Search Results (123)

Box compression strength (BCS) is a critical parameter for assessing the performance of shipping containers during transportation. Traditionally, BCS evaluation relies heavily on physical testing, which is both time-consuming and costly. These limitations have prompted industry to seek more efficient and cost-effective alternatives. This study explores the application of artificial neural networks (ANNs) to estimate BCS at an industry-applicable level. A real-world dataset—covering approximately 90% of the box dimensions commonly used in the industry—was utilized to train a generalized ANN model for BCS prediction. The model achieved a prediction error of approximately 10%. When validated against experimentally measured data from laboratory testing, with single-wall B-flute as a representative, the prediction error was at a much lower level, further demonstrating the model’s reliability. This study offers a novel approach to BCS prediction, providing a cost-effective and scalable alternative to traditional physical testing methods in the packaging industry. Full article

Deep groove ball bearings are important mechanical elements in the automotive and process industries, particularly in electric motors. One of the primary reasons for their failure is lubricant degradation due to stray shaft current. Thus, the present work exhibited the failure of bearings under simulated lubricated conditions similar to those of real time bearings failing in presence of stray electric current. The test was conducted using a full bearing test rig with an applied radial load, 496 N, an alternating current, 10 A, and a rotation of 2000 rpm for 24 h. The bearings (6206 series) were greased using two commercially available ester-polyalphaolefin oil-based greases with viscosity 46–54 cSt (Grease 1) and 32–35 cSt (Grease 2, also contained aromatic oil). The optical microscopic images of the bearing raceways after the tribo test indicated the superior performance of Grease 1 compared to Grease 2, with lesser formation of white etching areas, micro-pitting, spot welds, and fluting on the surfaces of the bearings. Additionally, 80% less vibrations were recorded during the test with Grease 1, indicating a stable lubricating film of Grease 1 during the test as compared to Grease 2. Furthermore, a higher extent of Grease 2 degradation during the tribo test was also confirmed using Fourier transform infrared spectroscopy. Statistical analysis (t-test) indicated the significant variation of the vibrations produced during the test with electrified conditions. The present work indicated that the composition of the greases plays a significant role in controlling the bearing failures. Full article

Achieving the appropriate primary stability for immediate or early loading in areas with low-density bone, such as the posterior maxilla, is challenging. A three-dimensional (3D) stabilization implant design featuring a tapered body with continuous cutting flutes along the length of the external thread form, with a combination of curved and linear geometric surfaces on the thread’s crest, has the capacity to enhance early biomechanical and osseointegration outcomes compared to implants with traditional buttressed thread profiles. Commercially available implants with a buttress thread design (TP), and an experimental implant that incorporated the 3D stabilization trimmed-thread design (TP 3DS) were used in this study. Six osteotomies were surgically created in the ilium of adult sheep (N = 14). Osteotomy sites were randomized to receive either the TP or TP 3DS implant to reduce site bias. Subjects were allowed to heal for either 3 or 12 weeks (N = 7 sheep/time point), after which samples were collected en bloc (including the implants and surrounding bone) and implants were either subjected to bench-top biomechanical testing (e.g., lateral loading), histological/histomorphometric analysis, or nanoindentation testing. Both implant designs yielded high insertion torque (ITV ≥ 30 N⋅cm) and implant stability quotient (ISQ ≥ 70) values, indicative of high primary stability. Qualitative histomorphological analysis revealed that the TP 3DS group exhibited a continuous bone–implant interface along the threaded region, in contrast to the TP group at the early, 3-week, healing time point. Furthermore, TP 3DS’s cutting flutes along the entire length of the implant permitted the distribution of autologous bone chips within the healing chambers. Histological evaluation at 12 weeks revealed an increase in woven bone containing a greater presence of lacunae within the healing chambers in both groups, consistent with an intramembranous-like healing pattern and absence of bone dieback. The TP 3DS macrogeometry yielded a ~66% increase in average lateral load during pushout testing at baseline (T = 0 weeks, p = 0.036) and significantly higher bone-to-implant contact (BIC) values at 3 weeks post-implantation (p = 0.006), relative to the traditional TP implant. In a low-density (Type IV) bone model, the TP 3DS implant demonstrated improved performance compared to the conventional TP, as evidenced by an increase in baseline lateral loading capacity and increased BIC during the early stages of osseointegration. These findings indicate that the modified implant configuration of the TP 3DS facilitates more favorable biomechanical integration and may promote more rapid and stable bone anchorage under compromised bone quality conditions. Therefore, such improvements could have important clinical implications for the success and longevity of dental implants placed in regions with low bone density. Full article

