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Fixture Design
for Vibration and Shock Testing

Course No. 157-5

(Course Outline shown below.)

For Whom Intended  This seminar is intended for dynamics test and evaluation personnel desiring an understanding of practical approaches to the design and fabrication of test fixtures used in vibration and shock testing. Tooling Engineers responsible for fixture design need this training.

Quality Assurance and Reliability specialists will find the course useful. So will test and instrumentation specialists. The writers of specifications for environmental tests and for manufacture of fixtures will benefit from knowing of practical limitations that exist. Product designers who are seeking solutions to vibration and shock problems will also find the course helpful.

A fixture designer must be able to design a test fixture that will transmit the intended input forces directly to the Device Under Test. To accomplish this, a designer must have specific skills as well as an understanding of vibration and shock, structures, dynamic theory, materials and fabrication.

Brief Course Description  This course incorporates a mechanical design fundamentals segment equivalent to Course 310, which runs concurrently and may be taken by itself. The course commences with an introduction to vibration and then covers basic dynamics theory including relationships between displacement, velocity and acceleration. Dunkerley's and Rayleigh's methods are introduced, with examples. Damping, transmissibility ratio and resonance stacking are addressed. The course then covers basic structural theory: tension, compression, stress, strain, torsion and moments of inertia. Examples show the torsional shape factors of different structures.

The instructor then addresses frequency and stiffness of beams, plates and gussets, providing useful graphs, formulas and examples. Bolted connections are covered next. Useful data on structures, bolted connections etc., is included in the course workbook which will be an invaluable reference tool back at the workbench.

Modal analysis is then discussed, with mention of multi-degree-of-freedom systems, modes and complex systems. Measurement and fixturing for modal analysis and testing are covered, before moving on to mechanical shock and its design implications. Methods of isolating assemblies from shock and vibration are covered.

Fatigue is covered, including discussion of crack growth rates, fracture mechanics, the S-N curve, and the use and abuse of accelerated testing, including Miner's hypothesis.

Material selection is then covered, with information on overall and design-limiting material properties. Tools are provided for comparing different materials. The design fundamentals segment concludes with chassis analysis and general design suggestions, such as methods for increasing natural frequencies.

The course then moves on to a brief discussion of random vibration, including power spectral density theory. The concept of RMS acceleration is discussed, followed by a basic introduction to shakers and vibration testing. General considerations in fixture design are discussed next, along with an introduction to instrumentation and sinusoidal vibration testing, as they apply to the fixture design and evaluation process.

The course outlines a variety of strategies for attaching test items to fixtures, from the simplest adaptor plates to massive custom-designed cast and welded fixtures. Practical simplified designs and fabrication techniques, including bonding, bolting and welding, are discussed and class projects are undertaken to design some typical fixtures.

Diploma Programs  This course may be used to satisfy the requirement for Course 310 in TTi’s Mechanical Design Specialist (MDS) Diploma Program. It may be used as an elective for any other TTi specialist diploma program.

Related Courses  The mechanical design portion of Course 157-5 is available separately in Course 310, which runs concurrently. Course 157-3, an abbreviated version of 157-5, is available for on-site presentation to experienced designers.

Prerequisites  A TTi Fundamentals of Vibration course would be helpful. Participants will need first-year college mathematics (or equivalent experience) and some facility with fundamental engineering computations. Some familiarity with electrical and mechanical measurements and vibration will be helpful, as will an understanding of and familiarity with tooling and manufacturing.

Text  Each participant will receive a course workbook, including most of the viewgraphs used during the 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.




Course Outline No. 157-5

Printable (.pdf) version of course outline no. 157-5 ( Adobe Acrobat Reader required).

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