Ladder frame processing method of aerial ladder fire truck

Abstract

The invention relates to a ladder assembly processing method of an aerial ladder fire truck. The ladder frame processing method comprises the following steps: acquiring a vibration point position according to the length of a ladder frame; cantilever rods are installed at the vibration point positions, and the ends of the cantilever rods extend out of the ladder frame in the width direction of the ladder frame; acquiring corresponding vibration parameters according to the vibration point positions; and according to the vibration parameters, the ladder frame is vibrated at the ends of the cantilever rods. The cantilever rods can amplify the vibration effect of vibration equipment, the vibration equipment can be accurately and finely adjusted conveniently to conduct vibration treatment on the ladder assembly, the stress reduction effect is improved, the vibration effect is amplified through the cantilever beams, smaller, cheaper and lighter vibration equipment can be used for completing work, the cost can be reduced, and the working efficiency is improved. The vibration equipment does not directly bear the counter-acting force of the ladder assembly, but acts on the relatively light cantilever rod, so that the impact on parts in the vibration equipment is reduced, the service life of the vibration equipment is prolonged, and the damage to the ladder assembly structure can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fire-fighting equipment, and in particular to a ladder rack processing method of a turntable ladder fire engine. BACKGROUND

[0002] The ladder rack of a turntable ladder is a main bearing component of the turntable ladder fire engine, and is also a running track of a lifting trolley. The welding quality directly affects the rescue smoothness of the vehicle. In order to solve the problem of obvious deflection of the ladder rack under load, a large turntable ladder rack usually adopts a "large circular arc" pre-deformation design. Therefore, a pre-deformation amount is applied by a tool before welding, and the deformation at the opening is also constrained. The turntable ladder rack is welded under the condition of very large external constraint, thereby increasing the residual stress of the structure. In the actual service process, the peak stress is reduced and the residual stress distribution is homogenized under the action of external load, thereby affecting the dimensional stability of the structure. SUMMARY

[0003] The present application provides a ladder rack processing method of a turntable ladder fire engine to improve the stress reduction effect.

[0004] The present application provides a ladder rack processing method of a turntable ladder fire engine, which includes the following steps: obtaining a vibration point according to the length of the ladder rack; installing a cantilever rod at the vibration point, and extending the end of the cantilever rod to the outside of the ladder rack in the width direction of the ladder rack; obtaining a corresponding vibration parameter according to the vibration point; and vibrating the ladder rack at the end of the cantilever rod according to the vibration parameter.

[0005] In some embodiments, the ladder rack includes a pair of lower chord rods extending in the length direction of the ladder rack. The ladder rack processing method includes: installing a cantilever rod at the vibration point of the lower chord rod, the cantilever rod extending in the width direction of the ladder rack, and the two ends of the cantilever rod respectively extending to the two sides relative to the pair of lower chord rods; and vibrating the ladder rack at the two ends of the cantilever rod in turn according to the vibration parameter.

[0006] In some embodiments, the ladder rack processing method includes: obtaining a plurality of interval vibration points in the length direction of the ladder rack; installing a cantilever rod at each vibration point in turn; obtaining a vibration parameter of each vibration point in turn; and vibrating the ladder rack at the end of the cantilever rod according to the vibration parameter of each vibration point in turn.

[0007] In some embodiments, obtaining a corresponding vibration parameter according to the vibration point includes: installing a vibration exciter at the end of the cantilever rod, and obtaining the resonance acceleration of the ladder rack at the vibration point by using the vibration exciter to perform pre-vibration frequency sweeping.

[0008] In some embodiments, the vibrating the ladder stand at the end of the cantilevered rod according to the vibration parameter includes adjusting an operating state of the exciter according to the resonance acceleration to make an actual vibration acceleration of the ladder stand at the vibration point within a preset acceleration range.

[0009] In some embodiments, the preset acceleration range includes 0.9ar≤as≤0.95ar, where as is the actual vibration acceleration of the ladder stand at the vibration point, and ar is the resonance acceleration of the ladder stand at the vibration point.

[0010] In some embodiments, adjusting the operating state of the exciter according to the resonance acceleration includes adjusting a rotating speed and / or an eccentricity of the exciter.

