Fatigue lifetime correction of structural joints of opencast mining machinery

Opencast mining machinery represents a group of large-scale individually manufactured technical objects operated with long-life requests. Since their manufacturers are obliged to provide product that will reach declared time of life, fatigue strength and durability conditions have to be taken into account for superstructures to meet the requirements. The paper highlights main problems occurring while assessing fatigue lifetime during design. Firstly, the short survey of current state of the art regarding the approach to this problem is presented. Secondly, the most important reasons of unsatisfactory accuracy of the assessments are discussed. As a main objective of the study, the authors introduce the unique method of continuous fatigue lifetime correction for the welded superstructures during the machine lifecycle, as a remedy for this group of machinery. Furthermore, results and experience from adapting the approach in real object are presented, including fatigue lifetime correction due to the real intensity of loading acquired from a bucket-wheel excavator during its longlasting operation. It is expected that proposed procedure can help to improve credibility of fatigue lifetime assessment of heavy earthmoving machinery

ANALYSIS AND DESIGN OF STRUCTURAL STEEL JOINTS AND CONNECTION: SOFTWARE IMPLEMENTATION

The paper presents COMET software which enables to design steel structural joints widely used in civil and industrial engineering. Algorithm for designing each joint prototype has been presented as a set of operations implementing the rules for determining the interrelated values of the joint parameters. Each prototype is developed as an independent program that performs a full cycle of designing the joint and verification of the joint parameters according to the specified design codes. Searching of unknown joint parameters has been transformed to a decision making problem based on analysis of the joint mathematical model. Automatic searching of unknown joint parameters has been implemented as a multiple targeted improvement of a certain initial joint design in order to satisfy load-carrying capacity constraints taking into account the structural and assortment-based constraints. Multiple improvement of current joint design is performed on the basis of sensitivity analysis relative to variation of governing joint parameters.

Advanced Joining Processes Unit

The Advanced Joining Processes (AJP) is an autonomous research unit at the Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI) that works closely with the Faculty of Mechanical Engineering of the University of Porto (FEUP). This unit is staffed by professors, post-doctoral researchers, PhD students, MSc students and research fellows. The AJP unit has four key competences, established to support all aspects related to the study of advanced joining processes: testing, simulation, production and machine design. The AJP unit has robust and fully independent competences in the manufacture of experimental specimens and components. The unit operates a fully equipped laboratory with all facilities necessary to manufacture specimens, moulds, test fixtures and testing equipment. The unit has extensive experience in testing complex specimens’ geometry under a wide range of conditions. Research is carried out to determine the performance of structural joints under quasi-static loads, high strain rates, fatigue and creep conditions, among many others. Complementarily, the unit also has a strong machine design capability, being experienced in the development and manufacture of custom designed testing equipment (such as creep testing machines, drop-weight testing machines, torsion testing machines, split Hopkinson pressure bars and devices for glass transition temperature measurement). These experimental capabilities are complemented with robust numerical simulation competencies, which allow to streamline the design process by creating powerful models that can accurately predict the mechanical behaviour of advanced structural joints. These capabilities enable the AJP unit to undertake new and challenging research projects, reacting quickly to current industrial demands and scientific trends, due to its autonomy. This work methodology allows the AJP unit to simultaneously operate in two main fronts. One is fundamental academic research, resulting in MSc and PhD thesis and scientific publication, and the other is comprised of knowledge-transfer activities with industrial partners, which generate funding that can be used to support additional fundamental research. By combining these two approaches, the AJP unit proves that sound technological based educational processes can be achieved while undertaking cutting edge research with practical and industrial value.