scholarly journals Evaluation of Occupant Volume Strength in Conventional Passenger Railroad Equipment

2008 ◽  
Author(s):  
Michael Carolan ◽  
Benjamin Perlman ◽  
David Tyrell
Keyword(s):  
Compressive Load ◽  
Compressive Force ◽  
Bending Moment ◽  
The United States ◽  
Fe Model ◽  
Structural Components ◽  
Single Beam ◽  
Current Test ◽  
Compressive Strength Test ◽  
Passenger Railroad

To ensure a level of occupant volume protection, passenger railway equipment operating on mainline railroads in the United States must be designed to resist an 800,000-lb compressive load applied statically along the line of draft. An alternative manner of evaluating the strength of the occupied volume is sought, which will ensure the same level of protection for occupants of the equipment as the current test, but will allow for a greater variety of equipment to be evaluated. A finite element (FE) model of the structural components of a railcar has been applied to examine the existing compressive strength test and evaluate selected alternate testing scenarios. Using simplified geometric and material properties, a generic single-level railcar model was constructed that captured the gross behaviors of the railcar without excessive processing time. When loaded, the carbody structure exhibits some single beam-like behaviors. Application of the existing 800 kip compressive load results in a significant bending moment as well as significant compressive forces. The alternative load cases examined show that a larger total compressive force may be distributed across the end structure of the railcar and result in similar stress levels throughout the structural frame as observed from application of the conventional proof load.

Finite Element Modeling of Self-Loosening of Bolted Joints

2004 ◽  
Author(s):  
Ming Zhang ◽  
Yanyao Jiang ◽  
Chu-Hwa Lee
Keyword(s):  
Finite Element ◽  
Contact Pressure ◽  
Bending Moment ◽  
Shear Loading ◽  
Transverse Load ◽  
Fe Model ◽  
Bolted Joint ◽  
Cyclic Bending ◽  
Second Stage ◽  
Cyclic Bending Moment

A three-dimensional finite element (FE) model with the consideration of the helix angle of the threads was developed to simulate the second stage self-loosening of a bolted joint. The second stage self-loosening refers to the graduate reduction in clamping force due to the back-off of the nut. The simulations were conducted for two plates jointed by a bolt and a nut and the joint was subjected to transverse or shear loading. An M12×1.75 bolt was used. The application of the preload was simulated by using an orthogonal temperature expansion method. FE simulations were conducted for several loading conditions with different preloads and relative displacements between the two clamped plates. It was found that due to the application of the cyclic transverse load, micro-slip occurred between the contacting surfaces of the engaged threads of the bolt and the nut. In addition, a cyclic bending moment was introduced on the bolted joint. The cyclic bending moment resulted in an oscillation of the contact pressure on the contacting surfaces of the engaged threads. The micro-slip between the engaged threads and the variation of the contact pressure were identified to be the major mechanisms responsible for the self-loosening of a bolted joint. Simplified finite element models were developed that confirmed the mechanisms discovered. The major self-loosening behavior of a bolted joint can be properly reproduced with the FE model developed. The results obtained agree quantitatively with the experimental observations.

J-Integral Analysis of Surface Cracks in Round Bars under Bending Moments

2011 ◽  
Vol 52-54 ◽  
pp. 43-48 ◽  
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
Ruslizam Daud
Keyword(s):  
Finite Element ◽  
Crack Depth ◽  
Crack Tip ◽  
Bending Moment ◽  
Limit Load ◽  
Fe Model ◽  
Surface Cracks ◽  
Element Analysis ◽  
Reference Stress ◽  
Proposed Model

