MGA Simulation Laboratory
The Simulation and Durability Test Laboratory is a division of MGA Research Corporation. MGA is an A2LA accredited leading-edge company which provides independent testing services, equipment, and fixtures to the automotive, military, aerospace and agricultural industries. The Simulation and Durability laboratory is part of MGA’s wide range of specialized test laboratories located in Troy, Michigan, near most major OEM’s and the automotive supplier base. The laboratory offers a wide range of services including test consultation, data analysis, fixture design and fabrication, data collection, Multi-Axis Simulation Table (MAST) testing, full vehicle shaker testing, block load cycle testing, and real-time multi-channel simulation testing. The staff at MGA is well versed in various industry accepted test specifications, protocols and standards. First-class professional service and quick turn-around on testing and reports are hallmarks of MGA’s Simulation and Durability Lab.

Simulation Testing

Applications

Full Vehicles
Exhaust Systems
Cooling Modules
Seats
Interiors and Cockpits
Fuel Tank Systems
Batteries
Trailer Hitches
Suspension and Axle Systems
Roof Racks and Roof Systems
Shipping Racks and Dunnage
Military/Aerospace Applications

Multi-Axis Simulation Tables

MGA utilizes both MTS and MGA Multi-Axis Simulation Tables (MAST). All MAST tables are controlled by the latest MTS FlexTest controllers and take advantage of the industry standard RPC ProTM and FlexTestTM control software. MGA operates nine (9) MAST tables in Michigan with additional tables in New York, Wisconsin and Mississauga, Ontario. The most common type of MAST testing is Road Load Simulation. The Road Load Simulation process includes collecting data from a vehicle and matching that data on a MAST to simulate the life of various components in that vehicle. Road Load Data (RLD) is acceleration (and/or strain) data that is collected from different road surfaces on a test track. Our Tables have the following capabilities:

Six (6) Degrees of Freedom
Environmental Conditioning
Table Dimensions up to 6×8
Sunload Lamps
Hot Exhaust Gas Simulation
Strain Correlation
Squeak and Rattle Evaluation

Component Simulation
Using MTS servo hydraulic controllers, such as the FlexTest 200, MGA is able to conduct simulation testing on full systems and components with direct inputs to the sample. When basic fatigue testing can not reproduce the effects of a complicated system, it is best to apply real road simulations directly. MGA can provide as many inputs as necessary to create complex rigs that accurately simulate real world conditions.

Road Load Data Acquisition (RLDA)
MGA Research is a full service testing laboratory that can handle all of the tasks related to Road Load Simulation testing. We will instrument the vehicle, collect data on a test track, analyze the data and perform the testing at one of our various locations. Our engineers have been trained in instrumentation of strain gages and accelerometers, along with nCodeTM for data analysis. To collect data, we use a SoMat® eDAQ data system with four high level analog layers. This allows for up to 64 channels of data collection. We are willing to travel to our customers’ proving grounds, or our Wisconsin facility also offers our customers access to a full proving ground where the RLD may be collected for future simulation testing.

Cyclic Durability Testing
In certain circumstances a supplier may need to validate the individual components of their system for durability and fatigue life. The MGA Hydraulic lab has over 100 loops of servo hydraulic actuators that are capable of fatigue testing in various fashions. Each activator can be configured with load, torque or displacement censors to meet test specifications we are provided. The fatigue and stress lab can apply loads from a few pounds up to 150,000 pounds with a frequency range of 0 to 100 Hz. The actuators can also be grouped together to provide multi-axis fatigue testing.

Full Vehicle 4-Post Simulation Testing
A Hydraulic Four-Post system is a collection of four hydraulic pedestal actuators positioned such that the four wheels of a vehicle can sit on the wheel carriages attached to the actuators. This system can be used to evaluate the vehicle body structure, frame, chassis, internal components, or interior and exterior squeaks and rattles. MGA’s Simulation and Durability Test Laboratory’s four-post system consists of four actuators- each with a force rating of 15,000 lbs, and a 220 gpm three-stage servo valve capable of hitting peak velocities of 170 in/sec. Our four-post system is rated for passenger cars or light-duty trucks.

