At Delserro Engineering Solutions (DES), our commitment to ensuring the highest standards of product reliability has reached new heights with our recent achievement: ISTA® certification. We are thrilled to announce that DES has been certified by the prestigious International Safe Transit Association (ISTA) as a qualified Transport Testing Laboratory. This certification is not merely a recognition; it is a testament to our unwavering dedication to excellence and precision in product testing.

Certification by ISTA ensures that a testing laboratory possesses not only the proper equipment but also the advanced capabilities required to conduct ISTA package performance testing. ISTA testing, with its focus on subjecting shipping containers to a series of rigorous hazards including shock, vibration, and various environmental conditions, mirrors the challenges products face throughout their distribution cycle. Achieving this certification demonstrates DES’s commitment to comprehensive testing methodologies, evaluating the robustness of products under real-world shipping conditions.

Secure your competitive advantage with DES’s ISTA-certified testing and watch your market trust and product integrity flourish.

ISTA Certification: Demonstrating Our Commitment to Quality Assurance

The achievement of ISTA certification is an unequivocal message to our clients and partners. It underscores our commitment to comprehensive testing methodologies that ensure the robustness of products under real-world shipping conditions. It reassures you that at DES, we do not compromise when it comes to the reliability and quality of your products.

Our dedication to quality does not stop at ISTA certification alone. DES is also accredited to ISO/IEC 17025 by the American Association for Laboratory Accreditation (A2LA). This dual recognition serves as a beacon of our strong technical competence and world-class equipment capabilities. We adhere to the highest industry standards, ensuring that every test conducted in our laboratory is reliable, accurate, and of unparalleled quality.

Our ISTA certification and A2LA accreditation offer our clients a unique advantage – the ability to evaluate both the reliability of their products and the performance of their package design under one roof. DES understands that a product’s journey doesn’t end at its reliability; it extends to its safe and consistent transportation to its final destination.

Your success begins with the right testing partner – choose DES.

Accredited Testing Laboratory: Ensuring Unparalleled Precision

At Delserro Engineering Solutions (DES), our distinction as an accredited testing laboratory goes beyond mere recognition; it embodies our unwavering commitment to ensuring unparalleled precision in every test we conduct. Being an accredited testing laboratory means adhering to the highest industry standards and consistently delivering results that meet the most rigorous quality criteria.

As an accredited testing laboratory, our suite of testing services is both comprehensive and customized to cater to the diverse needs of our clients. Whether it’s Accelerated Product Life Cycle Testing, Custom Test & Measurement, Dynamics Testing, Environmental & Climatic Testing, Package Testing, Production Screening, or Reliability Testing, we can design and implement specialized testing setups that cater to your unique product specifications.

In the competitive landscape of product development, precision matters. It is the key differentiator between products that merely make it to the market and products that dominate the market. At DES, our accreditation as a testing laboratory is your assurance of precision and quality. Partner with us, and let our accredited status enhance your products’ reliability and market success.

Contact DES, where precision meets passion for excellence.

The Essence of Excellence: DES as Your Trusted Testing Laboratory

Delserro Engineering Solutions (DES) is your trusted testing laboratory, dedicated to upholding excellence in product qualification and reliability testing. Our journey in this field spans over three decades, during which we have become a name synonymous with precision, reliability, and unwavering commitment to quality assurance.

Our legacy as a testing laboratory reflects not just our longevity but also the immense expertise we have amassed over the years. We have successfully completed testing projects for esteemed clients including Adidas, Crayola, Medtronic, Rolls Royce, Boeing, Lockheed Martin, and the U.S. Army. This extensive experience allows us to offer insights and expertise that are truly unparalleled in the industry.

Partner with us and experience the difference that our legacy of excellence can make for your products.

The post DES Testing Laboratory Achieves ISTA Certification appeared first on Delserro Engineering Solutions.

1. Incorporate HALT in your Product Development Cycle

Highly Accelerated Life Testing (HALT) is a rigorous reliability test method that is used to expose product weaknesses. The goal of HALT is to proactively find weaknesses and fix them, thereby increasing product reliability. Because of its accelerated nature, HALT is typically faster and less expensive than traditional testing techniques. 

During product development, HALT can find design weakness when changes are much less costly to fix. By finding weaknesses and making changes early, HALT can lower product development costs and compress time to market. When HALT is used at the time a product is being introduced into the market, it can expose problems caused by new manufacturing processes. When HALT is performed after a product has been introduced into the market, it can be used to audit product reliability caused by changes in components, manufacturing or suppliers etc. The bottom line is that HALT can reduce product development time and cost, reduce warranty costs, improve customer satisfaction, gain market share, and increase profits.

More information about HALT can be found in the following blog articles:

Circuit Board HALT Testing Case Study

Rapid HALT – A Cost Effective Alternative to HALT

What Is HALT And Why Perform HALT?

What Is A Typical HALT Procedure?

What Equipment Is Used For HALT?

What Kind Of Failures Occur During HALT?

