Dariusz Boroński

The Investigations of Fatigue Cracking of Laser Welded Joint with the Use of ‘FatigueVIEW’ System

In this paper, the possibilities of detection and measurement of fatigue crack length in welded joints made of steel of duplex type, have been presented. In the investigations there has been used an original research system FatigueVIEW employing advanced optoelectronic techniques and numerical methods of image analysis. The proposed approach enables analysis of the fatigue crack growth during fatigue tests and after their finishing in off-line mode.

Use of Thermography for the Analysis of Strength Properties of Mini-Specimens

This paper presents sample applications of passive infrared thermography for research on temperature changes of mini-specimens resulting from monotonously increasing or cyclically variable mechanical load. The MFS system developed in the Department of Machine Design at the University of Technology and Life Sciences in Bydgoszcz (Poland) and designed for testing mechanical properties of microelements were used for tests. The MFS system ensures nanometric measurement accuracy of many static and fatigue-related material properties, including, i.a., static tension curves, cyclic strain curves, fatigue life curves as a function of force, stress and strain. Measurements of the mini-specimens temperature were performed using thermographic camera equipped with microscope lens. The tests have shown that research on the passive infrared thermography may be successfully applied for determining strength properties of materials in micro scale. The used research instrumentation is characterized by sufficient sensitivity and resolution (camera with the microscope lens), while the MFS system ensures accurate load and position control.

Dual-Band Experimental System For Subsurface Cracks Testing

The authors of this article have presented a hybrid method for inspection in the visible and infrared bands. A model of a test stand equipped with a monochromatic CCD and thermovision cameras which enable execution of tests in the field of active and passive thermography has been presented. Application of two vision channels provides the possibility of observing the defects caused by cracks and non-uniformity of a material structure, in the subsurface layer. An analysis of experimental tests performed on selected objects has been presented. Images from both channels, effects of the image overlapping and profiled charts along characteristic lines in thermograms have been shown.

Analysis of Strain Distribution in Notch Zone in Aluminium FSW Joints for Irregular Fatigue Loading Conditions

Joining aluminium alloys with the use of welding techniques often impairs their strength properties and in some cases it is very difficult or even impossible. An alternative method for joining this type of material is friction welding including FSW welding. The airplane aluminium alloy 2024-T3 is an example of material that can be welded using this method. Heat emitted during the process, which contributes to the material plasticisation in the zones of welding, causes significant changes in the material structure, thus affecting the joint properties. Fatigue life calculations of this type of joint can be performed according to different approaches. One of them is a local approach which requires knowledge of local strains or stresses within the notch zone. This paper is a presentation of exemplary results of experimental and numerical tests of strain in the zone of notch that occur in a joint under time variable loading.

Robot Actions Planning Algorithms in Multi-Agent System

In this paper, the basic information about multi-agent systems is given. The authors propose robot control algorithms for managing virtual autonomous warehouses, where the task performed by the robots is transportation between specific locations in the warehouse and a number of distribution points. Algorithms control the work of a single robot, including the cooperation with other robots in the environment as well as collisions avoidance. Different routing algorithms are evaluated through simulations focusing on service time and waiting time of executing tasks. The impact of the proposed algorithms on energy consumption was also checked, since this is important for the working time between battery charges.

Material Properties Investigations With the Use of Microspecimen

In the paper there are discussed possibilities of performing static and cyclic investigations of a material properties with the use of small size specimens. An original research system developed at the University of Technology and Life Sciences in Bydgoszcz has been used for static and fatigue testing. Thanks to tests performed on microspecimens it is possible, among others, to determine the material local properties in objects with the material discontinuities. This research provides exemplary results of fatigue tests carried out on microspecimens taken from a laser welded joint.

Application of Digital Image Correlation in Fatigue Crack Analysis

In the paper method of displacement analysis in the cracking zone based on digital image correlation and advanced multi-processor graphic cards procedures was presented. The basic assumption for the discussed displacement and strain measurement method under time variable loads was obtaining high measurement sensitivity by simultaneously minimizing the measurement time consumption. The developed digital procedures for correlation of images has been used for an example of displacement analysis in the crack propagation testing in airplane riveted joints.

Experimental verification of the crack opening displacement using finite element method for CT specimens made of Ti6Al4V titanium alloy

When determining the characteristics of the fatigue crack growth rate, it is necessary, inter alia, to measure the crack length growth which must be combined with the number of accumulated load cycles. The length of the crack is determined using different testing methods. Recently, there is an increased interest in optical systems based on digital image correlation methods. These methods have however some limitations as regards, inter alia, the sharpness of pictures taken during tests e.g. at cryogenic temperatures. This paper presents a comparative analysis of the crack length “a” as a function of a crack-opening-displacement “δ” obtained by experimental and numerical method. The tests were performed under ambient temperature for CT type specimens made of Ti6Al4V titanium alloy. Numerical research was carried out by finite element method using ABAQUS software. Satisfactory results were obtained which gave the reasons for establishing a hybrid methods for the crack length determination.

Unique Optomechatronic Systems for Fatigue Monitoring

The authors present examples of the developed unique optomechatronic systems for the monitoring of fatigue of materials. The systems employ different solutions from the area of optomechatronic technologies like machine vision methods with single-camera and dual-camera vision systems. Additionally, the article discusses the most important functional features and application possibilities of the developed apparatus.

Experimental Study of Non-Uniform Distribution of Basic Mechanical Parameters in Steel-Titanium Bimetal

The scope of this work is to study the process of explosive welding on basic strength properties of the welding interface layer and layers of the material which is near the welding interface. For this purpose the results of tests of basic strength properties in selected layers of steel-titanium bimetal (S355J2, titanium Grade 1) made by explosive welding are presented in the work. Tests were carried out by using mini-samples taken from the welding interface and from places located near the welding interface. Strength tests were carried out on the original system for strength tests - Micro Fatigue System (MFS). Strain during the tests was defined on the basis of a field analysis of dislocations in the cameras field of observation by use of the digital image correlation method. The conducted tests showed that the explosive welding process had impact upon basic strength parameters of the material of particular layers of the plated product.