Quantification of banding on printed corrugated board using spatial frequency analysis

An accurate determination of the contact pressure and local sliding in a cold rolling process is an essential step towards the prediction of the roller’s life due to wear damage. This investigation utilized finite element analysis to quantify the local contact pressure and local sliding over the rolling bite in a plate cold rolling process. It was the first study to quantify the local sliding distance in a rolling process using the Finite Element Analysis (FEA). The numerical results indicate that the local contact pressure over the rolling bite demonstrates a hill profile, and the peak coincides with the neutral plane. The local sliding distance over the rolling bite demonstrates a double-peak profile with the two peaks appearing at the forward slip and backward slip zones respectively. The amplitude of sliding distance in the backward slip zone is larger than that in the forward slip zone. A stick zone was confirmed between the forward slip and backward slip zones. According to a parametric study, the local contact pressure and sliding distance decrease when the thickness reduction is reduced or the diameter of the roller is decreased. The location of the neutral plane always presents at the rolling exit side of the rolling bite’s center. The size of the stick zone enlarges and the sizes of slip zones shrink significantly when the friction coefficient is increased. Finally, a novel concept of wear intensity was defined to examine the wear of the roller based on the local contact pressure and local sliding distance. The results show that a two-peak wear response exists in the backward and forward slip zones. The magnitude of the wear in the backward slip zone is larger than that in the forward slip zone. For a given roller and blank material combination, using a smaller thickness reduction, a smaller diameter roller and a higher friction coefficient condition can reduce the wear of the roller for a single rolling cycle. The current paper develops an understanding of rolling contact responses to the wear of the roller in rolling process. The research method can also be applied to study other rolling or sliding wear problems.

Cartilage is responsive to the loading imposed during cyclic routine activities. However, the local relation between cartilage in terms of thickness distribution and biochemical composition and the local contact pressure during walking has not been established. The objective of this study was to evaluate the relation between cartilage thickness, proteoglycan and collagen concentration in the knee joint and knee loading in terms of contact forces and pressure during walking. 3D gait analysis and MRI (3D-FSE, T1ρ relaxation time and T2 relaxation time sequence) of fifteen healthy subjects were acquired. Experimental gait data was processed using musculoskeletal modeling to calculate the contact forces, impulses and pressure distribution in the tibiofemoral joint. Correlates to local cartilage thickness and mean T1ρ and T2 relaxation times of the weight-bearing area of the femoral condyles were examined. Local thickness was significantly correlated with local pressure: medial thickness was correlated with medial condyle contact pressure and contact force, and lateral condyle thickness was correlated with lateral condyle contact pressure and contact force during stance. Furthermore, average T1ρ and T2 relaxation time correlated significantly with the peak contact forces and impulses. Increased T1ρ relaxation time correlated with increased shear loading, decreased T1ρ and T2 relaxation time correlated with increased compressive forces and pressures. Thicker cartilage was correlated with higher condylar loading during walking, suggesting that cartilage thickness is increased in those areas experiencing higher loading during a cyclic activity such as gait. Furthermore, the proteoglycan and collagen concentration and orientation derived from T1ρ and T2 relaxation measures were related to loading.

Ink transfer and setting influence the achievable print quality and visual appearance. The pressure in the printing nip and the porosity of the substrate regulate the amount of ink that penetrates into a porous coating structure. The purpose of this study was to understand how print quality aspects could be related to ink penetration of water-based flexographic ink into coatings of differently engineered structures: calcium carbonate (GCC) of various particle size distribution (PSD), coatings with different amounts of latex binder, and coatings with various blends of GCC and kaolin. Calcium carbonate with broad pigment PSD resulted in a lower print density compared to coatings of narrowly distributed particle sizes. Coatings of larger pore volume and greater dominating pore radius showed a higher amount of z-directional ink penetration. A high ratio of uncovered areas (UCA) could be detected for samples with high amount of latex. However, increased printing force eliminated these artefacts. Increased printing force increased the print density to a higher degree than did a reduced ink viscosity for coatings with pure GCC. For coating layers containing both GCC and kaolin clay, decreased ink viscosity had a stronger impact on the print density than increased printing force. Print density was also affected by ink penetration, suggesting that the optical response is sensitive to the ink-substrate interaction layer. The result presented in this work also suggests that the print gloss decreases with increased amount of penetrated ink due to a higher rate of ink vehicle removal.

