Method for optimising the wrapping of palletized loads

Abstract

A method for creating a digital model (C') of a palletized load (C) formed by a group (110) of products (100) arranged on a pallet (150) and wrapped by a film or band (50) according to a certain wrapping configuration (A), comprising the steps of: - mechanically characterizing constituent elements (150, 100, 50, 120) of the palletized load (C) and interactions among the constituent elements (150, 100, 50, 120), the constituent elements comprising the pallet (150), the product (100), the film (50) and the interactions comprise friction coefficients between contact surfaces of adjacent products (100) and of products (100) and pallet (150); - digitizing the constituent elements (150, 100, 50, 120) in a CAD / CAE environment and obtaining respective digitized constituent elements (150', 100', 50', 120') with which to assemble said digital model (C') of said palletized load (C); - validating mechanical properties of the digitized elements (150', 100', 50', 120'); - building the finite elements digital model (C'), assembled in a CAD / CAE environment with the digitized constituent elements (150', 100', 50', 120'), setting contact behaviours between the digitized constituent elements (150', 100', 50', 120'); - validating the finite element digital model (C') of the palletized load (C); the method comprises digitizing the film (50) wrapped around the group (110) of products (100) according to the wrapping configuration (A) by modelling the film (50) as a set of distinct strips (F1, F2,...Fn) arranged adjacent along a vertical extension of the load; each strip (F1, F2,...Fn) has a respective thickness that is equal to the sum of the thicknesses of the wraps (a1, a2,...an) of film that form it and that have the same elongation (S1,...Sn), the elastic and dissipative properties of said film or band (50) being determined in the mechanical characterization step of the film or band (50).

Description

[0001] Method for optimising the wrapping of palletized loads

[0002] The invention relates to methods and systems for wrapping objects and products grouped and arranged on a pallet with a film or band of plastic and / or paper material and / or of fabric. In particular, the invention relates to a method for creating a digital model in a numerical environment of a palletized load formed by a group of products arranged on a pallet and wrapped by a film or band according to a certain wrapping configuration A and a method for determining by simulation in a numerical environment an optimal wrapping configuration of the film or band wrapped around a palletized load intended to be moved and / or transported along a defined path.

[0003] It is well known and widespread in the industrial packaging sector to use films of cold-stretchable plastic material to wrap and fix to a pallet a plurality of products or articles suitably superimposed and grouped so as to form a palletized load that can be easily handled by a forklift and loaded on different types of transport means. In particular, the products are wrapped and fixed to each other and to the pallet by distributing the film so as to form a plurality of strips or bands of films superimposed on each other and intertwined with a helical trend.

[0004] The plastic film, before being wrapped around the products, is generally stretched or elongated, in an elastic and / or plastic manner.

[0005] Typically, the plastic film is elastically stretched by a predetermined amount or percentage for it to be used at its best and acquire physical-mechanical characteristics such as to make it more suitable to withstand the forces acting on the load, in particular when it is moved and transported. More precisely, when the stretching force imparted to the film to elongate it ceases, the elastic return of the film results in a clamping force on the load that allows it to retain and contain the products that compose it and to constrain the latter firmly to the underlying pallet. Contributing to this containment and wrapping effect is also the tension or wrapping force imparted to the film during wrapping around the load.

[0006] The stretching or elongation of the film is generally expressed as a percentage of the ratio between the elongation of the film (difference between the final length of the stretched film and the original length) and the original length. Typically the elongation imparted to the plastic film is between 50 and 400 %, while the elongation imparted to the paper or fabric films is lower or even zero.

[0007] The stretching or pre-stretching force further allows to considerably reduce the thickness of the film (typically from about 25-20 pm to about 6-7 pm) so as to proportionately increase the length thereof in order to wrap a greater load perimeter with the same initial amount ofunwound film. This allows to limit the consumption of film and therefore the packaging costs.

[0008] The pre-stretching force also allows the mechanical characteristics of the film itself to be changed. In fact, the appropriately stretched material of the latter may change from an elastic type behaviour, in which the film tends to recover the original size thereof upon cessation of the stress, to a plastic type behaviour, in which the film undergoes a permanent deformation and does not recover the initial size thereof upon cessation of the stress. In the latter case, the plastic film behaves as a flexible and inextensible element, similar to a rope or belt, and can be used, for example, to wrap groups of unstable products which must be held firmly together.

[0009] To achieve an effective and stable wrapping, it is therefore necessary to choose a suitable plastic film (composition, initial thickness) and determine the correct wrapping parameters (percentage of pre-stretch, wrapping force, number of wraps of the film around the load, percentage of overlap of the strips of film, arrangement of the wraps around the load, etc.) depending on the characteristics of the film (thickness, composition, etc.) and the characteristics of the load (type of product - fragile, deformable - number of products, composition of the rows and layers of the grouped products) and the type and transport path (by road by truck, by ship, by air, etc.) to which the latter must be subjected.

[0010] It is also known and increasingly widespread in wrapping palletized loads the use of bands of paper or paper material, which allow to reduce the use and consumption of plastic films which, as is known, if not correctly managed and above all disposed of, contribute significantly to environmental pollution. Paper is instead an eco-friendly and eco-sustainable material obtainable both from recycling pre-existing paper and from sustainable productions. In particular, the use of Kraft-type paper, also called wrapping paper, is widely used, since this paper is characterized by a high resistance, in particular to traction and punctures and tears, and longitudinal and transverse elasticity. Kraft paper can be smooth or have creases or micro-creases that accentuate the extensibility thereof.

[0011] Unlike plastic films, paper bands are not stretched or elongated before being applied to the load, or are stretched or elongated to a much lesser extent than plastic films, while achieving a significant elastic containment force, due to the different construction characteristics of the paper compared to the plastic. Also in this case, in order to create a firm and stable wrapping, it is necessary to choose, in addition to a suitable paper band (composition and thickness), the correct wrapping parameters, which include wrapping force, number of wraps of the band around the load, percentage of overlap of the band strips and arrangement of the wrapsaround the load.

[0012] While the characteristics of the load and the products or articles that compose it are known, the stresses to which it is subjected during transport are generally unknown, which is why, as is known, a significant percentage of palletized loads (in particular in the case of fragile or easily deformable products, such as plastic bottles for beverages) are irreparably damaged during transport due to the dynamic stresses (linear, angular accelerations / decelerations, vibrations, oscillations, etc.) to which they are subjected. The palletized load can in fact tilt, bend laterally, deform and collapse locally as a result of the stresses, thereby resulting in the damage, crushing and breakage of the individual products.

[0013] In addition to the deterioration and damage of the products, an improper and incorrect wrapping of the palletized loads and therefore their failure and / or deformation is the cause of even serious accidents during transport, in particular in the case of road transport.

[0014] To overcome these drawbacks, a solution adopted is to wrap the load as tightly as possible (compatible with the characteristics of the products contained) and with a very high number of wraps, based on the experience acquired and empirical procedures. However, problem-free wrapping is not always obtained and, in addition, the consumption of plastic film or paper band increases considerably, significantly affecting packaging costs.

[0015] The need to optimise the wrapping or wrapping cycles of palletized loads is therefore very much felt in the packaging sector in order to obtain optimal containment and stabilisation of the palletized load and, at the same time, a reduction in the amount of film or band used, depending on both the characteristics of the load and the type and path of transport of the load.

