Reactive Engineering, Countering Durability Issue at the Later Stage of Product Development

Is your product subjected to vibration environment during its service life? Does your product need to undergo vibration/durability test during prototype testing? Do you frequently encounter issue during prototype vibration/durability testing?

When you find a design problem in your product during prototype durability test that related to vibration environment (broken part, excessive vibration, annoying sound, etc):

How many trials do you need to solve it?
How many prototypes are fabricated for re-testing?
How much manpower need to be deployed?
How long the product launching need to be delayed?

If we convert all the answers to above questions into quantitative cost, then summarize up, we will find the total additional cost due to a specific product durability issue. Furthermore, if we calculate the cost if the issue can be identified in the earlier phase of development and compare it with the cost if the issue happens during prototype testing, we will find that having product durability issue at the later stage of development will cost us much higher.

`Credit: Siemens Digital Industries Software`

Many industries are still running "trial and error" to find solution of vibration/durability issue during prototype testing. This option may be taken due to few reasons:

Cost

Running more systematic approach to find solution of vibration/durability issue may need some investment in terms of hardware, software, and also infrastructure. If the total prototyping cost is much smaller compared to this investment cost, may not justify the investment at the management point of view.

Manpower

Deploying more systematic approach to find solution of vibration/durability issue may also need talent with specific skill and experience in vibration testing, measurement, and analysis. It is not a secret anymore that this specific talent may not be available or easily find in the talent market. Meanwhile, developing the available talent may take time and may not be an easy option as well.

Why is it not easy to get solution on vibration/durability issue by running "trial and error"?

Having a vibration/durability issue is like having a person mad at us without telling us what or why is really wrong. If we understand the character of this person (what he/she likes or dislikes, how he/she wants or doesn't want to be treated, etc), then we will immediately understand the situation, and know how to control and how to response.

Therefore, having the same analogy, understanding the dynamic characteristic of our product will give us significant advantage on finding the solution for vibration/durability issue. The Dynamic Characteristic of our product will provide us a lot of insights, the big picture on how our product will behave due to specific type of vibration environment. Furthermore, if we obtain the dynamic characteristic prior to the vibration/durability test, we even may be able to predict the response of our product, prior to the test execution. Even further, by having sufficient additional database, predicting the life of some component may not be impossible as well.

What is this Dynamic Characteristics actually?

Structural Dynamic Characteristics is commonly defined a set of resonance frequencies, damping values and vibration mode shapes that represent the characteristic of our product structure. Understanding the Dynamic Characteristics of our product may give us idea on how to resolve the issue.

What are needed to obtain the Dynamic Characteristics?

Infrastructure

Depending on the type of our structure, and also the actual vibration environment during its service life, we may need special testing bench to run Frequency Response Function (FRF) Testing. For some industry, such as Aerospace and Satellite, we may need to run FRF Testing at Free-free Condition.

Hardware

In order to be able to run FRF Testing, we will also need Data Acquisition System (DAq). The size of a DAq will be depending on number of channels needed. Number of channels needed will be depending on number of sensors. The type of sensors we use will also affect the type of signal conditioner module to be integrated in our DAq. Those type of sensors include Accelerometer, Force Sensor, Strain Gauge, etc. Having a universal DAq module may provide us more flexibility during FRF Testing. The number of sensors needed will be depending on the size of the structure to be tested, how many modes of interest, frequency range, etc

Other than DAq, we will also need exciter(s). Exciter is needed to provide the excitation force which will be propagated to entire body of structure. There are two common exciters normally used, which are Vibration Shaker and Impact Hammer. Vibration shaker is normally used for relatively small structure, while Impact Hammer is mainly used for relatively large structure. Impact Hammer is quite portable, makes it easy to deploy without relatively complex testing bench setup. Meanwhile, many engineers prefer to use Vibration Shaker due to its good testing repeatability. But due to its size, it may not be easy to use Vibration Shaker for large structure. In order to overcome this, in some cases, multiple units of vibration shakers are used, to form a Multi Input Multi Output (MIMO) FRF Testing.

Software

In order to run FRF Testing and obtain the Dynamic Characteristics of our structure, the software needs to include the module to run FRF Testing. Software modules for running FRF Testing with Vibration Shaker and Impact Hammer are likely to be different. For FRF Testing with Impact Hammer, the DAq will be acting more like just data logger with certain triggering setup. For FRF Testing with Vibration Shaker, commonly the software module provides options for us to choose either Random Excitation or Sine Excitation.

Other than FRF Testing module, the software also needs the capability of Modal Analysis. This is a post-processing module where the FRF curves will be calculated to produce vibration modes.

Do you still run trial and error during prototype vibration/durability testing?

With our expertise and experience in durability and vibration, we are able to guide your team step by step, developing the systematic approach that is applicable for most of the cases that you encounter. Contact us by filling the below form.