This paper presents a non-linear numerical investigation of surface cracks in round bars under bending moment by using ANSYS finite element analysis (FEA). Due to the symmetrical analysis, only quarter finite element (FE) model was constructed and special attention was given at the crack tip of the cracks. The surface cracks were characterized by the dimensionless crack aspect ratio, a/b = 0.6, 0.8, 1.0 and 1.2, while the dimensionless relative crack depth, a/D = 0.1, 0.2 and 0.3. The square-root singularity of stresses and strains was modeled by shifting the mid-point nodes to the quarter-point locations close to the crack tip. The proposed model was validated with the existing model before any further analysis. The elastic-plastic analysis under remotely applied bending moment was assumed to follow the Ramberg-Osgood relation with n = 5 and 10. J values were determined for all positions along the crack front and then, the limit load was predicted using the J values obtained from FEA through the reference stress method.

scholarly journals Numerical Simulation of Dynamic Response and Evaluation of Flexural Damage of RC Columns under Horizontal Impact Load

2021 ◽  
Vol 11 (23) ◽  
pp. 11223
Author(s):  
Bin Hu ◽  
Jian Cai ◽  
Jiabin Ye
Keyword(s):  
Static Load ◽  
Impact Load ◽  
Bending Moment ◽  
Internal Force ◽  
Displacement Curve ◽  
Fe Model ◽  
Damage State ◽  
Rc Columns ◽  
Equivalent Static Load ◽  
The Impact

By using the ABAQUS finite element (FE) model, which has been verified by experiments, the deformation and internal force changes of RC columns during the impact process are investigated, and a parametric analysis is conducted under different impact kinetic energies Ek. According to the development path of the bottom bending moment-column top displacement curve under impact, the member is in a slight damage state when the curve rebounds before reaching the peak and in a moderate or severe damage state when the curve exceeds the peak, in which case the specific damage state of the member needs to be determined by examining whether there is a secondary descending stage in the curve. Accordingly, a qualitative method for evaluating the bending failure of RC column members under impact is obtained. In addition, the damage state of RC columns under impact can also be quantitatively evaluated by the ratio of the equivalent static load Feq and the ultimate static load-bearing capacity Fsu.

Field Investigation of Broken Cut Spikes on Elastic Fasteners Using Instrumented Spikes at FAST

2020 ◽  
Author(s):  
Yin Gao ◽  
Mike McHenry ◽  
Megan Brice ◽  
Jay Baillargeon
Keyword(s):  
Fatigue Limit ◽  
Bending Moment ◽  
The United States ◽  
Field Investigation ◽  
Technology Center ◽  
Screw Drive ◽  
Joint Program ◽  
Service Testing ◽  
Test Loop ◽  
High Degree

Abstract Elastic fasteners have been shown to reduce gage widening and decrease the potential for rail roll compared to conventional cut-spike-only systems. For this reason, elastic fastening systems have been installed in high-degree curves on many North American heavy-haul railroads. Field observations in the United States, however, have noted broken cut spikes and screw/drive spikes on this type of fastening system, especially in steep-grade, high-degree curve territories. It was found that spikes typically fracture between 1 to 1.5 inches below the top surface of the ties, making them difficult to detect by visual inspection alone. Notable recent derailments have been attributed to broken spikes as reported by Class I railroads. Transportation Technology Center, Inc. (TTCI), as part of a joint program between the Federal Railroad Administration (FRA) and the Association of American Railroads (AAR), completed the initial phase of a study investigating the root cause of these broken cut and screw/drive spikes. Previous research under this joint program has confirmed through metallurgical investigation that material fatigue was the failure mechanism, and subsequent numerical simulation has shown that the bending stress in spikes can exceed the fatigue limit of the spike material. To further investigate the in-track loading environment of spikes, cut spikes instrumented with strain gages were installed in the high-tonnage test loop of the Facility for Accelerated Service Testing (FAST) at FRA’s Transportation Technology Center The test investigated the loading environment of spikes by considering several in-track conditions. The results showed that the load transferred to spikes during insertion and train passing could cause spike stresses higher than the fatigue limit and therefore lead to the permanent bending of spikes. Moreover, the bending moment was primarily carried by one of the four spikes from the same plate. This paper provides an overview of the development of instrumented spikes as well as the results of the in-track testing using these spikes. The findings from this study will guide future revenue service testing, for which a high-grade, high-curvature location will be considered to further investigate the broken spike issue.