[0011] In some embodiments, adjusting the operating state of the exciter according to the resonance acceleration includes acquiring a stress monitoring point and detecting a dynamic strain of the stress monitoring point in real time, and after the actual vibration acceleration reaches the preset acceleration range, determining whether the dynamic strain of the stress monitoring point is within a preset strain range, and if not, continuing to adjust the operating state of the exciter to make the dynamic strain of the stress monitoring point within the preset strain range.

[0012] In some embodiments, the ladder stand includes a pair of lower chords, a pair of upper chords, and support rods connected between the upper chords and the lower chords, and acquiring the stress monitoring point includes selecting the stress monitoring point at the lower chord, the upper chord, the support rod, and a connection between the support rod and the upper chord according to a residual stress distribution simulated by welding numerical value of the ladder stand.

[0013] In some embodiments, the preset strain range includes -250με≤εt≤250με, where εt is the dynamic strain of the stress monitoring point.

[0014] According to the technical scheme provided in the application, the ladder frame processing method comprises the following steps: obtaining a vibration point according to the length of the ladder frame; installing a cantilever rod at the vibration point, and extending the end of the cantilever rod to outside the ladder frame in the width direction of the ladder frame; obtaining a corresponding vibration parameter according to the vibration point; and vibrating the ladder frame at the end of the cantilever rod according to the vibration parameter. The vibration device is installed at the end of the cantilever rod to perform vibration, and the vibration effect of the vibration device is amplified by the characteristics of the cantilever beam, so that the vibration device can be finely adjusted to vibrate the ladder frame, and the stress reduction effect is improved. In addition, the vibration device is directly installed on the ladder frame to perform vibration, and a larger power is required to drive the vibration device to achieve the stress reduction effect. The vibration effect is amplified by the cantilever beam, and smaller, cheaper and lighter vibration devices can be used to complete the work, which has strong economic efficiency and reduces the cost. The vibration device itself does not directly bear the reaction force of the ladder frame, but acts on the relatively light cantilever rod, which reduces the impact on the parts in the vibration device, prolongs the service life of the vibration device, and also reduces the damage to the structure of the ladder frame during the vibration process, thereby protecting the ladder frame. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings, which are included to provide a further understanding of the present disclosure and constitute a part of this application, illustrate certain illustrative embodiments of the present disclosure and are used to explain the present disclosure, but do not limit the present disclosure. In the drawings:

[0016] Figure 1 The schematic diagram of the state of the ladder frame of some embodiments of the present application vibrating at the first point by the exciter.

[0017] Figure 2 The schematic diagram of the state of the ladder frame of some embodiments of the present application vibrating at the first point by the exciter. Figure 1 The schematic diagram of the state of the ladder frame of some embodiments of the present application vibrating at the first point by the exciter.

[0018] Figure 3 The schematic diagram of the state of the ladder frame of some embodiments of the present application vibrating at the second point by the exciter.

[0019] Figure 4 The schematic diagram of the state of the ladder frame of some embodiments of the present application vibrating at the third point by the exciter.

[0020] Figure 5 The schematic diagram of the state of the ladder frame of some embodiments of the present application vibrating at the third point by the exciter. Figure 6 The schematic diagram of the principle of stress elimination by vibration.

[0021] Figure 7 The schematic diagram of the selected stress monitoring points of some embodiments of the present application.

[0022] Figure 8 The schematic diagram of the selected stress monitoring points of some embodiments of the present application. Figure 9The schematic diagram of residual stress comparison of different point positions before and after vibration for some embodiments of the present application.

[0023] Figures 10 to 12 The schematic diagram of residual stress comparison of different point positions before and after vibration for some embodiments of the present application. Figure 8 and Figure 9 The schematic diagram of residual stress comparison of different point positions before and after vibration for some embodiments of the present application.

