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Breakage of machine parts
When performing repairs because of the broken parts lay, knots and units of cars destroyed parts changed for new ones. Such a simple replacement may not be EF- good, until you have found and fixed the cause failure. Otherwise, the newly installed item doesn't work put the resource time and the repair could but consider poor quality. With a sufficiently high degree of probability the cause is breaking up can be determined by the condition of the surfaces indicated mA destroyed details. It is known that the destruction is not Pro- proceeds simultaneously along the entire cross section of the part. It starting by in a certain place, where spreads the "body" part. Consequently, the cause must be sought at the beginning of process of destruction. The start point of fracture and its character set is Xia by visual inspection. When the fault detection parts carefully inspected the surface of the fracture and observed their features. First, inspect all the parts of the destroyed parts in crude form. Pay attention to the presence of traces impact on the component's surface near fracture zone, estimated- newauth color of the fracture. Thus, the presence of traces of paint or- a particular colour of oxidized metal at the fracture point to that work was knowingly installed the defective part, i.e. having cracks in the "body" to its operation. For more information about the reasons fracture the fracture surface cleaned of rust and other contaminants by using solvents, for example kerosene, while it is undesirable to use a metal fir brushes. When cleaning parts made of aluminium and its alloys you can't use alkalines, as they cause rastres- Kiwanis surfaces. When visual inspection is made of the pattern of the fracture, which cause the characteristics of the structure. To includes: • the difference in grain size across the section; • the presence of characteristic lines in the form of scars, light or concentric circles; • the General inclination of the surface of the fracture in relation to the axis of the piece; • fibrous or granular (crystalline) structure- tion of the fracture; • the color of the fracture (matte or shiny). It is very important to pay attention to the surface, when- VH to fracture. Sagnotti edges ("neck") indicates on the plastic deformation of the metal before its time violated. The fracture surface in this case has Matho- vy color and fibrous structure. Identified by visual inspection features con- moving the surface of the fracture are explained as follows. Any destruction begins with the appearance of one tre- the bus interface or a network of cracks. The crack, which occurred the destruction is called trunk. If the highway- Naya crack passes through the merging of multiple cracks, in the rays appear fracture, scarring, fan-shaped rashomama- Xia beginning from the zone of destruction. On the surface parts near the fracture are usually cracked, pre- marching to destruction. As the crack speed its spread increases. Found that the greater the growth rate of the tre women, the rougher the fracture surface. Consequently, IU- CTE began the destruction of the roughness will be less than in the end. This fact is one of the signs by- allows to define the start point of destruction. In the area of the end of the fracture the fracture surface very hour it represents a stage of torn metal. If the details of the stress concentrator in the form of cracks of different origin, corrosion of isyas- representations, etc. failure occurs at the hub- of the voltages. It is important to know that in this case of plastic de- formation of metal missing near the fracture, and the fracture not sagnotti edges. Possible cause destruction — the existence of the defect. The surface has a metal chip metallic luster and crystalline structure. Signocast the edges of the parts in the destruction of the appears as a result of plastic deformation (thin places) metal that is usually caused by congestion in a single load- terms. The fracture surface has a matte color and volokno- hundred structure, due to the crushing of grains during plastic tration of metal deformation in the fracture zone. Fig. 153. Destruction details for different types of deformation: a — destruction with plastic deformation; b — fracture at stress concentrators The slope of the fracture surface indicates the direction action forces at the moment of destruction. The upper part of the fracture is the beginning of destruction. During the movement of cracks in sheet metal when its time violations on the surface fracture traces appear sometimes in the form of sharp corners, the tops of which indicate the place beginning of destruction. As surfaces all the kinks can be divided into- to pour on: • fragile; • fatigue; • plastic (ductile). Every destruction corresponds to a the cause of his appearance. Brittle fractures are characterized by the following special- values: • no sagnotti near the edges of the fracture, which is associated with the lack of plastic deformation in the place of the destr- of; • the surface of the fracture has a crystalline