Many products are manufactured to serve a single or limited use. Needs for these products, often consumable, are immediate, and buying decisions usually require limited research or comparisons.
Conversely, some products must be extremely reliable, durable, and built to last a long time. Buying decisions for these products often require more research to ensure they are highly rated, safe, and made from sturdy and reliable materials.
How do manufacturers determine how long a product should last with consistent use? What design decisions need to be made to improve product reliability? The answer is often found in the defined fatigue requirements of a product. In a product's test, measurement, and design phase, answers to these questions frequently require product and component testing with fatigue-rated load cells.
Fatigue is the weakening of a material caused by repeatedly applied loads. If you repeatedly bend a paper clip, it will weaken and break. The only way to test fatigue is to put product prototypes through stress tests for long periods or use an apparatus that tests the lifetime "wear and tear" in a few hours. The tool that reports the data gathered from stress tests is the load cell.
TOP 5 REASONS TO USE FATIGUE-RATED LOAD CELLS
Durability: Fatigue-rated load cells are built to withstand many loading cycles, making them more durable and longer-lasting than standard load cells. This is crucial for fatigue testing, where materials and structures undergo repeated stress.
Accurate Measurement Across Cycles: Fatigue-rated load cells maintain consistent accuracy and reliability throughout numerous loading and unloading cycles. This ensures that the measurements obtained during fatigue testing are reliable and reflect the material's or structure's true behavior over time.
High Sensitivity to Detect Miniscual Changes: Fatigue-rated load cells are sensitive sensors that detect subtle changes in the material or structure's behavior during fatigue testing. This high sensitivity is essential for identifying early signs of fatigue failure or damage.
Consistent Performance: Fatigue testing involves dynamic and cyclic loading conditions. Fatigue-rated load cells are designed to perform consistently in such dynamic environments, providing accurate readings even when subjected to varying forces and frequencies.
Compliance with Testing Standards: Fatigue testing is conducted according to specific industry standards and regulations. Using fatigue-rated load cells ensures compliance with these standards, as these load cells are designed and tested to meet the requirements of fatigue testing protocols.
Overall, fatigue-rated load cells ensure the reliability and accuracy of fatigue testing, providing researchers and engineers with trustworthy data for assessing the endurance and durability of materials and structures subjected to cyclic loading.
With Interface fatigue-rated load cells, designers and engineers can predict the time and force it will take for wear and tear to take its toll on their products. Based on the fatigue testing results, they can create customer safety instructions or redesign the product for better results.
Interface Fatigue-Rated Load Cells
Interface's most popular fatigue-rated solution is the Model 1000 series, a portfolio of fatigue-rated low-profile load cells with 300% safe overload, extremely low moment sensitivity of 0.1%/in, and higher fatigue life. If you need to measure 1 pound (4.45N) or 1 million pounds (4500kN) of force, Interface fatigue-rated load cells are built for this type of testing.
Interface fatigue-rated load cells are designed for an operational life of in excess of 100 million fully reversed cycles.
It's also important to note that Interface fatigue-rated load cells are based on fully reversed load cycles, which means they are rated in two directions. This type of loading cycle is considerably more stringent than unidirectional loading. It is the more common application of load cells. If a fatigue load cell is repeatedly loaded in only one direction, it can be loaded to about 133% of the bidirectional fatigue-rated capacity with no degradation of its fatigue rating.
FATIGUE TESTING APPLICATIONS
Interface fatigue-rated load cells are used in various industries, including aerospace, automotive, civil engineering, and manufacturing. They test various products, from prosthetics to industrial machinery.
Two examples of products dependent on fatigue-rated load cells for testing are aircraft wings and furniture stability.
In aircraft wing testing, load cells test the materials used to build the wings to ensure they are strong and lightweight. The load cells are also used in wind tunnels to test the stress of high winds on the wings over time.
Safety protocols manufacturing for furniture products require fatigue testing, seat testing, shock testing, and proof testing. These tests must be rigorously performed before entering the marketplace. Force testing simulations using fatigue-rated load cells help the manufacturer define max loads to protect manufacturers from liability due to damages resulting in the misuse or overloading of their products.
Aircraft Wing Fatigue
Before any aircraft can be put into operation, the wings must undergo fatigue testing in a controlled environment to ensure that they can withstand the forces encountered during real-world flight throughout the aircraft's lifetime. Highly accurate measurements must be recorded to ensure a near-exact replication of in-flight conditions. During fatigue tests, Interface’s 1248 Standard Precision Flange LowProfile™ Load Cells are installed in line with the hydraulic cylinders, which apply back-and-forth loading forces to the aircraft. This is carried out over 18 months to simulate in-flight stresses and strains on the wings. Load cells are connected to indicators, which record output. These Interface load cells can withstand more than 100 million (1×108) fully reversible load cycles, Interface’s LowProfile™ fatigue-rated load cells.
Furniture Fatigue Cycle Testing
Using Interface’s SSMF Fatigue Rated S-Type Load Cell along with the 9890 Strain Gage, Load Cell, & mV/V Indicator provides a solution that measures the force being applied in fatigue cycle testing of a furniture product, in this case testing the rocking mechanism in an office chair. Unlike similar load cells, the SSMF is fatigue-rated, making it highly suitable for fatigue testing. No fatigue failure of any fatigue-rated Interface load cell used within its ratings has ever been reported. View the complete application note here.
These applications require the most accurate data our load cells provide to ensure that testing results produce a quality product that lasts. Use our Load Cell Selection Guide to find the best fatigue-rated load cell for your use case.
Fatigue-rated load cells are one of the many Interface force measurement tools available to help customers develop quality products. Interface works with customers to provide our fatigue-rated load cells for products that can't fail. Our mission is to ensure that precision products are safe, reliable, and durable. If they do fail, it could result in significant harm.
Contributor: Jay Bradley, Sr. Electrical Engineer
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