[0016] Currently, manufacturers of wrapping machines and / or production companies carry out numerous tests on palletized loads to verify the quality of the wrapping and at the same time try to identify the optimal wrapping parameters for each type of load. However, these tests are quite long, laborious and are not able to provide information about the behaviour of the same palletized load that must be moved and transported along new and different paths from those known and tested. In the absence of such information, the loads may be banded insufficiently or excessively.

[0017] Furthermore these tests, carried out using acceleration slides or handling or loading platforms with several degrees of freedom for handling the load, are quite expensive since they require the use of one or more loads, i.e. products and wrapping film or band, which are generally no longer reusable, because they are partially or completely damaged and / or destroyed at the end of the test.It is also known to measure stresses (displacements, rotations, speeds, accelerations) by means of sensors fixed to the means of transport (truck, ship, plane, etc.) on which the load will be placed or fixed externally to the load. The data of the measured physical quantities are recorded and used to calculate empirically and on the basis of previous tests and analyses the wrapping parameters that can be used for wrapping similar loads that must be transported on similar means and along similar transport paths.

[0018] The results thus obtained are in any case imprecise and in any case cannot be used in the case of different transport paths or different types of load.

[0019] Furthermore, in the case of sensors applied to the means of transport, the measured data are inaccurate because they do not take into account the composition and structure of the load transported, while in the case of sensors fixed externally to the products it is observed that their positioning can affect the same measurements (since the sensors modify the structure, weight, the dynamic behaviour of the load itself). The sensors for the fixing mode can be subject to particular stresses (vibrations) to which the entire load is not subjected.

[0020] EP 3652074 Bl discloses a method for determining an optimal wrapping configuration with plastic film for a palletized load that must be moved and transported along a predefined path, in particular by road. More precisely, the method involves determining a set of kinematic quantities, such as displacements, speeds, accelerations to which a palletized load is subjected when moved along the predefined path, obtained as a composition of a series of elementary path sections identified and defined by digital mapping and / or cartography systems. Each section of elementary path is associated with a respective group of kinematic quantities acting on the palletized load moved along said section of elementary path. The set of kinematic quantities acting on the palletized load when moved along the predefined path can therefore be obtained as a composition of the groups of kinematic quantities associated with the elementary sections of the path forming said predefined path and can be used to program and operate a handling platform with several degrees of freedom on which the palletized load wrapped with the film or band is arranged according to a defined wrapping configuration.

[0021] By operating the handling platform, a physical simulation of the movements and / or stresses acting on the palletized load moved and / or transported along the defined path is thus performed. At the end of the simulation, it is verified whether the palletized load wrapped with the film according to the defined wrapping configuration has remained stable and / or compact or if it has deformed and / or partially or completely collapsed. In the latter case, the wrapping configuration is modified and a new palletized load is created (replacing thedamaged products if necessary) and the simulation on the handling platform is repeated. The method disclosed in EP 3652074 Bl therefore allows to physically simulate by means of a handling platform the movements and / or stresses to which a palletized load transported and / or moved along any road path selectable and identifiable by means of digital mapping and / or cartography systems so as to determine an optimal wrapping configuration that guarantees the stability and / or compactness of the load during transport along the selected path.

[0022] However, even in this case, the simulation tests on a handling platform are long, laborious and expensive since they require the repetition of a plurality of simulations and therefore the availability and use of a plurality of palletized loads, intended to be partially or totally damaged and / or destroyed.

[0023] It is an object of the present invention to improve the known methods for optimizing the wrapping processes with plastic and / or paper and / or fabric material film or band of loads formed by groups of superimposed products.

[0024] Another object is to provide a method that allows to create a two-dimensional or three-dimensional digital model of a palletized load wrapped by a film or band that is precise and accurate and such as to allow to perform valid and effective simulations in a numerical environment of its kinematic / dynamic behaviour following movements and / or stresses acting thereon.

[0025] A further object is to create a simulation method that allows to determine for any type of load and for any transport path an optimal wrapping configuration that ensures the necessary containment and fixing of the load and the lowest consumption of wrapping material, in particular that guarantees the stability and / or compactness and / or structural integrity of the palletized load during transport along a defined transport path.

[0026] Still another object is to provide a simulation method that is based on environmental sustainability and that allows to minimize and almost eliminate the consumption of raw materials and energy in the calculation of the optimal wrapping configuration for a load to be moved along a defined transport path.

[0027] A first aspect of the invention provides a method for creating a digital model in a numerical environment of a palletized load according to claim 1.

[0028] A second aspect of the invention provides a simulation method for determining a wrapping configuration of a film or band around a palletized load according to claim 2.

[0029] The invention can be better understood and implemented with reference to the attached drawings which illustrate an exemplary and non-limiting embodiment thereof, wherein:Figure l is a perspective view of a palletized load formed by a plurality of products, in particular packs of plastic bottles, arranged on superimposed layers on a pallet and wrapped with a plastic film;

[0030] Figure 2 is a perspective view of a product consisting of a pack of six plastic bottles; Figure 3 is a perspective view of the product of Figure 2 and of compressive forces acting thereon along three main directions during compression tests;

[0031] Figure 4 is a schematic perspective view of a product subjected to a shear stress test along a main plane;

[0032] Figure 5 is a graph illustrating the compressive force-displacement relationships in an experimental compression test (Test) and a finite element numerical compressive test (FEA) of the product along a main direction;

[0033] Figure 6 is a graph illustrating the shear force-displacement relationship along a main shear plane in an experimental shear stress test (Test) and finite element numerical shear stress test (FEA) of the product;

[0034] Figure 7 is a perspective view of a product subjected to a shear slide test along a main plane;

[0035] Figure 8 is a perspective view of shear forces acting on the product during the shear slide test along a main plane;

[0036] Figure 9 is a front view of a film or band specimen subjected to a tensile test;

[0037] Figure 10 illustrates the tensile curves of film or band specimens subjected to tensile tests;

[0038] Figure 11 illustrates an elasticity curve of the material of a film or band specimen subjected to tensile tests;

[0039] Figure 12 is a schematic perspective view of an instrumented load provided with sensors for measuring a wrapping force of the film or band;

[0040] Figure 13a illustrates a second order response surface within a development or design space that encloses the wrapping force values of the film or band for all possible combinations of elongations to which it may be subjected;

[0041] Figure 13b illustrates a table extrapolated from the response surface of Figure 13a that correlates the wrapping force values, percentage of pre-stretch and variation percentage of the length of the film or band;

[0042] Figure 14 illustrates a characterization test of a coefficient of friction between upper surfaces and lower surfaces of superimposed products with the interposition of interlayer elements;Figures 15 and 16 are front views of a 2D digital model of the palletized load respectively without and with wrapping film;

[0043] Figure 17a illustrates views in the main planes XZ and YZ of a six-bottle pack (2x3) and a corresponding digitized element in CAD / CAE environment (in 2D) subject to compressive forces along the respective two main directions;

[0044] Figure 17b is a perspective view of the six-bottle pack (2x3) of Figure 17a subjected to compressive forces along the three main directions X, Y, Z;

[0045] Figure 18 is a view in the main plane XZ of a six-bottle pack (2x3) digitally represented in CAD / CAE environment (in 2D) and subject to a shear stress force along the main plane XY;

[0046] Figure 19 is a front view of the digital model of the palletized load formed by the group of products superimposed according to multiple layers on a pallet;

[0047] Figure 20 is a front view of the digital model of the palletized load wrapped with the film or band in which the constraining reactions (bound contacts) between coinciding nodes of the finite element models of the products and the film or band are highlighted with points along an edge of the load;

[0048] Figures 21a and 21b are front views illustrating respectively the digital model of the palletized load wrapped with the film according to a defined wrapping configuration and the modelling of the wraps of film around the load as a plurality of distinct and superimposed bands;

[0049] Figures 22a and 21b are front views illustrating respectively the digital model of the palletized load wrapped with the film according to another defined wrapping configuration and the modelling of the wraps of film around the load as a plurality of distinct and superimposed film bands;

[0050] Figures 23 and 24 are front views of the 2D digital model of the palletized load before being subjected to simulation respectively with highlighting the film wraps and deformations present thereon;

[0051] Figures 25 and 26 are front views respectively of the deformed palletized load after being subjected to stresses and of its digital model with the deformations deriving from said stresses highlighted by different colours depending on the magnitude of the deformation;

[0052] Figures 27 and 28 are schematic views of a means of transport movable along a defined path, respectively with reference to a horizontal reference plane and a vertical reference plane, in which a local reference system is associated with the means of transport alongwhose directions local accelerations develop.

