Knurled Surface Research Articles

Roller compaction: Measuring ribbon porosity by terahertz spectroscopy and machine learning

Roller compaction is a crucial unit operation in pharmaceutical manufacturing, with its ribbon porosity widely recognised as a critical quality attribute. Terahertz spectroscopy has emerged as a fast and non-destructive technique to measure porosity in pharmaceutical products. From a sensing perspective, the irregular shape and uneven surface of fragmented ribbon pieces can affect the accuracy and precision of the measurements, particularly for techniques that probe only a small sampling volume. It is known that the porosity is not uniform within the ribbon structure, with variations expected across the width of the ribbon and in the microstructure corresponding to its surface texture. However, typical pharmaceutical analysis methods, such as envelope density, only report an average bulk porosity, are slow to operate and limited in accuracy. To address this challenge, we developed and trained convolutional neural network models using THz spectra as input to classify four types of topography typically encountered in ribbons: ridge, valley, flat plane and edge points. The classifiers achieved 91% validation accuracy in both identifying outliers and differentiating between ribbons of smooth and knurled surfaces. For the more challenging task of distinguishing between the ridges and valleys of knurled surfaces, an 81% testing accuracy was achieved. Once each measurement is paired with its topography, resolving the density distribution within the sample is possible. This data can be combined to arrive at an average bulk porosity value compatible with conventional pharmaceutical analysis.

A Study of Bacterial Flora Present on Disinfected Crash Cart Laryngoscopes

Background: Laryngoscope is an instrument to facilitate placement of endotracheal tube which finds its use both in OTs and in crash carts for emergency resuscitation of patients. The blade of the instrument comes in contact with the mucosal surface during this procedure. Yet, there is an absence of clear cut guidelines for disinfection of different parts (blade and handle) of this instrument. Materials and methods: This observational prospective study was conducted over a period of 5 months on previously used and disinfected laryngoscopes placed in the crash carts of various areas (emergency, ICUs) of our hospital. Swabs were collected from three different parts of each laryngoscope: surface of the blade (A), front part of the handle top (B), and front part of the handle's knurled surface (C). Bacterial growth and identification were noted using standard microbiological techniques. Data were entered and analyzed using standard MS Excel sheet. Results: In the study, 213 samples (71 each from A, B, C sites) were obtained from laryngoscopes from various areas of the hospital of which 32.4% were contaminated. The highest percentage of contaminated laryngoscopes belonged to Emergency department, a known high throughput area. Swabs from blades were positive in 16.9% (12/71) cases, from light in 14.08% (10/71) cases and from handle in 18.3% (13/71) cases. Among the organisms isolated, Coagulase negative Staphylococcus was the commonest (37.1%) followed by MSSA (22.9%) and MRSA (20%) from various sites of the laryngoscopes. Conclusion: A sensitization towards proper cleaning of laryngoscopes from crash carts is a must. Centralized disinfection services of all the parts of this instrument are a must for ensuring proper sterility.

Experimental study on enhanced heat transfer during rapid cooling of modified and oxidized rods

This research investigates the effects of surface modification and surface oxidation on pool boiling heat transfer performance. An experimental facility was designed and built to perform vertical quenching testings at atmospheric pressure and close to the saturation water pool. Three surface structures (smooth, threaded, and knurled) were fabricated to study the effect of surface area variation and surface oxidation on minimum film boiling temperature (Tmin). A visualization study was performed using a high-speed camera to capture the thermohydraulic behavior of the generated vapor around the heated sample. The results showed that surface features have a significant impact on the enhancement in heat transfer as the knurled surface exhibited a strong impact on increasing Tmin, quenching time, and heat transfer coefficient (HTC). The visualization study displayed different behaviors of the vapor layer breakage where the smooth and the threaded samples experienced larger bubbles and smoother movement of the quench front. Whereas smaller and intense bubbles were generated around the knurled sample at Tmin point. The successive experiments resulted in oxidation layers on the test samples, which proved that the oxidation mechanism depends on the surface finish that caused the surface to experience different heat fluxes. The comparison between the experimental results and available correlations in literature showed the importance of incorporating the surface characteristics effect in Tmin correlations due to its significant impact on pool boiling heat transfer performance.

