Progressive failure of metal–composite hybrid wheels under impact

Shun-Fa Hwang,Hui-Lun Yu,Yu-Jen Liu,Yuder Chen,Shih-Chieh Chen,Yueh-Chih Hsieh 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

An 18-in hybrid wheel consisting of an aluminum alloy disk and a composite rim under 13° impact test is considered in this study. The rim is made of carbon fabric/polyurethane composites fabricated by resin transfer molding. Explicit finite element analysis with progressive failure function is used to investigate the failure situation of the hybrid wheel and the suitable braid angle of the braided composite. The effective elastic constants and strengths of the braided composites predicted by basic finite element analyses are adopted, whereas the true stress–strain curve of aluminum is used for the disk. Simulation results indicate that the aluminum alloy disk is safe after the impact test, whereas the rim is damaged. The volume of failed elements after impact simulation is selected as an indicator to obtain a quantity that can be used to represent the damage situation of the rim. Compared with the test results of a real hybrid wheel with [±30°] fiber angle in the rim, the hybrid wheel with fiber angle in the rim that is greater than [±30°] could pass the impact test.

A genetic algorithm for the optimization of fiber angles in composite laminates

Shun-Fa Hwang,Ya-Chu Hsu,Yuder Chen 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.8

A genetic algorithm for the optimization of composite laminates is proposed in this work. The well-known roulette selection criterion,one-point crossover operator, and uniform mutation operator are used in this genetic algorithm to create the next population. To improvethe hill-climbing capability of the algorithm, adaptive mechanisms designed to adjust the probabilities of the crossover and mutationoperators are included, and the elite strategy is enforced to ensure the quality of the optimum solution. The proposed algorithm includes anew operator called the elite comparison, which compares and uses the differences in the design variables of the two best solutions tofind possible combinations. This genetic algorithm is tested in four optimization problems of composite laminates. Specifically, the effectof the elite comparison operator is evaluated. Results indicate that the elite comparison operator significantly accelerates the convergenceof the algorithm, which thus becomes a good candidate for the optimization of composite laminates.

Fabrication and Characterization of Two-Chamber and Three-Chamber Peristaltic Micropumps

Shun-Fa Hwang,Yu-Shiuan Shiu 한국정밀공학회 2010 International Journal of Precision Engineering and Vol.11 No.4

Two-chamber and three-chamber peristaltic micropumps with straight channels or tapered channels are fabricated by UV photolithography. Piezoelectric buzzers are chosen as actuation elements because they are cheap and have high actuation amplitude. A negative photoresistive material, SU8-25, is used as a structure material, and PDMS is chosen to bond different parts of the micropump. The effects of working phases and channel geometries are investigated and the performance of two-chamber and three-chamber micropumps is compared. The results indicate that three-chamber micropumps have better flow rates than two-chamber counterparts. For three-chamber micropumps, four-working phases have the best flow rate, six-working phased are the second, and three-working phases are the last. The channel length may have no clear effect on the flow rate, while the channel width and the angle of nozzle/diffuser have evident effects on the flow rates.

Perforation threshold energy of carbon fiber composite laminates

Shun-Fa Hwang,Jia-Ching Li,Ching-Ping Mao 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.2

Two carbon fiber composite laminates, [0/90]2S and [0/+45/90/−45]S, were considered in this work to find out the perforation threshold energy to complete the perforation process and the corresponding maximum contact force. Explicit finite element commercial software, LS-DYNA, was used to predict these values. According to the simulation results, these two types of composite laminates were tested by using a vertical drop-weight testing machine. After testing, the damage condition of these specimens were observed and compared with the results from finite element analysis. The testing results indicate that the perforation threshold energy is 6 Joules for [0/90]2S and 7 Joules for [0/+45/90/−45]S, which is in good agreement with the simulation results. Also, the maximum contact force at the case of perforation threshold energy is the lowest as compared to the maximum contact forces occurring at the impact energy that is larger or less than the perforation threshold energy.

