Forming Limit Diagram Prediction of Tailor-Welded Blank Using Experimental and Numerical Methods

The forming limit diagram (FLD) is a useful method for characterizing the formability of sheet metals. In this article, different numerical models were used to investigate the FLD of tailor-welded blank (TWB). TWBs were CO₂ laser-welded samples of interstitial-free (IF) steel sheets with difference in thickness. The results of the numerical models were compared with the experimental FLD as well as with the empirical model proposed by the North American Deep Drawing Research Group. The emphasis of this investigation is to determine the performance of these different approaches in predicting the FLD. These numerical models for FLD are: second derivative of thinning (SDT), effective strain rate (ESR), major strain rate (MSR), thickness strain rate (TSR), and thickness gradient (TG). Results of this research show necking will be happened, when the value of MSR, TSR, ESR criteria is maximum, TG????0.78 and SDT criterion has the first peak in forming process time. The value of dome height of TWB samples at failure was predicted based on the numerical models for samples with different widths. These numerical predictions were compared with the experimental results. The SDT model indicates a better agreement with experimental results in prediction of both the FLD and the limit dome height (LDH) in comparison to the other numerical models. Both numerical and experimental results show that minimum of LDH is happened in plane strain condition.     

Numerical and Experimental Investigation of Temperature Effect on Thickness Distribution in Warm Hydroforming of Aluminum Tubes

Reduction of weight and increase of corrosion resistance are among the advantageous applications of aluminum alloys in automotive industry. Producing complicated components with several parts as a uniform part not only increases their strength but also decreases the production sequences and costs. However, achieving this purpose requires sufficient formability of the material. Tube hydroforming is an alternative process to produce complex products. In this process, the higher the material formability the more uniform will be the thickness distribution. In this research, tube hydroforming of aluminum alloy (AA1050) at various temperatures has been investigated numerically to study temperature effect on thickness distribution of final product. Also a warm hydroforming set-up has been designed and manufactured to evaluate numerical results. According to numerical and experimental results in the case of free bulging, unlike the constrained bulging, increase of the process temperature causes more uniform thickness distribution and therefore increases the material formability.     

Functionally-graded shape memory alloy by diffusion annealing of palladium-coated NiTi plates

Diffusion annealing of palladium-coated Ti-Ni plates was performed at temperatures ranging from 900 °C to 1,000 °C, to accomplish a compositional gradient in Ti-rich, Ti-Ni shape memory alloys. The aim of this study was to increase the transformation temperatures and transformation temperature intervals. Palladium diffusion profiles were measured by energy dispersive spectroscopy, and the corresponding approximate diffusion coefficients of the annealed specimens were calculated. The Gaussian solution of Fick’s second law for the one-dimensional lattice diffusion of a tracer was used. The transformation behavior studies were performed by differential scanning calorimetry. It was depicted that annealed specimens show longer transformation intervals compared to the bare alloy. In addition, annealed specimens showed improved shape memory properties that were attributed to the lower amount of Ti₂Ni precipitates in the diffusion layer. The shape memory behaviour of the samples was detected using micro-indentation at room temperature, followed by heating them above the austenite formation temperature to calculate the shape recovery ratio.     

Comparison of the Calculated Drought Return Periods Using Tri-variate and Bivariate Copula Functions Under Climate Change Condition

Water Resources Management - Concerning the various effects of climate change on intensifying extreme weather phenomena all around the world, studying its possible consequences in the following...     

A 60‐GHz on‐chip slot‐array antenna in integrated‐passive‐device technology for antenna‐in‐package applications

A new millimeter‐wave antenna structure on a low‐cost, production platform integrated passive device technology is presented. The antenna consists of a 2‐by‐1 array of slot antennas at 60 GHz. An in‐house developed on‐chip antenna measurement setup was used to characterize the fabricated antenna. The measurement results show an antenna gain of more than 5 dBi with a return loss of 18 dB at 60 GHz. The better‐than‐10‐dB impedance bandwidth of the antenna covers the 60‐GHz unlicensed band from 57 to 64 GHz. The 3‐dB beamwidths of the antenna are 105° and 76° at E‐plane and H‐plane at 60 GHz, respectively. The size of the die of the antenna is 2 mm × 4.5 mm. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:155–160, 2014.     

