Influence Of Mechanical Action Research Articles

Influence of mechanical action on the development of electrodynamic phenomena in ionized gas

A special feature of this work is the study of the effect of mechanical mode disturbances on the discharge and plasma flow. It is found that the mechanical impact of a shock wave in a dense gas in an electric field of high intensity almost to the ignition voltage causes an electrical “breakdown” as current peaks. The ultrasonic effect on the flow of the reacting plasma of the air as shown by the analytical study of the thin layer of the plasma flow changes the type of flow.

The influence of mechanical action on felting shrinkage of wool fabric in the tumble dryer

Felting shrinkage of untreated wool fabric occurs easily during tumble drying. Mechanical action applied on fabrics plays a significant part in felting shrinkage of wool fabric. In general, the more severe the mechanical action of a washing or drying machine, the more rapid the felting shrinkage. However, both the degree and type of mechanical action applied on the fabric can influence felting shrinkage of untreated wool fabric. In the current study, fabric movement and felting shrinkage of untreated wool fabric at different rotation speeds of the drum in a tumble dryer without heating were studied. Based on the different fabric movements at different rotation speeds of the tumble drum, the extents of impact and rubbing forces at different rotation speeds were assessed by ranking. The total mechanical action applied on the fabric was expressed as the percentage of thread removal of “thread removal fabric” during the drying process. The results showed that lowest mechanical force on fabrics could be achieved when higher rotation speeds of the drum were used to dry wool fabrics in the tumble dryer, and could prevent wool felting shrinkage. It was also found that falling of the fabric followed by impact on the drum wall caused less felting shrinkage than sliding with rubbing between fabrics. Therefore, maintaining the falling movement could be a potential method to dry wool fabric in drying machines without causing severe felting shrinkage.

Dry-cleaning with high-pressure carbon dioxide—the influence of mechanical action on washing-results

Previous studies indicate that the removal of non-polar soils in CO 2 is comparable to the level of dry-cleaning in perchloroethylene (PER). However, these studies show that the removal of particulate soil is insufficient in CO 2 compared to PER. Particle removal can be increased by the use of more mechanical action and/or the use of surfactants. From experiments, it is concluded that the removal of relatively large particles like sand increases with increasing mechanical action. However, the level of mechanical action has no influence on the removal of relatively small particulate and non-particulate soils (with the exception of clay on wool). Increasing the amount of mechanical action is therefore not the solution that will lead to the increase of the washing-results for relatively small particles (like carbon black and clay) up to the level of the washing-results using PER. The removal of relatively small particulate soils in CO 2 can be improved by the use of suitable surfactants that reduce adhesion forces. A model for quantifying the amount of mechanical action has been developed. This model can be used to predict the optimal process conditions for relatively large particle removal. It is concluded (from the model and experiments) that the level of highest mechanical action in CO 2 is obtained in a two-phase environment at low pressure and temperature and that 75 RPM is the optimal number of revolutions in our system. At these conditions, however, the washing-results for small particles are not as good as the washing-results for these particles in PER.

Structural Changes in Hemp Fibers as a Result of Enzymatic Hydrolysis with Mixed Enzyme Systems

Hemp fabric is hydrolyzed with cellulase, hemicellulase/cellulase, and cellulase plus additional β-glucosidase. The effect of the admixture of hemicellulase and β-glucosi dase is evaluated in terms of hydrolysis rate and product properties. The influence of mechanical action during the treatment is also taken into account. Treated samples are characterized by weight loss per incubation time, tensile strength, crystallinity, acces sibility, and pore structure. The admixture of hemicellulase and,β-glucosidase produces only minor effects without mechanical action on the hydrolysis rate, but mechanical action applied during the treatment dramatically increases weight loss. While crystal linity changes upon hydrolysis are insignificant, the pore structure is strongly influenced by the choice of enzyme system. Hemicellulase seems to promote the formation of smaller pores, while cellobiase forms larger pores.

Mechanical and Tribochemical Effects During Accelerated Wear of Silicon Nitride in Diamond Slurries

The influence of mechanical action and tribochemical effects on the material removal mechanism during accelerated wear of silicon nitride balls was investigated. It was found that the tribochemical effects are more effective in material removal than the mechanical action of abrasive particles present in the slurry. Mechanical action is governed by the applied load, amount of slip within the contact area and the size of abrasive particles, while tribochemical effects depend mainly on the type of lubricating liquid used and the chemical nature of additives.

Effect of deformation on the rheokinetics of gelling of urea-formaldehyde oligomers

