STRESS MONITORING DURING THE OPERATION OF A COMPONENT

Abstract

A method for determining operating stress on a component during operation includes recording measured values for predefined measurement variables not equal to the operating stress on the component to be determined, during operation of the component for at least n≧2 predefined different operating modes, determining m≧2 and m≦n effect operands W.sub.1 to W.sub.m, in dependence on the measured values for each operating mode, recording a measured value of operating stress after operating the component for n operating modes, and setting up and solving an equation system having n equations to obtain m weighting factors a.sub.1 to a.sub.m weighting the m effect operands. A sum of weighted effect operands for each operating mode is equal to the measured value of the operating stress recorded for the operating mode. A calculation rule determining the operating stress during operation of the component uses the weighting factors.

Claims

1-10. (canceled)

11. A method for determining an operating stress of a component during operation of the component comprises the following steps: a. recording measured values for predefined measurement variables during operation of the component in an adjustment phase for at least n different predefined operating modes, where n≧2, the measurement variables not being equal to the operating stress of the component to be determined; b. determining m effect operands W.sub.1 to W.sub.m where m≦2 and m≦n in predefined dependence on the measured values for each of the n operating modes; c. recording a measured value of the operating stress after operation of the component for each of the n operating modes; d. setting up and solving a system of equations having n equations to obtain m weighting factors a.sub.1 to a.sub.m weighting the m effect operands W.sub.1 to W.sub.m, a sum of the weighted effect operands for each operating mode being equal to the measured value of the operating stress recorded for the corresponding operating mode; and e. providing a calculation rule for determining the operating stress during operation of the component in an operating phase using the obtained weighting factors.

12. The method according to claim 11, which further comprises the following steps following step e: f. recording measured values for the predefined measurement variables during operation of the component in the operating phase, the measurement variables not being equal to the operating stress of the component to be determined; g. determining the effect operands W.sub.1 to W.sub.m in predefined dependence on the measured values; and h. determining the operating stress of the component during operation of the component by using the calculation rule with the obtained weighting factors.

13. The method according to claim 11, which further comprises, before step f, exchanging the component with a component from a common group of identical components.

14. The method according to claim 11, which further comprises solving the system of equations set up in step d by using equivalence transformations.

15. The method according to claim 11, which further comprises outputting the operating stress of the component determined in step h during operation of the component.

16. The method according to claim 11, wherein the component is a brake lining of a rail vehicle.

17. The method according to claim 16, wherein the predefined measurement variables are at least one of time or braking distance or pressure in a brake cylinder of a compressed air brake of the rail vehicle.

18. The method according to claim 17, which further comprises obtaining three effect operands including: a first effect operand obtained from an integral of the square of the pressure in the brake cylinder of the compressed air brake of the rail vehicle over the braking distance of the rail vehicle, a second effect operand obtained from an integral of a multiplication of a speed of the rail vehicle and the pressure in the brake cylinder of the compressed air brake of the rail vehicle over the braking distance of the rail vehicle, and a third effect operand obtained from an integral of the pressure in the brake cylinder of the compressed air brake of the rail vehicle over the braking distance of the rail vehicle.

19. The method according to claim 11, which further comprises determining the effect operands by using mathematical operations exclusively using the recorded measured values for the predefined measurement variables and predefined constants as operands.

20. A rail vehicle, comprising: at least one non-transitory computer-readable medium with a computer program product stored thereon, that when executed by a processor, performs the steps of claim 11.

Description

[0035] The invention allows numerous embodiments. It will be explained in more detail with reference to the following example but should not be considered to be restricted to this.

[0036] A manufacturer of rail vehicles manufactures a first one of a fleet of identically constructed rail vehicles. It comprises a compressed-air-operated braking system. After completion, it is subjected to various test runs on a test section.

[0037] In this case, it is operated in various operating modes. In an adjustment phase in order to determine an operating stress of a brake lining, measured values for predefined measurement variables are initially recorded for each operating mode. The measurement variables are in this case not equal to the operating stress of the brake lining to be determined. The reduction in the thickness of the brake lining after each operation of the rail vehicle in the predefined operating modes is recorded here as the operating stress of the brake lining. Further examples for operating stresses can be: the abrasion or the groove depth of a brake disk, but also the instantaneous operating temperature of the brake disk. On the other hand, for example, the instantaneous vehicle speed, the braking distance or the time as well as the instantaneous pressure in a brake cylinder are predefined as measurement variables during operation.

[0038] Firstly, the vehicle is operated during the adjustment phase therefore in a predefined first operating mode, during operation the measured values for the predefined influencing factors are recorded and after operation the operating stress is measured. During the adjustment phase the vehicle is then operated in another predefined second operating mode different from the first operating mode, during operation the measured values for the predefined influencing factors are recorded and after operation the operating stress is measured.

