Comparison of Parent and Butt-Fusion Material Properties of Unimodal High-Density Polyethylene

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
P. Krishnaswamy ◽  
D.-J. Shim ◽  
S. Kalyanam
Keyword(s):  
Material Property ◽  
Material Properties ◽  
High Density Polyethylene ◽  
Fracture Resistance ◽  
Structural Integrity ◽  
Slow Crack Growth ◽  
Base Material ◽  
High Density ◽  
Nuclear Industry ◽  
Service Water

The U.S. nuclear power industry is seeking U.S. Nuclear Regulatory Commission (USNRC) approval to use high-density polyethylene (HDPE) in safety-related applications. The USNRC had granted approval for the use of HDPE for safety-related service water applications, with limitations, to Catawba (Duke Energy Corp., Catawba, SC) and Callaway (Union Electric Co., Callaway, MO) based on separate relief requests submitted by the licensees. The nuclear industry continues to show increasing interest in utilizing HDPE in safety-related piping systems. In order to evaluate and maintain the structural integrity of HDPE pipes, the material properties and the fracture resistance behavior must be fully characterized. Although there has been extensive work on material property development of HDPE, most of the investigations have been focused on the parent (base) material. Hence, the material property and fracture resistance behavior of the butt-fusion region have not been comprehensively investigated. In this paper, tensile, dynamic mechanical analysis (DMA), and slow crack growth (SCG) tests were performed for unimodal PE 4710 HDPE material. Specimens were machined from both parent piping material and butt-fusion regions. The test results indicate that the tensile and DMA properties show no significant differences between parent and butt-fusion joint materials. However, in terms of SCG resistance, the time to failure for butt-fusion joint material was an order of magnitude lower than that of the parent material.

Comparison of Parent and Butt Fusion Material Properties of High Density Polyethylene

2009 ◽  
Author(s):  
D.-J. Shim ◽  
P. Krishnaswamy ◽  
E. Focht
Keyword(s):  
Material Property ◽  
Material Properties ◽  
High Density Polyethylene ◽  
Fracture Resistance ◽  
Slow Crack Growth ◽  
Base Material ◽  
High Density ◽  
Nuclear Industry ◽  
Service Water ◽  
Fusion Material

The US nuclear power industry is seeking U. S. Nuclear Regulatory Commission (USNRC) approval to use high density polyethylene (HDPE) in safety-related applications. The USNRC has granted approval for the use of HDPE for safety-related service water applications, with limitations, to Catawba (Duke Energy Corp.) and Callaway (Union Electric Co.) based on separate relief requests submitted by the licensees. The nuclear industry continues to show increasing interest in utilizing HDPE in safety-related piping systems. In order to evaluate and maintain the structural integrity of HDPE pipes, the material properties and the fracture resistance behavior must be fully characterized. Although there has been extensive work on material property development of HDPE, most of the investigations have been focused on the parent (base) material. Hence, the material property and fracture resistance behavior of the butt fusion region have not been comprehensively investigated. In this paper, tensile, dynamic mechanical analysis (DMA), and slow crack growth (SCG) tests have been performed for PE 4710 HDPE material. Specimens were machined from both parent piping material and butt fusion regions. The test results indicate that the tensile and DMA properties show no significant differences between parent and butt fusion materials. However, in terms of SCG resistance, the time to failure for butt fusion material was an order of magnitude lower than that of the parent material.

Modern Bimodal High Density Polyethylene for the Nuclear Power Plant Piping System

2009 ◽  
Author(s):  
Adel N. Haddad
Keyword(s):  
High Density Polyethylene ◽  
Nuclear Power ◽  
Large Diameter ◽  
Water System ◽  
High Density ◽  
Nuclear Industry ◽  
Piping System ◽  
Service Water ◽  
Hdpe Pipe ◽  
Related Service

Originally introduced in the 1990s, bimodal HDPE, pipe resins are still finding new niches today, including even nuclear power plants. HDPE pipe grades are used to make strong, corrosion resistant and durable pipes. High density polyethylene, PE 4710, is the material of choice of the nuclear industry for the Safety Related Service Water System. This grade of polymer is characterized by a Hydrostatic Design Basis (HDB) of 1600 psi at 73 °F and 1000 psi at 140 °F. Additionally bimodal high density PE 4710 grades display >2000 hours slow crack growth resistance, or PENT. HD PE 4710 grades are easy to extrude into large diameter pipes; fabricate into fitting and mitered elbows and install in industrial settings. The scope of this paper is to describe the bimodal technology which produces HDPE pipe grade polymer; the USA practices of post reactor melt blending of natural resin compound with black masterbatch; and the attributes of such compound and its conformance to the nuclear industry’s Safety Related Service Water System.

