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In this paper, we evaluate various multi-cell design concepts to optimize the crash performances of thin-walled aluminum tubes. The crash performances of the tubes are evaluated by means of two metrics: the crush force efficiency (CFE) and the specific energy absorption (SEA). The CFE and SEA of the tubes are predicted through the use of the finite element analysis software LS-DYNA. Experiments are also conducted to validate the finite element models. Thirty different multi-cell design concepts are evaluated in terms of CFE and SEA, and the best design concept is selected for further evaluation. Next, we perform surrogate-based optimization of the selected design concept, upon which we find that optimum design for maximum CFE which utilizes smaller wall thickness values (except the wall thickness of the inner tube) and larger tube diameters than those of the corresponding ones for the optimum design for maximum SEA. Additionally, the optimized designs exhibit remarkable CFE and SEA performances. • 30 different multi-cell design concepts are explored for thin-walled Al tubes against crash. • The best design concept is selected based on crush force efficiency and specific energy absorption. • Surrogate based optimization of the selected design concept is performed. • The crash performances are evaluated through FE simulations and experiments. [ABSTRACT FROM AUTHOR]

There is an increasing trend in using aluminum foam-filled columns in crash management systems due to their light weight in automotive industry. The main goal of this study is to optimize the crashworthiness of aluminum foam-filled thin-walled multi-tubular circular columns under quasi-static loading. The existing studies in the literature considered only lateral foam filling (the foam lateral dimension is variable and the foam height is equal to the column height). In the present study, we considered both lateral and axial foam filling and compared the performances of these two options. In optimization, the column thicknesses, taper angle, foam density, and foam height/diameter are considered as design variables. The quasi-static responses of the columns are determined through explicit dynamic Finite Element Analysis (FEA) using LS-DYNA software, and validated with quasi-static tests conducted in our facilities. Response surface based crashworthiness optimization of the columns for maximum Crush Force Efficiency (CFE) and maximum Specific Energy Absorption (SEA) is performed. It is found that lateral foam filling is superior to axial foam filling in terms of both CFE and SEA maximization. The maximum CFE obtained through lateral foam filling is 19% larger than the maximum CFE obtained through axial foam filling. Similarly, the maximum SEA obtained through lateral foam filling is 6% larger than the maximum SEA obtained through axial foam filling. For both CFE and SEA maximization, the columns should be tri-tubular type and have a large thickness and a taper angle. To attain the maximum CFE, foam should be designed with large density and medium foam diameter. However, foam plays an adverse role in maximization of SEA because of its weight. The increase in energy absorption obtained by using foam does not compensate the additional weight introduced by the foam. [ABSTRACT FROM AUTHOR]

In this paper, the effects of introducing lateral circular cutouts on crash performances of tapered thin-walled tubes are explored within a simulation-driven surrogate-based multi-objective optimization framework. The crash performances of the tubes are measured using the crush force efficiency (CFE) and the specific energy absorption (SEA) criteria, which are computed using the finite element analysis code LS-DYNA. Surrogate-based optimization approach is followed to find out that optimum values of the wall thickness, the taper angle, the cutout diameter and the numbers of cutouts in horizontal and vertical directions to maximize CFE and SEA. Four different surrogate models are used: polynomial response surfaces, radial basis functions, and Kriging models with zeroth- and first-order trend models. It is found that the optimum CFE of the tubes with lateral circular cutouts is 27.4% larger than the optimum CFE of the tubes without cutouts. It is also found that the optimum SEA of the tubes with lateral circular cutouts is 26.4% larger than the optimum SEA of the tubes without cutouts. It is observed that the optimum SEA design has slightly reduced wall thickness, significantly reduced taper angle, significantly increased cutout diameter, increased number of cutouts in horizontal direction and slightly reduced number of cutouts in vertical direction compared to the optimum CFE design. In addition, multi-objective optimization of the tubes is performed by maximizing a composite objective function that provides a compromise between CFE and SEA. It is found that the CFE dominates the behavior of composite objective function. [ABSTRACT FROM AUTHOR]

