The detailed design of a turbo generator rotor system is highly constrained by feasible regions for the damped natural frequencies of the system. A major problem for the designer is to find a solution that fulfills the design criterion for the damped natural frequencies. The bearings and some geometrical variables of the rotor are used as the primary design variables in order to achieve a feasible design. This paper presents an alternative approach to search for feasible designs. The design problem is formulated as an optimization problem and a genetic algorithm (GA) is used to search for feasible designs. Then, the problem is extended to include another objective (i.e., multiobjective optimization) to show the potential of using the optimization formulation and a Pareto-based GA in this rotordynamic application. The results show that the presented approach is promising as an engineering design tool

We describe a method to verify the shape of manufactured objects by using their design model. A non-contact measuring method that consists of a stereo-camera system and a single projected fringe pattern is used. The method acquires one image from each camera. Additional shape information from the design model is also used. This surface-measurement method gives an accuracy of about 45 µm. Deviations from the design model within ±1.6 mm can be correctly detected. The measured surface representation is matched to the design model using the ICP-method. Fast performance has been considered adapting the method for on-line use.

Crack initiation, propagation and microfracture processes of austempered high silicon cast steel have been investigated by using an in-situ tensile stage installed inside a scanning electron microscope chamber. It is revealed that micro cracks always nucleate at the yielding near imperfections and the boundary of matrix-inclusions due to the stress concentration. There are four types of crack propagations in the matrix: crack propagates along the boundary of two clusters of bainitic ferrite; crack propagates along the boundary of ferrite-austenite in bainitic ferrite laths; crack propagates into bainitic ferrite laths; crack nucleates and propagates in the high carbon brittle plate shape martensite which is transformed from some blocky retained austenite due to plastic deformation. Based on the observation and analysis of microfracture processes, a schematic diagram of the crack nucleation and propagation process of high silicon cast steel is proposed.

Objective. The hypothesis that low light intensity and long but sufficient curing time can produce composites with volumetric shrinkage, degree of conversion (DC%) and Young's modulus (E-modulus) comparable to those of high light intensity cured composite was tested, when the contraction strain and heat generation were lower with low light intensity curing. Methods. Dental composites (Z100 and Z250, 3M ESPE) were investigated. Specimens were cured with light intensities of 200, 450 and 800 mW/cm2 for 140, 60 and 35 s from a distance of 7 mm. Strain-gages were used for contraction strain measurements. DC% was measured at the top and the bottom of 4 mm thick samples using FT-Raman spectroscopy. Volumetric polymerization shrinkage was determined using a water displacement method. E-modulus was determined in tension on composite specimens. Results. The results were analyzed using ANOVA and Duncan's multiple range tests and regular t-test. Polymerization stress level decreased significantly (p<0.05) when cured with 200 mW/cm2 rather than with 800 mW/cm2. Temperature rises were significantly different (p<0.05) for different composites and light intensity values. Reduction in light intensity did not decrease the DC% values significantly at the top surfaces. The most dramatic differences existed between top and bottom surfaces (p<0.05) rather than among curing groups. Measured E-modulus and volumetric shrinkage values were not significantly different (p>0.05) between different light intensity groups. Conclusion. DC%, E-modulus and the volumetric shrinkage values in cured composites were not affected by low light intensity, however, the contraction strain and polymerization's exotherm were decreased. Thus our results support the proposed hypothesis.

Exposing a laminate structure to thermal cycles and to temperatures close to the curing temperature, followed by mechanical fatigue, cause interlaminar and intralaminar cracks leading to degradation of the mechanical properties. The effect of thermal and mechanical fatigue, as well as thermal aging, on carbon fiber composite laminate structures is under study in the present paper.

