Evaluation of the Remaining Prestress Force and Center Negative Bending Moment in Crossties Removed From Track After 25 Years of Service

2019 ◽  
Author(s):  
James D. Scott ◽  
Robert J. Peterman ◽  
Aaron A. Robertson ◽  
B. Terry Beck ◽  
Kyle A. Riding
Keyword(s):  
Bending Moment ◽  
Test Method ◽  
Bending Test ◽  
Direct Tension ◽  
Longitudinal Splitting ◽  
Prestressing Steel ◽  
Prestressing Force ◽  
Four Point Bending ◽  
Negative Bending

Extensive research is currently being conducted by the team to understand the prestressing steel and concrete properties that cause high bonding stresses and lead to longitudinal splitting cracks, and how to mitigate this failure in future designs. One parameter of interest that affects the bonding stress is the amount of prestressing force in a crosstie. To help quantify the amount of prestress force necessary to provide a durable long-term crosstie, a study on existing crossties that have performed well in track for over 25 years was conducted to evaluate the center negative bending moment, and determine the remaining prestress force for each tie. The remaining prestress force in each tie was determined using a new proposed method in which ties are loaded in direct tension. The new test method was also conducted on new ties instrumented with vibrating wire strain gages to verify the method. The testing results reveal that a majority of the existing ties evaluated have a remaining prestress force in the range of 84–95 kips. These forces are significantly lower than the remaining prestress force after losses of newer tie designs. This can be seen when comparing the tension test results of the existing ties with the results of the new ties. Ties were loaded upside-down in four-point bending to determine their center negative cracking moments. The test setup and procedure used closely resembles the center negative bending moment test outlined in AREMA 30, with minor variations. For each different tie design in the study, the center negative design moment was calculated following the AREMA 30 procedure, and compared to the experimental cracking moments. Of the seven different existing tie designs investigated, four would meet the requirements of the current AREMA 30 center negative bending test.

Comparison of a standardized four-point bending test to an implant system test of an osteosynthetic system under static and dynamic load condition

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Christian Halbauer ◽  
Hendrik Schorler ◽  
Laura Liberto ◽  
Felix Capanni
Keyword(s):  
Load Condition ◽  
Bending Moment ◽  
Secondary Phase ◽  
Mechanical Analysis ◽  
Test Method ◽  
Bone Plate ◽  
Bending Test ◽  
Four Point Bending ◽  
Four Point Bending Test ◽  
Implant System

Abstract Current test standards of osteosynthetic implants examine the bone plate and screw separately leading to unrealistic load scenarios and unknown performance of the system as a whole, which prevents the identification of characteristic failures in clinical use. A standardized static and dynamic four-point bending test (ASTM F382) was performed on a bone plate. Based on that standard, an advanced implant system test (IST) was designed and performed to test a mechanical construct consisting of a bone plate, screws and an artificial bone substitute out of Polyoxymethylene (POM). The test object was an osteosynthetic system to treat fractured ulna bones. Both results of the conventional and advanced test method were analyzed and compared to one another. The static results show a similar yield point (YP) relative to the bending moment with just 9% difference. Dynamic results show a bi-phasic behavior of the displacement vs. cycle data for the IST. The secondary phase can be defined as a constantly increasing plastic deflection or ratcheting effect quantified by its slope in mm per one million cycles, leading to a 10 times higher slope for the IST than the conventional test. The IST has a high impact on the test results and the resultant interpretation of the mechanical behavior of the osteosynthetic system. A constantly increasing plastic deflection might lead to fatigue failures and to a loss of the mechanical durability. The development of new standardizations referring to the whole system within reasonable boundary conditions of individual biomechanical applications is crucial for high quality mechanical analysis.

scholarly journals Novel Bending Test Method for Polymer Railway Sleeper Materials

