it is possible to precisely model a wall made of VSG (Verbund Sicherheits Glas) laminated glass reinforced with a vinyl interlayer of appropriate thickness, and further, that such walls can constitute an element absorbing the impact energy of vehicles with specific parameters such as a passenger car, buses, and HGVs (Heavy Goods Vehicle). Based on the results of our study, new parameters were elaborated to determine the properties of PVB laminated glass exposed to vehicle impact. These new parameters were verified qualitatively by comparing the simulation results with experimental observations. We also assessed the strength of a wall of adequate thickness made of laminated glass at the ground floor level of a building exposed to a high-risk terrorist attack. The developed analytical model allows for a quick and reliable assessment during the initial design of safety glass, where a full-scale FE analysis is often too time-consuming.

Mechanical Action Mechanism and Crack Response Analysis of Slide Plate of No.12 Turnout

In the course of maintenance and repair, the railway workshops of the Lan-Qing railway found that the slide plate was prone to injury and damage. In order to study the actual stress state of the slide plate during the running of the train, a finite element model of the slide plate and related components was established based on ANSYS, Hypermesh was used for meshing and mesh quality control, and the Mooney-Rivlin constitutive intrinsic model was selected to simulate the rubber plate. The stress state of the slide plate when passing through the turnout in the straight and lateral directions is analyzed respectively. The results show that there is stress concentration at the root of the tongue depressor of the slide plate, and large deformation exists in the middle of the base plate, the front end of the platform plate and the position of the guide iron when passing through the turnout directly and laterally. The stress state of the slide plate is simulated when the rail brace fails, and the maximum stress is found to be 279.24 MPa, which exceeds the material yield limit. Therefore, we should pay attention to the inspection of the condition of the rail brace during the maintenance and repair. Presenting cracks at the weld seam location, it is found that the crack has a significant effect on the dewelding of the slide plate, and the heel position is the weakness of the slide plate. When the crack length reaches 1.2 mm, there is a tendency to crack at the weld seam position of the slide plate, and when the crack length continues to increase, the crack will further expand and jeopardizing structural safety. The research results can provide a theoretical basis for the improvement, disease prevention and maintenance of the slide plate.

Architectural and Urban Planning Solutions for the Protection of Heritage Buildings in the Context of Terrorist Attacks: Following the Example of Passive Protection Systems

Events in recent years showing numerous terrorist attacks raise awareness regarding the necessity of considering the safety of heritage buildings. The analysis of available data allows us to conclude that it is not possible to fully prevent terrorist attacks. On the other hand, it is possible to minimize the impact of such incidents through proper design of passive protection system (PPS) components. One possible architectural solution to be deployed as a passive defense system is laminated glass panel walls. The study presented in this article is innovative, considering there are no current standard documents or recommendations to determine the conditions of destruction as well as the methods of testing the strength of glass components used in laminated glass panel walls under vehicle impact. The present work represents the material used in PVB interlayers using the Mooney–Rivlin constitutive model, which correctly describes the non-linear characteristics of PVB. Based on the obtained results, new parameters of PVB laminated glass exposed to vehicle impact were developed. The newly developed parameters underwent quality verification through a comparison of results from experimental studies and numerical simulations. Finally, the strength of laminated glass panel walls was subject to evaluation, considering the amount and thickness of individual VSG glass layers and the number of PVB interlayers at ground floor level of a heritage building with high susceptibility to terrorist attacks. The newly developed parameters of laminated glass may be implemented as a premade input .mat file for the material available in the KEYWORD database under the name MAT_32-LAMINATED_GLASS in the LS-DYNA software.