Interference-fit joining of Cu-SS composite tubes by electromagnetic crimping for different surface profiles

This paper explores the possibility of producing an improved interference-fit tubular joint between pure copper and stainless steel tube by electromagnetic crimping (EMC). Successful joints are obtained with optimal parameters consisting of the outer surface profile of the inner tube and discharge energy. Joints exceeding the strength of the parent tube are formed without any metallic bond formation. Three destructive testings, namely, pull-out, compression and torsion tests, have confirmed the successful joint formation as the failure occurs in the copper base tube. Analysis of failure mechanisms has revealed joint behaviour at various discharge energies and surface profiles. Among smooth, knurled and threaded surface profiles with different discharge energy levels, knurled surface provides best joint strength at 6.2 kJ, which has shown a failure in the parent Cu tube during all three destructive testings. Radial deformation of the tubes is measured and compared for different discharge energy and surface profile. No metallic bond formation and the wavy interface are observed between the joining partners during microstructural analysis. Furthermore, no elemental overlapping is observed during energy dispersive spectroscopy mapping analysis indicating an absence of diffusion. Higher micro-hardness is observed near the Cu-SS tubular joint interface due to strain hardening caused by high-velocity impact.

A Study on Types of Lathe Machine and Operations: Review

In this paper, the review of this paper pertaining to the present research topic has been carried out to gain knowledge and to become familiar with the established techniques and methodology. Types of Lathe Machine and its Operations is a term that covers a large collection of manufacturing processes designed to remove unwanted material, usually in the form of chips, from a work-piece by different types of lathe machines. It also covers action of individual lathe. Machining is used to convert castings, forgings, or preformed blocks of metal into desired shapes, with size and finish specified to fulfil design requirements. Almost every manufactured product has components that require machining. The basic lathe that was designed to cut cylindrical metal stock has been developed further to produce screw threads, tapered work, drilled holes, knurled surfaces and crankshafts. The typical lathe provides a variety of rotating speeds and a means to manually and automatically move the cutting tool into the workpiece. Machinists and maintenance shop personnel must be thoroughly familiar with the lathe and its operations to accomplish the repair and fabrication of needed parts.

Experimental study on single phase operation of microjet augmented heat exchanger with enhanced heat transfer surface

The article presents experimental investigations on a prototype heat exchanger. Presented research is focused on combined active and passive enhancement techniques of surface modification and microjet impingement. The results were compared to reference plate heat exchanger without microjet impingement.The Wilson plot method was applied to determine the heat transfer coefficients in the single phase operation. The heat exchanger was capable of exchanging 300 W of thermal energy at LMTD of 40 K. The obtained overall heat transfer rates reach 600 W/m2.Introducing knurled surface resulted in ∼10% increase heat transfer area, and similar enhancement in transferred heat in reference to plate heat exchanger geometry. Knurled surface decreased heat transfer in combination with a multi-jet impingement in comparison to a smooth surface. A possible explanation of that effect is that the flow in wall jet region is disrupted by the knurled surface and directed in the bulk of the fluid. Initiating mixing with colder fluid, thicker thermal boundary layer, and affecting local temperature distribution.

Effects of micro-knurling and femtosecond laser micro texturing on aluminum long-term surface wettability

A comparison of the long-term evolution of a femtosecond laser and the mechanical knurling texturing of aluminum surfaces is performed. Both the femtosecond laser and knurling textured surfaces present similar topographical parameters in the micrometer range. To compare both texturing approaches, long-term physico-chemical characterizations are performed. These characterizations consist of wettability measurements and XPS analyses as a function of time following the texturing operations. The evolution of the wetting properties over time for the femtosecond laser textured surface is explained through chemical modifications of the extreme surface. High-resolution XPS spectra highlight a C-C/C-O bond ratio evolution over time. This time evolution of the chemical bonds of the extreme surface is corroborated with the static contact angle evolution. On the contrary, the mechanically knurled surfaces present a steady state after texturing: neither the evolution of the wetting properties nor the chemical composition of the extreme surface is measured.