The shape memory properties of Ni45.3Ti29.7Hf20Pd5 single crystals aged at 550 °C for 3 h and at 600 °C for 48 h were investigated along the [111], [011] and [-117] orientations in compression. The material was stronger along the [-117] orientation compared to the [111] and [011] orientations based on load-biased thermal cycling experiments. The shape memory properties such as reversible strain, temperature hysteresis, critical stress for stress-induced martensite transformation and Clausius-Clapeyron relations were also strong functions of orientation and aging condition (precipitate characteristics). Shape memory effect with no or negligible irrecoverable strain was observed under stress levels as high as 1000 MPa. After aging at 550 °C for 3 h, the maximum reversible strains were 2.2%, 2.7% and 0.7% along the [111], [011] and [-117] orientations, respectively. Aging at 600 °C for 48 h resulted in maximum reversible strains of 2.3%, 3.2% and 0.9% along the [111], [011] and [-117] orientations, respectively. In both cases, similar levels of transformation strain, as a function of orientation, were observed during superelastic testing. The maximum work output reached 27 J/cm3 in the [011] orientation after aging at 550 °C for 3 h. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ni45.3Ti39.7Hf10Pd5 alloys have transformation strain of up to 4.6% and work output of up to 29Jcm−3. [•] The alloy showed good superelastic behavior at 90°C with recoverable strain of 4.3%. [•] The alloy exhibited 1.6% two-way shape memory strain after a simple training procedure. [•] The formation of 〈011〉 type II twins in martensite plates results in large transformation strain. [ABSTRACT FROM AUTHOR]

Abstract: Systematic characterization of the shape memory properties of a quaternary Ni45.3–Ti29.7–Hf20–Pd5 (at.%) polycrystalline alloy was performed in compression after selected aging treatments. Precipitation characteristics were revealed by transmission electron microscopy. The effects of aging temperature and time on transformation temperatures, recoverable and residual strains, and temperature and stress hystereses were determined by differential scanning calorimetry, constant-load thermal cycling experiments and isothermal strain cycling (superelasticity) tests. The crystal structure and lattice parameters of the transforming phases were determined from X-ray diffraction analysis. It was revealed that precipitation hardening significantly improved the shape memory properties of the NiTiHfPd alloy. Under optimum aging conditions, shape memory strains of up to 4% under 1GPa were possible, and superelasticity experiments resulted in full strain recovery without any plastic deformation, even at stress levels as high as 2GPa. The NiTiHfPd polycrystalline alloy exhibited very high damping capacity/absorbed energy (30–34Jcm−3) and work output (30–35Jcm−3), which were attributed to the ability to operate at high stress levels without significant plastic deformation and to a high mechanical hysteresis (>900MPa) at temperatures ranging from 20°C to 80°C. [Copyright &y& Elsevier]

The effects of aging on the shape memory properties of [111] oriented Ni45.3Ti29.7Hf20Pd5 single crystals were investigated under compression. Thermal cycling under stress and superelasticity experiments were conducted after 3h aging at 550 and 600°C and were found to be dependent on aging condition. Reversible strain of up to 2.2% and a work output of 33Jcm−3 were possible at an ultra-high stress level of 1500MPa. [ABSTRACT FROM AUTHOR]

The superelastic behavior of an NiTiHfPd single-crystal shape memory alloy in compression along the [111] orientation was investigated as a function of temperature. In the range of −30 to 70°C, a perfect superelastic loop with 4.2% transformation strain was attained. In addition, this material exhibited an ultrahigh yield strength of more than 2500MPa and an exceptional damping capacity of 44Jcm−3. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the effects of tapering and introducing axisymmetric indentations on the crash performances of thin-walled tubes are investigated. The crash performances of the tubes are evaluated using two metrics: the crush force efficiency (CFE, the ratio of the average crushing load to the peak load), and the specific energy absorption (SEA, absorbed energy per unit mass). The optimum values of the number of the axisymmetric indentations, the radius of the indentations, the taper angle and the tube thickness are sought for maximum CFE and maximum SEA using surrogate based optimization. In addition, multi-objective optimization of the tubes is performed by maximizing a composite objective function that provides a compromise between CFE and SEA. The CFE and SEA values at the training points of surrogate models (metamodels) are computed using the finite element analysis code LS-DYNA. Polynomial response surfaces, radial basis functions, and Kriging are the different surrogate models used in this study. Surrogate based optimization of the tubes showed that the tubes with indentations have better crush performance than tubes without indentations. It is found that maximum CFE requires large number of indentations with high radius, small thickness, and medium taper angle, while maximum SEA requires small number of indentations with low radius, large thickness and small taper angle. It is also found that the globally most accurate surrogate model does not necessarily lead to the optimum. [ABSTRACT FROM AUTHOR]

Abstract: In some forensic cases, nuclear DNA is degraded and cannot be analyzed. In such a case mitochondrial DNA (mtDNA) is usually used in forensic cases for identification because of its special features as high number of copies per cell, maternal inheritance and high mutation rate. Single nucleotide polymorphisms (SNPs) represent the most abundant class of human polymorphisms. The aim of this study was optimization of 10 mtDNA SNPs by using SNaPshot minisequencing technique on ABI310 genetic analyser in forensic molecular genetics laboratory. At the end of this study, the optimization of minisequencing technique was done by changing some assay parameters. Also, during the optimization of 10 mtSNP loci in our laboratory. [Copyright &y& Elsevier]

