Dynamics & Acoustics

Acceleration Testing

The purpose of acceleration testing is to study how a product will respond to varying accelerations of force. These tests, which move slowly and steadily between low and high acceleration, are measured in g-forces. Acceleration tests are careful to exclude elements of shock, vibration and other types of impact that are employed in separate tests.

The goal of acceleration testing is to determine how many g-forces a product can withstand and still maintain its composition and functionality.In real-life settings, excess loads of acceleration can have damaging effects on numerous commercial and industrial products.

For example, printed circuit boards can be ruined on impact by intense acceleration loads. Other detrimental acceleration effects include:

• Structural damage
• Stressed, leaky seals
• Jammed actuators
• Broken mounting pieces
• Flickering sensors
• Ruined contacts

Acceleration tests are generally performed on products made for the aerospace industry, such as the exterior and interior pieces of airplanes. To past the test, a product must remain operable under peak loads.

At NTS, acceleration tests are performed on G-tables and in centrifuges ranging from 1ft (0.3m) to 62 ft (16m) in diameter and weight capacities from a few grams to 7,000 lb (3,175kg). In order to control and power each instrument during the test, electrical slip rings are used. If the test device is pneumatic or hydraulic, swivels are used to provide the necessary compressed air or water during the test. Swivels allow for high degrees of flexibility during the testing stage.

Overall, acceleration testing is employed with several methods, including centrifuge, cycling, multi-axis, thrust application and payload analysis, the last of which specifically applies to satellites and space probes. MIL-STD-202 is the industry standard for testing electrical components for durability in light of acceleration.

Acoustic Testing

The impacts of acoustic noise vary between different types of devices. When products are made for commercial or industrial use, it is crucial to test the noise threshold of each device. With acoustic noise testing, manufacturers can determine how a given device will handle various degrees of sound exposure in the noisiest possible settings.

Acoustic noise testing labs employ high-tech equipment that tests the noise threshold of products before they hit the market. Based on these results, manufacturers can determine whether a given product is ready for commercial, industrial or military use. If a device fails to handle acoustic noise within an expected range, the product is sent back for revisions.

At high altitudes and under intense velocity or torque, acoustic noise can have an intense impact on motorized components. Some of the harshest sources of acoustic noise include wind resistance and running motors. Therefore, the parts that comprise the engines of airplanes and vehicles must undergo acoustic testing in advance of their approval for market use.

If exposed to excess levels of acoustic noise, a product is liable to show some of the following symptoms:

• Tightened wires
• Worn and loosened parts
• Cracked surfaces
• Flickering electrical contacts
• Optical misalignment

In an enclosed, stationary setting, acoustic noise can penetrate a device. When a vehicle or aircraft is in motion, acoustic noise can graze the outer surfaces of parts.

Acoustic noise testing is employed on products used throughout the IT, military, regulatory and telecommunication sectors. Noise testing is most crucial for defense equipment to ensure that hearing loss and enemy detection don’t result from the noise levels generated by weapons and artillery. Acoustic noise testing is covered by numerous industry standards. Our state-of-the-art test facilities include a 5,000 cubic foot reverb chamber in a 1,400 square foot High Bay Class 100k clean room.

Bird Strike Testing

For the flying aircraft, one of the most unpredictable dangers is the oncoming bird. While it might seem odd that such small, organic creatures could endanger something as large and relatively invincible as an aircraft, collisions with birds have been the cause of untold sums of damage to commercial and military planes. Birds are dangerous to planes because of the high impact of opposing high speeds.

In some cases, bird strikes have even downed passenger airplanes. Take, for instance, U.S. Airways Flight 1549, which crashed into the Hudson River shortly after takeoff when each of the plane’s engines was struck by geese. The plane had to be ditched because both engines lost power on contact with the birds.

In most cases of engine impact, only one engine is stuck and the other engine is used to safely land the plane at the nearest airport. Overall, bird strikes cause upwards of $400 million in damages to aircraft each year. Most of these collisions occur on other parts of the plane, where birds can cause dents in metal and cracks in windshields.

Bird impact testing is performed with a strike simulator, or “chicken gun”, where organic and imitation birds in the 2.2 to 8-pound range are released at speeds as fast as 400 mph. The objective is to test if the parts of an aircraft or vehicle are strong enough to withstand high-speed impacts with the creatures.

Vibration Testing

For machines, vehicles, aircraft and electronics, vibration testing is a crucial part of the product-vetting process. The impacts of shakes and tremors can be damaging to the internal mechanisms of any product that lacks sound design. Therefore, vibration tests are performed on products before release in the military, aerospace and automotive sectors.

Amidst the speeds that vehicles and aircraft travel, vibrations must be withstood by the engine components that send each car and airplane into motion. In order to test the vibration resistance of these various components, tests are employed with shaker tables on which engine parts are subject to heavy tremors.

During a given day’s ride, any random passenger vehicle is liable to experience vibration due to surface irregularities along roads and highways. Likewise, artillery vibrates by sheer force of rocket and missile launches. Even on aircraft, wind resistance causes wings to vibrate at high altitudes.

In vibration testing, each applicable component undergoes a test that simulates the type of vibration that the engine, motor or metal part would likely face in the air, on the road or in a stationary setting. Vibration testing helps manufacturers identify design weaknesses that could cause engine components to crack or become disconnected from their corresponding joints. Moreover, vibration testing ensures that released components meet the minimum vibration thresholds of the automotive and aerospace industries.

