Field of the invention

The present invention relates to a machine for carrying out tests on materials, in particular for naval use, and to a method for carrying out accelerated tests on such a machine.

Background art

In the production and installation of materials for naval use, a significant problem for manufacturers and installers is to ensure the quality and strength of the product to the customer over time. In fact, the environmental stresses to which a material for naval use is subjected are especially demanding and varied when considering installations ranging from decks exposed to atmospheric agents and mechanical stresses, to environments for the accommodation of crews and passengers. The machines for carrying out accelerated or non accelerated tests on materials are usually specialized for the execution of tests related to a single or a couple of environmental stresses. It is unlikely that the analysis is carried out to estimate the combined effect of more than two parameters simultaneously subjected to tests of a different nature. In brief, today's market offers no machine able to carry out tests on several parameters of a different nature, which allows the estimate of the effects and interactions of different stresses, and which allow a prediction of the performance of the material in actual operating conditions through an accelerated test for much longer times than testing ones. The reasons related to such a deficiency are varied. US20030060987 describes a method to determining or testing mechanical properties of materials or more particularly to simulating indentation testing data to determine mechanical property such as stress strain behavior. A number of dimensionless functions are developed using dimensional analysis. But this documents says nothing about the possibility to apply simultaneously different physical stresses for accelerating the tests and for analyzing their combined effect. The presence of many simultaneous agents creates an enormous experimental difficulty. In fact, the machine must to be able to reproduce, in shorter times, the combined effect of many parameters characterizing the environmental stress considered. In the prior art there are no machines capable of managing the execution of tests to ensure the correct reproduction of the combined phenomena in reduced times according to a predetermined acceleration parameter. Moreover, the number of parameters involved that should be changed increases in a quickly unmanageable manner, because the possible combinations of the parameter values increase very quickly as the number of agents considered. Therefore, the experimenter would face the problem of choosing the many test parameters not knowing how they should be chosen so that the test carried out has a predictive significance of the material behavior under actual use conditions and moreover requiring the test to be carried out much faster than those carried out in operating conditions.

The need to provide a method, and a related machine, able to carry out tests on materials for nautical use which allows the aforesaid drawbacks to be overcome is therefore felt.

Summary of the invention

It is the primary object of the present invention to provide a machine for testing materials capable of carrying out tests on materials, in particular materials for nautical use but not only, having the ability to simultaneously carry out tests very different in nature.

It is another object of the invention to provide a machine capable of carrying out tests on materials having the ability to accelerate the tests compared to the actual use time of the above materials, being able to carry out short experiments, either days or months, but able to simulate and give directions on a scientific basis about the behavior of the material during its whole operating life that lasts for many years.

It is a further object of the invention, related to the previous one, to manage the tests by selecting the physical conditions of the test so that the test itself is not only accelerated, but that it is the fastest possible, consistent with the limits of the actuator systems installed in the machine itself, and retaining the predictive value of the test, and so that the physical and chemical parameters associated with said test are automatically determined by the machine itself on the basis of some data provided by the operator.

It is a further object of the invention to provide a machine capable of carrying out tests on materials with an automatic management capability of the accelerated test program using appropriate control software, and to alternate periods of environmental stress, carried out in a special test chamber, with periods of analysis of the damage undergone by the material by automatically moving the material specimen subjected to test in another chamber of the machine dedicated to this purpose, automatically following the evolution of the damage produced on the material specimen with the increasing time of action of the environmental stress.

The present invention thus aims to achieve the above objects by providing a material testing machine having the features of claim 1 .

A second aspect of the present invention provides a method for operating such a machine, according to claim 6.

The testing machine, object of the present invention, allows more or less accelerated tests of a different nature to be carried out on materials, in order to predict the combined effect of multiple parameters simultaneously subjected to the above tests. It includes a control system that uses a test organization and execution criterion based on the Dimensional Analysis to correctly and effectively identify, in a minimum number, the similarity parameters between the material specimen stressed in the test chamber and the material installed stressed in the actual use conditions and so that the duration of the tests is as short as possible. The dependent claims describe preferred embodiments of the invention.

Brief description of the drawings

Further features and advantages of the invention will become more apparent from the detailed description of preferred but non exclusive embodiments of a machine for testing materials, shown by way of a non limiting example with the aid of the accompanying drawings, in which:

Fig. 1 shows a functional architecture diagram of the machine according to the invention;

Fig. 2 shows the test chamber of the machine according to the invention;

Fig. 3 shows a diagram of the treatment system of the air to be introduced in the test chamber, located in the bottom part of the same test chamber in Fig. 2;

Fig. 4 shows the diagnostic chamber of the machine according to the invention; Fig. 5a and Fig. 5b show two variants of a detail of the rotating brush and of the connected devices for the dispersion of the abrasive powder contained in the support system of said rotating brush;

Fig. 6a shows a diagrammatic view of the self-cleaning glass lamps, such as infrared or solar spectrum lamps, with which the machine may be provided;

Figure 6b shows a sectional view along plane c-c in Figure 6a;

Fig. 7 shows a flow diagram of the set of operations carried out by the machine; Fig. 8 shows a block diagram of the functions carried out by the logical data processing unit;

Fig. 9 shows a block diagram of the functions carried out by the diagnostic chamber;

Fig. 10 shows an overall diagrammatic view of the machine according to the invention.

The same reference numerals in the figures identify the same elements or components.

Detailed description of a preferred embodiment of the invention

Figure 1 shows the general architecture of the machine for testing materials according to the present invention. Such a machine consists of five separate units:

- electronic interface unit or panel PIE with the operator, or simply interface;

- logical data processing unit UED;

- a command and control unit UCC;

- a test chamber or cell CAMP;

- a diagnostic chamber or cell CAMD.