2. Perform Accelerated Life Testing (ALT)

Accelerated Life Testing (ALT) is a method used to simulate the life of a product in a short period of time.  The stresses are higher than normal to compress time.  The higher the stresses used in the ALT, the shorter the test time.  ALT is best applied to components or less complicated products to focus on specific failure modes.  Typical ALT models are the Arrhenius Model, the Arrhenius-Peck Model and the Coffin-Manson Model. 

Some benefits of ALT include:

• Determining if a product will have wear-out failures
• Estimating a product’s field life using testing.  The life determined through ALT can be compared to desired product life goals and analytical predictions and simulations. 
• Finding additional weaknesses not found in HALT

Some key differences between HALT and ALT are:

• HALT will not estimate product life whereas ALT will. 
• ALT Tests will use one or two different stresses and typically run longer than HALT tests.  Therefore, ALT typically produces wear out failures.   An example would be an ALT for a product that sees thousands of temperature cycles in its lifetime, but not much vibration other than from shipping.  The ALT would be focused on temperature cycling only and would likely expose it to a few hundred cycles or more.  The HALT would expose the product to much fewer temperature cycles, but also incorporates vibration stresses.   Thus, different types of failures could result from each test.  In HALT perhaps a weakness caused by vibration will occur that could show up during shipping and handling in the field.  In ALT, perhaps a failure caused solely by thermal fatigue would occur.  So if you only perform only one type of test, perhaps a potential field failure mode could be missed. 

More information about ALT can be found in the following blog articles:

Accelerated Temperature Humidity Testing Using the Arrhenius-Peck Relationship

Constant Temperature Accelerated Life Testing using the Arrhenius Relationship

Door Open/Close Accelerated Life Test Case Study

Accelerated Life Product Reliability Testing of a Carrying Handle

Accelerated Life Cycle Testing of a Case Handle

3. Perform Design Verification Testing (DVT)

Design Verification Testing is a comprehensive process to verify a product will meet all if its design requirements.  DVT is also referred to as verification or validation testing.  Obviously, this is done in the design phase before final production.  Examples of some of the parameters that are checked during DVT are:

• All product functions such as Electrical and Mechanical functions
• Product performance
• Climatic or environmental testing
• Electromagnetic compatibility (EMC)
• Safety testing
• Software validation

For example, a product could be exposed to specific types of climatic stresses such as salt corrosion, solar (UV), temperature-altitude stresses or water ingress.  These types of stresses would not commonly be used in a HALT or ALT.  Therefore, unique failure modes could be exposed in DVT. 

4. Perform Reliability Demonstration Testing (RDT)

The purpose of an RDT is to demonstrate the Mean Time Between Failure (MTBF) of a product.  Reliability Demonstration Tests are usually performed at a system level.  For example, a computer server that contains many components such as hard drives, fans, etc. is an example of a system level test.  RDTs are commonly performed on repairable systems.

RDTs incorporate a reliability percentage R and a confidence level C.  They are limited in using only the stresses the product will see in the field.  RDTs are focused on demonstrating the MTBF in the steady state portion of the bathtub reliability curve, where ALT’s are focused on wear-out.  Some manufacturers are required to show a minimum MTBF on their products before they can sell them to their customers. 

5. Incorporate a HASS or ESS Program

HASS stands for Highly Accelerated Stress Screening.  ESS stands for Environmental Stress Screening. Both are screening methods used to expose manufacturing defects that would cause a failure in normal field environments including shipping, handling and use.  Both HASS and ESS are performed during manufacturing on production products or components. 

The types of stresses used for HASS are similar to those used in HALT. HASS uses combined temperature cycling, random vibration and electrical loading/monitoring. HASS screens are performed in the same type of chamber that is used for HALT. The vibration in HASS is randomly applied over a broad frequency range producing energy to 10,000 Hz in 6 degrees of freedom.

ESS originated out of the military to improve the reliability of their complex products.  ESS typically uses temperature cycling and random vibration applied separately.  Products are normally electrically powered and functional tested during ESS.  Random vibration is usually preformed on and electro dynamic shaker.  “Environmental Stress Screening of Electronic Equipment”, DOD-HDBK-344, is a military handbook that provides guidelines for developing ESS programs. 

Both HASS and ESS are effective screening programs that yield more rugged/reliable products with less field failures and warranty expenses .  More information about HASS and ESS can be found in the following pages:

What is HASS Testing?

How to Implement a HASS Program

An Informational Guide to HALT and HASS

Environmental Stress Screening (ESS Test)

All of these test methods provide different benefits.  Not all of them have to be performed to produce a reliable product.  Contact DES to help determine what makes sense for your product. 

The post How to Make Your Product More Reliable Through Testing appeared first on Delserro Engineering Solutions.

MIL-STD-810 is a public military test standard that is designed to assist in the environmental engineering considerations for product design and testing.  For the purposes of this blog series we will focus on Method 514.7, titled Vibration.  This section defines the environmental vibration conditions a material or product may experience during the product life cycle and translates these conditions into replicable test procedures.  Unfortunately, unless you’re familiar with this document, this section or any section for that matter may seem a little daunting.  This blog will hopefully provide some guidance into navigating your way through it.

