Collaborative optimization of NURBS curve cross-section in a telescopic boom

Aimin Ji,Changsheng Chen,Liping Peng,Pin Lv,Xiaodi He 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8

To improve the carrying capacity and reduce the weight of telescopic boom structure in a truck crane, a Collaborative optimization (CO) approach was applied to solve the problems of strength, stiffness and local stability in the telescopic boom structure. First, the complex optimization problem of the telescopic boom structure was decomposed into two-level optimizations: the system level and two subsystem levels for strength and local stability. Second, the underside curve of the boom’s cross-section was constructed by the Nonuniform rational B-Splines (NURBS) curve. 3D parametric solid model and the parametric finite element analysis model for the strength and the local stability were then established. Third, the mathematical models of the strength and local stability for the subsystem levels, and the system level were optimized, respectively. The adaptive relaxation factor algorithm and the penalty function approach were applied to improve the efficiency of CO. Next, the CO process which integrates the ANSYS package with ISIGHT platform was implemented. The optimal results show that the carrying capacity of the telescopic boom structure can be significantly improved and its weight efficiently is reduced. Finally, with the comparison of the stress values obtained from both the experimental test and the theoretical computation, highly coincident results could be obtained to verify the reliability of CO of a telescopic boom.

Numerical Investigation of Cracks at Girder Ends of Prefabricated Post-Tensioned Prestressed Concrete I-Girders

Aimin Yuan,Tongyi Wang,Jinjian Gu,Xinge Miao,Jianrong Xu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.10

Prefabricated post-tensioned prestressed concrete (PTC) girders with high degrees of prestressing have been developed continuously in recent bridge designs to reach longer spans, higher quality, and larger load-bearing capacity. However, during the prefabrication process, several inclined and horizontal cracks were observed at the ends of a new style post-tensioned concrete girder, which could have a negative impact on the girders' longevity. In this study, a nonlinear finite element analysis technique was utilized to illustrate how concrete reacts and the mechanisms behind typical cracking patterns during the actual post-tensioning sequence. The prestressing load of a PTC girder was simulated with an improved cooling temperature method that accounts for immediate prestress losses. The field of principle tensile strain patterns and primary strain trajectories explained the overall mechanism underlying typical cracking behaviors. The results showed that the horizontal cracks under the anchorage plate (behavior 1) were generated by the bursting force, whereas the inclined cracks (behavior 2) and the horizontal cracks between the strands N1 and N2 anchor plates (behavior 3) were caused due to the spalling force. The effects of self-weight, girder end forms, as well as the transfer length of the prestressing strands, were discussed. The result demonstrates that both the self-weight and girder end shapes have a considerable effect on the behaviors of the anchorage zone. It is suggested that the transfer length of the anchor head be greater than 26 times of strand diameter to achieve the same effective stresses as the theoretical values.

Hybrid collaborative optimization based on selection strategy of initial point and adaptive relaxation

Aimin Ji,Xu Yin,Minghai Yuan 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.9

There are two problems in Collaborative optimization (CO): (1) the local optima arising from the selection of an inappropriate initialpoint; (2) the low efficiency and accuracy root in inappropriate relaxation factors. To solve these problems, we first develop the Latinhypercube design (LHD) to determine an initial point of optimization, and then use the non-linear programming by quadratic Lagrangian(NLPQL) to search for the global solution. The effectiveness of the initial point selection strategy is verified by three benchmark functionswith some dimensions and different complexities. Then we propose the Adaptive relaxation collaborative optimization (ARCO)algorithm to solve the inconsistency between the system level and the disciplines level, and in this method, the relaxation factors are determinedaccording to the three separated stages of CO respectively. The performance of the ARCO algorithm is compared with the standardcollaborative algorithm and the constant relaxation collaborative algorithm with a typical numerical example, which indicates thatthe ARCO algorithm is more efficient and accurate. Finally, we propose a Hybrid collaborative optimization (HCO) approach, whichintegrates the selection strategy of initial point with the ARCO algorithm. The results show that HCO can achieve the global optimalsolution without the initial value and it also has advantages in convergence, accuracy and robustness. Therefore, the proposed HCO approachcan solve the CO problems with applications in the spindle and the speed reducer.

