Biomechanical Simulation of Peyronie’s Disease

A pathological disorder of human penile function, known as Peyronie’s disease, is characterized by the formation of plaque particles within the tunica albuginea. The plagues in the shape of rigid plate form in the scars as a result of the imperfect healing process. Due to high stiffness, plagues are the source of pain and anomalous deformations during erectile penis function. The authors simulate the biomechanical behavior of the penile structure by a 3D finite element model. The numerical model is based on the real geometrical shape and the tissue structure with consideration of large nonlinear deformations. The penile erection is modeled by the initial strains imposed on the corpus cavernosa. The stress analysis is performed in a case study of various plague locations. The Peyronie’s syndrome manifested by the penis angular deviation simulated by the analysis is compared with the clinical data. The computational simulations provide a rational explanation for the clinical observations on patients. The objective is to apply the proposed modeling approach for the development and validation of treatment methods based on the application of shock waves.

Contact interaction of a predeformed plate which lies without friction on rigid base with a parabolic indenter

Within the framework of linearized formulation of a problem of the elasticity theory, the stress-strain state of a predeformed plate, which is modeled by a prestressed layer, is analyzed in the case of its smooth contact interaction with a rigid axisymmetric parabolic indenter. The dual integral equations of the problem are solved by representing the quested-for functions in the form of a partial series sum by the Bessel functions with unknown coefficients. Finite systems of linear algebraic equations are obtained for determination of these coefficients. The influence of the initial strains on the magnitude and features of the contact stresses and vertical displacements on the surface of the plate is analyzed for the case of compressible and incompressible solids. In order to illustrate the results, the cases of the Bartenev – Khazanovich and the harmonic-type potentials are addressed.

The effect of surface plastic hardening technology, residual stresses and boundary conditions on the buckling of a beam

The complex influence of the surface plastic hardening technology, residual stresses, and boundary conditions on the bending of a hardened beam of EP742 alloy was performed. A phenomenological method of restoring the fields of residual stress and plastic deformations performed by its experimental verification in the particular case of ultrasonic hardening is given. The correspondence of the calculated and experimental data for the residual stresses is observed. For assess the influence of the formed residual stresses on convex cylinders, the calculation methods are used for initial strains based on using analogies between the initial (residual) plastic strains and temperature strains in an inhomogeneous temperature field. This allowed us to reduce the consideration of the problem to the problem of thermoelasticity, which was further solved by numerical methods. The effect of four types of boundary conditions for fixing the ends of the beams (rigid fastening and articulation of the ends and ribs in various combinations, cantilever) on the shape and size of the bending of the beam 10×10×100 mm after ultrasonic hardening is studied in detail. It was found that the minimum deflection is observed with a hard seal of both ends of the beam. The effect of the thickness of the beam, which varied from 2 to 10 mm, on their buckling under the same distribution of residual stresses in the hardened layer was studied, and the nonlinear nature of the increase in the deflection boom with decreasing thickness for all types of boundary conditions was established. It is shown that under all boundary conditions, the curvature along the length of the beam practically does not change, therefore it can be considered constant. The consequence of this is the preservation of the hypothesis of flat sections after the hardening procedure, which is confirmed by the calculated profile of the beam section in plane symmetry, close to a straight line. The influence of the anisotropy of surface plastic hardening on the buckling of the beam was found to be significant, which can serve as the basis for choosing the optimal hardening procedure. The performed parametric analysis of the task is presented in the form of graphical and tabular information on the results of the calculations.

DEVELOPMENT AND APPLICATION OF GLOBAL-PROCESS TENSION ANALYSIS SOFTWARE FOR SUSPEND-DOME BASED ON ANSYS

Suspend-dome includes a single-layer latticed shell and the bottom tensegrity system. The overall stress state is closely related to the construction tension process. In order to provide guidance for safe construction of suspend-dome and trouble-free operation, an iterative method to determine initial strains of the bottom tensegrity system under zero state was proposed, and software for global-process tension analysis was developed based on ANSYS. A transform interface module was developed for rapid ANSYS parametric modeling. The optimization was conducted to achieve optimal prestress. A computational module was developed for the form-finding, force-finding, and construction tension analysis. The construction process of a suspend-dome with a span of 106 m was simulated by using the construction simulation method. It was shown that the iterative tension analysis method provided accurate and reliable simulations, which could be further used to determine the prestress and form of suspend-dome. The presuppositions and obtained computation sequences of the construction simulation method agree well with the practical construction process. This construction simulation method can be utilized for construction simulation.

