The effects of preloading on tensile properties of braided polyarylate fiber ropes

In the present work, the effects of preloading on the tensile properties of braided polyarylate fiber ropes were investigated experimentally. Four kinds of samples with different pitch lengths were tested with designed preload levels. The deformation responses of the ropes were captured using digital image correlation (DIC) and micro-computed tomography (micro-CT). It is shown that the nonlinearity in the mechanical behavior of the ropes can be almost eliminated post-preloading with one cyclic loading, and the transverse strains are much greater than the longitudinal strains due to the compaction of rope structure because of the spiral interlaced path of braid yarns. The rope with shorter pitch length (larger braid angle) has larger longitudinal strain and smaller transverse strain due to the higher yarn crimp rate and tighter yarns, respectively. The preload level is the most important parameter for preloading. The chord modulus of the ropes reached an optimum level at the preload level of 40% break load, and the tensile strength can be increased by 15% at the preload level of 50% break load. Moreover, the stability of the tensile properties could be accelerated at the higher preload level. Consequently, preloading is vital to improve the tensile properties of braided polyarylate fiber ropes, with a preload level at least of 40% break load and 10 cyclic loadings.

Three-dimensional strain analysis of asphalt pavement based on vehicle–pavement model of interaction

This study analyzes the 3D (3D) strain on a pavement by using a model of a vehicle with seven degrees of freedom and that of a road in elastic half-space by using the finite element software ANSYS. The results are as follows: The 3D strain on the two wheels along the centerline was significantly influenced by the superposition of the wheel, and the 3D strain under a single wheel was far higher than that along the centerline of two wheels, and represented the most unfavorable position on the road. The vertical strain consisted mainly of compressive strain at different depths, and that at the bottom of the pavement was slightly higher than that on top. The longitudinal and transverse strains were all compressive strains on top of the pavement and tensile strains at the bottom, respectively. The longitudinal and transverse strains both on top and at the bottom of the pavement were similar. The authors then analyzed the influence of the thickness of the pavement, its modulus, and equivalent resilient modulus on the vertical compressive strain, longitudinal tensile strain, and transverse tensile strain in case of a single wheel. Furthermore, a model to predict the 3D strain under the comprehensive effect of the structural parameters of the road was established. It can provide the basis and a reference for the design, construction, fault detection, and maintenance of roads.

EVALUATION OF THE CONTACT SURFACE PARAMETERS AT KNURLING FINNED HEAT-EXCHANGING SURFACE BY KNURLS AT RING BLANKS

Tubular parts with an external finned heat-exchanging surface are usually produced by the laborious method of cutting on lathes. Besides, there is a method for the high-performance manufacturing of fins by cold knurling with ring-cut knurls, which, compared with cutting, reduces labor intensity by two to six times with a significant increase in the operational properties of the product. The disadvantage of the cold knurling method with ring-cut knurls can be unwanted surface defects and deformations of the entire product. Obtaining finned surfaces on ring blanks with high surface quality during knurling requires accurate calculation of the ratio of longitudinal and transverse strains. The most important factors determining the ratio of longitudinal and transverse strains (rolling-out and rolling-off) are the length and width of the contact surface. The need for a quantitative assessment of the parameters of longitudinal and transverse strains determined the purpose of this manuscript. This study aimed to develop a methodology for calculating the contact surface of a knurl with a ring blank (pipe) when knurling with ring-cut knurls. The proposed method for calculating the knurl's contact surface with a tube when knurling with ring-cut knurls allows for estimating the recommended range of pipe sizes for knurling. Based on the dependencies mentioned in the manuscript, the limiting sizes for blank pipes were calculated to ensure high-quality finning. Experiments on cold rolling of ribbing on pipes with different lengths and diameter ratios were carried out, confirming the possibility of using the proposed methodology for calculating the knurl's contact surface with a pipe when knurling heat-exchanging finning with ring-cut knurls.

