15 research outputs found
Thermal analysis of laser additive manufacturing of aluminium alloys: Experiment and simulation
No full textThe ice extrusion test: a novel test setup for the investigation of ice-structure interaction–results and validation
No full textUnderstanding ice-structure interaction is critical for an efficient and safe design of offshore structures and ships in ice-covered waters. During the last decades a variety of field experiments, full-scale measurements on ships and laboratory tests have been conducted. Within this paper, a novel experimental setup of the ice extrusion test for the investigation crushing loads is proposed. Due to the flexible design of the experiment brittle and ductile ice loads can be investigated in the laboratory at different load levels. A comprehensive test series with more than 350 tests has been carried out to investigate the system behaviour. The failure mode of the ice is mostly determined by the test speed. The ratio of gap height and sample diameter is the most important parameter for the load level. A validation against full-scale data showed that with this experimental setup it is possible to generate relevant nominal local ice pressures
Raw data of the temperature measurements on the ship structure of RV Polarstern during the MOSAiC expedition
No full textThe temperature measurement system on bord of the R.V. Polarstern is an autonomous system to record the temperature distribution of the ship's structure. For this purpose, 16 locations in the void spaces 92 and 100 at starboard side between frame 78 and frame 81 are instrumented with PT1000 temperature sensors. The sensors are installed on the outer shell, frames and on deck 1 (E-Deck) and deck 2 (F-Deck). To ensure a long run time with limited memory, only one data set is stored every five minutes by Driesen+Kern data loggers
Raw data of strain measurements on the ship structure of RV Polarstern during the MOSAiC expedition
No full textThe strain measurement system on bord of the R.V. Polarstern is an autonomous system to record the structural response caused by ice pressure on the ship's structure. For this purpose, 36 strain gauge full bridge circuits are installed on six frames and one deck 2 (F-Deck) in the void spaces 92 and 100 at starboard side between frame 78 and frame 81. The strain signals are measured time synchronously with a Gantner measuring amplifier with an internal sampling rate of 1000 Hz. To ensure a long run time with limited memory, only one data set per second and statistic variables (actual value, minimum and maximum value, mean value and standard deviation) over ten minutes measuring time each are stored on two redundant storage medias. Furthermore, the system is connected with the on-board power supply and the time synchronization server
Multiscale process simulation of residual stress fields of laser beam welded precipitation hardened AA6082
No full textIn this study, a multiscale modelling approach for the determination of residual stresses for the laser beam welded, precipitation hardened aluminium alloy AA6082-T6 is presented and applied. The material behaviour is described by an elasto-visco-plastic material model, specially suited for fusion welding processes. The microstructure evolu- tion during the welding process has a direct influence on the macroscopic mechanical properties. The modelling approach accounts for the change in the microstructure via a Kampmann–Wagner Numerical model which takes into account the kinetics of the precipitates. The macroscopic mechanical properties are determined via classic dislocation theory, which accounts for the interaction between dislocations and precipitates. The temperature field of the welding process is described by a highly efficient semi-analytical approach. The solution of the tem- perature field in connection with a three dimensional moving heat source is achieved by using the method of Green’s functions. By employing the method of Green’s functions, it is possible to reduce the numerical effort significantly. The results of this modelling approach are compared to temperature, hardness as well as residual stress measurements, obtained from synchrotron X-ray diffraction, for welded sheets to clarify the accuracy of the applied model
Ice pressure measurements with tekscan sensors-behaviour, calibration and application limits
No full textShips and offshore structures operating in ice-covered sea areas have to withstand ice loads. In particular, the distribution of ice pressure in the contact area is critical. The pressure dis-tribution changes temporally and spatially and depends on the ice failure behaviour. Experimental measurements of ice pres-sures are possible with pressure mapping systems. A commonly used system in academia uses sensors manufactured by TekScan. The resulting measurements can be used to gain insight into ice failure behaviour, to establish design pressure patches, and to develop numerical models. However, various issues emerge when using these pressure measurement systems, e.g., equilibra-tion and calibration, which result in measurement uncertainties. Hence, this paper summarize and discuss possible issues and gives recommendations to address them
ICE PRESSURE MEASUREMENTS WITH TEKSCAN SENSORS - BEHAVIOUR, CALIBRATION AND APPLICATION LIMITS
No full textShips and offshore structures operating in ice-covered sea
areas have to withstand ice loads. In particular, the distribution
of ice pressure in the contact area is critical. The pressure distribution changes temporally and spatially and depends on the
ice failure behaviour. Experimental measurements of ice pressures are possible with pressure mapping systems. A commonly
used system in academia uses sensors manufactured by TekScan.
The resulting measurements can be used to gain insight into
ice failure behaviour, to establish design pressure patches, and
to develop numerical models. However, various issues emerge
when using these pressure measurement systems, e.g., equilibration and calibration, which result in measurement uncertainties.
Hence, this paper summarize and discuss possible issues and
gives recommendations to address them
Experimental investigation of an accidental ice impact on an aluminium high speed craft
No full textHigh speed vessels are constructed according to the high speed craft codes. These codes enable very light ship structures, which are necessary for effective operation of fast vessels without taking ice loads into account. In the given case a conventional aluminium structure of a high speed ferry designed according to the DNV-GL HSLC code for an operation in Stockholm is investigated. For the determination of the consequences of an impact between a high speed craft and a single ice floe an analytical impact model and a series of drop tests with conical ice specimens against full-scale aluminium panels of the given vessel are presented. Plastic deformations are only observed at the stiffeners and the outer shell. The structural integrity is still given after the tests. The influence of the structural stiffness as well as the limited change in the maximum force at different energy levels during the impact is discussed
