The Role of a Stress Engineer
Are you looking to pursue a career in engineering? Do you enjoy Mathematics, Physics, Graphic Communication, or have a general interest in "how things work?" If so, this article is for you.
Stress Engineers operate specialist computer software to conduct Stress Analysis to better understand how a component will perform when subject to the conditions it will experience in a real-world environment. Stress Analysis is used in almost every engineering sector, from Aerospace to Oil and Gas. It’s the role of a Stress Engineer to operate the software, understand the results, and utilise the output. Stress Analysis can be used to refine the pre-production stages of a design, assess the impact of known defects discovered during routine maintenance of a component, or extend the life of a part which has been in operation past its expected lifespan.
Stress Analysis
To outline the role of a Stress Engineer, firstly we will cover what Stress Analysis is and why it is used. The application of Stress Analysis uses the Finite Element Method (FEM), which originates from the Ritz Method. FEM is a form of numerical modeling, in which a chosen component is split into a series of discreet elements. Adopting the Finite Element Analysis (FEA) process, differential equations are solved to understand how loading and constraint conditions have an impact on the component or assembly.
Stress Analysis when solved using FEA software involves importing a 2D or 3D model which represents the component under investigation. A 2D analysis is carried out for simplified investigations; a typical runtime can be 2-3 days. Whereas, a 3D analysis offers the ability to investigate the impact of set loading conditions on a complete representation of a component. This in turn results in longer run times, which can be up to 2-3 weeks.
The component's specific material is assigned to the model prior to commencing. The model is split into a geometrical mesh, comprising of a series of elements, hence the name Finite Element. Elements are the shapes which the mesh is made up of. A 2D mesh will typically comprise of quadrilateral or triangular elements, whereas it is common for a 3D mesh to use hexahedrons and tetrahedrons.
The results of the numerical modeling will be stress and displacement values. Although the model is split into elements, the number of calculations conducted by the computer is dependent on the number of nodes. Nodes are points at the intersection of each element. A standard 2D triangular mesh will have 3 nodes per element, whereas a 3D quadrilateral mesh will have 4 nodes per element. The number of nodes can be increased; this will result in an increased run time as engineering calculations take place where each node is located. A process called Mesh Refinement is carried out once the initial results of the analysis are completed. Mesh Refinement is used to increase the number of nodes at specific areas of a component. Areas of high stress or displacement, identified during the initial analysis, will undergo Mesh Refinement.
A Stress Engineer is required to produce an optimal mesh in areas where high stress or displacement is discovered. The Stress Engineer's knowledge and experience will support their ability to ensure a mesh is not too coarse or fine. Although Stress Analysis can be a time-consuming and expensive process, in most cases, the benefits outweigh the cost. The complex mathematical models conducted during Stress Analysis allow predictions to be made on safety-related conditions of a component, such as failure cases through setting conditions which are very difficult to replicate in a test facility. The cost and time associated with manufacturing a prototype, preparing and running a test in the conditions and environment the part will operate in can be significantly higher.
Example
The title image of this article shows a 3D model of a valve flange which has been imported into FEA Software. The model can be seen to have a tetrahedron mesh. Loading conditions have been set, and an initial set of results has been produced. The Stress Engineer will refine the mesh in areas of either high stress. The loading conditions and parameters have resulted in high stress levels around the bolt holes, represented in red (low stress is represented by blue). As discussed above, Mesh Refinement will result in an increased number of nodes in the areas of high stress, increasing the number of calculations. In an ideal Stress Analysis investigation, increasing the number of calculations by refining the mesh will result in a more accurate output.
The Role
Stress Engineers are trained to operate FEA software such as Abacus and Ansys. Similar to modern CAD software, FEA software has Graphic User Interfaces (GUI) which simplifies the operation and usability. However, the engineering calculations and complexity of the assessments conducted by the computer should not be underestimated. A Stress Engineer's role is not limited to operating the FEA software. Working in a team with other qualified engineers is part of the job requirement. Along with the other meta-skills, the ability to collaborate and communicate by sharing knowledge from lessons learned is integral when approaching desired outcomes in current projects.
What qualifications do you need to become a Stress Engineer? Typically a Stress Engineer will have acquired the correct school grades or college courses to enroll in a BEng/MEng in Mechanical Engineering. Each Mechanical Engineering course within Scotland covers Finite Element Analysis at some point. Specific courses such as BEng/MEng in Computer Aided Mechanical Engineering at Glasgow Caledonian University provide aspiring engineers with hands-on experience of Finite Element Analysis.
Conclusion
Stress analysis is an important element of engineering assessment, as many components will fail under load. Stress analysis is typically performed using Finite Element Analysis software which is operated by Stress Engineers. Despite being a timely and expensive process, conducting a FEA investigation can be significantly cheaper than manufactung a component and testing it in the conditions it will be subject to in-service. The Role of a Stress Engineer is so much more than operating the software; a Stress Engineers ability to collaborate and communicate is key to design processes and component life extension investigations.
References:
ASR Engineering. (2019, September 23). FEA Mesh Elements & Nodes Guide: Intro to FEA. Retrieved from https://asrengineering.com/2019/09/23/fea-mesh-elements-nodes-guide-intro-to-fea/
PV Engineering. (n.d.). A Step-by-Step Introduction to FEA Stress Analysis. Retrieved from https://www.pveng.com/home/fea-stress-analysis/a-step-by-step-introduction-to-fea/
Case, J., Chilver, L., & Ross, C. T. F. (1999). Strength of Materials and Structures (4th ed.).