This study presents a comprehensive analysis of defect detection in the manufacturing process of solid carbide milling tools. The creep-feed flute grinding technique was used to fabricate a milling tool, with cutting force signals recorded and examined using recurrence analysis and conventional statistical methods. The analysis identified four distinct dynamic fluctuations (cutting force amplitude jumps), which showed a direct correlation with the formation of microcracks on the flute surface. These jumps exhibited varying levels of reduction, ranging from 5% to 22% in amplitude. A detailed investigation, including recurrence plots and recurrence quantification analysis (RQA) with a moving-window approach, revealed that several recurrence indicators, such as the recurrence rate (RR), determinism (DET), and maximum diagonal line length (L_MAX), were highly effective in detecting microcracks, as their values significantly deviated from the reference level. These results were compared with conventional statistical analysis, and interestingly, the recurrence methods demonstrated greater sensitivity, successfully detecting additional very small cutting force jumps that conventional statistical methods could not identify. Full article

A pioneering detailed comparative study of the dynamics of plasma flows generated by high-power nanosecond and high-intensity femtosecond laser pulses with similar fluences of up to $3\times {10}^4$ J/cm² is presented. The experiments were conducted on the petawatt laser facility PEARL using two types of high-power laser radiation: femtosecond pulses with energy exceeding 10 J and a duration less than 60 fs, and nanosecond pulses with energy exceeding 10 J and a duration on the order of 1 ns. In the experiments, high-velocity (>100 km/s) flows of «femtosecond» (created by femtosecond laser pulses) and «nanosecond» plasmas propagated in a vacuum across a uniform magnetic field with a strength over 14 T. A significant difference in the dynamics of «femtosecond» and «nanosecond» plasma flows was observed: (i) The «femtosecond» plasma initially propagated in a vacuum (no B-field) as a collimated flow, while the «nanosecond» flow diverged. (ii) The «nanosecond» plasma interacting with external magnetic field formed a quasi-spherical cavity with Rayleigh–Taylor instability flutes. In the case of «femtosecond» plasma, such flutes were not observed, and the flow was immediately redirected into a narrow plasma sheet (or «tongue») propagating across the magnetic field at an approximately constant velocity. (iii) Elongated «nanosecond» and «femtosecond» plasma slabs interacting with a transverse magnetic field broke up into Rayleigh–Taylor «tongues». (iv) The ends of these «tongues» in the femtosecond case twisted into vortex structures aligned with the ion motion in the external magnetic field, whereas the «tongues» in the nanosecond case were randomly oriented. It was suggested that the twisting of femtosecond «tongues» is related to Hall effects. The experimental results are complemented by and consistent with numerical 3D magnetohydrodynamic simulations. The potential applications of these findings for astrophysical objects, such as short bursts in active galactic nuclei, are discussed. Full article

The cutting length of milling tools must be longer than the axial distance of the material to be processed. In fact, in most cases, the cutting length far exceeds the thickness of the material to be removed. Therefore, along the entire length of the milling-tool flutes, only the area farthest from the shank wears out, leaving the rest of the tool practically without any wear, especially in the area closest to the shank. This research analyses a toolpath model to use the complete length of the milling tool flutes, in those machining operations in which it is possible, with the objective of reducing the costs associated with tool wearing and resharpening. This improves the tool performance, which clearly increases the sustainability of the milling process. For this purpose, it is necessary to transform the numerical control programme that performs a flat (2D) toolpath into a helical (3D) one by decomposing the arcs and rectilinear segments into a succession of points within a precision range. A negative aspect of this method is that it can only be applied to bottomless contours in processes of air-contour milling. Full article

