Survivability assessment of electronics subjected to mechanical shocks up to 25,000g

2016 ◽  
Author(s):  
Pradeep Lall ◽  
Kalyan Dornala ◽  
Ryan Lowe ◽  
Jason Foley
Keyword(s):  
Mechanical Shocks

scholarly journals Simulation of Hydraulic Cylinder Cushioning

2021 ◽  
Vol 13 (2) ◽  
pp. 494
Author(s):  
Antonio Algar ◽  
Javier Freire ◽  
Robert Castilla ◽  
Esteban Codina
Keyword(s):  
Dynamic Model ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Computational Fluid Dynamic Simulation ◽  
Hydraulic Cylinder ◽  
Outlet Port ◽  
Optimal Behavior ◽  
Radial Movement ◽  
Mechanical Shocks ◽  
Radial Gap

The internal cushioning systems of hydraulic linear actuators avoid mechanical shocks at the end of their stroke. The design where the piston with perimeter grooves regulates the flow by standing in front of the outlet port has been investigated. First, a bond graph dynamic model has been developed, including the flow throughout the internal cushion design, characterized in detail by computational fluid-dynamic simulation. Following this, the radial movement of the piston and the fluid-dynamic coefficients, experimentally validated, are integrated into the dynamic model. The registered radial movement is in coherence with the significant drag force estimated in the CFD simulation, generated by the flow through the grooves, where the laminar flow regime predominates. Ultimately, the model aims to predict the behavior of the cushioning during the movement of the arm of an excavator. The analytical model developed predicts the performance of the cushioning system, in coherence with empirical results. There is an optimal behavior, highly influenced by the mechanical stress conditions of the system, subject to a compromise between an increasing section of the grooves and an optimization of the radial gap.

Effects of CSF Properties on Brain Response Under Impact Loading

2009 ◽  
Author(s):  
M. S. Chafi ◽  
V. Dirisala ◽  
G. Karami ◽  
M. Ziejewski
Keyword(s):  
Human Head ◽  
Brain Response ◽  
Pia Mater ◽  
Mechanical Shocks ◽  
The Central Nervous System ◽  
Simultaneous Loading ◽  
The Impact ◽  
Impact Experiments ◽  
The Brain

In the central nervous system, the subarachnoid space is the interval between the arachnoid membrane and the pia mater. It is filled with a clear, watery liquid called cerebrospinal fluid (CSF). The CSF buffers the brain against mechanical shocks and creates buoyancy to protect it from the forces of gravity. The relative motion of the brain due to a simultaneous loading is caused because the skull and brain have different densities and the CSF surrounds the brain. The impact experiments are usually carried out on cadavers with no CSF included because of the autolysis. Even in the cadaveric head impact experiments by Hardy et al. [1], where the specimens are repressurized using artificial CSF, this is not known how far this can replicate the real functionality of CSF. With such motivation, a special interest lies on how to model this feature in a finite element (FE) modeling of the human head because it is questionable if one uses in vivo CSF properties (i.e. bulk modulus of 2.19 GPa) to validate a FE human head against cadaveric experimental data.

Reliability of SAC 105 and SAC1205N under Drop Tests

2016 ◽  
Vol 2016 (1) ◽  
pp. 000106-000110
Author(s):  
Jia-Shen Lan ◽  
Stuwart Fan ◽  
Louie Huang ◽  
Mei-Ling Wu
Keyword(s):  
Fatigue Life ◽  
Solder Joint ◽  
Simulation Model ◽  
Drop Test ◽  
Test Execution ◽  
Fine Pitch ◽  
Mechanical Shocks ◽  
Drop Tests ◽  
Solder Joint Fatigue ◽  
Package Reliability

Abstract In this paper, the solder joint failure and the solder joint fatigue life in the Thin-profile Fine-pitch Ball Grid Array (TFBGA) Package was investigated by performing the drop test, and implementing a simulation model. Owing to the need to meet the increasing demands for functionality, microelectronic package reliability can be compromised and has become the key issue when executing drop tests. During impact in drop test, the deformation of PCB due to bending and mechanical shocks can cause solder joint crack. While this is a well-known issue, observing the solder joint responses during the test execution can be a challenge. Therefore, in this work, a simulation model approach has been developed to investigate the stress and strain of the solder joint during the drop test. In this research, the JEDEC Condition B drop test was simulated, characterized by 1500G peak acceleration and 0.5 ms duration. The drop test simulation model was successful in predicting the solder joint fatigue life with different solder joint materials, such as SAC105 and SAC1205N, while also facilitating result comparison to identify the most optimal structure.

Compression Strengthening of Plastic Bonded Explosives

1997 ◽  
Vol 3 (S2) ◽  
pp. 1249-1250
Author(s):  
Paul D. Peterson ◽  
Deanne J. Idar ◽  
John S. Gardner
Keyword(s):  
Material Flow ◽  
Compressive Loading ◽  
Polymer Binder ◽  
Material Behavior ◽  
Inert Material ◽  
Hard Phase ◽  
Compressive Properties ◽  
Soft Phase ◽  
Mechanical Shocks ◽  
Low Strain Rate

A recent study concluded that the most potentially dangerous scenarios for accidental detonation of a nuclear weapon were those involving weak thermal or mechanical shocks. For this reason, more data are needed to understand the material behavior of nuclear constituents under low strain rate scenarios.One of the components of many of these types of weapons is known as Plastic Bonded eXplosives (PBX). PBX is a paniculate composite material made of a hard phase explosive carried in a soft phase polymer binder. Recent work has showed that the stiffness of PBX increased under low rate compressive loading. This behavior was attributed to the shape of the test samples and cross-linking within the elastomer binder. Another theory proposed that the changing compressive properties could be attributed to the hard phase particles migrating together during material flow.Funk et al. demonstrated an inert material mock of PBX 9501, with the hard phase explosive replaced by granular sugar, also showed the same phenomena of compressive hardening.