[0024] Explanation of reference signs

[0025] 1, ladder frame; 11, upper chord; 12, lower chord; 13, support rod;

[0026] 2, connecting rod;

[0027] 3, cantilever rod; 4, elastic support pad; 5, exciter. DETAILED DESCRIPTION

[0028] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative in nature and is in no way intended to limit the disclosure, its application or uses, except as described by the appended claims. The present disclosure can be implemented in numerous different forms, as is required, and is not limited to the embodiments described herein. These embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the present disclosure to those skilled in the art. It should be noted that the relative arrangement of components and steps set forth in these embodiments, the components of the materials, numerical expressions, and numerical values are to be interpreted as merely exemplary, rather than as a limitation unless specifically stated otherwise.

[0029] The "first", "second", and similar words used in the present disclosure do not indicate any order, number, or importance, but are only used to distinguish different parts. "Include" or "contain" and similar words mean that the elements before the word cover the elements listed after the word, and do not exclude the possibility of also covering other elements. "Up", "down", "left", "right", and the like are only used to indicate relative positional relationships, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0030] In the present disclosure, when it is described that a specific device is located between a first device and a second device, there can be an intervening device between the specific device and the first device or the second device, or there can be no intervening device. When it is described that a specific device is connected to other devices, the specific device can be directly connected to the other devices without an intervening device, or can not be directly connected to the other devices with an intervening device.

[0031] All terms used in the present disclosure, including technical or scientific terms, have the same meanings as those understood by those having ordinary knowledge in the art to which the present disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense, unless expressly so defined herein.

[0032] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the specification where appropriate.

[0033] In order to ensure the size stability of the ladder frame of the aerial ladder fire truck during service, stress relief treatment can be carried out in advance to age the ladder frame in advance, thereby ensuring the reliability and safety of the aerial ladder fire truck during service.

[0034] First, the principle of vibration stress relief is introduced: vibration aging is to apply additional stress to the workpiece after processing (including welding, casting, cold extrusion, etc.) in the form of mechanical vibration. When the total stress obtained by superimposing the additional stress and the residual stress of the workpiece reaches or exceeds the yield stress, plastic deformation will occur in the stress concentration area, thereby reducing the peak value of the residual stress in that area and achieving the purpose of stress homogenization. In addition, vibration causes dislocation multiplication and slip, which raises the yield point of the material and improves the anti-deformation ability of the metal, thereby achieving the purpose of stabilizing the size of the workpiece and improving the running quality of the workpiece.

[0035] Some embodiments of the present application provide a ladder frame treatment method for an aerial ladder fire truck, which comprises the following steps:

[0036] S1, obtaining vibration point positions according to the length of the ladder frame 1;

[0037] S2, installing cantilever rods 3 at the vibration point positions, and extending the end portions of the cantilever rods 3 to the outside of the ladder frame 1 in the width direction of the ladder frame 1;

[0038] S3, obtaining corresponding vibration parameters according to the vibration point positions; and

[0039] S4, vibrating the ladder frame 1 at the end portions of the cantilever rods 3 according to the vibration parameters.

[0040] According to the treatment method provided by the present embodiment, first, the vibration point positions to be subjected to vibration treatment are determined on the ladder frame 1, then the cantilever rods 3 are installed at the vibration point positions, the cantilever rods 3 extend substantially in the width direction of the ladder frame 1, and a part of the cantilever rods 3 is fixedly arranged on the ladder frame 1, and the other part of the cantilever rods 3 extends relative to the ladder frame 1, and the cantilever rods 3 and the ladder frame 1 form a cantilever beam structure.

[0041] The vibration is performed by setting the vibration device at the end of the cantilever beam 3 (the end extending relative to the ladder frame), and the cantilever beam 3 can amplify the vibration effect of the vibration device by using the characteristics of the cantilever beam, so that the vibration device can be finely adjusted to vibrate the ladder frame 1, and the stress relief effect is improved. In addition, directly installing the vibration device on the ladder frame 1 to vibrate requires a larger power to drive the vibration device to achieve the stress relief effect, and the vibration effect is amplified by the cantilever beam, so that a smaller, cheaper and lighter vibration device can be used to complete the work, which has strong economy and reduces the cost. The vibration device itself does not directly bear the reaction force of the ladder frame 1, but acts on the relatively light cantilever beam 3, which reduces the impact on the parts in the vibration device, prolongs the service life of the vibration device, and also reduces the damage to the structure of the ladder frame itself during the vibration process, thereby protecting the ladder frame 1.

