Measurement of Mechanical Properties on Line Pipe: Comparison of Different Methodologies

2014 ◽  
Author(s):  
Steven Cooreman ◽  
Dennis Van Hoecke ◽  
Martin Liebeherr ◽  
Philippe Thibaux ◽  
Mary Yamaguti Enderlin
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Tensile Tests ◽  
Ring Expansion ◽  
Isotropic Hardening ◽  
Forming Process ◽  
Element Analysis ◽  
Line Pipe ◽  
Expansion Test ◽  
Round Bar

Line pipe manufacturers always have to verify the mechanical properties on pipe to make sure that the pipe meets the requirements specified by the standard and/or customer. This involves measurement of mechanical properties along the hoop direction. The most accurate way to do so is by performing a ring expansion test, which, however, requires dedicated tools. The two other methodologies consist of standard tensile tests on either non-flattened round bar samples or so called ‘flattened tensile samples’. Round bar samples have the disadvantage that only part of the pipe’s wall thickness is considered. Furthermore they can only be used in case of larger OD/t ratios. Tests on flattened samples, on the other hand, require a flattening operation, which induces additional plastic deformation. However, this flattening operation is not standardized. Moreover, it was observed that the mechanical properties — especially the yield strength — resulting from tensile tests on flattened samples largely depend on test parameters such as residual deflection, extensometer position, flattening procedure, etc. Most manufacturers prefer to test flattened samples, because sample preparation is straightforward and cheap. Moreover it only requires a standard tensile bench. An extensive FEA (Finite Element Analysis) study was launched to investigate the influence of those parameters on the measured yield strength. The applied FEA methodology consists of three steps. First the complete pipe forming process is modeled (in a simplified way). Next a pipe sample is flattened. Finally a tensile sample is cut from the flattened pipe sample and loaded in tension. The mechanical material behaviour is described by a combined kinematic-isotropic hardening model, which allows taking into account the Bauschinger effect. The results are also compared to simulations of ring expansion tests and tests on round bar samples. Next a dedicated experimental test campaign was performed to verify the results of FEA. Results of ring expansion tests are compared to results obtained on round bar samples and flattened tensile samples. The results of this study have shown that the applied methodology significantly affects the measured yield strength. Moreover tests on insufficiently flattened samples could considerably underestimate the actual yield strength on pipe. Finally some guidelines are provided to improve the reproducibility of the measured yield strength when using flattened samples.

The Effect of Sample Flattening on Yield Strength Measurement in Line Pipe

2010 ◽  
Author(s):  
Dave G. Crone ◽  
Laurie E. Collins ◽  
Yankui Bian ◽  
Paul Weber
Keyword(s):  
Tensile Strength ◽  
Yield Strength ◽  
Tensile Testing ◽  
Measurement Techniques ◽  
Base Material ◽  
Ring Expansion ◽  
Tensile Specimen ◽  
Forming Process ◽  
Line Pipe ◽  
Ongoing Research

Tensile testing is a key part of the qualification process of Line Pipe. When qualifying pipe products various items are considered when tensile testing; Yield Strength (YS), Ultimate Tensile Strength (UTS), Percent Elongation (%EL), and the Yield Strength to Tensile Strength Ratio (Y/T) are all important. Of these, the YS is the most critical and yet the most sensitive to both preparation and measurement techniques. During the pipe forming process, the base material is plastically formed into a curved shape, and then welded into the final product. The Transverse to Pipe Axis (TPA) tensile specimen removed for testing is curved and must be flattened prior to testing. The flattening process is varied in many facilities and the standards to which testing is conducted are not specific enough to ensure uniformity of procedures. ASTM acknowledges flattening processes and the degree of flatness “may affect test results”, though no guidance is given. This paper will provide an overview of ongoing research efforts, concerning the measurement of the Yield Strength of TPA tensile specimens and its relationship to curvature and flattening methods, prior to testing. By comparing flattened strap tests, to round bar and ring expansion tests, it is shown that the flattened strap test provides a conservative estimate of the actual YS of the pipe.

