Correctly define the problem

We were informed about the severe cracks in the parts reported by leading agricultural OEM in India and team has to report back as soon as the issue escalate further. Warranty hazards in a structural members are very severe due to their life threatening nature. Up on investigating, there were the signs of severe damage, such as an accidental situation. Service teams are creating panic situations; however, engineers should stay calm before reaching to any conclusion in hastened way.

Failed part

Try to figure out the source of problem

There might be the several reasons, such as improper usage, accidental condition, applying excessive torque to tighten, sudden deflation of air resulting in imbalance of vehicle.

Physical presence at the site of application is highly appreciated to understanding the loading conditions and usage patterns.

Conditions under which your part failed

After you reach at the site and the usage patterns are vivid to you, try to access the capture the maximum information in the form of pictures, videos, notes. Since this is your running part, being supplied throughout the years. The sudden failures are the result of change, here ‘’change’’ is the key thing which you have to co-relate. Whether it is the new area where vehicle was never sold or tested or the evolution of new application or change in application or change in mating part or change in vehicle model, where your part was never tested.

Check with the mating part

Here in my part there are the three possibilities: Change in tire size or change in axle hub design or change in vehicle model.

Up on conclusion it was found that the customer has changed the Hub-axle design as VA-VE initiative without intimation to the supplier, whose part is being suffered from severe failures.

Mating part

Any change in mating part would adversely affect the function of your part

The hub design has been changed to the extent that should have not been there, New engineers take initiatives of VA-VE in the greed of appreciation in terms of money and their idea eventually get approved by their in-experienced managers without understanding the severity of the function. Which therefore imparting pressure to modify the mating part, that otherwise makes no sense.

Old Hub Design New Hub Design

Use of bench marking techniques

By blue matching with the mating part, the problem becomes more vivid, as the definition of pressure works here (force acting on per unit area). The contact area here is negligible and pressure/load is same as in the case of old mating part, causing the more stress concentration and weakening of the area.

Blue impression with the mating part

Arresting the problem

More concrete is the foundation of your analysis, more accurate is the way out to arrest the problem. Here as we can see, the problem is more vivid after the analysis. The reduced contact is the key area to focus and with the help of cad data of the changed hub axle, we have further taken up the analysis at our work premises and ask the customer team for sometime and committed to come up with detailed analysis and final conclusion.

Brainstorming to find out the final solution

Once upon studying and mating the cad model, the picture becomes as it is like blue matching with the physical part, as you can see the yellow area is the key contact.

With the series of iterations and brainstorming sessions we have developed the concept design with increased contact area.

Now, next challenge is to validate its effectiveness.

Contact area study - Old design vs New design

Take the help of engineering techniques / Finite element analysis

To validate the effectiveness of modification, there are two methods - the first and most accurate is to physically test the sample under given loading conditions, which is the most accurate, however longest time taking.

Second is the, FEA method is effective to just have a brief comparison of stress levels of both conditions, low realibility, however quickest and easiest.

Lots of experience required to choose such methods, risky for people with little know how.

FEA study for Stress analysis - Old design vs New design

Solid foundation of your analysis is the key to success / Not plan A or B

As the description predict, the more concrete your foundation of analysis is, more reliable your solution is. Realistic people doesn't need plan B or further plans, it is the speculators who are not confident on their way of working, therefore having lots of inconsistency around them and looking for way out to eascape in the dark.

Here in this case, after successfully analyzing the design via FEA method, i have chosen to proceed with the tooled up samples for physical validation on internal test rig with the replica of the hub axle part, same as the modified by the customer.

It takes around 30 days to get the tooled up samples and the results were astonishing with huge gap in performance between old (1.5 lac cycles) and new (12.5 lac cycles) design. Based on which, we had successfully pass on our best proposal to the customer for their validation and testing.

Based on our study, they opt for direct implementation in to mass production.

Even today after 2 years of implementation, there are no field issues or complaints.

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