The machine for testing materials according to the present invention uses a test organization and execution criterion based on Dimensional Analysis, Buckingham's theorem, in the data processing unit UED and in the command and control unit UCC to correctly and effectively identify, in a minimum number, the similarity parameters between the material specimen subjected to the various tests in a suitable test chamber and the actual material installed. Moreover, the machine determines the test parameters so that the duration of the test itself is as short as possible. The machine is able to automatically set up for the execution of said accelerated tests on the material specimen, so that the results relating to damage of the material are representative of what happens in operation for much longer times than those used for the tests; it materially performs the necessary tests; it automatically monitors the damage produced; and finally, it automatically correlates the environmental stress parameters to those of damage produced. The machine is diagrammatically described in Fig. 10, where all the essential subcomponents of the five separate units mentioned above, adapted to ensure complete operation thereof, are shown. Specifically, in figure 10 and in all the other figures, the alphanumeric references correspond to the following elements: CAMP: test chamber of material

CAMD: diagnostic chamber of material

PIE: electronic interface panel

UED: logical data processing unit

UCC: a command and control unit

TA: terminal for data transmission to the chamber actuators

TS: terminal for data reception from the chamber sensors

IM: (thermal and sound) insulation machine casing

BM: machine base

PS: machine support floor

PT: material specimen, e.g. in the form of panel on which the tests are carried out. The test chamber CAMP is provided with:

LS: lamps with solar spectrum light

LIR: infrared lamps

SCP: test chamber sensors

SR: rotating brush

SSR: rotating brush support

M1 : revolution motor for arm D of the rotating brush support SSR

DT: system for motion transmission to arm B and for adjusting the contact pressure of the rotating brush

M2: rotation motor for rotating brush SR

MRL: roller motor for material specimen PT transfer from CAMP to CAMD and vice versa

RL: rolls of the material specimen PT transfer roller GRL: roll transmission belt

GS: gasket, for example rubber, for the separation between the top of the test chamber and the bottom part containing the air treatment system to control the atmosphere inside the test chamber

PV: vibrating table or surface

R: unbalanced rotors for the activation of the vibrating table PV, or more generally actuators to trigger the vibration of the table

SP: bearing structure of the vibrating table PV.

The lamp self-cleaning system in the test chamber includes:

PLMP: lamp holder

PSP: brush holder

SPZ: lamp brush

TENU: water seal

MRO: glass moving motor

VET: glass

CUS: bearing

MOV: glass moving reduction gears.

In cooperation with the rotating brush SR, the following is provided in the test chamber (Figures 5a and 5b):

MCO: Screw and blade moving motor

ACO: shaft with keyed screw and diffusion blades

SPO: powder tank

COC: screw

PAL: blades for powder distribution on the screen (Fig. 5a)

VAG: screen (Fig. 5a)

PAD: diffuser blades (Fig. 5b)

CAM: Bell for powder diffusion (Fig. 5b).

In the bottom part of the test chamber, the air treatment system comprises (Figures 2 and 3):

AE: outside air intake manifold

PF: pre-filter bench

MM: upstream mixing chamber F: main filter bench

BPR: pre-heating battery or thermal regenerator

BR/U: heating bench (heating machine) with attached humidifier

BF/D: cooling bench (refrigerating machine) with attached condensation dehumidifier

VM: upstream fan

MV: downstream mixing chamber

SAL: tank for adding chemically aggressive liquid solution

FS: exhaust filters

SE: external exhaust diffuser

IP: pneumatic isolators to isolate the machine base from vibration generated by actuators R

DF: treated air diffuser in test chamber CAMP

AR: intake/exit of recirculation flow from test chamber CAMP

V1 : selector servo-valve for air recirculation with and without mixing

V2: air splitter servo-valve on cooling/heating benches

V3: air splitter servo-valve for flow directing to cooling bench

V4: hot/cold air mixing servo-valve

V5: external air flow throttling servo-valve

V6: air splitter servo-valve for directing the thermal regenerator/downstream mixer.

The diagnostic chamber is provided with:

ICD: diagnostic chamber casing

MS: mobile partition, such as in the form of a motorized gate, to allow passage/isolation between chambers CAMP and CAMD

SRSD: diagnostic system rotating support

MSV: motor for rotating the diagnostic system rotating support

SO: diagnostic system adjustable supports

TL: diagnostic cameras

SL: test material specimen lighting bulb

MRL: roller motor for material specimen PT transfer from CAMP to CAMD and vice versa

RL: rolls of the material specimen PT transfer roller GRL: roll transmission belt

The following is provided in the electronic interface unit PIE with the operator:

TST: interface unit keyboard

TV: video terminal

SHE: external hardware support.

With reference to figures 4 and 10, the machine is provided with an electronic interface panel PIE, comprising the video terminal systems TV, a keyboard TST, and a support for external hardware SHE, with which the operator can interact. Through interface PIE, the machine displays to the operator all the physical parameters that may be involved in the identification of the environmental agents to which the material is subjected, for example: UV lighting time, intensity of such a lighting, thermal cycle period, maximum and minimum cycle temperature, salt concentration in the atmosphere, relative humidity, level of vibration (frequency bands and intensity), roughness features of the sliding surface on the material to simulate phenomena of abrasion from foot traffic, grain size of the abrasive powder interposed, contact pressure between the surfaces, contact speed between the surfaces, exposure time to abrasion, etc. In addition to these parameters that define the environmental stress, unit UED selects the objective parameters that identify the damage undergone by the material, for example related to the variation of surface roughness, the effects of opacification, the effects of permanent curvature induced on the material specimen, for example in the form of a panel, surface and through lesions, detachments.