Effect of Rubber Strain Rate on Performance of Aircraft Tire

An aircraft tire is a kind of rubber product with a complex structure. When subjected to impact load, the mechanical properties of rubber material on strain history and strain rate cannot be ignored. According to the previous impact compression experiment data of rubber materials, this paper built a dynamic constitutive model by modifying Mooney-Rivlin constitutive model to describe the rate-dependent material behavior. The calculated stress–strain values were in good agreement with the experimental ones. The proposed constitutive equation was implemented in ABAQUS via a user-defined subroutine (VUMAT) and used to predict the dynamic response of aircraft tire landing impact in the experiments for the first time. The model’s numerical results considering the strain rate effect are closer to the test results than the traditional model. It shows that considering the strain rate effect of rubber material in the case of tire impact can make the results more accurate.

Optimization and Experimental Study of the Subsea Retractable Connector Rubber Packer Based on Mooney-Rivlin Constitutive Model

The sealing performance of the rubber packer is of vital importance for the subsea retractable connector, and the cross-sectional shape of the rubber packer is one of the most important factors affecting it. The compression distance of the rubber packer is increased by 19.54% utilizing the established two-dimensional numerical model. In addition, a new parameter called the anti-shoulder extrusion variable was defined in this paper. Shoulder extrusion will not occur when using this variable as a constraint during simulation. In general, the upper end and the lower end of a rubber packer are subject to different constraints, and the structural parameters of the rubber packer affect each other in terms of sealing performance. Therefore, the importance and originality of this study are exploring the optimization of the thickness and chamfer angles of the upper and lower ends of the rubber packer by use of a combination of the response surface optimization method and the multi-objective genetic algorithm, taking the thickness and chamfer angles of the upper and lower ends as design variables, and the stress on the inner side of the casing wall and the axial force of the compressed rubber packer as optimization objectives. Besides that, the anti-shoulder extrusion variables are also introduced as constraints to prevent shoulder extrusion. Ultimately, the cross-sectional shape of the rubber packer with a smaller-thickness and larger-angle upper end, and a larger-thickness and smaller-angle lower end can be obtained. The result to emerge from the test in this paper is that the pipe pressure that can be sealed by the optimized rubber packer structure is 25.61% higher than that before optimization. The anti-shoulder extrusion variable and the asymmetric cross-sectional shape of the rubber packer proposed in this paper shed new light on the finite element simulation of rubber and the research on similar seals.

The Fluid-structure Coupling Analysis of Steel-Wire-Reinforced Flexible Pipe Under Inner Fluid Pressure Impact

Identifying dynamic characteristics of the fluid filled steel-wire-reinforced flexible pipe is vital in controlling the pipe vibration. A direct fluid-structure coupling method based on finite element analysis is proposed and validated by modal simulation of an oil filled T-shape pipe. An innovative way of modeling steel-wire-reinforced rubber pipe is put forward. The modeling method is validated by modal test of the water-filled pipe. The 2nd Mooney-Rivlin constitutive model is used for the rubber material. Transient dynamic simulations of a bending steel-wire-reinforced pipe filled with water under step and sine-shape pressure impact are performed for the first time. Different fluid turbulence models are used to evaluate the influences on pipe vibration. The dynamic characteristics of the water filled flexible pipe is researched under different fluid pressures. The vibration peak frequencies of the water-filled pipe under various impact excitations coincide well with the fluid-structure coupling modes of the pipe.

An improved energy prediction method to predict the fatigue life of laminated rubber-alloy spherical thrust elastomeric bearing under multiaxial loads

PurposeAn ideal method for predicting the fatigue life of spherical thrust elastomeric bearings has not been reported, thus far. This paper aims to present a method for predicting the fatigue life of laminated rubber spherical thrust elastomeric bearings.Design/methodology/approachFirst, the mechanical properties of standard rubber samples were tested; the axial stiffness, cocking stiffness, torsional stiffness and fatigue life of several full-size spherical thrust elastomeric bearings were tested. Then, the stiffness results were calculated using the neo-Hookean, Mooney–Rivlin and Yoeh models. Using a modified Mooney–Rivlin constitutive model, this paper proposes an improved method for fatigue life prediction, which considers the laminated characteristics of a spherical thrust elastomeric bearing and loads of multiple multi-axle conditions.FindingsThe Mooney–Rivlin model could accurately describe the stiffness characteristics of the spherical thrust elastomeric bearings. A comparative analysis of experimental results shows that the model can effectively predict the life of a spherical thrust elastomeric bearing within its range of use and the prediction error is within 20%.Originality/valueThe fatigue parameters of elastomeric bearings under multiaxial loads were fitted and corrected using experimental data and an accurate and effective multiaxial fatigue-life prediction expression was obtained. Finally, the software was redeveloped to improve the flexibility and efficiency of modeling and calculation.

