Variant 2 of the construction of the rotational barrel segment a) Strength calculations

As a result of numerical calculations the total reduced tension in the construction of the rotational segment was determined. The results in the form of the map of the reduced tension are presented in Figures from 69 to 71. The presented values of tension are expressed in [Pa].

Fig. 69. Distribution of reduced tension H-M-H resulting from loading with centrifugal force

Fig. 70. Distribution of reduced tension H-M-H resulting from loading with centrifugal force and internal pressure

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Fig. 71. Distribution of total reduced tension H-M-H resulting from loading with centrifugal force, internal pressure and temperature

The presented maps of reduced tension for the particular states of loading enable to estimate the influence of the given loading on the degree of tension of the material construction. From Figure 69 it turns out that reduced tension coming from the segment rotating with the speed n = 150 r/min practically does not load the segment because its maximum value is σz ≈ 0.0069 MPa. In the case of loading the rotating segment with the internal pressure p = 50 MPa (Fig. 70) the value of tension reaches the level of σz ≈ 187 MPa. A significant increase of the tension level is caused by the operation of a segment with an additional accounting for the conditions of thermal loading, corresponding to the continuous operation of a construction in the time t = 18000 s (5 hours). Maximum reduced tension in the elements of construction reaches the level of σz ≈ 840 MPa. The value of the received tension is not higher than the value of the yield point, which according to the accepted material properties for steel 40HM equals Re = 880 MPa. It means, that the level of reduced tension appearing in the construction for the considered case of loading does not threaten the safe operation of the construction.

Figure 72 presents total displacement of nodes of the numerical model closing element with a group of inlets expressed in [m].

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Fig. 72. Map of nodes displacements of the model

The received values of nodes displacement equal 0.045 mm, which constitutes a very small value, not threatening the correct operation of the construction.

b) Thermal calculations

As a result of thermal calculations, a fixed state of construction operation was received, consisting in reaching the temperature T = 150^oC by the whole segment, which corresponds to the temperature of loading the construction from the outside and inside – Figure 73.

Fig. 73. Temperature distribution in the model of variant 2 of the rotational barrel segment 4.3. Variant 3 of the construction of the rotational barrel segment

a) Strength calculations

As a result of numerical calculations the total reduced tension in the construction of the rotational segment was determined. The results in the form of the map of the

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reduced tension are presented in Figures from 74 to 76. The presented values of tension are expressed in [Pa].

Fig. 72. Distribution of reduced tension H-M-H resulting from loading with centrifugal force

Fig. 73. Distribution of reduced tension H-M-H resulting from loading with centrifugal force and internal pressure

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Fig. 74. Distribution of total reduced tension H-M-H resulting from loading with centrifugal force, internal pressure and temperature

The presented maps of reduced tension for the particular states of loading enable to estimate the influence of the given loading on the degree of tension of the material construction. From Figure 74 it turns out that reduced tension coming from the segment rotating with the speed n = 150 r/min practically does not load the segment because its maximum value is σz ≈ 0.0018 MPa. In the case of loading the rotating segment with the internal pressure p = 50 MPa (Fig. 75) the value of tension reaches the level of σz ≈ 176 MPa. A significant increase of the tension level is caused by the operation of a segment with an additional accounting for the conditions of thermal loading, corresponding to the continuous operation of a construction in the time t = 18000 s (5 hours). Maximum reduced tension in the elements of construction reaches the level of σz ≈ 885 MPa. However, the received value results from the way of fixing the model, which, in this case, causes a significant increase of the value of reduced tension. Taking into account this fact, it can be stated that the level of reduced tension appearing in the construction for the considered case of loading does not threaten the safe operation of the construction.

Figure 77 presents total displacement of nodes of the numerical model closing element with a group of inlets expressed in [m].

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Fig. 77. Map of nodes displacements of the model

The received values of nodes displacement equal 0.017 mm, which constitutes a very small value, not threatening the correct operation of the construction.

b) Thermal calculations

As a result of thermal calculations, a fixed state of construction operation was received, consisting in reaching the temperature T = 150°C by the whole segment, which corresponds to the temperature of loading the construction from the outside and inside – Figure 78.

