Experimental Study of U* Index Response to Structural and Loading Variations

2015 ◽  
Author(s):  
Khashayar Pejhan ◽  
Qingguo Wang ◽  
Igor Telichev
Keyword(s):  
Load Transfer ◽  
Experimental Testing ◽  
Minimum Weight ◽  
Index Theory ◽  
Load Path ◽  
Stress Concentrations ◽  
Structural Variations ◽  
Design Modification ◽  
Testing Procedures ◽  
Load Transfer Analysis

Load transfer analysis tracks the path, on which the imposed load is being carried through the structure. Recently, vehicle structure designers have paid growing attention to this aspect of structural analysis for designing lighter vehicle structures that can efficiently carry the imposed loads with minimum weight. There are two main procedures for load transfer analysis in automotive engineering: 1) Stress trajectory method and 2) U* index theory. The former method faces some difficulties in following load path in structures with stress concentrations made by geometrical irregularities. As a result the U* index theory has been utilized more frequently in this area. This theory has shown exceptional capacities in following load transfer in the structure and has provided innovative tools for design modification in automotive industry. Although it can be shown mathematically that U* index quantifies the internal stiffness of the structure there has not been an experimental validation for that. Moreover, the term internal stiffness itself is not an easy concept to follow and it can be easily mistaken for the structural stiffness of the structure. As a result in the current paper two experimental testing procedures are presented to distinguish the internal stiffness, that can be quantified with U* index and the structural (conventional) stiffness of the structure. Through these experiments, for the first time, physical evaluation of U* index response to loading and structural variations can be performed.

Extension of U* Index Theory to Nonlinear Case of Load Transfer Analysis

2015 ◽  
Author(s):  
Khashayar Pejhan ◽  
Qingguo Wang ◽  
Christine Q. Wu ◽  
Igor Telichev
Keyword(s):  
Load Transfer ◽  
Index Theory ◽  
Design Tool ◽  
Load Path ◽  
Nonlinear Load ◽  
Index Value ◽  
Transfer Index ◽  
Static Conditions ◽  
Nonlinear Elastic ◽  
Load Transfer Analysis

Load transfer analysis has been proved to be an effective approach for designing light weight vehicle structures in last two decades. There are two main procedures for predicting the load path in a vehicle: The stress trajectory method and the U* index theory. The first approach has shown some shortcomings in dealing with geometrical irregularities. As a result, automotive industries have mainly applied the U* index as a design tool to study the load transfer behavior in the vehicle structure. The U* index, is an indicator for the load transfer in the structure, i.e. higher U* index value indicates more significant role in the load transfer process. So, the distribution of the U* index in the structure can be used to predict the main load path in the structure. Nevertheless, this foundation of this theory is based upon the linear elasticity equations and consequently, it has always been limited to linear elastic problems in static or quasi static conditions. Eradicating this limitation and extending the U* Index theory to nonlinear elastic problems is the main objective of this study. An extension to nonlinear criteria for U* index theory is proposed in this paper. It is shown, for the very first time, that the extended nonlinear load transfer index (U*NL) is a true measure for the load transfer in the structure in a nonlinear elastic problem.

Experimental validation of the U* index theory for load transfer analysis

2017 ◽  
Vol 24 (3) ◽  
pp. 288 ◽  
Author(s):  
Khashayar Pejhan ◽  
Qingguo Wang ◽  
Christine Q. Wu ◽  
Igor Telichev
Keyword(s):  
Experimental Validation ◽  
Load Transfer ◽  
Index Theory ◽  
Load Transfer Analysis

Experimental validation of the U* index theory for load transfer analysis

2017 ◽  
Vol 24 (3) ◽  
pp. 288 ◽  
Author(s):  
Khashayar Pejhan ◽  
Igor Telichev ◽  
Christine Q. Wu ◽  
Qingguo Wang
Keyword(s):  
Experimental Validation ◽  
Load Transfer ◽  
Index Theory ◽  
Load Transfer Analysis

Application of Load Transfer Index (U*) in Structural Analysis in Comparison With Conventional Stress Analysis

2014 ◽  
Author(s):  
Khashayar Pejhan ◽  
Christine Q. Wu ◽  
Igor Telichev
Keyword(s):  
Stress Analysis ◽  
Load Transfer ◽  
Structure Design ◽  
Stress Distributions ◽  
Load Path ◽  
Additional Information ◽  
Path Index ◽  
Comprehensive Information ◽  
Transfer Index ◽  
Load Transfer Analysis