[0039] After operating the vehicle in three different operating modes, three measured values are now provided for the reduction in the thickness of the brake lining as well as a plurality of measured values for the instantaneous vehicle speed v and for the instantaneous brake cylinder pressure p for each operating mode. The instantaneous vehicle speed v and the instantaneous brake cylinder pressure p are in this case functions of the braking distance s (p=p(s) and p=p(s)) or the time t (p=p(t) and p=p(t)).

[0040] Also in this case at most three effect operands are determined in predefined dependence on the measured values for the instantaneous vehicle speed v and for the instantaneous brake cylinder pressure p for each of the three operating modes. Here the effect operands are obtained as:

[00001]$W_1={\int }_0^s.Math.p^2.Math.\mathrm{ds};$$W_s={\int }_0^s.Math.\left(v.Math.p\right).Math.\mathrm{ds};$$W_3={\int }_0^s.Math.\mathrm{pds}.$

[0041] Now an equation to calculate the operating stress for each operating mode can be set up. To this end the respective effect operands W.sub.1 to W.sub.3 are weighted with weighting factors a.sub.1 to a.sub.3 for each of the three operating modes in such a manner that the decrease in the thickness of the brake lining recorded directly for each operating mode is equal to a sum of the weighted effect operands. The decrease in the thickness of the brake lining is hereinafter designated by z. In general therefore for each operating mode it should hold that:

z=a.sub.1*W.sub.1+a.sub.2*W.sub.2+a.sub.2*W.sub.2.

[0042] As already explained above, for n operating modes accordingly a system of equations is generally obtained:

a.sub.1*W.sub.11+a.sub.2*W.sub.12+ . . . +a.sub.n*W.sub.1m=z.sub.1

a.sub.1*W.sub.21+a.sub.2*W.sub.22+ . . . +a.sub.n*W.sub.2m=z.sub.2

a.sub.1*W.sub.n1+a.sub.2*W.sub.n2+ . . . +a.sub.n*W.sub.nm=z.sub.n

and in the present case:

[00002]$z_1=a_1.Math.{\int }_0^{s_1}.Math.p_1^2.Math.{\mathrm{ds}}_1+a_2.Math.{\int }_0^{s_1}.Math.\left(v_1.Math.p_1\right).Math.{\mathrm{ds}}_1+a_3.Math.{\int }_0^{s_1}.Math.p_1.Math.{\mathrm{ds}}_1$$z_2=a_1.Math.{\int }_0^{s_2}.Math.p_2^2.Math.{\mathrm{ds}}_2+a_2.Math.{\int }_0^{s_2}.Math.\left(v_2.Math.p_2\right).Math.{\mathrm{ds}}_2+a_3.Math.{\int }_0^{s_2}.Math.p_2.Math.{\mathrm{ds}}_2$$z_3=a_1.Math.{\int }_0^{s_3}.Math.p_3^2.Math.{\mathrm{ds}}_3+a_2.Math.{\int }_0^{s_3}.Math.\left(v_3.Math.p_3\right).Math.{\mathrm{ds}}_3+a_3.Math.{\int }_0^{s_3}.Math.p_3.Math.{\mathrm{ds}}_3.$

[0043] Here the three different operating modes were also taken into account in the subscripts. The first operating mode here provided a braking with a predefined small jolt and a predefined mean braking acceleration from a mean predefined speed to a standstill. The braking required the braking distance s.sub.1. This resulted in a decrease in the thickness of the brake disk z.sub.1. The second operating mode here provided a braking with a predefined large jolt and a predefined large braking acceleration from a high predefined speed to a standstill. The braking required the braking distance s.sub.2 and resulted in a decrease in the thickness of the brake disk of z.sub.2. The third operating mode here on the other hand provided a braking with a predefined large jolt and a predefined large braking acceleration from a low predefined speed to a standstill which required a braking distance s.sub.3 and resulted in a decrease in the thickness of the brake disk of z.sub.3. The instantaneous speed for the braking of the first operating mode was designated by v.sub.1. The instantaneous pressure in the brake cylinder for the braking of the first operating mode was designated by p.sub.1. Similarly the instantaneous speeds and the instantaneous brake pressures for the braking of the second and third operating mode are designated by v.sub.2 or v.sub.3 and p.sub.2 or p.sub.3 respectively.

