An assessment of how penetration curve adjustment affects the California bearing ratio (CBR)

With the rapidly developing road transport, there is a demand for new roads to be constructed and for the existing ones to be repaired or extended. The base of any road is its foundation, usually made of crushed or uncrushed aggregate. To be used for road foundation purposes, a material needs to meet many requirements, as imposed by relevant standards. One of the basic tests to assess the suitability of an aggregate is to determine its California bearing ratio (CBR). This paper presents the results of CBR tests for mixed aggregate with the grading of 0–31.5 and 0–63 mm. Detailed assessments were carried out for penetration curves, which in many cases need to be adjusted to meet industry standards. The adjustment of plunger penetration curves in aggregate samples causes CBR to increase compared to the original curves.

Numerical investigation of the radial cold rolling process of the grooves

The radial cold rolling process is widely used in industry due to the advantages of chip removing processing. In this study, circular complex profiles were formed by cold-rolling with radial feed, using a patented device with two roller-tools. By achieving several numerical simulations of the radial rolling process, the study aimed to establish the influence that the maximum set force and the diameter of the workpiece have on the productivity of the process and the quality of the formed trapezoidal and metric grooves. The numerical simulations were performed with ABAQUS/Explicit software and by using a previously validated finite element model. The penetration curve of the roller-tools in the material was introduced in the simulation as an analytical function and was determined based on experimental researches. To express the dependency of the penetration curve coefficients on other rolling conditions, a multivariable analysis using a design of experiments technique was performed. The parameters that result from numerical simulations and were analyzed in this study are the profile forming time, the maximum radial force, the distribution of the equivalent strains in the axial section of the profiles, and the profile dimensions. The conclusions that were drawn from the analysis of the results regarding the influence of the set maximum force and the workpiece diameter on the analyzed parameters of the numerical simulations, together with the definition of efficient process criteria, allowed also the identification of the optimal conditions of the rolling process.

Testing Soil Accumulation of Cd from Reclaimed Water

The reuse of wastewater improves the comprehensive utilization of water resources, and reduces the shortage of water resources. In this paper, the accumulation of heavy metal Cd risk in reclaimed water irrigated soil to human health was analysised through experiments and simulations. Firstly, according to the static adsorption experiment of sandy clay loam, the fitting effect of Freundlich equation on Cd is better for the certainty coefficient R2 reaches 0.97. Then, use the more accurate DEM model of CXTFIT2.1 software to fit the Cl- penetration curve. Finally, made the heavy metal leading experiment, found that the TSM model has a good fitting effect on the penetration curve of Cd, with a determination coefficient close to 1 and a small standard error coefficient. Based on the results of the above experiments, the HYDRUS-1D was used to analyze and predict the cumulative risk of Cd in reclaimed water irrigated soil. The results showed that: after 100 years under current situations, the predicted concentration of Cd in soil may reach 0.742 mg/kg, which exceeded the national soil environmental quality standard, may be a serious health hazard. Measures should be taken to reduce the risk of human health by ingestion and accumulation of crops and vegetables.

Investigation of the Tooth Geometry of a Hob for Machining of Involute Gears (in the Tool-in-Use Reference System)

This paper is aiming at development of an analytical approach for computation of the geometrical parameters of cutting edges of an involute hob. It is well recognized that the involute hob geometry strongly affects the cutting tool performance, as well as the efficiency of gear hobbing operation. It is proven experimentally and by industrial practice that the optimal value of every geometrical parameter of the tool cutting edge exists and, thus, it can be found out. A method for computation of the cutting edge geometry is necessary for optimization of parameters of a gear hobbing operation. In this paper, an analytical method for the computation of the cutting edge geometry of a gear hob is reported. The method is based on wide application of elements of vector calculus and matrices. The analysis is performed in the tool-in-use reference system. An equation of the penetration curve is derived. The machining zone is partitioned onto several different sectors. The roughing sector and the generating sector are distinguished. Generating of the work-gear tooth profile occurs within the generating sector that is bounded by the penetration curve. The derived equations, as well as the worked-out computer codes are applicable for computation of the cutting edge geometry at any point of the cutting edge of the hob, and at a any instant of time. The equations and the computer codes enable one estimating the impact of (a) the hob diameter, (b) the hob number of starts, (c) the work-gear number of teeth, (d) the hob feed rate, and (e) the hob rotation onto the actual values of the geometrical parameters of the hob cutting edges. Numerical results of the investigation are computed using commercial software MATHCAD-SCIENTIFIC. The results of the computation of the cutting edge geometry of the involute hob enable the user (a) to avoid not-feasible values of any and all geometrical parameters of the cutting edge of the hob teeth, (b) to develop parameters of the hob grinding and reliving operations, which guaranteed the optimal values of any and all geometrical parameters of the hob cutting edges. Ultimately, the application of the hobs with optimal geometry of the cutting edges will result in an increase in the cutting tool performance and in the efficiency of the gear hobbing operation. The latter is of critical importance for high volute production of involute gears for the needs of the automotive industry. The reported research results are ready to be put into practice.

Comments on “Comment on the determination of mechanical properties from the energy dissipated during indentation” by J. Malzbender [J. Mater. Res. 20, 1090 (2005)]

Based on a comparison of relationships between energy dissipated during indentation and the ratio of hardness to reduced elastic modulus, Malzbender has recently proposed a procedure to determine both hardness and elastic modulus from a single loading–unloading indentation curve. However, a more accurate analysis of this relationship shows that, in fact, it suffers from the same limitations as the well-known Oliver and Pharr's method; i.e., in general, the true projected imprint area has to be measured in addition to the load–penetration curve or at least two such curves obtained with different indenter geometries are to be used to unequivocally determine the hardness and the elastic modulus of a material.

Absence of one-to-one correspondence between elastoplastic properties and sharp-indentation load–penetration data

The connection between parameters that can be measured by means of instrumented indentation with the real mechanical properties has been a matter of discussion for several years. In fact, even hardness is not a readily measurable magnitude since the real contact area depends on both the elastic and plastic properties of the sample. Recently, Dao et al. [ Acta Mater49, 3899 (2001)] proposed a method based on numerical fittings to calculate by a forward-reverse algorithm the elastoplastic properties of a sample from the load-penetration curve obtained with a sharp indenter. This work will show, in contrast, that it is not possible to measure uniquely these mechanical properties of a sample in that way.