On a New Method to Determine the Yield Stress in Lubricating Grease

An experimental study using both a controlled stress and a controlled strain rheometer has been undertaken to characterize lubricating grease in shear, creep, stress relaxation, and oscillatory flow, with a main focus on determining the yield stress. The yield stress was examined using a cone–plate and parallel-plate system with smooth and rough surfaces. Clear discrepancies were observed in the yield stress values obtained using different techniques where oscillatory strain sweep measurements seem to be the best choice. This technique is less sensitive to wall slip, shows good reproducibility, and is relatively easy to perform. The method also shows that the yield stress is a function of the imposed frequency and therefore of the time domain. At lower values of shear—that is, in the linear viscoelastic regime—there is no structural breakdown and the rheology of the grease can be described by the Maxwell model where the stress and the strain are almost proportional to each other. Based on this observation, a novel method to determine the yield stress is proposed: “The yield stress can be determined from the point where this linearity no longer applies.” This method is compared to those that are commonly used. The yield stress was found to depend exponentially on temperature and linearly on frequency

Aktivitetsbaserat arbetssätt inom akademin : En kvalitativ studie om medarbetare inom akademin och deras upplevelser av att arbeta aktivitetsbaserat

Aktivitetsbaserat arbetssätt har sedan några år tillbaka slagit igenom på marknaden och blivit en stor trend både i Sverige och resten av världen. Det är ett omstritt begrepp sombåde fått lovord och kritik. Studiens syfte är att undersöka hur medarbetare inom akademin upplever att arbeta i en aktivitetsbaserad miljö med fokus på psykosocial arbetsmiljö och sociala relationer samt om det finns ett samband mellan individens arbetsuppgifter och deras upplevelse. En kvalitativ studie har genomförts på ett universitet/högskola i Sverige, totalt sex semistrukturerade intervjuer har genomförts. Respondenternas uppfattning varierade gällande deras upplevelser av det aktivitetsbaserade arbetssättet dock var flertalet negativa. De huvudsakliga faktorerna som lyftes var ljudnivån och transparens, respondenterna nyttjar olika copingstrategier för att få bukt med problemen. Resultatet visar att de sociala relationerna på arbetsplatsen både förstärkts och försämrats. Respondenternas arbetsuppgifter belystes som problematiska inom ett aktivitetsbaserat arbetssätt. Utifrån studiens resultat var det som var mest påtagligt negativt för respondenternas psykosociala arbetsmiljö och upplevelsen av den aktivitetsbaserade miljön de faktorer som låg utanför individens egenkontroll, där lyckade copingstrategier inte var tillämpningsbara.Activity-based working has been on the rise for some years and has become a big trend both in Sweden and the rest of the world. It is a controversial concept that has both received praise and criticism. The aim of the study is to investigate how employees in the academia experience working in an activity-based office with a focus on psychosocial work environment and social relations, and whether there is a connection between the individual's tasks and their experience. A qualitative study has been conducted at a university/college in Sweden, a total of six semistructured interviews have been held. Respondents' perception of their experiences of the activity-based working varied, but the most respondents were negative. The main factors that were lifted were the sound level and the transparency, the respondents used different coping strategies to overcome the problems. The result shows that the social relations in the workplace have both been strengthened and deteriorated. The respondents' tasks were highlighted as problematic within an activity-based office. Based on the study's results, the most negative factor for the respondents' psychosocial work environment and the experience of the activitybased working were the factors that were outside the individual's control,where successful coping strategies were not applicable