Structural Health Monitoring of Adhesively Bonded Pipe-to-Socket Joints by Integration of Polymer Optical Fibers and Their Load-Dependent Transmission Properties.

Adhesively bonded pipe-to-socket joints are used in numerous industrial applications. One example is in the transport of media, e.g., in the gas industry or in structural joints for such sectors as construction, wind energy, and the vehicle industry. To monitor such load-transmitting bonded joints, this study investigates a method based on the integration of polymer optical fibers into the adhesive layer. Previous methods for monitoring the condition of pipes, such as acoustic or ultrasonic methods or the use of glass fiber optic-based sensors (FBG or OTDR), are very complex in methodology and require cost-intensive (opto-) electronic devices to generate and evaluate the sensor signals; they are therefore unsuitable for large-scale use. The method investigated in this paper is based on the measurement of integral optical transmission with a simple photodiode under increasing mechanical stress. When tried at coupon level (single-lap joint), the light coupling was varied to obtain a significant load-dependent sensor signal. Based on an angle-selective coupling of 30° to the fiber axis, a drop of 4% of the optically transmitted light power by a load of 8 N/mm2 can be detected for the adhesively bonded pipe-to-socket joint with the structural adhesive Scotch Weld DP810 (2C acrylate).

Enhanced osteogenic differentiation of human mesenchymal stromal cells as response to periodical microstructured Ti6Al4V surfaces.

Titanium-based alloys, for example, Ti6Al4V, are frequently employed for load-bearing orthopedic and dental implants. Growth of new bone tissue and therefore osseointegration can be promoted by the implant's microtopography, which can lead to improved long-term stability of the implant. This study investigates the effect that an organized, periodical microstructure produced by an electron beam (EB) technique has on the viability, morphology, and osteogenic differentiation capacity of human mesenchymal stromal cells (hMSC) in vitro. The technique generates topographical features of 20 µm in height with varying distances of 80-240 µm. Applied alterations of the surface roughness and local alloy composition do not impair hMSC viability (>94%) or proliferation. A favorable growth of hMSC onto the structure peaks and well-defined focal adhesions of the analyzed cells to the electron beam microstructured surfaces is verified. The morphological adaptation of hMSC to the underlying topography is detected using a three-dimensional (3D) visualization. In addition to the morphological changes, an increase in the expression of osteogenic markers such as osteocalcin (up to 17-fold) and osteoprotegerin (up to sixfold) is observed. Taken together, these results imply that the proposed periodical microstucturing method could potentially accelerate and enhance osseointegration of titanium-based bone implants.

Frequency dependence of nonlinear absorption in fused silica measured with picosecond pulses at various focal lengths.

Nonlinear absorption is the key process to generate laser-induced in-volume modifications in transparent dielectrics such as waveguides or three-dimensional data matrix codes. We present a comprehensive parameter study about nonlinear absorption in fused silica using a picosecond laser at various focal lengths. Beginning at a focal length of 100 mm, we measure a strong frequency dependence of the saturation absorption. Reducing the focal length results in a decrease of the saturation absorption. After passing a threshold focal length, the saturation absorption increases drastically and the frequency dependence starts to decrease. At the final focal length of 6 mm we measure almost no frequency dependence. In order to explain our measurements, we used the theory of optical breakdown and filamentation. Nonlinear absorption measurement can become a promising tool for better process control during the generation of in-volume modifications in transparent dielectrics.

Transparent high-pressure nozzles for visualization of nozzle internal and external flow phenomena.