The best place to start is Table 514.7-I which can be found shortly after the table of contents of Method 514.7.  This table basically acts as a summary for the section and directs you to the specific annex to look for the applicable environmental vibration category for your product.  Before you jump to the test profiles, there are some definitions and details worth pointing out.  The different types of test procedures, called out in the last column of the table, are defined further on in this section.  This is important because some of the test procedures require different or unusual test setups which may be more suitable to your product’s environmental vibration exposure.

Test I: General Vibration

This condition applies to material/products “to be transported as secured cargo or deployed for use on a vehicle.  This procedure applies to ground vehicles as well as fixed and rotary wing aircraft.  For this procedure, the test item is secured to a fixture or a vibration exciter, and vibration is applied to the test item as an input.

Test II: Loose Cargo Transportation

This condition applies to material/products “to be carried in/on trucks, trailers, or tracked vehicles and not secured to (tied down in) the carrying vehicle.  The test severity is not tailorable, and represents loose cargo transport in military vehicles traversing rough terrain.”  Essentially, worst case scenario.  For this procedure, the test item is not secured to the vibration exciter, and is free to move during the test.  Typically a fence is built around the vibration table to prevent the product from falling off of the table.

Test III: Large Assembly Transportation

This condition applies to “large assemblies of material installed or transported by wheeled or tracked vehicles.  It is applicable to large assemblies or groupings forming a high proportion of vehicle mass, and to materiel forming an integral part of the vehicle.”

Test IV: Assembled Aircraft Store Captive Carriage and Free Flight

This condition applies to “fixed wing aircraft carriage and free flight portions of the environmental life cycles of all aircraft stores, and to the free flight phases of ground or sea-launched missiles.”

Test procedures I and IV use standard laboratory vibration shakers while test procedures II and III require more specialized equipment.  For the most part, most of the categories in Table 514.7-I call for test procedures I and IV which most test laboratories should have and therefore can be configured to those test profiles.

Once you have determined the application type and test procedure your product/material falls under, you can move on to determining your test profile.  There are a variety of types of vibration profiles that are defined in Annexes B through E of MIL-STD-810 depending on the expected environmental vibration exposures of your product.  General definitions of the different types of vibration profiles can be found in Annex A of MIL-STD-810G Change 1, Method 514.7, however, more detailed understanding of sinusoidal, random and mixed vibration profiles can be found in the associated links as well as below.

Sinusoidal Vibration Testing

Sinusoidal & Random Vibration Testing Primer

The post MIL-STD-810 Vibration Testing Overview appeared first on Delserro Engineering Solutions.

A customer contacted DES, seeking to create a reliability test plan for their product based on customer usage, new features and design limits.  One of the concerns identified by the customer was the need for an accelerated life test which tested whether their “door assembly” product met the design specification for usage.  In other words, the goal was to create an automated test solution which opened and closed cabinet doors to the estimated amount they would see during a lifetime in the field.

Results

DES created a custom test set up, shown in the video above, which utilized control software, sensors and a motor to simulate the open and close motion seen in the field.  A goal was determined by the customer which represented the number of cycles the product was expected to see in the field.  The control software allowed DES to control and automate the movement, delays and speed of the motor.  In doing so, DES was able to condense the product lifespan into a week-long test.

The product withstood the grunt of testing with little to no observable damage.  The customer was very pleased with the results of the test and confident moving forward with the product design.  This was one of many rigorous customized reliability test solutions DES designed for this customer and product line.  DES has over 20 years of experience designing customized test solutions to fulfill your product and testing needs.  Contact us or call 610.253.6637 to find out what DES can do for you!

The post Door Open/Close Accelerated Life Test Case Study appeared first on Delserro Engineering Solutions.

Customer Goal

A customer approached DES looking to perform Highly Accelerated Life Testing (HALT) on a new circuit board design.  DES and the customer agreed to test the circuit boards using DES’s traditional HALT test procedure which calls for hot/cold temperature steps followed by rapid temperature ramping, vibration steps and combined temperature and vibration stresses.  HALT testing on electrical componentry is quite common across industry to expose design weaknesses; both mechanical and electrical (What is HALT and Why Perform HALT?).  Typical failures include poor solder connections, overheating, component failure, etc. (What Kind Of Failures Occur During HALT?)

Results

The hot/cold temperature steps exposed soft failures such as power resets and lack of communication for the circuit boards.  One hard failure was also exposed during this stage which proved to be a recurring problem and thus an area of weakness in the product design.  The units functioned properly during the vibration steps and rapid thermal ramping stages.  The combined temperature and vibration stage, however, revealed the same issue as seen in the first stage on two other units.

The circuit board featured potted componentry for purposes exclusive to the customer.  This potted feature cracked on multiple units throughout testing and caused all sorts of communication issues for the units.  In 3 days the customer was able to expose a product design weakness that would most likely have caused a number of warranty and reliability issues.  In the words of the customer:

“The results from this testing have identified strong and
more importantly weak areas in our design.”

