Papers by Author: Min You

Abstract: The effect of the elastic modulus of the adhesive for primer on the impact response of the steel butt joint bonded by multi-layer under the Izod impact test is investigated using the elasto-plastic finite element method (FEM). The results obtained from numerical simulation show that both the elastic strain and plastic strain occurred at the point 0.5 mm away from the upper or lower surface after a certain time is increased significantly when the elastic modulus of the primer is decreased from 2.875 GPa to 0.825 GPa. The absolute value of the stress Sx response at these to nodes is decreased when the elastic modulus of the primer is decreased. The value of the stress Seqv is the highest one after 0.1 ms at the points 0.5 mm away from the upper or lower surface when the butt joint is bonded by the multi layer consisted of Epoxy-Phenolic-Epoxy adhesives.

Abstract: The effect of the outer chamfered angle at the free end of adherend on the stress distribution in weld-bonded single lap aluminum joint was investigated using elasto-plastic finite element method (FEM). The results from the numerical simulation showed that the peak stress along the bondline at the end of lap zone decreases when the adherend is chamfered on the outside and it is decreased greatly as the chamfer angle decreased. Compared to the results from the normal joint, a 15 degree chamfer angle may be appropriate to optimize the stress distribution in the weld-bonded single lap aluminum joint.

Abstract: The effect of dual adhesives to form multi-layer on the stress distributed in adhesively bonded single lap aluminum joint was investigated using elasto-plastic finite element method (FEM). The results from the numerical simulation showed that the values of the peak stress along the bondline are influenced evidently when there is a multi-layer formed by a middle layer with higher elastic modulus adhesive and two layers with lower elastic modulus adhesive.

Abstract: Three groups of strain gauges were embedded in the epoxy adhesive coating deposited on the steel substrate with different depths. The transverse and longitudinal strains during the curing process were tested. It was found that the transverse and longitudinal strains decreased remarkably when the curing time was lower 24h. At a longer curing time, the strains almost kept steady. In addition, the more close to the surface of epoxy adhesive coating, the higher the strains were. The solidification contraction stress in the epoxy adhesive coating during the curing process were also estimated, and the attempts were made to relate them to the restrained contraction of the epoxy adhesive coating.

Abstract: The effect of dual adhesives with different length ratio on the stress distributed in adhesively bonded single lap steel joint was investigated using elasto-plastic finite element method (FEM). The results from the numerical simulation showed that the peak stress along the bondline moves from the ends of the overlap to the middle part of lap zone. Compared with the results from the mono-adhesive system, appropriate bond-length ratios is beneficial to optimize the stress distribution and it is 0.4 for bi-adhesive bonded single lap composite joint.

Abstract: The effect of the notch depth on the impact toughness of the adhesively bonded steel butt joint under Izod impact test is studied using both the finite element method and experimental method. The results obtained from numerical simulation showed that the response time with the peak stress Seqv occurred becomes little longer when the notch depth increased from 2 mm to 8 mm. And a negative longitudinal stress occurred when there is an 8 mm depth notch which might be beneficial to subject impact load. The results from the experiments showed that the effect of notch depth is evidently on the Izod impact properties. The impact energy absorbed by unit area of joint is increased as the notch depth increase

Abstract: The effect of 4 mm long metal block bonded to the end of the overlap zone on the stress distributed in adhesively bonded single lap steel joint was investigated using elasto-plastic finite element method (FEM). The results from the numerical simulation showed that the stress is varied a little when the joints with a couple of 4 mm long metal block adhered to both ends of the over lap or with a couple of adhesive fillet. Compared to the joint without the metal block, it is advantageous of reducing the peak stress in the adhesive layer near the ends of the lap zone in adhesively bonded single lap steel joints but its effect is less than that of the joint with a couple of adhesive fillet. There is no evidential difference in the effects between the steel and aluminum block.

Abstract: The effect of the impact velocity on the responses of the adhesively bonded steel butt joint during Izod impact test and the failure procedure is studied using the finite element method software ABAQUS. The results obtained show that the failure time of the element becomes little shorter when the impact velocity increased from 3.2 m/s to 10.2 m/s. The peak value of the Seqv in element 1 increases first and then decreased when the impact velocity reached 4.2 m/s. When the impact velocity is higher than 6.2 m/s, the peak value of the Seqv increased again as the impact velocity increased until 10.2 m/s. It is recommended that the impact velocity of 3.2 m/s or 5.2 m/s is suitable for Izod impact test for the adhesively bonded steel butt joint.

Abstract: Owing to the lack of a good theory method to obtain the accurate equivalent elastic constants of hexagon honeycomb sandwich structure’s core, the paper analyzed mechanics performance of honeycomb sandwich structure’s core and deduced equivalent elastic constants of hexagon honeycomb sandwich structure’s core considering the wall plate expansion deformation’s effect of hexagonal cell. And also a typical satellite sandwich structure was chose as an application to analyze. The commercial finite element program ANSYS was employed to evaluate the mechanics property of hexagon honeycomb core. Numerical simulation analysis and theoretical calculation results show the formulas of equivalent elastic constants is correct and also research results of the paper provide theory basis for satellite cellular sandwich structure optimization design.

Abstract: Four series of cermets with the SiC whisker content between 0 and 1.0 wt.% were prepared by vacuum sintering. The transverse rupture strength (TRS), hardness (HRA) and fracture toughness (K_IC) were also measured. The SiC whisker addition was located at the grain boundaries, which prevented grain boundary migration and restrained the grain growth. However, an increasing SiC whisker content decreased the wettability of the binder on the Mo₂FeB₂ hard phase. The highest TRS and fracture toughness was found for the cermets with 0.5 wt.% SiC whisker addition, whereas the cermets without SiC whisker addition exhibited the maximum hardness.