Nonlinear finite element analysis on the sealing performance of rubber packer for hydraulic fracturing

As the core component of a fracturing tool, a rubber packer plays a vital role during the well stimulation process. Its sealing performance significantly affects the fracturing effects. This study adopted a 3D multi-body contact nonlinear finite element analysis with the Mooney–Rivlin constitutive model to investigate the sealing performance of the hydrogenated nitrile butadiene rubber. The effects of key parameters such as the total thickness, sub-thickness, height, and rubber hardness on the sealing performance were systemically investigated. Numerical results indicated that maximum contact stress appeared around the rubber packer's upper part because of the combined effect of friction and axial compression. Besides, the numerical results were validated with theoretical and experimental results, in which the error between theoretical and numerical results was less than 7%, and that between the numerical results and experimental results was approximately 17.7%. Under the conditions considered, key parameters of rubber packer were optimized as a total thickness of 20 mm, a sub-thickness of 13 mm, a height of 70 mm, and a hardness of 70 International Rubber Hardness Degrees, in terms of the maximum contact stress and deformation displacement. The proposed numerical approaches could accurately predict rubber packer's deformation status, which consequently had technical guiding significance for the design of similar sealing components in various applications.

Finite Element Analysis of Adhesive Failure of Solid Composite Propellant Multi-material Structure for Underwater Intelligent Equipment

This paper is a consecutive work based on the last paper “Finite element analysis of viscoelastic/damage behaviors of composite solid propellant for underwater intelligent equipment”. This paper studies adhesive failure behaviors of multi-material structure in underwater intelligent equipment, which includes the propellant layer/lining layer/adiabatic layer/aluminum layer. First, the hyperelastic mechanical properties for ethylene–propylene–diene monomer for adiabatic layer are predicted by using the Mooney–Rivlin constitutive model, where the material parameters are fitted by combining with theoretical and experimental load curves. Second, the adhesive failure between the propellant layer and the lining layer is predicted for the designed multiple material layers under shear loads by combining with the bilinear cohesive model, the constitutive models for the propellant and adiabatic layer materials. Finally, the adhesive failure mechanisms and the load responses are studied for the shear specimens.

Wellbore trajectory control tool seal system leakage analysis based on steady gap flow

Lubricant leakage will inevitably occur during the working process of wellbore trajectory control tools. Even including the lubricant compensation system, serious leakage will still cause lacks lubrication of the internal mechanical structure as well as electronic system damaged by external infiltration fluid, especially when it comes to battery sub and other electronic equipment. Seal system leakage prediction method was presented based on the assumption of steady gap flow. It is assumed that there is a constant gap between the lip seal and the rotating shaft, the gap height is determined by oil film thickness, and the length of the gap was determined by the contact analysis using the Mooney–Rivlin constitutive model. The analysis results show that the contact length between the primary seal lip and the rotary shaft is about 0.1 mm under the condition of ensuring the contact between the deputy seal lip and the rotary shaft. The overall lubricant leakage finite element analysis model was established, and the relationship between the internal lubricant pressure of the tool and the total leakage was obtained. The results of analysis indicate that under the internal pressure of 0.03 MPa, the lubricant leakage is approximately 6 mL/h, which was verified by experiments.