Characterization of the Poroelastic Material Properties of Skeletal Repair Tissues Using Microindentation

2011 ◽  
Author(s):  
M. M. Sperry ◽  
L. N. M. Hayward ◽  
G. J. Miller ◽  
E. F. Morgan
Keyword(s):  
Material Properties ◽  
Repair Process ◽  
The United States ◽  
Fracture Site ◽  
Fe Model ◽  
Fracture Callus ◽  
Repetitive Injury ◽  
Poroelastic Material ◽  
Mechanical Factors ◽  
Callus Tissues

Nearly 10% of the approximately six million fractures that occur each year in the United States do not heal, causing lasting pain and repetitive injury [1]. Although the causes of poor healing are unknown in many cases, the sensitivity of the repair process to mechanical factors is well established. In an effort to understand how mechanical factors such as axial and shear micromotion at the fracture site affect healing, prior studies have sought to characterize the local mechanical environment using finite element (FE) analysis (e.g., [2,3]). However, a key set of inputs for the FE analyses is the distribution of material properties of the various tissues that comprise the fracture callus. Recent studies using nano- and microindentation have estimated these properties by approximating the tissues as linear elastic [4,5]. As a next step in this line of inquiry, the overall goal of this study was to estimate the linear, poroelastic material properties of callus tissues. The specific objectives were: 1) to develop an FE model for use in simulating microindentation experiments; and 2) to compare the results of the simulation to experimental microindentation data in order to derive the mechanical properties of the healing tissues.

Effects of Quadriceps and Hamstrings Ratio on ACL Strain During Landing Activities

2012 ◽  
Author(s):  
Carmen E. Quatman ◽  
Ata M. Kiapour ◽  
Ali Kiapour ◽  
Jason W. Levine ◽  
Samuel C. Wordeman ◽  
...  
Keyword(s):  
Knee Joint ◽  
Cruciate Ligament ◽  
Acl Injury ◽  
The United States ◽  
Implant Design ◽  
Reconstruction Technique ◽  
Fe Model ◽  
Acl Injuries

Over 100,000 anterior cruciate ligament (ACL) injuries occur annually in the United States [1]. Of these, 70% are classified as non-contact, many of which occur subsequent to a landing from a jump [2]. While most agree that quadriceps (Q) and hamstrings (H) have a significant contribution in knee biomechanics, the role of quadriceps and hamstrings muscle loads and their ratio (Q/H) in ACL injury remains controversial. Understanding muscle recruitment in high risk activities may improve our knowledge of ACL injury mechanisms. Such insight may improve current prevention strategies to decrease the risk of ACL injury and damage to secondary anatomical structures, all of which may in turn minimize associated posttraumatic knee osteoarthritis. As in vivo quantification of muscle loads remains challenging, especially under dynamic conditions, validated finite element (FE) models of the knee can be used to characterize the role of muscle loads in ACL injury. FE analysis has provided considerable insight into knee joint biomechanics, including ligament function, ligament reconstruction technique and implant design. This study utilized a validated FE model of the knee joint to study the effects of quadriceps to hamstrings ratio (Q/H) on ACL strain during a simulated landing from a jump. We hypothesized that both the ratio and magnitude of muscle loads are critical determinants of ACL loading. Further, a threshold may be reached as the magnitude of quadriceps load exceeds hamstrings load.

scholarly journals Influence of Comprehensive Joint Loads on Tibial Implant Micromotion in Total Ankle Arthroplasty

