Repair Of Metallic Structures Research Articles

Improvement of exploitation reliability of a magnetic-grab crane by means of removal of residual deformation in main beams

In hired results over of inspection of metal structures of main beams of bridge of magnetic-bucket crane are brought, his technical description is given. Reasons of origin of the remaining (negative) bending and his negative influence are educed on operating descriptions and safety of work of crane. The size of the negative bending of main beams of bridge is set in size of a 105 mm at the size of crane span 20 m. Such size of the building deflection resulted in rolling of two light carts of magnetic-bucket crane to the middle of span, their defect and leaning against three skating rinks. Such defect assisted strengthening of wear of flange and increased attenuation time of own vibrations. Previous repairs of beams by means of hot edit heating of areas of lateral walls to the temperature 800-900°C in future negatively affected on operating descriptions of crane metal construction. Expedient complex technology of repair of metal structures for span beams is offered technically with the purpose of extension of time of service of crane. Technology includes: method of hot edit of beam and method of preliminary tension. The sequence of works is described at implementation of repair these methods. The construction of stretching device and his bracing on main beams. In the construction of stretching device supports are included with the set tighteners (lug). Tensioning devices are fastened to the bottom belt of tension beams. In lugs the cored armature is set and she is laid on brackets. The pull of the cored armature is produced by means of hydraulic jacks, fixed by a nut and check-nut. Diagrammatized technological process of complex repair. The offered technology will allow to produce repair works without dismantling of crane and promote reliability of its exploitation

Towards robotic steel construction through adaptive incremental point welding

Additive manufacturing enables industries with a new production typology. For the metal manufacturing industry, this new means of production extends the spectrum of achievable building parts that can be fabricated and integrated into architectural designs. Consequently, this process is becoming increasingly relevant for construction industries. The application of additive manufacturing in metal fabrication industries requires high performance technology and extensive knowledge of material and process. Within this paper, we focus on the implementation of incremental point welding as a metal additive arc welding strategy. The goal is the realization and optimization of a manufacturing method which implements adaptive strategies in the control of this production process. In this research, incremental point welding is used for the production of branching structures. Incremental point welding is a type of metal arc additive manufacturing which deposits material by adding individual welding points rather than layering welding seams. This process is interesting for a number of reasons. The incremental application of individual metal drops simplifies the analysis and forecast of residual stress and temperature developments. Consistent arc initialization within point welding is hard to control and, therefore, requires further exploration. This led to the following research in developing an adaptive process. Furthermore, the potential of the process is increased by the possibility of tool-path adaptivity for a robotic system enabling the robot to produce welds at complex approach angles. This research developed a novel approach, able to manufacture complex branching structures while compensating for inaccuracies caused by the welding process using image processing and an adaptive strategy. First experiments showed the possibility to work at a range of overhang angle in addition to multiple approach angles up to 50°. This adaptive process increases the potential application of this technology for the extensions of existing structures as well as repair of metal structures through incremental point welding.

Interaction between adherend plasticity and adhesive damage in metal/composite joints: application to bonded composite repair of metallic structures

The plasticity in the crack region is a great influence on the fatigue life of aircraft structures, and the adhesive damage has negative effects on the durability of bonded joints. In this paper, the interaction effect between the crack tip’s plasticity and adhesive damage in a bonded composite repair of cracked metallic panels was analyzed using the three-dimensional finite element (FE) method. A damage criterion was implemented in the FE model to evaluate the damaged zone in the adhesive layer, and the plastic strain around the crack was extracted from the FE calculations. In this research, we have demonstrated that the applied load has very significant effects both on crack plasticity and adhesive damage, but the ductility of the repaired material has no significant effect on adhesive failure. Fatigue tests and SEM observations were performed to validate the numerical results.

Imitational modeling of residual stresses in materials employed for the repair of structural steels

Results of the calculations of residual stresses of composites based on polymer binder and glass fiber, which are used in the repair of metal structures of machines, by imitational modeling have been considered. Imitational modeling has been carried out using a special program that enables one to calculate required parameters with a very high rate after choosing initial data from preformed number sets. It has been determined that the modulus of glass plastics has the most sizeable effect on residual stresses.