– Customer

HALT testing is a necessity for products with electrical circuity in terms of preventing field failures and high product return rates.  Problems such as these can be really damaging to a company’s bottom line if not addressed early in the design process.  Fortunately this customer has had experience with HALT in the past and chose to perform HALT before finalizing the product design.  DES has over 20 years of experience performing HALT testing on a variety of medical, commercial, industrial and military products.  Schedule your next HALT test with us by contacting us or call us at 610.253.6637.

The post Circuit Board HALT Testing Case Study appeared first on Delserro Engineering Solutions.

A customer approached DES looking to find an accelerated test solution for an AC powered cooling fan used in one of their products.  The product had been established in the marketplace and the company was now looking for ways to reduce cost by looking at different cooling fan suppliers.  Most fans, however, have a mean life rated for over 20,000 hours, so a typical accelerated life test would require a significant amount of time and money. 

DES Solution

Performing a quantitative accelerated life test on cooling fans presents challenges because they have such a long lifespan.  Reasonably speaking, the shortest quantitative solution for determining the lifespan of a fan could take as long as a couple months.  DES proposed a qualitative solution, a Rapid HALT.  A Rapid HALT (Highly Accelerated Life Test) is designed to apply a variety of stresses, concurrently, to a product in order to significantly time compress a product’s lifespan.  A typical Rapid HALT lasts only one day which is extremely convenient for companies that need results quickly.

Results

A sample size of 3 cooling fans were tested for 4 different fan suppliers.  We will refer to these suppliers as Supplier A, B, C and D.  All 12 fans were placed in the chamber together and a Rapid HALT was conducted.  None of the four suppliers survived testing without some issues but the results were still differentiating.  Supplier A had no electrical issues in any of its samples but the fan blades on all 3 samples vibrated off the armature.  Fans of Supplier B, all experienced sputtering of the fan blade and eventually saw two of its fans current levels drop to 0.  By the time testing was completed, none of the fans were functioning.  Supplier C fared slightly better than A and B.  One of Supplier C’s fans lost current at the most extreme step and never recovered.  The other two however, experienced fan blade sputtering but were functioning normally upon final inspection.  Supplier D performed the best out of the four suppliers and thus would be considered the most durable of the suppliers tested.  Only one of the fans experienced any issues, in which it lost current at the most extreme step.  Upon final inspection all of the fans were functioning normally.

There are other factors to consider such as price and accessibility but these results were able to successfully assist our customer in differentiating between the reliability of the four fan suppliers.  While a HALT is qualitative and will not produce an actual estimated fan lifetime, it is a great comparison tool to evaluate the reliability of different suppliers faster and less expensive than traditional testing techniques.

The post Cooling Fan Reliability Testing Case Study appeared first on Delserro Engineering Solutions.

If you have not done so yet, please check out Part 1 – Defining your project and  Obtaining a Quote.

You obtained quotes from a couple of vibration test labs.  Your next task is to select a vibration test lab to perform your vibration test.  Your selection should not be based upon price alone.  Factors that should affect which lab you choose are capability, cost, timing, location, quality, and other special requirements.

Most importantly, the test lab must be capable of running your test.  Running a successful vibration test is not easy.  A good vibration test lab will make it look easy, but running a vibration test requires significant knowledge of vibration theory, fixture design, testing skills, and a skilled operator to run the vibration test equipment.

Of course, cost and timing should be a significant part of your decision.  If one quote is considerably lower than the other quotes, then you should question that lab to see if they misunderstood the project requirements.

Location can be important if you need to haul bulky support equipment to the test lab.  It can also be important if witnesses need to travel and be present during the test.

The lab should have up to date calibrated vibration test equipment.  If you have never used them before and this is a large project, then it would be a good idea to schedule a visit to review their equipment and capabilities.  If your company has special quality or other requirements, then review them with the lab.  Special requirements could be handling, lifting or Electro Static Discharge (ESD).

Planning & scheduling your test

After you have selected a lab, it is time to schedule your vibration test.  First contact the test lab to inquire about their vibration test schedule.  The test lab may be backed up with large projects and may need some time to schedule your test.  DES has multiple shakers with a goal to reduce scheduling time as much as possible.

If any special support equipment is required for the test, then it may take time to gather this equipment and to set it up.  If rental equipment is required, then the time to ship the equipment from the rental company must be considered.  Most importantly, significant time may be required to design and manufacture special fixtures.

Much or all of the planning could fall on the test labs shoulders if they are supplying everything.  Expediting schedules is always an option, but you will likely have to pay more.  It is important to know what each party is responsible to supply.  For instance if assembly is required, who will supply the bolts?  It is a lousy situation for all involved, to plan a test for weeks ahead and then to find that you are missing something during the test setup.  Good communication with the test lab is very important!

Fixture Design and Manufacture

Most vibration test labs can design and make fixtures.  Sometime you may have in-house fabrication capabilities.  However, you may not have the experience to design good vibration test fixtures.  Designing good vibration test fixtures requires specialized knowledge.