structure and metallic luster; • there are two fracture zones, one of which with small roughness, the other with coarse. Clear the separation between zones is usually not. Brittle fractures indicate that the reason for the development the agreement is the presence of stress concentrators. Itself the destruction in this case takes place at the hub- of voltages without plastic deformation. Stress concentrators are: • cracks of any origin (thermal, swar- nye, fatigue, etc.); • the separation of the metal; • speed the transition from one part size to another- mu; • deep risks after machining, thread; • corrosion pitting; • embrittlement of metal caused by welding, termites- coy treatment, galvanic voltages, etc. Site of origin of the destruction is the focus area with the chalk- coy roughness. The end is in destruction the second zone with coarse roughness. This type of fracture often occurs in details of cars Biel. Thus, the destruction of welded joints of the frame can be due to the presence of cracks, lack of fusion weld root, Krup- Chennai area near the weld. These defects are- Xia due to improper welding technology. Cracks and krupjanye areas in shafts, axes arise mainly because of wrongly chosen technology termites- coy processing. Brittle fracture of such parts can be and in places with an abrupt transition from one part size to another thread, if there are deep scratches after fur- technical processing, due to incorrect design- her shaft or violation of technology of mechanical treatment CI. A smooth transition of size, increase of purity treatment Ki reduces the risk of brittle fracture. Thus, brittle fracture indicates that the the reason for breakage of parts is one of the above defects, and this should be considered when replacement is broken parts with new. Fatigue fractures are characterized by the following particu- larities: • no sagnotti edges; • metallic luster; • crystalline structure; • special structure of the surface of fracture, it was observed- is four zones: the fracture zone mirror Shine, development zone crack, zone to- scrap. The first two zones are relatively rare, and it was not an entirely are mandatory for this type of destruction. The main determinant for fatigue fracture is is the third zone. It consists of concentric sub-zones, diverging from the starting point of destruction. The size of the zones and the roughness inside of them grow as the movement should talk- us to doloma. Area doloma is often represented in the form curbs and ledges. Sometimes on the surface of fractures view- NY rays, scars, spreading from the place of beginning La destruction. In this case, on the surface near the start destruction is a grid of cracks and the serve- if the cause of failure. A large number of subbands with very minor shero- the root mean square roughness indicates the fact that the item you are holding the calculated number of cycles alternating load- tion. Destruction details associated with the overage service. Detail worked the specified resource and its needs were replaced before the destruction. A small number of subbands (the number can be counted) rough the roughness of the inside of them is associated with overload details during the alternating loading. In this case not- necessary to establish the cause of the overload before- replace the item with a new one. Fatigue breaks occur in parts automotive blah, working in conditions of action of the alternating on- burden such as axles, brackets, etc. This kind destruction have frame, shaft, axle. Premature- tion of failure of frames is associated with the wrong technology welding and machining. Ductile fractures are characterized by the presence of plasti- tration of metal deformation near the fracture, which is expressed supplied in the thinning section detail and the appearance of sagnotti edges. Fracture surface has a matte color and in- loknyste structure in the form of tears metal. Plastic fracture indicates that the destruction of de- Tali was due overload. In this case, the need MoE to determine the cause of the overload that caused the destruction details. The causes of overload may be: • wrong calculation details; • wrong choice of metal lower than required mechanical properties; • destruction of one part can cause congestion another its subsequent destruction. When repairing the cause plastic the destruction of parts must be eliminated. Thus, to determine the causes of destruction car parts in structure to the external surface fracture offers some procedure to VI- RA: • carefully examine the fracture surface and its vicinity to clean, to note features of a structure; • clear kink from dirt, rust with RA- storytella — kerosene, gasoline, etc.; • to re-examine the fracture surface as possible with magnification up to 10 times, set the type of fracture and the place beginning of destruction; • carefully inspect the site of origin of the fracture and the near- of zi, the presence of defects, their nature, the location and give a possible conclusion in mind break about the cause of the destruction, deletion repetition |
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