Stress Singularities at Equal Angle Biwedges and Two-Material Composite Half Planes With Rough Interfaces

1976 ◽  
Vol 43 (1) ◽  
pp. 64-68 ◽  
Author(s):  
P. S. Theocaris ◽  
E. E. Gdoutos
Keyword(s):  
Friction Coefficient ◽  
Half Plane ◽  
Elastic Stress ◽  
Stress Singularity ◽  
Complex Variables ◽  
The Other ◽  
Stress Singularities ◽  
Equal Angle ◽  
Common Interface ◽  
Material Composite

The order of the elastic stress singularity developed either at the apex of an equal angle biwedge or at the vertex of a composite half plane is studied for the case when the two wedges adhere along their common interface according to Coulomb’s law of friction. The other two faces of the wedges are considered free from tractions in the vicinity of the apices of both types of biwedges. The study uses the well-known theory of complex variables, and the numerical results obtained for some special geometrical configurations and particular values of the friction coefficient are presented in Dundurs’ parallelograms which cover all physically interesting material combinations of the two wedges.

Elastic Stress Singularities: Implications for the Attachment of Tendon to Bone

2011 ◽  
Author(s):  
Yanxin Liu ◽  
Victor Birman ◽  
Chanqing Chen ◽  
Stavros Thomopoulos ◽  
Guy M. Genin
Keyword(s):  
Stress Distribution ◽  
Abrupt Change ◽  
Elastic Stress ◽  
Insertion Site ◽  
Stress Singularities ◽  
Local Stresses ◽  
Material Mismatch ◽  
Moduli Of Elasticity

The material mismatch at the attachment of tendon to bone is amongst the most severe for any tensile connection in nature. This is related to the large difference between the stiffness of tendon and bone, whose moduli of elasticity vary by two orders of magnitude. Predictably, such an abrupt change in the stiffness realized over a very narrow insertion site results in high local stresses. One of the implications of the stress distribution is a potential for stress singularities at the junction of the insertion to the bone.

Stress Singularity of Edge Delamination in Angle-Ply and Cross-Ply Laminates

1997 ◽  
Vol 64 (3) ◽  
pp. 525-531 ◽  
Author(s):  
Wen-Hwa Chen ◽  
Tain-Fu Huang
Keyword(s):  
Transverse Shear ◽  
Axial Strain ◽  
Stress Singularity ◽  
Shear Stresses ◽  
Explicit Solutions ◽  
Real Constant ◽  
Stress Singularities ◽  
General Solutions ◽  
Transverse Shear Stresses ◽  
Edge Delamination

By utilizing the general solutions derived for the plies with arbitrary fiber orientations under uniform axial strain (Huang and Chen, 1994), the explicit solutions of the edge-delamination stress singularities for the angle-ply and cross-ply laminates are obtained. The dominant edge-delamination stress singularities for the angle-ply laminates are found to be a real constant, −1/2, and a pair of complex conjugates, −1/2±i/2πln{(b+b2−a2)/a}. For the cross-ply laminates, the significant effect of transverse shear stresses of the laminate is considered and the dominant edge-delamination stress singularities are shown as −1/2 and −1/2±i/2πln{(c2+c22−4c1c3)/2c1}. a, b, cl, c2, and c3 are the corresponding combined complex constants. In addition, two elementary forms of edge-delamination stress singularity, say, r−1/2 and rδr(lnr)n(δr=n−3/2,n=1,2...) exist for both the angle-ply and cross-ply laminates. Excellent correlations between the present results and available solutions show the validity of the approach. The deficiencies of the solutions available in the literature are compensated. New results for other angle-ply and cross-ply laminates are also provided.

Finite Element Analysis of Stress Singularities in Attached Flip Chip Packages

2000 ◽  
Vol 122 (4) ◽  
pp. 301-305 ◽  
Author(s):  
A. Q. Xu ◽  
H. F. Nied
Keyword(s):  
Contact Angle ◽  
Finite Element ◽  
Glass Fiber ◽  
Flip Chip ◽  
Three Dimensional ◽  
Stress Singularity ◽  
Local Stress ◽  
Stress Singularities ◽  
Element Analysis ◽  
Three Dimensional Finite Element