All parameters, both of environmental stress and of damage, as shown, are in a very large number and make a machine dedicated to such tests complex both from the conceptual point of view, in the definition and management of all the significant and characteristic test parameters, and in the physical realization of the test chamber to produce the necessary desired environmental conditions, and for the analysis of data obtained from the tests carried out in the diagnostic chamber. Through the use of Dimensional Analysis, the data processing unit UED of the machine of the invention, by means of appropriate software, identifies all test parameters that are grouped in so-called adimensional groups, quantities obtained by multiplying some of the test parameters identified above, each raised to a characteristic power, and transfers such information to system UCC which controls all the actuators (Figure 1 ), also on the basis of the information provided by sensors, SCP, so as to ensure that the value of the adimensional test parameters is achieved and maintained for the times provided during the test. Such adimensional groups have the features of being less than the total number of test parameters involved, simplifying the analysis and the number of tests.

The software of the UED, through the combination of two special procedures for the analysis of data entered by the operator, notifies the operator of the adimensional groups identified, suggesting the so-called similarity between tests carried out with different values of the characteristic parameters but with the same value of the characteristic adimensional groups. The software of the UED also is capable of identifying the maximum parameter or acceleration factor of the test on the basis of the parameters previously entered, thus using in the best possible way the characteristics of the actuators installed in the test chamber.

The machine is set up by the UED, and through the UCC, to carry out similarity tests between the material in the test chamber CAMP and the same material installed in actual operating conditions. This means that all the adimensional groups between tests in the test chamber CAMP and material installed in actual operating conditions, such as on board a ship, are identical, but the characteristic test parameters in the test chamber CAMP and those in said actual operating conditions are not, and in particular the times of exposure to environmental agents are different: in the tests carried out in a test chamber CAMP, these times must be much shorter than the "actual" ones. All the physical parameters required by the test, as organized by the UED on the basis of data provided by the PI E, are then transmitted to the UCC, which controls the actuation systems of the CAMP and CAMD to ensure compliance with their preset values, using continuously also the data provided by sensors SCP as a feedback of the adjustment system of said parameters.

The present invention, on the basis of the above idea, enables the provision of a machine for testing materials which ensures the following basic requirements to the operator: Ability to perform simultaneous tests of a very different nature, ranging from exposure to salt spray, UV exposure, exposure to thermal cycles, abrasive wear from foot traffic, shock, vibration, corrosion, taking into appropriate account their mutual interaction;

- Ability to accelerate the tests, being able to carry out short (days or months) experiments but able to simulate and give directions on a scientific basis about the behavior of the material during its whole working life which lasts for many years, on the basis of a test control algorithm automatically managed by the machine based on the Dimensional Analysis (Buckingham's theorem);

- Ability to automatically manage the accelerated test program by appropriate control software which implements the principles of the Dimensional Analysis for carrying out tests in physical similarity between the material exposed to actual environmental stresses and the material specimen subjected to the tests in the dedicated test chamber;

- Ability to automatically analyze the damage undergone by the material subjected to the tests in the test chamber by a comparison between the features of the material specimen before and after the execution of the tests;

Ability to build in a progressive manner, during the repetitive use of the equipment, correlation laws between stress parameters and damage produced on the material as the time of exposure to environmental stress varies.

With reference to figures 2, 3, 4 and 10, from the mechanical point of view the machine performs the sequence of operations described below.

The specimen of material to be tested, for example in the form of a panel PT, is initially manually inserted into the test chamber CAMP where it is automatically subjected to a cycle of combined tests to be periodically and automatically transferred from chamber CAMP to the diagnostic chamber CAMD, through a system of motorized rollers (composed of components RL, MRL and GRL) passing through the motorized gate SM, to be subjected to the tests set by the UED and controlled by the UCC, as described hereafter.

The temperature cycles, the control of humidity and aggressive agents dispersed into the atmosphere during these cycles, are performed through the air or atmosphere treatment system (completely interlocked to the UCC, which in turn responds to the inputs of the UED and to the inputs of the feedback sensors SCP) which is located in the bottom part of the CAMP, below the vibrating support plane PV of material specimen PT to be tested, as seen in the assembly drawing in figure 10 and more schematically in figure 3.

The main air flow is drawn from the external environment through the intake manifold or inlet AE and directed to the treatment system through valve V5 which allows the possible throttling of the air flow entering the system. The group of prefilters PF includes to a filtering of the flow before it is sent to the upstream mixing chamber MM, where the mixing with the recirculation flow from the test chamber CAMP, through one of the output of the air valve V1 , occurs. Such a mixing may serve for the possible recovery of air already treated, i.e. in conditions of temperature and humidity which are closer to those that occur within chamber CAMP, thereby reducing the overall use of energy for air treatment. The mixing ratio between the air in external environmental conditions coming from AE and the air coming from the CAMP through V1 , is determined by the adjustment of the two servo-valves V5 and V1 , and will depend on the software protocols implemented in the UED that sends the inputs to the UCC which, in turn, will operate the electric actuation systems of the servo-valves V1 and V5 (such an interlocking mechanism is common to all valves V1 , V2, V3, V4, V5, V6 of the machine described in the present invention). In particular, by adjusting the servo-valves V1 and V5, it is possible to choose whether to fully re-treat the flow (by closing the V1 towards chamber MM and fully opening the V5) to prevent the air from the CAMP from crossing the system. Such a choice could be suggested where the aggressive chemicals dispersed in the atmosphere of the CAMP are believed to be harmful to some of the components used for air treatment.

