scholarly journals Determination of the limit load of statically indeterminate truss girders

2011 ◽  
Vol 9 (2) ◽  
pp. 217-229
Author(s):  
Zarko Petrovic ◽  
Bojan Milosevic ◽  
Marina Mijalkovic ◽  
Stanko Brcic
Keyword(s):  
Failure Mechanism ◽  
Limit Analysis ◽  
Limit Load ◽  
Efficient Manner ◽  
Load Calculation ◽  
Kinematic Theorem

The paper presents the procedure of limit load calculation of elasto-plastic trusses exposed to the action of proportional load which is gradually increased until the formation of failure mechanism. The calculation is based on the application of static and kinematic theorem of limit analysis which are the basis of the limit analysis of structures which produce the value of the limit load in a quick and efficient manner. Application of these theorems is displayed on the examples of truss girders loaded by one- and twoparameter load.

The Use of TMAH to Etch Silicon and Expose Metal Bridging Failures

2000 ◽  
Author(s):  
Mark Morris ◽  
James Mohr ◽  
Esteban Ortiz ◽  
Steven Englebretson
Keyword(s):  
Failure Mechanism ◽  
Schottky Diodes ◽  
Tetramethylammonium Hydroxide ◽  
Novel Approach ◽  
Failure Location ◽  
Metal Etching ◽  
Plastic Mold

Abstract Determination of metal bridging failures on plastic encapsulated devices is difficult due to the metal etching effects that occur while removing many of the plastic mold compounds. Typically, the acids used to remove the encapsulation are corrosive to the metals that are found within the device. Thus, decapsulation can result in removal of the failure mechanism. Mechanical techniques are often not successful due to damage that results in destruction of the die and failure mechanism. This paper discusses a novel approach to these types of failures using a silicon etch and a backside evaluation. The desirable characteristics of the technique would be to remove the silicon and leave typical device metals unaffected. It would also be preferable that the device passivation and oxides not be etched so that the failure location is not disturbed. The use of Tetramethylammonium Hydroxide (TMAH), was found to fit these prerequisites. The technique was tested on clip attached Schottky diodes that exhibited resistive shorting. The use of the TMAH technique was successful at exposing thin solder bridges that extruded over the edge of the die resulting in failure.

Shakedown and Limit Analysis of Kinematic Hardening Piping Elbows Under Internal Pressure and Bending Moments

2021 ◽  
Author(s):  
Heng Peng ◽  
Yinghua Liu
Keyword(s):  
Yield Strength ◽  
Internal Pressure ◽  
Limit Analysis ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Bending Moments ◽  
Plastic Limit ◽  
Plastic Limit Load ◽  
Interaction Curves ◽  
Shakedown Limit

Abstract In this paper, the Stress Compensation Method (SCM) adopting an elastic-perfectly-plastic (EPP) material is further extended to account for limited kinematic hardening (KH) material model based on the extended Melan's static shakedown theorem using a two-surface model defined by two hardening parameters, namely the initial yield strength and the ultimate yield strength. Numerical analysis of a cylindrical pipe is performed to validate the outcomes of the extended SCM. The results agree well with ones from literature. Then the extended SCM is applied to the shakedown and limit analysis of KH piping elbows subjected to internal pressure and cyclic bending moments. Various loading combinations are investigated to generate the shakedown limit and the plastic limit load interaction curves. The effects of material hardening, elbow angle and loading conditions on the shakedown limit and the plastic limit load interaction curves are presented and analysed. The present method is incorporated in the commercial finite element simulation software and can be considered as a general computational tool for shakedown analysis of KH engineering structures. The obtained results provide a useful information for the structural design and integrity assessment of practical piping elbows.