[0053] The method of the invention involves determining a wrapping configuration A of a film or band 50 made of plastic and / or paper and / or fabric material (film 50 for the sake of brevity) wrapped around a group 110 of products 100, in particular arranged on a pallet 150 in superimposed layers 101, to form a so-called palletized load C intended to be moved and / or transported along a defined path or route PR by a means of transport 200. More precisely, the method of the invention allows to determine which wrapping configuration of the film or band 50 around the load C ensures that the latter remains stable and / or compact and / or rigid and / or structurally intact when moved along an established transport path PR, for example a road transport path by truck, as means of transport 200 (Figures 21 and 22). Stable and / or compact and / or rigid load means a load whose final configuration, i.e. after being displaced and / or transported along a predetermined path, is substantially the same as its initial configuration, i.e. before being displaced and / or transported. Structurally intact means that all the elements forming the load (film or band, product units, products, etc.) are intact, that is, not ruined, damaged.

[0054] The configuration of the load comprises the overall shape and dimensions of the palletized load and the relative position of the stacked products / elements with a defined pattern and order on the pallet, in particular the relative position of the different superimposed layers of products. Therefore, a palletized load is stable and / or compact and / or rigid when it maintains almost its initial rectangular cuboid shape, that is, when the four side walls remain almost orthogonal to the lower side (resting on the upper surface of the pallet) and the arrangement and order of the stacked products remain unchanged without sliding of one or more layers of products or between the products of the same layer, without damage to products or escape of material.

[0055] The term "stable" means in fact "firmly fixed and not likely to move or change" and the term compact means "made up of parts positioned together tightly or in an orderly manner, using as little space as possible".

[0056] The EUMOS 40509:2020 regulation issued by the AISBL European Safe Logistic Association, which defines a method for testing the stability of a palletized load along a specific direction when subjected to an inertial force in this direction, defines "rigid" the load that, subjected to a specific acceleration along a specific direction, undergoes deformation and / or relative movements between the parts (i.e. between products or articles that compose it) that are less than acceptable upper limits and defined in the regulation itself (2. Terms and definitions). In particular, the rigidity of a load is expressed as the maximum acceleration ofthe test loading platform, on which the load is placed, along the specific direction that does not cause unacceptable deformations or unacceptable relative movements between the parts of the load without damaging it (3. Aim). Paragraph 5.3 (Test evaluation criteria) of the regulation specifies the three criteria that the load must meet in order to be defined as rigid and pass the test.

[0057] However, the EUMOS 40509 regulation only applies to a test that involves the application on the test platform of a horizontal acceleration and along a specific direction and not subjected to a set of linear and angular accelerations to which a palletized load is subjected when it is transported / moved along a path.

[0058] Wrapping configuration A means a set of wrapping parameters that, with the same film used, define the wrapping process of the load and comprise, for example, number of wraps or strips of film arranged around the load, percentages of superimposition of the wraps and their arrangement on the load (complete or partial superimposition, at the base and / or at the top of the load, etc.), percentage of pre-stretch applied to the film, if it is made of stretchable material, length of the film dispensed with each turn, overall elongation of the film, etc. The wrapping configuration A is chosen based on the characteristics of the film 50, the palletized load C and the transport path PR. In particular, the wrapping parameters are selected based on the characteristics of the film 50 used (thickness, type and composition of the material) and the characteristics of the palletized load C which comprise type of products 100 forming the load C, dimensions, shape, resistance and / or deformability of the products 100, total number of products 100, composition in superimposed rows 102 and layers 101 of grouped products 100.

[0059] The product 100 may also be formed by a plurality of product units 105 arranged on one or more parallel rows and grouped and wrapped by a packaging material 106, for example a pack or a box of bottles, vials, cans, and the like.

[0060] In particular, the product 100 can be, as illustrated in Figure 1, a pack formed by a plurality of plastic bottles 105 (six, twelve) grouped on two parallel rows (2x3, 2x6) and wrapped and made integral with a heat-shrinkable plastic film 106. The palletized load C illustrated in Figure 1, comprises for example four layers 101 of packs 100, formed by six bottles (2x3) and arranged on three parallel rows for each layer 101, the layers 101 being separated from each other by an interlayer element 120. The group of products 120 is positioned on a wooden pallet 150 and wrapped by a plastic film 50 according to a defined wrapping configuration A.

[0061] The method of the invention for creating a two-dimensional or three-dimensional digitalmodel C’ (digital twin) in a numerical environment of a palletized load C formed by a group 110 of products 100 arranged on a pallet 150 and wrapped by a film or band 50 of plastic and / or paper and / or fabric material according to a certain wrapping configuration A, comprises the following steps:

[0062] mechanically characterizing constituent elements 150, 100, 50, 120 of the palletized load C and interactions among said constituent elements 150, 100, 50, 120, wherein the constituent elements comprise the pallet 150, the product 100, the film 50 and wherein the interactions comprise friction coefficients between contact surfaces of adjacent products 100 and of products 100 and pallet 150;

[0063] digitizing the constituent elements 150, 100, 50, 120 in a CAD / CAE environment and obtaining respective digitized constituent elements 150’, 100’, 50’, 120’ with which to assemble said digital model C’ of said palletized load C;

[0064] validating mechanical properties of the digitized elements 150’, 100’, 50’, 120’ obtained by mechanically characterizing the constituent elements 150, 100, 50, in particular through finite element analysis (FEA);

[0065] building the finite elements digital model C’, assembled in a CAD / CAE environment with the digitized constituent elements 150’, 100’, 50’, 120’, setting contact behaviours between the digitized constituent elements 150’, 100’, 50’, 120’;

[0066] validating the finite element digital model C’ of the palletized load C;

[0067] wherein digitizing the constituent elements 150, 100, 50, 120 comprises digitizing the film 50 wrapped around the group 110 of products 100 according to the wrapping configuration A by modelling said film as a set of distinct and arranged strips Fl, F2, ..En, in particular partially superimposed, along a vertical extension of the load, wherein each strip Fl, F2,..En has a respective thickness that is equal to the sum of the thicknesses of the wraps al, a2,...an of films 50 that form it and that have the same elongation Sl,...Sn, the elastoplastic and dissipative properties of the film 50 being determined in the film 50 mechanical characterization step.