The U* index has been used for load transfer analysis to show its capability in giving general awareness regarding performance of structure. Although U* index and stress values have been proven to be useful indexes as structure design criteria, a thorough comparison between conventional stress analysis and loads transfer analysis (based on U* index) is lacking. In this study, we evaluate load transfer behaviors of a parcel rack of multiple passenger vehicles under different loading conditions using the U* index. Then by demonstrating the unique capabilities of U* as an index for stiffness, it is shown that the load path concept can be combined with the stress analysis results to provide comprehensive information about the structure responses to loading. In addition to the agreement between stress analysis and the U* analysis, it is shown that U* can provide additional information about the structure response that stress analysis fails. Such information includes: interpreting high and complicated stress distributions in structure and detection of questionable stiffness in certain parts of structure. More importantly, the load path index U* can detect the area where significant changes in the structure stiffness occurs. Such information can be used as a guideline for structure design with the goal to reduce the weight while still keeping the structure integrity.

Load Transfer Index for Composite Materials

2015 ◽  
Author(s):  
Qingguo Wang ◽  
Khashayar Pejhan ◽  
Christine Q. Wu ◽  
Igor Telichev
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Load Transfer ◽  
External Loading ◽  
Load Path ◽  
New Paradigm ◽  
Linear Elastic ◽  
Transfer Index ◽  
Fundamental Equations ◽  
Load Transfer Analysis

Load transfer analysis is a new paradigm for lightweight vehicle design. U* index has been proved to be an effective indicator for the load path. The U* theory indicates that the external loading mainly transfers through the parts with higher U* values in the structure. However, the fundamental equations of the theory are based on isotropic, homogenous, and linear elastic assumptions for the materials. Consequently, U* index is inadequate for composite materials which are increasingly used in automotive structures. In this study, a new load transfer index for composite structures, U*O, is proposed for the first time inspired by the basic U* theory. The U*O index considers the composite material as orthotropic instead of isotropic and eliminates the limitation of the basic U*. The effectiveness of the new U*O index on load path prediction is demonstrated by a case study for a general Graphite-epoxy lamina. The U*O index is capable to evaluate the accurate load path for the composite specimen. By contrast, the basic U* analysis shows the incorrect results.

Field Determined Live Load Distribution Factors for Modular Press-Brake-Formed Tub Girders

2021 ◽  
pp. 036119812098375
Author(s):  
Karl E. Barth ◽  
Gregory K. Michaelson ◽  
Adam D. Roh ◽  
Robert M. Tennant
Keyword(s):  
West Virginia ◽  
Experimental Testing ◽  
Field Performance ◽  
Live Load ◽  
Steel Bridge ◽  
Testing Procedures ◽  
Bending Capacity ◽  
Short Span ◽  
And Performance ◽  
Live Load Distribution

This paper is focused on the field performance of a modular press-brake-formed tub girder (PBFTG) system in short span bridge applications. The scope of this project to conduct a live load field test on West Virginia State Project no. S322-37-3.29 00, a bridge utilizing PBFTGs located near Ranger, West Virginia. The modular PBFTG is a shallow trapezoidal box girder cold-formed using press-brakes from standard mill plate widths and thicknesses. A technical working group within the Steel Market Development Institute’s Short Span Steel Bridge Alliance, led by the current authors, was charged with the development of this concept. Research of PBFTGs has included analyzing the flexural bending capacity using experimental testing and analytical methods. This paper presents the experimental testing procedures and performance of a composite PBFTG bridge.

Altered Load Transfer in the Pelvis in the Presence of Periprosthetic Osteolysis

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Jacob T. Munro ◽  
Justin W. Fernandez ◽  
James S. Millar ◽  
Cameron G. Walker ◽  
Donald W. Howie ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Load Transfer ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Fe Model ◽  
Stress Concentrations ◽  
Periprosthetic Osteolysis ◽  
Total Hip ◽  
Long Term Follow Up ◽  
Von Mises

Periprosthetic osteolysis in the retroacetabular region with cancellous bone loss is a recognized phenomenon in the long-term follow-up of total hip replacement. The effects on load transfer in the presence of defects are less well known. A validated, patient-specific, 3D finite element (FE) model of the pelvis was used to assess changes in load transfer associated with periprosthetic osteolysis adjacent to a cementless total hip arthroplasty (THA) component. The presence of a cancellous defect significantly increased (p < 0.05) von Mises stress in the cortical bone of the pelvis during walking and a fall onto the side. At loads consistent with single leg stance, this was still less than the predicted yield stress for cortical bone. During higher loads associated with a fall onto the side, highest stress concentrations occurred in the superior and inferior pubic rami and in the anterior column of the acetabulum with larger cancellous defects.

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