The vibration test fixtures should be stiff and light weight.  They should have a high natural frequency.  It is preferable that all resonances fall above the test frequency range, but many times that is not possible especially when testing to high frequencies of 2,000 to 3,000 Hz.  A good rule of thumb is to make natural frequencies as high as possible without adding too much weight.  Easier said than done!  When designing vibration test fixtures, many more bolts are required than for static loading to securely join the fixture to the vibration table and increase the fixture resonances.  Good materials for vibrating test fixtures are aluminum and magnesium.

Figure 1.  Fixture Cube Designed by DES

Computer analysis software such as Finite Element Analysis (FEA) is a great tool for estimating fixture resonances during fixture design.  If the lab is designing your fixture, inquire if they have FEA capability.

Test setup

Setting up the vibration test on the shaker is the responsibility of the test lab.  If the requirements are for your product to be operationally functional tested, then that may fall on your shoulders.  It is very common for DES’s customers to bring support equipment to functional test their specialized products during the test.  Many labs including DES, can also provide support equipment, but it if your product is very specialized, then it probably makes more sense for you to be responsible for this task.  Again, good communication with the test lab is very important to determine the responsibilities for each party.

The test setup may also involve a trial run with the fixtures alone to scan for severe resonances.  This is a good idea especially when testing to high frequencies of 2,000 to 3,000 Hz.  Control problems could occur if the fixtures have a severe resonance in the frequency range of the test causing the shaker controller to abort.  Sometimes (but not always) a large resonance can be “notched out” meaning that the test acceleration levels are reduced significantly at frequencies a little higher or lower than the resonance.  Note that some test specifications will not allow for notching.

Running the vibration test

Finally you are ready to run your vibration test.  Before starting the shaker, all support equipment and the DUT should be operated to verify that it is working acceptably.

Before the vibration testing begins, the shaker controller will first go through a “self-check” to make sure that the amplifier and the vibration accelerometers are connected and producing signal.  It is looking for a “closed loop” between the controller, the amplifier and the control vibration accelerometers.  Once the “self-check” is successful, the operator will start the vibration shaker.  A skilled operator is taught to start up at low vibration levels.  This is typically -12 (≈1/4 of full level) to -6dB (≈1/2 of full level) below the full vibration level (which is 0 dB).  Thus if anything such as a loose bolt was missed during the setup, it can be caught before reaching full level.  So it may take a couple of minutes to ramp up to full level even for an error free setup.  Once at full level, the shaker controller will be constantly adjusting the vibration table to meet the specification.  This is called running in “closed loop”.  The definition of “closed loop” control is contained below.  (Note, in some special cases the shaker can be run in “open loop”, meaning that the controller will not adjust the shaker, but that is a subject for another discussion).  There are abort limits in the controller software to automatically stop the test in case an accelerometer or cable breaks.  Also, if a failure occurs in the product or fixture, it will probably cause an abrupt change in the control accelerometer outputs causing the controller to abort the vibration test.  In addition, a skilled operator knows that a change in the audible sound coming from the vibration test could be a sign of an imminent failure.

Now the shaker starts moving.  What do you need to worry about?  At this point, if everyone did their homework, then the only thing to worry about would be if vibration fatigue causes a failure in your product or if your product does not operate properly.

Most vibration tests are performed along three orthogonal axes, but only one axis at a time.   Time will be needed when changing from one axis to another especially when switching from a horizontal to vertical axis.  Fixtures will need to be unbolted from the table and the lab may need to disconnect from the horizontal slip table, rotate the shaker vertically and then install a vertical head expander.  So if your vibration test is 8 hours in total duration, plan for extra time to switch axes which could mean that your test takes more than 1 day.  The time required to switch to a different axis could be less than 1 hour to 1 day depending upon the size of the product, the complexity of the test fixtures and the support equipment.

Hurray!  Your test completed, your product operated smoothly and no structural failures occurred.  Now it is time to clean up and for the lab to provide a test report.

The definition of running in closed loop is the following:  The vibration controller sends a drive signal to the amplifier.  The amplifier powers the shaker using the drive signal causing it to vibrate.  The vibration levels are sensed by the control accelerometers.  The output from these accelerometers is fed back to the controller.  The controller then adjusts the drive signal to make the vibration levels match the test specification. 

Test report

The vibration test lab should provide a thorough, accurate, well written test report with prompt delivery as a final step.  The test report should include:

1. Photographs of test set-up
2. Location of accelerometers
3. List of test equipment used and calibration status
4. Summary of the test procedure
5. Plots of vibration data
6. Visible observations of the product after the test and summary of the product operational test results (if product was operational during the test)
7. Photographs of any product failures

In conclusion, running a successful vibration test is difficult.  A good vibration test lab will make it look easy, but there are many specialized skills and knowledge required.  We hope that this two part article will help you gain perspective from a vibration test lab’s point of view and to understand what information that you need to provide to perform a successful vibration test.  Most importantly, good communications is essential for a positive experience.  DES looks forward to performing your next vibration test!

The post Choosing A Vibration Test Lab Part 2 appeared first on Delserro Engineering Solutions.

Part 1 – Defining your project and Obtaining a Quote

Vibration testing is a very specialized field, not very well understood by many.  There are different types of vibration and there are an enormous number of vibration test specifications.  Vibration testing equipment is very expensive to purchase forcing many companies to hire a vibration test lab to fulfill their vibration testing requirements.  So what should you expect when Choosing A Vibration Test Lab?