Research on dynamic performance and influence of new mesh-hole elastic pads for railway fasteners in an extremely cold environment

In order to research the dynamic properties of elastic pads for a new pattern mesh-hole in an extremely cold environment, a three-dimensional finite element model of a mesh-hole rail pad is established. The Mooney-Rivlin constitutive model is used to simulate the mechanical properties of rubber materials at different temperatures, and the temperature-dependent characteristics of dynamic stiffness and damping coefficients of the mesh-hole rail pads are analyzed. Based on the vehicle-track coupling dynamic theory, the driving safety and stability properties of the rail pads at extremely cold climate are calculated and analyzed, and the applicability of the mesh-hole rail pads in the extremely cold environment is further evaluated. The research conclusions are as follows. The mesh-hole rail pads have significant low-temperature sensitivity. Namely, above −10°C, the dynamic stiffness and damping coefficients of rail pads are stable, while below this temperature, the dynamic stiffness and damping coefficients of elastic pads increase rapidly. The mesh-hole rail pad has an obvious influence on the dynamic performance of a vehicle-track system when the temperature changes. Namely, the wheel-rail force and wheel load reduction rate increase rapidly with the decrease in temperature, while the vertical dynamic displacement of the rail decreases. Under the extremely cold climate, the wheel load reduction rate of a high-speed passenger vehicle increases sharply, so the method for reducing train speed should be adopted to ensure the safety of train operation.

Mimicking "J-Shaped" and Anisotropic Stress-Strain Behavior of Human and Porcine Aorta by Fabric-Reinforced Elastomer Composites.

An ex vivo heart perfusion device preserves the donor heart in a warm beating state during transfer between extraction and implantation surgeries. One of the current challenges includes the use of rigid and noncompliant plastic tubes, which causes injuries to the heart at the junction between the tissue and the tube. The compliant and rapidly strain-stiffening mechanical property that generates a "J-shaped" stress-strain behavior is necessary for producing the Windkessel effect, which ensures continuous flow of blood through the aorta. In this study, we mimic the J-shaped and anisotropic stress-strain behavior of human aorta in synthetic elastomers to replace the problematic noncompliant plastic tube. First, we assess the mechanical properties of human (n = 1) and porcine aorta (n = 14) to quantify the nonlinear and anisotropic behavior under uniaxial tensile stress from five different regions of the aorta. Second, fabric-reinforced elastomer composites were prepared by reinforcing silicone elastomers with embedded fabrics in a trilayer geometry. The knitted structures of the fabric provide strain-stiffening as well as anisotropic mechanical properties of the resulting composite in a deterministic manner. By optimizing the combination between different elastomers and fabrics, the resulting composites matched the J-shaped and anisotropic stress-strain behavior of natural human and porcine aorta. Finally, improved analytical constitutive models based on Gent's and Mooney-Rivlin's constitutive model (to describe the elastomer matrix) combined with Holzapfel-Gasser-Ogden's model (to represent the stiffer fabrics) were developed to describe the J-shaped behavior of the natural aortas and the fabric-reinforced composites. We anticipate that the suggested fabric-reinforced silicone elastomer composite design concept can be used to develop complex soft biomaterials, as well as in emerging engineering fields such as soft robotics and microfluidics, where the Windkessel effect can be useful in regulating the flow of fluids.

Characterizing the Biomechanical Properties of the Pubovisceralis Muscle Using a Genetic Algorithm and the Finite Element Method.

To better understand the disorders in the pelvic cavity associated with the pelvic floor muscles (PFM) using computational models, it is fundamental to identify the biomechanical properties of these muscles. For this purpose, we implemented an optimization scheme, involving a genetic algorithm (GA) and an inverse finite element analysis (FEA), in order to estimate the material properties of the pubovisceralis muscle (PVM). The datasets of five women were included in this noninvasive analysis. The numerical models of the PVM were built from static axial magnetic resonance (MR) images, and the hyperplastic Mooney-Rivlin constitutive model was used. The material parameters obtained were compared with the ones established through a similar optimization scheme, using Powell's algorithm. To validate the values of the material parameters that characterize the passive behavior of the PVM, the displacements obtained via the numerical models with both methods were compared with dynamic MR images acquired during Valsalva maneuver. The material parameters (c1 and c2) were higher for the GA than for Powell's algorithm, but when comparing the magnitude of the displacements in millimeter of the PVM, there was only a 5% difference, and 4% for the principal logarithmic strain. The GA allowed estimating the in vivo biomechanical properties of the PVM of different subjects, requiring a lower number of simulations when compared to Powell's algorithm.