[0042] In some embodiments, the ladder frame 1 includes a pair of lower chords 12 extending along the length direction of the ladder frame 1, and the ladder frame processing method includes:

[0043] S21, installing a cantilever beam 3 at the vibration point of the lower chord 12, the cantilever beam 3 extending along the width direction of the ladder frame 1, and the two ends of the cantilever beam 3 extending to the two sides relative to the pair of lower chords 12 respectively;

[0044] S41, sequentially vibrating the ladder frame 1 according to the vibration parameters at the two ends of the cantilever beam 3.

[0045] Specifically, the ladder frame 1 of the aerial ladder fire truck has a pair of parallel and spaced lower chords 12 extending along the length direction of the ladder frame. In this embodiment, the length of the cantilever beam 3 is greater than the width of the ladder frame 1, and when the cantilever beam 3 is installed, the two ends of the cantilever beam 3 extend to the outside of the ladder frame 1 relative to the two lower chords 12 (the area between the two lower chords 12 is defined as the inside of the ladder frame), and the cantilever beam 3 and the lower chord 12 form an overhanging beam structure. In the width direction of the ladder frame 1, the two lower chords 12 are the two fulcrums of the cantilever beam 3, and the lengths of the two ends of the cantilever beam 3 extending relative to the two lower chords 12 are the same.

[0046] In this embodiment, the vibration is performed on the two sides of the ladder frame 1 in a symmetrical manner, and the same vibration parameters can be used when vibrating on the two sides, for example, when the exciter 5 is used for vibration, the vibration on the two sides can use the same vibration time, the same eccentricity and the same rotating speed, so that the balance of the stress relief effect on the two sides can be effectively guaranteed, and the efficiency can be saved and the convenience can be improved.

[0047] In some embodiments, the ladder frame processing method includes:

[0048] S12, obtaining a plurality of interval vibration points along the length direction of the ladder frame 1;

[0049] S22, sequentially installing the cantilevered rods 5 at the vibration points;

[0050] S32, sequentially obtaining the vibration parameters of the vibration points; and

[0051] S42, sequentially vibrating the ladder stand 1 at the ends of the cantilevered rods 3 according to the vibration parameters of the vibration points.

[0052] Specifically, the ladder stand 1 of the aerial ladder fire truck usually has a long length. In order to achieve a better stress reduction effect, a plurality of vibration points are selected along the length direction of the ladder stand 1, and then the above-mentioned processing method is referred to, the cantilevered rods 3 are installed at each vibration point and are vibrated at both ends of the cantilevered rods, and then the same steps are performed on the next vibration point. The vibration parameters of each vibration point are different because the same excitation force is applied at different positions of the ladder stand 1, and the vibration response obtained is different. Therefore, when each vibration point is vibrated, the corresponding vibration parameters need to be reacquired and the vibration is performed according to the corresponding vibration parameters, so as to guarantee the stress reduction effect.

[0053] For example, three interval vibration points can be obtained along the length direction of the ladder stand 1, and the lower chord 12 on both sides is vibrated at each vibration point, a total of six times of vibration processing is performed on the ladder stand 1. In this way, the stress reduction can be performed on the points of the ladder stand 1 with large residual stress. Moreover, more vibration times and more vibration positions can also make the stress distribution of the ladder stand 1 after vibration processing more balanced, thereby improving the anti-deformation ability of the ladder stand 1 and improving the safety and reliability of the aerial ladder fire truck during operation.

[0054] In some embodiments, the step S3 of obtaining the vibration parameters according to the vibration points comprises:

[0055] S300, installing the exciter 5 at the end of the cantilevered rod 3, and obtaining the resonance acceleration of the ladder stand 1 at the vibration point by using the exciter 5 to perform pre-vibration frequency sweeping.

[0056] In this embodiment, the exciter 5 can be signal-connected with a vibration controller (not shown in the figure), and the vibration controller can control the exciter 5 to scan the ladder stand 1 from low frequency to high frequency, so as to determine the resonance acceleration of the ladder stand 1 at the vibration point. After the resonance acceleration of the vibration point is determined, the state of the exciter 5 can be adjusted according to the value of the resonance acceleration during subsequent vibration processing, so as to achieve a better stress reduction effect.