A new design for transparent high-pressure nozzles is presented in this work. This new design enables using the innovative Selective Laser Etching (SLE) method to manufacture transparent nozzles with outstanding accuracy. Therefore, not only the simultaneous visualization of the flow mechanics inside and outside the nozzle is enabled, but the manufacturing method applied also allows for the realization of individual nozzle geometries. Thus, nozzle internal flow phenomena (e.g., cavitation, swirl, and air inlet) and their influence on primary breakup can be analyzed with realistic nozzle geometries, e.g., for automotive applications. In addition, targeted three dimensional nozzle geometric parameters can be designed and manufactured in order to get specific tailor-made spray characteristics (e.g., droplet size distribution, spray angle, and penetration length). The basis for the transparent nozzle design is a two-parted nozzle, consisting of a re-machined original serial nozzle body and a transparent nozzle tip. The innovative SLE is used to produce the geometry of the transparent nozzle tip in fused silica, and laser polishing is utilized to achieve a maximum optical quality of nozzle surfaces for visualization. Bonding of both nozzle parts is achieved by a specially designed adhesive method. For a first feasibility study, a transparent nozzle with a simplified nozzle geometry is manufactured and used for a first study. In this study, simultaneous investigation of nozzle internal flow phenomena and their impact on spray breakup are visualized. First microscopic images of the nozzle internal flow show the formation of cavitation, its effect on nozzle internal temperature (apparent by differences in the fluid refractive index), and also the corresponding impact on spray breakup during injection. The penetration of ambient gas into the nozzle is verified at the end of injection as well as the influence of this air on the spray formation during the start of injection.

[Bone Cement Adhesion on Ceramic Surfaces - Deactivation of Surfaces and as a Consequence Inefficient Retention of Knee Prostheses Because of Adsorption of Atmospheric Water]. / Haftung von Knochenzement auf keramischen Oberflächen ­ Deaktivierung der Oberfläche als wirksame Retentionsfläche für Knieendoprothesen durch die Adsorption von atmosphärischem Wasser.

AIM: CoCrMo alloys are contraindicated for sufferers from allergy. For these patients, uncemented and cemented prostheses made of non-allergenic titanium alloy are indicated. Knee prostheses machined from that alloy, however, may have poor tribological behaviour, especially in contact to UHMWPE inlays. Therefore, high-strength oxide ceramics may be especially suitable for knee replacement in allergy patients with mobile bearing prostheses. For adhesion to bone cement, the ceramic surface only exhibits mechanical retention spots that are less adequate than those with a textured metal surface. Generating undercuts by corundum blasting is highly efficient for mechanical adhesion to a CoCrMo surface, but is not possible on a ceramic surface, due to the brittleness of ceramics. Lack of retention of bone cement promotes micromotions of the prostheses. As a consequence of micromotions, early aseptic loosening is predictable. Silicoating (silicate and silane layering) of the ceramic surface would allow specific adhesion and hence would result in increased and hydrolytically more stable bonding between the bone cement and the prosthesis surface - thereby preventing early aseptic loosening. Silicoating, however, presupposes a chemically active surface that is not blocked by a layer of chemisorbed molecules, e.g. water. Desorption of this chemisorbed layer is mandatory and can be attained by baking out the surface. METHOD: In order to evaluate the effectiveness of surface activation via thermal treatment by baking out, with subsequent silicoating of the surface, the bond strengths of thermally treated and silicate layered ZPTA samples were compared with thermally treated surfaces that had not been silicoated. In our study of thermal surface treatment for baking out the surface, we focused on the question of whether there is a minimal "critical" temperature Ts for effective desorption of a chemisorbed water layer. The samples were prepared for the traction-adhesive strength test (sequence: ceramic disc, silicate and silane layering, protective lacquer ("PolyMA" layer), bone cement, TiAlV probes for the traction-adhesive strength test) and their traction-adhesive strengths were then measured. RESULTS: The bond strength was measured as a function of temperature for ceramic discs that had been baked out and subsequently silicoated. This was graduated, exhibits with a pronounced increase in the bond strength at a baking temperature of Ts ≈ 350 °C. The observed bond strengths before the step are ≤ 20 MPa and after the step ≥ 30 MPa. CONCLUSION: Silicoating is effective in achieving high bond strength of bone cement on surfaces of oxide ceramics and can also stabilise the long term behaviour of the bond strength, provided the surface has been thermally treated prior to silicoating. Because of the proposed migration of the silicoating layer, micromotions and debonding should be widely reduced or even eliminated.

Assessment of the Biological Effects of Welding Fumes Emitted From Metal Active Gas and Manual Metal Arc Welding in Humans.