At the exit of the MM there is the main filter bank F which purifies the air after the possible mixing between external flow and recirculation flow (i.e. removing any powders blown inside the CAMP potentially dispersed in the recirculation flow from the exit of the V1 towards the MM). Thereafter, the flow encounters the pre- heating battery BPR, which is a heat exchanger designed to a partial recovery of the thermal energy of the air flow exiting from the CAMP, started at the BPR by the V1 and then the V6. The flow rate of the recirculation flow sent to the BPR depends on the settings of the V1 and V6, whereby the units UED and UCC can manage the portion of recirculation flow directly mixed with the flow of outside air and sent to the heat exchanger BPR. For example, if the software protocol implemented in the UED believes that the atmosphere coming from the CAMP is harmful for the air treatment system, the output from the servo-valve V1 to the MM will be closed, and the inlet of the V6 to the BPR will be opened, thus recovering at least a portion of the thermal energy of the recirculation flow. After the BPR, the flow is sent by means of the splitter servo-valve V2 to the two parallel batteries or benches or BR/U and BF/D, which are the heating and humidification battery and the cooling and dehumidification battery, respectively. The servo-valve V2, which is also governed by the UCC on the basis of the data sent by the UED, allows the air flow rate to be split by adjusting the air flow rates sent individually to batteries BF/D and BR/U. The servo-valve V3 then allows part of the flow treated in the BF/D to be sent back to the heating battery, such circulation being aimed at an air dehumidification by cooling and condensation in the BF/D and subsequent heating in the BR/U. Finally, the output flows from the two batteries BF/D and BR/U are again mixed by the servo-valve V4. Through the adjustments of the V2, V3 and V4, the system thus allows determining the desired temperature and humidity conditions at the inlet of the downstream mixing chamber MV. In said chamber, through a suitable adjustment of the servo-valve V6 again by the UCC, there is the further opportunity to mix the recirculation flow coming from the CAMP by the valves V1 and V6, with the flow of treated air coming from the V4, with the advantage of not making the recirculation atmosphere pass through the components of the air treatment system. Finally, the tank SAL contains a possible chemically aggressive additive, which is added in the mixing chamber MV to the treated flow, only immediately before the introduction into the CAMP through diffuser DF, to prevent the aggressive additive from passing through the components of the air treatment system that could potentially deteriorate. The air flow thus treated is introduced in the CAMP where there is the panel to be tested PT, or other material specimen, thereby determining, under the control of units UCC and UED, the pattern of temperature, humidity and concentration of chemical aggressive in the atmosphere of the chamber over time. In the CAMP there are further components of the machine adapted to implement the desired values of the other test parameters.

The abrasion system includes a motor M1 which sets in rotation, by means of a conventional system DT that integrates the transmission and a vertical action actuator with connected actuation sensor, allowing the adjustment of the contact pressure between brush SR and test material specimen PT, arm B about the axis of rotation a-a; arm B carrying a second motor M2 which rotates about axis b-b the support SSR of the rotating brush SR to the shaft of said motor M2, again integral to the same rotating brush SR which rotates in contact with panel PT on which the machine carries out the test. The speed of rotation of motors M1 and M2 and the vertical pressure exerted by the SR through the integrated system DT are determined by the UED and controlled through the UCC which receives, via the optionally wireless terminal TS, information on the contact pressure between brush and panel PT and on the abrasion speed of the brush with respect to panel PT. Figures 5a and 5b provide the detail of the contact powder dispersion system accommodated inside the rotating brush SR. More precisely, the powder dispersion system can be implemented according to the scheme in figure 5a or according to the variant in figure 5b. Tank SPO is filled with the powders required by the tests that must be performed. On tank lid there is the motor that, through shaft ACO, moves screw COC and blades PAL for the even distribution of powders on sieve VAG or, alternatively, blades PAD that push the powders against bell CAM.

The heating system of panel PT, in addition to the system already described for controlling the temperature, humidity and aggressive chemical cycles, is completed with an irradiation heating system by infrared lamps LIR always controlled by system UED and UCC (see figures 2 and 10). The irradiation system with a spectrum similar to the solar spectrum is carried out through lamps LS, also controlled through systems UED and UCC (see figures 2 and 10). All the lamps with which the machine is provided have a possible self-cleaning system of the external surface in order to eliminate any opacification effects due to the stagnation of condensation by means of a rotating cylinder and fixed brush system, described in detail hereafter. More precisely, the system for cleaning the lamps (LS or LIR) is implemented according to the diagram in figure 6. Glass VET isolates the lamps and the relative lamp holder PLMP from the humid environment in the CAMP through the use of appropriate seals. Such a glass is kept clean by brushes SPZ, anchored to the brush holder PSP and in relative motion with respect to the glass itself. In the disclosed solution, the glass is moved through the use of the electric motor MRO and the reduction gears MOV while the brushes are kept fixed; another solution would be to put in rotation the brushes and keep the glass still. This latter variant can be used in cases in which the movement of the shadow projected by the brushes on the component does not affect the test validity.

Units UED and UCC command and control the opening of the motorized gate SM (see figure 10) which, according to times determined by the UED and by the UCC, allows the passage of the PT from the CAMP to the CAMD, using an automatic transport system which consists of the motors of rollers MRL that drive belts GRL that run on rolls RL, dragging material specimen PT. Once the PT has been transferred to the CAMD, the motorized gate SM is closed. Figure 9 shows the diagram of the steps performed in the diagnostic chamber CAMD.