• Shape memory behavior of Ni 45,3 Ti 34,7 Hf 15 Pd 5 polycrystalline alloys are strongly tailored by post-aging cooling rates. • Thermal hysteresis in the WQ-alloy were higher compared to the FC-alloy. • Maximum of 70 °C thermal hysteresis was observed in the WQ-alloy while it was at most 54 °C at 1000 MPa. • The strain-temperature curves depend on the cooling rate and related microstructures. Effects of post-aging cooling rate (water quenched, WQ, and furnace cooled, FC) on the shape memory properties of polycrystalline Ni 45.3 Ti 34.7 Hf 15 Pd 5 alloys were studied. Their functional properties such as transformation temperatures, hysteresis, elastic energy, superelastic behavior and recoverable strain were found to be closely related to the post-aging cooling rate. Martensite start temperature decreased from 77 °C for WQ sample to 22 °C for FC sample. Impressive shape memory effect was observed under a huge compressive stress of 1 GPa with recoverable strains of 2.2 % and 2.5 % for the water quenched and furnace cooled samples, respectively. While both WQ and FC alloys showed perfect superelasticity for a wide temperature range, the WQ sample showed superelasticity at higher temperatures above 100 °C. [ABSTRACT FROM AUTHOR]

Temperature dependent compressive response and two-way shape memory effect (TWSME) of Ni 50.8 Ti 49.2 (at.%) shape memory alloys were systematically investigated. It was found that solutionized Ni 50.8 Ti 49.2 alloys could show positive and negative TWSME if they are plastically deformed in martensite and austenite (above M d), respectively. The maximum positive TWSME strain was 1.4% after martensite deformation of 8% at −90 ° C and maximum negative TWSME strain of 0.5% was obtained after austenite deformation of 8% at 200 ° C. Image 1 • Two-way shape memory effect of solutionized Ni50.8Ti49.2 (at.%) was studied. • Positive TWSME was observed after it is deformed in martensite. • Negative TWSME was observed after it is deformed in austenite (above Md). • The maximum positive TWSME strain was 1.4%. • The maximum negative TWSME strain was 0.5%. [ABSTRACT FROM AUTHOR]

Abstract: In the last few years genetic identification and paternity testing have begun to make increasing use of autosomal SNP (Single Nucleotide Polymorphism) typing as a supplement or alternative to STR analysis. With the improvement in detection technology SNP analysis is likely to be easier and more sensitive, with the generation of new methods and multiplex systems for a growing array of SNP markers. SNPforID consortium developed 52 SNP PCR multiplex for human identification purposes detected with 23 plex and 29 plex single base extension reactions (Auto1 and 2 respectively). In this study, internal validation for the 29 SNPs of Auto2 was carried out by performing a 29 plex PCR and single base extension reaction on control samples and previously analyzed forensic casework and subsequent detection with an AB 310 Genetic Analyzer. We tested the accuracy, precision, sensitivity and reproducibility of the Auto2 multiplex with this instrument in our laboratory. We used 9947A control DNA samples of the AmpFℓSTR Identifiler™ kit to test the validation parameters together with non-probative DNA samples from whole blood and buccal swab samples of 29 healthy donors from different parts of Istanbul. Good results were obtained but interpretation of the peak patterns obtained on the AB 310 requires care and thorough optimization before they can be readily compard to those obtained from multiple capillary AB 31xx Analyzers. We succesfully optimized and validated the SNPforID Auto2 multiplex system for identification analyses in our laboratory. [Copyright &y& Elsevier]

Abstract: The use of ChrX-STRs is enormous in forensic case as these have proven to be powerful tools, mainly in deficiency paternity cases when the disputed child is female, and also some special cases involving blood relatives, incest cases, fetal typing in abortion material. The Mentype® Argus X-8 kit is a commercial multiplex system which contains Amelogenin for gender determination as well as gonosomal STR markers (DXS8378, HPRTB, DXS7423, DXS7132, DXS10134, DXS10074, DXS10101 and DXS10135). Validation studies were being performed on blood obtained from the volunteers in Turkish population. In this study, some parameters were taken under consideration for validation like DNA extraction using different protocols, quantitated by using commercially available Invitrogen Qubit Fluorometer, reaction volume validation of Master Mix and the analysis of female/male, female/female and male/male mixtures were performed. The conditions were optimized and validated using GenAmp 9700 and reducing reaction volume from 25μl to 12.5μl and 6.5μl. After reducing the total volume of the reaction, the results were same and there was no effect on peak height and quality when analyzed on ABI 310 genetic analyzer. 2 paternity cases were also performed which gave the same power of discrimination as has been mentioned in Mentype® Argus X-8 kit. [Copyright &y& Elsevier]