(55a) Structure Induced Breakage
However, breakage also depends on the structure of the material. In some cases a uniform quasi-homogenous material may have a weak cleavage plane along a preferred crystal orientation. The orientation of these crystal planes in the particle can dictate the breakage pattern. In some cases the material comprising the particle is more or less homogenous, but the particle itself has a complex structure. Consider a potato chip with ridges, or a twisted pretzel, or a complex cereal particle designed with a pseudo-fibrous texture but made of homogenous dough and then baked. These particles are sensitive to breakage problems, but the mode of breakage is dictated by the structure of the particles. These structured particles are present in all industries. The ceramic scaffolding in catalytic converters is one example. The complex pressed or extruded ceramic shapes used as in electronic components are intricate shapes made of a very homogenous material. These intricate shapes are often prone to breakage. In cases where the structure of the particle determine the mode of breakage, a systematic look at stresses induced by random contacts of structured contacts can help determine the selection functions used in population balance models to describe breakage of these structured particles. We studied seven systems of structure particles. In each case the material making the structured particle was homogenous, but the particle was complex. We used a 3D CAD system to design particles with structures similar to the structure particles studied and then a FEM stress analysis to determine the critical stresses on the material when loaded with random contact points. The FEM analysis gave the pattern of stress distribution in the particle as well as the shape and size of the fragment that would form if the stress event was large enough to exceed the yield condition of the material. These fragments predicted from the FEM analysis were stored and used to determine the breakage selection function for the material. We also looked at the breakage sizes generated by a simple 3D truss model of the complex particles loaded with random contact loads. These are used to predict the selection function for the material and compared with breakage data from a tester that imposes simple stress-strain breakage on particles.