The diagnostic chamber CAMD (see figures 4 and 10) is provided with a motor adapted to rotate the rotating support SRSD about a vertical axis, on which both cameras TL and the lighting lamps SL of material specimen PT are attached. Both cameras TL and lamps SL are mounted on the rotating support SRSD by means of further motorized adjustable supports SO. Through the rotation of support SRSD and of the individual rotations of supports SO, all rotations controlled by systems UED and UCC, it is possible to vary the characteristic lighting angles of material specimen PT by lamps SL. The damage of the sample can be evaluated by means of the images recorded by cameras TL themselves, by means of software that executes an image analysis, and more specifically through the detection of the variation of chromatic effects when moving the lighting lamps SL, thus avoiding contact analyses performed by feelers. More precisely, the image analysis is comparative between the material specimen shot before and after each re-insertion of the material specimen in the test chamber CAMP. Precisely, the geometrical damage such as loss of planarity and local roughing, can be detected by means of a monolateral grazing lighting that determines a strong shading of a part of the surface, leaving another part perfectly lighted. The ex-ante and ex-post comparative analysis of the image detects the change in the average intensity of the pixels by opacification, while the standard luminosity deviation on the cluster of pixels is estimated for the color non-uniformity.

The technique described allows the objective quantification of damage by simple adimensional parameters. The technique described, by way of example, in particular for materials for naval use, may be modified and new variants may be conceived without departing from the scope of the inventive concept. It is clear, for example, that such a method and machine for testing materials can be used for other materials and other conditions that are not only specific of the naval field. From the logical-functional point of view, the machine then performs the following operations and interfaces with the operator in the following way, as shown in figure 7, which describes a flow diagram thereof:

a) the operator inserts the material specimen of material to be tested in the test chamber CAMP;

b) the machine, through interface PIE, provides the operator with a double menu, the first menu on the possible environmental stresses to be imposed to the material specimen in the test chamber CAMP, the second menu on the damage to be monitored by the sensors installed in the diagnostic chamber CAMD;

c) the operator provides to the logical data processing unit UED, through interface PIE, the data related to the type of actual environmental stress that the material must withstand, as a non limiting example UV lighting time, intensity of such a lighting, thermal cycle period, maximum and minimum temperatures of such a cycle, salt concentration in the atmosphere, relative humidity, level of vibration (frequency bands and intensity), roughness features of the sliding surface on the material to simulate phenomena of abrasion from foot traffic, grain size of the abrasive powders interposed, contact pressure between the surfaces, contact speed between the surfaces, exposure time to abrasion, etc. In a more sophisticated version of the machine, database DB can store information relating to the use conditions of the material associated with a certain location on the ship; in this latter case, the operator can select from video TV of the electronic interface PIE the standard room where the material is intended to be installed, the software itself providing for the extraction of the characteristic environmental stress parameters from the database to be sent to the machine;

d) the operator provides the data relating to the type of damage to be monitored to the logical data processing unit UED, through interface PIE;

e) interface PIE provides the maximum acceleration parameter of the test to the operator, calculated by the logical data processing unit UED, which the machine is able to ensure respecting the similarity methodology implemented by the logical unit, described hereafter. The operator sets the desired acceleration parameter compatible with the maximum value displayed by the machine;

f) interface PIE transmits the data selected by the operator in steps c), d) and e) to the logical unit UED which, on the basis of the algorithms described hereafter, determines the characteristic environmental stress parameters to be imposed in the test chamber CAMP, defining the typical adimensional parameters and their numerical value that are displayed to the operator;

g) possible execution of a diagnostic test in the diagnostic chamber CAMD; h) the test execution starts for the times set by the logical unit UED and stabilized by the control unit UCC using the information sent by the chamber sensors SCP (temperature, humidity, concentration of aggressive chemical additive sensors, etc.);

i) the periodic interruption of test is produced to perform the diagnostic tests, automatically (or manually) transferring, through motors MRL and rolls RL driven by the belt transmission GRL, material specimen PT from chamber CAMP to the diagnostic chamber CAMD, by opening the motorized gate SM to start the operations described above;

j) the data detected by cameras TL of the diagnostic chamber are sent at the end of each diagnostic test to the logical data processing unit UED for carrying out the correlations between environmental stress parameters and damage parameters.

Below is the description of the functions carried out by the logical data processing unit UED, represented in the block diagram in figure 8. In particular, the description of the test management algorithm implemented in the logical unit consists of the following steps:

1 ) Displaying to the operator, through interface PIE, the first menu with the list of the various environmental stresses available and/or the list of the possible destinations of the material, and the second menu with the list of the various damages to be monitored;

2) Selecting, by the operator, the environmental stresses and/or destinations, and selecting the damage of interest;

3) Displaying to the operator the list of possible parameters to be monitored;

4) Selecting the parameters to be monitored;

5) Analyzing the data entered by the operator possibly integrated by consulting database DB;

6) Calculating the characteristic adimensional parameters of the test;

7) Displaying to the operator, through interface PIE, the set of adimensional parameters and the maximum test acceleration factor value;

8) Selecting by the operator a value of the acceleration factor and possibly modifying the data by the operator with subsequent recalculation of the adimensional test parameters; entering the arbitrary physical parameters by the operator;

9) Sending the test parameters to the control unit UCC.

The logical data processing unit UED implements the protocol described in steps 1 ) to 9) in the manner detailed hereafter.

At step 1 ), interface PIE submits, for example, to the operator the choice between some of, possibly all, the following six environmental stresses:

- ABRASION

- THERMAL STRESS

- HUMIDITY AND SALINITY IN THE ATMOSPHERE

- UV IRRADIATION

- VIBRATIONS

- CORROSION.

