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m o r e t h a n t e c h n o l o g y

m o r e t h a n t e c h n o l o g y. ” High Accelerated Life Test : Translating Theory in to Design Solutions for the Implementation Tool ”. “solid-edge design”. INTRODUCTION. The Environmental Test Chambers are today compulsory for developing any product reliability,

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m o r e t h a n t e c h n o l o g y

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  1. m o r e t h a n t e c h n o l o g y ” High Accelerated Life Test :Translating Theory in to Design Solutions for the Implementation Tool” “solid-edge design”

  2. INTRODUCTION • The Environmental Test Chambers are today compulsory for developing any product reliability, • The one which is becoming more and more popular is the chamber for : Highly Accelerated Environmental Test or “HALT”. The chamber is easy recognized by high environmental performance and integrated shaker, but… this is not all what is required to an environmental chamber to perform accelerated tests

  3. ACCELERATED TESTING • The theory behind the accelerated testing has been explored in many academic contexts, the advantages have been broadcasted all over the world for the benefit of every one • The object is now how to translate the accelerated test requirements in the proper technical solutions for the tool which has to implement the test : the environmental test chamber. • basic philosofy for accelerating environmental tests : to provide high stress to the product by rapid cycling between extreme environmental conditions and by strong stimulation of the full spectrum failure modes.

  4. HALT requires Outstanding Performance 1 - Extreme change rate chamber 2 - Multi-axis Random Vibrations 3 - Maximum Vibration Transmissibility 4 - Maximum Thermal Transmittance 5 - Adjustable Air Flow 6 - Reliability and Usability 7 - Supplier qualification

  5. 1- Extreme Temperature Change Rates • When temperature rate goes to extreme (20 - 30 °C/min), the cost effective solution for the cooling ramps is to use the evaporation of LN2 (Liquid Nitrogen). • Being the evaporation temperature at ambient pressure -196°C and the calorific value 40-50 Kcal/Kg, it gives the LN2 a very high cooling power to rapidly cool down the systems which include : the air inside the chamber, the walls and components of the chamber and…. the specimen.

  6. 1- Extreme Temperature Change Rates • Considering also a price which all over the world is under the 0.25 USD per Kg, the LN2 solution is convenient when the LN2 supply facility is already available in the laboratory. Traditional compressor refrigeration system for this application would require tenths of HP, even if the electrical energy consumption cost will save some money in comparison with the LN2 consumption.

  7. 1- Extreme Temperature Change Rates • As far as heating the solution refers to the traditional technology of electrical heat dissipation from resitors : easy to implement and fast to be controlled. The associated power has to be adequately increased, for a 1 m3 chamber with 20 kg of electronic specimen to be heated at 60°C/min, the dissipated, and electrically supplied, power is in the range of 100 Kw !

  8. 2 - Multi Axis random Vibration • Accelerating the test means also to test "in parallel" as it can be done with a multiaxial shaker which wich avoids rotation of the specimen and test repeatition. Furthermore it has been demonstrated that some product failures are detected by : - correlation effect of multiple axes vibration ; - application of a vibration signal which is random as far as possible (flat and extended frequency band). The cost-effective solution is to use multiple pneumatic actuators.

  9. 2 - Multi Axis random Vibration • This experimented system satisfy the technical requirements but also is available at costs which are considerably less than complex 6 DoF system which use different technology (i.e electrodynamic). • Vibration levels up to 60 G’s.

  10. Multi-Axis Repetitive Shock Vibration • The instateneous pressure of the supplied air controls the "movement speed" of each actuator, viceversa when the actuator works it affects the instaneous air pressure and consequently the "speed" of other actuators, pratically each of the actuators moves randomly and in different direction. Not only the intensity of the acceleration vector is random but also the direction

  11. Multi Axis random Vibration • Wide frequency band in the PSD A potential disadvantage is that the vibrations are basically not controllable as far as spectrum shape (they are random only) but they can be controlled only in total rms level. Nevertheless this is what HALT requires.

