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The plastic deformation under the influence of an inflated balloon in a stent design. The foreshortening and dogboning are investigated.
The Nonlinear Structural Materials Module augments the mechanical capabilities of the Structural Mechanics Module and the MEMS Module with nonlinear material models, including large strain plastic deformation capabilities. When the mechanical stress in a structure becomes large, certain nonlinearities in the material properties force you to abandon linear material models. This situation also occurs in some operating conditions, such as high temperature. The Nonlinear Structural Materials Module adds elastoplastic, viscoplastic, creep, and hyperelastic material models.
User-defined material models based on stress or strain invariants, flow rules, and creep laws can easily be created directly in the user interface with the built-in constitutive laws as a starting point. You can both combine material models and include multiphysics effects. The tutorial models that accompany the module illustrate this by showcasing combined creep and plasticity, thermally induced creep and viscoplasticity, as well as orthotropic plasticity. The Nonlinear Structural Materials Module also has important applications where it is combined with the Fatigue Module and the Multibody Dynamics Module.
This example demonstrates how to use temperature dependent materials within the Nonlinear Structural Materials Module.
A large container holds pressurized hot water. Several pipes are attached to the pressure vessel. Those pipes can rapidly transfer cold water in case of an emergency cooling. The pressure vessel is made of carbon steel with an internal cladding of stainless steel. In case of a fast temperature transient, the differences in thermal expansion properties between the materials will cause high stresses.
A stent is a wire-mesh tube used to open a coronary artery during angioplasty, a process for the removal or compression of plaque. Their design is of significance for percutaneous transluminal angioplasty with stenting. During this procedure, a stent is deployed into the blood vessel by means of a balloon. The expanded stent acts as a scaffold that keeps the blood vessel open.
During this procedure, damage can be inflicted on the artery by both the nonuniform expansion of the stent, as well as by its foreshortening. To check the viability of a stent design, you can study the deformation process under the influence of the radial pressure that expands the stent. With this model you can both monitor the dogboning and foreshortening effects, and draw conclusions on how to change the geometry design parameters for optimum performance.
This example studies viscoplastic creep in solder joints under thermal loading using the Anand viscoplasticity model, which is suitable for large, isotropic, viscoplastic deformations in combination with small elastic deformations.
The geometry includes two electronic components (chips) mounted on a circuit board by means of several solder ball joints. Significant plastic flow appears after about 40 s of thermal loading.
This model aims to investigate the inflation of a rubber balloon with different hyperelastic material models, and compare the results to analytical expressions.
A controlled inflation could benefit clinical applications, cardiovascular research, and the medical device industry, thus the importance of understanding the hyperelastic behavior during balloon inflations. The example is taken from the book “Nonlinear Solid Mechanics”, by G. Holzapfel.
The elastoacoustic effect is a change in the speed of elastic waves that propagate in a structure undergoing static elastic deformations. The effect is used in many ultrasonic techniques for nondestructive testing of prestressed states within structures.
This example studies the elastoacoustic effect in steels typically used in railroad rails. The analysis is based on the Murnaghan hyperelastic material model, which is based on a 3rd order expansion of the elastic potential in terms of displacement gradients. This material model can be used to study various nonlinear effects in materials and structures, of which the elastoacoustic effect is an example.
A circular metal bar of elasto-plastic material with nonlinear isotropic hardening behavior is subjected to uniaxial tension. Affected by significant stresses the bar experiences high plasticity. The phenomenon of necking is captured and its growth is accurately simulated. The change in radius is in good agreement with results found other literature. This example is a classical benchmark for large strain plasticity codes.
A pressure vessel is designed to hold liquids or gases at substantially higher or lower pressures than the ambient pressure. A high pressure difference requires a correct design in order to avoid catastrophic failures.
The Stress Analysis of a Pressure Vessel app is an example of how you can design a tool for checking a family of components with a parameterizable geometry. The purpose of the app is to determine if the vessel will be able to sustain the applied internal pressure without exceeding a specified limit on the volume fraction of the material, which has exceeded the yield limit. The app solves for orthotropic plasticity using the Hill Orthotropic Criterion.
You can adjust the geometric parameters of the vessel, internal pressure, material properties, and the volume fraction of the vessel that is allowed to exceed the yield limit. Results from the app include the pressure at which initial yield occurs, the yielded volume fraction below the allowed limit, and the pressure at which the yielded volume fraction reaches the specified limit.
This example simulates the insertion of a snap hook in its groove. Fasteners like this are common in the automotive industry, for example, in the control panel of a car. In this case it is important to know the force that must be applied in order to place the hook in the slot and also the force needed to remove it. From a numerical point of view, this is a highly nonlinear structural analysis, due to the contact interaction between the hook and the slot, the elasto-plastic constitutive law selected for the hook, and the geometrical nonlinearity originated from the large displacement.