[0068] The simulation method of the invention for determining a wrapping configuration of a film or band 50 made of plastic and / or paper and / or fabric material wrapped around a group 110 of products 100, in particular arranged according to layers 101 and superimposed on a pallet 150, to form a palletized load C, in particular to be moved and / or transported along a defined path PR by a means of transport 200, comprises the following steps:

[0069] identifying a set of kinematic quantities G_amax, in particular acting on the means oftransport 200 while if follows the established path PR;

[0070] by means of the method described above, creating a two-dimensional or three- dimensional digital model C’ of the palletized load C wrapped with the film or band 50 according to a defined wrapping configuration A;

[0071] starting a simulation of movements and / or stresses acting on the load digital model C’ using the values of the set of kinematic quantities G amax as boundary conditions, i.e. as operating parameters of the simulation;

[0072] at the end of the simulation, verifying if the digital model C’ of the palletized load C wrapped with the film or band 50 according to the defined wrapping configuration A has remained stable and / or compact and / or rigid and / or structurally intact; modifying the defined wrapping configuration A if the load digital model C’ has not remained stable and / or compact and / or rigid and / or structurally intact after the simulation; and

[0073] repeating the simulation by means of load digital model C’ and / or modifying the defined wrapping configuration A until the load digital model C’ remains stable and / or compact and / or rigid and / or structurally intact.

[0074] The simulation method further involves the step of storing as stability wrapping configuration Asthe wrapping configuration of the film or band 50 around the palletized load C with which the load digital model C’ has remained stable and / or compact and / or rigid and / or structurally intact after the simulation and therefore adapted to maintain the corresponding palletized load C stable and / or compact and / or rigid and / or structurally intact when moved and / or transported along the established path PR.

[0075] The set of kinematic quantities to be used as boundary conditions i.e. as input data for the execution of the simulation in a numerical environment, comprises for example at least one set of maximum accelerations G amax acting on the means of transport 200 when moved and / or transported along the defined path PR, wherein the set of maximum accelerations G amax comprises, for example, the local accelerations atj, an,j, azj having higher values,

[0076]

[0077] acting along the path PR on the means of transport 200, for example a truck, with reference to a local reference system t, n, z’ of the aforementioned means of transport 200. In particular, with reference to Figures 24 and 25 illustrating a means of transport by road (truck) movable along a road path PR, the acceleration vector aj acting on the transport means 20 at each instant tj can be broken down into the tangential component atj, and the normal component an,j directed respectively along the tangential direction t and the normal direction on ahorizontal reference plane X, Y and into the vertical component azj along the vertical direction z’ perpendicular to the reference plane X, Y.

[0078] The set of kinematic quantities to be used as boundary conditions for the simulation may also comprise only the maximum accelerations along a specific direction, for example the tangential direction / , in the case where the digital model processed for the palletized load is two-dimensional.

[0079] The load C may also comprise interlayer elements 120 interposed between one layer 101 and the other of the products 100 to increase the stability of the products during transport and made of plastic and / or paper material. The interlayer elements 120 at the structural and mechanical level are negligible and affect the dynamic behaviour of the palletized load only by modifying the friction between the layers 101 of the products 100. For this reason, in the process of creating the digital model C’ of the palletized load, the interlayer elements 120 as constituent elements of the load are mechanically characterized only by the interactions that they introduce and, more precisely, by the interactions between the aforementioned interlayer elements 120 and the products 100. Such interactions comprise a friction coefficient between the surfaces in contact with product 100 and the interlayer element 120. According to the method, mechanically characterizing the product 100 comprises performing compressive stress tests (Fig. 3) and shear stress tests (fig. 4) along three main directions X, Y, Z and along three main planes XY, XZ, YZ, orthogonal to each other, to determine normal elastic moduli Ex, Ey, Ez(or Young's moduli) and tangential elastic moduli Gxy, Gxz, Gyz(or shear moduli) of the product 100 along the main directions X, Y, Z and along the main planes XY, XZ, YZ. In particular, the product 100 is compressed between two plates of a press along each of the three main directions X, Y, Z and during the test the compressive force Fx, Fy, Fzand the relative displacements of the plates of the press are measured so as to derive the compressive force-displacement relationship (Fig. 5) along each main direction and then derive the tensile and stress values and with Hooke's law the values of the normal elastic moduli Ex, Ey, Ez.

[0080] The shear stress tests involve exerting a shear force F along a surface of the load 100 parallel to a main plane defined by two of the main directions, for example the upper surface on the main plane XY, or shear plane, as illustrated in Figure 4, and keeping the opposite surface locked (the lower surface always parallel to the plane XY) and measuring, in addition to the shear force F, the displacement (Fig. 6) and then calculating the shear stressT, shear strain y and tangential elastic modulus G with reference to the specific plane, for example the mainplane XY, according to the known formulas:

[0081] > ^xy > FXy / Ac > F ’ I

[0082]

[0083] xyYxyAx / l A ■ Ax

[0084] where:

[0085] Fxy is the force acting on the surface area Axy of the load 100 on the main plane XY;

[0086] Txy is the shear stress on the main plane XY (MPa);

[0087] Yxy is the shear strain on the main plane XY equal to Ax / 1 = tan 0;

[0088] Ax is the relative transverse displacement (mm) along a direction parallel to the shear force F;

[0089] 1 is the distance (mm) between the two surfaces (upper and lower) of the load 100.

[0090] Similarly, shear forces Fxzand Fzy acting respectively on the main planes XZ and YZ can be applied to measure the corresponding shear strains yxzand yyzand then calculate the tangential elastic moduli Gxz, Gyz.

[0091] If the product 100 is formed by a plurality of product units 105 grouped and wrapped by a wrapping material 106, for example a pack of plastic bottles wrapped in a heat-shrinkable plastic film, mechanically characterizing said product 100 comprises performing shear slide tests of the product units 105 along the three main planes XY, XZ, YZ, in particular by measuring along said main planes XY, XZ, YZ the shear forces F’ acting on, and relative displacements of, rows of product units 105 arranged on opposite sides of the product 100 so as to determine shear slide elastic moduli G’xy, G’xz, G’yzalong the aforementioned main planes XY, XZ, YZ (Figs. 7 and 8).

[0092] In fact, the shear slide tests allow to measure the relative translation of the product units 105 within the product 100, i.e. to determine the yieldability of the product 100. More precisely, the shear slide tests involve locking a row 107 of product units of one end of the product 100 between two fixed plates and the row 107 of product units of the opposite end of the product 100 between two movable plates and then exerting by means of the latter a shear force F’ on a main plane (for example the main plane XZ of Figure 8). By measuring the applied shear force (and calculating the relative shear stress T) and displacement or slide it is possible to calculate the shear slide elastic modulus G’xy, G’xz, G’yzalong the corresponding main plane (e.g. the main plane XZ).

[0093] If the shear displacement or slide along the three main planes XY, XZ, YZ determined by the shear slide tests is greater than the transverse displacement generated by the shear stresstests, the method involves mechanically characterizing the product 100 using, in addition to the normal elastic moduli Ex, Ey, Ez, the shear slide elastic moduli G’xy, G’xz, G’yz.

[0094] The mechanical characterization of the pallet 150 through specific tests is not necessary since the mechanical properties of the pallet 150, generally made of wood, i.e. the corresponding normal and tangential elasticity moduli, friction coefficients of the resting and supporting surfaces of the products, are known and can be found in the literature.

[0095] To mechanically characterize the film or band 50, the method involves subjecting specimens 55 of the film or band 50 to tensile tests along a longitudinal direction and along a transverse direction (Fig. 9) so as to determine the elastoplastic properties of the film or band 50, i.e. of the plastic and / or paper material with which said film or band is made, in particular a respective tensile curve Ct (load-stroke) and an elasticity curve Ce (tension-strain) of the material of said film or band (Figs. 10 and 11) .