OBJECTIVE: Emissions from a particular welding process, metal inert gas brazing of zinc-coated steel, induce an increase in C-reactive protein. In this study, it was investigated whether inflammatory effects could also be observed for other welding procedures. METHODS: Twelve male subjects were separately exposed to (1) manual metal arc welding fumes, (2) filtered air, and (3) metal active gas welding fumes for 6 hours. Inflammatory markers were measured in serum before, and directly, 1 and 7 days after exposure. RESULTS: Although C-reactive protein concentrations remained unchanged, neutrophil concentrations increased directly after exposure to manual metal arc welding fumes, and endothelin-1 concentrations increased directly and 24 hours after exposure. After exposure to metal active gas and filtered air, endothelin-1 concentrations decreased. CONCLUSIONS: The increase in the concentrations of neutrophils and endothelin-1 may characterize a subclinical inflammatory reaction, whereas the decrease of endothelin-1 may indicate stress reduction.

Adhesion of human mesenchymal stem cells can be controlled by electron beam-microstructured titanium alloy surfaces during osteogenic differentiation.

Several studies focusing on bone tissue engineering demonstrated that given microstructuring of an implant surface has a strong effect on its interaction with cells, and their adhesion and differentiation. In the present study, geometrically structured titanium alloy surfaces are shown to be able to guide cell adhesion during differentiation in vitro. For this reason, using an electron beam texturing technique, TiAl6V4 surfaces were selectively targeted in the micrometer range. The effect of such textured titanium alloy surfaces on cell adhesion during osteogenic differentiation was analyzed for human mesenchymal stem cells (MSC), the natural precursor cells of bone tissue. Cytotoxicity, cell viability and differentiation were analyzed. Immunofluorescence stainings demonstrated that in contrast to MSC in an expansion medium, MSC in an osteogenic induction medium produce adhesion proteins such as ß3-integrins and thereby connect in an oriented way to the generated microstructures on titanium alloy surfaces. These results are of relevance for developing tailored titanium alloy implant surfaces which exhibit an improved cell response.

Human biomonitoring of aluminium after a single, controlled manual metal arc inert gas welding process of an aluminium-containing worksheet in nonwelders.

PURPOSE: Several existing field studies evaluate aluminium welding works but no thoroughly controlled exposure scenario for welding fume has been described yet. This study provides information about the uptake and elimination of aluminium from welding fumes under controlled conditions. METHODS: In the Aachen Workplace Simulation Laboratory, we are able to generate welding fumes of a defined particle mass concentration. We exposed 12, until then occupationally unexposed participants with aluminium-containing welding fumes of a metal inert gas (MIG) welding process of a total dust mass concentration of 2.5 mg/m(3) for 6 h. Room air filter samples were collected, and the aluminium concentration in air derived. Urine and plasma samples were collected directly before and after the 6-h lasting exposure, as well as after 1 and 7 days. Human biomonitoring methods were used to determine the aluminium content of the samples with high-resolution continuum source atomic absorption spectrometry. RESULTS: Urinary aluminium concentrations showed significant changes after exposure compared to preexposure levels (mean t(1) (0 h) 13.5 µg/L; mean t(2) (6 h) 23.5 µg/L). Plasma results showed the same pattern but pre-post comparison did not reach significance. CONCLUSIONS: We were able to detect a significant increase of the internal aluminium burden of a single MIG aluminium welding process in urine, while plasma failed significance. Biphasic elimination kinetic can be observed. The German BAT of 60 µg/g creatinine was not exceeded, and urinary aluminium returned nearly to baseline concentrations after 7 days.

Human biomonitoring of chromium and nickel from an experimental exposure to manual metal arc welding fumes of low and high alloyed steel.

