Development of a 100-km/h Reusable High-Molecular Weight/High-Density Polyethylene Truck-Mounted Attenuator

1998 ◽  
Vol 1647 (1) ◽  
pp. 75-88
Author(s):  
John F. Carney ◽  
Subhasish Chatterjee ◽  
Richard B. Albin
Keyword(s):  
Molecular Weight ◽  
Kinetic Energy ◽  
High Molecular Weight ◽  
High Density Polyethylene ◽  
Full Scale ◽  
High Density ◽  
Crash Test ◽  
Crash Testing ◽  
Impact Attenuation ◽  
Risk Parameters

A reusable truck-mounted attenuator has been developed that dissipates kinetic energy through the lateral deformation of a nested cluster of high-molecular weight/high-density polyethylene cylinders. This 100-km/h impact attenuation device, called the Vanderbilt truck-mounted attenuator (VTMA), satisfies the crash testing requirements of NCHRP Report 350. It has been approved by the Federal Highway Administration for use on the national highway system under these NCHRP Report 350 guidelines. Most impact attenuation devices currently employed require the replacement of damaged structural components and spent-energy-dissipating elements following an impact event. Until these repairs and refurbishments are carried out, these safety devices are largely ineffective because they are unable to dissipate kinetic energy in a subsequent impact in an acceptable manner such that relevant occupant risk parameters are within prescribed limits. The VTMA is a reusable and self-restorative truck-mounted attenuator. It can dissipate large amounts of kinetic energy, undergo significant deformations and strains without fracturing, and then, essentially, regain its original shape and energy-dissipation potential on removal of the load. The VTMA design was optimized through finite-element modeling using DYNA3D. This inexpensive modeling tool resulted in a reduction in the number of expensive full-scale crash tests required to develop the system. Computer modeling can optimize the probability for success of a given full-scale crash test, removing the trial-and-error approach to appurtenance design.

Development of Reusable High-Molecular-Weight–High-Density Polyethylene Crash Cushions

1996 ◽  
Vol 1528 (1) ◽  
pp. 11-27 ◽  
Author(s):  
J. F. Carney ◽  
M. I. Faramawi ◽  
S. Chatterjee
Keyword(s):  
Molecular Weight ◽  
Finite Element ◽  
Finite Element Modeling ◽  
High Molecular Weight ◽  
High Density Polyethylene ◽  
Full Scale ◽  
High Density ◽  
Scale Model ◽  
Model Experiments ◽  
Element Modeling

The development of a family of low-maintenance, reusable crash cushions that employ energy dissipaters made of high-molecular-weight–high-density polyethylene is described. This “smart” energy dissipating thermoplastic is self-restorative and reusable and possesses excellent hysteresis characteristics. The design process involved quasi-static and impact scale model experiments, finite-element modeling, and a full-scale crash testing program conducted according to the guidelines of NCHRP Report 350. A treatment of all of these design components is presented. It is demonstrated that scale model experiments and finite-element modeling are cost-effective tools whose employment can minimize the number of costly full-scale crash tests required to qualify devices as acceptable for use on the National Highway System.

scholarly journals Applicability of the Cox-Merz Rule to High-Density Polyethylene Materials with Various Molecular Masses

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1218
Author(s):  
Raffael Rathner ◽  
Wolfgang Roland ◽  
Hanny Albrecht ◽  
Franz Ruemer ◽  
Jürgen Miethlinger
Keyword(s):  
Molecular Weight ◽  
Pressure Drop ◽  
High Molecular Weight ◽  
High Density Polyethylene ◽  
Parallel Plate ◽  
Empirical Relationship ◽  
Polymer Processing ◽  
High Density ◽  
Viscosity Data ◽  
Molecular Masses

The Cox-Merz rule is an empirical relationship that is commonly used in science and industry to determine shear viscosity on the basis of an oscillatory rheometry test. However, it does not apply to all polymer melts. Rheological data are of major importance in the design and dimensioning of polymer-processing equipment. In this work, we investigated whether the Cox-Merz rule is suitable for determining the shear-rate-dependent viscosity of several commercially available high-density polyethylene (HDPE) pipe grades with various molecular masses. We compared the results of parallel-plate oscillatory shear rheometry using the Cox-Merz empirical relation with those of high-pressure capillary and extrusion rheometry. To assess the validity of these techniques, we used the shear viscosities obtained by these methods to numerically simulate the pressure drop of a pipe head and compared the results to experimental measurements. We found that, for the HDPE grades tested, the viscosity data based on capillary pressure flow of the high molecular weight HDPE describes the pressure drop inside the pipe head significantly better than do data based on parallel-plate rheometry applying the Cox-Merz rule. For the lower molecular weight HDPE, both measurement techniques are in good accordance. Hence, we conclude that, while the Cox-Merz relationship is applicable to lower-molecular HDPE grades, it does not apply to certain HDPE grades with high molecular weight.