Direct Analysis of Post-Shakedown Quantities With the STPZ Considering Multi-Parameter Loading

If a structure is subjected to cyclic loading, strain, displacements etc. may accumulate cycle by cycle due to a ratcheting mechanism. Design Codes frequently require strain limits to be satisfied at the end of the specified lifetime of the structure. Usually, this is requested to be done considering all load sets pairwise. However, this leads to the fact that ratcheting cannot be detected, if it occurs only because of multi-parameter loading. Ordinary incremental step-by-step calculations can easily exceed time and hardware resources. This is particularly true for travelling loads, where many load steps are required for one load cycle. As an alternative, the Simplified Theory of Plastic Zones (STPZ) is used in the present paper. Being a direct method, effects from load history are disregarded. The elastic-plastic behavior in the state of either elastic or plastic shakedown is estimated on the basis of purely elastic analyses. Two kinds of linear elastic analyses are to be performed, fictitious elastic analyses for each set of loading, and a number of modified elastic analyses. Few of these analyses are usually sufficient to obtain reasonable estimates of the post-shakedown quantities. Trilinear material behavior is adopted along with kinematic hardening, a Mises yield surface and an associated flow law. The modified elastic analyses are performed making use of modified elastic parameters (Young’s modulus and Poisson’s ratio) in the plastic zone and applying suitably defined initial strains. The results obtained can be improved iteratively. The theory of the method is briefly explained and its application is shown using an example with multi-parameter loading.

Short-Term and Long-Term Mechanical Models of Wellbores Considering Cement Consolidation and Formation Creep

Summary With oil and gas wells extending deeper and deeper, downhole conditions become increasingly complicated, and thus increasingly sophisticated wellbore models are needed. Current wellbore models usually neglect the coupling effect in the cement–consolidation process and do not sufficiently consider the whole operation process of the wellbore. To overcome these shortcomings, short–term and long–term mechanical wellbore models while considering the relevant stages in wellbore life are built. In the short–term model, wellbore–operation stages include casing running, cement displacement, and cement consolidation. The governing equation of cement consolidation while considering the coupling effect between cement hardening and volume change is presented. In the long–term model, the governing equation of formation creep while considering prestresses and initial strains is given. The elastic/viscoelastic–correspondence principle and stress–superposition method are used to simplify the derivation. Next, the effects of relevant factors on short–term and long–term wellbore stresses are analyzed. The results show that wellbore stresses caused by cement consolidation will be underestimated when the coupling effects are neglected. The most vulnerable positions for wellbore failure are on different cylinder elements under different wellbore stages. Wellbore properties, short–term stresses, and formation creep greatly affect wellbore mechanical behaviors. Therefore, the new model provides an important basis for wellbore–failure prediction and optimal design.

Algorithms for Solving Boundary Value Problems of Deformable Solid Mechanics in View of Creep Strain

Further development of power and, primarily, engine engineering is associated with significantly increasing specific indicators. For example, the main trend in development of gas turbine engines is to increase gas parameters before the turbine. At the same time, there is an intensive growth of thermal and mechanical tension, and first of all this applies to the parts and components of the flow range. The destruction of these structural elements may have grave consequences. Increasing reliability and durability of responsible components of engines under operating conditions of complex cyclic thermo-mechanical loading is one of the priority tasks of modern engine engineering.One of the factors to determine a design performance is high-temperature creep. When solving the problems of deformable solid mechanics (DSM) in terms of creep, various options of the theory of hereditary creep and three main technical theories of aging, flow and hardening are widely used. There are also theories known that use an apparatus of the structural models and mechanical analogues to describe the creep. Most theories satisfactorily describe the creep strain under constant or slowly changing loads. Analysis of stress-strain states under variable loads is better described by the theories of flow and hardening, and the theory of hardening has some advantages over the theories of flow, as it gives more exact approximation for experiment results. From the point of view of the computing cycle arrangement, the technical theories have well-known advantages over the hereditary ones.When using the finite element method (FEM) to solve the boundary value problems of DSM considering the creep strain, an explicit or implicit Euler scheme is very often used. Depending on the features of the problem under consideration, a solution algorithm is constructed either in accordance with the method of initial stress, or by the method of initial strains. The method of initial strains when solving the problems in terms of creep is used more often, because the application of an initial stress method for this class of problems is technically much more complicated. The paper examines the explicit and implicit Euler schemes in combination with FEM. Both schemes are formulated in accordance with the method of initial strains. A constitutive relation was chosen in the form of the theory of flows.

