Design of overpressure beam repair

Contents

Introduction

1 Substantiation of part repair method

1.1 Part Design Analysis

1.2 Operation malfunction analysis

1.3 Analysis of basic repair process, substantiation of part repair method

2 Improvement of the repair process

2.1 Assembly Process - Disassembly

2.2 Defective Process

2.3 Design of Friday Recovery Process

2.3.1 Design of operations for expansion of worn out surface layers of the part

2.3.2 Design of machining operations for recoverable

details

2.4 Equipment and Process Tooling Design

3 Technical and economic calculations

3.1 Rationing of process operations

3. 2 Determination of part repair cost

Conclusion

Bibliographic list

Appendix: Process Documentation Package

Demo Sheets:

Sheet Overpressure Beam Drawing

General view of sheet surfacing accessory

Sheet surfacing operating map

Project Description

The course project contains 32 pages, 6 figures, 2 tables, 12 sources, 1 annex.

Process, part, workpiece, machine, accessory, cutting tool,

The object of development is the process of overpressure beam repair.

The purpose of the work is to develop a technological process for repairing the support surface of the overpressure beam, for this it is necessary to carry out a complete analysis of the basic technological process, design the technological process of restoring the part, machining operations, select bases, select equipment, develop equipment, carry out technical and economic calculations: rationing of technological operations; cost of part repair, issue process documentation.

Introduction

The design of the technological process in the course project under the section "Repair of rolling stock" of the discipline "Production technology and repair of rolling stock" is an important task in this field and an important stage in preparing the student for work on a diploma project on railway topics. This task is labor-intensive enough, requires a lot of material, intellectual costs to implement the technological process when organizing a new production. The correct and fast solution of the task can be carried out based on the rich experience and design skills of the technologist of the repair processes of parts in mechanical engineering.

The purpose of the project is to design a single process of overpressure beam repair, to master the main stages of process design under conditions of small-scale production. It is also necessary to further evaluate the technological, economic feasibility of this technological process of part repair; invention proposes ways of changing the technological process to increase repair efficiency and reduce the cost of the product.

Justification of unit repair method

Part Design Analysis

Superspring beam made of steel of grades 20FL or 20GFL, having hollow structure of closed cross section and shape close to bar of equal resistance to bending. It is cast together with a bearing, which serves as a support for the car body, and supports for sliders. Inverted boxes 8 with adjusting gaskets 9 are placed on each of two supports of slides. This design compared to the one used earlier (the boxes were cast integral with the overspring beam, and the slider inserts were laid in them, which in operation led to the accumulation of wear products and an unacceptable reduction in the gaps between the sliders of the trolley and the car body) ensures self-removal of wear products and the consistency of adjusted gaps between the sliders.

Operation malfunction analysis

Currently, the operation of the car fleet takes place in conditions of increased use of the load capacity of the car and high speeds. As a result, even when moving along rectilinear sections with V = 11 m/s, the inertia force reaches values ​ ​ sufficient to detach the patches from the flat surface of the bearing.

As a result, the edge support of the Friday and the redistribution of loads on the Friday and, as a result, increased damage in the zone of the patches are possible.

The crack of the support column is a consequence of defects of foundry origin. These cracks are detected through technological windows of upper and lower belts with illumination. Annular cracks are a consequence of the edge support of the heel on the bearing, especially with the additional effect of centrifugal and wind loads on the car body. As a rule, these cracks are created in the zones of the thrust bearings located along the transverse axis of the car. It is allowed to brew ring cracks provided that its length does not exceed 250 mm and does not pass through the outer side to the plane of the upper belt.

The formation of an annular crack in the vicinity of the pivot ledge is also affected by the action of the torque forming the heel on the bearing during longitudinal displacement, especially in the presence of significant wear of the bearing bead and the thrust surfaces of the heel. In this case, it is possible to form cracks around the entire boss for the pivot with the subsequent breaking of this boss and falling it inside the volume of the pressurizer beam.

Cracks of the outer side are formed more often in the sections of the side along the longitudinal axis of the car with significant wear of the inner surfaces from interaction with the heel.

When examining the overpressure beams, it was established that the depth of wear of the bearing bearing surfaces, thrust surfaces of the outer and inner beads increased sharply. This is due to the increased intensity of moving Friday along the bearing.

Movement of the heel along the bearing under additional influence of the edge support of the heel on the bearing and rotation of the heel relative to the bearing when the curves pass lead to wear of the bearing surface with maximum depth of wear near the outer side along the transverse axis of the car. The wear rate is approximately 0.30.4 mm per year.

The wear of the outer and inner sides has a pronounced orientation along the longitudinal axis of the car and a sickle shape.

The breakaways also have an orientation along the longitudinal axis of the car and are formed under the influence of longitudinal forces, provided that the side is significantly worn out.