MGA Simulation Lab Flyer

 While most people notice how comfortable their seat feels, they don’t realize all of the design and testing that goes into making their seats not only comfortable but also safe. While a lot of the seat features are luxury items, many are safety related.  Active head restraints, side airbags, lower anchorage, and tethers for child car seats, to name a few, are all examples of items that many people do not look for when purchasing a vehicle.  These items not only provide safety but the also add weight and complexity to the seat.  This extra weight and complexity creates obstacles when it comes to testing.

 MGA’s simulation group provides data acquisition and vibration testing to help suppliers and OEMs overcome these obstacles.  Added weight in the seatback and head restraint can shorten the life span of a seat’s structure due to the constant vibration that a vehicle experiences.  Therefore, to determine the integrity of a seat after a vehicle life, we can test the seats at an accelerated pace. This accelerated testing provides critical information to suppliers and OEMs to expedite time between design and production.

 Typically a vehicle seat is instrumented with accelerometers which collect acceleration data as the vehicle drives down a test track. That data is then used with a Multi Axis Simulation Table (MAST) to reproduce the acceleration that the seat experiences during the drive down the test track.  Multiple test tracks are used and the data collected is looped to create a drive file which represents many surfaces and situations that a vehicle comes in contact with.  The simulation testing includes weighted dummies held in place by seatbelts which are vehicle representative. 

 MGA Research offers hydraulic testing capabilities along with 13 MAST tables spread out across its Troy MI, Burlington WI, Akron NY and Greer SC facilities to accommodate customers’ needs.  Along with data acquisition and vibration testing, MGA’s experienced staff can provide a complete seat validation test plan to verify all OEM specifications and Federal Regulations are met.

Stricter emissions regulations have caused designers to come up with lighter designs that have additional components such as urea pumps and afterburners. Different catalytic materials have been selected to control the effect of exhaust gas on the environment. Some engineers have even experimented with plastics and composites to create innovative new light weight, high strength designs. All of which must pass laboratory testing before they can be released.

Every consumer would be happy to learn about the rigorous tests their exhaust system undergoes before it is put into production. The most advanced test that a system will undergo is a full road simulation. This test utilizes one or two Multi-Axis Simulation Tables with 6 degrees of freedom synchronized to simulate the vibration and damage induced by the road. Acceleration, Strain, and Displacement data is collected on the road surfaces and then duplicated on the test rig using the full exhaust system and the engine block. Hot exhaust gas is pumped through the sample while it is under test. This rig uses advanced software and servo hydraulic controls to accurately reproduce road load events. A test effectively represents a lifetime of use in only a few short weeks. In addition to full system testing, each component is tested individually. These tests include vibration, thermal shock, fatigue testing, and impact testing. These types of tests are conducted on a component level such as manifolds, hanger rods, catalytic converters, and mufflers.

At MGA research we regularly conduct these types of test for both OEMS, Tier 1, and Aftermarket Suppliers. We have the capability to run multiple full system simulation tests as well as hundreds of servo loops for fatigue testing. MGA also operates five individual 1 million BTU hot gas burners for hot exhaust gas testing such as thermal shock and durability. Additionally, there are eight electro-dynamic shakers for vibration testing. If you are an exhaust system designer or validation engineer please contact our exhaust group. MGA can help you identify what your testing needs are and develop a protocol to accurately predict fatigue life through physical test and help improve designs. MGA Troy is home to a full service exhaust testing lab capable of performing a complete validation plan for even the largest high volume programs.

“Test Methods for Multi-Axis Simulation Testing per MIL-STD-810G” written and presented by David Nagle; Co-Authors Gerald Roesser, Terry Wilhelm (ArmorWorks); Presentation Date/Time: April 13, 2010 at 1:20 p.m.

David Nagle has been a test engineer at MGA for the past 3 years. He works in the Hydraulic Durability group specializing in Vibration MAST testing. Dave’s expertise spans across a variety of industry standards; from automotive to military application. Dave is a graduate of the University of Michigan – Ann Arbor with a Bachelors Degree in Mechanical Engineering.