Influence of Processing Aids and Hydroxyapatite as Fillers on Flow Behaviour and Mechanical Properties of Ultra High Molecular Weight Polyethylene/High Density Polyethylene Composites

2011 ◽  
Vol 471-472 ◽  
pp. 827-832 ◽  
Author(s):  
Mazatusziha Ahmad ◽  
Mat Uzir Wahit ◽  
Mohammed Rafiq Abdul Kadir ◽  
Khairul Zaman Mohd Dahlan
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
High Density Polyethylene ◽  
Flexural Modulus ◽  
High Density ◽  
Compression Moulding ◽  
Biomedical Implant ◽  
Bone Properties ◽  
Ultra High Molecular Weight

In this study, blends of ultra high molecular weight polyethylene/high density polyethylene/polyethylene glycol (UHMWPE/HDPE/PEG) and the composites containing Hydroxyapatite (HA) as reinforcement filler were prepared via single screw extruder nanomixer followed by compression moulding. PEG (2phr) was used as processing aid and HA loadings were varied from 10 to 50 phr. HDPE and PEG were introduced to improve the extrudability of UHMWPE. Rheological behavior was studied via capillary rheometer while flexural and izod impact tests were conducted in order to investigate the mechanical properties of the blends and composites. Melt viscosity of the blends was found to decrease with increasing shear rate indicating a pseudoplastic behaviour. Incorporation of PEG shows a synergism effect on the reduction of blends viscosity. Blend of 40% UHMWPE/ 60% HDPE/ 2 phr PEG was chosen as the optimum blend composition with a balance properties in terms of the mechanical properties and processability. The incorporation of HA fillers from 10 to 50 phr into the blend resulted in the increase of flexural modulus and flexural strength with a slight decline of impact strength values. It can be concluded that the composites having adequate strength and modulus within the range of cancellous bone properties were succesfully developed to be used as biomedical implant devices.

scholarly journals High-density polyethylene crystals with double melting peaks induced by ultra-high-molecular-weight polyethylene fibre

2018 ◽  
Vol 5 (7) ◽  
pp. 180394 ◽  
Author(s):  
Weijun Miao ◽  
Hao Zhu ◽  
Tianchen Duan ◽  
Hongbing Chen ◽  
Feng Wu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
High Density Polyethylene ◽  
Fibre Composite ◽  
Crystal Form ◽  
High Density ◽  
Scanning Calorimetry ◽  
Orthorhombic Crystal ◽  
Fibre Composites ◽  
Ultra High Molecular Weight

High-density polyethylene (HDPE)/ultra-high-molecular-weight polyethylene (UHMWPE) fibre composites were prepared via solution crystallization to investigate the components of epitaxial crystal growth on a highly oriented substrate. Scanning electron microscopy morphologies of HDPE crystals on UHMWPE fibres revealed that the edge-on ribbon pattern crystals that were formed initially on UHMWPE fibres converted afterwards to a sheet shape as crystallization progressed. Wide-angle X-ray diffraction confirmed that the polymer chain oriented along the fibre axis and the orthorhombic crystal form of HDPE remained unchanged in HDPE/UHMWPE fibre composite systems. The thermal behaviour of the fibre composites measured by differential scanning calorimetry showed double melting peaks, the nature of which, as disclosed by partial melting experiments, is ascribed to bilayer components existing in the induced crystals: the inner layer is composed of more regularly folded chain crystals induced by UHMWPE fibres, and the outer layer formed on the inner one with a thinner and lower ordered crystal structure.

Study of the Nature of the Influence of some Oligophosphonates on the Rheological Properties of High-Density Polyethylene

2021 ◽  
Vol 899 ◽  
pp. 606-612
Author(s):  
Abubekir Kh. Shaov ◽  
Asya N. Beslaneeva ◽  
Gennady B. Shustov ◽  
Albina M. Altueva
Keyword(s):  
Molecular Weight ◽  
Rheological Properties ◽  
High Molecular Weight ◽  
High Density Polyethylene ◽  
Functional Group ◽  
High Density ◽  
Low Molecular Weight ◽  
Phosphorus Containing ◽  
Cyclic Compounds

High molecular weight compounds with organophosphorus backbones are usually obtained by polycondensation of phosphorus-containing monomers, leading, most often, to products of low molecular weight at low yields. This fact is explained [1] by several reasons: a decrease in the reactivity of the second functional group of the monomer after the first one has reacted; the possibility of the formation of cyclic compounds; hydrolytic instability of the phosphorus-heteroatom bond (usually P-O, P-N), etc.

Sign in / Sign up

Export Citation Format

Share Document