Background: The use of tapered monobloc stems in revision total hip arthroplasty (RTHA) has shown excellent results, with low implant-dependent failures due to aseptic loosening. Infection is one of the main failure reasons, but further problems, like periprosthetic fractures (PPFs), may endanger the function and duration of the implant in the long run. Methods: A consecutive series of 121 cases after femoral RTHA with a monobloc device was retrospectively investigated, and a Kaplan–Meier analysis was performed. The mean follow-up was 13.0 (range: 0.8–23.8) years. Results: PPF occurred in six patients during follow-up. The cumulative risk for PPF was 5.2% (95% CI: 1.1–9.4%) after 23.8 years. Female gender was associated with a significantly higher risk compared to male gender (9.1% (95% CI: 2.1–16.1%) after 23.1 years vs. 0% after 23.8 years; log-rank p = 0.0034). Patients operated with stems with a length equal to or longer than the calculated median length were also at a significantly higher risk of PPF during follow-up (10.2% (95% CI: 2.4–17.9%) after 23.8 years vs. 0% after 23.1 years; log-rank p = 0.0158). Diabetes at the time of index operation also significantly influenced the occurrence of a PPF during follow-up (n = 4 patients with PPF out of 107 without (4.0% (95% CI: 0.2–7.8%) after 23.8 years vs. n = 2 out of 14 with diabetes (15.4% (95% CI: 0–35.0%) after 21.1 years; log-rank p = 0.0368). The failure rate with implant removal as an endpoint due to aseptic loosening was 0%, and with infection it was 3.4% (95% CI: 0.1–6.7%), after 23.8 years. Conclusions: Although no removal of the implant due to a PPF was necessary, the cumulative risk for PPF after femoral revision with a tapered and fluted monobloc stem was higher in this long-term follow-up series compared to implant failure due to infection or aseptic loosening. Female gender and diabetes was associated with a significantly higher risk of PPF during follow-up. The use of longer stems than necessary is not preventive of PPF, and should be avoided. Full article

The incremental hole-drilling method is widely used to measure residual stress distribution versus depth. In this study, a two-flute carbide end mill that was 1.5 mm in diameter operated at different rotational speeds, used to create a hole that was 2.0 mm in diameter through orbital technology milling, were used to measure machining-induced residual stress (MIRS). Additionally, a finite element model was developed to calculate distortion, with MIRS as the input. A 25 × 25 × 1 mm³ thin sample containing a machining surface was cut free from large samples by a wire electrical discharge machining after milling, and distortion was measured by a 3D profile meter. It can be concluded that the calculated maximum distortion on one of the diagonals can reach 89% of the measured maximum distortion when the rotational speed is more than 20,000 rpm, and the deviation in the measured MIRS can be controlled within 35 MPa. The shear stress increases rapidly by 63% when the rotational speed is less than 10,000 rpm. Full article

Sustainability has increasingly emphasized the importance of recycling and repairing materials. Cutting tools, such as milling cutters and drills, play a crucial role due to the high demands placed on products used in CNC machining. As a result, the repair and regrinding of these tools have become more essential. The geometric differences among machining tools determine their specific applications: twist drills have spiral flutes and pointed cutting edges designed for drilling, while end mills feature multiple sharp edges around the shank, making them suitable for milling. Taps and form cutters exhibit unique geometries and cutting-edge shapes, enabling the creation of complex profiles. However, measuring and classifying these tools for repair or regrinding is challenging due to their optical properties and coatings. This research investigates how lighting conditions affect the classification of tools for regrinding, addressing the shortage of skilled workers and the increasing need for automation. This paper compares different training strategies on two unique tool-specific datasets, each containing 36 distinct tools recorded under two lighting conditions—direct diffuse ring lighting and normal daylight. Furthermore, Grad-CAM heatmap analysis provides new insights into relevant classification features. Full article

