Drop Test Simulation

Understanding Drop Test Simulation: A Critical Tool for Product Validation

In today's competitive manufacturing landscape, ensuring product durability and safety has never been more important. Drop test simulation represents one of the most valuable applications of finite element analysis (FEA), allowing engineers to predict how products, packaging, and components will respond to impact events without the expense and time constraints of physical testing. For manufacturers across Atlantic Canada, from consumer electronics to marine equipment, mastering drop test simulation can mean the difference between a successful product launch and costly field failures.

At its core, drop test simulation models the complex physics that occur when an object impacts a surface. This includes stress wave propagation, material deformation, energy absorption, and potential failure modes. Modern simulation tools can capture these phenomena with remarkable accuracy, providing engineers with detailed insights into product behaviour under impact conditions that would be difficult or impossible to measure physically.

The Physics Behind Drop Test Analysis

Drop test simulation involves some of the most challenging physics in structural analysis. Unlike static loading scenarios, impact events occur over extremely short time periods—typically measured in milliseconds—and involve rapidly changing loads, large deformations, and complex material responses. Understanding these fundamentals is essential for setting up accurate simulations.

Impact Dynamics and Energy Transfer

When a product strikes a surface, the kinetic energy accumulated during the fall must be dissipated or absorbed. For a typical drop height of 1.0 metre, an object reaches an impact velocity of approximately 4.43 metres per second. The resulting deceleration can easily exceed 1,000 g for rigid products, placing enormous stress on components and connections. The simulation must accurately capture how this energy transfers through the product structure and where stress concentrations develop.

Material Behaviour Under High Strain Rates

Materials behave differently under impact loading compared to static conditions. Most materials exhibit strain-rate sensitivity, meaning their strength and stiffness change depending on how quickly they are loaded. For example, many plastics can show a 20-50% increase in yield strength at strain rates typical of drop impacts. Accurate drop test simulations must incorporate appropriate material models that account for these rate-dependent effects, such as Johnson-Cook or Cowper-Symonds formulations.

Contact Mechanics and Surface Interactions

The contact between the product and the impact surface plays a crucial role in determining stress distribution and damage patterns. Simulation software must handle complex contact scenarios, including initial impact, sliding, and potential secondary impacts as the product bounces or rotates. The coefficient of friction, surface geometry, and impact angle all influence the resulting loads and must be carefully specified in the analysis setup.

Setting Up an Effective Drop Test Simulation

Successful drop test simulation requires careful attention to model setup, material characterisation, and solver parameters. The choices made during model development directly affect both accuracy and computational efficiency.

Geometry Simplification and Meshing Strategies

Creating an appropriate mesh for drop test analysis requires balancing accuracy against computational cost. Impact simulations typically require finer meshes than static analyses, particularly in regions where contact occurs or where stress concentrations are expected. A common approach uses element sizes of 1-3 mm in critical areas, with coarser meshes in regions away from impact zones. For a typical consumer electronics enclosure, this might result in models containing 500,000 to 2,000,000 elements.

Mesh quality is particularly important for explicit dynamic simulations. Poor element aspect ratios or highly distorted elements can cause numerical instabilities and inaccurate results. Most analysts aim for element aspect ratios below 3:1 and Jacobian values above 0.6 in critical regions.

Boundary Conditions and Initial Velocities

Drop test simulations typically specify an initial velocity rather than modelling the actual fall. This approach significantly reduces computation time while providing equivalent results. For a drop height h, the impact velocity is calculated as v = √(2gh), where g is gravitational acceleration (9.81 m/s²). Common test specifications include:

• Consumer electronics: 1.0-1.5 m drop height (4.43-5.42 m/s impact velocity)

• Industrial equipment: 0.5-1.0 m drop height (3.13-4.43 m/s impact velocity)

• Shipping containers: 0.8-1.2 m drop height (3.96-4.85 m/s impact velocity)

• Military specifications (MIL-STD-810): Up to 1.22 m for transit drop requirements

The impact surface is typically modelled as a rigid body with appropriate friction characteristics. For standard testing on concrete or steel surfaces, friction coefficients between 0.3 and 0.5 are commonly used.

Solver Selection and Time Integration

Drop test simulations almost universally employ explicit time integration methods due to their superior handling of contact, large deformations, and short-duration events. The explicit method advances the solution in small time increments, with the stable time step determined by the smallest element in the mesh and the material wave speed. Typical time steps range from 1×10⁻⁷ to 1×10⁻⁶ seconds, meaning a 10-millisecond impact event might require 10,000 to 100,000 time steps.

Applications Across Maritime Industries

The diverse manufacturing base across Nova Scotia and Atlantic Canada presents numerous applications for drop test simulation. From the fishing industry to aerospace suppliers, understanding impact resistance is crucial for product success.

Marine and Offshore Equipment

Equipment deployed in marine environments faces unique challenges, including handling during vessel loading, deck impacts in rough seas, and deployment stresses. Drop test simulation helps manufacturers of fish finders, navigation equipment, and offshore monitoring systems ensure their products can withstand the rigours of maritime use. For equipment rated to IP67 or IP68 standards, drop testing often forms part of the qualification process, with typical requirements calling for survival after drops from 1.0-1.5 metres onto concrete.