[0096] The specimens of film 55 have the same proportions (width / length ratio) as the strip of film or band 50 that is wrapped around the load.

[0097] If the film or band 50 is made of stretchable material, for example plastic material, mechanically characterizing the film or band 50 comprises performing tensile tests on a plurality of specimens 55 of film or band 50, the film or band of each specimen 55 being previously subjected to a respective elongation or stretching S, in particular longitudinal, i.e. along the unwinding direction.

[0098] Such elongation or stretching S is according to a value or percentage of pre-stretch PS imparted to the film or band 50, in particular during its unwinding from a reel and before wrapping around the load, and of a percentage variation of length VLF of the film or band 50 wrapped around the load C; this combination of elongations, which can be added or subtracted, determines the elastic return of the film or band after wrapping around the load. The pre-stretch is, as known, the elongation imparted to the film or band 50 by an unwinding unit of a wrapping machine by adjusting the rotation speed of two pre-stretch rollers and / or by adjusting the unwinding speed of the film or band from the reel.

[0099] The change in length of the film is the difference between the length of the film or band (possibly pre- stretched) dispensed by the unwinding unit of the machine at each turn of rotation around the load C and the length of a perimeter in plan PCP of the load C. In particular, the percentage of pre-stretch PS and the percentage variation of length VLF are defined by the following formulas:

[0100] PS = (LFS - LFO) / LFOVFL = (LFS - PCP) / PCP

[0101] where:

[0102] LFS (mm) is the length of pre-stretched film or band wrapped at each turn around the load (C);

[0103] LFO (mm) is the length of non-stretched film or band unwound from a reel;

[0104] PCP (mm) is the perimeter of the load (C).

[0105] As is known, the elongation S of the film or band determines the amount of the wrapping force or tension T, also called "pull", exerted by the film or band 50 on the load C. In other words, the wrapping force T is a function of the pre-stretch value PS imparted to the film 50 and of the percentage variation of length VLF of the film 50 wrapped around the load C. In particular, with the same pre-stretch imparted to the film or band and with reference to a zero percentage variation of length (VLF=0%), a positive percentage variation of length (VLF > 0%) determines a smaller wrapping force T and a negative percentage variation of length (VLF < 0%) determines a greater wrapping force T.

[0106] To mechanically characterize the film or band 50 with regard to the wrapping tension T, i.e. to determine the wrapping force that the film or band 50 can exert, the film or band 50 is wrapped around an instrumented load CS, i.e. provided with sensors 40 adapted to measure a value of the wrapping force T exerted by the film or band 50 on the instrumented load CS (Fig. 12).

[0107] If the film or band 50 is of stretchable material, for example it is a stretchable plastic film, the wrapping force T that the film or band 50 exerts on the load C varies as the elongation imparted to the film or band varies, i.e. in accordance with the combination of pre-stretch values PS and length change VLF. In this case, the mechanical characterization of the film or band 50 with regard to the wrapping force T involves wrapping around the instrumented load CS individually and separately a plurality of sections of the film or band 50 each of which previously subjected to a respective elongation S so as to measure the values of the wrapping force T exerted by the film or band 50 on the load when subjected to that respective elongation S.

[0108] The applicant has verified that with a number of tests equal to or greater than eleven, carried out considering the combinations of pre-stretch values PS and length change VLF of the end film or band 50 of the development or design space that encloses all the possible combinations of elongations S to which the film or band 50 can be subjected, it is possible to obtain a response surface SR of the second order by means of which all the values of the wrapping force T inside the aforementioned development space can be calculated, each ofwhich associated with a respective combination of pre-stretch values and length change of the film or band. In particular, Figure 13a shows the response surface in the response space (T, VLF, PS) and Figure 13b shows a table with the values of the wrapping force T obtainable with different combinations of pre-stretch values PS (percentage) and length change VLF (percentage).

[0109] The method further involves mechanically characterizing the film 50 by determining a hysteretic damping of the film 50 by dissipative characterization tests, which comprise cyclic load-unload tensile tests performed on one or more specimens 55 of the film 50 to determine the dissipated energy and at least one equivalent hysteretic damping parameter 6.

[0110] Alternatively, it is envisaged to mechanically characterize the film 50 by determining a hysteretic and Coulombian damping of the film 50 by characterizing the dynamic behaviour of the palletized load C which comprises wrapping with the film 50 a sample palletized load formed by a plurality of superimposed products 100 and subjecting it to an acceleration test according to at least one main direction X, Y, Z and then analysing the displacements of markers positioned on the sample palletized load to calculate the parameters of said hysteretic and Coulombian damping of the film 50, in particular to obtain damping 6, damping ratio , and oscillation frequency f characteristic of the film 50.

[0111] The aforesaid tests performed on the film or band 50 therefore allow the mechanical characterization thereof, i.e. the identification of its physical-mechanical properties.

[0112] To mechanically characterize the friction coefficient between surfaces in contact with said products 100, it is envisaged to stack and / or place side by side a plurality of products 100 separated or not by interlayer elements 120 and measure a tensile force Fa applied to a product 100 of said plurality of products such as to determine the first detachment or displacement of the product and then calculate the friction coefficient as a function of the tensile force Fa and a weight force of the product or acting on the product 100.

[0113] By way of example, the characterization test of a friction coefficient between upper and lower surfaces of products 100 superimposed on several layers with interposition of interlayer elements 120 can be carried out, for example, by stacking three products 100 (formed by twelve product units 106 on two rows) separated by respective interlayer elements 120 (Fig. 14), and applying a tensile force Fa to the central product along a main direction (for example X) and then measuring the maximum value of said tensile force Fa that determines the displacement (first detachment) of the central product with respect to the underlying product. By measuring this maximum tensile force Fa and knowing the mass ofthe moved product on which the force Fa acts and the mass of the overlying product, the friction coefficient p can be calculated with the following formula:

[0114] I

[0115]

[0116] a1~ —Fd / / mg

[0117] where g is the acceleration of gravity.

[0118] Similar tests can be carried out to measure the friction coefficient between contacting side surfaces of two adjacent products 100.

[0119] The friction coefficients of the resting and supporting surfaces of the products of the pallet 150 are known and can be found in the literature.

[0120] The method involves digitizing each product 100 of the product group 110 as a Representative Volume Element (RVE) having in a numerical environment the mechanical properties, in particular the normal elastic moduli Ex, Ey, Ezand the tangential elastic moduli Gxy, Gxz, Gyzand / or the shear slide elastic moduli G’xy, G’xz, G’yzdetermined in the mechanical characterization step of the product 100 (Figs. 15-18).

[0121] In the construction of the digital model C’ of the palletized load C it is envisaged, as already highlighted, to digitize the film 50 wrapped around the group 110 of products 100 according to the established wrapping configuration A by modelling such film (and more precisely by modelling the plurality of wraps of the film around the load) as a set of strips Fl, F2, ..Fn which are distinct and arranged, for example partially superimposed, along the vertical extension of the load, in which each strip Fl, F2, ..Fn has a thickness equal to the sum of the thicknesses of the wraps al, a2,..., an of films that form it and that are subject to the same elongation SI, S2,...S6, derived from a defined pre-stretch PS and / or defined percentage variation of length VLF. The value of the pre-stress PS and that of the percentage variation of length VLF can also be equal to zero.