One of the fatigue tests used for friction materials is the so called “bump test”. In this test, one of the reaction disks in a pack of disks has machined bumps across the contact surface. These bumps generate locally high contact pressure and temperature. In this way, severe contact conditions like that arising in service can be reproduced. The major difficulty in utilizing the “bump test” is estimation of the local pressure and temperature. In this paper, a model is developed and experimental verification of thermoelastic contact is presented. The model represents a multi-surface contact problem for a pack of disks. Due to the presence of bumps, contact surfaces are not conforming. To solve this strongly nonlinear contact problem, a robust finite element code is used. The model also includes thermal effects generated by frictional heating. The coupled elastic contact and thermal problems are solved sequentially. Contact pressure at interfaces is measured in static conditions (without sliding) using pressure sensitive film. Good agreement between the model and the measurement is observed in sense of contact length and magnitude of pressure. In order to verify the full thermoelastic model, the transient temperature inside one of the disks is measured by thermocouples. The results agree with model predictions. The study shows that the local contact pressure is an order of magnitude higher than nominal pressure. Also temperatures are much higher than that predicted for uniform contact conditions. The developed model helps to understand complex thermoelastic effects accompanying the test and to control the test parameters.

This study presents a practical approach for the characterization and control of hydrodynamic cavitation (HC) behavior in microfluidic devices by utilizing real-time static pressure measurements. Two geometrically identical micro-orifice devices were specifically designed for this purpose. Pressure measurement locations were strategically positioned along the embedded microchannel in both devices. These locations were determined as a function of the hydraulic diameter of the microchannel. Pressure measurements were simultaneously made with high-speed imaging. Particular attention was directed to the prediction and monitoring of cavitation inception, cavitating flow patterns, and cavitation development. Thus, the dynamic and complex nature of hydrodynamic cavitation in microdomains could be captured by local pressure variations along the microchannel walls. According to the results, cavitation inception and subsequent formation of twin sheet cavities could be detected by changes in local pressure values. Moreover, the analysis of local pressure variations could be employed to predict the length of sheet cavities. The findings of this study offer valuable guidelines for designing microfluidic systems involving hydrodynamic cavitation. Moreover, this study proves the potential of local wall pressure measurements as a stand-alone practical approach, which will reduce reliance on high-speed visualization. It could thus enhance the affordability and accessibility of HC-on-a-chip platforms for emerging applications, including biomedical engineering, wastewater treatment, and 2D material exfoliation.

One of the major digital printing technologies used for production printing is dry-toner electrophotography. The main technical challenge is print quality and many researches have been done to improve it in the recent years. In our study, dry-toner color electrophotography was compared to conventional offset printing. A Xerox iGen3 press and a Heidelberg Speedmaster press were used. The substrates used were different uncoated and coated paper stocks. The GATF 11x17 Four-Color Test Form was printed on the papers by both printing presses. Print quality, such as color gamut, dot gain, print contrast, and trapping, were evaluated and compared. Higher dot gains were found on Speedmaster than on iGen3 except for black color. Higher print contrast values were found for iGen3 than for Speedmaster except for black color. Wider color gamuts were achieved on iGen3 than on Speedmaster, especially on uncoated papers. With high print quality, it is expected that more production printing will be done by dry-toner color electrophotography.

Numerical optimization of wear performance – Utilizing a metamodel based friction law

In the cross wedge rolling process (CWR), plastic deformation is geared by a driving torque transmitted by friction on die surface. Friction plays a role which has to be further identified in this metal forming process. The local contact pressure between a cylindrical billet and flat dies seems to be a relevant parameter to characterize the severe contact conditions during the rolling. This paper deals with an experimental measurement technology, which has been designed and implemented on a semi‐industrial CWR test bench with plate configuration. This measurement system using pin and piezoelectric sensor is presented, with an analysis of the system operation and design detail. Characterization of systematic error and calibration tests are then explained. Additional tests performed on hot steel preforms allow to check the ability of the contact pressure measurement system to resist under severe operating conditions. Realistic results for varying temperatures are then discussed.

Dynamic Evaluation of Contact Pressure and the Effects of Graft Harvest With Subsequent Lateral Release at Osteochondral Donor Sites in the Knee

This paper presented a numerical approach to solving the problem of a flat-ended punch in contact with a half-space matrix embedded with multiple three dimensional arbitrary-shaped inhomogeneities. Based on the semi-analytical method (SAM) and the equivalent inclusion method, numerical procedures were developed and the effects of inclusion shape and distribution were analyzed. Fast Fourier transform technique was implemented to accelerate the calculation of surface deformation and subsurface stress. Interactions of inter-inclusions and inclusion-matrix were taken into account. Numerical results showed the presence of inhomogeneities (i.e., microstructures in solids) indeed had a great effect on local contact pressure and a strong disturbance to the subsurface stress field in the vicinity of inclusions. The effects were dependent on the shape and distribution of inclusions and inter-inclusion interactions. The physical significance of this study is to provide an insight into the relation between the material microstructure and its response to the external load, and the solution approach and procedures may find useful applications, for example, the analysis of fatigue and crack propagation for composite materials, prediction of stress field in solids containing material defects, and study of the mechanism of chemical-mechanical polish (CMP) for inhomogeneous materials, etc.