Resistance Welding Process Development and Optimization for Recycled High-Density Polyethylene (HDPE)

2015 ◽  
Author(s):  
Peter F. Baumann ◽  
Lucas Sendrowski
Keyword(s):  
Tensile Strength ◽  
Response Surface ◽  
High Density Polyethylene ◽  
Heating Temperature ◽  
Base Material ◽  
Heating Time ◽  
High Density ◽  
Hot Plate ◽  
Initial Testing ◽  
Hot Plate Welding

Large recycled high-density polyethylene (HDPE) structural members, difficult to manufacture by extrusion processes, have been created by the hot plate welding of simple plastic lumber sections. Hot plate welding generates better joint strength than any other welding method currently employed in plastic manufacturing. However, to achieve the desired temperature of the thick plate to melt the polymer uniformly, the process needs a high amount of heat energy requiring furnace (or resistance) heating of a considerable mass. A new method which could combine the heating element and a thin plate into one source could be more efficient in terms of heat loss and thus energy used. The premise of this investigation is to replace the hot plate with a very thin piece of high resistance nickel-chromium alloy ribbon to localize the application of heat within a plastic weld joint in order to reduce energy loss and its associated costs. This resistance ribbon method uses electrical current to reach an adequate temperature to allow for the welding of the HDPE plastic. The ribbon is only slightly larger than the welding surface and very thin to reduce the loss of excess heat through unused surface area and thick sides. The purpose of this project was to weld recycled high-density polyethylene (HDPE) using resistance welding and to match the tensile strength results considered acceptable in industry for hot plate welding, that is, equal to or greater than 80% of the base material strength. Information obtained through literature review and previous investigations in our laboratories established welding (heating) temperature and time as testing factors. Designed experimentation considered these factors in optimizing the process to maximize the weld tensile strength. A wide-ranging full-factorial experimental design using many levels was created for the initial testing plan. Tensile strengths obtained after welding under the various condition combinations of weld temperature and time revealed a region of higher strength values in the response surface. After the wide-range initial testing, the two control parameters, heating temperature and heating time, were ultimately set up in a focused Face Centered Cubic (FCC) Response Surface Method (RSM) testing design and the tensile strength response was then analyzed using statistical software. The results obtained indicated a strong correlation between heating time and heating temperature with strength. All welded samples in the final testing set exhibited tensile strength of over 90% base material, meeting the goal requirements. A full quadratic equation relationship for tensile strength as a function of welding time and temperature was developed and the maximum tensile strength was achieved when using 280°C for 60 seconds.

Application of Crack Layer in Modeling of Slow Crack Growth in High-Density Polyethylene

2013 ◽  
Author(s):  
Haiying Zhang ◽  
Zhenwen Zhou ◽  
Alexander Chudnovsky
Keyword(s):  
Crack Growth ◽  
High Density Polyethylene ◽  
Slow Crack Growth ◽  
Growth Failure ◽  
High Density ◽  
Large Set ◽  
Layer Model ◽  
Crack Layer ◽  
Basic Parameters ◽  
Engineering Polymers

Crack layer model provides a comprehensive foundation for modeling of fracture growth, failure analysis, and lifetime prediction. During the past two decades, it has been widely applied for modeling various aspects of brittle fracture in general. This paper illustrates in details the procedure of implementation by an example of slow crack growth in a commercialized high-density polyethylene undergoing creep conditions. Firstly, we determine experimentally the basic parameters employed in constitutive equations of crack layer model such as draw ratio λ, the specific energy of transformation γtr, and drawing stress σdr, etc.. Secondly, we implement crack layer model numerically in lab-developed “Simulator”. The paper provides a paradigm for implementation of crack layer model in slow crack growth, and a blueprint for potential software development that can be used in ranking and the lifetime assessment of a large set of engineering polymers.

