Field structure at mode Ⅲ dynamically propagating crack tip in elastic-viscoplastic materials

An elastic-viscoplastic mechanics model is used to investigate asymptotically the mode Ⅲ dynamically propagating crack tip field in elastic-viscoplastic materials. The stress and strain fields at the crack tip possess the same power-law singularity under a linear-hardening condition. The singularity exponent is uniquely determined by the viscosity coefficient of the material. Numerical results indicate that the motion parameter of the crack propagating speed has little effect on the zone structure at the crack tip. The hardening coefficient dominates the structure of the crack-tip field. However, the secondary plastic zone has little influence on the field. The viscosity of the material dominates the strength of stress and strain fields at the crack tip while it does have certain influence on the crack-tip field structure. The dynamic crack-tip field degenerates into the relevant quasi-static solution when the crack moving speed is zero. The corresponding perfectly-plastic solution is recovered from the linear-hardening solution when the hardening coefficient becomes zero.

Detonation Propagation Characteristics of Superposition Explosive Materials

In order to investigate detonation propagation characteristics of different charge patterns,the detonation velocities of superposition strip shaped charges made up of a detonating cord and explosives were measured by a detonation velocity measuring instrument under conditions of different ignition.The experimental results and theoretical analysis show that the maximum detonation propagation velocity depends on the explosive materials with the maximum velocity among all the explosive materials.Using detonating cord in a superposition charge can shorten detonation propagation time and improve the efficiency of explosive energy.The measurement method of detonation propagation velocity and experimental results are presented and investigated.

Effects of Different Propagation Materials and Cultivation Years on the Yield of Polygonatum odoratum under the Forest

This paper mainly studies the effects of different propagation materials and cultivation years on the yield of Polygonatum odoratum under the forest.In this study,the cultivation experiment of P.odoratum was carried out by using the stem tip,stem body and seeds of P.odoratum as propagation materials.The yield of P.odoratum in different cultivation years with propagation by rhizome was also investigated.That is,the continuous growth of P.odoratum and the yield of P.odoratum each year after cultivation was statistically analyzed.The results showed that the germination rate under stem tip cultivation was fast,and the emergence time was also fast,which was more than 2 weeks earlier than that under stem body cultivation,and the seedling emergence rate reached 100%.The stem body was a new plant formed by sprouting from the buds of internodes,and the emergence rate was more than 95%.P.odoratum propagated by rhizome was harvested in the third or fourth year after cultivation,and the third year was the best harvest time.