Durability and failure investigations of products are of high interest to determine the risk of failure in engineering applications. Traditionally fracture mechanics is based on stress intensity factors and J-Integral. However, they are strictly valid under limited applications (for ex., monotonic loading, elastic materials etc.) The needs for fracture for nonlinear materials is sought by several of our customers. Electronics packaging, solders, tires, composites are typical examples. With this in mind, we introduced a novel approach in ANSYS 15.0, viz., Material force. You will find a clear description of the approach in a whitepaper that is available on our website.
This approach is vaild for linear-elastic, elastic-plastic material under complex loading condition such as cyclic loads. In ANSYS 16.0, we have extended the approach to hyperelasticity. For better understanding of the concept, a simple illustration is given here that the material force is imagined as a force closes a zipper (see image) in a pre-cracked structure. If the crack driving force gets large enough to reach the critical value or the fracture toughness of the material, fracture occurs and the crack propagates in the direction of the inverse of the crack driving force at the sharp crack tip.
Schematic definition of crack tip material force as force to open an equivalent zipper.
The material force concept offers a physically meaningful and clearly defined fracture mechanics parameter for general structural integrity assessment and crack growth prediction. The material force approach is applicable for, but not limited to, elasticity, plasticity, strain rate effect such as viscoelasticity and visco-plasticity and hyperelasticity, orthotropic and anisotropic materials. It is applicable for both small strain and larger strain formulation. It is also applicable for various loading condition such as monotonic and cyclic loading, etc.
It is shown that in the case of linear elastic and elasto-plastic material, the material force is equivalent to the energy release as well as J-Integral for plasticity material.
As illustrated in the image above, material force also helps determine the direction of crack growth. This opens up exciting opportunities for us to offer crack growth analysis. We welcome you to explore the details in the whitepaper, and the features released in ANSYS 15 & 16. We love to hear your feedback.
The post Material Forces for Fracture appeared first on ANSYS Blog.