Assessment of confinement’s influence on a concrete target’s ability to approximate semi-infinite perforation performance

The ability to accurately evaluate impact penetration resistance of a structural element in an experimental setting often requires the experimental impact specimen configuration to be as close as possible to a structural element in a fielded protective design scheme. This includes the target’s capability to estimate the semi-infinite response of a structural element such as a wall where inertial confinement is provided by undamaged material surrounding the area damaged by impact. Artificially simulating this confinement in an experimental target can take several forms, including use of a circumferential steel ring as a confining medium. Experimental data gathered from impact tests were utilized to create a representative numerical simulation of a confined target design. This simulation evaluated artificial and inertial confinement on concrete perforation by varying target to projectile diameters with and without artificial confinement. Perforation performance was found to be unaffected by confinement type when the target diameter to projectile diameter ratio was 16. Semi-infinite surface approximation was found to occur when the target diameter to projectile diameter ratio was 64 despite the confinement type at higher impact velocities; however, this ratio could be reduced while maintaining semi-infinite performance for lower velocity impacts.

Effect of Process Parameters on Repeatability Precision of Weight for Microinjection Molding Products

The repeatability precision of weight for injection molded products is important technical parameter to measure the quality and accuracy of injection molded products and evaluate the performance of injection molding machine. The influence of mold temperature, melt temperature, packing pressure, and packing time on the weight of microinjection molding products was studied by Taguchi orthogonal experiment. The influence of peak cavity pressure on the weight of products also was analysed. The experimental results show that the packing pressure is the most important process parameter affecting both the weight of the tensile and the impact specimens. With the increase of the packing pressure, the weight of the tensile and the impact specimens increases. When the peak cavity pressure reaches a certain value, the pressure value of the tensile specimen is 65 MPa, and the pressure value of the impact specimen is 68 MPa, the weight of the product increases quickly. The packing pressure increased from 85 MPa to 100 MPa, the weight of the tensile specimen increased from 0.544g to 0.559g, an increase of 2.7%, and the weight of the impact specimen increased from 0.418g to 0.425g, an increase of 1.7%.

Effect of Micro-Segregation on Impact Toughness of 2.25Cr-1Mo Steel after Post Weld Heat Treatment

2.25Cr-1Mo steel with high strength at high temperatures and good hydrogen resistance is widely used for power generation boiler material in high temperature and pressure use environments. Following the test evaluation of the ASME Boiler and Pressure Vessel Code, specimens from the base metal of a boiler pipe were found to have impact toughness values of 285 and 21 ft-lb, which are drastically different values. The analysis of the fracture surface of the 21 ft-lb test specimen revealed MnS inclusions, and it was found that cracks initiated at the inclusions. Observation of the cross-section of the crack propagation front revealed that cracks propagated along the ferrite regions and precipitate voids. Inclusions were also found in the 285 ft-lb impact specimen; however, the volume fraction of the inclusions was significantly less than that of the 21 ft-lb specimen. It was also found that the ferrite and carbide content of the 285 ft-lb specimen was less than 21 ft-lb specimen. The reason that the inclusions, ferrite, and carbide content differed in the two adjacent impact test specimens was analyzed. The effects of micro-segregation, such as MnS inclusions on ferrite and carbide, were compared and analyzed.

Experimental and numerical analyses of the dynamic failure processes of symmetric Taylor impact specimens

Failure processes encountered in the Taylor impact specimen are of two kinds, Mode II cracks initiating within adiabatic shear bands and tensile cracks. Because friction occurring with the single Taylor configuration influences the failure processes, it is necessary to use the symmetric loading procedure providing frictionless interfaces. Numerical simulations of the symmetric Taylor test have been conducted to reproduce the failure processes observed with a highly ductile nickel and a high strength tungsten alloy. Because the adiabatic shear failure process is occurring along a three dimension path, the 3D module of the hydrocode AUTODYN was used.