Effect of Knurled Fin Surface on Thermal Performance of Perforated Fin Heat Sink

Fabricating perforations in fins causes improvement in heat dissipation rate with lower pressure drag up to a specific perforation number and size of perforation. Again knurled surfaces augment heat transfer rate due to turbulence promotion as well as substantial increase in surface area. The present work investigates thermal performance of heat sink using perforated pin fins with different knurled surfaces. Three-dimensional computational fluid dynamics simulations have been performed to explore the effects of various different knurling geometries on fin surface, perforation number, and size on system performance. A multicriteria decision-making optimization method such as Multi-Objective Optimization under Ratio Analysis (MOORA) has been applied to select the best heat sink configuration. It has been observed that the rate of heat transfer for perforated fins up to a particular perforated area is always greater than the solid fins, and with the variation in knurling geometry on fin surface, heat dissipation rate enhances significantly. Conversely, pressure drop around heat sink decreases with the increment of number and size of perforations. However, due to knurling on fin surface, pressure drop increases. Finally, exergy analysis has also been carried out to calculate second law efficiencies of circular perforated fins using different knurling patterns with increasing number of knurling teeth.

Bacterial Contamination and Disinfection Status of Laryngoscopes Stored in Emergency Crash Carts

ObjectivesTo identify bacterial contamination rates of laryngoscope blades and handles stored in emergency crash carts by hospital and area according to the frequency of intubation attempts.MethodsOne hundred forty-eight handles and 71 blades deemed ready for patient use from two tertiary hospitals were sampled with sterile swabs using a standardized rolling technique. Samples were considered negative (not contaminated) if no colonies were present on the blood agar plate after an 18-hour incubation period. Samples were stratified by hospital and according to the frequency of intubation attempts (10 attempts per year) using the χ2-test and Fisher exact test.ResultsOne or more species of bacteria were isolated from 4 (5.6%) handle tops, 20 (28.2%) handles with knurled surfaces, and 27 (18.2%) blades. No significant differences were found in microbial contamination levels on the handle tops and blades between the two hospitals and two areas according to the frequency of intubation attempts. However, significant differences were found between the two hospitals and two areas in the level of microbial contamination on the handles with knurled surfaces (p<0.05).ConclusionsProtocols and policies must be reviewed to standardize procedures to clean and disinfect laryngoscope blades and handles; handles should be re-designed to eliminate points of contact with the blade; and single-use, one-piece laryngoscopes should be introduced.

Influence of metallic substrate surface engineering on peel resistance of adhesively bonded polymer film

The peel resistance of adhesively bonded polymer films to a stainless steel sheet substrate (SSSS) with different engineered surface characteristics was examined in two different loading directions and for two different peel speeds. The SSSS was laminated with two thin polymeric adherends using two different pressure-sensitive adhesives. The SSSS surface was altered by grinding and knurling techniques before lamination and the effects of surface alterations on peel resistance were compared with peel resistance of the adherend from as-received SSSS with a bright annealed surface condition. For ground surface, an increase in adherend peel resistance was observed and the increase was attributed to increase in contact area between the adhesive and SSSS surface. For knurled surfaces which involved deeper and less frequent grooves, however, a decrease in peel resistance was observed. This was attributed to a more complex stress state at the peel front in the SSSS groove region during peeling. An increase in peel speed enhanced the peel resistance from both ground and knurled surfaces.

Mechanical fastening of carbon composite tubes, numerical calculation of axial loading capacity and experimental verification

This contribution improves the mechanical fastening technology for a CFRP-tube with a rough surface texture (knurled surface [11]) in the contact area. Numerical analysis (extended by Puck’s fracture condition) and experimental analysis are used in this paper to investigate which knurled geometry has the best rate of fiber failure, and also the inter fiber failure in relation to the increased friction force of the mechanical joint. In contrast to the position generally held in the literature it is possible to achieve high loading capacity, even if the laminate is damaged partly and locally by the joining technology, as shown by the following analysis with conclusions. Furthermore, it gives the opportunity to integrate a ductile behavior in the material structure. Overall, this leads to new ways of designing components with CFRP.