A copy of this document can be downloaded from the SAE International website: http://www.sae.org/technical/papers/2010-01-0284.  The technical paper abstract as seen on the link can be seen below:

“One of the primary military standards used for vibration testing has been updated to incorporate multi-axis simulation. The latest revision of this standard is MIL-STD-810G in which the addition of Method 527 allows for real-time road load data to be used for multi-axis simulation. This revision is looking to improve upon the previous vibration test method of single-axis random vibration in each direction. This document will overview the changes to the standard, provide a summary of the previous test methods, detail a test procedure using real-time data for multi-axis simulation, and present the procedure for the testing conducted with this data. In addition, it will help to demonstrate a method for using multi-axis simulation for MIL-STD-810G and help its readers gain a better understanding of this new method.”

For any questions regarding MGA’s involvement in SAE or more information on this technical paper, please contact David Nagle at david.nagle@mgaresearch.com.

For the purposes of this presentation we will be discussing simulation testing as it relates to automotive vehicle durability development with a special emphasis on Multi-Axis Simulation Table or “MAST” testing. However, these same principals can be applied to many types of transportation vehicles that are utilized in a wide range of industries.  In today’s automotive industry, the primary goal is to design a vehicle that is both safe and durable. This design goal provides the best in value for customers and helps to build the manufacturers reputation for quality and dependability.

Historically, the durability of a vehicle is assessed in several different ways. The simplest form of testing is to merely drive the vehicle through its normal usage. If a vehicle is driven for 100,000 miles or 6 years, one will very accurately be able to assess its reliability over 100,000 miles. This test driving method, while obviously being the most accurate is not the most efficient. As a consequence, test tracks have been created to simulate these road conditions. A typical proving ground test track will be made up of several types of road surfaces that the vehicle will see in the course of its product life. These surfaces are able to condense the amount of time it takes to expose a vehicle to an equivalent amount of fatigue exposure as it would be exposed to over a period such as 10 years. For example a test track can be designed to have a 40 to 1 ratio where one mile on the track is comparable to 40 miles in real world conditions. This is an effective test method but can only be conducted very late in the design process when an assembled prototype is available. It requires drivers and a large investment in time and labor. Also, road surfaces can be custom tailored to specific vehicles or regions but this process can be time consuming and expensive.

A third test method is basic fatigue or block cycle testing. This type of testing can be highly effective on a component level basis when the life expectancy of a component is already known based on past history. This approach is excellent for suppliers. With this type of testing, one can predict the reliability of a component by saying part A is stronger than part B. If part B has historically been a reliable part, then it is accepted that part A will be at least as good. This method is not as accurate for complex systems and is not representative of the multitude of inputs that a vehicle will see in the real world.  Finally, there is Real Time Simulation Testing. This form of testing has the best of both worlds as it can be highly correlated to real world performance and also save costly development time. The remaining portion of this presentation will focus on the test methods and the process for conducting this type of testing.

Simulation testing as described in this presentation is the technique of predicting the structural integrity and durability of a product by using an advanced form of physical testing. This test method incorporates the use of actual road data combined with a durability schedule based upon the market and region in which the vehicle will be used. Time history data is collected on vehicles while being driven through conditions normal to the context for which they were designed. Using advanced analysis techniques, the data can be optimized to create a physical test rig in a laboratory environment that will be highly correlated to real world conditions while saving valuable time and money.

This flow chart demonstrates the general simulation test method. First, determine the appropriate road and driving conditions for the vehicle in development. This is done by doing a market study and considering the products end use. Next, collect road load data by instrumenting the vehicle. The collected data is then analyzed and reduced.  The test length is calculated while holding fixtures are designed. Next, the sample is mounted to test rig, and excited such that the response matches the desired road data through an iterative process. If after the test there are failures then there may be a design change and the test will be run again.

The first step is to determine the type of data that needs to be collected and how to use it. Normally, when a vehicle is designed, it is intended for use within a certain market and/or region. A study is performed to understand the in-service conditions. This study will take into account the various types of road surfaces, road speeds, and environmental conditions. The frequency or distribution of occurrences of each type of road surface is also taken into account. A document called a durability schedule is produced which will detail this statistical information. The durability schedule will later be used to determine the test length and the number of times each road surface simulation is repeated. Each of these surfaces must be sampled in a process called Road Load Data Acquisition or (RLDA)

Example of a Generic Durability Schedule

For example, if a product is designed to be a delivery truck in rural areas with 50% of the roads unpaved then the durability schedule will conclude that half of the simulation data must be sampled from these dirt roads. This chart is an example of a generic durability schedule. In addition to the vibration, certain components such as radiators and exhaust systems are exposed to temperature and environmental conditions simultaneously. This is accomplished in the lab using extreme temperature chambers and hot gas burners.

