What is a Drop Test?

A drop test is a controlled study of what happens to a product when dropped onto a hard surface from a specific set of drop heights and orientations. Engineers measure the impact magnitude, the effect on functionality, and any cosmetic damage after each test. They use that information to either improve the design or determine that the configuration is acceptable.

Although most people are familiar with testing consumer electronic products like their mobile phones, engineers employ drop testing across a wide variety of industries, including aerospace, consumer goods, heavy machinery, medical devices, and even nuclear material transportation.

The goal of any drop test is to ensure that product and package design enables the product to survive a reasonable number of falls by staying safe, operating correctly, and not suffering cosmetic damage. In addition to physical testing, most companies use simulation to virtually conduct drop testing earlier in the design process and at a lower cost.

Drop tests look at potential product damage under two areas of ownership. The first is during transport and storage before use, and the second is when the device is in use. The product is usually in some type of packaging during the pre-usage stage, so a package drop test is done to evaluate the durability of the packaging. It is then tested on its own to see what happens if the end user drops it. 

The key to effective and informative drop testing is establishing a drop test procedure that meets industry standards, provides useful information to the design team, and establishes validation of the packaging and product design. 

Drop Testing Goals

The first step in any drop testing project is to establish the goals and objectives of the testing. In some cases, the only goal is to meet the required standards of shippers like FedEx or distributors like Amazon or Sam’s Club. In other cases, design teams use the test data to optimize the product or package design. The goals should be clearly documented and used to develop the test plan. 

Variables Used in Drop Tests

Products can be dropped from an infinite number of heights, with many different orientations and under a multitude of environmental conditions. These are all variables that may be defined by standards or by the design team. An effective drop test should include clear definitions of the following variables: 

• Drop height: Gravity accelerates an object in free fall, so the height of the drop determines the velocity of the test specimen when it hits the impact surface and, therefore, the energy of the impact. 
• Product orientation: When an object lands on a corner or an edge, the load on the object is concentrated, and the damage is greater than when it lands on a large, flat surface. That is why drop tests include multiple orientations. 
• Number of drops: A product or package may survive one or two drops, but every time it experiences an impact, additional damage can be done. Many tests have a specification for the number of drops an object must survive for different heights. 
• Impact surface material: The material of the flat impact surface significantly affects the amount of energy transferred into the object being dropped. Some common drop-test surfaces are concrete, polished concrete, steel, plywood over concrete, and vinyl tile over concrete. 
• Temperature and humidity: An important variable, especially for cardboard packaging, is the temperature and humidity in the test cell. Both variables drive the material properties of the product, packaging, and the drop surface. 

Drop Testing Standards

There is a wide variety of standards for drop testing. Some are set by industries, some by companies that ship or distribute products, and others by international standards groups. Some of the most common are: 

• ASTM D5276: Standard Test Method for Drop Test of Loaded Containers by Free Fall
• ASTM D7386: Standard Practice for Performance Testing of Packages for Single Parcel Delivery Systems
• ISTA 3A: Parcel Delivery System Shipments 150 lb (70kg) or Less
• ISO 2248: Vertical impact test by dropping
• IEC 60068-2-31: Tests - Test Ec: Rough handling shocks, primarily for equipment-type specimens
• MIL-STD-810G 516.6: Environmental Engineering Considerations and Laboratory Test: Tests: Shock

Drop Test Equipment

Vertical drop tests generally use a small set of test equipment to conduct the test and measure the results. Test planners should specify equipment that can handle the size and mass of the test objects, accurately measure the input variables for the test, and capture needed data from the test. 

Drop Tester

A drop tester is used to consistently drop the test object using the desired parameters for height, orientation, and impact surface. It consists of an impact surface and a mechanism that holds and then releases the test object at the desired height and orientation. Most machines automate the lifting and release of the test specimens. 

Rotating Drum Drop Tester

Small electronic components and devices like mobile phones are tested with a rotating drum drop-test machine. The test object is placed into a drum that spins, repeatedly lifting and dropping the test object. Companies use this type of equipment to verify that every potential drop orientation is checked with testing. 

Accelerometers

Acceleration is a key piece of information that engineers need to help them understand what loads a product sees during an impact event. Testers use accelerometers to measure acceleration in the packaging and at key locations on the product. 

Optical Inspectors

Engineers also need to know the cosmetic damage and physical deformation of the test object after impact. This can be done through visual inspection by a technician using various calibrated measurement devices, through high-quality cameras, or with optical light scanning to obtain the deformed surface. 

Product Testing Fixtures

When product functionality is one of the test requirements, test fixtures are used to automate functional testing. 

Typical Steps in a Drop Test

1. Planning: Test engineers use goals, product specifications, and industry or company standards to plan the most efficient set of tests that meet all the requirements.
2. Equipment calibration and setup: The drop test equipment should be calibrated and configured for the tests. This includes addressing safety concerns and implementing automation and data acquisition where needed. 
3. Sample preparation: Technicians must then prepare the test object itself. This may be a prototype of the packaging and product or samples pulled from production for testing. Accelerometers are attached, and markings are applied as needed. Mass should be verified as well at this phase. 
4. Execution: The test is carried out using the test equipment as described in the drop test plan. It is important that every step in the execution is consistent and follows the test plan. 
5. Inspection and analysis: After each drop test, technicians and engineers inspect the test object and capture any geometry, cosmetic, or functional changes. The results are also analyzed to obtain data required by the test or the engineering team. 
6. Documentation and reporting: The output of any test program is a complete and detailed report of what was done, the data obtained, and any exceptions to the test plan. 

