Application of Vibration Correlation Technique for Open Hole Cylinders

As non-destructive method for axial buckling load determination - Vibration Correlation Technique (VCT) showed major advantages for a range of industrial application. Particular technique for validation of structural limit state in accordance to numerical model prediction for large (true) scale structures are getting the required momentum. The Vibration Correlation Technique (VCT) allows to correlate the ultimate load or instability point with rapid decrement of self-frequency response. Nevertheless this technique is still under development for thin-walled shells and plates. The current research discusses an experimental verification of extended approach, applying vibration correlation technique, for the prediction of actual buckling loads on unstiffened isotropic cylindrical shells with circular cut-outs, loaded in axial compression. Validation study include several aluminium cylinders which were manufactured and repeatedly loaded up to instability point. In order to characterize a correlation with the applied load, several initial natural frequencies and mode shapes were measured during tests by 3D laser scanner. Results demonstrate that proposed vibration correlation technique allows one to predict the experimental buckling load with high reliability, by loading up to % of ultimate load. Additional experimental tests including geometric imperfections from initial manufacturing and postbuckling mode shape are currently under development to further validation ofproposed approach

Buckling of imperfection sensitive shell structures: experimental characterization of the knock-down factor using the Multiple Perturbation Load Approach

This work presents an experimental study to compare the effects on the buckling load of imperfection sensitive cylindrical shell structures using the Multiple Perturbation Load Approach (MPLA) and the Single Perturbation Load Approach (SPLA). A benchmark case is developed using a composite cylindrical shell with a radius over thickness ratio of 400. An experimental test setup is set to provide reliable results. The knock-down factor on the buckling load using one, two and three perturbation loads distributed along the surface of the cylinder is characterized, presented and discussed in this paper. The experimental result shows that lowest knock-down factor are achieved when the number of perturbation loads is increased

Structure and function of CutC choline lyase from human microbiota bacterium Klebsiella pneumoniae

Publisher Copyright: © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.CutC choline trimethylamine-lyase is an anaerobic bacterial glycyl radical enzyme (GRE) that cleaves choline to produce trimethylamine (TMA) and acetaldehyde. In humans, TMA is produced exclusively by the intestinal microbiota, and its metabolite, trimethylamine oxide, has been associated with a higher risk of cardiovascular diseases. Therefore, information about the three-dimensional structures of TMA-producing enzymes is important for microbiota-targeted drug discovery. We have cloned, expressed, and purified the CutC GRE and the activating enzyme CutD from Klebsiella pneumoniae, a representative of the human microbiota. We have determined the first crystal structures of both the choline-bound and choline-free forms of CutC and have discovered that binding of choline at the ligand-binding site triggers conformational changes in the enzyme structure, a feature that has not been observed for any other characterized GRE.publishersversionPeer reviewe

Automatic washing machine for tin cans

Kalnins, K. (2011). Automatic washing machine for tin cans. http://hdl.handle.net/10251/11093.Archivo delegad

Materialu plisuma un plastiskuma ipasibu petijumi

Available from Latvian Academic Library / LAL - Latvian Academic LibrarySIGLELVLatvi

An Experimental and Numerical Study of Low Velocity Impact of Unsaturated Polyester/Glass Fibre Composite

In this paper validation of experimental and numerical results of low-velocity impact tests of unsaturated polyester/glass fibre composite laminate has been carried out. Impact response of composite laminates was experimentally studied with drop-tower Instron 9250HV determining impact force, energy absorption and deflection. In addition, quasi-static testing equipment Zwick Z100 has been used to determine material mechanical properties to ensure good input data for numerical predictions. Numerical model has been created with the finite element commercial code ANSYS/LS-DYNA to simulate impact response of composite laminate. Also non-destructive ultrasonic B- and C- scan imagining with USPC&nbsp;3010 system has been used to identify the deformation regions in the specimens and compare to simulation results. During the impact test all samples were perforated, showing brittle response followed by matrix cracking and delamination. Overall good agreement between experimental and simulation results was achieved, comparing impact characterizing parameters as load, energy and deflection. Discrepancy has been observed between ultrasonic scanning and simulation code ANSYS/LS-DYNA results of rupture and delamination. Simulation shows less uniform and larger deformation than it was experimentally observed.http://dx.doi.org/10.5755/j01.ms.17.4.773</p

NCP_WIDE.NET Bulletin 6

Editors: Wojciech Adamiak, Kristin Kraav, Anna Mossolova.NCP_WIDE.NET project which promotes “Spreading Excellence and Widening Participation” programme enhances the quality of services offered by the NCPs and provides tools for sharing information. This Newsletter is yet another means for doing just that.N

Flexural behavior of sandwich panels with cellular wood, plywood stiffener/foam and thermoplastic composite core

A series of experimental tests have been carried out on three types of novel sandwich panels mainly designed for application in lightweight mobile housing. Two types of the panels are manufactured entirely from wood-based materials while the third one presents a combination of plywood for surfaces and corrugated thermoplastic composite as a core part. All sandwich panels are designed to allow rapid one-shot manufacturing. Mechanical performance has been evaluated in four-point bending comparing the data to the reference plywood board. Additionally, finite element simulations were performed to evaluate global behavior, stress distribution and provide the basis for a reliable design tool. Obtained results show sufficient mechanical characteristics suitable for floor and wall units. Compared to a solid plywood board, sandwich alternative can reach up to 42% higher specific stiffness, at the same time maintaining sufficient strength characteristics.Aerospace Structures & Computational Mechanic

Buckling of imperfection sensitive shell structures: experimental characterization of the knock-down factor using the Multiple Pertubation Load Approach

Buckling of imperfection sensitive shell structures: experimental characterizatio