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1359
Author(s):  
Choman Salih ◽  
Allan Manalo ◽  
Wahid Ferdous ◽  
Rajab Abousnina ◽  
Peng Yu ◽  
...  
Keyword(s):  
Prestressed Concrete ◽  
Bending Moment ◽  
Test Method ◽  
Bending Test ◽  
Bending Moments ◽  
Flexural Behaviour ◽  
Wheel Load ◽  
Bending Modulus ◽  
Negative Bending ◽  
Railway Sleeper

Alternative sleeper technologies have been developed to address the significant need for the replacement of deteriorating timber railway sleepers. The review of the literature indicates that the railway sleepers might fail while in service, despite passing the evaluation tests of the current composite sleeper standards which indicated that these tests do not represent in situ sleeper on ballast. In this research, a new five-point bending test is developed to evaluate the flexural behaviour of timber replacement sleeper technologies supported by ballast. Due to the simplicity, acceptance level of evaluation accuracy and the lack of in-service behaviour of alternative sleepers, this new testing method is justified with the bending behaviour according to the Beam on Elastic Foundation theory. Three timber replacement sleeper technologies—plastic, synthetic composites and low-profile prestressed concrete sleepers in addition to timber sleepers—were tested under service loading condition to evaluate the suitability of the new test method. To address the differences in the bending of the sleepers due to their different modulus of elasticities, the most appropriate material for the middle support was also determined. Analytical equations of the bending moments with and without middle support settlement were also developed. The results showed that the five-point static bending test could induce the positive and negative bending moments experienced by railway sleepers under a train wheel load. It was also found that with the proposed testing spans, steel-EPDM rubber is the most suitable configuration for low bending modulus sleepers such as plastic, steel-neoprene for medium modulus polymer sleepers and steel-steel for very high modulus sleepers such as concrete. Finally, the proposed bending moment equations can precisely predict the flexural behaviour of alternative sleepers under the five-point bending test.

Long-Term Reliability Assessment of Bioceramics for Artificial Joints Using Microdamage Monitoring by AE

2006 ◽  
Vol 309-311 ◽  
pp. 1191-1194
Author(s):  
Shuichi Wakayama ◽  
Teppei Kawakami ◽  
Junji Ikeda
Keyword(s):  
Critical Stress ◽  
Reliability Assessment ◽  
Physiological Saline ◽  
Bending Test ◽  
Unstable Fracture ◽  
Artificial Joints ◽  
Bending Tests ◽  
Four Point Bending

Microfracture process during bending tests of alumina ceramics used for artificial joints was evaluated by acoustic emission (AE) technique. Four-point bending tests were carried out in air, refined water, physiological saline and simulated body fluid. AE behavior during bending test inhibited the rapid increasing point of AE events and energy prior to the final unstable fracture. It was understood that the bending stress at the increasing point corresponds to the critical stress for maincrack formation. The critical stress was affected by water in environments more strongly than fracture strength. Consequently, it was suggested that the characterization of maincrack formation is essential for the long-term reliability assessment of load-bearing bioceramics.

scholarly journals Long-term Laminated Glass Four Point Bending Test with PVB, EVA and SG Interlayers at Different Temperatures

2013 ◽  
Vol 57 ◽  
pp. 996-1004 ◽  
Author(s):  
Tomas Serafinavičius ◽  
Jean-Paul Lebet ◽  
Christian Louter ◽  
Tomas Lenkimas ◽  
Artiomas Kuranovas
Keyword(s):  
Bending Test ◽  
Laminated Glass ◽  
Four Point Bending ◽  
Different Temperatures ◽  
Four Point Bending Test

Study on the Creep Properties of Resin Concrete

2014 ◽  
Vol 472 ◽  
pp. 649-653
Author(s):  
Hui Cun Shen ◽  
Kui Tian ◽  
Yan Hua Hu
Keyword(s):  
Dynamic Stiffness ◽  
Structure Design ◽  
Test Method ◽  
Bending Test ◽  
Creep Properties ◽  
Four Point Bending ◽  
Long Term Effect ◽  
Urgent Task ◽  
Machined Parts ◽  
New Material