Ring Expansion Testing Innovations: Hydraulic Clamping and Strain Measurement Methods

2020 ◽  
Author(s):  
William Walsh ◽  
Sandeep Abotula ◽  
Bharath Konda
Keyword(s):  
Tensile Testing ◽  
Point Contact ◽  
Ring Expansion ◽  
Hydraulic Pressure ◽  
Stress Strain ◽  
Line Pipe ◽  
Pipe Surface ◽  
Expansion Test ◽  
Round Bar ◽  
Dial Indicator

Abstract Ring expansion testing is one of the three accepted methods in API 5L for the measurement of yield strength for line pipe. The other two are flattened-strap tensile testing and round-bar tensile testing. A novel-concept ring expansion test machine has recently been commissioned which uses hydraulic pressure to clamp the top and bottom pressure-reacting plates rather than a traditional bolting arrangement. The benefit of hydraulic clamping is vastly reduced set-up times. This paper describes the design approach and the pitfalls that were overcome in commissioning the ring expansion test unit. Expansion measurements are taken using two different methods: a chain extensometer and an LVDT with a band wrapping the circumference of the pipe. Both approaches are used simultaneously to generate and compare two stress-strain curves for one pressure test. In addition, a 3-Point contact approach is developed to determine the hoop strain during pipe expansion. The 3-point contact approach is an attempt to infer the full hoop expansion behavior by measuring the radius change over a segment of the circumference. The device has two rollers which contact the pipe surface while a dial indicator midway between measures the radius change. As the pipe expands, the rollers maintain contact with the pipe surface while the dial indicator records the change in radius. Tests are performed on HFI, SAWL, and SAWH pipes ranging in outer diameter from 20-inch (508 mm) to 48-inch (1219 mm) and wall thicknesses from 0.375-inch (9.5 mm) to 0.969-inch (24.4 mm). The differences in the stress-strain behavior of these pipe forms are described and related to the residual-stress profiles generated by their respective manufacturing operations. The comparison to flattened-strap and round-bar tensile results are presented in a companion paper. The results of the 3-Point contact approach show that the radius change during early stages of expansion are not uniform around the pipe circumference and different patterns are observed in the HFI, SAWL, and SAWH pipe forms.

Comparison Between Yield Strength Results Obtained From Methods Using Both Flattened and Non-Flattened Specimens

2020 ◽  
Author(s):  
Pratham Nayyar ◽  
Dimitris Dimopoulos ◽  
William Walsh
Keyword(s):  
Yield Strength ◽  
Large Diameter ◽  
Longitudinal Direction ◽  
Ring Expansion ◽  
Test Methods ◽  
Production Test ◽  
Pipe Axis ◽  
Line Pipe ◽  
Expansion Test ◽  
Weld Properties

Abstract Tensile properties of API 5L large diameter pipes are typically determined with the use of full thickness flattened strap samples extracted in the transverse direction with respect to the longitudinal pipe axis (TPA) [1, 2, 3, 4]. It has been well established that the process of sample flattening has a significant influence on determination of the yield strength of the pipe [5, 6]. The flattening process is sensitive to a number of variables such as method of flattening, equipment used, number/sequence of strokes, and operators conducting the flattening. As a result, issues with repeatability are frequently encountered and despite several efforts, the industry lacks any type of official standard for universal use. Historically, the industry has been focused on ensuring that the actual strength of pipes was safely higher than the specified minimum. Recently, there has been interest to also establish an upper limit on pipe strength particularly in the longitudinal direction with respect to the pipe axis (LPA) in order to avoid under matching between pipe and girth weld properties. These new requirements create the need for enhanced process control to minimize the variation due to flattening. Samples obtained from longitudinally welded (SAWL) and helically welded (SAWH) seam Grade X70M line pipe of various nominal wall thickness to diameter (t/D) ratios were flattened using different procedures, measured for curvature, and tensile tested, all in controlled laboratory environments with minimized repeatability variation. Special attention was given to the definition and measurement of different types of curvatures observed through the range of different t/D ratios and effort was made to assess criteria for curvature measurement prior to testing. Additionally, non-flattened specimens were tensile tested using round bar and full ring expansion test methods, and a comparison between the results obtained from both flattened and non-flattened specimen methods was made. The sample transverse yield strength results confirmed the expected variation between samples flattened by different methods. In addition, a much greater variation was observed when comparing the yield strength results between flattened and non-flattened samples. Considerations of extending the use of non-flattened specimens as a production test and benefits or limitations associated with such practice are discussed.