The overpressure beam is supported by inclined surfaces located at an angle of 45 °, on friction wedges. In the course of movement of the car, the overstress beam and wedges mutually move along and across the car, which leads to wear of their inclined surfaces. Therefore, all types of repairs measure the wear of inclined surfaces using a template.

Clearances in horizontal slides have a significant effect on the dynamics of the car and on the stressed state of the parts. At reduction of total clearances between slides from 20 to 6 mm. the dynamics coefficient decreases by about 2-3 times. But at the same time, horizontal transverse forces increase when moving along curved sections, i.e., guide forces increase by 0.51 tons, which impairs fit into curves and can lead to derailment of cars.

The gap increases due to wear of the friction plane of the removable slide cap.

Design (improvement) of repair process

When designing operations, equipment, accessories, cutting and measuring tools should be selected for each of them, tolerances for operational dimensions and spatial deviations should be assigned, allowances and operational dimensions, modes and time standards should be calculated. The operation is divided into process and auxiliary transitions, installations, items, working and auxiliary moves.

2.2. Defective Process

Parts are defected in order to determine their technical condition: deformation and wear of surfaces, material integrity, change of properties and characteristics of working surfaces, shape deviations. Deformation is carried out in accordance with technological conditions or requirements for repair of the trolley. The reliability of the defect largely determines the quality of the restored parts. The following operations are characteristic of the defect: visual inspection with the naked eye or using optical means, blanking, etc. (cracks, nicks, hairlines, debris, dents, gags, corrosion, weakening of landing density are detected); measurement using a universal and special measuring tool (determine the geometric parameters of the parts); examination of surfaces of parts by means of optical, color, magnetic and other methods of non-destructive testing (determination of hidden surface defects); examination of depth layers of parts using ultrasonic, X-ray means (detection and identification of internal defects located below the surface on the opposite side).

Inspection of side frames and overspring beams using magnifying glass, 36 V portable light fixture, metal brush, measuring instruments. Surface of side frames and overpressure beams are inspected, paying special attention to cleanliness of surface of control zones subject to NDT, if necessary, they are cleaned for the second time. The value of wear and tear by templates and devices is determined. Overpressure beams and side frames with permissible wear for repair are supplied to ferrozond inspection.

Most often, cracks in overstress beams appear in inclined support surfaces, in collars limiting the transverse movements of the friction wedge, in upper, lower and vertical belts, in slides and the support surface of the bearing. One of the reasons for the formation of cracks in the overpressure beams may be the absence or increased clearance in the sliding legs of the car. Cracks in the places where the pivot is located, directed towards the shoulder of the bearing, are formed as a result of the production of the pivot hole and the occurrence of sharp shocks during dissolution from the sorting slides.

The overspring beam is defected on the trolley conveyor after washing, in the following sequence: 1) visual inspection using a 36 V portable light fixture and a metal brush (for cleaning of control areas), flaw detection VD12NF or at the ferrozond installation DF 201.1. 2) measurement of all parameters of the overpressure beam by templates. During inspection of the overpressure beam, the integrity of the upper, lower vertical belts and the column is determined, if they are present, the support part of the bearing place, the serviceability of the tide for the sliding cap and wear of the friction surfaces.

2.3. Design of overpressure beam recovery process

When choosing a method for restoring worn parts, it should be borne in mind that up to 85% of defective parts are welded and welded by arc methods.

The workflow recommends a sequence of operations and transitions that restore a worn part. The main stages of development of the surfacing process are:

- preparation of parts for surfacing;

- selection of built-up materials;

- calculation of surfacing mode parameters;

- selection of surfacing equipment and accessories;

- development of technique for execution of surfacing operations;

- selection of surfacing control method; compiling an operating map.

Parts to be built-up are cleaned from dirt, oil, rust, after which they are sorted and the possibility and expediency of restoration by build-up is determined. After cleaning the parts, the value and the wear pattern of the part, the presence of cracks, dents, rivets, etc. are determined. Cracks not removed before build-up remain under the layer of built-up metal and during operation propagate to the main and built-up metal.

When welding parts having holes on the surface to be restored, slots or grooves to be preserved are sealed with copper, graphite or coal inserts. The surfaces of the part to be protected from splashes of molten metal are covered with asbestos.

Welding techniques are determined by the build-up method.

Calculation is made for case of bearing surface wear.

Conclusion

In this course design, the technological process of repairing the worn-out bearing surface of the overpressure beam was developed, the main stages of designing the technological process under conditions of small-scale production were mastered: analysis of the design of the unit, malfunctions in operation, the basic technological process of repair, justification of the repair method of the unit were performed; calculations of surfacing modes, cutting modes, technical and economic calculations were made; determination of cost price, selected equipment, all necessary process documentation is issued. The developed process, after further correction, can be presented as a present process for repairing this part or be considered as an example for compiling processes of parts similar in design and process characteristics