Experimental Study of Lubricating Grease Flow inside the Gap of a Labyrinth Seal Using Microparticle Image Velocimetry

In this study, the flow of lubricating greases in a labyrinth seal geometry is studied using microparticle image velocimetry (µPIV). The aim is to evaluate the grease velocity distribution inside the gap of a labyrinth seal and to find a relationship between the grease consistency and the transferred speed from the rotating ring in order to choose the correct grease as a sealing medium. In addition, the grease flow characteristics are important for the understanding of fracture due to grease layer displacement. For these purposes, four greases with different rheological properties were used in µPIV experiments. It was found that the grease consistency plays a crucial role in speed development as well as the grease composition and presence of a slip effect at the grease–rotating wall interface.     

Économies d'énergie dans les logements déjà construits

Dans l'un des projets pilotes financés par le Swedish Council of Building Research, le Service de la Technologie du Bâtiment de l'Institut Royal de la Technologie de Stockholm a montré comment la consommation d'énergie pouvait être réduite de plus de 50 % dans un groupe d'immeubles type de trois étages construit vers 1940. Les niveaux d'isolation thermique y étaient faibles par rapport aux normes suédoises – les murs et les toitures ayant des coefficients de transmission thermique de 1,2 W/m.².°C — et la consommation de fuel y atteignait 60 litres par m² de surface habitable nette.     

Glass covering of large building volumes

Results from Phase I of interdisciplinary research study led by Professor Ingemar Höglund with Göran Ottoson and Robert Öman from the Department of Building Technology, Stockhohn, show benefits outweigh negative aspects in covering 4000 square metres of pedestrian streets, revitalizing the Skärholmen Shopping Centre in south‐west Stockhohn in 1984. By incorporating district heating, double glazing and replacing brick with marble floor finishes, this had a positive effect on shoppers, staff and managers and increased sales. The heating consumption has remained the same.     

Parameter influence on moisture induced eigen-stresses in timber

Moisture induced stress in timber is dependant on many factors. The driving force behind is the moisture variation in the surrounding air which causes induced stress due to restraint of hygro-expansion within timber elements (this can to some extent be seen analogous to thermally induced stress in steel). Today's computational power together with advanced constitutive models offers a??valuable tool towards understanding and determining moisture actions on timber. However, it seems that the issue concerning uncertainties of the input parameters is seldom addressed. This paper presents results on how various factors affect the resulting moisture induced stress by a??parametric study of the input values. A small numerical change of one parameter may possibly result in a??major change of calculated stress levels. It is for example, shown that coating (paint) and cross-sectional dimensions play an important role for spatial stress distribution.     

Time-series modeling of moisture exposure on timber structures

This paper presents a methodology with the purpose of modeling and simulating outdoor temperature and relative humidity (vapor concentration) related to moisture exposure on timber structures. The methodology is based on time-series analysis with recorded meteorological data used as input. In situations where recorded data is missing or consists of limited sequences, this methodology offers the possibility to use synthetic data instead. It was found that temperature and vapor concentration could be modeled by a combination of deterministic functions and stochastic processes, which consider the dynamics of the climate, including slow seasonal variations and fast daily changes. Specifically, a model for temperature and vapor concentration in Stockholm, Sweden, is presented together with simulation results. It is shown that the model produces simulated sequences with statistical properties close to the real recorded ones.     

Rheological properties of lithium,lithium complex,and sodium greases

The rheological properties of two lithium, two lithium complex, and two sodium greases, all with the most common NLGI grade two, have been investigated. The greases are based on a mineral and a synthetic oil. The apparatus used was a cone-and-plate rheometer and an impacting-ball apparatus. The impacting-ball apparatus used a steel ball, which impacted a lubricated sintered carbide plate, to measure the shear stress-pressure coefficient, γ, of the lubricant. At pressures found in elastohydrodynamic contacts this coefficient determined the limiting shear stress. The γ-value thus affects the coefficient of friction and consequently, lower γ-value means less friction. The results from the impacting-ball apparatus showed that the γ-value was lower for the greases with a synthetic base oil and that the lithium greases gave a lower γ-value than the corresponding base oils. Results from the cone-and-plate rheometer showed the characteristic shear thinning behaviour of the greases and the influence of shear history and temperature. The results from the cone-and-plate rheometer have also been fitted to a four parameter rheological model.     

