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Aimin Zhang,Guoqun Zhao,Jialong Chai,Junji Hou,Chunxia Yang,Guilong Wang 한국섬유공학회 2020 Fibers and polymers Vol.21 No.12
The crystalline behavior and mechanical properties of PP/GF (glass fibers) composites molded by rapid heat cyclemolding (RHCM) and conventional injection molding (CIM) were compared. SEM, DSC and XRD were utilized to studycrystallization behavior of PP and PP/GF composites. Furthermore, universal testing machine was employed to investigatethe mechanical properties. Results proved that higher degree of crystallinity and larger crystal size can be obtained in RHCMin comparison to CIM. GF can induce more crystal nuclei and then reduce the crystal size due to shear stress which isgenerated in polymer matrix around fibers. Nucleating agent (NA) has a positive effect on refine grains. The average crystaldiameter of PP/NA/30 %GF is about 1.7 μm which is one-tenth of PP/30 %GF (14 μm) in RHCM. XRD tests illustrated thatα-form crystal is the main crystal type for PP and PP/GF composites in RHCM and CIM. However, there is a little β-formcrystal in RHCM for PP/GF composites without NA. NA accelerates the formation of α-form crystal and restrains theemergence of β-form crystal. The plastic parts obtained in RHCM exhibited higher strength and modulus compared with thatobtained in CIM for both tensile and flexural tests.
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Evaluation of a pyramid die extrusion for a hollow aluminum profile using FE simulation
Liang Chen,Guoqun Zhao,Junquan Yu,Wendong Zhang 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5
The pyramid die extrusion for a hollow aluminum profile was analyzed to investigate the potential of such innovative dies. For thispurpose, the pyramid and conventional porthole dies were respectively designed for a given hollow aluminum profile. And the extrusionprocess was comprehensively studied by performing different types of finite element simulation, such as the analysis of steady state,transient state and billet skin tracking. The effects of pyramid angle on the evaluation parameters of extrusion, such as extrusion load,material flow, exit temperature, length of transverse weld, quality of longitudinal weld, back end defect and die stress were overall analyzedand compared with the conventional porthole die. Through this study, the advantages and shortcomings of pyramid die were wellconcluded, which should be important information for die designers and makers.
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