Investigation of the Impact of Micro-Structuring on the Bonding Performance of Beechwood (Fagus Sylvatica L.)

Although glueing softwood is well mastered by the industry, predicting and controlling bond quality for hardwood is still challenging after years of research. Parameters such as the adhesive type, resin–hardener ratio, and the penetration behaviour of the wood are determinants for the bond quality. The aim of this work was to assess to what extent the glueing behaviour of beechwood can be improved by using structural planing. The different surfacing methods were characterised by their roughness. The bond strength of the micro-structured surfaces was determined according to EN 302-1, and the delamination resistance was tested as indicated by EN 302-2 for type I adhesives. Micro-structured surfaces were compared with different surfaces (generated by surfacing methods such as dull/sharp planing and sanding). In dry test conditions, all surfacing methods gave satisfying results. In the wet stage, the bond strength on the finer micro-structured surface slightly outperformed the coarse structure surface. For the delamination resistance, a clear improvement could be observed for melamine-formaldehyde-bonded specimens since, when using the recommended amount of adhesive, micro-structured surfaces fulfilled the requirements. Nevertheless, structural planing cannot lead to a reduction in the applied grammage since no sample with a smaller amount fulfilled EN 302-2 requirements even by observing the recommended closed assembly waiting time. Adhesion area enlargement of the micro-structuring is minor. The good delamination performance without waiting time (CAT) is not caused by surface enlargement, since finer micro-structured surface with negligible area increase and delivered even better delamination resistance. Subsurface analysis should be carried out to thoroughly investigate this phenomenon.

Integrated Hydraulic Fracture Geometry Evaluation Based on Pre-Cambrian Tight Silicylate Reservoir in South Oman Salt Basin

Pre-Cambrian South Oman tight silicilyte reservoirs are very challenging for the development due to poor permeability less than 0.1 mD and laminated texture. Successful hydraulic fracturing is a key for the long commercial production. One of the main parameter for frac planning and optimization is fracture geometry. The objective of this study was summarizing results comparison from different logging methods and recommended best practices for logging program targeting fracture geometry evaluation. The novel method in the region for hydraulic fracture height and orientation evaluation is cross-dipole cased hole acoustic logging. The method allows to evaluate fracture geometry based on the acoustic anisotropy changes after frac operations in the near wellbore area. The memory sonic log combined with the Gyro was acquired before and after frac operations in the cased hole. The acoustic data was compared with Spectral Noise log, Chemical and Radioactive tracers, Production Logging and pre-frac model. Extensive logging program allow to complete integrated evaluation, define methods limitations and advantages, summarize best practices and optimum logging program for the future wells. The challenges in combining memory cross-dipole sonic log and gyro in cased hole were effectively resolved. The acoustic anisotropy analysis successfully confirms stresses and predominant hydraulic fractures orientation. Fracture height was confirmed based on results from different logging methods. Tracers are well known method for the fracture height evaluation after hydraulic frac operations. The Spectral Noise log is perfect tool to evaluate hydraulically active fracture height in the near wellbore area. The combination of cased hole acoustic and noise logging methods is a powerful complex for hydraulic fracture geometry evaluation. The main limitations and challenges for sonic log are cement bond quality and hole conditions after frac operations. Noise log has limited depth of investigation. However, in combination with production and temperature logging provides reliable fit for purpose capabilities. The abilities of sonic anisotropy analysis for fracture height and hydraulic fracture orientation were confirmed. The optimum logging program for fracture geometry evaluation was defined and recommended for replication in projects were fracture geometry evaluation is required for hydraulic fracturing optimization.

Characterization of Wire-Bonding on LDS Materials and HF-PCBs for High-Frequency Applications

Thermosonic wire bonding is a well-established process. However, when working on advanced substrate materials and the associated required metallization processes to realize innovative applications, multiple factors impede the straightforward utilization of the known process. Most prominently, the surface roughness was investigated regarding bond quality in the past. The practical application of wire bonding on difficult-to-bond substrates showed inhomogeneous results regarding this quality characteristic. This study describes investigations on the correlation among the surface roughness, profile peak density and bonding quality of Au wire bonds on thermoplastic and thermoset-based substrates used for high-frequency (HF) applications and other high-end applications. FR4 PCB (printed circuit board flame resitant class 4) were used as references and compared to HF-PCBs based on thermoset substrates with glass fabric and ceramic filler as well as technical thermoplastic materials qualified for laser direct structuring (LDS), namely LCP (liquid crystal polymer), PEEK (polyether ether ketone) and PTFE (polytetrafluoroethylene). These LDS materials for HF applications were metallized using autocatalytic metal deposition to enable three-dimensional structuring, eventually. For that purpose, bond parameters were investigated on the mentioned test substrates and compared with state-of-the-art wire bonding on FR4 substrates as used for HF applications. Due to the challenges of the limited thermal conductivity and softening of such materials under thermal load, the surface temperatures were matched up by thermography and the adaptation of thermal input. Pull tests were carried out to determine the bond quality with regard to surface roughness. Furthermore, strategies to increase reliability by the stitch-on-ball method were successfully applied.

