In the interest of developing a comprehensive understanding of the drilling process using the hole saw tool, this article aims to build a three-dimensional (3D) micromechanical model representing the ...orthogonal cutting of CFRP using one tooth of the hole saw tool. For this purpose, a finite element model is developed using Abaqus Explicit code. The influence of various drilling parameters like rake angle, inclination angle and cutting-edge radius on the drilling quality is explored. Especially, chip formation mechanisms, cutting force and lateral damage are analyzed. Through finite element simulations and computational analyses, it is found that these outputs results are highly influenced by drilling parameters. When the fiber orientation angle is set to 0°, increasing the rake angle results in a change in the chip formation mechanism from buckling to bending. In contrast, with a fiber orientation angle of 90°, bending and shear governs the chip formation process, irrespective of the rake angle. In both cases, whether the fiber orientation angle is 0° or 90°, chips tend to fragment more favorably with increasing the inclination angle. Regarding the cutting-edge radius, when the fiber orientation angle is 0°, an increase in the cutting-edge radius leads to a transition in the chip-forming mechanism from buckling to bending. However, for a fiber orientation angle of 90°, the chip formation remains governed by bending even as the cutting-edge radius changes. Decreasing the rake angle, the inclination angle, and the cutting-edge radius contribute to a reduction of the cutting force. As the inclination angle and the cutting-edge radius increase, the lateral damage increases, while the rake angle has showed a negligible impact on the damage. These results provide a guidance on the appropriate hole saw tool parameters for a good drilling quality namely, a rake angle of 20°, an inclination angle of 5° and a cutting-edge radius of 0.03 mm.
Due to complex geological formations, lateral damage often occurs during excavation in mountainous layered soft rock double-track tunnels. This paper discusses the stresses and the damage ...characteristics of the surrounding rock under overload in a mountainous layered soft rock double-track tunnel through indoor model experiments to provide a basis for the effective control of lateral damage. The experiments show that the conventional support method cannot effectively control the lateral damage due to interlayer sliding. Therefore, the negative Poisson’s ratio (NPR) anchor/cable control method is proposed. And the scientificity and feasibility of the NPR anchor/cable control technology are proved by the field application and monitoring data of the Minxian Tunnel and Changning Tunnel. It is further demonstrated that high preload is the most effective way to control the lateral damage in layered soft rock tunnels.
We study the potential formation damage effects due to radial jet drilling on Bentheim sandstone, a homogeneous sandstone that is well established in terms of mechanical properties and widely used as ...reservoir analogue. We quantify how properties degrade with distance from a jetted hole on μm scale (porosity) and cm scale (compressive, tensile and acoustical properties). Moreover, we perform true-triaxial compression tests on samples with and without a jetted hole. It is concluded that, for this material, jetting has no direct influence on the surrounding area. No significant changes compared to intact material is found, nor can a significant change be detected with respect to distance to a jetted hole. Differences fall within the intra-block variability, and differences between blocks can be well explained by block-to-block variation. Differences in results of the true-triaxial compression tests can be attributed to a different sample geometry, which is corroborated by a numerical simulation. We conclude that the stress field around the jetted hole can therefore be well approximated by the Kirsch equations, modified for compression, and thereby accurately describe the stability of the lateral borehole.
•Potential damage caused by jet drilling is assessed by tests at various scales.•No significant trends could be observed with distance to the jetted borehole.•Borehole stability of jetted laterals can be modelled using the Kirsch-equations.
The objective of this work was to investigate compression after low-velocity impact (CAI) properties of a multistitched composite. It was found that the CAI strength of the multistitched composite ...was high compared to the unstitched composites. In addition, stitching density, stitching type, stitching direction, and stitching fibers were found to be important structural parameters. The CAI load on the multistitched composites resulted in lateral damages near the impacted indentation region. The structures showed large damaged areas, but the out-of-plane layer delamination was confined to relatively small areas. Thus, the multistitching enhanced the CAI properties of the composite.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Many bridges are subject to lateral damage for their girders due to impact by over-height vehicles collision. In this study, the optimum configurations of carbon fiber reinforced polymers (CFRP) ...laminates were investigated to repair the laterally damaged prestressed concrete (PS) bridge girders. Experimental and analytical investigations were conducted to study the flexural behavior of 13 half-scale AASHTO type II PS girders under both static and fatigue loading. Lateral impact damage due to vehicle collision was simulated by sawing through the concrete of the bottom flange and slicing through one of the prestressing strands. The damaged concrete was repaired and CFRP systems (longitudinal soffit laminates and evenly spaced transverse U-wraps) were applied to restore the original flexural capacity and mitigate debonding of soffit CFRP longitudinal laminates. In addition to the static load tests for ten girders, three more girders were tested under fatigue loading cycles to investigate the behavior under simulated traffic conditions. Measurements of the applied load, the deflection at five different locations, strains along the cross-section height at mid-span, and multiple strains longitudinally along the bottom soffit were recorded. The study investigated and recommended the proper CFRP repair design in terms of the CFRP longitudinal layers and U-wrapping spacing to obtain flexural capacity improvement and desired failure modes for the repaired girders. Test results showed that with proper detailing, CFRP systems can be designed to restore the lost flexural capacity, sustain the fatigue load cycles, and maintain the desired failure mode.
AbstractThis research investigated flexural behavior of repaired RC beams that experienced simulated lateral damage to replicate vehicle impact/collision. The experimental program included the ...testing of 34 RC beams, which were laterally damaged and then repaired using carbon-fiber-reinforced polymer (CFRP) fabrics. The damaged beams were repaired using various levels of strengthening (number of CFRP soffit layers) and multiple configurations of anchoring CFRP U-wrapping. Specific attention was paid to understanding the effects of intermediate U-wrapping on strains developed in the longitudinal soffit laminates and the beams’ ultimate capacity. Other details for the flexural repair system, such as end-peeling previsions, were also addressed. The test results indicated that CFRP repairs have the ability to restore and enhance the capacity of damaged RC beams by up to 353%. The results also suggest an optimum range for spacing intermediate U-wrappings to suppress strains felt by longitudinal soffit laminates, thereby mitigating premature debonding failures. Design considerations and recommendations for optimum CFRP configuration, level of strengthening, and application details for repairing laterally damaged RC beams are proposed.
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