OBJECTIVES: The uptake and elimination of metals from welding fumes is currently not fully understood. In the Aachen Workplace Simulation Laboratory (AWSL) it is possible to investigate the impact of welding fumes on human subjects under controlled exposure conditions. In this study, the uptake and elimination of chromium or chromium (VI) respectively as well as nickel was studied in subjects after exposure to the emissions of a manual metal arc welding process using low or high alloyed steel. METHODS: In this present study 12 healthy male non-smokers, who never worked as welders before, were exposed for 6h to welding fumes of a manual metal arc welding process. In a three-fold crossover study design, subjects were exposed in randomized order to either clean air, emissions from welding low alloyed steel, and emissions from welding high alloyed steel. Particle mass concentration of the exposure aerosol was 2.5mg m(-3). The content of chromium and nickel in the air was determined by analysing air filter samples on a high emission scenario. Urine analysis for chromium and nickel was performed before and after exposure using methods of human biomonitoring. RESULTS: There were significantly elevated chromium levels after exposure to welding fumes from high alloyed steel compared to urinary chromium levels before exposure to high alloyed welding fumes, as well as compared to the other exposure scenarios. The mean values increased from 0.27 µg l(-1) to 18.62 µg l(-1). The results were in good agreement with already existing correlations between external and internal exposure (German exposure equivalent for carcinogenic working materials EKA). The variability of urinary chromium levels was high. For urinary nickel no significant changes could be detected at all. CONCLUSIONS: Six-hour exposure to 2.5mg m(-3) high alloyed manual metal arc welding fumes lead to elevated urinary chromium levels far higher (7.11-34.16 µg l(-1)) than the German biological exposure reference value (BAR) of 0.6 µg l(-1) directly after exposure. On the other hand mean urinary nickel concentrations slightly increased, but did not exceed background levels due to lower bioavailability. We could underline with our single exposure experiment that a welding work related chromium exposure can be measured immediately after the work shift, while the same is not possible for nickel exposure due to lower nickel bioavailability. The data provide useful information for real occupational welding work places.

Biological effects of emissions from resistance spot welding of zinc-coated material after controlled exposure of healthy human subjects.

OBJECTIVE: Do emissions from a resistance spot welding process of zinc-coated materials induce systemic inflammation in healthy subjects after exposure for 6 hours? METHODS: Twelve healthy male subjects were exposed once for 6 hours either to filtered ambient air or to welding fume from resistance spot welding of zinc-coated material (mass concentration approximately 100 µg m). Biological effects were measured before, after, and 24 hours after exposure. RESULTS: At the concentrations used in this study, however, the suspected properties of ultrafine particles did not lead to systemic inflammation as reflected by high-sensitivity C-reactive protein or other endpoint parameters under consideration. CONCLUSIONS: Ultrafine particles from a resistance spot welding process of zinc-covered materials with a number concentration of about 10 cm and a mass concentration of about 100 µg m did not induce systemic inflammation.

Relationship between welding fume concentration and systemic inflammation after controlled exposure of human subjects with welding fumes from metal inert gas brazing of zinc-coated materials.

OBJECTIVES: It has been shown that exposure of subjects to emissions from a metal inert gas (MIG) brazing process of zinc-coated material led to an increase of high-sensitivity C-reactive protein (hsCRP) in the blood. In this study, the no-observed-effect level (NOEL) for such emissions was assessed. METHODS: Twelve healthy subjects were exposed for 6 hours to different concentrations of MIG brazing fumes under controlled conditions. High-sensitivity C-reactive protein was measured in the blood. RESULTS: For welding fumes containing 1.20 and 1.50 mg m zinc, high-sensitivity C-reactive protein was increased the day after exposure. For 0.90 mg m zinc, no increase was detected. CONCLUSIONS: These data indicate that the no-observed-effect level for emissions from a MIG brazing process of zinc-coated material in respect to systemic inflammation is found for welding fumes with zinc concentrations between 0.90 and 1.20 mg m.

Experimental exposure of healthy subjects with emissions from a gas metal arc welding process--part II: biomonitoring of chromium and nickel.

OBJECTIVES: The objective of this study was to investigate whether there is a relationship between the external exposure dose of chromium and nickel caused by a metal active gas welding process with a solid high-alloyed steel welding wire and inner exposure of subjects. In order to perform welding fume exposure under controlled and standardized conditions, the investigations were conducted in the "Aachen Workplace Simulation Laboratory". METHODS: To perform biological monitoring of chromium and nickel, blood and urine samples of 12 healthy male non-smokers who never worked as welders were collected before and after a 6-h exposure to ambient air (0 mg/m(3)) and to welding fumes of a metal active gas welding process once with a concentration of the welding fume of 1 mg/m(3) and once with a concentration of 2.5 mg/m(3). RESULTS: Although the internal exposure to chromium and nickel in this study was comparatively low, the subjects showed significantly increased concentrations of these metals in urine after exposure to welding fume compared to the values at baseline. Moreover, the observed increase was significantly dose dependent for both of the substances. CONCLUSION: For the biological monitoring of chromium and nickel in urine of subjects exposed to welding fumes, a dependency on exposure dose was seen under standardized conditions after a single exposure over a period of 6 h. Thus, this study contributes to a better understanding of the relationship between ambient and biological exposures from welding fumes and provides a good basis for evaluating future biological threshold values for these metals in welding occupation.