Cement Conundrum: Valuable Lessons Learned for Sustaining Production

Addressing wellbore integrity through cement evaluation has been an evergreen topic which frequently catches major operators by surprise due to premature water or gas breakthrough causing low production attainability from the wells. Managing idle well strings arising from integrity issues is also a challenge throughout the production period. The remedial solutions to these issues do not come conveniently and require high cost during late life well intervention which often erodes the well economic limit. A critical element of wellbore barrier which is cement integrity evaluation is proposed to be uplifted and given a new perspective to define success criteria for producer wells to achieve certain reserves addition and production recovery. This paper will highlight integrated factors affecting cement bond quality, impact to well production, potential remedies for poor cement bond observed leveraging on the enhanced workflow and new technology and way forward to proactively prevent the unwanted circumstances in the first opportunity taken. A set of recommendations and prioritization criteria for future cement improvement will be also highlighted. Several case specific wells logged with variable cement bond evaluation tools are re-assessed and deep-dived to trace the root causes for unsatisfactory cement bond quality observed which include reservoir characteristics, understanding anomalies during drilling and cementing operation, identifying cement recipe used, log processing parameters applied and observing best practices during cementing operation to improve the quality. New and emerging cement evaluation technology inclusive of radioactive-based logging to meet specific well objectives will be also briefly discussed in terms of differences and technical deliverables. Looking at each spectrum, results show that there are several interdependent factors contributing to poor cement bond quality observed. Accurate understanding of formation behavior, designing fit-for-purpose cement recipe and adequate planning for cementing operation on well-by-well basis are among the top- notch approaches to be applied for an acceptable cement bond quality and placement. Statistics show that 27% to 64% of production attainability is achieved by wells with good cement quality within the first 3 months of production and this increases to 85% to 98% up until 7 months of production period, while only 12% production attainability achieved for those wells with adverse cement quality issue. In another well, water cut as high as 47% since the first day of production is observed which keeps increasing up to 40% thereafter. In a nutshell, cement evaluation exercise shall not be treated as vacuum, instead it requires an integrated foundation and close collaboration to materialize the desired outcomes. Arresting the issue with the right approach in the first place will be the enabler for optimum well performance and productivity to exceed the recovery target.

Multi-Objective Optimization Under Uncertainty of Part Quality in Fused Filament Fabrication

This work presents a data-driven methodology for multi-objective optimization under uncertainty of process parameters in the fused filament fabrication (FFF) process. The proposed approach optimizes the process parameters with the objectives of minimizing the geometric inaccuracy and maximizing the filament bond quality of the manufactured part. First, experiments are conducted to collect data pertaining to the part quality. Then, Bayesian neural network (BNN) models are constructed to predict the geometric inaccuracy and bond quality as functions of the process parameters. The BNN model captures the model uncertainty caused by the lack of knowledge about model parameters (neuron weights) and the input variability due to the intrinsic randomness in the input parameters. Using the stochastic predictions from these models, different robustness-based design optimization formulations are investigated, wherein process parameters such as nozzle temperature, nozzle speed, and layer thickness are optimized under uncertainty for different multi-objective scenarios. Epistemic uncertainty in the prediction model and the aleatory uncertainty in the input are considered in the optimization. Finally, Pareto surfaces are constructed to estimate the trade-offs between the objectives. Both the BNN models and the effectiveness of the proposed optimization methodology are validated using actual manufacturing of the parts.

Quantifying In Situ Tack Coat Performance Using the TackBond Tester for Quality Control

In light of the various quality assurance (QA) issues pertaining to tack coats that occur during construction, there is a need for a means of verifying interlayer bond quality in situ. Despite the immense use of tack coat as a constituent in paving, there are no construction specifications with provisions for the quantification of tack coat bond quality in laboratory or field settings. In this study, a construction QA process for tack coat bond performance was proposed. A novel field tack coat bond strength test device, TackBond, was developed and used for this purpose. The performance of engineered (new tack coat technologies that are tracking less) and conventional tack coats was also evaluated in the laboratory and the field using the developed TackBond test system. The TackBond device was improved in this study by adding features that render it more practical, portable, accurate, and better suited for a variety of pavement surface conditions. Engineered tack coat performance was compared with that of tack coats used conventionally on both milled and overlay surface types. The suitability of the TackBond Test device for capturing the true response of each tack coat was first evaluated by comparing results from TackBond laboratory tests with monotonic direct shear tests (DST) on laboratory-produced samples. Strong correlations between the two test types were achieved. Results of field and laboratory TackBond tests showed that the in situ QA control process developed in this study could be effectively used to improve the in situ tack coat bond performance.