[0044] However, an operating mode can also comprise a plurality of identical decelerations. The vehicle is then accelerated multiple times to the predefined speed and decelerated in a predefined manner. The operating stress, here therefore the decrease in the thickness of the brake lining, is only measured thereafter. A higher significance is advantageous. If x were the number of successively executed decelerations per operating mode, where x is a natural number greater than one, without further adaptation of the subscripts the equations of the system of equations would appear as follows:

[00003]$Z_n=a_n.Math.\underset{i=1}{\overset{x}{.Math.}}.Math.{\int }_0^{s_n}.Math.p_n^2.Math.{\mathrm{ds}}_n+a_n.Math.\underset{i=1}{\overset{x}{.Math.}}.Math.{\int }_0^{s_n}.Math.\left(v_n.Math.p_n\right).Math.{\mathrm{ds}}_n+a_n.Math.\underset{i=1}{\overset{x}{.Math.}}.Math.{\int }_0^{s_n}.Math.p_n.Math.{\mathrm{ds}}_n.$

[0045] In order to determine the weighting factors, the system of equations set up above is now solved so that values for the weighting factors a.sub.1 to a.sub.3 are obtained.

[0046] The values for the weighting factors as well as the said calculation rules are then stored in a computer-readable data carrier of each rail vehicle of the fleet of structurally identical rail vehicles of the manufacturer. After delivery of the rail vehicles to the customer, these are put into operation. The operating phase of a rail vehicle comprises the now-following runs in regular operation of the customer including the operation of the brakes as intended.

[0047] The rail vehicles are each fitted with different but structurally identical brakes. Nevertheless, the operating stress can be determined with the stored data and with the measured values for the predefined measurement variables recorded during operation in the operating phase. A replacement of the brake linings with structurally identical brake linings is also irrelevant.

[0048] In the operating phase of one of the vehicles following the adjustment phase, measured values for the predefined measurement variables are firstly recorded during operation of the component, which measurement variables are not equal to the operating stress of the component to be determined. The effect operands W.sub.1 to W.sub.m are then determined in predefined dependence on the measured values and the operating stress of the component during operation of the component is determined by means of the provided calculation rule using the weighting factors obtained. To this end the calculation rules and the weighting factors are read out from the memory or the computer-readable data carrier for further processing and processed in the evaluation unit.

[0049] Advantages of the invention are in particular that the operating stress of the component during operation of the component in an operating phase can be estimated indirectly by the method according to the invention without directly recording this, specifically when a measurement of the operating stress during operation is not possible, the operating stress therefore cannot be recorded directly. Measurements of the abrasion or influencing factors as predefined measurement variables during operation of the component are sufficient for this. A model of the operating stress forms the basis thereof. During operation of the component in the operating phase, the method according to the invention is therefore free from a direct recording of the operating stress. The model maps the influence of individual effect operands on the operating stress in various operating modes. In order to determine the parameters, it is merely necessary to run through at least two different operating modes in an adjustment phase and distinguish the measured values for the predefined measurement variables and evaluate according to the model. The model is described mathematically by the predefined calculation rule. This is made possible by the separation of the adjustment phase from the operating phase. In the adjustment phase the model is created and stored, in the operating phase this model is then used.

[0050] A signal, for example, an alarm can be output when a predefined limiting value for the operating stress is exceeded and the vehicle driver can thus be warned in good time of any failure of the component. Instead of the output of a signal, the determined operating stress can also be further processed, for example, for planning inspections or even for adaptation of the inspection intervals. Furthermore, it is possible to estimate the lifetime of the component still to be expected and to implement a quasi-continuous stress monitoring over the lifetime of the component.

[0051] The influence of environmental conditions, for example, climate can also be taken into account by means of the empirical determination of the weighting factors of the calculation rule. Since the component can be operated as intended under different environmental conditions, measured values for external conditions such as, for example, for air temperature or air humidity of the surroundings of the component can also be recorded and the effect operands can be determined accordingly also in dependence on the recorded measured values for the environmental conditions.

[0052] The determined calculation rule is valid for components from a group of structurally identical components in structurally identical vehicles and can be expanded to generic vehicles. Thus, only an adjustment phase is required. This is primarily advantageous for operating stresses which can only be recorded very expensively. The operation of the component in different operating modes during the adjustment phase itself also need not be carried out with the same component but merely with a component from a group of structurally identical components from which the component from the operating phase then originates.

[0053] Optimal operating modes for the component can also be determined with the method according to the invention. To this end the method comprises a corresponding process step following process step e.

[0054] The different operating stress of components of different manufacturers can thus also be easily determined.

[0055] Since the operating modes can also only differ marginally, for example, in distance, time duration or environmental conditions, no particular operating conditions need be simulated during the adjustment phase, in particular no special run programs need be executed. It is sufficient to monitor the corresponding measured values during usual maintenance trips.