Foamed polypropylene (PP) composites containing inorganic particles were prepared using a combined in-mold decoration and microcellular injection molding (IMD/MIM) method, and supercritical fluid-nitrogen was used as the physical blowing agent. Calcium carbonate (CaCO₃) and montmorillonite (MMT) with particle size that varied from nanometer to micron were selected as reinforcement particles. The effect of inorganic particle type and size on the crystallization, mechanical properties, and cellular structure of the parts were investigated. The results showed that the polymer chains were not well inserted into the MMT layer, and there was almost no increase in the interlayer spacing. As the particle size decreased, the relative amount of β-crystal and mechanical properties increased. The addition of CaCO₃ was more effective than MMT at increasing the volume fraction of the β-crystal form when the particle size was reduced to the nanometer level. In the vertical and parallel section, the average cell diameter of the composites decreased and the cell density increased as the particle size decreased. As the particle size of the inorganic filler decreased, the deformation degree of cells gradually increased.

In this work, the effects on dry wear behavior of cold ring rolling (CRR) of GCr15 bearing steel, after quenching and tempering (QT) heat treatment are investigated. The effects on steel microstructures and wear mechanisms of CRR with different austenitizing times are also discussed. The results show that, with a short austenitizing time of 10 min, CRR can increase the retained austenite content, decrease the undissolved carbide content and improve the hardness of the specimen, thus reducing ploughing and fatigue flaking, and decreasing the wear loss of the CRR specimen. With the longer austenitizing time of 20 min, the retained austenite content increases, the undissolved carbide content decreases, and the hardness increases significantly, both in specimens with and without CRR, so that ploughing, fatigue flaking, and wear loss can all be decreased. However, with an austenitizing time of less than 20 min, the effects of CRR on retained austenite content, undissolved carbide content, and hardness are not significant. Thus, CRR of less than 20 min cannot further improve wear morphology or decrease wear loss.

High forming force is often needed when high-strength and low-plasticity materials are processed by fine blanking. Too high forming force increases the load of the die and greatly increases the risk of die failure. If the forming force is reduced, the material will fracture prematurely, which will lead to poor quality parts. Aiming at this problem, a new force variation load fine-blanking technology is proposed in this paper. During the loading process, the forming force does not remain constant but changes with the blanking stroke. A 2D finite element fine-blanking model was established for the TC4 material. The mechanism of force variation fine blanking is also revealed. This paper proposes a method to design the loading route of the forming force with variable load. This method combines finite element simulation with neural network and a multi-objective genetic algorithm. Finally, the application of variable load fine blanking production and the application of traditional fine blanking production parts are verified by the experimental method. The same results are obtained from both simulation and experiment. It is found that the variable load fine blanking process can greatly reduce the load of the die on the premise of ensuring the quality of fine-blanking parts.

Polypropylene nanocomposites containing varying amounts of Styrene-ethylene-butadiene-styrene block copolymer (SEBS) were prepared through the supercritical nitrogen microcellular injection-molding process. Maleic anhydride (MAH)-grafted polypropylene (PP-g-MAH) copolymers were used as compatibilizers. The influence of SEBS content on the cell structure and toughness of the SEBS/PP composites was investigated. Upon the addition of SEBS, the differential scanning calorimeter tests revealed that the grain size of the composites decreased, and their toughness increased. The results of the rheological behavior tests showed that the melt viscosity of the composite increased, playing a role in enhancing the cell structure. With the addition of 20 wt% SEBS, the cell diameter decreased from 157 to 66.7 μm, leading to an improvement in the mechanical properties. Compared to pure PP material, the impact toughness of the composites rose by 410% with 20 wt% of SEBS. Microstructure images of the impact section displayed evident plastic deformation, effectively absorbing energy and improving the material’s toughness. Furthermore, the composites exhibited a significant increase in toughness in the tensile test, with the foamed material’s elongation at break being 960% higher than that of pure PP foamed material when the SEBS content was 20%.

Polypropylene (PP)-composite foams were prepared by a combination process of microcellular injection molding (MIM) and in-mold decoration (IMD). The effect of ethylene propylene diene monomer (EPDM) on the crystallization properties, rheological properties, microstructure, and mechanical properties of PP-composite foams was studied. The effect of the additives on the strength and toughness of PP-composite foam as determined by the multiscale simulation method is discussed. The results showed that an appropriate amount of EPDM was beneficial to the cell growth and toughening of the PP blends. When the content of EPDM was 15 wt%, the PP-composite foams obtained the minimum cellular size, the maximum cellular density, and the best impact toughness. At the same time, the mesoscopic simulation shows that the stress concentration is the smallest, which indicates that 15 wt% EPDM has the best toughening effect in these composite materials.