You contact a lab to obtain a quote for vibration testing.  The lab replies with many questions.  You ask yourself, why does the lab ask so many questions just to prepare a quote?  The answer is that details matter and can significantly affect the vibration test time and cost.  This article is written from a vibration test lab’s point of view to help explain what information is needed to perform a successful vibration test.

Before contacting the lab, it might help to ask yourself, what is the purpose of your test? Do you need to comply with customer qualification requirements, improve your product reliability, estimate life expectancy, perform package testing, etc.?  It is more effective to contact the lab after your goals are clear.  It is also helpful if you can prepare a list of requirements or a statement of work or a test plan.  The following are questions that a vibration test lab may ask you:

1. What are the vibration test specifications?
2. What is the size and weight of the product or Device Under Test (DUT), what does it look like and how many samples need to be tested?
3. How will the DUT be mounted?
4. Does the DUT need to be powered and monitored during the test?
5. Do you need response accelerometers on the DUT?
6. Are combined environments (such as temperature) and vibration required?
7. Are any other unique requirements needed for the vibration test?

1. What are the vibration test specifications?

There are many different vibration test specifications and test parameters that need to be defined.  A few common test standards are: MIL-STD-810, MIL-STD-883, MIL-STD 167, RTCA DO-160, IEC 60068-2-64, and IEC 60068-2-6.  However there are many more.  The types of vibration can be random, sinusoidal (sine), sine dwell, sine on random, random on random, sine on random on random.  The most common types of vibration testing services conducted by vibration test labs are sinusoidal and random.  A decision will have to be made as to what type of vibration is needed and if a test specification applies.  Some other test parameters that need to be defined are: acceleration or G level, frequency range, how many axes to be tested, duration per axis, sinusoidal sweep rate and number of sweeps for sine testing, random vibration PSD profile or sine vibration curve.

Many times all of the test parameters above are well defined in a test specification such as MIL-STD-810.  However sometimes they are not and then you will need to provide these details to the test lab.  The reason is that the details do matter and can significantly affect the test time and cost.  For instance a sine sweep from 10 to 2,000 Hz at a rate of 1 octave per minute takes approximately 7.5 minutes.  Performing the same sweep at a rate of 60 Hz/minute will take approximately 33 minutes.  So if you need to perform 10 sweeps per axis x 3 axes, the time to complete each test will be approximately 225 minutes (3.75 hours) at a rate of 1 octave/minute vs. 990 minutes (16.5 hours) at a rate of 60 Hz/minute.  Obviously a test that takes 16.5 hours to complete will cost more than one that takes only 3.75 hours.

Test requirements such as G level and random vibration PSD profile greatly affect the overall difficulty of the test.  Testing at high G levels for larger, heavier products may be beyond the capabilities of some vibration test equipment.  The frequency range of the test will affect the design of the vibration test fixtures.

2. What is the size and weight of the product or Device Under Test (DUT), what does it look like and how many samples need to be tested?

The lab is going to ask you to provide the dimensions of the DUT and the mounting foot print.  This information is required to assess vibration test fixtures and also to determine if the DUT will fit on the vibration shaker table.  A drawing or sketch or picture with some overall dimensions is very helpful.  Ideally the DUT should be mounted to a rigid vibration table or fixture.  It is not a good idea for the product to hang over the sides of the table because that could affect its vibration response.  The size and weight will also affect how many products can fit on the table simultaneously or if multiple groups need to be tested.

That leads into the question of how much does the DUT weigh?  This is important because it may be easier for a vibration shaker to test a 200 pound product at 1 G than a 10 pound product at 20 G’s, (neglecting handling!!).  Vibration shakers are rated for maximum force.  The maximum force is determined from the formula

Force = Mass (or Weight) x Acceleration

The units for Mass are usually pounds or kilograms and Acceleration units are usually G’s or m/s².  Someone inexperienced with vibration testing might think that the same amount of force is required to test a 200 pound DUT at 1G and 10 pound DUT at 20G because the forces are equal using F=MA.  It is important to note that the Mass is not only from the DUT’s but is also from the moving masses of the shaker and fixtures per the formula below:

MASS or Weight = weight of shaker armature + shaker table (slip table or head expander or cube or angle fixtures etc.) + DUT fixture + DUT’s + weight of any other adapter fixtures or significant added moving weight.

For example, let’s say the 200 and 10 pound products will use the same test fixtures and will be used on the same vibration shaker.  Using the assumed weights in the table below, the total moving weight is 425 pounds for the 200 pound product and 235 pounds for the 10 pound product.

Don’t stress too much.  You will only need to provide the weights of components that you are supplying such as the product to be tested, the DUT fixture weight if you are supplying this fixture, and any other significant moving weights that you are supplying such as heavy cables.  The test lab will calculate the required shaker force.The total force required for the shaker is 425 pounds for the 200 pound product and 4,700 pounds for the 10 pound product.  The required shaker force is more than 10 times greater for a product weighing 10 times less!!  The 4,700 pounds of force required for the 10 pound product may overload some small to medium shakers.

