Stress analysis-an engineering discipline based on solid mechanics-is a crucial element of mechanical engineering. Why? Because an engineering component can fail due to stress, often with dire consequences.
Whether the object of study is a table leg, a cell phone in a drop test, a human spine, or an integrated circuit, the method of inquiry-stress analysis-is essentially the same. It can help you find the best design for a part or assembly and ensure it performs without failure.
So, how do engineers carry out stress analysis?
First, they have to turn a real-world situation into a mathematical model, considering things like stress distribution, displacement, geometry, applied load, and other conditions. Then, they take out a pen and paper and…
Not really!
Today, almost all stress analysis is carried out using computer simulation software, usually finite element analysis software. This simulation tool speeds up the process by removing the mathematical burden and helps engineers solve more complicated problems faster than they could by hand.
Despite the essential nature of computers in modern stress analysis, engineers still have a crucial role to play. They have to input the correct data, set the conditions, and determine if the results are realistic. We discuss all this and more below.
How Is Stress Testing Performed?
Finite element analysis (FEA) is the primary method for simulating stress analysis. It predicts what will happen to an object when subject to physical forces like vibration, heat transfer, mechanical stress, electrostatics, and motion.
Finite element analysis doesn’t analyze products or even single components as a whole. Instead, it breaks components down into tiny elements connected by nodes. Together, these elements and nodes form a mesh.
Engineers apply material properties, boundary conditions, and load cases to the mesh, and FEA software calculates the stress on each element’s nodes, averaging them to create an outcome.
Why Is Stress Analysis Required?
Stress analysis is an essential part of product development and a way to learn about the world around us. It’s the basis of every major technological breakthrough and the key to making better engineering decisions and keeping everybody safe.
Stress analysis provides value across four key dimensions:
- Improves product safety: Stress analysis prevents product and structural deformation or collapses to prevent harm or even death. It simulates outcomes in a near-infinite number of scenarios without the additional cost. It enables manufacturers to provide clear safety factor guidance to users and protect themselves from legal action. Physical product testing (think crash test dummies) can only occur under limited conditions.
- Prevents mechanical failure: Engineers can use stress analysis to weed out any mechanical design problems before they occur in the real world. Uncovering potential issues at the conception stage can save vast sums of money later down the line when products go into production and are sold to customers.
- Improves product design process: Designers and engineers can iterate designs faster by simulating product performance on a computer. The more they repeat, the better product quality, longevity, and customer satisfaction become.
- Saves money: The earlier design phase decisions are made, the more money manufacturers save. Stress analysis also reduces the cost of design change, prototyping, and wastage, which has an environmental and financial impact.
What Is the Stress Analysis Process?
Stress analysis is a highly iterative process. The engineer sets the constraints, runs a simulation, and then uses the results to tweak and repeat the process until they finally have satisfactory results.
This is what the typical process for stress analysis looks like:
- Set expectations: Using a conceptual model, the engineer estimates how the object will behave under stress. (In other words, they use their best guess.)
- Preprocessing: The engineer defines loads and constraints, i.e., the conditions under which the simulation runs. This is the tricky bit (more on this later).
- Solving: The engineer presses “Enter” (or something similar), and the computer runs the simulation, generating the solution.
- Post-processing: The engineer displays and studies the results.
- Review expectations: The engineer considers whether their expectations were accurate or not.
- Conclusion: If results match expectations, the engineer gives themselves a pat on the back and moves on. If not, they modify the inputs and begin the process again.
What Is the Role of the Engineer in Stress Analysis?
These days, stress analysis is done by computer. But, it’s clear from the stress analysis process outlined above that the engineer still has a critical role. Rather than replace the engineer, computers augment their scientific powers. Pen and paper may no longer be required, but a deep understanding of the underlying mechanics is essential.
First, engineers have to decide the given conditions under which the simulation takes place. These conditions aren’t always known or absolute, and a good amount of scientific reasoning is required. The purpose of the study and the resources available (time and money) also have to be taken into account.
Furthermore, the engineer has to decide on the object’s geometry-what to include and what to take out. Sounds easy enough, but it’s a balancing act because the more complicated the geometry, the more noise and the more complex the results.
In addition to the geometry, the engineer has to determine whether to include external bodies (other objects that might impact the analysis.) Say, for example, you’re carrying out a stress analysis on a railway coupling (the mechanism used to connect two train carriages.) You probably have to include the adjoining carriages in your analysis, but what about the next carriages down the train? And what about the people walking between carriages?
Finally, the engineer has to be able to interpret the findings of the analysis. And then put them to good use in designs, improving safety, cost-efficiency, and performance.
Summary
We might not realize it, but stress analysis lies at the heart of our daily lives. It’s responsible for the things we use, our human environment, and our safety as we experience both.
Using FEA software to analyze product behavior under stress has changed how engineers work, making them far more productive and accurate than would have been considered realistic just a few decades ago.
Still, we mustn’t discount the importance of the engineer in simulation. Not only do they establish the necessary geometries and boundary conditions, but they turn the results into better, cheaper, and safer products for us all to use.