Estimate of the Ultimate Load on Structural Members Subjected to Lateral Loads

2001 ◽  
Vol 38 (03) ◽  
pp. 169-176
Author(s):  
L. Belenkiy ◽  
Y. Raskin
Keyword(s):  
Finite Element ◽  
Limit Analysis ◽  
Ultimate Load ◽  
Limit Load ◽  
Plastic Behavior ◽  
Lateral Loads ◽  
Ship Structures ◽  
Strength Assessment ◽  
Stiffened Panels ◽  
Plate Elements

This paper examines plastic behavior of typical ship structures, specifically beams, grillages, and plates subjected to predominantly lateral loads. The ultimate loads, determined on the basis of the theorems of limit analysis [1,2], are evaluated using nonlinear finite-element plastic analysis. The relationships between analytical and finite-element models for prediction of ultimate loads of beams, stiffened panels, and grillages are illustrated. It has been shown that the ultimate loads, obtained from the theorems of limit analysis, can be successfully used for strength assessment of stiffened ship structures subjected to lateral loads. The effect of shear force on ultimate load is analyzed using the finite-element method. This paper confirms that in the case of beams and grillages under lateral loading, the ultimate load may characterize the threshold of the load at which a stiffened ship's structure fails by the development of excessive deflections. For plate elements, on the other hand, the plastic deflections represent the permissible limit of external load better than the ultimate limit load.

Shakedown and Limit Analysis of Kinematic Hardening Piping Elbows Under Inner Pressure and Bending Moments

2020 ◽  
Author(s):  
Heng Peng ◽  
Yinghua Liu
Keyword(s):  
Yield Strength ◽  
Limit Analysis ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Bending Moments ◽  
Plastic Limit ◽  
Inner Pressure ◽  
Plastic Limit Load ◽  
Interaction Curves ◽  
Shakedown Limit

Abstract The stress compensation method (SCM) for shakedown and limit analysis was previously proposed and applied to elastic-perfectly plastic (EPP) piping elbows. In this paper, the SCM is extended to account for limited kinematic hardening (KH) material model based on the extended Melan’s static shakedown theorem using a two-surface model defined by two hardening parameters: initial yield strength and ultimate yield strength. To validate the extended SCM, a numerical test on a cylinder pipe is performed. The results agree well with ones from literature. Then the extended SCM is applied to the shakedown and limit analysis of KH piping elbows subjected to inner pressure and cyclic bending moments. Various loading combinations are investigated to create the shakedown limit and plastic limit load interaction curves. The effects of the material hardening, angle of the elbow and loading conditions on the shakedown limit and plastic limit load interaction curves are presented and analysed. The present method is incorporated in the commercial software of Abaqus and can be considered as a general computational tool for shakedown analysis of KH engineering structures. The obtained results provide a useful information for the structural design and integrity assessment of practical piping elbows.

Bending the Curve: Preoperative Determination of Bypass Graft Length and Trajectory With Curved Planar Reformatted Computed Tomography Angiography: Technical Note

2011 ◽  
Vol 70 (suppl_2) ◽  
pp. onsE327-onsE331
Author(s):  
Jeffrey C. Markham ◽  
Christopher S. Eddleman ◽  
David Uhrbrock ◽  
Babu G. Welch
Keyword(s):  
Computed Tomography ◽  
Bypass Graft ◽  
External Carotid Artery ◽  
Technical Note ◽  
Cerebral Revascularization ◽  
External Carotid ◽  
Efficient Manner ◽  
Curved Planar Reformation ◽  
Graft Length

ABSTRACT BACKGROUND AND IMPORTANCE: Cerebral revascularization continues to be an important technique for the treatment of cerebrovascular and vaso-occlusive diseases, and determination of appropriate graft sources and recipients is paramount to the success of the procedure. A tension-free anastomosis requires that harvested grafts be of an appropriate length to avoid complications. Volume-rendered contrast-enhanced computed tomography data sets may be useful in determining the desired length and path of the bypass graft and in the evaluation of appropriate recipient vessels. Curved planar reformation techniques may allow these properties to be determined in a novel, inexpensive, and efficient manner. CLINICAL PRESENTATION: A 63-year-old patient with a left hemispheric perfusion deficit and without an external carotid artery was in need of high-flow cerebral revascularization. A radial artery graft spanning from the vertebral artery to the middle cerebral artery was proposed. Preoperative determination of graft length necessary and most efficient subcutaneous placement was desired. A standard computed tomography angiogram of the head and neck was obtained and imported into a computer workstation with curved planar reformatting capabilities. CONCLUSION: Curved planar reformation technique can be used for preoperative planning of cerebral bypass procedures and is a novel, inexpensive, and efficient means of determining the desired length and path of the bypass graft and in the evaluation of appropriate recipient vessels.

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