[0057] In some embodiments, the step S4 of vibrating the ladder stand 1 at the end of the cantilevered rod 3 according to the vibration parameters comprises:

[0058] Step S400, adjusting the operating state of the exciter 5 according to the resonance acceleration so that the actual vibration acceleration of the ladder frame 1 at the vibration point position is in the preset acceleration range.

[0059] In the embodiment, the preset acceleration range is a numerical range determined according to the resonance acceleration of the vibration point position, and the actual vibration acceleration of the vibration point position on the lower chord 12 is taken as the control target. By adjusting the operating state of the exciter 5, the actual vibration acceleration of the vibration point position is in the preset acceleration range, so that a better stress reduction effect can be achieved.

[0060] In some embodiments, the preset acceleration range includes: 0.9ar≤as≤0.95ar, where as is the actual vibration acceleration of the ladder frame 1 at the vibration point position, and ar is the resonance acceleration of the ladder frame 1 at the vibration point position.

[0061] For example, for a certain vibration point position, after frequency sweeping, the determined acceleration of the ladder frame resonance is 47.1 m / s 2 , the preset acceleration range can be advantageously set to 42.39~44.75 m / s 2 , so that a better stress reduction effect can be achieved.

[0062] Advantageously, in some embodiments, the preset acceleration of the ladder frame 1 at the vibration point position is configured to be 0.947*ar, and in the case of the acceleration of the ladder frame 1 resonance being 47.1 m / s 2 , the actual acceleration at the vibration point position should be adjusted to 44.6 m / s 2 , so that a better stress reduction effect can be achieved.

[0063] In some embodiments, in step S400, adjusting the operating state of the exciter 5 according to the resonance acceleration includes:

[0064] Adjusting the rotational speed and / or eccentricity of the exciter 5.

[0065] Specifically, only the rotational speed of the exciter 5 can be adjusted, only the eccentricity of the exciter 5 can be adjusted, or the rotational speed and eccentricity of the exciter 5 can be adjusted at the same time, as long as the actual acceleration of the ladder frame 1 at the vibration point position is adjusted to the preset acceleration range.

[0066] In some embodiments, the eccentricity of the exciter 5 is adjusted between 30~60%.

[0067] In some embodiments, in step S400, adjusting the operating state of the exciter 5 according to the resonance acceleration includes:

[0068] The dynamic strain of the stress monitoring point is acquired and detected in real time. After the actual vibration acceleration reaches the preset acceleration range, it is judged whether the dynamic strain of the stress monitoring point is in the preset strain range. If not, the running state of the exciter 5 is continuously adjusted to make the dynamic strain of the stress monitoring point in the preset strain range.

[0069] As shown in Figure 5 and 6 , assuming that the welding residual stress of a certain point corresponds to the point (ε0, σ0), in the mechanical stress relief process, the external pressure and the residual stress are superimposed. When the stress exceeds the yield stress σs of the material and reaches σp, plastic deformation is caused. The loading process is elastic-plastic deformation, and the unloading process is only elastic. Therefore, after the external load is removed, the plastic deformation returns to the original strain state, reaching the point (ε0, σr). Therefore, the application of mechanical pressure can reduce the residual stress from σ0 to σr. After multiple cyclic vibrations, until the superimposed external stress and residual stress is less than the yield strength of the material, the residual stress will not be reduced. At this time, the stress reduction is completed.

[0070] In the embodiment, the dynamic stress range of the stress monitoring point in the vibration process can be reflected by detecting the dynamic strain, thereby ensuring that the vibration process is effective, or in other words, ensuring that the superimposed external stress and residual stress at the stress monitoring point can exceed the yield stress of the material, causing plastic deformation of the material, thereby advantageously ensuring the stress reduction effect.

[0071] It is worth understanding that after the actual vibration acceleration of the exciter 5 adjusted to the vibration point position conforms to the preset acceleration range, if the dynamic strain of the stress monitoring point is not in the preset strain range, the rotational speed and eccentricity of the exciter 5 need to be adjusted by the vibration controller to make the dynamic strain of the stress monitoring point in the preset strain range. Since the exciter 5 is installed on the cantilever rod 3, and the vibration amplification of the cantilever rod 3 is used, only the rotational speed and eccentricity of the exciter 5 need to be fine-tuned. Therefore, the adjustment process of the exciter 5 is more precise and convenient based on the ladder processing method provided in the embodiment.