To collect Road Load Data (RLD) a vehicle must be instrumented and driven across a sampling of the road surfaces travelled during normal usage. The data collected can include many types of measurements. The following are some of the most common types:

1. Wheel Force Transducers
2. Wheel end to body displacement
3. Chassis, body, or component tri-axial accelerometers
4. Wheel-end acceleration
5. Strain Gages
6. Vehicle Speed
7. GPS
8. Environmental Conditions

Once the RLDA has been performed and the durability schedule has been agreed upon, it is time to start optimizing the data for use on a multi-axis test rig. The durability schedule will tell you statistical data about how often each surface should be used while the expected end-use of the product will dictate the test goal and test length. Ideally we would like to simulate these road surfaces on the test rig in as short of time as possible while retaining the maximum amount of correlation to the real world. The data is edited and any errors or dead space is removed. If there are areas with relatively no input then these are removed as well.

At this phase the collected data must be normalized so that relative comparisons can be made between different road surfaces, events, and recordings made from the test rig itself. There must be a method in place so that accurate correlations can be derived. In order to compare surfaces, correlate to the real world, or find the worst case vibration scenario, the fatigue damage must be calculated. With a time history file, it can be difficult to compare the relative effect the inputs have on a sample. This process makes that easier.

Relative Fatigue Damage Analysis is conducted by reducing the data or vehicle inputs to a series of cyclic events using a method such as Rainflow counting. When used in combination with an S/N curve, a transfer function can be developed that will predict the relationship between the inputs and accumulated damage. The data is there by normalized so that relative comparisons can be made and the total damage incurred from testing can be assessed.  The data is also dependent on frequency, speed, and acceleration so a Fatigue Damage Spectrum is produced.  The fatigue damage spectrum is a spectral representation of a fatigue damage index as a function of any system’s natural frequency. This spectrum is computed directly from the Power Spectral Density function representing the field conditions and provides a relative fatigue damage estimate based on acceleration levels and exposure time.  The damage number attached to a set of data is an effective way to compare data sets and correlate the test rig to the real world. This method helps us to ensure that one mile on the road is equivalent to one virtual mile in the laboratory.

In very simple terms Damage is a unit-less number that represents the severity of a time history file based on its maximum and minimum peaks, as well as the RMS of the data. A software program called Glyphworks, which is produced by nCode®, is used to cut sections of these time history files, and analyze them for damage retention. Each channel of acceleration data is used to calculate an individual damage number prior to any data editing.  Following the data editing, another damage calculation is performed and a percentage comparison is used to make sure that the edited files have retained most of the damage from the original files. This data compression technique is used to shorten the test duration and make the testing process more efficient.  The significance of this process is substantial, as in some cases, it can likely compress a test of the vehicle’s durability life from over a month to just a week or less.  This method of accelerated testing is thought to realistically validate a product in a rapid manner.  By decreasing test duration, one will see improvements in productivity and cost savings.

Upon editing and optimizing the data, it is time to select an appropriate test rig for your application. There several types of real-time simulation rigs and many ways to apply these inputs to your product. Real-Time simulation can mean applying force inputs, acceleration, displacement or even strain to your product on as many axes as collected in the field.

MGA conducts simulation testing on MAST tables, Four Post Actuators, Electro-Dynamic Shakers as well as direct coupled multi-axis system tests where the actuators are attached directly to the sample. This type of rig is common in suspension testing where for example six actuators may be attached directly to the corner of a vehicle. Another example is connecting directly to the frame of a vehicle for testing such as “cab shake” where the Cab is being validated as it responds to inputs on the frame.

For this article I will be using MAST or Multi-Axis Simulation Table testing as the example. A MAST rig is made up of 6 hydraulic actuators connected to a table capable of moving in 6 degrees of freedom. This includes x, y, z, roll, pitch and yaw. The table is capable of reproducing vibration frequencies from 2 to 50 Hz.  Each actuator is instrumented with an LVDT to measure displacement. Samples are mounted to the table top so that road inputs can be applied to actuators and road surfaces can be simulated. In the case of a MAST test, the desired data is presented as acceleration or strain. Accelerometers are mounted to the table top and sample while the actuators are stroked until there is a match. I will elaborate more on that process later. For other types of components or systems, the desired data signals may be presented as force. In this case actuators can be connected to the sample with a load cell and the desired load data is matched. Further, there are cases such as torsion bar testing where a displacement file is given and the objective is to simulate the rotational displacement that a torsion bar experiences in the field. Basically any data set collected in the field can be simulated in the lab regardless of its type.