At NTS, we are capable of generating up to 70,000 force pounds with tandem shakers and up to 45,000 force pounds on a single shaker. NTS has performed vibration testing in excess of 200 GRMS in a single band and can hook up in excess of 100 data channels.

Corrosion Testing

Components destined for a variety of industries must undergo corrosion testing to ensure that they are physically sound in highly corrosive environments. The trouble is, corrosion can take months and sometimes years to form and spread along a metal surface. For corrosion tests to be effectively employed without holding up the production of a given product, the parts must be subjected to an artificial environment that rapidly accelerates the corrosive process.

With accelerated corrosion testing, manufacturers can gain a more accurate idea of how long a given product will resist the corrosive effects of an environment. At NTS, parts are subjected to corrosion testing and monitoring under a set of conditions that speed several years of corrosive effects into the span of several days.

Depending on the type of environment in which a machine or vehicle is intended to operate, a corrosion test might require specialized standards. For example, if a machine is built for use at a plant with high acidity levels, the test will need to simulate these more extreme effects to determine whether the machine and its various parts will withstand these environmental factors for the span of its expected lifecycle.

For products intended for use in settings with average corrosive factors, a basic salt-fog test is generally applied. Several industry standards — including MIL-STD-810, ASTM B117 and GM9540P — apply to corrosion testing. At NTS, corrosion tests are performed on products for the aerospace, automotive, military and medical industries. Basic tests, such as salt spray testing, are also performed on commercial products.

Thermal Shock Testing

In thermal shock testing, products are subjected to extreme, abrupt fluctuations in temperature. The goal is to test the temperature threshold at both ends of the hot-cold spectrum to determine how these products would fare under these changes. Thermal shock testing is typically performed on products that are made for use in environments where abrupt temperature changes are a regular occurrence.

Shock testing is also employed to determine a product’s durability amid sharp accelerations and deceleration’s of pressure. In effect, the response of products to shocking surges in heat, cold and pressure are studied to see whether a product is ready in its current design for mass production. The intensity of a shock test depends on the which industry standard applies to the product in question.

Mechanical Shock Testing

At NTS, mechanical shock testing is employed in various forms, including pyro-shock and shipboard shock testing. Pyro-shock simulates the shock of of an explosive attached to the test article, while shipboard shock, also known as heavyweight shock, simulates the shock equipment on deck would receive when the explosive is detonated in the water below the ship is conducted using a Floating Shock Platform. Lightweight shock is conducted using hammershock techniques on shipboard machinery, equipment, systems and structures. Medium weight shock simulates hull level inputs with rest articles under 7,4000 lbs.

Drop Testing

What goes up must come down and if an object does not land as planned, it will inevitably cause some degree of impact. With drop testing, products and/or packaging is tested to determine the height from which these products can drop and remain intact after impact. Drop testing is important for products and packaging in all sectors.

Drop testing is often used to test the durability of packaging arrangements for small consumer items. For example, testing how well a shipping box full of calculators or smartphones withstands a drop of 3 to 5 feet. The height from which a product is test-dropped is proportionate to the heights from which a product is liable to fall in a real-life situation, barring negligence or foul play. The ISTA standards are the most commonly used for shipping containers, some organizations, like FedEx and Amazon, have their own sets of ISTA requirements for package testing.

At NTS, the steepest drop tests are performed at heights of 80 feet to determine a product’s resilience should a real-life drop occur during the stages of transportation or handling. Drop towers are also used to induce mechanical shocks of between 15,000g and 20,000g in test products.

HALT testing, HASS testing, HATS testing

For manufacturers, it is important to know how each product is likely to endure the process of aging during its expected lifespan. This way, manufacturers can perform design revisions, if necessary, to render products more resilient and reduce the frequency of failures and warranty claims. To that end, tests are performed on products to accelerate the aging process.

The tests that employ age-accelerating processes include Highly Accelerated Life Testing (HALT), Highly Accelerated Stress Screening (HASS) and Highly Accelerated Thermal Shock (HATS) testing.

HALT tests are employed to find weaknesses within a given test device. During a HALT test, heat and vibration are applied for short periods at high volumes to see how the product will weather the exposure. Ultimately, the objective is not to see whether a product can survive the test but to determine how long and at what levels of exposure the product can function and hold its composition before failing.

HALT tests are conducted in five steps — high-temperature stress, low-temperature stress, vibration, thermal and combined environment. For the manufacturer, HALT tests make it possible to render products strong enough for maximum possible endurance throughout the five testing cycles before cracks, warps and other problem symptoms take hold.

The purpose of HASS testing is to see whether defects are present in a product during stages of manufacturing. While HALT testing is employed to test products in beta form, HASS tests challenge the durability of each product in revised form. Highly Accelerated Thermal Shock (HATS) testing, as the name implies, tests the durability and operability of products in the event of thermal shock.

HALT and HASS testing methods serve purposes similar to fatigue testing, which is performed on industrial materials such as metal, plastic and polymer. With fatigue testing, a material’s resistance to deformation and decomposition are tested under a range of stress volumes. Fatigue testing allows manufacturers to determine the strength and resilience of a given material before it is used in a product.

Dynamics Testing at NTS

Before a product is manufactured and released for use in large quantities, it is crucial to have it tested for maximum strength and durability. Whether a given part is designed for use in an aircraft, vehicle, military weapon, factory machine or commercial product, lives and property could be at stake if the product fails to perform its intended function. To put your product to a series of ultimate tests, contact NTS today to request a free quote.