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Approach for investigation of a failure case

Tooth fracture
Tooth fracture

As an independent engineering company, we investigate machine failures in order to identify the related root causes and describe proper counter measures. Most of our cases are related to the following applications:

  • Automotive
  • Railway
  • Agricultural and construction equipment
  • Industrial drives
  • Mining
  • Rolling mills
  • Water turbines
  • Wind energy converters

Inspection / Endoscopy

Endoskopuntersuchung Windenergieanlage

At the beginning of the investigation, typically the whole technical system needs to be inspected. This leads to a first impression on which parts are affected, what kind of damages have to be faced and which parts need to be replaced. Apart from that, inspection on site allows precise identification of operation conditions and ensures that all traces of usage can be identified and considered later on.
Especially in case of large or hardly accessible plants such as large industrial gearboxes, wind energy converters etc., it might be useful to do the inspection by means of endoscopy. For this purpose, endoscopes with 3 m length and two-directional swiveling sensor is available at Elgeti Engineering which allows detailed investigation avoiding the necessity of dismantling the related aggregate. A regular gearbox endoscopy can also be part of preventive maintenance, e. g. in order to detect damaged bearings or gears or extraordinary wear at an early stage.

Identification of failed part

Getriebeschaden einer Windenergieanlage
Fracture of inner ring of cylindrical roller bearing

Subsequent to identification of the failed part, its damage pattern and traces of usage will be detected by means of visual inspection. Based on documented findings, one can decide which kind of further investigations are necessary to deeply understand the root cause of the failure.

Fracture face investigation

Schwingbruch eines Innenrings
Fatigue fracture

In case of this cylindrical roller bearing, fracture of the inner ring has been detected. Fracture face investigation led to identification of fatigue as relevant damage mechanism and to discovery of the crack origin. Both contribute valuable information to description and understanding of the damage root cause.
Fracture face investigation is typically carried out by means of optical microscopy or scanned electron microscopy.

Material analysis / Metallography

Structure of a bearing

By means of metallographic investigation of the related parts, conspicuous microstructure, internal defects, inclusions etc. can be detected. Apart from grain size and degree of cleanliness, both chemical composition and hardness are part of the investigation.
In our materials laboratory, we have the option to take material samples even out of larger parts without thermal influences and to prepare them for metallographic assessment. Typically, this is done by means of optical microscopy.


Finite Elemente Methode
Finite Elements Analysis

Possible scenarios or responses to certain kinds of loading can be studied by means of finite elements analysis considering different load cases. Here, especially stress distribution and deflections but also vibrations and thermal behaviour will be considered.
As a matter of course, it can be verified by means of structural analysis whether a part is strong enough for regular operation conditions. In such cases, analytic strength assessment according to relevant standards will be carried out subsequent to numerical simulation.


Bearing test rig

In order to reproduce very special damage mechanisms, extreme conditions can be simulated on our bearing test benches. E. g. the influences of poor lubrication or contamination on lifetime of a part or on the damage pattern itself can be investigated in order to verify possible damage hypothesis. Such investigations are also helpful during verification of counter measures.

Measurements of operation loads and vibrations

Strain gauge

In some particular cases, it is necessary to measure loads and vibration during regular operation. For this purpose one uses different kinds of sensors such as strain gauges, piezo sensors etc. which have to be applied on the related parts.

Final assessment and definition of valid counteractions

If the executed investigations led to a clear result, the related scenario will be described and explained in a detailed report. After that, the gathered deep comprehension of the relevant issues will be used to define valid counteractions in order to prevent further damages of the same kind.