When a new product is under development, the engineering team focuses on how well it functions during normal operation. That normal operation includes accounting for dropping the device at multiple points throughout the product life cycle. Drop testing has become a critical part of product quality for a variety of reasons, including:

1. Safety

The most important benefit of drop testing is product safety. If the structural integrity of a product fails after a drop, it may leak chemicals, overheat, catch on fire, or operate in a way that can cause harm. Design teams use drop testing or drop test simulation to optimize the material and structure of the product and its packaging to meet safety specifications.

2. Product Durability and Functionality

After meeting safety requirements, the next goal of drop testing is to verify that the product is durable enough to function properly after drops. What this means depends on the product undergoing testing. An IoT sensor can be dented and scratched, but as long as it continues to gather accurate data, it is considered functional. 

Functionality becomes critical in the medical and defense industries, in which loss of capability can significantly impact patients and warfighters. Drop testing helps design teams validate their design for durability under a reasonable number of drops. 

3. Customer Satisfaction

The state of a product after a drop can have a significant impact on how a customer feels about a product and a brand, especially if functionality is diminished. In addition, the cosmetic state of the package on delivery or the product itself after a drop has a significant impact on customer satisfaction. Dents, scratches, and cracks may not affect functionality, but they do negatively impact the customer's impression of the product. 

Drop testing can not only avoid such damage, it can also help the design team work with marketing and customer support to set expectations of the end user on what a survivable drop is. 

4. Size, Material, Shipping, and Storage Cost Reduction

The easy way to make a product survive free-fall from various heights is to add material to the packaging and the product itself. However, this increases the overall cost of the product by increasing the cost of materials, shipping, and storage. Drop testing helps engineers verify if their design for packaging and the product minimizes cost while still meeting the drop requirements. 

5. Replacement, Repair, and Warranty Cost Reduction

The cost of replacing products damaged in shipping or during usage can add up quickly. Drop testing can help establish what types of drops are covered under warranty and what the requirements for shippers are. In addition, drop testing can improve the product's durability and packaging to reduce the potential costs associated with damaging falls. 

Physical drop testing is a well understood and effective part of quality assurance, but physical testing can only be conducted after a packaging design and a testable version of the product exists. It is also expensive and time-consuming, not to mention the cost of changing the design so late in the development process. That is why many companies use simulation to conduct virtual drop testing as part of the product design process, not as a step after the process is completed. 

Ansys LS-DYNA® software is the standard simulation tool for drop test simulation in most industries. It is a finite element analysis (FEA) platform that solves in the time domain and takes mass, momentum, complex materials, and complex contact conditions into account — just what engineers need to simulate drop tests. Not only can simulation help engineers understand the drop behavior of their products and its packaging, but they can also quickly conduct parametric “what-if” studies to drive those designs.

A simulation has the added advantage of giving engineers a way to look inside the package or product and view the internal behavior over time during an impact event, delivering greater insight than a physical test. Engineers who deploy simulation for drop testing can access accelerations, stresses, deformations, contact forces, plastic deformation, and displacement at any location in their assembly.

When using simulation to virtually conduct drop testing, engineers should consider the following best practices:

• Create a high-quality, accurate mesh using hexahedral (hex) elements where possible, sufficient elements through the thickness, and higher-order elements when needed. It is also key to have relatively uniform element sizes. There are a variety of mesh tools in the Ansys suite that can help with this process. 
• Used bonded contact to attach components that are attached to one another in the product, and use frictional contact to represent surfaces that might slide relative to one another during an impact event. There are a wealth of tools to establish and manage contact connections in LS-DYNA software. 
• Leverage new features added to LS-DYNA software in every new release. Capabilities like multi-case modeling, cardboard materials, and new meshing tools improve the capability and user experience for drop testing. 
• Leverage high-performance computing (HPC) either on your own hardware or in the cloud. LS-DYNA software supports multicore parallel processing, enabling larger models and shorter solve time.

The expectations of customers and distribution partners are constantly changing, driving the technology and expectations around drop testing. Sustainability is also having a significant impact on what materials products use and how they are packaged. 

Here are five trends that engineers should consider when planning their future drop test efforts.

Sustainability

Sustainability is driving the biggest changes in the systems in which products are packaged. In some cases, the expectation of both consumers and retail partners is to be able to ship products in their own packaging without any protective packaging for shipping. Environmental concerns are also pushing for products and their packaging to use more sustainable materials and to use less material overall.

Cost Reduction

The cost of manufacturing, packaging, and shipping can be considerable, and companies are constantly looking for ways to reduce costs wherever they can. Drop testing will play an even more important role — especially simulation for drop testing — in helping engineers make design changes to reduce the cost of products and their packaging while making sure their impact durability meets specifications. 

Increased User Expectations

Users continue to increase their expectations about the cosmetic look of packaging, and the ability of products to survive drops from ever-increasing heights. Engineers need to use simulated drop testing early in the design process to meet these expectations and give their products a competitive advantage. 

Shelf Appeal and Unboxing Experience

Another area of growing user expectation is how products look on both physical and virtual shelves and what the unboxing experience is like. These aesthetic concerns will have a growing influence on design features needed for impact durability. This is also where simulated drop testing can give engineers the tools they need to try out more visually pleasing packaging designs early in the development cycle. 

Multiphysics Simulation

In the area of simulation, there is a strong push to leverage the multiphysics capabilities in tools like LS-DYNA software, coupling it with Ansys Mechanical™ software, the Ansys Sherlock™ tool, Ansys Icepak® software, and the Ansys Fluent® application. This assesses how the loading and deformation from a drop impact the performance and reliability of the product. 

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