Double-Sided Mechanical Shocks Provoke Larger Seated Postural Reactions Compared With Single-Sided Mechanical Shocks

Spine ◽  
2018 ◽  
Vol 43 (8) ◽  
pp. E482-E487 ◽  
Author(s):  
Tobias Carl Stenlund ◽  
Fredrik Öhberg ◽  
Ronnie Lundström ◽  
Ola Lindroos ◽  
Charlotte K. Häger ◽  
...  
Keyword(s):  
Postural Reactions ◽  
Mechanical Shocks

scholarly journals CnaA domains in bacterial pili are efficient dissipaters of large mechanical shocks

2016 ◽  
Vol 113 (9) ◽  
pp. 2490-2495 ◽  
Author(s):  
Daniel J. Echelman ◽  
Jorge Alegre-Cebollada ◽  
Carmen L. Badilla ◽  
Chungyu Chang ◽  
Hung Ton-That ◽  
...  
Keyword(s):  
Single Molecule ◽  
Pathogenic Bacteria ◽  
Mechanical Energy ◽  
Bacterial Attachment ◽  
Gram Positive ◽  
Covalent Bonds ◽  
Single Molecule Force Spectroscopy ◽  
Hydrophobic Collapse ◽  
Gram Positive Bacteria ◽  
Mechanical Shocks

Pathogenic bacteria adhere despite severe mechanical perturbations induced by the host, such as coughing. In Gram-positive bacteria, extracellular protein appendages termed pili are necessary for adherence under mechanical stress. However, little is known about the behavior of Gram-positive pili under force. Here, we demonstrate a mechanism by which Gram-positive pili are able to dissipate mechanical energy through mechanical unfolding and refolding of isopeptide bond-delimited polypeptide loops present in Ig-type CnaA domains. Using single-molecule force spectroscopy, we find that these loops of the pilus subunit SpaA of the SpaA-type pilus from Corynebacterium diphtheriae and FimA of the type 2 pilus from Actinomyces oris unfold and extend at forces that are the highest yet reported for globular proteins. Loop refolding is limited by the hydrophobic collapse of the polypeptide and occurs in milliseconds. Remarkably, both SpaA and FimA initially refold to mechanically weaker intermediates that recover strength with time or ligand binding. Based on the high force extensibility, CnaA-containing pili can dissipate ∼28-fold as much energy compared with their inextensible counterparts before reaching forces sufficient to cleave covalent bonds. We propose that efficient mechanical energy dissipation is key for sustained bacterial attachment against mechanical perturbations.

A method of health hazard assessment for human exposure to repeated mechanical shocks

1997 ◽  
Vol 101 (5) ◽  
pp. 3185-3185
Author(s):  
James Morrison ◽  
Jordan Nicol ◽  
Daniel Robinson ◽  
George Roddan ◽  
Julie Springer ◽  
...  
Keyword(s):  
Hazard Assessment ◽  
Human Exposure ◽  
Health Hazard ◽  
Mechanical Shocks

The Application of Vibration Assessment in Mining Vehicles to Return-to-Work Protocols

1997 ◽  
Vol 16 (2) ◽  
pp. 73-79
Author(s):  
D.G. Robinson ◽  
S.H. Martin ◽  
G. Roddan ◽  
G.H. Gibbs ◽  
J. Dutnall
Keyword(s):  
Oil Sands ◽  
Vehicle Classification ◽  
Whole Body ◽  
Light Truck ◽  
Mechanical Shocks ◽  
Vehicle Operation ◽  
Light Trucks ◽  
Peak Shock ◽  
Iso 2631 ◽  
Mining Vehicles

Whole body vibration assessment was performed for 11 mining vehicles during regular operations at Suncor Oil Sands near Ft. McMurray, Canada. Vehicles included heavy haulage trucks, light trucks and earth moving machines (dozers, a grader and a bucket loader). Vibration severity and shock severity were assessed according to ISO 2631 using the root mean square (RMS) and crest factor methods. The BS 6841 vibration dose value (VDV) accumulated over a single 12-hour shift was estimated for an exposure duration of 6 hours and for the maximum anticipated duration of vehicle operation during a shift. Severe mechanical shocks with crest factors greater than 10 were observed for all vehicles except the supervisor's light truck. Motion profiles contained peak-to-peak shock amplitudes as large as 38 m·s−-2 in some vehicles. Vibration levels (RMS) exceeded the ISO 2631/1 guidelines for all vehicles except a new D10 dozer and the 789 heavy hauler. The recommended daily VDV was exceeded by all vehicles except the 789 hauler. Vehicles were ranked for relative severity of motion exposure to provide guidance in the planned integration of injured workers back into daily mine operations. Within each vehicle classification, the most favourable motion profiles were observed for the 789 heavy hauler, the new D10 dozer and the supervisor's light truck.

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