Numerical Analysis of Effectiveness of Strengthening Concrete Slab in Tension of the Steel-Concrete Composite Beam Using Pretensioned CFRP Strips

One of the methods to increase the load carrying capacity of the reinforced concrete (RC) structure is its strengthening by using carbon fiber (CFRP) strips. There are two methods of strengthening using CFRP strips - passive method and active method. In the passive method a strip is applied to the concrete surface without initial strains, unlike in the active method a strip is initially pretensioned before its application. In the case of a steel-concrete composite beam, strips may be used to strengthen the concrete slab located in the tension zone (in the parts of beams with negative bending moments). The finite element model has been developed and validated by experimental tests to evaluate the strengthening efficiency of the composite girder with pretensioned CFRP strips applied to concrete slab in its tension zone.

EXPERIMENTAL STUDY OF CREEP AND SHRINKAGE STRAINS IN FINE- AGGREGATE CONCRETES

The paper studies creep and shrinkage processes running in fine-aggregate concretes with plasto-elastic properties (deformations) under short-time loading are different from those of standard heavy concretes. Experimental studies of creep and shrinkage strains in fine-aggregate concretes that are based on sands with different fineness moduluses permit to compare prestress losses resulting from the creep and shrinkage of concrete. Usually these factors produce an aggregate effect, which makes the study of the processes that run in concrete under long-time influence noticeably complicated. There paper contains analysis results obtained by experimental studies of concrete prisms at different initial strains in the range of , with loading age of t= 14 or 28 days and different properties of concrete mixes. Concrete mix properties were modified by using sands with different fineness modulus. Likewise in order to determine creep and shrinkage deformations due to long-time loads the samples were tested under stress during 14, 73 and 180 days. All experimental data have been systematized in tables and are represented by diagrams. The analysis has helped to investigate the effects of relative stains on the creep deformation in concrete and to define the boundary line between linear and non-linear creep with relation to the stresses in concrete. Analytical description of non-linear deformations was performed with the help of N.H.Arutyunyan’ and I.I.Ulitsky methods. The resultant calculations formed a basis for the recommendations to simplify problem solving methods considering non-linear creep of concrete.

Actuation of Parabolic Cylindrical Shell Panels With Light-Activated Shape Memory Actuators

Parabolic cylindrical shell panels are used in optical and aerospace structures. Light-activated shape memory polymer (LaSMP) is a novel smart material and it is capable of offering a non-contact actuation and control in room temperature. In this study, the parabolic cylindrical shell panels laminated with LaSMP actuators are analyzed. Firstly the dynamic equations of the parabolic cylindrical shell panels coupled with the LaSMP actuators are established; the modal control force of LaSMP actuators is derived with the modal expansion method. Then the strain variation of the LaSMP actuators are modeled based on the chemical kinetics. Further, the shape-memory recovery effect of an LaSMP actuator with initial strains is measured in laboratory. The experiment data of strain variation are used to validate the established strain model. Finally, in the case study the modal control forces of LaSMP actuators for the first four shell modes, i.e., the (1,3), (1,4), (2,4) and (2,5) modes are analyzed. The study shows that LaSMP actuators can induce strains not only in the x, Ψ directions but also in the xΨ direction (induced by the warping effect). The reason is that LaSMP actuators are easy to be cut in any shapes and be deformed in any directions. Thus, LaSMP actuators have potential applications for the non-contact vibration control of double-curvature shells.