2020 ◽  
Vol 5 (4) ◽  
pp. 2473011420S0008
Author(s):  
Brett D. Steineman ◽  
Constantine A. Demetracopoulos ◽  
Jonathan T. Deland ◽  
Brett D. Steineman ◽  
Fernando Quevedo Gonzalez ◽  
...  
Keyword(s):  
Finite Element ◽  
Ankle Joint ◽  
Compressive Load ◽  
Compressive Force ◽  
Axial Loading ◽  
Loading Conditions ◽  
Bone Implant ◽  
Level Walking ◽  
Joint Loads

Category: Ankle Introduction/Purpose: Biologic fixation of total joint replacements by bone ingrowth requires minimal bone-implant micromotion [1]. Computational finite element (FE) models used to evaluate the interaction between implant and bone typically only consider simplified loading conditions based on the peak compressive force which occurs near toe-off [2,3]. However, a previous study focused on cementless knee replacements demonstrated that peak micromotion during activity cycles occurred with sub-maximal forces and moments [4]. Our objective was to calculate multi-axial loading at the ankle joint throughout level walking and evaluate tibial fixation of ankle replacements under these loading conditions. We hypothesized that peak micromotion would occur with sub-maximal loads and moments instead of at the instant of peak compressive load. Methods: Our validated six-degree-of-freedom robotic simulator utilizes in vivo data from human subjects to replicate the individual bone kinematics in cadaveric specimen throughout activity [5]. We rigidly fixed retro-reflective markers using bone pins to the tibia, talus, and calcaneus bones of three cadaveric specimens to record individual bone kinematics using motion capture cameras. We recorded the ground reaction and muscle-tendon forces during the simulated stance phase of level walking. Musculoskeletal models were then developed in OpenSim using the specimen-specific morphology and implant position from CT- scans and from the simulator outputs to determine the loading profile at the ankle joint during stance. The calculated loads were then applied to specimen-specific finite element models to evaluate the bone-implant interaction. Peak micromotion at each time point of loading was measured and compared to the loading profile to determine if it corresponded with the peak compressive load. Results: For all specimens, the peak compressive load at the ankle joint was accompanied by multi-axial moments and relatively small shear forces (Figure 1). The peak compressive load for each specimens was between 750 N and 850 N and occurred during 75-80% of gait. The largest moment experienced by all specimens was an internal moment late in stance. The peak micromotion for each specimen did not correspond to the instance of peak compressive load, as indicated in Figure 1. Instead, peak micromotion occurred at 54%, 88%, and 96% of gait. For each specimen, these instances corresponded to the combination of a sub-maximal compressive load with high eversion and internal moments. Conclusion: We have developed a workflow to calculate ankle joint loads corresponding to cadaveric simulations that reproduce a daily activity based on in vivo data. The specimen-specific, multi-axial loading profile at the ankle for our initial results suggests that peak micromotion at the bone-implant interface of the tibial implant does not coincide with the peak compressive force. The instant of peak compressive load may not capture the worst-case scenario for the interaction between the implant and the bone. Instead, the multi-axial forces and moments at the ankle joint throughout activity should be considered when evaluating implant fixation.

Numerical Modelling of FRCM Materials Using Augmented-FEM

2019 ◽  
Vol 817 ◽  
pp. 23-29
Author(s):  
Santi Urso ◽  
Houman A. Hadad ◽  
Chiara Borsellino ◽  
Antonino Recupero ◽  
Qing Da Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
The United States ◽  
Design Guidelines ◽  
Constitutive Law ◽  
Analytical Models ◽  
Fiber Reinforced Polymers ◽  
Fe Model

