Research And Improvement On The Problem Of Commercial Vehicle Body Cracking

Energy conservation and environmental protection safety has been the subject of today’sauto industry development. Currently in the process of development of commercial vehiclesat home and abroad is also along the light direction. Lightweight structure, lightweightmaterials are widely used in the commercial vehicle cab. In the process of lightweight design,the body stiffness and strength are faced with new problems. So in the process of experiment,the trial car will emerge some problem such as Body cracking, bad tightness, widenoise. InThis Article, the writer researched the several typical commercial car white body crackingproblems, expounded the process to analyze and solve the cracking problems. Based onthose white body cracking problems, the writer pointed out the crack position and crackforms and the causes of cracking, then extended to find the key factors influencing theintensity of the white body, summarize the typical structural characteristics, accumulate oftypical design method, strive for avoiding the white body cracking phenomenon.First there is a new commercial vehicle cab, after the experiment, the corner of enginehatch cracked. The writer analyses the problem of cracking, find out some reasons for thesmall webmaster section flexural capacity is insufficient. and the asymmetric structure of thecorner is also cause the cracking, and there is small strengthening beam severe stressconcentration phenomenon. Inside the nacelle strengthen structure flexural capacity isinsufficient, and is discontinuous stiffness, the low strength of materials is also the reason ofthe cracking. After detailed analysis of vehicle load the writer formulate some solutions toavoid cracking, such as optimizing the section of floor, rearranging the beam structure,improving the material strength. The improvement of effect is obvious. The finite elementanalysis of the body bridge stiffness and fatigue life under the same load have greatlyimproved, the crack position stress value is decreased obviously. Through subsequentstrengthening road and off-road vehicle test, the improvement body don’t crack.The writer researched the reason for the problem of a side common column cracking.The first reason is the small corner easy to appear stress concentration in this position. Thesecond reason is the bad manufacturability of stamping parts and so on. Analysis the stressdistribution, and raise the solution: enlarge the rounded corners; improving the partsstamping manufacturability. The improved body can improved the cracking phenomenon. The writer also study of the roof panel window cracking problem, the reasons to the crackingis discontinuous roof top reinforcement, and the small corners of reinforcement. There isstress concentration phenomenon. For the cause of the above analysis, the writer developstructure improvement plan. First of all, enlarge the corner of the reinforcement, theimproved structure can effectively reduce the strain.At the last the writer study the problem of cracking in floor longitudinal beam, find outthe reasons for the cracking. The first is the asymmetry body structure. The asymmetry bodystructure lead the stress imbalance; Co2gas shielded welding destroyed the floor under thelongitudinal beam surface, produced stress concentration; and the bridge load-bearing framelayout is unreasonable,lead the power transmission is not reasonable. Through analyzingload, the writer developed the solution. First the writer optimized the cab main framestructure at the same time strength the local structure design. Second use the Q345steel.Finally based on the research of the typical body crack position and the improvement, thewriter summarizes the key factors affecting the white body stiffness, and gives the referencefor the later design performance of the white body.