Modelling and Simulation on the Effect of Hot Forming Damage on Three-Point Bending Performance of Beam Components

The effects of forming damage are analyzed,which occur during hot stamping process,on the load-carrying capacity and failure mode of hot stamped beams.A damage-coupled pre-forming constitutive model was proposed,in which the damage during hot stamping process was introduced into the service response.The constitutive model was applied into the three-point bending simulation of a hot stamped beam,and then the influences of forming damage on the load-carrying capacity and cracks propagation were investigated.The results show that the forming damage reduces the maximum load capacity of the hot stamped beam by 7.5%.It also causes the crack to occur earlier and promotes crack to propagate along the radial direction of the punch.

Heterogeneous Fracture Simulation of Three-point Bending Plain-concrete Beam with Double Notches

Plain concrete is regarded as a two-phase material comprising randomly distributed aggregates and mortar matrix. A series of three-point bending concrete beams with symmetric or asymmetric double notches are modeled using the modified random aggregate generation and packing algorithm. The cohesive zone model is used as the fracture criterion and the cohesive el- ements are inserted into both the mortar matrix and the aggregate-mortar interfaces as potential micro-cracking zones. The dead and alive crack phenomena are studied experimentally and nu- merically; and the influences of notch location, aggregate distribution and gradation on fracture are numerically evaluated. Some important conclusions are given.

Peridynamic Modeling and Simulation of Fracture Process in Fiber-Reinforced Concrete

In this study,a peridynamic fiber-reinforced concrete model is developed based on the bond-based peridynamic model with rotation effect(BBPDR).The fibers are modelled by a semi-discrete method and distributed with random locations and angles in the concrete specimen,since the fiber content is low,and its scale is smaller than the concrete matrix.The interactions between fibers and concrete matrix are investigated by the improvement of the bond’s strength and stiffness.Also,the frictional effect between the fibers and the concrete matrix is considered,which is divided into static friction and slip friction.To validate the proposed model,several examples are simulated,including the tensile test and the three-point bending beam test.And the numerical results of the proposed model are compared with the experiments and other numerical models.The comparisons show that the proposed model is capable of simulating the fracture behavior of the fiber-reinforced concrete.After adding the fibers,the tensile strength,bending strength,and toughness of the fiber-reinforced concrete specimens are improved.Besides,the fibers distribution has an impact on the crack path,especially in the three-point bending beam test.

Elastic Modulus of 304 Stainless Steel Coating by Cold Gas Dynamic Spraying

304 stainless steel coating was deposited on the IF steel substrate by cold gas dynamic spraying （CGDS）, and the elastic modulus of the 304 stainless steel coating was studied. The elastic modulus of cold sprayed 304 stain- less steel coating was measured using the three-point bend testing and the compound beam theory, and the other me- chanic parameters （such as the equivalent flexural rigidity and the moment of inertia of area） of the coatings were also calculated using this compound beam theory. It is found that the calculated results using the above methods are accu- rate and reliable. The elastic modulus value of the cold sprayed 304 stainless steel coating is 1. 179 X 105 MPa, and it is slightly lower than the 304 stainless steel plate （about 2 X 105 MPa）. It indicates that the elastic modulus of the cold sprayed coatings was quite different from the comparable bulk materials. The main reason is that the pores and other defects are existed in the coatings, and the elastic modulus of the coatings also depends on varies parameters such as the feed stock particle size, porosity, and processing parameters.