Cytogenetic analysis of pancreatic carcinomas: intratumor heterogeneity and nonrandom pattern of chromosome aberrations

Twenty-nine nonendocrine pancreatic carcinomas (20 primary tumors and nine metastases) were studied by chromosome banding after short-term culture. Acquired clonal aberrations were found in 25 tumors and a detailed analysis of these revealed extensive cytogenetic intratumor heterogeneity. Apart from six carcinomas with one clone only, 19 tumors displayed from two to 58 clones, bringing the total number of clones to 230. Karyotypically related clones, signifying evolutionary variation, were found in 16 tumors, whereas unrelated clones were present in nine, the latter finding probably reflecting a distinct pathogenetic mechanism. The cytogenetic profile of pancreatic carcinoma was characterized by multiple numerical and structural changes. In total, more than 500 abnormal chromosomes, including rings, markers, homogeneously stained regions, and double minutes, altogether displaying 608 breakpoints, were detected. This complexity and heterogeneity notwithstanding, a nonrandom karyotypic pattern can be discerned in pancreatic cancer. Chromosomes 1, 3, 6, 7, 8, 11, 12, 17, and 19 and bands 1q12, 1q21, 3q11, 6p21, 6q21, 7q11, 7q22, 7q32, 11q13, 13cen, 14cen, 17q11, 17q21, and 19q13 were most frequently involved in structural rearrangements. A total of 19 recurrent unbalanced structural changes were identified, 11 of which were not reported previously: del(1)(q11), del(3)(p11), i(3)(q10), del(4)(q25), del(11)(p13), dup(11)(q13q23), i(12)(p10), der(13;15)(q10;q10), del(18)(q12), del(18)(q21), and i(19)(q10). The main karyotypic imbalances were entire-copy losses of chromosomes 18, Y, and 21, gains of chromosomes 7, 2, and 20, partial or whole-arm losses of 1p, 3p, 6q, 8p, 9p, 15q, 17p, 18q, 19p, and 20p, and partial or whole-arm gains of 1q, 3q, 5p, 6p, 7q, 8q, 11q, 12p, 17q, 19q, and 20q. In general, the karyotypic pattern of pancreatic carcinoma fits the multistep carcinogenesis concept. The observed cytogenetic heterogeneity appears to reflect a multitude of interchangeable but oncogenetically equivalent events, and the nonrandomness of the chromosomal alterations underscores the preferential pathways involved in tumor initiation and progression.     

L.S.I. circuit design

A c.a.d. system for the custom design of CMOS l.s.i. circuits, in use at ASEA-HAFO Sweden, is described. The software is based on programs developed inhouse for nonlinear d.c.- and transient simulation, logic simulation and layout activities, such as digitizing, checking, plotting and photomask data generation. The equipment used includes a PDP-15 minicomputer together with a computer-controlled photomask system and l.s.i. test systems.Twenty-two complex circuits have been designed using the system.     

A new method for determining the mechanical stability of lubricating greases

Mechanical stability is of central importance when dealing with the long-term service-length of grease-lubricated roller bearings. Poor stability will lead to consistency degradation of the grease, because of mechanical forces between the rolling parts of the bearing. The result can be leakage of grease through seals, or at worst a total failure of the bearing. The present investigation was initiated because present-day methods for prediction of mechanical stability show weak correlation with real service-length. The aim of the project was to develop a useful alternative. In order to fulfil this, both field tests and laboratory tests were carried out. In the field tests, nine different commercial greases were examined in the wheel bearings of five ore waggons, used for transporting ore by railroad from the Kiruna Mine in northern Sweden to Narvik in northern Norway for shipping to foreign markets. The test ore waggons travelled a distance of about 300,000 km during a period of 3 years. Small samples of greases were taken, on eight different occasions, for consistency testing. After the end of the test period, the damage on the bearings was also studied. In the laboratory tests, new undestroyed greases of the same brand as in the field tests were examined using conventional methods, such as the V2F, the Roll Stability Test and the Grease Worker. Comparisons between the field tests and these laboratory tests indicate poor correlation. In addition to these conventional methods, the relevance of the shear strength of the greases to the prediction of the mechanical stability was also tested. The shear stress τ_L depends on the applied pressure p, thus τ_L=τ₀+γ·p where τ₀ is the shear stress at atmospheric pressure. γ is a property of the lubricant in the same way as viscosity or density. It was found that γ correlates well with the mechanical stability in service. Increased γ values lead to a decrease in the mechanical stability. One reasonable explanation is that high γ values correspond to high shear stresses in the grease, and thus severe conditions for the thickener.