This post provides the approach to extract the plastic strain in MD simulation. We can compute the atom displacement as the trajectory from the MD simulation, but the strain is the concept in continuum mechanics, it is really hard to compute the tensor in a discrete system. Recently, some tools provide this function based on a theory that accounting the effects of the neighbor atoms. While considering the relative displacement with the neighbor atom and using the weight function, the deformation gradient tensor can be calculated. Therefore, the strain tensor is obtained. Plastic strain can be expressed as,

LAMMPS has the capability to restart the job from the binary file. According to the description from the official website, the command restart can write out a binary restart file with the current state of the simulation every certain timestep. This command has two modes: write the binary file or the data file. If you wish to use the data file, then a convert command is needed in this scenario. Here we do not consider the data file.

Since the previous post already obtained the stress intensity factor and energy release rate, we can use them to simulate the crack growth progress. In fracture mechanics, a typical example for energy release rate calculation is the double cantilever beam (DCB). Also, the DCB test is one of the widely used test metdho to measure the Mode I fracture toughness of different materials (ASTM D5528). This post will use a double cantilever beam to simulate the crack growth based on VCCT, this is also a classical example in Ansys document.

I previously analyzed the stress intensity factor for an edge crack of a plate. Now, I want to extend the previous example to calculate the crack energy release rate. The energy release rate calculation is quite straightforward since Ansys CINT supports the VCCT method to obtain the energy release rate. In this example, I move the crack to the plate center and set different material properties for the left and right side of the plate.

In structural analysis, the reticulated shell is one of the structure forms used for long span spatial structure design. There are several types for reticulaed shell structures. I am interested in creating such structure in Ansys. Hence, this post mainly focuses on the creation and buckling analysis for single-layer reticulated shell structure.

Since my study has something to do with the fatigue under dynamic loading, I have to simulate the crack behavior and its SIF with dynamic effect. Thus, this post analyzes an example including the evolution of crack stress intensity factor under dynamic loading. In the prevous post, we do not have to set the density since the model is under static analysis. However, for dynamic loading, density is critical and should be set correctly

Since Ansys can support various fracture analysis types, this post analyze a typical 2D fracture behavior under the thermal effect. Unlike the general static analysis, the thermal effect analysis requires us to save the results file first. Therefore, we should split the analysis into two steps.

Previously, I analyzed the crack stress intensity factor for a 2D plate. An edge crack is created at the bottom of the plate and the SIF is obtained at the crack tip. When I try to create a 3D model, I found there are some difference for defining parameters associated with the crack tip. So, I create another example to determine the SIF in a 3D model.

To determine the stress intensity factors with Ansys, we analyze the following 2D example with an edge crack. The width and height of the plate are W = 1.0 m and H = 1.0 m respectively. The left edge is fixed while the stress of 5 MPa is applied to the right edge. At the bottom edge, there exists an edge crack with the length a = 0.2 m. The thickness of the plate is 5 mm. The model is shown in the following figure,

Working with Abaqus explicit calculations recently, I encountered a common issue: the model and materials were fine, and calculations were possible, but the computation speed was extremely slow. With the stable time increment step at the magnitude of $10^{-7}$, even simulating just one second could require thousands of hours of computation, which is impractical. After studying various sources, I’ve summarized methods to accelerate Abaqus explicit calculations.