[0122] Figures 21a, 21b illustrate by way of example a load C wrapped with the film 50 according to a first wrapping configuration A that includes eighteen wraps of film that can be divided into seven (n=7) groups of wraps al, a2,...a7, the wraps of film of each group having the same elongation SI, S2,...S7.

[0123] With this first wrapping configuration A the model of the film 50 wrapped around the load therefore comprises seven modelling strips F1-F7 (with n=7), in which:

[0124] a first strip Fl (starting from the top of the load) comprising three first wraps al of film 50 having the same first elongation SI, the first strip Fl therefore having a thickness equal to three times the thickness of a first wrap al and subject to the first elongation SI; a second strip F2, below the first strip Fl, comprising two second wraps a2 of film 50having the same second elongation S2, the second strip F2 thus having a thickness equal to twice the thickness of a second wrap a2 and subject to the second elongation S2; a third strip F3, below the second strip F2, comprising two third wraps a3 of film 50 having the same third elongation S3, the third strip F3 thus having a thickness equal to twice the thickness of a third wrap a3 and subject to the third elongation S3;

[0125] a fourth strip F4, below the third strip F3, comprising two fourth wraps a4 of film 50 having the same fourth elongation S4, the fourth strip F4 thus having a thickness equal to twice the thickness of a fourth wrap a4 and subject to the fourth elongation S4; a fifth strip F5, below the fourth strip F4, comprising two fifth wraps a5 of film 50 having the same fifth elongation S5, the fifth strip F5 thus having a thickness equal to twice the thickness of a fifth wrap a5 and subject to the fifth elongation S5;

[0126] a sixth strip F6, below the fifth strip F5, comprising five sixth wraps a6 of film 50 partially wound down to form a rope and having a same sixth elongation S6, the sixth strip F6 thus having a thickness equal to five times the thickness of a sixth wrap a6 and subject to the sixth elongation S6; and

[0127] a seventh closing strip F7, substantially superimposed on the first strip Fl and comprising two seventh wraps a7 of film 50 having the same seventh elongation S7, the seventh strip F7 thus having a thickness equal to twice the thickness of a seventh wrap a7 and subject to the seventh elongation S7.

[0128] Two or more elongations SI, S2,...S7 may be equal to each other or one or more elongations may be null.

[0129] The wrapping force or tension T exerted by each strip Fl, F2,.., Fn is equal to the sum of the wrapping forces F exerted by each of the wraps al, a2,..., an that form the aforementioned strip.

[0130] Figures 22a, 22b illustrate the load C wrapped with the film 50 according to a second wrapping configuration A’ that includes fourteen wraps of film that can be divided into six (n=6) groups of wraps al, a2,...a6, the wraps of film of each group having the same elongation SI, S2,...S6.

[0131] With this second wrapping configuration A’ the model of the film 50 wrapped around the load therefore comprises six modelling strips F1-F6 (with n=6), in which:

[0132] a first strip Fl (starting from the base of the load) comprising two first wraps al of film 50 having the same first elongation SI, the first strip Fl thus having a thickness equal to twice the thickness of a first wrap al and subject to the first elongation SI;

[0133] a second strip F2, superimposed on the first strip Fl, comprising three second wraps a2of film 50 partially wound on the bottom to form a rope and having the same second elongation S2, the second strip F2 thus having a thickness equal to three times the thickness of a second wrap a2 and subject to the second elongation S2;

[0134] a third strip F3, above the second strip F2, comprising two third wraps a3 of film 50 having the same third elongation S3, the third strip F3 thus having a thickness equal to twice the thickness of a third wrap a3 and subject to the third elongation S3;

[0135] a fourth strip F4, above the third strip F3, comprising two fourth wraps a4 of film 50 having the same fourth elongation S4, the fourth strip F4 thus having a thickness equal to twice the thickness of a fourth wrap a4 and subject to the fourth elongation S4; a fifth strip F5, above the fourth strip F4, comprising three fifth wraps a5 of film 50 having the same fifth elongation S5, the fifth strip F5 thus having a thickness equal to three times the thickness of a fifth wrap a5 and subject to the fifth elongation S5; a sixth closing strip F6, substantially superimposed on the first strip Fl and the second strip F2 and comprising two sixth wraps a6 of film 50 having the same sixth elongation S6, the sixth strip F6 thus having a thickness equal to twice the thickness of a sixth wrap a7 and subject to the sixth elongation S7.

[0136] In digitizing the film or band 50, it is also envisaged to introduce a coefficient of thermal expansion a [°C'1] of the material of the film or band 50 and an appropriate thermal load AT [°C] to subject, in particular during the simulation as a boundary condition, on the film or band 50 in a numerical environment to model the wrapping force or tension T exerted by the film or band 50 on the palletized load C and due to the elastic return following elongation, i.e. to the combination of pre-stretch values PS and length change VLF to which the film or band 50 is subjected, wherein the appropriate thermal load AT is a function of a specific and respective elongation S to which the film or band 50 is subjected before (pre-stretch PS) and during (length change VLF) the wrapping.

[0137] In particular, if the relationship between (elastic) deformation s [mm / mm] of the film or band 50 due to the wrapping force T [N] is:

[0138] aT / A /

[0139] £ = — = — - —

[0140]

[0141] E E

[0142] where

[0143] E [Pa] is the normal elastic modulus of the film or band

[0144] Af [mm2] is the cross-sectional area of the film or band (thickness x strip width) and the relationship between thermal expansion st[°C / °C] of the film or band due to thethermal load AT is:

[0145]

[0146] = a ■ AT

[0147] The thermal load to be imposed in the simulation to model the wrapping force is given by the following relationship:

[0148]

[0149] a a a - E

[0150] With reference to the modelling of the film 50 wrapped around the load C as a plurality of modelling strips Fl, F2,...Fn, in digitizing the film or band 50 it is envisaged to define for each strip Fl, F2,...Fn a respective thermal load AT [°C] to which the strip Fl, F2,...Fn of film is subjected during the simulation in a numerical environment in order to model the wrapping force T exerted by the wraps of films forming the aforementioned band on the palletized load C and due to the elastic return following the elongation S to which the film is subjected in each of the wraps.

[0151] Once all the constituent elements 150, 100, 50, 120 have been digitized in the CAD / CAE environment in order to obtain respective digitized constituent elements 150’, 100’, 50’, 120’ with which to assemble the digital model C’ (digital twin) of the palletized load C (physical twin), the aforementioned digitized constituent elements 150’, 100’, 50’, 120’ are validated by finite element analysis (FEA). In particular, as is known, the mechanical properties of the digitized constituent elements 150’, 100’, 50’, 120’, obtained in the mechanical characterization step, are compared with those of the constituent elements 150, 100, 50, 120 of the real (physical twin) model, i.e. of the palletized load C. If the differences are minimal and negligible, the mechanical properties of the digitized constituent elements 150’, 100’, 50’, 120’ are validated (Figures 5 and 6).

[0152] To build the finite element digital model C’ or digital twin of the palletized load C assembled in a CAD / CAE environment with the digitized elements 150’, 100’, 50’, 120’ it is necessary to set the contact behaviours between the digitized constituent elements 150’, 100’, 50’, 120’. More precisely, the contact behaviours between adjacent products 100 and between products 100 and pallets 150 (Fig. 19) are modelled as frictional contact behaviours 201 calculated on the basis of the friction coefficients determined in the mechanical characterization step of the interactions between constituent elements. The contact behaviours between film or band 50 and products 100 are modelled as bonded contact behaviours 202, in particular with multipoint-constraint formulation (Fig. 20). The bonded type contacts 202 are in particular located at the vertical edges of the load. Figure 20indicates, with points distributed along an edge of the digitized model of the load, the binding reactions (bonded contacts) between coincident nodes of the finite element models of the products and of the film or band.