A basic question in the analysis of kinetic relations for the change in viscosity during solidification is the effect of deformation, since the viscosity change itself unavoidably gives rise to mechanical loading of the material being tested. Diverse information about the behavior of polymers in mechanical fields is presented in the literature, but most investigations concern mechanochemical effects, i.e., destruction of polymer molecules under mechanical action [1]. It is obvious that in such cases quite high mechanical loads, capable of breaking covalent bonds, are studied. There are only a few works [2-7] on relatively weak mechanical actions associated with any technological operation (synthesis of polymers in devices with mixers, transport in pipelines, etc.). Investigations of the influence of mechanical fields on reaction systems show that for homogeneous systems, in the absence of any isothermal distortions of the solidification process, no appreciable effect of deformation on viscosity kinetics is observed [8-10]. The kinetic role of deformation is manifested, as a rule, only when the reaction system becomes two-phase. Then the shear stress changes the rate of the process, affecting the conditions of phase separation [2]. For this reason it is of interest to study the influence of the intensity of deformation of the rheokinetic solidification of an initially inhomogeneous system, such as a water suspension of urea-formaldehyde oligomers. We investigated water suspensions of urea-formaldehyde oligomer with total molar ratio urea:formaldehyde 1:1.2, employed in industry as a binder for preparing wood-chip boards and plywood. The mass content of the oligomer in the suspension ranged from 40 to 60. The experiments were performed under different conditions of deformation on VPN-02 (under conditions of constant shear stress r = const) and Reotest2 (under different shear rates) rotational viscosimeters at stresses ranging from 10 to 600 Pa in the temperature range 40-65~ The typical experimental results on the viscosity change of resin as a function of time under different shear stresses are displayed in Fig. 1. These curves have a characteristic maximum, similar to the one observed during gelling of a number of homogeneous resins [2, 11]. In contrast to homogeneously solidifying systems, however, the characteristic section of the viscosity drop is associated not with microgelling, but rather with sedimentation instability of the suspension due to an increase in particle size. The applied stress significantly influences the kinetics of the viscosity change, but this influence is not unique. When the shear stress increases to r ~-. 300 Pa, the process slows down. Essentially analogous results, characterizing the influence of mechanical action, were obtained in the study of the influence of periodic deformation on solidification kinetics of epoxy resins [3] and viscosimetric study of solutions of ureaformaldehyde oligomers [12]. Further increase of the stress gives rise to the opposite effect - the gelling rate increases. This nature of the influence of mechanical action was observed for pressure processing of rigid thermosetting plastics [1]. Figure 2 displays the gelling time t* and the precipitation time tp (which corresponds to the maximum on the curves ~/(t)) as functions of the applied stress. This extremal character of the influence of the shear stress on the gelling kinetics is connected with the different aspects of the mechanical action of solidification of heterogeneous systems. Slowing of gelling, in all probability, is connected with inhibition of the growth of particles of the dispersed phase in the mechanical field. Acceleration of the process is probably due to dissipative losses, resulting in an increase of the temperature of the reaction mass, as shown in [13] in a study of the reprocessing of rigid thermosetting plastics. The case at hand concerns relatively low stresses, which, in all probably, can result in small temperature disturbances. As shown in [2, 14], the viscosity properties of gelling systems are described satisfactorily by the equation

Experimental verification of the theory of thixotropy of viscoelastic polymer media

Previous studies [1, 2] were devoted to the formulation of a phenomenological theory of the reversible changes (thixotropy) in the physicomechanical properties of viscoelastic media, in particular, polymer systems. The basis of this theory is the idea that the reversible changes in the structure and properties of viscoelastic thixotropic media under the influence of mechanical action are due to a change in their relaxation spectrum. In this case the behavior of the mechanical properties is entirely and uniquely determined by two material functions which completely characterize the given material: the relaxation time (frequency) distribution function, which describes the behavior of the material in the linear region of deformation, and the thixotropy function, which determines the nature of the changes compression) of the relaxation spectrum on transition to the nonlinear region. The object of this approach is to reflect the effect of the change in supramolecular and molecular structures associated with the flow of polymer system, or in the bonds and orientation of the particles in disperse systems, on the viscoelastic and viscosity properties of the systems concerned. The essential validity of this approach was demonstrated in [3], where it was shown that at sufficiently high strain rates changes occur in the structure of the polymer leading to a change in mechanical properties. In [4] the basic structural functions were found. These, in conjunction with the proposed theory of thixotropy, characterize the behavior of a broad group of polymer systems in both the linear and the nonlinear regions of deformation. In this connection it should be noted that whereas for the linear region the accuracy of the laws obtained lies within the limits ± 100%, on transition to the nonlinear region the error may increase, Therefore, for the purposes of a rigorous quantitative verification of the theory we shall use not the universal functions obtained in [4], but the more precise characteristics of the specific material on which the experiments are performed, since those effects with respect to which it is desired to test the theory usually lie within the limits of 30% of the measured quantities.

A Fatigue Cracking Test for Tire Tread Compounds. Some of the Laws of Fatigue

Abstract AN IMPORTANT factor in the service rendered by a tire tread is its ability to resist cracking. Cracking of tire treads in service may be classified into two kinds or phases—the initiation or start of cracks, and the growth of cracks or cuts once started—and the two phases must be differentiated. Nearly all tires in service soon develop small cracks or “checking” due to the action of ozone in the atmosphere (9), and may suffer cuts due to sharp objects on the road. In many cases such cuts and ozone cracks may be harmless, but if the cracks grow too rapidly they will extend to the carcass before the tire is worn out (4). We define the growth of cracks under the influence of mechanical action as fatigue cracking. The quality of rubber in respect to its resistance to fatigue cracking can be improved by addition of antioxidants (3, 7), and by such factors as the proper choice of accelerators (4), the proper balance of fillers (1, 3), and the proper cure. The quantitative evaluation of such chemicals and compounding ingredients in the laboratory depends upon the validity and precision of a test. It is the purpose of this paper to describe a laboratory test which has been found to correlate with shoulder cracking in tires, and to present data from which certain laws of fatigue cracking have been deduced.