Combined Analyses Procedure of Failure Modes and Risk Phenomena Using the Concept of Normal State Conditions

Normal failure or risk analyses procedure contains the following steps: 1) modeling process, 2) assessment process of its hazardous extent. 1) Modeling process is the considering procedure that sets the sequence of happening failures or risks. 2) Assessment process is the evaluation procedure that express its hazardous extent quantitatively or qualitatively (probability, seriousness of injury etc.). According to ISO14120 (Risk assessment process), ranking procedure of risks are established. However, there is no logical procedure for 1. Modeling process and these steps still highly depends on designer’s knowledge or experiences of failures and accidents. It is necessary to establish a logical guideline of failure modeling process for fresh designers in order to effectively conduct failure and risk analyses with their acceptable workloads. This study aims at proposing the logical failure modeling process based on the SSM (Stress-strength model) and the normal-state conditions. In the beginning, designers make a stress-strength model of considering components and its “normal condition”. Introducing “deviations” in normal conditions of stress-strength state and surrounding environmental conditions can lead the designers to easily predict failure modes caused by the proposed deviations. Similar steps are applied in the process of considering risk phenomena caused by failure modes. A case study of assessing the safety of micro windmill demonstrated the effectiveness of our proposed procedures.