Correlation among Microstructure, Texture, and Properties along the Thickness Direction in As-Hot-Rolled and As-Solution-Quenched Al7055 Thick Plates

2021 ◽  
Vol 1026 ◽  
pp. 65-73
Author(s):  
Kai Zhu ◽  
Hong Wei Yan
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Tensile Tests ◽  
Rolled Plate ◽  
Uniaxial Tensile ◽  
Thickness Direction ◽  
Electron Backscattered Diffraction ◽  
Thick Plates ◽  
Aluminum Plates ◽  
Hot Rolled

Both microstructure inhomogeneity and mechanical property diversity along the thickness direction in rolled thick aluminum plates have been considered to have a remarkable impact on the performance and properties of the products made from the plates. In this study, scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) characterizations of microstructure and texture types along the thickness directions of Al7055 thick plate specimens prepared using two conditions, hot-rolling and solution-quenching, were performed. To examine the mechanical properties, uniaxial tensile tests were also carried out on specimens machined from both types of thick plates, using a layered strategy along the thickness direction. The results indicate that both the microstructure and mechanical properties are inhomogeneous under the two conditions. Furthermore, it is evident that there is a hereditary relationship between the mechanical properties of the two plates—areas with higher yield strength in the as-hot-rolled plate correspond to areas with the higher yield strength in the as-solution-quenched plate

Finite Element Analysis of Incremental Sheet Forming for Metal Sheet

2018 ◽  
Vol 783 ◽  
pp. 148-153
Author(s):  
Muhammad Sajjad ◽  
Jithin Ambarayil Joy ◽  
Dong Won Jung
Keyword(s):  
Mechanical Properties ◽  
Sheet Metal ◽  
Tool Path ◽  
Incremental Forming ◽  
Single Point ◽  
Machining Process ◽  
Machining Parameters ◽  
Forming Process ◽  
Element Analysis ◽  
Tool Diameter

Incremental sheet metal forming, is a non-conventional machining process which offers higher formability, flexibility and low cost of production than the traditional conventional forming process. Punch or tool used in this forming process consecutively forces the sheet to deform locally and ultimately gives the target profile. Various machining parameters, such as type of tool, tool path, tool size, feed rate and mechanical properties of sheet metal, like strength co-efficient, strain hardening index and ultimate tensile strength, effects the forming process and the formability of final product. In this research paper, Single Point Incremental Forming was simulated using Dassault system’s Abaqus 6.12-1 and results are obtained. Results of sheet profile and there change in thickness is investigated. For this paper, we simulated the process in abaqus. The tool diameter and rotational speed is find out for the production of parts through incremental forming. The simulation is done for two type of material with different mechanical properties. Various research papers were used to understand the process of incremental forming and its simulation.

scholarly journals New Numerical Model of Composite Fabric Behaviour: Simulation of Manufacturing of thin Composite Part

2000 ◽  
Vol 9 (3) ◽  
pp. 096369350000900 ◽  
Author(s):  
J.L. Billoet ◽  
A. Cherouat
Keyword(s):  
Mechanical Properties ◽  
Tensile Tests ◽  
Woven Fabrics ◽  
Woven Fabric ◽  
Forming Process ◽  
Composite Part ◽  
Initial Shape ◽  
Shaping Process ◽  
Mechanical Approach ◽  
Behaviour Simulation

The present study concerns the modelling of the behaviour of pre-impregnated woven fabric during the forming process. The mechanical approach is based on a mesostructural model. It allows us to take into account the mechanical properties of fibres and resin and the various dominating mode of deformation of woven fabrics during the forming process. Shear and tensile tests of composite fabric specimens are proposed and compared with the experimental results in order to demonstrate the efficiency of our approach. Different numerical simulations and experiments of shaping process have been carried out in order to validate the proposed computational formulation. The various forming parameters examined have included the initial shape of fabric, fibre orientations and viscosity of resin.