Calf massager: Intervention for body muscle discomfort during prolonged standing

Many occupations require workers to stand for long periods of time without proper interventions, which causes discomfort in the back and lower limbs. Therefore, this study aims to assess the effectiveness in alleviating body muscle discomfort during prolonged standing through the use of a calf massager. This study was conducted among male workers at a manufacturer with production line workers and the list was obtained from the HR Department and simple random sampling was done by number categorization. A total of 100 respondents (50 respondents for both the control and the experimental groups) participated in this study. The experiment took place in a room with a similar setup for the production line. Each respondent was requested to perform the simulated task for 2 hr. For the experimental group, the calf massager was turned on every 15 min. At every 15‐min interval after turning on the calf massager, respondents from both groups were required to evaluate their discomfort level on a Borg's scale CR‐10 questionnaire. The results showed that the level of body discomfort among respondents in the experimental group reduced (20–30%) compared with that of the control group. Multivariate analysis results revealed that the discomfort rating for the lower back, knees, thighs, calves, and feet was significantly lower (p < .05) among the experimental group compared with the control group. For lower body parts, the lower back region was statistically significant (p < .05) at the 90th, 105th, and 120th min; the thigh region was statistically significant (p < .05) at the 120th min; the knee region was statistically significant (p < .05) at the 105th and 120th min; the calf region was statistically significant (p < .05) at all minute intervals except the 15th and 45th min, while the feet region, was statistically significant at the 105th and 120th min. Therefore, this study indicates that calf massage treatment is capable of reducing body muscle discomfort during prolonged standing and highlights the significance of calf massage.     

Investigation of the effect of temperature and layup on the press forming of polyvinyl chloride-based composite laminates and fiber metal laminates

Semi-crystalline thermoplastic-based composite laminates and fiber metal laminates have a narrow forming temperature window, which limits formability of these products. The intention of this study was investigation of non-melting amorphous polyvinyl chloride as a proper matrix to increase the formability and forming temperature window of these products. For this, [45/?45] and [0/90] layups of polyvinyl chloride-based composite laminates and fiber metal laminates were produced using the film-stacking procedure and later press formed into channel sections at six temperatures in the range of 80 to 200 °C. The effects of the layups and forming temperatures on the forming loads and spring back of the formed profiles were measured, and their effects on the fiber buckling, wrinkling, and delamination of the profiles were evaluated using optical microscope images. The effects of layups and forming temperatures on the deformation mechanisms were also analyzed using the grid strain analysis method. Of the fiber metal laminates, 160 °C was found as the minimum forming temperature, and for the composite laminates, 120 and 160 °C were found as the minimum proper forming temperatures of [45/?45] and [0/90] layups, respectively. Finally, the forming temperature windows and formability of polyvinyl chloride matrix composite laminates and fiber metal laminates were found higher than semi-crystalline matrices.     

Feasibility study on optimized process conditions in warm tube hydroforming

Feasibility study has been performed to estimate the optimized process conditions in warm tube hydroforming based on the simulated annealing optimization method. Precise prediction and control of process parameters play an important role in forming at warm conditions. Optimal pressure and feed loading paths are obtained for aluminium AA6061 tubes through the simulated annealing algorithm in conjunction with finite element simulations. Numerous axisymmetric geometries are investigated and the effects of expansion ratio, corner fillet to thickness ratio, and initial diameter to thickness ratio are studied. For the feasibility estimation, warm hydroforming experiments have been conducted on aluminum AA6061 under optimal designed conditions. The results show that the optimization procedure used in this research is a reliable and feasible tool in determination of optimal process conditions for the sound warm hydroforming process.