Nonlinear Motion Simulation and Design Optimization

By Phil Pisczak 
Project Engineer 
Preformed Line Products (PLP®) 
Cleveland, Ohio 

Back in the mid-eighties, I changed the way I worked when I learned that linear static stress analysis software could give me stress information before a part was made. Today, I wouldn’t think of doing a linear static stress analysis when I can obtain stress results over time with Mechanical Event Simulation (MES) software.

There are very few scenarios I look at that I know up-front will be truly static and linear. Therefore, I now perform nearly every analysis with ALGOR’s MES software. 

MES calculates motion and stresses with built-in linear and nonlinear material models. Unlike the typical linear static stress analysis, the setup of an MES relies on physical data, rather than calculated or assumed loads and constraints. The combination of motion and stress analysis considering full inertial effects enables me to see motion and its results, such as impact, buckling, permanent deformation and displacement. 

In dynamic scenarios, MES provides more information than can be extracted from a laboratory test. Take, for example, a recent impact simulation on a large, heavy anchoring component for telecommunications towers. Impact analysis and testing is more challenging than static testing. When parts are tested in the lab on the tensile bed, the equipment provides a plot of the part’s behavior during breakage. With an impact analysis, it’s more difficult to get that kind of information in the laboratory. Strain gauges can be used, but the sensors may be destroyed in the course of an impact experiment. In addition, high-speed cameras do not capture small vibrations very well. 

MES allowed me to look at what is happening in the impact event without high-speed cameras or complicated laboratory tests. It was a microscope into the dynamic impact process. We obtained motion, dynamic loading and stress results from MES. The software even allowed us to see the wave of resonance travel up and down the part. Without the use of MES software, it would have been more difficult to make necessary changes to the geometry of the part. 

In cases where the material is nonlinear or the part experiences large deformations, MES is valuable because it can consider nonlinear material properties along with time-dependent behavior. Take, for example, the case of a thin, plastic communications housing subjected to pressure testing. Linear static stress analysis is often used for that kind of scenario, although the part deflects a significant amount for that type of material under pressure and the material exhibits nonlinear behavior at relatively low stresses. 

Whereas a linear static stress analysis would produce stresses at an abstract moment in time, performing an MES with nonlinear material input lets me see how and where the stresses originate and how they propagate as the pressure is applied over time. The results from the MES are more useful information than the results from a linear static stress analysis, because “hot spots” in the stress contour may appear at different locations on the model at different moments in time. If the hot spots converge on a particular part of the component, it clarifies where the geometry needs to be optimized as opposed to if the stresses are better distributed across the model. 

MES provides full dynamic visualization of the behavior of the part as the event transpires. As a result, a whole new level of information is available to enhance the design process and parts often need to be verified by less physical prototype testing, thus reducing costs and time-to-market. 

PLP is a $200 million global leader in the manufacture of cable anchoring systems. Phil Pisczak holds Bachelor of Science and Master of Engineering degrees from Case Western Reserve University and has been using FEA since 1984.

Click here for more on how PLP used ALGOR software.