[0072] In some embodiments, the ladder 1 includes a pair of lower chords 12, a pair of upper chords 11, and support rods 13 connected between the upper chords 11 and the lower chords 12. The stress monitoring point is acquired by:

[0073] According to the residual stress distribution of the welding numerical simulation of the ladder 1, stress monitoring points are selected at the lower chords 12, the upper chords 11, the support rods 13, and the connection between the support rods 13 and the upper chords 11.

[0074] Specifically, according to the finite element analysis, as shown in Figure 7As shown, the positions with higher residual stress are selected as stress monitoring points at the lower chord 12, the upper chord 11, the support rod 13 and the connection between the support rod 13 and the upper chord 11, respectively, which are points D1-D4. By monitoring the dynamic strain of these positions with higher residual stress during the vibration process, the effectiveness of the vibration stress relief process can be ensured.

[0075] In some embodiments, the preset strain range includes -250με≤εt≤250με, where εt is the dynamic strain of the stress monitoring point.

[0076] Specifically, according to GB / T 25712-2010 “Vibration Stress Relief Process Parameter Selection and Effect Evaluation Method”, the ladder 1 is a welded part, and the equivalent peak value of the dynamic stress of the concerned part during the vibration stress relief should be selected in the range of 20-80 MPa. In order to ensure the stress relief effect, taking the elastic modulus of the ladder as 200 GPa for example, the calculated dynamic strain range should be in the range of 100-400με. Therefore, an intermediate value of 250με is selected as the boundary value of the preset strain range. By controlling the dynamic strain of the stress monitoring point in the range of -250με≤εt≤250με during the vibration process, a better stress relief effect can be obtained.

[0077] In some embodiments, the ladder treatment method further includes the step S0 of arranging a plurality of elastic support pads 4 (for example, rubber pads) uniformly spaced on the lower side of the lower chord 12. Arranging the elastic support pads 4 can ensure that the overall structure of the ladder 1 can vibrate.

[0078] Next, the vibration treatment process of the ladder of the aerial ladder fire truck in one specific embodiment of the present application will be briefly described with reference to Figures 1 to 12

[0079] Referring to Figure 1 The ladder 1 of the aerial ladder fire truck includes a pair of parallel lower chords 12, a pair of parallel upper chords 11, a connecting rod 2 connected between the lower chords 12, a connecting rod 2 connected between the upper chords 11, and a support rod 13 connected between the lower chords 12 and the upper chords 11.

[0080] The lower chord 12 is equally divided into three parts along the length direction, and rubber pads are placed on the lower side of both ends of the middle part to ensure that the overall structure of the ladder can vibrate;

[0081] Three vibration points are selected along the length direction of the ladder 1 or the lower chord 12. For ease of description, the three vibration points are defined as a first point, a second point and a third point. The distance between the first point and the second point is equal to the distance between the second point and the third point, and the distance between the first point and the first end of the lower chord is equal to the distance between the third point and the second end of the lower chord.

[0082] Still referring to​Figure 1 The cantilever rod 3 is fixed on the upper side of the lower chord 12 of the ladder frame 1 according to the position of the divided first point, and the length of the cantilever rod 3 is longer than the width of the ladder frame 1, wherein the length of the cantilever rod 3 is 2 m, and the overhanging amount of the two ends of the cantilever rod 3 relative to the two lower chords 12 should be guaranteed to be 500-1000 mm;

[0083] The exciter 5 is installed on the overhanging end of the cantilever rod 3, and the exciter 5 is connected with the vibration controller, first, an eccentricity is set according to the characteristics of the ladder frame 1, for example, 60% is selected, and then the exciter is controlled by the vibration controller to obtain the resonance acceleration of the first point in the form of automatic frequency sweeping, for example, 47.1 m / s 2 Then the rotation speed of the exciter 5 is adjusted by the vibration controller to control the actual vibration acceleration of the first point to be 44.6 m / s 2 ;

