Study On The Dynamic Behavior Of Foam Metals Based On Path Line Method

Foams are widely used in many industrial fields, such as aerospace, automotive, construction and so on because of their low relative dens ity, high specific strength and superficial area, light weight, sound insulation, heat insulation, as well as good permeability. As a new kind of excellent protective materials, foams tend to be under impact. So the dynamic behavior of foams under high-speed impact is very important. Scholars had many related research achievements, but whether the foams are strain rate sensitivity or not still exists a great of disputes.In this paper, the path line method was used to study the dynamic behavior of foams. The problems in the process of dynamic experiment using the path line method were discussed in detail combined with the finite element simulation and the path line method. The new partition rule was acquired to improve the accuracy of the path line method experiment. The precision was higher when enough zones were divided in the velocity field than the divis ion of the characteristic inflection point while it could guarantee the stability of the difference scheme and reduce the accumulation error. The rule of velocity field partition should consider both the phase speed of partic le velocity and the characteristics of the velocity curves. In addition the phase speed of partic le velocity in each zones in half of the maximum value should be greater than the minimum value. A three dimensional random Voronoi models was established to study the mechanical properties of foams. The complete dynamic stress strain curve was obtained combined with the inverse impact experiment of finite element simulation and the path line method. Graphics were used to express the relation between velocity-time curve and dynamic stress-strain curve more intuitively.In this paper, the pore size or the wall thickness on the effect of dynamic properties of foams were studied based on the path line method. Results show that when the strain rate ranged in the 104s-1 ~ 105s-1, the platform stress of 4 mm hole diameter of foams was larger than which of 2 mm pore size, that means the foam has a certain aperture effect. The strain rate in the case of the foam pore size is 2 mm is an order of magnitude higher than which the pore size is 4 mm, but the platform stress when the foam pore size is 4 mm is higher, which shows that the aperture effect relative to the strain rate effect plays a more important role when studying the dynamic behavior of the foam. Us ing the entity model and three-dimensional random Voronoi models to study the dynamic behavior of the foam, the results showed that the platform stress under the condition of high strain rate was bigger compared with which under the condition of quasi static case as the path line method eliminates the influence of inertia effect. The enhancement part of the platform stress is a function of strain rate effect of foams. The conclusion showed that the foam is a kind of strain rate sensitive material. We must consider the strain rate effect when studying the dynamic behavior of foams.