Analytical solutions to magneto-electro-elastic beams

Aimin Jiang,Haojiang Ding 국제구조공학회 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.18 No.2

Effect of Resin Viscosity and Lubricants on Surface and Mechanical Properties of Glass Fiber Reinforced Polymer in Rapid Heat Cycle Molding

Aimin Zhang,Yang Hui,Junji Hou 한국고분자학회 2018 폴리머 Vol.42 No.6

Conventional injection molding (CIM) and rapid heat cycle molding (RHCM) methods are used to prepare ABS and (acrylonitrile-butadiene-styrene)/glass fiber copolymer (ABS/GF) plastic parts. Pentaerythritol stearate (PETS) and silicon particles are chosen as lubricants. Effect of resin viscosity and lubricants on properties of plastic parts was investigated. The results show that resin viscosity has some effect on surface quality of plastic parts in CIM process but no effect in RHCM process. ABS/GF plastic parts molded in RHCM process exhibit higher tensile, higher flexural strength and lower impact strength. Silicon is more effective in RHCM process than in CIM process.

Crystallization and Mechanical Properties of Glass Fiber Reinforced Polypropylene Composites Molded by Rapid Heat Cycle Molding

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.

Extended state observer-based backstepping sliding mode control for an electromagnetic valve actuator

Aimin Fan,Siqin Chang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.2

This paper presents an extended state observer-based backstepping sliding mode control method (ESO-based BSMC) to achieve precise motion control for the electromagnetic valve actuator (EMVA). The extended state observer is introduced to compensate external disturbance and model uncertainties of the system, the backstepping method is used to decompose the system into some subsystems, and the sliding mode control is designed to guarantee the valve to follow the desired valve motion. The stability of the proposed control system is verified through Lyapunov stability theorem. Simulation results demonstrate that the proposed method avoids chattering problem, and it is robust to external disturbance and model uncertainties. Experimental results show the similar behavior as the simulations within an acceptable error. A transition time of 3.9 ms and a seating velocity less than 0.03 m/s are obtained to prove the effectiveness of the proposed method. Moreover, fully flexible valve actuator has been fulfilled and the valve motion profiles are given.

Green’s functions and boundary element method for a magneto-electro-elastic half-plane

Aimin Jiang,Haojiang Ding 국제구조공학회 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.2

Behavior and Efficiency of Corrosion Damaged Half-bottle Shaped Struts

Aimin Yuan,Donghui Xu,Shoulong Qian 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.11

This study investigated the behaviors, strut efficiency factor, and the effective width of corrosion-damaged half-bottle shaped struts. Six half-bottle shaped struts were subjected to varying aimed corrosion levels (0%, 3%, 6%) with different reinforcement mat rotation angles (0o, 45o), and their behaviors and typical failure modes ascertained. Strut efficiency factors and effective width were calculated and evaluated. Average strength of 6% corroded struts was 30% less than those of uncorroded struts. The AASHTO LRFD 2013 process predicted strut efficiency factor of corrosion damaged struts better than ACI 318-14 and EN 1992. Strut effective width also reduced with increasing reinforcement corrosion. The theoretical effective width near the load bearing plate was underestimated compared to the measured effective width, while the effective width far from the load bearing plate was overestimated.

Analytical solutions for density functionally gradient magneto-electro-elastic cantilever beams

Jian, Aimin,Ding, Haojiang Techno-Press 2007 Smart Structures and Systems, An International Jou Vol.3 No.2

The general solution for two-dimensional magneto-electro-elastic media in terms of four harmonic displacement functions is proposed analytically. The expressions of specific solutions of magneto-electro-elastic plane problems with specific body forces are derived. Finally, based on the general solution in the case of distinct eigenvalues and the specific solution for density functionally gradient media, two kinds of beam problems with body forces depending only on the z or x coordinate are solved by the trial-and-error method.