Once the environmental stresses to which the material specimen will be subjected have been selected, interface PIE prompts to set the values of all actual quantities related to the subject environmental stress parameters. Database DB may be used by the logical unit to set the numerical values of such parameters on the basis of only the indication of the intended use of the material, for example, indoor or outdoor use, use as floor, wall or ceiling, use in cabin room, bathroom or utility room, etc. By way of example, suppose that in step 2) the operator only select the first four environmental stresses while not selecting the last two. The environmental stresses selected are associated by the operator, or even directly by the UED, to the set of physical parameters q,, i = 1 ,2,..N, communicating them, by means of the PIE, to the machine itself, specifying the physical dimensions, i.e. the typical units of measurement in a measurement system consistent for all, for example in the International System. In this case, again only by way of a non exclusive example, the physical parameters for each environmental stress can be determined as follows:

- ABRASION

The abrasion phenomenon is produced in the test chamber CAMP using a rotating brush SR of which the peripheral speed V and the average contact pressure p can be controlled. Also provided is the powder dispersion system to disperse, in the vicinity of the contact area between brush and the surface of the test material specimen PT, a powder of variable particle size having characteristic dimension δ. Therefore, the physical parameters related to the abrasion phenomenon are in this case V, p, δ, i.e. qi = V, q ₂ = P, q ₃ = δ. Interface PIE prompts to set the values of all quantities V, p, δ related to abrasion, possibly with the aid of database DB.

- THERMAL STRESS

The atmosphere in the test chamber CAMP, through the atmosphere treatment system described above, has a temperature which can be varied in a cyclic manner, for example with characteristic period Δ and which allows switching from the minimum temperature e _mir , to the maximum temperature e _max according to a predetermined law. In the example herein, we therefore have that the physical parameters related to the thermal stress are q ₄ = Δ, q ₅ = e _m in, qe= 6 _ma x- Interface PIE then prompts to set the values of all actual quantities related to the thermal stress.

- HUMIDITY AND SALINITY IN THE ATMOSPHERE This can be characterized by two stress parameters in operating conditions: water concentration per cubic meter and salt concentration (or other aggressive chemical) per cubic meter. The logical unit UED may assume as test parameters the amount of water m _a (by mass) dissolved in the volume of the test chamber CAMP and the amount of salt (or other aggressive chemical) m _s (by mass) dispersed in the test chamber CAMP, volume V ₀ i of said test chamber being known. Therefore we still have, in the example herein, q ₇ =m _a , q ₈ =m _s , q ₉ =V ₀ |. Interface PIE prompts to set the actual values related to the environmental humidity and salinity.

- UV IRRADIATION

Such an environmental stress could be characterized only by the radiating power of the solar spectrum lamp LS. Therefore, q ₀ = I-

Interface PIE prompts to set the actual values of the radiating power intercepted by the material.

Moreover in step 2), interface PIE prompts the operator to monitor the following effects of the damage:

- GEOMETRICAL DAMAGE

- CHROMATIC DAMAGE

Assume, for example, that the operator selects both types of damage.

Geometrical damages are damages that produce a geometrical alteration of the material specimen tested. This category includes two types of damage:

- Bending and loss of planarity;

- Local roughing.

These types of damage are detected in the CAMD through the shading effects produced by the grazing light of lamps SL suitably oriented by rotations of the rotating support SRSD and of the adjustable supports SO, detected by cameras TL and analyzed using suitable image analysis software be implemented in the UED.

On the other hand, chromatic damage is a damage that produces effects attributable to a modification of the coloring of the item surface, due to both purely chromatic phenomena and to effects of modification of the surface geometry which can be more easily detected by a colorimetric analysis of the material specimen itself, again carried out by image analysis. Chromatic damage includes:

- Opacification;

- Non-uniformity of coloration.

More precisely, the opacification is detectable by a mean lowering of the brightness reflected by the material specimen surface by comparing the image recorded by cameras TL before and after a test period of material specimen PT, subjected to the same lighting intensity produced by lamps SL. The non-uniformity of coloration refers to all the surface spotting phenomena, both for the effect of a local alteration of the color, and for the presence of effects of exfoliation of the coating films or fracture of the coating materials of the surface itself. The damage parameters can be made quantitative, by way of a non limiting example, for example through the initial brightness of image l_i and luminosity L ₂ , L ₃ ... etc., periodically detected by cameras TL in the CAMD at regular time intervals T-i , T ₂ , T ₃ ... etc., under the same lighting conditions, by transferring the material specimen from the CAMP to the CAMD. Again by way of a non limiting example, the standard deviations σ-ι , σ ₂ , a ₃ ...etc, of the brightness of the pixels of the images detected by cameras TL of the CAMD may be measured at regular time intervals T _; T ₂ , T ₃ ... etc., under the same lighting conditions, by transferring the material specimen from the CAMP to the CAMD. The interpolation curves L(T) and σ(Τ) obtained from the previous measurements, using the described devices and procedures, are part of the objects of the present invention.

On the basis of the selections made by the operator about the diagnostic monitoring, chamber CAMD is set to perform the monitoring operations with the optical devices described above. A diagram of the functions performed by the CAMD is shown in figure 9.

Steps 5) and 6) relate to the processing of data selected by the operator. Buckingham's theorem allows for an analysis of the most significant adimensional parameters of the test undergone by the material specimen. The algorithm for the organization of the tests implemented by the UED is divided into two separate sequential Procedures, the first algorithmic Procedure is used to generate all possible sets of adimensional parameters; the second algorithmic Procedure is used to select the set of adimensional parameters which ensures, compatibly with the hardware of the machine, the maximum possible acceleration factor of the tests, as well as the final determination of the physical parameters to be set by the UCC in the test chamber CAMP.