Cracking and delamination at the interfaces of different materials in plastic IC packages is a well-known failure mechanism. The investigation of local stress behavior, including characterization of stress singularities, is an important problem in predicting and preventing crack initiation and propagation. In this study, a three-dimensional finite element procedure is used to compute the strength of stress singularities at various three-dimensional corners in a typical Flip-Chip assembled Chip-on-Board (FCOB) package. It is found that the stress singularities at the three-dimensional corners are always more severe than those at the corresponding two-dimensional edges, which suggests that they are more likely to be the potential delamination sites. Furthermore, it is demonstrated that the stress singularity at the upper silicon die/epoxy fillet edge can be completely eliminated by an appropriate choice in geometry. A weak stress singularity at the FR4 board/epoxy edge is shown to exist, with a stronger singularity located at the internal die/epoxy corner. The influence of the epoxy contact angle and the FR4 glass fiber orientation on stress state is also investigated. A general result is that the strength of the stress singularity increases with increased epoxy contact angle. In addition, it is shown that the stress singularity effect can be minimized by choosing an appropriate orientation between the glass fiber in the FR4 board and the silicon die. Based on these results, several guidelines for minimizing edge stresses in IC packages are presented. [S1043-7398(00)00904-X]

Two types of reservoir-induced seismicity

1988 ◽  
Vol 78 (6) ◽  
pp. 2025-2040
Author(s):  
D.W. Simpson ◽  
W.S. Leith ◽  
C.H. Scholz
Keyword(s):  
Normal Stress ◽  
Pore Pressure ◽  
Induced Seismicity ◽  
Elastic Stress ◽  
Pore Space ◽  
Temporal Distribution ◽  
The Other ◽  
Elastic Response ◽  
Reservoir Induced Seismicity ◽  
Effective Normal Stress

Abstract The temporal distribution of induced seismicity following the filling of large reservoirs shows two types of response. At some reservoirs, seismicity begins almost immediately following the first filling of the reservoir. At others, pronounced increases in seismicity are not observed until a number of seasonal filling cycles have passed. These differences in response may correspond to two fundamental mechanisms by which a reservoir can modify the strength of the crust—one related to rapid increases in elastic stress due to the load of the reservoir and the other to the more gradual diffusion of water from the reservoir to hypocentral depths. Decreased strength can arise from changes in either elastic stress (decreased normal stress or increased shear stress) or from decreased effective normal stress due to increased pore pressure. Pore pressure at hypocentral depths can rise rapidly, from a coupled elastic response due to compaction of pore space, or more slowly, with the diffusion of water from the surface.

Investigating the Effects of the Friction Coefficient and Tool Geometry on the Cup Thickness in the Deep Drawing Process of SPXI250 Alloy

2013 ◽  
Author(s):  
Iman Rostamsowlat ◽  
Ahmad Afsari ◽  
Maziar Janghorban
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Deep Drawing ◽  
The Other ◽  
Tool Geometry ◽  
Drawing Process ◽  
Nose Radius ◽  
Deep Drawing Process ◽  
Simulation Results ◽  
Thickness Variations

In this paper, effects of friction coefficient and tool geometry on the thickness variations of a cylindrical cup were studied. Blank is made of SPXI250 alloy sheet which was analyzed by Finite Element Method (FEM). This not been studied yet. Finite Element modeling of the deep drawing process was conducted using ABAQUS/EXPLICIT software. A set of appropriate die and punch were designed for experimental tests. The results of the simulation showed that a change in the friction coefficient of the die-blank interface leads to a significant changes in the cup thickness. Moreover, the results revealed that the influence of die nose radius on the final cup thickness variations is greater than that of the punch nose radius. The simulation results of this study were compared with the experimental results and those of the other investigators’. The comparisons of the experimental and simulation results with those of the other researchers were so satisfactory.

Stochastic Theory of Human Slipping

2002 ◽  
Author(s):  
Ralph L. Barnett ◽  
Susanne A. Glowiak ◽  
Peter J. Poczynok
Keyword(s):  
Friction Coefficient ◽  
Duty Cycle ◽  
Stochastic Theory ◽  
The Other ◽  
Extreme Value Statistics ◽  
Conventional Theory ◽  
Low Friction ◽  
Friction Coefficients ◽  
Duty Cycles ◽  
New Concepts