Resin concrete is a new material which can be made into machine bed instead of the traditional pieces of gray cast iron as the machine base, it can improve the dynamic stiffness of machine tools and the quality of machined parts, and extend the campaign life, reduce noise and improve efficiency. However, due to the long-term effect of load of the resin concrete, the elastic deformation occurs in its component, and the strain will increase over time. Thus it can affect the resin concretes service life, and the calculation of creep has become an urgent task in structure design and use, which should be taken seriously. In this paper, the bending creep properties of resin concrete beam were studied and analyzed by using four-point bending test method. The creep curve under different load levels were obtained, and the viscoelastic properties were analyzed.

Investigation on Mechanical Properties of Fiberglass Reinforced Flexible Pipes Under Bending

2019 ◽  
Author(s):  
Yifan Gao ◽  
Shan Jin ◽  
Peng Cheng ◽  
Peihua Han ◽  
Yong Bai
Keyword(s):  
Mechanical Behavior ◽  
Virtual Work ◽  
Experimental Studies ◽  
Bending Moment ◽  
Element Model ◽  
Bending Test ◽  
Flexible Pipe ◽  
Four Point Bending ◽  
Flexible Pipes ◽  
Bending Behavior

Abstract Fiberglass reinforced flexible pipe (FRFP) is a kind of composite thermoplastic pipe, which has many advantages compared to boned flexible pipes. This paper describes an analysis of the mechanical behavior of FRFP under bending. The bending behavior of FRFP was investigated by experimental, analytical and numerical methods. Firstly, this paper presents experimental studies of three 10-layer FRFP in a typical four-point bending test. Curvature-bending moment relations were recorded during the test. Then, based on the nonlinear ring theory and the principle of virtual work, a simplified method was proposed to study the mechanical behavior of FRFP. In addition, a finite element model (FEM) including reinforced layers and high density polyethylene (HDPE) layers was established to simulate the HDPE layers and reinforced layers, respectively. The result of Curvature-bending moment relations obtained from three methods agree well with each other, which proves that the simplified analytical model and FEM are accurate and reliable. The conclusions of this paper could be useful to manufacturing engineers.

scholarly journals Investigation of Interlaminar Defects and their Influence on Interlaminar Strength

1996 ◽  
Vol 5 (4) ◽  
pp. 096369359600500
Author(s):  
J Ziao ◽  
J Tao
Keyword(s):  
Tensile Strength ◽  
Large Scale ◽  
Peel Strength ◽  
Test Method ◽  
Bending Test ◽  
Four Point Bending ◽  
Transverse Tensile ◽  
Interlaminar Shear ◽  
Transverse Tensile Strength ◽  
Set Up

In this paper, we directed our attention to the interlaminar defects and their influence on the interlaminar strengths. With the aid of a S-570 scanning electron microscope, the morphology and distribution of interlaminar defects were inspected and documented. According to their shape, size and cause of formation, the defects were classified into five types: flakiness void, irregular shaped debond, local imperfectly cured resin, debond in two multi-directional plies, and inhomogeneous fibers and the large scale debond by these fibers. The cause of defects formation was discussed by analyzing the manufacturing process of composites. The influence of defects on the interlaminar strength and its mechanism was analyzed experimentally and theoretically. The results indicate that these defects, with different effects, decrease the interlaminar strength because they form interlaminar cracks, and the interlaminar shear strength is less affected than interlaminar tensile strength, which is measured according to GB4944 test method. To comprehend defects distribution effect, a four-point-bending test method was introduced to measure the interlaminar peel strength, and a discussion was made on the correlation between the interlaminar tensile strength, interlaminar peel strength and in-plane transverse tensile strength. Finally the concept of interlaminar defect coefficient, which can be used to characterize the defects, was set up and the formula to calculate it was proposed.

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