Effects of the material properties and thickness on the minimum formable radius in the subtle feature forming process.

The subtle feature geometry also called a feature line, is considered an important geometric characteristic of automotive outer panels. The influences of material properties and thickness on the radius of curvature of subtle features were investigated in this study. First, the stamping process was simplified to a combined forming process between tensile and bending deformation. Subsequently, test materials, namely, 180B2, 210B2, CR2, CR3, and CR4, with various thickness values were adopted in the finite element analysis and experiments. In addition, the radius of curvature with respect to the material, thickness, punch radius, and punch angle was studied. The simulation results were compared with the experimental results for verification. From this comparison, it was found that the simulation results were in good agreement with the experimental data. Finally, the forming characteristics of the subtle feature-forming process were investigated to determine the effects of the material properties and thickness on the radius of curvature. The reason for the minimum formable radius when the radius of the punch was zero was studied. The results showed that, as the material thickness increased, more concentrated deformation occurred in the central region. In contrast, the radius of curvature of the subtle features increased as the thickness of the central region decreased. Similarly, decreased n-value results were identified for the same reason as the increased radius of curvature.

Optimization of Forming Parameters in Incremental Sheet Forming of AA3003-H18 Sheets Using Taguchi Method.

The surface finish is an important characteristic in the incremental sheet forming (ISF) process and is often influenced by numerous factors within the forming process. Therefore, this research was aimed at identifying the optimal forming parameters through the Taguchi method to produce high-quality formed products. The forming tool radius, spindle speed, vertical step increment, and feed rate were chosen as forming parameters in the experimental design, with surface roughness as the response variable. Taguchi L16 orthogonal array design and analysis of variance (ANOVA) test were used to identify the parameter's optimal settings and examine the statistically significant parameters on the response, respectively. Results confirmed that a significant reduction in surface roughness occurred with a drop in vertical step size and an increase in feed rate. In detail, the vertical step size has the most significant influence on the surface roughness, followed by the feed rate and the forming tool radius. In conclusion, the optimum level settings were obtained: forming tool radius at level 3, spindle speed at level 1, vertical step size at level 1, and feed rate at level 4. Additionally, confirmation experiment results based on the optimal settings indicated a good agreement against the experimental observation. Further, the response surface methodology (RSM) was also exploited to devise a mathematical model for predicting the surface roughness. The results comparison confirmed that both techniques could effectively improvise the surface finish.

Tool Path Design of the Counter Single Point Incremental Forming Process to Decrease Shape Error.

Incremental sheet metal forming can manufacture various sheet metal products without a dedicated punch and die set. In this study, we developed a two-stage incremental forming process to decrease shape errors in the conventional incremental forming process. The forming process was classified into the first single point incremental forming (1st SPIF) process for forming a product and the counter single point incremental forming (counter SPIF) process to decrease shape error. The counter SPIF gives bending deformation in the opposite direction. Furthermore, the counter SPIF compensates for shape errors, such as section deflection, skirt spring-back, final forming height, and round. The tool path of the counter SPIF has been optimized through a relatively simple optimization method by modifying the tool path of the previous step. The tool path of the 1st SPIF depends on the geometry of the product. An experiment was performed to form a circular cup shape to verify the proposed tool path of the 1st and counter SPIF. The result confirmed that the shape error decreased when compared to the conventional SPIF. For the application, the ship-hull geometry was adopted. Experimental results demonstrated the feasibility of the two-stage incremental forming process.

Characterization of Bacillus amyloliquefaciens DA12 Showing Potent Antifungal Activity against Mycotoxigenic Fusarium Species.

In an attempt to develop a biological control agent against mycotoxigenic Fusarium species, we isolated Bacillus amyloliquefaciens strain DA12 from soil and explored its antimicrobial activities. DA12 was active against the growth of mycotoxigenic F. asiaticum, F. graminearum, F. proliferatum, and F. verticillioides both in vitro and in planta (maize). Further screening using dual culture extended the activity range of strain DA12 against other fungal pathogens including Botrytis cinerea, Colletotrichum coccodes, Endothia parasitica, Fusarium oxysporum, Raffaelea quercus-mongolicae, and Rhizoctonia solani. The butanol extract of the culture filtrate of B. amyloliquefaciens DA12 highly inhibited the germination of F. graminearum macroconidia with inhibition rate 83% at a concentration of 31.3 µg/ml and 100% at a concentration of 250 µg/ml. The antifungal metabolite from the butanol extract was identified as iturin A by thin layer chromatography-bioautography. In addition, volatile organic compounds produced by DA12 were able to inhibit mycelial growth of various phytopathogenic fungi. The volatile compounds were identified as 2-heptanone, 5-methyl heptanone and 6-methyl heptanone by gas chromatography-mass spectrometry (GC-MS) analysis. These results indicate that the antagonistic activity of Bacillus amyloliquefaciens DA12 was attributable to iturin A and volatile heptanones, and the strain could be used as a biocontrol agent to reduce the development of Fusarium diseases and mycotoxin contamination of crops.

Growth characteristics and biofilm formation of various spoilage bacteria isolated from fresh produce.

UNLABELLED: This study investigated the characteristics of spoilage bacteria isolated from fresh produce including growth at various temperatures, biofilm formation, cell hydrophobicity, and colony spreading. The number of spoilage bacteria present when stored at 35 °C was significantly greater than when stored at lower temperatures, and maximum population size was achieved after 10 h. However, Bacillus pumilus, Dickeya zeae, Pectobacterium carotovorum subsp. Carotovorum Pcc21, and Bacillus pumilus (RDA-R) did not grow at the storage temperature of 5 °C. The biofilm formation by Clavibacter michiganensis, Acinetobacter calcoaceticus, and A. calcoaceticus (RDA-R) are higher than other spoilage bacteria. Biofilm formation showed low correlation between hydrophobicity, and no significant correlation with colony spreading. These results might be used for developing safe storage guidelines for fresh produce at various storage temperatures, and could be basic information on the growth characteristics and biofilm formation properties of spoilage bacteria from fresh produce. PRACTICAL APPLICATION: Growth of spoilage bacteria was different depending on the bacteria strains and storage temperature. Between biofilm formation and cell hydrophobicity was low correlation on spoilage bacteria. Therefore, growth characteristics and biofilm formation of spoilage bacteria might be used for developing safe storage guidelines for fresh produce at various storage temperatures.

Characterization and genomic analysis of two Staphylococcus aureus bacteriophages isolated from poultry/livestock farms.

Staphylococcus aureus is one of the most important pathogens, causing various diseases in humans and animals. As methicillin-resistant S. aureus (MRSA) has become increasingly prevalent, controlling this pathogen with standard antibiotic treatment has become challenging. Bacteriophages (phages) have attracted interest as alternative antibacterial agents to control MRSA. In this study, we isolated six S. aureus phages from soils of poultry/livestock farms. Based on the results of host range determination with 150 S. aureus strains and restriction enzyme treatment of phage DNA, two phages, designated SP5 and SP6, were selected for further characterization and genome sequencing. Both SP5 and SP6 were classified as members of the family Siphoviridae. The genome of SP5 comprises 43 305 bp and contains 63 ORFs, while the SP6 genome comprises 42 902 bp and contains 61 ORFs. Although they have different host spectra, the phage genomes exhibit high nucleotide similarity to each other. Adsorption assay results suggested that the host range determinants of the two phages are involved in both adsorption and infection. Comparative genomic analyses of the two phages provided evidence that the lysogenic/lytic control module and tail proteins may be important for host specificity.