Work collaboration is today normal practice in developing modern products. Engineering collaborative work involve a number of team members that need to share and exchange design ideas working with engineering analysis tools, such as mechanical computer aided engineering systems. This work presents a data mediation approach, using active database technology, which enables exchange of engineering information among distributed team members in a timely manner. The distributed data is automatically synchronised between different places using a database management system that support event-condition-action (ECA) database rules. Only the updates introduced at one location are distributed to the other locations, minimizing the information transfer and enhancing the performance. Members working at different locations can therefore interactively manipulate the same set of information at the same time

For butt joint welding of 8 mm and of 16 mm thick stainless steel a 15 kW fibre laser was applied, achieving full penetration for a welding speed of 7 m/min and 3 m/min, respectively. Optics with a focal length ranging from 500 mm to 150 mm focus the laser beam to a spot diameter of 0.65 to 0.2 mm with a focal depth of 18 to 4 mm and a cw-power density of 4 to 48 MW/cm2. Although narrow sound welds can be achieved, heavy spatter ejection along with underfill can take place at the top and root side, particularly for high power density and for low line energy. Various advanced analysis methods were developed. Spatter was observed by high speed imaging of the weld pool surface and of the keyhole. Quantitative evaluation of the drop size and flight trajectories enabled categorisation into four spatter modes, revealing favoured conditions for spatter suppression. Modelling subsequent to the drop evaluation provided additional analysis. An illustrative theoretical description and the formulation of a standard documentation methodology were developed. This aims to generalise and transfer knowledge as a guideline for spatter suppression in other laser welding situations.

Many rotating machineries are supported by bearings with clearance, which are further clamped in, compared to the bearing stiffness, weak pedestals. As have been reported in several studies, it is essential to choose a proper clearance in order to avoid unwanted vibrations. When rotating machineries supported by bearings with clearance are subjected to stationary loads (gravity, magnetic pull etc.), it may not loose contact between the shaft and the bearing (i.e. full contact). However, even in full contact unwanted dynamics can occur which is of interest in this paper. It is found that the clearance give raise to anisotropic pedestal stiffness. It is further shown that some of the resonance frequencies decrease with the clearance.

For fibre laser welding of an eccentric corner joint, the quality of the resulting weld cross section was studied with respect to the dependence on process parameters like lateral laser beam alignment, beam inclination, focal plane position or welding speed. The complex load situation of the support beamer was simplified to bending of one corner. Due to fatigue load, the weld properties causing the peak stress are essential, in particular the top and root shape of the weld cross section. For the parameters varied, the resulting shapes were categorized into different top and root classes, determined by certain key dimensions, considering also welding defects like undercuts. The shapes are boundary conditions for Finite Element Analysis of the joint under load for quantitative comparative analysis of the maximum stress. As two high strength steel grades were joined, the hardness transition across the weld was of interest, too. High speed imaging of the weld pool surface shape provided additional information on the relation between the parameter input and quality output. The different trends identified were discussed and guidelines were derived. As the systematic documentation of results is unsatisfactory in welding, a new method was developed and applied for the first time, called the Matrix Flow Chart. It enables an illustrative view on the resulting welding trends in a combined manner and is extendable by other researchers.

Composites ability to retain functionality in the presence of damage is a crucial safety and economic issue. Generally the first damage mode in composite laminates is matrix cracking, which affects the mechanical properties of the structure long before its load-bearing capacity is exhausted. In this paper, a detailed analysis of the effect of matrix cracking on the behaviour of cross-ply [0/90]s and unbalanced symmetric [0/45]s glass/epoxy laminates loaded statically in tension is performed. Theoretical predictions of stiffness reduction due to damage are based on the Equivalent Constraint Model (ECM), which takes into account concurrent matrix cracking in all plies of the laminate, although matrix cracking under consideration is developing only within the off-axis ply of the laminates. The longitudinal Young's modulus predictions are compared to experimentally derived data obtained using laser Raman spectroscopy (LRS). The good agreement between predicted and measured values of the reduced longitudinal Young's modulus validates the ECM model and proves that its basic assumptions are accurate. Thus, the predictions for all the mechanical properties by the ECM model are within a realistic range, while experimental evidence is required for further validation.

