Volume 56, Issue 3

Residual stresses in mechanical components can result in both detrimental but also beneficial effects on the strength and lifetime of the components. The most detailed knowledge of the residual stress state is of advantage or a pre-requisite for the assessment of the component performance. The mechanical methods for residual stress measurement are divided into the groups of non-destructive and destructive methods. Two commonly used mechanical methods for determination of residual stresses are the hole drilling method (HDM) and the ring core method (RCM) which can be regarded as semi-destructive. This investigation will experimentally determine the calibration functions for residual stress measurements of the HDM and RCM. These functions are used for RS analyses using the differential method. With a four point bending testing machine a defined stress can be triggered between the middle bearings. The strain in this area can be measured with strain gauges, so the stress is well-known. In this defined loading area, the strains in two load cases with HDM configuration and RCM configuration were measured using strain gauge rosettes. With these measured strains and the actually known stresses, the specific calibration functions can be calculated and were presented together with the numerical functions.

The effect of Mo on the abrasive wear resistance of (20–23)Cr-(7–8)Nb hard-faced S355JR steel by shielded metal arc welding (SMAW) was studied. Four types of flux, consisting of fixed Cr and Nb but varying Mo contents, coated on hard-facing electrode were used. Microstructure, micro hardness, and abrasive wear resistance of the hard-faced surface were investigated by ASTM G65 D procedure. The original microstructures consist of the primary coarse and eutectic carbides. Mo affects morphology of carbides by decreasing primary carbide size. When Mo content in the hard-faced surface was up to 6.43 wt.-%, the highest abrasive wear resistance and micro hardness were obtained. The decrease of primary carbide size is attributed to the increased nucleation induced by Mo addition. Network structure was observed when the Mo content reaches 10.19 wt.-%. The main mechanisms of wear are micro-cutting and carbide pulling out.

In this study, construction and standardization of a track for performing fatigue and reliability tests of light commercial vehicles are described. Such a test track is necessary for design and manufacturing verification of these vehicles. Fatigue characteristics of Turkish roads were determined by analyzing fifty different roads. This paper focuses on defining the load spectrum and equivalent fatigue damage of the leaf spring resulting from accelerated tests on a route. Fatigue analysis and estimated lifetime of the part were calculated using Finite Element Analyses and verified by the Palmgren-Miner rule. When as customer profile the Turkish automotive user is taken into consideration and accelerated test tracks are designed for the reliability and fatigue tests of the related company, linear FEA of the spring represents a convenient procedure.

In this study, two different heating methods have been used for the hot forging process of ANSI 1050 steel. Some specimens were heated by induction generator at 250 kW, 3.2 kHz up to a temperature of 1250 °C ± 5 °C in 5 minutes under ambient conditions via a continuous conveyor belt system. Other steel specimens were heated continuously in a conventional furnace up to a temperature of 1230 °C ± 40 °C at ambient conditions in 30 minutes. All specimens were subjected to Charpy, three-point bending, fracture strain, and hardness tests (surface and cross-section measurements). Almost all mechanical test results were better for the specimens heated by the induction generator and also appeared as more stable than those for the specimens heated by conventional furnace which varying some showed results. Grain growing was found in the microstructure of the conventional heated specimens. Induction heated specimens were heated more homogenously than the conventional heated specimens which is the reason for more stable results.

This study describes the investigation of wear characteristics of circular cBN/diamond saws produced by hot pressing. In order to determine the usability of cBN instead of diamond, cBN and diamond grains were added to the bronze matrix. Production of the saws was performed at a sintering temperature of 600–700 °C for a sintering time of 3 minutes. Sawing tests were carried out to determine the wear characteristics of the saws by sawing natural stone. It is concluded that cBN together with diamond could be added to the matrix with a concentration of 12 (the rest of concentration of 30 is diamond) and that the saws will have more wear if this concentration is exceeded. After sawing, SEM analyses of the saws indicate that there were more fractures and wear in cBN grains in comparison to the diamond grains. The results concluded that cBN can be used to saw softer natural stones, or can be added to the matrix together with diamond.

The effect of boronizing on commercial H320LA steel sheets of 1 mm and 2 mm thickness was evaluated. The boronizing treatments were carried out in a solid medium at 1173 K for 5 h using the powder pack method. The boride layers formed on the surface were characterized and microhardness measurements were conducted on the borides and the substrate. Mechanical properties and deformation behaviour were compared by bending, tensile, deep drawing, and ballistic tests. The ballistic behaviour was investigated impacting against lead alloy core projectiles of 358 ± 12 m/s velocity at normal impact angle. The microhardness of the boride layers was approximately 1225–1455 HV 0.1 . Bend tests revealed a sharp decrease in flexural strengths of the boronized specimens. Deep drawability was impaired, while ballistic properties of the plates were improved with boronizing treatment due to improved surface hardness.

