Mechanical Failures of Products due to Presence of Stress Raisers

Most mechanical failures and fractures due to fatigue start from small geometric features such as holes, sharp corners, fillets and surface imperfections . These geometric discontinuities cause the local stresses to rise above the nominal values. These geometric discontinuities are known as stress concentrations, or simply stress raisers.

During early stages of design (sizing/dimensioning) these stress raisers are often ignored for ease of calculation. However for long term survivability and safe operation, effects of these stress raisers should be incorporated in the design process so the life of the structure/device can be predicted.

One of the simplest and most common ways of estimating life in a structural integrity assessment is by using an appropriate S-N high cycle fatigue curve. For this method it is critical that the peak stresses at the location of stress raiser be correctly determined. The peak stresses are a function of geometric feature as well as the type of loads. Calculation of peak stresses by hand for simple stress raisers as well as the appropriate treatment of them using finite element analysis are discussed in our Practical Stress Analysis and Finite Element Analysis course.

Official Launch of DreamCatcher Mechanical Designs and Systems Portfolio

Apart from Practical Stress Analysis and Finite Element Analysis, we have also launched the following new courses to support the human capital development of our engineers from the mechanical, production, process and other similar disciplines:

1) Fundamentals of Acoustics and Human Sound Perception (http://dreamcatcher.asia/training/courseprofile.php?id=MS277)

2) Design for Manufacture and Assembly (http://dreamcatcher.asia/training/courseprofile.php?id=MS263)

3) Essentials of Design of Experiment for Engineers (DOE) (http://dreamcatcher.asia/training/courseprofile.php?id=RQ283 - also for engineers from all disciplines)

4) Essentials of Plastic Injection Moulding Technology (http://dreamcatcher.asia/training/courseprofile.php?id=MS266)

5) Plastic Injection Moulding Process Optimisation and Defects Troubleshooting (http://dreamcatcher.asia/training/courseprofile.php?id=MS267)

6) Practical Heat Transfer - Fundamentals and Applications (http://dreamcatcher.asia/training/courseprofile.php?id=MS281)

7) Computational Fluid Dynamics - Fundamentals and Practical Applications (http://dreamcatcher.asia/training/courseprofile.php?id=MS298)

More courses will be announced in the near future.

Dr KC Tang

DreamCatcher Technical Training

November 2010