The previous termeffect of carbonnext term activity and CO pressure in the furnace previous termatmospherenext term is investigated with respect to the phase reactions during heat treatment of TiC/Si powders. Special attention is given to the production and decomposition of Ti3SiC2. Samples were heated in graphite and alumina furnaces, connected to a dilatometer which enabled the in-situ analysis of the phase reactions. The phase compositions of the heat treated samples were determined by x-ray diffraction. The reducing previous termatmospherenext term of the graphite furnace enhanced the reactivity of the starting powder and enabled phase reactions to take place at a lower temperature than in the alumina furnace. TiSi2 and SiC phases formed at temperatures below the melting point of Si and were continuously consumed at higher temperatures. Ti3SiC2 formed at the melting point of Si regardless of furnace previous termatmosphere.next term No decomposition of the Ti3SiC2 was observed in either furnace.

In the modern building industry wood as a building material has been looked on as one of the solutions to lower the environmentally impact of the building industry. Building types that normally have been reserved for concrete and steel are today being built with wood as main load bearing component. However, the structural robustness of high-rise wood building has been questioned. The concern relates to wood’s brittle failure-mode and therefore the capacity of wood buildings to withstand catastrophic events where a loadbearing structural part its removed from the construction. To counteract a brittle failure mode in wood and create a ductile failure mode that allows alternative load paths, ductile steel connectors are seen as a solution. With inspiration from the concrete and steel industry, catenary action is brought forward as the most efficient method to create an alternative load path in high-rise wood buildings. To create catenary action, a tube connector that allows excessive deformation with increasing strength was believed to have sufficient capacity. A test method for testing tube connector capacity in a catenary event was developed with a main focus on tube capacity and forces created on the surrounding structure in a catastrophic event. To achieve this, a long stroke reversed 4-point bending test was formed and testing of traditional fasteners and the tube connector was conducted. Test result from catenary capacity testing showed low to no capacity for traditional fastening methods, however, traditional fastening method created arcing action in the beginning of the test cycles. The traditional fasteners showed a consistency in failure mode with arching and wood crushing before connection failure in form of screw withdrawal. Tube connectors had low to no consistency in failure modes, but higher consistency in capacity. Failure mode regarding tubes consisted of steel failure in tube and wood failure in the test specimen. In general, the tubes connector showed promising capacity and ductility to create alternative load paths with the help of catenary action. The project has shown that some design development for the tube connector and lager scale testing are needed to completely understand tube connector capacity and failure mode. 

The coke oven plant has a central role in the iron and steel making process in an integrated steel plant. The subject of this research is to study how the production and energy system at the steel industry, with a connected combined heat and power plant, is affected by renovation of the coke oven. The aim is to investigate the interaction between the different processes and how the choice of system boundary affects the operation practice for the steel plant. MILP-based optimization models have been developed and used for the evaluation. The analysis shows that it is very important to take the interactions between the different production units in the system into consideration when making the analysis. A system optimization with a boundary including the whole system has a greater potential for minimizing the total system cost than one that only includes the processes where the actual changes are made. Conclusions are also drawn regarding the production practice for the specific system

We prove that combinations of small eccentricity, ovality and/or triangularity in the rotor and stator can produce complex whirling motions of an unbalanced rotor in large synchronous generators. It is concluded which structures of shape deviations that are more harmful, in the sense of producing complex whirling motions, than others. For each such structure, we derive simplified equations of motions from which we conclude analytically the relation between shape deviations and mass unbalance that yield non-smooth whirling motions. Finally we discuss validity of our results in the sense of modeling of the unbalanced magnetic pull force

The potential of biocomposites in engineering applications is demonstrated by using aligned flax fibre/polylactate composites as a materials model system. The failure stress of flax fibres is measured by tensile testing of single fibres and fibre bundles. For both fibre configurations, it is found that failure stress is decreased by increasing the tested fibre volume. Based on two types of flax fibre preforms: carded sliver and unidirectional non-crimp fabric, aligned flax fibre/polylactate composites were fabricated with variable fibre content. The volumetric composition and tensile properties of the composite were measured. For composites with a fibre content of 37 % by volume, stiffness is about 20 GPa and failure stress is about 180 MPa. The tensile properties of the composites are analysed with a modified rule of mixtures model, which includes the effect of porosity. The experimental results are well predicted by the model. The back-calculated effective stiffness and failure stress of the flax fibres are in the ranges 56-60 GPa and 515-730 MPa, respectively. Finally, the model is used for parametric analysis and overall guidelines for the comparisons between tensile performance of flax fibre composites and traditional fibre composites (exemplified by glass fibre composites) are presented. The stiffness per volume, per weight and per cost is compared for these two types of composites.