The use of externally-bonded composite materials for strengthening and rehabilitation of existing structures is among the most popular reinforcement techniques. Technologies, such as Fabric Reinforced Cementitious Matrix (FRCM) have been recently developed to address some of the issues of Fiber Reinforced Polymers (FRP), such as sensitivity to elevated temperatures and UV, impermeability, restricted application in presence of moisture or uneven substrate. For a detailed strengthening design with FRCM composites, the mechanical properties of the materials are required. Analytical models in literature discuss the interaction between the FRCM matrix and fabric using a fracture mechanics approach. These analytical laws were simplified using a trilinear curve in which a constant branch correlated to the friction is added. In the United States, “Acceptance Criteria AC434” includes the test methods to evaluate the mechanical properties of the FRCM through a direct tensile test which uses clevis grips. The material characterization per AC434 is in harmony with ACI 549.4R design guidelines. This study deals with the analysis of FRCM materials using 2D Augmented-Finite Element Method (A-FEM) approach. Constitutive material behaviors were used to implement on A-FE model, which can predict the failure modes of the composite material. The damage of the mortar was described by a trilinear curve, and the number and position of the cracks were fixed preliminarily. The fabric was modelled as a continuum layer attached to the mortar with no-thickness cohesive elements. The cohesive law between fabric and mortar was taken from the literature. The tensile test on the FRCM coupon with one layer of fabric was numerically modeled and compared to the experimental stress-strain curves. Results show that the numerical curves matched the experimental ones and capture the three branches of the FRCM constitutive law as well as the failure mode. This modelling tool will allow researchers to predict the constitutive law of an FRCM mater

EFFECTS OF THE INITIAL DEFLECTION SHAPE ON THE MOMENT AMPLIFICATION FACTOR OF BEAM-COLUMNS

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Haruna Utsunomiya ◽  
Masayuki Haraguchi ◽  
Masae Kido ◽  
Keigo Tsuda
Keyword(s):  
Amplification Factor ◽  
Slenderness Ratio ◽  
Compressive Force ◽  
Bending Moment ◽  
Load Ratio ◽  
Longitudinal Direction ◽  
Initial Deflection ◽  
Axial Compressive Force ◽  
Beam Columns ◽  
The Moment

In the design of slender steel beam-columns, the moment amplification factor is used to estimate the maximum moment along with the longitudinal direction. While formulas for evaluating the factor have been presented on the basis of elastic or elastic-plastic analysis, the initial deflection of the column is not considered. The effect that the initial deflection on the strength and behavior of the column has been shown only when the initial deflection shape is half sine wave. This paper discusses the effect of the initial deflection shape on the value of the moment amplification factor by performing the analytical work. The analytical model is the hinged-end beam-column subjected to constant axial compressive force and end moments. First of all, the equilibrium differential equation which governs the problem is solved and the formula for calculating the bending moment is presented. In the parametric study, magnitude of initial deflection, initial deflection shape, axial load ratio, slenderness ratio and end moment ratio are selected as the parameters. In this paper, we discuss the effects of the amount of the initial deflection and the initial deflection shape.

Strength and Deformation Capacity of Corroded Pipes: The Joint Industry Project

2013 ◽  
Author(s):  
Erik Levold ◽  
Andrea Restelli ◽  
Lorenzo Marchionni ◽  
Caterina Molinari ◽  
Luigino Vitali
Keyword(s):  
Failure Modes ◽  
State Of The Art ◽  
Local Buckling ◽  
Bending Moment ◽  
External Pressure ◽  
Fe Model ◽  
Deformation Capacity ◽  
Offshore Pipelines ◽  
Strength And Deformation ◽  
Bending Loading

Considering the future development for offshore pipelines, moving towards difficult operating condition and deep/ultra-deep water applications, there is the need to understand the failure mechanisms and better quantify the strength and deformation capacity of corroded pipelines considering the relevant failure modes (collapse, local buckling under internal and external pressure, fracture / plastic collapse etc.). A Joint Industry Project sponsored by ENI E&P and Statoil has been launched with the objective to quantify and assess the strength and deformation capacity of corroded pipes in presence of internal overpressure and axial/bending loading. In this paper: • The State-of-the-Art on strength and deformation capacity of corroded pipes is presented; • The full-scale laboratory tests on corroded pipes under bending moment dominated load conditions, performed at C-FER facilities, are shown together with the calibrated ABAQUS FE Model; • The results of the ABAQUS FEM parametric study are presented.

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