  12. 3 - Maximum Vibration transmissibility Mounting products on Aluminum standoffs provides maximum transmissibility of vibration input from table

  13. 4 - Powerful Airflow Thermal power is nothing without the ability to transfer the power to the the real subject of the test : the specimen. One of the most important parameter affecting the thermal transfer is the “thermal resistance” between the air and specimen. It depends from material and shape of the specimen, density (temperature and pressure) and humidity of the air, airspeed. The factor controllable by the chamber is the airspeed : the higher is the airspeed the lower is the thermal resistance and the most part of the thermal energy is transferred to the specimen.

  14. 4 - Powerful Airflow High airspeed for a given volume requires powerful fans (2 - 4 HP of total power), likely two fans which in combination with a flexible configuration of air ducts give a good airflow distribution.

  15. 5 - Adjustable Airflow • Precise control of air direction provides faster product change rates • Up to four ducts can direct air onto different products

  16. Adjustable Air Flow • Air slot can be open or closed • When slot is closed, air is directed to the ducts allowing air to be directed onto the product • Allows flexibility in controllingairflow to maximize air velocity across the product

  17. Adjustable Air Slot

  18. 6 - system reliability & safety : Vibration • Top of the line Teflon Coated Impactorsfor long life and high MTBF

  19. 6 - system reliability & safety : CE Mark The system has to comply with the latest requirements of the European Community. The package includes : • proper grounding procedures, • specified components, • screw type terminal connections, • Electromagnetic shielding/immunity • as well as filters for the heating system to reduce electrical noise

  20. 6 - “Usability” • Convenient Table Height • Front and Rear doors for unrestricted product access • 18” X 18” Windows for observation • Access Ports for product interconnect, and product monitoring sensors • Access Panels

  21. 7 - Supplier Qualification • Broad product line and experience in environmental chambers • Turn-Key System : chamber, controls, and vibration system. • Local Sales and Service. Provide factory trained professionals. • In house design and manufacturing of the system, from sheetmetal to electronics, electrical subsystems, etc. This assures full control of the production.

  22. Saving energy is today an "ambientalist" issue but also affect very much the money budget to run a particular chamber like an accelerated test chamber which use 100 kW of electrical power and hundreds of kg of LN2. Efficiency considerations

  23. do not waste energy special care has to devoted to : - minimize the thermal capacity of the chamber internal elements in order do not absorb useless energy especially during the temperature transients - minimize the thermal capacity of the chamber walls and of the shaker table having the necessary thermal insulation; - improve the thermal transfer characteristics with an adequate airspeed and good air circulation around the specimen ; Efficiency considerations

  24. - minimize the pressure drop and turbolence along the airflow circuit in such a way to reduce the dissipated power, the fan motor power and its heating transferred inside the chamber. Careful consideration the above points can considerably reduce the energy consumption Efficiency considerations

  25. Chamber Typical Performance • Temperature Range:-100°C / +200°C • Temperature variation rate:60°C/min cooling from +150°C to –60°C 60°C /min heating up from –60°C to +150°C • Air speed:20 m/sec • Acceleration:Up to 60 grms • Frequency range:Up to 10000 Hz • Vibration table size:36 x 36 inches • Chamber internal dimension:1000 litres (adjustable) • Vibrator features:The system provides vibration using impact excitors with 6 degrees of freedom equally distribuited il all 3 axes and in all 3 rotations • Heating:100,000 Watts by Nicrome heaters • Cooling:Liquid nitrogen expansion • Noise pressure level : 76 dB(a)

  26. HALT & HASS ChamberMod.UHS 300 UHS 1200

  27. HALT & HASS ChamberMod.UHS300 • Temperature Range: -70°C / +150°C • Temperature variation rate: 30°C/min cooling from +120°C to –40°C 30°C /min heating up from –40°C to +120°C • Air speed: 5 m/sec • Acceleration: Up to 60 grms • Frequency range: Up to 2000 Hz • Vibration table size: 24 x 24 inches • Chamber internal dimension: 300 litres • Vibrator features: The system provides vibratio using impact excitors with 6 degrees of freedom equally distribuited il all 3 axes and in all 3 rotations • Heating: Nicrome heaters • Cooling: Liquid nitrogen expansion • Power: 45 kW

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