Among the multiple zoomorphic and geometric images that dominate Upper Paleolithic decorated cave walls in Europe, some intriguing human hand stencils and finger flutings stand out. Dozens of these marks are attributed to toddlers and children aged 2–12. Accompanied by older group members, they entered these deep, oxygen-depleted and sensory-deprived spaces, climbing and crawling in dark, wet, difficult-to-navigate environments where one might easily get lost or separated from the group. So, why would anyone bring young children into such dangerous locations? Relevant archaeological and anthropological studies form the basis of our hypothesis that the journeys of Upper Paleolithic hunter-gatherers to the depths of deep caves along with their young children should be seen in the framework of active connection with the cosmos as practiced by many indigenous societies worldwide. Indigenous societies often view children as liminal agents with unique physical, cognitive, and mental qualities that allow them to return to the supernatural realm more easily than adults. This makes them especially adept mediators between the world of the living and that of the spirits. In this paper, we examine children’s contribution to the creation of Paleolithic cave art as active agents. Their presence in caves (liminal spaces in themselves) and their participation in the creation of rock art might thus reflect their unique role in early human cosmology and ontology. Full article

Background: Although tapered and fluted stems are frequently used in revision total hip arthroplasty (RTHA), major complications following the implantation of these implants, like periprosthetic fractures, are less investigated. As epidemiological data do not exist yet, the incidence of PPF in a mid- to long-term follow-up is unknown and potential risk factors have not been detected. Methods: Propensity score matching (PSA) of two retrospectively investigated cohorts after femoral RTHA with either modular (n = 130) or monobloc prosthesis (n = 129) was executed. A total of 186 cases, including 93 of each device, were finally analyzed during a mean follow-up period of 9.1 (0.5–23.1) years. The time-dependent risk of PPF was calculated using a Kaplan–Meier analysis. Results: The cumulative risk for PPF of the whole cohort was 5.7% (95% CI: 1.7–9.8%) at 23.1 years, for the modular device, 13.0% (95% CI: 0–26.0%) after 13.7 years and the monobloc stem, 3.4% (95% CI: 0–7.1%) after 23.1 years, without a significant difference between the two designs (log-rank p = 0.1922). All eight fractures occurred in women and there was one collapse of the fracture after open reduction and internal fixation. The cumulative risk was 10.1% (95% CI: 3.1–17.1%) at 23.1 years compared to 0% after 21.4 years in men (log-rank p = 0.0117). Diabetes was significantly associated with the presence of PPF during follow-up (non-diabetic, 4.4% (95% CI: 0–8.2%) after 21.3 years vs. diabetic, 16.6% (96% CI: 0–34.5%) after 13.3 years; log-rank p = 0.0066). Longer reconstructions showed also a significantly higher fracture risk (equal or longer than median implant length vs. shorter; 10.5% (95% CI: 3.1–17.1%) after 21.4 years vs. 1.0% (95% CI: 0–3.1%) after 23.1 years; log-rank p = 0.0276) but did not correlate with a preoperative defect situation. Conclusions: The cumulative risk for PPF after femoral revision with tapered and fluted devices is a relevant failure reason in this mid- to long-term investigation. There was no difference between the monobloc stem or modular implant. Women and diabetics are at risk, and the choice of a longer implant than necessary is neither prophylactical for PPF nor useful in the case of the operative treatment of a PPF after femoral RTHA with these revision devices. Full article

In the packaging industry, corrugated boards are widely used due to many factors like biodegradability, a high strength-to-weight ratio, and also ease of manufacturing. In this study, the finite element analysis of corrugated cardboards under the flat compression test was performed using the open source FEA software Salome-meca. A corrugated board consists of a flute sandwiched between a top and bottom liner. This study was performed with the help of Python scripting in order to iteratively perform many studies by varying the geometric shape of the flute. The pressure distribution along the top and the bottom liner was analyzed. The load–deflection curve for the corrugated cardboard was also analyzed as a part of this study. The boundary condition and the loading condition were chosen in such a way as to correctly represent the situation in real life using the flat crush test in the lab. The contact zone was identified a priori and defined during the preparation of the study. Finally, Code-Aster (the solver utilized by Salome-Meca) was used to solve the finite element solution to the problem. Full article

