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The problem of understanding and modeling the complicated physics underlying the action and response of the interfaces in typical structures under dynamic loading conditions has occupied researchers for many decades. This handbook presents an integrated approach to the goal of dynamic modeling of typical jointed structures, beginning with a mathematical assessment of experimental or simulation data, development of constitutive models to account for load histories to deformation, establishment of kinematic models coupling to the continuum models, and application of finite element analysis leading to dynamic structural simulation. In addition, formulations are discussed to mitigate the very short simulation time steps that appear to be required in numerical simulation for problems such as this. This handbook satisfies the commitment to DOE that Sandia will develop the technical content and write a Joints Handbook. The content will include: (1) Methods for characterizing the nonlinear stiffness and energy dissipation for typical joints used in mechanical systems and components. (2) The methodology will include practical guidance on experiments, and reduced order models that can be used to characterize joint behavior. (3) Examples for typical bolted and screw joints will be provided. 3 AcknowledgmentThe authors thank the many managers and members of technical staff who have worked on this challenging problem at various times since its inception. For all of them, this involved a tremendous amount of hard work and for our management team it involved taking a substantial risk. To put significant resources year-after-year into a problem that had so successfully resisted the best efforts of the scientific community can be a gutsy decision on the part of manager. The authors believe that we have justified our managers' faith in us.Among the managers who should be recognized are

MicroE!ectroMechanicrd Systems (MEMS) were subjected to a vibration environment that had a peak acceleration of 120g and spanned frequencies from 20 to 2000 Hz. The device chosen for this test was a surface-micromachined microengine because it possesses many elements (springs, gears, rubbing surfaces) that may be susceptible to vibration. The microengines were unpowered during the test. We observed 2 vibration-related failures and 3 electrical failures out of 22 microengines tested. Surprisingly, the electrical failures also arose in four microengines in our control group indicating that they were not vibration related. Failure analysis revealed that the electrical failures were due to shorting of stationary comb fingers to the ground plane. INTRODUCnON An element of the success of MicroElectroMechanical Systems (MEMS) as they reach commercialization depends on reliability studies and predictions. MEMS are typically classified as sensors or actuators. Brown et al. performed extensive experiments on MEMS acceleration sensors including shock, vibration, temperature cycling, and flight tests on artillery projectiles [1]. He saw promising results on automobile-grade accelerometers. However, sensors differ from microactuators in that they do not have rubbing surfaces. Surfaces in intimate contact during the environmental test may be at risk. This was demonstrated in reports on humidity effects and wear [2, 3]. Microactuators are used to drive many different types of devices from gear trains to pop-up mirrors [4]. During vibration experiments by Lee et al. [5, 6], reflected optical patterns from a clamped micromirror were monitored and were determined to be error free over a range of frequencies from 200 Hz to 10 kHz. They claim no effect from vibration of the clamped mirror on this scale. But what happens when an actuator is not clamped and is free to move? Vibration causes motion in the actuator promoting the surfaces to rub and thus mimics normal operation. In addition, vibration perpendicular to the normal operation direction will impact guides or constraints. Both of these effects can generate wear debris leading to failure. One of the first experiments [7] to show wear as a dominant failure mechanism during operation ran polysilicon mi-croturbines [8] and gears at rotational speeds up to 600,000 rpm. A focused air jet directed at the turbine induced the rotation. Previous experiments [9] on the lifetime of the Sandia-designed surface-micromachined rnicroengine [10] investigating frequency dependence revealed wear as the dominant failure mechanism. We subjected our MEMS actuator to vibration. The microengine has springs that flex, guides that can be impacted, and surfaces that rub maldng it a good candidate for vibration studies. The resonant frequency of the microengine (about 1500 Hz) is in the range of our system-requirement frequencies, which may be of concern. The objective was to determine any susceptibility of the microengine to vibration with the understanding that the results would apply to a broader ran...

Two force reconstruction techniques were used to evaluate the impact test of a scale model nuclear transportation cask dropped 30 ft. onto an unyielding target. The two techniques are: the sum of weighted acceleration technique (SWAT) and the deconvolution technique (DECON). A brief description and the calibration of the techniques as applied to the cask are presented. For the impact test, both techniques yielded very similar resultant forces and provided more accurate definition of the force-time history for the cask than is available from conventional data reduction methods. An applied moment, measurement previously unobtainable from conventional accelerometer data reduction techniques, was determined with SWAT. The angular velocity calculated with SWAT was verified with photometric measurements.