First algorithmic Procedure of the UED: generating sets of adimensional parameters

All the N physical and chemical parameters q, associated to the environmental stresses as previously described, are added to the duration D of the environmental stress. The logical unit UED therefore determines the total number of parameters N+1 ; in the above example, there are 1 1 parameters comprising D: q ₂ =p, q ₃ =5, q ₄ = Δ, q ₅ = e _min , q ₆ = e _max , q ₇ =m _a , q ₈ =m _s , q ₉ =V ₀ i, qi ₀ =l, qn=D. G denotes the number of fundamental physical quantities gi g2- - . gG, i.e. those through which it is possible to express all the other quantities qi q ₂ . . .qN+i involved in the tests that the machine must carry out. More precisely, each quantity q, can be expressed as the product of the G fundamental quantities gi g2- - - gG each raised to a particular power an _, <¾ _,... a _iG, powers that can be obtained from the UED on the basis of the information provided by the operator to the PIE about the units of measurement of the single quantities q,, therefore:

In the example analyzed, we can introduce G=4 fundamental quantities gi g ₂ g3 g4 ! namely, we assume gi = mass, g ₂ = length, g ₃ = time, g ₄ = temperature. In the subject example we have:

¾ =

?6 = 0m

Unit UED builds a number M of adimensional parameters which, as known from Buckingham's theorem, is equal to M=N+1 -G, which in the exemplary case becomes M=7. The group of M adimensional parameters can be determined in a partially arbitrary manner. In particular, the logical unit UED determines a number P of groups of M adimensional parameters. P is equal to the number of ways in which G different quantities can be extracted from a set of N+1 parameters, according to the combinatorial calculation. Then, the logical unit UED proceeds to the determination of P distinct groups of M adimensional parameters as follows. Precisely, for the generic h-th group of the total groups P to be determined, we have:

- Extraction of a combination of G parameters qi _(h) q2(h) - - -qG(h) other than that selected for the other groups 1 , 2, ...h-1 , already determined.

- r ( set h )

- Determination of the M adimensional parameters ^k of the h-th group by the equation:

(set h) _ A(h)k (h)k Aj(ft)t

^{L L} k ~ k ¾1(¾) ¾2(¾) " · ¾G(ft)

Expressing all physical quantities q appearing in the above equation in terms of the fundamental quantities gi g2 - - -gG, we have:

And therefore:

In the above equation, the unknowns to be determined are represented by

( set h )

coefficients A _i(h)k . Since parameter ^k is adimensional, i.e. it is expressed in the form:

(set h) _ 0 0 0 0 the logical unit UED can determine said coefficients A _mk by the resolution of the following system of linear equations:

G

∑a _mr A _tWk - a _kr = 0, r = l,2,...G

=1

Having calculated said coefficients, these can be introduced in the equation:

(set h) _ A(h)k (h)k As(ft)t

^{L L} k ~ k \(K) ¾2(¾) " · ¾G(ft)

to determine the desired adimensional groups.

By way of example only, and on the basis of the parameters mentioned above by way of example only, one of the possible sets of M=7 adimensional groups which can be determined by the above Procedure is: m _a / V

π, = ol

m _s / V ol

V D δ

(vj

Second algorithmic Procedure of the UED: selection of the set of adimensional parameters for the maximum acceleration of tests

Having built groups P of M adimensional parameters according to the algorithm of the previous section by knowing parameters A^- k, unit UED proceeds to further processing to select the most advantageous group from the point of view of obtaining the biggest test acceleration factor compatible with the physical characteristics of the actuators installed in the test chamber CAMP. The logical unit then activates the second algorithm described hereafter:

a) calculating the values of all N+1-G adimensional parameters (n _k ^(seth) ) _T RUE entering, for each set h, the values of the quantities of the N+1 environmental physical parameters in the actual operating conditions (true);

b) determining the minimum and maximum values achievable in the test chamber CAMP for each physical parameter controllable among the N available (excluding duration D);

c) setting a first attempt value D _att empt of the test duration, which means a first attempt value for the test acceleration factor equal to ratio D _true / Dattempt;

d) calculating, using the interval algebra or other equivalent algorithm, the range of variation ^| _k ^{(set h)} of each k-th adimensional parameter (n _k ^(seth) ) _A TTE PT related to the h-th set, determined with the physical parameters achievable in the test chamber entered at point b);

e) carrying out the verification of the compatibility condition: (n _k ^(seth) ) _T RUE e lk ^{(set h)} - The verification of the compatibility condition is positive for h-th set of adimensional parameters if for each k-th adimensional parameter, the compatibility condition is satisfied.

If the verification is negative for all sets of adimensional parameters, then the process returns to step c), setting a larger value of D _a ttempt- If the verification is positive for some of the set of adimensional parameters, all sets of adimensional parameters for which the verification was negative are eliminated and the process returns to step c), setting a smaller value of Dattempt- The algorithm stops when after a decrease in the value of D _a tt _empt also the last set of adimensional parameters is negative to the verification in point e). In such a last set of adimensional parameters, the optimal one is determined and the maximum acceleration factor compatible with the machine is the last value D _true / D _atte mpt that gave a positive result to the verification in point e).

At the end of this operation, the result can be displayed to the operator by completing step 7).

