HDPE Geomembranes for Environmental Protection: Two Case Studies

High-density polyethylene (HDPE) geomembranes have been used for different applications in engineering including sanitation, such as landfills and waste liquid ponds. For these applications, the material can be exposed to aging mechanisms as thermal and chemical degradation, even to UV radiation and biological contact, which can degrade the geomembrane and decrease the material’s durability. This paper aims to present an experimental evaluation of two exhumed HDPE geomembranes, the first was used for 2.75 years in a sewage treatment aeration pond (LTE sample) and another was used for 5.17 years in a municipal landfill leachate pond (LCH sample). Physical and thermal analyses were used such as thermogravimetry (TG), differential thermal analysis (DTA), differential scanning calorimetry (DSC) and dynamic mechanic analysis (DMA). The thermogravimetric analyses showed significant changes in the LCH sample’s thermal decomposition probably caused by the interaction reactions between the polymer and the leachate. For the DSC analyses, the behavior seen in the LTE sample was not observed in the LCH sample. In the DMA analyses, the behavior of the LTE sample storage module shows which LCH sample is less brittle. The LTE sample presented low stress cracking resistance and low tensile elongation at break, following the DMA results.

The Development of A Versatile Movable Barrier Solution

To reduce the accident risk of work zone on highway, a new movable barrier solution is presented in this paper. The barrier is effective, affordable, environment-friendly and versatile. It can raise the level of highway safety performance in work zone, median opening and tidal lane. The development of the versatile movable barrier took reliability, mobility, economical efficiency, construction convenience into account. Researchers optimized structure by finite element analysis as well as mechanic analysis. The finite element analysis was accomplished by LS-DYNA. This barrier set eventually passed simulated impact tests, which proved that it is able to fulfil the requirement of 160kj-level safety performance.

New Needs of Fracture Mechanic Analysis at Design and Operation Level: Status of French Nuclear Mechanical Codes

Based on ASME Boilers and Pressure Vessels Code the major fracture mechanic analysis is limited to protection of class 1 components to brittle fracture. All the Operators of future plants have to enlarge the scope of these analyses to different concepts, at design or operation stage: - brittle and ductile analysis of hypothetical large flaw - leak before break approach - break exclusion concept - incredibility of failure of high integrity components - end of fabrication acceptable defect - in-service inspection performance - acceptable standards in operation - Long Term Operation (LTO) All these requirements needs a procedure, an analysis method with material properties and criteria. After a short overview of each topic, the paper will present how RCC-M, RSE-M French Codes and ASME III and XI take care of all these new modern regulatory requirements.

Wave Loads Computation for Offshore Floating Hose Based on Partially Immersed Cylinder Model of Improved Morison Formula

Aimed at wave load computation of floating hose, the paper analyzes the morphologic and mechanical characteristics of offshore hose by establishing the partially immersed cylender model, and points out that the results of existing Morison equation to calculate the wave loads of floating hose is not precise enough. Consequently, the improved Morison equation has been put forward based on its principle. Classical series offshore pipeline has been taken as example which applied in the water area of different depth. The wave loads of pipeline by using the improved Morison equation and compared the calculation results with the existing Morison equation. Calculations for wave loads on pipelines in different depth were accomplished and compared by the improved Morison equation and the existing Morison equation. Results show that the improved Morison equation optimizes the accuracy of the computation of wave load on floating hose. Thus it is more suitable for analyzing the effects of wave loads on floating hose and useful for mechanic analysis of offshore pipeline.

Characterization of the Damping Behavior of Thin Films With Dynamic Mechanic Analysis in Bending Mode

Usually damped structures, consisting of a constrained layer damping (CLD) and free layer damping (FLD) design, are characterized via dynamic mechanic analysis (DMA) in bending mode. Since laminates with thicknesses from 10 to 100 μm exhibit a very low bending stiffness it isn’t possible to determine their damping properties in bending mode with standard DMA setups. Therefore in the present work the main objective was to introduce a new method to overcome this drawback. Two main geometries were used, such as a variation of the bending mode where the laminates were clamped at the outer supports and on the other hand a set-up where the geometry of a support of loudspeakers was replicated, which was called “speaker” mode. The damping behavior of the laminates then was characterized via the mechanical loss factor tan δ and subsequently compared to results in DMA shear mode. The second objective was to characterize the influence of the design, with a 2-layer laminate consisting of a free layer damping design and a 3-layer laminate with a constrained layer damping design. A method in DMA “speaker” mode was successfully set up. The test parameters were chosen in order to resemble the support of loudspeakers. Therefore with the laminates two beads with a height of approximately 1 mm were formed symmetrically in gaps of 3 mm between the outer fixtures and the drive shaft. Furthermore in the test the laminates were loaded with a dynamic displacement of 600 μm. Due to the low bending stiffness of the laminates the highest test frequency was limited to 10 Hz. In accordance with literature for the 2-layer laminates significant lower damping levels were found than for the 3-layer laminates. Whereas the constrained layer damping laminate (3-layer) showed a good correlation between measurements in “speaker” and in shear mode, the 2-layer laminate showed a significant loss factor increase at high temperatures in shear mode, which was related to entropy elastic effects.

Research on Natural Frequency of MEMS Structure with Meander Suspensions by Mechanical Character Analysis

A new concept of using four meander suspensions as a constraint is proposed to construct planar spring-like energy harvester actuators with larger displacement. Meander suspensions with multi-folded beams having three vibrating directions. This paper introduce a new structure of “-type” to calculate modulus of elasticity of one meander suspensions. Based upon the micro deformation theory and the displacement superposition theory, the expression on the displacement for the movement end of the meander beams by outer forces and force moments are deduced. Since the energy harvester is geometric symmetry, elasticity coefficient and natural frequency of the energy harvester will be deduce by above given information. The finite-element analysis was used to model the performances and verified the above mentioned mechanic analysis method.

The Mechanic Analysis and Construction Method on Damaged Beam of External Prestressing Reinforcement

In order to investigate the feasibility of reinforcement transformation schemes for actual engineering, Combined with the characteristics of the project, the reinforcement transformation designs of the roof beams is carried out, three kinds of reinforcement transformation design schemes are put forward, they are carbon fiber reinforced polymer strengthening, internal prestressing strengthening and external prestressing strengthening. The external prestressing reinforcement scheme is selected after comparing. Numerical simulation analysis of the reinforcement system is done by ANSYS software, and nonlinear finite element model of simply supported beam with crack is built, through analysis deformation, cracks and stress distribution of reinforced beam are obtained. The results show that the using function of beam is improved obviously. The rationality and feasibility of this reinforcement scheme is validated. These can provide references for reinforcement transformation of similar existing buildings.

Finite Element Analysis of the Packer at Fracturing

According to the working principle and structural feature of compressive packer, mechanic analysis of rubber tubes was done with adopting Mooney-Rivlin model. The contact stress between rubber tube and the casing and axial compression distance were figured out at 83MPa of the differential pressure between inside and outside string. The results show that the middle tube has the function of beginning to set the paker and the lower tube seals and separate the layers. Upper tubing should be installed the equipment to prevent shoulder protruding.