Effect of tool geometry on ultrasonic welding process

Ultrasonic welding of pure aluminum sheets is performed using two weld tools, one with a knurled surface and one with a cylindrical surface. Relative motion behaviors of each weld tool, with respect to the working materials, during ultrasonic welding tests are analyzed using the digital correlation method. Weld microstructure development is investigated on the basis of transitional weld stages in the context of relative motion behaviors. The dominant relative motion is between the two work materials at the beginning of the weld but changes to be the motion between the weld tool and the work material it is in contact with as weld time increases. Thermo-mechanical effects of the relative motion of the weld tool and the work materials, on the development of weld microstructure, are discussed.

Experimental investigation on anti-gravity loop heat pipe based on bubbling mode

Traditional loop heat pipes (LHPs) have disadvantages including high operating temperature, large heat resistance and low heat transfer efficiency under anti-gravity condition. An anti-gravity loop heat pipe (AG-LHP), in which a bubbler is added between the condenser and the compensation chamber (CC), is studied and analyzed in this paper. The bubbler is designed to enforce circumfluence of the working fluid. Integral outside fins (IOF) are used as inner cylinder surface structure of the bubbler. Bubbling experiment was conducted to evaluate the performance of the bubbler with IOF surface structure, compared with those with smooth and knurled surface structures. The infrared ray (IR) thermal imaging method was used to investigate the working process of the bubbler. Furthermore, start-up experiment was carried out to investigate the start-up phenomenon and the performance at steady state of the AG-LHP. The results of the bubbling experiment under different heating power showed that the bubbler with IOF inner cylinder surface structure had the highest bubbling height and the shortest steady time, which demonstrated that the IOF surface structure effectively improved the thermal and steady performance of the bubbler. The start-up experiment confirmed that the AG-LHP could achieve steady state in 20min and could easily adapt to different heating loads under anti-gravity condition. The thermal resistance of the AG-LHP can approach to a value as high as 150W/K with the heating load of 80W.

Contamination of laryngoscope handles

Despite use of sterile or disposable laryngoscope blades for each patient, disinfection of laryngoscope handles does not routinely occur, and these devices present a potential route of transmission of pathogens between patients and staff. A total of 192 specimens from 64 laryngoscope handles deemed 'ready for patient use' in the anaesthetic rooms of 32 operating theatres were semiquantitatively assessed for bacterial contamination. A further 116 specimens from 58 of the handles were tested for occult blood contamination. One or more species of bacteria were isolated from 55 (86%) of the handles, and included organisms such as enterococci, meticillin-susceptible Staphylococcus aureus, Klebsiella and acinetobacter. Cultures did not yield any anaerobes, fungi, meticillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci or multiply-resistant Gram-negative bacilli. No occult blood contamination was demonstrated. Although the majority of organisms isolated were not pathogenic, their presence indicates the potential for transmission of pathogens from laryngoscope handles. Strategies to address contamination of handles include revision of procedures for disinfection and storage prior to use, introduction of disposable handles or sheaths, and re-design of handles to eliminate knurled surfaces and contact points.

An experimental study of sound generated by flows around cylinders of different cross-section

The sound radiated by rigid cylinders placed transversely in a uniform stream has been measured in an anechoic wind tunnel over a range of Mach numbers ( M = 0.09 – 0.2 ). The cylinders have different cross-sections, e.g., circular, square, rectangular, elliptic, and circular with lateral ribs or knurled surfaces. Different length to diameter ratios of the cylinders are also investigated. Results are presented as narrow band spectra, measured in the far field (acoustic as well as geometric). All spectra are presented with dimensionless (scaled) axes, as well as the original dimensional scales. It is shown that elliptic cross-sections are less noisy, compared to all other cylinders, but noise abatement techniques such as lateral ribs and knurled surfaces can also reduce tonal radiated noise. Two practical applications of these experiments are the reduction of radiated noise from pantographs of high-speed railway trains, and from the landing gear of modern passenger aircraft.

Strength and Fatigue Resistance of Thoracolumbar Spine Implants

Results of strength and endurance tests of several screw/rod thoracolumbar spinal implants are presented. The devices tested were: AcroMed ISOLA, CD systems, Depuy systems, and Synergy systems. The AcroMed ISOLA devices had the greatest stiffness and strength. The Synergy and AcroMed systems had the greatest fatigue resistance. The predominant failure mode was screw bending, although several instances of rod fracture and screw fracture were observed. A number of design improvements are identified, including reducing the number of components, thereby reducing the number of failure mechanisms; avoiding notches and knurled surfaces to provide greater resistance to crack initiation; and strengthening attachments between components, particularly between pedicle screws and horizontal rods.