Let’s briefly explain the parts involved.  The vibration shaker armature is part of the electrodynamic shaker.  Typically a magnesium head expander is bolted to the armature when testing in a vertical configuration, Figure 1.  A magnesium slip table is bolted to the armature when testing in horizontal configurations, Figure 2.  (Note, we will refer to the head expander or slip table as a vibration table.) These tables have a generic hole pattern.  Usually an adapter plate is used to adapt the mounting pattern of the product to the magnesium shaker tables.

3. How will the DUT be mounted?

The mounting hole pattern of your product will probably not match the hole pattern of the vibration test lab’s tables.  So an adapter plate or DUT fixture will be required as seen in Figures 1 and 2.  The DUT fixture will need to be bolted to the test lab’s vibration table.  Then the product will be mounted to the DUT fixture.  Test labs will not drill holes in their vibration tables because they are expensive specialized fixtures usually made with magnesium.  The DUT fixture is typically an aluminum plate with two sets of hole patterns.  One pattern matches the vibration table while the other pattern matches the product mounting.  To reduce cost and lead-time, DES has generic aluminum adapter plates available and will add holes to fit your product.  Bars and threaded rods can be used to attach products to the vibration shaker for products that do not have mounting holes such as a cell phone.  So the DUT fixture is a cost that will have to be accounted for by you or the test lab.  This cost is usually non-recurring.

4. Does the DUT need to be powered and monitored during the test?

If the DUT needs to be powered and monitored during the test, then clearly this will require support equipment.  This can be a simple or very complicated task.  One complicated setup for a past test took DES months of planning.  It required 3 phase electric, cooling water flowing through the product, and many measurements to be made during the vibration test.

Power can be simply provided from 120 alternating current (AC) single phase wall outlets or it can require complex high voltage 3 phase power from the facility or power supplies. Sometimes AC power requires special frequencies such as 400 Hz for some military equipment.  This is provided from special AC power supplies.  Direct Current (DC) power can be provided from DC power supplies or batteries.

Another important consideration will be if the DUT needs to be electrically loaded during the test.  This can be resistive loading from components such as heaters.  The loading can be inductive from AC motors.  DES has previously built a 6 foot tall test rack of resistors to draw a high load through a product.  On another test, DES had large blowers on the floor to load an air conditioning unit for a rail car.

Monitoring can be from simple visual observations or it can require complex measurements.  Typical monitoring equipment are data loggers, digital multi-meters and oscilloscopes.  Different kinds of sensors can be used to provide monitoring data such as thermocouples or speed sensors.

The big question is who will provide this equipment.  Test labs can typically provide most needed equipment at added cost.  Nobody has every piece of test equipment, but there are test equipment rental companies that provide calibrated test and measurement equipment.

5. Do you need response accelerometers on the DUT?

Some test specifications such as RTCA DO-160 require a resonance scan on the DUT.  This involves installing response accelerometers on the DUT, then performing a resonance scan with low level accelerations (usually 0.5 or 1G) over a frequency range such as 10 to 2,000 Hz.  Or perhaps you are interested in examining the response of your product under vibration loading.  Response accelerometers are usually small and are typically attached to the product with an adhesive such as superglue, Figure 3.  They are not used for control.  Control accelerometers are typically mounted in the DUT fixture.

If you want or need response accelerometers, it is helpful to specify this up front.  While installing response accelerometers on the DUT is typically not a big task (however it can be!), there may be some cost added for this effort.  It does take extra time to install response accelerometers, take pictures for documentation in the report, setup extra data acquisition channels and process a resonance search plot for inclusion in a test report, Figure 4.

6. Are combined environments (such as temperature) and vibration required?

Obviously vibration testing in combined environments is much harder and will be more costly than testing at room temperature.  For now, let’s consider combined temperature and vibration testing.  First, there is some time and effort involved in setting up the chamber over the shaker, Figure 5.  While it varies from lab to lab, the vibration table will be inside the chamber or the table will be flush with the floor of the chamber.  The chamber will be fixed.  There will be space between the chamber and the vibration table.  A rubber membrane will be used to seal the chamber to the vibration table.  The vibrations will occur inside the chamber in a confined workspace.

Many chambers only fit over the shaker when it is oriented vertically and do not fit over a horizontal slip table.  If that is the case, then different types of fixtures are required since testing in 3 axes requires rotating the fixtures, not moving the fixtures from a vertically mounted table to a horizontal slip table, Figure 6.

Also, special charge mode accelerometers are needed for working in extreme temperature environments because standard accelerometers will drift under these conditions.  Accelerometers should be mechanically mounted because many adhesives do not stand up to extreme temperatures.

7. Are any other unique requirements needed for the vibration test?

Unique requirements can be very challenging.  Unique requirements could be mechanical loading, internal pressure, fluid flow, etc.  For mechanical loading, it is preferred to use a spring or bolt mechanism to apply a steady load to keep weight to a minimum.  DES has also performed vibration tests with internal pressure applied to products and fluid flowing through heat exchanger products.  Adding extra weight to vibration tests can demand much more force from the shaker.  Testing with fluids may cause sloshing and extra risk of spillage onto expensive shakers.

