About the project

The scientific problem in target of the project is to study the influence of shapes and arrangements of holes in flat, perforated plates, used as sieves on the form and extent of damage in biological material (grains, seeds), during automated sifting processes. In addition, chosen types of sieves will be analyzed towards the intensity of local stress concentration or wear and the resulting risk of damage initiation in the perforated plates themselves. Vibration mode shapes and the respective natural frequencies (eigenfrequencies) will also be taken into account, as the movement of the sieves is cyclic. The development of scientific methods for assessing the reliability of sieves would allow to skip the time consuming trial-and-error tests of machinery, which could reduce the total cost of energy and other resources, the more nowadays efficient numerical methods for damage processes simulations are available. The need for the study stems from striving to increase the quality and the efficiency of sifting processes, at simultaneous reduction of energy expenditure, as well as knowledge-based technical solutions and a development of new structural materials. A proven fact is the influence of the degree of damage, which is determined by the presence of micro- and macro-damages, on the parameters of the perforated sieve. The known classical research methods are limited and do not allow to model the probable extent of damage and to reduce it measurably, depending on the perforated plates geometry and mechanical characteristics. The absence of research on the patterns of local stress concentrations and wear of different sieves, with respect to mechanical properties of the material they are made of, taking into account the characteristics of biological material – including the degree of grain devastation, induces a need for deeper investigation of damage phenomena occurring in sifting processes. In general, perforated plates are used to split bulk biological materials into size (type) fractions, by forced vibrations of the sieves. Unwanted increase in the number of damaged grains and their particles has negative impact on the reliability of sieves, caused by a trend to increase the productivity, accompanied by abrasive wear phenomena in perforated plates, in the presence of intense movement and friction of the bulk biological material. The availability of knowledge-based recommendations on geometrical and material characteristics of perforated plates, dimensions and shape of holes etc. are limited only to simple types of holes and as such are not very useful for complex geometry of sieves; possibilities of using modern structural materials, e.g. composites seem not to be well recognized either. The novelty of the planned project is a complex study on damage phenomena in sifting processes, taking into account devastation of the biological material, as well as the sieves, along with increasing the productivity, reliability and energy efficiency.

The research hypothesis: Damage in the sifted grains and in the sieves can be limited based on the numerical-experimental study, by adjusting the geometry of perforated plates, their strength and vibratory properties.

The work plan can be itemized, as follows.
1. Preliminary analysis of research objects: reliability of perforated sieves and damage of seeds, substantiation of boundary and initial conditions, establishment of significant factors of the investigated sifting processes.
2. FE-modeling stress of perforated surfaces with different types of holes.
3. Processing of conclusions based on the results of numerical analysis and preparation of guidelines for experiments.
4. Experiments on the reliability of perforated surfaces and the level of damage to biological material.
5. Processing of experimental conclusions – verification of FE-modeling methods and data processing schemes.

Three specific research goals can be defined:
• to develop test configurations for the reliability of perforated surfaces with holes of complex geometry,
• to elaborate a universal model of stress concentration for perforated surfaces based on FE for successful simulation of the initiation and propagation of deformations,
• to deepen the problem of the dependence of damage to biological material on the parameters of perforated sieves

 Keywords: sieving, grain damage, stress concentration, vibration, strength