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Pass the Shock Test: a Case Study in Designing a Custom Isolator

June 15, 2023
A team of engineers leverage custom design and analysis to build a reliable isolator solution for the Navy’s Columbia-class submarine.

Military equipment deployed by the United States Navy must operate consistently and reliably under harsh conditions and in dangerous environments. Whether it’s a period of war or peace, American and allied interests rely on advanced precision technology for protection and mission success. Ensuring this technology works correctly involves many considerations, but solving shock and vibration challenges is a critical aspect of the puzzle.

A well-known defense company working on electronic control equipment for the Navy’s Columbia-class submarine turned to Hutchinson Aerospace and Industry to help solve a shock problem that a competitor could not. Through a rigorous system analysis and strategic design, Hutchinson’s engineering team helped create a dependable solution that eliminated the need for a complete system redesign and saved the customer about a year of time and money.

A Shocking Problem

Hutchinson Aerospace and Industry assists the military and other industries by creating reliable engineered rubber products for shock and vibration solutions. The engineering team consists of custom system design specialists who not only provide data and evaluations for shock and vibration, but for electromechanical system assemblies and electrification solutions. 

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Before Hutchinson’s engineering team could get started on a solution, they first needed to gain a holistic understanding of the problem.

The engineers learned the defense company was working on a bulkhead-mounted enclosure featuring an internal circuit card deck that had limited deflection space. However, the internal circuit card deck needed to stay under the maximum acceleration limit during shock events. 

When the customer performed 901E shock testing on the enclosure, they discovered that a competitor’s isolator configuration and proposed isolator were not performing the way they needed to. In particular, the system transmitted high acceleration levels to the internal circuit card assembly during shock events—resulting in a failed test.

With this knowledge in hand and knowing the customer had limited time to solve this shock problem, the team of engineers got to work on creating a solution. 

A System Analysis Inspires a Custom Solution

Along with customer-provided shock input time history, Hutchinson’s engineers used the company’s CAD capability (including non-linear 3D FEA) and in-house proprietary analytical tools to analyze the system and gain a holistic understanding of the problem. To make sure the system passed the shock test—and to achieve the customer’s desired acceleration requirements—the engineers were able to tap into their knowledge of materials to determine that a custom elastomer blend used in one of the existing isolator designs, as well as a different mounting system, was needed.

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With the results of the precision system analysis in the back pocket, the engineers created a custom elastomer formulation that was 50% stiffer than the standard elastomer. They used the new elastomer in the existing isolator geometry. In addition, they implemented stabilizer mounts at the upper corners of the system’s card deck to allow for better motion control and lower transmitted acceleration.

Once the team completed the isolator design and validated the isolator’s performance in the Hutchinson Test Lab, the team of engineers provided the customer with samples they could use in trial testing. 

A Passing Grade

The results of the trial testing were just as expected: their isolator was successful in meeting the company’s maximum acceleration levels, using only half the allowable deflection space to do so. In addition, the isolator in the actual system passed 901E shock tests. 

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Ultimately, the design and analysis support meant the customer did not have to go back and redesign the entire assembly, an extremely costly process that would have taken about a year and delayed the project. Hutchinson’s team was able to analyze the existing system, finding innovative ways to create a reliable and custom solution accurately and quickly. 

Focused on Solutions

The isolator example is just one of many that illustrates how the team routinely combines expertise in shock and vibration isolation, knowledge of materials, large existing product catalog and system analysis expertise to create custom solutions for customers. But for these engineers, coming up with a custom solution to ensure an optimal outcome is a welcome challenge.

Tim Russell, Hutchinson regional sales engineer – U.S. Northeast / Defense Aftermarket sales manager can be reached at (508) 417-7000.

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