Effect of Artificial Aging on Microstructures and Mechanical Properties of Extruded Mg Alloy ZK60

2014 ◽  
Vol 697 ◽  
pp. 72-75
Author(s):  
De Liang Yin ◽  
Jian Qiao ◽  
Hong Liang Cui
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Aging Time ◽  
Artificial Aging ◽  
Aging Treatment ◽  
Tensile Tests ◽  
Tensile Yield Strength ◽  
Uniaxial Tensile ◽  
Fracture Elongation ◽  
Strength And Ductility

An extruded ZK60 magnesium alloy was subjected to artificial aging at 180 oC for an investigation of the effect of aging time on its precipitation behavior and mechanical properties. Uniaxial tensile tests were conducted to obtain the mechanical properties. Optical microscopy and transmission electron microscopy (TEM) were employed to observe microstructure change before and after aging treatment. It is shown that, both tensile yield strength and ultimate tensile strength increases with aging time. The fracture elongation after aging for 20 h reaches up to 21.0%, and the yield strength increases to 269.5 MPa, 19.4% higher than that of extruded specimens (un-aged), showing a good match of strength and ductility. Three newly-formed precipitates were observed after aging for over 20 h, among which particulate and dispersive precipitates should be responsible for the good combination of strength and ductility.

The Precise Determination of the Johnson–Cook Material and Damage Model Parameters and Mechanical Properties of an Aluminum 7068-T651 Alloy

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
B. Bal ◽  
K. K. Karaveli ◽  
B. Cetin ◽  
B. Gumus
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Physical Simulation ◽  
Damage Model ◽  
Rolling Direction ◽  
Stress Triaxiality ◽  
Material Model ◽  
Tensile Tests ◽  
Model Parameters ◽  
Element Analysis

Al 7068-T651 alloy is one of the recently developed materials used mostly in the defense industry due to its high strength, toughness, and low weight compared to steels. The aim of this study is to identify the Johnson–Cook (J–C) material model parameters, the accurate Johnson–Cook (J–C) damage parameters, D1, D2, and D3 of the Al 7068-T651 alloy for finite element analysis-based simulation techniques, together with other damage parameters, D4 and D5. In order to determine D1, D2, and D3, tensile tests were conducted on notched and smooth specimens at medium strain rate, 100 s−1, and tests were repeated seven times to ensure the consistency of the results both in the rolling direction and perpendicular to the rolling direction. To determine D4 and D5 further, tensile tests were conducted on specimens at high strain rate (102 s−1) and temperature (300 °C) by means of the Gleeble thermal–mechanical physical simulation system. The final areas of fractured specimens were calculated through optical microscopy. The effects of stress triaxiality factor, rolling direction, strain rate, and temperature on the mechanical properties of the Al 7068-T651 alloy were also investigated. Damage parameters were calculated via the Levenberg–Marquardt optimization method. From all the aforementioned experimental work, J–C material model parameters were determined. In this article, J–C damage model constants, based on maximum and minimum equivalent strain values, were also reported which can be utilized for the simulation of different applications.

scholarly journals Performance of Thermo-Mechanically Processed AA7075 Alloy at Elevated Temperatures—From Microstructure to Mechanical Properties

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 884 ◽  
Author(s):  
Seyed Vahid Sajadifar ◽  
Emad Scharifi ◽  
Ursula Weidig ◽  
Kurt Steinhoff ◽  
Thomas Niendorf
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Forming Process ◽  
Softening Mechanism ◽  
Rate Dependent ◽  
Heat Treated ◽  
Different Temperatures ◽  
Die Forming

This study focuses on the high temperature characteristics of thermo-mechanically processed AA7075 alloy. An integrated die forming process that combines solution heat treatment and hot forming at different temperatures was employed to process the AA7075 alloy. Low die temperature resulted in the fabrication of parts with higher strength, similar to that of T6 condition, while forming this alloy in the hot die led to the fabrication of more ductile parts. Isothermal uniaxial tensile tests in the temperature range of 200–400 °C and at strain rates ranging from 0.001–0.1 s−1 were performed on the as-received material, and on both the solution heat-treated and the thermo-mechanically processed parts to explore the impacts of deformation parameters on the mechanical behavior at elevated temperatures. Flow stress levels of AA7075 alloy in all processing states were shown to be strongly temperature- and strain-rate dependent. Results imply that thermo-mechanical parameters are very influential on the mechanical properties of the AA7075 alloy formed at elevated temperatures. Microstructural studies were conducted by utilizing optical microscopy and a scanning electron microscope to reveal the dominant softening mechanism and the level of grain growth at elevated temperatures.

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