Course Outline no. 117
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Course Outline no. 117 .
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Applications Random vibration is important in most engineering applications where the product is exposed to vibration and shock during transport and service. The need to understand the effects of vibration and shock on product reliability is paramount today where electronic/computer components are part of almost every product.
For whom intended Many engineers need specialized education to properly measure, quantify, and analyze this generally unfamiliar environment and to reproduce it in environmental test laboratories. This course is for design engineers, test engineers and project managers. It also helps quality and reliability specialists and acquisition personnel in government and military activities and their contractors. It is designed to serve the needs of personnel in a wide range of industries where equipment problems may be encountered during the shipment and use of their product.
The instructor maintains good balance between theory and practical applications Project personnel, structures and packaging engineers learn about developmental testing. Product assurance and acquisition specialists learn to evaluate test facilities and methods, and to interpret specifications.
Brief course description This course is the initial course in TTi's Mechanical Design Specialist Certificate program. It covers a wide range of topics associated with vibration and shock applications in order to enable the course participants to acquire a basic understanding of the complex field of vibration and shock. Each of the subject areas covered in this course have expanded coverage in their own three day courses for those individuals who need a more thorough understanding for their application.
Lectures and videotaped physical demonstrations show for example: how structures behave when mechanically excited, how to use pickups to sense input and response forces and motions, how to read out and evaluate the resulting electrical signals.
The course commences with an introduction to vibration and its effects and then proceeds to cover the basic theory needed to understand the material covered during the three days. While mathematics is kept to a minimum, it is necessary to cover a sufficient amount so that the concepts of vibration can be understood. The use and application of decibels (dB) is described, then the theory of dynamics is covered including the relationships between displacement, velocity and acceleration. Damping theory and its effect on transmissibility ratio and resonance stacking and on product design is addressed.
Random vibration theory, including power spectral density theory, is discussed and video demonstrations show the effects of sinusoidal and random vibration. Various types of vibration exciters or shakers are discussed and the concept of test fixture design for vibration testing is covered.
The course proceeds to present some basic theory of electronic filters and vibration measurement systems to provide a background for understanding data acquisition and analysis topics of Spectral Analysis. Various types of vibration testing using sinusoidal and random vibration tests is discussed and the theory of material fatigue and the correct use of S-N curves for designing product life testing and developing accelerated product development testing procedures is covered. An introduction to model analysis and testing theory and application is addressed and its use for product design. Mechanical shock applications and environmental stress screening including HALT and HASS applications are addressed.
The various standards and specifications which are applicable in product design to meet various environmental conditions are discussed and the differences and possible conversion between design procedures and various documents is covered. Methods for tailoring of requirements for the test department are discussed. A brief description of the effects of seismic events and a review of designing to withstand vibration and shock completes the course presentation. Classroom and nightly review problems measure progress. (Bring an electronic calculator to class).
Certificate Programs This course is required for TTi's Mechanical Design Specialist Certificate Program and may be used as an elective for an of TTi's other Specialist Certificate Programs.
Prerequisites There are no definite prerequisites. Supervisors are invited to telephone or write to TTi on prospective attendees' backgrounds and needs.
Text Each student will receive a course workbook, including most of the viewgraphs used in the course presentation.
Course Hours, Certificate and CEUs Open courses meet seven hours per day. Upcoming presentation dates can be found on our current open course schedule. 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.
Introduction to Vibration Design and Testing for Vibration and Shock, Prolonged Excitation of Natural Frequency
Understanding Decibels (dB) and Octaves Decibels, Power and Voltage Ratio, dB Ratio Conversions, Logarithmic vs. Linear Scaling, Sound Perception, Octaves
Electronic Filters & Measurement Systems Capacitors in DC Circuits, Integrating Circuits, Differentiating Circuits, Filtering, Low-pass, High-pass and Bandpass Networks, Bandpass Filter, Band Pass Filter Shape and Technology, Sine Wave, Understanding RMS, Complex Signals, Pyroshock Time History, Random Signals
