240 Accelerated Testing: ESS, HALT and HASS
FOR WHOM INTENDED: This course is for individuals such as quality and reliability specialists who specify screens and interpret results, project managers wishing to reduce life cycle costs, production and inspection managers whose people screen and interpret results, environmental test specialists who help develop optimum screens, and design engineers using stress testing for product development and design verification.
BRIEF COURSE DESCRIPTION This course shows why Environmental Stress Screening (ESS) and its modern descendents, HALT (Highly Accelerated Life Testing) and HASS (Highly Accelerated Stress Screening) are important steps in the development, design and manufacture of both commercial and military systems that require high-reliability performance. It demonstrates the purpose of screening, which is to precipitate and make visible any existing latent flaws. Well-screened systems have greatly improved mean time between failure (MTBF) rates, their life cycle costs are lower, their reliability is higher. Environmental Stress Testing and HALT have long been used in the development and design of new products.
This course addresses thermal and vibration environments and test facilities, how to prepare before performing HALT, and how to run HALT tests. Single-environment tests are discussed, and then combined environments. Fixturing, HALT profile writing, failure types and analysis and data analysis topics are considered. The HASS section of the course shows how to develop an effective screening process. The course concludes with a discussion of HALT/HASS specifications.
The course is presented as a series of highly-interactive lecture/discussion sessions. Problems for individual and group solution are interspersed throughout the course to act as training aids and to evaluate class progress. There will be a class exercise in writing a HALT profile—class members will give suggestions while five common profiles are written in a user friendly interface.
Special-interest discussions are encouraged outside of the regular course sessions.
PREREQUISITES TTi recommends that this course be taken after Course No. 116, Fundamentals of Vibration For Test Applications and either Course 230, Climatic Test Techniques or Course 425, Environmental Testing Procedures.
DIPLOMA PROGRAMS This course is required for TTi‘s Climatic Test Specialist (CTS) and Mechanical Design Specialist (MDS) diploma program. It may be used as an elective for any other TTI specialist diploma program.
Text Each student will receive 180 days access to the on-line electronic course workbook. Renewals and printed textbooks are available for an additional fee.
Internet Complete Course 240 features almost ten hours of video as well as more in-depth reading material. All chapters of course 240 are also available as OnDemand Internet Short Topics. See the course outline below for details.
Course Hours, Certificate And CEUs Class hours/ days for on-site courses can vary from 14–35 hours over 2–5 days as requested by our clients. Upon successful course completion, each participant receives a certificate of completion and one Continuing Education Unit (CEU) for every ten class hours.
Click for a printable course outline (pdf).
Chapter 1 - Introduction to Environmental Testing
- Test Objective
- Integrated Product or Process Teams
Chapter 2 - Environmental Stress Screening (ESS)
- Flaw Populations
- Failures vs. Cycles
- Quantitative Verification
- Test Strength
- ESS Process Plan
- How to Design an ESS Process
- Process Control
- NAVMAT P-9492
- Sample ESS Profiles
- ESS & Reliability
Chapter 3 - Environmental Forcing Functions: Vibration
- Best Forcing Functions?
- Sample Requirements
- Example of Clients’ Additional Requirements
- Effects of Vibration
- Types of Shakers Used in ESS
- Repetitive Shock vs. E-D Shaker
- Properties of an Efficient Vibration Screen
- Selecting Vibration Screen Development Method
- Axes of Excitation
- Screen Duration
- ESS Methods
- Tailored Response
- Step Stress
- Fault Replication
- % Useful Life
- Nine Hidden Vibration Test Assumptions
- Screening Configurations
- Screening Effectiveness
- Level of Assembly
Chapter 4 - Environmental Forcing Functions: Thermal and Others
- Thermal Environments
- Constant Temperature
- High Temperature Burn In and Electrical Stress
- Power Cycling
- Thermal Cycling
- S-N Curve
- Typical Endurance Limits
- Thermal Profile
- Commonly Used Temperature Ranges, Rates of Change
- Thermal Shock
- Thermal Survey
- Dwell Times
- Power-on vs Power Off Dwell Times
- Combined Environments
Chapter 5 - HALT: Highly Accelerated Life Testing
- Test Time Compression
- Assumptions: The Horsepower Behind Accelerated Testing
- Reduced Test Time? Not Always
- What Does an Accelerated Test Accelerate?
- Information Customers Need
- Different environments produce different results
- Types and Rates of Test Time Acceleration
- Effects of
- Thermal Cycling
- Power cycling
- Are accelerated tests always shorter?
- “Life” Tests
- Fatigue life vs. service life
- Accelerated Test Cautions
Chapter 6 - Equipment Needed for a HALT Test
- Liquid nitrogen
- Reasons for Using
- Equipment for handling LN2
- Prolonging liquid state
- Repetitive Shock Vibration
- Repetitive Shock Equipment
- Sensor attachment
- Special Equipment for Humidity
Chapter 7 - Performing HALT: Highly Accelerated Life Test
- When to Use HALT
- HALT considerations
- How Many Samples?
- How to run the tests
- The test series
- Single environments
- Combining environments wisely
- Sensor Placement
- Tests and Profiles
- Cold Only
- Heat Only
- Combined Test
- “Super HALT”
- Failure types for each test above
- HALT with not enough samples
- Safest Practice
- Why Reuse is Dangerous
- Data analysis
- Non-Electronic/Visual Monitoring
- Test reports
Chapter 8 - HASS: Highly Accelerated Stress Screening
- Comparison with ESS
- Writing a HASS Profile
- Example: Finding HASS Limits
- Two main styles of HASS screens
- Differences in Profiles
- Ramp Rates and Dwell Times for Two Types of Cycles
- Number of Cycles
- Guidance for sampling
Chapter 9 - Specifications for HALT & HASS
- IEST Recommended Practice (Draft)
- Common Mistakes (from RP)
- HASS Process Without Prior HALT
appendix A - Glossary of Terms and Acronyms
Appendix B - Overview of Accelerated Testing Analytical Models
Appendix C - Draft Statement of Work for Generic ESS Process Development
Appendix D - A Brief History of ESS
Summary, Final Review
Award of Certificates for Successful Completion
Click for a printable course outline (pdf).