Noise and vibration dampening connector to a two piece transmission shift lever assembly

A noise and vibration dampening connector for a two-piece transmission shift lever assembly includes a lower shift lever member and an upper shift lever member which are connected together by the dampening connector. The upper end of the lower shift lever member is cylindrical in shape, having a flat formed thereon. The lower end of the upper shift lever member has a cylindrical knurled surface. The dampening connector includes a hollow cylindrical sleeve having an axial bore formed therethrough. The axial bore is stepped so as to form an internal shoulder which divides the sleeve into an upper portion and a lower portion. The upper portion of the sleeve has a relatively large internal diameter and a relatively thin wall thickness, while the lower portion of the sleeve has a relatively small internal diameter and a relatively thick wall thickness. A welch plug is seated on the internal shoulder, and a cup-shaped rubber isolator is seated on the welch plug. The lower end of the upper shift lever member extends into the rubber isolator and is secured to the sleeve by crimping the wall of the upper portion thereagainst. A threaded aperture is formed through the wall of the lower portion of the sleeve, and a set screw is partially threaded therein. The upper end of the lower shift lever member extends within lower portion of the sleeve such that the flat formed thereon is aligned with the partially threaded set screw. Then, the set screw is further threaded within the wall of the lower portion of the sleeve so as to extend into a recess formed in the flat to secure the upper end of the lower shift lever member to the sleeve.

Experimental investigation of heat transfer in a horizontal tube falling film absorber with aqueous solutions of LiBr with and without surfactants

To learn about the physical background of the absorption process, the accompanying heat transfer was studied experimentally. A horizontal tube heat exchanger, similar to commercial absorbers, was built. Two different types of tubes were tested, one with a plain, the other with a knurled surface. The solution volume flow, the temperatures of the cooling water and of the solution, and the concentration of the solution were varied to search for correlations of the heat-transfer coefficient with the physical properties of the solution. The heat-transfer coefficients decrease with increasing viscosity and augmenting surface tension. They also depend on the fluid regime of the solution film, i.e. they increase with growing solution volume flow. The influence of two surfactants — 1-octanol and 2-ethyl-1-hexanol in various concentrations — on the absorption process was examined quantitatively. An increase of 60–140% was measured for the heat-transfer coe coefficients.

Effect of Surface Geometry on Steam Absorption into Falling Film of Aqueous Solution of LiBr.

Absorption chillers are becoming attractive since they do not use Freon gases which destroy ozone layer, and can be driven by heat. Improvement of the absorber is necessary to make absorption chillers compact. In this paper, heat transfer surfaces which show maximum absorption performance are sought. Grooved pipes are known to be effective for promoting gas absorption into falling water. They are tested for water vapor absorption with four different groove depths as well as two different knurled surfaces. The pipe with the deepest groove shows enhancement of about 1.5-1.9 in the Reynolds number range of 200-500. The knurled surfaces are not effective for the absorption, but they have better wettability at a lower flow rate and furthermore for higher knurl height, absorption increases at larger flow rate. Film thickness is measured by the contact probe method. The average film thickness curve has large undulation for deeper grooves but it is flat for the shallow grooves.

The production of permanent joints by plastic flow

This paper presents the results of a series of tests involving the production of permanent joints between two metallic components. This was achieved by forging discs of aluminium onto shafts of copper, mild steel, alloy steel and titanium onto which grooves of various geometries had been machined. The groove geometries used included, square and triangular sectioned grooves, a helical screw thread and a knurled surface used in conjunction with the square and triangular shaped grooves. The influence of groove geometry on the degree of metal flow, or “fill-out” into the grooves and the resulting joint strength under both axial and torsional loading was assessed for a range of applied forging loads. The relationship between the relative hardness of the disc and shaft material on the integrity of the joints formed was also investigated. The results obtained indicated that this plastic flow technique can be used to produce high strength permanent joints using relatively unsophisticated tooling. In addition the process lends itself to automation and could provide an inexpensive method of producing sound permanent joints.