Number size distribution of fine and ultrafine fume particles from various welding processes.

Studies in the field of environmental epidemiology indicate that for the adverse effect of inhaled particles not only particle mass is crucial but also particle size is. Ultrafine particles with diameters below 100 nm are of special interest since these particles have high surface area to mass ratio and have properties which differ from those of larger particles. In this paper, particle size distributions of various welding and joining techniques were measured close to the welding process using a fast mobility particle sizer (FMPS). It turned out that welding processes with high mass emission rates (manual metal arc welding, metal active gas welding, metal inert gas welding, metal inert gas soldering, and laser welding) show mainly agglomerated particles with diameters above 100 nm and only few particles in the size range below 50 nm (10 to 15%). Welding processes with low mass emission rates (tungsten inert gas welding and resistance spot welding) emit predominantly ultrafine particles with diameters well below 100 nm. This finding can be explained by considerably faster agglomeration processes in welding processes with high mass emission rates. Although mass emission is low for tungsten inert gas welding and resistance spot welding, due to the low particle size of the fume, these processes cannot be labeled as toxicologically irrelevant and should be further investigated.

Biological effect markers in exhaled breath condensate and biomonitoring in welders: impact of smoking and protection equipment.

PURPOSE: The objective of this study was to investigate the effect of welding as well as the impact of smoking and protection measures on biological effect markers in exhaled breath condensate. Additionally, biomonitoring of chromium, aluminium and nickel in urine was performed to quantify internal exposure. METHODS: Exhaled breath condensate (EBC) and urine samples of 45 male welders and 24 male non-exposed control subjects were collected on Friday pre-shift and after 8 h of work post-shift. In EBC, biological effect markers such as malondialdehyde, nitrite, nitrate, 3-nitrotyrosine, tyrosine, hydroxyproline, proline, H(2)O(2) and pH-value were measured while aluminium, nickel, and chromium were measured in the urine samples. RESULTS: Although internal exposure to aluminium, nickel and chromium in this study was low, welders showed significantly increased concentrations of all these parameters at baseline compared to non-exposed controls. Moreover, welders had higher nitrate concentrations in EBC at baseline and after shift. Nitrate concentration was considerably lower after shift if personal protection equipment was used. H(2)O(2) was increased only when subjects smoked during shift. CONCLUSION: It has been shown that welding-associated long-term and short-term health effects could be detected in a population of welders. The results also showed that using personal protection equipment is of high importance and H(2)O(2) may be an effect marker associated with smoking rather than with welding fumes, while nitrate in EBC seems to be sensitive to welding fume exposure.

Spirometry, impulse oscillometry and capnovolumetry in welders and healthy male subjects.

BACKGROUND: Welding processes emit fine and ultrafine aerosol particles which are potentially harmful to the lungs of welders. In the past, changes in lung function were mostly determined by conventional spirometry. In this study spirometry was combined with new techniques such as Impulse Oscillometry (IOS) and Capnovolumetry (CVS) in order to assess welding associated changes in lung function. METHODS: 45 Male welders and 24 non-welders were investigated at two time points: before work shift (baseline) and after work shift. RESULTS: At baseline there were no differences between both study populations in spirometric, IOS, and CVS parameters. However, parameters of the flow-volume curve decreased with increasing long-term welding fume exposure (welding years). Airway resistances measured by IOS increased with welding years. IOS central airway resistance and several parameters of CVS increased during the work shift indicating airway narrowing and more inhomogeneous ventilation. CONCLUSIONS: In this study it has been shown that welding associated long-term and short-term effects could be detected in a population of welders, although exposure conditions were quite heterogeneous. The parameters of IOS and Capnovolumetry showed effects even more pronounced than conventional lung function parameters. Thus, these techniques may be considered as an additional tool for occupational medicine research.