JP6032045B2 - Fatigue evaluation method for spindle - Google Patents

Description

  The present invention relates to a spindle fatigue evaluation method.

  A rolling roll of a rolling mill is connected and driven by a motor shaft and a spindle of a driving motor installed at a distant position (for example, Patent Document 1).

  If fatigue is increased due to repeated stress applied to the spindle, it may cause equipment failure, etc., so it is necessary to accurately evaluate the fatigue level of the spindle.

  As a conventional spindle fatigue evaluation method, as shown in FIG. 5, the rolling roll 1, the roll side cross pin 2, the spindle 3, the motor side cross pin 4 and the motor shaft 5 of the rolling mill are modeled as simple elastic bodies and driven. A technique for diagnosing spindle fatigue damage by converting a motor current value into a torque is known.

  Conventionally, this problem has been dealt with by directly measuring the torque of the electric motor and considering it as the torque generated in the spindle. In this method, however, the current value of the drive motor is mechanically coupled to convert the torque. The problem is that vibration cannot be measured directly.

  Further, as shown in FIG. 5, the rolling roll 1, the roll side cross pin 2, the spindle 3, the motor side cross pin 4 and the motor shaft 5 are modeled as simple elastic bodies, and the torque of each spindle is calculated from the result of torque measurement, and the spindle A technique for diagnosing fatigue damage is known.

  However, the conventional technology has a problem in that accurate life evaluation cannot be performed because high-frequency vibration of several hundreds to several kHz generated at the fastening portion of the spindle is not considered in the model.

In particular, the fatigue damage degree is an expression [Equation 1] explaining the calculation of the fatigue damage degree, an expression [Equation 2] explaining the case where the contribution rate of the fatigue damage degree is divided in the frequency band, and the stress amplitude as shown in FIG. Since it depends on the size and the frequency of occurrence, if the vibration generated in the high frequency range cannot be taken into account, the estimated life will give a result that is estimated to be lower than the actual remaining life. Therefore, a method for calculating the degree of fatigue damage while predicting vibrations in a high frequency range online is important.

  Furthermore, in recent years, a technique for accurately modeling the whole by formulating a drive system by a finite element method and calculating the weakest part of each element from a given torque has been known.

  However, the above-described conventional technique has a problem that the calculation model is large and it is impossible to perform online calculation one by one based on actually measured data.

JP 2002-192208 A

  The object of the present invention is to solve the above-mentioned problems and to consider vibrations (hundreds of Hz to several kHz) generated at a fastening part (spindle coupling element) important for spindle deterioration management. The object is to provide a spindle fatigue evaluation method applicable to the remaining life evaluation.

  The spindle fatigue level evaluation method of the present invention, which has been made to solve the above-mentioned problems, is generated in each machine element from a torque measurement step of actually measuring torque data using torque measurement means installed on the spindle, and the torque results. The torque estimation process and the ratio of the torque and weakest part stress in each machine element are calculated in advance, and the torque data estimated in the torque estimation process and the calculated ratio are used to generate the weakest part of each spindle part. It is characterized by having a cumulative fatigue damage degree calculating step of calculating a cumulative fatigue damage degree by calculating a stress frequency from the generated stress by a rain flow method after obtaining the stress.

  According to the second aspect of the present invention, in the torque estimation step according to the first aspect, the coupled vibration represented by the equation of motion [Equation 3] generalizing the torsional vibration of the spindle in consideration of the vibration between the intermediate cross pins. Torque estimation is performed using a Kalman filter on the discrete time state space expression [Equation 5] that discretizes the equation and reflects the measurement of the torque monitor.

  The invention described in claim 3 is characterized in that the ratio is calculated in advance by the finite element method in the calculation of the torque and the weakest part described in claim 1.

  According to a fourth aspect of the present invention, in the spindle fatigue level evaluation method according to the first aspect, the torque measurement means is a non-contact power supply type permanent torque monitor.

  In the spindle fatigue level evaluation method according to the present invention, the torque generated in each machine element is estimated from the actual torque at the measurement point, and the generated stress at the weakest part in each machine element and part is further estimated to obtain the time series. By calculating the stress frequency from the data and calculating the cumulative fatigue damage level, it is possible to evaluate the fatigue level of each part of the spindle that could not be captured online. That is, according to the present invention, as shown in FIG. 3, it is applicable to the evaluation of the remaining lifetime of a practical device by using a model that takes into account a part (spindle coupling element) important for spindle deterioration management. The fatigue level can be evaluated with accuracy.

It is explanatory drawing of a rolling mill. It is principal part explanatory drawing. It is an elastic body model explaining the present invention. It is a figure which shows the calculation flow of this invention. It is an elastic body model explaining a prior art. It is a figure explaining the number of repetitions and stress amplitude.

  Preferred embodiments of the present invention are shown below. As shown in FIG. 1, a rolling roll 1 of a rolling mill is connected to a motor shaft of a drive motor 6 by a spindle 3.