Background: Complications such as periprosthetic fractures necessitate challenging revision surgeries. In particular, femoral stem revisions can be complicated by poor bone quality, making primary stability and leg length restoration difficult to achieve. Modular fluted tapered stems (MFTSs) have emerged as a viable option for these complex cases. This study aims to describe a reproducible three-step technique for femoral stem revision using MFTSs. The technique focuses on (1) obtaining distal primary stability, (2) restoring leg length, and (3) ensuring overall implant stability. Materials and methods: We conducted a retrospective analysis of ten patients who underwent revision THA using this three-step technique, with a minimum follow-up of 12 months. The mean patient age was 70.7 years, and the average follow-up was 24.2 months. Limits were the small sample size, the lack of clinical outcomes and the short-term follow-up. Results: There was no subsidence, a mean leg length discrepancy of 4 mm (p: 0.604), and no dislocations. However, heterotopic ossifications (HOs) were observed in 25% of patients, although no trochanteric migrations occurred. One patient experienced an intraoperative femoral fracture, which was successfully treated. Conclusions: This three-step approach can break down the revision procedure, making it more accessible to surgeons. The findings suggest that this technique is effective in achieving reliable outcomes in femoral stem revisions, potentially improving the standard of care for patients requiring complex THA revisions. Full article

Osseodensification is an innovative surgical instrumentation technique based on additive (non-cutting) drilling using special burs. It is known from the literature, that the osseodensification burs should operate in a clockwise direction to drill holes and in a counterclockwise direction to compact the osteotomy walls. For these purposes, the burs have special design features, like conical contour shape, increased number of helical flutes, and negative rake angle on the peripheral part. However, although other parameters and features of the burs define their overall performance, they are not described sufficiently, and their influence on surgical quality is almost unknown both for clinicians and tool manufacturers. The purpose of the present research is to identify the key design features of burs for osseodensification and their functional relationship with the qualitative indices of the procedure based on an analytical review of research papers and patent documents. It will help to further improve the design of osseodensification burs and thereby enhance the surgical quality and, ultimately, patient satisfaction. Results: The most important design features and parameters of osseodensification burs are identified. Thereon, the structural model of osseodensification bur is first represented as a hypergraph. Based on the analysis of previous research, functional relationships between design parameters of osseodensification burs, osseodensification procedure conditions, and procedure performance data were established and, for the first time, described in the comprehensive form of a hypergraph. Conclusions: This study provides formal models that form the basis of database structure and its control interface, which will be used in the later developed computer-aided design module to create advanced types of burs under consideration. These models will also help to make good experimental designs used in studies aimed at improving the efficiency of the osseodensification procedure. Full article

The design of the chip flute in indexable insert drills significantly influences chip removal efficiency, drill diameter deflection, and drill deformation in the metal drilling process, which are crucial for maintaining drill stability and minimizing deviations in the diameter of the drilled hole. However, traditional chip flute designs fail to meet production standards when drilling deep holes in 42CrMo, particularly at depths reaching up to seven times the hole diameter. This study introduces an innovative optimization method for the chip flute design of indexable insert drills specifically intended for metal deep-cutting applications, which involves refining both the cross-sectional and circumferential profiles of the chip flute. A novel combined cross-section for the chip flute was developed and tested against the conventional double U-profile in drilling experiments on 42CrMo. Based on the chip shape of the inner and outer inserts, the inner insert flute section is designed into a U-shaped section and the outer insert flute section is designed into trapezoidal section, respectively, so as to increase the proportion of the effective chip removal area in the chip flute, which reduces the chip flute section area and increases the core thickness of the tool holder. Additionally, the circumferential profile was enhanced through orthogonal simulation experiments. The findings revealed that the drill diameter deflection using the newly designed combined cross-section was reduced by 21.76% compared to the traditional double U-profile in the metal drilling process. The indexable insert drill featuring this optimized chip flute configuration exhibited significant improvements in the drill diameter deflection, drill deformation, and drilled hole diameter accuracy, outperforming the standard drill design. Full article