Fig. 78. Temperature distribution in the model of variant 3 of the rotational barrel segment

5. Conclusions

The conducted numerical analysis using the method of finished elements enables to formulate conclusions concerning the strength and thermal estimation of the

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analyzed variants of the extruder rotational barrel segment. On the basis of the received results of numerical calculations it was stated that the designed construction operates within a safe range. This is confirmed by the values of tension in the elements of construction, which are not higher than the values of the yield point 880 MPa.

Moreover, the received temperature distributions in the construction area, corresponding to 5 hours of the continuous operation of the unit, confirm a stable operation of the segment in the temperature T = 150°C in the whole area of the segment.

Acknowledgement

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734205-H2020-MSCA-RISE-2016.

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Ivan Gajdoš¹, Janusz Sikora², Emil Spišák¹, František Greškovič¹ SIMULATION ANALYSIS OF SINGLE SCREW EXTRUDER

IN ANSYS POLYFLOW

Abstract: As the technology of polymer extrusion becomes more sophisticated, demand on possibility to accurate simulate extrusion process in full 3D rises.

Significant. This paper deals with steps necessary to carry out successful simulation.

Description and analysis of ANSYS Polyflow package and available mesh types is presented in the work. Theoretical background of calculation and adoption of Mesh Superposition Technique is described. In practical part a preprocessing setup for calculations is presented with subsequent evaluation of results in ANSYS CFD-Post.

Keywords: Ansys Polyflow, extrusion, numerical calculation.

1. Introduction

The single screw extruder (SSE) is one of the most widely used tools, not only in the plastics and rubber industry but also in other areas such as food processing. Almost in every technology processing the raw materials (injection molding, extrusion, blow molding, etc.), SSE are involved to melt, convey, compress and mix the different compounds and those steps can affect considerably the quality of the process.

This wide application can explain the intensive research focused on SSE analysis in the literature and, the numerous attempts to model SSEs through numerical simulations. However, the problem and challenges coupled in such simulations (moving parts, thermal behavior, difficult meshing and remeshing tasks, partial filling, to mention just a few) led to many simplifications of the problem. Several approaches have been applied by researchers. 1D models [1, 2] provide a global vision of average values along the flow direction (pressure, temperature, etc.) based on some simplifying assumptions. 1D models do not permit the calculation of detailed flow field’s which are of great importance, among others, to the mixing analysis. 2 D & 2 1/2D models [3] provide one of the major popular, less restrictive, simplifications which can offer somewhat more precise local information of the flow field behavior in SSE analysis.

Simulation with 3D FEM models allow for a more accurate representation of the flow field. To solve the 3D time-dependent motion of the screws rotating about their axe, an approach with simulating a sequence of several instantaneous positions can be used.

These “slides”' are combined to reconstruct the overall effect of the screws motion on

1) Technical University of Košice, Department of CAx Technologies, Mäsiarska 74, 040-01, Košice, Slovak Republic, e-mail: ivan.gajdos@tuke.sk

2) Lublin University of Technology, Department of Technology and Polymer Processing, ul.

Nadbystrzycka 36, 20-618 Lublin, Poland

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the polymer flow. This method requires a considerable effort and lot of resources in the meshing of each individual relative position of the screw body.

The boundary elements method (BEM) has been used [4] to offer an alternative to the large meshing effort. But the basic advantage of the BEM is almost totally lost as soon as non-linearities are introduced in the simulation (including realistic features such as shear-thinning fluids, non-isothermal cases, viscous heating, etc.).

The most proper technique has to combine the power of FEM to deal with strong non-linearities with the simplicity of the mesh generation and absence of remeshing of the BEM. In order to simplify the setup of a 3D unsteady SSE simulation and to avoid the use of a remeshing algorithm, two techniques referred to as the mesh superposition technique [5] and sliding mesh technique have been implemented in the ANSYS POLYFLOW® software. This robust technique dramatically simplifies the meshing of the geometric entities, avoids the use of any remeshing algorithms and does not present the complexities and limitations of the sliding meshes technique.