Experimental characterization and comparison of planar and corrugated aluminum sheets

To evaluate the effect of the corrugation [1] on the mechanical behavior of aluminum plates, a corrugated sheet on aluminum alloy Al1050 is characterized under tensile mechanical tests at room temperature. To characterize anisotropic behavior of the material, tensile experiments are carried out in three different tensile directions i.e. 0, 45 and 90° with respect to the rolling direction. All experiments are performed until final failure using both planar and corrugated sheets for comparison issues. Concerning the experimental supplies, a tensile testing machine is used which can handle forces until 5 kN and can perform monotonic tensile as well as cyclic displacement and force controlled tests. The tensile machine is connected with a digital image correlation background. The measurement apparatus is equipped with two cameras for the detection of displacement fringes. The equipment is able to detect transversal and longitudinal displacements and calculate strain values at also virtual rectangular gauges or along straight lines. The responses of both planar and corrugated plates are compared in the macroscopic level within the force-displacement curves, damage localization zones and macroscopic crack propagation paths. The experimental data for Al1050 is quite interesting because it will be used for the material parameters identification of anisotropic elasto-plastic models combined with mixed hardening and isotropic damage [2]. The implemented models are validated later by comparisons between finite element simulations of Marciniack tests in the FE code Abaqus® and complementary experimental data

Implicit integration scheme for porous viscoplastic potential-based constitutive equations

This paper deals with a viscoplastic potential-based model allowing thermomechanical damage behavior modeling of porous materials. The model describes rate dependent effects, hardening, creep as well as defects coalescence and propagation. Kinematic and isotropic hardening effects are taken into account by a set of internal state variables. The integration and implementation of the model into the FE code using a fully implicit integration scheme is exposed. Finally, it 19s used to predict mechanical behaviour degradation of solder layers used in power electronic packaging. Stress-strain behaviour and the evolution of volumic fraction of voids for the material under cyclic loading are presented

Tension-compression asymmetry and shear strength of titanium alloys

The relation between the tension-compression asymmetry (TCA) and shear strength in a wide variety of Ti alloys was examined. For this purpose, uniaxial tensile and compression, and double shear strength tests were performed on 13 Ti alloys, which have different microstructural phases (α, α+β, and β) and underwent different thermo-mechanical histories. Results show that the tensile-to-compressive yield strength and shear-to-tensile strength ratios of the alloys vary widely (between 0.79 to 1.24 and 0.52 to 0.86, respectively). A linear dependence between shear yield strength and tensile or compressive yield strength (whichever is lower) of all the alloys is found. While the ultimate shear and tensile strengths also show a linear dependence, data obtained on the fully β alloys are distinct. Finite element analyses employing the Drucker-Prager (DP) yield condition (to account for pressure-dependence on yield), Ludwick's strain hardening model, and Rice-Tracey failure criterion were performed to gain insights into the experimental trends. Results show that TCA decreases the shear yield stress while the shear strength is sensitive to the rate of hardening. A good correlation between the experimental and simulated shear-to-tensile yield strength ratios was observed. Based on a large, simulated dataset (generated using different combinations of material parameters), an empirical relation between shear strength, TCA, and tensile strengths was identified.Agency for Science, Technology and Research (A*STAR)This work was supported by the funding from A∗STAR, Singapore via the Structural Metals and Alloys Programme (No. A18B1b0061)

Acupuncture versus titrated morphine in acute renal colic: a randomized controlled trial

Kaouthar Beltaief,1,2 Mohamed Habib Grissa,1,2 Mohamed Amine Msolli,1,2 Nasri Bzeouich,1,2 Nizar Fredj,1,2 Adel Sakma,1,2 Hamdi Boubaker,1,2 Wahid Bouida,1,2 Riadh Boukef,1,3 Semir Nouira1,2 1Emergency Department, Fattouma Bourguiba University Hospital, 2Research Laboratory LR12SP18, University of Monastir, Monastir, 3Emergency Department, Sahloul University Hospital, Sousse, Tunisia Objective: The objective of this study was to compare the analgesic effect and tolerance profile of acupuncture versus intravenous (IV) titrated morphine in patients presenting to the emergency department (ED) with renal colic.Materials and methods: A total of 115 patients were randomized into two groups. Patients in the IV titrated-morphine group (n=61) received 0.1 mg/kg morphine every 5 minutes until pain score dropped by at least 50% of its baseline value. Patients in the acupuncture group (n=54) received an acupuncture session of 30 minutes following a prespecified protocol. The visual analog scale (VAS) was used to assess pain intensity at baseline and at 10, 20, 30, 45, and 60 minutes following the start of the treatment protocol. Possible treatment side effects were also recorded.Results: No significant differences were found between the two groups concerning age, sex, or baseline VAS score. From the 10th minute until the end of the intervention, acupuncture was associated with a deeper analgesic effect than titrated morphine (P<0.05 from the 10th minute and over). Analgesia was also faster in the acupuncture group, with time to obtain 50% reduction of baseline VAS of 14 minutes in the acupuncture group versus 28 minutes in the IV titrated-morphine group (P<0.001). Only three patients in the acupuncture group experienced minor side effects versus 42 in the morphine group (P<0.001). No major side effects were observed in this study.Conclusion: In ED patients with renal colic, acupuncture was associated with a much faster and deeper analgesic effect and a better tolerance profile in comparison with titrated IV morphine. Keywords: acupuncture, morphine, renal coli