Reliability Engineering

The word “Reliability” is a broad term and has been defined differently by various Reliability scholars. Without intricating it further, we will try to understand the Reliability fundamentals in simple words. Reliability may be defined as the probability that an item will perform its intended function for a specified time interval under stated use condition.

In more simpler words, It may also be defined as the ability of a product to perform its intended function.

Now the question is that “Why we needed to understand Reliability fundamentals and predict it for a product??” It all started because :

  • Many unpredicted failure occurred in second world war. The failures cost many lives and off course money and effort.
  • Many disastrous military and industrial failures like Chernobyl nuclear explosion resulted due to bad planning and unreliable approach.
  • Products started becoming more complex.
  • New world understood the value of Reliability fundamentals and its studies as unreliability of a product was a financial and reputational loss for the companies now.

Basic purpose of Reliability

  • Basis for selection among competing designs
  • Disclose critical reliability limiting items in design
  • Assess Sensitivity of design to various stress and part quality
  • Calculate and predict the reliability
  • Provide inputs to design

Historical background

You will be surprised to know that an old Egyptian tablet or around 429 BC have been found stating :

“As concerns the gold ring set with an Emerald, we guarantee that for 20 years the emerald will not fall out of the gold ring. If the emerald should fall out of the gold ring before the end of 20 years, we shall pay unto Bel-Nadin-Shumu and indemnity of 10 mana of silver.”

What’s this?? This my friend is itself a reliability term that this product will work as intended and in defect free state for a defined life cycle of 20 years. Just think, how old this Reliability term is.

However, Reliability evaluation in this modern world is being widely used and developed from last 75 years. Here is a brief overview of last 75 years:

Reliability History

In our next post, we  will discuss the advantages of Reliability in detail. Till then, Keep learning and take care of yourself.