Once the appropriate type of test rig is selected as a validation tool, the holding fixture design becomes very important. The goal of the holding fixture is to provide a means to attach input actuators to the sample. In the case of a MAST test, the fixtures job is to hold the sample in the vehicle ride attitude on the tabletop while accurately matching the attachments to the vehicle. The fixture must not induce any additional stresses or contribute a response due to its natural frequency that affects the vibration placed on the sample

Several things must be considered during fixture design. The fixture must not  have a natural frequency in the frequency band of the test data. For a MAST test, the Natural frequency has to be at least above 50hz if not 200Hz for assurance. The fixture must also be light weight so as to not add too much moving mass to the test rig. This will also keep the natural frequency high, this in combination with the stiffness. It is important that the fixture mounting points are accurate. Normally CAD data is used to generate the fixture. This will ensure that the sample is mounted exactly as it would be on the vehicle and no extraneous stresses are induced. Often a test fixture itself can be run through a computer simulation to determine where improvements can be made.

Now that the data has been collected and analyzed, and the test fixture has been designed and built it is time to mount the sample and begin to match the system response to the input data.  This process of matching the desired data to the response is the same no matter what the test type is. These basic principals apply to frame coupled testing, 4 post testing, MAST testing and all types of simulation testing. Today we will go into depth on the iterative process used to match desired data to the response on a MAST system.

This stage of the test setup is what is known as the drive file iteration process. The drive file is the corrected data set that is generated to accurately match the desired data. In general a closed loop servo-hydraulic system such that is used in a MAST test will not immediately be able to match the desired data on command until the required offsets are calculated and the data is corrected for the dynamics of the system. If you are familiar with control systems you will know that a servo-hydraulic loop employs closed loop PID tuning to ensure that the feedback matches the command. In a fixed frequency, fixed amplitude test this tuning method is very easy to control. A few simple adjustments will allow a user to accurately correct the command-feedback loop until a match is achieved. With a complex time history file, this task quickly becomes much more complicated. It is very difficult to get the command and feedback on a multi-axis system with crosstalk and complex dynamics at play to converge. This is where advanced software such as RPC Pro and hardware in modern hydraulic controllers are called in to make the process easier.

To start the drive file iteration process, accelerometers are mounted to a test fixture or the sample just as they were when the data was collected. Usually at least three tri-axial accelerometers are used to define a space and give greater resolution  Strain gages are sometimes applied to help match the road data and provide a more accurate picture of the damage induced by the vibration.  Next, a random (white noise) input is commanded to each of the drive channels as the accelerometer response is recorded.

This response yields a transfer function which can be used to match the acceleration response with the desired acceleration data collected from the road surfaces.  A filter is created to omit any data that is beyond the workable range of the test equipment.  Each of the desired channels is generally filtered from 2-50 Hz, and an initial drive file is created using the transfer function and inverse transfer function.

The next step is to play-out of this drive file on the test rig. The accelerometer response is filtered and error is calculated. If the response does not match the desired file then the drive file must be adjusted to command a better match.  RPC Pro software allows for specific gains to be applied to each of the acceleration response channels, and based on the error of the previous drive file play-out, the drive command is adjusted and acceleration is recorded again.  This process is repeated until the desired acceleration is matched.  The screenshots show how a file will begin to converge after each iteration. The second plot is an example of a good match after several passes.

The example plot shows an overlay of desired acceleration and response acceleration data for a single channel.  In some simulation tests such as a MAST test, the control mode may not be the same as the feedback mode. For example if acceleration is the data type the test engineer is trying to match, the control mode may be displacement. The drive file will then adjust displacement control as it measures the error in acceleration feedback. This method can make it easier to control the table in some cases as displacement is a more stable control mode and less susceptible to noise and other transient influences.