[0084] According to the residual stress distribution of the welding numerical simulation of the ladder frame 1, stress monitoring points D1-D4 are selected at the lower chord 12, the upper chord 11, the support rod 13 and the connection between the support rod 13 and the upper chord 11, and when the actual vibration acceleration of the first point is controlled to be 44.6 m / s 2 , the dynamic strain of these stress monitoring points also needs to be guaranteed to be between-250 με and 250 με, if the dynamic strain does not meet this range, the rotation speed and eccentricity of the exciter 5 are fine-tuned by the vibration controller to reach this strain range, then the vibration is performed for 10-15 minutes under this condition, then the same vibration condition is used, as shown in Figure 2 , the other end of the cantilever rod 3 is vibrated by the exciter 5 for the same time;

[0085] After the vibration of the first point is completed, as shown in Figure 3 , the cantilever rod 3 is changed to be installed at the second point, and then the above steps are repeated, and similarly, after the vibration of the second point is completed, as shown in Figure 4 , the vibration of the third point is continued, and finally the ladder frame 1 is completed for 6 times of vibration treatment.

[0086] According to the residual stress distribution of the welding numerical simulation of the aerial ladder ladder frame, the residual stress measuring point positions before and after the vibration stress relief are determined, and the test method is the blind hole method, Figure 8 shows the point position selection schematic of the outside of the ladder frame, Figure 9 shows the point position selection schematic of the inside of the ladder frame, B1-B4 are the residual stress measuring points before vibration, V1-V4 are the residual stress measuring points after vibration, and the positions before and after vibration correspond.

[0087] Figure 10The maximum stress of each test point before and after vibration is shown. As can be seen from the figure, the maximum stress of the four test points before vibration is tensile stress. The maximum stress of the 1# test point is the largest, about 645 MPa, the maximum stress of the 4# test point is the second, about 330 MPa, and the maximum stress of the 2# and 3# test points is smaller. After vibration, the maximum stress of 1#, 3# and 4# is reduced, and the maximum stress of 2# is slightly increased. The maximum stress of 1# is reduced from 645 MPa to 444 MPa, a decrease of 31.2%, the maximum stress of 3# is reduced from 211 MPa to 120 MPa, a decrease of 43.1%, the maximum stress of 4# is reduced from 330 MPa to 80 MPa, a decrease of 75.8%, and the maximum stress of 2# is increased from 113 MPa to 164 MPa, an increase of 45.1%. The reason for the stress increase of 2# is due to the stress redistribution after stress relief. According to GB / T 25712-2010 "Vibration aging process parameter selection and effect evaluation method", the stress relief rate of the welded part should be greater than 30%, and the homogenization rate should be greater than 20%. As can be seen from the stress test results, the maximum stress peak is reduced by 31.2%, which meets the requirement that the stress relief rate is greater than 30%. Through vibration stress relief, the maximum stress range is reduced from 113 MPa to 645 MPa to 120 MPa to 440 MPa, and the homogenization rate is 39.8%, which meets the requirement that the homogenization rate is greater than 20%.

[0088] Figure 11 The minimum stress of each test point before and after vibration is shown. The minimum stress of 2# test point is compressive stress, and the minimum stress of other three points is tensile stress. The minimum stress of 1# increases, the compressive stress of 2# decreases, and the tensile stress of 3# and 4# decreases. As can be seen from the figure, the stress distribution is homogenized, and the minimum stress range changes from -146 MPa to 154 MPa to -34 MPa to 233 MPa.

[0089] Figure 12 The shear stress (calculated according to the third strength theory) of each test point before and after vibration is shown. The maximum shear stress before vibration is 254 MPa, and the maximum shear stress after vibration is 105 MPa, a decrease of 58.7%. As can be seen from the figure, the shear stress distribution of the four test points is uniform, which improves the safety of the welded structure.