The operator, in step 8), displays the values of the adimensional parameters provided through the PIE by the UED. Because the dimensionless parameters are in number M, with the numerical values bound by the corresponding actual values, and the physical parameters that can be set in the test chamber are in greater number, and equal to N, it follows that N-M physical parameters can be arbitrarily selected by the operator, or automatically by the machine according to criteria that will depend on the programming of the machine itself. For example, the UED can automatically select the N-M remaining parameters according to a criterion of minimum power consumption of the machine, notifying the operator via the TV of the selection made on the free N-M parameters. The operator is in any case free to change this selection. Therefore, the PIE, through the TV, gives in any case the opportunity to the operator to indicate the values of the N-M remaining parameters, indicating the ranges of minimum and maximum value that for each of the N physical parameters can actually be achieved by the systems and actuators inside the test chamber CAMP. In particular, the UED uses the relationships described above

n _t = _{¾ ¾ ¾} ^½ ... _?c ^½ , k = \,2...M where the values of coefficients A _ik and of the adimensional parameters n _k are known at the end of the procedures already described, and instead the N values of the physical parameters q _i to be set during the tests must be determined. In the above relationships, in a number of M, the N-M arbitrary values selected by the operator are introduced, thus having only M unknown values M' of the physical parameters q _i which are uniquely determined by the UED through calculation algorithms of the prior art. The operator then proceeds to start the test by sending the data of the physical parameters q _i to the control unit UCC, completing step 9).

By way of example only, to clarify how the machine can carry out the similarity tests between the actual conditions and the conditions in the test chamber CAMP, Assume again that the M=7 adimensional parameters which can be determined by the two Procedures described above are: p V {V _ol ) ^{2 / 3} _π 0 _{max π} D m _a / V ₍

Π, = -— , Π , = - ^∑ ≡ ^. _i Π , = - , Π ₄ =—2 °-

I ² <S ³ Δ ' ⁴ m _s / V _ol

where:

p = average contact pressure of the rotating and translating brush;

V = peripheral speed of the rotating and translating brush;

Voi = volume of the test chamber CAMP;

I = radiating power of the lamp or lamps LS.

δ = characteristic dimension of variable particle size of the abrasive powder;

θ,π ₃ χ = maximum temperature of the atmosphere in the test chamber CAMP;

Brnin = minimum temperature of the atmosphere in the test chamber CAMP;

Δ = characteristic period of the cyclic variation of temperature of the atmosphere in the test chamber CAMP;

D = duration of the environmental stress;

m _a = amount of water, in mass, dissolved in the volume of the test chamber

CAMP;

m _s = amount of salt (or other aggressive chemical), in mass, dispersed in the volume of the test chamber CAMP.

Assuming, for example, that the second Procedure stops for an acceleration ratio 20, i.e. one hour of tests would correspond to 20 hours of actual environmental stress, we would have, considering the equality between the actual conditions and the test conditions as regards the adimensional parameter Π ₅ i.e.

(Π5

Then, considering the equality between the actual conditions and the test conditions as regards the adimensional parameter Π ₆ i.e. (nj^^nj /^ATTEMPT

Finally, considering the equality between the actual conditions and the test conditions as regards the adimensional parameter Π ₃ i.e. n ₃ ) _muE = n ₃ ) / _A ATTEMPT "

:20

Assume, for example, that the volume of the atmosphere in the test chamber is comparable with the volume of the actual atmosphere, using material specimens of the same size in the actual and test conditions, the tests in chamber CAMP would indicate the need, in order to keep the physical similarity with respect to the actual conditions, to:

(i) increase, in the tests in chamber CAMP, the abrasion pressure and possibly the particle size of the powder blown compared to the actual conditions, to satisfy the relationship:

(ii) increase the contact speed in the abrasion in the tests in chamber CAMP compared to the actual conditions, to satisfy the relationship: (iii) increase the thermal cycle frequency in the tests in chamber CAMP compared to the actual conditions, to satisfy the relationship:

TRUE = 20

However, group π ₇ excludes the possibility to increase the particle size of the powder, so the similarity of group π ₅ must be ensured only by increasing the contact pressure p and possibly by decreasing the concentration of the aggressive dissolved m _s in the atmosphere. Group ττ ₄ then implies that the humidity must be decreased in the tests as a result of the decrease of concentration of aggressive (salt or other), which can be achieved in the test chamber. Group π ₂ still implies extreme temperatures in the same actual ratio in the day/night cycle, which condition is easy to be obtained through the atmosphere treatment system. Finally, there is group ττι which requires an increase of the radiating power of lamp LS with respect to the solar radiation, having to compensate both the increase in pressure and the increase in the contact sliding speed.

The example shows how the machine of the present invention, using algorithms based on the dimensional analysis and Buckingham's theorem managed by the UED and through the systems and devices described above controlled by the UCC, allows tests to be carried out faster than in the actual operating conditions of the material while maintaining the physical similarity between the actual tests and the tests in chamber CAMP. It is also noted, however, that, as already described above, since in general we have M adimensional parameters at the end of the second Procedure, their value being assigned and equal to that of the actual environmental stresses, and the physical parameters being in the number of N, the operator can freely select N-M physical parameters to be set during the test, keeping the similarity, the desired acceleration factor, and the compatibility with the values of the physical parameters that can be reached by the systems with which the machine is provided. In particular, in the present example, N-M=10-7=3 physical quantities can be arbitrarily set, compatibly with the extreme values of such quantities achievable in the test chamber CAMP by all the systems described. The UED sends to the PIE the request to the operator to indicate the option on the N-M remaining physical parameters to be determined. The operator can then provide the values of the N-M quantities to be arbitrarily selected to the machine, through terminal PIE. Such values allow the UED to send the entire set of physical parameters to be set during the test to the UCC.