Search Results

1 - 10 of 46 items :

  • "Fatigue resistance" x
Clear All
Effect of 16 Weeks of Resistance Training on Fatigue Resistance in Men and Women

References Abe T, DeHoyos DV, Pollock ML, Garzarella L. Time course for strength and muscle thickness changes following upper and lower body resistance training in men and women. Eur J Appl Physiol, 2000; 81: 174-180 American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc, 2009; 41: 687-708 Avin KG, Naughton MR, Ford BW, Moore HE, Monitto-Webber MN, Stark AM, Gentile AJ, Law LA. Sex differences in fatigue resistance are muscle group

Open access
Safe choice of structural steels in a region of ultra-high number of load cycles

Abstract

In this paper the authors introduce their own selected experimental results in the field of the investigation of fatigue resistance of structural steels. The experiments were carried out on the nine structural steels including high strength steels, DOMEX 700MC, HARDOX 400, HARDOX 450, 100Cr6 (UTS from 446 MPa to 2462 MPa) at high-frequency cyclic loading (f = 20 kHz, T = 20 ± 5 °C, R = -1) in the region of number cycles ranged from N ≈ 2×106 to N ≈ 2×109 cycles of loading. The continuous decrease of fatigue strength in dependence on the number of loading cycles was observed with the average value of ratio σa2×109/σa2×106 = 0.69.

Open access
Testing of thermal fatigue resistance of tools and rolls for hot working

Materials and Structures, 4/2, pp. 179-195. [7] Hadder, N., Fissolo, A. (2005): 2D simulation of the initiation and propagation of crack array under thermal fatigue. Nuclear Engineering and Design, 235, pp. 945-964. [8] Pellizzari, M., Molinari, A., Straffelini, G. (2003): Thermal fatigue resistance of gas and plasma nitrided 41CrAlMo7 steel. Materials Science and Engineering, 352, pp. 186-194. [9] Delagnes, D., Lamesle, P., Mathon, M.H., Mebarki, N., Levaillant, C. (2005): Influence of silicon content on the precipitation

Open access
An Efficient Method of Key-Frame Extraction Based on a Cluster Algorithm

Abstract

The purpose of the present study was to investigate the effects of different configurations of repetitions within a set of deadlifts on the mechanical variables of concentric force, concentric time under tension, impulse, work, power, and fatigue. Eleven resistance trained men (age: 21.9 ± 1.0 years; deadlift 1 repetition maximum: 183.2 ± 38.3 kg) performed four repetitions of the deadlift exercise with a load equivalent to 90% of 1 repetition maximum under three different set configurations: Traditional (continuous repetitions); Doubles cluster (repetitions 1 and 2, and 3 and 4 performed continuously with a 30 s rest inserted between repetitions 2 and 3); Singles cluster (30 s rest provided between repetitions). The order of the sessions was counterbalanced across the subjects and the mechanical variables were calculated during each repetition from the synchronized signals recorded from force platforms and a motion analysis system. Relative to the Traditional set, the insertion of rest periods in the cluster set configurations resulted in greater time under tension (p < 0.001) and therefore, greater impulse (p < 0.001) during the repetitions. Reductions in power were observed during the cluster sets compared to the Traditional set (p = 0.001). The Doubles cluster set resulted in greater fatigue scores for power compared to the Traditional set (p = 0.04). The influence of cluster sets on mechanical variables appears to be mediated by the mechanical characteristics of the exercise (i.e. stretch-shortening cycle) and the competing physiological mechanisms of fatigue and potentiation.

Open access
Use of Unconventional Aggregates in Hot Mix Asphalt Concrete

Abstract

Annually 100 to 200 thousand tons of steel slag aggregates are produced in Latvia. The study investigates the use of dolomite sand waste as a filler or/and sand material plus BOF steel slag as a fine and coarse aggregate for the design of high performance asphalt concrete.

Various combinations of steel slag, dolomite sand waste and conventional aggregates were used to develop AC 11 asphalt concrete mixtures. The tests of mix properties included resistance to permanent deformations (wheel tracking test, dynamic creep test) and fatigue resistance. Laboratory test results showed that asphalt concrete mixtures containing steel slag and local limestone in the coarse portion and dolomite sand waste in sand and filler portions had high resistance to plastic deformations and good resistance to fatigue failure.

