Finite Element Simulation of Flexible Roll Forming with Supplemented Material Data and the Experimental Verification

Flexible roll forming is a promising manufacturing method for the production of variable cross section products. Considering the large plastic strain in this forming process which is much larger than that of uniform deformation phase of uniaxial tensile test, the widely adopted method of simulating the forming processes with non-supplemented material data from uniaxial tensile test will certainly lead to large error. To reduce this error, the material data is supplemented based on three constitutive models. Then a finite element model of a six passes flexible roll forming process is established based on the supplemented material data and the original material data from the uniaxial tensile test. The flexible roll forming experiment of a B pillar reinforcing plate is carried out to verify the proposed method. Final cross section shapes of the experimental and the simulated results are compared. It is shown that the simulation calculated with supplemented material data based on Swift model agrees well with the experimental results, while the simulation based on original material data could not predict the actual deformation accurately. The results indicate that this material supplement method is reliable and indispensible, and the simulation model can well reflect the real metal forming process. Detailed analysis of the distribution and history of plastic strain at different positions are performed. A new material data supplement method is proposed to tackle the problem which is ignored in other roll forming simulations, and thus the forming process simulation accuracy can be greatly improved.

Experimental Study on 308nm Laser Interaction with Materials

A 10 J, 4o us XeCl laser interaction with LY12 aluminum and optical glass K9 targets is reported. The properties of laser-produced plasma (LPP) are analyzed. As a result, some parameters such as plasma ignition threshold and plasma plume expansion velocity are obtained. Also, Laser induced pulse on irradiated targets are given.

Experimental Investigation into Shaping Particle-reinforced Material by WEDM-H

Al 2O 3 particle-reinforced material (6061 alloy ), which is one of new composites and characterized by high strength and small spe cific gravity, good wear resistance and corrosion resistance, has been widel y used in industry. But it is difficult to machine. Because of electric conducti vity, it can be shaped and processed by electro-machining means. However, this kind of material is mixed with the electrically conductive substances and the di electrically conductive substances, its machining process shows substantially di fferent from the machining of ordinary metal materials. This paper, based on a c ontrast experiment, investigates the machining mechanism and technique by WEDM t o shape the material and gives the optimum selection for the electric paramete rs in operation. The technologic index of shaping the new material by WEDM includes the cutting r ate and the surface roughness. There are a lot of factors that affect the techno logic index of WEDM, in which the electric parameters such as the machining volt age and current as well as the pulse duration, interval and frequency, play an i mportant part. In this experiment, the study focus mainly on the effect of the e lectric parameters on machining process and an orthogonal design is employed to select the proper electric parameters. By experiment, we find how the voltage and current affect machining process and study the removal mechanism by WEDM-HS to machine Al 2O 3 particle-reinforce d material. Besides the machining current and voltage, there are still other fac tors that can affect machining process and state. In order to find out which is the most important factor and to optimize the electric parameters, the orthogona l design has been adopted to perform the experiment. By the analysis to the rela tive differences among different factor levels, the rank of significance for fou r factors is in turn the pulse duration, the voltage, the machining current and the pulse interval. At last we can draw a conclusion that 6061 alloy can be shaped by WEDM-HS, and give the suitable electric parameters to obtain good surface roughness and high machining efficiency.

Experimental Study on Material Surface Modification of Tool Steel

This paper presents the surface temperature behavior of M42 high-speed tool steel samples during N+ implantation in an industrialized GLZ-100 metal-ion implantation machine. A detail study has been made on the parameters of N+ implantation. Optimized technical parameters have been presented. The microhardness of the sample surface implanted under these parameters has been increased by a factor of 2.3, and the wear-resistance has been improved by about 5.4 times. The research on the mechanism of surface modification of M42 steel by nitrogen ion implantation has also been made.

A METHOD OF ESTIMATING THE INFLUENCE OF EXPERIMENTAL ERRORS ON THE EXPERIMENTAL RESULTS OF MATERIAL PARAMETERS AND THE CRITERIA TO VALUE THIS INFLUENCE

In this paper the main sources causing the scatter of the experimental results of the material parameters are discussed. They can be divided into two parts: one is the experimental errors which are introduced because of the inaccuracy of experimental equipment, the experimental techniques, etc., and the form of the scatter caused by this source is called external distribution. The other is due to the irregularity and inhomogeneity of the material structure and the randomness of deformation process. The scatter caused by this source is inherent and then this form of the scatter is called internal distribution. Obviously the experimental distribution of material parameters combines these two distributions in some way; therefore, it is a sum distribution of the external distribution and the internal distribution. In view of this , a general method used to analyse the influence of the experimental errors on the experimental results is presented, and three criteria used to value this influence are defined. An example in which the fracture toughness KIC is analysed shows that this method is reasonable, convenient and effective.