The potential of biocomposites in engineering applications is demonstrated by using aligned flax fibre/polylactate composites as a materials model system. The failure stress of flax fibres is measured by tensile testing of single fibres and fibre bundles. For both fibre configurations, it is found that failure stress is decreased by increasing the tested fibre volume. Based on two types of flax fibre preforms: carded sliver and uniaxial non-crimp fabric, aligned flax fibre/polylactate composites were fabricated with variable fibre content. The volumetric composition and tensile properties of the composite were measured. For composites with a fibre content of 37 % by volume, stiffness is about 20 GPa and failure stress is about 180 MPa. The tensile properties of the composites are analysed with a modified rule of mixtures model, which includes the effect of porosity. The experimental results are well predicted by the model. The back-calculated effective stiffness and failure stress of the flax fibres are in the ranges 56-60 GPa and 515-730 MPa, respectively. Finally, model predictions are used to present overall guidelines for the comparisons between tensile performance of flax fibre composites and traditional fibre composites (exemplified by glass fibre composites). The stiffness per volume, per weight and per cost is compared for these two types of composites.

The effect of wood fiber ultrastructure and cell wall hygroelastic properties on wood fiber composite hygroexpansion has been analyzed. An analytical concentric cylinder model extended to include also free hygroexpansion of orthotropic phase materials has been used on several length scales. Using properties of the three main wood polymers, cellulose, hemicellulose and lignin the longitudinal and transverse hygroexpansion coefficients for the microfibril unit cell were obtained and the volume fraction change of the wood polymers in the microfibril unit cell depending on relative humidity was calculated. The fiber cell wall was modeled regarding each individual S1, S2 and S3 layer and the cell wall longitudinal hygroexpansion coefficient was determined depending on microfibril angle in the S2 layer. A homogenization procedure replacing the S1, S2 and S3 layers with one single layer was found not to influence the results significantly for low microfibril angles. Finally the hygroexpansion coefficients of an aligned softwood fiber composite were calculated.

In this study we have focused on exploring the photoacoustic signal generated by laser induced dielectric breakdown process in pure water, under normal conditions. In this case the dielectric breakdown will lead to a formation of a shock wave. We investigated the relation between pulse energy and amplitude, group velocity and power spectrum of the shock wave. Also, the threshold for dielectric breakdown is estimated. A pulsed, high power Nd:YAG laser with λ = 532 nm and a pulse duration of 12 ns was used. The laser pulse energy ranges from 0.1 mJ to 7.4 mJ. Only photoacoustic signals generated from dielectric breakdown was considered. We found that the amplitude and the average group velocity of the shock wave correlates to the laser pulse energy. The frequency contents of the photoacoustic signal changes due to both non-linear behaviour and dissipative effects. We estimated the dielectric breakdown threshold to be 0.44 × 1011Wcm-2.