Open access
Surface Hardening Vs. Surface Embrittlement in Carburizing of Porous Steels

Abstract

Carburizing increases the contact fatigue resistance of sintered steels, but the surface hardening may result the formation of surface brittle cracks due to the combined effect of high hardness and porosity. The effect of carburizing on the embrittlement of the case of a 7.3 g/cm3 1.5%Mo - 0.25%C sintered steel was studied. The phenomenon was analyzed theoretically and verified by experiments. The resistance of the carburized steel to surface brittle cracking increases with the load bearing surface and the decrease of the maximum pore size, of the surface microhardness and the friction coefficient. The theoretical analysis was implemented in a design procedure for parts subject to contact stresses.

Open access
The Use of Polyethylene Terephthalate Waste for Modifying Asphalt Concrete Using the Marshall Test

Abstract

This study considers the use of polyethylene terephthalate (PET) waste for modifying asphalt concrete. In the study, the optimum bitumen content of asphalt concrete was replaced with 4%, 6%, 8%, 10%, 12%, 14% and 16% of PET waste; the Marshall test was conducted on the samples. A comparison of the unmodified and PET-modified asphalt concrete showed that the stability of the modified asphalt concrete was reduced. The maximum stability for the PET waste-modified asphalt concrete was recorded at a content of 12% PET waste. This gives about a 20.4% reduction in stability. The study reveals that the addition of PET waste to the asphalt concrete causes a reduction in the flow value except with the addition of 14% and 16 % waste. This implies that the introduction of PET waste could improve the permanent deformation resistance of asphalt, although there is concern about a reduction in fatigue resistance.

Open access
The Analysis of Fatigue Crack Propagation in the Elements of Aluminum Alloy D16CZATW with a Notch in the Formof A Cylindrical Hole

The Analysis of Fatigue Crack Propagation in the Elements of Aluminum Alloy D16CZATW with a Notch in the Formof A Cylindrical Hole

In this work, the fatigue life of specimens made from the aluminum alloy D16CzATW has been determined. To this aim, flat specimens with notches in the form of cylindrical holes made by drilling and reaming have been investigated. The research was carried out under the conditions of constant-amplitude bending at the stress ratio of R = -1. The results obtained were compared with the fatigue life of specimens with calibrated holes and specimens without notches. Fatigue life was determined for specimens plated on both sides and those without this protecting layer. Very large differences in fatigue resistance were observed. These differences can be explained by the negative effect of the brittle protecting layer on the fatigue crack initiation process. A complex fracture mechanism was observed, in which micro-mechanisms of brittle and ductile fracture were appearing at different stages of fatigue crack propagation.

Open access
Advances in Carbon Fiber Reinforced Polyamide-Based Composite Materials

Abstract

Carbon fiber has been used to reinforce both aliphatic and aromatic polyamides. Aliphatic polyamide is known as nylon and aromatic polyamide is often referred to as aramid. Among aliphatic polyamides, polyamide 6, polyamide 6,6, polyamide 11, polyamide 12, and polyamide 1010 have been used as matrices for carbon fiber. Factors affecting the properties of polyamide/carbon fiber composites are: fiber amount, fiber length, fiber orientation, matrix viscosity, matrix-fiber interactions, matrix-fiber adhesion, and conditions encountered during manufacturing processes. This article presents a state-of-the-art review on polyamide/carbon fiber composites. Polyamide/carbon fiber composites are lightweight and exhibit high strength, modulus, fatigue resistance, wear resistance, corrosion resistance, gear, electrical conductivity, thermal conductivity, chemical inertness, and thermal stability. Incorporation of oxidized or modified carbon fiber and nanoparticle modified carbon fiber into polyamide matrices have been found to further enhance their physical properties. Applications of polyamide/carbon fiber composites in aerospace, automobile, construction, and other industries have been stated in this review. To fully exploit potential of polyamide/carbon fiber composites, concentrated future attempts are needed in this field.

Open access
Influence Of Large Non-Metallic Inclusions On Bending Fatigue Strength Hardened And Tempered Steels

Abstract

The article discusses the effect of large oxide impurities (a diameter larger than 10 μm in size) on the fatigue resistance of structural steel of high purity during rotary bending. The study was performed on 7 heats produced in an industrial plant. The heats were produced in 140 ton electric furnaces. All heats were desulfurized.

The experimental material consisted of semi-finished products of high-grade, carbon structural steel with: manganese, chromium, nickel, molybdenum and boron. Steel sections with a diameter of 18 mm were hardened from austenitizing by 30 minutes in temperature 880°C and tempered at a temperature of 200, 300, 400, 500 and 600°C for 120 minutes and air-cooled. The experimental variants were compared in view of the heat treatment options. Fatigue tests were performed with the use of a rotary bending machine at a frequency of 6000 cpm. The results were statistical processed and presented in graphic form.

This paper discusses the results of the relative volume of large impurities, the fatigue strength for various heat processing options.

Open access