Dynamic Force and Motion Laws of Motion, Stress-Strain Relationship, Weight vs Mass, Work, Power, Energy, Fundamentals of Dynamics, A Simple Dynamic System, Degrees of Freedom, Undamped Vibration, Relationship between Displacement, Velocity and Acceleration, Single Degree of Freedom - Forced Vibration, Transmissibility, Isolation, Damping, Critical Frequencies, Vibration Considerations for Design Engineers, Degrees of Freedom, The Vibration Calculator (slide rule)
Vibration Exciters (called Shakers) Mechanical Shakers, Electrohydraulic (EH) Shakers, Electrodynamic Shakers, Force Rating and Available Acceleration, Displacement and Velocity Limits of Electrodynamic Shakers, Piezoelectric Shakers, Extending Table Diameter, Table (Head) Expander, Horizontal Accessory - Oil-Slip Tables, Combined Environmental Reliability Testing (CERT), Stroke vs. Frequency Range, Shaker Ratings
Random Vibration and Spectral Analysis Sinusoidal vs Complex vs Random Vibration, "Single Sweep" Time History, Demonstration of the Effects of Random Vibration, Special Definitions for Random Vibration, Why use frequency domain?, Phase of Frequency Domain Components, Time and Frequency Domain, Spectral Analysis, Power Spectral Density, Shaker Power Spectral Density Response, Equalization to Correct PSD, Calculating the RMS From the PSD, Developing Total RMS from Spectral Plot, RMS Calculation, Transmissibility Derived From Random Vibration, The Fourier Transform, Discrete Fourier Analysis, Fast Fourier Transform, Spectrum Analyzers
Introduction to Test Fixtures Purpose of a Fixture, Basic Considerations for Fixtures, Fixture Fabrication Methods, Typical Machined Fixture, Evaluating Fixtures, Fixture Weight Relative to Test Item Weight, Orthogonal Motion in Sinusoidal System, Shaker Crosstalk - Orthogonal Motion, Design Criteria
Vibration Measurement Velocity Sensing, Measuring Vibration Displacement, Displacement Readout: Integration, Acceleration Readout: Differentiation, Accelerometers, Wire Strain Gage Accelerometer
Vibration Testing Development, Qualification, Acceptance, Screening, Reliability Tests, Statistics of Life Testing, What is the Environment, The Applied Environment .. Philosophy, Control System Function, Function Generators, Multiple Degrees of Freedom Testing, Sine Vibration Testing, Slow Sweep, Swept Sine Resonant Search-Example, Plotting Crossover Frequency, Vibration Nomograph, Random Vibration Testing, Calculating RMS From PSD, Gaussian Random Signal, Standard Deviation, Statistical Degrees of Freedom, Random Vibration Control, Random Vibration Structural Analysis-Example, Random Vibration Test Spectrum
Fatigue How Materials Behave: The S-N Curve, Failure Models & Mechanism, Time-Dependent Failures, First Passage Model (Time to Failure), Exceeding a Critical Stress Value During Random Vibration, Inverse Power Law Model-Time to Failure, Fatigue Damage Model Based on S-N Curve - Cycles to Failure, Idealized S-N Curve for Structural Materials, Goodman Diagram, Constant Life Diagram, Fatigue Damage Model Based Upon Crack Growth Rate, Crack Growth Rate vs. Stress Intensity Factor, Stress Concentration, Miner's Hypothesis for Mechanical Fatigue Damage Accumulation, Effective Excitation, Endurance Limits, &ndquo;S-N" Curve from Fatigue Testing, Accelerated Testing, Durability and Functional Tests
Modal Analysis Introduction, Applications, Modes, Theoretical Approach, Measurement System, Exciting a Structure Impulsively, Modal Testing Hammer Calibration, Structural Dynamic Relationships, Basic Components of Measurement System, Mounting of Sensors-for Modal Testing
Accelerated Testing Step Stress Tests, HALT: Highly Accelerated Life Test, HASS / ESS, Monitored Ambient Random Vibration Profile, Margins, Assumptions, What Does an Accelerated Test Accelerate?, Which Environmental Forcing Functions?, What Does Vibration Do?, Vibration Test Assumptions, Linear vs. Nonlinear Product Response, Accelerated Test Prediction, Coffin-Manson Inverse Power Law, Cautions, Basic Principles of Test Time Compression, Unrealistic Failure Modes and Mechanisms, Synergistic Failure Exaggeration, Number of Cycles, Accelerated Testing Traps and Pitfalls
Environmental Stress Screening Exponential Failure Model, ESS vs. Test, Objective: Remove Flawed Equipment, ESS Process Plan, Sample ESS Process Flow Chart, Thermal Environments, Vibration Environment, Step Stress Tests, Highly Accelerated Stress Screening (HASS) and Highly Accelerated Life Testing (HALT)
Introduction to Mechanical Shock Causes of Shock, Effects and Remedies of Shock, Transient or Shock Tests, Shock Pulses, Shock Testing on Various types of Machines, Use of Shock Response Spectrum in Shock Testing, Fourier Spectrum Analysis, SRS vs. Fourier Analysis
Design to Withstand Shock Shock Isolation vs. Vibration Isolation, Isolators Which Approach the Ideal, Shock Isolation Example, Protective Packaging, Potentially Harmful Environments, Drop Height vs. Probability, Product Fragility, Damage Boundary Theory, Step Velocity and Step Acceleration Tests
Standards vs. Specifications Standards vs. Specifications, Why are Standards needed?, Why are specifications needed?, Prominent Standards
Final Examination
Award of Certificates for Successful Completion
Printable (.pdf) version of course outline no. 117 ( Adobe Acrobat Reader required).
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