The drive file iteration process is complete when all time history response files have been adequately matched to the desired data. From our previous experience in vibration testing, the RMS value of each channel should be at least within 5% of the desired RMS value, and the maximum and minimum acceleration peaks should be within 10% of the desired peaks.  This criteria is usually determined by the customer but can be altered depending on the application.

Another factor used to determine if a time history match is satisfactory is to overlay the desired and response spectrums and make sure they are the same level across the entire frequency range.  This will show if there are any issues with matching certain frequencies due to resonance of the fixture or system.

Once the acceleration data is matched and a satisfactory match in the time and frequency domain is achieved for all road surfaces, the drive inputs are saved and played in a specific sequence to simulate the vehicle life. The sequence is determined by the durability schedule that was created at the beginning of this process. Typical tests can be anywhere from 1 day to 2 weeks depending on the complexity and length of the data.

Modern shock absorbers typically create a linear curve as the velocity of the shaft increases. This means that as the velocity increases on the shaft, the force required to move the shaft, or the damping, also increases. In many cases it is desirable to have a specific slope or linearity to this curve. In other cases, the designer of the shock may wish to have the damping decrease as the velocity increases. The process of collecting data for these curves is what is known as shock absorber characterization. A designer may have a goal in mind that is either determined by race track data, past performance, or customer specifications.

In order to collect this data, a shock dynamometer is employed. This is a machine that is capable of moving the shaft of the shock absorber at varying velocities and recording the resultant forces. It is important that the velocity be controlled precisely so that an accurate characterization can be made. The designer can then make changes to the shock as needed to find how that will affect the performance.

MGA Shock Absorber Dynamometer

At MGA, we utilize an MTS servo-hydraulic actuator on our shock dyno. This machine is capable of moving 90 inches per second. This velocity is an advantage when collecting data for highly advanced shock absorbers requiring high speed articulation. Located in the Metro Detroit laboratory and soon in our South Carolina location, it is easily accessible to all industries including military, automotive, and racing.

In addition to shock absorber characterization, this machine can be used for all types of high speed impact, compression or tensile tests.

Over the past few years, MGA has continually expanded the facilities and array of services offered for real-time simulation durability testing. Typically, these facilities include systems and expertise related to Multi-Axis Simulation Tables (MAST), Electro-Dynamic (ED) vibration systems, and multi-channel fatigue capabilities. This fall, MGA has made its largest expansion yet into this area of testing technology. This expansion is part of a multi-year plan to convert the Elliott campus of buildings, purchased in 2005, to specialized test laboratories serving the needs of the automotive industry.

Previously, MGA started with two MASTs and various component-level fatigue testing stations at the Executive Laboratory facility. In 2006, four additional MASTs, a 4-post simulation rig, and two ED shakers were brought on-line. For personnel, experts in dual MAST simulation and data editing/processing were added to our staff. The new laboratory, referred to as “Elliott II”, represents one of the biggest investments that MGA has made in the Michigan-based labs. Facilities added this summer include:

• Four additional 5’ x 7’ Six Degree of Freedom  (DOF) MASTs with the latest MTS FlexTest controls
• Super-sized 12’ x 12’ Six DOF MAST with 35 KIP actuators
• 3 ED vibration systems of various sizes
• Lab infrastructure including 400 gpm pump, multiple HSMs, and additional capabilities for   extreme temperature cycling with vibration
• Two additional hot gas flow simulators for high heat/exhaust application

MGA’s Director of Business Development, Paul Sapiano, comments, “It’s been great to see the continued quest by the team to continue to strive to help our customers meet their goals. We have gained a great deal of experience over the last couple of years in conducting higher level tests that combine real-time simulation with other environmental factors such as extreme climatic conditions, pressure cycling, hot gas flow, etc. Elliott II allows us to handle much greater volumes of higher level work including dual MAST exhaust test applications.”

MGA’s overall scope of facilities in this area now includes 11 MASTs, 15 inertial masses/bedplates, 120 servo loops, and numerous other items related to this type of work. MGA’s staff has also grown, both in number and expertise. The team at MGA is well versed in many industry and OEM-specific test protocols. As with all MGA facilities, staffing has been set up to conduct testing 24/7.