[0153] It should be noted that friction-type and bonded-type contact behaviours are two types of contact behaviour that are known and widely used in the numerical environment to simulate contacts and constraints between digitized constituent elements of a finite element digital model.

[0154] Once the finite element digital model C’ (digital twin) of the palletized load C is constructed, assembled in 2D or 3D in a CAD / CAE environment, such a digital model C’ must be validated, that is, the results of a simulation conducted with such a digital model C’ must be compared with those of a real simulation conducted on the real model (physical twin), that is, on the palletized load C subjected to an acceleration slide or on a motion platform to movements and / or stresses generated using the same set of kinematic quantities G amax for the operation of the slide or platform.

[0155] Once validated, the digital model C’ of the pallet C can be used to perform a plurality of different simulations using different wrapping configurations A in order to identify the one (the stability wrapping configuration As) that ensures stability and / or compactness and / or rigidity of the palletized load C, for example, after handling and / or transport along the defined path PR, that is, after having undergone the movements and / or stresses generated by the set of kinematic quantities G_amax, typically the maximum accelerations, which act on the means of transport 200 that transports the load while travelling the defined path PR. In other words, the finite element simulation method of the invention provides information on the deformations of the palletized load C when subjected to accelerations and information about the capacity of the film 50 wrapped around the load C according to different combinations of the wrapping parameters (wrapping configurations) to contain the inertial effects of the displacements of the products 101 forming the layers 101 of the load C. The simulation with the digital model C’ of the palletized load allows to have a representation of the wrapping cycle and to modify the wrapping configuration, for example by changing the arrangement and / or the number of wraps and / or the elastoplastic characteristics of the film (pre-stretch value, wrapping force) in the portions of the load in which the deformations are excessive, thus optimizing the use of the film and maximizing the stabilization of the load at the same stresses.

[0156] Figure 25 shows the deformations undergone by the palletized load C wrapped by the filmaccording to a defined wrapping configuration A (for example that of Figure 21a) after having undergone the movements and / or stresses generated by a set of kinematic quantities G amax, for example a linear acceleration along the axis X.

[0157] Figure 27 shows the deformations of the digital model C’ of the palletized load C wrapped by the film according to the same wrapping configuration A after having undergone the movements and / or stresses generated by the same set of kinematic quantities G amax- The values of the local deformations in the various portions of the digital model C’ are indicated by respective colours as defined in the scales of the total deformations along the two axes X, Y.

[0158] It is immediately noted that the shape of the digital model C’ (Figure 26) overlaps almost perfectly with that of the palletized load (Figure 25), demonstrating the accuracy and precision of the results obtained with the simulation in a numerical environment.

[0159] Thanks to the method of the invention, it is therefore possible to determine a stability wrapping configuration Asof a film or band 50 wrapped around a group of products 110 to form a palletized load C, capable of keeping the latter stable and / or compact and / or rigid and / or structurally intact in particular when moved and / or transported along any desired road transport path PR.

[0160] The highest values of the local accelerations at,j, an,j, azj acting on the means of transport 200 that transports the load C, stored in a set of maximum accelerations G amax can in fact be used to perform simulations of movements and / or stresses on the digital model C’ (digital twin) of the palletized load C, created according to the method of the invention, in particular by mechanically characterizing the constituent elements 150, 100, 50, 120 of the load C and the interactions therebetween and CAD / CAE modelling the constituent elements and the relative interactions and then parametric CAD / CAE modelling the overall palletized load. By using a digital model C’ of the palletized load C for the simulation, it is possible to completely eliminate the consumption of raw materials and energy in determining an optimal wrapping configuration for a palletized load to be moved along a defined transport path PR. More precisely, the method of the invention does not require destructive tests, which involve the use and partial and complete destruction of real products and the use of large amounts of film and / or band, nor does it require transporting a plurality of palletized loads to be tested at the site where the test equipment is present, such as the acceleration slide or the handling platform.

[0161] Furthermore, depending on the available computing power, digital model simulations (two-dimensional or three-dimensional) are very fast and allow to evaluate a plurality of different wrapping configurations for the same load along the same path in a short time, leading quickly and effectively to the identification of the optimal wrapping configuration.

Claims

CLAIMS1. Method for creating a two-dimensional or three-dimensional digital model (C’) in a numerical environment of a palletised load (C) formed by a group (110) of products (100) arranged on a pallet (150) and wrapped by a film or band (50) of plastic and / or paper and / or fabric material according to a certain wrapping configuration (A), said method comprising the steps of:- mechanically characterizing constituent elements (150, 100, 50, 120) of said palletized load (C) and interactions among said constituent elements (150, 100, 50, 120), said constituent elements comprising said pallet (150), said product (100), said film or band (50) and wherein said interactions comprise friction coefficients between contact surfaces of adjacent products (100) and products (100) and pallets (150);- digitizing said constituent elements (150, 100, 50, 120) in a CAD / CAE environment and obtaining respective digitized constituent elements (150’, 100’, 50’, 120’) with which to assemble said digital model (C’) of said palletized load (C);- validating mechanical properties of said digitized elements (150’, 100’, 50’, 120’) obtained by said mechanically characterizing said constituent elements (150, 100, 50), in particular through finite element analysis (FEA);- building said finite elements digital model (C’), assembled in a CAD / CAE environment with said digitized constituent elements (150’, 100’, 50’, 120’), setting contact behaviours between the digitized constituent elements (150’, 100’, 50’, 120’);- validating said finite element digital model (C’) of the palletized load (C); wherein digitizing said constituent elements (150, 100, 50, 120) comprises digitizing said film or band (50) wrapped around said group (110) of products (100) according to said wrapping configuration (A; A’) by modelling said film or band (50) as a set of distinct and arranged strips (Fl, F2, .En), in particular partially superimposed, along a vertical extension of the load, wherein each strip (F 1 , F2, .. En) has a respective thickness that is equal to the sum of the thicknesses of the wraps (al, a2,...an) of film or band (50) that form it and that have the same elongation (Sl,...Sn), the elastoplastic and dissipative properties of said film or band (50) being determined in the film or band (50) mechanical characterization step.

2. Simulation method for determining a wrapping configuration of a film or band (50) of plastic and / or paper and / or fabric material wrapped around a group (110) of products(100), in particular arranged according to layers (101) and superimposed on a pallet (150), to form a palletized load (C), in particular to be moved and / or transported along a defined path (PR) by a means of transport (200), said method comprising the steps of: - identifying a set of kinematic quantities (G amax), in particular kinematic quantities acting on said means of transport (200) while it follows a defined path (PR);- by means of the method according to claim 1, creating a two-dimensional or three- dimensional digital model (C’) of said palletised load (C) wrapped with said film or band (50) according to a defined wrapping configuration (A);- starting a simulation of movements and / or stresses acting on said digital model (C’) using the values of said set of kinematic quantities (G amax) as boundary conditions; - at the end of said simulation, verifying if said digital model (C’) of the palletised load (C) wrapped with said film or band (50) according to said defined wrapping configuration (A) has remained stable and / or compact and / or rigid and / or structurally intact;- modifying said defined wrapping configuration (A) if said digital model (C’) has not remained stable and / or compact and / or rigid and / or structurally intact after the simulation;- repeating said simulation by means of a digital model (C’) and / or modifying said defined wrapping configuration (A) until said digital model (C’) is stable and / or compact and / or rigid.