We report on a systematic study of the influence of laser irradiation on the Raman spectra of HiPco-produced single-wall CNTs. Specifically, we have examined the Raman response of bundled CNTs to: i) laser power density; ii) exposure time and iii) photon energy (1.96 and 2.33 eV). Our results show that irreversible destruction of CNTs in the bundles can occur at even low laser power density (0.15 kW/cm2). The tubes with smaller diameters are influenced first and the rate of CNT destruction increases with photon energy. Finally, we determined that when investigating destruction of CNT bundles, the use of a low laser power density is required because changes in the structure of the bundles can lead to sample temperature changes for otherwise identical measurement parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A variety of samples made via different routes were investigated. Samples are nanostructured (average grain sizes are about 20 nm). The advantage of high-pressure (HP)-manufactured (2 GPa, 800-1050 degrees C, 1 h) MgB2 bulk is the possibility to get almost theoretically dense (1-2% porosity) material with very high critical current densities reaching at 20 K, in 0-1 T j(c) = 1.2 - 1.0 . 10(6) A/cm(2) (with 10% SiC doping) and j(c) = 9.2 - 7.3 10(5) A/cm(2) (without doping). Mechanical properties are also very high: fracture toughness up to 4.4 +/- 0.04 MPa . m(0.5) and 7.6 +/- 2.0 MPa . m(0.5) at 148.8 N load for MgB2 undoped and doped with 10% Ta, respectively. The HP-synthesized material at moderate temperature (2 GPa, 600 degrees C, 1 h) from B with high amount of impurity C (3.15%) and H (0.87%) has j(c) = 10(3) A/cm(2) in 8 T field at 20 K, highest irreversibility fields (at 18.4 K H-irr = 15 T) and upper critical fields (at 22 K H-C2 = 15 T) but 17% porosity. HP materials with stoichiometry near MgB12 can have T-c = 37 K and j(c) = 6 . 10(4) A/cm(2) at 0 T and H-irr = 5 T at 20 K. The spark plasma synthesized (SPS) material (50 MPa, 600-1050 degrees C 1.3 h, without additions), demonstrated at 20 K, in 0-1 T j(c) = 4.5 - 4 10(5) A/cm(2). Dispersed inclusions of higher magnesium borides, which are usually present in MgB2 structure and obviously create new pinning centers can be revealed by Raman spectroscopy (for the first time a spectrum of MgB7 was obtained). Tests of quench behavior, losses on MgB2 rings and material thermal conductivity show promising properties for fault current limiters. Due to high critical fields, the material can be used for magnets.

The objective of this paper is to analyze fiber/matrix debond crack growth in unidirectional (UD) composites during high stress cyclic tension-tension loading. High stress loading means that fiber breaks and consecutive fiber/matrix interface debond growth are expected. Fracture mechanics concepts are applied to analyze damage evolution

Swedish prefabricators of domestic buildings need to become more effective and efficient; the aim of this paper is to investigate the usefulness of rule-based IT support tools for this purpose. The current sales and design process at a Swedish timber volume element prefabricator is presented. The process was mapped and the early design phase was evaluated regarding information management and standardisation. It was found that information management during early design is often ad hoc and person dependent; therefore searching for information that could lead to reuse of past solutions is rather time demanding. There is a need for standardisation to promote reuse due to a mentality of designing one-of-a-kind buildings. Knowledge-based engineering is seen as an enabler to enhance the current situation and an IT support approach is suggested. A demonstrator stair tool is tested, which lets the seller discuss needs with the customer and then use the tool to assess cost and manufacturability. If design flaws can be found early on, waste activities downstream can be reduced. Standardisation could be realised through modularisation, which the implementation of an IT support tool could gain from.

A study was conducted to compare the fibrillation efficiency of micro fibrillated cellulose (MFC) production using two different refining equipment, such as a super mass colloider and ZRI mechanical ultrasonic disintegration unit. The two approaches were tested with two never-dried softwood cellulose fibers, such as bleached Kraft and dissolving cellulose. The two celluloses were tested without pre-treatments and after NaOH alkali treatment. Energy consumption was measured and the properties of the refined materials were analyzed. The two celluloses were also investigated without any treatment and in an alkali-treated form. Alkali treatment was carried out by storing the celluloses overnight in a NaOH solution of pH 13 in a refrigerator. It was found that the consistency the pulp during storage was 3% and dissolution of pulp to refining consistency was done with a NaOH solution of pH 13.

WTaN hard films with Ta/(W+Ta)=46at.% were deposited on single crystal Si (111) substrates using direct current magnetron sputtering. The effect of nitrogen partial pressure (pN2) on crystal structure, surface topography, adhesion strength, and hardness of WTaN films was investigated. With increasing pN2, the phase composition changes from pure fcc W-Ta-N phase to a mixture of fcc WTaN phase and hexagonal δ-W(Ta)N phase, and then to pure hexagonal δ-W(Ta)N phase; the average grain size decreases monotonously; the surface becomes more and more smooth; the hardness initially increases and then decreases after passing a maximum of 41GPa at pN2=0.5Pa, while the adhesion strength varies in an opposite trend to the hardness. The maximum hardness could be due to the combined effect of reduced crystallite size and the coexistence of two phases.