Experimental Study on Tensile Behavior of Cement Paste, Mortar and Concrete under High Strain Rates

Effects of the strain rate on cement paste, mortar and concrete were studied. A modified SHPB testing technique with fl attened Brazilian disc（FBD） specimen was developed to measure the dynamic tensile stress-strain curve of materials. A pulse-shaped split Hopkinson pressure bar（SHPB） was employed to determine the dynamic tensile mechanical responses and failure behavior of materials under valid dynamic testing conditions. Quasi-static experiments were conducted to study material strain rate sensitivity. Strain rate sensitivity of the materials was measured in terms of the stress-strain curve, elastic modulus, tensile strength and critical strain at peak stress. Empirical relations between dynamic increase factor（DIF） and the material properties were derived and presented.

Progress of Materials Science in Space Technology in China(2020-2022)

In this paper,the main research work and related reports of materials science research in China’s space technology field during 2020-2022 are summarized.This paper covers Materials Sciences in Space Environment,Materials Sciences for Space Environment,Materials Behavior in Space Environment and Space experimental hardware for material investigation.With the rapid development of China’s space industry,more scientists will be involved in materials science,space technology and earth science researches.In the future,a series of disciplines such as space science,machinery,artificial intelligence,digital twin and big data will be further integrated with materials science,and space materials will also usher in new development opportunities.

Effect of annealing on the microstructures and Vickers hardness at room temperature of intermetallics in Mo-Si system

The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated. Lamellar structure consisted of Mo_5Si_3 (D8m) phaseand MoSi_2 (C11_b) phase was observed in all the alloys. For Mo_5Si_3-MoSi_2 hypoeutectic alloy, thelamellar structure was found only after annealing and developed well with fine spacing on the orderof hundred nanometers after annealing at 1200℃ for 48 h. But when the annealing time was up to 96h, the well-developed lamellar structure was destroyed. For Mo_5Si_3-MoSi_2 hypereutectic alloy, thelamellar structure was found both before and after annealing. However the volume fraction andspacing of the lamellar structure did not change significantly before and after annealing. Theeffects of the formation, development and destruction of lamellar structure on Vickers hardness ofalloys were also investigated. When Mo_5Si_3-MoSi_2 hypoeutectic alloy annealed at 1200℃ for 48 h,the Vickers hardness was improved about 19% compared with that without annealing and formation oflamellar structure. The highest Vickers hardness of Mo5Si3-MoSi_2 hypereutectic was increasing about18% when annealing at 1200℃ for 48 h.

Primary study of the isothermal phase diagram of the Cu_2O-Al_2O_3-SiO_2 ternary system at 1150℃ in air

The isothermal phase diagram of the Cu2O-Al2O3-SiO2 ternary system at 1150℃ was reported for the samples which were prepared from sol-gel method and quenched by water after being heated at 1150℃ for 12 h. Based on the conventional X-ray powder diffraction （XRD） and in situ high-temperature XRD quantitative analysis,in addition to scanning electron microscopy measurement,the phase identification was achieved. Combining the deduction from the component phase diagrams of the binary systems using the phase equilibrium theorem,the primary isothermal phase diagram was plotted over the composition area Cu2O-mullite-SiO2. In this area,the approximate composition areas of two two-phase regions and one three-phase region,（L2＋Cr）,（L2＋M）,and （L1＋L2＋Tr）,were determined. Moreover,the precise composition areas of both of the three-phase regions （L2＋Cr＋M） and （L2＋M＋A） were determined according to the results of conventional and in situ high-temperature XRD quantitative analysis by Rietveld method.

Process of Microcellular Propellants with Adjustable Skin Thickness

Microcellular propellants show a vast applicable prospect due to their special shell-pore structure. The effects of saturation pressure and desorption time on skin thickness are studied. The skin thickness is observed and measured using scanning electron microscope (SEM). The results show that the skin thickness decreases when saturation pressure increases from 15 MPa to 30 MPa. In contrast, the skin thickness increases as the desorption time changes from 2 min to 20 min.Therefore, the microcellular propellants with adjustable skin thickness can be obtained under the variable process conditions such as saturation pressure and desorption time.

Experimental Study on Application of Shaped Charge to Rock Materials Cutting

The mechanic affection on the blast holewalls is simply analyzed and cracking propaga-tion caused by shaped charge is explained inthis paper. In the rock materials cutting, pri-