In Silico Analysis of Glucose Oxidase from Aspergillus niger: Potential Cysteine Mutation Sites for Enhancing Protein Stability

Glucose oxidase (GOx) holds considerable advantages for various applications. Nevertheless, the thermal instability of the enzyme remains a grand challenge, impeding the success in applications outside the well-controlled laboratories, particularly in practical bioelectronics. Many strategies to modify GOx to achieve better thermal stability have been proposed. However, modification of this enzyme by adding extra disulfide bonds is yet to be explored. This work describes the in silico bioengineering of GOx from Aspergillus niger by judiciously analyzing characteristics of disulfide bonds found in the Top8000 protein database, then scanning for amino acid residue pairs that are suitable to be replaced with cysteines in order to establish disulfide bonds. Next, we predicted and assessed the mutant GOx models in terms of disulfide bond quality (bond length and α angles), functional impact by means of residue conservation, and structural impact as indicated by Gibbs free energy. We found eight putative residue pairs that can be engineered to form disulfide bonds. Five of these are located in less conserved regions and, therefore, are unlikely to have a deleterious impact on functionality. Finally, two mutations, Pro149Cys and His158Cys, showed potential for stabilizing the protein structure as confirmed by a structure-based stability analysis tool. The findings in this study highlight the opportunity of using disulfide bond modification as a new alternative technique to enhance the thermal stability of GOx.

DYNAMICS OF CHANGE OF REQUIREMENTS OF STANDARDS TO DURABILITY OF WOOD-SHAVING PLATES: REASONS AND CONSEQUENCE

Drevesno – chip plates are widely used in production of case furniture. The volume of their production constantly grows in Russia. If in 2013 it has been made 7270, then in 2017 – 8370, in 2018 – 9789, in 2019 – 9986 thousand m3 of plates. However, one of the main shortcomings of plates of the plates released by the industry is their low durability. It especially concerns one of the main strength performances of plates – ultimate strength at bend. So, in comparison with requirements of GOST 10632-77 durability of plates at bend of the most widespread thickness (13-20 mm) in accordance with GOST 10632-89 has decreased on 9 and 21, in accordance with GOST 10632-2007 on 21 and 29, and by current GOST 10632-2014 – by 38 and 43% depending on brand of plates. Decrease in durability at stretching perpendicular to plate face less noticeable. One of the main reasons of such decrease, use in technology of plates of low-toxic carboamidoformaldehyde (KFS) pitches the content of free formaldehyde in which generally is makes about 0,15%. It is known, than more free formaldehyde is in pitch of subjects bond quality of wood and wood-base materials, with use of this pitch, above. However such big decrease in durability of plates for furniture makers is big shortcoming. It is necessary to change approaches to designing of furniture from such plates. Manufacturers of plates, using low requirements of the present standard, sometimes manipulate due to decrease in density of plates that results in friability of plates, problem of fastening of plates in furniture designs. The purpose of our work was studying of dynamics of decrease in durability of plates according to requirements of standards, since 1977 till present, establishment of the reasons and possible consequences from such decrease.

The Factors That Affect the Expansion of the Tape for It to Avoid Side Effects in the Production of Composites in Online LATP Technology

During LATP (laser automated tape placement), the compaction roller contacts the prepreg and affects the pressure distribution directly. Moreover, the design parameters of the roller are optimized with the aim of improving pressure uniformity. This paper examines the impact of the contact line and surface that depends on the compaction force, the design of the roller, the angle of inclination and the angle of inclination of the strip. These factors significantly affect the expansion of the tape, and it is important to determine it to avoid side effects in the production of composites (formation of gaps or overlaps). Their presence increases the percentage of pores of the final material and thus reduces the mechanical properties. The results show that the pressure uniformity can be improved significantly by design optimization of the roller, which indicates that higher bond quality between layers is achieved. The lower the speed and higher the compact force in this technology give better intimate contact with a lower percentage of voids and good mechanical characteristics.

Experimental Evaluation of the Bending Behavior of a Drilled Shaft with Partial Casing under Lateral Loads

Few studies, especially those related to field tests, have examined the bending behaviors of drilled shafts with partial casings (DSPCs). This work reports the results of experimental studies on the behavior of DSPCs under lateral loads, including an in situ test and a set of laboratory tests. First, a DSPC with a diameter of 2 m and length of 87.9 m was studied in clay beds, and a steel casing with a diameter of 2.0 m and length of 33 m was used. In this test, strain gauges were distributed along the steel rebars in the concrete pile and the wall of the steel tube at different depths, and thus the longitudinal strains of the concrete pile and the steel tube could be studied. Second, laboratory experiments were implemented with reinforced concrete-filled steel tubular columns under pure bending conditions. In these tests, strain gauges were distributed along the steel rebars in the concrete pile and the walls of the steel tubes at the pure bending section of the specimens. Different wall thicknesses and drilling fluid conditions were considered. The field test results show that the strain of the concrete piles and the steel tubes were linearly distributed at the same cross-section. This means that a DSPC remains a flat plane after it deforms. Whereas a correction coefficient related to the loading level need to be considered in the calculation of the bending stiffness. Laboratory studies show that the strain of DSPCs was linearly distributed at a small bending moment under the best bond-quality condition, whereas obvious nonlinear behaviors were shown under a large bending moment with poor bond-quality conditions.