The conventional approach to human slipping is essentially deterministic; it states that no slipping will occur when the average friction coefficient is greater than some critical friction criterion. Under this condition, pedestrians will not slip when they encounter the average friction coefficient. On the other hand, to successfully negotiate a walk of n-steps they must not slip when they encounter the smallest of the n friction coefficients. Consequently, a new slip theory has been formulated as a problem in extreme value statistics. An elegant relationship is obtained among the probability of slipping, the critical friction criterion, the number of steps taken by the walker, and the central measure, scatter, and asymmetry of the distribution of friction coefficients. The new theory reveals the structure of human slipping in a startling way that introduces completely new concepts: the go/no go nature of classical slip predictions is replaced by a probability of slipping; low friction floor/footwear couples may lead to fewer slips than high friction ones; slipping can occur in any case where conventional theory predicts “no slip”; and the number of slips depends on the distance traveled by a pedestrian. Finally, this paper develops the idea that the slipperiness of a real floor must be evaluated for a duty-cycle. Duty-cycles can be represented as frequency histograms when a floor is homogeneous and isotropic.

Effect of Applied DC Voltage to Stainless Steel Pin and CNx Coated Disk in Pin-on-Disk Sliding Test on Tribological Properties

2005 ◽  
Author(s):  
Noritsugu Umehara ◽  
Takahiro Yamamoto ◽  
Yoshio Fuwa
Keyword(s):  
Stainless Steel ◽  
Friction Coefficient ◽  
Friction And Wear ◽  
The Other ◽  
Electric Voltage ◽  
Dc Voltage ◽  
Negative Voltage ◽  
Positive Voltage ◽  
Sliding Test ◽  
Pin On Disk

The effect of applied DC voltage on the friction and wear of CNx sliding against stainless steel pin in air was clarified. Friction coefficient decreased with the increasing negative voltage to apply to the ball and disk in air. On the other hand, positive voltage increased friction coefficient. Friction coefficient of CNx in air decreased from 0.22 to 0.05 by applying electric voltage of DC −200 V. Specific wear rate was decreased with the increasing applied positive and negative voltage. It was considered that the oxidation of CNx was controlled by electric field.

scholarly journals Reduction of the Coefficient of Friction of Steel-Steel Tribological Contacts by Novel Graphene-Deep Eutectic Solvents (DESs) Lubricants

Lubricants ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 37 ◽  
Author(s):  
Ignacio Garcia ◽  
Silvia Guerra ◽  
Juan de Damborenea ◽  
Ana Conde
Keyword(s):  
Mechanical Properties ◽  
Ionic Liquids ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Adhesive Wear ◽  
Choline Chloride ◽  
Deep Eutectic Solvents ◽  
The Other ◽  
Graphene Flakes ◽  
The Coefficient Of Friction

Deep eutectic ionic liquids (DES) possess similar properties to conventional ionic liquids (ILs). However, ILs cannot be considered as environmentally friendly compounds due to both its processing and synthesis, which could have significant polluting effects. On the contrary, deep eutectic solvents (DESs) can be biodegradable, non-toxic, and have a lower price than most ILs, making them potentially useful in a wide variety of advanced technological applications, such as tribology. On the other hand, graphene has recently been proposed as an extremely promising lubricant due to its combination of mechanical properties and chemical stability as well as its “green” character. In the present paper, graphene flakes (≈250 nm) have been used as an additive to DES composed of choline chloride (ChCl)-urea, ChCl-ethylene glycol, and ChCl-malic acid. According to the results, the addition of 1 wt% graphene reduces friction coefficient (COF) and, notably, prevents adhesive wear, reducing wear rate on steel-steel sliding contacts.

RSE-M - ASME XI - API 579: Comparison of Failure Assessment Diagrams (FAD)

2018 ◽  
Author(s):  
Claude Faidy
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Elastic Stress ◽  
Short Review ◽  
The Other ◽  
Ductile Tearing ◽  
Reference Stress ◽  
Failure Assessment ◽  
Tearing Resistance ◽  
Applied Stresses

After a short review of the 3 Codes in term of flaw evaluation, this paper will consider the Failure Assessment Diagrams (FAD) proposed in each of them. The cracked components are evaluated by a dedicated diagram for margin evaluation of ductile tearing resistance of the components: the elastic stress intensity factor of the crack normalized by the toughness of the material on one axis and the applied stresses normalized by a Reference Stress in the other axis. The 2017 Edition of RSE-M Appendix 5.4 and 5.6, the 2017 Edition of ASME XI Appendix H and the 2016 Edition of API 579 Part 9 will be used in this first comparison.

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