Fragmentation of brittle spheres compressed statically and dynamically between two rigid platens

Department of Civil and Environmental EngineeringRefereed conference pape

Dynamic and static compressions of rock-like spheres between two flat platens

For static compressions of spheres, a new stress analysis for isotropic elastic spheres compressed between two rigid platens is proposed by incorporating the Hertz contact stress. The predictions of the failure load for various sizes and strengths of spheres agree very well with our experiments. For dynamic compressions of spheres, a simple crushing, analysis illustrates that the size of the contact zone can be estimated quite accurately in terms of the size of the sphere, the dynamic hardness, and the impact energy alone. We found that although the maximum contact force is larger in the dynamic case than in the static case, the energy required to fracture the sphere is larger under dynamic situation. By comparing the static and dynamic tests, we found that the dynamic impact energy required to fracture a sphere can be approximated as 1.5 times of those for the static test. As expected, the dynamic impact energy increases monotonically with the size and strength of the spheres. However, the contact time at failure does not exhibit a clear trend with the changes in size and strength of the spheres

Dynamic breakage and fragmentation of brittle single particles of various sizes and strength

Breakage,comminutioa,crushing and fragmentation of brittle solids under dynamic impacts are an important applied mechanics and rock mechanics problem.In civil engineering applications,impact-induced-fragmentation relates to crushing of rock mass during mining process,tunneling,and aggregate production.The main objective of this paper is to outline some of our recent experimental,analytical and numerical efforts in studying the dynamic fragmentation process in brittle particle.First,an analytical solution of a solid sphere compressod dynamically between two rigid flat platens is derived analytically.Secondly,a sequence of double impact tests on spheres were conducted using an impactor Dynatup 8250 at HKUST,with both impact velocity and contact force at the impactor measured accurately.Finally,a newly developed computer program,DIFAR,is used to investigate the mechanism of dynamic fragmentation.The paper will summarize and discuss briefly all three aspects of our comprehensive approach.Department of Civil and Environmental Engineerin