Combination Of Performance Properties Research Articles

Prediction of Casing Collapse Resistance by 3D Finite Element Modeling

Summary 3D outside diameter (OD) and wall thickness mapping of a casing joint consists of synchronized OD laser scanning and ultrasonic testing (UT) wall thickness measurement at a resolution of every 1 in. along the length and every 1° or 2° around the circumference. This full-length mapping data can then be used to construct a 3D finite element analysis (FEA) model that captures the geometric attributes, including OD, wall thickness, OD ovality, and wall eccentricity, of a casing joint. Together with the actual nonlinear material plasticity model and the measured as-manufactured residual stress, the 3D FEA model can predict the casing collapse strength with good accuracy. Also, the Klever-Tamano ultimate limit-state (KT ULS) collapse equation per API TR 5C3 (2018) together with a moving-average (MA) scheme can calculate the joint’s collapse strength. Results predicted by 3D FEA and KT ULS collapse models are compared to the actual full-scale collapse test results. A 3D FEA model generally produces more accurate results than the KT collapse equation. In addition, both 3D FEA and KT collapse models predict a collapse pressure slightly lower than the actual collapse pressure, which is therefore on the conservative side. The prediction of casing collapse strength can be beneficial to the end user in sorting and ranking the casing joints by collapse resistance, and therefore provides valuable information that can be used in the end user’s risk assessment. Furthermore, the end user may potentially select the joints with the highest predicted collapse strength for the portion of the casing string where the highest collapse resistance is desired. In addition, the OD and wall mapping data together with the actual material tensile properties (yield strength, ultimate tensile strength, and strain hardening parameters) can be used in estimating the internal yield, ductile rupture pressures, and other performance properties. This is outside the scope of this paper and can be pursued in future work. These predicted casing performance properties may then be used in sorting and ranking the joints based on a specific performance property of interest or a combination of performance properties.

Exploration of pros and cons of polyetherimide solutions with varying concentrations as the sizing agents for graphite fibers in graphite fabric-PAEK composites

Some specialty polymers such as polyetheretherketone (PEEK), Polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyamideimide (PAI), and polyimide (PI) are the ideal choices for developing high performance bidirectionally reinforced composites that would excel in specific strength performance. However, these polymer composites are extremely challenging from a processing point of view and have limited choices. Most of the time, a lot of compromises are to be made on the fiber-matrix wetting issues. The current research elaborated on a method to exploit two techniques together to opt for advantages from both. Polyetherimide (PEI) solutions of various concentrations/viscosities were used as sizing agents for the fibers so as to wet the cross-over points on graphite fabric and inter-tow filaments. It was expected that the PEI and PAEK would form a blend at the interface, although fiber would necessarily be covered with only PEI. It was also anticipated that there could be an optimum amount of PEI on the fibers’ surface for the best performance properties. Based on the in-depth studies on the performance properties, it was concluded that PEI solution in the range of 5–10 wt. % would lead to the best combination of performance properties. Compared to the classical method of developing PAEK-graphite fabric composites by film technique, the current method of combination of impregnation and film technique led to excellent results.

Optimization of graphite contents in PAEK composites for best combination of performance properties

Graphite is one of the most widely used solid lubricants in both, anti-friction and friction materials. The influence of particles in the composite mainly depends on its size, amount, its combination with fibers and other fillers etc. No efforts were done to optimize the amount of graphite to achieve very low friction and wear. A series of Polyaryl ether ketone (PAEK) composites with GF (short glass fibers) and increasing amount of graphite particles (10, 15, 20 and 25 wt %) were developed and characterized for various properties such as physical, mechanical, thermal along with adhesive wear performance in severe operating conditions (high pressure and velocity (PV)). Inclusion of graphite led to deterioration in strength and modulus but increase in thermal conductivity. The composites showed very low μ (friction coefficient) in the range of 0.04 and K0 (specific wear rate) (∼2 × 10−16 m3/Nm). Composite with 15 wt % graphite proved to be significantly superior by showing highest PVlimit value (154 MPa m/s) and very low μ (0.04) and K0 (1.91 × 10−16 m3/Nm). The typical inferences were supported by various techniques such as Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), 3D profilometer, Raman spectroscopy on the worn surfaces.

Tribological studies on polyetherimide composites based on carbon fabric with optimized oxidation treatment

Abstract Chemical inertness and hence limited wettability of carbon fibers (CF) with a selected matrix is the major problem for exploiting its full potential as reinforcement. Oxidation of CF with nitric acid is a classical method for treatment of CF which increases oxidative groups on fiber surface leading to enhanced adhesion with the matrix, but at the cost of damage to the fibers leading to reduction in strength. Thus the treatment has to be for optimum time to strike a balance between these opposite effects so that the composite will have best combination of performance properties. In depth studies on this aspect, however, are not reported especially in tribological studies. Hence nitric acid treatment was employed to carbon fabric for various time intervals (15–180 min). Eight composites with untreated and acid treated fabrics were developed based on polyetherimide (PEI) matrix and evaluated for mechanical and abrasive wear properties. It was observed that 90 min treatment time was ideal one to achieve maximum possible enhancement in strength and tribological properties. Fiber–matrix adhesion was improved due to inclusion of oxygenated functional groups as supported by Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and increased surface roughening of fibers as supported by scanning electron microscopic (SEM) studies.

Optimization of brass contents for best combination of tribo-performance and thermal conductivity of non-asbestos organic (NAO) friction composites

Thermal conductivity (TC) of composites especially friction composites plays a vital role in the performance during braking. Low TC renders the tribo-surface vulnerable for degradation of organic ingredients affecting the braking capability adversely while too high TC on the other hand, results in adverse effect on brake-fluid. Simultaneously it is also required that the composite should exhibit best possible combination of performance properties as a friction material. The optimum combination of various properties hence is to be tailored with right contents of metallic fillers. In this paper the effect of brass fibers in increasing amount on friction and wear performance of non-asbestos organic (NAO) friction composites was studied. Four friction materials based on parent composition and with varying amount of brass (0, 4, 8 and 12 wt%) and barite (35, 31, 27, and 23 wt%) in a complementary manner were developed as brake pads and were characterized for physical, chemical and mechanical properties. These were further tested for their friction and wear behavior in fade and recovery (F & R) mode on a Krauss machine as per ECE R 90 schedule. Moreover, the small specimens (24 mm × 24 mm) of the brake pad were evaluated for studying their friction sensitivity for loads and speeds in simulated braking conditions against a commercial disc on a reduced scale prototype (RSP). Composite with 8% brass fibers (where TC was not highest) proved to exhibit best combination of performance parameters related to friction and wear in both the testing modes. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) were employed to understand wear mechanisms.