Fracture mechanisms of softwood under longitudinal tensile load at the cell wall scale

This study was undertaken to elucidate the longitudinal tensile fracture behaviors of softwood at the cell wall scale by means of microscopic analyses. The fracture types of the tracheids at the different fracture surfaces were also distinguished. The results indicated that the main tracheid fracture of the earlywood (EW) sample was transverse transwall breakage. The tracheid fracture process of the transverse transwall breakage was initiated as a fracture in the S2 layer, with the crack propagating into the S1/S2 interface. For the EW/latewood (LW) sample, the strain concentration and initial crack under longitudinal tensile load generally occurred in wood rays in the EW part, which caused the tracheids to experience transverse transwall breakage. The differences in longitudinal and transverse strains between EW and LW under longitudinal tensile load led to shear stress and parallel-to-grain cracks occurring at the growth ring border. When the crack propagated along the wood grain in the EW tissue or growth ring boundary, this resulted in EW longitudinal transwall breakage. However, when the crack propagates along the wood grain in the LW tissue, it could cause the LW tracheid to undergo intrawall breakage, with the crack occurring predominantly at the compound middle lamella (CML)/S1 interface region.

Directional Response of Randomly Dispersed Carbon Nanotube Strain Sensors

Tests on a double lap bonded joint, with transverse strips of randomly oriented carbon nanotubes (CNT) sprayed onto an epoxy adhesive film, showed a positive increment in electrical resistance under tensile load, even though the transverse strains were negative. Other experiments included in this work involved placing longitudinal and transversal CNT sensors in a tensile loaded aluminum plate, and, as reported by other authors, the results confirm that the resistance change is not only dependent on the strains oriented with the electrode line, while the other strain components also influence the response. This behavior is quite different to that of conventional strain gages which have a near zero sensitivity to strains not aligned to the sensor direction. The dependence of the electrical response on all the strain components makes it quite difficult, possibly unfeasible, to experimentally determine the individual strain components with this kind of sensors; however, the manufacturing of aligned CNT sensors could deal with this issue.

Tensile and transverse strength of novel copolymers for denture base.

Objectives: Compare tensile and transverse strength of new copolymers for denture base. Materials and methods: The specimens were prepared from heat cured acrylic resin with three types of additives: Acryester B, Ethoxycarbonylethylene, and Propenoic acid at a percentage of 5% and 10%. The tensile and transverse strains were tested, recorded and compared. Results: The analysis of variance display statistically significant difference. The p-value was 0.001 for each of tensile and transverse strain tests. Conclusions: The tensile strength of the novel copolymers increased. The transverse strength of some of the novel copolymers increased.

On application of high-precision instrumentation and numerical methods in hull manufacturing

This paper presents calculation procedure for welding-induced transverse strains of hull plating and floors in ANSYS software package. The results have been confirmed by an experiment performed in real factory conditions.

Evaluation of Strains at the Bottom of the Asphalt Base Layer of a Semi-Rigid Pavement Under a Class 6 Vehicle

A newly constructed pavement on US-287 near Mansfield, TX was instrumented with gauges installed at the bottom of the asphalt concrete base layer to measure the longitudinal and transverse strains developed under a test vehicle. The finite element program Abaqus was used to compute the strains at the location of the gauges; they were found in good agreement with the measured strains. The research showed that the strains under the steering axle were of similar magnitude as the strains under the rear tandem axle. The measured transverse strains were in general slightly bigger than the corresponding longitudinal strains, while the finite element model computed higher strains in the longitudinal direction. These findings suggest the need to account for the strain responses from the steering axle of trucks and to account for both the longitudinal and the transverse strains when computing the fatigue damage induced by trucks.

Towards the solution of creep problems of thin-shelled tubular elements in isotropic nonlinear viscoelastic materials

A new approach to the creep strains analysis of thin-shelled tubular elements in isotropic nonlinear viscoelastic materials under combined loading with uniaxial tension and torsion has been proposed. The system of equations that is constructed according to the deviators proportionality hypothesis has been chosen as the creep constitutive equations the nonlinearity of viscoelastic properties in which is given with respect to the creep strain intensity and volumetric strain by the Rabotnov type models. The kernels of creep strain intensity and volumetric strain are given by the relations that establish the relationships between these kernels and one-dimensional creep kernels determined from a system of base experiments. One-dimensional tension with the measurement of longitudinal and transverse strains as well as one-dimensional tension and pure torsion with the measurement of longitudinal and shearing strains have been considered as base experiments. The functions of nonlinearity of viscoelastic properties are given by smoothing cubic splines. The problems of the analysis of longitudinal, transverse and shearing strains of thin-shelled tubular specimens made of “high density polyethylene PEHD” have been solved and experimentally approved.