[0090] In conclusion, the stress elimination method and device of the ladder rack of the aerial ladder fire truck provided by the application has the advantages of short vibration time, simple operation, more than 30% reduction of the maximum stress peak, nearly 40% homogenization rate of the maximum stress range, nearly 60% reduction of the maximum shear stress, excellent stress reduction effect, the purpose of homogenizing the residual stress of the ladder rack, the increase of dislocation and slip caused by vibration, the increase of the yield point of the material, the improvement of the deformation resistance of the metal, the purpose of stabilizing the size of the ladder rack, and the improvement of the operation stability of the ladder rack.

[0091] Based on the above-mentioned embodiments of the present disclosure, the technical features of one of the embodiments can be beneficially combined with one or more of the other embodiments without explicit negation or conflict.

[0092] The principles and implementation modes of the present disclosure are described by applying specific embodiments herein, and the above embodiment descriptions are only used to help understand the method of the present disclosure and its core idea. It should be noted that, for ordinary skilled persons in the technical field, some improvements and modifications can be made to the present disclosure without departing from the principles of the present disclosure, and these improvements and modifications also fall within the protection scope of the claims of the present disclosure.

Claims

1. A ladder rack handling method for an aerial apparatus, characterized by, The ladder processing method includes the following steps: The vibration points are determined based on the length of the ladder frame. Install a cantilever rod at the vibration point, and make the end of the cantilever rod extend beyond the ladder frame in the width direction; Obtain the corresponding vibration parameters based on the vibration points; and The ladder frame is vibrated at the end of the cantilever rod according to the vibration parameters.

2. The rack processing method of claim 1, wherein, The ladder frame includes a pair of lower chords extending along the length of the ladder frame. The ladder frame processing method includes: The cantilever rod is installed at the vibration point of the lower chord rod, the cantilever rod extends along the width direction of the ladder frame, and the two ends of the cantilever rod extend to the sides relative to the pair of lower chord rods respectively; The ladder frame is vibrated sequentially at both ends of the cantilever rod according to the vibration parameters.

3. The rack processing method of claim 1, wherein, The ladder rack processing method includes: Multiple vibration points are obtained at intervals along the length of the ladder frame; The cantilever rods are installed sequentially at each of the aforementioned vibration points; The vibration parameters of each vibration point are obtained sequentially; and The ladder frame is vibrated at the end of the cantilever rod according to the vibration parameters at each vibration point in sequence.

4. The rack handling method according to any one of claims 1 to 3, characterized in that, Obtaining the corresponding vibration parameters based on the vibration location includes: An exciter is installed at the end of the cantilever rod, and the exciter is used to perform a pre-vibration frequency sweep to obtain the resonant acceleration of the ladder frame at the vibration point.

5. The rack processing method of claim 4, wherein, According to the vibration parameters, vibrating the ladder frame at the end of the cantilever rod includes: The operating state of the exciter is adjusted according to the resonant acceleration so that the actual vibration acceleration of the ladder frame at the vibration point is within the preset acceleration range.

6. The rack processing method of claim 5, wherein, The preset acceleration range includes: 0.9ar≤as≤0.95ar, where as is the actual vibration acceleration of the ladder frame at the vibration point, and ar is the resonant acceleration of the ladder frame at the vibration point.

7. The rack processing method of claim 5, wherein, Adjusting the operating state of the exciter based on the resonant acceleration includes: Adjust the rotational speed and / or eccentricity of the exciter.

8. The rack processing method of claim 5, wherein, Adjusting the operating state of the exciter based on the resonant acceleration includes: The system acquires stress monitoring points and detects the dynamic strain at these points in real time. After the actual vibration acceleration reaches the preset acceleration range, it determines whether the dynamic strain at the stress monitoring points is within the preset strain range. If not, it continues to adjust the operating state of the exciter to bring the dynamic strain at the stress monitoring points within the preset strain range.

9. The rack processing method of claim 8, wherein, The ladder frame includes a pair of lower chords, a pair of upper chords, and a support rod connecting the upper chords and the lower chords. The acquisition of stress monitoring points includes: Based on the residual stress distribution obtained from the numerical simulation of the welding of the ladder frame, stress monitoring points are selected at the lower chord, the upper chord, the support rod, and the connection between the support rod and the upper chord.

10. The ladder rack processing method according to claim 8, characterized in that, The preset strain range includes: -250με≤εt≤250με, where εt is the dynamic strain at the stress monitoring point.

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