3. Method according to claim 1 or 2, wherein said constituent elements (150, 100, 50, 120) of said palletised load (C) comprise interlayer elements (120) interposed between one layer (101) and the other of said products (100), said mechanically characterising said interlayer elements (120) comprising obtaining a coefficient of friction between product contact surfaces (100) and interlayer element (120).

4. Method according to one of the preceding claims, wherein mechanically characterizing said product (100) comprises performing compressive stress tests and shear stress tests along three main directions (X, Y, Z) and along main planes (XY, XZ, YZ) to determine normal elastic moduli (Ex, Ey, Ez) and tangential elastic moduli (Gxy, Gxz, Gyz) of said product (100) along said main directions (X, Y, Z) and said main planes (XY, XZ, YZ).

5. Method according to one of the preceding claims, wherein if said product (100) is composed of a plurality of product units (105) grouped and wrapped by a wrapping material (106) said mechanically characterizing said product (100) comprisesperforming shear slide tests of the product units (105) along three main planes (XY, XZ, YZ), in particular by measuring along the three main planes (XY, XZ, YZ) forces acting on, and relative displacements of, rows of product units (105) arranged on opposite sides of the product (100) so as to determine shear slide elastic moduli (G’xy, G’xz, G’yz) along the main planes (XY, XZ, YZ) of said product (100).

6. Method according to one of the preceding claims, wherein said mechanically characterizing said film or band (50) comprises subjecting at least one specimen (55) of said film or band (50) to tensile tests along a longitudinal direction and a transverse direction to determine elastoplastic properties of said film or band (50), in particular a respective tensile curve (Ct) and an elasticity curve (Ce) of said film or band (50).

7. Method according to one of the preceding claims, wherein if said film or band (50) is made of cold-stretchable material, said mechanically characterizing said film or band (50) comprises performing tensile tests on a plurality of specimens (55) of film or band (50), the film or band of each specimen (55) being previously subjected to a respective longitudinal elongation.

8. Method according to claim 7, wherein said elongation (S) is a function of a percentage of pre-stretch (PS) imparted to the film or band (50), in particular during its unwinding from a reel and before wrapping around the palletised load, and / or of a percentage variation of length (VLF) of the film or band (50) wrapped around the palletised load (C), said percentage of pre-stretch (PS) and said percentage variation of length (VLF) being defined by the following formulae:PS = (LFS - LFO) / LFOVFL = (LFS - PCP) / PCPwhere:LFS (mm) is the length of pre-stretched film or band wrapped at each turn around the load (C);LFO (mm) is the length of non-stretched film or band unwound from a reel;PCP (mm) is the perimeter of the palletised load (C).

9. Method according to one of the preceding claims, wherein said mechanically characterizing said film or band (50) comprises determining:- a hysteretic damping of said film or band (50) by dissipative characterization tests, comprising cyclic load-unload tensile tests performed on at least one specimen (55) of said film or band (50) to determine the dissipated energy and at least oneequivalent hysteretic damping parameter; or- a hysteretic and Coulombic damping of said film or band (50) by characterization of the dynamic behaviour of the palletized load (C) which comprises wrapping with said film or band (50) a sample palletized load formed by a plurality of superimposed products (100) and subjecting it to an acceleration test according to at least one main direction (X, Y, Z) and analysing the displacements of markers positioned on said sample palletized load to calculate parameters of said hysteretic and Coulombian damping of the film or band (50), in particular to obtain damping (6), damping ratio (Q and oscillation frequency (f) characteristic of said film or band (50).

10. Method according to one of the preceding claims, wherein said mechanically characterizing said film or band (50) comprises wrapping said film or band (50) around an instrumented load (CS) provided with sensors (40) adapted to measure a value of a wrapping force (T) exerted by said film or band (50) on said instrumented load (CS).

11. Method according to one of the preceding claims, wherein if said film or band (50) is of stretchable material, said mechanically characterizing said film or band (50) comprises wrapping around an instrumented load (CS), provided with sensors (40) adapted to measure a value of a wrapping force (T) exerted by said film or band (50), individually and separately a plurality of sections of said film or band (50) each of which previously subjected to a respective elongation so as to measure the values of wrapping force (T) exerted on said load by said section of film or band (50) when subjected to said respective elongation.

12. Method according to one of the preceding claims, wherein said mechanically characterizing said friction coefficient between contact surfaces of said products (100) comprises stacking and / or placing side by side a plurality of products (100), separated or not separated by interlayer elements (120), and measuring a tensile force (Fa) applied to a product of said plurality of products such as to determine the first detachment or displacement of said product and then calculate said friction coefficient as a function of said tensile force (Fa) and of a weight force of said product or acting on said product (100).

13. Method according to one of the preceding claims, wherein said digitizing said constituent elements (150, 100, 50) comprises digitizing said product (100) as a volume representative element having in a numerical environment the mechanical properties, in particular the normal elastic moduli (Ex, Ey, Ez) and the tangential elastic moduli (Gxy,Gxz, Gyz) and / or the shear slide elastic moduli (G’xy, G’xz, G’yz), determined in the mechanical characterization step of the product (100).

14. Method according to one of the preceding claims, wherein digitizing said film or band (50) further comprises introducing a coefficient of thermal expansion (a) of the material of said film or band (50) and an appropriate thermal load (AT) to be subjected to said film or band (50) in a numerical environment to model a wrapping force (T) exerted by said film or band (50) on said palletized load (C) due to the elastic return following elongation (S) of said film or band (50), said appropriate thermal load (AT) being a function of a specific and respective elongation (S) to which said film or band (50) is subjected before and during wrapping.

15. Method according to one of the preceding claims, wherein the contact behaviours between adjacent products (100) and between products (100) and pallets (150) are frictional contact behaviours calculated on the basis of the friction coefficients determined in the mechanical characterization step of the interactions between constituent elements and wherein the contact behaviours between film or band (50) and products (100) are bonded contact behaviours, in particular with multipoint-constraint formulation.

16. Method according to one of the preceding claims, comprising storing as a stability wrapping configuration (As) the wrapping configuration of said film or band (50) for which said digital load model (C’) is stable and / or compact and / or rigid and / or structurally intact after simulation and therefore adapted to maintain the corresponding palletized load (C) stable and / or compact and / or rigid and / or structurally intact when moved and / or transported along said established path (PR).

17. Method according to one of the preceding claims, wherein said set of kinematic quantities comprises at least one set of maximum accelerations (G aum) acting on said means of transport (200) when moved along said defined path (PR), wherein said set of maximum accelerations (G amax) comprises local accelerations (atj, an,j, az,j) acting along said path (PR) on said means of transport (200) with reference to a local reference system (t, n, z ’) of said means of transport (200) and having higher values.

18. Method according to one of the preceding claims, wherein said wrapping configuration (A) of said film or band (50) around said palletised load (C) comprises a plurality of wrapping parameters including one or more of the number of wraps or strips of films arranged around the load, percentages of overlapping of the wraps and their arrangementon the load, percentage of pre-stretch (PS) applied to the film, length of the film delivered at each turn, overall elongation (S) of the film, said wrapping parameters being a function of characteristics of said film or band (50) and / or of said palletised load (C) and / or of said established path (P), in particular the characteristics of the palletised load (C) comprising type of products (100), size, shape, strength and / or deformability of the products (100), total number of products (100), composition in rows (102) and superimposed layers (101) of said products (100) grouped together.

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