黑料不打烊

鈥淯nbreakable鈥�. It鈥檚 common to hear this word used in sales pitches describing a superior, invincible product. 鈥淚t鈥檚 engineered to last. It鈥檚 drop-proof, water-proof, bullet-proof,鈥� and the list goes on. 

Engineers like me snicker when we hear these claims. We laugh because we know that nothing is truly 鈥渦nbreakable鈥�. It may very well be a superior product 鈥� perhaps it鈥檚 even built to last. But in the real world, anything can be broken if subjected to enough force, impact, loading cycles, or harsh environment. Think Titanic. 

So when a product does fail, who is to blame? The designer? The manufacturer? The salesperson?  The user? Gremlins? Let鈥檚 not be hasty 鈥� a failure is often not as it first may seem. 

Failure analysis methods 

Failure analysis is a process by which a failed product is inspected to determine what caused it to fail. There are various methods that failure analysts use 鈥� for example, Ishikawa 鈥渇ishbone鈥� diagrams, failure modes & effects analysis (FMEA), or fault-tree analysis (FTA). Methods vary in approach, but all seek to determine the root cause of the failure by looking at the characteristics and clues left behind. 

So suppose you have a product failure. Why go through all the trouble of performing a failure analysis? I鈥檇 like to suggest 3 benefits: 

1. Determine the root cause of the failure

It鈥檚 beneficial to understand why your product failed. Perhaps there was a design flaw that prevented it from performing its intended function. Perhaps it had a manufacturing or material defect. Perhaps the product was misused or abused. Or maybe it exceeded its useful life and wore out.

By closely inspecting the product, its fracture surfaces, and its environment, an experienced failure analyst is able to collect the evidence and observations needed to make conclusions regarding the root cause(s) of failure.

In the context of mechanical system failures, the failure analyst often uses visual inspection, microscopy, and various metallurgical tests (e.g. chemical analysis, hardness & tensile testing) to collect evidence. The analyst may even attempt to recreate the failure in a controlled environment. 

2. Prevent similar product failures in the future 

Once the root cause of the product鈥檚 failure has been determined, it is possible to develop a corrective action plan to prevent the recurrence of the same failure mode. Here are some common root causes, and their corresponding corrective actions: 

• Design deficiency caused failure鈫� Revisit in-service loads & environmental effects, modify design appropriately
• Manufacturing defect caused failure 鈫� Revisit manufacturing processes (e.g. casting, forging, machining, heat treat, coating, assembly) to ensure design requirements are met
• Material defect caused failure 鈫� Implement raw material quality control plan
• Misuse or abuse caused failure 鈫� Educate user in proper installation, use, care, and maintenance of the product
• Product exceeded its useful life 鈫� Educate user in proper overhaul/replacement intervals

3. Improve future products

Understanding what caused one product to fail may allow us to improve next-generation versions of the product or other products. In performing failure analysis on one product, often we鈥檒l learn something about our design process, manufacturing processes, material properties, or actual service conditions. This valuable insight may allow us to foresee and avoid potential problems before they occur in the future. 

鈥淎n expert is a person who has made all the mistakes that can be made in a very narrow field.鈥� 鈥� Niels Bohr (1885-1962)

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