Unusual Joint Failure Steam Pipe Range

Reliability of electronic assemblies at board level and solder joint integrity depend upon the stress applied to the assembly. The stress is often of thermomechanical or of vibrational nature. In both cases, the behavior of the assembly is strongly influenced by the mechanical boundary conditions created by the printed circuit board (PCB) to casing fasteners. In many previously published papers, the conditions imposed to the fasteners are mostly aiming at an increase of the fundamental frequency and a decrease of static or dynamic displacement values characterizing the deformation. These conditions aim at reducing the fatigue in different parts of these assemblies. In the photomechanics laboratory of INSA Rouen, the origins of solder joint failure have been investigated by means of full-field measurements of the flexure deformation induced by vibrations or by forced thermal convection. The measurements were done both at a global level for the whole printed circuit board assembly (PCBA) and at a local level at the solder joints where failure was reported. The experimental technique used was phase-stepped laser speckle interferometry. This technique has a submicrometer sensitivity with respect to out-of-plane deformations induced by bending and its use is completely nonintrusive. Some of the results were comforted by comparison with a numerical finite elements model. The experimental results are presented either as time-average holographic fringe patterns, as in the case of vibrations, or as wrapped phase patterns, as in the case of deformation under thermomechanical stress. Both types of fringe patterns may be processed so as to obtain the explicit out-of-plane static deformation (or vibration amplitude) maps. Experimental results show that the direct cause of solder joint failure may be a high local PCB curvature produced by a supplementary fastening screw intended to reduce displacements and increase fundamental frequency. The curvature is directly responsible for tensile stress appearing in the leads of a large quad flat pack (QFP) component and for shear in the corresponding solder joints. The general principle of increasing the fundamental frequency and decreasing the static or dynamic displacement values has to be checked against the consequences on the PCB curvature near large electronic devices having high stiffness.

Download Full-text

Tribology: A portal to understand joint failure?

Arthritis & Rheumatism ◽

10.1002/art.22973 ◽

2007 ◽

Vol 56 (11) ◽

pp. 3511-3513 ◽

Cited By ~ 3

Author(s):

Markus A. Wimmer ◽

Thomas M. Schmid ◽

Joshua J. Jacobs

Keyword(s):

Joint Failure

Download Full-text

Fatigue Variability of Alloy 625 Thin-Tube Brazed Specimens

Metals ◽

10.3390/met11081162 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1162

Author(s):

Seulbi Lee ◽

Hanjong Kim ◽

Seonghun Park ◽

Yoon Suk Choi

Keyword(s):

Fatigue Life ◽

Heat Exchanger ◽

Room Temperature ◽

Metal Layer ◽

Outer Diameter ◽

Multiple Crack ◽

Joint Failure ◽

Alloy 625 ◽

Thin Tube ◽

Brazed Joint

As an advanced heat exchanger for aero-turbine applications, a tubular-type heat exchanger was developed. To ensure the optimum performance of the heat exchanger, it is necessary to assess the structural integrity of the tubes, considering the assembly processes such as brazing. In this study, fatigue tests at room temperature and 1000 K were performed for 0.135 mm-thick alloy 625 tubes (outer diameter of 1.5 mm), which were brazed to the grip of the fatigue specimen. The variability in fatigue life was investigated by analyzing the locations of the fatigue failure, fracture surfaces, and microstructures of the brazed joint and tube. At room temperature, the specimens failed near the brazed joint for high σmax values, while both brazed joint failure and tube side failure were observed for low σmax values. The largest variability in fatigue life under the same test conditions was found when one specimen failed in the brazed joint, while the other specimen failed in the middle of the tube. The specimen with brazed joint failure showed multiple crack initiations circumferentially near the surface of the filler metal layer and growth of cracks in the tube, resulting in a short fatigue life. At 1000 K, all the specimens exhibited failure in the middle of the tube. In this case, the short-life specimen showed crack initiation and growth along the grains with large through thickness in addition to multiple crack initiations at the carbides inside the tube. The results suggest that the variability in the fatigue life of the alloy 625 thin-tube brazed specimen is affected by the presence of the brazed joint, as well as the spatial distribution of the grain size and carbides.

Download Full-text

Thermo-mechanical analysis of bolted X20 steam pipe-flange assembly

Materials Today Proceedings ◽

10.1016/j.matpr.2020.04.882 ◽

2020 ◽

Cited By ~ 1

Author(s):

Smith Salifu ◽

Dawood Desai ◽

Festus Fameso ◽

Olugbenga Ogunbiyi ◽

Samson Jeje ◽

...

Keyword(s):

Mechanical Analysis ◽

Steam Pipe

Download Full-text

Verification of creep analyzes of a steam pipe system, Swedish Energy Agency

Impact ◽

10.21820/23987073.2018.86 ◽

2018 ◽

Vol 2018 (1) ◽

pp. 86-88

Author(s):

Jan Storesund ◽

Rikard Norling

Keyword(s):

Energy Agency ◽

Pipe System ◽

Steam Pipe

Download Full-text

Planning Fail-Safe Trajectories for Space Robotic Arms

Frontiers in Robotics and AI ◽

10.3389/frobt.2021.710021 ◽

2021 ◽

Vol 8 ◽

Author(s):

Oliver Porges ◽

Daniel Leidner ◽

Máximo A. Roa

Keyword(s):

Degrees Of Freedom ◽

Fault Tolerant ◽

Robotic Manipulators ◽

Task Completion ◽

Joint Failure ◽

Space Applications ◽

Robotic Arms ◽

Hazardous Environments ◽

Potential Risks ◽

Fail Safe

A frequent concern for robot manipulators deployed in dangerous and hazardous environments for humans is the reliability of task executions in the event of a joint failure. A redundant robotic manipulator can be used to mitigate the risk and guarantee a post-failure task completion, which is critical for instance for space applications. This paper describes methods to analyze potential risks due to a joint failure, and introduces tools for fault-tolerant task design and path planning for robotic manipulators. The presented methods are based on off-line precomputed workspace models. The methods are general enough to cope with robots with any type of joint (revolute or prismatic) and any number of degrees of freedom, and might include arbitrarily shaped obstacles in the process, without resorting to simplified models. Application examples illustrate the potential of the approach.

Download Full-text