Strip walking phenomena on a roll which forms itself into a saddle-type thermal crown are analyzed theoretically. Both strict and simplified methods are proposed to predict the velocity of strip walking for the given roll crown profile. The strict method considers the balances of external forces as line tension, local contact pressure and friction force from the roll. The simplified method considers the strip as a beam and determines the walking velocity from its bending angle. After verification of the simplified method from comparison between these two methods, strip walking is simulated using the simplified method. It is shown that the period and stroke of strip walking agree well with those observed at the production line.

Experimental study on the lateral thrust generated by core buckling in bolted-BRBs

Total knee arthroplasty (TKA) is one of the most successful operative procedures over the last decades in orthopedic surgery; however, some patients suffer from pain, limited range of motion, instability, infections or other complications postoperatively. Patellofemoral pain (PFP) in particular is a common problem after TKA and often necessitates revision surgery. Mainly increasing and localized contact pressure and patella maltracking are held responsible for PFP but the reasons vary. Diagnostics and therapy of PFP is not easy to manage and should be treated following a clinical pathway. The authors suggest that patients with PFP should be categorized after basic diagnostic measures according to the suspected diagnosis: (1) tendinosis, (2) mechanical reasons, (3) intra-articular non-mechanical reasons and (4) neurogenic/psychiatric reasons. Efficient application of special diagnostic measures and further therapy is facilitated by this classification.

In order to rival the quality of silver halide photographs, digital printing systems need to satisfy issues of high print quality as well as image stability. Our research and development efforts have focused on thermal dye transfer and ink jet printing systems, with extraordinarily good results in each system.Discussion will focus on the chelate reaction between dye molecules and metal ions in the thermal dye transfer printing system, which has greatly improved the image stability issues, well in excess of original targets.As for ink jet printing, attention was paid to improving the print quality. These efforts led to the world's first production of micro porous printing media with an RC-paper base. The combination of the printing media and dye inks brings the expected print quality together with other features such as quick drying cased by high ink-absorption speed, resistance to water.Work on improving image stability in ink jet systems will also be discussed.

Foam reduces gas mobility and can help improve sweep efficiency in an enhanced oil recovery process. For the latter, long-distance foam propagation is crucial. In porous media, strong foam generation requires that local pressure gradient exceeds a critical value (∇Pmin). Normally, this only happens in the near-well region. Away from wells, these requirements may not be met, and foam propagation is uncertain. It has been shown theoretically that foam can be generated, independent of pressure gradient, during flow across an abrupt increase in permeability (Rossen, 1999). Experimental studies testing the limits of this phenomenon at field-like velocities have not been conducted. The objective of this study is to validate theoretical explanations through experimental evidence and to quantify the effect of fractional flow on this process. This article is an extension of a recent study (Shah et al., 2018) investigating the effect of permeability contrast on this process. In this study the effects of fractional flow and total superficial velocity are described. Coreflood experiments were performed in a cylindrical sintered glass porous medium with two homogeneous layers and a sharp permeability jump in between, representing a lamination or cross-lamination. Unlike previous studies, gas and surfactant solution were co-injected at field-like velocities into a medium at steady-state to gas-brine co-injection. Pressure gradient is measured across several sections of the core. X-ray computerized tomography (CT) is used to generate dynamic phase saturation maps as foam generates and propagates through the core. We investigate the effects of velocity and injected gas fractional flow on foam generation and mobilization by systematically changing these variables through multiple experiments. The core is thoroughly cleaned after each experiment to remove any trapped gas and to ensure no hysteresis. Local pressure measurements and CT-based saturation maps confirm that foam is generated at the permeability transition, which then propagates downstream to the outlet of the core. A significant reduction in gas mobility is observed, even at low superficial velocities, however, the limit of foam propagation is reached at the lowest velocity tested. CT images were used to quantify the accumulation of liquid near the permeability jump, causing local capillary pressure to fall below the critical capillary pressure required for snap-off. This leads to foam generation by snap-off. At the tested fractional flows, no clear trend was observed between foam strength and fg. For a given permeability contrast, foam generation was observed at higher gas fractions than predicted by previous work (Rossen, 1999). Significant fluctuations in pressure gradient accompanied the process of foam generation, indicating a degree of intermittency in the generation rate - probably reflecting cycles of foam generation, dryout, imbibition, and then generation. The intermittency of foam generation was found to increase with decreasing injection velocities and increasing fractional flow. Within the range of conditions tested, the onset of foam generation (identified by the rise in ∇P and Sg) occurs after roughly the same amount of surfactant injection, independent of fractional flow or injected rate.