REPORT WM_811: JULY 2017

The WIAP® MEMV® system complete with printer. In the picture Jim Peter Widmer.

The V-excitation OV20 on the DV device. Left Sven Widmer, right Jim Peter Widmer.

Left 2pcs. 12 tonnes rollers for WIAP® MEMV® treat.

A complete WIAP® MEMV® system; packed in transport boxes for the external and internal operating custom work order. 

1A) INTRODUCTION

When machining workpieces made of metal, for example during welding are formed in the workpiece voltages. These undesirable stresses remain in the workpiece. Also casting, forging or machining operations can cause permanent tensions. These stresses reduce the load capacity of the workpiece and can have a negative impact, if the workpiece to another, in particular machining is to be subjected. In addition to the impaired dimensional stability even later corrosion resistance of the workpiece may suffer. Known and widespread is the relaxation of workpieces by heating or annealing. But this is time-consuming, energy-consuming and expensive. But it is not without problems also relative to the workpiece, for both the heating and the cooling can easily change its dimensional stability and distort the workpiece. Flame-related workpieces have locally on a state of tension, which communicates with the environment in balance. If this workpiece annealed posed by deformation of a new state of tension and the workpiece is then bent. Subsequent processing is then doing not have a great influence on the straightness. Also formed during annealing scale, which must be removed in a further step back from the workpiece surface. For example, by sandblasting, which can lead to new tensions in the workpiece. Decades ago, it was proposed to reduce the residual stresses induced in the metal by the machining by shaking or vibration of the workpiece again. For this purpose, the workpiece is vibrated on a vibration table or by means of an attached vibration device or vibrated. That may be about 5 to 30 minutes. For larger and heavier workpieces also significantly longer vibration times were known, but this is to be avoided for several reasons. When vibrating the residual stresses over the entire workpiece are brought into balance, not just on the surface. The workpiece can be processed further. The residual stress relaxation is strongest at the beginning of the vibration, but then the effectiveness levels off quite quickly. This process is often associated with several unknowns and requires some materials and expertise or proper instruction. Although it has many advantages over the heat relax.

There are three types of residual stresses. The internal stress of the first type is macroscopically and thermally formed by the fact that the edge and the core of a workpiece after appropriate heating to cool down at different rates. When the internal stresses of the second kind occurs by phase transitions or formation of precipitates to local microstructural tension. The residual stress of the third type dislocations are surrounded by a field of tension. Prerequisite for many proven successful form of stabilization by vibration is a reduction of the macroscopic residual stress in the workpiece, that is, the voltages of the first type. The voltage degradation caused an at least local exceeding of the yield limit of what is affected by various factors. Mention may be high residual stresses, which are superimposed on the rectified load voltage or local increases of load and residual stresses due to notches, cracks or flaws. The difficulty is that the internal stresses of a workpiece are hardly measurable yet. Especially since the workpiece for this purpose must not be destroyed. Instead, side effects are measured. Although one example has tried to X-ray workpieces, but that can be seen only near-surface areas. In metal processing factories and workshops this suitable rather for testing laboratories approaches are hardly feasible. It has also tried to understand with the stress relief holes, but allows best only conclusions about the well area. It has also been tried with limited success, to draw conclusions as to the progress of the vibration relaxation by measuring the changing power consumption of the electric motor used to drive an eccentric. This too is ultimately very little meaningful and draw conclusions about the entire component without zones to have information. Even the application of a sensor on the workpiece does not really lead to reliable results. On the basis of these findings, the new WIAP® MEMV® sets the object to provide the measurement of the residual stress of workpieces that can be used in vibration relaxation, is practicable for metal processing operations, and leads to reliable measurement results methods.

Thanks to the obtained by the WIAP® MEMV® process values ​​with respect to the internal stress of workpieces can be the subsequent relaxation. That is, to perform the voltage degradation and dimensional stabilization of the workpieces and better targeted. This is especially true for the vibration relaxation. Mainly for testing purposes, this measuring process but also commonly used for the detection of residual stresses, of course even with workpieces that have been relaxed in other ways. It has been always thought that a workpiece thereby vibrate uniformly, that is, at every point of its surface and its volume approximately equal. Through many trials with the WIAP® MEMV® process was recognized, however, that this is not the case. Actually arising in the vibration relief regions in which the material of the workpiece respond differently to the induced vibration. The G-value corresponds to 1G = 9.81 m/s² is the same everywhere. Rather, these shifts and G-value on the axis of vibration is variously changed according to the prevailing there in each case, different residual stresses of the respective workpiece. This is detected accurately with the new WIAP® MEMV® method, which can be used to significantly better results by the relaxation vibration relaxation. Both the time and the energy consumption can also be greatly reduced by more targeted work.

1B) WHAT CAN MOVE WIAP DATES WITH VIBRATION

In the new method, the WIAP® MEMV® is measured displacements that the change per measurement point moves, that is, at the beginning has, according to the arrangement of the V-pathogen in the axial direction for example 0 degrees or 45 degrees or 90 degrees, a value is detected. Thereafter, the change of the G value at each measurement point between before and after, and within a few minutes, confirming the statement which is already in reports that the largest stress relief takes place at the first duty cycles and the changes migrates differently depending on the measurement point and axis. The conventional vibration relax, where simply an axial direction is excited, obtains only a partial success because since the WIAP all directions measures and stimulates it is recognized that the Y direction and Z direction vibrate, that the axial direction X has no stimulation. We rotate 90 degrees, we encourage the Y axis and X axis, gets the Z axis virtually no suggestions. We rotate 45 degrees, passes through the that depending on the mass fraction ratio of the length Z to the width X and the angle of the example can not be 30 degrees, even 3 axes can be simultaneously excited, which is interesting in the arrangement that the displacement takes place most extensively in the case, which in turn means that we hitherto always vibrated only 0 or 90 degrees, thereby still not achieved a sufficient axis. In the hundreds of components, that we have now measured in practice, which could be well recognized.

The newest V exciter NV20 can go up slowly from the lowest speed to 100% eccentric step and automatically adjust the % level during startup. This model has the great advantage that it can stimulate species in one part of the adjustment % more load cycle, that this device can obtain again more than anything Conventional. Along with the axis directions and the eccentric adjustment will be achieved much more. And the double V pathogen is still available at the same time, meaning that the same not only 2D is possible with change of direction, but 3D double change of direction, the whole topic Metal relax with vibration also highlight a very reliable processing kind. What good is it to measure stresses in the surface, but if it also has component voltages deep? How to measure for these? Below measurements of annealed and non-annealed a 12 tons roller subject to G shift, relaxed and tested with the WIAP® MEMV® method.