Aerospace and Defence Components

Atlantic Canada's growing aerospace sector demands rigorous qualification testing for components and assemblies. Drop test simulation allows suppliers to demonstrate compliance with specifications such as RTCA DO-160 for airborne equipment or MIL-STD-810 for military applications. These standards often require survival after multiple drops at various orientations, making simulation particularly valuable for identifying the most critical impact scenarios before physical testing.

Consumer Products and Packaging

For manufacturers of consumer goods, drop test simulation helps optimise both product design and protective packaging. The International Safe Transit Association (ISTA) publishes test protocols that simulate distribution handling, with drop heights based on package weight. Simulation enables engineers to evaluate packaging designs virtually, reducing the number of physical prototypes required and accelerating time to market.

Interpreting Results and Validating Designs

The value of drop test simulation lies in the actionable insights it provides. Proper interpretation of results enables engineers to identify problems, optimise designs, and make informed decisions about product robustness.

Key Output Parameters

Drop test simulations generate enormous amounts of data, but several key parameters deserve particular attention:

• Peak acceleration: Maximum deceleration experienced by critical components, typically reported in g-units. Sensitive electronics often have limits of 500-1,500 g.

• Von Mises stress: Comparison against material yield strength identifies regions of permanent deformation.

• Plastic strain: Quantifies permanent deformation; values exceeding 5-10% often indicate potential failure.

• Contact forces: Peak loads at interfaces help evaluate connection integrity and bearing stresses.

• Energy absorption: Distribution of kinetic energy into elastic strain, plastic work, and frictional dissipation.

Correlation with Physical Testing

While simulation provides tremendous value, correlation with physical drop tests remains important for validation. Accelerometers mounted on test specimens can measure deceleration pulses, which should match simulation predictions within 10-20% for well-calibrated models. High-speed video, typically captured at 5,000-10,000 frames per second, provides visual confirmation of deformation patterns and failure modes. Establishing this correlation builds confidence in simulation predictions for future design iterations.

Best Practises and Common Challenges

Successful drop test simulation requires attention to several factors that can significantly influence accuracy and usefulness of results.

Material Characterisation

Accurate material data is perhaps the most critical factor in drop test simulation accuracy. This includes not only basic properties like elastic modulus and yield strength, but also strain-rate sensitivity, failure criteria, and damping characteristics. For plastics and polymers, temperature effects may also be important, particularly for products used in the variable climate conditions common across Atlantic Canada.

Assembly Modelling Considerations

Real products consist of multiple components joined by fasteners, adhesives, snap fits, and other connections. Accurately representing these interfaces is essential for realistic results. Common approaches include:

• Tied contacts: For bonded interfaces where separation is not expected

• Beam elements: For bolted connections, capturing stiffness and potential failure

• Cohesive elements: For adhesive joints where delamination is possible

• Spot weld definitions: For sheet metal assemblies with discrete weld locations

Computational Resources and Efficiency

Drop test simulations are computationally demanding, often requiring 4-24 hours of wall-clock time on modern workstations. Parallel processing across multiple CPU cores provides significant speed improvements, with most commercial solvers showing good scaling up to 16-32 cores. For companies running multiple simulations, investment in appropriate computing infrastructure pays dividends through faster design iterations.

The Economic Value of Virtual Drop Testing

Implementing drop test simulation delivers measurable benefits throughout the product development cycle. For Nova Scotia manufacturers competing in global markets, these advantages can provide significant competitive differentiation.

Physical drop testing typically costs $500-2,000 per test when accounting for prototype fabrication, test setup, and data acquisition. A comprehensive test programme evaluating multiple orientations and conditions might require 20-50 individual tests. Simulation allows engineers to evaluate hundreds of virtual drops at a fraction of this cost, reserving physical testing for final validation.

Perhaps more importantly, simulation enables earlier identification of design weaknesses. Issues discovered through virtual testing during detailed design cost far less to address than problems found during prototype testing or, worse, after production release. Studies across various industries suggest that addressing problems during the design phase costs 10-100 times less than corrections required during production or field service.

For products requiring regulatory certification or customer qualification testing, simulation provides valuable pre-test confidence. Understanding expected behaviour before committing to expensive physical tests reduces the risk of failed certifications and associated schedule delays.

Partner with Sangster Engineering Ltd. for Your Drop Test Simulation Needs

Drop test simulation represents a powerful capability for product development teams seeking to ensure durability, meet certification requirements, and optimise designs for impact resistance. However, extracting maximum value from these analyses requires expertise in explicit dynamics, material modelling, and results interpretation.

Sangster Engineering Ltd. brings decades of engineering analysis experience to manufacturers across Nova Scotia and the Maritime provinces. Our team has conducted drop test simulations for products ranging from consumer electronics to industrial equipment, helping clients reduce development costs and bring robust products to market faster. Based in Amherst, we understand the unique challenges facing Atlantic Canadian manufacturers and provide responsive, practical engineering support.

Whether you're developing a new product, qualifying an existing design for demanding applications, or investigating field failures, our simulation capabilities can provide the insights you need. Contact Sangster Engineering Ltd. today to discuss how drop test simulation can support your next project and help ensure your products perform reliably when it matters most.

Partner with Sangster Engineering

At Sangster Engineering Ltd. in Amherst, Nova Scotia, we bring decades of engineering experience to every project. Serving clients across Atlantic Canada and beyond.

Contact us today to discuss your engineering needs.