Vibration test labs are more than happy to help you with your vibration test requirements.  But please do understand that some effort is needed on your part to define your vibration test requirements.  Good communications is essential for a positive experience.  DES looks forward to hearing from you!

The post Choosing A Vibration Test Lab Part 1 appeared first on Delserro Engineering Solutions.

Mixed Mode Vibration Testing is less common than Sinusoidal and Random Vibration Testing.  However, it does have a special purpose for simulating specialized helicopter vibration or vibration from tracked vehicles such as tanks.

The three mixed modes of vibration testing are:

• Sine-on-Random (SoR)
• Random-on-Random (RoR)
• Sine-on-Random-on-Random (SoRoR)

Some common test standards that have specifications for Mixed Mode Vibration Testing are:

• MIL-STD-810 Department of Defense Test Method Standard for Environmental Engineering Considerations and Laboratory Tests
• RTCA DO-160 Environmental Conditions and Test Procedures for Airborne Equipment

Sine-on-Random (SoR) Vibration Testing

Sine-on-Random (SoR) vibration testing contains sine tones that are superimposed on a low level of broadband random vibration.  The sine tones can be fixed frequency or sweeping.  If they are sweeping, they are normally very narrow frequency bands.  Some examples of SoR vibration are from helicopters, propeller driven airplanes and aircraft rapid gun-fire events.

All aircraft have some levels of random vibration.  In helicopters and propeller driven airplanes, the sine tones are produced by the main rotary components.  In addition, sine tones can come from rapid gun fire events.  Figure 1 shows a typical SoR helicopter vibration test profile from MIL-STD-810G.

Random-on-Random (RoR) Vibration Testing

Random-on-Random (RoR) vibration testing has narrow band random peaks that are superimposed on a low level of broadband random vibration.  Typical applications that contain RoR vibration are tracked vehicles such as tanks or a truck changing speed while driving over a rough road.  For example, the pitch of the tracks produces rhythmic random vibration peaks at specific frequencies versus speed of the vehicle.  Figure 2 shows a typical tracked vehicle vibration test profile from MIL-STD-810G.

Sine-on-Random-on-Random (SoRoR) Vibration Testing

Sine-on-Random-on-Random (SoRoR) vibration testing contains both sine tones and narrow band random peaks superimposed on broadband random vibration.  Applications that contain SoRoR vibration could be a rapid gun-fire event on a tracked vehicle or components mounted near a turbine engine with various rotating machinery elements and background random vibration produced by air turbulence.

Whether your vibration testing needs are complex or simple, DES has the experience and knowledge to perform your test.  For more information on Vibration Testing or other testing services contact DES or call 610.253.6637.

The post Mixed Mode: Sine on Random Vibration Testing, RoR, SoRoR appeared first on Delserro Engineering Solutions.

If the product fails to operate, the temperature or vibration will be changed toward ambient room conditions followed by a short dwell period to see if the product recovers. If the product is non-operational after dwelling at ambient conditions, trouble shooting will take place to find the failed component. The failed component will then be removed, repaired or replaced with a new component (as is practical) in an effort to expand the test stresses.

Relevant Failures

All HALT failures are relevant unless it is determined that the failure was caused by a condition external to the product which is not a test requirement. Relevant failures may include, but are not limited to the following:

• Design and Workmanship Failures
• Failures caused by Poor Manufacturing
• Component Part Failures
• Multiple Failures
• Intermittent Failures
• Built-in-Test Failures

All relevant failures represent an opportunity for improvement and should be thoroughly investigated to determine their root cause. All relevant failures should be evaluated as to whether or not they can be corrected with a reasonable amount of effort and cost. However, all failures that prevent a product from functioning in its normal environment should be fixed! Figures 1 through 3 show examples of relevant HALT failures.

In Figure 1, the mounting tabs used to hold a power supply in place failed during vibration. Larger tabs with better stress relief grooves should be used in this case to better withstand the vibrations. The capacitor leads in Figure 2 failed due to repeated fatigue stresses from vibration. Improved mounting such as placing an adhesive under the capacitor could be used to prevent this type of failure which is common for large components connected by thin metal leads.

In the case of temperature related failures such as seen in Figure 3, the temperature at which failure occurred should be well outside of the expected operating range of the equipment.

Even in this case, an evaluation should be performed to determine if a component with an improved temperature rating can be economically substituted because the failing component may be a weak point in the product design.

Non-Relevant Failures

Failures listed below may be considered as non-relevant:

• Failures directly attributable to erroneous product manufacturing or operation.
• Failures resulting from improper test setup or procedure.
• Dependent failures, unless caused by degradation of items of known limited life.
• Failures occurring during test “down-time” such as during troubleshooting on the bench unrelated to the HALT Procedure.

Care should be taken when determining if a failure is non-relevant as this may result in missing an opportunity for product improvement.

The post What Kind Of Failures Occur During HALT? appeared first on Delserro Engineering Solutions.