  In this embodiment, as shown in FIG. 2, a non-contact power supply type torque monitor 7 is installed on the spindle, and the torque data of the spindle is continuously measured. The actually measured torque data is sent to a personal computer for analysis through a torque estimation process. In FIG. 2, 8 indicates a coupling, and 9 indicates a journal bearing.

The torque estimation process is a process of estimating the torque generated in each machine element from the actual torque at the measurement site, and generalized the torsional vibration of the spindle considering the vibration between the intermediate cross pins shown in FIG. Equation of motion [Equation 3]
Continuous-time state space expression [Equation 4] considering observations,
A state space expression [5] that is made discrete.
Can be used. This equation of motion [Equation 3] is an equation of motion [Equation 6] which is a conventional spindle model.
Unlike the above, the rigidity of the intermediate cross pin can be expressed. For this reason, it is possible to represent torsional vibration with higher accuracy. The continuous-time state-space expression [Equation 4] can increase the rank of the observation matrix C by measuring the intermediate vibration of the spindle. By using this characteristic, the discretized state space expression [Equation 5] can accurately estimate the angle and angular velocity of the intermediate position by applying a Kalman filter which is a state estimation method.

If the angle / angular velocity of the intermediate position estimated by the Kalman filter can be calculated, it is possible to estimate the torque by using the torsional rigidity and the angle difference between the elements shown in Equation [7].

  In the personal computer for analysis, the stress ratio data of the weakest part and torque point of each spindle part is calculated and input. The method for obtaining the weakest part of each spindle component is not particularly limited, but it is possible to use a method by specifying a stress concentration location by a finite element method, an actual measurement by a strain gauge, or the like. Typical examples of the weakest part include points A to E in FIG. 2 (A: slipper metal, B: throat, C and E: journal bearing, D: stress concentration portion).

  In the personal computer for analysis, the generated stress of each part of the spindle is obtained from the stress ratio data and the torque data actually measured by the torque monitor, and the stress frequency is calculated from the generated stress by the rain flow method and accumulated. Calculate the degree of fatigue damage.

  In this way, the stress ratio between each part of the spindle and the torque measurement point is calculated in advance, and the generated stress of each part of the spindle is obtained from the torque data actually measured in the torque measurement process and the calculated stress ratio. Thus, by calculating the stress frequency from the generated stress by the rain flow method and calculating the cumulative fatigue damage degree, it is possible to evaluate the fatigue level of each spindle component that could not be captured in the past. That is, according to the present invention, as shown in FIG. 3, it is applicable to the evaluation of the remaining lifetime of a practical device by using a model that takes into account a part (spindle coupling element) important for spindle deterioration management. The fatigue level can be evaluated with accuracy. FIG. 4 shows this series of calculation / estimation procedures. First, torque is measured with a torque monitor. Next, the angle and angular velocity are estimated by a Kalman filter using the pre-calculated discrete-time state space expression. Calculate the torque generated inside based on the estimated angle and angular velocity. Next, the stress at the weakest point is calculated by applying a stress ratio from the torque generated inside. The fatigue damage degree is calculated by the rainflow method from the stress calculation value obtained every moment in this way.

  The calculated cumulative fatigue damage degree is input to the spindle management table so that deterioration tendency management of points A to E can be performed collectively. In addition, data such as rolling time, number of passes, rolling number, number of rotations, rolling load, torque current, plate thickness before rolling, plate thickness after rolling, etc. are also input to the spindle management table via the process controller. Trends can be easily associated with operating conditions.

DESCRIPTION OF SYMBOLS 1 Roll of rolling mill 2 Roll side cross pin 3 Spindle 4 Motor side cross pin 5 Motor shaft 6 Drive motor 7 Torque monitor 8 Coupling 9 Journal bearing

Claims (4)

A torque measurement step of actually measuring torque data using torque measurement means installed on the spindle;
Torque estimation process generated in each machine element from the torque results, the ratio of the torque and the weakest part stress in each machine element is calculated in advance, from the torque data estimated in the torque estimation process and the calculated ratio, After obtaining the generated stress at the weakest part of each spindle part,
A spindle fatigue level evaluation method comprising a cumulative fatigue damage level calculation step of calculating a cumulative fatigue damage level by calculating a stress frequency from the generated stress by a rain flow method. In the torque estimation process, the coupled vibration equation expressed by the equation of motion [Equation 1] that generalizes the torsional vibration of the spindle, taking into account the vibration between the intermediate cross pins, was discretized to reflect the measurement of the torque monitor. 2. The spindle fatigue level evaluation method according to claim 1, wherein torque estimation is performed using a Kalman filter on the discrete-time state space expression [Equation 2].
  2. The method for evaluating the fatigue level of a spindle according to claim 1, wherein a ratio is obtained in advance by a finite element method in calculating the torque and the weakest part according to claim 1.   2. The spindle fatigue level evaluation method according to claim 1, wherein the torque measurement means is a non-contact power supply type permanent torque monitor.