Kinematic and dynamic analysis of a Sit-Ski for smproving the vibrational comfort

This paper reports both procedures for the kinematic design and the results of dynamic analyses of three models of sit-ski in order to evaluate their vibrational comfort. The model described in the US Patent US 6,019,380 has been assumed as a reference in the following kinematic and dynamic analyses of the new models proposed. The two main features to be considered while designing a sit-ski are the manoeuvrability and the range of vision of the driver. These two features appear to be important considering that the sit-ski is generally used by disabled people (e.g. paraplegic). Thus the kinematic design phase should account for the fulfillment of these requirements. On the basis of these, three new models have been proposed and herein named: Flex, modified Flex and eightbar linkage (Smarrini 2003). Once the kinematic synthesis and analysis have been completed the dynamic performance of each model is investigated. For this purpose two kinds of slope profiles are simulated in order to reproduce the stresses which may likely occur during a downhill race. In particular the position and the acceleration of the seat have been monitored during the simulations. This is important in order to test the range of vision and handling requirements. The seat acceleration is also important to evaluate the vibrational comfort of the sit-ski according to the British standard BS 6841 (Griffin 1990). The dynamic simulation is first executed by means of the multibody dynamics code NumDyn3D, then the vibrational comfort analysis is performed using in-house developed software (Vita 2001, Valentini and Vita 2003)

Kinematic and dynamic analysis of a Sit-Ski for smproving the vibrational comfort

This paper reports both procedures for the kinematic design and the results of dynamic analyses of three models of sit-ski in order to evaluate their vibrational comfort. The model described in the US Patent US 6,019,380 has been assumed as a reference in the following kinematic and dynamic analyses of the new models proposed. The two main features to be considered while designing a sit-ski are the manoeuvrability and the range of vision of the driver. These two features appear to be important considering that the sit-ski is generally used by disabled people (e.g. paraplegic). Thus the kinematic design phase should account for the fulfillment of these requirements. On the basis of these, three new models have been proposed and herein named: Flex, modified Flex and eightbar linkage (Smarrini 2003). Once the kinematic synthesis and analysis have been completed the dynamic performance of each model is investigated. For this purpose two kinds of slope profiles are simulated in order to reproduce the stresses which may likely occur during a downhill race. In particular the position and the acceleration of the seat have been monitored during the simulations. This is important in order to test the range of vision and handling requirements. The seat acceleration is also important to evaluate the vibrational comfort of the sit-ski according to the British standard BS 6841 (Griffin 1990). The dynamic simulation is first executed by means of the multibody dynamics code NumDyn3D, then the vibrational comfort analysis is performed using in-house developed software (Vita 2001, Valentini and Vita 2003)

Service perspectives’ trends in marketing research: a bibliometric analysis

Purpose: This contribution identifies marketing research trends concerning the latest advances in service marketing, with particular focus on the perspective of service and value co-creation. Methodology: This work is based on a bibliometric analysis of the publications on Service-Dominant logic in marketing literature. Bibliographical data gathered from the ISI Web of Science has been examined through the adoption of a web-based social network analysis (SNA) on the citation data. Findings: New service perspectives have been granted increasing attention in academic circles and are contributing to the emergence of innovative trends that reflect the need to change the outdated principles of marketing toward new concepts more suited to current market characteristics. Practical implication: By highlighting the relevance of new marketing perspectives focused on service, the study could suggest to practitioners how to overcome outdated approaches that limit the mind-set for seeing opportunities for co-creation of value with customers and other stakeholders of the firm. Originality and value: Efficient network analysis on citation data could help researchers to propose straightforward solutions and new ideas about service and value co-creation theories

Roller bearing under high loaded oscillations: Life evolution and accommodation mechanisms

High loaded oscillating bearings are used on several industrial fields such as robotics, wind power, aeronautics and aerospace. These bearings are subjected to extremely high local contact pressures and relatively low oscillatory speed. In this work, endurance tests on commercial single row spherical roller bearings enable to propose a degradation scenario for the bearing lifecycle. Topographical analyses carried out at each phase of the bearing life allowed to understand the degradation evolution at the interface between the inner-ring raceway and rolling elements. The analysis of the experimental results, with the support of numerical stress analysis, led to the understanding of the involved accommodation mechanisms. Then, a comparison with the wear processes in deep-groove ball bearings is provided