Memory-dependent derivatives theory of thermo-viscoelasticity involving two-temperature

Shun-Fa Hwang,Min-Chien Shen,Bin-Bin Hsu 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.10

A new model of two-temperature generalized thermo-viscoelasticity theory based on memory-dependent derivative is constructed. Theequations of the new model are applied to one-dimensional problem of a half-space. The bounding surface is taken to be traction free andsubjected to a time dependent thermal shock. Laplace transforms technique is used. A direct approach is applied to obtain the exact formulasof heat flux, temperature, stresses, displacement and strain in the Laplace transform domain. Application is employed to our problemto get the solution in the complete form. The considered variables are presented graphically and discussions are made.

Deformation measurement around a high strain-gradient region using a digital image correlation method

Shun-Fa Hwang,Wei-Jie Wu 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.10

Digital image correlation could provide deformation information of a specimen by processing two digital images captured before and after the deformation. In this study, a hybrid genetic algorithm, in which a simulated annealing mutation process and adaptive mechanisms are added to a real-parameter genetic algorithm, is used to search for the deformed images to obtain both the strain and displacement data simultaneously. This method is applied to obtain the strain in a high strain-gradient region around a hole in a plate under uniaxial tensile testing. These data are compared with those obtained by using a strain gauge to judge the quality of the obtained strain data. The result indicates that the strain in a high strain-gradient region could be reasonably determined by using the present method.

Perforation threshold energy of carbon fiber composite laminates

Hwang, Shun-Fa,Li, Jia-Ching,Mao, Ching-Ping Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.2

Two carbon fiber composite laminates, $[0/90]_{2S}$ and $[0/+45/90/-45]_S$, were considered in this work to find out the perforation threshold energy to complete the perforation process and the corresponding maximum contact force. Explicit finite element commercial software, LS-DYNA, was used to predict these values. According to the simulation results, these two types of composite laminates were tested by using a vertical drop-weight testing machine. After testing, the damage condition of these specimens were observed and compared with the results from finite element analysis. The testing results indicate that the perforation threshold energy is 6 Joules for $[0/90]_{2S}$ and 7 Joules for $[0/+45/90/-45]_S$, which is in good agreement with the simulation results. Also, the maximum contact force at the case of perforation threshold energy is the lowest as compared to the maximum contact forces occurring at the impact energy that is larger or less than the perforation threshold energy.

Strain measurement of polymer materials by digital image correlation combined with finite-element analysis

Shun-Fa Hwang,Min-Chien Shen,Bin-Bin Hsu 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.10

Digital image correlation (DIC) can provide deformation information of a specimen by processing its two digital images captured beforeand after the deformation. In this study, a DIC method based on a modified coarse–fine iterative method is combined with finiteelementanalysis to obtain the strain and displacement data. This method is first verified with the use of an aluminum specimen underuniaxial testing. For polymer materials, polypropylene specimens with and without short glass fibers and polydimethylesiloxane specimenswith and without dyes are tested. Results indicate that the present method can capture the strains of these specimens even underhigh elongation and without artificial speckle pattern on their surfaces. Thus, the mechanical behavior of polymer materials can be characterizedand the effects of additional ingredients added to the materials can be assessed through the developed DIC method.

Experimental Investigation on the Design of Nozzle/ Diffuser for Micropumps

Shun-Fa Hwang,Ying-Min Ji 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.

To design a planar nozzle/diffuser, its divergence angle and slenderness are experimentally investigated in this work according to theflow rates of the assembled micropumps. Thirteen micropumps with different design of nozzle/diffuser were chosen from the no stallregion, transitory region, and bistable steady stall region in a complete stability map of diffuser flow patterns. These micropumpsactuated by piezoelectric buzzer were fabricated by UV photolithography. The measured volume flow rates indicate that thosemicropumps having better performance are located in the transitory region where the flow is strongly unsteady. Among them, the besttwo nozzles/diffusers occur at the line of the maximum pressure recovery.