An operator splitting strategy for fluid–structure interaction problems with thin elastic structures in an incompressible Newtonian flow

We present a computational framework based on the use of the Newton and level set methods to model fluid–structure interaction problems involving elastic membranes freely suspended in an incompressible Newtonian flow. The Mooney–Rivlin constitutive model is used to model the structure. We consider an extension to a more general case of the method described in Laadhari (2017) to model the elasticity of the membrane. We develop a predictor–corrector finite element method where an operator splitting scheme separates different physical phenomena. The method features an affordable computational burden with respect to the fully implicit methods. An exact Newton method is described to solve the problem, and the quadratic convergence is numerically achieved. Sample numerical examples are reported and illustrate the accuracy and robustness of the method.

Development of a modified Mooney-Rivlin constitutive model for rubber to investigate the effects of aging and marine corrosion on seismic isolated bearings

In this study, aging and marine corrosion tests of a large number of rubber material and rubber bearings have been carried out. The constitutive Mooney-Rivlin model parameters for a rubber isolated bearing have been determined. By applying the least-square method to the experimental data, the relationships between the aging time and the marine corrosion time with the constants in the constitutive model for a rubber bearing have been derived. Next, the Mooney-Rivlin model has been modified accordingly. Further, using the modified Mooney-Rivlin model and the Abaqus software, the performance of the rubber isolated bearings has been simulated. The simulation results have been compared to the experimental results so as to verify the accuracy of the modified model. The comparison shows that the maximum errors for the vertical and horizontal stiffnesses are 16.8% and 0.49%, respectively. Since these errors are considered acceptable, the accuracy of the modified constitutive model can be considered verified. The results of this study can provide theoretical support for the performance study on rubber isolated bearings under the complex ocean environment and the life-cycle performance evaluation of bridges and other offshore structures.

THE INFLUENCE OF PELVIC ORGAN PROLAPSE ON THE PASSIVE BIOMECHANICAL PROPERTIES OF PELVIC FLOOR MUSCLES

The biomechanical properties of the female pelvic floor tissues, such as muscles, fascia or ligaments are relevant when explaining pelvic disorders, since these may result from changes in the properties of those tissues. The aim of this study is to understand the influence of pelvic organ prolapse (POP) on the passive biomechanical properties of the pelvic floor muscles. For this purpose, magnetic resonance images at Valsalva maneuver were used, and an inverse finite element analysis technique was applied. The numerical models of the pubovisceralis muscle and pelvic bones were built from axial magnetic resonance images acquired at rest. The numerical simulation was based on the finite element method (FEM), by which the material constants were determined for three different constitutive models (Neo-Hookean, Mooney–Rivlin and Yeoh). The ratio between the values of the material constants for women with and without prolapse was approximately 43% for the parameter [Formula: see text] in the Neo-Hookean constitutive model, 57% and 24% for [Formula: see text] and [Formula: see text] in the Mooney–Rivlin constitutive model, and 35%, 21% and 14% for [Formula: see text], [Formula: see text] and [Formula: see text] in the Yeoh constitutive model. For the three constitutive models, the mean values of the material properties related with stiffness were higher for the muscles of women with POP. These increases in stiffness are in line with other experimental works involving vaginal tissue, which showing that the elasticity module is significantly higher in the prolapsed tissue when compared with normal tissue. The present work presents a noninvasive methodology based on the application of the FEM, which allows the establishment of a relationship between the stiffness of the pelvic floor muscles of women with POP and without this pathology.