Thermal Analysis by Numerical Methods of Debonding Effects near the Crack Tip under Composite Repairs

Composite patch repair of metallic structures has become a rapidly grown technology in the aerospace field due to the demand for significant increases in the useful life of both military and civilian aircraft. This has led to significant advances overall in the repair technology of cracked metallic structures. Adhesively bonded composite reinforcements offer remarkable advantages such as mechanical efficiency, repair time, cost reduction, high structural integrity, repair inspectability, damage tolerance to further causes of future strains, anticorrosion and antifretting properties. However, because of the different nature and properties of the materials that form a repair (metals, composites, adhesives), side-effects may occur: debonding due to high stress concentration in the vicinity of the crack, thermal residual stresses because of different thermal expansion coefficients of the adherents, etc. In this paper a three-dimensional finite elements analysis of the area around a patch repaired crack of a typical aircraft fuselage is performed, taking into account both the properties and the geometry of the involved materials. Examined in this case are 2024-T3 aluminum alloy as base material, FM-73 as the adhesive system and F4/5521 boron/epoxy prepreg as the patch material. Through the thickness stresses near the crack tip and along the patch edges with and without temperature effects are calculated and debonding near the crack tip is examined. Finally, the calculated results are compared with existing theories.

Methodology to analyse aerospace structures repaired with a bonded composite patch

Adhesively bonded composite repair of metallic structures is one of the candidate technologies that has enormous potential in the ageing aircraft. A computational tool to analyse the repaired aerospace structure using an adhesively bonded composite patch is presented. This involves the three-layer technique based on the two-dimensional finite element method for adhesively bonded composite patch repair of cracked structures. This technique is capable of characterizing the crack growth and debond growth behaviour, as well as predicting the fatigue life extension of the repaired structure with a perfectly or imperfectly bonded patch. Also, the thermal effects which may develop during bonding or during service and the non-linear material behaviour of the adhesive are incorporated in this technique. The results from the three-layer technique show good agreement with experimental results as well as a previous investigator's published numerical results. Besides the accuracy of the technique, the advantage of the two-dimensional three-layer technique is cost-effectiveness when compared with the three-dimensional finite element or performing expensive experiments on various patch configurations for design purposes. An overview of the three-layer technique to investigate a cracked metallic plate repaired with bonded composite patch is presented in this paper.

Composite material repairs to metallic airframe components

The repair of metal structures by using composite materials is a technology that was pioneered in Australia, and excellent results have been obtained in over 500 repairs of corrosion and fatigue cracking. This paper will present details of the first in-service composite material repair applied to metal structure on USAF C-141B operational aircraft. This engineering study evaluated five locations representing both fatigue and corrosion cracking susceptible areas on the C-141B strategic airlift transport aircraft. Repairs using either boron/epoxy or graphite/epoxy are beneficial for crack retardation, end fastener effect relief, and field stress reduction. The most obvious time saving feature of these repairs is that no fastener removal or installation is involved. Extensive structural analysis utilizing finite element modeling was done to ensure that the repair design not only would have the requisite strength and durability but also would reduce the inspection burden after the aircraft was returned to service. A test program was also undertaken to substantiate the analytical investigation. Typical results from the finite element models as well as the specimen and component tests will be presented. Finally, the step-by-step procedure by which an actual boron/epoxy repair was applied to a fatigue crack on a C-141 center wing will be reported and lessons learned will summarize the benefits of applying the technology.

Analysis of bonded repairs to damaged fibre composite structures

This paper describes a finite element method for analysing the behaviour of flaws in thin fibre composite sheets which are repaired with a bonded overlay. The method is an extension of the authors' previous work on the repair of metal structures. As illustrative examples the repair of a hole and a crack in various graphite/epoxy laminates is discussed and it is shown that in each case a bonded overlay of either boron/epoxy or titanium provides an effective repair.