Determination of Updated Fatigue Properties of PE 4710 Cell Classification 445574C High Density Polyethylene

2014 ◽  
Author(s):  
Timothy M. Adams ◽  
Shawn Nickholds ◽  
Douglas Munson ◽  
Jeffery Andrasik
Keyword(s):  
Carbon Steel ◽  
Pressure Vessel ◽  
High Density Polyethylene ◽  
Nuclear Power ◽  
Fatigue Testing ◽  
High Density ◽  
Labor Costs ◽  
Cell Classification ◽  
Service Water ◽  
Hdpe Pipe

For corroded piping in low temperature systems, such as service water systems in nuclear power plants, replacement of carbon steel piping with high density polyethylene (HDPE) is a cost-effective solution. Polyethylene pipe can be installed at much lower labor costs that carbon steel pipe and HDPE pipe has a much greater resistance to corrosion. The ASME Boiler and Pressure Vessel Code, Section III, Division 1 currently permits the use of non-metallic piping in buried safety Class 3 piping systems. Additionally, HDPE pipe has been successfully used in non-safety-related systems in nuclear power facilities and is commonly used in other industries such as water mains and natural gas pipelines. This report presents the results of updated fatigue testing of PE 4710 cell classification 445574C pipe compliant with the specific Code requirements. This information was developed to support and provide a strong technical basis for material properties of HDPE pipe for use in ASME Boiler and Pressure Vessel Code, Section III New Construction and Section XI repair or replacement activities. The data may also be useful for applications of HDPE pipe in commercial electric power generation facilities and chemical, process and waste water plants via its possible use in the B31 series piping codes. The report provides fatigue data in the form of Code S-N curves for fusion butt joints in PE 4710 cell classification 445574C HDPE pipe.

Slow Crack Growth Resistance of Parent and Joint Materials From PE4710 Piping for Safety-Related Nuclear Power Plant Piping

2011 ◽  
Author(s):  
S. Kalyanam ◽  
D.-J. Shim ◽  
P. Krishnaswamy ◽  
Y. Hioe
Keyword(s):  
Crack Growth ◽  
Nuclear Power ◽  
Power Plants ◽  
Slow Crack Growth ◽  
Nuclear Industry ◽  
Pipe Material ◽  
Service Water ◽  
Hdpe Pipe ◽  
Pipe Materials ◽  
Hdpe Pipes

HDPE pipes are considered by the nuclear industry as a potential replacement option to currently employed metallic piping for service-water applications. The pipes operate under high temperatures and pressures. Hence HDPE pipes are being evaluated from perspective of design, operation, and service life requirements before routine installation in nuclear power plants. Various articles of the ASME Code Case N-755 consider the different aspects related to material performance, design, fabrication, and examination of HDPE materials. Amongst them, the material resistance (part of Article 2000) to the slow crack growth (SCG) from flaws/cracks present in HDPE pipe materials is an important concern. Experimental investigations have revealed that there is a marked difference (almost three orders less) in the time to failure when the notch/flaw is in the butt-fusion joint, as opposed to when the notch/flaw is located in the parent HDPE material. As part of ongoing studies, the material resistance to SCG was investigated earlier for unimodal materials. The current study investigated the SCG in parent and butt-fusion joint materials of bimodal HDPE (PE4710) pipe materials acquired from two different manufacturers. The various stages of the specimen deformation and failure during the creep test are characterized. Detailed photographs of the specimen side-surface were used to monitor the specimen damage accumulation and SCG. The SCG was tested using a large specimen (large creep frame) as well as using a smaller size specimen (PENT frame) and the results were compared. Further, the effect of polymer orientation or microstructure in the bimodal HDPE pipe on the SCG was studied using specimens with axial and circumferential notch orientations in the parent pipe material.

Distributed Design of Two-Scale Structures With Unit Cells

2019 ◽  
Author(s):  
Xingchen Liu
Keyword(s):  
Material Property ◽  
Material Properties ◽  
Volume Fraction ◽  
Base Material ◽  
Structure Design ◽  
Unit Cell ◽  
Steady Increase ◽  
Coarse Scale ◽  
Cell Structures ◽  
Wide Range

Abstract The use of unit cell structures in mechanical design has seen a steady increase due to their abilities to achieve a wide range of material properties and accommodate multi-functional requirements with a single base material. We propose a novel material property envelope (MPE) that encapsulates the attainable effective material properties of a given family of unit cell structures. The MPE interfaces the coarse and fine scales by constraining the combinations of the competing material properties (e.g., volume fraction, Young’s modulus, and Poisson’s ratio of isotropic materials) during the design of coarse scale material properties. In this paper, a sampling and reconstruction approach is proposed to represent the MPE of a given family of unit cell structures with the method of moving least squares. The proposed approach enables the analytical derivatives of the MPE, which allows the problem to be solved more accurately and efficiently during the design optimization of the coarse scale effective material property field. The effectiveness of the proposed approach is demonstrated through a two-scale structure design with octet trusses that have cubically symmetric effective stiffness tensors.

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