Elliott II is just a short walk from the 2807 Elliott laboratory and a very short drive from the Executive lab. Gerald Roesser, MGA’s Hydraulic Durability Business Unit Leader, comments, “Elliott II is another exciting step our company is taking in meeting the needs of our customers. I am highly confident that our customers will be pleased with this facility. Our staff has worked very hard in conjunction with our MGA-NY counterparts in bringing this facility on-line. We are excited about the horsepower this adds to our offerings, and are looking forward to more challenging and complex tests at Elliott II.”

For over 50 years, Mercedes-Benz has exposed its vehicles to a vigorous test track known as Heide-dauerlauf*. Located in Germany, this route provided Mercedes with a means of testing the life of a vehicle and its components in an accelerated manner*. In the modern era, Mercedes has re-created the conditions of this track at their facilities in Stuttgart and Sindelfingen*. Each vehicle is instrumented with accelerometers, and a courageous driver endures the vibrations of the test track at a regulated speed as acceleration is recorded at various locations*. This acceleration data is then delivered to the test lab where specialized software and equipment is used to reproduce the same vibrations.

MGA has performed Heide-dauerlauf or “Heide” testing on various seat programs for 6 years for various automotive suppliers. Currently, MGA-MI is capable of performing this vibration test on eight different test rigs. Each rig, known as a Multi-Axis Simulation Table (MAST), is capable of reproducing the six degree-of-freedom vibrations seen on the Heide track. The MGA facility in Troy, MI uses MTS FlexTest™ IIm and IIs software to operate each of the MAST systems. RPC Pro™ (MTS) is used to match the road load data provided by the customer.

Heide testing is used to validate our customers’ Design and Production Level seats for Mercedes and Chrysler programs alike. At MGA, we strive to simulate the on-road conditions with consistency and accuracy. For every test performed, the seat is mounted to a rigid fixture (fabricated at MGA) as it would be attached in the vehicle. The seat is set in its design position, and a dummy representative of a driver is secured to the fully trimmed seat with the correct D-ring location and seat belt tension. In addition, 24-hour test monitoring provides a simple way to fully test each seat in a short period of time.

Using this type of test methodology, MGA can perform similar tests for OEMs and suppliers using data collected at their proving grounds or the MGA test track in Burlington, Wisconsin.

In recent history, a major concern for military vehicle seating suppliers has been the seat’s performance in the event of a mine blast.  Many of our soldiers have been severely injured or killed in this scenario, and military design engineers are working to prevent these tragedies by equipping their vehicles with seats capable of preventing spinal or brain injury under these attacks.  MGA Research has worked with many different military seat suppliers in testing for seat safety during mine blast simulation using our drop tower.  This testing has helped our military customers develop energy absorption (EA) technology which is currently being used in the field.  This testing is very useful, but we think vibration testing would prove to be equally as important.  Vibration testing could prove to be a useful method of determining the structural integrity of the energy absorption mechanisms when exposed to stress in directions other than vertical.  Our drop tower tests were conducted on new production seats, which raises an interesting question: would the seats perform nearly as well after the combat vehicle has been exposed to the rough terrain conditions seen in Afghanistan or Iraq?

Following a series of mine blast simulation tests, MGA developed an experimental vibration test for an un-tested military seat.  This test was developed from a generic 6-axis rough road simulation profile.  The military seat was secured to the surface of the Multi-Axis Simulation Table (MAST) which is a rig powered by six hydraulic actuators that is used to match 6-Degree-of-freedom (6-DOF) acceleration data.  The seat was occupied with a dummy representative of a soldier equipped with their gear, and this dummy was secured to the seat.  Throughout the duration of the test, we observed several occurrences of structural issues.  We consulted the mine blast simulation engineers and discovered that we produced similar failures, as well as some new failures.

Vibration durability test setup on a 6-DOF MAST system

Moving forward, we would like to work on developing a better representation of a 6-axis military vehicle simulation by collecting data from such a vehicle in a rough terrain setting similar to the rough terrain zones at our current US military locations.  From this data, we would be able to more accurately define how a vibration test equates to the amount of vibration actually seen by these vehicles overseas.  More information on this subject was included to the latest revision of Military Standard 810G (MIL-STD-810G) in the section labeled “Method 527.”  This testing method is a generic description of the procedure and theory of Road Load Data Acquisition (RLDA) techniques.  We have reviewed this material, and have experience in vibration testing that will aid us in the development of such simulation tests.