Fracture Mechanics and ANSYS Capabilities

You yes hi everyone I hope you can all hear me today we are going to talk about Fracture Mechanics and the capabilities in ANSYS. First, a company overview: we are the ANSYS Elite Channel Partner in California and Nevada.

We provide sales, marketing, training, technical support, and consulting services for the ANSYS software products. Our offerings include structural, fluids, electronics, multi-physics, optics, and a VR system that works with the ANSYS products. We also have an Ozen cloud computing platform.

We collaborate with other offices on the East Coast with Mallett technology and CatFam in Michigan. We also offer a Fracture Mechanics class, a two-day class where we go through the history of Fracture Mechanics, crack initiation, crack propagation, theory, and implementation in ANSYS.

Workshops are included. These classes are offered in our Sunnyvale location. According to Battelle, NBS study, fracture costs about $120 billion a year. This was quoted in 1983. So, fracture mechanics is the study of flows and cracks in materials.

It mostly deals with crack growth and life estimation. We are looking into how cracks propagate and how cracks form in parts. The strength of material approach does not anticipate the presence of cracks in the material.

The stress in a panel when a force F is applied and the cross-sectional area is A is sigma F divided by A. However, if a small crack is present in that panel, the stress goes up drastically at the tip of the crack.

The presence of cracks can significantly decrease the structural strength and reliability. Flow size, crack size, denoted as A, is an important parameter in Fracture Mechanics. The larger the crack size, the larger the difference in stress intensity factor.

Fracture toughness replaces strength of materials in Fracture Mechanics. In Linear Elastic Fracture Mechanics (LEFM), fracture toughness of a material is determined from stress intensity factor, denoted as K1C. This is a material property, just like ultimate strength and yield stress of a material.

If there is a lot of plasticity ahead of the crack tip, we talk about J1C, determined by the J integral. The J integral is a path-independent line integral that measures the strength of the singular stresses and strains near the crack tip. Crack growth is the separation process of two crack phases.

The most general approach is the energy release rate method. A simple criterion based on energy release rate can be expressed as a condition for life.

In ANSYS, stress intensity factors are output as K1, K2, and K3 for mode 1, mode 2, and mode 3, and they characterize the stress state near the crack tips. They are applicable for linear isotropic elasticity. The J integral is used for isotropic plasticity.

Energy release rate, G, is used for linear isotropic, orthotropic, and anisotropic elasticity. Material force is used for linear and nonlinear materials, like hyper-elasticity and plasticity.

Fracture mechanics modes include mode 1, mode 2, and mode 3. Crack growth usually takes place in mode 1 or very close to it. The crack realigns itself such that the load is perpendicular to the crack face.

In ANSYS, the software can do automatic semi-elliptical crack and arbitrary crack, semicircular crack, pre-mesh crack, interface delamination, and contact debonding. The smart crack growth method is used for mode 1 dominant crack growth in 3D.

It assumes linear elastic isotropic materials, and it ignores large deflection, finite rotation effects, crack tip plasticity effects, and crack tip closure or compression effects. The fracture criteria for static crack growth include critical stress intensity factor and J integral.

Fatigue crack growth is based on Paris law, given by DA over DN is equal to C times Delta K to the M power. To do crack propagation, an initial crack must be input in ANSYS. This can be a pre-mesh crack or a semi-elliptical or arbitrary crack.

The smart crack growth option can then be inserted, and the crack growth can be set to static or fatigue. The Paris law constants must be specified for fatigue crack growth. The crack growth methodology can be set to lifecycle prediction or cycle by cycle.

The minimum and maximum increments of crack extension can be controlled. The simulation can be stopped at maximum crack extension. In the example given, a model is subject to a thermal load. The thermal load contribution is enabled.

Surface pressure loads and tabular pressure loads as a function of time are supported. PCG and spar solvers are also supported. Distributed answers can be used with fracture mechanics problems, and they can make the runs a lot faster. Thank you for attending our webinar.

If you have any questions, please feel free to send an email to info at ozeninc.com. All of these seminars can be found on our website, ozeninc.com, in the resources webinar library. We are Ozen Engineering, the channeled pipeline partner out on the West Coast.

Our address is in Sunnyvale, California.