Why Did the Connecting Rod in an Ultra-Light Vehicle's Engine Fail?

[manuni]

Hey Guys,
Please help me out.
Q. The connecting rod of a newly developed internal combustion engine for ultra-light vechicle failed catastrophically during testing, damaging the crankshaft and smashing the engine block into two. An emamination of the fracture surfaces revealed that the cause of failure was fatigue and that the crack had initiated from the root ofone of the conrod threads.
I've begun my own investigation by carrying out some preliminary finite element analysis. By doing so, l was able to find out the distribution of hoop stress around surface of pin hole.

I need to write a full-detailed report about too many points but am mostly struggling with
1- cause of cracking,
2- any recommended modifications.
3- justification for the recommended modifications.

Please help me.I am seeking for details on those points.
Many thanks

Regards
xx

 

[minger]

Conrod bolt torquing is one of the most important torque specs on an engine. I've often heard that when doing it yourself, it isn't too safe to do it with one torque wrench three times (torquing, backing off, 3x) then checking with 2 other torque wrenches.

Do you perhaps have a picture of the conrod, also maybe a picture of a good one so we can critique the design?

 

[ravenprp]

Hello xx,

I am sorry to hear about the failure of the connecting rod in your newly developed internal combustion engine. It can be frustrating and disheartening to encounter such a setback during testing.

Based on the information provided, it seems that the root cause of the failure was due to fatigue. This means that the connecting rod was subjected to repeated stress cycles, causing it to weaken and eventually fracture. The fact that the crack initiated from the root of one of the conrod threads suggests that there may have been a flaw or defect in the material or manufacturing process of the connecting rod.

To prevent similar failures from occurring in the future, it is important to identify and address the root cause of the cracking. This could involve conducting further investigations and analysis, such as metallurgical testing and stress analysis, to determine the exact reason for the fatigue failure. Once the cause has been identified, appropriate modifications can be made to improve the design and manufacturing process of the connecting rod.

In terms of recommended modifications, it is difficult to provide specific details without further information about the engine and the testing conditions. However, some general recommendations could include using stronger and more durable materials for the connecting rod, improving the manufacturing process to eliminate any potential flaws or defects, and ensuring that the engine is not being pushed beyond its intended limits during testing.

As for the justification for these recommended modifications, it is important to provide evidence and data from your investigation and analysis to support your recommendations. This could include results from the finite element analysis you have already conducted, as well as any other relevant data or findings. It is also important to consider the cost and feasibility of implementing these modifications, as well as the potential impact on the overall performance and efficiency of the engine.

I hope this helps you in your report writing process. Best of luck with your investigation and finding a solution to prevent future failures.