Conservation of cultural heritage is extremely important not only from a cultural point of view, but also from a practical one. It is our duty to pass on to future generations the cultural heritage left to us by our ancestors. Wood is one of the most common materials used to generate works of art which are in a state of constant change and/or deterioration. In order to optimize the knowledge of artworks together with their conservation, it is necessary to use the most advanced scientific and technological tools. In the following paper, we will show the tomographic results which can be achieved by application of complementary techniques based on the combined use of X-ray and neutron radiography as structural probes.

Intense competitive environment and customers' changing demands and needs apply temporal and financial pressure to product development process. For this reason interest in design and innovation is inevitable. Reducing project duration also affects further applications as well as new tooling materials and methods become more important to catch up project schedule. Conventional methods of stamping process usually do not suit to prototype or low volume production in terms of project schedule and cost. In this study a polymer metal carcass die structure was introduced in order to stamp large sheet metal prototype parts. Dimensional conformance of prototype sheet metal parts was compared with actual production and as a result polymer metal carcass die method is an effective method for prototype sheet metal parts to meet the tolerance interval. Therefore, this method is cost effective and helps to meet the project schedule in time.

In Algeria, the aging of palms is a significant constraint, since 30 % of the palms are over the age of production and they will consequently waste planting areas. A series of experiments have been accomplished to observe the possibility of converting the date palm stem into valuable woodworking products. This paper reports the results of an experimental investigation on the physical, chemical and mechanical properties of date palm trunk (Phoenix dactylifera L.) from Biskra oasis in Algeria. First, their chemical composition was studied and showed that they have amounts of holocellulose, lignin and cellulose similar to those encountered in softwood and hardwood. Results of flexural strength showed that the modulus of elasticity (MOE) and modulus of rupture (MOR) were 6647.04 MPa and 35.04 MPa, respectively. The compression modulus and strength were 5.35 MPa and 2.338 MPa in parallel compressive tests, respectively.

This study reports on the thermo-mechanical synthesis of carbon nano onions from elemental graphite powders. Initially, amorphous carbon was obtained by high energy ball milling technique from graphite powders. X-ray spectra taken from ball milled samples indicated that the hexagonal graphite, composed of layers, was transformed into the amorphous carbon for a shorter milling time of 5 h by high energy input about 78 times of gravity. Subsequent isothermal annealing of milled graphite powders was conducted at 1400 °C for 4 h in Ar gas. It was revealed via investigation of transmission electron microscopy that carbon nano onions were formed after annealing.

Friction welding is a type of solid state welding which plays an important role in joining metal surfaces with the help of frictional heat accompanied with high force. Optimization of process parameters of friction welding is important for all types of materials. Optimization of input parameters of friction welding also plays a very significant role in determining the quality of a weld joint. Purpose of this study is to optimize the welding process parameters in friction welding of AISI 904L super austenitic stainless steel by using regression analysis and evolutionary algorithms. This study is to determine optimimum welding process parameters of friction welding with the help of genetic algorithm (GA) and simulated annealing (SA). Also, it explains how to obtain near optimum welding conditions in a wide range by conducting a relatively small number of experiments. Results of these evolutionary computational techniques were compared with experimental results. Finally, an optimization parameter is obtained for a maximum fatigue life and a minimum welding time.

Phenol is a major environmental contaminant produced by various industries. In this study, phenol degradation was achieved using ozone treatment. The main parameter affecting the phenol degradation, i. e., ozone concentration, H 2 O 2 /phenol molar ratio and reaction time, were studied using statistical design of experiments to optimize the phenol degradation in terms of studied parameters. The results of the statistical design indicated that the ozone oxidation can be used for phenol degradation reaching high efficiency of 100 %. It was indicated that there is not only one condition at which the complete degradation can be carried out but also several design points lead to the same results. For instance, the complete degradation can be achieved at six hours reaction time, 0.03 H 2 O 2 /phenol molar ratio, and 10 g/m 3 ozone concentration.

The influences of hole dimension and position on the lateral buckling behaviour of woven fabric laminated composite cantilever beams having a square hole were investigated. Firstly, the theoretical, experimental and numerical characteristics of critical buckling loads of the beams without holes were investigated and compared with each other. It was shown that there is a good agreement among the theoretical, experimental and numerical results. The ANSYS finite element program was used for the numerical analyses. Furthermore, the numerical analyses of some models with various hole dimensions, different layer thicknesses, square shapes and fiber directions were performed by changing the distance between the hole. It is concluded for a square hole that the increase of the hole dimensions causes decrease of critical lateral buckling loads.