Study on the Influence of Compression Ratio on the Rail Contact Fatigue Resistance Property and Its Mechanism

Contact fatigue resistance properties of four commercial steel rails were systematically studied and compared. The contact fatigue limit cycles, fracture toughness, and fatigue crack growth rate of the corresponding rails with different compression ratios were tested and analyzed, which showed a close relationship between them. Moreover, microstructures of the rails were carefully observed by using the TEM to elucidate the scientific mechanisms. Observations and obtained results indicated that pearlite lamellar spacing further decreased with the rise of compression ratio, which greatly and rightly contributed to the improved fatigue resistance property.

Using Wastes from the Process of Blasting with Steel Shot to Make a Radiation Shield in Mortar

The waste generated from the process of steel shot blasting must be safely disposed of due to its classification, non-hazardous and non-inert, and, consequently, is sent to landfills. One of the possibilities for reusing this waste is in the cement materials industry. In this context, the aim of this study was to evaluate the addition of waste from steel shot blasting, thereby replacing natural sand, for the manufacture of cementitious material with properties that shield against ionizing radiation. Three forms of steel shot (commercial steel shot—AG1, intermediate steel shot waste—AG2, and steel shot dust—AG3) were used to replace natural sand in different proportions (0%, 10%, 20%, 30%, and 40% by volume). Compressive strength results were found with values above the minimum compressive strength (20 MPa) requirement of structural concrete. The results indicated that AG1, AG2, and AG3 can be used to attenuate X-ray radiation. Regarding the reference samples (mortar developed without natural sand replacement), an increase in X-ray shielding of 76.7%, 72.5%, and 59.3% was found for samples with AG1, AG2, and AG3, respectively. Therefore, the waste generated in the steel shot blasting process had the potential to be used in mortar developed to attenuate X-ray radiation.

Bond Stress between Steel-Reinforced Bars and Fly Ash-Based Geopolymer Concrete

Geopolymer concrete has been regarded as one of the most important green construction materials, which has been restrained in engineering applications partially due to a lack of bond studies. The structural performance of the reinforced concrete components primarily relies on the sufficient bond between the concrete and the reinforcing bars. Before being utilized in any concrete structure, GPC must demonstrate that it possesses understandable bond behaviour with commercial steel reinforcements. This work presents an experimental investigation on the bond stress of steel bars in reinforced geopolymer concrete (GPC) structures. Standard beam-end pull-out tests were conducted on GPC specimens reinforced with 16 mm plain and ribbed bars that were equipped with electrical resistance strain gauges. The longitudinal variation in the bond stress in the GPC beams during the pull-out tests was calculated and plotted, as well as the stress in steel bars. The cracks on the bond area of the GPC were compared with those of the corresponding ordinary Portland cement concrete (OPC), as well as the steel stress and bond stress. The results showed that the relative slip between plain bar and geopolymer concrete varies from 30–450 microns from the loaded end to the free end when the bond stress decreased by 83%. The relative slip between ribbed bar and geopolymer concrete varies from 280–3,000 microns from the loaded end to the free end when the bond stress decreased by 57%. Generally, GPC is different from OPC in terms of bond stress distribution.

Analysis of Corrosion Rate With Addition of Pumps in Commercial Steel in Sea Water Media

Corrosion or rusting is very common in metals is a decrease in the ability of a metal due to the environment or chemicals. Sea water is a corrosive environment for metals because it contains sodium chloride (NaCl), calcium sulfate (CaSO4), calcium carbonate (CaCO3), and dissolved oxygen (O2) which affect the corrosion process of the material. The presence of dissolved oxygen will cause the rate of corrosion in metals to increase with increasing oxygen content (O2), the solubility of oxygen in water is a function of pressure, temperature and chloride content. The process of corrosion is almost the same for all materials, especially in metals occurs slowly but surely, corrosion can cause a material to have a limited service life, where the material expected to be used for a long time turns out to have a shorter life span than the average usage life.

Near Solidus Forming (NSF): Semi-Solid Steel Forming at High Solid Content to Obtain As-Forged Properties

Near solidus forming (NSF) of steels is a novel process under the umbrella of semi-solid forming technologies midway between classical hot forging and semi-solid technologies. This article presents the work done at Mondragon Unibertsitatea to develop this technology and demonstrates the great potential of the NSF process. The study proves the capability of the process to reduce raw material consumption by 20%, reduce forming loads from 2100 t to 300 t, and reduce forming steps from three to one, to obtain as-forged mechanical properties, as well as the excellent repeatability of the process. The work demonstrates that manufacturing commercial steel components in a single step using several off-the-shelf alloys is possible thanks to the flowing pattern of the material, which enables near-net shaping. In the first part of the article, a general overview of the semi-automated near solidus forming cell, together with a description of the NSF manufacturing trials, is provided, followed by the presentation and discussion of the results for the selected steel alloys.

APPLICATION OF LEAN METHODS FOR PRODUCTIVITY IMPROVEMENT IN STEEL FABRICATION SHOPS: A CASE STUDY

The objective of this paper is to identify tools and methodologies to increase productivity in commercial steel fabrication shops. The effectiveness of these tools and methodologies has been demonstrated through a case study in a Canadian steel fabrication shop. Three different productivity improvement concepts were identified as suitable for the steel fabrication environment. Lean, Six Sigma, and the Theory of Constraints (TOC). Lean was retained as being the most suitable to steel fabrication due to its low cost, focus on quality, and built in continuous improvement process. In the case study, Lean tools were identified and applied to address three top productivity issues. A baseline was established for existing productivity for a fitting station over a period of two weeks. Selected tools were implemented, and a session was conducted to educate the workers on the new processes and tools. Lastly, the productivity was recalculated, the results were analyzed, and recommendations were made.